The article discusses the question of the necessity and expediency of using austenitic manganese cast iron for valve seats of internal combustion engines operating on gas motor fuel. Information is given on mass-produced valve seats for internal combustion engines of cars, the most common alloys for the manufacture of seat parts, their shortcomings, the imperfection of the alloys used in operation, and the reasons for the low life of parts of this type are described. As a solution to this problem, it is proposed to use austenitic manganese cast iron. Based on many years of research on the properties of manganese cast iron, it was proposed to use this alloy for the manufacture of valve seats for automobile engines with gas motor fuel. The main properties possessed by the proposed alloy are considered. The research results are positive, and the resource of new saddles is 2.5 ... 3.3 times longer than serial ones.
cylinder head
supply system
wear
parts resource
natural gas motor fuel
ICE car
1. Vinogradov V.N. Wear-resistant steels with unstable austenite for parts of gas-field equipment / V.N. Vinogradov, L.S. Livshits, S.N. Platonov // Vestnik mashinostroeniya. - 1982. - No. 1. - S. 26-29.
2. Litvinov V.S. Physical nature of hardening of manganese austenite / V.S. Litvinov, S.D. Karakishev // Heat treatment and physics of metals: interuniversity coll. - Sverdlovsk, UPI. - 1979. - No. 5. - S. 81-88.
3. Maslenkov S.B. Steels and alloys for high temperatures. Reference book: in 2 volumes / S.B. Maslenkov, E.A. Maslenkov. - M. : Metallurgy, 1991. - T. 1. - 328 p.
4. Stanchev D.I. Prospects for the use of special austenitic manganese cast iron for parts of friction units of forest machines / D.I. Stanchev, D.A. Popov // Actual problems of development of the forest complex: materials of the international scientific and technical conference of VSTU. - Vologda, 2007. - S. 109-111.
5. Engineering technology. Restoration of quality and assembly of machine parts / V.P. Smolentsev, G.A. Sukhochev, A.I. Boldyrev, E.V. Smolentsev, A.V. Bondar, V.Yu. Sklokin. - Voronezh: Publishing House of the Voronezh State. those. un-ta, 2008. - 303 p.
Introduction. The use of gas motor fuel as a fuel for internal combustion engines is associated with a number of technical issues, without which the efficient operation of vehicles on dual-fuel power systems is impossible. One of the most pressing issues of the technical operation of vehicles running on gas motor fuel is the low resource of the “seat-valve” interface.
An analysis of the damage to the seat made it possible to establish the causes of their occurrence, namely: plastic deformation and gas erosion caused by the deterioration of the fit of the friction pair during operation. Figures 1 and 2 show the main characteristic damage to seats and valves when operating on gas fuel.
Traditionally, for gasoline engines, valve seats are made of gray cast iron grades SCH25, SCH15 according to GOST 1412-85 or carbon and alloy steels 30 HGS according to GOST 4543-71, which provide satisfactory operational reliability and durability of the interface throughout the guaranteed engine life. However, when switching to a dual-fuel power supply system for internal combustion engines, the interface resource is sharply reduced, according to various estimates, repair of the block head is required after 20,000-50,000 thousand kilometers. The reason for the decrease in the interface resource is the low combustion rate of the gas-air mixture in operating modes with a high crankshaft speed and, as a result, a significant heating of the seat metal, loss of its strength and further deformation from interaction with the valve.
Thus, to ensure a guaranteed service life of the seat-valve interface, when using gas motor fuel, materials require not only high antifriction properties, but also increased heat resistance.
Purpose of the study. Research results. The purpose of the research is to substantiate the feasibility of using manganese austenitic cast iron for the manufacture of valve seats. It is known that steels and cast irons of the ferritic-pearlitic and pearlitic class do not differ in heat resistance and are not used for parts operating at temperatures above 700 ºС. For work in extreme conditions, at operating temperatures of about 900 ºС, in particular, heat-resistant austenitic cast irons with a minimum amount of free graphite in the structure are used. These alloys include austenitic manganese cast iron, the binding base of which is austenite containing carbide inclusions and fine lamellar graphite. Traditionally, such cast iron is used as antifriction cast iron under the AChS-5 brand and is used for plain bearings.
Long-term studies of manganese cast iron have revealed the valuable qualities of this material, achieved by improving the properties of the alloy by modifying it and improving the production technology. In the course of the work performed, the effect of manganese concentration in the alloy on the phase composition and service properties of austenitic cast iron was studied. To do this, a series of melts was made, in which only the manganese content varied at four levels, the composition of the remaining components, the conditions and mode of smelting were constant. The microstructure, phase composition and properties of the cast irons obtained are shown in Table 1.
Table 1 - Influence of manganese concentration on the structural composition and mechanical properties of manganese cast iron in the cast state
|
microstructure (etched section) |
Hardness |
Microhardness, 10 ∙ MPa |
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|
austenite |
martensite |
|||||
|
Austenitic-martensitic mixture, martensite, carbides of medium and small sizes. Martensite predominates. Large lamellar graphite |
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|
Austenite, austenite-martensite mixture, carbides, fine graphite. Predominance of austenite |
||||||
|
Austenite, a small amount of martensite, carbide network, fine graphite. Predominance of austenite |
||||||
|
austenite, significant the amount of large carbides, unevenly distributed, isolated fields of ledeburite |
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As a result of the study of the microstructure, it was noted that with an increase in the manganese content in cast iron, the ratio of phase components changes (Fig. 3): the ratio of the gamma phase to the alpha phase of iron increases, the amount of the carbide phase (Fe3C, Mn3C, Cr3C2) increases and the amount of graphite decreases .
As the results of X-ray studies have shown, with an increase in the manganese content, the ratio of the areas of integral intensities occupied by the gamma phase of austenite and the alpha phase of martensite (I111/I110), respectively, on the X-ray pattern of the surface of the section increases. With a manganese content of 4.5% I111/I110 = 0.7; at 8.2% I111/I110 = 8.5; at 10.5% I111/I110 = 17.5; at 12.3% I111/I110 = 21.
To establish the effect of manganese on the physical and mechanical properties of cast iron, tests were carried out, in particular, for wear resistance under conditions of dry friction and uncontrolled frictional heating. Comparative tests for wear of cast irons with different manganese content were carried out on the SMTs-2 machine according to the "block-roller" friction scheme at a specific pressure of 1.0 MPa and a sliding speed of 0.4 m/s. The test results are shown in Figure 4.
With an increase in the manganese content from 4.5 to 10.5% in cast iron, the amount of austenite contained in the structure increases. An increase in the proportion of austenite in the metal matrix of cast iron provides reliable retention of the carbide phase in the base. An increase in the manganese content above 12% did not lead to a significant increase in the wear resistance of cast iron. This circumstance is explained by the fact that the increment of the carbide phase (separate fields of ledeburite are observed) does not significantly affect the wear resistance of the material under these friction modes.
Based on the results obtained when testing experimental cast iron with different manganese content, cast iron containing 10.5% Mn has the highest wear resistance. This content of manganese ensures the creation of an optimal structure from the point of view of frictional contact, formed by a relatively plastic austenitic matrix uniformly reinforced with carbide inclusions.
At the same time, the alloy containing 10.5% Mn differed in the most optimal ratio of phase components, as well as their shape and arrangement. Its structure was predominantly austenite, reinforced with medium and small-sized heterogeneous carbides and finely dispersed graphite inclusions (Fig. 5). Relative wear tests in dry friction, carried out with samples of cast irons with different manganese concentrations, showed that manganese cast iron containing 10.5% Mn was 2.2 times superior in wear resistance to cast iron with 4.5% Mn.
An increase in manganese content above 10.5% led to a further increase in the amount of austenitic and carbide phases, but carbides were observed in the form of separate fields, and the wear resistance of cast iron did not increase. Based on this, the chemical composition of cast iron was chosen for further research and testing, %: 3.7 C; 2.8Si; 10.5 Mn; 0.8Cr; 0.35 Cu; 0.75Mo; 0.05B; 0.03S; 0.65p; 0.1Ca.
In order to study the effect of heat treatment on the structural composition and properties of austenitic manganese cast iron of the proposed chemical composition, the samples (blocks) were subjected to hardening. Volumetric hardening of the samples was carried out in running water from a heating temperature of 1030–1050 °C and a holding time during heating: 0.5, 1, 2, 3, 4 h.
Studies of the structure of samples after volumetric hardening showed that the heating temperature, the duration of exposure during heating, and the cooling rate play a significant role in the formation of the structure of manganese cast iron. Hardening in the general case led to almost complete austenization, obtaining grains of medium and small size. Heating ensures the dissolution of carbides in austenite. The completeness of these transformations increases with an increase in the duration of exposure of the samples in the oven. The martensite present in the casting structure was completely dissolved in austenite during heating and did not precipitate during quenching. Carbides, depending on the duration of exposure during heating, having partially or completely dissolved in austenite, are released again upon cooling. After quenching, the amount of graphite in the cast iron structure becomes significantly less compared to the cast state. In hardened cast iron, the plates of graphite inclusions are thinner and shorter. Brinell hardness of quenched manganese cast iron is reduced, toughness is increased and machinability is improved.
In order to determine the hardening mode that provides the maximum wear resistance of the experimental manganese cast iron, samples with different holding times during hardening were subjected to wear. The study of wear resistance was carried out on a friction machine SMTs-2 at a specific pressure on the sample of 1.0 MPa and a sliding speed of 0.4 m/s.
As a result of tests, it was found that increasing the holding time to 2∙3.6∙103 s at the quenching temperature causes an increase in the relative wear resistance of manganese cast iron, after which its wear resistance does not change. These tests confirm the assumption that the structural composition of manganese cast iron obtained by quenching after holding for 2∙3.6∙103 s is the most perfect and is capable of providing high performance in dry friction.
In addition, reducing the hardness to 160-170 HB of austenitic manganese cast iron during hardening is likely to have a positive effect on damage and wear of the counterbody (roller) simulating a locomotive wheel. In this regard, for subsequent laboratory and operational tests, austenitic manganese cast iron in the cast (ACHl) and quenched state, obtained after a 2-hour holding at the quenching temperature (ACHz), was used.
Based on the research and testing carried out, it was possible to develop a special composition of austenitic cast iron, obtained by modifying manganese, which is characterized by high wear resistance in dry friction conditions (brakes, friction clutches), characterized by high frictional heating up to 900 ºС (“Wear-resistant cast iron”, RF patent No. 2471882) . The results of testing this composition of cast iron under the conditions and loading modes of the “seat-valve” interface of the timing showed a high performance of the material, exceeding the resource of saddles made of gray cast iron SCH 25 according to GOST 1412-85 and 30 HGS according to GOST 4543-71 in 2.5-3, 3 times. This allows us to consider such cast iron promising for use in conditions of dry friction and high temperatures, in particular for valve seats, clutch pressure plates, brake drums of hoisting and transport machines, etc.
Findings. Thus, it can be concluded that the use of austenitic manganese cast iron for the manufacture of valve seats will significantly increase the service life of the cylinder head of engines converted to gas motor fuel and using a combined power supply system (gasoline-gas).
Reviewers:
Astanin V.K., Doctor of Technical Sciences, Professor, Head of the Department of Technical Service and Engineering Technologies, Voronezh State Agrarian University named after Emperor Peter I, Voronezh.
Sukhochev G.A., Doctor of Technical Sciences, Professor of the Department of Mechanical Engineering Technologies, Voronezh State Technical University, Voronezh.
Bibliographic link
Popov D.A., Polyakov I.E., Tretyakov A.I. ON THE FEASIBILITY OF APPLICATION OF AUSTENITIC MANGANESE CAST IRON FOR ICE VALVE SEATS OPERATING ON GAS ENGINE FUEL // Modern Problems of Science and Education. - 2014. - No. 2.;URL: http://science-education.ru/ru/article/view?id=12291 (date of access: 01.02.2020). We bring to your attention the journals published by the publishing house "Academy of Natural History"
Restoration of valve seats. When the wear of the valve seats does not exceed the maximum allowable, restoring their performance is reduced to the formation of the required chamfer angle. Before chamfering the valve seats, replace the worn valve stem guide bushings with new ones and process them with a reamer installed in the mandrel. The machined hole is used as a technological base for countersinking the chamfer of valve seats, which ensures the necessary alignment of the holes of the guide bushings and valve seats. The valve seats are processed using a floating cartridge. If the valve seats are worn above the permissible level, they are restored by installing valve seats.
When restoring valve seats by pressing the seats, the immobility of the connection is ensured by tension. The required strength is achieved in this case due to stresses arising in the material of the seat and cylinder head. With prolonged exposure to heat, stresses can decrease, thereby reducing the strength of the fit. Therefore, for the manufacture of valve seats, it is necessary to use high-strength heat-resistant materials: cast iron VCh50-1.5, special cast iron No. 3 TM 33049. Recently, the EP-616 alloy based on chromium-nickel has become widespread. The holes for the saddles are processed with a special countersink, which is installed in a special mandrel. The diameter of the countersink is selected in accordance with the size of the hole to be machined for the valve insert. The centering of the tool is carried out using guide collet mandrels installed in the holes for the valve bushings. This provides a high concentricity of the machined surfaces under the seat inserts and the centering surface. In addition, the use of rigid guides makes it possible to machine holes on a 2H135 vertical drilling machine and obtain the required dimensional and geometric accuracy of machined surfaces. When boring, the head is installed in a special fixture.
First, the valve seats are pre-bored, and then finally at 100 rpm of the machine spindle, manual feed in one pass. Seats (Fig. 58 and 59) are pressed into the valve seats prepared in this way using a mandrel. In this case, the cylinder head is preheated to a temperature of 80...90°C, and the seats are cooled in liquid nitrogen to -100 - ... 120°C. The heads are heated in an OM-1600 heating bath, and cooled using a Dewar vessel. The rings must be pressed into the undercuts of the head to failure and without distortion (Fig. 60). After pressing, the seats are caulked at four points evenly on an arc through 90°. Then the cylinder head is installed on the stand OR-6685 for chamfering the valve seats, holes are drilled in the guide bushings and the chamfers of the valve seats are countersinked. The holes in the bushings are reamed at 50 rpm and a feed of 0.57 mm/rev in one pass, countersinking is performed at 200 rpm of the countersink, feed of 0.57 mm/rev in several passes.
As a result of repeated processing of the plane of the cylinder heads by milling or grinding, the lower wall of the head becomes thinner and less durable, therefore, for this group of parts, the restoration of valve seats by pressing the seats is not sufficiently reliable. In this case, the valve seats should be restored with gas surfacing. If the head, in addition to worn valve seats, also has cracks, then you must first restore the seats, and then weld the cracks.
When working on the engine, as a result of mechanical and thermal loads, significant internal stresses accumulate in the lower plane of the cylinder head, the values and nature of the distribution of which can be very different. The accumulated stresses lead to warping of the heads, and in some cases - to the appearance of cracks. If cold arc welding is used, then the resulting welding stresses, adding up in separate areas with residual, as well as assembly (when the head is tightened) and workers, will cause new cracks to appear. Therefore, for surfacing nests, it is necessary to use a method that would reduce residual stresses and would not lead to the emergence of new ones. This method is hot welding, which provides high quality welds with minimal stress on the part.
In hot welding, the head is preheated to a temperature of 600 ... 650 ° C and welded at a temperature of the part not lower than 500 ° C. The lower heating limit is set based on the properties of cast iron, the ductility of which drops sharply below this temperature, which leads to the appearance of welding stresses. Before heating, the valve seats of the heads are carefully cleaned.
To heat the head, a heating chamber furnace with electric or other heating is used. It is advisable to use the H-60 chamber electric furnace, in which up to five heads can be heated simultaneously.
Of great importance is the rate of heating and cooling of parts. Rapid heating of the cylinder head can cause additional stresses.
At the end of heating, a movable welding table is moved to the furnace opening and the head is placed on it.
Welding is performed with an oxy-acetylene torch GS-53 or GS-ZA ("Moscow"), using tips No. 4 or 5, depending on the size of the crack. To ensure the high quality of the weld metal, a well-formed, sharply defined torch flame should be used, for which the welding torch mouthpiece must be in good technical condition. When welding cracks and surfacing valve seats, the reducing part of the flame is used, which protects the metal from oxidation due to the content of hydrogen, carbon dioxide and carbon monoxide in the flame. The core of the flame in the process of surfacing should be at a distance of 2...3 mm from the surface of the part. Welding is carried out with uniform continuous heating of the weld pool.
As a filler rod, cast iron rods of brand A are used (composition in%): 3 ... 3.6C; 3...2.5 Si; 0.5...0.8 MP; Р 0.5...0.8; S0.08; 0.05 Cr; 0.3 Ni. Bar diameter - 8... 12mm (choose depending on the width of the crack groove). The surface of the bars must be thoroughly cleaned and degreased. Finely ground calcined borax or its 50% mixture with dried soda ash is used as a flux.
Good results are also obtained by the use of fluxes FSC-1, ANP-1 and ANP-2.
After welding is completed, the cylinder head is placed back in the furnace to relieve welding stresses. The head is heated to 680°C and then cooled, first slowly (with an oven), to 400°C, and then in dry sand or a thermos, following the schedule. Completely cooled heads are cleaned of slag and scale and sent for machining. First, the mating plane is milled on a horizontal milling machine type 6H82 with a cylindrical cutter 180X X125 mm or on a vertical milling 6M12P end mill with insert cutters VK6 or VK8.
After machining the plane, the quality of welding is controlled. Welded places must be clean, without shells and slag inclusions. The chamfering of the valve seats is carried out with a countersink similar to the chamfering of the seats described above.
Valve lapping. Before disassembling the cylinder heads, clean them of oil and carbon deposits and mark the serial numbers of the valves on the ends of the plates in order to install them in their places during assembly.
To dry out the valves, it is necessary to install the cylinder head without nozzles, rocker arms, rocker arm axles and rocker arm axle mounting studs with the mating surface on the plate so as to provide a stop for the valves. Drying is carried out using the device shown in Fig. 84. For this purpose, screw the stop bolt 1 of the device into the hole for the stud for attaching the rocker arm axis, install the pressure plate 2 of the device on the spring plate of the corresponding valve and, pressing the handle 3 of the device lever, press the valve springs, remove the crackers and remove all parts of the valve assembly. In the same way, successively loosen all other valves and remove the valve springs and associated parts.
Turn the cylinder head and remove the valves from the guide bushings. Thoroughly clean valves and seats from dirt, carbon deposits and oil deposits, wash in kerosene or a special detergent solution, dry and inspect to determine the degree of repair. It is possible to restore the tightness of the valve by lapping only if there are slight wear and small shells on the working facet, and only if the plate and the stem are not warped and there are no local burnouts on the facets of the valve and seat.
In the presence of such defects, lapping should be preceded by grinding seats and valves or replacing defective parts with new ones.
To lap the valves, use a special lapping paste prepared by thoroughly mixing three parts (by volume) of green silicon carbide micropowder with two parts of engine oil and one part of diesel fuel. Stir the lapping mixture thoroughly before use, since in the absence of mechanical stirring, the micropowder can precipitate.
Install the cylinder head on a plate or special tool with the mating surface up. Apply a thin, even layer of lapping paste to the valve face, lubricate the valve stem with clean engine oil and install it in the cylinder head. It is allowed to apply the paste on the chamfer of the saddle. Grinding is performed by reciprocating rotational movements of the valves using a special tool or a drill with a suction cup. Pressing the valve with a force of 20 ... 30 N (2 ... 3 kgf), turn it 1/3 turn in one direction, then, loosening the force, 1/4 turn in the opposite direction. Do not rub in circular motions.
Periodically lifting the valve and adding paste to the chamfer, continue lapping, as indicated above, until a continuous matte belt with a width of at least 1.5 mm appears on the chamfers of the valve and seat. Ruptures of the matte belt and the presence of transverse scratches on it are not allowed. With proper lapping, the matte belt on the face of the valve seat should start at the larger base.
After grinding in, thoroughly wash the valves and cylinder head with kerosene or a special cleaning solution and dry.
Attention! The presence of even slight residues of lapping paste on the valve or cylinder head can lead to chafing and accelerated wear of the cylinder liners and piston rings.
Install the valves, springs and their mounting parts on the cylinder head and dry the valves using the tool (see Fig. 84).
Check the quality of grinding in the valve-seat interface for leaks by pouring kerosene or diesel fuel, pouring it alternately into the inlet and outlet channels. Well lapped valves should not let kerosene or diesel through for one minute.
It is acceptable to check the quality of lapping with a pencil. To do this, apply 10-15 dashes at regular intervals with a soft graphite pencil across the chamfer of the ground-in clean valve, then carefully insert the valve into the seat and, pressing strongly against the seat, turn it 1/4 turn. With good lapping quality, all dashes on the working chamfer of the valve should be erased. If the results of the lapping quality check are unsatisfactory, it must be continued.
The invention relates to powder metallurgy, in particular to iron-based sintered alloys. Can be used to make valve seat inserts for internal combustion engines. A sinter-hardenable powder material for an internal combustion engine valve seat insert is obtained from a mixture containing 75-90 wt.% of a sinter-hardenable powder based on iron pre-alloyed with 2-5 wt. wt % nickel, tool steel powder and a solid lubricant. At the same time, copper is introduced into it by impregnation during sintering. EFFECT: increased thermal wear resistance, improved machinability. 4 n. and 24 z.p. f-ly, 2 tab.
State of the art
The present invention generally relates to iron-based sintered alloy compositions used for the manufacture of valve inserts for internal combustion engines. Valve seat inserts (VSI) operate in extremely corrosive environments. Alloys used in the manufacture of valve seat inserts require resistance to abrasion and/or adhesion caused by the surface of valve seat mating parts, resistance to softening and fracture due to high operating temperatures, and resistance to corrosion-induced degradation caused by combustion products.
Valve seat inserts are machined after they have been inserted into the cylinder head. The cost of machining valve seat inserts is a major part of all cylinder head machining costs. This poses a major problem in the development of valve seat insert alloys, since the hard material phases that make the alloy wear resistant also cause significant wear to cutting tools during machining.
Sintered alloys have replaced cast alloys in valve seat inserts in most passenger car engines. Powder metallurgy (pressing and sintering) is a very attractive method of manufacturing VSI due to the flexibility of this method in the composition of alloys, which allows the coexistence of highly dissimilar phases, such as carbides, soft ferrite or pearlite phases, hard martensite, Cu-rich phase, etc. .d., as well as the possibility of obtaining a product close to the desired shape, which reduces the cost of machining.
Sintered alloys for valve seat inserts have emerged as a result of the need for higher power density in internal combustion engines, which implies higher thermal and mechanical loads, alternative fuels to reduce emissions and extend engine life. Such sintered alloys are mainly of four types:
1) 100% tool steel,
2) a matrix of pure iron or low-alloy iron with the addition of solid phase particles to improve wear resistance,
3) high carbon steel with a high chromium content (>10 wt%), and
4) alloys based on Co and Ni.
These materials meet most requirements for durability (resistance). However, all of them are difficult to machine, despite the use of a large number of additives that facilitate machining.
Types 1, 2 and 3 are high carbide materials. US Pat. exhaust valves.
Increasing the amount and size of carbide particles in the alloy, while improving durability (hardness), is detrimental to the processing (compressibility and green sand strength) and machinability of finished valve seat inserts. In addition, the strength of the sintered product is significantly reduced when carbide particles or large hard particles are present.
US Pat. No. 6,139,598 describes a valve seat insert material with a good combination of compressibility, high temperature wear resistance and machinability. The mixture used to obtain such a material is a complex mixture of steel powder containing Cr and Ni (>20% Cr and<10% Ni), порошка Ni, Cu, порошка ферросплава, порошка инструментальной стали и порошка твердой смазки. Несмотря на то что такой материал может обеспечить значительное улучшение прессуемости и износостойкости, большое количество легирующих элементов определяет высокую стоимость материала (Ni, инструментальная сталь, обогащеннный Cr стальной порошок, ферросплавы).
US Pat. No. 6,082,317 describes a valve seat insert material in which cobalt based solids are dispersed in an iron based alloy matrix. Compared to traditional solids (carbides), cobalt based solids are claimed to be less abrasive, resulting in less mating valve wear. Such a material is said to be suitable for those applications where direct contact between the metal surfaces of the valve and valve seat is required, such as in internal combustion engines. Although cobalt alloys show a good balance of properties, the price of Co makes these alloys extremely expensive for automotive applications.
DETAILED DESCRIPTION OF THE INVENTION
The present invention aims to overcome the disadvantages mentioned above by providing a compacted and sintered alloy with excellent machinability and high temperature and wear resistance.
The present invention solves the problem of machining by providing a unique combination of high strength, low carbon martensitic matrix, finely divided carbides, machining aids, and a "network" of Cu-rich pore-filling phase. The amount of hard particles dispersed in the hard martensitic matrix is relatively small, which reduces the cost of the alloy.
In accordance with the present invention, the sinter hardening alloy has a matrix containing: 2-5 wt.% Cr; 0-3 wt% Mo; 0-2 wt.% Ni, the rest is Fe, which is preferably completely pre-alloyed with these elements. To improve wear resistance and temperature resistance, 5-25 wt.% of tool steel and at least one of the machining aids selected from the group MnS, CaF 2 or MoS 2 are added in an amount of 1-5 wt.%. To significantly improve the thermal conductivity, the pores are filled with Cu alloy in the amount of 10-25 wt.%, added by impregnation of the compact during sintering. Copper impregnation also improves the machinability of the alloy.
For a better understanding of the present invention, the following are the main properties in comparison with the properties of a typical prior art valve seat insert material. The composition of the powder mixture (composition) for the exemplary materials is presented in Table 1, and the properties are presented in Table 2.
In Table 1, Fe is the base powder used in the mixture, which is either pure iron powder or alloy steel powder. The tool steel powder is the second component of the mixture and was introduced into the mixture as M2 or M3/2 type tool steel powder. Cu is added by impregnating the compact during the sintering process; graphite and a solid lubricant are added to the mixture as powdered elements.
All powders are mixed with a vaporizable lubricant, pressed to 6.8 g/cm 3 and sintered at 1120°C (2050°F). Heat treatment is carried out after sintering by tempering in air or in a nitrogen atmosphere at 550°C.
After processing, the critical properties were determined on typical samples of each alloy. Machinability was determined by making face notches and plunge cutting for 2000 valve seat inserts made from exemplary materials. Tool wear was measured after every fifty cuts. A wear graph was plotted against the number of notches and a linear regression analysis was performed. The slope of the regression line indicates the wear rate and was used as a measure of machinability. In addition, at the end of each machinability test, the depth of the notch on the plug-in seat was measured along the side edges of the notch. The depth of the notches was also used as an indicator of the machinability of the tested materials.
Measurement of wear resistance at high temperatures was carried out in the device for testing wear under conditions of high temperature sliding. Polished rectangular rods made of the tested materials were fixed and ensured the sliding of the aluminum oxide ball in both directions over the polished smooth surface of the samples. The test samples were maintained during the test at a temperature of 450°C. The depth of the scratches was an indicator of the wear resistance of the sample under these conditions.
High temperature hardness was measured at different sample temperatures, recording at least five readings at the same temperature and averaging the results.
Thermal conductivity values were calculated by multiplying the measured values of specific heat capacity, thermal diffusivity and density at a given temperature.
Table 2 shows all the properties of the new material compared to existing valve seat insert materials that contain five times the amount of tool steel. The material of the present invention ("new alloy") is 2.5 to 3.7 times better machined than exemplary materials having the same high temperature wear resistance and comparable high temperature hardness.
| Table 2: Properties of Example Materials |
||||
| Property | New alloy | Valve seat material A | Valve seat material | |
| Compressibility (density before sintering at a pressure of 50 tons / square inch (tsi), g / cm 3 | 6,89 | 6,79 | 6,86 | |
| Machinability | Average wear rate (µm/notch) | 8.31E-5 | 7.00E-4 | 4.19E-3 |
| Average wear notch depth (µm) | 38 | 95 | 142 | |
| Wear resistance (average volume of wear cuts after high temperature wear test), mm 3 | 6,29 | 2,71 | 6,51 | |
| Thermal conductivity | W m -1 K -1 at RT | 42 | 46 | 32 |
| W m -1 K -1 at 300°С | 41 | 46 | 27 | |
| W m -1 K -1 at 500°С | 41 | 44 | 23 | |
| High temperature hardness | HR30N at CT | 55 | 66 | 49 |
| HR30N at 300°C | 50 | 62 | 47 | |
| HR30N at 500°C | 39 | 58 | 41 | |
Given that the maximum expected operating temperature for valve seat inserts is approximately 350°C, the results presented in Table 2 clearly show that the new material will perform better than valve seat material B and almost as well as valve seat material A, while exhibiting significantly better machinability than material A. The combined effect of machinability, cost, thermal conductivity and wear resistance makes this material an ideal replacement for expensive engine materials such as valve seat inserts.
It is obvious that various modifications and variations of the present invention are possible, taking into account the above indications. Therefore, it should be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described. The invention is defined by the claims.
CLAIM
1. A sinter-hardenable powder material for an internal combustion engine valve seat insert obtained from a mixture containing iron-based powder, tool steel powder, a solid lubricant and copper, characterized in that it is obtained from a mixture containing 75-90 wt. hardenable during sintering powder based on iron, pre-alloyed 2-5 wt.% chromium, up to 3 wt.% molybdenum and up to 2 wt.% Nickel, and copper introduced by impregnation during sintering.
2. Material according to claim 1, characterized in that the mixture contains from 5 to 25 wt.% tool steel powder.
3. Material according to claim 1, characterized in that the tool steel is selected from the group consisting of M2 and M3/2 tool steel.
4. Material according to claim 3, characterized in that the tool steel is M2 steel.
5. The material according to claim 1, characterized in that copper is introduced into it in an amount of 10-25 wt.% of the mass of the mixture.
6. Material according to claim 1, characterized in that it contains 89% by weight of iron-based powder.
7. The material according to claim 2, characterized in that it contains 8 wt.% powder M2 tool steel.
8. The material according to claim 1, characterized in that it contains 3 wt.% solid lubricant.
9. The material according to claim 5, characterized in that copper is introduced into it in an amount of 20 wt.% of the mass of the mixture.
10. The material according to claim 1, characterized in that it is obtained from a mixture containing, wt.%:
and copper is introduced in the amount of 20 wt.% by weight of the mixture.
11. Sintered powder material for an internal combustion engine valve seat insert with improved machinability, wear resistance and high thermal conductivity, obtained from a mixture containing chromium-alloyed iron-based powder, tool steel powder, solid lubricant and copper, characterized in that it is obtained from a mixture containing a sinter-hardenable iron-based powder pre-alloyed with 2-5 wt.% chromium, up to 3 wt.% molybdenum and up to 2 wt.% nickel, and copper is introduced by impregnation during sintering.
12. Sintered material according to claim 11, characterized in that after sintering in a furnace without accelerated cooling, it has a martensitic microstructure.
13. Sintered body according to claim 11, characterized in that it contains 5-25 wt.% tool steel powder.
14. Sintered material according to claim 11, characterized in that copper is introduced into it in an amount of 10-25 wt.% of the mass of the mixture.
15. A sintered valve seat insert for an internal combustion engine with improved machinability, wear resistance and high thermal conductivity, having a matrix obtained by sintering a mixture including iron-based chromium powder, tool steel powder, a solid lubricant and containing copper, characterized in that the matrix is obtained by sintering a mixture containing a sinter-hardenable powder based on iron, pre-mixed with or alloyed with 2-5 wt.% chromium, up to 3 wt.% molybdenum and up to 2 wt.% nickel, and copper introduced by impregnation during sintering.
16. A sintered valve seat insert according to claim 15, characterized in that, after sintering without accelerated cooling, it has a fully martensitic microstructure.
17. Sintered valve seat insert according to claim 15, characterized in that it contains a matrix obtained from a mixture containing 5-25 wt.% tool steel powder.
18. Sintered valve seat insert according to claim 17, characterized in that the mixture contains M2 tool steel powder as tool steel powder.
19. Sintered valve seat insert according to claim 17, characterized in that it contains a matrix obtained from a mixture containing 8 wt.% tool steel powder.
20. Sintered valve seat insert according to claim 17, characterized in that it contains a matrix obtained from a mixture containing 1-5 wt.% solid lubricant, representing at least one substance selected from the group MnS, CaF 2 , MoS 2.
21. Sintered valve seat insert according to claim 20, characterized in that the matrix is obtained from a mixture containing 3 wt.% solid lubricant.
22. Sintered insert valve seat according to claim 15, characterized in that the matrix is impregnated with copper in an amount of 10-25 wt.% of the mass of the mixture.
23. Sintered insert valve seat according to claim 22, characterized in that the matrix is impregnated with copper in an amount of 20 wt.% by weight of the mixture.
24. A method of manufacturing a valve seat insert for internal combustion engines with improved machinability, wear resistance and high thermal conductivity, including the preparation of a mixture containing sinter-hardened and chromium-alloyed iron-based powder, tool steel powder and solid lubricant, pressing, sintering and copper impregnation , characterized in that in the preparation of the mixture, an iron-based powder hardened during sintering is used, pre-alloyed with 2-5 wt.% chromium, up to 3 wt.% molybdenum and up to 2 wt.% nickel, and impregnation with copper is carried out simultaneously with sintering.
25. The method according to claim 24, characterized in that after sintering the workpiece is cooled without quenching, thus obtaining a completely martensitic structure.
26. The method according to claim 24, characterized in that a mixture is prepared containing 5-25 wt.% tool steel powder.
27. The method according to claim 24, characterized in that during sintering, the compact is impregnated with copper in an amount of 10-25 wt.% of the mass of the mixture.
28. The method according to claim 24, characterized in that a mixture is prepared containing, wt.%:
and during sintering, the compact is impregnated with copper in an amount of 20 wt.% by weight of the mixture.
Objective: draw up a technological process for restoring the valve, seat and “seat-valve” interface and perform it practically.
To achieve this goal, it is necessary to perform the following tasks:
Choose a measuring tool, method and means of control;
To master the correctness of filling technological documentation.
Initial data for work performance
Working drawings (poster);
List of valve defects, valve seats (set by the teacher);
Specifications for repairs (poster);
Safety instructions are given in Appendix 16 .
Workplace equipment
To perform laboratory work, the workplace has the following equipment:
Machine for grinding chamfers of valves, model SShK-3 GOSNITI;
Universal machine for grinding valves type OPR-1841 A;
The device for checking the concentricity of the working chamfer of the valve;
Indicator head type 0.01 GOST 577-68;
The device for checking the tightness of the "saddle-valve" interface;
Universal device GARO-2215 for grinding valve seats or an electric drill with a fixture (floating chuck);
Device for checking the concentricity of the working chamfer of the seat;
Device for assembling a valve pair;
Lapping paste;
Locksmith table;
corner templates.
Work sequence
Get acquainted with the organization of the workplace, and check its completeness (poster on the organization of the workplace);
Get acquainted with the methods of restoration and processing features when restoring the valve, seat and “seat-valve” interface;
To study the equipment and equipment used;
Choose a measuring tool, method and means of control (poster);
Draw up a valve recovery process for a given combination of defects and perform it practically;
Draw up a technological process for restoring the chamfer of the seat and perform it practically;
Draw up a technological process for restoring the “seat-valve” interface and perform it practically;
Assemble the valve pair and carry out quality control of grinding;
Prepare and submit a performance report.
Brief design and technological characteristics of the valve, valve seat and information about the recovery technology
The object of repair is the cylinder head and assembly of the KamAZ-740 engine.
The cylinder head is cast from aluminum alloy. Cast-iron seats and ceramic-metal valve guides are pressed into the head, which are bored after pressing. Valves are made of heat-resistant steels: inlet - 4Kh10S2M, outlet 5Kh20NCHAG9M, total surface hardness of valves after hardening HRC 30…35. Valve face hardness HRC 50…55, hardening depth 2…4 mm.
The conical surface of the exhaust valve head is directed along the chamfer by the VZK stellite of the following chemical composition: C=1.0...1.5%; C r =28...32%; S i \u003d -6 ... 2.8%; N i =2.0...3.0%; W=4.0...5.0%; C 0 =58...62%. The content of Fe in stellite after surfacing is max 3%. The hardness of the deposited layer is HRC 40...45.
The exhaust valve head is smaller than the intake valve head. The stems of both valves are coated with graphite at a length of 125 mm from the end (for this, the valve stems are placed in a solution of graphite and water) in order to improve running-in.
Drawing up the technological process for the restoration of the valve, seat and interface "saddle-valve" is carried out at the level of drawing up the technological route with an indication of their content, which is filled in the route map in accordance with ESTD GOST 3.1118-82 form 1.2.
Valve recovery (chamfer and face)
The chamfer of the valve and the end face are ground on the machine SSHK-3 with a grinding wheel PP 125x10x32 24 A 40PS2- ST19K5A GOST 2424-75, which provides roughness R a = 0.63 ... 0.16 microns. Grinding allowance 0.2 ... 0.6 mm, the accuracy of the resulting size and shape 1T5-1T7.
The circumferential speed of the grinding wheel (V k) depends on the type of bond and the profile of the wheel, V k =25...50 m/s.
For circles whose diameter is less than 150 mm V k = 25 ... 30 m / s.
At V k =30…35 m/s and grinding of hardened steel, the speed of rotation of the part is V D =25…30 m/min.
To perform the valve chamfer grinding operation (Fig. 15), it is necessary:
Install the wheel dresser and dress with a diamond pencil.
Remove the wheel dresser.
Check whether the setting of the collet chuck corresponds to the chamfer angle of the valve to be ground.
The position of the collet chuck is set as follows: the nut and the body of the chuck are loosened, the angle is set corresponding to the angle of the chamfer of the valve to be ground (α=45 0) according to the table mark. To facilitate installation, the body of the collet chuck is fixed with a pin at an angle of 45 0, after which the nut is tightened again.
Rice. fifteen. Chamfer grinding scheme (a) and valve end (b)
Install the collet required for the diameter of the valve stems. In order to set the required collet according to the diameter of the valve stem, it is necessary to unscrew the clamping handle from the thread of the cartridge and remove the collet and replace it with another of the required size. After that, the valve stem is inserted into the collet and clamped by screwing the clamping handle. The collet, sleeve and chuck must be exceptionally clean from dirt and abrasive dust.
Turn on the machine with the permission of the teacher or laboratory assistant, bring the table with the clamping chuck to the grinding wheel using the manual lever.
Feed the grinding wheel onto the valve face by turning the handwheel to the right until valve grinding begins. Then the table with the chuck moves to the left until the valve moves away from the grinding wheel. The largest turn to the right of the handwheel is set to the depth of cut.
With a uniform movement, bring the valve to the grinding wheel and grind over the entire surface of the wheel, without going beyond its width. Repeat this process until the valve is ground. At the end, move the valve to the grinding wheel with a very small grinding depth.
Note. Depth of cut cannot be set if the valve is engaged with the grinding wheel.
At the end of grinding, by turning the handwheel to the left, the grinding wheel with the support should be retracted, the machine turned off and the valve removed.
At the end of the grinding operation of the chamfer of the valve, it is necessary to check the runout of the chamfer on the fixture (Fig. 16). The runout of the chamfer relative to the valve stem must not exceed 0.02 mm.
Rice. sixteen. Valve chamfer control scheme.
To perform the operation of grinding the valve end (Fig. 15b), it is necessary:
Install a special stand for grinding the ends of the valve stem using a guide lug and fasten it with a nut in the groove of the chuck table.
Set the table so that the front side of the stand is about 12 mm away from the grinding wheel.
Place the valve on the fixture prism. When grinding the end of the valve stem with the right hand, the valve is pressed against the grinding wheel and rotates on the stand around its axis, and is pressed against the prism with two fingers of the left hand.
Grind the butt “as clean”.
Valve seat and seat-valve interface restoration
Valve seats are restored by grinding. Grinding as a method of preliminary and final processing of the chamfer of the seat provides surface roughness R a = 1.25 ... 0.8 μm and the accuracy of size and shape 1T6 ... 1T7.
For grinding the chamfer of the valve seat, a set of the instrument model TsKB-2447 is used, which includes a grinding machine with a planetary grinding mechanism.
In laboratory conditions, an electric drill and a grinding device are used (Fig. 17)
When the wear of the valve seats does not exceed the maximum allowable, restoring their performance is reduced to the formation of the required chamfer angle. Before chamfering the valve seats, replace the worn valve stem guide bushings with new ones and process them with a reamer installed in the mandrel. The machined holes are used as a technological basis for grinding the chamfer of the valve seats, which ensures the necessary alignment of the holes of the guide bushings and valve seats. If the valve seats are worn above the allowable level, they are restored by installing new valve seats.
To perform the valve seat grinding operation (Fig. 17), it is necessary:
to edit the grinding wheel (the grinding wheel is straightened on a lathe assembly with a mandrel with a diamond pencil in a special device, or a machine for grinding valves SSHK - 3 can be used for this purpose;
install the mandrel with the spindle head into the valve guide;
connect the spindle head with an electric drill and by pressing the drill on the spindle head, grind the bevel of the seat "as cleanly".
Rice. 17. Valve seat grinding pattern
At the end of grinding, the alignment of the valve seat and the guide sleeve is checked. Control is carried out using an indicator device (Fig. 18). The measurement is made by turning the fixture sleeve 360°. The runout of the chamfer should be no more than 0.04 mm.
Rice. eighteen. Alignment indicator
The tightness of the “seat-valve” interface is achieved by grinding. Lapping ensures high dimensional and shape accuracy (IT5 and above) surface roughness, R a =0.16 µm.
The valve is lapped on a special machine type OPR-841. And for lapping the valves of automobile engines (with a lapping speed of 10 ... 3 Ohm / min). Technical data and the arrangement of the main components of the machine are presented on the poster.
During operation, the spindles transmit force to the valve with a variable load. The reciprocating rotational movement of the spindles through 360° is produced from the gearbox through the connecting rod and crank mechanism, rack and pinion of the spindles. In addition to reciprocating motion in the horizontal plane, the spindles have reciprocating motion in the axial direction, which is carried out from the connecting rod-crank mechanism for lifting the spindles. The displacement of the initial positions of the spindles is carried out using a hydraulic displacement mechanism. As a result of the combination of such movements, the machine, as it were, copies the manual lapping mode. The heads are set to the desired height either manually - by a flywheel through a worm gear and rack and pinion, or by an electric motor through a V-belt drive.
Setting up the machine for grinding valves consists in arranging the machine spindles at center distances.
Lapping is performed in one, two, and in some cases even three operations. In this case, an allowance of 0.02-0.005 mm per diameter or less is removed. Lapping is carried out with free abrasive grains, which, mixed with a binding liquid, are applied to the working surface of the lap.
Lapping pastes based on abrasive powders and synthetic diamonds are used for lapping valves. For example, micropowder of white electrocorundum with grain size M 20 or M14 (GOST 3647-80), boron carbide M 40 (GOST 5744-74). Mineral oil, diesel fuel are used as a binding medium. For example, diesel oil DL-11 (GOST 8581-78).
The composition of the valve lapping paste is as follows: 1.5 parts (by volume) of green silicon carbide micropowder, one part of engine oil and 0.5 parts of diesel fuel. Before use, the lapping paste is mixed (micropowder is able to precipitate). The lapping paste is applied to the face of the valve seat in an even layer. The valve stem is lubricated with engine oil.
The lapping speed decreases with increasing requirements for the quality of surfaces (interfaces).
The pressure of the tool on the surface to be treated is set depending on the operation being performed. With preliminary grinding 0.2 ... 0.5 MPa, and with the final 0.1 ... 0.15 MPa.
Lapping is considered complete if continuous annular strips 2-3 mm wide appear on the working chamfers of the valve and seat.
To perform the valve grinding operation, you must:
insert the valve into the cylinder head after putting the spring on the rod;
install the heads on the plate and fix;
raise the angle of the lifting platform;
remove the casing covers and loosen the nuts of the spindle bushings;
arrange the spindles along the axes of the valves;
Fasten the lower and upper nuts of the spindle bushings. After fixing both bushings, the spindle must move by hand in the axial direction under the action of the spring;
Turn the handwheel to raise the spindle housing to the upper position;
Insert the adapters so that their squares fit into the hole of the spindle coupling (connection to the valves by means of suction cups);
Raise the plate so that with the upper position of the spindle housing, the gap between the valve disc and the seat is 8-10 mm;
Apply the paste and turn on the machine.
The machine lapping time of the valves depends on the quality of the grinding of the valve, the valve seat, as well as on the lapping paste used.
To obtain a good matte surface of the chamfers, it is recommended to loosen the pressure on the valve before the end of grinding, for which it is necessary to lower the lifting platform while the machine is moving so that the gap between the valves and the seat is 20-25 mm.
Valve Lapping Quality Control Methods
The tightness of the valves to the seats can be checked in the following way:
pencil test (erasing of radial pencil marks applied to the chamfer of the valve when turning it in the seat in one direction or another);
breakdown on the paint when applying Prussian blue to the seat and alternately turning the valve;
leakage of kerosene through the tested interface when pouring it into the pipe of the cylinder head;
Checking for tightness by the time of air fall in the chamber located above the valve;
With high-quality lapping, the pencil marks will be erased, a trace of paint will remain on the valve chamfer in the form of an even annular surface 1.5 ... 2 mm wide, kerosene does not leak through the valve-seat interface; the air pressure (P = 0.02 MPa) in the chamber does not fall within 10 s.
Cylinder head assembly and lapping quality control:
To perform the cylinder head assembly operation, you must:
Insert intake and exhaust valves;
Install the head in the head assembly tool so that the pins go into the hole for the head mounting bolts;
put on the springs and valve plate;
by rotating the knob of the device, press the valve springs with a plate;
insert bushings and crackers of valves;
unscrew the screw from the traverse by reverse rotation of the knob;
remove the cylinder head from the fixture;
install the cylinder head alternately with the inlet and outlet ports up and fill them with diesel fuel. Well-lapped valves should not let it through at the sealing points for 30 seconds. If fuel leaks, tap the valve head with a rubber mallet. If leakage persists, lap the valves again.
indicate the purpose and objectives of the work;
choose a measuring tool;
give a metrological description of the measuring tool and instruments;
specify the name and brand of the material of the part;
draw a sketch of the part;
formalize the recovery process at the level of the route map, indicating the content of the operation.
A sample of the report, filling out the route map and the necessary information on the items listed are given on the posters.
The report is protected by a test poll.
The report form is given in Appendix. sixteen.
test questions
Name the material of the KamAZ-740 engine block head.
Name the material of the intake, exhaust valve, seat and surface hardness.
Name the brands of the wheel for grinding the valve, the resulting roughness and accuracy after processing, the linear speed of the wheel and the details.
Name the method of restoring the valve seat, the required roughness and machining accuracy.
What kind of accuracy and surface roughness does lapping provide?
How is valve lapping performed?
How is the operation of restoring the chamfer and end of the valve?
How is a valve seat repair performed?
Name the composition of grinding pastes.
What is the pressure of the tool on the work surface during lapping?
How to determine the end of the lapping process?
Name the methods for assessing the quality of lapping.
Before processing the plane or diagnosing the valve mechanism, the cylinder head is pressure tested. The only operation performed before this is a technological wash. Pressure testing is a check of the cooling jacket for tightness. If damage is detected, the possibility of further repair is assessed. Based on the results of the assessment, a decision is made on the advisability of repairing this cylinder head. Crimping is also carried out after removing nozzles, fragments of glow plugs, replacing seats and technological plugs, welding work carried out on this cylinder head (cylinder head).
Under the repair of the cylinder head, they also mean work with the valve group. Valve lapping, valve seat replacement, valve bushing replacement.
It should be noted that pressure testing of the block head is one of the services provided by MotorIntekh LLC. This technology is used for pressing:
- radiators;
- heat exchangers;
- collectors in passenger cars;
- mentioned cylinder head.
We are ready to offer you a full range of services for the diagnosis and repair of cylinder head. Thanks to our professionalism, vast experience and the availability of all the necessary tools, we can identify all existing problems and effectively eliminate them. We guarantee you the high quality of all work, including the repair of the cylinder head, and our employees will also help you select liners.
Engine cylinder head repair
Are you interested in a favorable price for the repair of the engine cylinder head? The most affordable cost is ready to offer you a specialized center LLC MotorIntekh. Only professionals can be trusted with all work related to the engine as a whole and with the repair of the cylinder head. Why? For the simple reason that without the appropriate experience and knowledge, without a professional tool, the motor will remain “not fully cured” to the end.
The correct operation of the cylinder head is the main component of the successful operation of the engine as a whole. The highest quality cylinder head repair is possible only with high-tech equipment and qualified specialists.
Cylinder head repair includes several stages: preparatory work (washing and pressure testing, disassembly and fault detection), repair of valve mechanism parts, repair of camshaft beds, repair of threaded connections and holes, processing of planes and final assembly.
Preparatory work
Any cylinder head repair work begins with the dismantling of attachments and technological washing. This allows you to clean the cylinder head from oil deposits, combustion products and other contaminants that can hide surface defects in the repaired part. The initial assessment of the scope of work and the order of their implementation in the event of detection of such defects can vary significantly.
The next stage of preparation for repair is cylinder head pressure testing, during which the tightness of the cooling jacket is checked, if microcracks are found, in most cases the cylinder head must be replaced. Pressure testing is also carried out after replacing burnt, worn or destroyed valve seats. Crimping work is carried out by specialists of MotorIntekh LLC using special equipment in conditions as close as possible to engine operating conditions.
To further determine the condition of the repaired head, it is necessary to disassemble the valve mechanism and its subsequent fault detection. Even such an insignificant operation should be performed exclusively by professionals, which guarantees the safety of the disassembled parts and the possibility of their further use. Detection of repaired cylinder heads is carried out using a special measuring tool. In the course of fault detection, the scope of forthcoming work on the repair of the cylinder head is determined.
Repair of cylinder head parts
After carrying out the preparatory work, the worn and deformed parts are replaced with new ones. In the absence of factory valve guide bushings, they can be made in our specialized center LLC MotorIntekh from similar alloys. All rubber parts, gaskets and seals are always replaced.
The greatest difficulty is the restoration of cylinder head camshafts and their beds. Defects that occur during improper operation of the engine (work without lubrication, engine overheating) lead to deformation of the camshafts and wear of the bearing journals and cams, the formation of scoring, deep scratches and scratches both on the shafts themselves and on their beds, which can lead to irreversible consequences up to the failure of the entire engine. Modern repair technologies in most cases allow you to restore worn surfaces of beds and camshafts, thereby extending the life of the cylinder head. The exception is hollow lightweight camshafts, which, in case of any damage, must be replaced.
If you have any problems related to the restoration of Camshafts and RV beds, please contact our specialized center of MotorIntekh LLC, and we will quickly and efficiently solve your problems.
The next step is to restore all kinds of threaded and fasteners, threads of candle wells, and on diesel heads, a block of holes for injectors and glow plugs.
One of the final operations for the repair of the cylinder head is the milling of the mating plane. The operation is reduced to leveling the cylinder head plane on a milling or grinding machine to ensure a tight connection between the cylinder head and the cylinder block over the entire area of the plane and to exclude possible leakage of technical fluids circulating in the channels of the lubrication and cooling systems. Many manufacturers allow a slight reduction in the height of the cylinder head and produce repair gaskets of increased thickness.
Before the final assembly of the valve mechanism, it is necessary to machine the seats and chamfers of the valves to ensure that the inlet and outlet channels are tightly closed during engine operation. The parts of the valve mechanism are processed in a specialized center of Motorintekh LLC on modern high-precision machines, and the quality of the work performed is checked on special measuring units.
In conclusion, on some models of modern car engines, manual adjustment of valve drive clearances using measuring probes is necessary.
Replacing valve guides
Replacing valve guides is one of the services provided by our specialized center. Contact MotorIntekh LLC, and be sure that all work was done professionally, efficiently, on time.
Why should this type of work be entrusted to professionals? Maybe a beginner will cope with the task, following the instructions available on the Internet? The answer is unambiguous: valve grinding and replacement of valve guides should only be carried out by specialists in the workshop.
What else is required for the work:
- bake;
- special tool for removing and installing guide bushings;
- a mandrel with which the guide is installed in the body of the cylinder head;
- reamers for calibrating holes in the guide bushing.
If the holes for the guide bushing are broken and there is no way to install a standard bushing, and repair bushings do not exist or it is problematic to buy a bushing, then we will be happy to help you by manufacturing a guide bushing.
Cylinder heads are made of aluminum alloys, which have a much higher thermal expansion coefficient than those materials from which the guide bushings are made. Thus, after heating the cylinder head in the furnace, with the help of a special tool, you can freely press the guides. In this case, there is no deformation of the seat directly in the body of the head.
When it comes to cast iron heads, the replacement of valve guides is carried out without heating.
Cylinder head plane processing
The often used expression cylinder head boring is the processing (milling) of the mating surface of the head with the cylinder block.
As the engine is used, and also after it overheats, a geometry violation occurs, which entails deformation of the cylinder head.
In cases where it is provided by the manufacturer, this problem can be solved by processing (aligning) the plane.
Block sleeves or head boring cannot be done by yourself. Without the right knowledge and equipment, you can only aggravate the situation. It is better to entrust the professionals of MotorIntech LLC with the work they face every day.
Camshaft bed repair
Camshaft bed repair is one of the services provided by MotorIntekh LLC. To assess the problem with the camshaft bed, we need: the cylinder head itself, the camshaft, the camshaft mounting covers with bolts or studs. First, an external inspection and measurements of the camshaft and its landing sites are carried out. Next, the RV fastening system is installed - these can be covers or a common plate. There is also a tunnel system for mounting the camshaft. In all cases, measurements are made and the gap between the shaft and the bed is calculated. If it does not correspond to the value specified by the manufacturer, the camshaft bed needs to be repaired.
We offer you:
- performing all types of diagnostics and repairs, as well as repairing the spark plug hole;
- guaranteed quality of all works;
- strict adherence to established deadlines;
- democratic prices for all services provided.
The usual repair of the camshaft bed is carried out in several stages. To begin with, all parts are thoroughly cleaned of oil, dirt and chips. Next, the camshaft is checked, if necessary, the necks are corrected and polished. The bed is measured, the covers are lowered and the bed is bored in several passes. At the end, a control assembly with a camshaft is carried out.
But there are a lot of types of cylinder head, respectively, and the repair of the bed carried out with each individual head has its own characteristics. Therefore, it is possible to say unambiguously the question of how the bed will be repaired only after a preliminary diagnosis.
Spark plug repair
Repair of a candle hole, including the restoration of its thread, is a small part of the services that our specialized technical center provides to its customers. If you need to promptly and efficiently carry out diagnostics and perform all types of repair work, then it's time to contact MotorIntekh LLC.
Thanks to experience, knowledge, the availability of all the necessary professional tools and the right repair technique, you can fix the problem, that is, restore the thread of the candle hole, very quickly and efficiently. We repair both cast iron and aluminum cylinder heads.
For such repairs, as a rule, are used:
- special tool for removing fragments of candles;
- tools for installing a futorka in the cylinder head;
- actually futorki having a certain design;
- heat-resistant sealants that are able to prevent gas corrosion in the fittings installed in the cylinder head.
The entire repair process can be divided into several operations. This is the removal of debris, cutting a new thread, installing a futorka and fixing it. Contact our masters if you are interested in repairing a spark plug hole or repairing an engine block.
Saddle repair
Seat repair is one of the types of work that is carried out during the repair of the cylinder head. To carry out this, as well as all other types of repair work, the specialists of MotorIntekh LLC are ready. We will do all the work for you:
- qualitatively;
- professionally;
- promptly;
- not expensive.
We can repair a damaged saddle, as well as manufacture and replace it if necessary.
In order for everything to be done correctly, not only experience and knowledge are needed. It is very important to use a special, professional tool for each type of work. The tool is an important factor in ensuring the quality of the repair of all damaged parts and an important factor in the quality of the replacement of all parts that have already worn out. The material and technical base of our specialized center allows us to carry out repairs in accordance with all the technical requirements of manufacturers, as well as in strict accordance with the technology for repairing engine parts. The engine is the main unit of any vehicle, and its repair should be treated as responsibly as possible.
We note once again: the cylinder head of any engine is an extremely complex complex, consisting of many mechanisms and assemblies. And every stage at which the engine cylinder head is repaired, every type of work, including the repair of seats, should be entrusted to highly qualified specialists.
Lapping of valves
The valves are lapped to achieve maximum compression. During this repair, the chamfer of the valve and the chamfer of the seat are first processed on a specialized machine, then, if necessary, the surfaces are rubbed with a lapping paste. The control is carried out with a vacuum gauge. This type of work is carried out by our specialized center MotorIntekh LLC.
Naturally, replacing a valve or repairing seats is much more profitable than buying a new cylinder head (there are exceptions). It is much easier to entrust this work to specialists than to delve into the intricacies of choosing a lapping paste and purchase special tool kits necessary for professional lapping.
Our company can offer you the following services:
- repair or replacement of saddles;
- engine cylinder head repair;
- cylinder head pressure testing;
- selection of liners;
- shaft straightening and many other works.
Lapping is carried out on the removed cylinder head. It is equally important to check the effectiveness of the grinding. Get in touch with us to have your valves lapped professionally and efficiently.
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