Valve seat material Easily machinable iron based sintered alloy for valve seat inserts. Valve plates with welded chamfers. Technological process of valve disc recovery

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 provide High Quality 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 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.

Raising the valve periodically 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. At good quality lapping, 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.

6.10.1 Plasma welding of valves .

The exhaust valves of medium-speed marine diesel engines (for example, "SULZERA 25") are made of steels 40X9C2 and 40X10C2M.

To ensure increased valve performance, the sealing belt of the plate is hardened by surfacing. To ensure optimal properties of the deposited metal, HAZ and base metal, a process of automatic plasma surfacing with self-fluxing powder PR-N77Kh15SZR2 has been developed. (Previously, manual argon-arc surfacing with stellite was used for this).

Plasma surfacing is carried out on the UPN-303 installation with the following mode parameters: direct polarity arc current 100-110A, arc voltage 35-37V, powder consumption 2kg/h, surfacing speed 7-8 m/h. The powder is blown into the plasma. Surfacing is performed with transverse oscillations of the plasma torch. Argon is used as a plasma-forming, shielding and transporting gas. Before surfacing, the valve disc is heated with an acetylene-oxygen flame to a temperature of 200-250 0 C.

Edge preparation is performed according to Fig. 1. To ensure the horizontal position of the plane of the welded band, the valve stem in the manipulator of the welding installation is placed at an angle of 30 0 to the vertical. Surfacing is carried out in one layer.

After surfacing, annealing is performed at a temperature of 700 0 C.

The valves have the required hardness of the base metal HRC 24-25, the required increased hardness of the deposited HRC 38-41 and the acceptable hardness of the HAZ metal HRC 36-37.

6.10.2 Welding of valves with stellite.

The valves of powerful marine diesel engines are also surfacing with stellite.

Cobalt alloys with chromium and tungsten, the so-called stellites, are distinguished by remarkable performance properties: they are able to maintain hardness at high temperatures ah, resistant to corrosion and erosion, and also have excellent wear resistance in dry metal-to-metal friction. By itself, cobalt does not have high heat resistance, this property is given to alloys by additives of chromium (25-35%) and tungsten (3-30%). An important component is also carbon, which forms special hard carbides with tungsten and chromium, which improve the resistance to abrasive wear.

Engine valves are welded with cobalt alloys internal combustion, sealing surfaces of steam fittings of ultra-high parameters, dies for pressing non-ferrous metals and alloys, etc. When surfacing steels, it is necessary to strive for a minimum transition of iron from the base metal to the deposited metal, otherwise the properties of the latter deteriorate sharply. The deposited metal is prone to the formation of cold and crystallization cracks, therefore, the surfacing is carried out with preliminary and often with concomitant heating of the parts.

Ensuring the minimum proportion of the base metal and compliance with the necessary thermal conditions are the most important features of the technological process of surfacing cobalt alloys. Surfacing is carried out by gas flame or argon-arc welding with rods made of V2K and VZK alloys, as well as coated electrodes of the TsN-2 brand with a rod made of VZK rod.

Parts are heated to a temperature of 600-700 0 C. With such heating, the proportion of the base metal is large (up to 30%), therefore, to obtain a minimum iron content, surfacing has to be performed in three layers. This increases the consumption of a very expensive surfacing material and increases the complexity of the work.

1

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 solving which efficient operation vehicles on dual-fuel power systems is not possible. 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, valve seats for gasoline engines 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. To work in extreme conditions, at operating temperatures of the order of 900 ºС, in particular, heat-resistant cast irons of the austenitic class 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
				austenite	martensite
	Austenitic-martensitic mixture, martensite, carbides of medium and small sizes. Martensite predominates. Large lamellar graphite
	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

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 from 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, the proposed chemical composition 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 quenching 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.

Conclusions. 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 // Contemporary Issues 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"

It is installed in the holes of the cylinder head, designed to install valves and distill the air-fuel mixture and exhaust gases through them. The part is pressed into the cylinder head at the factory.

Performs the following functions:

• hole tightness;
• transfers excess heat to the cylinder head;
• provides the necessary air flow when the mechanism is open.

Replacement of the valve seat is required in the event that it is not possible to restore its tightness by mechanical processing (numerous processing in the past, burnout, heavy wear). You can do it yourself.

Parts are repaired when:

• plate burnout;
• after replacing the guide bushings;
• with a moderate degree of natural wear;
• in case of violation of the tightness of the connection of the ring with the plate.

Editing worn and damaged saddles at home is done using cutters. In addition, a welding machine or a powerful gas burner may be required, a standard set wrenches required for dismantling and disassembling the cylinder head, lapping paste, drill.

Seat Replacement

The replacement procedure consists of two critical procedures: the removal of old parts and the installation of new ones.

Removing old planters

Valve seats are replaced on a dismantled cylinder head with a disassembled gas distribution mechanism. You can remove the old ring using a welding machine, if the material from which it is made allows this.

To perform the procedure, a valve seat puller is made - an old unnecessary valve is taken, the plate of which must be machined to the size of the inner diameter of the seat.

After that, the resulting tool is sunk into the seat, not reaching the edge of 2-3 mm and “tacked” by welding in 2-3 places. After the valve, together with the metal ring, is knocked out with reverse side hammer.

Important! A procedure using welding may result in some deformation of the seat. In this case, the standard saddles will have a weak fastening, which can lead to their spontaneous dismantling during the operation of the motor. Requires rings of increased diameter, which are not sold in stores, but are made to order.

A valve seat made of non-weldable metals can be removed by screwing a piece of pipe into it to be used as a valve seat puller. To do this, a thread is cut on the inner surface of the ring. A similar thread is applied to the outer surface of a metal pipe of suitable diameter.

An old valve is taken, which is pre-welded to the end of the pipe in the reverse position. In this case, the valve stem is inserted into the hole intended for it, the pipe is screwed into the thread, after which the element is removed by tapping on the stem.

Installing new saddles

Before starting the installation procedure for new saddles, the seats for them are cleaned of dirt. After the cylinder head, it should be evenly heated to a temperature exceeding 100 ° C. In this case, the metal expands, allowing the ring to be pressed in.

The part to be mounted is cooled with liquid nitrogen. In its absence, you can use a combination of ice and acetone, which allows you to reduce the temperature of the metal to -70 ° C. The dimensions of the parts are selected so that the difference between the diameter of the seat and the ring is no more than 0.05-0.09 mm on cold parts.

The valve seat is pressed in using a special mandrel or a piece of pipe of suitable diameter. The part should fit into the seat with little effort. In this case, it is important that the ring stands up without skew.

After pressing and cooling the cylinder head, you should check if the element is hanging on the seat. If there is no gap, and the replaced element is firmly held in place, the replacement procedure can be considered completed. Next, cutting of the valve seats is required using cutters.

Important! With the standard procedure for replacing the plates of all valves, they are planted quite high. However, some experts recommend that the chamfers be machined so that the exhaust valves sit slightly deeper than the normal position. The inlet valve seat is left in its original position.

Saddle repair

Repair of valve seats is carried out with their natural wear and loose fit of the plate to its seat.

In order to restore the geometry of the rings, cutters for valve seats are used - a set of milling heads that allow you to make the necessary angles.

Rollers can be used in combination with special equipment. However, it is costly. Therefore, at home, a ratchet wrench with an extension cord is used. Correctly processed places have angles of 30˚, 60˚ and 45˚. The processing of valve seats to create each of them is carried out with an appropriate cutter.

Valve seat grinding does not require heating or other processing. The groove is made "dry". In the future, at the time of lapping, it is necessary to use a special lapping paste. For best results, lapping into new seats is recommended to be done by hand rather than with a drill.

Another type of repair is the groove of seats for repair inserts. To do this, according to the algorithm described above, the saddles are removed, after which, with a special cutting tool, the places under them are machined. The size of the repair site should be 0.01-0.02 cm smaller than the insert. Installation is carried out after heating the cylinder head and cooling the mounted elements.

You can try to properly bore yourself at your own peril and risk. However, given the complexity of the procedure and the required high accuracy of work, such manipulations are best done in a qualified car repair shop or car repair plant.