Valve of internal combustion engine, method of its manufacture, and heat resistant titanium alloy used for its manufacture

FIELD: mechanical engineering; piston internal combustion engines.

SUBSTANCE: invention relates to valve of internal combustion engine, method of its manufacture and heat-resistant titanium alloy used for manufacture of valve consisting of following components, mass %: aluminum 7.5-12.5; molybdenum 1.6-2.6; zirconium 1.4-2.4; silicon 0.1-0.2' yttrium 0.005-0.1; titanium - the rest. It has α+α2+β phase composition with intermetallide α2 phase on Ti3Al base dispersed in α phase. Proposed method includes forming of valve from cylindrical blank by deformation machining with preliminary heating and subsequent heat treatment. Preliminary heating of part of blank related to rod done to temperature 5-20oC lower than temperature of complete polymorphic transformation of alloy, and its deformation machining is carrying out by wedge cross rolling. Deformation machining of part of blank related to head is done by forging with preliminary heating to temperature 5-50oC higher than temperature of complete polymorphic transformation of alloy corresponding to beginning of forging, and forging is finished at temperature lower than complete polymorphic transformation of alloy to form plate head of valve and transition section provided smooth changing of head into rod. Invention provides designing of valve, method of its manufacture and heat-resistant alloy used in manufacture of valve making it possible to operate valve within operating temperature range owing to increased long-term strength and creep resistant of valve head material and increased strength, modulus of elasticity and hardness of valve rod material.

EFFECT: improved quality of valve and increased reliability in operation.

16 cl, 3 tbl, 1 ex, 15 dwg

 

The technical field. The invention relates to the field of engineering, more specifically to engine, and can be used in reciprocating internal combustion engines (ice).

The prior art. Over a long period of development of internal combustion engines for different purposes and based on the experience of their operation worked out the design, materials and methods, heat strengthening for intake and exhaust valves, which mainly provide the reliability and durability of the engine. As materials for the manufacture of ice valves are usually used for special steel grades. However, in the manufacture of valves of steel, having a high density (ρ=7,63...8.0 g/cm3), the mass of the valve is obtained considerable, which is a negative factor for valve mechanisms of the modern high-speed engines operating with high speeds and accelerations. High inertial loads caused by the weight of the valves, lead to high loads in the links of the actuators of the valves, a significant shock loads during landing valves in the saddle. This, in turn, causes a decrease in reliability and dependability timing and engine in General. Of the total number of failures gasoline engines on the timing accounts for up to 45% of failures, and about the main their share associated with defects exhaust valves. The mass of the valves is one of the limiting factors in creating a highly accelerated by the speed of the motors special versions and engine sports cars. Valves of reciprocating internal combustion engines (especially the exhaust) work under high thermal loads. So, considering the diversity of produce reciprocating internal combustion engines: stationary, transport (marine, tractor, aviation, automobile, motorcycle) and a special design, the steady-state temperature at the center of the heads of the valves are for the intake valves 500...650°With, for prom - 650...900°With (see Fig and 15). In the zone of transition from the valve head to the stem gives rise to large temperature differences, reaching 200-300°in the axial direction. In the cylinder valve the temperature difference reaches 150-200°in the radial direction. This causes a high level of thermal stresses in the valve head and in the transition zone and accelerated destruction of the valves (see internal combustion Engines: Design and strength calculation of piston and combined engines. Edited Asellina, Mggrava. - 4th ed., revised and enlarged extra - M.: Mashinostroenie, 1984, str-250, 258. / Raikov IA, Rytwinski GN. Design of automobile and tractor engines. M.: Higher school, 1986, p.115-119).

To reduce mA the son of the valves, improve their long-term heat resistance and the creation of preconditions for improvement of a structure of internal combustion engine with significantly improved fuel economy and exhaust emissions is the search for new materials with lower density and increased heat resistance, as well as methods of manufacture of these valves timing. New materials these conditions are largely responsible alloys based on titanium and intermetallic compounds of titanium of the titanium-aluminum (Ti-Al), which have a high heat resistance at low density (ρ=3,9-4,2 g/cm3). The most actively studied and prepared for the use of alloys based on the intermetallic compounds containing α2-phase-based connection Ti3Al or γ-phase-based compound TiAl. These compounds and alloys based on them have advantages in heat resistance and modulus of elasticity over traditional titanium alloys; operating temperature for them is 750-900°C. the Alloys based on the intermetallic TiAl containing γ-phase, have very low ductility at room temperature (δ=0,5-1,5%) and are producing mainly for foundry technology. Known alloys γ-phase level operating temperatures up to 850°With, including the creation of the exhaust valves (see Table 1, items 1, 2). However, valves, and is prepared by casting technologies, the inherent porosity due to the distributed shrinkage of the shell and typical cast structure with the crystallization porosity. “Heal” casting porosity is only possible at high temperature satisaction. As a result, the ice valves are made of alloys based on γ-phase have increased the cost of manufacturing (see Structure and properties of semi-finished products of alloy Ti-48Al-2Nb-2Cr-based intermetallic TiAl obtained by the method of shaped castings (Lukjanychev HE and other Technology of light alloys, 1996, No. 3, p.16. / A. Choudhury, M.Blum, P.Busse, D.Lupton, M.Gorywoda. Herstellung von TiAl-Ventilen Durch Schlendergub in Metallische Dauerformen. Symposium 2: Werkstoffe für die Verkehrstechnik, 12997 by DGM Informationsgesellshaft mbh, p.49-54).

The alloys of the group on the basis of α2-phase aluminum content 8-14 wt.%, refer to alloys deformation type with low technological plasticity. These alloys have a high resistance, slightly less than it alloys based on γ-phase, and have advantages for manufacturability and cost of manufacture as compared with these alloys.

The number of heat-resistant titanium alloys have been developed for aerospace equipment, including, as the most heat-resistant, highlight the grades WTO and vt25u alloy (Russia), IMI 829 and IMI 834 (England), Ti-6242 Si and Timetal 1100 (USA) (see table 1, 3-8). This complex alloyed alloys of deformation the type. Subject to very strict temperature-time multi-modes of deformation processing and heat treatments in these alloys is provided by the formation of the necessary macro - and microstructures and receiving range of useful properties: strength, heat resistance, fatigue resistance, etc. At the same time prolonged operation at elevated temperatures is limited to these alloys range 500-600°With (see Opolonin, Sgullugunu. Heat-resistant titanium alloys. M.: metallurgy, 1976, p.61-128. Titanium 95: Science and Technology. Igor V. Gorynin "Research and Fabrication and Development of Titanium in the CIS", p.32). Low operating temperatures (up to 600° (C) not be used for exhaust valves of the engine.

Also known titanium alloy containing intermetallic (α2-phase-based connection Ti3Al (RU # 2081929) (see Table 1, item 9). Phase composition of alloy α+α2. To improve its technological plasticity of the proposed hydrogen technology based on the use of reversible alloying alloy hydrogen and heat. The technology allows to improve the structure of titanium alloys systems (α+α2and α2and to improve their mechanical properties (see A. M. Mamonov, Kusakina YU.N., Ilyin A.A. Regularities of formation of the phase composition and structure in the heat-resistant titanium alloy and termitarium padding when alloying with hydrogen /Metal 1999, No. 3, p.84-87). However, this operation is technologically complex, expensive and not applicable for mass production of valves of the engine.

Analogs of the present invention, the Valve of the internal combustion engine are known valves of the combined execution, made of industrial titanium alloys in which to reduce the cost of the valve rod are made from low-alloy titanium alloys, and head to the transition area in the rod are made of heat resistant alloy titanium alloys (US No. 5169460, JP No. 03009008, JP No. 62-197610) (see Table 1, PP-12). Separately manufactured head and the rod is then joined by welding or zapressovyvajutsja. However, constructed so the valves do not possess the required strength and reliability.

Another analogue is a valve (JP No. 06184683), which is made from wire 2-phase (α+β) titanium alloy. In various parts of the valve, the rod and the cylinder, deformation processing created two different microstructure with grain size in one part of the valve 1-4 microns and the second - more than 300 μm. A disadvantage of the known valve is that it does not have the required fire resistance in accordance with the conditions of its long-term mechanical and thermal loading.

The closest in technical is some entity similar to the proposed “Valve of the internal combustion engine is titanium valve, having different microstructure in their parts, the stem and head (US No. 4729546). Known valve made of heat-resistant titanium alloy (α+β) the phase composition and consists of a cylindrical rod, the head disc shape and area, providing smooth pairing of the stem and head, and has a different microstructure in their parts. The microstructure of the rod and the piece that connects the rod with the valve head mainly comprises a mixture of areas of fine equiaxial grains α-phases and zones with microstructure types of colonies, with a grain size of 5-50 μm, with high tensile strength and high fatigue strength. The cylinder valve with a substantially homogeneous area with microstructure types of colonies, with the size of the colonies 50-300 μm, has a low creep resistance at temperatures of 760°equal to 1% strain, when the voltage of 27.5 MPa for 100 hours.

A disadvantage of the known valve is that used for the manufacture of two-phase (α+β) titanium alloys and their microstructure do not provide the necessary strength properties of the valves of internal combustion engines, operating in conditions of long-term thermal and short-term high-temperature (up to 900° (C) loading. In particular, for the valve head, the chemical composition of alloys (see Table 1, p-16) and the microstructure does not provide its the STV long-term heat resistance at temperatures above 600° C. the heat Resistance of titanium alloy is determined by the α-phase. To improve the heat resistance α-phase only additional doping. Any structural transformation of two-phase titanium alloys, as is done in the known valve, do not lead to a significant improvement in heat resistance. In addition, a homogeneous microstructure in the valve head, type colonies, not enhancing the creep resistance of the material of the valve. The microstructure of the valve stem and in the transition area of the rod into the head of the Poppet forms known in the patent is a mixture of areas of fine equiaxial grains α-phases and zones with microstructure type colonies with a grain size of 5-50 μm. This microstructure provides no increased long-term strength for the transition area, especially the exhaust valve operating under creep at high temperatures (600-700°see Fig), and reliable operation of the valve as a whole. The valve stem operating in conditions of cyclic tensile and bending loads, also does not provide the desired properties due to low values of elastic modulus, hardness and strength at elevated temperatures. This causes deformation and elongation of the valve stem in the process. This is particularly evident in the work of uprated.

Most b is izkuyu technical substance analog of the present invention, the Method of manufacturing a valve of the internal combustion engine” is a method of manufacturing a valve with various regulated by the microstructure (US No. 4675964). According to this method, the valve of the engine, including the exhaust, made of industrial heat-resistant 2-phase (α+β) titanium alloys (see Table 1, p-16). The technical result of this method is to obtain valve with dual microstructure. In the manufacturing process in the rod and the valve head deformation methods and subsequent heat treatments are different microstructure with properties close to the conditions of mechanical and thermal loading of the valve during its operation in internal combustion engines.

A known method of manufacturing a valve of the internal combustion engine from heat-resistant titanium alloy is that of the workpiece in the form of rod, the deformation processing and subsequent heat treatment, to form a valve with different microstructures in his rod and the cylinder. Deformation processing and subsequent heat treatment are in two stages, with the formation of the first stage of the microstructure of the rod, and the second microstructure head. At the first stage using extrusion processing deformation effects are a part of the procurement related to the terminal. Before deformation of the workpiece is heated to a temperature below the temperature of complete polymorphic transformation for a given alloy (TPP). On the second stud and a portion of the workpiece, related to the head of the valve, formed by stamping, pre-heating it to a temperature higher than the temperature of complete polymorphic transformation for a given alloy (TPP). As a result of deformation and heat treatment get in the rod and the cylinder, different microstructure, providing properties that are close to the conditions of mechanical and thermal loading of the parts of the valve in the engine. Thus the microstructure of the first zone valve (rod and the piece that connects the rod with a head) contains mainly a mixture of areas of fine equiaxial grains α-phase zones and types of colonies with a size of 5-50 μm and has a high strength and fatigue strength at room temperature. The microstructure of the second zone valve (head) contains a homogeneous microstructure, mainly type colonies with the size of the colonies 50-300 microns.

The disadvantages of this method include:

- Using an extrusion process, it is impossible to form the valve stem when used for its manufacture of high-temperature alloys with low technological plasticity.

The extrusion process of the valve stem is accompanied by rapid deterioration of press tools, made of expensive heat-resistant steels, especially during extrusion of titanium alloys in the mushy α+β field.

- Heating across just the Cai under hot pressing of the valve stem leads to undesirable grain growth in the part of the workpiece, related to the valve head, which reduces its quality in the stamping process.

- Heating the entire workpiece under extrusion method, as a rule, is carried out in furnaces with an external heat source. In this case, the heating time of preparation under deformation is not less than 10 minutes Such prolonged heating leads to the formation of a solid oxide layer with thickness of 0.1-0.3 mm, causing the deterioration of press tools and additional difficulties during subsequent machining or requires additional measures to protect the workpiece from oxidation.

- Demanding heat treatment to provide a large temperature difference between the head and the valve stem. As the valve head when the heat treatment is heated above TPPand the rod is heated to a temperature below TPPthe temperature gradient between the head and the valve stem is 10-205°with exposure at these temperatures from 0.5 to 8 hours. Implement virtually scheme of heat in the mass production process is quite difficult.

- Formed by a known method structure in the valve stem does not provide the desired properties of the valve due to low values of elastic modulus, hardness and strength at elevated temperatures.

- Formed by a known method in the cylinder valve homogeneous microstr the established levels, types of colonies, with the size of the colonies 50-300 μm, while the size of the primary β-grains in the microstructure can exceed the size of the colonies in 3 times or more, does not provide the required operability of the valve at high temperatures, as it does not have a high creep resistance and long-term strength (see Table I Relationships between critical microstructural features and mechanical properties of titanium alloys. ASM Handbook, vol.2, 1990, R. Reviewed by Gerhard Welsch, Case Western Reserve University, and Rodney Boyer, Boeing Commercial Airplane Company).

The closest analogue of the present invention, “Heat-resistant titanium alloy” is an alloy used to manufacture the valve timing of internal combustion engine by means of hot deformation of Ti-6Al-2Sn-4Zr-2Mo-0,1Si (US No. 4675964). This titanium alloy (α+β) the phase composition. Made from such alloys valves of internal combustion engine capable of long-term work only at temperatures of 550-600°C. are Known from US patent No. 4675964 2-phase (α+β) titanium alloys (see Table 1, p-16) provide properties long-term heat resistance (creep rupture strength, creep resistance) only up to temperatures of 600°C. This fact is confirmed by the author of the US patents No. 4675964, 4729546 in his article contains the results of tests of the valves of the 2-phase titanium alloys (J.E. Allison, Sherman A.M., Bapna M.R. Titanium in engine valve system. "J. Metals, 1987, 39, No. 3. p.15-18).

Disclosure of inventions.

The objective of the invention is to increases the reliability and infallibility of the valves of internal combustion engine and to increase the durability of the engine. When this is achieved technical result consists in the improved material properties of the valve, ensuring operability of the valve internal combustion engine in the operating temperature range, by increasing long-term heat resistance of the valve head (long-term strength, creep resistance) and increase the mechanical properties of the valve stem (strength at elevated temperatures, the modulus of normal elasticity, hardness). This gives you the opportunity to: a) increase the working temperature of the valve head to 850°after prolonged operation of the engine, and up to 900°when used in high-powered engines with a limited period of operation; b) to reduce the structural size of the valve stem and part of the transition from the stem to the head.

The present invention allows:

- to increase the durability of the engine by increasing the reliability and dependability of operation of the engine valves;

- to reduce the weight of the valve by 10-20% due to the reduction of the structural size of the valve stem and the crossing section of the rod in the cylinder, and also to reduce dynamic loads on the parts of the valve mechanism;

to reduce efforts valve springs that will provide additional reducing pressures in the valve mechanism, the reduction of friction losses and improve performance of the engine;

- to speed up the engine on the frequency of BP is recorded, thereby increasing its effectiveness;

- to manage the properties of the valves of internal combustion engines, making them necessary and sufficient heat resistance for motors for various purposes and level crossing;

- use in the manufacture of valves of ice deformation processes in areas of limited technological plasticity of titanium alloys, achieving high performance and low cost in mass production.

This technical result and correct deficiencies in the proposed valve of the internal combustion engine from heat-resistant titanium alloy containing a cylindrical rod, cylinder, disc shape and the transition area, providing smooth coupling rod and head, is achieved in that the titanium alloy has a α+α2+β-phase composition with intermetallic α2-phase-based connection Ti3Al, dispersed distributed in α-phase, while the microstructure of the rod is a combination of three types of microstructures, smoothly transitioning from one type to another in the radial direction, from the surface to the center: equiaxial, bimodal and lamellar accordingly, the microstructure of the head is a mixture of microstructures of two types: basket weaving and plate, and the area has mixed the microstructure, consisting of microstructures characteristic of the rod and head.

In private cases, the execution of the invention, the rod has a microstructure with a grain size 3-40 μm, and the head of the microstructure with the grain size is 50-200 μm.

Mass fraction of intermetallic α2phase-based connection Ti3Al is from 7 to 80 wt.% when the content of aluminum in the alloy from 7.5 to 12.5 wt.%.

In the present invention eliminate the above deficiencies is through the creation valve with different microstructures for the rod and head and additional content in the alloy, which is made valve, intermetallic α2phase-based connection Ti3Al, which dispersed distributed in α-phase. The content material of valve α2-phase dispersed distributed in α-phase, and the combination of these microstructures in the valve stem provides increased tensile strength at elevated temperatures, the modulus of normal elasticity and hardness, and resistance to the initiation and fatigue crack propagation, fracture toughness and toughness. This increases strength and heat resistant properties of the valve. The content material of the valve head α2-phase dispersed distributed in α-phase, and a mixture of microstructures in th is information valve gives it the properties of long-term heat resistance by increasing long-term strength and creep resistance.

Additional alloying heat-resistant titanium alloy aluminum translates alloy of two-phase (α+β) in-phase (α+β+α2), while α2phase-based connection Ti3Al dispersed distributed in α-phase and secreted mainly during the heat treatment. The selection in the alloy α2-phase occurs when arranging αphase containing dissolved aluminum superequilibrium concentration. For example, the solubility of aluminum in α-phase at 550°is 7.0-7.5 percent (see Titan. Sources, composition, properties, metallogeny and application. Kornilov I.I. M.: Nauka, 1975, str). At high concentrations of aluminum at this temperature is dispersed allocation α2phase representing a solid solution based on the connection Ti3Al. This improves the heat resistance of the alloy up to 750-900°depending on the number α2-phase. The desired combination of mechanical properties and heat resistance (depending on the operating temperature of the valve is achieved when the content α2-phase in the alloy from 7 to 80 wt.%. A more detailed confirmation and justification of the essential features of the invention, the Valve of the internal combustion engine” see section “Example implementation of the invention”.

The specified technical result is t and shortcomings of the proposed method of manufacturing a valve of the internal combustion engine from heat-resistant titanium alloy, including the formation of a cylindrical billet valve by deformation processing with pre-heating and subsequent heat treatment, is achieved in that the titanium alloy has a α+α2+β-phase composition with intermetallic α2-phase-based connection Ti3Al, dispersed, distributed α-phase, pre-heating part, related to the terminal, hold until temperature for 5-20°C below the temperature of complete polymorphic transformation of the alloy, and its deformation processing performed by the V-cross rolling to obtain the rod smoothly transitioning from one type to another in the radial direction, from the surface to the center of the combination of three types of microstructures: equiaxial, bimodal and lamellar accordingly, deformation processing part, related to the head, carried out by stamping with pre-heating to a temperature of at 5-50°With higher temperature the full polymorphic transformation of the alloy corresponding to the beginning of the stamping, and the stamping is carried out at a temperature below the temperature of complete polymorphic transformation of the alloy, forming the head of the valve disc shape with a mixed microstructure of two types: basket weaving and plate and the transition area, providing smooth otrazhenie head with the shank and having a mixed microstructure, consisting of microstructures characteristic of the rod and head.

In private cases, the execution of the invention after fabrication of the valve rod has a microstructure with a grain size 3-40 μm, and the head - 50-200 microns.

Preheating the part relating to the terminal, hold-contact method.

Preheating the part relating to the terminal, carried out with the speed of 10-50°C/sec.

Klinovuyu cross rolling is conducted with a degree of deformation of 30-55%.

Preheating the part relating to the head,

conduct induction method.

Preheating the part relating to the head, carried out with the speed of 20-50°C/sec.

Stamping blanks relating to the head, carried out with the degree of deformation of 40-60%.

Preheating the part relating to the head, and the part relating to the terminal, carried out at the temperature control.

The heat treatment is carried out by annealing.

Annealing is performed by heating the pieces obtained after deformation processing of its parts related to the terminal and to the head, to a temperature of 650-950°C, holding at this temperature for 0.1-5.0 hours, cooling to a temperature of 500-650°C, followed by holding at this temperature for 5-50 hours, klaid the deposits.

Thus, the inventive method of manufacturing valve based on the application of deformation technologies, alternating with heat treatment. This allows you to get the valve of the internal combustion engine with microstructure corresponding to the conditions of its mechanical and long-term thermal loading in internal combustion engines, including for high-powered engines. More confirmation and justification of the materiality of signs for the invention “Method of manufacturing a valve of the internal combustion engine” see section “Example implementation of the invention”.

This technical result and correct deficiencies in the proposed heat-resistant titanium alloy containing aluminum, molybdenum, zirconium and silicon, is achieved by the fact that it additionally contains yttrium in the following ratio, wt.%: aluminum 7,5-12,5, molybdenum 1,6-2,6, zirconium 1,4-2,4, silicon of 0.1-0.2, yttrium 0,05-0,1, titanium - rest and has α+α2+β - phase composition with intermetallic α2-phase-based connection Ti3Al, dispersed distributed in α-phase.

The use for the manufacture of valves both intake and exhaust, titanium alloys, advanced reinforced intermetallic α2-phase-based connection Ti3Al, dispersed distributed in α-phase, ensure the AET increased mechanical properties of the valve internal combustion engine, first of all heat-resistant, and long for them to work with a limited period of operation at temperatures in the cylinder, 900°for exhaust valves uprated engine.

Brief description of drawings.

The invention is illustrated by drawings, where:

1 shows a General view of the valve of the internal combustion engine;

figure 2 shows the original cylindrical workpiece;

figure 4 shows the billet valve of the internal combustion engine after stamping;

figure 5 shows a equiaxial microstructure, located on the surface of the valve stem;

figure 6 shows a bimodal microstructure, located in the intermediate part of the valve stem;

figure 7 shows lamellar microstructure, located in the Central area of the valve stem;

on Fig-10 shows the microstructure of the valve stem for the case of heating it under klinovuyu cross rolling to a temperature above the declared (maximum) temperature range (TPP-5° (C)when it is impossible to obtain a desired combination of microstructures in the valve stem;

figure 11 shows the microstructure of the valve head, which is a mixture of the two microstructures: basket weaving and lamellar;

on Fig shows a fragment of the lamellar microstructure in the head of the valve, on an enlarged scale;

on Fig image the wives fragment microstructure, basket weaving in the valve head, in an enlarged scale;

on Fig presents the estimated distribution of temperatures in the inlet valve on the example of the engine mid-level forcing;

on Fig presents the estimated distribution of temperatures in the exhaust valve on the example of the engine mid-level forcing.

An example implementation of the invention.

The valve (figure 1) contains a terminal 1 of a constant diameter and the cylinder 2 disc form, including the transition area 3, providing smooth coupling rod and head.

The intake and exhaust valves are made of titanium alloy with different aluminum content in the range of 7.5 to 12.5 wt.% (see 17 table 1 and Table 3). These alloys are additionally reinforced intermetallic α2-phase dispersed distributed in α-phase, increase the heat resistance of the alloy to 900°C. Used in the manufacture of the valve deformation processing and heat treatment, by the present method, in terminal 1, the cylinder 2 and the transition area 3 created different microstructure.

The microstructure in the rod 1 is a combination of three types of microstructures: equiaxial, bimodal and lamellar. These patterns gradually change from one type to another in the radial direction, from the surface to the center in the direction specified.

To achieve maximum is different strength characteristics in the valve stem creates a heterogeneous microstructure, consisting of three microstructures.

On the surface of the valve stem is created equiaxial microstructure (figure 5). Equiaxial microstructure contributes to the strength, ductility, fatigue limit, and increase resistance to nucleation of fatigue cracks and resistance to low cycle fatigue (see Kolachev B.A., Polkin I.S., Talalaev E Titanium alloys in different countries., ed. VILS, 2000, str). Thus, an increased resistance to the nucleation of fatigue cracks in a complex with other positive features of this microstructure (strength, flexibility, endurance) requires no additional surface treatment of the valve stem (shot blasting, polishing, etc. to improve its fatigue strength.

Between the surface of the valve stem and its Central part is bimodal microstructure (Fig.6). Bimodal microstructure allows to achieve an optimum combination of mechanical properties of alloy and advantages of equiaxial and lamellar microstructures. In addition, the formation of a bimodal microstructure in the transition layer between equiaxial and lamellar microstructures, promotes a smooth transition from one microstructure to another and has a positive impact on the enhancement of the mechanical properties of the material of the valve stem.

In the Central zone erased the nya is located lamellar microstructure (Fig.7). Lamellar microstructure can improve the fracture toughness, resistance to growth of fatigue cracks, impact strength and creep resistance and long lasting durability. Formation in the Central zone of the valve stem fine-grained lamellar microstructure (grain size less than 40 microns) allows to obtain a higher fracture toughness, impact strength and resistance to the growth of fatigue cracks, soglasuyushchiesya with nature acting on the valve stem, with a high frequency, cyclic tensile loads percussive nature. The formation of this microstructure is positive and part of the exhaust valve stem adjacent to the hot cylinder and operating in the temperature range of 500-650°With (see Fig), i.e. under conditions of creep and increased resistance long lasting durability. It also improves the strength properties of the valve stem.

This combination of microstructures will allow you to create the valve stem with high reliability and durability.

The best technical result from the point of view of reliability and durability of the valve stem is achieved when the grain size for the microstructure of the valve stem 3-40 μm. The grain is less than 3 μm causes during deformation processing of internal strain and the formation of microcracks. Grain more than 40 μm reduces the mechanical and fatigue properties of the valve.

The microstructure of the head 2 of the valve is a mixture of microstructures of two types (11): basket weaving and plate and, consequently, has all the advantages of such microstructures. Lamellar microstructure, the valve head (Fig), provides improved fracture toughness, impact strength, resistance to growth of fatigue cracks, creep resistance, and resistance to long-term strength. Microstructure, basket weaving (Fig) provides increased long-term strength and creep resistance. A mixture of microstructures, basket weaving and plate formed in the valve head has a chaotic nature, without distinct areas that are most conducive to combining the positive properties inherent in each of these microstructures. Microstructure, basket weaving to a greater degree provides increased resistance durability at a sufficiently high creep resistance. Coarse-grained lamellar microstructure (grain size of 50-200 μm) to a greater degree provides increased creep resistance, as well as other positive properties characteristic of the lamellar microstructure. This mixture of microstructures adequate is about fully consistent with the nature of the loading of the valve head (cyclic alternating loads of percussion character with a high frequency in the temperature range of 600-850° With, and in some cases up to 900°). This leads to increased reliability and infallibility of the valves of internal combustion engine and increases the durability of the engine.

The best technical result is achieved when the grain size for the microstructure in the valve head in the range of 50-200 μm. The increase in grain than 200 microns leads to a decrease in strength due to the weakening of grain boundaries. The reduction of grain less than 50 μm reduces the creep resistance at high temperatures.

In the area of transition 3 is a smooth transition from one type of microstructures related to the valve stem, for a different kind of microstructures related to the valve head, which allows to ensure reliable operation of the transition section of the valve when the temperature gradient, from a high operating temperature in the cylinder valve to the working temperature in the valve stem (see Fig and 15).

Application for valves (both intake and exhaust), titanium alloys, advanced reinforced intermetallic α2-phase on the basis of Ti3Al, dispersed distributed in α-phase, with high heat resistance, ensures continuous operation of engine valves for various purposes and the level crossing at temperatures in the valve head from 600 to 900°C, whereas the known titanium alloys the level of heat-resistance does not exceed 600°C. is the valve stem and in the transition area provides increased hardness and modulus of normal elasticity due to the content α 2-phase dispersed distributed in α-phase. This reduces the constructive dimensions of the rod and the crossing section of the valve, which reduces the mass of the valve by 10-20% in comparison with the alloy of the prototype. According to the data given in Table 3, PP and 9, shows the superiority of the claimed properties of the alloy on the properties of the alloy according to patent US 4729546. So the values of specific strength values (σ/ρ) and stiffness (E/ρ) for the developed alloy exceeds these values for alloy prototype: σ/ρ (800° (C) from 2 to 4 times, and for E/ρ (at room temperature) 11-27%.

The solubility of aluminum in αphase ranges from 6 to 7.5 wt.%. At the higher its content in the alloy is allocated dispersed distributed α2phase representing a solid solution based on intermetallic compounds of Ti3Al, which further improves the heat resistance of the alloy and the modulus of normal elasticity. At the same time, this leads to the reduction of technological plasticity. The required level of technological plasticity is achieved ratio αand β-phases in the alloy. This ratio can be adjusted by the amount in the alloy αand β-stabilizing elements. The most effective stabilizer α-phase is aluminum. Molybdenum is one of the most the effective stabilizers β -phase. With this in mind, designed titanium (α+β) alloy, dispersed hardened α2-phase is composed of:

- aluminum, increasing the heat resistance of the alloy and which determines the content of α2-phase;

- molybdenum, stabilizing β-phase and affect the ductility of the alloy (a relative decrease in the content of molybdenum in the alloy with increasing aluminum content further reduces the plasticity and adaptability);

- Zirconia, expanding the scope of homogeneity α-phase and influencing the allocation of α2-phase quantity, especially at low concentrations of aluminum.

It is known that dissolved oxygen in the alloy significantly reduces its ductility. The introduction of yttrium in the alloy allows you to organize the process of internal deoxidize the alloy. Yttrium, dissolved in the alloy during the melting process, interacts with dissolved oxygen to form the oxide Y2O3that reduces the oxygen content dissolved in the αand β-phases, and increases process flexibility.

In the proposed heat-resistant titanium alloy, the aluminum content is 7.5 to 12.5 wt.%. Thus, increasing the aluminum content of more than 6-7,5%, without changing the content of other elements leads to an additional reduction of technological plasticity splavovi content in aluminium alloy, molybdenum and zirconium, and yttrium, you can modify the heat-resistant properties of the alloy while maintaining the technological plasticity on the level, allowing for deformation processing of the alloy.

The production of heat-resistant titanium alloy was carried out by double vacuum arc remelting. The alloy ingot with a diameter of 350 mm was extrudible in the bar with a diameter of 50 mm and rolled into rods with a diameter of 16-22 mm after rolling bars and Rods were subjected to annealing.

The rods were cut on a cylindrical workpiece 4 gauge length depending on the dimensions of valves (figure 2).

To obtain the proposed microstructure, different for stem and valve head, spent two stages of deformation processing, pre-heating before deformation and subsequent heat treatment.

Heating billets under klinovuyu cross rolling was carried out by the electric-contact method. Supply current is carried through the water-cooled copper contacts. Harvesting in the contact zone remained cold, and the Central part of the billet is heated to a predetermined temperature is a variable or constant current. Temperature control heating was performed using an infrared pyrometer. When the set temperature is reached, thermometer has sent a signal to a microprocessor controller that transmitted the control signal grant the preliminary arrangements with pneumatic drives, and the heated workpiece with minimum time delays were delivered in the area of rolling.

In the first stage of deformation processing of the workpiece cylindrical wedge method of cross rolling was awarded the workpiece intermediate form for further forging of the valve head (Fig 3). During the V-cross rolling was formed structure of the valve stem. A distinctive feature of the V-cross rolling is to heat the workpiece only in zone 5, which is subjected to rolling. Heating only the deformable part avoids undesirable grain growth in the undistorted part 6 and to facilitate the formation of the valve head by forging, which is essential for difficult-to-deform alloys.

Klinovuyu cross rolling was carried out with the degree of deformation of 30-70%.

Experimentally it was found that in this range of degrees of deformation in the valve stem, the result is a combination of three types of microstructures: equiaxial, bimodal and lamellar for achieving the desired technical effect. When the degree of deformation less than 30% were not able to accumulate a sufficient number of metal stamped part for the subsequent formation of the valve head. When the degree of deformation of more than 70% was break the workpiece during rolling.

PPfor this alloy, that is α+β-region of the alloy. Experimentally it was found that in this temperature range transverse wedge rolling provides reception in the core the combination of microstructures in three types: fine-grained equiaxial, bimodal and lamellar required to obtain achieved technical result. When the temperature rolling is less than the lower limit (TPP-20° (C) occurs breakage of the workpiece. When the temperature of the rolling above the upper limit (TPP-5° (C) not receive the necessary combination of microstructures (Fig-10).

In the process of V-cross rolling to the microstructure in the valve stem received grain size 3-40 μm. Since the deformation effect of the V-cross rolling decreases from the surface to the center, the surface layers of the transformation of the original structure of the preform rod in equiaxial, and in the Central zone, where the deformation effect is minimal, got lamellar microstructure characteristic of the undeformed alloy subjected to heat.

Electrocontact heating the deformable portion of the workpiece under klinovuyu transverse rolling fought with the speed of 10-50°C/sec. Direct electric heating allows to implement t the Kie, sufficiently high heating rate and to ensure uniformity of temperature over the cross section and length of the workpiece. At a heating rate of more than 50°/s Central part of the preform rod is heated to a lower temperature than the surface, which leads to deterioration of the quality of rolling. At speeds less than 10°is the oxidation of the surface of the workpiece and the appearance of unwanted oxide layer.

Wedge transverse rolling allows you to receive the blank for stamping with high performance, around 4-5 blanks in minutes, with minimal deformation tool (rolls). Resistance rolls wedge rolling 10-20 times higher extrusion resistance of the matrix.

Hot stamping of the valve head carried on the mechanical crank press.

Heating under stamping led induction method only the part of the workpiece which is subjected to deformation during the forming of the valve head. The heating rate was 20 to 50°C/sec. After heating to a predetermined temperature were stamping the valve head (figure 4).

Start stamping was carried out at temperatures of deformation at 5-50°With the higher point complete polymorphic transformation (TPPfor this alloy. The final stage of formation of the valve head occurred at temperatures below TPP. Using stamps and was formed in the head 7 of the valve disc shape with a smooth section 8 of the passage in the rod 9. Experimentally it was found that this temperature stamping provides the mixture of the microstructures of two types: basket weaving and plate with grain size of 50-200 μm, necessary to ensure the heat resistance of the valve head. For the crossing received a mixed microstructure consisting of microstructures characteristic of the rod and the head, which ensured a smooth transition of microstructures and properties of the valve from one of its parts (rod) to another (the head).

Overheating blanks for stamping, i.e. its heating above the temperature TPP+50°, undesired grain growth above 200 microns, which reduces the strength properties of the valve head due to the weakening of grain boundaries.

Insufficient heating of the workpiece below the temperature Tβ+5°C, is the cracking of the valve head in the stamping process.

Quick and single heat deformable portion of the workpiece is not possible to form on the surface of the dross and oxide layer that contributes to a more favorable course of deformation processes for stamping, reduced resistance to deformation and good surface forming without cracking, folds and wrinkles.

Heating with a rate of more than 50°/s led to high heterogeneity heating the title is ovci, because of what the Central part had no time to warm up to the preset temperature, while the surface is too hot. This has led to poor quality stamping. Heat speeds of less than 20°C/sec reduced performance stamping.

After deformation processing conducted heat treated billet valve. The heat treatment was carried out by quenching and annealing or using only annealing.

In the first embodiment, heat treatment, quenching was performed immediately after each of the stages of the deformation process. After the V-cross rolling was performed hardening of the workpiece, for example in water. In the valve stem occurred fixation patterns in two-phase (α+β) region and the termination of the allocation process α2-phase. During hardening after forming was fixing the microstructure in the valve head. According to the phase diagram of the titanium - aluminium allocation α2phase begins at temperatures of 500-650° (see Titan. Sources, composition, properties, metallogeny and application. Kornilov I.I. M.: Nauka, 1975, SCR-197). The higher the process temperature, the larger the selection α2-phase. The best results in the dispersion selection α2-phase receive as a result of diffusion processes at temperatures of 500-650°C. In this case, when the learn is allocated α 2-phase with the size of the discharge 20-50 nm. At temperatures below 500°With diffuse processes are very slow. At temperatures above 650°size α2-phase high. Annealing in the claimed temperature range leads to increased heat resistance. Heating the billet to a temperature of 650-950°With objective - the removal of internal stresses.

In the second embodiment, heat treatment, annealing was performed after the formation of the valve, i.e. after the second stage of deformation processing. Annealing was performed for the procurement of the valve as a whole.

Annealing the first and second embodiments, the heat treatment was performed in two stages. At the first stage annealing was performed by heating the billet to a temperature of 650-950°C, holding at that temperature for 0.1 to 5.0 hours, and cooling to a temperature of 500-650°C.

At the second stage of annealing osushestvljali the shutter speed of the workpiece at a temperature of 500-650°for 5-50 hours and then cooled.

In the first embodiment of the heat treatment, the best results were achieved when the content in the alloy α2-phase number 7-25 wt.%. In this case, the increase in mechanical properties occurs according to the mechanism of hardening 2-phase (α+β) alloys and due to the dispersed allocation α2-phase. The effect of hardening, tempering and annealing exceeds the effect strengthen the means of allocating α 2-phase number 7-25 wt.%. Conducting conducting heat treatment in the first embodiment is preferable for the alloy containing aluminum in the range of 7.5 to 9.5 wt.%. As a result of this heat treatment was given ice valves (mainly intake), which provides continuous operation in the temperature range of 600-650°With (see Table 2).

The heat treatment according to the second variant is useful to content α2-phase in the amount of 25-80 wt.%. In this case, the enhancement of the mechanical properties is mainly due to the dispersed allocation α2-phase. Conducting a heat treatment on the second version is preferable for the alloy containing aluminum from 9.5 to 12.5 wt.%. Valves (both exhaust and intake) alloy aluminum content Mac.%: 9,5-10,5, 10,5-11,5 and 11,5-12,5 provide continuous operation in the temperature range of 650-700°C, 700-800°and 800-850°respectively, for engines with a long period of operation (see Table 2). Valves with aluminium content of 11.5 to 12.5 wt.% provide a limited period of operation in the temperature range up to 900°for high-powered engines (see Table 2).

Performing deformation and heat treatments on the declared modes in the manufacture of valve internal combustion engine from an alloy of aluminum content from 7.5 to 12.5 wt.% provides reception of neo the required mechanical properties in the valves of internal combustion engines, given in Table 3.

From Table 3 it can be seen that the alloy with an aluminum content of 7.5 to 12.5 wt.%, reinforced intermetallic α2-phase has the following higher mechanical properties in the temperature range up to 900°With (compared with the properties of the alloys according to the prototype):

strength is 3.5 times higher for the alloy with an aluminum content of 7.5 to 9.5 wt.% at temperatures 700-760°and 4 times higher than that for alloy aluminum content of 9.5 to 10.5 wt.%;

- the strength of the alloy by increasing the content of aluminum from 7.5 and 9.0 wt.% to 12.0-12.5 wt.% increases in 2 times in the case of the valve head at a temperature of 800°C and voltages in the range from 260 to 520 MPa;

- when increasing the aluminum content from 7.5 to 12.5 wt.% specific strength (σin/ρ) higher in 2-4 times in the temperature range of 760 to 800°and specific stiffness (E/ρ) above 11-27% at room temperature (it's possible to produce a valve with a smaller structural dimensions for the rod and the crossing section of the rod in the plate and thereby reduce the weight of the valve 10-20%);

the creep resistance of the alloy at temperatures of 600-800°significantly higher than for the prototype.

Manufactured as described above billet valve was subjected to mechanical treatment known methods, such as t is the treatment and grinding. After machining the outer surface of the valve was secured, for example, by nitriding at a depth of 50-100 microns.

The proposed method of manufacturing valve allows you to get the valves of internal combustion engines, which are consistent with the level of thermal loading in engines for various purposes and force level. In the manufacturing process can be controlled by the properties of the valves, varying material properties, primarily heat. The proposed method is based on the use of high-deformation technology and can be applied for mass production of valves of the engine.

Table 1.

Chemical composition and properties of titanium alloys-analogues used for valves of the engine.
№ p/pMark opleveChemical composition, wt.%Basic properties
1 Ti-48Ai+2Cr-2NbThe base alloy TiAl (γ). Low plasticity (δ=0,5-1,5%)Podvergautsya the forming mainly for foundry technology. Tmax=750-900°
2 Ti-46Al-1Cr-0,2Si In accordance with paragraph 1.
3VTUTi-6,5Al-2,5Sn-4Zr-1Nb-0,7Mo-0,15Siσin=1075 MPa*, δ=12,5%*. long-term strength up to 600°C.
4Vt25u alloyTi-65Al-18Sn-4Zr-4Mo-1W-0,2Siσin=1230 MPa*, δ=43,5%*, long durability up to 550°C.
5IMI829Ti-55Al-3,5Sn-3Zr-1Nb-0,25Mo-0,3Siσin,=950 MPa*, δ=11%*combination of properties: creep resistance up to 540°and oxidation resistance.
6MTi-5,8Al-4Sn-3,5Zr-0,7Nb-0,5Mo-0,35Siσin=1050 MPa*, δ=42%*increased tensile strength and creep resistance up to 600°
7Ti-6242STi-6Al-2Sn-4Zr-2Mo-0,08Siσin=1030-1176 MPa*, δ=8-10%*good creep resistance tensile and fatigue to 540°C.
8imetal1100Ti-6Al-2,8Sn-4Zr-0,4Mo-0,5Siσin=1000 MPa*, δ=8-11%*, the high-temperature creep resistance, long life & energy saving is the main operation in temperatures up to 600°
9Patent RU No. 2081929Ti-(13-15)Al-(34)Nb-(2-4)V-(0,5-1)ZrHeat resistance up to 850°C, low plasticity. To improve the technological plasticity of the proposed reversible doping of hydrogen.
10The US patent No. 5169460Ti-(2-4)Al-(1,5-3,5)V-rod valve

Ti-(2-7)Al-(3-20)V-valve head
Casting technology of the valve head with its inherent disadvantages
11The JP patent No. 03009006Ti-(7-12)Al-(0,5-5)Sn-(0,5-5)Zr-(0,5-5)MoCasting technology with its inherent disadvantages
12The JP patent No. 62-197610Ti-6Al-4V-terreni valve

Ti-6Al-2Sn-4Zr-2Mo-0,08Si-valve head
σin=1030-1176 MPa*, δ=8-10%*. good creep resistance tensile and fatigue to 540°
13The US patent No. 4679964Ti-6Al-4Vσin=950-1050 MPa*, δ≥10%*, alloy belongs to a class of heat-resistant, it is recommended to use up to 400°
14-"-Ti-6A-2Sn-4Zr-2Mo-0,08Si σin=1030-1176 MPa*, δ=8-10%*good creep resistance tensile and fatigue to 540°
15-"-Ti-5Al-5Sn-2Zr-4Mo-0,3SiLong-term heat resistance up to 600°
16-"-Ti-5Al-6Sn-2Zr-1Mo-0,3SiLong-term heat resistance up to 600°
17According to the inventionTi-(7,5-12,5)Al-(1,6-2,6)Mo-(1,4-2,4)Zr-(0,1-0,2)Si-(0,05-0,1)YCm. Table 3, long-term heat resistance in the temperature range of 600-850°and for short periods up to 900°
Notes:

*)properties are given at room temperature

properties of foreign alloys taken from Kolachev B.A., Polkin ACTING, Talalaev E Titanium alloys in different countries. Guide-M: VILS, 2000.
Table 2.

Approval of the developed alloy with the appointment of ice valves in terms of their thermal load and depending on the aluminum content in the alloy.
The aluminum content in the alloy, wt.%:Valve typeThe range of maximum temperatures to the Apana, °
7,5-9,5inlet650
9,5-10,5inlet, outlet650-700
10,5-11,5final700-800
11,5-12,5final800-850
11,5-12,5Outlet for high-powered internal combustion engine with a limited period of operation900
Table 3.

Properties of heat-resistant alloys based on titanium reinforced intermetallic and2-phase (Ti3A1) in accordance with the invention and patent-prototype.
№ p/pProperties of alloys based on titaniumIn accordance with the invention, depending on the aluminum content in the alloy, wt.%In patent No. 4.729.546 (USA)
  7,5-9,59,5-10,510,5-11,511,5-12,5the placeholder
1.Density (ρ), g/cm3of 4.384,354,334,34,54 (for the alloy Ti-6Al-2Sn-4Zr-2Mo-0,1Si)
2.Hardness (after annealing), NV340-380380-420318 (for the alloy Ti-6Al-2Sn-4Zr-2Mo-0,1Si)
3.Ultimate tensile strength (σin),IPA:     
 -at 20°1175-12501140-11651100-11501000-1040965-1240
 -when 600°670-760730-770780-800800-820620-725(510°)
 -at 800°180-210280-330380-430500-520≥138 (760°)
 -at 900°--110-14090-220 -
4.The normal elasticity modulus (E), tensile HPa122-127129-131133-135139-142115-118 (for the alloy Ti-6AI-2Sn-4Zr-2Mo-0,1Si)
5.Long-term strength (σ100), IPA:    In patent
 -when 600°-260--no data
 -at 800°-46--given
6.Yield strength, MPa:     
 strain of 0.1% at 600°With over 100 hours.-155,0---
 strain of 1% at 760°With over 100 hours. ----27,5
 strain of 0.1% at 800°With over 100 hours.-21,0-62,0-
7.Specific strength (σin/ρ, m·10-3:     
 -at 20°26,8 is 28.526,2 by 26.825,4 of 26.523,25-24,2each holding 21.25 is 27.3
 -at 800°4,1-4,8of 6.3 and 7.68,8-9,9the 11.6-12,1≥3.04 from(760°)
8.The specific stiffness (E/ρ, m·106278,5-290297-301307-312323-330253-260

1. The valve of the internal combustion engine from heat-resistant titanium alloy containing a cylindrical rod, cylinder, disc shape and the transition area, providing smooth coupling rod and head, Otley is audica fact, what titanium alloy has α+α2+β the phase composition of the intermetallic α2-phase-based connection Ti3Al, dispersed distributed in α-phase, and the rod has a microstructure that is a combination of three types of microstructures, smoothly transitioning from one type to another in the radial direction, from the surface to the center: equiaxial, bimodal and lamellar accordingly, the head has a microstructure composed of a mixture of microstructures of two types: basket weaving and plate, and the area has a mixed microstructure consisting of microstructures characteristic of the rod and head.

2. The valve according to claim 1, characterized in that the rod has a microstructure with a grain size 3-40 μm, the head - 50-200 microns.

3. The valve according to claim 1, characterized in that the mass fraction of intermetallic α2phase-based connection Ti3Al is from 7 to 80 wt.% when the content of aluminum in the alloy from 7.5 to 12.5 wt.%.

4. A method of manufacturing a valve of the internal combustion engine from heat-resistant titanium alloy, including the formation of a cylindrical billet valve by deformation processing with pre-heating and subsequent heat treatment, characterized in that the titanium alloy has a α+α2+β phase SOS is AB with intermetallic α 2-phase-based connection Ti3Al, dispersed distributed in α-phase, while preheating the part relating to the terminal, hold until temperature for 5-20°C below the temperature of complete polymorphic transformation of the alloy, and its deformation processing performed by the V-cross rolling to obtain the rod smoothly transitioning from one type to another in the radial direction from the surface to the center of the combination of three types of microstructures: equiaxial, bimodal and lamellar accordingly, deformation processing part, related to the head, carried out by stamping with pre-heating to a temperature of at 5-50°With higher temperature full polymorphic transformation of the alloy corresponding to the beginning of the stamping, and the stamping is carried out at a temperature below the temperature of complete polymorphic transformation of the alloy, forming the head of the valve disc shape with a mixed microstructure of two types: basket weaving and plate and the transition area, providing smooth coupling of the head with the shank and having a mixed microstructure consisting of microstructures characteristic of the rod and head.

5. The method according to claim 4, characterized in that after the manufacture of the valve rod has a microstructure with a grain size of 3-4 microns, and head - 50-200 microns.

6. The method according to claim 4, characterized in that the preheating part, related to the terminal, hold-contact method.

7. The method according to claim 4 or 6, characterized in that the preheating part, related to the terminal, carried out with the speed of 10-50°With a/C.

8. The method according to claim 4, characterized in that klinovuyu transverse rolling part, related to the terminal, carried out with the degree of deformation of 30-55%.

9. The method according to claim 4, characterized in that the preheating part, related to the head, conduct induction method.

10. The method according to claim 4 or 9, characterized in that the preheating part, related to the head, carried out with the speed of 20-50°C/sec.

11. The method according to claim 4, characterized in that the stamping blanks relating to the head, carried out with the degree of deformation of 40-60%.

12. The method according to any of claims 4, 6, 7, 9 and 10, characterized in that the preheating part, related to the terminal, and the part relating to the head, is carried out at a temperature monitoring.

13. The method according to claim 4, characterized in that the heat treatment is carried out by annealing.

14. The method of item 13, wherein the annealing is performed by heating the workpiece obtained after deformation processing of its parts related to the terminal and g is lowke, to a temperature of 650-950°C, holding at this temperature for 0.1 to 5.0 h, cooling to a temperature of 500-650°C, followed by holding at this temperature for 5-50 hours and cooling.

15. Heat-resistant titanium alloy containing aluminum, molybdenum, zirconium and silicon, characterized in that it additionally contains yttrium in the following ratio, wt.%:

Aluminum 7,5-12,5

Molybdenum 1,6-2,6

Zirconium 1,4-2,4

The silicon of 0.1-0.2

Yttrium 0,05-0,1

Titanium Else

and has α+α2+β-phase composition with intermetallic α2-phase-based connection Ti3Al, dispersed distributed in α-phase.



 

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FIELD: mechanical engineering; piston internal combustion engines.

SUBSTANCE: invention relates to valve of internal combustion engine, method of its manufacture and heat-resistant titanium alloy used for manufacture of valve consisting of following components, mass %: aluminum 7.5-12.5; molybdenum 1.6-2.6; zirconium 1.4-2.4; silicon 0.1-0.2' yttrium 0.005-0.1; titanium - the rest. It has α+α2+β phase composition with intermetallide α2 phase on Ti3Al base dispersed in α phase. Proposed method includes forming of valve from cylindrical blank by deformation machining with preliminary heating and subsequent heat treatment. Preliminary heating of part of blank related to rod done to temperature 5-20oC lower than temperature of complete polymorphic transformation of alloy, and its deformation machining is carrying out by wedge cross rolling. Deformation machining of part of blank related to head is done by forging with preliminary heating to temperature 5-50oC higher than temperature of complete polymorphic transformation of alloy corresponding to beginning of forging, and forging is finished at temperature lower than complete polymorphic transformation of alloy to form plate head of valve and transition section provided smooth changing of head into rod. Invention provides designing of valve, method of its manufacture and heat-resistant alloy used in manufacture of valve making it possible to operate valve within operating temperature range owing to increased long-term strength and creep resistant of valve head material and increased strength, modulus of elasticity and hardness of valve rod material.

EFFECT: improved quality of valve and increased reliability in operation.

16 cl, 3 tbl, 1 ex, 15 dwg

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