RU2134308C1 - Method of treatment of titanium alloys - Google Patents

Abstract

FIELD: treatment of titanium alloys. SUBSTANCE: method includes heating of billet and its deformation in heated tools at 400 C - Tpt, where Tpt is temperature of full polymorphic transformation. In so doing, quantity of stages and their temperatures are set proceeding from grain sizes d_o of initial billet and required grain final size d_f and temperature Tf corresponding to required grain final size. The process is carried out as follows. Determined experimentally is dependence of size of recrystallized grains on temperature d = f(T) in the entire indicated temperature range. The latter is divided into two sections and boundary between them is determined by temperature T^* corresponding to grain size

and the latter is determined from relation lg d_o/d^*=2.4-2.6 for alloys with stabilization factor Kβ < 1.4, and lg d_o/d^*=1.8-2 for alloys with stabilization factor Kβ ≥ 1.4. If deformation temperature Tf is within range of ( T^* - Tpt), deformation is effected for one stage, and if deformation temperature is within (400 C - T^*), deformation is effected for several stages. In the latter case, quantity and temperature of stages are determined by successive adding to temperature Tf of temperature difference between stages determined by curve d = f(T) as value ensuring reduction of grain sizes at stages by 2-10 times until deformation temperature exceeds or becomes equal to T^*. In this case deformation at stage is effected with reduction ratio e amounting to not less than 0.6, and heating at the next stage is carried out to temperature not exceeding deformation temperature of the preceding stage. EFFECT: higher efficiency. 42 cl, 12 dwg

Description

 The invention relates to the field of metallurgy, and more particularly to methods for processing titanium alloys mainly with a lamellar structure, and can be used in the manufacture of bulk semi-finished products by pressure treatment for the subsequent production of critical products of various configurations, including large ones, for example, for the aerospace industry, such as disks , blades, body parts, which are mainly made of titanium alloys.

 Titanium alloys are classified as difficult to deform. The increase in the technological plasticity of titanium alloys is largely reduced to the search for methods for producing microcrystalline structures in alloys with a grain size of less than 10 microns. In this case, the microcrystalline structure was obtained on small semi-finished products, for example, on hot-rolled bars with a diameter of up to 60 mm. Meanwhile, most semi-finished products have a coarse-grained lamellar microstructure with a grain size of more than 100 microns in combination with a pronounced crystallographic and metallographic texture. Moreover, with an increase in the diameter of the semi-finished product, the microstructure becomes coarser. This leads to a low complex of mechanical and operational properties. The coarse-grained lamellar structure in semi-finished products is characterized by a high degree of structural heterogeneity, it is characterized by a combination of low strength with low ductility, low fatigue properties, and a significant variation in the values of mechanical properties. It is impossible to grind a coarse-grained lamellar structure by heat treatment. Whereas the microcrystalline structure in titanium alloys, if necessary, can be easily coarsened by simple annealing not only at temperatures corresponding to the single-phase β region, but also at temperatures corresponding to the two-phase (α + β) region. Thus, obtaining a homogeneous microcrystalline structure in titanium alloys makes it possible to sharply increase their technological properties during pressure processing and significantly reduce the power of the required equipment by reducing the stresses of plastic flow. At the same time, the high mechanical properties of the semi-finished products are ensured, and it is also possible to improve the mechanical properties during subsequent heat treatment.

 It is known that a sharp supercooling from a liquid state makes it possible to obtain a microcrystalline structure in a titanium alloy. However, taking into account the low heat and thermal diffusivity of titanium alloys, this method is not applicable for industrial titanium ingots obtained by existing modern technologies. This method is mainly used in powder metallurgy.

 It is known that when using powder metallurgy, it is possible to achieve fineness in the alloy due to the use of small granule sizes (50 ... 100 microns) and their very fine structure due to the high crystallization rate during gas-static pressing of granules (powders). Significant disadvantages of this method are the need for evacuation and sealing of capsules with powder, greatly limiting the size and dimensions of the resulting product, the high duration and complexity of the process, and the extremely high cost of the resulting semi-finished product. In addition, a noticeable grain growth due to the duration of the gas-static pressing process at high temperatures in the upper part of the (α + β) region and the inheritance of harmful impurities from the surfaces of granules (powders) in the resulting semi-finished product lead to a deterioration in the properties of the alloy as a whole compared to alloys obtained traditional methods.

There is also known a method for processing titanium alloys, selected for the prototype, including the initial deformation by compression at temperatures 56 ^o C below the temperature of recrystallization, followed by heating and deformation at the temperature of recrystallization of the processed alloy. The formation of the microcrystalline structure is achieved by recrystallization after hot hardening during subsequent processing. The indicated method for preparing the microcrystalline structure, due to the low technological ductility of titanium alloys, is mainly applicable to semi-finished products that underwent preliminary intense hot deformation in the (α + β) region. In the processed titanium alloys, sharp crystallographic and pronounced metallographic textures are formed, leading to significant anisotropy of the mechanical properties. A narrow processing temperature range of not more than 60 ^o C significantly reduces the possibility of regulating the structure in the alloys being processed and, consequently, the mechanical and operational properties of the latter.

 Thus, based on the data published in the technical and patent literature, obtaining a homogeneous microcrystalline structure in large titanium semi-finished products is a real technological problem.

 The objective of the invention is to provide a method for processing titanium alloys, which allows to obtain semi-finished products with a regulated microstructure, including in micro- and submicrocrystalline states, without a metallographic texture, and to provide them with the necessary set of mechanical properties. Also, the objective of the invention is the provision of the possibility of manufacturing large-sized semi-finished products with practically unlimited dimensions and shape.

The problem is solved:
a method for processing titanium alloys with a β-stabilization coefficient K _β <1.4, including heating the initial billet and its deformation in a heated tool, characterized in that the deformation is carried out at 400 ^o C ... T _pp , where T _pp is the temperature of the complete polymorphic conversion, the number of stages of deformation and the temperature is set, based on the grain size in the original preform d _o, the desired final grain size d _{to the} last and corresponding _{to the} temperature T, as follows: the experimentally determined dependence of the size of rivers istallizovannyh grains temperature deformation d = f (T) in the specified temperature range, the latter is divided into two portions, the boundary between which is set at a temperature T ^*, appropriate grain size d ^*, determined from the ratio of ^{_{lg (d o / d *)}} = 2 , 4 ... 2.6, and if the deformation temperature T _k is in the range (T ^* ... T _pp ), the deformation is carried out in one step, if in the range (400 ^o C ... T _* ) - several stages;
a method for processing titanium alloys with a β-stabilization coefficient K _β <1.4, including heating the initial billet and its deformation in a heated tool, characterized in that the deformation is carried out at 400 ^o C ... T _pp , where T _pp is the temperature of the complete polymorphic conversion, the number of stages of deformation and the temperature is set, based on the grain size in the original preform _of d, the required final grain size d _{to the} last and corresponding _{to the} temperature T, as follows: the experimentally determined dependence of the size of rivers istallizovannyh grains from deformation temperature d = f (T) in the specified temperature range, the latter is divided into two portions, the boundary between which is set at a temperature T ^*, appropriate grain size d ^*, determined from the ratio of ^{_{lg (d o / d *)}} = 1 , 8 ... 2, and if the deformation temperature T _k is in the range (T ^* ... T _pp ), the deformation is carried out in one step, if in the interval (400 ^o C ... T ^* ) - in several steps .

где d_n - размер зерен перед началом n-го этапа, T_n - температура деформации n-го этапа в градусах Кельвина, T_пл - температура плавления материала заготовки в градусах Кельвина, а - коэффициент, принимающий значение а=1 при d_т≥ 10 мкм; а=1,5 при 1 мкм d_т≤10 мкм; а=2 при 0,5 мкм ≤ d_n < 1 мкм, а=3 при d_n < 0,5 мкм;
- деформацию на этапе осуществляют за несколько переходов при температуре этапа;
- по крайней мере, между первым и вторым переходами заготовку охлаждают до комнатной температуры со скоростью 5...100^oC/с;
- после каждого перехода осуществляют поворот осей деформирования на 45. ..90^o;
- количество переходов на заключительном этапе выбирают не менее четырех, при этом поворот оси деформирования осуществляют в одной плоскости;
- деформацию осуществляют в интервале скоростей 10^-4 ...10^-2 с^-1;
- температуру деформации корректируют с учетом объема полуфабриката умножением на коэффициент, принимающим значение 0,98 для объема до 1 дм³, 0,97 для объема от 1 до 10 дм³ и 0,95 для объема более 10 дм³
- заготовку с размером β- превращенного зерна более 2000 мкм подвергают предварительной деформации при температуре выше T_пп+(10...50^oC) и при выборе режима основной обработки за исходный считают полученный размер зерен;
- заготовку с размером β- превращенного зерна более 2000 мкм подвергают предварительной деформации со степенью не менее 0,3 и скоростью в интервале 10^-2. ..10³ с^-1 при температуре деформации T_пп-(30...50^oC) и последующем нагреве до температуры T_пп+(20...70^oC) и при выборе режима основной обработки за исходный считают полученный размер зерен;
- заготовку, нагретую до температуры T_пп+(20...70^oC), охлаждают до комнатной температуры со скоростью 5...100^oC/с;
- заготовку непосредственно перед деформацией нагревают до температуры T_пп+(20. . . 70^oC) и охлаждают до комнатной температуры со скоростью 5... 100^oC/с;
- перед деформацией осуществляют проведение термоциклической обработки в температурном интервале 500^oC...T_пп с числом циклов 1...5;
- деформацию заготовки осуществляют в штамповом инструменте, нагретом на 10...50^oC выше температуры нагрева деформируемого сплава;
- осуществляют формообразование заготовки при температуре не ниже температуры заключительного этапа деформации заготовки;
- формообразование осуществляют в состоянии сверхпластичности;
- используют схему локального деформирования;
Задача, заключающаяся в получении не лимитируемых по габаритам заготовок с микро- и субмикрокристаллической структурой решается, если:
- собирают блок из заготовок, при сборке блока обеспечивают их прилегание без зазоров и осуществляют осадку блока при скорости 10^-5 ...10^-2 с^-1 со степенью деформации не менее 0,2 в температурном интервале 400^oC...T_пп, при этом температуру осадки выбирают не ниже температуры формообразования заготовок с максимальным размером зерен;
- собирают блок заготовок из сплавов с разным химическим составом и, соответственно, с различными температурами формообразования, при этом температуру осадки блока выбирают не ниже наибольшей из указанных температур;
- собирают блок по крайней мере из двух заготовок, между ними устанавливают заготовку в виде прокладки из того же материала с размером зерен (d) на порядок меньше, чем в заготовках, а толщину прокладки выбирают не менее 10 d и осуществляют осадку блока при скорости 10^-5 ...10^-2 с^-1 со степенью деформации не менее 0,2 в температурном интервале 400^oC...T_пп, при этом температуру осадки выбирают не ниже температуры заключительного этапа деформации, при которой получен размер зерен прокладки;
Сущность изобретения основана на том, что однородная мелкозернистая структура с требуемым размером зерен, вплоть до субмикрокристаллических, формируется в результате развития динамической рекристаллизации в широком температурном интервале 400^oC...T_пп. При температурах ниже 400^oC динамическая рекристаллизация в титане и его сплавах затруднена из-за значительного снижения диффузионной подвижности атомов и при использовании традиционного оборудования практически не обеспечивается. При температурах выше T_пп отмечается интенсивный рост зерен как при деформации, так и по ее окончании.The task for alloys of both types is also solved if:
- when carrying out the deformation in several stages, the number and temperature of the stages is determined by successively adding to the temperature T _to the temperature difference between the stages, determined by the curve d = f (T) as a value that provides a decrease in grain size at the stages by 2 ... 10 times until the deformation temperature exceeds or becomes equal to T ^* , moreover, the deformation at the stage is carried out with a degree of e not less than 0.6, and the heating at the next stage is carried out to a temperature not exceeding the deformation temperature of the previous stage;
- at least after the first stage of deformation, the workpiece is cooled to room temperature at a rate of 5 ... 100 ^o C / s;
- deformation inside the stage is carried out with a total degree of deformation

where d _n is the grain size before the beginning of the n-th stage, T _n is the deformation temperature of the n-th stage in degrees Kelvin, T _PL is the melting temperature of the workpiece material in degrees Kelvin, and is the coefficient taking the value a = 1 for d _t ≥ 10 microns; a = 1.5 at 1 μm d _t ≤10 μm; а = 2 at 0.5 μm ≤ d _n <1 μm, а = 3 at d _n <0.5 μm;
- deformation at the stage is carried out in several transitions at the temperature of the stage;
- at least between the first and second transitions, the workpiece is cooled to room temperature at a rate of 5 ... 100 ^o C / s;
- after each transition, the axis of deformation is rotated by 45. ..90 ^o ;
- the number of transitions at the final stage is chosen at least four, while the rotation of the axis of deformation is carried out in one plane;
- the deformation is carried out in the speed range 10 ^-4 ... 10 ^-2 s ^-1 ;
- the deformation temperature is adjusted taking into account the volume of the semi-finished product by multiplying by a coefficient assuming a value of 0.98 for a volume of up to 1 dm ³ , 0.97 for a volume of 1 to 10 dm ³ and 0.95 for a volume of more than 10 dm ³
- a preform with a β-transformed grain size of more than 2000 μm is subjected to preliminary deformation at a temperature above T _pp + (10 ... 50 ^o C) and when choosing the main processing mode, the obtained grain size is considered as the initial one;
- a preform with a β-transformed grain size of more than 2000 μm is subjected to preliminary deformation with a degree of at least 0.3 and a speed in the range of 10 ^-2 . ..10 ³ s ^-1 at a deformation temperature T _pp - (30 ... 50 ^o C) and subsequent heating to a temperature T _pp + (20 ... 70 ^o C) and when choosing the main processing mode, the resulting size is considered as the initial grains;
- the workpiece heated to a temperature of T _PP + (20 ... 70 ^o C), cooled to room temperature at a speed of 5 ... 100 ^o C / s;
- the workpiece immediately before deformation is heated to a temperature of T _PP + (20... 70 ^o C) and cooled to room temperature at a speed of 5 ... 100 ^o C / s;
- before deformation, thermocyclic processing is carried out in the temperature range of 500 ^o C ... T _pp with the number of cycles 1 ... 5;
- deformation of the workpiece is carried out in a stamping tool, heated to 10 ... 50 ^o C above the heating temperature of the wrought alloy;
- carry out the shaping of the workpiece at a temperature not lower than the temperature of the final stage of deformation of the workpiece;
- shaping is carried out in a state of superplasticity;
- use a local deformation scheme;
The task of obtaining blanks that are not limited in size with a micro- and submicrocrystalline structure is solved if:
- assemble the block from the workpieces, during assembly of the block ensure their fit without gaps and carry out the draft of the block at a speed of 10 ^-5 ... 10 ^-2 s ^-1 with a degree of deformation of at least 0.2 in the temperature range 400 ^o C ... T _pp , while the temperature of the precipitate is chosen not lower than the temperature of the forming blanks with a maximum grain size;
- collect the block of billets from alloys with different chemical composition and, accordingly, with different temperatures of forming, while the temperature of the precipitation of the block is chosen not lower than the highest of these temperatures;
- a block is assembled from at least two blanks, a blank is installed between them in the form of a gasket of the same material with a grain size (d) of an order of magnitude smaller than in the blanks, and the thickness of the gasket is selected at least 10 d and the block is sedimented at a speed of 10 ^-5 ... 10 ^-2 s ^-1 with a degree of deformation of at least 0.2 in the temperature range of 400 ^o C ... T _pp , while the temperature of the precipitation is chosen not lower than the temperature of the final stage of deformation, at which the grain size of the gasket is obtained;
The invention is based on the fact that a homogeneous fine-grained structure with the required grain size, up to submicrocrystalline, is formed as a result of the development of dynamic recrystallization in a wide temperature range of 400 ^o C ... T _pp . At temperatures below 400 ^o C dynamic recrystallization in titanium and its alloys is difficult due to a significant decrease in the diffusion mobility of atoms and when using traditional equipment is practically not provided. At temperatures above T _pp , intense grain growth is observed both during deformation and at its end.

The actual processing of the alloy in the indicated temperature range can be carried out subject to a certain temperature treatment and mandatory consideration of the initial state of the material. For this, it is necessary to construct a dependence of the size of recrystallized grains on the deformation temperature of the alloy d = f (T). The obtained dependence is valid for an alloy of a certain chemical composition and does not depend on the initial microstructure of the workpiece. The influence of the initial microstructure is taken into account by introducing the calculated value of recrystallized grains d ^* and the strain temperature T ^* corresponding to it along the curve d = f (T). The value of d ^{* is} determined from the experimentally established ratio lg (d _о / d ^* ) = 2.4. . .2.6 for titanium alloys with β-stabilization coefficient K _β <1.4 or log (d _о / d ^* ) = 1.8 ... 2 for Kβ alloys ≥ 1.4, where d _о is the grain size in source blank. In accordance with the above experimental dependence, the temperature T ^* represents a certain temperature range, depends on the size of the initial grains (d _о ) and increases with their increase, approaching the temperature of the complete polymorphic transformation.

The temperature T ^* is the boundary that divides the claimed temperature range into two sections: T _pp ... T _* and T ... 400 ^o C. In the first section, including the values of T ^* , the processing is carried out in one step, and in the second - in stages with a decrease in temperature. The latter is due to the fact that the technological plasticity of titanium alloys substantially depends on their microstructure, therefore, at the previous stage of deformation, it is necessary to obtain a microstructure with a grain size that makes it possible to achieve the required level of technological plasticity at a subsequent stage.

When processing workpieces of a particular alloy with a known initial grain size (d _о ) to obtain a microstructure with the required grain size (d _k ), the deformation temperature (T _k ) is determined from the curve d = f (T), which ensures the formation of this grain size, as well as the temperature T ^* . Depending on which temperature section of the curve the temperature T _k is located, a technological processing scheme is selected, namely, in one or several stages. In the latter case, the number and temperature of the steps is determined as follows: the regulated temperature difference is successively added to the temperature T _to until the deformation temperature exceeds or becomes equal to the temperature T ^* .

 The claimed solution uses the value of the true degree of deformation (e), since it is equivalent for various loading schemes and allows you to calculate the required degree of deformation for processes such as upsetting, broaching, extrusion, rolling, torsion. The degree of deformation of at least 0.6 at each stage provides dynamic recrystallization in the entire volume of the workpiece and, therefore, obtaining a homogeneous fine-grained microstructure. In the case of multi-stage deformation, heating at each stage is carried out to a temperature not exceeding the deformation temperature of the previous stage. Otherwise, grain will grow during heating.

 The invention is further developed and clarified using the following techniques.

 - In case of multi-stage deformation, it is advisable to reduce the temperature after each stage by an amount that ensures a decrease in grain size by 2 ... 10 times. It was experimentally established that the temperature difference at the stages should correspond to a difference in the sizes of recrystallized grains by at least two times. Reducing the grain size by less than 2 times is technologically impractical, since the complexity of the processing process increases. If the grain size is reduced by more than 10 times, the plasticity of the material using traditional equipment will be insufficient for the full development of dynamic recrystallization at the next stage of deformation, as a result of which an inhomogeneous microstructure will form. The lower the deformation temperature, the lower the resource of plasticity of the material, therefore, in the lower part of the proposed interval, a decrease in temperature between stages should provide a decrease in grain size by 2 ... 3 times, and at higher temperatures - by 8 ... 10 times.

позволяющее определять степень деформации, достаточную для получения однородной микроструктуры, в зависимости от температуры и размера зерен на этапе.- The inhomogeneity of plastic deformation substantially depends on the temperature and the initial microstructure of the workpiece. It decreases with increasing strain temperature and a decrease in grain size. Therefore, to obtain a homogeneous microstructure with the required grain size at different initial states and strain temperatures during processing, a different degree of deformation is necessary. In this regard, the relation was experimentally established

allowing to determine the degree of deformation sufficient to obtain a homogeneous microstructure, depending on the temperature and grain size at the stage.

 - In the case of using a traditional stamping tool, in particular flat dies, with deformation degrees close to 0.6, stagnation zones can remain in the workpiece, the volume fraction of which increases with decreasing deformation temperature. In addition, the required degree of deformation, determined depending on the temperature and grain size at the stage, can significantly exceed a value of 0.6, which cannot be realized in a single transition with the selected deformation scheme. In this case, during processing, the deformation at the stage is carried out in several transitions, the transition being a deformation at the temperature of the stage. After each transition, it is recommended to change the deformation axis by 45 or 90 degrees in order to destroy the stagnant zones that arose at the previous stages or transitions. The deformation of the workpiece at each transition is performed with a degree of not less than 0.1, but not more than 0.5. At lower degrees of deformation, conditions are not created for the development of dynamic recrystallization processes. The limitation of the upper limit of the degree of deformation is caused by the fact that during the subsequent transition, the workpiece may lose stability after changing the axis of deformation. Using a similar processing scheme allows you to gain the required degree of deformation, work out stagnant zones and obtain a homogeneous structural state without a metallographic texture.

- One of the ways to increase technological plasticity and, as a result, the uniformity of deformation is to reduce the rate of deformation. It is recommended that the deformation during processing be carried out in the speed range 10 ^-4 ... 10 ^-2 s ^-1 . In the indicated speed range, dynamic recrystallization, depending on the initial state, can result in a superplastic flow, which will further increase the uniformity of the microstructure.

 - Titanium alloys have low thermal conductivity and when machining massive workpieces due to deformation heating and insufficient heat removal in its central part, there will be a higher temperature and, consequently, a larger grain will be formed. Therefore, in the claimed solution, the heating temperature, depending on the dimensions of the workpiece, is adjusted downward by multiplying by experimentally established coefficients. In this case, grain size discontinuity is eliminated by heating, during which grains at the periphery of the workpiece are enlarged.

- Titanium alloys with β-transformed grains larger than 2000 microns have low technological ductility at temperatures below T _pp and to increase the uniformity of their microstructure, it is necessary to increase the total degree of deformation using multi-transition at the stage. In addition, for such alloys, the temperature T ^* is close to T _pp . Therefore, before the main processing of the material with a β-transformed grain size of more than 2000 μm, it is advisable to carry out a preliminary deformation. Preliminary deformation can be carried out in various modes: 1) at a temperature above T _PP + (10 ... 50 ^o C); 2) at a temperature of 30 ... 50 ^o C below T _PP , but with a degree of deformation of at least 0.3 and a speed in the range of 10 ^-2 ... 10 ^-1 s ^-1 followed by annealing at a temperature of T _PP + ( 20. ..70 ^o C). This allows you to grind the initial structure and as a result significantly facilitate subsequent processing, as well as significantly expand the temperature range, where the processing is carried out in one step. When choosing the main processing mode, the grain size obtained after preliminary deformation is considered as the initial one. - The increase in the plasticity and uniformity of deformation of two-phase titanium alloys is facilitated by an increase in the dispersion of phase plates, since thinner plates are easier to transform into equiaxed grains. An increase in the dispersion of the plate structure is possible due to heating to a temperature above T _pp and regulated cooling. The use of this technique before the first stage or between stages, or between transitions at the stage of deformation is especially effective in obtaining a microstructure with a grain size of less than one micrometer.

- The implementation before deformation of the preliminary thermocyclic treatment in the range of 500 ^o C ... T _pp leads to some refinement of the microstructure and increase in the grains of the dislocation density as a result of phase hardening and thermal stresses. As a result of this, subsequent deformation facilitates the development of recrystallization and, consequently, the uniformity of the microstructure.

- The main reason for the formation of stagnant zones is significant friction in the contact zone of the workpiece with the stamping tool. Usually, high-temperature lubricants, which are glass enamels, are used to reduce it. However, when they are used, the workpiece sticks to the surface of the tool. This makes it difficult to conduct deformation in several transitions with a change in the axis of deformation. It is recommended to heat the stamping tool 10 ... 50 ^o C above the temperature of the workpiece, which reduces the effect of friction and in turn leads to a decrease in the proportion of stagnant zones.

 - To obtain the shape of the workpiece closest to the shape obtained from this workpiece of semi-finished products, a technique is used, which consists in selecting the sequence of turns of the workpiece during multi-transition deformation at the final stage. So, when receiving the shape of the bar at the final stage of processing, the axis of deformation of the workpiece is rotated between the transitions in one plane, and the number of transitions is chosen at least four.

 - Upon receipt of the workpiece of the desired shape, its shaping is carried out at a temperature not lower than the temperature of the final stage of processing the workpiece. Otherwise, the grain obtained by previous processing will grow. Moreover, the strain rate during shaping can be chosen so as to ensure the implementation of superplastic deformation. This will further improve the uniformity of the microstructure and makes it possible to obtain a high level of mechanical properties after the final heat treatment.

 - In order to reduce the complexity and energy costs, shaping can be carried out according to the local deformation scheme, for example, by rolling.

 The essence of additional methods of the invention, allowing to obtain not limited in size blanks, is as follows.

Since micro- or submicrocrystalline structures without a metallographic texture are much easier and more economically feasible to obtain in small workpieces, the technological possibilities of obtaining such a structure in an unlimited size workpiece are significantly expanded and facilitated if a block of a given size is assembled from small workpieces obtained by the proposed method and undergoing preliminary shaping in accordance with the proposed additional methods of the method, when assembling the unit and ensure their fit without gaps and then carry out the deformation of the block, for example, by sediment, at a speed of 10 ^-5 ... 10 ^-2 s ^-1 with a degree of deformation of at least 0.2 in the temperature range 400 ^o C ... T _pp . In this case, the specific deformation temperature of the block is chosen not lower than the temperature of the formation of blanks with a maximum grain size. This is determined by the need to ensure the state of the superplastic flow during block deformation. The main mechanism of superplastic deformation is grain boundary slippage (CGP), which manifests itself in a turn and shear displacement of neighboring grains relative to each other. The development of CHP in the process of block deformation allows to obtain a solid-phase connection between small workpieces, and with a degree of deformation of 0.2 or more, the block is monolithic, and the interface between the workpieces making up the block completely disappears. This is achieved by eliminating possible discontinuities and pores in the zone of connection of the workpieces by filling them with grains as a result of the development of HRP. A degree of deformation of at least 0.2 is required for a guaranteed transition of superplastic deformation to its steady state stage with the maximum development of the mechanism of grain boundary slippage, which ensures the formation of a high-quality solid-phase compound. The large-sized workpieces thus obtained can be used as initial components to obtain even larger workpieces.

 For a number of large-sized products of critical use, for example, disks for aircraft engines, the requirements for physical, mechanical, or service properties for different sections of the same part differ markedly. One of the methods of manufacturing such products is the assembly of a block of billets from alloys of various chemical compositions, respectively, with different temperatures of the final stage of deformation and, therefore, with different temperatures of forming. The block is deformed at a temperature not lower than the highest of the indicated temperatures.

 In some cases, in the manufacture of large-sized workpieces, it is technologically expedient to install a workpiece between them in the form of a gasket of the same material with a grain size of an order of magnitude smaller than in large workpieces. This makes it possible to obtain large-sized billets at low temperatures, in some cases use only local heating in the zone of formation of the solid-phase compound, and use less powerful equipment. The use of such gaskets provides the localization of superplastic deformation in the zone of formation of a solid-phase compound and accelerates the formation of high-quality compounds. The thickness of the gasket at the same time is selected not less than ten times the size of the grains in the gasket. Otherwise, it is impossible to kinetically realize the development of the HGP mechanism.

 When analyzing the prior art on patent and scientific and technical sources of information regarding methods for processing titanium alloys, a method was not found that is characterized by features identical to all the essential features of the claimed invention. Therefore, the claimed invention meets the condition of "novelty."

 When analyzing the distinguishing features, it was revealed that the claimed invention does not follow explicitly from the prior art. For the first time, a wide temperature range has been proposed for heating and deformation of titanium alloys, in which, accordingly, it is possible to set and obtain the required grain sizes while ensuring uniformity of structure in industrial semi-finished products. However, it is not possible to realize these requirements even in stages with a decrease in temperature, without taking into account the initial microstructure in the workpiece. Therefore, a systematic approach is proposed for selecting a sequence of deformation stages and the temperature of these stages, which allows both the required grain size and the initial state of the workpiece to be taken into account. The listed fundamental features of the invention are new and non-obvious. Therefore, the claimed invention meets the condition of "inventive step".

The invention is illustrated by the following graphic materials:
FIG. 1. Dependence of the size of recrystallized grains on the deformation temperature of the VT8 titanium alloy at a speed of 7 • 10 ^-4 s ^-1 and the degree of deformation e = 0.6. The shading marks the regions for the values of d ^* and T ^* at d _o = 1000 μm.

 FIG. 2. The microstructure of the VT8 titanium alloy in the initial state.

FIG. 3. The microstructure of the titanium alloy VT8 after deformation at 950 ^o C.

FIG. 4. The microstructure of the VT8 titanium alloy after deformation at 650 ^o C.

FIG. 5. Dependence of the size of recrystallized grains on the deformation temperature of technical titanium VT1-00 at a speed of 3 • 10 ^-4 s ^-1 and the degree of deformation e = 0.6. The shading marks the regions for d and T at d _o = 200 μm.

 FIG. 6. The microstructure of technical titanium VT1-00 in the initial state.

FIG. 7. The microstructure of technical titanium VT1-00 after deformation at 670 ^o C.

FIG. 8 Microstructure of technical titanium VT1-00 after deformation at 400 ^o C.

FIG. 9. Dependence of the size of recrystallized grains on the deformation temperature of the VT30 titanium alloy at a speed of 3 • 10 ^-4 s ^-1 and the degree of deformation e = 0.6. The shading marks the regions for the values of d ^* and T ^* at d _о = 200 μm.

 FIG. 10. The microstructure of the titanium alloy VT30 in the initial state.

FIG. 11. The microstructure of the titanium alloy VT30 after deformation at 740 ^o C.

FIG. 12. The microstructure of the titanium alloy VT30 after deformation at 550 ^o C.

 The possibility of carrying out the invention is illustrated by examples. Three alloys were processed, the chemical composition and grade of which are given in the table (see the end of the description).

 Example 1

We cut out samples of size ⌀ 10 × 15 mm from alloy A, which are then deformed with a draft on an Instron universal dynamometer at different temperatures from the interval 400 ... 1000 ^o C to the degree of deformation e = 0.6. In this case, the temperature of 1000 ^o C corresponds to T _PP alloy. The size of the recrystallized grains is determined in the central part of the deformed sample. In FIG. Figure 1 shows the dependence of grain size on the temperature of deformation of the alloy.

Alloy A in the form of cylindrical billets with a size of ⌀150 × 300 mm in the initial state has an average size β of transformed grains of 1000 μm (Fig. 2). After processing, it is required to obtain a microstructure with an average grain size d _k = 5 μm. According to the curve d = f (T) of FIG. 1. such a grain size is formed at a temperature T _k = 950 ^o C. Using the relation log (d _о / d ^* ) = 2.4 ... 2.6, we determine that d ^* = 2.5. ..4 μm, then from the dependence d = f (T) we determine the corresponding temperature T ^* = 860 ... 920 ^o C. The temperature T ^* divides the interval 400 ... 1000 ^o C into two sections. Since the temperature T _k to obtain the desired grain size is greater than T ^* , the alloy is processed in the first temperature range in one step.

где d_n= 1000 мкм, T_n ≈ 1220 К, T_пл ≈ 1970 К, а = 1, определяем, что необходимая степень деформации e должна быть не меньше 2,45. Для набора данной величины e используем схему деформации, состоящую из следующих переходов:
- осадка заготовки по высоте на e=0,45;
- поворот заготовки на 90^o и осадка по образующей на e=0,4;
- поворот заготовки на 90^o таким образом, чтобы направление приложения усилия (ось деформирования) совпадало с направлением максимального размера заготовки после предыдущей осадки, и осадка заготовки на e=0,45;
- поворот заготовки на 90^o таким образом, чтобы ось деформирования осталась в той же плоскости, в которой находилась ось деформирования предыдущей осадки, и осадка на e=0,3;
- шесть переходов с осадкой на e=0,25 и поворотом заготовки на 45^o после каждого перехода таким образом, чтобы ось деформирования оставалась в одной плоскости.The volume of the workpiece with a size of ⌀150 × 300 mm does not exceed 10 dm ³ , therefore, taking into account the correction factor 0.97, the heating temperature is 925 ^o C. The billet is placed in a KS-500 electrical resistance furnace, and the heating time is determined from the condition that for one a minute warms up 1 mm of the diameter of the workpiece and it is at least 150 minutes. We stand the billet in the furnace and transfer it to an isothermal die block, in which the flat strikers from the heat-resistant alloy ZhS6-U are heated to a temperature of 950 ^o C by a low-frequency inductor. The deformation of the workpiece at the stage is performed at an average speed of 7 • 10 ^-4 s ^-1 . Given the ratio

where d _n = 1000 μm, T _n ≈ 1220 K, T _pl ≈ 1970 K, a = 1, we determine that the required degree of deformation e must be at least 2.45. To set this quantity e, we use a deformation scheme consisting of the following transitions:
- draft of the workpiece in height at e = 0.45;
- rotation of the workpiece by 90 ^o and sediment along the generatrix at e = 0.4;
- rotation of the workpiece by 90 ^o so that the direction of application of the force (the axis of deformation) coincides with the direction of the maximum size of the workpiece after the previous draft, and the draft of the workpiece by e = 0.45;
- rotation of the workpiece by 90 ^o so that the axis of deformation remains in the same plane as the axis of deformation of the previous draft, and the draft by e = 0.3;
- six transitions with a draft at e = 0.25 and rotation of the workpiece by 45 ^o after each transition so that the axis of deformation remains in the same plane.

Then, the final shaping of the workpiece onto a bar of the required diameter is carried out by drawing the workpiece at a temperature of 925 ^° C. The microstructure of the manufactured bar is shown in FIG. 3.

 Example 2

A blank of size ⌀50 × 100 mm from alloy A with an initial β-transformed grain size of 2000 μm must be processed so as to obtain a microstructure with an average grain size d _k = 0.2 μm. We determine that T _k = 650 ^o C, d ^* = 5 ... 8 μm and T ^* = 950 ... 990 ^o C Since the temperature T _{k is} less than T ^* , the alloy is processed in several stages, the number of which choose as follows. The grain size before the final stage is three times larger than the required one, i.e. 0.6 microns. A grain size of 0.6 μm along the curve of FIG. 1 corresponds to a temperature of 730 ^o C, which does not exceed T ^* , then another step is necessary. At the next stage, in comparison with the previous one, we take the grain size 10 times larger, and it will be 6 microns. The grain size of 6 μm corresponds to a temperature of 975 ^o C, which is already in the range T ^* ... T _PP , therefore, this step will be the first. Thus, the temperatures of the first, second and third stages are respectively equal to 975, 730 and 650 ^o C. The required degrees of deformation at each stage, determined taking into account the deformation temperature of the stage and the initial grain size before the beginning of each stage, are e ₁ ± 2.45 , e ₂ ≥ 1.5, e ₃ ≥ 1.1.

Before processing the alloy, we carry out thermocyclic processing, which consists in five-fold heating to 1000 ^o C and cooling to 500 ^o C. Deformation of the workpiece at each stage is carried out in several transitions as in example 1.

 At the final stage of processing the workpiece we give the shape of a bar having in cross section either an equilateral triangle, or a square, or an equilateral hexagon. The microstructure of the alloy after processing is shown in FIG. 4.

 Example 3

A billet of alloy A with a size of ⌀200 × 400 mm with an initial size of β-transformed grains of 10,000 μm must be processed so as to obtain a blank of a disk having a microstructure with an average grain size of 3 μm. In this case, it is advisable to preliminarily grind the initial structure by conducting deformation in the β-region. To do this, we heat the workpiece to a temperature of T _PP +100 ^o C (1100 ^o C) and deform on flat strikers according to the draft scheme at e = 0.5 and the subsequent broaching to the original height. In this case, the temperature of the workpiece should not fall below T _pp +10 ^o C (1010 ^o C), otherwise carry out intermediate heating. As a result of this operation, the β-transformed grain was ground to 1000 μm and this grain size is used to determine the temperature T ^* , which, as in Example 1, corresponds to 860 ... 920 ^o C. The temperature T _k for obtaining 3 μm grains is determined from the dependence in FIG. 1, it is 880 ^o C and is in the range T ^* ... T _pp , therefore, the processing of the alloy is carried out in one step. Analogously to example 1, we determine the heating temperature of the workpiece, the required degree of deformation, and according to the same scheme we carry out the deformation. However, unlike example 1, the die tool is heated to a temperature of 900 ^o C. After the preparation of the structure to the workpiece, we give the shape of a washer with a diameter of 350 mm, and we obtain the final shape of the disk by rolling under conditions of superplasticity.

 Example 4

In a billet of alloy A 100 × 100 × 200 mm in size with an initial β-transformed grain size of 5000 μm, it is required to obtain a microstructure with an average grain size of 2 μm. In this case, it is also advisable to grind the initial structure. To do this, we heat the workpiece to a temperature of T _PP -40 ^o C (960 ^o C) and upset on flat strikers in height at e = 0.25 at a speed of 10 ^-2 s ^-1 , then draw it back to its original shape and heat to a temperature T _pp + 20 ^o C (1020 ^o C). After this treatment, the size of β-transformed grains decreases to 500 μm, and this grain size is then used to determine the temperature T ^* . In this case, it is 780 ... 830 ^o C. The temperature T _k , which ensures the formation of grains of 2 μm in size, is determined from the curve in FIG. 1, it is 830 ^o C. This temperature is in the range T ^* . ..T _pp , therefore, the preparation of the required microstructure is carried out in one step. The heating temperature and the required degree of deformation are determined in the same way as in example 1. Deformation is carried out at an average rate of 10 ⁻³ s ⁻¹ for 6 transitions with the workpiece rotated after each transition by 90 ^° so that the sediment is carried out according to the maximum size of the workpiece. The degree of deformation at each transition will be e = 0.4.

If you need to obtain a workpiece in the form of a bar having a cross section in the form of a square or equilateral triangle and hexagon, we carry out the final shaping of the workpiece in superplastic conditions at a temperature of 830 ^o C
Example 5

In a blank of alloy A with a size of 100x100x200 mm with an initial size of β-transformed grains of 5000 μm, it is required to obtain a microstructure with an average grain size of 1.2 μm. In this case, it is also advisable to grind the initial structure. To do this, we heat the billet to a temperature of T _PP -40 ^o C (960 ^o C) and upset on flat strikers in height at e = 0.25 at a speed of 10 ^-2 s ^-1 , then draw it back to its original shape. Next, heat to a temperature T _pp + 20 ^o C (1020 ^o C) and cool in water to room temperature. After this treatment, the size of β-transformed grains decreases to 500 μm and this grain size is used to determine the temperature T ^* , which is 780 ... 830 ^o C. The temperature T _k , which provides the formation of grain with a size of 1.2 μm, is determined from the dependence d = f (T) for alloy A (Fig. 1), it is 790 ^o C. This temperature is in the range T ^* ... T _pp , therefore, the preparation of the required microstructure is carried out in one step. The heating temperature and the required degree of deformation are determined similarly as in example 1. Deformation is carried out at an average rate of 10 ^-3 s ^-1 for 6 transitions with the workpiece rotated after each transition by 90 ^o so that the sediment is carried out at the maximum size of the workpiece. The degree of deformation at each transition will be e = 0.40.

 Example 6

We cut out samples of ⌀10 × 15 mm size from alloy B, which we deform with a draft on an Instron universal dynamometer in the temperature range 400. ... 900 ^o C to a degree of deformation e = 0.6. In this case, the temperature of 900 ^o C corresponds to T _PP alloy. The size of the recrystallized grains is determined in the central part of the deformed sample. In FIG. Figure 5 shows the dependence of the size of recrystallized grains on the deformation temperature of the alloy.

In the alloy B preform with a size of ⌀50 × 100 mm and an initial grain size of 200 μm (Fig. 6), it is required to obtain a microstructure with an average grain size of 5 μm. We determine the temperatures T _k and T ^* , the values of which are respectively 700 ^o C and 520. ..550 ^o C. Since the temperature T _k exceeds T ^* , the workpiece is processed in one step. The choice of the degree of deformation, heating temperature and the deformation scheme is also performed as shown in example 1.

 At the final shaping we get a blank in the form of a square box with a side of a square of 55 mm. The microstructure of the alloy after processing is shown in FIG. 7.

 Example 7

In the alloy B preform with a size of ⌀50 × 100 mm and an initial grain size of 200 μm (Fig. 6), it is necessary to obtain a microstructure with an average grain size of 0.1 μm. We determine the temperatures T _k and T ^* , the values of which are respectively 400 ^o C and 520..550 ^o C. Since the temperature T _{k is} lower than the temperature T ^* , the workpiece is processed in several stages, the amount of which is determined as follows. The grain size before the final stage is chosen to be twice as large as required, i.e. 0.2 microns. A grain size of 0.2 μm from the curve in FIG. 5 corresponds to a temperature of 450 ^o C, which does not exceed T ^* , then another step is necessary. At the next stage, in comparison with the previous one, we take the grain size also 2 times larger, and it will be 0.4 μm. The grain size of 0.4 μm corresponds to a temperature of 500 ^o C, which also does not exceed T ^* , therefore, another step is necessary again. The grain size preceding this stage is chosen 10 times larger, i.e. 4 μm, and it corresponds to a temperature of 670 ^o C, which falls on the plot T ^* ... T _PP .

Thus, the processing of the workpiece is carried out in four stages and the temperatures of the stages are 670, 500, 450 and 400 ^o C. The degree of deformation at each stage is determined taking into account the deformation temperature of the stage and the initial grain size before each stage. The deformation of the workpiece at each stage is carried out in several transitions similarly to example 1.

 At the final shaping we get a blank in the form of a bar having a cross section of a square or equilateral triangle and hexagon. The microstructure of the alloy after processing is shown in FIG. eight.

 Example 8

We cut out samples of size ⌀10 × 15 mm from alloy C, which we deform with a draft on an Instron universal dynamometer in the temperature range of 400.. .740 ^o C to the degree of deformation e = 0,6. In this case, the temperature of 740 ^o C corresponds to T _PP alloy. The size of the recrystallized grains is determined in the central part of the deformed sample. FIG. Figure 9 shows the dependence of grain size on the strain temperature of the alloy.

In the blank of alloy C with a size of ⌀50 × 100 mm and an initial grain size of 200 μm (Fig. 10), it is necessary to obtain a microstructure with an average grain size of 5 μm / We determine the temperatures T _k and T ^* , the values of which are respectively 740 ^o C and 710 .. .725 ^o C. The temperature T _k exceeds T ^* and is equal to T _pp , the workpiece is processed in one step at a temperature of 740 ^o C. The choice of the degree of deformation, heating temperature and the deformation scheme is carried out similarly to that shown in example 1 Microstructure of the alloy after processing presented in FIG. eleven.

 Example 9

In the alloy C preform with a size of ×50 × 100 mm and an initial grain size of 200 μm (Fig. 10), it is necessary to obtain a microstructure with an average grain size of 0.3 μm. We determine the temperatures T _k and T ^* , the values of which are respectively equal to 550 ^o C and 710 ... 725 ^o C. Since the temperature T _{k is} less than T ^* , the workpiece is processed in several stages. At the penultimate stage, the grain size is chosen 2 times larger than the required (0.6 μm). From the dependence d = f (T) for alloy C (Fig. 9), the grain size of 0.6 μm corresponds to a temperature of 645 ^o C. In the next step, we select the grain size 5 times larger (3 μm) of the previous one, it corresponds to a temperature of 730 ^o C , which is between T ^* and T _pp and, therefore, this step will be the first in the processing of the alloy. The choice of the degree of deformation, the heating temperature and the deformation scheme at each transition is performed as in example 1. In this case, after the first stage of deformation, the workpiece is cooled to room temperature in water. The microstructure of the alloy after processing is shown in FIG. 12.

 Example 10

In a C alloy billet with a size of ⌀50 × 100 mm and an initial grain size of 40 μm, it is necessary to obtain a microstructure with an average grain size of 0.5 μm. We determine the temperatures T _k and T ^* , whose values are respectively 625 ^o C and 600 ... 645 ^o C. Since the temperature T _k is in the range T ^* ... T _pp , we process the workpiece in one step. Before the main processing, the workpiece is heated to a temperature of 760 ^o C and cooled to room temperature in water. The choice of the degree of deformation, heating temperature and the deformation scheme is performed as in example 1.

 Example 11

In an alloy A preform of size ⌀200 × 400 mm with a β-transformed grain size of 2000 μm, it is necessary to obtain a microstructure with an average grain size of 5 μm. From the curve in FIG. 1 we determine the temperatures T _k and T ^* , whose values are respectively 950 ^o C and 950 ... 990 ^o C. Since the temperature T _k is in the range T ^* ... T _pp , processing is carried out in one step. We determine that the required degree of deformation e must be at least 2.7. To set this value of e, we use the following deformation scheme:
- heating the workpiece to a temperature of 950 ^o C, deformation of the workpiece in height by e = 0.25, followed by cooling to room temperature in water,
- heating the preform to a temperature of 950 ^o C, deformation of the preform along the generatrix for five transitions with a degree of deformation at the transition e = 0.25 and rotation of the preform between transitions by 90 ^o with subsequent cooling to room temperature in water,
- repeat the two previous paragraphs.

 At the final shaping we get a bar with a diameter of 100 mm.

 Example 12

From a bar заготов20 mm of alloy B with a submicrocrystalline microstructure with an average grain size of 0.1 μm, cylindrical workpieces with a height of 40 mm are cut. The billets are heated in an electric furnace with a protective argon atmosphere to a temperature of 400 ^o C and precipitated with an average deformation rate of 5 • 10 ^-4 s ^-1 to a height of 10 mm using a hydraulic 100-ton press on a flat head, heated by an inductor to 400 ^o C. Get the workpiece type washers with a diameter of about 40 mm The grain size in the washers is kept equal to 0.1 μm. The washers are machined mechanically to a diameter of 38 mm, the lower and upper planes are ground to ensure their parallelism, and at least 0.5 mm of the metal thickness is removed from each side. During machining operations, the heating temperature of the surface of the processed washer should not exceed 50 ^o C. Surfaces after grinding are washed, dried and degreased. Then, from nine blanks with a diameter of 38 mm and a height of 9 mm, installing them coaxially one on top of the other, a block is assembled in the form of a cylinder with a diameter of 38 mm and a height of 81 mm. To fix the assembled block and protect the internal contacting surfaces of the workpieces from oxidation, laser welding is performed along the annular line of the junction of the workpieces to a depth of not more than 0.3 mm.

Next, the block of preforms is heated in an electric furnace with a protective argon atmosphere to a temperature of 400 ^o C and precipitated with an average deformation rate of 5 • 10 ^-4 s ^-1 to a height of 10 mm on flat strikers heated by an inductor to 400 ^o C. Receive a preform with a diameter of about 108 mm and a height of 10 mm with a grain size of 0.1 μm throughout the volume and with the absence of pores in the zones of the solid-phase compound.

 Similarly, continuing the process further, it is possible to obtain a blank of the type of a disk or washer with a submicrocrystalline microstructure of almost any size required for the current level of industrial development using the heating and pressing equipment available in the industry.

 Example 13

Cylindrical billets with a height of 60 mm are cut from a мкм30 mm rod of alloy A with an average grain size of 0.4 μm. The preforms are heated in an electric furnace with a protective argon atmosphere to a temperature of 700 ^o C and precipitated with an average deformation rate of 5 • 10 ^-4 s ^-1 to a height of 10 mm on flat strikers heated by an inductor to 700 ^o C. Receive washers such as washers with a diameter of about 74 mm and a height of 10 mm. The grain size in the washers is kept equal to 0.4 μm. The washers are machined mechanically to a diameter of 72 mm, the lower and upper planes are ground to ensure their parallelism, and at least 0.5 mm of the metal thickness is removed from each side. During machining operations, the heating temperature of the surface of the washer should not exceed 50 ^o C. Surfaces after grinding are washed, dried and degreased. From 16 blanks with a diameter of 72 mm and a height of 9 mm, coaxially mounting one on top of another, a block is assembled in the form of a cylinder with a diameter of 72 mm and a height of 144 mm. To fix the assembled unit and protect the internal contacting surfaces of the workpieces from oxidation, laser welding is performed along the annular line of the joint of the workpieces to a depth of not more than 0.3 mm.

Next, the block of preforms is heated in an electric furnace with a protective argon atmosphere to a temperature of 700 ^o C and precipitated with an average deformation rate of 5 • 10 ^-4 s ^-1 to a height of 20 mm on flat strikers heated by an inductor to 700 ^o C. Thus, a preform with a diameter of about 192 mm and a height of 20 mm. In this case, the grain size remains equal to 0.4 μm over the entire volume of the preform; pores in the zones of the solid-phase compound are not metallographically detected.

 Similarly, continuing the process, it is possible to obtain a blank like a disk or washer with a submicrocrystalline structure of almost any size required for the existing level of industrial development, using the heating and press equipment available in the industry.

 Example 14

Cylindrical billets with a height of 100 mm are cut from a ⌀50 mm rod of alloy C with an average grain size of 2 μm. The billets are heated in an electric furnace with a protective argon atmosphere to a temperature of 700 ^o C and precipitated with an average deformation rate of 5 • 10 ^-4 s ^-1 to a height of 10 mm on flat strikers heated by an inductor to 700 ^o C. Receive billets with a diameter of about 158 mm and 10 mm high. The grain size in the washers is kept equal to 2 μm. The washers are machined mechanically to a diameter of 156 mm, the lower and upper planes are ground to ensure their parallelism, and at least 0.5 mm of the metal thickness is removed from each side. During machining operations, the heating temperature of the treated surface should not exceed 50 ^o C. The surfaces after grinding are thoroughly washed, dried and degreased.

From 34 blanks with a diameter of 156 mm and a height of 9 mm, coaxially mounting one on the other, a block is assembled in the form of a cylinder with a diameter of 156 mm and a height of 306 mm. The assembly is carried out directly on the lower flat head mounted on a 1600-ton hydraulic press. After assembly, the block is pulled together by lowering the upper flat striker. The compression force does not exceed 10 tons. The inductors heat the strikers together with the block of preforms in an argon atmosphere to a temperature of 700 ^o C and then precipitate with an average strain rate of 5 • 10 ^-4 s ^-1 to a height of 30 mm. To reduce the coefficient of friction and to prevent sticking, the working surfaces of the flat dies from the ZhS6-U alloy are preliminarily coated with a thin layer of boron nitride. Thus, a blank of the disk type is obtained with a diameter of about 498 mm and a height of 30 mm. The grain size in the obtained preform remains equal to 2 μm throughout the volume, pores in the zones of the solid-phase compound are not detected metallographically.

 Similarly, continuing the process, it is possible to obtain a blank type of a disk with a regulated structure of almost any size required for the current level of industrial development, using the heating and press equipment available in the industry.

 Example 15

From a bar ⌀20 mm of alloy A with a submicrocrystalline microstructure with an average grain size of 0.2 μm, a blank of the type of a disk with a diameter of 300 mm and a height of 50 mm is made similarly to the above examples. In this case, the deformation temperature is 650 ^o C. By the mechanical, anodic-mechanical or electrospark method, a central cylindrical part is cut from this disk and an annular blank is obtained with an outer diameter of 300 mm and an inner diameter of 100 mm.

From a bar ⌀20 mm of alloy C with an average grain size of 0.5 μm, a cylindrical billet with a diameter of 100 mm in the minus tolerance of 0.15 mm and a height of 50 mm is also made, similarly to the examples above, with a deformation temperature of 650 ^o C. From the ring billet of the alloy A and a cylindrical billet of alloy C assemble a block in the form of a disk with a diameter of 300 mm and a height of 50 mm by installing a cylindrical billet in the center of the ring. Before assembling the block, the flat surfaces of the workpieces are ground, not allowing heating above 50 ^o C. The surfaces after grinding are washed, dried and degreased. To protect the internal contacting surfaces of the workpieces from oxidation after assembly of the block, laser welding is performed along the outer ring line of the joint on both planes of the assembled block to a depth of not more than 0.5 mm.

The block of blanks is then mounted on the lower flat striker of a 1600-ton hydraulic press. Press it by lowering the upper flat striker. The compression force does not exceed 10 tons. The inductor is used to heat the strikers together with the block of preforms in an argon atmosphere to a temperature of 650 ^o C and precipitate with an average deformation rate of 5 • 10 ^-4 s ^-1 to a height of 25 mm. To reduce the coefficient of friction and protect against sticking, the working surfaces of the strikers are pre-coated with a thin layer of boron nitride. In this way, a monolithic semi-finished disk with a diameter of 424 mm and a height of 25 mm is obtained, the central part of which is represented by alloy C with a grain size of 0.5 μm, and the rim - alloy A with grain size of 0.2 μm.

 Example 16

According to the above examples, cylindrical washers with a diameter of 350 mm and a height of 70 mm with a grain size of 3 μm are made of alloy A by superplastic deformation at a temperature of 900 ^° C. From a bar ⌀20 mm of the same alloy having a grain size of 0.2 μm, superplastic deformation at 650 ^o C, then by upsetting and rolling, machining, sheet blanks with a diameter of 350 mm, 1 mm thick are made.

Next, between each cylindrical washer coaxially mounted on top of one another, a sheet blank is laid. In this way, a block is assembled in the form of a cylinder with a diameter of 350 mm and a height of 354 mm. Before assembling the block, the flat surfaces of the workpieces are ground, not allowing heating above 50 ^o C. The surfaces after grinding are washed, dried and degreased. The assembly is carried out directly on the lower flat head mounted on a 1600-ton hydraulic press. After assembly, the block is pulled together by lowering the upper flat striker. The compression force does not exceed 10 tons. The inductors heat the strikers together with the block of preforms in an argon atmosphere to a temperature of 650 ^o C and precipitate to a height of 351 mm, providing an average deformation rate in strips of sheet preforms of 5 • 10 ^-4 s ^-1 . To reduce the coefficient of friction and protect against sticking, the working surfaces of the strikers are pre-coated with a thin layer of boron nitride. Thus, a monolithic cylindrical billet with a diameter of 350 mm and a height of 351 mm is obtained.

Using two such blanks and installing between them once again a gasket from a sheet blank, in the same way, after upsetting by 0.8 mm, a monolithic cylindrical blank of double length is obtained. In this case, local heating by the inductor of only the block of blanks is used without mandatory heating of the strikers. To eliminate the heterogeneity caused by the presence of submicrocrystalline grains from the sheet gaskets, the preform is annealed at a temperature of 900 ^o C. After this treatment, the resulting bar stock with a diameter of 350 mm has a uniform microcrystalline structure with a grain size of 3 μm.

Claims (42)

1. A method of processing titanium alloys with a β-stabilization coefficient Kβ <1.4, including heating the initial billet and its deformation in a heated tool, characterized in that the deformation is carried out at 400 ^o C ... T _pp , where T _pp is the temperature of the full polymorphic transformation, the number of stages of deformation and the temperature is set, based on the grain size in the original preform d _o, the desired final grain size d _{to the} last and corresponding _{to the} temperature T, as follows: the experimentally determined dependence of the size of rivers istallizovannyh grains temperature deformation d = f (T) in the specified temperature range, the latter is divided into two portions, the boundary between which is set at the temperature T ^* corresponding grain size d ^*, determined from lg ratio (d _o / d ^*) = 2 , 4 - 2.6, and if the deformation temperature T _k is in the range (T ^* ... T _pp ), the deformation is carried out in one step, if in the interval (400 ^o C ... T ^* ), in a few stages. 2. The method according to claim 1, characterized in that when the deformation is carried out in several stages, the number and temperature of the steps is determined by successively adding to the temperature T _to the temperature difference between the steps, determined by the curve d = f (T) as a value that provides a decrease in size grains in stages 2 to 10 times until the deformation temperature exceeds or becomes equal to T ^* , and the deformation in the stage is carried out with a degree of at least 0.6, and the heating in the next step is carried out to a temperature not exceeding the deformation temperature previous stage. 3. The method according to claim 2, characterized in that at least after the first stage of deformation, the workpiece is cooled to room temperature at a speed of 5 ... 100 ^o C / s. 4. The method according to claim 2, characterized in that the deformation inside the stage is carried out with a total degree of deformation

where d _n is the grain size before the beginning of the nth stage;
T _PL - the melting temperature of the workpiece material in degrees Kelvin;
T _n is the temperature of the n-th stage in degrees Kelvin;
a is a coefficient taking values: a = 1 for d _n ≥ 10 μm, a = 1.5 for 1 μm ≤ d _n <10 μm, and = 2 at 0.5 μm ≤ d _n <1 μm, a = 3 with d _n <0.5 μm.  5. The method according to claim 1 or 2, characterized in that the deformation at the stage is carried out in several transitions at the temperature of the stage. 6. The method according to claim 5, characterized in that at least between the first and second transitions, the workpiece is cooled to room temperature at a rate of 5-100 ^o C / s. 7. The method according to claim 5, characterized in that after each transition, the deformation axes are rotated by 45 - 90 ^° .  8. The method according to claim 7, characterized in that the number of transitions at the final stage is chosen at least four, while the rotation of the axis of deformation is carried out in one plane. 9. The method according to claim 1, characterized in that the deformation is carried out in the range of speeds 10 ^-4 - 10 ^-2 s ^-1 . 10. The method according to claim 1, characterized in that the deformation temperature is adjusted taking into account the volume of the semi-finished product by multiplying by a coefficient assuming a value of 0.98 for a volume of up to 1 dm ³ , 0.97 for a volume of 1 to 10 dm ³ and 0.95 for a volume of more than 10 dm ³ . 11. The method according to claim 2, characterized in that the preform with a β-transformed grain size of more than 2000 μm before the first stage is subjected to preliminary deformation at a temperature above T _PP + (10 ... 50 ^o C) and when choosing the main processing mode for The initial is considered to be the obtained grain size. 12. The method according to claim 2, characterized in that the preform with a β-transformed grain size of more than 2000 μm before the first stage is subjected to preliminary deformation with a degree of not less than 0.3 and a speed in the range of 10 ^-2 - 10 ^-3 s ^-1 at the strain temperature T _PP - (30 ... 50 ^o C) and subsequent heating to a temperature T _PP + (20 ... 70 ^o C) and when choosing the main processing mode, the obtained grain size is considered as the initial one. 13. The method according to any one of claims 1, 2, 11 and 12, characterized in that the preform is heated immediately before deformation to a temperature T _pp - (20 ... 70 ^o C) and cooled to room temperature at a speed of 5 ... 100 ^o C / s. 14. The method according to claim 1, characterized in that before deformation, thermocyclic treatment is carried out in the temperature range 500 ... T _pp with the number of cycles 1 to 5. 15. The method according to claim 1, characterized in that the deformation of the workpiece is carried out in a stamping tool heated to 10 ... 50 ^o With above the heating temperature of the wrought alloy.  16. The method according to claim 1 or 2, characterized in that they carry out the shaping of the semi-finished product of a given shape from the workpiece at a temperature not lower than the temperature of the final stage of deformation of the workpiece.  17. The method according to clause 16, characterized in that the deformation for shaping is carried out in a state of superplasticity.  18. The method according to clause 16 or 17, characterized in that the deformation is carried out using a local deformation scheme. 19. The method according to claim 2, characterized in that the block is assembled from blanks, during assembly of the block they are secured without gaps and the block is upset at a speed of 10 ^-5 ... 10 ^-2 with a degree of deformation of at least 0.2 in temperature the range of 400 ^o C. ..T _PP , while the temperature of the precipitate is chosen not lower than the temperature of the final stage of deformation of the workpiece with a maximum grain size.  20. The method according to p. 19, characterized in that the assembled block of billets from alloys with different chemical compositions and, correspondingly, with different temperatures of the final stage of deformation of the billets, while the temperature of the settlement of the block is chosen not lower than the highest of these temperatures. 21. The method according to claim 2, characterized in that the assembly of at least two blanks is assembled, a blank is installed between them in the form of a gasket of the same material with a grain size (d) of an order of magnitude smaller than in the blanks, and the thickness of the gasket is selected at least 10 d and carry out the settlement of the block at a speed of 10 ^-5 ... 10 ^-2 with a degree of deformation of at least 0.2 in the temperature range of 400 ^o C ... T _pp , while the temperature of the precipitation is chosen not lower than the temperature of the final stage of deformation at which the grain size of the gasket is obtained. 22. A method for processing titanium alloys with a β-stabilization coefficient Kβ ≥ 1.4, including heating the initial billet and its deformation in a heated tool, characterized in that the deformation is carried out at 400 ^o С ... T _pp , where T _pp is the temperature of the full polymorphic transformation, the number of stages of deformation and the temperature is set, based on the grain size in the original preform _of d, the required final grain size d _{to the} last and corresponding _{to the} temperature T, as follows: the experimentally determined dependence of the size p crystallized grains of deformation temperature d = f (T) in the specified temperature range, the latter is divided into two portions, the boundary between which is set at the temperature T ^* corresponding grain size d ^*, determined from the ratio of ^{_{lg (d o / d *)}} = 1 , 8 ... 2, and if the deformation temperature T _k is in the range (T ^* T _pp ), the deformation is carried out in one step, if in the range (400 ^o C ... T ^* ), in several stages. 23. The method according to p. 22, characterized in that when the deformation is carried out in several stages, the number and temperature of the steps is determined by successively adding to the temperature T _to the temperature difference between the steps, determined by the curve d = f (T) as a value that provides a decrease in grain sizes at stages 2 to 10 times, until the deformation temperature exceeds or becomes equal to T ^* , moreover, the deformation at the stage is carried out with a degree of e not less than 0.6, and the heating at the next stage is carried out to a temperature not exceeding the deformation temperature The previous phase. 24. The method according to item 23, wherein at least after the first stage of deformation, the workpiece is cooled to room temperature at a speed of 5 ... 100 ^o C / s. 25. The method according to item 23, wherein the deformation inside the stage is carried out with a total degree of deformation

where d _n is the grain size before the beginning of the nth stage;
T _n is the temperature of the n-th stage in degrees Kelvin;
T _PL - the melting temperature of the workpiece material in degrees Kelvin;
a is a coefficient taking values: a = 1 for d _n ≥ 10 μm, a = 1.5 for 1 μm ≤ d _n <10 μm, and = 2 at 0.5 μm ≤ d _n <1 μm, a = 3 with d _n <0.5 μm.  26. The method according to p. 22 or 23, characterized in that the deformation at the stage is carried out in several transitions at the temperature of the stage. 27. The method according to p. 26, characterized in that at least between the first and second transitions, the workpiece is cooled to room temperature at a speed of 5 ... 100 ^o C / s. 28. The method according to p. 26, characterized in that after each transition, the axis of deformation is rotated by 45 - 90 ^o .  29. The method according to p. 28, characterized in that the number of transitions at the final stage is chosen at least four, while the rotation of the axis of deformation is carried out in one plane. 30. The method according to item 22, wherein the deformation is carried out in the range of speeds 10 ^-4 - 10 ^-2 s ^-1 . 31. The method according to item 22, wherein the strain temperature is adjusted taking into account the volume of the semi-finished product by multiplying by a coefficient assuming a value of 0.98 for a volume of up to 1 dm ³ , 0.97 for a volume of 1 to 10 dm ³ and 0.95 for a volume of more than 10 dm ³ . 32. The method according to item 23, wherein the preform with a β-transformed grain size of more than 2000 μm before the first stage is subjected to preliminary deformation at a temperature above T _PP + (10 ... 50 ^o C) and when choosing the main processing mode for The initial is considered to be the obtained grain size. 33. The method according to item 23, wherein the preform with a β-transformed grain size of more than 2000 μm before the first stage is subjected to preliminary deformation with a degree of not less than 0.3 and a speed in the range of 10 ^-2 - 10 ³ s ^-1 at a temperature deformation T _PP - (30 ... 50 ^o C) and subsequent heating to a temperature T _PP + (20 ... 70 ^o C) and when choosing the main processing mode, the obtained grain size is considered as the initial one. 34. The method according to any one of paragraphs.22, 23, 32 and 33, characterized in that the preform is heated immediately before deformation to a temperature T _pp + (20 ... 70 ^° C) and cooled to room temperature at a speed of 5 ... 100 ^o C / s. 35. The method according to p. 22, characterized in that before deformation, thermocyclic treatment is carried out in the temperature range 500 ... T _pp with the number of cycles 1 to 5. 36. The method according to p. 22, characterized in that the deformation of the workpiece is carried out in a stamping tool heated to 10 ... 50 ^o With above the heating temperature of the wrought alloy.  37. The method according to item 22 or 23, characterized in that they carry out the shaping of the semi-finished product of a given shape from the workpiece at a temperature not lower than the temperature of the final stage of deformation of the workpiece.  38. The method according to clause 37, wherein the deformation for shaping is carried out in a state of superplasticity.  39. The method according to clause 37 or 38, characterized in that the deformation is carried out using a local deformation scheme. 40. The method according to item 23, wherein the block is assembled from blanks, during assembly of the block they are secured without gaps and the block is upset at a speed of 10 ^-5 ... 10 ^-2 with a degree of deformation of at least 0.2 in temperature the range of 400 ^o C. ..T _PP , while the temperature of the precipitate is chosen not lower than the temperature of the final stage of deformation of the workpiece with a maximum grain size.  41. The method according to p. 40, characterized in that the assembled block of billets from alloys with different chemical composition and, accordingly, with different temperatures of the final stage of deformation of the billets, while the temperature of the block precipitation is chosen not lower than the highest of these temperatures. 42. The method according to item 23, wherein the block is assembled from at least two blanks, a blank is installed between them in the form of a gasket of the same material with a grain size (d) of an order of magnitude smaller than in the blanks, and the thickness of the gasket is selected not less than 10 d and carry out the settlement of the block at a speed of 10 ^-5 . . . 10 ^-2 with a degree of deformation of at least 0.2 in the temperature range of 400 ^o C ... T _PP , while the temperature of the precipitation is chosen not lower than the temperature of the final stage of deformation, at which the grain size of the gasket is obtained.

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