Method for production of strained feed from titanium-based alloy and product made from the same

FIELD: metallurgy, in particular feed from titanium-based alloy for aircraft industry and engineering.

SUBSTANCE: claimed method includes feed heating, deformation thereof in die, heated to temperature of total titanium-based alloy polymorphous conversion or above: isothermal holding at die temperature for time effective to total titanium-based alloy recrystallization; and quench. Feed is heated up to temperature by 10-30oC lower than the same of total polymorphous conversion; deformation is carried out in two steps: in the first one deformation rate is sufficient to feed heating up to die temperature, and deformation degree is 30-60 %, and in the second one rate is 10-2-10-4 s-1, and deformation degree is 10-30 %; isothermal holding is carried out under pressure of 10-150 MPa.

EFFECT: strained feed with homogenous recrystallized structure and β-grain size of 10-30 mum; with high strength and improved coefficient of metal utilization.

5 cl, 2 tbl, 1 ex

 

The invention relates to metallurgy, in particular to methods of producing billets of titanium alloys, and may find application in the aviation industry, and mechanical engineering as power parts of the airframe and GTE.

The material from which the workpiece is a high-strength two-phase titanium alloy based on titanium with a total content of vanadium and molybdenum more than 8 weight percent. Deformed billet of these alloys are subjected to heat treatment to obtain a strength of more than 1200 MPa and high levels of fracture toughness.

In the production of deformed semi-finished products of these alloys the most important scientific and practical tasks are homogeneous (regulated) fine-grained macro - and microstructure, increasing the level and uniformity of mechanical properties and improved processability and increase the utilization of metal. The solution of these problems, for example, for parts of aircraft technology will reduce the cost, improve performance and reliability of aircraft.

Currently known methods of production of titanium splavov, allowing to achieve a uniform recrystallized structure, increasing values of reliability and the level of mechanical properties For the manufacture of products using technology isothermal deformation of the ingot or intermediate pieces using thermomechanical processing, providing recrystallized structure.

A known method of deformation processing (forging or stamping) billets of titanium alloys in the profiled the strikers or curly dies heated to a temperature of not lower than 200°usually 300-500°C.

The process involves the following:

- heating the workpiece at a temperature of β-areas that depending on the type of alloy is 1050-1300°calculation of time of heating 40-60 with 1 mm thickness of the workpiece;

the deformation in the die tool with the degree not less than 40%;

- subsequent heating of the workpiece at lower temperatures β-the area at 1000-1130°C;

- final deformation.

To improve the structure of the workpiece may be subjected to additional strain on an advanced technological scheme includes the following additional operations:

- heating the workpiece at a temperature (α+β)-field;

- warp to the degree of not less than 40%;

- heating the workpiece at a temperature of β-field;

- deformation with a degree no less than 40-50%;

(Titanium alloys, Semi-finished products from titanium alloys. Moscow. JIST VILS. 1996 str-186, 372-374, 379, 409-410).

Billet obtained by the simple scheme of deformation at a temperature of βan area characterized by heterogeneous coarse-grained structure with a grain size 6-8-what about the points on a 10-point scale, due to the instability and non-uniformity of the deformation process, the cooling down of the metal surface, the formation of zones of the complicated deformation and low plasticity.

Strain through a complicated scheme allows to improve the macrostructure of the blanks, but the magnitude of micrograins corresponds 4-7 score, the degree of deformation should be at least 40-50%. In geometrically-complex forgings formed heterogeneous structure associated with a large temperature gradient material-stamp, the formation of zones of the complicated deformation and heterogeneity of deformation in the cross section of the forging. The formation of a heterogeneous structure leads to a decrease of mechanical properties and their stability in the products obtained from these forgings.

Prolonged heating at temperatures of β-the field is accompanied by a significant gas superficial layers of metal that requires an increase in the allowance for machining and is accompanied by a decrease in the utilization of metal and mnogoprohodnym stamping increases the complexity of manufacture.

A method of processing titanium alloys to reduce crack growth in (α+β) titanium alloy containing significant amounts of β-phase and more than 3% molybdenum, including the following:

forging above the pace of atory β transformation (TPP) with the degree of deformation sufficient for the subsequent recrystallization;

- cooling of the material below the temperature β transformation (TPPwith speed 11-55°C/min;

hardening heat treatment including quenching with temperature 27-82°below TPPand aging. (U.S. patent No. 4543132). The above process allows you to reduce the size of recrystallized β-grains due to the high cooling rate of β-field, to be applied in one heating and reduce the complexity of the casting.

However, the process has the same significant deficiencies described above by way of: associated with a large temperature gradient material-stamp uneven deformation, the formation of zones of the complicated deformation, prolonged heating at temperatures of β-area and high gasanalysis surface layers of the metal, which requires an increase in the allowance for machining and is accompanied by a decrease in the utilization of metal. In addition, the high speed deformation during forging is also accompanied by the formation of zones of intense metal flow and uneven structure, resulting in reduction of mechanical properties and their stability in the products.

Closest to the proposed invention is a method of gaining the fine blanking with a maximum size β -grains less than 0.5 mm, taken as a prototype (U.S. Patent No. 5026520).

The method includes:

- heating billets from the full temperature of polymorphic transformation (TPP) to TPP+45°C;

- deformation on the press dies are heated to a temperature close to the temperature of the workpiece (isothermal forging) with intermediate aged 4-10 minutes;

- isothermal exposure at a temperature close to the temperature of the die and the workpiece for a time sufficient to complete the full primary recrystallization, but insufficient for further grain growth;

- quenching (rapid cooling) of the workpiece after removal from the press to a temperature below the temperature of complete polymorphic transformation to prevent further growth of grain and obtain a microstructure with size β-grains less than 0.5 mm (500 microns).

Prototype method allows you to avoid prolonged annealing after deformation at temperatures above the full polymorphic transformation to obtain a recrystallized structure by conducting isothermal aging from 4 to 10 minutes directly after deformation, which allows to obtain a grain size less than 0.5 mm and to reduce the thickness of the gas layer forming.

The disadvantages of the prototype method is to heat source procurement β-region (above TPP

The disadvantage of the prototype method is the high complexity associated with the need for long-term intermediate exposure (4-10 minutes) in the deformation process. The total time of the extracts may be 10-20 minutes.

The disadvantage of the prototype method is that when using the proposed method is formed directional structure, which provides high-only properties in the radial direction (the direction of intensive metal flow). Billets with a similar structure have significant anisotropy properties and limited scope, for example, to drive the CCD.

The technical object of the present invention is to provide a method of producing deformed billet of titanium alloys that form in the deformed blank of uniform recrystallized structure with size β-grain 10-30 μm high and the Yu strength in thermally hardened state, the absence of anisotropy, increase the utilization of the metal by reducing the depth of gas-saturated layer, requiring removal by machining in the manufacture of products.

To achieve these objectives, a method for receiving deformed billet of titanium alloy comprising heating the workpiece deformation in the stamp is heated above the temperature of complete polymorphic transformation of titanium alloy, isothermal exposure at the temperature of the stamp in a period of time sufficient for complete recrystallization of titanium alloy, and hardened, the heating of the workpiece is conducted to a temperature below the full polymorphic transformation 10-30°C, the deformation in the heated stamp is carried out with variable speed: beginning at a rate sufficient to heat the workpiece to the temperature of the die and the degree of deformation of 30-60% and then at a rate of 10-2-10-4with-1and the degree of deformation of 10-30%, and isothermal exposure is performed under load 10-150 MPa, and the heat stamp spend 10-30°With higher temperature full polymorphic transformation. Quenching procurement spend with speed 15-50°C/min to a temperature below the temperature of complete polymorphic transformation. To obtain the products strength of more than 1200 MPa after hardening conduct heat treatment the blanks.

There is also a product of the billets produced by the proposed method.

In the production of deformed semi-finished products with a recrystallized structure of two-phase titanium alloys are the most widely used technology, including heating billets in β-region (above TPP), stamping with the end of the deformation at a temperature of β-area and regulated by the shutter speed and the cooling rate.

Heating of billets of titanium alloys in single-phase β-the field is accompanied by a significant increase in the grain of the original piece. Therefore, even when significant subsequent deformation cannot obtain fine-grained recrystallized structure. The formation of the deformed blank of large recrystallized structure is accompanied by a decrease in ductility after heat treatment at a high strength.

In addition, the heating and curing of the workpieces at temperatures of β-the field is accompanied by a significant gas superficial layers of metal and the formation of defective hard and brittle layer, reduce the operational properties of the products. To remove this layer is used machining and losing 40-50% of metal.

The major difference of the proposed method is to heat the workpiece to a temperature below the full polemo mnogo transformation (T PP) 10-30°that inhibits the grain growth of the original piece and allows you to get during the subsequent deformation of the improved structure with a grain size of 10-30 μm, promotes the full course of the process of recrystallization in a shorter time, and the original fine grain limits the growth of β-grain during isothermal aging.

In the end, not only reduces the size of recrystallized β-grain, but there is an opportunity to improve process performance and reduce the loss of metal due to the fact that decreases the depth of gas-saturated layer, requiring removal by machining, while the defective layer can be removed without the use of mechanical processing, namely chemical etching.

When heated billet lower temperature TPP-30°not provided With heating to a temperature TPP+(10-30)°at the first stage of deformation, which allows you to get a fully recrystallized structure. Heating billets above TPP-10°accompanied by the growth of the grains, which does not allow to obtain a homogeneous fine-grained structure in the deformed blank.

Significant difference between the proposed method is that the deformation in the die heated to a temperature TPP+(10-30)°C, is carried out with a variable speed in two stages: the 1st stage with the article is singing deformation of at least 30-60% and speed, sufficient to heat the workpiece due to heat deformation, as well as establishing density of dislocations in the metal (work hardening), sufficient for the occurrence of dynamic recrystallization, and the 2nd stage with the degree of deformation of 10-30% and a rate of 10-2-10-4with-1that provides a flow of dynamic recrystallization in the workpiece, forming a structure with a grain size of 10-20 μm and a degree of recrystallization of 85-95%. The result is not only reduced the size of the β-grain, but also increases the efficiency of the process, because the main deformation is carried out at a higher speed and intermediate isothermal exposure.

Reducing the heating temperature of the stamps below TPP+10°leads to the formation of a mixed structure, since the contact layers of the workpiece due to powstawania saved precrystallization structure. Increasing the temperature of the stamp above TPP+30°leads to growth β-grain up to 50-80 μm in the surface layer of the workpiece by heating in the contact zone.

Deformation at the 1st stage with degree less than 30% does not provide the desired density of dislocations (work hardening) in the workpiece, and does not allow to increase the temperature of the workpiece to TPP+(10-30)°did not provide a flow of dynamic recrystallization on the 2nd stage stamping. In addition, velocipede total time warp, that increases the complexity of manufacturing forgings.

Deformation at the 2nd stage with a speed of more than 10-2with-1results patterns with the degree of recrystallization of 40-60%, which does not provide a complete recrystallization during isothermal aging and leads to the formation of inhomogeneous structures. Deformation speeds of less than 10-4with-1leads to significant grain growth and the formation of a structure with a grain size of 40-60 microns.

Deformation with degree less than 10% provides a degree of recrystallization of 40-50%, which is insufficient to produce a fully recrystallized structure during subsequent isothermal aging. Deformation with degree more than 30% leads to the formation of grains elongated in the direction of intensive metal flow, and the maximum size in this direction is 35-45 microns.

The major difference of the proposed method is isothermal aging under load 10-150 MPa for a time sufficient to complete recrystallization (0.5 to 1.5 minutes), which provides the structure with a grain size of 10-30 μm and a degree of recrystallization 100%. The net result is not only a fully recrystallized structure, but decreases the thickness of the gas layer development due to the discontinuation oxidizing environment (air) to the surface of the workpiece and smart who agrees the time of isothermal aging by increasing the speed of recrystallization at constant load, which leads to the reduction of the time of the technological cycle and reducing the complexity of the manufacturing forgings.

Aging in the stamp under a load of less than 10 MPa does not provide discontinuation oxidizing environment to the surface of the stamping, causing an increase in thickness of the gas-saturated layer. Furthermore, the reduced rate of recrystallization, leading to increased time of isothermal holding under load and complexity of manufacturing forgings.

Aging in the stamp under the load of more than 150 MPa followed by plastic deformation of the workpiece that does not provide a complete recrystallization and leads to the formation of mixed patterns.

The difference of the proposed method is also quenching (rapid cooling) of the workpiece to a temperature below TPPwith the speed of 15-50°C/min, which inhibits the grain growth due to the rapid excretion α-phase grain boundaries and its stabilizing effect on the grain growth. In addition, increasing the utilization rate of the metal by reducing the thickness of the gas-saturated layer.

Increasing temperature above TPP-60°to which is accelerated cooling and slow cooling below 15°C/min accompanied by an increase in gas-saturated layer, which leads to reduction of the rate of use of the project for a metal. In addition, the size of recrystallized grains is increased to 45-60 microns.

Increasing the cooling rate above 50°C/min leads to significant thermal stresses and changes the geometry of the workpiece, which requires an increase in allowance for machining and reduces the utilization of metal.

Carrying out a hardening heat treatment after quenching (fast cooling) provides strength not less than 1200 MPa in the deformed blank.

The example implementation.

For the practical implementation of selected high-strength two-phase titanium alloys W 22 W 23, from which was made the punching panel with ribs and developed surface.

Method of test sakaluk samples of the alloy in the range 820-920°was determined temperature of polymorphic transformation (TPP), is equal to 870°for alloy W 22 890°for W 23. As the original piece was used rod size β-grain 60 microns.

Parameters technology die forgings are presented in table 1, where items 1-3 - the proposed method for alloy W 22, item 4 - the proposed method for alloy W 23, p.5 - prototype method for alloy W 22. Table 2 shows the properties of forgings after treatment by the proposed method and the method prototype.

Of the cloth forming the panels made education the hospitals to study the microstructure and determination of the temporal resistance (σ in) tensile characterizing strength. The results of the study of the microstructure shown in table 1, and the results of the tensile tests in table 2. KIM - utilization of metal.

The study of the microstructure shows the proposed method of obtaining products, finer β-grain forgings and improve temporal resistance (σincompared with the method of the prototype.

Technology of production of forgings is simplified, the utilization rate of the metal is increased in 2 times. Thus, the proposed method of producing forgings of titanium alloys can reduce the grain size to improve the properties of products and KIM, as well as to simplify the manufacturing process, reducing the time and energy costs of the proceeding.

Products obtained in this way have enhanced strength and can be used in highly loaded structures of aircraft.

1. The method of obtaining the deformed billet of titanium alloys, including heating of the workpiece, the deformation of the stamp is heated above the temperature of complete polymorphic transformation of titanium alloy, isothermal exposure at the temperature of the stamp in a period of time sufficient to floor the second recrystallization of titanium alloy and quenching, characterized in that the heating of the workpiece is conducted to a temperature below the full polymorphic transformation 10-30°C, the deformation in the heated stamp is carried out in two stage variable speed: at the first stage at a rate sufficient to heat the workpiece to the temperature of the stamp, and the degree of deformation of 30-60%, in the second stage at a rate of 10-2-10-4with-1and the degree of deformation of 10-30%, and isothermal exposure is performed under load 10-150 MPa.

2. The method according to claim 1, characterized in that the heating of the stamp spend 10-30°With higher temperature full polymorphic transformation.

3. The method according to claim 1, characterized in that the quenching of the workpiece is carried out with the velocity of 15-50°C/min to a temperature below the temperature of complete polymorphic transformation.

4. The method according to claim 1, characterized in that after quenching conduct heat treatment of the workpiece.

5. The product of a titanium alloy, characterized in that it is made of deformed billet, produced according to any one of claims 1 to 4.



 

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26 cl, 4 dwg

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16 cl, 3 tbl, 1 ex, 15 dwg

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26 cl, 4 dwg

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5 cl, 2 tbl, 1 ex

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1 dwg, 1 ex

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2 ex

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7 cl, 1 dwg, 1 tbl, 1 ex

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8 cl, 5 tbl, 6 dwg, 4 ex

FIELD: non-ferrous metallurgy; methods of titanium alloy bricks production.

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FIELD: processes and equipment for diffusion welding of tubular adapters of zirconium and steel sleeves.

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FIELD: plastic metal working, possibly manufacture of intermediate blanks of titanium alloys by hot deforming.

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EFFECT: possibility for producing blank with globular-plate microstructure, lowered level of structural defects at ultrasonic flaw detection of turned blank.

1 ex

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