RU2236322C1 - Method for making one-piece rolled wheels of titanium alloys - Google Patents

Abstract

FIELD: plastic metal working, possibly manufacture of one-piece rolled wheels of titanium alloys.

SUBSTANCE: method comprises steps of beginning warm rolling out of ring in β-range or in β-range and in (α+β)-range and terminating it according to cooling degree of blank in (α+β)-range; performing rolling out at deformation rate from 3·10^-3c^-1 1/s until 1 1/s; terminating preparation of initial annular blank by forging operation in (α+β)-range. Deformation degree of ring in (α+β)-range consists at least 30% of total realized deformation value. Heat rolling out of ring is started in (α+β)-range.

EFFECT: manufacture of articles with uniform normalized finely dispersed structure, enhanced efficiency, improved manufacturing possibilities of standard equipment.

4 cl, 4 tbl, 3 ex

Description

The invention relates to the field of metal forming and can be used to obtain seamless rolled rings from titanium alloys. The method is intended for the manufacture of parts for gas turbine engines, and may also find application in other industries where ring-shaped products from titanium alloys are used.

It is known that the properties of metals and alloys during processing by pressure are most strongly affected by three main factors: temperature and strain rate, as well as the type of stress state.

An increase in temperature usually contributes to a decrease in deformation resistance and an increase in the ductility of a metal, since the energy of thermal motion of atoms increases, and conditions are created for the simultaneous action of the most effective mechanisms of plastic deformation. Along with this, at high temperatures, the process of plastic deformation is complicated and the following processes are initiated:

- physical and chemical processes (for example, phase transformations)

- mutual displacements of grains

- subgrain formation

- grain boundary migration

- return and recrystallization

- formation and development of discontinuities (pores, cracks) and their healing

- the formation of bands of accommodation, etc.

Some of these processes directly or indirectly lead to coarsening of the metal structure.

Another, no less important factor influencing the processes: grain growth, nucleation, growth and healing of discontinuities, and therefore, non-ductility and deformation resistance, is the strain rate. The dependence of the above properties and processes is ambiguous in various speed ranges and for various groups of alloys. It follows from this that the influence of temperature on the deformation mechanism cannot be considered separately from the velocity. To develop optimal technological conditions for the manufacture of rolled rings, it is necessary to take into account the temperature and strain rate of the material.

A known method of manufacturing a rolled ring blanks of aging nickel alloys (RF patent No. 2088365, 21 N 1/06, 1997.08.27). In the technological process, workpieces made by upsetting, flashing and overclocking are used as initial ones. Cutting is eliminated by heating the workpiece in a homogeneous region followed by preliminary rolling with a degree of deformation of at least 15-20%, and step heating for thermal rolling is carried out directly after the preliminary rolling without cooling. Preliminary and final deformation is carried out in different calibers. This method provides the expansion of technological capabilities and the saving of scarce expensive alloys.

The disadvantage of this method is that it is intended only for aging alloys, because it uses the effect of increasing the deformability of aging alloys under conditions of deformation close to isothermal.

A known method of manufacturing rolled annular blanks from high alloy alloys (RF patent No. 2173598, 21 N 1/06, 09/20/2001, bull. No. 26 - prototype). The method consists in the fact that the initial welded from hot-rolled profiles or seamless annular billets of rectangular or channel cross-section from titanium alloys are heated before rolling at a temperature of 950-800 ° C, kept for at least 0.5 hours, removed from the furnace and installed in the rolls of a ring rolling mill , and warm rolling starts at 900-750 ° C, and in the range at 900-800 ° C, the temperature of the rings for rolling is taken based on the fact that it is lower than the polymorphic transformation temperature of this alloy by at least 30 ° C. The method provides for the manufacture of ring billets from titanium alloys with a uniform regulated structure and a consistently high level of mechanical properties.

The disadvantage of this method is the lack of ductility of titanium alloys in this temperature range, which necessitates multi-junction rolling of the workpiece, quick cooling, especially thin-walled workpieces. In addition, the technological process does not take into account the rate of deformation of the material, which does not allow you to choose the optimal technological modes of processing the product.

The problem to which this invention is directed is to obtain products with a uniformly regulated finely divided microstructure while increasing the productivity and technological capabilities of standard equipment.

The technical result achieved by the implementation of the claimed invention is to obtain a workpiece with a uniformly regulated microstructure, reducing the number of outbursts and associated heat, metal fumes, reducing the complexity of the manufacturing process of products, in addition, it is possible to manufacture rolled precision rings with high geometric accuracy on standard equipment the dimensions.

The specified technical result is achieved by the fact that in the known method for manufacturing solid-rolled rings from titanium alloys, including the manufacture of the initial ring billet, warm rolling of the ring and subsequent heat treatment, at each transition, warm rolling of the ring begins to be carried out in the β-region, or β- and (α + β) -regions, and as the workpiece cools, they finish in the (α + β) -regions and lead at a strain rate of 3 · 10 ^-3 s ^-1 to 1 s ^-1 .

The essence of the invention is as follows.

The annular billet is heated to the temperature of the β-region or β- and (α + β) -regions, where the deformation resistance is significantly lower (P.G. Miklyaev. Mechanical properties of light alloys at temperatures and speeds of pressure treatment, - M .: Metallurgy, 1994 g., pp. 85-97). This allows you to have a reserve of plasticity, which, with the same efforts on a rolling mill, allows you to produce rings of larger geometric dimensions, while reducing the number of offsets. The rolling of the ring is carried out with a strain rate of from 3 · 10 ^-3 s ^-1 to 1 s ^-1 . In the process of rolling, the workpiece is chilled, and the deformation process passes into the (α + β) region. At a strain rate of more than 1 s ^-1 , the heat released during the deformation does not have time to dissipate into the environment and the product temperature during rolling does not drop to the required temperature (α + β) -region. At a strain rate of less than 3 · 10 ^-3 s ^-1 in the β-region or β- and (α + β) -region, the metal structure coarsens, and in the (α + β) -region, grain refinement and optimal formation are not intensive enough macro- and microstructures over the entire cross section of the product, which can cause a decrease in the physico-mechanical properties of the metal during processing.

When rolling the whole-rolled rings, initial billets are used, the manufacture of which is completed by the forging operation in the (α + β) -region.

In the subsequent rolling of this workpiece in the β-region following this operation, deformation is accompanied by metal recrystallization with grain refinement.

In the manufacture of seamless-rolled rings, ring deformation in the (α + β) region can be at least 30% of the total volume of deformation.

The final deformation of the whole-rolled ring in the (α + β) region at a degree of deformation of 30% or more translates the metal structure into (α + β) -deformed, uniform throughout the cross section, and increases the ductility of the metal.

Possibly, in the method for manufacturing solid-rolled rings from titanium alloys, thermal rolling of the rings begins to be carried out in the (α + β) region.

This improves the physical and mechanical properties of the metal by 2-5% compared with the process in which the rolling of the rings begins in the β-region or β- and (α + β) -regions, but the number of transitions and the associated costs increase 2 or more times, as well as 25-30% reduced equipment capabilities in the manufacture of bulky products.

The proposed method was tested in the manufacture of solid-rolled rings from VT20 and 5B titanium alloys, the rolling of which began in the β-region and of the seamless-rolled rings from VT20d2 alloy, the rolling of which began in the (α + β) -region. The parts were manufactured on a RAW 100/80 ring rolling mill with rolling forces of up to 100 tons and rolling speeds in the range of 0.6-1.6 m / s.

Example 1

From the ring billet with an external diameter of 483 mm, an internal diameter of 250 mm, and a height of 184 mm from VT-20 titanium alloy with a polymorphic transformation temperature of TPP = 965 °, a seamless-rolled ring was made with the dimensions: with an external diameter of 1065 mm, an internal diameter of 989 mm, and a height of 179 mm each the following operational-technological scheme shown in table 1.

D, mm - outer diameter of the ring;

d, mm is the inner diameter of the ring;

N, mm - the height of the ring;

S, mm - wall thickness of the ring;

λ,% - drawing coefficient;

ε _s ,% - degree of deformation of the ring wall;

с^-1, - средняя скорость деформации;

s ^-1 , is the average strain rate;

t, sec - time of deformation.

The degree of deformation in 1 and 2 outflows amounted to about 40-45% of the total volume for each outflow.

The resulting ring was subjected to heat treatment according to TU (annealing at a temperature of 850 ° C for 1 hour). The results of the mechanical tests are shown in table 2.

The macrostructure was monitored on the microsections in the tangential direction and along the height of the ring. The macrostructure on the sections does not have cracks, delaminations, sunsets, voids, metal and non-metallic inclusions. A study was carried out by the method of "deep" etching to control porosity - porosity was not detected.

The resulting microstructure corresponds to type 4-5 of the 9-type scale of microstructures, the macrostructure corresponds to 5-6 points (OST 192131-92 according to the instructions of VIAM No. 1054).

To obtain a similar one-piece ring at the beginning of rolling at a temperature of 935 ° C (TPP-30 ° C), at least 6 offsets are required.

Example 2

A 5B titanium alloy with a polymorphic transformation temperature of TPP = 1055 ° was used to fabricate a single-rolled ring with dimensions of an outer diameter of 1065 mm, an inner diameter of 989 mm and a height of 179 mm according to the following operational flow chart shown in Table 3.

The level of properties and structure of the metal comply with the requirements of OST192131-92.

To obtain a similar, seamless-rolled ring at the beginning of rolling the workpiece in the (α + β) -region, at least 7 transitions are required.

Example 3

From a ring billet with an outer diameter of 427 mm, an inner diameter of 220 mm, and a height of 182 mm from VT20d2 titanium alloy with a polymorphic transformation temperature of TPP = 975 ° C, a seamless-rolled ring was made with dimensions of an outer diameter of 944 mm, an inner diameter of 878 mm, and a height of 177 mm.

The rolling was completed in 4 transitions. Each rolling was started in the (α + β) region at 945 ° C (TPP-30 ° C), with a strain rate from 4 · 10 ^-3 s ^-1 to 2.5 · 10 ^-2 s ^-1 . The results of the mechanical tests are shown in table 4.

The macrostructure was monitored on the microsections in the tangential direction and along the height of the ring. The macrostructure on the sections does not have cracks, delaminations, sunsets, voids, metal and non-metallic inclusions. A study was conducted by the method of "deep" etching to control porosity - porosity was not detected.

The obtained macrostructure (OST192131-92 according to the instructions of VIAM No. 1054) corresponds to 5-6 points in the tangential direction and 4-5 points in the high direction.

Carrying out part of the deformation in the β-region and the β- and (α + β) -regions allows to reduce by 2 or more times the number of transitions with heating and laboriousness in comparison with the known method, and also allows you to produce larger products using standard equipment. In the manufacture of rings from titanium alloys completely in the (α + β) -region, the strain rate in the range from 3 · 10 ^-3 s ^-1 to 1 s ^-1 allows the most optimal combination of efficiency and quality criteria.

Claims (4)

1. A method of manufacturing solid-rolled rings from titanium alloys, including the manufacture of the original ring billet, warm rolling of the ring and subsequent heat treatment, characterized in that at each transition, warm rolling of the ring begins to be carried out in the β-region or in β- and (α + β) -regions, and as the workpiece cools, they end in the (α + β) -regions and lead at a strain rate of 3 · 10 ^-3 s ^-1 to 1 s ^-1 . 2. The method according to claim 1, characterized in that the manufacture of the initial annular billet is completed with a forging operation in the (α + β) region. 3. The method according to claim 1, characterized in that the volume of deformation of the ring in the (α + β) region is at least 30% of the total volume of deformation. 4. The method according to claim 1, characterized in that the warm rolling of the ring begins to be carried out in the (α + β) region.