CN111375715B

CN111375715B - Method for improving yield of TC17 titanium alloy bars

Info

Publication number: CN111375715B
Application number: CN201811633302.7A
Authority: CN
Inventors: 杨磊; 钱杰; 张磊; 金成�
Original assignee: Baowu Special Metallurgy Co Ltd
Current assignee: Baowu Special Metallurgy Co Ltd
Priority date: 2018-12-29
Filing date: 2018-12-29
Publication date: 2022-11-15
Anticipated expiration: 2038-12-29
Also published as: CN111375715A

Abstract

A method for improving the yield of a TC17 titanium alloy bar comprises the following steps: 1) Preparing before forging, cleaning oxide skin in a heating furnace before loading a titanium alloy ingot into the furnace, aiming at ensuring the uniform heating temperature of a blank and preparing heat insulation cotton and glue; 2) Heating, namely heating the titanium alloy ingot in a heating furnace to 100 +/-10 ℃, then keeping the temperature for 0.5 to 1 hour, then coating an anti-oxidation coating, and after coating, air cooling for 0.5 to 1 hour, and then heating in the heating furnace; starting a heating process before forging, feeding the titanium alloy ingot with the temperature of less than or equal to 200 ℃ into a heating furnace, uniformly heating for 6-7 hours, keeping the temperature for 2-3 hours, discharging the titanium alloy ingot at 850 +/-10 ℃, covering the middle part of the titanium alloy ingot with heat insulation cotton, returning the titanium alloy ingot after covering, keeping the temperature for 1-1.5 hours, and then discharging the titanium alloy ingot out of the furnace for forging; 3) And forging, wherein 7 heating times are adopted for forging, and the upsetting reduction is less than or equal to 40 percent per heating time.

Description

Method for improving yield of TC17 titanium alloy bar

Technical Field

The invention relates to a forging process, in particular to a method for improving the yield of a TC17 titanium alloy bar.

Background

Titanium alloy has the characteristics of high strength, good toughness, hardenability, thermal stability, high fatigue strength and the like, is used for manufacturing aircraft engines, compressor disks and engine blades, and is widely used in military and civil aviation engines. However, the surface cracks, end cracks and other phenomena often occur in the forging process, and the internal quality after forging does not reach the standard, so that the process yield of the TC17 product is only about 60%.

The bar material original forging process flow comprises the following steps: the first fire to the seventh fire are longitudinally lengthened after upsetting, see figure 1; and eighth fire: using flat tongs to perform drawing operation; the ninth fire: and (5) performing material forming operation. However, the following problems arise during the production process:

firstly, because multiple-fire upsetting and longitudinal drawing are adopted, the interior cannot be completely forged, the production period is long, and the energy consumption is high; secondly, the surface and the end part of the forging stock are cracked in the production process due to temperature drop; finally, the upsetting longitudinal elongation operation is unreasonable, so that the internal structure of the product is uneven, and the requirement of the technical standard cannot be met.

The problems existing in the production process of the titanium alloy bar are summarized as follows:

1) Titanium alloy products are very sensitive to forging temperatures and, once the temperature is not as desired, can develop cracks on the male and female surfaces and surfaces.

2) Since the titanium alloy has high internal requirements, the structure is improved by repeated upsetting and drawing, the number of production fire is large, and the increase of surface cracks is caused.

3) If cracks occur in the production process, the yield is influenced by the pull-down grinding.

4) Some titanium alloys can only be enlarged due to deep cracks and are saved by increasing turning, so that the surface quality and yield are seriously affected.

Disclosure of Invention

The invention aims to provide a method for improving the yield of a TC17 titanium alloy bar, which can improve the yield of the product as much as possible and form a set of novel forging process for the TC17 titanium alloy bar in the fields of aerospace and aviation.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for improving the yield of a TC17 titanium alloy bar comprises the following steps:

1) Preparation before forging

Cleaning an oxide skin in a heating furnace before loading a titanium alloy ingot into the furnace, aiming at enabling the blank to be heated at a uniform temperature and preparing heat insulation cotton and glue;

2) Heating, wherein after the heating furnace is heated to 100 +/-10 ℃, the titanium alloy ingot enters the furnace, heat preservation is carried out for 0.5 to 1 hour, then anti-oxidation coating is coated, after coating, air cooling is carried out for 0.5 to 1 hour, and then the titanium alloy ingot enters the heating furnace for heating; starting a heating process before forging, feeding the titanium alloy ingot with the temperature of less than or equal to 200 ℃ into a heating furnace, uniformly heating for 6-7 hours, keeping the temperature for 2-3 hours, discharging the titanium alloy ingot at 850 +/-10 ℃, covering the middle part of the titanium alloy ingot with heat insulation cotton, returning the titanium alloy ingot after covering, keeping the temperature for 1-1.5 hours, and then discharging the titanium alloy ingot out of the furnace for forging;

3) Forging

Forging by 7 times, wherein the upsetting reduction is less than or equal to 40 percent per time; wherein, the 1 st fire is upsetting reversing elongation, the 2 nd and 3 rd fires are upsetting longitudinal elongation, the 4 th fire is upsetting reversing elongation, the 5 th fire is upsetting longitudinal elongation, the 6 th fire is elongation by using flat tongs, and the 7 th fire is finished.

The method disclosed by the invention utilizes a free forging principle, combines the particularity of a titanium alloy material, utilizes the throwing pliers to carry out reversal drawing-out after upsetting, and replaces the original end part with the original end part by four times of reversal drawing-out, thereby improving the requirement on the internal quality; and the original requirement of nine-fire finished products is changed into seven-fire finished products, thereby shortening the forging period. The blank is drawn and forged by adopting a 5/4 drawing method, the end part is well closed, the blank is completed without an obvious convex end, the end part is free from cracks, and the yield is greatly improved. Finally, the energy is reduced, the labor force is reduced, and the product quality is improved.

The invention has the following advantages:

for TC17 products with a narrow deformation temperature range, the rapid forging machine set (40 MN rapid forging machine set) can realize one-fire reversing upsetting at the finish forging temperature of above 800 ℃.

The two-phase region (alpha + beta/beta transformation point-30 ℃) is forged, and in order to obtain a uniform and refined structure, the original process, namely the traditional repeated upsetting-drawing process, usually needs to be subjected to repeated upsetting-drawing for 7 times or more. In the rapid forging, when the material is deformed by pressing down, the metal in the vicinity under the contact surface is subjected to a large compressive stress, so that the region is deformed first, but becomes a hard deformation region or a dead region [1] soon, and the region other than the dead region is a deformation region. As can be seen from the classical upsetting model (FIG. 4), zone I is a hard deformation zone, zone II is a large deformation zone, and zone III is a small deformation zone [2]. Repeated axial upsetting and axial drawing-out, the parts of the hard deformation area and the small deformation area are always in the positions which can not be fully deformed.

The 'kneading-type' twice reversing upsetting-drawing process is realized through flexible and efficient operation of a 40MN quick forging machine set. The height-diameter ratio of the intermediate blank is controlled to be 1.8-2.0, so that the intermediate blank is in a single-drum shape after upsetting. After the intermediate blank is axially upset, the four side faces are corrected to be nearly cubic, the intermediate blank with the original specification is drawn and grown along the original arbitrary radial direction (see figure 5), and the end face of the original intermediate blank becomes the side face of the reversing blank. The same deformation is used for the second reverse upsetting to change the original end of the billet back to the end (see fig. 6). The deformation of single fire is increased by reversing upsetting and drawing, so that the center of the blank obtains more deformation, the forging penetration is favorably improved, and the hard-to-deform area is converted with other areas by the dough kneading type deformation mode, so that the hard-to-deform area is also fully deformed.

FIGS. 7 to 10 show the high power structure of a conventional upset forging bar, and it can be seen from the figures that the center structure of the bar is thicker at a radius of 1/2. In addition, a significant difference occurs between the transverse and longitudinal structure of the material, in which the alpha structure of the longitudinal structure occurs along the axial direction.

FIGS. 11 to 16 show the high power structure of the forged bar material in the upset-reverse manner, and it can be seen from the figures that the central structure of the bar material is similar to the structure at the 1/2 radius, and in addition, the transverse structure and the longitudinal structure of the center of the material have no obvious difference, and the transverse structure and the longitudinal structure are uniform equiaxial structures.

The comparison shows that the structure of the material subjected to reversing upsetting is more refined. Due to the influence of the rod specification, the conventional forging method is limited by the forging penetration, and the core structure cannot be sufficiently crushed, so that the α of a partial strip is not sufficiently crushed. The 40MN quick forging machine set realizes reversing upsetting in a narrow temperature range, after a strip alpha in the axial direction of the core part of the bar is greatly compressed, the strip alpha is twisted or broken at the weakest position, and the twisted or broken strip alpha crystals are converted into equiaxial alpha through merging, growing or recrystallization. In addition, the deformation time of the material subjected to reversing upsetting is slightly long, so that the alpha content of the material subjected to reversing upsetting is higher than that of the material subjected to traditional upsetting under the same heating condition.

Meanwhile, the surface and end cracks are also changed in the drawing process. Referring to fig. 17-19, which are schematic drawing views, 10 is an upper flat anvil, 20 is a lower flat anvil, and 30 is a blank.

It can be seen that the 3/1 flat anvil drawing-out shown in fig. 17 and the 2/1 flat anvil drawing-out shown in fig. 18 both have the phenomena of severe end protrusion, end cracks and the like, resulting in the current situation of low yield, therefore, the invention adopts the 5/4 drawing-out shown in fig. 19 to forge, the ends are well closed, no obvious convex ends exist, the ends have no cracks, and the yield is greatly improved.

Drawings

FIG. 1 is a schematic diagram of longitudinal drawing after upsetting is performed on the first fire to the seventh fire in the original bar forging process flow;

FIG. 2 is a schematic view of the 1 st and 4 th fires of the forging process of the present invention;

FIG. 3 is a schematic view of the 2 nd, 3 rd and 5 th fires of the forging process of the present invention;

FIG. 4 is a schematic view of a classical upset model;

FIG. 5 is a schematic illustration of a single reverse upset elongation in the forging process of the present invention;

FIG. 6 is a schematic illustration of a secondary reverse upset elongation in the forging process of the present invention;

FIG. 7 is a high power structure (100 x, central transverse direction) of a conventional upsetting-pulling type forged bar (phi 300 mm);

FIG. 8 is a high power structure (100X, 1/2 radius transverse) of a conventional upsetting forging bar (phi 300 mm);

FIG. 9 is a high magnification organization (100 x, central longitudinal direction) of a conventional upsetting-pulling type forged bar (phi 300 mm);

FIG. 10 is a high magnification tissue (100X, 1/2 radius longitudinal direction) of a conventional upsetting-and-drawing type forging bar (phi 300 mm);

FIG. 11 is a high power structure (100 x,1/2 radius transverse) of a reverse upsetting forging bar (phi 300 mm) of the present invention;

FIG. 12 shows the high power structure (500X, 1/2 radius transverse) of a reverse upsetting forged bar (300 mm) according to the present invention;

FIG. 13 shows a high power structure (100X, central transverse direction) of a reverse upsetting-type forged bar (300 mm) according to the present invention;

FIG. 14 shows a high power structure (500X, center transverse) of a reverse upsetting forged bar (300 mm) according to the present invention;

FIG. 15 shows a high power structure (100 x, central longitudinal direction) of a reverse upsetting type forged bar (phi 300 mm) according to the present invention;

FIG. 16 shows a high power structure (500X, central longitudinal direction) of a reverse upsetting type forged bar (300 mm) according to the present invention;

FIG. 17 is a schematic illustration of a 3/1 flat anvil drawing process;

FIG. 18 is a schematic illustration of a 2/1 flat anvil drawing process;

FIG. 19 is a schematic illustration of a 5/4 flat anvil drawing process.

Detailed Description

The invention is further illustrated by the following examples and figures.

In the embodiment of the invention, 650 octagonal mm and 1400mm blanks are used as raw materials.

1) Before production, firstly, the uniformity of the temperature of a heating furnace is ensured, the needed heat insulation cotton and glue are prepared, and the oxide skin in the furnace is cleaned before the titanium alloy ingot is loaded into the furnace, so that the blank can be uniformly heated, and the material can be loaded at the moment;

2) Heating, namely heating the titanium alloy ingot in a heating furnace to 100 +/-10 ℃, then keeping the temperature for 0.5 hour, then coating the coating, after coating, air cooling for 0.5 hour, and then heating in the furnace; starting a heating process before forging, feeding titanium alloy ingots with the temperature of less than or equal to 200 ℃ into a furnace, uniformly heating for 6 hours, keeping the temperature for 2 hours, then discharging the titanium alloy ingots at the temperature of 850 +/-10 ℃, packaging heat insulation cotton in the middle of the titanium alloy ingots, discharging the titanium alloy ingots after returning and keeping the temperature for 1 hour, and forging;

3) Forging

7 fire passes are adopted for production to phi 320mm, and the upsetting reduction is less than or equal to 40 percent per fire pass; the 1 st fire is upsetting reversing and lengthening, the 2 nd and 3 rd fires are upsetting longitudinal lengthening, the 4 th fire is upsetting reversing and lengthening, the 5 th fire is upsetting longitudinal lengthening, and the 6 th and 7 th fires are direct longitudinal lengthening to form materials; the current forging process flow chart is shown in FIGS. 2 and 3; fire 6: using a flat clamp to perform drawing operation; fire 7: performing a material forming operation; wherein the drawing length of each fire is 600mm +/-20 mm square (from the first fire to the fifth fire) through drawing length deformation; the sixth fire uses the flat tongs to perform drawing operation, the size is 450mm square, and the seventh fire finished product is 450mm square to phi 320mm.

Due to the improvement of the process, the forging fire is changed from the original 9 fire to the 7 fire of the invention, the energy is saved by about 30 percent, the one-time yield is improved by 13.3 percent, and the finished product yield is improved by 7.46 percent.

And (4) conclusion:

1. compared with the original process, the method reduces the difference between the transverse tissue and the longitudinal tissue of the bar through the forged bar subjected to the 2-time reversing upsetting-drawing process, and simultaneously well eliminates the long-strip alpha tissue.

2. Compared with the original process, the 2-time reversing upsetting-drawing process of the invention reduces 2 times, saves about 30 percent of energy, improves the one-time yield by 13.3 percent and improves the finished product yield by 7.46 percent.

Claims

1. The method for improving the yield of the TC17 titanium alloy bar is characterized by comprising the following steps of:

1) Preparation before forging

2) Heating, namely heating the titanium alloy ingot in a heating furnace to 100 +/-10 ℃, then keeping the temperature for 0.5 to 1 hour, then coating an anti-oxidation coating, and after coating, air cooling for 0.5 to 1 hour, and then heating in the heating furnace; starting a heating process before forging, feeding the titanium alloy ingot with the temperature of less than or equal to 200 ℃ into a heating furnace, uniformly heating for 6-7 hours, keeping the temperature for 2-3 hours, discharging the titanium alloy ingot at 850 +/-10 ℃, covering the middle part of the titanium alloy ingot with heat insulation cotton, returning the titanium alloy ingot after covering, keeping the temperature for 1-1.5 hours, and then discharging the titanium alloy ingot out of the furnace for forging;

3) Forging

Forging by 7 times, wherein the upsetting reduction is less than or equal to 40 percent per time; wherein, the 1 st fire is upsetting reversing elongation, the 2 nd and 3 rd fires are upsetting longitudinal elongation, the 4 th fire is upsetting reversing elongation, the 5 th fire is upsetting longitudinal elongation, the 6 th fire is elongation by using flat tongs, and the 7 th fire is finished product operation; wherein, in the 1 st fire to the 5 th fire, the height-diameter ratio of the intermediate billet is between 1.8 and 2.0.

2. The method for increasing the yield of the TC17 titanium alloy bar as recited in claim 1, wherein in the step 3), the drawing adopts a 5/4 flat anvil drawing method.