CN111375715A

CN111375715A - Method for improving yield of TC17 titanium alloy bar

Info

Publication number: CN111375715A
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: 2020-07-07
Anticipated expiration: 2038-12-29
Also published as: CN111375715B

Abstract

A method for improving the yield of TC17 titanium alloy bars comprises the following steps: 1) preparing before forging, namely cleaning iron scales in a heating furnace before loading steel ingots into the furnace, so as to ensure that the blank is heated at uniform temperature and prepare heat insulation cotton and glue; 2) heating, wherein steel ingots enter a heating furnace after the heating furnace is heated to 100 +/-10 ℃, heat is preserved for 0.5-1 hour, then an anti-oxidation coating is coated, and after the coating is finished, the steel ingots are cooled in air for 0.5-1 hour and then enter the heating furnace for heating; starting a heating process before forging, feeding the steel ingot with the temperature of less than or equal to 200 ℃ into a heating furnace, uniformly heating for 6-7 h, preserving heat for 2-3 h, discharging the steel ingot at 850 +/-10 ℃, coating heat insulation cotton in the middle of the steel ingot, returning the steel ingot to the furnace after the steel ingot is coated, preserving heat for 1-1.5 h, and discharging the steel ingot for forging; 3) forging, wherein 7 times of heating are adopted for forging, and the upsetting reduction is less than or equal to 40% per time of heating.

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 the like 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 elongated after upsetting, which is shown in figure 1; and eighth fire: using a flat clamp to perform drawing operation; the ninth fire: and (5) performing material forming operation. However, the following problems arise in 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 new forging process of the TC17 titanium alloy bar for the aerospace field.

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

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

1) preparation before forging

Cleaning iron scales in a heating furnace before loading steel ingots into the furnace, aiming at enabling the blank heating temperature to be uniform and preparing heat insulation cotton and glue;

2) heating, wherein steel ingots enter a heating furnace after the heating furnace is heated to 100 +/-10 ℃, heat is preserved for 0.5-1 hour, then an anti-oxidation coating is coated, and after the coating is finished, the steel ingots are cooled in air for 0.5-1 hour and then enter the heating furnace for heating; starting a heating process before forging, feeding the steel ingot with the temperature of less than or equal to 200 ℃ into a heating furnace, uniformly heating for 6-7 h, preserving heat for 2-3 h, discharging the steel ingot at 850 +/-10 ℃, coating heat insulation cotton in the middle of the steel ingot, returning the steel ingot to the furnace after the steel ingot is coated, preserving heat for 1-1.5 h, and discharging the steel ingot 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 perform reversing and drawing after upsetting, and replaces the original end part with the original end part by four times of reversing and drawing, so that the requirement on the internal quality is improved; and the original requirement of nine-fire finished products is changed into seven-fire finished products, thereby shortening the forging period. The 5/4 drawing method is adopted for forging in the process of drawing the blank, 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 a product with a relatively narrow deformation temperature range of TC17, the quick forging unit (40MN quick forging unit) can realize reversing and upsetting by one fire above the finish forging temperature of 800 ℃.

In the process of quick forging and forging, when a material is pressed and deformed, the metal in the area nearby the contact surface is subjected to large compressive stress, so that the area is firstly deformed, but quickly becomes a difficult deformation area or dead area [1], and the deformation area is arranged outside the dead area [ 4 ].

The 'kneading-type' twice reversing upsetting-pulling process is realized by flexible and efficient operation of a 40MN quick forging unit. The height-diameter ratio of the intermediate blank is controlled to be 1.8-2.0, so that the thickened intermediate blank is in a single-drum shape. After the intermediate blank is axially thickened, the four side faces are modified into a nearly cubic shape, the intermediate blank with the original specification is elongated along the original arbitrary radial direction (see fig. 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 reversing upsetting increases the deformation of a single heating number, so that the center of the blank obtains more deformation, the forging penetration of the blank is improved, and the dough kneading type deformation mode converts the hard deformation area and other areas, so that the hard deformation area is fully deformed.

The high power structure of the conventional upset forging bar is shown in fig. 7-10, 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, the transverse structure and the longitudinal structure of the material are obviously different, and a α structure of a strip along the axial direction is present in the longitudinal structure.

Fig. 11-16 show the high power structure of the forged bar material in the upset-reverse manner, and it can be seen from the pictures that the central structure of the bar material is similar to the structure at the radius of 1/2, 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 structure of the reversely upset and pulled material is more refined under the influence of the specification of the bar, the traditional forging mode is limited by forging penetration, the core structure cannot be fully crushed, so that part of strips α are not fully crushed, the 40MN quick forging machine set realizes reverse upset and pull in a narrower temperature range, strips α are twisted or broken at the weakest position after the strips α in the axial direction of the core of the bar are greatly compressed, the twisted or crushed strips α are transformed into equiaxial α by merging and growing or recrystallizing, in addition, the deformation time of the reversely upset and pull material is slightly longer, so that the α phase content of the reversely upset and pulled material is higher than that of α of the traditional upset and pull 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 3/1 flat anvil drawing is shown in fig. 17, and 2/1 flat anvil drawing is shown in fig. 18, which have the phenomena of severe end protrusion, end cracks and the like, resulting in the current situation of low yield, so that the invention adopts the 5/4 drawing method shown in fig. 19 to forge, the ends are well closed, no obvious protruding ends exist, the ends also have no cracks, and the yield is greatly improved.

Drawings

FIG. 1 is a schematic diagram of longitudinal drawing after upsetting is adopted for the first fire to the seventh fire in the original bar forging technological process;

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 view of upsetting and lengthening by one reversing in the forging process of the present invention;

FIG. 6 is a schematic view of upsetting and upsetting at two times in the forging process of the present invention;

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

FIG. 8 is a high magnification texture (100X, 1/2 transverse to the radius) of a conventional upset-draw forging bar (300 mm diameter);

FIG. 9 shows a high power structure (100x, central longitudinal direction) of a conventional upsetting-drawing type forged bar (φ 300mm)

FIG. 10 is a high magnification texture (100X, 1/2 radius longitudinal) of a conventional upset-draw forging bar (300 mm diameter);

FIG. 11 shows the high magnification organization (100x, 1/2 radius transverse) of the reverse upsetting mode forged bar (300 mm) of the present invention;

FIG. 12 is a high magnification texture (500X, 1/2 radius transverse) of a reverse upsetting mode forged bar (300 mm) of 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 (100x, central longitudinal direction) of a reverse upsetting type forged bar (phi 300mm) 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 the 3/1 flat anvil drawing process;

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

FIG. 19 is a schematic illustration of the 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, a blank 650 octagonal × 1400mm is used as a raw material.

1) Before production, firstly, the uniformity of the furnace temperature of a heating furnace is ensured, the needed heat insulation cotton and glue are prepared, and iron scales in the furnace are cleaned before steel ingots are charged into the furnace, so that the blank is heated at a uniform temperature, and the blank can be charged at the moment;

2) heating, wherein after the heating furnace is heated to 100 +/-10 ℃, the steel ingot enters the furnace, the coating is coated after the heat is preserved for 0.5 hour, and after the coating is finished, the steel ingot enters the furnace again for heating after air cooling for 0.5 hour; starting a heating process before forging, feeding steel ingots at 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 steel ingots from the furnace to the temperature of 850 +/-10 ℃, wrapping heat insulation cotton in the middle of the steel ingots, discharging the steel ingots from the furnace after the steel ingots are wrapped and keeping the temperature for 1 hour, and forging the steel ingots;

3) forging

7 fire times are adopted for production until phi is 320mm, and the upsetting reduction is less than or equal to 40 percent per fire time; 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, and the 6 th and 7 th fires are directly longitudinal elongation to form a finished product; the current forging process flow chart is shown in figures 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 utilizes flat tongs to carry out drawing length operation, the size is 450mm square, and the seventh fire finished product is from 450mm square to 320mm phi.

Due to the improvement of the process, the forging fire is changed from the original 9 fires to the 7 fires 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 α 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. A method for improving the yield of TC17 titanium alloy bars is characterized by comprising the following steps:

1) preparation before forging

3) forging

2. The method for increasing the yield of the TC17 titanium alloy bar as set forth in claim 1, wherein the elongation in step 3) is performed by a 5/4 flat anvil elongation method.