A method for forming a TA3 titanium alloy tee joint forging

Abstract

This invention belongs to the field of forging and hot working, and relates to a method for forming TA3 titanium alloy tee pipe joint forgings. The process includes: determining the final forging die, wherein the cavity of the final forging die is identical to the shape of the forging, adopting a 1-die, 2-cavity design, consisting of an upper die and a lower die, with the two forging cavities distributed back-to-back at the center of the die, and the parting surface located at the centerline of the cross-section of the tee pipe joint; the forging parting uses a planar parting; heating the billet: heating temperature: Tβ-(70~110)℃, holding time: 1~1.3mm / min; upsetting the heated billet to obtain a rough shape, the height of the rough shape matching the final forging dimensions, wherein the upsetting deformation is 30%~50%; heating the final forging die: die temperature: 200~300℃; placing the heated rough shape into the heated final forging die cavity for final forging: final forging deformation: 20%~40%, transfer time ≤10s, cooling method: diffused air cooling; and performing heat treatment on the forging after final forging by machining, sandblasting, and grinding.

Description

Technical Field

[0001] This invention belongs to the field of forging and hot working, and relates to a method for forming TA3 titanium alloy tee pipe joint forgings. Background Technology

[0002] Titanium alloy tee pipe fitting forgings are a standard aerospace component with huge market demand. In the early stages of production, existing technology uses a forging temperature of Tβ-(20~50)℃ for α+β forging, and the forming method generally employs a two-stage forging process: pre-forging + final forging. However, this forming method for TA3 titanium alloy tee pipe fitting forgings results in a long processing cycle, multiple grinding and spraying processes, large burrs, and 50%–60% material waste. Furthermore, a deformation dead zone (rounding to rounding) exists in the final forging, and the finished product may have bright lines in the low-magnification core or uneven microstructure. Summary of the Invention

[0003] Purpose of the invention: To design a method for forging TA3 titanium alloy tee pipe fittings, by providing appropriate key process parameters such as forging heating temperature, upsetting deformation, die forging deformation, heat preservation coefficient, cooling method, and heat treatment through reasonable mold design, so as to stably produce TA3 forgings with uniform structure and excellent performance.

[0004] Technical solution:

[0005] A method for forging a TA3 titanium alloy tee pipe fitting includes:

[0006] The final forging die is determined, wherein the cavity of the final forging die is the same as the shape of the forging, and a 1-die-2-cavity die is adopted, consisting of an upper die and a lower die. The two forging cavities are distributed back to back in the center of the die, and the parting surface is located at the center line of the cross-section of the tee pipe joint; the forging parting adopts a planar parting.

[0007] Heating the billet: heating temperature: Tβ-(70~110)℃, holding time: 1~1.3mm / min;

[0008] The heated billet is upset to obtain a rough shape, the height of which matches the final forging dimensions, wherein the upsetting deformation is 30% to 50%;

[0009] Heating the final forging die: Die temperature: 200~300℃;

[0010] The heated rough shape is placed into the heated final forging die cavity for final forging: final forging deformation: 20%~40%, transfer time ≤10s, cooling method: air cooling;

[0011] After final forging, the forgings are machined, sandblasted, and polished before undergoing heat treatment.

[0012] Furthermore, the distance between the cavities of the two forgings is consistent with the width of the mold bridge.

[0013] Furthermore, an upsetting platform is provided on the lower die. After the upper and lower dies are closed, the height of the upsetting platform from the lower surface of the upper die corresponds to the height of the upsetting rough shape, and the height dimension of the upsetting rough shape matches the final forging.

[0014] Furthermore, the heating furnace is a high-temperature electric converter with a diameter of 1m.

[0015] Furthermore, the forgings after final forging undergo machine sandblasting and grinding followed by heat treatment, specifically including:

[0016] Annealing: Temperature: 820℃, holding time: 90±9 minutes, furnace cooling to below 500℃ and then air cooling.

[0017] Furthermore, the final forging equipment is a 1000T electric screw press.

[0018] Furthermore, the final forging die is made of hot work die steel H13 / HM3.

[0019] Furthermore, the final forging die has damping grooves around the die bridge section.

[0020] Beneficial effects:

[0021] The TA3 titanium alloy tee pipe fitting forging method of the present invention: The mold adopts 1 mold 2 cavities, the forging process is 1 heat 2 steps, upsetting + final forging are combined into one, and the forging heating temperature, forging deformation amount, heat holding coefficient, heat treatment and other parameters are reasonably controlled to avoid the uneven high and low magnification structure of the final titanium alloy tee pipe fitting forging caused by uneven deformation amount, thereby improving the comprehensive performance and fatigue life of the tee pipe fitting forging. It can produce tee pipe fitting forging with uniform structure and excellent comprehensive performance, and the material utilization rate is 80%, which is 30% to 40% higher than that of ordinary titanium alloy tee pipe fitting forging, and the production efficiency is increased by more than 4 times. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the mold;

[0023] Figure 2 This is a schematic diagram of the lower model cavity;

[0024] Figure 3 This is a low-magnification microstructure diagram of the forging in the transverse direction;

[0025] Figure 4 This is a high-magnification microstructure diagram of the forging in the transverse direction. Detailed Implementation

[0026] A method for forming TA3 titanium alloy tee pipe joint forgings, the method comprising: 1) mold design; 2) final forging; 3) annealing treatment, and finally producing forgings whose microstructure and properties meet the standard requirements.

[0027] The mold design described above:

[0028] The final forging die is prepared with a cavity corresponding to the shape of the forging. It adopts a 1-die, 2-cavity design, with two forgings back-to-back (the distance between the two forgings is consistent with the width of the die bridge) distributed in the center of the die. It consists of an upper die and a lower die. The parting surface is located at the center line of the cross-section of the tee pipe joint. An upsetting platform is set on the lower die. After the upper and lower dies are closed, the height of the upsetting platform from the lower surface of the upper die corresponds to the upsetting rough shape height. The upsetting rough shape height can match the final forging without secondary die adjustment. Damping grooves are designed around the die bridge to effectively change the metal flow trend. This type of parting is a planar parting. The die size is based on the size of the die base cavity and the maximum outline size of the forging.

[0029] The forging process described above:

[0030] Curd heating temperature: Tβ-(70~110)℃, holding time: 1~1.3mm / min, mold temperature: 200~300℃.

[0031] Forging process: first upsetting, then die forging; upsetting deformation: 30%–50%;

[0032] While ensuring that the material grains are fully broken down, the temperature rise of the core of the forging is not too high, thus avoiding the formation of "X"-shaped bright lines in the core of the forging.

[0033] Forging deformation: 20%~40%, transfer time ≤10s, cooling method: diffused air cooling, completed in 1 heat.

[0034] The forging process is divided into two steps: upsetting and die forging. Controlling the forging transfer time ensures that the deformation in the die forging process is separate. Dividing the original deformation process into two steps makes the deformation of each forming process evenly distributed, avoiding the formation of bright lines caused by excessive accumulation of core deformation.

[0035] The heat treatment process:

[0036] Annealing, temperature: 820℃, holding time: 90±9 minutes, furnace cooling to below 500℃, and air cooling after removal from the furnace.

[0037] The TA3 annealing standard is (630℃~815℃)×(60~120min), air cooling. Forgings produced using this standard have excessive hardness that cannot meet customer requirements. For α-type titanium alloys, the main delivery condition is annealed. Increasing the annealing temperature allows the distortion energy caused by defects such as dislocations to be released more fully than when the annealing temperature is lower, resulting in a softer hardness. At this time, if the cooling rate is slower, the stress release process can be accelerated, thereby reducing the hardness of the forging.

[0038] The final forging equipment is a 1000T electric screw press, the heating furnace is a high-temperature electric converter with a diameter of 1m, and the final forging die is a hot work die steel with good overall plasticity, toughness, wear resistance, hardenability and machinability: H13 / HM3.

[0039] The present invention will be further described in detail below through specific implementation examples.

[0040] The TA3 titanium alloy tee pipe fitting requires die forging. The present invention employs a die-forging method combining upsetting and die forging, using a 1-die-2-cavity mold, a 1-fire 2-step forging process.

[0041] Step 1: Based on the customer's part drawing and design requirements, use computer numerical simulation to design reasonable upsetting and forging deformation amounts: upsetting: 35%~40%, forging: 25%~35%;

[0042] Step 2: Prepare the final forging die. The cavity of the final forging die corresponds to the shape of the forging. It adopts a two-cavity die with two forgings back-to-back (the distance between the two forgings is consistent with the width of the die bridge) distributed in the center of the die. It consists of an upper die and a lower die. The parting surface is located at the center line of the cross-section of the tee pipe joint. The lower die is designed with an upsetting platform. The height of the upsetting rough shape can match the final forging, without the need for secondary die adjustment. Damping grooves are designed around the die bridge. This type of die parting is a planar parting. The die size is selected as a 240×150×120mm insert die based on the size of the die base cavity and the maximum outline size of the forging. The die drawing is attached. Figure 1 As shown;

[0043] Step 3: Material preparation process

[0044] Bar stock specifications: Φ100×42±1mm, both ends of the bar stock are chamfered with R5 and the end faces are flat, shot blasted with steel grit, etched, and sprayed with high-temperature glass lubricant and protective agent.

[0045] Step 4: Forging

[0046] a. Heat the billet to (Tβ-100)℃ and hold for 45-50 minutes. In the first step, upset the billet to 25.5+1-0.5mm with a deformation of ~40% and an upsetting impact energy of 300 tons.

[0047] b. In the second step, the upset billet is placed directly into the cavity of the final forging die for forging. The vertical dimensions are forged to the tolerance range required by the tee pipe fitting forging drawing, with a deformation of ~30%. The final forging impact energy is 800 tons. The forging is shown in the attached figure. Figure 2 As shown.

[0048] c. The entire transfer time of upsetting and forging is ≤10 seconds, completed in one heat, and then air-cooled.

[0049] d. Perform laser edge cutting, shot blasting with steel grit, etching, and polishing on the forging.

[0050] Step 5: Heat treatment

[0051] Annealing, in a box furnace. Temperature: 820℃, holding time: 90±9 minutes, furnace cooling to below 500℃, and air cooling after removal from the furnace.

[0052] The final forging equipment is an electric screw press, the heating furnace is a high-temperature electric converter, and the final forging die is H13.

[0053] Table 1 Mechanical Properties

[0054]

[0055] The mold of this invention adopts a 1-mold-2-cavity design, and the forging process includes 1 heating and 2 steps, combining upsetting and final forging. By rationally controlling parameters such as forging heating temperature, forging deformation, heat holding coefficient, and heat treatment, a uniform microstructure is successfully produced. Figure 3 / Figure 4 TA3 titanium alloy tee pipe fitting forgings with excellent performance (Table 1) and improved material utilization and production efficiency.

Claims

1. A method for forging TA3 titanium alloy tee pipe fittings, characterized in that, include: The final forging die is determined, and the cavity of the final forging die is the same as the shape of the forging. It adopts a 1-die 2-cavity design, consisting of an upper die and a lower die. The two forging cavities are distributed back to back in the center of the die, and the parting surface is located at the center line of the cross-section of the tee pipe joint. The forging parting adopts a planar parting. An upsetting platform is set on the lower die. After the die is closed, the height of the upsetting platform from the lower surface of the upper die corresponds to the upsetting rough shape height. The upsetting rough shape height dimension matches the final forging. The die bridge of the final forging die has damping grooves around it. Heating the billet: Heating temperature: Tβ - (70~110)℃, holding time: 1~1.3mm / min; The heated billet is upsetting to obtain a rough shape, the height of which matches the final forging dimensions, with an upsetting deformation of 30%~50%. Heating of the final forging die: Temperature: 200~300℃; The heated rough shape is placed into the heated final forging die cavity for final forging: final forging deformation: 20%~40%, transfer time ≤10s, cooling method: air cooling; After final forging, the forgings are machined and sandblasted before undergoing annealing heat treatment: temperature: 820℃, holding time: 90±9 minutes, furnace cooling to below 500℃, and then air cooling.

2. The forging method for TA3 titanium alloy tee pipe joints according to claim 1, characterized in that, The distance between the cavities of the two forgings is consistent with the width of the mold bridge.

3. The forging method for TA3 titanium alloy tee pipe joints according to claim 1, characterized in that, The heating furnace is a high-temperature electric converter with a diameter of 1m.

4. The forging method for TA3 titanium alloy tee pipe joints according to claim 1, characterized in that, The final forging equipment is a 1000T electric screw press.

5. The forging method for TA3 titanium alloy tee pipe joints according to claim 1, characterized in that, The final forging die is made of hot work die steel H13 / HM3.

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