A forming method for increasing the effective size of square billet forgings and improving deformation uniformity

Abstract

This invention belongs to the field of titanium alloy material preparation technology, and relates to a forming method for increasing the effective size of square billet forgings and improving deformation uniformity. This invention uses free forging pre-forming above the phase transformation point, which can eliminate curved edges through multiple shaping processes. Even with large deformation, a uniform lamellar structure can be formed, exhibiting good fracture toughness. Reversible forging and drawing allows for the interchange of longitudinal and transverse directions of the cuboid billet, balancing the total deformation in both directions and ensuring uniformity of microstructure and properties. By pressing a circular arc groove, curved edges can be avoided during subsequent forging processes, improving billet flowability, increasing the effective size of the forging, and improving yield. By controlling the deformation in the two-phase region, both the continuous grain boundary α phase can be broken, and the degree of recrystallization can be controlled, retaining short rod-shaped α phases and achieving a good balance between fracture toughness and strength.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material preparation technology, and relates to a forming method that increases the effective size of square billet forgings and improves deformation uniformity. Background Technology

[0002] During the forming process of forgings, as the height decreases, the metal continuously flows outwards. Due to friction between the billet and the die, the corners of the billet become concave, while the center of the edges protrudes, forming arc-shaped edges. In free forging, these arc-shaped edges can be corrected by repeated upsetting and drawing. However, free forging also suffers from uneven deformation temperature and speed, leading to unsatisfactory microstructure and properties of the forging. Isothermal forging with a flat die can solve the problem of uneven deformation temperature and speed, but during deformation, the arc-shaped edges cannot be repeatedly corrected, resulting in a reduction in the effective size of the square billet forging and an increase in the weight of the forging. To meet both the microstructure and property requirements and increase the effective size of the forging, a forming method that increases the effective size of the square billet and improves deformation uniformity is proposed. Summary of the Invention

[0003] The purpose of this invention is to provide a forming method that improves the effective size of square billet forgings, which can improve the arc-shaped edges and uneven microstructure and properties caused by uneven deformation during the forging process of square billet forgings.

[0004] The above-mentioned objective of this invention is achieved through the following technical solution:

[0005] A forming method for increasing the effective dimensions of a square billet forging and improving deformation uniformity includes: the dimensional characteristics of the square billet forging are: L / B≥1.5, B / H≥1.3, 50mm≤H≤150mm, where L, B, and H are the dimensions in the length, width, and height directions of the forging, respectively. The forming of the square billet forging includes the following steps:

[0006] Step 1: Design two anvils with arcs. The radius of the arc of anvil a is R1 and the height of the arc is W1 = 4L(H1-H) / (L+B). The radius of the arc of anvil b is R2 and the height of the arc is W2 = 4B(H1-H) / (L+B).

[0007] Step 2: Heat the bar stock in an electric heating furnace, and repeatedly forge and draw it into a pre-formed square billet, then air cool it.

[0008] Step 3: Place the precast square billet obtained in Step 1 in (T) β Heating at -20℃, T β To determine the phase transformation point of the alloy, the billet is subjected to longitudinal and transverse upsetting.

[0009] Step 4: Align the center of the arc-shaped anvil a with the center of the long side of the precast square billet, press it into an arc groove, and then cool it; align the center of the arc-shaped anvil b with the center of the short side of the precast square billet, press it into an arc groove, and then cool it to obtain a cuboid billet with arc grooves on all four sides.

[0010] Step 5: Heat the cuboid billet obtained in Step 4 below the phase transformation point and press it down along the height direction for isothermal forging.

[0011] The heating temperature in the electric heating furnace mentioned in step two is T. β +(10~15)℃.

[0012] The dimensional characteristics of the precast square billet are: L1 / B1=(0.9~1.1)L / B, H1=(1.3~1.55)H, where L1, B1, and H1 are the dimensions of the precast square billet in the length, width, and height directions, respectively.

[0013] The number of times for reversing and upsetting in step three is 1 to 3.

[0014] The reversing upsetting process in step three involves upsetting the long side of the rectangular blank into a short side, and upsetting the short side into a long side, while keeping the height unchanged.

[0015] The radius R1 of the anvil surface arc is (L1 / 2). 2 +(H1-H) 2 / 2(H1-H); the radius R2 of the anvil surface arc is (B1 / 2). 2 +(H1-H) 2 / 2(H1-H).

[0016] The heating temperature below the phase transition point in step five is (T) β -20)℃.

[0017] The deformation amount of the isothermal forging in step five is between 30% and 55%.

[0018] The technical advantages of this invention are as follows: Free forging preforming above the phase transformation point allows for the elimination of curved edges through multiple shaping processes. Even with large deformation, a uniform lamellar structure can be formed, exhibiting good fracture toughness. Reversible forging and drawing enables the interchangeability of longitudinal and transverse directions in cuboid billets, balancing the total deformation in both directions and ensuring uniformity of microstructure and properties. Pressing a circular arc groove prevents the formation of curved edges during subsequent forging processes, improving billet flowability, increasing the effective size of the forging, and improving yield. By controlling the deformation in the two-phase region, both continuous grain boundary α phases can be broken, and the degree of recrystallization can be controlled, preserving short rod-shaped α phases and achieving a good balance between fracture toughness and strength. Detailed Implementation

[0019] To better understand the purpose, technical solution, and advantages of this invention, the following detailed description is provided in conjunction with embodiments.

[0020] A forming method for increasing the effective size of a square billet forging and improving deformation uniformity includes:

[0021] The dimensional specifications for the square billet forging are: L / B≥1.5, B / H≥1.3, 50mm≤H≤150mm, where L, B, and H are the length, width, and height dimensions of the forging, respectively. The forming process for the square billet forging includes the following steps:

[0022] Step 1: Design two anvils with curved surfaces. Anvil a has a radius of radius R1 and a height W1 = 4L(H1-H) / (L+B). Anvil b has a radius of radius R2 and a height W2 = 4B(H1-H) / (L+B). The radius R1 of each anvil is (L1 / 2). 2 +(H1-H) 2 / 2(H1-H); the radius R2 of the anvil surface arc is (B1 / 2). 2 +(H1-H) 2 / 2(H1-H).

[0023] Step 2: Heat the bar stock in an electric heating furnace to a temperature of T. β +(10~15)℃; Free forging and repeated upsetting and drawing to form a precast square billet. The dimensional characteristics of the precast square billet are: L1 / B1=(0.9~1.1)L / B, H1=(1.3~1.55)H, where L1, B1, and H1 are the length, width, and height dimensions of the precast square billet, respectively; then air-cooled.

[0024] Step 3: Place the precast square billet obtained in Step 1 in (T) β Heating at -20℃, T β To determine the phase transformation point of the alloy, the square billet undergoes longitudinal and transverse reversible upsetting and drawing, with 1 to 3 upsetting cycles. Reversible forging and drawing allows for the interchange of longitudinal and transverse directions in the cuboid billet, balancing the total deformation in both directions and ensuring uniformity of microstructure and properties. The reversible upsetting and drawing involves upsetting the long side of the cuboid billet into a short side, and then upsetting the short side into a long side, while keeping the height unchanged.

[0025] Step 4: Align the center of the arc-shaped anvil a with the center of the long side of the precast square billet, press it into an arc groove, and then cool it; align the center of the arc-shaped anvil b with the center of the short side of the precast square billet, press it into an arc groove, and then cool it to obtain a cuboid billet with arc grooves on all four sides.

[0026] Step 5: Heat the rectangular billet obtained in Step 4 below its phase transformation point. The heating temperature below the phase transformation point is (T). β-20)℃; isothermal forging is performed by pressing down along the height direction, and the deformation of isothermal forging is between 30% and 55%.

[0027] Example 1:

[0028] The method for forming a square billet with dimensions L = 602 mm, B = 340 mm, and H = 70 mm involves the following steps:

[0029] Step 1: Heat the Ф320mm bar stock in an electric heating furnace to 815℃, and then repeatedly forge and draw it into a pre-formed square billet with dimensions L1 = 475mm.

[0030] B1=280mm, H1=107.7mm and air cooled after forging.

[0031] Step Two: Heat the precast square billet obtained in Step One to 780℃, and then perform reverse upsetting and drawing. The long side of the rectangular billet is upset into a short side, and the short side is upset into a long side, while the height remains unchanged. Reversible forging and drawing allows for the interchangeability of the longitudinal and transverse directions of the rectangular billet, balancing the total deformation in both directions and ensuring the uniformity of the microstructure and properties in both directions.

[0032] Step 3: Design two anvils with rounded edges. Anvil a has a radius of R1 = 766 mm and an arc height of W1 = 96 mm. Anvil b has a radius of R2 = 278 mm and an arc height of W2 = 54 mm. Align the center of anvil a with the centers of the two long sides of the precast square billet and press them into rounded grooves. Align the center of anvil b with the centers of the two short sides of the precast square billet and press them into rounded grooves before cooling.

[0033] Step 4: Heat the rectangular billet obtained in Step 3 to 780℃, press it down along the height direction for isothermal forging, and control the deformation of the two-phase region to 35% to complete the forming.

[0034] Example 2:

[0035] The method for forming a square billet with dimensions L = 700 mm, B = 420 mm, and H = 100 mm involves the following steps:

[0036] Step 1: Heat the Ф320mm bar in an electric heating furnace to 815℃, and then repeatedly forge and draw it into a pre-formed square billet with dimensions L1 = 550mm.

[0037] B1=320mm, H1=167mm and air cooled after forging.

[0038] Step Two: Heat the precast square billet obtained in Step One to 780℃, and then perform reverse upsetting and drawing. The long side of the rectangular billet is upset into a short side, and the short side is upset into a long side, while the height remains unchanged. Reversible forging and drawing allows for the interchangeability of the longitudinal and transverse directions of the rectangular billet, balancing the total deformation in both directions and ensuring the uniformity of the microstructure and properties in both directions.

[0039] Step 3: Design two anvils with rounded edges. Anvil a has a radius of R1 = 597 mm and an arc height of W1 = 168 mm. Anvil b has a radius of R2 = 224 mm and an arc height of W2 = 100 mm. Align the center of anvil a with the centers of the two long sides of the precast square billet and press them into rounded grooves. Align the center of anvil b with the centers of the two short sides of the precast square billet and press them into rounded grooves. Let them cool.

[0040] Step 4: Heat the rectangular billet obtained in Step 3 to 780℃, press it down along the height direction for isothermal forging, and control the deformation of the two-phase region to 40% to complete the forming.

Claims

1. A forming method for increasing the effective dimensions of a square billet forging and improving deformation uniformity, comprising: The dimensional specifications for the square billet forging are: L / B ≥ 1.5, B / H ≥ 1.3, 50mm ≤ H ≤ 150mm, where L, B, and H are the length, width, and height dimensions of the forging, respectively. The forming process for the square billet forging includes the following steps: Step 1: Design two anvils with arcs. Anvil a has an arc radius of R1 and an arc height of W1 = 4L(H1-H) / (L+B). Anvil b has an arc radius of R2 and an arc height of W2 = 4B(H1-H) / (L+B). Step 2: Heat the bar stock in an electric heating furnace, and repeatedly forge and draw it into a precast square billet, then air cool it; The dimensional characteristics of the precast square billet are: L1 / B1=(0.9~1.1)L / B, H1=(1.3~1.55)H, where L1, B1, and H1 are the dimensions of the precast square billet in the length, width, and height directions, respectively; Step 3: Place the precast square billet obtained in Step 2 in (T) β Heating at -20℃, T β To determine the phase transformation point of the alloy, the billet is subjected to longitudinal and transverse upsetting. Step 4: Align the center of the arc-shaped anvil a with the center of the long side of the precast square billet, press it into an arc groove and then cool it; align the center of the arc-shaped anvil b with the center of the short side of the precast square billet, press it into an arc groove and then cool it to obtain a cuboid billet with arc grooves on all four sides. Step 5: Heat the cuboid billet obtained in Step 4 below the phase transformation point and press it down along the height direction for isothermal forging.

2. The method according to claim 1, characterized in that, The second step involves heating in an electric furnace at a temperature of T. β + (10~15)℃.

3. The method according to claim 1, characterized in that, The third step involves reversing the upsetting process 1 to 3 times.

4. The method according to claim 1, characterized in that, Step three, the reversing upsetting, involves upsetting the long side of the rectangular blank into a short side, and upsetting the short side into a long side, while keeping the height unchanged.

5. The method according to claim 1, characterized in that, The radius R1 of the anvil's arc is [(L1 / 2)]. 2 +(H1-H) 2 ] / 2 (H1-H); the radius R2 of the anvil arc is [(B1 / 2)] / 2 (H1-H); 2 +(H1-H) 2 ] / 2 (H1-H).

6. The method according to claim 1, characterized in that, The heating temperature below the phase transition point mentioned in step five is (T) β -20)℃.

7. The method according to claim 1, characterized in that, The deformation amount of isothermal forging described in step five is between 30% and 55%.