A method for forging a large TC18 titanium alloy "right trapezoid" free forging

Abstract

The application belongs to the field of titanium alloy forging, and particularly relates to a forging method of a large TC18 titanium alloy 'right-angle trapezoidal' free forging piece. The method comprises the following steps: in the first heating: the TC18 titanium alloy φ400 specification bar is upset to a length direction deformation amount of 20%-50%, and a forging blank is obtained; the forging blank is chamfered and expanded; in the second heating: the forging blank is collected along the hypotenuse of the 'right-angle trapezoidal', and then the thickness size is corrected, and the deformation amount is controlled to be 20%-50%; the length of the collected forging blank should not be greater than the length of the forging piece; in the third heating: the collected and corrected forging blank is forged along the thickness direction, and the deformation amount is controlled to be 25%-35%; in the fourth heating: the forged forging blank is corrected to the size required by the drawing, and the deformation amount is controlled to be 5%-10%.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of titanium alloy forging, and particularly relates to a forging method of a large TC18 titanium alloy 'right-angle trapezoidal' free forging piece. BACKGROUND

[0002] Titanium alloy is widely applied in the fields of aerospace and medical instruments due to small density, high strength and corrosion resistance. The super-high strength titanium alloy represented by TC18 titanium alloy has excellent comprehensive performance and plays an important role in materials for large aircraft manufacturing, and is often used for manufacturing large stress structural parts such as large beams, stringers and reinforcing frames.

[0003] At present, titanium alloy aircraft structural parts are mainly formed by using a forging process. Due to the special working environment, in the design and manufacturing process of the aircraft parts, the strength and rigidity of the structural parts are mainly enhanced, and the stress corrosion resistance and fracture toughness of the structural parts are improved as technical indexes. In the initial stage of aircraft research and development, titanium alloy forgings are mostly in the form of free forgings, which is convenient for structural optimization and change and flexible adjustment. In order to save materials, the free forgings are often designed and used according to the shape of the parts, which breaks the inherent thinking mode of the traditional free forgings 'cuboid shape'. However, this brings great challenges to free forging. SUMMARY

[0004] The purpose of the application is to provide a forging method of a large TC18 titanium alloy 'right-angle trapezoidal' free forging piece, which can ensure the forming of the forging piece and avoid unstable forging piece organization, and further improve the uniformity and stability of product organization and performance.

[0005] TECHNICAL SCHEME

[0006] The application provides a forging method of a large TC18 titanium alloy 'right-angle trapezoidal' free forging piece, which comprises the following steps:

[0007] First heating: TC18 titanium alloy φ 400 specification bar stock is upset to a length direction deformation amount of 20%-50% to obtain a forging blank; and the forging blank is chamfered and expanded;

[0008] Second heating: the forging blank is collected along the hypotenuse of the 'right-angle trapezoidal', and then the thickness size is corrected, and the deformation amount is controlled to be 20%-50%; the length of the collected forging blank should not be greater than the length of the forging piece;

[0009] Third heating: the collected and corrected forging blank is forged along the thickness direction, and the deformation amount is controlled to be 25%-35%;

[0010] Fourth heating: the forged forging blank is corrected to the size required by the drawing, and the deformation amount is controlled to be 5%-10%.

[0011] Further, the whole forging transfer process is required to be completed within 50 seconds; the first, second and fourth heating temperature ranges are 30-35℃ below the phase transition point, and the third heating temperature range is 12-15℃ above the phase transition point; the cold material heating and holding time is 1.5-2.5min / mm calculation; the hot material recycling holding time is 0.8-1.5min / mm calculation.

[0012] Further, the third heating process is not allowed to recycle hot material.

[0013] Further, a special measuring tool is made according to the size requirements of the drawing, and the target size is measured in real time during the forging process.

[0014] Further, the first, second and fourth forging processes are required to be completed within 5-10 minutes, and the third forging process is required to be completed within 3-5 minutes, and the final forging temperature is greater than or equal to 720℃ after forging.

[0015] Further, the feeding amount is ≤2 / 3 of the anvil during the whole forging process.

[0016] Further, the pressure reduction amount is 100-200mm per hammer.

[0017] Further, the pressure reduction speed is 5-10mm / s. Advantages

[0018] Through the three-time forging of the technical scheme, the material organization is qualified and stable, and the "right angle trapezoidal" size requirement of the forged piece is met. The material organization is a key factor to determine the material performance, and only the qualified organization of the forged piece can ensure the qualified performance of the forged piece, and then ensure the qualification of the forged piece. The present application can meet the above two requirements at the same time, and the mechanical properties of the forged piece are also qualified and can achieve a good match of strength and plasticity. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a schematic diagram of the final size of the forged piece.

[0020] Figure 2 It is a high-magnification microstructure photograph

[0021] Figure 3 It is a low-magnification microstructure photograph DETAILED DESCRIPTION EMBODIMENT

[0022] 1) blanking: Φ400×1887mm material grade: TC18

[0023] Mark: smelting furnace number or code, ingot number, material grade, forged piece drawing number tail number.

[0024] 2) forging:

[0025] 1st heating: forging size Φ400x1887 upsetting to Φ500x~1200, then transversely elongating and squaring to 640x246x~1506;

[0026] 2nd heating: forging size 640x246x~1506, squaring and shaping to 640(506)x246x~1690

[0027] 3rd heating: forging size, thickness direction 246 to 172, and using special template to compare slope size;

[0028] 4th heating: finishing size to final size of forging 640(455)x172x~2340, as shown in Figure 1 .

[0029] Equipment: 45MN fast forging machine

[0030] Heating equipment: electric furnace.

[0031] 1st heating temperature: 30°C below phase transition point, holding for 320 min;

[0032] 2nd heating temperature: 30°C below phase transition point, holding for 200 min;

[0033] 3rd heating temperature: 30°C below phase transition point, holding for 200 min, furnace temperature rising to 15°C above phase transition point, holding for 90 min;

[0034] 4th heating temperature: 30°C below phase transition point, holding for 140 min;

[0035] Forging technical requirements:

[0036] a) preheating anvil and tools to 150-350°C before forging;

[0037] b) blank transfer time ≤60s;

[0038] c) 4th heating is completed;

[0039] d) final forging temperature ≥720°C.

[0040] 3) Heat treatment: according to special heat treatment process

[0041] Primary annealing: 830±10°C x 180±15 min, furnace cooling to 750±10°C, holding for 180±15 min, and air cooling after furnace discharge;

[0042] Secondary annealing: 616±5°C x 360±15 min, air cooling.

[0043] 4) Physical and chemical: physical and chemical detection is performed according to sampling diagram.

[0044] 2.3 Trial results

[0045] 1) H content (wt. %): 0.0015.

[0046] 2) High magnification: composed of lath and spheroid α phase and β transformed structure, in accordance with the standard Figure 2 of 6 grade. High magnification structure photograph is shown in Figure 2 .

[0047] 3) Low magnification: low magnification flow line distribution is basically along the contour, without through flow and serious vortex. Low magnification is free of shrinkage hole, porosity, delamination, segregation, crack, metallic and non-metallic inclusion and other metallurgical defects. Low magnification is in accordance with the standard Figure 1 of 4 grade, low magnification structure is shown in Figure 3 .

[0048] 4) Mechanical properties

[0049]

Claims

1. A method of forging a large TC18 titanium alloy "right trapezoid" open-die forging, characterized in that, The method comprises the following steps: First heating: the TC18 titanium alloy φ400 rod is heated at 30-35 ℃ below the phase transition point, upset to a length direction deformation of 20%-50%, to obtain a forging blank; the forging blank is chamfered and expanded; Second heating: the forging blank is heated at 30-35 ℃ below the phase transition point, collected along the hypotenuse of the "right trapezoid", and then the thickness size is trimmed, with a deformation of 20%-50%; the length of the collected forging blank should not be greater than the length of the forging; Third heating: the collected and trimmed forging blank is heated at 12-15 ℃ above the phase transition point, forged along the thickness direction, with a deformation of 25%-35%; the third heating does not allow hot material to be recycled; Fourth heating: the forged forging blank is heated at 30-35 ℃ below the phase transition point, trimmed to the size required by the drawing, with a deformation of 5%-10%; The first, second and fourth forging processes are completed within 5-10 minutes, the third forging process is completed within 3-5 minutes, and the final forging temperature is greater than or equal to 720 ℃ after the forging is completed.

2. The method of claim 1, wherein, The whole forging out-of-furnace transfer process is completed within 50 seconds; the cold material heating and holding time is calculated as 1.5-2.5 min / mm; the hot material recycling holding time is calculated as 0.8-1.5 min / mm.

3. The method of claim 1, wherein, The feeding amount in the whole forging process is less than or equal to 2 / 3 of the anvil.

4. The method of claim 1, wherein, A special measuring tool is made according to the size requirements of the drawing, and the size of the hypotenuse of the "right trapezoid" is measured in real time during the forging process.

5. The method of claim 1, wherein, The pressure reduction amount is 100-200 mm per time.

6. The method of claim 1, wherein, The pressure reduction speed is 5-10 mm / s.

7. The method of claim 1, wherein, The weight of the TC18 titanium alloy "right trapezoid" free forging is greater than 1000 kg.

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