Die forging method for special-shaped titanium alloy spray pipe shell

Abstract

The invention belongs to the technical field of titanium alloy forging, and relates to a die forging method for a special-shaped titanium alloy spray pipe shell. In order to solve the problems that in the prior art, the material utilization rate is low, the machining efficiency is low, and a metal flow line is damaged, a pre-forging die and a finish-forging die are integrated into an integrated multi-cavity die, and the forging process is simplified. The method comprises the specific steps of designing and machining a die, preheating the die, heating a bar and forging a pre-forged piece, transferring the pre-forged piece into a finish forging die to forge a formed piece, and then carrying out surface treatment, heat treatment and machining. The method can improve the material utilization rate, save the production cost, ensure the stable product performance, simplify the technological process, reduce the labor intensity of workers and the cost, and have wide application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy forging, and in particular relates to a die forging method for a special-shaped titanium alloy nozzle shell. Background Art

[0002] Titanium alloy nozzle shell is an important component of solid rocket engine and an important part of rocket engine energy conversion. The nozzle is the outlet of high-temperature and high-pressure gas in the combustion chamber. When the engine is working, it is necessary to maintain a certain combustion chamber pressure. The structural integrity of the nozzle directly affects the performance of the engine.

[0003] For the die forging of special-shaped nozzle shells, the following methods are often used: Figure 1 The die is designed in the manner of a rotating body as shown. Although this process is simple in die forging, convenient in forming, and has relatively regular blanks, it has obvious problems: low material utilization, large machining allowance, and low machining efficiency. It often requires multiple machining and heat treatment processes, and the processing flow is long, resulting in a significant increase in product costs. In addition, the forgings formed by this die will destroy the metal streamlines of the die forgings in the subsequent machining process, resulting in changes in the material stress characteristics, which will affect the integrity of the internal material structure of the nozzle, posing a certain threat to the operating conditions of the nozzle shell. Summary of the invention

[0004] In order to overcome the deficiencies in the prior art, the present invention provides a die forging method for a special-shaped titanium alloy nozzle shell, which integrates the dies used for pre-forging and final forging, simplifies the forging process, reduces the processing steps, and solves the problems existing in the above background, and has broad application prospects.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The present invention provides a die forging method for a special-shaped titanium alloy nozzle shell, comprising the following steps: Design and process a one-mold multi-cavity mold that integrates a pre-forging mold and a final forging mold, the mold comprising an upper mold and a lower mold; Preheating the die, heating the bar material, placing the heated bar material in a pre-forging die of the die, and forging after closing the upper die and the lower die to obtain a pre-forged part; The pre-forged part is transferred to the final forging die, and the upper die and the lower die are fastened together for forging to obtain a formed part; After the surface treatment of the formed parts, heat treatment and machining are carried out to obtain the final forgings.

[0006] Preferably, the die increases the margin of 1-5 mm according to the shape of the final forging.

[0007] Preferably, before heating the bar, the bar is also pre-processed, specifically: determining the height and diameter of the bar according to the weight and size of the final forging, and selecting the bar; rounding both end faces of the bar, and setting a draft angle based on any end face.

[0008] Further preferably, the ratio of the height to the diameter of the bar is (1-4):1, and the draft angle is 1°-6°.

[0009] Preferably, the final forging die is also provided with a keyway.

[0010] Preferably, the mold is preheated at 200°C to 400°C.

[0011] Preferably, the heating of the rod material is specifically to heat the rod material to a temperature of 0°C to 60°C below the phase change point, and the thermal insulation coefficient is (0.4 to 1.5) min / mm.

[0012] Preferably, the surface treatment of the molded part is specifically sandblasting the surface of the molded part and cleaning the surface oxide scale.

[0013] Preferably, the roughness of the cavity of the contact surface between the die and the forging is 0.8-1.6 μm.

[0014] Preferably, graphite lubricant is sprayed on the surface of the mold before use.

[0015] Preferably, the heat treatment of the molded part includes: primary annealing, keeping at 960°C for 2 hours, and air cooling; secondary annealing, keeping at 550°C for 5 hours, and air cooling.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The die forging method of special-shaped titanium alloy nozzle shells proposed in the present invention designs different die forging dies for different nozzle shells, and obtains special-shaped forging blanks through pre-forging and final forging of bar materials. In the die forging method proposed in the present invention, although the pre-forging and final forging processes are formed in stages, by integrating the pre-forging and final forging dies into an integrated multi-cavity die, and sizing the same die forging die, there is no need to return the blank to the furnace, so that the pre-forging process and the final forging process can use the same set of dies. The die forging method proposed in the present invention does not require the replacement of dies during the forging process, and does not require multiple die preheating, which can save the time for replacing dies and the time for returning the blank to the furnace for heating, which can not only save the heating cost, but also save time and has high productivity. At the same time, the size difference between the pre-forged forging and the terminal forging is small, the die forging forging is high in precision and good in surface quality, the rough machining process can be less or no machining, and the final forging does not need to be machined as a whole, avoiding the subsequent machining to damage the stable material structure formed during the heat treatment forging process of the final forging. The streamline distribution of the forging is not cut off during the product machining process, so that the material stress characteristics do not change significantly, which will be beneficial to the subsequent material service life; it also greatly reduces the material machining allowance, significantly improves the utilization rate of raw materials, and saves production costs. At the same time, through the integrated one-piece multi-cavity mold, the process flow can be simplified, the technical requirements for workers are not high, and the labor intensity and cost of workers are significantly reduced, ensuring that the product has stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A mold designed in the form of a rotating body in the prior art; Figure 2 A schematic diagram of a special-shaped titanium alloy nozzle shell prepared by the process of the present invention; Figure 3 A schematic diagram of a titanium alloy bar prepared by the process of the present invention; Figure 4 A schematic diagram of an upper die forging die prepared by the process of the present invention; Figure 5 A schematic diagram of a lower die for forging prepared by the process of the present invention; Figure 6 A TC11 titanium alloy special-shaped nozzle housing forging prepared by the process of the present invention; Figure 7 A TC4 titanium alloy special-shaped nozzle housing forging prepared by the process of the present invention; Figure 8 A process flow chart of the method proposed by the present invention; Among them, bar draft angle 1, bar end face radius 2, bar 3, pre-forging die 4, upper die 5, final forging die 6, keyway 7, lower die 8, TC11 titanium alloy special-shaped nozzle shell forging 9, TC4 titanium alloy special-shaped nozzle shell forging 10, mold designed in the form of a rotating body 11, special-shaped titanium alloy nozzle shell 12. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0019] The steps of the die forging method of the special-shaped titanium alloy nozzle shell provided by the present invention are shown in Figure 8 , specifically including the following steps: S1, mold processing Design and process the pre-forging die 4 and the final forging die 6, and integrate the pre-forging die 4 and the final forging die 6 into a one-mold multi-cavity mold, the mold includes an upper mold 5 and a lower mold 8, the structure of the upper mold 5 is as follows Figure 4 As shown, the structure of the lower mold 8 is as follows Figure 5 As shown, the roughness of the cavity of the contact surface between the die and the forging is 0.8~1.6μm; The pre-forging die 4 and the final forging die 6 in the step 1 die are designed to increase the margin of 1 to 5 mm according to the product shape.

[0020] S2, bar preparation The required diameter and height of the bar 3 are calculated according to the weight and size of the forging, and the height-to-diameter ratio of the bar 3 is controlled in the range of 1 to 4, completing the blanking process.

[0021] The chamfer 2 of both end faces of the bar 3 is R5~R15mm to prevent cracks when hammering. Then, take any end face of the bar 3 as the reference and set the draft angle 1. The angle is set to 1°~6°. Figure 3 , ensuring that the conical surface of the bar 3 is smoothly placed into the lower die 8.

[0022] S3, pre-forging The upper die 5 and the lower die 8 are installed on the die forging equipment, and the die is preheated at a temperature of 200°C to 400°C, and graphite emulsion is sprayed on the pre-forging die 4 and the final forging die 6 of the die cavity, and then the heated bar material 3 is placed in the pre-forging die 4 of the lower die 8, and hammered until the upper die 5 and the lower die 8 are fitted to complete the pre-forging; In step S3, the die forging equipment is a forging hammer or an electro-hydraulic hammer; the titanium alloy bar 3 is heated, wherein the heating temperature is 0°C to 60°C below the phase transition point of the material, and the thermal insulation coefficient is (0.4 to 1.5) min / mm.

[0023] S4, final forging The pre-forged blank in S3 is transferred to the final forging die 6 of the lower die 8 and hammered until residual burrs appear on the parting surface, thus completing the final forging.

[0024] A keyway 7 is provided on the final forging die 6 to facilitate demoulding of the forging. In step S4, the demoulding operation is to put a flat-headed pry bar into the keyway 7, extend it to the burr, and pry the forging to demould.

[0025] S5, Surface treatment The forging surface is sandblasted to clean the surface oxide scale.

[0026] S6, Heat Treatment and Machining The forgings after surface treatment are heat treated and then machined to obtain the final product. Figure 2 .

[0027] The die forging method of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments: Example 1 See also Figure 6 , is the TC11 titanium alloy special-shaped nozzle housing forging prepared in this embodiment, and the specific processing process is as follows: S1, mold processing The mold design is to increase the margin of 2mm according to the product shape, and the pre-forging and final forging dies are processed. The cavity roughness of the contact surface between the mold and the forging is 1.6μm.

[0028] S2, bar preparation According to the weight and size of the forging, the required bar diameter is Φ80mm and the height is 210mm, with a height-to-diameter ratio of 2.625. After the blanking process is completed, one end is chamfered by R5 and the other end is chamfered by R8 to prevent cracks during hammering. Subsequently, the draft angle is set to 2° based on any end face of the bar.

[0029] S3, pre-forging The upper and lower dies are installed on the forging hammer, and the dies are preheated at a temperature of 250°C. The die cavity is sprayed with graphite emulsion, and then the titanium alloy bar is heated. The heating temperature is 950°C and the insulation coefficient is 0.8min / mm. The heated bar is placed in the lower die pre-forging die and hammered until the upper and lower dies fit together to complete the pre-forging.

[0030] S4, final forging Transfer the pre-forged billet to the lower die forging die and hammer it until residual burrs appear on the parting surface to complete the final forging. Put the flat-headed pry bar into the keyway, extend it to the burrs, and pry the forging to demould.

[0031] S5, Surface treatment The forging surface is sandblasted to clean the surface oxide scale.

[0032] S6, Heat Treatment and Machining Heat treatment of TC11 titanium alloy special-shaped nozzle shell forgings: primary annealing: 960℃ for 2h, air cooling; secondary annealing: 550℃ for 5h, air cooling; then machining to obtain the finished forgings.

[0033] Example 2 See also Figure 7 , is the TC4 titanium alloy special-shaped nozzle housing forging prepared in this embodiment, and the specific processing process is as follows: S1, mold processing The mold design is to increase the margin of 1mm according to the product shape, and the pre-forging and final forging dies are processed. The cavity roughness of the contact surface between the mold and the forging is 1.6μm.

[0034] S2, bar preparation According to the weight and size of the forging, the required bar diameter is calculated to be Φ110mm and the height is 270mm, with a height-to-diameter ratio of 2.45. After the blanking process is completed, one end is chamfered by R5 and the other end is chamfered by R8 to prevent cracks during hammering. Subsequently, the draft angle is set to 3° based on any end face of the bar.

[0035] S3, pre-forging The upper and lower dies are installed on the forging hammer, and the dies are preheated at 300°C. The die cavity is sprayed with graphite emulsion, and then the titanium alloy bar is heated at 940°C and the insulation coefficient is 0.6min / mm. The heated bar is placed in the lower die pre-forging die and hammered until the upper and lower dies fit together to complete the pre-forging.

[0036] S4, final forging Transfer the pre-forged billet to the lower die forging die and hammer it until residual burrs appear on the parting surface to complete the final forging. Put the flat-headed pry bar into the keyway, extend it to the burrs, and pry the forging to demould.

[0037] S5, Surface treatment Sandblast the forging surface to clean the surface oxide scale; S6, heat treatment and machining: The TC4 titanium alloy special-shaped nozzle shell forgings were kept at 780℃ for 2h, air-cooled, and then machined to obtain the finished forgings.

[0038] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A die forging method for a special-shaped titanium alloy nozzle housing, characterized in that: The following steps are involved: Design and process a one-mold multi-cavity mold that integrates a pre-forging mold and a final forging mold, the mold comprising an upper mold and a lower mold; Preheating the die, heating the bar material, placing the heated bar material in a pre-forging die of the die, and forging after closing the upper die and the lower die to obtain a pre-forged part; The pre-forged part is transferred to the final forging die, and the upper die and the lower die are fastened together for forging to obtain a formed part; After the molded part is surface treated, it is heat treated and machined to obtain the final forging.

2. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: The die increases the margin of 1 to 5 mm according to the shape of the final forging.

3. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: Before heating the bar material, the bar material is pre-processed, specifically: The height and diameter of the bar are determined according to the weight and size of the final forging, and the bar is selected; both end faces of the bar are rounded, and a draft angle is set based on any end face.

4. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 3, characterized in that: The ratio of the bar height to the diameter is (1-4):1, and the draft angle is 1°-6°.

5. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: The final forging die is also provided with a keyway.

6. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: The mold is preheated at 200°C to 400°C.

7. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: The heating rod material is specifically to heat the rod material to a temperature of 0°C to 60°C below the phase change point, and the thermal insulation coefficient is (0.4 to 1.5) min / mm.

8. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: The surface treatment of the molded part is specifically to perform sandblasting on the surface of the molded part and clean the surface oxide scale.

9. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: The cavity roughness of the contact surface between the die and the forging is 0.8-1.6 μm.

10. The die forging method of a special-shaped titanium alloy nozzle shell according to claim 1, characterized in that: After the mold is preheated, graphite lubricant is sprayed in the pre-forging mold and the final forging mold cavity of the mold.

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