A method for die forging a contoured titanium alloy nozzle case

Abstract

The present application belongs to the technical field of titanium alloy forging, and relates to a die forging method of a special-shaped titanium alloy nozzle shell. In view of the problems of low material utilization, low processing efficiency and damaged metal streamline in the prior art, the present application proposes to integrate the pre-forging and finish-forging dies into an integrated multi-cavity die, thereby simplifying the forging process. The specific steps include designing and processing the die, preheating the die, heating the bar and forging the pre-forging piece, transferring the pre-forging piece to the finish-forging die to forge the formed piece, and then performing surface treatment, heat treatment and machining. The present application can improve the material utilization, save the production cost, ensure the stable product performance, simplify the process flow, reduce the labor intensity and cost of workers, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy forging, and particularly relates to a die forging method for a special-shaped titanium alloy nozzle shell. BACKGROUND

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

[0003] For die forging of a special-shaped nozzle shell, a die is often designed in the manner of a rotary body as shown in the figure. Figure 1 Although the die forging process is simple, forming is convenient, and the blank is relatively regular, there are obvious problems: the material utilization rate is low, the machining allowance is large, the machining efficiency is low, multiple machining and heat treatment processes are often required, the machining process is long, and the product cost is greatly increased; in addition, the metal flow line of the forged piece formed by the die is damaged in the subsequent machining process, which changes the stress characteristics of the material and affects the integrity of the internal material structure of the nozzle, which poses a certain threat to the use conditions of the nozzle shell. SUMMARY

[0004] In order to overcome the deficiencies in the prior art, the application provides a die forging method for a special-shaped titanium alloy nozzle shell, which integrates the dies used for pre-forging and finish-forging, simplifies the forging process, and reduces the machining steps, so as to solve the problems in the above background and has a wide application prospect.

[0005] To achieve the above-mentioned purpose, the following technical solutions are adopted:

[0006] The application provides a die forging method for a special-shaped titanium alloy nozzle shell, which comprises the following steps:

[0007] An integrated one-die multi-cavity die of a pre-forging die and a finish-forging die is designed and machined, and the die comprises an upper die and a lower die;

[0008] The die is preheated, a rod is heated, and the heated rod is placed in the pre-forging die of the die. After the upper die and the lower die are buckled, forging is performed to obtain a pre-forging piece;

[0009] The pre-forging piece is transferred to the finish-forging die, the upper die and the lower die are buckled for forging, and a formed piece is obtained;

[0010] After surface treatment of the formed piece, heat treatment and machining are performed to obtain a finish-forging piece.

[0011] Preferably, the die has an allowance of 1-5 mm with respect to the shape of the finish-forging piece.

[0012] Preferably, the heating bar material further comprises pre-processing of the bar material, specifically: determining the height and diameter of the bar material according to the weight and size of the final forging piece, and selecting the bar material; rounding the two end faces of the bar material, and setting a draft angle with any one end face as a reference.

[0013] Further preferably, the ratio of the height and diameter of the bar material is (1-4):1, and the angle of the draft angle is 1°-6°.

[0014] Preferably, the final forging die is further provided with a key groove.

[0015] Preferably, the die is preheated at 200-400°C.

[0016] Preferably, the heating bar material specifically has a heating temperature of 0-60°C below the phase transition point, and a holding coefficient of (0.4-1.5) min / mm.

[0017] Preferably, the surface treatment of the formed piece specifically comprises sandblasting treatment of the surface of the formed piece, and cleaning of the surface oxide skin.

[0018] Preferably, the roughness of the die and the forged piece is 0.8-1.6 μm.

[0019] Preferably, the die is sprayed with graphite lubricant on the surface before use.

[0020] Preferably, the heat treatment of the formed piece comprises: primary annealing at 960°C for 2h, and air cooling; secondary annealing at 550°C for 5h, and air cooling.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0024] Figure 2 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0025] Figure 3 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0026] Figure 4 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0027] Figure 5 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0028] Figure 6 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0029] Figure 7 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0030] Figure 8 The die forging method of the special-shaped titanium alloy nozzle shell is characterized in that different die forging dies are designed for different nozzle shells, and the special-shaped forged blank is obtained through pre-forging and finish-forging of a bar.

[0031] Wherein, the bar material drawing angle 1, the bar material end face round angle 2, the bar material 3, the pre-forging die 4, the upper die 5, the finish-forging die 6, the keyway 7, the lower die 8, the TC11 titanium alloy special-shaped nozzle shell forging 9, the TC4 titanium alloy special-shaped nozzle shell forging 10, the mold 11 designed in a rotary body mode, the special-shaped titanium alloy nozzle shell 12. DETAILED DESCRIPTION

[0032] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0033] The die forging method of the special-shaped titanium alloy nozzle shell provided by the present application comprises the following steps: Figure 8 , and specifically comprises the following steps:

[0034] S1, mold processing

[0035] The pre-forging die 4 and the finish-forging die 6 are designed and processed, the pre-forging die 4 and the finish-forging die 6 are integrated into one mold with multiple cavities, the mold comprises the upper die 5 and the lower die 8, the structure of the upper die 5 is as shown in Figure 4 , the structure of the lower die 8 is as shown in Figure 5 , and the roughness of the mold and the forging contact surface cavity is 0.8-1.6 μm;

[0036] Step 1: the pre-forging die 4 and the finish-forging die 6 in the mold are designed to have a 1-5 mm excess amount of the product shape.

[0037] S2, bar material preparation

[0038] The diameter and height of the required bar material 3 are calculated according to the weight and size of the forging, the height-diameter ratio of the bar material 3 is controlled in the range of 1-4, and the blanking process is completed.

[0039] The two end faces of the bar material 3 are rounded 2 with R5-R15 mm to prevent cracks from occurring during hammering. Then, the drawing angle 1 is set with reference to the arbitrary end face of the bar material 3, the angle is set to 1°-6°, as shown in Figure 3 , to ensure that the tapered surface of the bar material 3 is smoothly put into the lower die 8.

[0040] S3, pre-forging

[0041] The upper die 5 and the lower die 8 are installed on a die forging equipment, preheating of the die is performed at a temperature of 200-400 DEG C, graphite milk is sprayed on the preforming die 4 and the finish forging die 6 of the die cavity, then the heated bar 3 is placed in the preforming die 4 of the lower die 8, hammering is performed until the upper die 5 and the lower die 8 are attached, and preforming is completed;

[0042] 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 0-60 DEG C below the phase transition point of the material, and the holding coefficient is (0.4-1.5) min / mm.

[0043] S4, finish forging

[0044] The preformed blank in S3 is transferred to the finish forging die 6 of the lower die 8, hammering is performed until residual burrs appear on the parting surface, and finish forging is completed.

[0045] The key groove 7 is arranged on the finish forging die 6, facilitating the ejection of the forged piece. In step S4, the flat-headed lever is placed in the key groove 7 and inserted into the burr, and the forged piece can be ejected by prying.

[0046] S5, surface treatment

[0047] The surface of the forged piece is sandblasted to clean the surface oxide skin.

[0048] S6, heat treatment and machining

[0049] The forged piece after surface treatment is subjected to heat treatment and then machining to obtain the final product, and the appearance is shown in Figure 2 .

[0050] The die forging method of the present application is further described in detail below in combination with the drawings and examples:

[0051] Example 1

[0052] Please refer to Figure 6 , the TC11 titanium alloy special-shaped nozzle shell forged piece prepared for this example, the specific processing process is as follows:

[0053] S1, die processing

[0054] The die is designed to have a 2mm excess margin along the product shape, and the preforming and finish forging dies are processed, and the roughness of the die and forged piece contact surface cavity is 1.6 μm.

[0055] S2, bar preparation

[0056] According to the weight and size of the forging, the required bar diameter is Φ80mm and the height is 210mm, the height-diameter ratio is 2.625, the blanking process is completed, one end is chamfered R5 and the other end is chamfered R8 to prevent cracks during hammering, and then the bar end face is set as the reference, and the draft angle of 2° is set.

[0057] S3, pre-forging

[0058] The upper and lower dies are installed on the forging hammer, and the die preheating is performed at a temperature of 250°C, the die cavity is sprayed with graphite milk, and then the titanium alloy bar is heated, wherein the heating temperature is 950°C and the holding coefficient is 0.8min / mm. The heated bar is placed in the lower die pre-forging mold, and hammering is performed until the upper and lower dies are fitted, and the pre-forging is completed.

[0059] S4, final forging

[0060] The pre-forged blank is transferred to the lower die final forging mold, and hammering is performed until the parting surface appears residual burrs, and the final forging is completed. The flat-headed lever is placed in the keyway and inserted into the burr, and the forging can be demolded by prying.

[0061] S5, surface treatment

[0062] The surface of the forging is sandblasted to clean the surface oxide skin.

[0063] S6, heat treatment and machining

[0064] The TC11 titanium alloy special-shaped nozzle shell forging is heat treated: primary annealing: 960°C for 2h, air cooling; secondary annealing: 550°C for 5h, air cooling; and then machined to obtain the finished forging.

[0065] Example 2

[0066] See Figure 7 The TC4 titanium alloy special-shaped nozzle shell forging prepared for this example is processed as follows:

[0067] S1, mold processing

[0068] The mold is designed with a 1mm excess margin added to the product shape, and the pre-forging and final forging molds are processed, and the mold and forging contact surface cavity roughness is 1.6μm.

[0069] S2, bar preparation

[0070] According to the weight and size of the forging, the required bar diameter is Φ110mm and the height is 270mm, the height-diameter ratio is 2.45, the blanking process is completed, one end is chamfered R5 and the other end is chamfered R8 to prevent cracks during hammering, and then the bar end face is set as the reference, and the draft angle of 3° is set.

[0071] S3, pre-forging

[0072] The upper and lower dies are installed on the forging hammer, and the die preheating is performed at a temperature of 300 DEG C, the die cavity is sprayed with graphite emulsion, and then the titanium alloy bar is heated, wherein the heating temperature is 940 DEG C, the holding coefficient is 0.6 min / mm, the heated bar is placed in the lower die pre-forging die, and hammering is performed until the upper and lower dies are fitted, and the pre-forging is completed.

[0073] S4, final forging

[0074] The pre-forged blank is transferred to the lower die final forging die, hammering is performed until the parting surface appears residual burrs, and the final forging is completed. The flat-end crowbar is placed in the key groove and inserted into the burr, and the forged piece can be demoulded by prying.

[0075] S5, surface treatment

[0076] The surface of the forged piece is sandblasted to clean the surface oxide scale.

[0077] S6, heat treatment and machining:

[0078] The TC4 titanium alloy special-shaped nozzle shell forging is heat treated at 780 DEG C for 2h, air cooled, and then machined to obtain the finished forging.

[0079] The above content only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A die forging method for an irregularly shaped titanium alloy nozzle housing, characterized in that, Includes the following steps: Design and manufacture a multi-cavity mold that integrates a pre-forging mold and a final forging mold, the mold including an upper mold and a lower mold; Before heating the bar stock, the bar stock is pre-processed, specifically: the height and diameter of the bar stock are determined according to the weight and size of the final forging, and the bar stock is selected; the two ends of the bar stock are rounded, and a draft angle is set with any one end face as a reference. The mold is preheated, the bar stock is heated, the heated bar stock is placed in the pre-forging mold of the mold, the upper mold and the lower mold are closed and forging is carried out to obtain the pre-forged part; The pre-forged part is transferred to the final forging die, and the upper and lower dies are engaged to forge the part and obtain the finished part; the final forging die is also provided with a keyway. After surface treatment of the formed part, heat treatment and machining are performed to obtain the final forging; the heat treatment of the formed part includes: one annealing, holding at 960℃ for 2 hours, and air cooling; Secondary annealing, holding at 550℃ for 5 hours, followed by air cooling.

2. The die forging method for the irregularly shaped titanium alloy nozzle housing according to claim 1, characterized in that, The mold has an allowance of 1-5mm as the final forging shape is adjusted.

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

4. The die forging method for the irregularly shaped titanium alloy nozzle housing according to claim 1, characterized in that, The mold is preheated at 200℃~400℃.

5. The die forging method for the irregularly shaped titanium alloy nozzle housing according to claim 1, characterized in that, The heating bar stock is specifically heated to a temperature of 0℃~60℃ below the phase change point, with a heat preservation coefficient of (0.4~1.5) min / mm.

6. The die forging method for the irregularly shaped titanium alloy nozzle housing according to claim 1, characterized in that, The surface treatment of the molded part specifically involves sandblasting the surface of the molded part and removing the surface oxide scale.

7. The die forging method for the irregularly shaped titanium alloy nozzle housing according to claim 1, characterized in that, The surface roughness of the contact surface between the mold and the forging is 0.8~1.6μm.

8. The die forging method for the irregularly shaped titanium alloy nozzle housing according to claim 1, characterized in that, After the mold is preheated, graphite lubricant is sprayed into the cavity of the pre-forging mold and the final forging mold.

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