A method for forming large-size titanium alloy circular ring deep cavity parts by stretching

Abstract

The present invention relates to a method for extending and forming a large-sized titanium alloy circular ring deep cavity part, comprising: designing and manufacturing a hot forming mold; reserving a certain margin around the circumference, performing laser cutting and blanking, and spraying an anti-oxidation coating; correctly assembling the blank holder ring with the lower mold of the mold, so that the blank holder ring can move vertically up and down under the constraint of the lower mold; heating the mold, and using the rising of the equipment's top rod to lift the blank holder ring and make it flush with the highest point of the lower mold forming surface; starting the equipment, and moving the upper platform equipped with the upper mold downward, so that the upper mold first contacts the titanium alloy blank; removing the margin of the formed blank to ensure that the circumferential angle of each part is fixed; and forming a large-sized titanium alloy circular ring with a U-shaped cross-section. The present invention breaks through the limitation of equipment size and performs segmented forming. During the forming process of the plate, the metal flows more freely, effectively reducing the thinning rate during the forming process, making the structure more uniform and having better strength.

Description

Technical Field

[0001] The invention relates to a method for stretching and forming a large-size titanium alloy circular ring deep cavity part, and belongs to the technical field of titanium alloy precision forming, processing and manufacturing. Background Art

[0002] Titanium alloys possess excellent physical and mechanical properties, such as high-temperature resistance, corrosion resistance, and high specific strength, and are widely used in aerospace, shipbuilding, biomedical, petrochemical, and other fields. Under high-temperature conditions, titanium alloys' plasticity can be significantly improved, resulting in excellent formability. However, deep-cavity titanium alloy parts require significant deformation, placing higher demands on their formability. During the forming process, they are prone to wrinkling, severe localized thinning, and even cracking. Typical processing options for these deep-cavity parts include profile bending and superplastic forming. Summary of the Invention

[0003] The technical problem addressed by this invention is to overcome the shortcomings of existing technologies by proposing a method for the stretch forming of large-sized titanium alloy circular ring deep-cavity parts. By dividing the large-sized circular ring deep-cavity parts into several identical sections, each formed separately and then welded, this method enables the rapid manufacture of large-sized circular ring deep-cavity parts. Compared with integral forming, this forming method overcomes the limitations of equipment size. The segmented forming method allows for freer metal flow during the sheet forming process, effectively reducing the thinning rate during the forming process, resulting in a more uniform structure and improved strength.

[0004] The solution of the present invention is:

[0005] A method for forming a large-size titanium alloy circular ring deep cavity part by stretching, comprising:

[0006] Step 1: Design and manufacture a thermoforming mold. The mold includes an upper mold, a lower mold, and a blank holder. The upper mold is an integral unit with a weight-reducing groove on the top and an oblong groove on the side for fixing the upper mold on the upper platform of the thermoforming machine. Reinforcing ribs are provided on the inner side of the arc.

[0007] The lower die is a whole, with a weight-reducing groove at the bottom and an oblong groove on the side for fixing the lower die to the lower platform of the thermoforming machine. Reinforcement ribs are provided on the inner side of the arc, and several through holes are machined on both sides of the forming area of the lower die for the passage and up and down movement of the thermoforming machine's ejector rod.

[0008] The blank holder is a flat plate with an arc-shaped hole in the middle that is the same as the arc of the part. There is a certain gap between the outer dimensions of the arc hole and the outer dimensions of the forming surface of the lower die, so the blank holder can be inserted into it and move freely vertically up and down. The relative position relationship between the upper die and the lower die is achieved by coupling two trapezoidal positioning structures;

[0009] Step 2: Based on the mold and part model in step 1, a certain margin is reserved around the circumference, laser cutting is performed, and anti-oxidation coating is sprayed;

[0010] Step 3: Fix the mold manufactured in step 1 on the upper platform of the thermoforming machine through the upper mold of the pressing plate, and fix the lower mold on the lower platform of the thermoforming machine. The blank holder is properly assembled with the lower mold of the mold, and the blank holder can move vertically up and down under the constraint of the lower mold;

[0011] Step 4: Heat the mold and use the rising push rod of the equipment to lift the blank holder to be flush with the highest point of the lower mold forming surface. Set the push rod pressure and place the sheet laser cut in step 2 flat on the blank holder according to the positioning pin position. Keep warm for at least 10 minutes.

[0012] Step 5: Start the equipment, and the upper platform equipped with the upper die moves downward. The upper die first contacts the titanium alloy blank. The titanium alloy blank is pressed in the middle position by the upper die and the blank holder. There is a pressure difference of at least 100 tons between the hot forming machine ejector and the hot forming machine upper platform. When the blank holder and the upper die are forced to press the titanium alloy blank again, the friction force is equivalent to the pulling force of the surrounding ring on the titanium alloy blank, and the titanium alloy blank moves downward together until the die is closed. The part is finally formed and kept warm and pressurized for at least 20 minutes.

[0013] Step 6: Use milling to remove the excess of the formed blank to ensure that the circumferential angle of each part is fixed;

[0014] In step 7, the parts milled in step 6 are welded to finally produce a large-sized titanium alloy ring with a U-shaped cross-section.

[0015] Furthermore, the mold material in step 1 is medium silicon molybdenum ductile iron or high temperature resistant stainless steel heat resistant mold material.

[0016] Furthermore, in step 1, the number of through holes is 3 to 10.

[0017] Furthermore, in step 1, there is a gap between the outer dimensions of the arc hole and the outer dimensions of the forming surface of the lower die, and the gap is 0.5 to 2 mm.

[0018] Furthermore, in step 2, the thickness of the titanium alloy is 0.5 to 5 mm.

[0019] Furthermore, in step 4, the forming temperature is 600-750° C. for titanium alloy, 800-950° C. for high-temperature alloy, and 300-400° C. for aluminum alloy.

[0020] Furthermore, in step 6, the circumferential angle is 360 / n, where n is an integer, n=2-6.

[0021] Furthermore, the through hole has a diameter of 55-65 mm.

[0022] Furthermore, the ram pressure is set to at least 50 tons.

[0023] Furthermore, in step 4, the mold is heated to 700°C.

[0024] The beneficial effects of the present invention compared with the prior art are:

[0025] (1) The present invention evenly divides the parts into three equal parts. This division method minimizes the weld length and can effectively avoid deformation caused by welding heat in and out;

[0026] (2) The present invention reasonably sets the ejector pressure. During the forming process, the parts are constrained to slide. By adjusting the pressure difference between the upper die and the blank holder, the thinning rate of the plate can be controlled to the greatest extent, and the thinning rate can be controlled within 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The mold composition of the present invention;

[0028] Among them, 1-upper die, 2-lower die, 3-blank holder;

[0029] Figure 2 Upper mold for the mold of the present invention;

[0030] Among them, 4-reinforcement rib, 5-weight reduction groove, 6-long circular groove, 7-trapezoidal positioning structure;

[0031] Figure 3 It is the lower mold of the mold of the present invention;

[0032] Among them, 8-forming surface, 9-through hole;

[0033] Figure 4 The titanium alloy blank of the present invention;

[0034] Figure 5 It is the placement position of the titanium alloy blank of the present invention;

[0035] Figure 6 The titanium alloy forming blank of the present invention;

[0036] Figure 7 It is a large-sized titanium alloy ring of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the embodiments.

[0038] A method for forming a large-size titanium alloy circular ring deep cavity part by stretching, comprising:

[0039] Step 1: Design and manufacture the hot forming mold. The mold consists of three parts: the upper mold, the lower mold and the blank holder. The mold material is high temperature resistant medium silicon molybdenum ductile iron. The mold is cast according to the design model and then milled. Figure 1 shown.

[0040] The upper mold of the mold is a whole. A weight-reducing groove is set on the top of the mold. An oblong groove is set on the side of the mold to fix the mold on the upper platform of the thermoforming machine. A reinforcing rib is set on the inner side of the arc. Figure 2 shown.

[0041] The lower die of the mold is a whole. A weight-reducing groove is set at the bottom of the mold. An oblong groove is set on the side of the mold to fix the mold on the lower platform of the thermoforming machine. A reinforcing rib is set on the inner side of the arc. 10 through holes with a diameter of 60mm are processed on both sides of the forming area of the lower die of the mold to allow the thermoforming machine's ejector rod to pass through and move up and down. Figure 3 shown.

[0042] The mold blank holder is a flat plate with an arc-shaped hole in the middle that is the same as the arc of the part. There is a 0.5mm gap between the outer dimensions of the arc hole and the outer dimensions of the forming surface of the lower mold. It can be inserted into it and can move freely vertically up and down. The relative position relationship between the upper mold and the lower mold is achieved by coupling two trapezoidal positioning structures.

[0043] Step 2: Based on the mold and part model in step 1, a certain margin is reserved around the circle, and laser cutting is performed, and anti-oxidation coating is sprayed. The thickness of the titanium alloy blank is 4mm and the shape is as follows: Figure 4 shown.

[0044] Step 3: Fix the mold manufactured in step 1 on the upper platform of the thermoforming machine through the upper mold of the pressing plate, and fix the lower mold on the lower platform of the thermoforming machine. Assemble the blank holder and the lower mold of the mold correctly. The blank holder can move vertically up and down under the constraint of the lower mold.

[0045] Step 4: Heat the mold to 700℃, use the rising of the equipment ejector to lift the blank holder ring to be flush with the highest point of the lower mold forming surface, set the ejector pressure to 50 tons, and place the sheet laser cut in step 2 flat on the blank holder ring according to the position of the positioning pin. Figure 5 Keep warm for 10 minutes.

[0046] Step 5, start the equipment, the upper platform with the upper die moves downward, set the pressure to 150 tons, the upper die first contacts the titanium alloy blank, the titanium alloy blank is pressed in the middle position by the upper die and the blank holder, there is a pressure difference of 100 tons between the thermoforming machine top rod and the upper platform of the thermoforming machine, forcing the blank holder and the upper die to press the titanium alloy blank again, the effect of friction is equivalent to the titanium alloy blank being subjected to the tension of the circumference, and moving downward together until the mold is closed, the part is finally formed, and kept warm and pressurized for 20 minutes. The formed blank is as follows Figure 6 shown.

[0047] Step 6: Use milling to remove the excess of the formed blank to ensure that the circumferential angle of each part is 120°.

[0048] Step 7: Weld the parts milled in step 6 to make a large-sized titanium alloy ring with a U-shaped cross section. Figure 7 shown.

[0049] The mold material in step 1 is heat-resistant mold material such as medium silicon-molybdenum ductile iron and high-temperature resistant stainless steel.

[0050] In step 1, there are 3 to 10 through holes.

[0051] In step 1, there is a gap of 0.5 to 2 mm between the outer dimensions of the arc hole and the outer dimensions of the forming surface of the lower die.

[0052] In step 2, the material is titanium alloy, aluminum alloy, high temperature alloy, etc.

[0053] The thickness of the titanium alloy in step 2 is 0.5 to 5 mm.

[0054] The forming temperature in step 4 is 600-750°C for titanium alloy, 800-950°C for high-temperature alloy, and 300-400°C for aluminum alloy.

[0055] Step 6: The circular angle is 360 / n, where n is an integer, n=2-6.

[0056] The present invention evenly divides the parts into three equal parts. This division method minimizes the weld length and can effectively avoid deformation caused by welding heat in and out.

[0057] The present invention reasonably sets the ejector pressure, and during the forming process, the parts are constrained to slide. By adjusting the pressure difference between the upper die and the pressure ring, the thinning rate of the plate can be controlled to the greatest extent, and the thinning rate can be controlled within 5%.

[0058] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for forming a large-size titanium alloy ring deep cavity part by stretching, characterized in that: include: Step 1: Design and manufacture a thermoforming mold. The mold includes an upper mold, a lower mold, and a blank holder. The upper mold is an integral unit with a weight-reducing groove on the top and an oblong groove on the side for fixing the upper mold on the upper platform of the thermoforming machine. Reinforcing ribs are provided on the inner side of the arc. The lower die is a whole, with a weight-reducing groove at the bottom and an oblong groove on the side for fixing the lower die to the lower platform of the thermoforming machine. Reinforcement ribs are provided on the inner side of the arc, and several through holes are machined on both sides of the forming area of the lower die for the passage and up and down movement of the thermoforming machine's ejector rod. The blank holder is a flat plate with an arc-shaped hole in the middle that is the same as the arc of the part. There is a certain gap between the outer dimensions of the arc hole and the outer dimensions of the forming surface of the lower die, so the blank holder can be inserted into it and move freely vertically up and down. The relative position relationship between the upper die and the lower die is achieved by coupling two trapezoidal positioning structures; Step 2: Based on the mold and part model in step 1, a certain margin is reserved around the circumference, laser cutting is performed, and anti-oxidation coating is sprayed; Step 3: Fix the mold manufactured in step 1 on the upper platform of the thermoforming machine through the upper mold of the pressing plate, and fix the lower mold on the lower platform of the thermoforming machine. The blank holder is properly assembled with the lower mold of the mold, and the blank holder can move vertically up and down under the constraint of the lower mold; Step 4: Heat the mold and use the rising push rod of the equipment to lift the blank holder to be flush with the highest point of the lower mold forming surface. Set the push rod pressure and place the sheet laser cut in step 2 flat on the blank holder according to the positioning pin position. Keep warm for at least 10 minutes. Step 5: Start the equipment, and the upper platform equipped with the upper die moves downward. The upper die first contacts the titanium alloy blank. The titanium alloy blank is pressed in the middle position by the upper die and the blank holder. There is a pressure difference of at least 100 tons between the hot forming machine ejector and the hot forming machine upper platform. When the blank holder and the upper die are forced to press the titanium alloy blank again, the friction force is equivalent to the pulling force of the surrounding ring on the titanium alloy blank, and the titanium alloy blank moves downward together until the die is closed. The part is finally formed and kept warm and pressurized for at least 20 minutes. Step 6: Use milling to remove the excess of the formed blank to ensure that the circumferential angle of each part is fixed; In step 7, the parts milled in step 6 are welded to finally produce a large-sized titanium alloy ring with a U-shaped cross-section.

2. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: The mold material in step 1 is medium silicon molybdenum ductile iron or high temperature resistant stainless steel heat resistant mold material.

3. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: In step 1, there are 3 to 10 through holes.

4. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: In step 1, there is a gap between the outer dimensions of the arc hole and the outer dimensions of the forming surface of the lower die, and the gap is 0.5 to 2 mm.

5. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: The thickness of the titanium alloy in step 2 is 0.5 to 5 mm.

6. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: The forming temperature in step 4 is 600-750°C for titanium alloy, 800-950°C for high-temperature alloy, and 300-400°C for aluminum alloy.

7. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: Step 6: The circular angle is 360 / n, where n is an integer, n=2-6.

8. A method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1 or 3, characterized in that: The through hole diameter is 55-65mm.

9. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: Set the ram pressure to at least 50 tons.

10. The method for forming a large-size titanium alloy circular ring deep cavity part by stretching according to claim 1, characterized in that: In step 4, the mold is heated to 700°C.

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