High-strength steel flat head for underwater pressure equipment and integrated forging method thereof

Abstract

The application provides a high-strength steel flat head for underwater pressure equipment and an integrated forging method thereof. The flat head is integrally formed by a forging blank under the cooperation of a forging press and a forging die. The forging die comprises a matched upper die and a lower die. During the forming process, the lower die is located in the upper die. In use, the forging blank is placed on the lower die of the forging die, and the upper die is placed above the forging blank. The center lines of the three coincide. The upper die is acted on by the forging press to complete the forging of the flat head. The method realizes the integrated forming of the flat head, eliminates the need for welding, avoids the technical problems of welding stress and the decrease in the strength of the steel plate after cold bending, and improves the strength of the flat head.

Description

Technical Field

[0001] This invention relates to the field of underwater flat plate head manufacturing technology, specifically to a high-strength steel flat plate head for underwater pressure-resistant equipment and its integrated forging method. Background Technology

[0002] Chromium-nickel-molybdenum-vanadium series high-strength steel is a commonly used high-strength steel for underwater pressure equipment in my country. It has advantages such as high strength, high toughness, good weldability and strong resistance to seawater corrosion, making it more suitable for shipbuilding processes. Therefore, it is widely used in the manufacture of underwater pressure equipment.

[0003] Currently, the supply of high-strength chromium-nickel-molybdenum-vanadium steel in China is relatively limited, consisting mainly of quenched and tempered hot-rolled steel plates. For high-strength steel flat end caps used in underwater pressure equipment, if quenched and tempered hot-rolled steel plates are used, the process involves hot-rolled steel plate blanking, beveling, cold bending, conical shell welding, flat plate welding, weld inspection, and finishing. Therefore, when using quenched and tempered hot-rolled steel plates for flat end caps, two problems arise: firstly, the flat end caps require welding, leading to the superposition of structural stress and welding stress at the corners; secondly, the strength of the steel plate decreases after cold bending, affecting the strength of the flat end cap.

[0004] It is evident that providing a high-strength steel flat end cap structure for underwater pressure-resistant equipment to overcome the aforementioned problems is of great significance to the industry. Summary of the Invention

[0005] In view of this, the present invention provides a high-strength steel flat end cap for underwater pressure-resistant equipment and its integrated forging method. In this method, a forging die is used to forge the forging billet into a flat end cap, realizing the integrated forming of the flat end cap without welding. This avoids the technical problems of welding stress and the decrease in steel plate strength after cold bending, and ensures the material strength of the flat end cap.

[0006] The technical solution of the present invention is as follows:

[0007] A high-strength steel flat end cap for underwater pressure-resistant equipment is integrally formed from a forging billet under the combined action of a forging press and a forging die;

[0008] The forging blank is disc-shaped and includes M part and N part connected in sequence. The longitudinal section of M part is rectangular and the longitudinal section of N part is isosceles trapezoidal. A through hole A is provided on M part and a through hole B is provided on N part. The through hole A and the through hole B are coaxially arranged and have the same diameter.

[0009] The forging die includes an upper die and a lower die used together. During the forming process, the upper die is located inside the lower die.

[0010] The upper mold includes parts E, F, and G connected in sequence. Part E has a structure that is smaller at the bottom and larger at the top, and its longitudinal section is an isosceles trapezoid. Part F has a rectangular longitudinal section. The top surface dimension of Part E is the same as the bottom surface dimension of Part F. The bottom surface dimension of Part G is smaller than the top surface dimension of Part F.

[0011] The top of the lower mold is provided with a downward recessed groove, which is composed of parts A, B, C and D connected in sequence;

[0012] The longitudinal section of part A is rectangular, the longitudinal section of part B is an isosceles trapezoid, the longitudinal section of part C is rectangular, and the longitudinal section of part D is trumpet-shaped; the trumpet-shaped design of part D facilitates the movement of the forging billet into the groove.

[0013] During forging, part B of the lower die corresponds to part E of the upper die, and part C of the lower die corresponds to part F of the upper die.

[0014] In use, the forging blank is placed on the lower die, and the upper die is placed on the forging blank. The center lines of the upper die, the forging blank and the lower die are aligned. Under the action of the forging press, the upper die moves downward in the vertical direction until the flat end cap is stamped and formed, thus achieving one-piece forming.

[0015] Preferably, the edge of the D part protrudes into the groove, which can prevent the forging billet from deforming and affecting the shape of the finished product when it moves into the groove, thereby improving product quality.

[0016] Preferably, the outer diameter of the flat end cap is <5000mm and the wall thickness is ≤120mm.

[0017] An integrated forging method for high-strength steel flat end caps used in underwater pressure-resistant equipment, the process of which is as follows:

[0018] (1) The electroslag ingots are prepared by electric arc furnace roughing, refining in a ladle furnace, vacuum degassing, vacuum casting and electroslag remelting process. The chemical composition meets the chemical composition range requirements of chromium-nickel-molybdenum-vanadium series high-strength steel, [O]≤30ppm, [N]≤60ppm, [H]≤2ppm;

[0019] (2) The electroslag ingot is heated and forged using a forging press to obtain billet A;

[0020] (3) The billet A is flattened by rotating it 1 to 2 times to complete the forging and shape, and a disc-shaped billet B is obtained;

[0021] (4) The forged billet B is subjected to heat treatment after forging, and then the surface and inner hole are machined to ensure that there are no cracks or missing parts on the surface, so as to obtain the forged billet;

[0022] (5) Heat the finished forging billet and place the heated forging billet on the lower die of the forging die, and place the upper die on top of the forging billet, with the center lines of the three coinciding;

[0023] (6) Under the action of the forging press, the upper die moves downward in the vertical direction until the flat end cap is stamped and formed;

[0024] (7) After the stamped flat end cap is demolded, it undergoes post-forging heat treatment;

[0025] (8) Ensure the dimensional requirements of each part of the flat end cap by machining, and complete the integrated forging of the flat end cap.

[0026] Preferably, in step (2), the electroslag ingot is heated as follows: heating rate <100℃ / h, holding at 650℃±10℃ for 5h~8h, continuing to heat up, holding at 1250℃±10℃ for 12h~20h, and then forging.

[0027] Preferably, in step (2), the head and tail removal rates of the electroslag ingot are not less than 5% of the weight of the electroslag ingot, the total forging ratio is not less than 6.0, and the forging temperature range is 800℃~1250℃.

[0028] Preferably, in step (2), the forging process is to pass the electroslag ingot through 3 to 4 heats to complete the forging process of drawing, upsetting, drawing, and upsetting of the steel ingot, so as to ensure that the forging is sufficient.

[0029] Preferably, in step (5), the forging billet is heated at a rate of <100℃ / h, held at 650℃±10℃ for 2h~4h, and then heated to 1150℃±10℃ for 3h~6h before use.

[0030] Preferably, in steps (4) and (7), the post-forging heat treatment is normalizing and tempering. The normalizing holding temperature is 900℃±15℃ and the holding time is not less than 4h; the tempering holding temperature is 630℃±15℃ and the holding time is not less than 8h; the heating rate of both normalizing and tempering is <150℃ / h, and the cooling method is air cooling.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention achieves the integrated molding of flat end caps by using a forging die, eliminating the need for welding, avoiding the technical problems of welding stress and the decrease in steel plate strength after cold bending, and ensuring the material strength of the flat end caps. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the forging billet.

[0034] Figure 2 This is a schematic diagram of the upper mold structure.

[0035] Figure 3 This is a schematic diagram of the lower mold structure.

[0036] Figure 4 This is a schematic diagram of a flat end cap.

[0037] Figure 5 This is a schematic diagram of the structure of billet A.

[0038] Figure 6 This is a schematic diagram of the structure of billet B.

[0039] Figure 7 This is a schematic diagram of the assembly of the forging billet and the forging die.

[0040] Figure 8 This is a schematic diagram of the forging process.

[0041] Figure 9 This is a schematic diagram of the stamping process.

[0042] In the figure, 1-forging billet, 101-M section, 102-N section, 2-upper die, 201-E section, 202-F section, 203-G section, 3-lower die, 4-through hole A, 5-through hole B, 6-groove, 601-A section, 602-B section, 603-C section, 604-D section. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0044] Example 1

[0045] Combination Figures 1-4 The present invention provides a high-strength steel flat end cap for underwater pressure-resistant equipment, which is integrally formed by forging billet 1 under the action of forging press and forging die;

[0046] The forging billet 1 is in the shape of a disc, including part M 101 and part N 102 connected in sequence. The longitudinal section of part M 101 is rectangular, and the longitudinal section of part N 102 is an isosceles trapezoid. A through hole A4 is provided on part M 101, and a through hole B5 is provided on part N 102. The through holes A4 and B5 are coaxially arranged and have the same diameter.

[0047] The forging die includes an upper die 2 and a lower die 3 for use together. During the forming process, the upper die 2 is located inside the lower die 3.

[0048] The upper mold 2 includes E part 201, F part 202 and G part 203 connected in sequence. E part 201 has a structure that is smaller at the bottom and larger at the top, and its longitudinal section is an isosceles trapezoid. The longitudinal section of F part 202 is rectangular. The top surface dimension of E part 201 is the same as the bottom surface dimension of F part 202. The bottom surface dimension of G part 203 is smaller than the top surface dimension of F part 202.

[0049] The top of the lower mold 3 is provided with a downward recessed groove 6, which is composed of part A 601, part B 602, part C 603 and part D 604 connected in sequence;

[0050] The longitudinal section of part A 601 is rectangular, the longitudinal section of part B 602 is an isosceles trapezoid, the longitudinal section of part C 603 is rectangular, and the longitudinal section of part D 604 is trumpet-shaped; the trumpet-shaped setting of part D 604 facilitates the movement of the forging billet 1 into the groove 6.

[0051] The edge of part D 604 protrudes into the groove 6. When the forging billet 1 moves into the groove 6, it can prevent it from deforming and affecting the shape of the finished product, thus improving product quality.

[0052] During forging, part B 602 of the lower die 3 corresponds to part E 201 of the upper die 2, and part C 603 of the lower die 3 corresponds to part F 202 of the upper die 2.

[0053] In use, the forging blank 1 is placed on the lower die 3, and the upper die 2 is placed on the forging blank 1. The center lines of the upper die 2, the forging blank 1 and the lower die 3 coincide. Under the action of the forging press, the upper die 2 moves vertically downwards until the flat end cap is stamped and formed, thus achieving one-piece forming.

[0054] Example 2

[0055] An integrated forging method for high-strength steel flat end caps used in underwater pressure-resistant equipment, the process of which is as follows:

[0056] (1) The electroslag ingots were prepared by electric arc furnace roughing, refining in a ladle furnace, vacuum degassing, vacuum casting and electroslag remelting process. The chemical composition met the requirements of the chemical composition range of chromium-nickel-molybdenum-vanadium series high-strength steel, with [O] 25ppm, [N] 42ppm and [H] 1.1ppm.

[0057] The high-strength steel flat end cap is integrally formed from a forging billet using a forging press and the forging die of Example 1.

[0058] (2) Heat the electroslag ingot at a rate of 90℃ / h, hold it at 650℃ for 6h, then heat it to 1250℃ and hold it for 16h before taking it out of the furnace;

[0059] The head and tail of the electroslag ingot were removed, with a removal rate of 5.5% of the weight of the electroslag ingot. Then, it was forged using a forging press with a total forging ratio of 6.5. The forging start temperature was 1220℃ and the forging end temperature was 870℃.

[0060] The electroslag ingot undergoes a forging process involving three heating cycles, including drawing, upsetting, drawing again, and upsetting, to obtain billet A. (See...) Figure 5 ;

[0061] (3) The billet A is flattened by rotating it twice to complete the forging process, resulting in a disc-shaped billet B, see below. Figure 6 ;

[0062] (4) The forged billet B was subjected to post-forging heat treatment. The normalizing holding temperature was 905℃ and the holding time was 7h; the tempering holding temperature was 625℃ and the holding time was 10h. The heating rate for both normalizing and tempering was 90℃ / h, and the cooling method for both was air cooling. Then, the surface and inner hole were machined to obtain the forged billet, see Figure 1 ;

[0063] (5) Heat the finished forging billet at a rate of 90℃ / h, hold at 650℃ for 3h, continue heating, hold at 1150℃ for 4.5h, and set aside for use; then place the heated forging billet on the lower die of the forging mold, place the upper die on top of the forging billet, and align the center lines of the three parts, see Figure 7 ;

[0064] (6) Under the action of the forging press, the upper die moves downward in the vertical direction until the flat end cap is stamped and formed, see Figures 8-9 ;

[0065] (7) After the stamped flat end cap is demolded, it is subjected to post-forging heat treatment. The normalizing holding temperature is 910℃ and the holding time is 5h; the tempering holding temperature is 625℃ and the holding time is 9h; the heating rate of normalizing and tempering is 85℃ / h, and the cooling method is air cooling.

[0066] (8) Ensure the dimensional requirements of each part of the flat end cap by machining, and complete the integrated forging of the flat end cap; in this embodiment, the outer diameter of the flat end cap is 4000mm and the wall thickness is 110mm.

[0067] Example 3

[0068] An integrated forging method for high-strength steel flat end caps used in underwater pressure-resistant equipment, the process of which is as follows:

[0069] (1) The electroslag ingots are prepared by electric arc furnace roughing, refining in a ladle furnace, vacuum degassing, vacuum casting and electroslag remelting process. The chemical composition meets the chemical composition range requirements of chromium-nickel-molybdenum-vanadium series high-strength steel, [O] 20ppm, [N] 50ppm, [H] 1ppm;

[0070] The high-strength steel flat end cap is integrally formed from a forging billet using a forging press and the forging die of Example 1.

[0071] (2) Heat the electroslag ingot at a rate of 70℃ / h, hold at 640℃ for 5h, then heat to 1240℃ and hold for 20h before removing from the furnace;

[0072] The head and tail of the electroslag ingot are removed, with a removal rate of 6% of the weight of the electroslag ingot. Then, it is forged using a forging press with a total forging ratio of 7. The forging start temperature is 1200℃ and the forging end temperature is 800℃.

[0073] The electroslag ingot undergoes four heating cycles to complete the forging process of drawing, upsetting, drawing, and upsetting of the steel ingot, resulting in billet A.

[0074] (3) The billet A is flattened by rotating it once to complete the forging and form a disc-shaped billet B;

[0075] (4) The forged billet B is subjected to heat treatment after forging. The normalizing holding temperature is 890℃ and the holding time is 5h; the tempering holding temperature is 620℃ and the holding time is 9h; the heating rate of normalizing and tempering is 80℃ / h, and the cooling method is air cooling; then the surface and inner hole are processed by machining to obtain the forging billet.

[0076] (5) Heat the finished forging billet at a heating rate of 80℃ / h, hold at 640℃ for 4h, continue heating, hold at 1140℃ for 6h, and set aside for use; then place the heated forging billet on the lower die of the forging mold, place the upper die on top of the forging billet, and make sure the center lines of the three coincide.

[0077] (6) Under the action of the forging press, the upper die moves downward in the vertical direction until the flat end cap is stamped and formed, see Figures 7-8 ;

[0078] (7) After the stamped flat end cap is demolded, it is subjected to post-forging heat treatment. The normalizing holding temperature is 915℃ and the holding time is 6h; the tempering holding temperature is 615℃ and the holding time is 9h; the heating rate for both normalizing and tempering is 120℃ / h, and the cooling method is air cooling.

[0079] (8) Ensure the dimensional requirements of each part of the flat end cap by machining, and complete the integrated forging of the flat end cap; in this embodiment, the outer diameter of the flat end cap is 3000mm and the wall thickness is 100mm.

[0080] Example 4

[0081] An integrated forging method for high-strength steel flat end caps used in underwater pressure-resistant equipment, the process of which is as follows:

[0082] (1) The electroslag ingots were prepared by electric arc furnace roughing, refining in a ladle furnace, vacuum degassing, vacuum casting and electroslag remelting process. The chemical composition met the requirements of the chemical composition range of chromium-nickel-molybdenum-vanadium series high-strength steel, [O] 25ppm, [N] 35ppm, [H] 1ppm;

[0083] The high-strength steel flat end cap is integrally formed from a forging billet using a forging press and the forging die of Example 1.

[0084] (2) Heat the electroslag ingot at a rate of 95℃ / h, hold it at 660℃ for 8h, then heat it to 1250℃ and hold it for 12h before taking it out of the furnace for forging.

[0085] The head and tail of the electroslag ingot were removed, with a removal rate of 6.5% of the weight of the electroslag ingot. Then, it was forged using a forging press with a total forging ratio of 7.5. The forging start temperature was 1230℃ and the forging end temperature was 920℃.

[0086] The electroslag ingot undergoes three heating cycles to complete the forging process of drawing, upsetting, drawing, and upsetting of the steel ingot, resulting in billet A;

[0087] (3) The billet A is flattened by rotating it twice to complete the forging process and obtain a disc-shaped billet B;

[0088] (4) The forged billet B is subjected to heat treatment after forging. The normalizing holding temperature is 915℃ and the holding time is 5.5h; the tempering holding temperature is 645℃ and the holding time is 9h; the heating rate of normalizing and tempering is 120℃ / h, and the cooling method is air cooling; then the surface and inner hole are machined to obtain the forging billet.

[0089] (5) Heat the finished forging billet at a heating rate of 70℃ / h, hold at 660℃ for 4h, continue heating, hold at 1160℃ for 6h, and set aside for use; then place the heated forging billet on the lower die of the forging mold, place the upper die on top of the forging billet, and make sure the center lines of the three coincide.

[0090] (6) Under the action of the forging press, the upper die moves downward in the vertical direction until the flat end cap is stamped and formed;

[0091] (7) After the stamped flat end cap is demolded, it is subjected to post-forging heat treatment. The normalizing holding temperature is 910℃ and the holding time is 5h; the tempering holding temperature is 625℃ and the holding time is 9h; the heating rate of normalizing and tempering is 85℃ / h, and the cooling method is air cooling.

[0092] (8) Ensure the dimensional requirements of each part of the flat end cap by machining, and complete the integrated forging of the flat end cap; in this embodiment, the outer diameter of the flat end cap is 4500mm and the wall thickness is 120mm.

[0093] Although the present invention has been described in detail with reference to preferred embodiments, it is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A high-strength steel flat end cap for underwater pressure-resistant equipment, characterized in that, The flat end cap is integrally formed from a forging billet using a forging press and a forging die. The forging blank is disc-shaped and includes M part and N part connected in sequence. The longitudinal section of M part is rectangular and the longitudinal section of N part is isosceles trapezoidal. A through hole A is provided on M part and a through hole B is provided on N part. The through hole A and the through hole B are coaxially arranged and have the same diameter. The forging die includes an upper die and a lower die used together. During the forming process, the upper die is located inside the lower die. The upper mold includes sections E, F, and G, which are set from bottom to top and connected in sequence. Section E has a structure that is smaller at the bottom and larger at the top, and its longitudinal section is an isosceles trapezoid. The longitudinal section of section F is rectangular. The top surface dimension of section E is the same as the bottom surface dimension of section F. The bottom surface dimension of section G is smaller than the top surface dimension of section F. The top of the lower mold is provided with a downward recessed groove, which is composed of parts A, B, C and D connected in sequence from bottom to top; The longitudinal section of part A is rectangular, the longitudinal section of part B is an isosceles trapezoid, the longitudinal section of part C is rectangular, and the longitudinal section of part D is trumpet-shaped. The edge of part D protrudes into the groove. The outer diameter of the flat end cap is <5000mm, and the wall thickness is ≤120mm.

2. The integrated forging method for high-strength steel flat end caps for underwater pressure-resistant equipment as described in claim 1, characterized in that, The process is as follows: (1) The electroslag ingots are prepared by electric arc furnace roughing, refining in a ladle furnace, vacuum degassing, vacuum casting and electroslag remelting process. The chemical composition meets the chemical composition range requirements of chromium-nickel-molybdenum-vanadium series high-strength steel, [O]≤30ppm, [N]≤60ppm, [H]≤2ppm; (2) The electroslag ingot is heated and forged using a forging press to obtain billet A; (3) The billet A is flattened by rotating it 1 to 2 times to complete the forging and shape, and a disc-shaped billet B is obtained; (4) The cake-shaped billet B is subjected to heat treatment after forging, and then the surface and inner hole are machined by machining. (5) Heat the finished forging billet and place the heated forging billet on the lower die of the forging die, and place the upper die on top of the forging billet, with the center lines of the three coinciding; (6) Under the action of the forging press, the upper die moves downward in the vertical direction until the flat end cap is stamped and formed; (7) After the stamped flat end cap is demolded, it undergoes post-forging heat treatment; (8) Ensure the dimensional requirements of each part of the flat end cap by machining, and complete the integrated forging of the flat end cap.

3. The integrated forging method for high-strength steel flat end caps for underwater pressure-resistant equipment as described in claim 2, characterized in that, In step (2), the electroslag ingot is heated at a rate of <100℃ / h, held at 650℃±10℃ for 5h~8h, and then heated to 1250℃±10℃ for 12h~20h before being taken out of the furnace for forging.

4. The integrated forging method for high-strength steel flat end caps for underwater pressure-resistant equipment as described in claim 2, characterized in that, In step (2), the head and tail removal rates of the electroslag ingot are not less than 5% of the weight of the electroslag ingot, the total forging ratio is not less than 6.0, and the forging temperature range is 800℃~1250℃.

5. The integrated forging method for high-strength steel flat end caps for underwater pressure-resistant equipment as described in claim 2, characterized in that, In step (2), the forging process involves the electroslag ingot being heated 3 to 4 times to complete the forging process of drawing, upsetting, drawing, and upsetting of the steel ingot.

6. The integrated forging method for high-strength steel flat end caps for underwater pressure-resistant equipment as described in claim 2, characterized in that, In step (5), the forging billet is heated at a rate of <100℃ / h, held at 650℃±10℃ for 2h~4h, and then heated to 1150℃±10℃ for 3h~6h before use.

7. The integrated forging method for high-strength steel flat end caps for underwater pressure-resistant equipment as described in claim 2, characterized in that, In steps (4) and (7), the post-forging heat treatment is normalizing and tempering. The normalizing holding temperature is 900℃±15℃ and the holding time is not less than 4h. The tempering holding temperature is 630℃±15℃ and the holding time is not less than 8h. The heating rate of both normalizing and tempering is <150℃ / h, and the cooling method is air cooling.

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