Heat treatment forming method for end socket

Abstract

The invention discloses an end socket heat treatment forming method, which belongs to the technical field of heat forming welding, and comprises the following steps: welding a welding seam of a base layer; a lining plate is embedded in a welding seam of the coating, and the lining plate and the coating are fixed; thermally forming and pressing the end socket; the lining plate is taken down, and a welding seam of the coating is welded; according to the method, during thermal forming of the end socket, the lining plate embedded in the welding seam of the coating replaces a traditional welding seam of the coating, the lining plate can be conveniently removed after thermal forming of the end socket, the welding seam at the position of the coating can be subjected to repair welding, the intergranular corrosion resistance of the position of the coating cannot be reduced, meanwhile, the lining plate is not a disposable article and can be repeatedly used, and the cost is reduced. And double welding materials do not need to be used at the welding seam of the coating, so that the cost is effectively saved, the operation is simple and quick, and excessive polishing and welding procedures are not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoforming welding, and particularly relates to a forming method for heat treatment of a head. Background Art

[0002] Intergranular corrosion is a kind of corrosion that spreads inward along the grain boundaries of metals. Due to the difference in chemical composition between the grain surface and the interior, as well as the existence of grain boundary impurities or internal stresses, intergranular corrosion will damage the bonding between grains, greatly reducing the mechanical strength of metals. Moreover, after the corrosion occurs, the surface of the metal and alloy still maintains a certain metallic luster, showing no signs of damage, but the bonding force between grains is significantly weakened, and the mechanical properties deteriorate, and it cannot withstand knocking. Therefore, it is a very dangerous corrosion, usually occurring in brass, hard aluminum alloys, and some stainless steels and nickel-based alloys. Intergranular corrosion of stainless steel welds is a major problem in the chemical industry.

[0003] When conducting welding procedure qualification for the hot forming of nickel-based composite plate heads of pressure vessels, the situation of unqualified intergranular corrosion often occurs and repair is required. To avoid this situation, the existing solution is to weld the clad layer weld before the hot forming of the head and remove the clad layer weld after the hot forming of the head. Specifically: after welding the base layer, directly weld the clad layer. After hot forming, grind off the weld at the clad layer and then repair weld the weld at the clad layer, so that the weld at the clad layer in contact with the medium does not undergo the normalizing and annealing states, and the problem of intergranular corrosion is also solved. However, this solution requires using double the amount of welding materials at the clad layer weld, and also requires personnel to grind inside the head. Not only is the operation difficult and there are safety hazards, but also secondary welding is required, wasting welding materials and manpower, and the waste of manpower and material resources is serious, which does not conform to the concept of sustainable development and is unacceptable in terms of cost.

[0004] Therefore, it is an urgent problem to be solved at present to research and develop a forming method for heat treatment of a head that can effectively solve the problem of intergranular corrosion, save costs, and is simple and fast to operate. Summary of the Invention

[0005] For the problems existing in the prior art, the present invention provides a forming method for heat treatment of a head. When hot forming the head, a lining plate embedded in the weld of the clad layer is used to replace the traditional clad layer weld. After the hot forming of the head, the lining plate is removed and the clad layer is repair welded, so that the intergranular corrosion resistance at the clad layer does not decrease. While the lining plate can be reused, it is no longer necessary to use double the amount of welding materials at the clad layer weld, effectively saving costs and being simple and fast to operate.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a forming method for heat treatment of a head, which is applied to a head having a base layer and a clad layer, and the clad layer is attached to the base layer. The method is characterized by comprising the following steps: S1: Weld the weld seam of the base layer; S2: Insert a backing plate into the weld seam of the clad layer and fix the backing plate to the clad layer; S3: Thermoform and press the head; S4: Remove the backing plate and weld the weld seam of the clad layer.

[0007] As a preferred technical solution, before step S2, measure the dimensions of the groove on the clad layer and the head, and process a backing plate capable of covering the weld seam of the head.

[0008] As a preferred technical solution, in step S2, the backing plate is fixed to the weld seam of the clad layer by tack welding. The welding current of the tack welding is set to 70 - 170 A, the welding voltage is set to 10 - 18 V, the welding speed is set to 50 - 200 mm / min, and the interpass temperature is not higher than 150 °C.

[0009] As a preferred technical solution, the material of the base layer is set as carbon steel; and / or, the material of the clad layer is set as nickel-based alloy.

[0010] As a preferred technical solution, the groove on the head is set as a V-shaped internal groove. The root face of the V-shaped internal groove is set to 2 - 3 mm, the gap is set to 0 - 2 mm, and the angle is set to 53 - 57°; the single-side peeling width of the clad layer is set to 4 - 6 mm; and / or, the method for welding the weld seam of the base layer is set as SAW; the welding wire is set as a wire with a diameter of 4.0 mm, and the material of the welding wire is set as F55P3 - EF3; the welding current is set to 400 - 670 A, the welding voltage is set to 26 - 38 V, and the welding speed is set to 400 - 600 mm / min.

[0011] As a preferred technical solution, the material of the backing plate is set as stainless steel or nickel-based alloy; and / or, the backing plate is in a strip shape, and the length L of the backing plate is set to , the width B of the backing plate is set to , the thickness T of the backing plate is set to , where D 1 is the diameter of the head before forming, D 2 is the shortest distance from the seam of the head to its center of the circle, B 1 is the single-side peeling width of the clad layer, B 2 is the gap of the V-shaped internal groove, T 1 is the thickness of the clad layer; And / or, the shape of the liner matches the shape of the weld of the clad layer.

[0012] As a preferred technical solution, in step S3, the head is hot formed and pressed at least twice; during the first hot forming and pressing, the furnace charging temperature is not greater than 800 °C, the holding temperature is set to 890 - 950 °C, the holding time is set to 40 - 80 min, and the final pressing temperature is set to 820 - 880 °C; during subsequent hot forming and pressing, the holding temperature is set to 890 - 950 °C, the holding time is set to 20 - 40 min, and the final pressing temperature is set to 820 - 880 °C; after the last hot forming and pressing, the head is air cooled.

[0013] As a preferred technical solution, in step S4, the solder joints of the tack welds are ground and the liner is removed.

[0014] As a preferred technical solution, the weld of the clad layer is welded by surfacing.

[0015] As a preferred technical solution, the head is a pressure vessel head.

[0016] The beneficial effects of the present invention are as follows: 1. In the present invention, during the hot forming of the head, a liner embedded in the weld of the clad layer is used to replace the traditional clad layer weld. After the hot forming of the head, the liner can be conveniently removed and the weld at the clad layer can be repaired by welding, so that the intergranular corrosion resistance at the clad layer will not decrease. At the same time, the liner is not a disposable item and can be reused, and it is no longer necessary to use double the amount of welding materials at the weld of the clad layer, saving the amount of welding materials for one welding. At the same time, it saves the labor for one welding and one grinding compared with the existing method, and reduces the accidents that may occur during personnel operation; taking a 2000 - mm - long weld as an example, the cost of one welding plus one grinding plus the amount of welding materials for one welding has exceeded one thousand yuan, effectively saving costs, and no longer requiring excessive grinding and welding processes, and the process steps are simpler, making it more suitable for use in manufacturing plants and head factories.

[0017] 2. In the present invention, during the hot forming of the head, the liner embedded in the weld of the clad layer can also increase the structural strength at the weld, and the situation where the head cracks due to the stress generated by the relatively thin weld thickness at the base layer will not occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of an embodiment of a method for heat treatment and forming of a head according to the present invention; Figure 2 It is a schematic structural diagram of the head after welding the base layer weld in an embodiment of a method for heat treatment and forming of a head according to the present invention; Figure 3This is a schematic diagram of the structure after fixing the lining plate and the clad layer in an embodiment of a method for heat treatment and forming of a head in the present invention.

[0019] In the figure: 1 - base layer, 2 - clad layer, 3 - lining plate. Detailed implementation manners

[0020] For the convenience of those skilled in the art to understand, the present invention will be further described below with reference to the accompanying drawings. Embodiment 1

[0021] Please refer to Figures 1 - 3 , which is an embodiment of a method for heat treatment and forming of a head provided by the present invention, and is applied to a head having a base layer 1 and a clad layer 2. The head is a pressure vessel head, and the material of the head is N06625 composite plate; the groove on the head is a V-shaped internal groove, the root face of the V-shaped internal groove is set to 2 - 3 mm, the gap is set to 2 mm, the angle is set to 55°, and the groove gap is 2 mm; the clad layer 2 is attached to the base layer 1, the unilateral peeling width of the clad layer 2 is 10 mm, the material of the base layer 1 is SA516Gr70, and the material of the clad layer 2 is set to Ni6625, and it includes the following steps: S1: Weld the weld seam of the base layer 1. Specifically, the method for welding the weld seam of the base layer 1 is set to submerged arc welding. Submerged arc welding is an automatic welding method, which can significantly improve the welding efficiency, is applicable to the welding of steel plates of various thicknesses, especially suitable for the welding of plates with a thickness greater than 8 mm. The groove filling efficiency of submerged arc welding is significantly higher than that of argon arc welding or plasma welding, and the welding speed of submerged arc welding is significantly better than that of manual welding, and the efficiency can be increased by 30% - 50%; at the same time, the degree of automation of submerged arc welding is high, and the operator only needs to control the welding machine, which reduces the labor intensity and can effectively reduce the medium- and long-term production costs; moreover, the welding process of submerged arc welding is stable, the weld formation is uniform and of high quality, the heat distribution is uniform during the welding process, which reduces the welding stress and the welding deformation; further, the smoke and harmful gases generated during the welding process of submerged arc welding are less, and the pollution to the environment is small; The welding consumables are set to a welding wire with a diameter of 4.0 mm, and the material of the welding consumables is set to F55P3 - EF3. Using the welding wire for submerged arc welding can better control the weld composition and performance, and the welding quality is stable; the welding current is set to 400 - 670 A, the welding voltage is set to 26 - 38 V, and the welding speed is set to 400 - 600 mm / min. The above welding parameters can ensure the consistency and quality of the weld, reduce the occurrence of defects such as pores and cracks, and can ensure the mechanical properties such as tensile, bending, and impact of the weld and the service performance such as intergranular corrosion, meeting the material performance while ensuring a high welding efficiency; Furthermore, due to the reduction of welding defects and the decrease of rework rate, material waste and labor costs are reduced. At the same time, stable welding parameters can avoid frequent adjustment by operators, enabling operators to focus more on the welding process, reducing the operation difficulty, increasing the welding speed and overall production efficiency. Meanwhile, it can reduce the impact on welding equipment and extend the service life of the equipment; Before step S2, it is also necessary to measure the groove on the head and the size of the clad layer 2, and then process the backing plate 3 that can cover the weld of the head; specifically, as Figure 3 shown, the backing plate 3 should be strip-shaped, and the length L of the backing plate 3 is set to and the width B of the backing plate 3 is set to and the thickness T of the backing plate 3 is set to where D 1 is the diameter before the head is formed, D 2 is the shortest distance from the seam of the head to its center of the circle, B 1 is the unilateral peeling width of the clad layer 2, B 2 is the gap of the V-shaped inner groove, T 1 is the thickness of the clad layer 2; the backing plate 3 can effectively meet the requirements of covering the weld of the head at this size.

[0022] S2: Embed the backing plate 3 in the weld of the clad layer 2 and fix the backing plate 3 to the clad layer 2. The backing plate 3 can form a temporary clad layer at the weld of the clad layer 2; Specifically, the material of the backing plate 3 is duplex stainless steel, specifically it can be S31803 or S32205. The backing plate 3 is preferably fixed to the weld of the clad layer 2 by tungsten inert gas welding with a nickel-based welding consumable. This method of spot welding is more economical in welding consumables than welding the entire backing plate 3 to the weld of the clad layer 2 and then removing it, and it is also more convenient to remove the backing plate 3; the head is a nickel-based composite plate head (N06625), preferably the thickness of the backing plate 3 of the nickel-based composite plate head is above 20 mm, and the specific welding parameters are shown in Table 1; Table 1 Spot welding parameters for the backing plate of the nickel-based composite plate head

[0023] Furthermore, the material of the backing plate 3 is set to carbon steel or stainless steel, and the backing plate 3 is preferably strip-shaped. The shape of the backing plate 3 should match the shape of the weld of the clad layer 2. When the backing plate 3 is fixed to the weld of the clad layer 2, it can effectively increase the structural strength of the weld, and the situation of the head cracking due to stress caused by the relatively thin weld thickness at the base layer 1 will not occur; S3: Hot forming and pressing the head; the specific process is as follows: first, heat the circular plate used to form the head, then hoist the heated circular plate onto the workbench of the stamping machine, and use the punch for stamping to achieve hot forming and pressing; it should be noted that the punch can be replaced according to the size of the circular plate. Specifically, the head is hot formed and pressed 2 - 3 times; during the first hot forming and pressing, the furnace loading temperature is not more than 800 °C, the heat preservation temperature is set at 890 - 950 °C, the heat preservation time is set at 40 - 80 min, and the final pressing temperature is set at 820 - 880 °C; during subsequent hot forming and pressing, the heat preservation temperature is set at 890 - 950 °C, the heat preservation time is set at 20 - 40 min, and the final pressing temperature is set at 820 - 880 °C; after the last hot forming and pressing, the head is air-cooled.

[0024] S4: Remove the lining plate 3. Specifically, the lining plate 3 can be conveniently and quickly removed by slightly grinding the tack weld points; then, the weld seam at the clad layer 2 is welded by surfacing, which can effectively ensure the intergranular corrosion resistance at the weld seam of the clad layer 2. Embodiment Two

[0025] The main difference between this embodiment and Embodiment One is that the head is a duplex stainless steel composite plate head (the material is S31803, S32205, etc.), the material of the lining plate 3 is stainless steel, specifically it can be S31603, and the thickness of the lining plate 3 is more than 20 mm. At this time, the specific welding parameters for the tack welding of the lining plate 3 to the weld seam of the clad layer 2 are shown in Table 2. Table 2 Tack Welding Parameters for the Lining Plate of the Duplex Stainless Steel Composite Plate Head

[0026] In addition, in this embodiment, the weld seam of the base layer 1 is welded by semi-automatic submerged arc welding, and the semi-automatic welding method can also improve the efficiency. Embodiment Three

[0027] The main difference between this embodiment and Embodiment One is that the head is a 904 composite plate head, the material of the lining plate 3 is nickel-based alloy, specifically it can be N06625, and the thickness of the lining plate 3 is more than 20 mm. At this time, the specific welding parameters for the tack welding of the lining plate 3 to the weld seam of the clad layer 2 are shown in Table 3. Table 3 Tack Welding Parameters for the Lining Plate of the 904 Composite Plate Head

[0028] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for heat treatment and forming of a head, applied to a head having a base layer (1) and a coating layer (2), wherein the coating layer (2) is attached to the base layer (1), characterized in that: The following steps are involved: S1: welding the weld of the base layer (1); S2: embedding a lining plate (3) in the weld of the cladding layer (2), and fixing the lining plate (3) to the cladding layer (2); S3: hot forming and pressing the head; S4: removing the lining plate (3) and welding the weld of the cladding layer (2).

2. A head heat treatment forming method according to claim 1, characterized in that: Before step S2, the dimensions of the coating (2) and the groove on the end cap are measured, and a lining plate (3) capable of covering the weld of the end cap is processed.

3. A head heat treatment forming method according to claim 1 or 2, characterized in that: In step S2, the lining plate (3) is fixed to the weld of the cladding layer (2) by spot welding, wherein the welding current of the spot welding is set to 70-170A, the welding voltage is set to 10-18V, the welding speed is set to 50-200mm / min, and the interlayer temperature is not higher than 150°C.

4. A head heat treatment forming method according to claim 1 or 2, characterized in that: The material of the base layer (1) is set to be carbon steel; And / or, the material of the coating (2) is set to be a nickel-based alloy.

5. A head heat treatment forming method according to claim 1 or 2, characterized in that: The groove on the end cap is set as a V-shaped inner groove, the blunt edge of the V-shaped inner groove is set to 2-3 mm, the gap is set to 0-2 mm, and the angle is set to 53-57°; the single-side peeling width of the coating (2) is set to 4-6 mm; And / or, the method for welding the weld of the base layer (1) is set to submerged arc welding; the welding material is set to a welding wire with a diameter of 4.0 mm, and the material of the welding material is set to F55P3-EF3; the welding current is set to 400-670A, the welding voltage is set to 26-38V, and the welding speed is set to 400-600mm / min.

6. A head heat treatment forming method according to claim 5, characterized in that: The material of the lining plate (3) is set to be stainless steel or nickel-based alloy; And / or, the lining plate (3) is in the shape of a long strip, and the length L of the lining plate (3) is set to , the width B of the lining plate (3) is set to , the thickness T of the lining plate (3) is set to , wherein D1 is the diameter of the end cap before forming, D2 is the shortest distance between the end cap joint and the center of the circle, B1 is the single-side peeling width of the coating (2), B2 is the gap of the V-shaped inner groove, and T1 is the thickness of the coating (2); And / or, the shape of the lining plate (3) matches the shape of the weld of the cladding layer (2).

7. A head heat treatment forming method according to claim 1, characterized in that: In step S3, the head is hot-formed and pressed at least twice; during the first hot-forming pressing, the furnace temperature is not greater than 800°C, the insulation temperature is set to 890-950°C, the insulation time is set to 40-80min, and the final pressing temperature is set to 820-880°C; during the subsequent hot-forming pressing, the insulation temperature is set to 890-950°C, the insulation time is set to 20-40min, and the final pressing temperature is set to 820-880°C; after the last hot-forming pressing, the head is air-cooled.

8. A head heat treatment forming method according to claim 3, characterized in that: In step S4, the spot welding points are polished and the lining plate (3) is removed.

9. A head heat treatment forming method according to claim 8, characterized in that: The weld seam of the coating (2) is welded by surfacing.

10. The head heat treatment forming method according to claim 1, characterized in that: The end cap is configured as a pressure vessel end cap.

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