Dissimilar metal welding method applied to nickel-copper alloy and stainless steel

Abstract

The invention provides a dissimilar metal welding method applied to nickel-copper alloy and stainless steel, and belongs to the technical field of dissimilar metal welding. The dissimilar metal welding method comprises the following steps that the welding faces of a nickel-copper alloy bar and a stainless steel hanging bar are cleaned; the non-welding end of the nickel-copper alloy bar is preheated; the non-welding area of the nickel-copper alloy bar and the stainless steel hanging bar is covered with a heat preservation material; welding the welding areas of the nickel-copper alloy bar and the stainless steel hanging bar by adopting a non-nickel-base alloy welding material; after welding, the welding area of the nickel-copper alloy bar and the stainless steel hanging bar is covered with a heat preservation material; and after the temperature of the welding area is reduced to the preset temperature, the heat preservation material is removed, and welding slag in the welding area is cleaned. According to the dissimilar metal welding method applied to the nickel-copper alloy and the stainless steel, nickel-based welding rods or welding wires do not need to be used, and the problem of hot cracks during welding of the nickel-copper alloy and the stainless steel is effectively solved by optimizing welding process steps and parameters.

Description

Technical Field

[0001] The present invention belongs to the technical field of dissimilar metal welding, and more specifically, relates to a dissimilar metal welding method applied to nickel-copper alloy and stainless steel. Background Art

[0002] In the production process of nickel-copper alloy bars, it is necessary to perform electroslag remelting and purification treatment on the nickel-copper alloy billets obtained by primary melting and casting. At present, in the electroslag remelting and purification process of nickel-copper alloy billets in factories, stainless steel lifting bars are usually welded to the axial ends of nickel-copper alloy billets. During operation, after the crane lifts the nickel-copper alloy billet by lifting the stainless steel lifting bar, the nickel-copper alloy billet is slowly placed into the electroslag furnace for electroslag remelting and purification treatment.

[0003] However, in actual operation, since the welding of nickel-copper alloy and stainless steel belongs to dissimilar metal welding, and the heat dissipation of nickel-copper alloy is much better than that of stainless steel at low temperatures, during the welding process of nickel-copper alloy billets and stainless steel lifting bars, the nickel-copper alloy billets dissipate heat quickly and conduct heat quickly, resulting in a temperature difference at the welding joint with the stainless steel lifting bars, and thus thermal cracks are likely to form at the weld, making the welding not firm, and further causing the remaining tails of the nickel-copper alloy billets to fall into the electroslag furnace before the remelting and smelting is completed, affecting the product quality.

[0004] In view of the above situation, in order to avoid cracks in welding, the conventional welding method is to use nickel-based alloy welding wires and electrodes such as Monel 400 body or ENiCu-7 for welding. However, since the order quantity of nickel-copper alloy bars in factories is small and the prices of nickel-based alloy welding wires and electrodes are high, in order to ensure the production profit of factories, it is urgent to develop a welding method that does not use nickel-based alloy welding wires and electrodes to solve the above welding crack problem. Summary of the Invention

[0005] The purpose of the present invention is to provide a dissimilar metal welding method applied to nickel-copper alloy and stainless steel, aiming to solve the problem of welding cracks when welding nickel-copper alloy billets and stainless steel lifting bars.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: providing a dissimilar metal welding method applied to nickel-copper alloy and stainless steel, including the following steps: S1. Clean the welding surfaces of the nickel-copper alloy billet and the stainless steel lifting bar; S2. Preheat the non-welding end of the nickel-copper alloy billet; S3. Cover the non-welding areas of the nickel-copper alloy billet and the stainless steel lifting bar with heat-insulating materials; S4. Weld the welding areas of the nickel-copper alloy billet and the stainless steel lifting bar with non-nickel-based alloy welding materials; S5. After welding, cover the welding area of the nickel-copper alloy rod and the stainless-steel hanging rod with heat-insulating material; S6. After the temperature of the welding area drops to the preset temperature, remove the heat-insulating material and clean the welding slag in the welding area.

[0007] In a possible implementation, in step S2, the preheating temperature of the preheating treatment is not less than 200 °C, and the preheating duration is not less than 0.5 h.

[0008] In a possible implementation, in step S2, the heating methods of the preheating treatment include but are not limited to resistance heating, induction heating, and gas heating.

[0009] In a possible implementation, the heat-insulating material is ceramic fiber felt.

[0010] In a possible implementation, step S4 includes: The first welding is carried out by shielded metal arc welding with a solid wire using carbon dioxide gas as the shielding gas. The welding current of the first welding is 445 - 455 A, the welding voltage is 25 - 35 V, and the welding speed is 2 - 3 mm / min. A gouged groove is formed at the weld of the first welding, and the depth of the gouged groove is not less than 0.5 mm; The second welding is carried out by manual arc welding with an electrode on the weld formed by the first welding. The welding current of the second welding is 180 A, the welding voltage is 103 V, and the welding speed is 2 - 3 mm / min. The second welding fills the gouged groove.

[0011] In a possible implementation, the time interval between the end of the first welding and the start of the second welding is less than 5 min.

[0012] In a possible implementation, the gouged groove is continuously formed circumferentially on the weld of the first welding.

[0013] In a possible implementation, the wire is a solid wire, and the electrode is a low-alloy steel electrode.

[0014] In a possible implementation, in step S1, one or more of mechanical machining, manual polishing, or chemical cleaning are used for cleaning.

[0015] In a possible implementation, the implementation order of step S2 and step S3 is interchanged.

[0016] The beneficial effects of a dissimilar metal welding method for nickel - copper alloy and stainless steel provided by the present invention are as follows: Compared with the prior art, in the dissimilar metal welding method for nickel - copper alloy and stainless steel of the present invention, the pre - heating treatment of the nickel - copper alloy rod improves the temperature of the nickel - copper alloy rod before welding, thereby weakening the heat conduction speed of the nickel - copper alloy rod during welding, making the temperature difference between the nickel - copper alloy rod and the stainless - steel hanging rod small during welding, reducing the problem of cracking during welding. Also, by using heat - insulating materials to cover the nickel - copper alloy rod and the stainless - steel hanging rod, the heat dissipation speed of the nickel - copper alloy rod and the stainless - steel hanging rod after welding can be reduced, avoiding the appearance of cracks in the weld due to too rapid temperature reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 It is a process flow chart of a dissimilar metal welding method for nickel - copper alloy and stainless steel provided by an embodiment of the present invention; Figure 2 It is a cross - sectional structural schematic diagram of a nickel - copper alloy rod and a stainless - steel hanging rod covered with heat - insulating materials provided by an embodiment of the present invention.

[0019] Explanation of the reference numerals in the drawings: 1. Nickel - copper alloy rod; 2. Stainless - steel hanging rod; 3. Heat - insulating material. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the following further details the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] Please refer to Figure 1 and Figure 2 , and now a dissimilar metal welding method for nickel - copper alloy and stainless steel provided by the present invention is described. The dissimilar metal welding method for nickel - copper alloy and stainless steel includes the following steps: S1. Clean the welding surfaces of the nickel - copper alloy rod 1 and the stainless - steel hanging rod 2.

[0022] In this step, one or more of machining, manual polishing, or chemical cleaning can be used to clean the welding surface of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2. The purpose is to remove impurities such as scale and remaining welding beads on the welding surface of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2. Preferably, a combination of machining and chemical cleaning is used for cleaning. By machining the welding surface before welding, not only can most of the scale and remaining welding beads be removed, but also the welding surface can be machined flat, so that the subsequent docking fit of the welding surfaces of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2 is good, facilitating welding. In addition, after machining cleaning, using a chemical agent such as an acidic solution to clean the welding surface of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2 can play a role in chemical polishing and further improve the flatness of the welding surface of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2. It should be noted that after cleaning with chemical reagents, the welding surface of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2 needs to be rinsed with clean water to remove the remaining chemical reagents and the residual moisture should be dried in time.

[0023] S2. Preheat the non-welding end of the nickel-copper alloy rod 1.

[0024] In this step, the heating methods for preheat treatment include but are not limited to resistance heating, induction heating, or gas heating. The preheat temperature for preheat treatment is not less than 200 °C, and the preheat duration is not less than 0.5 h.

[0025] In this step, the non-welding end refers to all regions except the welding end face of the nickel-copper alloy rod 1, including but not limited to the axial middle region and the end region axially far from the welding surface in the physical form of the nickel-copper alloy rod 1. In practical applications, preferably, the end region of the nickel-copper alloy rod 1 axially far from the welding surface is preheated. The purpose of preheat treatment is to create a heat source on the nickel-copper alloy rod 1, and this heat source transfers heat to the welding surface end of the nickel-copper alloy rod 1 before welding starts. After welding starts, a large amount of welding heat is generated at the welding surface. Due to the existence of the heat source generated by preheat treatment, the transfer speed of welding heat on the nickel-copper alloy rod 1 can be reduced, thereby reducing the temperature difference between the welding surfaces of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2 and avoiding cracks during welding.

[0026] In actual welding, the welding heat generated at the welding surface gradually increases. In this step, by selecting the preheating treatment area at the end of the nickel-copper alloy bar 1 axially away from the welding surface, the heat source created by the preheating treatment can form unidirectional heat transfer, gradually heating the end of the nickel-copper alloy bar 1 at the welding surface, so that the temperature difference between the end of the nickel-copper alloy bar 1 at the welding surface and the heat generated at the initial stage of welding is not too large at the start of welding. As the welding operation continues, the welding heat gradually increases, and the heat transferred by the heat source created by the preheating treatment also gradually increases. In this way, the heat obtained by the end of the nickel-copper alloy bar 1 at the welding surface from the above heat sources and the heat obtained by welding heat can be maintained relatively stable, thereby reducing the heat transfer of the welding surface and lowering the temperature difference between the welding surfaces of the nickel-copper alloy bar 1 and the stainless steel hanging bar 2, and avoiding cracks during welding.

[0027] S3. Use the heat insulation material 3 to cover the non-welding areas of the nickel-copper alloy bar 1 and the stainless steel hanging bar 2.

[0028] In this step, the non-welding area refers to all areas of the nickel-copper alloy bar 1 and the stainless steel hanging bar 2 except the end of the welding surface. In this step, by using the heat insulation material 3 to cover the nickel-copper alloy bar 1, the heat dissipation of the nickel-copper alloy bar 1 after preheating treatment can be reduced, and the heat source created by the preheating treatment on the nickel-copper alloy bar 1 can last longer to meet the subsequent welding requirements.

[0029] In this step, the heat insulation material 3 used can be a ceramic fiber felt. The ceramic fiber felt is light in weight, low in thermal conductivity, and soft, and it is easy to operate to wrap the nickel-copper alloy bar 1 and the stainless steel hanging bar 2 with the ceramic fiber felt. To ensure the heat insulation effect, the thickness of the selected ceramic fiber felt is not less than 10 mm.

[0030] In actual operation, to maintain the duration of the heat source created by the preheating treatment on the nickel-copper alloy bar 1, multiple layers of ceramic fiber felt can be additionally added to the preheating treatment area of the nickel-copper alloy bar 1.

[0031] S4. Weld the welding areas of the nickel-copper alloy bar 1 and the stainless steel hanging bar 2 using a non-nickel-based alloy welding material.

[0032] In this step, the welding process includes the first welding and the second welding. Among them, in the first welding, a solid wire is used for shielded metal arc welding with carbon dioxide gas. The welding current for the first welding is 445 - 455 A, the welding voltage is 25 - 35 V, and the welding speed is 2 - 3 mm / min. In specific operations, the wire is a solid wire, such as the relatively common JQMG70S-6 copper-plated solid wire. This type of wire is relatively inexpensive and is a commonly used wire in daily use. Combining common welding equipment can complete the welding operation. In general shielded metal arc welding with a wire, usually the welding current is between 50 - 250 A, and the welding speed is 5 - 30 cm / min. In this step, the welding current of 445 - 455 A is much larger than the current parameters selected for conventional welding, and the welding speed of 2 - 3 mm / min is much smaller than the welding speed parameters selected for conventional welding. The purpose of such settings is to form a gouged groove at the weld of the first welding. The so-called gouged groove refers to a welding defect. It is a concave pit or groove left after the base metal at the edge of the weld is melted by the arc or flame during the welding process and fails to be replenished by the filler metal. In this step, through the output of a large current, the welding torch can melt more nickel-copper alloy bar stock 1 base metal and stainless steel hanging bar 2 base metal at the welding position, forming a molten pool with a depth of more than 1 cm. After the wire and the melted nickel-copper alloy bar stock 1 base metal and stainless steel hanging bar 2 base metal are mixed and cooled in the molten pool, a weld is formed. The wire diameter used in this step is 0.8 - 1.2 mm, which is not enough to replenish the formed molten pool. After the first welding is completed, a continuous gouged groove will be formed circumferentially around the weld. The depth of the gouged groove is not less than 0.5 mm, which is equivalent to forming a welding groove on the butt joint surface of the nickel-copper alloy bar stock 1 and the stainless steel hanging bar 2 for the second welding. In this step, increasing the welding current and reducing the welding speed of the first welding are both to melt more nickel-copper alloy bar stock 1 base metal and stainless steel hanging bar 2 base metal to form the above-mentioned gouged groove.

[0033] In the second welding, a welding rod is used for manual arc welding on the weld formed in the first welding. The welding current for the second welding is 180 A, the welding voltage is 103 V, and the welding speed is 2 - 3 mm / min. The welding rod used in the second welding is a conventional low-alloy steel welding rod, such as the 507 welding rod. In the second welding, conventional welding current and voltage are used, but the welding speed of the second welding is much smaller than the conventional parameter selection. In this step, the purpose of the second welding is to melt the welding rod and the weld of the first welding, fuse the welding rod material with the weld of the first welding to form a new weld, and fill the gouged groove (welding groove) formed in the first welding. The selection of a welding speed much lower than the conventional welding parameters can ensure that the gouged groove is fully filled, improve the quality of the weld formed after the second welding, and make the nickel-copper alloy bar stock 1 and the stainless steel hanging bar 2 welded firmly.

[0034] In this step, the time interval between the end of the first welding and the start of the second welding is less than 5 minutes. Since the interval between the two weldings is short, the temperature of the weld seam drops less, and the welding temperature difference can be reduced during the second welding, avoiding the occurrence of welding cracks.

[0035] S5. After welding, use the heat-insulating material 3 to cover the welding area of the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2. In this step, the heat-insulating material 3 used is ceramic fiber felt. After welding is completed, use the ceramic fiber felt to wrap the welding area, and use straps or tapes to bind the ceramic fiber felt to enable the temperature of the welding area to decrease slowly, avoiding cracks caused by too rapid a temperature drop.

[0036] S6. After the temperature of the welding area drops to the preset temperature, remove the heat-insulating material 3 and clean the welding slag in the welding area.

[0037] In this step, the preset temperature is lower than 40°C. In applications, existing temperature detection devices such as infrared thermometers can be used to monitor the temperature of the welding area. When the welding area reaches the preset temperature, a tool can be used to cut open the ceramic fiber felt, remove the ceramic fiber felt, and clean the welding slag in the welding area to inspect the weld seam of the second welding.

[0038] In some embodiments, the implementation order of the above step S2 and step S3 is interchanged, and the nickel-copper alloy rod 1 is covered with the heat-insulating material 3 before the preheating treatment, which can reduce the heat loss of the nickel-copper alloy rod 1 caused by thermal radiation during the preheating process and reduce the energy consumption of the preheating device.

[0039] Comparative Example 1 The nickel-copper alloy rod 1 was not preheated, and the nickel-copper alloy rod 1 and the stainless-steel lifting rod 2 were not covered with the heat-insulating material 3, and cracking occurred during welding.

[0040] Comparative Example 2 In step S4, the second welding was not performed. After step S6 was completed, cracks were found in the weld seam.

[0041] A dissimilar metal welding method for nickel-copper alloy and stainless steel provided by the present invention, compared with the prior art, does not require the use of nickel-based electrodes or welding wires, and only uses the welding wires and electrodes commonly used in daily life, and can complete the welding operation in combination with common equipment, reducing the welding cost. Through the optimization of the welding process steps and parameters, the problem of hot cracks during the welding of nickel-copper alloy and stainless steel is effectively solved, the welding quality and the reliability of the product are improved. This welding method is simple to operate and is easy to be popularized and applied in production units of different scales, and has high practicability and economic benefits.

[0042] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, 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 dissimilar metal welding method applied to nickel-copper alloy and stainless steel, characterized in that, It includes the following steps: S1. Clean the welding surface of the nickel-copper alloy bar and the stainless steel hanging bar; S2. Preheat the non-welded end of the nickel-copper alloy bar; S3. Cover the non-welded areas of the nickel-copper alloy bar and the stainless steel hanging bar with heat-insulating materials; S4. Weld the welding area of the nickel-copper alloy bar and the stainless steel hanging bar using non-nickel-based alloy welding materials; S5. After welding, cover the welding area of the nickel-copper alloy bar and the stainless steel hanging bar with heat-insulating materials; S6. After the temperature of the welding area drops to the preset temperature, remove the heat-insulating materials and clean the welding slag in the welding area.

2. The method for joining dissimilar metals of nickel-copper alloy and stainless steel according to claim 1, characterized in that, In step S2, the preheating temperature of the preheating treatment is not less than 200 °C, and the preheating duration is not less than 0.5 h.

3. A dissimilar metal welding method for nickel-copper alloy and stainless steel as described in claim 1, characterized in that, In step S2, the heating methods of the preheating treatment include but are not limited to resistance heating, induction heating, and gas heating.

4. A method for dissimilar metal welding of nickel-copper alloy and stainless steel according to claim 1, characterized in that, The heat-insulating material is ceramic fiber felt.

5. A dissimilar metal welding method for nickel-copper alloy and stainless steel as described in claim 1, characterized in that, Step S4 includes: The first welding is carried out by using a welding wire with carbon dioxide gas shielded welding. The welding current of the first welding is 445 - 455 A, the welding voltage is 25 - 35 V, and the welding speed is 2 - 3 mm / min. A gouging groove is formed at the weld of the first welding, and the depth of the gouging groove is not less than 0.5 mm; The second welding is carried out by using a welding electrode with manual arc welding on the weld formed by the first welding. The welding current of the second welding is 180 A, the welding voltage is 103 V, and the welding speed is 2 - 3 mm / min. The second welding fills the gouging groove.

6. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 5, characterized in that, The time interval between the end of the first welding and the start of the second welding is less than 5 min.

7. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 5, characterized in that, The gouging groove is continuously formed circumferentially on the weld of the first welding.

8. A dissimilar metal welding method for nickel-copper alloy and stainless steel as claimed in claim 5, characterized in that, The welding wire is a solid welding wire, and the welding electrode is a low-alloy steel welding electrode.

9. A dissimilar metal welding method for nickel-copper alloy and stainless steel as claimed in claim 1, characterized in that, In step S1, cleaning is carried out by one or more of mechanical processing, manual polishing, or chemical cleaning.

10. A method for joining dissimilar metals of nickel-copper alloy and stainless steel according to claim 4, characterized in that, The implementation order of step S2 and step S3 is interchanged.

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