A dissimilar metal welding method for nickel-copper alloy and stainless steel

Abstract

The present invention provides a dissimilar metal welding method for nickel-copper alloy and stainless steel, which belongs to the technical field of dissimilar metal welding and comprises the following steps: cleaning the welding surface of nickel-copper alloy rod and stainless steel hanger; preheating the non-welding end of nickel-copper alloy rod; covering the non-welding area of ​​nickel-copper alloy rod and stainless steel hanger with thermal insulation material; welding the welding area of ​​nickel-copper alloy rod and stainless steel hanger with non-nickel-based alloy welding material; covering the welding area of ​​nickel-copper alloy rod and stainless steel hanger with thermal insulation material after welding; after the temperature of the welding area drops to a preset temperature, removing the thermal insulation material and cleaning the welding slag in the welding area. The dissimilar metal welding method for nickel-copper alloy and stainless steel provided by the present invention does not require the use of nickel-based welding rods or welding wires, and effectively solves the problem of thermal cracking when welding nickel-copper alloy and stainless steel by optimizing the 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] During the production of nickel-copper alloy bars, the bars obtained from the initial casting process require electroslag remelting and purification. Currently, this process in factories typically involves welding stainless steel hanger bars to the axial ends of the bars. During this process, a crane hoists the bars using the stainless steel hanger bars and slowly lowers them into an electroslag furnace for electroslag remelting and purification.

[0003] However, in actual operation, since the welding of nickel-copper alloy and stainless steel is dissimilar metal welding, the heat dissipation of nickel-copper alloy is much better than that of stainless steel under low temperature conditions. Therefore, in the welding process of nickel-copper alloy rods and stainless steel hangers, the nickel-copper alloy rods dissipate heat quickly and conduct heat quickly, resulting in a temperature difference between the welding point between the nickel-copper alloy rods and the stainless steel hanger rods, which easily forms thermal cracks at the weld, making the welding unstable, and causing the remaining tail of the nickel-copper alloy rods to fall into the electric slag furnace before the remelting smelting is completed, affecting the product quality.

[0004] To address this issue, conventional welding methods use nickel-based alloy wires and rods, such as Monel 400 or ENiCu-7, to prevent cracking. However, due to the factory's limited nickel-copper alloy bar orders and the high cost of nickel-based alloy wires and rods, a method that avoids nickel-based alloy wires and rods is urgently needed to address the aforementioned cracking issue and maintain profitability. Summary of the Invention

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

[0006] To achieve the above object, the technical solution adopted by the present invention is to provide a dissimilar metal welding method for nickel-copper alloy and stainless steel, comprising the following steps:

[0007] S1. Clean the welding surface of nickel-copper alloy bar and stainless steel hanging rod;

[0008] S2. Preheating the non-welding end of the nickel-copper alloy bar;

[0009] S3. Use insulation material to cover the non-welding area of ​​the nickel-copper alloy rod and the stainless steel hanging rod;

[0010] S4. Welding the welding area of ​​the nickel-copper alloy bar and the stainless steel hanging rod using non-nickel-based alloy welding materials;

[0011] S5. After welding, use insulation material to cover the welding area of ​​the nickel-copper alloy rod and the stainless steel hanging rod;

[0012] S6. After the temperature of the welding area drops to the preset temperature, remove the insulation material and clean the welding slag in the welding area.

[0013] In a possible implementation, in step S2, the preheating temperature of the preheating treatment is not less than 200°C, and the preheating time is not less than 0.5h.

[0014] In a possible implementation, in step S2, the heating method of the preheating treatment includes but is not limited to resistance heating, induction heating, and gas heating.

[0015] In a possible implementation, the thermal insulation material is ceramic fiber felt.

[0016] In a possible implementation, step S4 includes:

[0017] The first welding is performed using a carbon dioxide gas shielded welding wire. The welding current of the first welding is 445-455A, the welding voltage is 25-35V, and the welding speed is 2-3mm / min. A bite groove is formed at the weld of the first welding, and the depth of the bite groove is not less than 0.5mm.

[0018] The second welding is performed by manual arc welding on the weld formed by the first welding using a welding rod. The welding current of the second welding is 180A, the welding voltage is 103V, and the welding speed is 2-3mm / min. The second welding fills the undercut groove.

[0019] 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 minutes.

[0020] In a possible implementation, the undercut groove is formed continuously along the circumference of the weld of the first welding.

[0021] In a possible implementation, the welding wire is a solid welding wire, and the welding rod is a low-alloy steel welding rod.

[0022] In a possible implementation, in step S1 , cleaning is performed by one or more of mechanical processing, manual polishing, or chemical cleaning.

[0023] In a possible implementation, the order of executing step S2 and step S3 is interchanged.

[0024] The beneficial effect of the dissimilar metal welding method for nickel-copper alloy and stainless steel provided by the present invention is that: compared with the existing technology, the dissimilar metal welding method for nickel-copper alloy and stainless steel provided by the present invention increases the temperature of the nickel-copper alloy bar before welding by preheating the nickel-copper alloy bar, thereby reducing the heat conduction speed of the nickel-copper alloy bar during the welding process, making the temperature difference between the nickel-copper alloy bar and the stainless steel hanger small during welding, reducing the problem of cracking during welding, and also using insulation material to cover the nickel-copper alloy bar and the stainless steel hanger, thereby reducing the heat dissipation speed of the nickel-copper alloy bar and the stainless steel hanger after welding, avoiding too rapid temperature drop and cracking in the weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A process flow chart of a dissimilar metal welding method for nickel-copper alloy and stainless steel provided in an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of the cross-sectional structure of the nickel-copper alloy rod and the stainless steel hanger provided in an embodiment of the present invention after being covered with insulation material.

[0028] Description of reference numerals:

[0029] 1. Nickel-copper alloy bar; 2. Stainless steel hanging rod; 3. Thermal insulation material. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] See also Figure 1 and Figure 2 The present invention provides a method for welding dissimilar metals between a nickel-copper alloy and stainless steel. The method comprises the following steps:

[0032] S1. Clean the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanging rod 2.

[0033] In this step, the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanger 2 can be cleaned by one or more methods such as mechanical processing, manual polishing or chemical cleaning. The purpose is to remove the impurities such as oxide scale and residual solder beans on the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanger 2. Preferably, the method of combining mechanical processing with chemical cleaning is used to clean. Before welding, the welding surface is mechanically processed to remove most of the oxide scale and residual solder beans. The welding surface can also be smoothed so that the welding surface of the subsequent nickel-copper alloy bar 1 and the stainless steel hanger 2 has a good butt joint fit and is convenient for welding. In addition, after mechanical processing cleaning, the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanger 2 is cleaned using chemicals such as acidic solution, which can play the role of chemical polishing and further improve the flatness of the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanger 2. It should be noted that after using chemical reagents to clean, the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanger 2 also needs to be rinsed with clean water to remove residual chemical reagents and dry residual moisture in time.

[0034] S2. Preheating the non-welding end of the nickel-copper alloy bar 1.

[0035] In this step, the heating method of the preheating treatment includes but is not limited to resistance heating, induction heating or gas heating. The preheating temperature of the preheating treatment is not less than 200° C., and the preheating time is not less than 0.5 h.

[0036] In this step, the non-welding end refers to all areas other than the welding end surface of the nickel-copper alloy bar 1, including but not limited to the axial middle area of ​​the nickel-copper alloy bar 1 in terms of physical form and the end area axially away from the welding surface. In practical applications, it is preferred that the end area of ​​the nickel-copper alloy bar 1 axially away from the welding surface is preheated. The purpose of the preheating treatment is to create a heat source on the nickel-copper alloy bar 1, which transfers heat to the welding surface end of the nickel-copper alloy bar 1 before welding begins. After welding begins, a large amount of welding heat is generated on the welding surface. Due to the presence of the heat source generated by the preheating treatment, the transfer speed of the welding heat on the nickel-copper alloy bar 1 can be reduced, thereby reducing the temperature difference between the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanger rod 2, thereby avoiding cracks during the welding process.

[0037] In actual welding, the welding heat generated by welding the welding surface gradually increases. In this step, by selecting the area for preheat treatment at the end of the nickel-copper alloy bar 1 axially away from one end of the welding surface, the heat source created by the preheat treatment can form a one-way heat transfer, and gradually heat the welding surface end of the nickel-copper alloy bar 1, so that the temperature difference between the temperature of the welding surface end of the nickel-copper alloy bar 1 at the beginning of welding and the heat generated in the initial stage of welding is not too large. As the welding operation continues, the welding heat gradually increases, and the heat transferred by the heat source created by the preheat treatment also gradually increases, so that the heat obtained by the welding surface end of the nickel-copper alloy bar 1 through the above-mentioned heat source and the heat obtained through welding heat can be maintained relatively stable, thereby reducing the heat transfer of the welding surface, reducing the temperature difference between the welding surface of the nickel-copper alloy bar 1 and the stainless steel hanger 2, and avoiding cracks during the welding process.

[0038] S3. Use insulation material 3 to cover the non-welding area of ​​the nickel-copper alloy rod 1 and the stainless steel hanger rod 2.

[0039] In this step, the non-welding area refers to all areas on the nickel-copper alloy rod 1 and the stainless steel hanger 2 except the ends of the welding surface. In this step, by using the thermal insulation material 3 to cover the nickel-copper alloy rod 1, the heat loss of the nickel-copper alloy rod 1 after preheating treatment can be reduced, so that the heat source created by the preheating treatment on the nickel-copper alloy rod 1 can last for a long time to meet the subsequent welding requirements.

[0040] In this step, the insulation material 3 used can be ceramic fiber felt. Ceramic fiber felt is lightweight, has low thermal conductivity, and is soft. Using ceramic fiber felt to cover the nickel-copper alloy rod 1 and the stainless steel hanging rod 2 is easy to handle. To ensure the insulation effect, the thickness of the selected ceramic fiber felt is not less than 10 mm.

[0041] In actual operation, in order to maintain the duration of the heat source created by the preheating treatment on the nickel-copper alloy rod 1, multiple layers of ceramic fiber felt can be added to the preheating treatment area of ​​the nickel-copper alloy rod 1.

[0042] S4. Use non-nickel-based alloy welding materials to weld the welding area of ​​the nickel-copper alloy bar 1 and the stainless steel hanging rod 2.

[0043] In this step, the welding process includes a first weld and a second weld. The first weld is performed using CO2 gas shielded welding with a current of 445-455A, a voltage of 25-35V, and a welding speed of 2-3mm / min. In this specific operation, the welding wire is solid, such as the more common JQMG70S-6 copper-plated solid wire. This type of wire is relatively inexpensive and is commonly used. It can be completed with common welding equipment. In conventional wire double welding, the welding current is usually between 50-250A and the welding speed is 5-30cm / min. However, in this step, the welding current is 445-455A, which is much higher than the current parameters selected for conventional welding, and the welding speed is 2-3mm / min, which is much lower than the welding speed parameters selected for conventional welding. The purpose of such setting is to form an undercut groove at the weld of the first welding. The undercut groove refers to a welding defect, which is a pit or groove left behind when the base material at the edge of the weld is melted by the arc or flame during the welding process and is not replenished with filler metal. In this step, the output of high current can cause the welding gun to melt more nickel-copper alloy bar 1 base material and stainless steel hanger rod 2 base material at the welding point, forming a molten pool with a depth of more than 1cm. The welding wire and the molten nickel-copper alloy bar 1 base material and stainless steel hanger rod 2 base material are mixed and cooled in the molten pool to form a weld. The welding wire used in this step has a diameter of 0.8-1.2mm, which is insufficient to replenish the molten pool. After the first weld, a continuous undercut groove forms around the weld seam. The depth of this undercut groove is no less than 0.5mm, effectively forming a weld groove on the interface between the nickel-copper alloy bar 1 and the stainless steel hanger rod 2, preparing for the second weld. In this step, increasing the welding current and reducing the welding speed during the first weld both aim to melt more of the nickel-copper alloy bar 1 and the stainless steel hanger rod 2, forming the undercut groove.

[0044] The second welding is performed by manual arc welding on the weld formed by the first welding using a welding rod. The welding current of the second welding is 180A, the welding voltage is 103V, and the welding speed is 2-3mm / min. The welding rod used for the second welding is a conventional low-alloy steel welding rod, such as a 507 welding rod. In the second welding, conventional welding current and voltage are used, but the welding speed of the second welding is much lower 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 undercut groove (welding groove) formed in the first welding. The selection of a welding speed far lower than the conventional welding parameters can ensure that the undercut groove is fully filled, improve the quality of the weld formed after the second welding, and firmly weld the nickel-copper alloy bar 1 and the stainless steel hanging rod 2.

[0045] 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. The interval between the two weldings is short, the temperature drop of the weld is small, and the welding temperature difference can be reduced during the second welding to avoid welding cracks.

[0046] S5. After welding, use insulation material 3 to cover the welding area of ​​nickel-copper alloy bar 1 and stainless steel hanging rod 2;

[0047] In this step, the insulation material 3 used is ceramic fiber felt. After welding is completed, the welding area is wrapped with ceramic fiber felt, and the ceramic fiber felt is bound with a strap or tape to slowly reduce the temperature of the welding area to avoid cracks caused by too rapid a temperature drop.

[0048] S6. After the temperature of the welding area drops to a preset temperature, the heat-insulating material 3 is removed and the welding slag in the welding area is cleaned.

[0049] In this step, the preset temperature is lower than 40°C. In application, existing temperature detection equipment such as infrared thermometers can be used to monitor the temperature of the welding area. When the welding area reaches the preset temperature, the ceramic fiber felt can be cut with a knife, the ceramic fiber felt can be removed, the welding slag in the welding area can be cleaned, and the weld of the second welding can be inspected.

[0050] In some embodiments, the above-mentioned steps S2 and S3 are implemented in an interchangeable order, and the nickel-copper alloy bar 1 is covered with the insulation material 3 before being preheated. This can reduce the heat loss of the nickel-copper alloy bar 1 caused by thermal radiation during the preheating process and reduce the energy consumption of the preheating device.

[0051] Comparative Example 1

[0052] The nickel-copper alloy rod 1 was not preheated, and the nickel-copper alloy rod 1 and the stainless steel hanger rod 2 were not covered with the insulation material 3, resulting in cracking during welding.

[0053] Comparative Example 2

[0054] No second welding was performed in step S4. After step S6 was completed, cracks were found in the weld.

[0055] The present invention provides a dissimilar metal welding method for nickel-copper alloy and stainless steel. Compared with the prior art, the present invention does not require the use of nickel-based welding rods or welding wires. Only the welding wires and welding rods used in daily use can be used in combination with common equipment to complete the welding operation, thereby reducing welding costs. By optimizing the welding process steps and parameters, the problem of thermal cracking when welding nickel-copper alloy and stainless steel is effectively solved, and the welding quality and product reliability are improved. The present welding method is simple to operate, easy to promote and apply in production units of different sizes, and has high practicality and economic benefits.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for welding dissimilar metals used for nickel-copper alloy and stainless steel, characterized in that: The following steps are involved: S1. Clean the welding surface of nickel-copper alloy bar and stainless steel hanging rod; S2. Preheating the non-welding end of the nickel-copper alloy bar; S3. Use insulation material to cover the non-welding area of ​​the nickel-copper alloy rod and the stainless steel hanging rod; S4. Welding the welding area of ​​nickel-copper alloy bar and stainless steel hanging rod with non-nickel-based alloy welding materials, including: The first welding is performed using a carbon dioxide gas shielded welding wire. The welding current of the first welding is 445-455A, the welding voltage is 25-35V, and the welding speed is 2-3mm / min. A bite groove is formed at the weld of the first welding, and the depth of the bite groove is not less than 0.5mm. The second welding is performed on the weld formed by the first welding by manual arc welding using a welding rod. The welding current of the second welding is 180A, the welding voltage is 103V, and the welding speed is 2-3mm / min. The second welding fills the undercut groove. S5. After welding, use insulation material to cover the welding area of ​​the nickel-copper alloy rod and the stainless steel hanging rod; S6. After the temperature of the welding area drops to the preset temperature, remove the insulation material and clean the welding slag in the welding area.

2. The dissimilar metal welding method for 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 time is not less than 0.5h.

3. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 1, characterized in that: In step S2, the heating method of the preheating treatment includes but is not limited to resistance heating, induction heating, and gas heating.

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

5. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 1, characterized in that: The time interval between the end of the first welding and the start of the second welding is less than 5 minutes.

6. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 1, characterized in that: The undercut groove is continuously formed in the circumferential direction of the weld of the first welding.

7. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 1, characterized in that: The welding wire is a solid welding wire, and the welding rod is a low alloy steel welding rod.

8. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 1, characterized in that: In step S1 , cleaning is performed by one or more of mechanical processing, manual polishing, or chemical cleaning.

9. The dissimilar metal welding method for nickel-copper alloy and stainless steel according to claim 4, characterized in that: The execution order of step S2 and step S3 is interchanged.

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