Copper pipe and stainless steel pipe argon arc welding process, welding pipe and application

Abstract

The invention discloses a copper pipe and stainless steel pipe argon arc welding process, a welded pipe and application. The welding technology comprises the following steps that a stainless steel pipe with the diameter phi being 10 * 1 mm and the inner diameter being 8 mm is taken, and acid pickling and oil removing are conducted; a phi 8 * 0.8 mm copper pipe is taken, and the copper pipe is inserted into the stainless steel pipe; a plurality of spot welding points are evenly distributed on the welded workpiece through the argon arc welding technology under the condition that welding wires are not used, so that assembly points are formed; welding process parameters are adjusted, specifically, the welding current ranges from 93 A to 94 A, the welding time ranges from 20 s to 30 s, the cooling temperature ranges from 25 DEG C to 35 DEG C, and argon protection is adopted; the tungsten needle and the welding workpiece are fixed through a welding clamp tool, so that the tungsten needle surrounds a welding area of the welding workpiece in a horizontal state; welding is started, the stainless steel pipe is melted through the temperature of the tungsten needle, and the stainless steel pipe is combined with the copper pipe. The scheme has the advantages of being convenient to operate and simple in process, the cost is reduced, the welding efficiency is improved, and the problem that the copper and stainless steel welding cost of pressure-bearing equipment is high is solved.

Description

Technical Field

[0001] The invention relates to the field of welding, in particular to a argon arc welding process for a copper pipe and a stainless steel pipe and a welded pipe. Background Art

[0002] Low-temperature welded insulated gas cylinders are the main storage packaging for industrial gas supply. Because they store low-temperature liquids (liquid nitrogen, liquid oxygen, liquid argon, liquefied natural gas and other media) and have good thermal insulation effects through double-layer high vacuum insulation. The gas supply principle of low-temperature welded insulated gas cylinders is that the liquid exchanges heat through the copper tube and the welded tube formed by stainless copper, and is converted from liquid to gas for gas supply. This is because copper has good thermal conductivity and is widely used in heat exchange in the cryogenic industry; the existing stainless steel pipe and copper pipe welding process generally uses oxygen-acetylene gas welding for welding, and the high temperature achieved by burning acetylene melts the silver welding rod. The silver welding rod is used as a bonding filling material, which helps to achieve qualified welding, but the cost of the silver welding rod is too high, which is not conducive to the production cost of the welded pipe. Summary of the invention

[0003] The purpose of the present invention is to propose a argon arc welding process for copper pipes and stainless steel pipes. The argon arc welding process is used for copper pipes and stainless steel pipes without adding welding wire. It has the advantages of convenient operation and simple process, and also reduces costs and improves welding efficiency, and can replace the existing welding process.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] A argon arc welding process for a copper tube and a stainless steel tube comprises the following steps:

[0006] (1): Take a φ10×1mm stainless steel tube with an inner diameter of 8mm and pickle and remove oil;

[0007] (2): Take a φ8×0.8mm copper tube and insert it into a stainless steel tube to form a welding workpiece; use argon arc welding technology without welding wire to evenly distribute multiple spot welding points on the welding workpiece to form an assembly point;

[0008] (3): Adjust the welding process parameters: welding current is 93-94A, welding time is 20-30s, cooling temperature is 25-35℃, argon protection is used during welding, and the argon flow rate is 12-15L / min;

[0009] (4): Use a welding clamp to fix the tungsten needle and the welding workpiece so that the tungsten needle is horizontally placed around the welding area of ​​the welding workpiece;

[0010] (5): Start welding, the temperature of the tungsten needle melts the stainless steel tube, and the stainless steel tube is combined with the copper tube.

[0011] Preferably, in step (4), at least one tungsten needle is used to horizontally contact the welding area of ​​the welding workpiece, and the tungsten needle is perpendicular to the welding workpiece;

[0012] In the step (5), welding is started and the tungsten needle is driven to rotate around the axis of the welding workpiece.

[0013] Preferably, in step (2), the end of the stainless steel tube is made into a spigot, the end of the copper tube is made into a socket, the copper tube and the stainless steel tube are welded together in a spigot-and-socket type, and a fillet weld is performed.

[0014] Optimally, in step (2), the length of the copper tube inserted into the stainless steel tube is 4-6 mm.

[0015] Preferably, in step (2), four welding spots are evenly distributed on the welding workpiece.

[0016] Optimally, in step (3), the purity of argon gas is 99.990-99.999%.

[0017] Preferably, in step (1), pickling and degreasing are performed using a pickling paste.

[0018] Optionally, the method further comprises step (6);

[0019] The step (6) is as follows: connecting the welded workpiece to a gas supply device, increasing the gas pressure to 2 MPa, maintaining the pressure for at least 30 seconds, and selecting the workpiece without leakage as a qualified workpiece.

[0020] A welded pipe is made by using the above copper pipe and stainless steel pipe argon arc welding process.

[0021] Optimally, the pressure resistance value of the welded pipe is 2Mpa.

[0022] The invention discloses an application of a welded pipe in a heat exchange element. The welded pipe is made by using the above-mentioned argon arc welding process between a copper pipe and a stainless steel pipe.

[0023] Compared with the prior art, one of the above technical solutions has the following beneficial effects:

[0024] The present invention provides a argon arc welding process for copper tubes and stainless steel tubes, which adopts the argon arc welding process for copper tubes and stainless steel tubes without adding welding wire, has the advantages of convenient operation and simple process, reduces cost and improves welding efficiency, can replace the existing welding process, and solves the problem of high cost of copper and stainless steel welding for pressure-bearing equipment. DETAILED DESCRIPTION

[0025] For ease of understanding of the present invention, the present invention is described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the documents in this area or the product instructions are carried out. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained by commercial purchase.

[0026] A argon arc welding process for a copper tube and a stainless steel tube comprises the following steps:

[0027] (1): Take a φ10×1mm stainless steel tube with an inner diameter of 8mm and pickle and degrease it;

[0028] Pickling and degreasing is mainly to remove oil stains on the surface of stainless steel pipes to prevent welding defects such as unmelted and pores during welding;

[0029] (2): Take a φ8×0.8mm copper tube and insert it into a stainless steel tube to form a welding workpiece; use argon arc welding technology without welding wire to evenly distribute multiple spot welding points on the welding workpiece to form an assembly point;

[0030] Argon arc welding is a welding technology that uses argon as a shielding gas. Argon shielding gas is passed around the arc welding to isolate the air outside the welding area to prevent oxidation of the welding area. The inner diameter of the φ10×1mm stainless steel pipe is 8mm, which just fits the copper pipe φ8. Using argon arc welding without filling the welding wire, the spot welding points are evenly distributed to make the assembly point fixed;

[0031] (3): Adjust the welding process parameters: welding current is 93-94A, welding time is 20-30s, cooling temperature is 25-35℃, argon protection is used during welding, and the argon flow rate is 12-15L / min;

[0032] This solution is based on the thinner pipe wall and limits the welding current to 93-94A. This is mainly because the range of welding current needs to be determined in combination with the sizes of the stainless steel pipe and the copper pipe. If the current is too large, it is easy to weld through and cause slag inclusion, and if the current is too small, it is not easy to weld through. Therefore, when the small current is 93-94A, the welding can be completed in only 20-30s, without the need to add welding wire, and the requirement of withstanding 2Mpa pressure can be met.

[0033] (4): Use a welding clamp to fix the tungsten needle and the welding workpiece so that the tungsten needle is horizontally placed around the welding area of ​​the welding workpiece;

[0034] The welding fixture can fix the tungsten needle and the welding workpiece at a specific angle, and this solution preferably surrounds the tungsten needle around the welding workpiece composed of the copper tube and the stainless steel tube to ensure that the shape around the welding area is consistent during welding;

[0035] (5): Start welding, heat the tungsten needle, and melt the stainless steel tube through the temperature of the tungsten needle, so that the stainless steel tube is combined with the copper tube.

[0036] Since the tungsten needles are distributed around the welding area of ​​the welding workpiece, the tungsten needles will not melt under high temperature heating. The heating temperature when the welding current is 93-94A is enough to melt the stainless steel, so that the copper tube and the stainless steel tube are combined into one.

[0037] The present invention provides a argon arc welding process for copper tubes and stainless steel tubes, which adopts the argon arc welding process for copper tubes and stainless steel tubes without adding welding wire, has the advantages of convenient operation and simple process, reduces cost and improves welding efficiency, can replace the existing welding process, and solves the problem of high cost of copper and stainless steel welding for pressure-bearing equipment.

[0038] In one embodiment of this solution, in step (4), multiple tungsten needles can be directly distributed around the welding area of ​​the welding workpiece. In the best embodiment, only one tungsten needle is needed. Specifically:

[0039] Preferably, in step (4), at least one tungsten needle is used to horizontally contact the welding area of ​​the welding workpiece, and the tungsten needle is perpendicular to the welding workpiece;

[0040] In the step (5), welding is started and the tungsten needle is driven to rotate around the axis of the welding workpiece.

[0041] The tungsten needle of the present solution can be vertically pressed against the welding area of ​​the welding workpiece, and then in step (5) the tungsten needle can be driven to rotate 360 ​​degrees so that the tungsten needle surrounds and contacts the welding area of ​​the welding workpiece, thereby melting the stainless steel tube through the temperature of the tungsten needle and combining the stainless steel tube with the copper tube. Therefore, only a single tungsten needle is needed to fully cover the welding area of ​​the welding workpiece.

[0042] Preferably, in step (2), the end of the stainless steel tube is made into a spigot, the end of the copper tube is made into a socket, the copper tube and the stainless steel tube are welded together in a spigot-and-socket type, and a fillet weld is performed.

[0043] This solution uses a socket-type fillet weld. The socket-type means that one end of the copper tube is made into a socket (i.e., the insertion end) and the stainless steel tube is made into a spigot (i.e., the inserted end). On the one hand, it does not require complex tools and equipment, and the operation is relatively simple. On the other hand, the tungsten needle can be distributed around the outer periphery of the spigot of the stainless steel tube. When the tungsten needle is heated, the heat can be transferred to the stainless steel tube, thereby melting the welding area of ​​the stainless steel. The fillet weld is a weld welded along the intersection of two orthogonal or nearly orthogonal parts when the spigot and the socket are connected. This ensures that the welding in step (4) is firm.

[0044] Optimally, in step (2), the length of the copper tube inserted into the stainless steel tube is 4-6 mm.

[0045] The insertion range of the copper tube in the stainless steel tube is limited to 4-6mm. This solution uses a small current welding current. Combined with the advantages of the socket fillet weld, this solution can complete the welding in 20 to 30 seconds at a smaller welding current, reducing costs and improving welding efficiency.

[0046] Preferably, in step (2), four welding spots are evenly distributed on the welding workpiece.

[0047] The welding points of four-point welding are evenly distributed, the welding points restrain each other, the force balance between the welding points is better, and the connection stability between the copper tube and the stainless steel tube is higher.

[0048] Optimally, in step (3), the purity of argon gas is 99.990-99.999%.

[0049] During the welding process, argon is used as a shielding gas, and its purity has a significant impact on the welding quality. 99.990-99.999% high-purity argon can effectively isolate the air and prevent the weld metal from chemically reacting with oxygen and nitrogen in the air at high temperatures, thereby avoiding oxidation and nitridation of the weld, thereby ensuring the mechanical properties of the welded joint and improving the appearance of the weld. The outer surface of the weld area is easy to handle after welding.

[0050] Preferably, in step (1), pickling and degreasing are performed using a pickling paste.

[0051] The pickling paste is a strong acid mixed with multiple acids in a certain proportion. It is a transparent paste with strong dirt removal ability and no corrosion to the substrate. It is very suitable for pretreatment before assembly of this solution.

[0052] Optionally, the method further comprises step (6);

[0053] The step (6) is as follows: connecting the welded workpiece to a gas supply device, increasing the gas pressure to 2 MPa, maintaining the pressure for at least 30 seconds, and selecting the workpiece without leakage as a qualified workpiece.

[0054] After welding is completed, this solution can strictly select workpieces that can withstand 2MPa gas pressure as qualified products. The welded pipes with a pressure resistance of 2Mpa and no leakage are qualified workpieces. This mainly shows that the applicable scenarios of this process can meet the transportation of media such as liquid nitrogen, liquid oxygen, liquid argon, and liquefied natural gas. This solution uses argon arc welding technology for copper pipes and stainless steel pipes without adding welding wire, which greatly reduces the welding cost and can also meet the existing welding standards in terms of pressure resistance requirements.

[0055] A welded pipe is made by using the above copper pipe and stainless steel pipe argon arc welding process.

[0056] Optimally, the pressure resistance value of the welded pipe is 2Mpa.

[0057] The invention discloses an application of a welded pipe in a heat exchange element. The welded pipe is made by using the above-mentioned argon arc welding process between a copper pipe and a stainless steel pipe.

[0058] Performance test of this solution:

[0059] Visual inspection: Visually inspect the welding area. Products with welding defects such as weld penetration, slag inclusion or leakage are considered unqualified products.

[0060] Pressure test: The welding workpiece is connected to the nitrogen gas supply device and pressurized to 2MPa; the welding workpiece is placed in soapy water and the pressure is maintained for 30 seconds. It is qualified if there is no leakage.

[0061] Embodiment 1:

[0062] Step (1): Clean a φ10×1mm stainless steel tube with an inner diameter of 8mm with pickling paste to remove surface oil stains;

[0063] Step (2): insert the φ8×0.8mm copper tube into the 10×1mm stainless steel tube, with the length of the copper tube inserted into the stainless steel tube being 5mm. Use argon arc welding without filler wire to evenly spot weld 4 points to fix the assembly point, and the connection method is a socket fillet weld;

[0064] Step (3): Selection of welding process parameters: low current 93.5A, welding time 23 seconds, cooling temperature 30°C, high-purity 99.999% argon protection during welding, flow rate 15L / min;

[0065] Step (4): Use a welding fixture to fix the tungsten needle and the welding workpiece in a horizontal state to ensure that the shape around the welding area is consistent during welding;

[0066] Step (5): Start welding mode.

[0067] Comparative Example:

[0068] Step (1): Clean a φ10×1mm stainless steel tube with an inner diameter of 8mm with pickling paste to remove surface oil stains;

[0069] Step (2): insert a φ8×0.8mm copper tube into a 10×1mm stainless steel tube, the length of the copper tube inserted into the stainless steel tube is 5mm, and preheat the tube body with a welding torch;

[0070] Step (3): Use a welding clamp to fix, apply a silver welding rod in the welding area, use an oxygen-acetylene flame to melt the silver welding rod, weld the copper tube and the stainless steel tube together, and cool them.

[0071] The performance of Example 1 and the comparative example were tested, and the results are shown in Table 1.

[0072] Table 1 - Performance test results of Example 1 and Comparative Example

[0073] Test Group Visual inspection Pressure test Example 1 qualified qualified Comparative Example qualified qualified

[0074] illustrate:

[0075] By comparing Example 1 with the comparative example, it can be seen that Example 1 adopts argon arc welding process for copper tubes and stainless steel tubes without adding welding wire; the comparative example adopts oxyacetylene flame process, melts silver welding rods at high temperature, and uses silver welding rods as pasting filling materials to achieve qualified welding. Example 1 and the comparative example are qualified in visual inspection and pressure test, but the cost of the comparative example is relatively high, mainly because the purchase cost of silver welding rods is high. However, this solution can achieve the performance of using silver welding rods without using welding wire, meeting the requirements of low-temperature welding.

[0076] Embodiment 2:

[0077] Step (1): Clean a φ10×1mm stainless steel tube with an inner diameter of 8mm with pickling paste to remove surface oil stains;

[0078] Step (2): insert the φ8×0.8mm copper tube into the 10×1mm stainless steel tube, and the length of the copper tube inserted into the stainless steel tube is 6mm. Use argon arc welding without filler wire to evenly spot weld 4 points to fix the assembly point, and the connection method is a socket fillet weld;

[0079] Step (3): Selection of welding process parameters: low current 93A, welding time 30 seconds, cooling temperature 25°C, high purity 99.990% argon protection during welding, flow rate 14L / min;

[0080] Step (4): Use a welding fixture to fix the tungsten needle and the welding workpiece in a horizontal state to ensure that the shape around the welding area is consistent during welding;

[0081] Step (5): Start welding mode.

[0082] Embodiment 3:

[0083] Step (1): Clean a φ10×1mm stainless steel tube with an inner diameter of 8mm with pickling paste to remove surface oil stains;

[0084] Step (2): insert the φ8×0.8mm copper tube into the 10×1mm stainless steel tube, with the length of the copper tube inserted into the stainless steel tube being 4mm. Use argon arc welding without filler wire to evenly spot weld 4 points to fix the assembly point, and the connection method is a socket fillet weld;

[0085] Step (3): Selection of welding process parameters: low current 94A, welding time 20 seconds, cooling temperature 35°C, high purity 99.999% argon protection during welding, flow rate 12L / min;

[0086] Step (4): Use a welding fixture to fix the tungsten needle and the welding workpiece in a horizontal state to ensure that the shape around the welding area is consistent during welding;

[0087] Step (5): Start welding mode.

[0088] The performance of Examples 2 and 3 was tested, and the results are shown in Table 2.

[0089] Table 2 - Performance test results of Examples 2 and 3

[0090] Test Group Visual inspection Pressure test Example 2 qualified qualified Example 3 qualified qualified

[0091] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A copper tube and stainless steel tube argon arc welding process, characterized in that: The following steps are involved: (1): Take a φ10×1mm stainless steel tube with an inner diameter of 8mm and pickle and remove oil; (2): Take a φ8×0.8mm copper tube and insert it into a stainless steel tube to form a welding workpiece; use argon arc welding technology without welding wire to evenly distribute multiple spot welding points on the welding workpiece to form an assembly point; (3): Adjust the welding process parameters: welding current is 93-94A, welding time is 20-30s, cooling temperature is 25-35℃, argon protection is used during welding, and the argon flow rate is 12-15L / min; (4): Use a welding clamp to fix the tungsten needle and the welding workpiece so that the tungsten needle is horizontally placed around the welding area of ​​the welding workpiece; (5): Start welding, the temperature of the tungsten needle melts the stainless steel tube, and the stainless steel tube is combined with the copper tube.

2. The argon arc welding process for copper tube and stainless steel tube according to claim 1 is characterized in that: In the step (4), at least one tungsten needle is used to horizontally contact the welding area of ​​the welding workpiece, and the tungsten needle is perpendicular to the welding workpiece; In the step (5), welding is started and the tungsten needle is driven to rotate around the axis of the welding workpiece.

3. The argon arc welding process for copper tube and stainless steel tube according to claim 1 is characterized in that: In the step (2), the end of the stainless steel tube is made into a spigot, the end of the copper tube is made into a socket, the copper tube and the stainless steel tube are welded together in a spigot-and-socket type, and a fillet weld is performed.

4. The argon arc welding process for copper tube and stainless steel tube according to claim 3 is characterized in that: In step (2), the length of the copper tube inserted into the stainless steel tube is 4-6 mm.

5. The argon arc welding process for copper tube and stainless steel tube according to claim 1 is characterized in that: In the step (2), four welding spots are evenly distributed on the welding workpiece.

6. The argon arc welding process for copper tube and stainless steel tube according to claim 1 is characterized in that: In the step (3), the purity of the argon gas is 99.990-99.999%.

7. The argon arc welding process for copper tube and stainless steel tube according to claim 1 is characterized in that: In the step (1), pickling and degreasing are performed using a pickling paste.

8. A copper tube and stainless steel tube argon arc welding process according to any one of claims 1 to 7, characterized in that: Also includes step (6); The step (6) is as follows: connecting the welded workpiece to a gas supply device, increasing the gas pressure to 2 MPa, maintaining the pressure for at least 30 seconds, and selecting the workpiece without leakage as a qualified workpiece.

9. A welded pipe, characterized in that: The copper tube and the stainless steel tube are made by the argon arc welding process described in any one of claims 1 to 8.

10. Application of a welded pipe in a heat exchange element, characterized in that: The welded pipe is made by the argon arc welding process of a copper pipe and a stainless steel pipe as described in any one of claims 1 to 7.