Welding method for balance pipeline of mixed refrigerant compressor

Abstract

The invention provides a welding method for a balance pipeline of a mixed refrigerant compressor. The welding method comprises the steps that a to-be-welded part of the balance pipeline is subjected to groove machining treatment; and multiple welding operations are conducted on the to-be-welded part subjected to groove machining treatment in an argon arc welding mode, so that a welding seam is formed in the to-be-welded part. The balance line thus welded may operate at a temperature of-45 DEG C or less required by a mixed refrigerant compressor.

Description

TECHNICAL FIELD

[0001] The present application relates to a welding method, in particular to a welding method for a balance pipeline of a mixed refrigerant compressor. BACKGROUND

[0002] The balance pipeline is an important component of the compressor, and the medium in the balance pipeline is the same as the working medium of the compressor. For a cryogenic compressor such as a mixed refrigerant compressor, the temperature of the working medium can reach-45℃, so the balance pipeline is required to work in the medium at-45℃. The strength of the weld, the low-temperature impact toughness, the hardness, and the crack control of the balance pipeline are particularly strict. It is required that the impact value of the weld, the fusion line, and the heat-affected zone at-45℃ is greater than or equal to 20J on the basis of ensuring the strength, and it is very difficult to achieve such a requirement for the welded fusion line. In order to ensure the hydrogen-induced cracking resistance and require the hardness value of the weld, the fusion line, and the heat-affected zone to be less than or equal to 200HV. After the pipeline is welded, the post-weld heat treatment cannot be performed because the flange sealing surface cannot be damaged, so it is difficult to ensure this hardness value. In addition, the cut surface needs to be subjected to metallographic detection to check whether the weld has micro cracks. SUMMARY

[0003] Therefore, the present application provides a welding method for a balance pipeline of a mixed refrigerant compressor. The welding method comprises: performing a beveling processing on a to-be-welded part of the balance pipeline; and performing a multi-pass welding operation on the to-be-welded part by means of argon arc welding to form a weld at the to-be-welded part.

[0004] Specifically, when the beveling processing is performed, a single-sided single-bevel structure can be formed at the to-be-welded part of the balance pipeline. When the weld is formed, 5G horizontal fixed welding can be performed at the to-be-welded part subjected to the beveling processing.

[0005] In the example in which the material of the balance pipeline is ASTM A350LF2Cl.1 and / or ASTM A333Gr.6, the step of forming the weld can perform a multi-pass welding operation by using a nickel-free argon arc welding wire. Specifically, a multi-pass welding operation can be performed by using an argon arc welding wire of type ER70S-3, wherein in the argon arc welding wire of type ER70S-3, C≤0.15(wt.%), Mn≤1.4(wt.%), and Ni=0(wt.%).

[0006] When the weld is formed, the temperature at the to-be-welded part can be controlled to be not higher than 120℃ before each welding operation is performed.

[0007] In the example where the thickness of the end of the to-be-welded portion of the balance pipeline is 5 mm to 12 mm, the step of forming the weld includes: each welding operation can be performed by a straight welding pass small-current rapid welding method. Here, the welding speed of each welding operation can be 60 mm / s to 65 mm / s, and the welding heat input of each welding operation can be controlled to be no more than 2 kJ / mm.

[0008] In the forming of the weld, one of the multiple welding operations can be performed to form a weld layer with a thickness of 1.5 mm to 2.5 mm. Then, after the one welding operation is completed, surface grinding can be performed on the weld layer formed by the one welding operation to remove a portion of the weld layer with a thickness of 1 mm to 1.5 mm. Then, the next one of the multiple welding operations can be performed to form a next weld layer with a thickness of 1.5 mm to 2.5 mm on the weld layer that has been surface ground. Then, surface grinding can be performed on the next weld layer formed by the next welding operation to remove a portion of the next weld layer with a thickness of 1 mm to 1.5 mm.

[0009] After the multiple welding operations and the subsequent surface grinding operations are performed, a cap welding operation of the multiple welding operations can be performed to form a cap weld layer on a previously formed and surface ground weld layer formed by a previous welding operation of the multiple welding operations. Then, a next welding operation of the multiple welding operations can be performed to form a next weld layer on the surface of the cap weld layer. The next weld layer is 1 mm to 1.5 mm away from the end of the to-be-welded portion on both sides. In this way, by performing the next welding operation after the cap welding and subsequently removing the next weld layer, the cap weld layer can be tempered, the welding stress can be eliminated, the toughness of the weld and the heat-affected zone can be improved, and the hardness can be reduced. Finally, the next weld layer is ground to remove the next weld layer.

[0010] In addition, in the forming of the weld, by performing the multiple welding operations, a symmetrical weld structure can be formed.

[0011] According to the welding operation of the exemplary embodiments, a weld and a balance pipeline of a mixed refrigerant compressor connected by the weld that meet specific requirements can be formed, so that the strength of the weld, the fusion line, the heat-affected zone, the -45°C impact, the hardness, and the absence of microcracks can be ensured on the basis of ensuring the sealing performance of the flange. BRIEF DESCRIPTION OF DRAWINGS

[0012] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, so that the above and other features and advantages of the present application can be more clearly understood by those skilled in the art.

[0013] Figure 1 a flowchart showing a welding method according to an exemplary embodiment;

[0014] Figure 2 a cross-sectional view showing a multi-pass weld layer formed by a welding method according to an exemplary embodiment.

[0015] Figure 3 a flowchart showing a step of forming a weld by a welding method according to an exemplary embodiment.

[0016] Reference numerals are as follows:

[0017] S100: beveling process

[0018] S300: forming a weld

[0019] S301: one-pass welding operation

[0020] S303: surface grinding

[0021] S305: next one-pass welding operation

[0022] S307: surface grinding

[0023] S311: cap welding operation

[0024] S313: cap post-weld one-pass welding operation

[0025] S315: surface grinding DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions, and advantages of the present application clearer, the following further describes the present application with examples.

[0027] Figure 1 a flowchart showing a welding method according to an exemplary embodiment, Figure 2 a cross-sectional view showing a multi-pass weld layer formed by a welding method according to an exemplary embodiment. The welding method according to an exemplary embodiment can be applied to welding of a balance line of a low-temperature compressor using a mixed refrigerant. For example, the working medium temperature in such a mixed refrigerant compressor and its balance line can reach about -45°C. In the following description, a balance line having a weld end thickness of about 6 mm as shown in FIG. 1 will be described as a welding object (i.e., a workpiece) to be welded, and it will also be understood by those skilled in the art that the welding method according to an exemplary embodiment can be applied to various sizes of welding objects included in a low-temperature compressor. Figure 2 As shown in FIG. 2, the welding method according to an exemplary embodiment includes a beveling process S100, a first one-pass welding operation S301, a surface grinding S303, a second one-pass welding operation S305, a surface grinding S307, a cap welding operation S311, a cap post-weld one-pass welding operation S313, and a surface grinding S315.

[0028] As shown in FIG. 2, the welding method according to an exemplary embodiment includes a beveling process S100, a first one-pass welding operation S301, a surface grinding S303, a second one-pass welding operation S305, a surface grinding S307, a cap welding operation S311, a cap post-weld one-pass welding operation S313, and a surface grinding S315. Figure 1As shown in , the welding method according to the exemplary embodiment may include groove processing S100 and forming a weld S300. In the groove processing S100, the weldment may be pre-processed for groove processing, for example, the end of the balance pipeline as the part to be welded may be groove processed. Figure 2 As shown in , during groove processing, a single-sided, single-sided groove structure can be formed at the portion to be welded (i.e., the end) of the balance pipeline. This allows for accurate testing of the toughness and hardness of the weld fusion line during and / or after the welding operation.

[0029] Then, during weld formation ( S300 ), multiple passes of welding can be performed using argon arc welding at the groove-processed portion to be welded, thereby forming a weld at the portion to be welded. It should be noted that one, more, or all of the multiple passes of welding included in weld formation ( S300 ) can be 5G horizontal fixed welding to improve weld quality. 5G horizontal fixed welding is a term used in pipeline welding to represent all-position welding of horizontally fixed butt welds. Furthermore, as described above, one, more, or all of the multiple passes of welding included in weld formation ( S300 ) can be performed using argon arc welding. That is, arc welding is performed using argon as the shielding gas. Furthermore, in one example, the material of the balancing line can be ASTM A350LF2C1.1 and / or ASTM A333Gr.6. Here, the materials "ASTM A350LF2C1.1" and "ASTM A333Gr.6" are both ferritic steels for low-temperature use specified in the American Society for Testing and Materials (ASTM) standards. One or more or all of the multiple weld passes included in forming the weld seam S300 can be performed using a nickel-free argon arc welding wire. Typical low-temperature welding materials may contain a certain amount of nickel, but nickel is not beneficial for resisting SCC sulfide corrosion cracking. The presence of nickel in low-alloy steel can easily lead to the risk of H2S stress cracking. Therefore, in an exemplary embodiment of the present invention, a customized nickel-free argon arc welding wire with a low carbon and manganese alloy content is used. For example, a specially customized ER70S-3 argon arc welding wire can be used for the welding operation here. The material requirements for this ER70S-3 argon arc welding wire are specifically customized to include C ≤ 0.15 (wt.%), Mn ≤ 1.4 (wt.%), and Ni = 0 (wt.%), thereby improving resistance to sulfide corrosion cracking.

[0030] The following will refer to Figure 2 and Figure 3 Next, the step S300 of forming a weld will be described. Figure 2 A cross-sectional view showing an example of a weld layer formed with a balancing pipeline having an end thickness of approximately 6 mm as a welding object. Figure 3is a flow chart showing a step of forming a weld S300 of a welding method according to an exemplary embodiment. More specifically, in the example shown in Figure 2 the end portion of the balance line has a thickness of about 6 mm, the balance line has a diameter of about 168 mm, the single-sided single-bevel joint formed by the beveling process S100 is formed as an angle of about 60°, and the spacing between the welding objects is about 2 mm to 4 mm. Further, Figure 2 only the first layer of weld formed by the first layer of deposition welding, the surface of the cap weld layer formed by the cap welding operation, and the weld layer formed on the surface of the cap weld layer and subsequently removed are shown in

[0031] As shown in Figure 2 and Figure 3 at the bevelled welding site S100, a welding operation is performed by means of argon arc welding to form a weld layer having a predetermined thickness. For example, when performing the first welding operation (i.e., the first layer of deposition welding) S301 of the multi-pass welding operation, a first layer of weld can be formed as shown in Figure 2 The first layer of weld formed by the first layer of deposition welding can have a thickness of between about 1.5 mm to 2.5 mm, for example, about 2 mm as shown in Figure 2 The first layer of weld formed by the first layer of deposition welding can be surface ground S303 to remove a portion of the first layer of weld having a thickness of about 1 mm to 1.5 mm. Then, the next welding operation S305 is performed to form the next layer of weld on the surface ground layer of weld. The layer of weld formed by each welding operation can have a thickness of between about 1.5 mm to 2.5 mm, for example, about 2 mm. Then, the next layer of weld can be surface ground S307 to remove a portion of the next layer of weld, for example, a portion having a thickness of about 1 mm to 1.5 mm. Preferably, each surface grinding removes about 1 / 2 of the thickness of the layer of weld. As described above, by grinding the weld surface after each layer of weld is completed, removing about 1 / 2 of the filler metal before the next layer of weld is performed, the mechanical properties of the weld, the fusion line, and the heat affected zone can be improved.

[0032] After the multi-pass welding operation and the surface grinding operation are performed as described above, a cap pass welding operation S311 can be performed to form a cap pass weld layer on the previously formed and surface ground previous weld layer formed by the previous pass welding operation performed prior to the cap pass welding operation. Then, a final pass welding operation in the multi-pass welding operation, i.e., a cap post pass welding operation, can be performed to form a post pass weld layer on the surface of the cap pass weld layer. Here, the post pass weld layer can be formed to have a distance of about 1 mm to 1.5 mm from the end of the weld site. For example, the cap post pass welding operation can use a small diameter (e.g., about φ 2.0 mm) welding material. Further, the post pass weld layer can be ground to remove the post pass weld layer S315. In this way, the cap pass weld layer can be tempered by performing the cap post pass welding operation and then removing the post pass weld layer to relieve some welding stress and to improve the toughness and reduce the hardness of the weld and the heat affected zone. Thus, the weld can be formed at the weld site.

[0033] Further, when performing the multi-pass welding operation described above, the symmetrical weld structure can be formed by controlling the operation, and thus the pipe deformation can be controlled.

[0034] Further, when performing the multi-pass welding operation described above, the temperature of the weld site can be controlled, and the welding speed and / or the welding heat input can be controlled. For example, the temperature of the weld site can be controlled to be no higher than 120°C before each pass welding operation is performed. That is, the inter-pass temperature can be controlled, and the preheating temperature can be controlled to be no higher than 120°C. In Figure 2 In the example shown in FIG. 6 in which the thickness of the end of the weld site of the balance pipe is 6 mm, each pass welding operation can be performed by a straight pass small current rapid welding. For example, the welding speed of each pass welding operation can be 60 mm / s to 65 mm / s, and in one example, can be 63 mm / s. Meanwhile, the welding heat input of each pass welding operation can be controlled to be no more than 2 kJ / mm. Thus, the optimal T8 / 5 time, i.e., the time required for the welded joint to cool from 800°C to 500°C, can be obtained. Further, a contact type temperature measuring pen can be used to measure the temperature of each pass welding to prevent grain coarsening.

[0035] Further, the weld cross section can be metallographically examined to confirm that the formed weld has no micro cracks.

[0036] According to the exemplary embodiments, by using a specially customized argon arc welding wire, using a specific welding operation method, performing multi-pass welding at the to-be-welded part of the mixed refrigerant compressor balance pipeline which has been subjected to groove processing, while removing a part of the weld layer formed by the previous pass before each welding operation, in addition, by controlling the temperature at the to-be-welded part and the heat input of the welding operation, a qualified welding structure can be finally obtained, that is, the impact toughness value of the weld, fusion line and weld heat-affected zone at-45℃ is not less than 20J, and the hardness value is not higher than 200HV, which has excellent resistance to hydrogen-induced cracking. Therefore, the balance pipeline welded in this way can work at-45℃ or lower temperature conditions.

[0037] The above description is merely preferred embodiments of the present application, but not to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A welding method for a mixed refrigerant compressor balance line, characterized in that: The welding method comprises: Performing groove processing on the portion to be welded of the balance pipeline (S100); At the portion to be welded that has been grooved, a multi-pass welding operation is performed by argon arc welding to form a weld at the portion to be welded ( S300 ).

2. The welding method according to claim 1, wherein: The step of performing groove processing includes: forming a single-side single-face groove structure at the position to be welded of the balance pipeline.

3. The welding method according to claim 1, wherein: The steps of forming the weld include: performing 5G horizontal fixed welding at the welded portion that has been processed with groove processing.

4. The welding method according to claim 1, wherein: The material of the balancing pipeline is ASTM A350 LF2Cl.1 and / or ASTM A333 Gr.6, and the steps of forming the weld include: performing a multi-pass welding operation using a nickel-free argon arc welding wire.

5. The welding method according to claim 4, wherein: The steps of forming a weld include: performing a multi-pass welding operation using an argon arc welding wire of model ER70S-3, wherein in the argon arc welding wire of model ER70S-3, C≤0.15 (wt.%), Mn≤1.4 (wt.%), and Ni=0 (wt.%).

6. The welding method according to claim 5, wherein: The steps to forming a weld include: Before each welding operation, the temperature of the welded area should be controlled to be no higher than 120℃.

7. The welding method according to claim 6, wherein: The thickness of the end of the balance pipeline to be welded is 5mm to 12mm. The steps of forming the weld include: Each welding operation is performed by fast welding with a small current in a straight weld, wherein the welding speed of each welding operation is 60mm / s to 65mm / s, and the welding heat input of each welding operation is controlled to be no more than 2kJ / mm.

8. The welding method according to claim 7, wherein: The steps to forming a weld include: Performing one welding operation (S301) among multiple welding operations to form a weld layer with a thickness of 1.5 mm to 2.5 mm; After the welding operation is completed, the weld layer formed by the welding operation is surface-grinded to remove a portion of the weld layer having a thickness of 1 mm to 1.5 mm (S303); The next welding operation in the multi-pass welding operation is performed (S305) to form a next weld layer having a thickness of 1.5 mm to 2.5 mm on the surface-ground weld layer.

9. The welding method according to claim 8, wherein: The steps to forming a weld include: Performing a cap welding operation (S311) in a multi-pass welding operation to form a cap weld layer on a previous weld layer formed in a previous welding operation performed before the cap welding operation and subjected to surface grinding; Performing a last welding operation of the cap welding in the multi-pass welding operation (S313) to form a last weld layer on the surface of the cap weld layer, wherein the distance between both sides of the last weld layer and the end of the to-be-welded portion is 1 mm to 1.5 mm; The last weld layer is ground to remove the last weld layer (S315).

10. The welding method according to claim 1, wherein: The step of forming the weld includes forming a symmetrical weld structure by performing a multi-pass welding operation.

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