Welding method for reducing residual stress of welding seam of thick-wall austenitic stainless steel structural part

Abstract

The invention provides a welding method for reducing residual stress of a welding seam of a thick-wall austenitic stainless steel structural member, which comprises the following steps of: preparing a base material, selecting a stainless steel pipe fitting with the thickness of 20-40mm as the base material, and processing an annular welding groove; assembling and positioning, aligning the welding groove of the base metal to form a welding seam, and performing spot welding on the welding seam to fix the base metal; double-layer welding is carried out, double-layer tungsten electrode inert gas shielded welding is adopted for welding, the double-layer tungsten electrode inert gas shielded welding comprises first-layer welding and second-layer welding, after the first-layer welding is completed, the temperature is reduced to be smaller than or equal to 150 DEG C, and then the second-layer welding is carried out; and stress testing: detecting the residual stress of the welding seam by adopting an X-ray diffraction method after welding is completed. Compared with the prior art, the welding method in the scheme solves the process problem that the welding stress of the austenitic stainless steel large-scale structural member is large, and has great popularization and application values.

Description

Technical Field

[0001] This invention relates to the fields of material processing and welding technology, and in particular to a welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components. Background Technology

[0002] Austenitic stainless steel is widely used in thick-walled structural components such as chemical equipment, energy pipelines, and precision instrument sensors due to its excellent corrosion resistance, high-temperature strength, and low-temperature toughness. However, during the welding process, the localized high-temperature heating and rapid cooling of these materials can lead to severe residual stress accumulation. Residual stress can cause welding deformation, crack initiation, and reduce the fatigue strength and dimensional stability of the structure. Therefore, the presence of residual stress not only affects the long-term reliability of structural components but may also trigger failure modes such as stress corrosion cracking, posing a potential threat to engineering safety.

[0003] Traditional solutions primarily rely on post-weld stress relief treatments, such as low-temperature annealing at 600℃ or vibration aging techniques. While these can partially alleviate stress concentration, they have significant limitations: the processes are complex and costly, and the high-temperature treatment may lead to degradation of the base material's properties, such as increased susceptibility to intergranular corrosion or decreased mechanical properties. Furthermore, for thick-walled structural components, traditional methods struggle to achieve uniform stress distribution elimination, easily leaving stress concentration zones in critical areas. Summary of the Invention

[0004] This invention provides a welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components, thereby solving the technical problem of difficulty in reducing stress during the welding process of austenitic stainless steel structural components.

[0005] This invention provides a welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components, comprising the following steps: For base material preparation, select stainless steel pipe fittings with a thickness of 20-40mm as the base material and process the circumferential welding bevel; Assembly and positioning: Align the welding bevels of the base material to form a weld, and perform spot welding on the weld to fix the base material. Double-layer welding is performed using double-layer tungsten inert gas (TIG) shielded welding. The double-layer TIG welding consists of a first layer and a second layer. After the first layer is welded, the temperature is cooled to ≤150℃ before the second layer is welded. The current for the first layer is 18A-30A higher than that for the second layer, and the diameter of the welding wire for the second layer is 0.3mm-0.5mm larger than that for the first layer. Both the first and second layer welding processes are protected with argon gas at a flow rate of 8-12 L / min. Stress testing: After welding, residual stress in the weld is detected by X-ray diffraction.

[0006] In one embodiment of the present invention, the base material is 316L stainless steel pipe.

[0007] In one embodiment of the present invention, the angle of the welding bevel is 37°.

[0008] In one embodiment of the present invention, after the base material is prepared, it is cleaned before welding by using an ultrasonic cleaner in H-01 degreasing cleaning agent solution to remove grease, dirt and other impurities from the surface of the base material.

[0009] In one embodiment of the present invention, during assembly and positioning, the weld seam is ≤0.5mm, and the weld seam is subjected to argon arc spot welding.

[0010] In one embodiment of the present invention, the current for the first layer welding is 20 A higher than that for the second layer welding, and the diameter of the welding wire for the second layer welding is 0.4 mm larger than that for the first layer welding.

[0011] In one embodiment of the present invention, the first layer of welding is performed using ER316L welding wire with a diameter of 1.6 mm and a welding current of 130A; the second layer of welding is performed using ER316L welding wire with a diameter of 2.0 mm and a welding current of 110 A.

[0012] In one embodiment of the present invention, after the first layer is welded and before the second layer is welded, the protective gas flow rate is maintained at 15-25 L / min.

[0013] In one embodiment of the present invention, the X-ray diffraction method is performed in accordance with the GB / T 7704-2017 standard, with four test points evenly distributed along the circumferential direction of the weld and one test point along the axial direction, including at least five test points.

[0014] In one embodiment of the present invention, the chemical composition of 316L stainless steel is: C ≤0.03%, Si ≤1.00%, Mn ≤2.00%, Cr 16.00-18.00%, Ni ≤10.00-14.00%, Mo 2.00-3.00%, P ≤0.045%, S ≤0.03%.

[0015] The beneficial effects of this invention are as follows: The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components proposed in this invention, through double-layer tungsten inert gas (TIG) welding, can reduce the circumferential stress fluctuation range of the weld and achieve a more uniform stress distribution. Experimental results show that, compared with traditional single-layer welding, the double-layer TIG welding process can reduce axial residual stress by up to 37%. Furthermore, the welding method in this solution simplifies the process; due to the reduced residual stress, subsequent stress-relief processes such as annealing can be reduced or eliminated, lowering production costs by more than 30%. Compared with existing technologies, the welding method in this solution solves the technological challenge of high welding stress in austenitic stainless steel structural components and has significant potential for widespread application. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0017] In the attached diagram: Figure 1 This is a schematic diagram showing the location for testing residual stress in the weld seams of thick-walled austenitic stainless steel structural components. Detailed Implementation

[0018] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0019] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0020] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0021] The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to the present invention includes the following steps: For base material preparation, select stainless steel pipe fittings with a thickness of 20-40mm as the base material and process the circumferential welding bevel; Assembly and positioning: Align the welding bevels of the base material to form a weld, and perform spot welding on the weld to fix the base material. Double-layer welding is performed using double-layer tungsten inert gas (TIG) shielded welding. The double-layer TIG welding consists of a first layer and a second layer. After the first layer is welded, the temperature is cooled to ≤150℃ before the second layer is welded. The current for the first layer is 18A-30A higher than that for the second layer, and the diameter of the welding wire for the second layer is 0.3mm-0.5mm larger than that for the first layer. Both the first and second layer welding processes are protected with argon gas at a flow rate of 8-12 L / min. Stress testing: After welding, residual stress in the weld is detected by X-ray diffraction.

[0022] Among them, "Austenitic Stainless Steel" refers to stainless steel with an austenitic structure at room temperature; "Tungsten Inert Gas Welding" refers to a welding method that uses the heat of an electric arc to melt the base material and filler wire under argon protection to form a joint; "Residual Welding Stress" refers to the internal stress remaining in the welded structure due to the constraint of deformation during the welding process.

[0023] In practical implementation, double-layer tungsten inert gas (TIG) welding reduces the circumferential stress fluctuation range of the weld and results in a more uniform stress distribution. Tests show that compared to traditional single-layer welding, double-layer TIG welding can reduce axial residual stress by up to 37%. Furthermore, the welding method in this solution simplifies the process; due to the reduced residual stress, subsequent stress-relieving processes such as annealing can be reduced or eliminated, lowering production costs by over 30%. The welding method in this solution employs pre-welding processes to prevent excessive stress, eliminating the need for additional subsequent annealing.

[0024] In some embodiments, 316L stainless steel pipe fittings are used as the base material. 316L stainless steel exhibits outstanding corrosion resistance, mechanical properties, and processing adaptability, making it particularly suitable for applications with high material requirements, such as petrochemicals, medical devices, and food processing. The requirements for weld joints are even higher, therefore, this welding method uses 316L stainless steel as the base material, which can better solve welding problems.

[0025] In some embodiments, the weld bevel angle is 37°. This is a common range for bevels in welding, effectively balancing ease of fabrication and weld strength, and is particularly suitable for welding medium and heavy plates. This angle balances penetration depth and filler volume, reduces the risk of deformation, and ensures root penetration.

[0026] In some embodiments, after the base material is prepared, pre-welding cleaning is performed using an ultrasonic cleaner in an H-01 degreasing cleaning agent solution to thoroughly remove grease, dirt, and other impurities from the base material surface. Using an ultrasonic cleaner in conjunction with H-01 degreasing cleaning agent to clean the base material effectively removes grease and dirt, laying a good foundation for subsequent welding.

[0027] In some embodiments, during assembly and positioning, if the weld seam is ≤0.5mm, argon arc spot welding is performed on the weld seam. During spot welding, it must be ensured that the base material does not shift, or at least there is no visible displacement, to guarantee the quality of the spot weld.

[0028] In some embodiments, the current for the first layer welding is 20 A higher than that for the second layer welding, and the diameter of the welding wire for the second layer welding is 0.4 mm larger than that for the first layer welding.

[0029] In some embodiments, after the first layer is welded and before the second layer is welded, the protective gas flow rate is maintained at 15-25 L / min.

[0030] In some embodiments, the X-ray diffraction test is performed according to the GB / T 7704-2017 standard, with four test points evenly distributed along the circumferential direction of the weld and one point along the axial direction, comprising at least five test points. This method can comprehensively assess the residual stress distribution in the weld area, ensuring that the welding quality meets the standard requirements.

[0031] In some embodiments, the chemical composition of 316L stainless steel is: C ≤0.03%, Si ≤1.00%, Mn ≤2.00%, Cr 16.00-18.00%, Ni ≤10.00-14.00%, Mo 2.00-3.00%, P ≤0.045%, S ≤0.03%.

[0032] The feasibility of this application was verified by the following test methods: the selected base material was 35 mm thick 316L stainless steel pipe fittings, with a single-sided bevel of 37°, a blunt edge of 2 mm, and an assembly gap of 0.5 mm. A total of 3 samples were obtained (numbered 1-3), of which 1# and 2# were double-layer welded, and 3# was single-layer welded. The welding process parameters for Examples 1, 2, and 3 are shown in Table 1.

[0033] Table 1. Welding process parameters

[0034] The chemical composition of the 316L stainless steel used in the embodiments of the present invention, by mass percentage, is C 0.0221%, Si 0.541%, Mn 1.336%, Cr 16.87%, Ni 10.019%, Mo 2.07%, P 0.03%, and S 0.001%.

[0035] Example 1: A welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components, the specific steps of which are as follows: (1) Select the base material of sample #1 as thick-walled 316L stainless steel pipe fittings for butt welding, and design the welding groove as an annular groove; (2) Clean the sample from step (1) before welding. Use an ultrasonic cleaner to clean it in H-01 degreasing cleaning agent solution to remove surface grease, dirt and other impurities. (3) Assemble and position the sample from step (2), and fix the weld position with argon arc welding. (4) The sample from step (3) was welded using tungsten inert gas welding (TIG). The welding parameters were as follows: two welding layers were used, ER316L welding wire was used, the diameter of the welding wire for the first layer was 1.6 mm and the welding current was 130 A; the diameter of the welding wire for the second layer was 2.0 mm and the welding current was 110 A. The interlayer temperature was controlled by allowing the first layer to cool naturally to ≤150℃ before welding the second layer to avoid stress superposition caused by overheating between layers. (5) After welding, residual stress is tested on the sample from step (4). Four test points are selected along the weld axis (evenly distributed clockwise). The specific locations are as follows: Figure 1 As shown, residual stress was detected using X-ray diffraction, with test directions including circumferential (parallel to weld) and axial (perpendicular to weld).

[0036] The residual stress of the weld after welding the 316L stainless steel in this embodiment is shown in Table 2. Table 2 shows that the axial residual stress of sample #1 is -251.6 MPa (test point 1), and the circumferential stress is -8.1 to 152.8 MPa. The circumferential direction is mainly under compressive stress, while a small tensile stress appears at test point 1 #1. The difference between the circumferential and axial stresses is significant.

[0037] Example 2: A welding method for thick-walled austenitic stainless steel structural components, the specific steps of which are as follows: (1) Select the base material of sample #2 as thick-walled 316L stainless steel pipe for butt welding, and design the welding groove as an annular groove; (2) Clean the sample from step (1) before welding. Use an ultrasonic cleaner to clean it in H-01 degreasing cleaning agent solution to remove surface grease, dirt and other impurities. (3) Assemble and position the sample from step (2), and fix the weld position with argon arc welding. (4) The sample from step (3) was welded using tungsten inert gas welding (TIG). The welding parameters were as follows: two welding layers were used, ER316L welding wire was used, the diameter of the welding wire for the first layer was 2.0 mm and the welding current was 130 A; the diameter of the welding wire for the second layer was 2.0 mm and the welding current was 110 A. In terms of interlayer temperature control, the first layer was naturally cooled to ≤150℃ after welding before the second layer was welded to avoid stress superposition caused by overheating between layers. (5) After welding, residual stress is tested on the sample from step (4). Four test points are selected along the weld axis (evenly distributed clockwise). The specific locations are as follows: Figure 1 As shown, residual stress was detected using X-ray diffraction, with test directions including circumferential (parallel to weld) and axial (perpendicular to weld).

[0038] The residual stress of the weld after welding the 316L stainless steel in this embodiment is shown in Table 2. Table 2 shows that the axial residual stress of sample #2 is -285.5 MPa (test point 1), and the circumferential stress is -66.6 to -210.4 MPa. The circumferential stress is entirely compressive, with no tensile stress, while the axial stress is greater.

[0039] Example 3: A welding method for thick-walled austenitic stainless steel structural components, the specific steps of which are as follows: (1) Select the base material of sample #3 as thick-walled 316L stainless steel pipe for butt welding, and design the welding groove as an annular groove; (2) Clean the sample from step (1) before welding. Use an ultrasonic cleaner to clean it in H-01 degreasing cleaning agent solution to remove surface grease, dirt and other impurities. (3) Assemble and position the sample from step (2), and fix the weld position with argon arc welding. (4) The sample from step (3) was welded by tungsten inert gas welding (TIG), with the following welding parameters: 1 welding layer, ER316L welding wire, 2.0 mm diameter welding wire, and 110 A welding current. (5) After welding, residual stress is tested on the sample from step (4). Four test points are selected along the weld axis (evenly distributed clockwise). The specific locations are as follows: Figure 1 As shown, residual stress was detected using X-ray diffraction, with test directions including circumferential (parallel to weld) and axial (perpendicular to weld).

[0040] The residual stress of the weld after welding the 316L stainless steel in this embodiment is shown in Table 2. Table 2 shows that the axial residual stress of sample #3 is -175.6 MPa (test point 1), and the circumferential stress is -160.1 to 158.1 MPa. The circumferential direction is entirely under compressive stress, with no tensile stress, and the difference between the circumferential and axial stresses is small.

[0041] The residual stress results of 316L stainless steel after welding in Examples 1, 2, and 3 are compared and analyzed in Table 2. It can be seen that, compared with the traditional process, the 316L stainless steel treated by the process of this invention has lower post-weld stress. By comparing the stress data of different processes, it can be seen that double-layer welding has lower stress than single-layer welding, single-layer welding has greater axial stress fluctuation, and smaller welding wire diameter results in lower stress.

[0042] Table 2. Welding Residual Stress

[0043] The welding method described in this invention solves the technical problem of large residual stress generated after welding thick-walled austenitic stainless steel structural parts, and has great promotion and application value.

[0044] The above is a detailed description of the specific embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0045] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components, characterized in that, Includes the following steps: For base material preparation, select stainless steel pipe fittings with a thickness of 20-40mm as the base material and process the circumferential welding bevel; Assembly and positioning: Align the welding bevels of the base material to form a weld, and perform spot welding on the weld to fix the base material. Double-layer welding is performed using double-layer tungsten inert gas (TIG) shielded welding. The double-layer TIG welding consists of a first layer and a second layer. After the first layer is welded, the temperature is cooled to ≤150℃ before the second layer is welded. The current for the first layer is 18A-30A higher than that for the second layer, and the diameter of the welding wire for the second layer is 0.3mm-0.5mm larger than that for the first layer. Both the first and second layer welding processes are protected with argon gas at a flow rate of 8-12 L / min. Stress testing: After welding, residual stress in the weld is detected by X-ray diffraction.

2. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 1, characterized in that: The base material is 316L stainless steel pipe fittings.

3. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 1, characterized in that: The angle of the weld bevel is 37°.

4. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 1, characterized in that: After the base material is prepared, pre-welding cleaning is carried out using an ultrasonic cleaner in H-01 degreasing cleaning agent solution to remove grease, dirt and other impurities from the surface of the base material.

5. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 1, characterized in that: During assembly and positioning, the weld seam should be ≤0.5mm, and the weld seam should be argon arc spot welded.

6. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 1, characterized in that: The current for the first layer of welding is 20 A higher than that for the second layer of welding, and the diameter of the welding wire for the second layer of welding is 0.4 mm larger than that for the first layer of welding.

7. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 6, characterized in that: First layer welding: ER316L welding wire, diameter 1.6 mm, welding current 130 A; Second layer welding: ER316L welding wire, diameter 2.0 mm, welding current 110 A.

8. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 7, characterized in that: After the first layer is welded and before the second layer is welded, maintain a shielding gas flow rate of 15-25 L / min.

9. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to any one of claims 1-8, characterized in that: The X-ray diffraction method is performed in accordance with the GB / T 7704-2017 standard. The test points are evenly distributed along the weld circumferentially at 4 points and along the axial direction at 1 point, which includes at least 5 test points.

10. The welding method for reducing residual stress in welds of thick-walled austenitic stainless steel structural components according to claim 2, characterized in that: The chemical composition of 316L stainless steel is: C ≤0.03%, Si≤1.00%, Mn≤2.00%, Cr16.00-18.00%, Ni ≤10.00-14.00%, Mo2.00-3.00%, P ≤0.045%, S ≤0.03%.

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