A welding control method for hard stainless steel

Abstract

This invention discloses a welding control method for hard stainless steel, comprising the following steps: S1, selecting a powder welding material with a specific composition; wherein the composition of the powder welding material, by weight percentage, includes: C: 0.13%~0.18%, Si≤0.8%, Mn≤1.2%, Cr: 15.5%~17.5%, Ni: 2.5%~3.5%, P≤0.03%, S≤0.01%, with the balance being iron and unavoidable impurities; S2, performing laser powder feeding welding on the base material using a laser powder feeding cladding device; S3, subjecting the weld to ultrasonic impact treatment to obtain a hard stainless steel welded product. This invention ensures the structural strength of the welded joint to meet the application requirements of hard stainless steel in the aerospace field.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel welding technology, and specifically relates to a welding control method for hard stainless steel. Background Technology

[0002] Hardened stainless steel refers to a type of high-strength stainless steel that, based on solution-treated austenitic stainless steel, undergoes controlled cold rolling and other plastic deformation processes to enhance its strength and hardness through work hardening, resulting in yield strength and tensile strength far exceeding those of the solution-treated state. Due to its superior high-temperature performance, hardened stainless steel has now replaced aluminum alloys as a material for spacecraft, especially reusable heavy-lift rockets.

[0003] However, the strength of currently hardened stainless steel welded joints typically does not reach 80% of the standard value of the base material, failing to fully realize its high strength potential. This is mainly due to two reasons: firstly, the weld metal forms a cast structure after welding remelting, losing its original hardening effect; secondly, the heat-affected zone undergoes annealing and softening under the action of welding thermal cycling, and its strength is also lower than that of the hardened base material.

[0004] Therefore, the development of specialized welding materials and methods that enable hardened stainless steel welded joints to achieve a strength of over 90% of the base material standard has become a critical technological bottleneck that urgently needs to be overcome in the aerospace field. Summary of the Invention

[0005] In order to solve all or some of the above problems, the purpose of this invention is to provide a welding control method for hard stainless steel, which can ensure the structural strength of the welded joint to meet the requirements of hard stainless steel in the aerospace field.

[0006] This invention provides a welding control method for hard stainless steel, comprising the following steps: S1, Select powder welding material with specific composition; The components of the powder welding material, by weight percentage, include: C: 0.13%~0.18%, Si≤0.8%, Mn≤1.2%, Cr: 15.5%~17.5%, Ni: 2.5%~3.5%, P≤0.03%, S≤0.01%, balance is iron and unavoidable impurities; S2, laser powder feeding cladding equipment is used to laser powder feeding welding of the base material; S3 involves ultrasonic impact treatment of the weld seam to obtain a hardened stainless steel welded product.

[0007] Optionally, in S2, the proportion of welding material in the weld is controlled to be ≥90%.

[0008] Optionally, in S2, the weld bevel is controlled to be a V-shape of 80°-100°.

[0009] Optionally, in S2, a ceramic backing is installed on the back side of the bevel to be welded during welding.

[0010] Optionally, in S2, the size of the laser spot is controlled to completely cover the upper edge of the weld bevel.

[0011] Optionally, in S2, the laser power is controlled to be 1~4kW, the spot diameter to be 1~6mm, the scanning speed to be 3~20mm / s, and the powder feeding rate to be 5~90g / min. Pure Ar is used as the shielding gas for welding, and the gas flow rate is 20L / min.

[0012] Optionally, in S3, ultrasonic impact treatment is performed on the entire weld area and an area of ​​not less than 2 mm on both sides of the fusion line.

[0013] Optionally, in S3, an impact needle with a diameter of 3-5 mm is used, and the ultrasonic impact amplitude is controlled at 30-50 μm. The impact is repeated along the longitudinal direction of the weld, and the ultrasonic impact coverage is not less than 100%.

[0014] As can be seen from the above technical solution, the welding control method for hard stainless steel provided by the present invention has the following advantages: This welding control method can effectively solve the problem of insufficient joint strength caused by softening of the weld and heat-affected zone after welding hardened austenitic stainless steel. The tensile strength of the welded joint is ≥1035MPa, which significantly improves the strength of the welded joint and thus enhances the reliability of aerospace structures.

[0015] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0016] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0017] Figure 1 This is a flowchart of an embodiment of the present invention; Figure 2 This is a schematic diagram of the welding bevel in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be arbitrarily combined with each other.

[0019] like Figure 1 , Figure 2The illustration shows an embodiment of the present invention, which discloses a welding control method for hard stainless steel, comprising the following steps: S1, Select powder welding material with specific composition; S2, laser powder feeding cladding equipment is used to laser powder feeding welding of the base material; S3, ultrasonic impact treatment is performed on the weld to obtain hardened stainless steel welded products; In S1, the composition of the powder welding material, by weight percentage, includes: C: 0.13%~0.18%, Si≤0.8%, Mn≤1.2%, Cr: 15.5%~17.5%, Ni: 2.5%~3.5%, P≤0.03%, S≤0.01%, balance is iron and unavoidable impurities.

[0020] In this embodiment, the preferred composition of the welding material is: C: 0.15%~0.18%, Si≤0.5%, Mn≤0.8%, Cr: 15.8%~16.8%, Ni: 2.7%~3.3%, P≤0.03%, S≤0.01%.

[0021] By controlling the composition of the welding material and ensuring that the proportion of welding material in the weld is ≥90%, a martensitic + austenitic dual-phase structure of the weld can be obtained, thereby improving the strength of the weld.

[0022] In step S2, a laser powder feeding cladding device is used to perform laser powder feeding welding on the base material. To reduce the adverse effects of base material dilution on the weld composition, the weld bevel is controlled to be an 80°-100° V-shape, without gaps or blunt edges. In this embodiment, the weld bevel angle is preferably 85°-95°. Simultaneously, a ceramic backing is installed on the back side of the bevel to be welded during welding; that is, the bevel is placed on the ceramic backing to assist in the formation of the back side of the weld. Furthermore, the laser spot size is controlled to completely cover the upper edge of the weld bevel.

[0023] In S2, the process parameters for controlling the laser powder feeding and cladding equipment are as follows: The laser power is 1~4kW, the spot diameter is 1~6mm, the scanning speed is 3~20mm / s, and the powder feeding rate is 5~90g / min. Meanwhile, the welding uses pure Ar as the shielding gas and the gas flow rate is 20L / min.

[0024] In S3, ultrasonic impact treatment is performed on the entire weld area and at least 2 mm on both sides of the fusion line. At the same time, an impact needle with a diameter of 3-5 mm is used, and the ultrasonic impact amplitude is controlled at 30-50 μm. The impact is repeated along the longitudinal direction of the weld, and the ultrasonic impact coverage is not less than 100%. Finally, a continuous, uniform, and bright groove is formed at the fusion line. At the same time, over-treatment should be avoided to avoid damaging the material surface.

[0025] The welding control method for hardened stainless steel in this embodiment is applicable to the welding of 1-3mm thick hardened austenitic stainless steel. At the same time, the welded joint obtained by this method has a tensile strength ≥1035MPa, which fully meets the requirements of aerospace.

[0026] To illustrate this application more clearly, the following are specific embodiments: Example 1 Welding is performed on 2mm thick hardened stainless steel 301-1 / 2H.

[0027] S1, the chemical composition of the base material and welding material powder (particle size 45~150μm) is shown in Table 1.

[0028] Table 1. Chemical composition (wt%) of base metal and welding material

[0029] S2, control the weld bevel to a 90° V-shape, with no gaps or blunt edges, and add a ceramic backing on the back. Simultaneously, control the welding parameters as follows: The laser power is 3.6kW, the spot diameter is 4.4mm, the scanning speed is 10mm / s, the powder feeding rate is 36g / min, and the protective gas is pure Ar with a gas flow rate of 20L / min.

[0030] S3, ultrasonic impact treatment is performed on a 2mm range on both sides of the weld and fusion line, with an impact needle diameter of 3mm, an output amplitude of 40μm, and a treatment coverage of ≥100%.

[0031] Results: No visible defects such as pores or cracks were found on the surface of the welded joint. The tensile test fracture occurred in the heat-affected zone, and the tensile strength was 1077 MPa.

[0032] Example 2 Welding is performed on 1.5mm thick hardened stainless steel 304-1 / 2H.

[0033] The chemical composition of S1 base material and welding powder (particle size 45~150μm) is shown in Table 2.

[0034] Table 2 Chemical composition (wt%) of base metal and welding material

[0035] S2, control the weld bevel to a 90° V-shape, with no gaps or blunt edges, and add a ceramic backing on the back. Simultaneously, control the welding parameters as follows: The laser power is 2.8kW, the spot diameter is 3.2mm, the scanning speed is 8mm / s, the powder feeding rate is 15g / min, and the protective gas is pure Ar with a gas flow rate of 20L / min.

[0036] S3, ultrasonic impact treatment is performed on a 2mm range on both sides of the weld and fusion line, with an impact needle diameter of 3mm, an output amplitude of 35μm, and a treatment coverage of ≥100%.

[0037] Results: No visible defects such as pores or cracks were found on the surface of the welded joint. The tensile test fracture occurred in the heat-affected zone, and the tensile strength was 1052 MPa.

[0038] As described above, this welding control method provides a dedicated welding powder and employs a laser powder feeding cladding equipment to implement a laser powder feeding welding process, specifically designed to solve the welding strength problem of hardened stainless steel for aerospace applications. Through a combined approach of "composition design + process control + post-treatment strengthening," the tensile strength of the weld joint in 1-3mm thick plates consistently reaches over 1035MPa, with excellent weld quality. Furthermore, ultrasonic impact treatment, while strengthening the weld, also helps adjust the distribution of residual welding stress and strengthens the surface of the weld joint.

[0039] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should have the ordinary meaning as understood by one of ordinary skill in the art.

[0040] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A welding control method for hard-state stainless steel, characterized in that, Includes the following steps: S1, Select powder welding material with specific composition; The components of the powder welding material, by weight percentage, include: C: 0.13%~0.18%, Si≤0.8%, Mn≤1.2%, Cr: 15.5%~17.5%, Ni: 2.5%~3.5%, P≤0.03%, S≤0.01%, balance is iron and unavoidable impurities; S2, laser powder feeding cladding equipment is used to laser powder feeding welding of the base material; S3 involves ultrasonic impact treatment of the weld seam to obtain a hardened stainless steel welded product.

2. The welding control method for hard stainless steel according to claim 1, characterized in that, In S2, the proportion of welding material in the weld is controlled to be ≥90%.

3. The welding control method for hard stainless steel according to claim 1, characterized in that, In S2, the weld bevel is controlled to be a V-shape of 80°-100°.

4. The welding control method for hard stainless steel according to claim 1, characterized in that, In S2, a ceramic backing is installed on the back side of the bevel to be welded during welding.

5. The welding control method for hard stainless steel according to claim 1, characterized in that, In S2, the size of the laser spot is controlled to completely cover the upper edge of the weld bevel.

6. The welding control method for hard stainless steel according to claim 1, characterized in that, In S2, the laser power is controlled at 1~4kW, the spot diameter at 1~6mm, the scanning speed at 3~20mm / s, and the powder feeding rate at 5~90g / min. Pure Ar is used as the shielding gas for welding, and the gas flow rate is 20L / min.

7. The welding control method for hard stainless steel according to claim 1, characterized in that, In S3, ultrasonic impact treatment is performed on the entire weld seam and on both sides of the fusion line, with a minimum area of ​​2 mm.

8. The welding control method for hard stainless steel according to claim 1, characterized in that, In S3, an impact needle with a diameter of 3~5mm is used, and the ultrasonic impact amplitude is controlled at 30~50μm. The impact is repeated along the longitudinal direction of the weld, and the ultrasonic impact coverage is not less than 100%.

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