Welding wire and welding method for reducing the breakage rate of normalized welds in high-silicon non-oriented silicon steel

Abstract

This invention discloses a welding wire and welding method for reducing the breakage rate of normalized welds in high-silicon non-oriented silicon steel. The welding wire comprises the following chemical composition by mass percentage: C: 0.15%–0.20%, Si: ≤0.35%, Mn: 2.0–2.5%, Ni: 2.0–2.5%, Cr: 0.8–1.0%, with the remainder being Fe. The welding method includes laser welding of non-oriented silicon steel using the above welding wire as filler material. This invention, through optimization of the welding wire composition and welding process, controls the weld microstructure, forming a bainitic structure, enhancing ductility and toughness, achieving a 100% cupping test pass rate, and a normalized weld breakage rate ≤0.05%.

Description

Technical Field

[0001] This invention relates to the field of all-process non-oriented silicon steel production technology, specifically to a welding wire and welding method for reducing the breakage rate of normalized welds in high-silicon non-oriented silicon steel. Background Technology

[0002] In recent years, non-oriented silicon steel has been developing towards higher grades. The normalizing process, a crucial step in non-oriented silicon steel production, requires welding of the preceding and following strips to achieve continuous production; therefore, the quality of the weld directly determines whether production can proceed smoothly.

[0003] Excessive Si content can lead to the following issues affecting welding quality during the welding process: 1) It easily reacts with oxygen to form pores. The higher the Si content, the greater the probability of pore formation, thus affecting the weld quality; 2) Excessive Si content can cause coarse dendritic grains to form at the weld, resulting in decreased mechanical properties and reduced ductility and toughness; 3) Excessive Si content can increase the sensitivity to hot and cold during welding, making it easier for cracks to form after welding, etc.

[0004] During the normalization production of high-grade non-oriented silicon steel, the high Si content results in a significant difference between the microstructure at the weld and the base material. Furthermore, the coarse dendritic grains exhibit poor mechanical properties, frequently leading to weld breakage in actual production. This disrupts the production rhythm and significantly impacts output.

[0005] Chinese patent document CN201110142365.4 discloses a "Method for Welding Non-oriented Silicon Steel with Filler Wire". This document uses low-silicon material as the lead wire and optimizes the welding process to reduce strip breakage during rolling. However, this method is only applicable to non-oriented silicon steel with a silicon content of 1.0% to 3.5%, and is not applicable to high-grade non-oriented silicon steel. Furthermore, the strip breakage situation differs between normalizing mills, and this document does not address weld microstructure control.

[0006] Chinese patent document CN201710501693.X discloses a method for welding low-grade non-oriented silicon steel using a laser welding machine. This document applies to low-grade non-oriented silicon steel, which has a low silicon content and undergoes austenitization at high temperatures. The resulting weld microstructure after cooling has small grains, and its strength is not significantly different from the base metal. However, when using this method alone with high-grade non-oriented silicon steel, the weld microstructure does not undergo phase transformation, resulting in coarse ferrite and low weld strength. Summary of the Invention

[0007] To overcome the shortcomings of the above-mentioned technologies, the present invention provides a welding wire and welding method for reducing the breakage rate of normalized welds in high-silicon non-oriented silicon steel, improving weld strength and toughness, ensuring weld quality, and thus ensuring the production efficiency of high-silicon non-oriented silicon steel.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A welding wire for reducing the breakage rate of normalized welds in high-silicon non-oriented silicon steel comprises the following chemical composition by mass percentage: C: 0.15%–0.20%, Si: ≤0.35%, Mn: 2.0–2.5%, Ni: 2.0–2.5%, Cr: 0.8–1.0%, with the remainder being Fe.

[0010] A welding method for reducing the breakage rate of normalized weld seams in high-silicon non-oriented silicon steel includes: using the aforementioned welding wire as filler material to perform laser welding on the non-oriented silicon steel.

[0011] Preferably, the mass percentage of Si in the non-oriented silicon steel is ≥3.3%.

[0012] Preferably, the welding gap of the laser welding is 0.45mm to 0.05mm.

[0013] Preferably, the laser welding speed is 2.2 to 2.7 m / min and the wire feeding rate is 3 to 3.5 m / min.

[0014] Preferably, when performing the laser welding, the laser power is 3.0 to 3.5 kW, the preheating power is 8 to 14 kW, and the postheating power is 12 to 18 kW.

[0015] Preferably, the non-oriented silicon steel produced by the welding method has a normalized weld breakage rate of <0.1%.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] For non-oriented silicon steel with a silicon content of 3.3% or higher, the high Si content at the weld joint during normalized welding leads to the formation of coarse dendritic ferrite, resulting in poor strength, ductility, and toughness. The microstructure differs significantly from the base metal, leading to an extremely high breakage rate at the weld joint during production, which disrupts production schedules. Therefore, improving the weld quality of high-Si non-oriented silicon steel is a pressing issue.

[0018] This invention optimizes the welding wire composition and welding process to control the weld microstructure, forming a bainitic structure, enhancing plasticity and toughness, achieving a 100% pass rate in cupping tests, and a normalized weld breakage rate of ≤0.05%.

[0019] (1) Optimization of weld zone composition: Taking into account the characteristics of high-Si non-oriented silicon steel, and considering the use of low-Si welding wire materials containing elements such as Cr, Mn, and Ni, the composition and microstructure of the weld are optimized and controlled. Cr and Mn are austenite stabilizing elements, which can lower the Bs point and promote the formation of bainite microstructure during the weld solidification process. Ni can refine the grains and improve the weld strength;

[0020] (2) Welding process optimization reduces the width of the heat-affected zone while controlling the weld quality to ensure weld penetration and formation stability. Attached Figure Description

[0021] Figure 1 This is a weld microstructure diagram of Example 2;

[0022] Figure 2 This is a weld microstructure diagram of Comparative Example 2. Detailed Implementation

[0023] To better explain the present invention, the main contents of the present invention are further illustrated below with reference to specific embodiments and accompanying drawings, but the contents of the present invention are not limited to the following embodiments.

[0024] Example 1

[0025] A welding wire that reduces the weld breakage rate during the normalization process of high-silicon non-oriented silicon steel comprises the following chemical composition by mass percentage: C: 0.18%, Si: 0.25%, Mn: 2.3%, Ni: 2.4%, Cr: 0.88%, with the remainder being Fe.

[0026] A welding method for reducing the breakage rate of normalized welds in high-silicon non-oriented silicon steel involves laser welding of the high-silicon non-oriented silicon steel using welding wire with the aforementioned composition. The mass percentage of Si in the non-oriented silicon steel is 3.40%.

[0027] Welding process:

[0028] 1. To ensure weld quality and avoid burn-through and incomplete penetration, the weld gap should be 0.05mm.

[0029] 2. The welding speed is controlled at 2.6 m / min. Taking into account the material properties of the welding wire and the base material, the wire feeding speed is slightly higher than the welding speed, controlled at 3.1 m / min.

[0030] 3. The laser power for welding is controlled at 3.2KW, the preheating power is controlled at 12KW, and the postheating power is controlled at 15KW.

[0031] When producing high-silicon non-oriented silicon steel using the above-mentioned normalized welding scheme, the weld cupping test pass rate is 100%, and the normalized weld breakage rate is 0.008%.

[0032] Example 2

[0033] A welding wire that reduces the weld breakage rate during the normalization process of high-silicon non-oriented silicon steel comprises the following chemical composition by mass percentage: C: 0.20%, Si: 0.29%, Mn: 2.4%, Ni: 2.2%, Cr: 0.95%, with the remainder being Fe.

[0034] A welding method for reducing the breakage rate of normalized welds in high-silicon non-oriented silicon steel involves laser welding of the high-silicon non-oriented silicon steel using welding wire with the aforementioned composition. The mass percentage of Si in the non-oriented silicon steel is 3.40%.

[0035] Welding process:

[0036] 1. To ensure weld quality and avoid burn-through and incomplete penetration, the weld gap should be 0.05mm.

[0037] 2. The welding speed is controlled at 2.6 m / min. Taking into account the material properties of the welding wire and the base material, the wire feeding speed is slightly higher than the welding speed, controlled at 3.1 m / min.

[0038] 3. The laser power for welding is controlled at 3.2KW, the preheating power is controlled at 12KW, and the postheating power is controlled at 15KW.

[0039] When producing high-silicon non-oriented silicon steel using the above-mentioned normalized welding scheme, the weld cupping test pass rate is 100%, and the normalized weld breakage rate is 0.01%.

[0040] Comparative Example 1

[0041] High-silicon non-oriented silicon steel is laser-welded without filler material. The mass percentage of Si in the non-oriented silicon steel is 3.4%.

[0042] Welding process:

[0043] 1. To ensure weld quality and avoid burn-through and incomplete penetration, the weld gap should be 0.05mm.

[0044] 2. The welding speed should be controlled at 2.3 m / min;

[0045] 3. The laser power for the above welding is controlled at 3.2KW, the preheating power is controlled at 12KW, and the post-heating power is controlled at 15KW.

[0046] When producing high-silicon non-oriented silicon steel using the above-mentioned normalized welding scheme, the weld cupping test pass rate is 0% and the normalized weld breakage rate is 0.3%.

[0047] Comparative Example 2

[0048] Laser welding was used for high-silicon non-oriented silicon steel. The mass percentage of Si in the non-oriented silicon steel was 3.40%.

[0049] Welding process:

[0050] 1. Chemical composition of the welding wire used: C: 0.20%, Si: 0.8%, Mn: 1.45%, Ni: 0.05%, Cr: 0.01%, the remainder being Fe.

[0051] 2. To ensure weld quality and avoid burn-through and incomplete penetration, the weld gap should be 0.05mm.

[0052] 3. Laser weld the welding wire with the above chemical composition to high-silicon non-oriented silicon steel;

[0053] 4. The welding speed should be controlled at 2.3 m / min, and the wire feeding speed should be slightly higher than the welding speed, controlled at 3.1 m / min.

[0054] 5. The laser power for welding is controlled at 3.2KW, the preheating power at 12KW, and the post-heating power at 15KW.

[0055] When producing high-silicon non-oriented silicon steel using the above-mentioned normalized welding scheme, the weld cupping test pass rate is 28%, and the normalized weld breakage rate is 0.3%.

[0056] Comparative Example 3

[0057] Laser welding was used for high-silicon non-oriented silicon steel. The mass percentage of Si in the non-oriented silicon steel was 3.40%.

[0058] Welding process:

[0059] 1. Chemical composition of the welding wire used: C: 0.20%, Si: 0.8%, Mn: 1.45%, Ni: 0.05%, Cr: 0.01%, the remainder being Fe.

[0060] 2. To ensure weld quality and avoid burn-through and incomplete penetration, the weld gap should be 0.1mm.

[0061] 3. Laser weld the welding wire with the above chemical composition to high-silicon non-oriented silicon steel;

[0062] 4. The welding speed should be controlled at 2.3 m / min, and the wire feeding speed should be slightly higher than the welding speed, controlled at 3.1 m / min.

[0063] 5. The laser power for welding is controlled at 3.2KW, the preheating power at 12KW, and the post-heating power at 22KW.

[0064] When producing high-silicon non-oriented silicon steel using the above-mentioned normalized welding scheme, the weld cupping test pass rate is 16%, and the normalized weld breakage rate is 0.35%.

[0065] Comparative Example 4

[0066] Laser welding was used for high-silicon non-oriented silicon steel. The mass percentage of Si in the non-oriented silicon steel was 3.40%.

[0067] Welding process:

[0068] 1. Chemical composition of the welding wire used: C: 0.20%, Si: 0.29%, Mn: 2.4%, Ni: 2.2%, Cr: 0.95%, the remainder being Fe.

[0069] 2. To ensure weld quality and avoid burn-through and incomplete penetration, the weld gap should be 0.05mm.

[0070] 3. Laser weld the welding wire with the above chemical composition to high-silicon non-oriented silicon steel;

[0071] 4. The welding speed is controlled at 2.6 m / min, taking into account the material properties of the welding wire and the base material, and the wire feeding speed is controlled at 4.0 m / min.

[0072] 5. The laser power for the above welding is controlled at 3.2KW, the preheating power is controlled at 8KW, and the postheating power is controlled at 22KW.

[0073] When producing high-silicon non-oriented silicon steel using the above-mentioned normalized welding scheme, the weld cupping test pass rate is 95%, and the normalized weld breakage rate is 0.05%.

[0074] The welding wire composition, welding process, and product performance of Examples 1, 2, and Comparative Examples 1-4 are shown in Tables 1-3.

[0075] As shown in Table 3 and Figures 1-2 As shown, the weld obtained by the welding method in Example 2 has a bainitic microstructure, exhibiting high strength and good ductility and toughness. In contrast, the weld obtained by the welding method in Comparative Example 2 has a coarse dendritic ferrite microstructure, exhibiting low strength and poor ductility and toughness.

[0076] As can be seen from Examples 1-2 and Comparative Examples 1-4, the present invention optimizes the welding wire composition and welding process to control the weld microstructure, form a bainitic structure, enhance plasticity and toughness, achieves a 100% pass rate in cupping tests, and has a normalized weld breakage rate of ≤0.05%.

[0077] Table 1: Welding wire composition

[0078]

[0079] Table 2: Welding Process

[0080]

[0081] Table 3: Weld Inspection Results

[0082]

Claims

1. A welding wire for reducing the breakage rate of normalized weld seams in high-silicon non-oriented silicon steel, characterized in that: It includes the following chemical composition by mass percentage: C: 0.15%–0.20%, Si: ≤0.35%, Mn: 2.0–2.5%, Ni: 2.0–2.5%, Cr: 0.8–1.0%, with the remainder being Fe.

2. A welding method for reducing the breakage rate of normalized weld seams in high-silicon non-oriented silicon steel, characterized in that: Includes the following steps: Laser welding of non-oriented silicon steel is performed using the welding wire described in claim 1 as filler material.

3. The welding method according to claim 2, characterized in that: The mass percentage of Si in the non-oriented silicon steel is ≥3.3%.

4. The welding method according to claim 2, characterized in that: The welding gap for laser welding is 0.45mm to 0.05mm.

5. The welding method according to claim 2, characterized in that: The laser welding speed is 2.2–2.7 m / min, and the wire feed rate is 3–3.5 m / min.

6. The welding method according to claim 2, characterized in that: When performing the laser welding, the laser power is 3.0 to 3.5 kW, the preheating power is 8 to 14 kW, and the postheating power is 12 to 18 kW.

7. The welding method according to any one of claims 2 to 6, characterized in that: The non-oriented silicon steel produced by the aforementioned welding method has a normalized weld breakage rate of <0.1%.

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