420mpa grade wheel steel welding wire and laser-arc hybrid welding process

Abstract

The application discloses a 420MPa grade wheel steel welding wire and a laser-arc hybrid welding process, and the chemical components of the welding wire are as follows: C 0.04-0.06%, Si 0.40-0.70%, Mn 1.30-1.70%, Ni 0.70-0.90%, Cu 0.20-0.50%, Ti 0.03-0.08%, S≤0.010%, P≤0.010%, and the balance is Fe and inevitable impurities.The application provides a 420MPa grade wheel steel laser-arc hybrid welding matching welding material and welding process, and the welding joint obtained has good mechanical properties, the welding joint strength coefficient is 1.0, the impact absorption energy at-20 DEG C is greater than or equal to 120J, the fatigue limit σ 0.1b is greater than or equal to 400MPa.

Description

Technical Field

[0001] This invention relates to material welding technology, and in particular to a welding wire for 420MPa grade wheel steel and a laser-arc composite welding process. Background Technology

[0002] With the development of automobile manufacturing technology, 420CL wheel steel (yield strength 420MPa) is widely used in the automotive industry. In this application, flash butt welding is the primary welding method for 420CL wheel steel. However, due to the high fatigue performance requirements of welded joints in automotive wheel steel under certain operating conditions, flash butt welding often results in coarse Widmanstätten structures at the interface, insufficient plasticity, and poor fatigue performance. Furthermore, laser-arc hybrid welding lacks necessary supporting welding materials and application guidance, and suffers from low welding efficiency and poor weld quality. Therefore, there is an urgent need to develop welding wire for 420CL wheel steel and research its efficient and high-quality welding technology.

[0003] As a highly efficient and high-quality welding method, laser-arc hybrid welding features fast welding speed, deep penetration, high precision, and good adaptability. It combines the advantages of laser welding (fast speed, small heat-affected zone, narrow weld, and good weld appearance) with the advantages of gas metal arc welding (GMAW) in terms of energy efficiency, gap bridging capability, cooling rate, and energy coupling power. The increased welding speed and reduced heat input significantly reduce welding deformation.

[0004] In summary, laser-arc hybrid welding of 420MPa grade wheel steel can effectively reduce welding deformation, improve the welding quality and efficiency of thin-plate structures in vehicles, meet the needs of industry applications, and enhance my country's core automotive manufacturing capabilities. However, given the characteristics of laser-arc hybrid welding, there is currently a lack of suitable welding materials for laser-arc hybrid welding of 420MPa grade wheel steel. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a welding wire for 420MPa grade wheel steel with good welding effect; the present invention also provides a laser-arc composite welding process for 420MPa grade wheel steel.

[0006] To solve the above-mentioned technical problems, the chemical composition adopted in this invention is as follows (by weight percentage): C 0.04%–0.06%, Si 0.40%–0.70%, Mn 1.30%–1.70%, Ni 0.70%–0.90%, Cu 0.20%–0.50%, Ti 0.03%–0.08%, S≤0.010%, P≤0.010%, with the balance being Fe and unavoidable impurities.

[0007] Furthermore, the welding wire is suitable for 3-8mm thick 420MPa grade wheel steel.

[0008] The design mechanism of each component in this invention is as follows: Carbon (C) is the main strengthening element in welds, and increasing the C content can significantly improve strength. However, excessively high C content will reduce toughness, and excessively low C content cannot guarantee weld strength. Therefore, the C content is controlled between 0.04% and 0.06%.

[0009] Si is dissolved in ferrite and has a solid solution strengthening effect, belonging to the category of strengthening alloying elements. Increasing the Si content promotes the formation of MA components in the weld, reducing the weldability and low-temperature impact toughness of the material. Therefore, the Si content should be controlled within the range of 0.40–0.70% as much as possible.

[0010] Mn is a major alloying element in steel. Appropriate Mn content can promote and refine acicular ferrite to improve strength; in addition, Mn can also promote weld deoxidation. However, excessive Mn content can cause Mn segregation and the formation of large bulk MA components, resulting in coarse grains and decreased toughness. Therefore, the Mn content is controlled between 1.30% and 1.70%.

[0011] Ni is an important alloying element in welds. Adding appropriate amounts of Ni to a low-carbon base can not only improve strength but also minimize damage to toughness. Ni can also reduce the resistance to dislocation movement in the lattice and decrease the energy of interaction between dislocations and interstitial elements, thereby promoting stress relaxation, lowering the brittle transition temperature, and significantly improving the low-temperature toughness of the material. Considering both cost control and low-temperature toughness requirements, the Ni content is generally controlled between 0.70% and 0.90%.

[0012] Appropriate amounts of Cu can improve the corrosion resistance of steel and the conductivity of welding wire, but a high Cu content will increase the tendency to crack. Therefore, the Cu content must be strictly controlled, and the Cu content should be controlled between 0.20% and 0.50%.

[0013] Ti can form fine, dispersed composite oxides during welding. These oxides provide nucleation sites for acicular ferrite, thereby promoting its formation. Furthermore, these oxides can also appear at austenite grain boundaries, effectively suppressing grain coarsening, improving weldability, and enhancing low-temperature impact toughness. Therefore, the Ti content can be controlled between 0.03% and 0.08%.

[0014] Sulfide (S) readily forms compounds such as FeS and MnS in welds and tends to segregate at grain boundaries. Due to the low eutectic temperature and network distribution of sulfides, this reduces the material's impact toughness. During welding, S easily promotes hot cracking and reduces weldability; therefore, the S content in the weld must be strictly controlled, keeping it at 0.010% or below.

[0015] Phosphorus (P) can form phosphides in steel and is completely soluble in ferrite, significantly affecting welds and easily causing cold brittleness. Due to the low melting point of phosphides, segregation occurs at grain boundaries during rapid cooling, leading to hot cracking. While increasing P content can improve weld strength and hardness, it also drastically reduces the material's plasticity and toughness. Therefore, P content should be controlled at 0.010% or below.

[0016] The process of this invention uses the above-mentioned welding wire, and the welding process parameters are: laser power 4.5~6.0kW, wire spacing 3~5mm, welding speed 1.0~2.0m / min, wire feed speed 5~10m / min, welding voltage 20~28V, and welding current 160~280A.

[0017] Furthermore, the protective gas used is a mixture of Ar + 2% to 5% O2 or Ar + 5% to 20% CO2.

[0018] The beneficial effects of adopting the above technical solution are as follows: This invention provides a set of welding materials and welding process for laser-arc hybrid welding of 420MPa grade automotive steel. The resulting welded joint has good mechanical properties, with a welded joint strength coefficient of 1.0, an impact absorption energy of ≥120J at -20℃, and a fatigue limit σ 0.1b ≥400MPa. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a microstructure diagram of the weld zone obtained by laser-arc hybrid welding in Embodiment 1 of the present invention. Detailed Implementation

[0021] Example 1: The welding wire and laser-arc hybrid welding process for this 420MPa grade wheel steel are described below.

[0022] For 6mm thick 420MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition of the welding wire by weight percentage is: C 0.044%, Si 0.47%, Mn 1.40%, Ni 0.82%, Cu 0.25%, Ti 0.047%, S 0.005%, P 0.005%, with the balance being Fe and unavoidable impurities.

[0023] The welding parameters are as follows: laser power 5.5kW, wire spacing 4mm, welding speed 1.4m / min, wire feed speed 6m / min, welding voltage 22V, current 200A, and shielding gas is a mixture of Ar + 2% O2 in volume ratio, that is, the oxygen volume is 2% of the total volume of argon and oxygen.

[0024] The resulting microstructure of the laser-arc hybrid weld zone mainly consists of proeutectoid ferrite, acicular ferrite, and lath bainite, such as... Figure 1 As shown. The welded joint exhibits good mechanical properties; the tensile specimen fractures at the base material; the welded joint strength coefficient is 1.0; the impact energy absorbed at -20℃ is 145J; and the fatigue limit σ... 0.1b It is 450 MPa.

[0025] Example 2: The welding wire and laser-arc composite welding process for this 420MPa grade wheel steel are described below.

[0026] For 8mm thick 420MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition of the welding wire by weight percentage is: C 0.050%, Si 0.51%, Mn 1.30%, Ni 0.90%, Cu 0.26%, Ti 0.035%, S 0.003%, P 0.008%, with the balance being Fe and unavoidable impurities.

[0027] The welding parameters are as follows: laser power 6.0kW, wire spacing 5mm, welding speed 1.2m / min, wire feed speed 7.5m / min, welding voltage 23.3V, welding current 212A, and shielding gas is a mixture of Ar + 5% O2 by volume.

[0028] The resulting welded joint exhibits excellent mechanical properties; the tensile specimen fractures at the base material; the welded joint strength modulus is 1.0; the impact energy absorbed at -20℃ is 139 J; and the fatigue limit σ0 is [not specified]. 0.1b It is 415 MPa.

[0029] Example 3: The welding wire and laser-arc hybrid welding process for this 420MPa grade wheel steel are described below.

[0030] Except for the protective gas used, which was a mixture of Ar and 3% O2 ​​by volume ratio, the rest was the same as in Example 1. The resulting welded joint exhibited good mechanical properties; the tensile specimen fractured at the base material; the welded joint strength coefficient was 1.0; the impact absorption energy at -20℃ was 144 J; and the fatigue limit σ... 0.1b It is 443 MPa.

[0031] Example 4: The welding wire and laser-arc composite welding process for this 420MPa grade wheel steel are described below.

[0032] For 4mm thick 420MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition of the welding wire by weight percentage is: C 0.052%, Si 0.61%, Mn 1.62%, Ni 0.73%, Cu 0.26%, Ti 0.046%, S 0.006%, P 0.007%, with the balance being Fe and unavoidable impurities.

[0033] The welding parameters are as follows: laser power 4.5kW, wire spacing 3mm, welding speed 1.4m / min, wire feed speed 5m / min, welding voltage 20.4V, welding current 160A, and shielding gas is a mixture of Ar + 5% CO2 by volume.

[0034] The resulting welded joint exhibits good mechanical properties; the tensile specimen fractures at the base material; the welded joint strength coefficient is 1.0; the impact energy absorbed at -20℃ is 123 J; and the fatigue limit σ... 0.1b It is 435 MPa.

[0035] Example 5: The welding wire and laser-arc composite welding process for this 420MPa grade wheel steel are described below.

[0036] For 6mm thick 420MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition of the welding wire by weight percentage is: C 0.049%, Si 0.41%, Mn 1.35%, Ni 0.83%, Cu 0.30%, Ti 0.053%, S 0.008%, P 0.004%, with the balance being Fe and unavoidable impurities.

[0037] The welding parameters are as follows: laser power 5.5kW, wire spacing 5mm, welding speed 1.5m / min, wire feed speed 5m / min, welding voltage 20.4V, welding current 160A, and shielding gas is a mixture of Ar + 20% CO2 by volume.

[0038] The resulting welded joint exhibits good mechanical properties; the tensile specimen fractures at the base material; the welded joint strength modulus is 1.0; the impact energy absorbed at -20℃ is 127 J; and the fatigue limit σ0 is [not specified]. 0.1b It is 405 MPa.

[0039] Example 6: The welding wire and laser-arc composite welding process for this 420MPa grade wheel steel are described below.

[0040] Except for the protective gas used, which was a mixture of Ar and 12% CO2 in volume ratio, the rest was the same as in Example 5. The resulting welded joint exhibited good mechanical properties; the tensile specimen fractured at the base material; the welded joint strength coefficient was 1.0; the impact absorption energy at -20℃ was 127 J; and the fatigue limit σ... 0.1b It is 407 MPa.

Claims

1. A laser-arc hybrid welding process for 420 MPa grade wheel steels, characterized in that, The chemical composition of the welding wire is as follows: C 0.04%-0.06%, Si 0.40%-0.70%, Mn 1.30%-1.70%, Ni 0.70%-0.90%, Cu 0.20%-0.50%, Ti 0.03%-0.08%, S≤0.010%, P≤0.010%, and the balance of Fe and inevitable impurities; the welding process parameters are as follows: laser power 4.5-6.0 kW, light-wire distance 3-5 mm, welding speed 1.0-2.0 m / min, wire feeding speed 5-10 m / min, welding voltage 20-28 V, and welding current 160-280 A. The welding wire is suitable for 3-8 mm thick 420 MPa grade wheel steel.

2. The 420 MPa grade wheel steel laser-arc hybrid welding process according to claim 1, characterized in that: The protective gas is Ar+2%-5% O2 or Ar+5%-20% CO2 mixed gas.

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