Welding wire for 420 MPa grade wheel steel and laser-electric arc hybrid welding process

Abstract

The invention discloses a welding wire for 420 MPa grade wheel steel and a laser-arc hybrid welding process. The welding wire comprises the following chemical components in percentage by weight: 0.04%-0.06% of C, 0.40%-0.70% of Si, 1.30%-1.70% of Mn, 0.70%-0.90% of Ni, 0.20%-0.50% of Cu, 0.03%-0.08% of Ti, less than or equal to 0.010% of S, less than or equal to 0.010% of P and the balance of Fe and inevitable impurities. According to the 420 MPa grade vehicle steel laser-electric arc hybrid welding matched welding material and the welding technology, an obtained welding joint has good mechanical performance, the strength coefficient of the welding joint is 1.0, the impact absorption energy at the temperature of-20 DEG C is larger than or equal to 120 J, and the fatigue limit sigma 0.1b is larger than or equal to 400 MPa.

Description

Technical Field

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

[0002] With the development of automobile manufacturing technology, 420CL wheel steel (yield strength 420MPa) has been widely used in the automotive field. In the application process, the main welding method for 420CL wheel steel is flash butt welding. Since the use conditions have high requirements on the fatigue performance of automobile wheel steel welded joints, coarse Widmanstätten structure is prone to appear in the flash butt welding interface area, which has insufficient plasticity and poor fatigue performance. However, the use of laser-arc hybrid welding lacks the necessary supporting welding materials and their application guidance, and there are problems such as low welding efficiency and poor welding quality. Therefore, it is urgent to carry out the research and development of 420CL wheel steel welding wire and its high-efficiency and high-quality welding technology.

[0003] As an efficient and high-quality welding method, laser-arc hybrid welding has the characteristics of fast welding speed, deep penetration, high precision and good adaptability. Laser-arc hybrid welding has the advantages of fast laser welding speed, small heat-affected zone, narrow weld and good weld appearance, and combines the advantages of gas metal arc welding in energy efficiency, gap bridging ability, cooling speed and energy coupling power. The increase in welding speed and the reduction in heat input greatly reduce welding deformation.

[0004] In summary, the use of laser-arc hybrid welding for 420MPa wheel steel can effectively reduce welding deformation, improve the welding quality and efficiency of vehicle thin plate structures, 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 supporting welding materials for laser-arc hybrid welding of 420MPa 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] In order to solve the above technical problems, the chemical components adopted in the present invention 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 unavoidable impurities.

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

[0008] The design mechanism of each component of the present invention is: C is the main strengthening element in the weld, and increasing the C content can significantly increase the strength. However, too high a C content will reduce toughness, and too low a C content cannot guarantee weld strength, so the C content is controlled at 0.04-0.06%.

[0009] Si is dissolved in ferrite structure and has solid solution strengthening effect, which is a strengthening alloy element. The increase of Si content promotes the formation of MA components in the weld, which reduces the weldability and low temperature impact toughness of the material. Therefore, the Si content is controlled at 0.40-0.70% as much as possible.

[0010] Mn is the main alloying element in steel. Appropriate Mn can promote and refine acicular ferrite to improve strength; in addition, Mn can also promote weld deoxidation. However, excessive Mn content will cause Mn segregation and produce large blocky MA components, resulting in coarse grains and reduced toughness. Therefore, the Mn content is controlled at 1.30-1.70%.

[0011] Ni is an important alloying element in welds. Adding appropriate Ni on the basis of low C can not only improve strength but also have less damage to toughness. Ni can also reduce the resistance to dislocation movement in the lattice and reduce the interaction energy between dislocations and interstitial elements, thereby promoting stress relaxation, reducing the brittle transition temperature, and significantly improving the low-temperature toughness of the material. At the same time, considering the control cost and low-temperature toughness requirements, the Ni content is generally controlled at 0.70-0.90%.

[0012] Appropriate Cu element can improve the corrosion resistance of steel and the conductivity of welding wire, but a large Cu content will increase the tendency to crack, so the Cu content must be strictly controlled, and the Cu content should be controlled at 0.20-0.50%.

[0013] Ti can form fine dispersed composite oxides during welding, which can provide nucleation sites for acicular ferrite, thereby promoting the formation of acicular ferrite. In addition, these oxides can also appear at the austenite grain boundaries, thereby effectively inhibiting the coarsening of grains, improving the weldability of the material, and improving the low-temperature impact toughness. Therefore, the Ti content can be controlled at 0.03-0.08%.

[0014] S easily forms compounds such as FeS and MnS in the weld and segregates at the grain boundaries. Since the sulfide eutectic temperature is low and distributed in a network, it will reduce the impact toughness of the material. During the welding process, S easily promotes the formation of hot cracks and reduces weldability, so the S content in the weld must be strictly controlled to 0.010% or less.

[0015] Phosphide can be generated in steel and can be completely dissolved in ferrite, which has a significant impact on the weld and easily causes cold brittleness. Due to the low melting point of phosphide, segregation will form at the grain boundary during rapid cooling, resulting in hot cracks. Although the increase in P content can improve the strength and hardness of the weld, it will also cause a sharp drop in the plasticity and toughness of the material. Therefore, the P content is controlled at 0.010% or less.

[0016] The process of the present invention adopts 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 feeding speed 5-10m / min, welding voltage 20-28V, and welding current 160-280A.

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

[0018] The beneficial effects of the above technical solution are as follows: the present invention provides a 420MPa grade lathe steel laser-arc hybrid welding supporting welding material and welding process, the obtained welded joint has good mechanical properties, the welded joint strength coefficient is 1.0, the -20℃ impact absorption energy is ≥120J, and the fatigue limit σ 0.1b ≥400MPa. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Figure 1 This is a microstructure diagram of the laser-arc hybrid welding weld zone obtained in Example 1 of the present invention. DETAILED DESCRIPTION

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

[0022] For 6 mm thick 420 MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition weight percentage of the welding wire is: C 0.044%, Si 0.47%, Mn 1.40%, Ni 0.82%, Cu 0.25%, Ti 0.047%, S0.005%, P 0.005%, and the balance is Fe and unavoidable impurities.

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

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

[0025] Example 2: The welding wire for 420MPa grade wheel steel and the laser-arc hybrid welding process are described as follows.

[0026] For 8 mm thick 420 MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition weight percentage of the welding wire is: C 0.050%, Si 0.51%, Mn 1.30%, Ni 0.90%, Cu 0.26%, Ti 0.035%, S0.003%, P 0.008%, and the balance is Fe and unavoidable impurities.

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

[0028] The obtained welded joint has good mechanical properties. The tensile specimen breaks at the base material. The welded joint strength coefficient is 1.0, the impact absorption energy at -20℃ is 139J, and the fatigue limit σ 0.1b It is 415MPa.

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

[0030] Except that the protective gas used is a mixed gas of Ar+3%O2 by volume, the rest is the same as in Example 1. The obtained welded joint has good mechanical properties, the tensile specimen breaks at the base material, the welded joint strength coefficient is 1.0, the -20℃ impact absorption energy is 144J, and the fatigue limit σ 0.1b It is 443MPa.

[0031] Example 4: The welding wire for 420MPa grade wheel steel and the laser-arc hybrid welding process are described as follows.

[0032] For 4 mm thick 420 MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition weight percentage of the welding wire is: C 0.052%, Si 0.61%, Mn 1.62%, Ni 0.73%, Cu 0.26%, Ti 0.046%, S0.006%, P 0.007%, and the balance is Fe and unavoidable impurities.

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

[0034] The obtained welded joint has good mechanical properties. The tensile specimen breaks at the base material. The welded joint strength coefficient is 1.0, the impact absorption energy at -20℃ is 123J, and the fatigue limit σ 0.1b It is 435MPa.

[0035] Example 5: The welding wire for 420MPa grade wheel steel and the laser-arc hybrid welding process are described as follows.

[0036] For 6 mm thick 420 MPa grade wheel steel, the following welding wire is used for laser-arc hybrid welding. The chemical composition weight percentage of the welding wire is: C 0.049%, Si 0.41%, Mn 1.35%, Ni 0.83%, Cu 0.30%, Ti 0.053%, S0.008%, P 0.004%, and the balance is Fe and unavoidable impurities.

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

[0038] The obtained welded joint has good mechanical properties. The tensile specimen breaks at the base material. The welded joint strength coefficient is 1.0, the impact absorption energy at -20℃ is 127J, and the fatigue limit σ 0.1b It is 405MPa.

[0039] Example 6: The welding wire for 420MPa grade wheel steel and the laser-arc hybrid welding process are described as follows.

[0040] Except that the protective gas used is a mixed gas of Ar+12%CO2 by volume, the rest is the same as in Example 5. The obtained welded joint has good mechanical properties, the tensile specimen breaks at the base material, the welded joint strength coefficient is 1.0, the -20℃ impact absorption energy is 127J, and the fatigue limit σ 0.1b It is 407MPa.

Claims

1. A 420MPa grade wheel steel welding wire, characterized in that: Its chemical composition 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%, Ti0.03%~0.08%, S≤0.010%, P≤0.010%, and the balance is Fe and unavoidable impurities.

2. The 420MPa grade wheel steel welding wire according to claim 1, characterized in that: The welding wire is suitable for 3-8 mm thick 420 MPa grade wheel steel.

3. A 420MPa grade wheel steel laser-arc hybrid welding process, using the welding wire according to claim 1, characterized in that: The welding process parameters are: laser power 4.5~6.0kW, wire spacing 3~5mm, welding speed 1.0~2.0m / min, wire feeding speed 5~10m / min, welding voltage 20~28V, welding current 160~280A.

4. The 420MPa grade wheel steel laser-arc hybrid welding process according to claim 3 is characterized in that: The protective gas used is a mixed gas of Ar+2%~5%O2 or Ar+5%~20%CO2.

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