A gas shielded welding process for a 420mpa grade yield strength steel for marine corrosion resistance

Abstract

The application discloses a gas shield welding process for a yield strength 420 MPa marine corrosion resistant steel, and adopts an easy-to-operate gas shield welding process to weld the yield strength 420 MPa marine corrosion resistant steel, so that the welded joint has a low-temperature impact energy KV2 of greater than or equal to 47 J at-40 DEG C, a tensile strength of greater than or equal to 540 MPa, excellent corrosion resistance, a weld atmospheric corrosion resistance index V of greater than or equal to 1.2, no obvious step in a simulated industrial atmospheric periodic immersion / drying cycle corrosion test, and good comprehensive performance of the welded joint, and is suitable for welding the yield strength 420 MPa marine corrosion resistant steel with a thickness of 16-60 mm.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel material welding, in particular to a gas shielded welding process for a yield strength 420 MPa grade marine corrosion resistant steel. BACKGROUND

[0002] The coastal region of China has a large span, complex geological conditions, and large climate differences, especially in the offshore area, the atmospheric salt fog amount is high, which makes the traditional weathering steel unable to form a stable protective rust layer. Nanjing Iron and Steel Co., Ltd. develops a yield strength 420 MPa grade marine corrosion resistant steel based on the atmospheric salt fog amount in the offshore area to meet the application requirements of steel structure without coating in high salt content areas.

[0003] There is a matching contradiction between the high corrosion resistance, low yield strength ratio and easy welding of the yield strength 420 MPa grade marine corrosion resistant steel, and the comprehensive performance is difficult to control, and the research and production are difficult, so a new welding process needs to be developed to obtain a welding joint with good comprehensive performance. SUMMARY

[0004] The present application provides a gas shielded welding process for a yield strength 420 MPa grade marine corrosion resistant steel, which forms a welding joint with good comprehensive performance.

[0005] Technical scheme: The gas shielded welding process for a yield strength 420 MPa grade marine corrosion resistant steel according to the present application is characterized by comprising the following steps:

[0006] 1) Welding base material: The yield strength of the base steel plate is greater than or equal to 420 MPa, and the tensile strength is greater than or equal to 540 MPa. The chemical composition and weight percentage of the base steel plate are as follows: C: ≤0.08%, Mn: 0.40-1.50%, Si: 0.50-0.70%, S: ≤0.01%, P: ≤0.01%, Ni: 1.5-10.0%, Mo: 0.30-0.50%, Cu: 0.25-1.00%, and the balance is Fe and unavoidable impurities;

[0007] 2) Welding material: The welding material is selected to be a diameter of 1.2 mm gas shielded welding wire, and the chemical composition and weight percentage of the gas shielded welding wire are as follows: C: 0.04-0.10%, Mn: 0.8-1.8%, Si: ≤0.08%, S: ≤0.015%, P: ≤0.020%, Ni: 1.60-1.80%, Cu: 0.25-0.60%, Mo: 0.10-0.30%, and the balance is Fe and unavoidable impurities;

[0008] 3) welding parameters: the groove form is symmetrical X type groove, the angle is 45°-55°, the root face size is 1mm-3mm, the groove assembly leaves 1mm-2mm gap; no preheating before welding, the interpass temperature is ≤100℃, the reverse surface is exempted from the root treatment; the shielding gas is pure CO2, the gas flow is 15L / min-22L / min; the gas shielded welding is adopted, the welding current is 220A-320A, the arc voltage is 26V-32V, the welding speed is 24cm / min-36cm / min, and the welding heat input is 9kJ / cm-26kJ / cm; and the welding joint is obtained.

[0009] In the step 1), the elongation of the base steel plate is ≥19%, the impact energy KV2 at -40℃ is ≥100J, and the atmospheric corrosion resistance index V is ≥1.2.

[0010] In the step 2), the deposited metal of the gas shielded welding wire has the impact energy KV2 at -40℃ of ≥47J, and the tensile strength of the welding wire is ≥580MPa.

[0011] In the step 3), the welding joint obtained has the impact energy KV2 at -40℃ of ≥47J, and the tensile strength of the welding joint is ≥540MPa.

[0012] The welding joint has the atmospheric corrosion resistance index V of ≥1.2.

[0013] In the step 1), the thickness of the base steel plate is 16mm-60mm.

[0014] Preferably, in the step 3), the groove form is symmetrical X type groove, the angle is 50°, the root face size is 2mm, and the groove assembly leaves 1mm gap; no preheating before welding, the interpass temperature is 30℃-90℃, the reverse surface is exempted from the root treatment; the shielding gas is pure CO2, the gas flow is 18L / min; the gas shielded welding is adopted, the welding current is 220A, the arc voltage is 26V, the welding speed is 36cm / min, and the welding heat input is 9.5kJ / cm; and the welding joint is obtained.

[0015] Preferably, in the step 3), the groove form is symmetrical X type groove, the angle is 52°, the root face size is 2mm, and the groove assembly leaves 1mm gap; no preheating before welding, the interpass temperature is 32℃-95℃, the reverse surface is exempted from the root treatment; the shielding gas is pure CO2, the gas flow is 19L / min; the gas shielded welding is adopted, the welding current is 260A, the arc voltage is 29V, the welding speed is 29cm / min, and the welding heat input is 15kJ / cm; and the welding joint is obtained.

[0016] Preferably, the groove form in step 3) is a symmetrical X-type groove with an angle of 53° and a root face size of 3mm, and the groove is assembled with a gap of 1mm; no preheating before welding, interpass temperature of 29-100℃, back face free of root pass treatment; the protective gas is pure CO2 with a gas flow of 20L / min; gas shielded welding is adopted with a welding current of 300A, an arc voltage of 30V, a welding speed of 26cm / min and a welding heat input of 21kJ / cm; and a welded joint is obtained.

[0017] Preferably, the groove form in step 3) is a symmetrical X-type groove with an angle of 49° and a root face size of 3mm, and the groove is assembled with a gap of 1mm; no preheating before welding, interpass temperature of 31-85℃, back face free of root pass treatment; the protective gas is pure CO2 with a gas flow of 21L / min; gas shielded welding is adopted with a welding current of 320A, an arc voltage of 32V, a welding speed of 24cm / min and a welding heat input of 26kJ / cm; and a welded joint is obtained.

[0018] Beneficial effects: Compared with the prior art, the present application has the following remarkable advantages: the present application adopts an easy-to-operate gas shielded welding process to weld the yield strength 420MPa grade marine corrosion resistant steel, guarantees that the welded joint has a low temperature impact energy KV2≥47J at-40℃, the tensile strength of the welded joint is ≥540MPa, the welded joint has excellent corrosion resistance, the weld has an atmospheric corrosion resistance index V≥1.2, and the welded joint has no obvious steps after the simulation of industrial atmospheric periodic immersion / drying cycle corrosion test, the welded joint formed by the welding process has good comprehensive performance, and is suitable for welding the yield strength 420MPa grade marine corrosion resistant steel with a thickness of 16-60mm. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. 1 is a structural schematic view of the welding groove of the present application;

[0020] Figure 2 Fig. 4 is a metallographic structure diagram of the welded joint obtained in Example 1 of the present application after periodic immersion for 216 hours;

[0021] Figure 3 Fig. 5 is a metallographic structure diagram of the welded joint obtained in Example 2 of the present application after periodic immersion for 216 hours;

[0022] Figure 4 Fig. 6 is a metallographic structure diagram of the welded joint obtained in Example 3 of the present application after periodic immersion for 216 hours;

[0023] Figure 5 Fig. 7 is a metallographic structure diagram of the welded joint obtained in Example 4 of the present application after periodic immersion for 216 hours. DETAILED DESCRIPTION

[0024] The technical solutions of the present application are further described below in combination with the drawings and specific embodiments.

[0025] 1) Base metal for welding: the yield strength of the base metal is ≥420 MPa, the tensile strength is ≥540 MPa, the elongation is ≥19%, the impact energy at -40℃ is ≥100 J, the atmospheric corrosion resistance index V is ≥1.2, the chemical composition and the weight percentage are as follows: C: ≤0.08%, Mn: 0.40-1.50%, Si: 0.50-0.70%, S: ≤0.01%, P: ≤0.01%, Ni: 1.5-10.0%, Mo: 0.30-0.50%, Cu: 0.25-1.00%, and the balance is Fe and inevitable impurities.

[0026] 2) Welding material: for the steel, when the welding material is selected, the first consideration is to obtain a complete welded joint, and to ensure that the low-temperature impact energy at -40℃ of the welded joint is ≥47 J, the tensile strength of the welded joint is ≥540 MPa, the welded joint has excellent corrosion resistance, the atmospheric corrosion resistance index V of the weld is ≥1.2, there is no obvious step in the welded joint in the simulated industrial atmospheric periodic immersion / drying cycle corrosion test. The welding material is selected as a gas shielded welding wire with a diameter of Φ1.2 mm, the deposited metal has a low-temperature impact energy at -40℃ of ≥47 J, and the tensile strength of the welding wire is ≥580 MPa. The chemical composition and the weight percentage of the gas shielded welding wire are as follows: C: 0.04-0.10%, Mn: 0.8-1.8%, Si: ≤0.08%, S: ≤0.015%, P: ≤0.020%, Ni: 1.60-1.80%, Cu: 0.25-0.60%, Mo: 0.10-0.30%, and the balance is Fe and inevitable impurities.

[0027] 3) welding parameters: since the welding process parameters affect the heat cycle process of the welded joint, the element burnout, thereby affecting the performance of the weld metal and the heat-affected zone of the welded joint, the present application studies the effects of different welding processes on the comprehensive mechanical properties and welding quality of the welded joint, respectively measures the -40℃ impact energy of the weld and the heat-affected zone, the tensile properties and the bending properties of the welded joint, and simulates the industrial atmospheric periodic immersion / drying cycle corrosion test. The results show that when the welding process parameters described in the present application are used for welding, the comprehensive mechanical properties of the welded joint are excellent, the -40℃ impact energy KV2 of the weld and the heat-affected zone is ≥47J, the tensile strength Rm is ≥540MPa, the side bending d of the welded joint is 4a, 180°, without cracks, the atmospheric corrosion resistance index V of the weld is ≥1.2, the simulated industrial atmospheric periodic immersion / drying cycle corrosion test, the welded joint has no obvious step: 1, the groove form is symmetrical X-type groove, the angle is 45-55°, the blunt edge size is 1-3mm, and the groove assembly leaves a gap of 1-2mm. 2, no preheating before welding, the interlayer temperature is ≤100℃; the reverse side is exempted from the root cleaning treatment. 3, the shielding gas is pure CO2, and the gas flow is 15-22L / min. Gas shielded welding is adopted, the welding current is 220-320A, the arc voltage is 26-32V, the welding speed is 24-36cm / min, and the welding heat input is 9-26kJ / cm.

[0028] Example 1:

[0029] The base material is a marine corrosion resistant steel with yield strength ≥420MPa, tensile strength ≥540MPa, elongation ≥19%, -40℃ impact energy KV2 ≥100J, and atmospheric corrosion resistance index V ≥1.2. The welding test plate combination is 16mm+16mm, and the test plate size is 600mm(long)×200mm(width)×16mm(thickness);

[0030] The welding material is selected to be a gas shielded welding wire with a diameter of Φ1.2mm, and the deposited metal has a -40℃ low temperature impact energy KV2 ≥47J, and the tensile strength of the welding wire is ≥580MPa. The chemical composition of the gas shielded welding wire used and the weight percentage are as follows: C: 0.04-0.10%, Mn: 0.8-1.8%, Si: ≤0.08%, S: ≤0.015%, P: ≤0.020%, Ni: 1.60-1.80%, Cu: 0.25-0.60%, Mo: 0.10-0.30%, and the balance is Fe and unavoidable impurities.

[0031] The groove type is X-type groove, the groove angle is 50°, the blunt edge is 2mm, and the groove assembly gap is 1mm;

[0032] No preheating before welding, the interlayer temperature is 30-90℃; the reverse side is exempted from the root cleaning treatment before welding, and the following welding process is selected to ensure that the front bottoming is not burned through and the back welding can be penetrated;

[0033] The shielding gas is pure CO2, and the gas flow is 18 L / min.

[0034] The gas shielded welding is adopted, the welding current is 220 A, the arc voltage is 26 V, the welding speed is 36 cm / min, and the welding heat input is 9.5 kJ / cm.

[0035] Example 2

[0036] The base material is a marine corrosion resistant steel with yield strength ≥420 MPa, tensile strength ≥540 MPa, elongation ≥19%, impact energy KV2 ≥100 J at-40℃, and atmospheric corrosion resistance index V ≥1.2, the welding test plate combination is 16mm+16mm, and the test plate size is 600mm (length) x 200mm (width) x 16mm (thickness).

[0037] The welding material is a gas shielded welding wire with a diameter of Φ1.2mm, the deposited metal has a low temperature impact energy KV2 ≥47 J at-40℃, and the tensile strength of the welding wire is ≥580 MPa, the chemical composition of the gas shielded welding rod used is as follows: C: 0.04-0.10%, Mn: 0.8-1.8%, Si: ≤0.08%, S: ≤0.015%, P: ≤0.020%, Ni: 1.60-1.80%, Cu: 0.25-0.60%, Mo: 0.10-0.30%, and the balance is Fe and inevitable impurities.

[0038] The groove type is X-type groove, the groove angle is 52°, the bevel is 2mm, and the groove assembly gap is 1mm.

[0039] No preheating before welding, the interlayer temperature is 32-95℃; no cleaning treatment before reverse welding, the following welding process is selected to ensure that the front bottoming is not burned through and the back welding can be penetrated.

[0040] The shielding gas is pure CO2, and the gas flow is 19 L / min.

[0041] The gas shielded welding is adopted, the welding current is 260 A, the arc voltage is 29 V, the welding speed is 29 cm / min, and the welding heat input is 15 kJ / cm.

[0042] Example 3

[0043] The base material is a marine corrosion resistant steel with yield strength ≥420 MPa, tensile strength ≥540 MPa, elongation ≥19%, impact energy KV2 ≥100 J at-40℃, and atmospheric corrosion resistance index V ≥1.2, the welding test plate combination is 32mm+32mm, and the test plate size is 600mm (length) x 200mm (width) x 32mm (thickness).

[0044] The welding material is selected as a diameter Φ1.2mm gas shielded welding wire, the deposited metal-40℃ low temperature impact energy KV2≥47J, the tensile strength of the welding wire≥580MPa, the chemical composition and weight percentage of the used gas shielded welding wire are as follows: C: 0.04-0.10%, Mn: 0.8-1.8%, Si: ≤0.08%, S: ≤0.015%, P: ≤0.020%, Ni: 1.60-1.80%, Cu: 0.25-0.60%, Mo: 0.10-0.30%, and the balance is Fe and inevitable impurities.

[0045] The groove type is X-type groove, the groove angle is 53°, the root face is 3mm, and the groove assembly gap is 1mm;

[0046] No preheating before welding, the interlayer temperature is 29-100℃; no cleaning treatment before reverse welding, the following welding process is selected to ensure that the front bottoming is not burnt through and the back welding can be penetrated;

[0047] The protective gas is pure CO2, and the gas flow is 20L / min;

[0048] The gas shielded welding is adopted, the welding current is 300A, the arc voltage is 30V, the welding speed is 26cm / min, and the welding heat input is 21kJ / cm.

[0049] Example 4:

[0050] The base material is selected as a marine corrosion resistant steel with yield strength≥420MPa, tensile strength≥540MPa, elongation≥19%, and-40℃ impact energy KV2≥100J; the atmospheric corrosion resistance index V≥1.2; the welding test plate is combined as 60mm+60mm, and the test plate size is 600mm(length)×200mm(width)×60mm(thickness);

[0051] The welding material is selected as a diameter Φ1.2mm gas shielded welding wire, the deposited metal-40℃ low temperature impact energy KV2≥47J, the tensile strength of the welding wire≥580MPa, the chemical composition and weight percentage of the used gas shielded welding wire are as follows: C: 0.04-0.10%, Mn: 0.8-1.8%, Si: ≤0.08%, S: ≤0.015%, P: ≤0.020%, Ni: 1.60-1.80%, Cu: 0.25-0.60%, Mo: 0.10-0.30%, and the balance is Fe and inevitable impurities.

[0052] The groove type is X-type groove, the groove angle is 49°, the root face is 3mm, and the groove assembly gap is 1mm;

[0053] No preheating before welding, the interlayer temperature is 31-85℃; no cleaning treatment before reverse welding, the following welding process is selected to ensure that the front bottoming is not burnt through and the back welding can be penetrated;

[0054] The shielding gas is pure CO2, and the gas flow is 21 L / min.

[0055] The gas shielded welding is used, the welding current is 320 A, the arc voltage is 32 V, the welding speed is 24 cm / min, and the welding heat input is 26 kJ / cm.

[0056] The welding method of the above examples 1-4 is used to weld a yield strength of 420 MPa grade marine corrosion resistant steel, and the mechanical properties of the welded joint are detected.

[0057] The impact, tensile and bending properties of the welded joint are shown in Tables 1-3:

[0058] Table 1 Impact properties of the welded joint

[0059]

[0060] Table 2 Tensile and side bending properties of the welded joint

[0061]

[0062] Table 3 Corrosion resistance of the welded joint

[0063]

[0064] As Figures 2-5 It can be seen that the comprehensive mechanical properties of the welded joint obtained by examples 1-4 are excellent. The impact energy KV2 of the weld and the heat affected zone at-40℃ is ≥47J, the tensile strength Rm is ≥540MPa, the side bending of the welded joint is d=4a, 180°, no crack, the atmospheric corrosion resistance index V of the weld is ≥1.2, the simulated industrial atmosphere periodic immersion / drying cycle corrosion test, the welded joint has no obvious step.

[0065] The application relates to a gas protection welding process for a yield strength 420MPa marine corrosion resistant steel, which adopts suitable welding materials and welding process, welding current 220-320A, arc voltage 26-32V, welding speed 24-36cm / min and welding heat input 9-26kJ / cm. The process provided by the application is simple in implementation and has strong applicability. The process meets the key technology of the gas protection welding process for the yield strength 420MPa marine corrosion resistant steel with thickness 16-60mm, excellent comprehensive performance of the welded joint and the like. The suitable welding materials and welding process can guarantee that the low-temperature impact energy KV2 of the welded joint is greater than or equal to 47J at-40 DEG C, the tensile strength of the welded joint is greater than or equal to 540MPa, the welded joint has excellent corrosion resistance, the atmospheric corrosion resistance index V of the weld is greater than or equal to 1.2, the welded joint has no obvious step in the simulation industrial atmospheric periodic immersion / drying cycle corrosion test, and the welded joint formed by the welding process has good comprehensive performance.

Claims

1. A gas shielded welding process for marine corrosion-resistant steel with a yield strength of 420 MPa, characterized in that: Includes the following steps: 1) Base metal for welding: The yield strength of the base metal steel plate is ≥420MPa, and the tensile strength is ≥540MPa. The chemical composition and weight percentage of the base metal steel plate are as follows: C: ≤0.08%, Mn: 0.40~1.50%, Si: 0.50~0.70%, S: ≤0.01%, P: ≤0.01%, Ni: 1.5~10.0%, Mo: 0.30~0.50%, Cu: 0.25~1.00%, with the balance being Fe and unavoidable impurities; the thickness of the base metal steel plate is 16mm~60mm. 2) Welding materials: 1.2mm diameter gas-shielded welding wire is selected. The chemical composition and weight percentage of the gas-shielded welding wire are as follows: C: 0.04~0.10%, Mn: 0.8~1.8%, Si: ≤0.08%, S: ≤0.015%, P: ≤0.020%, Ni: 1.60~1.80%, Cu: 0.25~0.60%, Mo: 0.10~0.30%, with the balance being Fe and unavoidable impurities; 3) Welding parameters: The bevel type is a symmetrical X-type bevel with an angle of 45° to 55° and a blunt edge size of 1mm to 3mm. A gap of 1mm to 2mm is left between the bevels. No preheating is required before welding. The interpass temperature is ≤100℃. No root cleaning is required on the reverse side. The shielding gas is pure CO2 with a flow rate of 15L / min to 22L / min. Gas shielded welding is used with a welding current of 220A to 320A, an arc voltage of 26V to 32V, a welding speed of 24cm / min to 36cm / min, and a welding heat input of 9kJ / cm to 26kJ / cm. A welded joint is obtained.

2. The gas shielded welding process for marine corrosion-resistant steel with a yield strength of 420 MPa according to claim 1, characterized in that: In step 3), the bevel is a symmetrical X-shaped bevel with an angle of 50° and a blunt edge size of 2mm. A 1mm gap is left during bevel assembly. No preheating is required before welding. The interpass temperature is 30℃~90℃, and root cleaning is not required on the reverse side. The shielding gas is pure CO2 with a gas flow rate of 18L / min. Gas shielded welding is used with a welding current of 220A, an arc voltage of 26V, a welding speed of 36cm / min, and a welding heat input of 9.5kJ / cm. A welded joint is obtained.

3. The gas shielded welding process for marine corrosion-resistant steel with a yield strength of 420 MPa according to claim 1, characterized in that: In step 3), the bevel is a symmetrical X-shaped bevel with an angle of 52° and a blunt edge dimension of 2mm. A 1mm gap is left during bevel assembly. No preheating is required before welding. The interpass temperature is 32℃~95℃, and root cleaning is not required on the reverse side. The shielding gas is pure CO2 with a gas flow rate of 19L / min. Gas shielded welding is used with a welding current of 260A, an arc voltage of 29V, a welding speed of 29cm / min, and a welding heat input of 15kJ / cm. A welded joint is obtained.

4. The gas shielded welding process for marine corrosion-resistant steel with a yield strength of 420 MPa according to claim 1, characterized in that: In step 3), the bevel is a symmetrical X-shaped bevel with an angle of 53° and a blunt edge dimension of 3mm. A 1mm gap is left during bevel assembly. No preheating is required before welding, and the interpass temperature is 29℃~100℃. No root cleaning is required on the reverse side. The shielding gas is pure CO2 with a gas flow rate of 20L / min. Gas shielded welding is used with a welding current of 300A, an arc voltage of 30V, a welding speed of 26cm / min, and a welding heat input of 21kJ / cm. A welded joint is obtained.

5. The gas shielded welding process for marine corrosion-resistant steel with a yield strength of 420 MPa according to claim 1, characterized in that: In step 3), the bevel is a symmetrical X-shaped bevel with an angle of 49° and a blunt edge dimension of 3mm. A 1mm gap is left during bevel assembly. No preheating is required before welding, and the interpass temperature is 31℃~85℃. No root cleaning is required on the reverse side. The shielding gas is pure CO2 with a gas flow rate of 21L / min. Gas shielded welding is used with a welding current of 320A, an arc voltage of 32V, a welding speed of 24cm / min, and a welding heat input of 26kJ / cm. A welded joint is obtained.

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