A double-wire gas shielded welding method for flat angle connection of high-strength steel medium and thick plates

Abstract

The invention discloses a double-wire gas shielded welding method for flat angle joint of medium and thick plates of high-strength steel, the welding position is a flat angle joint position, no groove is opened, and the root gap is 0-1mm; flux-cored wire double-wire gas shielded welding is adopted, the welding shielding gas is Ar-CO2 mixed gas, and the flow rate of the shielding gas is 18-22L / min; both sides of the weld are formed by single-pass welding, the fillet weld is not melted through, the front wire welding current is 196-213A, the front wire welding voltage is 28.5-29V; the rear wire welding current is 197-207A, and the rear wire welding voltage is 27-27.6V; the welding speed is 38-42cm / min; the welding heat input is 16.2-17.7KJ / cm. The invention reduces the number of cladding passes to achieve efficient welding, the weld is beautifully formed, welding spatter is reduced, the post-weld surface treatment work is reduced, and the welding efficiency is improved by more than 38%.

Description

Technical Field

[0001] The invention belongs to the technical field of corrosion-resistant steel welding, and in particular relates to a double-wire gas shielded welding method for flat angle connection of medium and thick high-strength steel plates. Background Art

[0002] As a means of transporting crude oil at sea, crude oil tankers are of great significance to offshore resource exploitation and energy transportation. Their corrosion resistance is directly related to the safety of ship structures and the environmental protection of the marine environment. Marine crude oil corrosion-resistant steel can replace special ship coatings. It has good crude oil corrosion resistance and easy maintenance performance. It can be widely used in ship cargo oil tanks and related piping systems, and has good application prospects.

[0003] Double-wire gas shielded welding can effectively improve the welding efficiency of ships and reduce construction costs. At present, the welding method used on domestic crude oil tankers is mainly single-wire CO2 gas shielded welding with flux-cored wire, and the double-wire gas shielded welding process has not yet been applied on actual ships. Due to the addition of corrosion-resistant alloy elements, the metal fluidity of the molten pool during welding is poor, and magnetic blow is prone to occur. Therefore, when conventional pure CO2 gas is used for welding, a large amount of spatter is easily generated, which directly affects the formation of the welded joint and increases the workload of post-weld surface treatment. If the multi-gas flux-cored wire gas shielded welding method is adopted, excellent arc characteristics and very stable droplet transfer characteristics can be obtained. It is easier to obtain a good welding protection effect than using a single gas, which is conducive to the diffusion of trace elements and the full metallurgical reaction, while ensuring the weld penetration and weld formation quality.

[0004] Patent document CN112496505A discloses a double-wire gas shielded welding method for medium and thick plates of high-strength steel for ships, which adopts double-wire welding in front wire pulse mode and rear wire CMT mode, with a double-wire spacing of 3-4mm. During welding, the front wire is perpendicular to the parent material, and the rear wire is tilted forward, and the tilting angle is 28-32°; the front wire welding current is 200-225A, and the welding voltage is 23-24V; the rear wire welding current is 178-199A, and the welding voltage is 18-19V; the welding speed is 6-8mm / s; and the swing amplitude is 5-12mm. However, this document is aimed at flat butt welding of high-strength steel plates, and adopts double-wire welding in front wire pulse mode and rear wire CMT mode, which cannot be used for welding of flat angle joints of medium and thick plates of high-strength steel. Patent document CN113319465A discloses a set of double-wire gas shielded welding wires and welding methods for ultra-high-strength steel welding. However, this document is aimed at flat butt welding of high-strength steel plates, and requires beveling of the parts of the ultra-high-strength steel to be connected, and preheating and post-weld heat treatment of the ultra-high-strength steel.

[0005] At present, the welding of right-angle joints of crude oil corrosion-resistant high-strength steel for ships mainly adopts pure CO2 gas single-wire flux-cored wire gas shielded welding. There is no multi-gas flux-cored wire double-wire gas shielded welding process suitable for the right-angle joints of domestic crude oil corrosion-resistant high-strength steel for crude oil ships. Summary of the invention

[0006] The purpose of the present invention is to provide a double-wire gas shielded welding method for flat angle connection of high-strength steel medium and thick plates, so as to solve the problems of poor fluidity of welding molten pool and magnetic blow in welding caused by adding alloy elements to high-strength steel for shipbuilding resistant to crude oil corrosion.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] The invention discloses a double-wire gas shielded welding method for flat angle connection of medium and thick high-strength steel plates, characterized in that the welding position is a flat angle connection position, no groove is opened, and the root gap is 0-1 mm; flux-cored double-wire gas shielded welding is adopted, the welding shielding gas is Ar-CO2 mixed gas, and the flow rate of the shielding gas is 18-22 L / min; both sides of the weld are formed by single-pass welding, the fillet weld is not melted through, the front wire welding current is 196-213 A, and the front wire welding voltage is 28.5-29 V; the rear wire welding current is 197-207 A, and the rear wire welding voltage is 27-27.6 V; the welding speed is 38-42 cm / min; the welding heat input is 16.2-17.7 KJ / cm;

[0009] The high-strength steel medium and thick plate is a crude oil corrosion resistant high-strength steel plate with a thickness of 13 to 20 mm, and the mass fraction of the chemical composition of the crude oil corrosion resistant high-strength steel is C: ≤0.18%, Si: ≤0.5%, Mn: 0.9% to 1.6%, S: ≤0.035%, P: ≤0.035%, Cr: ≤0.2%, Ni: ≤0.4%, Cu: ≤0.35%, Mo: ≤0.08%, V: ≤0.03% to 0.10%, Nb: 0.019% to 0.05%, Ti: ≤0.02%, Fe: balance and unavoidable impurities;

[0010] The flux-cored welding wire has a wire diameter of 1.2 mm, and the mass fractions of the chemical components of the deposited metal are: C≤0.10%, Si:≤0.5%, Mn:≤1.5%, S:≤0.015%, P:≤0.015%, Ni:≤0.6%, Cu:≤0.5%, and Mo:≤0.2%.

[0011] Preferably, the welding shielding gas is a mixed gas of 80% to 85% Ar gas and 15% to 20% CO2; more preferably, the welding shielding gas is a mixed gas of 82% Ar gas and 18% CO2.

[0012] Preferably, the surface of the test plate within a range of 20 to 30 mm near the welding area is cleaned.

[0013] Compared with the prior art, the present invention reduces the number of deposition passes to achieve efficient welding, the weld is beautifully formed, welding spatter is greatly reduced, the post-weld surface treatment work is alleviated, the welding efficiency is improved by more than 38%, and efficient welding with low heat input of multi-gas double-wire flux-cored welding wire for flat angle joints is achieved; the appearance inspection of the welded joint meets the quality requirements, without significant surface defects, and the surface coloring of the corrosion-resistant steel welded joint after welding is defect-free; after the single-sided weld is broken, the cross section of the specimen is free of defects such as cracks and looseness; the welded joint has excellent corrosion resistance, and after the standard corrosion test of the inner bottom plate that meets the IMO standard, the welded joint has no obvious step-like corrosion morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of double-wire gas shielded welding for flat angle connection of medium and thick high-strength steel plates of the present invention;

[0015] In the figure: 1- high-strength steel medium and thick plate web, 2- high-strength steel medium and thick plate bottom plate. DETAILED DESCRIPTION

[0016] Those skilled in the art should recognize that the present embodiment is only used to illustrate the present invention, and is not used to limit the present invention. Any changes or modifications to the embodiment within the scope of the present invention are within the scope of the claims of the present invention.

[0017] Example 1

[0018] (1) Welding materials

[0019] Domestic high-strength steel resistant to crude oil corrosion, 13mm medium and thick plates and 18mm medium and thick plates, the mass fraction of chemical composition is: C: ≤0.18%, Si: ≤0.5%, Mn: 0.9%~1.6%, S: ≤0.035%, P: ≤0.035%, Cr: ≤0.2%, Ni: ≤0.4%, Cu: ≤0.35%, Mo: ≤0.08%, V: ≤0.03%~0.10%, Nb: 0.019%~0.05%, Ti: ≤0.02%, Fe: balance and unavoidable impurities.

[0020] The wire diameter of the flux-cored welding wire is 1.2mm, and the mass fraction of the chemical composition of the deposited metal is: C≤0.10%, Si:≤0.5%, Mn:≤1.5%, S:≤0.015%, P:≤0.015%, Ni:≤0.6%, Cu:≤0.5%, Mo:≤0.2%; no preheating is required.

[0021] (2) Welding method

[0022] The domestic crude oil corrosion resistant high-strength steel plate with a thickness of 13mm is used as the web plate, and the domestic crude oil corrosion resistant high-strength steel plate with a thickness of 18mm is used as the bottom plate. The welding position is a right angle joint position, without a groove, and the root gap is 0.5mm; the surface of the test plate within 20-30mm near the welding area is cleaned;

[0023] Flux-cored double-wire gas shielded welding is adopted, the welding shielding gas is 82% Ar gas and 18% CO2 mixed gas, and the flow rate of the shielding gas is 18L / min; both sides of the weld are formed by single-pass welding, the fillet weld is not melted through, the front wire welding current is 196~200A, the front wire welding voltage is 28.5~28.6V; the rear wire welding current is 197~202A, and the rear wire welding voltage is 27.0~27.6V; the welding speed is 40cm / min; the welding heat input is 16.2~17.7KJ / cm; the welding is carried out at room temperature with an ambient temperature of not less than 0℃, and the other welding process parameters are shown in Table 1.

[0024] Example 2-3

[0025] (1) The materials of welding materials (base material and welding wire) are the same as those in Example 1.

[0026] (2) Example 2: A domestic crude oil corrosion resistant high-strength steel plate with a thickness of 13 mm is used as the web plate, and a domestic crude oil corrosion resistant high-strength steel plate with a thickness of 18 mm is used as the bottom plate. The welding position is a right angle joint position, no groove is opened, and the root gap is 0.5 mm; the surface of the test plate within a range of 20 to 30 mm near the welding area is cleaned;

[0027] Flux-cored double-wire gas shielded welding is adopted, and the welding shielding gas is a mixed gas of 82% Ar gas and 18% CO2, and the flow rate of the shielding gas is 22L / min; both sides of the weld are formed by single-pass welding, and the fillet weld is not melted through. The front wire welding current is 206-213A, and the front wire welding voltage is 28.5-28.8V; the rear wire welding current is 203-207A, and the rear wire welding voltage is 27-27.3V; the welding speed is 40cm / min, and the welding heat input is 16.2-17.7KJ / cm; the welding is carried out at room temperature with an ambient temperature of not less than 0°C, and the other welding process parameters are shown in Table 1.

[0028] (3) Example 3: The domestic crude oil corrosion resistant high-strength steel plate with a thickness of 13 mm is used as the web plate, and the domestic crude oil corrosion resistant high-strength steel plate with a thickness of 18 mm is used as the bottom plate. The welding position is a right angle joint position, no groove is opened, and the root gap is 1.0 mm; the surface of the test plate within 20 to 30 mm near the welding area is cleaned;

[0029] Flux-cored double-wire gas shielded welding is adopted, the welding shielding gas is 82% Ar gas and 18% CO2 mixed gas, and the flow rate of the shielding gas is 20L / min; both sides of the weld are formed by single-pass welding, the fillet weld is not melted through, the front wire welding current is 200-205A, the front wire welding voltage is 28.6-28.8V; the rear wire welding current is 200-207A, and the rear wire welding voltage is 27.3-27.6V; the welding speed is 40cm / min, and the welding heat input is 16.2-17.7KJ / cm; the welding is carried out at room temperature with an ambient temperature of not less than 0°C, and the other welding process parameters are shown in Table 1.

[0030] Table 1 Welding process parameters of Examples 1 to 5

[0031]

[0032] Example 4

[0033] (1) The materials of welding materials (base material and welding wire) are the same as those in Example 1.

[0034] (2) Welding method

[0035] The domestic crude oil corrosion resistant high-strength steel plate with a thickness of 13mm is used as the web plate, and the domestic crude oil corrosion resistant high-strength steel plate with a thickness of 20mm is used as the bottom plate. The welding position is a right angle joint position, without a groove, and the root gap is 0.5mm; the surface of the test plate within 20-30mm near the welding area is cleaned;

[0036] Flux-cored double-wire gas shielded welding is adopted, and the welding shielding gas is a mixed gas of 80% Ar gas and 20% CO2, and the flow rate of the shielding gas is 20L / min; both sides of the weld are formed by single-pass welding, and the fillet weld is not melted through. The front wire welding current is 190-200A, and the front wire welding voltage is 28.3-28.5V; the rear wire welding current is 192-205A, and the rear wire welding voltage is 27.0-27.2V; the welding speed is 38cm / min; the welding heat input is 16.2-17.7KJ / cm; the welding is carried out at room temperature with an ambient temperature of not less than 0°C, and the other welding process parameters are shown in Table 1.

[0037] Example 5

[0038] (1) The materials of welding materials (base material and welding wire) are the same as those in Example 1.

[0039] (2) Welding method

[0040] The domestic crude oil corrosion resistant high-strength steel plate with a thickness of 15mm is used as the web plate, and the domestic crude oil corrosion resistant high-strength steel plate with a thickness of 20mm is used as the bottom plate. The welding position is a right angle joint position, without a groove, and the root gap is 0.5mm; the surface of the test plate within 20-30mm near the welding area is cleaned;

[0041] Flux-cored double-wire gas shielded welding is adopted, and the welding shielding gas is a mixed gas of 83% Ar gas and 17% CO2, and the flow rate of the shielding gas is 20L / min; both sides of the weld are formed by single-pass welding, and the fillet weld is not melted through. The front wire welding current is 205-215A, and the front wire welding voltage is 28.8-29.0V; the rear wire welding current is 210-217A, and the rear wire welding voltage is 27.6-27.8V; the welding speed is 38cm / min; the welding heat input is 16.2-17.7KJ / cm; the welding is carried out at room temperature with an ambient temperature of not less than 0°C, and the other welding process parameters are shown in Table 1.

[0042] (3) Test results

[0043] According to the China Classification Society's "Material and Welding Specifications", welding test pieces were inspected on the welded joints, and surface coloring, macro and fracture tests were completed; the test results are shown in Table 2, which meet the standard requirements.

[0044] Table 2 Performance of welding joints in Examples 1 to 5

[0045]

[0046] The corrosion resistance of the welded joints of corrosion-resistant steel after welding of the examples 1 to 5 was tested according to the IMO289 (89) standard crude oil tank cargo tank corrosion resistance steel assessment procedure. After the welded joints were placed in a 10% by weight NaCl solution with a pH value of 0.85 for 168 hours (inner bottom plate corrosion test), the welded joints were magnified 1000 times to observe that there was no step on the surface boundary between the weld metal and the base material.

Claims

1. A double-wire gas shielded welding method for flat angle connection of medium and thick high-strength steel plates, characterized in that: The welding position is a flat angle joint, without groove, and the root gap is 0-1mm; flux-cored double-wire gas shielded welding is adopted, the welding shielding gas is Ar-CO2 mixed gas, and the flow rate of the shielding gas is 18-22L / min; both sides of the weld are formed by single-pass welding, and the fillet weld is not melted through. The front wire welding current is 196-213A, and the front wire welding voltage is 28.5-29V; the rear wire welding current is 197-207A, and the rear wire welding voltage is 27-27.6V; the welding speed is 38-42cm / min; the welding heat input is 16.2-17.7KJ / cm; The high-strength steel medium and thick plate is a crude oil corrosion-resistant high-strength steel plate with a thickness of 13 to 20 mm; the mass fraction of the chemical composition of the crude oil corrosion-resistant high-strength steel is C: ≤0.18%, Si: ≤0.5%, Mn: 0.9% to 1.6%, S: ≤0.035%, P: ≤0.035%, Cr: ≤0.2%, Ni: ≤0.4%, Cu: ≤0.35%, Mo: ≤0.08%, V: 0.03% to 0.10%, Nb: 0.019% to 0.05%, Ti: ≤0.02%, Fe: balance and unavoidable impurities; The mass fractions of the chemical composition of the deposited metal of the flux-cored welding wire are: C≤0.10%, Si:≤0.5%, Mn:≤1.5%, S:≤0.015%, P:≤0.015%, Ni:≤0.6%, Cu:≤0.5%, Mo:≤0.2%; After the weld joint was placed in a 10% by weight NaCl solution with a pH value of 0.85 for 168 hours, the weld joint was magnified 1000 times to observe that there was no step on the surface boundary between the weld metal and the base material.

2. The double-wire gas shielded welding method according to claim 1, characterized in that: The diameter of the flux-cored welding wire is 1.2 mm.

3. The double-wire gas shielded welding method according to claim 1, characterized in that: The welding shielding gas is a mixed gas of 80% to 85% Ar gas and 15% to 20% CO2.

4. The double-wire gas shielded welding method according to claim 1, characterized in that: The welding shielding gas is a mixed gas of 82% Ar gas and 18% CO2.

5. The double-wire gas shielded welding method according to claim 1, characterized in that: Clean the surface of the test plate within 20 to 30 mm near the welding area.

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