CN111992853A - Mixed gas shielded welding process for low-alloy steel plate with thickness of 10-20 mm - Google Patents

Abstract

The invention discloses a mixed gas shielded welding process of a low-alloy steel plate with the thickness of 10-20 mm, which is characterized in that a Q345B low-alloy high-strength structural steel plate with the thickness of 10-20 mm is used as a base material, an ER70S-6 welding wire material with the diameter of 1.2mm is selected, a double-sided V-shaped groove is formed, the single side of the groove angle is 30 degrees, the root gap is 2mm, 90% Ar + 10% CO is formed, and the single side of the groove angle is 30 degrees₂Argon-rich mixed gas shielded welding, the welding is first: the welding current is 104-114A, the welding voltage is 16-18V, the power supply is in direct current reverse connection, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and the wire feeding speed is 2.5-3.5 m/min; and (3) welding a second step: welding current is 220-240A, welding voltage is 24-26V, power supply direct current is reversely connected, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and wire feeding is carried outThe speed is 2.5-3.5 m/min. The invention does not need preheating before welding and heat treatment after welding, and has good welding quality and high production efficiency.

Description

Mixed gas shielded welding process for low-alloy steel plate with thickness of 10-20 mm

Technical Field

The invention relates to a welding process of a steel plate, in particular to a mixed gas shielded welding process of a low-alloy steel plate with the thickness of 10-20 mm, and belongs to the technical field of structural steel welding processing.

Background

General useIn the form of welding gas protection of CO₂Gas protection, Ar protection and mixed gas protection, wherein the mixed gas protection is commonly used and mainly comprises Ar and CO₂Mixing the gas with pure CO₂Compared with gas shielded welding, the welding efficiency and welding quality are high, the cost is low, and the value is obvious.

The Q345B low-alloy high-strength steel plate with the thickness of 10-20 mm is used for manufacturing a special guide rail truss structure for the robot, the special characteristic of bearing the operation load for a long time and the requirement on the service life are met, and the high design requirement on mechanical properties such as toughness, plasticity and the like of a welding seam is met. In the welding and cooling process of the Q345B steel, a heat affected zone is easy to form a quenched structure, namely martensite, so that the hardness of a near seam zone is improved, the plasticity is reduced, and cracks and lamellar tearing occur after welding. In order to prevent cracks, the welding construction efficiency is often reduced and the construction conditions are often improved, for example, the processes of pre-welding preheating and post-welding heat treatment are adopted, so that the welding process is complicated, the production cost is increased, and particularly for large-scale welding structures, the welding process is difficult to implement in actual production.

Disclosure of Invention

The invention aims to provide a mixed gas shielded welding process of a low-alloy steel plate with the thickness of 10-20 mm aiming at the defects of the prior art. By selecting proper welding materials and matching proper welding process parameters, the generation of cracks is avoided. Preheating is not needed before welding, heat treatment is not needed after welding, the working procedure is simplified, and the production efficiency is high.

In order to achieve the purpose, the invention adopts the following technical scheme:

1. base material: the Q345B low-alloy high-strength structural steel plate with the thickness of 10-20 mm has the tensile strength of 537MPa, the mass fraction of C is less than or equal to 0.20%, the mass fraction of Mn is less than or equal to 1.70%, the mass fraction of Si is less than or equal to 050%, the mass fraction of Cr is less than or equal to 0.30%, the mass fraction of Ni is less than or equal to 0.50%, the mass fraction of Cu is less than or equal to 0.30%, the mass fraction of S is less than or equal to 0.035%, the mass fraction of Nb is less than or equal to 0.07%.

2. Welding wire materials: ER70S-6, tensile strength 620MPa, mass fraction C0.02%, Mn1.9%, P0.01%, S0.01%, Si0.69%, Cr19.6%, Ni9.9%, Mo0.10%, Cu0.10%, N0.07%, and welding wire diameter 1.2 mm.

3. Groove preparation: a double-sided V-shaped groove is adopted, the angle of the groove is unilateral 30 degrees, and the root gap is 2 mm.

4. Welding gas: using 90% Ar + 10% CO₂And (4) argon-rich mixed gas.

5. Welding: the first way is that: the welding current is 104-114A, the welding voltage is 16-18V, the power supply is in direct current reverse connection, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and the wire feeding speed is 2.5-3.5 m/min; and a second step: the welding current is 220-240A, the welding voltage is 24-26V, the power supply is in direct current reverse connection, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and the wire feeding speed is 2.5-3.5 m/min.

The process parameters are strictly controlled. Welding current and arc voltage are matched key welding parameters, and improper selection can affect welding quality; the purity of the gas cannot be lower than 99.5 percent, for example, the gas flow is too small, the stiffness of the protective gas is insufficient, and the welding seam is easy to generate air holes and other defects; the gas flow is too large, the oxidability is enhanced, and the quality of a welding seam is reduced; if the speed is too slow, the mechanical property of the welding seam is not good, if the speed is too fast, the cooling speed of the welding seam is also fast, the strength of the welding seam is reduced, and cracks are easy to appear.

The invention has the beneficial effects that:

Q345B low-alloy high-strength structural steel plate with the thickness of 10-20 mm is used as a base material, and ER70S-6 welding wire and Ar 90% + CO are selected₂The 10% mixed gas shielded welding method has the advantages that technological parameters are strictly controlled, preheating is not needed before welding, heat treatment is not needed after welding, a welding joint has high strength, high impact toughness and cold bending performance, the welding process is simple, the welding quality is good, and the production efficiency is high.

Detailed Description

Base material: the Q345B low-alloy high-strength structural steel plate with the thickness of 20mm is selected, the mass fraction C is less than or equal to 0.20%, the Mn is less than or equal to 1.70%, the Si is less than or equal to 050%, the Cr is less than or equal to 0.30%, the Ni is less than or equal to 0.50%, the Cu is less than or equal to 0.30%, the S is less than or equal to 0.035%, the Nb is less than or equal to 0.07%, the V is less than or equal to 0.15%, the Ti is less than or equal to 0.20%, the P is less than or equal to 0.035.

Welding wires: selecting ER 70S-6: the tensile strength is 620 MPa; 0.02% of C, 1.9% of Mn1, 0.01% of P, 0.01% of S, 0.69% of Si, 19.6% of Cr19.9% of Ni9.9%, Mo0.10%, Cu0.10%, 0.07% of N, and 1.2mm of the diameter of the welding wire.

The groove adopts a double-sided V-shaped groove, the angle of the groove is unilateral 30 degrees, and the root gap is 2 mm. Welding gas adopts 90% Ar + 10% CO₂And (4) argon-rich mixed gas.

Welding: the first way is that: the welding current is 104-114A, the welding voltage is 16-18V, the power supply is in direct current reverse connection, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and the wire feeding speed is 2.5-3.5 m/min; and a second step: the welding current is 220-240A, the welding voltage is 24-26V, the power supply is in direct current reverse connection, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and the wire feeding speed is 2.5-3.5 m/min.

And (3) test results:

after the welding is finished for 24 hours, magnetic powder detection is carried out on the welded joint after the welding of the embodiment of the invention, and the result is as follows: the surface of the welding line is free of defects, and the 2X requirement of GB/T26952-2011 is met; ultrasonic detection is carried out on the welded joint, and the result is as follows: the interior of the welding seam is free from defects, and the requirement of GB/T29712-2013 on level 2 is met.

The mechanical property of the welding joint of the embodiment of the invention is detected, and the mechanical property of the joint is as follows: tensile strength Rm: 580MPa, fracture site: the cold bending d of the joint of the base metal is 4a, the temperature is 180 degrees, and the impact energy AKv of the weld metal at normal temperature is as follows: 169J, impact energy AKv at normal temperature 1mm outside the heat affected zone fusion line: 150J.

Claims (1)

1. The mixed gas shielded welding process of the low-alloy steel plate with the thickness of 10-20 mm is characterized by comprising the following steps of:

base material: the Q345B low-alloy high-strength structural steel plate with the thickness of 10-20 mm has the tensile strength of 537MPa, the mass fraction C of less than or equal to 0.20 percent, the Mn of less than or equal to 1.70 percent, the Si of less than or equal to 050 percent, the Cr of less than or equal to 0.30 percent, the Ni of less than or equal to 0.50 percent, the Cu of less than or equal to 0.30 percent, the S of less than or equal to 0.035 percent, the Nb of less than or equal to 0.07 percent, the V of less than or equal to 0.15 percent, the;

welding wire materials: ER70S-6, tensile strength 620MPa, mass fraction C0.02%, Mn 1.9%, P0.01%, S0.01%, Si 0.69%, Cr 19.6%, Ni 9.9%, Mo 0.10%, Cu 0.10%, N0.07%;

groove preparation: a double-sided V-shaped groove is adopted, the angle of the groove is unilateral 30 degrees, and the root gap is 2 mm;

welding gas: using 90% Ar + 10% CO₂An argon-rich mixed gas;

welding: the first way is that: the welding current is 104-114A, the welding voltage is 16-18V, the power supply is in direct current reverse connection, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and the wire feeding speed is 2.5-3.5 m/min; and a second step: the welding current is 220-240A, the welding voltage is 24-26V, the power supply is in direct current reverse connection, the air flow is 15-20L/min, the welding speed is 20-25 mm/min, and the wire feeding speed is 2.5-3.5 m/min.