Submerged-arc welding technology of big-thickness low-temperature steel plate with yield strength of 690MPa grade

Abstract

The invention relates to a submerged-arc welding technology of a big-thickness low-temperature steel plate with yield strength of 690MPa grade. The method comprises the following steps: (1) carrying out a welding cold crack sensitivity test on the steel plate to confirm the needed lowest preheating temperature; (2) adopting a welding groove with a symmetrical double-U shape, wherein the groove angle is 25-35 degrees, the thicknesses of truncated edges are 3-5mm, and the gaps between the truncated edges are 1-2mm; (3) adopting a welding wire with the tensile strength of more than or equal to 830MPa and the impacting energy of more than or equal to 100J at the temperature of -60 DEG C; (4) controlling the welding current to be 450-680A, the welding voltage to be 29-36V, the welding speed to be 38-50cm/ min, the weld heat input to be 15-40kJ/ cm and the flux baking system to be 350 DEG C*2.5h; (5) adopting gas shield welding with a single-sided welding and two-sided molding STT technology to carry out backing weld, and then carrying out unfolding submerged-arc welding until the steel plate is fully filled. All mechanical properties of a welding joint obtained by the method meet the requirements of the classification society, and particularly, a weld seam area and a welding heat affected zone can maintain higher low temperature impact toughness.

Description

technical field [0001] The invention relates to a submerged arc welding process, in particular to a submerged arc welding process of a low-temperature steel plate with a yield strength of 690 MPa and a thickness specification of 80-100 mm. Background technique [0002] With the rapid development of my country's shipbuilding and ocean engineering industries, equipment manufacturing industries such as ultra-large ships, oil and gas drilling platforms, and pipelines have developed rapidly, and have been included in the country's "Twelfth Five-Year" development plan. It has been included in the national catalog of emerging key industries. The development of the above-mentioned equipment manufacturing industry has put forward an urgent demand for high-strength, high-toughness, and large-thickness steel plates. The most representative ultra-high-strength ship plate F690 with a thickness of 100mm has a yield strength of ≥690MPa and a tensile strength of ≥ 830MPa, elongation ≥ 16%, ...

AI Technical Summary

Problems solved by technology

[0004] This type of steel has a high alloy content and a carbon equivalent of more than 0.60, which leads to a high sensitivity to welding cold cracks and a strong sensitivity to delayed cracks after welding; in addition, because the thickness specification reaches 100mm, the crack tendency is further increased

In welding practice, it is difficult to ensure the quality and performance of welded joints. For example, the strength of welded joints is low, and the -60°C impact energy of weld metal is not up to standard. It is difficult to take into account the two indicators of strength and impact toughness, which cannot meet the current requirements The requirements of the industry restrict the development of this type of steel and related industries

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