700MPa-tensile strength steel for large heat input welding structure and manufacturing method thereof

Abstract

The invention provides 700MPa-tensile strength steel for a large heat input welding structure and a manufacturing method thereof. The 700MPa-tensile strength steel for the large heat input welding structure comprises the components: 0.04-0.08 percent of carbon (C), 0.05-0.5 percent of silicon (Si), 1.40-1.85 percent of manganese (Mn), 0.2-0.4 percent of chromium (Cr), 0.010-0.060 percent of niobium (Nb), 0.005-0.03 percent of titanium (Ti), 0.02-0.04 percent of vanadium (V), 0.10-0.30 percent of copper (Cu), 0.10-0.40 percent of nickel (Ni), 0.10-0.30 percent of molybdenum (Mo), 0.0020-0.0050 percent of zirconium (Zr), 0.015-0.050 percent of aluminum (Al) and the balance of ferrum (Fe) and inevitable impurities. The manufacturing method comprises smelting, continuous casting and rolling. The temperature of heating before rolling is 1150-1230 DEG C; the rolling temperature of a recrystallization zone is not lower than 1000 DEG C; the rolling temperature of a non-recrystallization zone is 830-930 DEG C; the time of relaxation after rolling is 10-120s; the cooling speed is 3-30 DEG C/S; the final cooling temperature is 380-500 DEG C; and then, air cooling and tempering are carried out. The 700MPa-tensile strength steel for the large heat input welding structure has a reasonable component design and a simple process; thermal refining is not needed; the welding performance of a product is good; preheating is not needed before welding; thermal treatment is not needed after welding; and a heat affected zone has very high toughness.

Description

technical field [0001] The invention belongs to the technical field of metal materials, and in particular relates to a steel for large heat input welded structures with a tensile strength of 700 MPa and a manufacturing method thereof. Background technique [0002] With the enlargement of various steel structures, people put forward higher requirements for the strength, toughness and weldability of steel. In order to improve welding efficiency, it is inevitable to adopt large heat input welding technology. The disadvantage of traditional low-alloy high-strength steel (HSLA) is that its impact toughness and weldability decrease significantly while its strength increases. When high-heat energy welding is performed, the structure of the welding heat-affected zone (HAZ zone) is easily coarsened, and the toughness deteriorates. Therefore, while improving the strength of the steel plate, ensuring that the steel plate has good toughness in the HAZ zone under the condition of high i...

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Problems solved by technology

[0007] (3) Quenching and tempering treatment is required, which increases the manufacturing cost

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