High strength low yield ratio welding structure steel and production method thereof

Abstract

The invention belongs to welded structural steel with high strength and low yield ratio and a production method thereof, aiming at solving the defects that a steel plate or a steel coil with the specification smaller than 25mm can only be produced, the process is long, and the like. The invention adopts the measures that the welded structural steel contains chemical components by weight that: 0.04-0.10 percent of C, 0.60-2.00 percent of Si, 1.50-2.50 percent of Mn, less than or equal to 0.030 percent of P, less than or equal to 0.010 percent of S, 0.20-0.50 percent of Cu, 0.40-0.80 percent of Cr, 0.35-0.80 percent of Ni, 0.0008-0.0030 percent of B, and at least three of the following components: less than or equal to 0.60 percent of Mo, 0.015-0.060 percent of Nb, 0.030-0.120 percent of V, less than or equal to 0.030 percent of Ti, less than or equal to 0.040 percent of Als and less than or equal to 0.010 percent of Zr, and the rest is Fe and unavoidable impurities; and meanwhile, Mn and Cr also need to satisfy the condition that Mn and Cr are equal to 2.20-2.80 percent, and the welding cold crack sensitivity coefficient Pcm is equal to C plus Si / 30 plus (Mn plus Cu plus Cr) / 20 plus Mo / 15 plus Ni / 60 plus V / 10 plus 5B and is less than or equal to 0.30 percent; the production method comprises the following steps of heating a steel billet, rough rolling, finishing rolling, relaxing and laminar cooling, and the laminar cooling comprises the following steps of slow cooling, quick cooling and natural cooling to room temperature.

Description

technical field [0001] The invention relates to low-alloy steel and its production method, in particular to a high-strength low-yield-ratio welded structural steel and its production method. Welded structural steel and methods for its production. Background technique [0002] While the strength of traditional welded structural steel is increasing, the yield ratio is also increasing. Especially when the tensile strength reaches above 780MPa, the yield ratio of steel is generally above 0.90. Based on safety considerations, the high yield ratio limits the application of this type of steel in the field of engineering structures. The dual-phase steel developed in recent years and widely used in domestic and foreign automobile industries has high strength and low yield ratio. This type of steel is generally produced by hot rolling and heat treatment. The traditional hot-rolled dual-phase steel is required to be rolled in the two-phase area, so the rolling pressure of the rolli...

AI Technical Summary

Problems solved by technology

However, the requirements for the final rolling temperature of this steel type are too low, only 650-800°C. When the final rolling temperature is greater than 800°C, the grain refinement of the steel is not sufficient, and the required microstructure transformation is not complete. Coil) The final rolling temperature requirement is low, so a large rolling pressure is required, so it is only suitable for rolling thinner steel plates (coils)