800 MPa-grade low-yield-ratio structural steel plate and production method thereof

Abstract

The method relates to an 800 MPa-grade low-yield-ratio structural steel plate and a production method thereof. The steel comprises the chemical components in percentage by weight: 0.045 to 0.075 percent of C, 0.30 to 0.55 percent of Si, 1.55 to 1.95 percent of Mn, less than or equal to 0.01 percent of P, less than or equal to 0.0025 percent of S, 0.012 to 0.035 percent of Al, 0.15 to 0.25 percent of Cr, 0.15 to 0.3 percent of Mo, 0.2 to 0.4 percent of Cu, 0.2 to 0.4 percent of Ni, 0.008 to 0.04 percent of Nb, 0.008 to 0.04 percent of V, 0.008 to 0.03 percent of Ti, 0.0008 to 0.0015 percent of B, and the balance of Fe and inevitable impurities. The steel is subjected to RH vacuum treatment, ladle furnace (LF) external refining, full protection casting, a thermo mechanical control process (TMCP), and tempering heat treatment to form the steel plate with low yield ratio, high strength and high work hardening rate. The steel plate has the thickness specification of between 10 and 40 mm, the yield strength of more than or equal to 550MPa, the tensile strength of more than or equal to 800 MPa and the yield ratio of less than 0.70, and has excellent low temperature compact performance, cold forming performance and welding performance.

Description

technical field [0001] The present invention relates to iron and steel material technology, specifically the present invention relates to low-carbon high-strength steel material technology, and more specifically the present invention relates to a production technology of 800MPa grade low yield ratio steel plate. Background technique [0002] With the continuous development of low-carbon low-alloy high-strength steel, it has become the most important structural material. At the same time, with the continuous development of design and welding technology, large-scale steel structures have been more and more widely used. Put forward higher requirements, not only from basic indicators such as strength and toughness, but also from indicators such as welding performance, bending performance, and yield ratio. In large-scale steel structures and components with high safety factor requirements, there are high requirements for the strength and yield ratio of steel plates. Through the ...

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Problems solved by technology

Steel plates produced by quenching + tempering mainly add precious alloying elements such as Cr-Mo-Cu-Ni as hardenability elements. Also increased production costs, such as reference documents 2, 6, 7, 8

Or use a special rolling method, such as comparison documents 2 and 5 through air cooling before entering the water, which seriously affects the production rhythm of the steel plate

Or its composition process is only suitable for the production of thinner gauge steel plate by hot continuous rolling process, as shown in reference document 4

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