Easy-to-weld ultra-high strength steel with cold crack sensitivity coefficient less than or equal to 0.25 and production method

Abstract

The invention relates to easy-to-weld ultrahigh-strength steel with cold crack sensitivity coefficient less than or equal to 0.25. The easy-to-weld ultrahigh-strength steel comprises the following components in percentage by weight: 0.07-0.10% of C, 0.15-0.30% of Si, 1.6-2.0% of Mn, less than or equal to 0.010% of P, less than or equal to 0.002% of S, 0-0.04% of Nb, 0.09-0.13% of Ti and 0.20%-0.35% of Mo + Cr, wherein each of Mo and Cr is not zero; a production method comprises the steps of desulfurizing molten iron, smelting and casting into a blank; heating the casting blank; rough rolling;finish rolling; cooling, coiling and tempering. On the premise of ensuring that the yield strength of a steel plate is not less than 822MPa, the tensile strength is not less than 860MPa, the elongation A50 is not less than 18%, the low-temperature toughness at -20 DEG C is not less than 78J, and the transverse and longitudinal cold bending properties can meet the requirements that D = a and is qualified at 180 degrees, crystalline grains are refined through the TMCP + ultra-fast cooling + tempering process, the structure is uniform, the welding performance is excellent, and the cost performance is high; preheating-free welding can be achieved, internal stress is uniform, and strength and toughness are excellent.

Description

technical field [0001] The invention relates to a steel for mechanical engineering and commercial vehicles and a production method, in particular to an easy-to-weld ultra-high-strength steel with a cold crack sensitivity coefficient ≤0.25 and a production method, which is especially suitable for mechanical engineering and commercial steel with a thickness of 3-8 mm. Automotive steel and its production. Background technique [0002] Ultra-high-strength steel is widely used in industries such as construction machinery and commercial vehicles. Domestic mainstream steel companies mainly adopt high-alloying and off-line quenching + tempering processes for mass production. The microstructure is tempered martensite / troostite / sorbite type, stable quality, and excellent performance, which have been recognized by the downstream industry. Some steel companies also use the TMCP process to produce ultra-high-strength steel. The required microstructure, the grains, especially the grains ...

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Problems solved by technology

Although the thickness of the steel plate is 70-120mm, the yield strength is 460MPa and above, and the Charpy impact energy at the 1 / 4 thickness and 1 / 2 thickness of the steel plate at -60°C are both ≥ 100J, but this document involves medium and heavy plates, after rolling Straightening-stack slow cooling-quenching-tempering is required, the production process is long, the alloy contains Ni, Mo and other precious elements, and the cost of the alloy is high

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