60kg-level low-cost and high-toughness steel plate and production method thereof

Abstract

Disclosed are a 60kg-level low-cost and high-toughness steel plate and a production method thereof. The 60kg-level low-cost and high-toughness steel plate comprises, in weight percentage, 0.145%-0.185% of C, not less than 0.30% of Si, 1.35%-1.65% of Mn, not less than 0.013% of P, not less than 0.003% of S, not less than 0.25% of Cu, not less than 0.25% of Ni, 0.005%-0.015% of AlS, 0.150%-0.190% of V, 0.015%-0.020% of N, 0.001%-0.003% of Ca, and the balance of Fe and unavoidable impurities. Based on an alloyed component system of medium C, low Si, high Mn, ultralow AlA and high V with metallurgical technical control, RCR-NT (recrystallization controlled rolling-normalized tempering) processes are optimized, the microstructure of the finished steel plate includes even and small ferrite, pearlite and trace granular bainite, average grain size of the ferrite is smaller than 15 micrometers, even and fine match of high toughness and high plasticity is obtained, and the steel plate has extremely fine low-temperature toughness. The steel plate is especially applicable to large-sized steel structured containers, such as bearing components, petroleum storage tanks, mobile tankers and the like.

Description

Technical field [0001] The present invention relates to the manufacture of low-carbon, high-strength, low-alloy steel, in particular to a 60 kg-level low-cost, high-toughness steel plate and a manufacturing method thereof. The yield strength of the steel plate is ≥460MPa, the tensile strength is ≥600MPa, and the Charpy impact energy of -40°C ( Single value) ≥ 47J, excellent weldability. Background technique [0002] As we all know, low-carbon (high-strength) low-alloy steel is one of the most important engineering structural materials. It is widely used in oil and gas pipelines, offshore platforms, shipbuilding, bridge structures, boiler vessels, building structures, automobile industry, railway transportation and machinery manufacturing. in. The performance of low-carbon (high-strength) low-alloy steel depends on its chemical composition and the process system of the manufacturing process. Among them, strength, plasticity, toughness and weldability are the most important proper...

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Problems solved by technology

[0003] The traditional steel plate with tensile strength greater than 600MPa is mainly produced by reheating quenching + tempering (RQ+T), the so-called off-line quenching and tempering method, in order to ensure that the steel plate has sufficiently high strength, excellent low temperature toughness and microstructure With the uniform performance, it is inevitable to add alloy elements such as Cr, Mo, Ni, Cu, etc. to the steel, which will greatly increase the manufacturing cost, see Japanese patent No. 59-129724, flat 1-219121; It not only leads to high manufacturing cost of steel plate, but also relatively high carbon equivalent Ceq and welding cold crack sensitivity index Pcm, which brings great difficulties to on-site welding. The preheating temperature before welding is high, heat treatment is required after welding, and the welding processing cost increase, welding production efficiency decreases, and the working environment of the welding site deteriorates

A large number of existing patent documents only explain how to realize the strength and low-temperature toughness of the base metal of the quenched and tempered steel plate, so as to improve the weldability of the steel plate and obtain excellent low-temperature toughness of the welding heat-affected zone HAZ. Hardenability to ensure the strength and toughness of the steel plate and the uniformity of strength and toughness along the thickness direction of the steel plate. -308035, Ping 3-264614, Ping 2-250917, Ping 4-143246 and US Patent4855106, US Patent5183198, USPatent4137104

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