Low-temperature high-strength, high-toughness steel and preparing method therefor

Abstract

The invention relates to a low-temperature, high-intensity, high-toughness steel and the making method thereof, applicable to the environment down to -60 deg.C, adopting low-carbon Cr-Ni-Si-Mn-Mo-V alloy, and its chemical composition includes in mass percent (mass%): C: 0.16-0.24,Si:1.0-1.4, Mn:1.10-1.50,Cr:0.80-1.20,Ni:1.00- 1.40,Mo:0.20-0.40,V:0.05-0.20,S=<0.035,P=<0.035,Cu =<0.050, and the rest Fe. And its making method comprises: (1) smelting; (2) forging: heating at 1280-1320deg.C, where initial forging temperature: 1100-1250deg.C, final forging temperature >=850deg.C; annealing after forging, where heating temperature: 700+-30deg.C, and tapping temperature =<300deg.C; (3) thermal treatment: normalizing: air cooling at 930-950deg.C; tempering: air cooling at 790-720deg.C; quenching: oil cooling at 900-930deg.C; and tempering: air cooling at 200-260deg.C; (4) supersonic crack detection and magnetic particle crack detection. And it is especially applied to the materials for flying rings, hocks, pin shafts, etc, in the lifting systems of mechanical facilities.

Description

technical field [0001] The invention relates to a high-strength, high-toughness steel used in a low-temperature (low to -60°C) environment and a manufacturing method thereof, and is especially suitable for hoisting rings, hoisting rings, and hoisting rings in lifting systems of petroleum machinery, mining machinery, and construction machinery. Materials for hooks and pins. Background technique [0002] At present, the main stress-bearing parts such as lifting rings, lifting rings, hooks and pin shafts in petroleum machinery, mining machinery and construction machinery are required to be light in weight, high in safety factor, between 2.0 and 3.0, and able to serve at low temperature. The most authoritative American Petroleum Institute API Specification 8C 2003 edition requires that the V-notch impact energy Akv (-20°C) of the materials used in the lifting system should be ≥ 42J. When the design service temperature T is lower than -20°C, the additional requirement Akv (T)≥27...

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Problems solved by technology

[0005] Impact energy A listed in Table 1 k It is a U-notch impact specimen, and there is no impact energy data of a V-notch specimen. The parts manufactured according to this standard do not meet the requirements of the American Petroleum Institute API Specification 8C 2003 edition. To enter the international market, the lifting system material must meet the requirements of the American Petroleum Institute. According to the 2003 edition of APISpecification 8C, 40CrNiMoA steel is selected, although the impact energy is A Kv It can meet the requirements, but due to the low strength, under the premise of ensuring the safety factor, the part size is large and heavy, and it lacks competitiveness; the alloy elements are selected to meet the resource advantages of our country 20SiMn2MoVA steel, but the low temperature impact energy Akv (-40 ℃) and (-60°C) are 25J and 21J respectively, which cannot meet the requirement of Akv(T)≥27J in the 2003 edition of API Specification8C

Sampling and analysis of the products of BVM company in the United States, the physical characteristic index σ b ≥1382MPa, yield strength σ 0.2 ≥1159MPa, elongation δ 5 ≥12%, reduction of area ψ≥45%, V-notch impact energy Akv(-20℃)≥42J, Akv(-60℃)≥27J, but the content of precious metal Cr and Ni is as high as 4-5%, and the cost is relatively high high

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