Low-temperature steel for large-line energy welding with yield ratio not more than 0.85 and production method of low-temperature steel

Abstract

The invention discloses low-temperature steel for large-line energy welding with a yield ratio being not more than 0.85. The low-temperature steel comprises the following components in percentage by weight: 0.04%-0.07% of C, not more than 0.20% of Si, 0.8%-1.2% of Mn, not more than 0.013% of P, not more than 0.003% of S, 0.35%-0.85% of Ni, 0.10%-0.30% of Cr, 0.008%-0.02% of Ti, 0.01%-0.02% of Nb and not more than 0.005% of N, wherein Pcm is equal to C+Si/30+(Mn+Cr+Cu)/20+Ni/60+Mo/15+V/10+5B being not more than 0.18%, Nb is not more than 0.358C, Ti/n is between 2.5 and 3.5. The low-temperature steel is prepared from the following steps: continuously casting the components into blank after desulphurization smelting; heating up the casting blanks; descaling by high-pressure water; rolling step by step; relaxing for 30-90 seconds; cooling; air cooling to the room temperature; tempering; and air-cooling to the room temperature. The yield ratio is not more than 0.85, and the impact work KV2 is not less than 60 J at -80 DEG C, and the impact work (Heat Affected Zone) is not less than 27J at -80 DEG C. The low-temperature steel has good low-temperature toughness and weldability.

Description

technical field [0001] The invention relates to a low-temperature steel and a production method thereof, in particular to a high heat input welding low-temperature steel with a yield ratio ≤ 0.85 and a production method thereof. Background technique [0002] With the continuous development of modern technology and the enlargement of various steel structures, people have put forward higher requirements for the strength, toughness, strong plasticity matching and weldability of steel, that is, while ensuring the low cost of manufacturing, the comprehensiveness of steel plates has been greatly improved. Mechanical properties and performance. On the premise of ensuring the tensile strength, reducing the yield ratio, that is, increasing the difference between TS and YS, can improve the stability and safety of the steel during use, and improve the safety, stability and cold and hot workability of the steel structure; At the same time, on the premise of optimizing the composition, ...

AI Technical Summary

Problems solved by technology

[0004] 1) More alloying elements are added, Cu, Cr, Nb and other components are high, and the Pcm value is high. At the same time, adding B and other elements can ensure excellent impact toughness according to the instructions, but the yield strength is high, and it is difficult to ensure that the yield ratio is ≤ 0.86, that is, there is potential instability and unsafety in the steel plate during use;

[0005] 2) The process is more complicated, and normalizing or tempering treatment is required, which increases the manufacturing cost;

[0006] 3) It does not specify how to reduce the yield strength under the premise of ensuring the tensile strength, that is, to reduce the yield strength ratio (US patent 4855106 US patent 4137104);

[0007] 4) The quantitative relationship between C, Nb, Ti, N, etc. is not given, resulting in unstable low-temperature toughness and HAZ zone performance of the steel plate, affecting the normal service life and safety of the steel plate

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