Steel series with high linear energy and low weld crack sensitivity and its preparing process

Abstract

A high-strength steel as low-alloy steel contains low-C, Ti, Nb, B and two or more of Ni, V, Cu, Mo, Zr and RE, and is prepared through rolling and modifying heat-treatment to obtain high-toughness tempered sorbite texture and the high-smelting-point second-phase points and compound educed phase to suppress growth of welding coarse crystal region. Its advantages are high linear energy (60-70 kg) and low sensitivity to weld cracking.

Description

【Technical field】 [0001] The invention relates to a series of high-strength steels of 60kg and 70kg grades with large input energy and low welding crack sensitivity, which belong to the field of low-alloy steel manufacturing. 【Background technique】 [0002] Before the present invention, there is the patent (JP08232043) of Japanese Kawasaki application " by hot rolling, air accelerated cooling to form ferrite, pearlite and (or) bainite structure and be used for shipbuilding, bridge, pressure vessel etc. Energy welded steel", Japan's Nippon Steel applied for a patent (JP04346636) "Containing C, Mn, P, S, Al, B, N, Ni and (or) Cu HAZ with toughness of high manganese ultra-high strength steel", ( JP2704810, JP06049586) "The method of producing large heat input welding high-strength steel by forming MnS compound particles through complete deoxidation of Al". The disadvantage of the above three is that although the steel plates all have high heat input welding performance, they d...

AI Technical Summary

Problems solved by technology

The disadvantage of the above three is that although the steel plates have high heat input welding performance, they do not have low welding crack sensitivity.

Its disadvantage is that 0.30-0.80% Cr is added to the steel, which increases the production cost, and high Cr will cause tempering cracks and reduce the toughness of the steel

In addition, because the B content in the steel is very small, it is not conducive to the hardening of the steel plate, so the strength level of the steel plate is not high, and the lower limit of the tensile strength is only 570MPa, which cannot reach the level of 60kg and 70kg

[0003] Another example is the patent (JP08209238) applied by NKK "Manufacturing method of high-strength steel with excellent welding crack sensitivity obtained by heating Si, Mn, Mo, Ni, V, Al, Ti, B". Crack sensitivity and high heat input resistance welding performance, but the Nb and V content in the steel are limited by the formula 625Nb+250V+210Ceq=40+t (t is the thickness of the steel plate in mm), which is different from the composition design idea of ​​the steel of the present invention , and the patent does not show the specific strength level of the steel plate