Steel plate with low welding crack sensitivity and manufacturing method thereof

Abstract

The invention relates to a steel plate with low welding crack sensitivity and a manufacturing method thereof. The steel plate is composed of, by weight, 0.03%-0.09% of C, 0.20%-0.60% of Si, 1.40%-1.80% of Mn, 0-0.020% of P, 0-0.005% of S, 0.15%-0.45% of Cr, 0.03%-0.06% of Nb, 0.006%-0.04% of Ti, 0.015%-0.04% of Als, 0.0008%-0.003% of B, 0-0.04% of As, 0-0.03% of Sn, 0-0.005% of N, 0-0.003% of O, 0-0.0002% of H, and the balance Fe and inevitable impurities. By the adoption of the technologies of controlled rolling, relaxation and quick cooling, the heat treatment procedure of quenching and tempering or the heat treatment procedure of tempering or the like is not needed, the ultrafine bainite plate is obtained, and working procedure cost is reduced while strength, toughness and welding performance are guaranteed.

Description

technical field [0001] The invention belongs to the technical field of metallurgical manufacturing, and relates to a low welding crack sensitivity steel plate with a yield strength of 690 MPa and a manufacturing method thereof. Background technique [0002] With the development of construction machinery and coal mining machinery in the direction of large-scale equipment, light weight, and heavy loads, the strength of steel plates used has developed from the traditional yield strength of 460 to high-strength steels of 550 and 690 MPa, and the amount of high-strength steel plates has shown an increasing trend. [0003] In the prior art, there are documents introducing bainite high-strength steel and low crack sensitivity steel plate. [0004] Chinese patent CN1218115 discloses "copper-boron low-carbon and ultra-low-carbon bainite high-strength steel". Its composition design adopts the composite addition of ultra-low carbon to low carbon, copper and Nb, and uses elements such a...

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Problems solved by technology

[0004] Chinese patent CN1218115 discloses "copper-boron low-carbon and ultra-low-carbon bainite high-strength steel". Its composition design adopts the composite addition of ultra-low carbon to low carbon, copper and Nb, and uses elements such as copper and boron to promote bainite. Phase transformation, while using ε and Nb, Ti composite precipitation to obtain high strength; the disadvantage is that Cu element is added, the content is about 0.5%, the cost is high, and it increases the difficulty of smelting and continuous casting. If the heating temperature is not appropriate, Defects such as cracks are easy to appear on the surface of the steel plate, and the thickness of the steel plate that can be produced is only below 16mm

Using low-carbon micro-alloying design, through TMCP+tempering process, a matrix structure dominated by refined bainite is obtained, so as to obtain a good match of strength, plasticity and toughness. The disadvantage is that the alloy design also increases Cr, Mo and V, alloy cost increases, and tempering process is required to compensate for low elongation, increase heat treatment cost and affect delivery timeliness

The disadvantage is that the precious alloy Mo needs to be added, the cost of the alloy increases, and the toughness only meets -20°C, which cannot meet the requirements of higher toughness steel grades

Different degrees of pre-weld preheating and post-weld heat treatment are required during welding, which not only increases the production cost of steel enterprises, but also increases the production cost of downstream users

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