Low welding crack sensitivity steel plate with yield strength of 690MPa grade and method for producing the same

Abstract

The invention provides a low crack sensitivity steel plate with the yield strength of 690MPa grade and a method for manufacturing the same. The chemical components of the low crack sensitivity steel plate are as follows: 0.03 to 0.06 weight percent of C, 0.05 to 0.40 weight percent of S, 1.30 to 2.00 weight percent of Mn, 0.05 to 0.15 weight percent of Cr, 0.10 to 0.25 weight percent of Mo, 0.03 to 0.08 weight percent of Nb, 0.04 to 0.12 weight percent of V, 0.02 to 0.04 weight percent of Al, 0.004 to 0.030 weight percent of Ti, 0.0010 to 0.0020 weight percent of B, and the balance being Fe and inevitable impurities, wherein the weld crack sensitivity index Pcm is less than or equal to 0.20 percent. The invention adopts a controlled thermo-mechanical rolling and cooling technology to obtain a matrix structure mainly based on a thinned bainite, which is advantageous for improving the steel strength, the plasticity and the toughness of the steel plate. The yield strength of the low weld crack sensitivity steel plate is greater than 690 MPa; the tensile strength is greater than 700 MPa; the Charpy impact energy Akv (20 DEG C below zero) is more than or equal to 150 J; the plate thickness can reach 60 millimeters; and the welding performance is good.

Description

technical field [0001] The invention relates to high-strength structural steel, in particular, the invention relates to a steel plate with a yield strength of 690 MPa and low crack sensitivity. Background technique [0002] Welding cold cracks are the most common welding process defects, especially when welding low- and medium-alloy strength steels. As the strength level increases, the tendency of cold cracks to appear is increasing. In order to prevent cold cracks, it is usually preheated before welding and heat treated after welding. The greater the strength, the higher the preheating temperature, which causes the complexity of the welding process and inoperability under special circumstances, endangering the safety of the welded structure Reliability, especially for large steel structures. In view of the characteristics of petrochemical, high-rise buildings, bridges, shipbuilding and other industries that do not preheat or post-weld heat treatment for large-scale high-st...

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Problems solved by technology

[0007] As can be seen from Table 1, except for the ultra-high-strength welded steel disclosed in WO99 / 05334, the chemical composition of the steel disclosed in other patent applications has added alloy element Ni to varying degrees. Increase the cost of steel and reduce its market competitiveness, and Ni will form oxide skin on the surface of the steel plate, affecting the surface quality of the steel plate

Except for WO99 / 05334, WO99 / 05335 and CN1932064, Cu is added to the chemical composition of the steel disclosed in other patent applications, and the precipitation of Cu is used to increase the strength of the steel plate, but Ni needs to be added at the same time to avoid copper brittleness, which further increases the strength of the steel plate. manufacturing cost

Although the steel grades disclosed in WO99 / 05334 and WO99 / 05335 are relatively simple in composition, they all adopt quenching treatment, which increases the production process of the steel plate, causes an increase in the production cost of the steel plate, and their Pcm values ​​are all relatively high, which has a great impact on weldability. have adverse effects

[0008] In addition, the steel types listed in Table 1 have been quenched + tempered or tempered, because the only way to reduce Pcm is to reduce the addition of carbon and alloy elements, and for high-strength steel produced by quenching + tempering process In general, reducing the addition of carbon and alloying elements will inevitably lead to a reduction in steel strength, and the manufacturing process is complicated

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