Steel plate with excellent low-temperature toughness in large heat-input weld heat affected zone and production method thereof

Abstract

The invention discloses a steel plate with excellent low-temperature toughness in a large heat-input weld heat affected zone, which comprises the following chemical components in percentage by weight: 0.03-0.06% of C, 0.05-0.12% of Si, 1.30-1.60% of Mn, 0.007-0.015% of Nb, 0.007-0.015% of Ti, at most 0.01% of Al, 0.0035-0.0060% of N, at most 0.009% of P, at most 0.0052% of S and the balance of Fe and inevitable impurities. The invention adopts a low-C low-Si low-Al high-Mn-Nb microalloy composition, and the Ti/N ratio is 2.0-3.0. The production method adopts an advanced TMCP-AcC technique, so that the steel plate microstructure is an acicular ferrite of which the dimension is at most 10 mu m, and has excellent strength and low-temperature toughness; under the condition that the weld heat input is up to 200kJ/cm, the Charpy impact work of the weld heat affected zone at -20 DEG C is at least 179J; and the invention is applicable to ships, low-temperature pressure containers, ocean platforms and the like.

Description

technical field [0001] The invention belongs to the field of low-alloy low-temperature steel medium-thick plate manufacturing, and particularly relates to a steel plate with excellent low-temperature toughness in a large heat input welding heat-affected zone and a production method thereof. Background technique [0002] During the welding process of the steel plate, its structure and properties, especially the structure and properties of the welding heat-affected zone, will change. Usually when the welding heat input reaches 50-150kJ / cm, the toughness of the welding heat-affected zone will deteriorate sharply, even lower than the standard requirement value of the base metal. [0003] At present, the welding line energy that can be tolerated by steel used in ordinary ships, offshore platforms and other fields is about 30-40kJ / cm. The welding heat input used in construction practice is 25-30kJ / cm. According to the traditional welding method, for a 30mm thick plate, submerged...

AI Technical Summary

Problems solved by technology

It can be seen that the traditional welding method has low production efficiency, which will result in long construction period and high construction cost.

[0004] For ordinary steel plates, the high heat input welding technology will bring the following two problems: 1) the toughness of the welding heat-affected zone (HAZ) deteriorates; 2) the sensitivity to welding cold cracks increases, which brings difficulties to on-site welding construction

Although the welding performance has been improved, it is difficult to smelt the steel with this technology. The quality and performance of the steel are affected by various factors such as the oxygen content in the molten steel before deoxidation, the amount of alloy added, the way of addition, and temperature control. The control window is narrow, and there is a slight deviation, and the welding performance of the steel plate will fluctuate greatly, resulting in a low product qualification rate, which brings difficulties to the market application of this type of steel

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