Low-temperature-resistant and easy-to-weld ultra-low-carbon steel thick plate and preparation method thereof

Abstract

The invention relates to a low-temperature-resistant and easy-to-weld ultra-low-carbon steel thick plate and a preparation method thereof. The low-carbon steel is prepared from the following components in percentage by weight: 0.04% to 0.07% of C, 0.15% to 0.35% of Si, 0.10% to 0.30% of Cr, 1.20% to 1.60% of Mn, 0.10% to 0.20% of Mo, 0.03% to 0.07% of Nb, 0.01% to 0.04% of V, 0.002% to 0.010% of Ti, 0.05% to 0.30% of Cu, 0.01% to 0.02% of Ni, 0.01% to 0.03% of Al, 0.0015% to 0.0050% of Ca and the like, and the balance of Fe and inevitable impurities; and steel making, continuous casting, heating, rough rolling, finish rolling and multi-stage cooling are adopted, the low-carbon steel with a ferrite and bainite dual-phase structure and small grain size is obtained, and the low-carbon steel has the advantages of being high in low-temperature strength, high in crack arrest toughness, low in yield ratio and the like.

Description

technical field [0001] The invention relates to the field of ultra-low carbon steel and its preparation, and specifically provides an ultra-low carbon steel thick plate that is resistant to low temperature and easy to weld and a preparation method thereof. Background technique [0002] With the optimization of the energy consumption structure, the demand for oil and gas will maintain a rapid growth trend, and most oil and gas resources will be transported through long-distance pipelines, and long-distance pipelines will face the challenges of complex and harsh service environments. Take the China-Myanmar line as an example , Yunnan, Guizhou, Sichuan, etc. are located on the Himalayan-Mediterranean seismic belt. They are the areas with the most intense seismic activity and frequent large earthquakes in China. At the same time, due to their high mountains, rainy and karst landforms, they are also important for debris flow and landslide disasters in my country. disaster areas, an...

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Problems solved by technology

[0003] In the prior art, patent CN112375997A discloses a manufacturing scheme of X70M ultra-low carbon steel plate used under ultra-low temperature conditions, adopts low-carbon composition design, and determines the effective rolling reduction rate of the final pass by studying the grain height and size , in order to ensure the strength and hardenability of the steel, the content of alloying elements such as Mo and Ni has been greatly increased, resulting in a decrease in the toughness of the steel plate and weakened weldability

In addition, the structure of the steel plate obtained by this technical scheme is mainly ferrite, which is not suitable for low temperature environment

Patent CN110616383B discloses a preparation scheme of ultra-low carbon steel for -45°C low temperature environment. It adopts the composition design of low C and micro Ti, cooperates with rolling high reduction, low temperature final rolling, rapid cooling and other processes to obtain relatively low carbon steel. High content of small-sized polygonal ferrite improves the low-temperature toughness of the steel plate, but the yield ratio at room temperature exceeds 0.82, and the resistance to large deformation is poor

It can be seen that the ultra-low carbon steel in the prior art cannot meet the needs of pipeline transportation steel pipes

In addition, the thickness of the steel plate prepared in the prior art does not match its performance, some have a large thickness and poor welding performance, and some have a small thickness but the mechanical properties of the steel cannot meet the requirements of the transportation pipeline

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