A low-yield ratio steel plate with a yield strength of 690mpa and its preparation method

Abstract

The invention belongs to the technical field of iron and steel and in particular relates to a low-yield ratio steel plate with yield strength of 690MPa and a preparation method of the steel plate. The low-yield ratio steel plate with the yield strength of 690MPa comprises the following chemical components in percentage by weight: 0.04-0.10% of C, 0.20-0.40% of Si, 1.40-1.90% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.03-0.06% of Nb 0.008-0.025% of Ti, 0.10-0.40% of Cr, 0-0.20% of Ni, 0-0.25% of Mo, 0.015-0.050% of Als, 0.0008-0.0020% of B, less than or equal to 40ppm of N, less than or equal to 20ppm of O, less than or equal to 2ppm of H and balance of Fe and inevitable impurities, wherein Als is Alsol, and welding crack sensitivity index Pcm of the steel plate is less than or equal to 0.25%. The steel plate provided by the invention has superior integrated mechanical properties, is hardly crack or break and also has good plasticity, toughness, welding property and seismic performance.

Description

technical field [0001] The invention belongs to the technical field of iron and steel, in particular, the invention relates to a steel plate with a yield strength of 690 MPa and a low yield ratio steel plate and a preparation method thereof. Background technique [0002] Economic construction and social development require a large amount of high-strength steel. With the vigorous development of domestic steel structure industry, construction machinery, mining machinery and other industries, at the same time, in order to adapt to the large-scale, With the trend of high-strength market demand, the demand for high-strength, high-quality steel for construction machinery is increasingly strong. At the same time, in order to meet the requirements of high-strength steel for reducing the sensitivity of welding cracks, major iron and steel enterprises have invested a lot of manpower and material resources in research and development. [0003] In the Chinese patent CN101812634A, a met...

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Problems solved by technology

Although this patent also provides a production method of 80kg grade steel plate with low welding crack sensitivity, the disadvantage is that it fails to make full use of the fine grain, phase transformation and dislocation strengthening mechanism of controlled rolling and controlled cooling in the rolling process. At the same time, the steel plate also needs to be quenched and tempered off-line, resulting in an increase in production costs

Although this patent provides a method for producing 80kg-class steel with low welding crack sensitivity without any heat treatment, 0.04-0.12% of precious metal V is added, resulting in high cost of the steel alloy

[0005] In Chinese patent CN100439545C, a method for manufacturing 800MPa grade high-toughness and low-yield ratio thick steel plate is disclosed. 0.30% to 0.70% of precious metal Ni is added to the composition design of the steel, resulting in high alloy cost, and the steel plate The yield strength can only be guaranteed to be greater than 540MPa

[0006] After analyzing the existing technology, it is found that the yield strength of most of the steel plates in the published literature is not higher than 690MPa, or the yield strength reaches the level of 80kg, but the production cost is high and the yield strength ratio is high, and the safety is insufficient.

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