Thick steel plate with excellent rack arrest property and preparation method of thick steel plate

Abstract

The invention belongs to the field of preparing steels and in particular relates to a thick steel plate with excellent rack arrest property and a preparation method of the thick steel plate. The thick steel plate is prepared from the following chemical components including a plain carbon steel or a microalloy steel. The preparation method comprises the following steps: water cooling while carrying out rolling deformation on a billet after being discharged out of a furnace, ensuring the temperature of the surface of the billet to be cooled to 400-800 DEG C during each rolling, ultra rapid cooling to 600-700 DEG C with the cooling speed to be larger than or equal to 15 DEG C / s after rolling is finished, and finally, air cooling to room temperature. According to the thick steel plate and the preparation method disclosed by the invention, the tissue of the thick steel plate takes ferrite as a parent phase and a second phase as a pearlite, the upper and lower surface layers of the thick steel plate are both an ultra-fine grain layer, the thickness of a single-sided ultra-fine grain layer is larger than or equal to 0.1 times of the thickness of the thick steel plate, the ferrite average grain size of each ultra-fine grain layer is smaller than or equal to 3 microns, and the grain boundary density of a large angle boundary is larger than or equal to 0.676 microns<-1>. The thick steel plate is excellent in rack arrest property and improved in core toughness and can be used for shipbuilding, in particular to structure materials of large container ships, offshore platforms, crude oil, natural gas conveying pipelines and the like.

Description

technical field [0001] The invention belongs to the field of steel product manufacturing, and in particular relates to a thick steel plate with excellent crack arrest performance and a manufacturing method thereof. Background technique [0002] For steels used in ships, buildings, bridges, marine structures, crude oil and natural gas pipelines, etc., in order to ensure the safety of use and avoid harm to the environment during use, it is required that the steel is difficult to brittle fracture, which requires the steel to have excellent Excellent crack arrest performance, so that brittle cracks can be quickly stopped during propagation. [0003] On the other hand, due to the need to reduce transportation costs, improve efficiency and reduce emissions, container ships are becoming larger. At the same time, with the recovery of the economy, the recovery of international trade has greatly increased the transportation volume of containers, further driving the demand for large c...

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Problems solved by technology

[0004] The methods for improving the crack arrest performance of steel plates in the prior art include adding alloying elements and refining the structure. For example, patent CN 101341269 B provides a kind of adding alloying elements Ni and The method of controlling the cooling rate after rolling is a method of developing a steel plate with excellent crack arrestability. The disadvantage of this method is that the precious metal Ni is used, which increases the cost, and at the same time increases the carbon equivalent Ceq, which deteriorates the weldability; The improvement is not very effective; the document "Development of thick steel plate with ultra-fine grain on the surface" (Zhao Sixin, Yao Liandeng, Zhao Xiaoting. World Steel, 2009, 5: 18-22.) proposes to use the traditional production line in the rolling process The ACC cooling system cools and controls the temperature of the billet to produce superfine-grained steel on the surface. The disadvantage of this method is that the ACC cooling system on the traditional production line is far away from the rolling mill, resulting in insufficient control freedom and low production efficiency; at the same time, ACC Insufficient cooling capacity of the cooling system

[0005]For the traditional controlled rolling and controlled cooling process (Thermal Mechanical C ontroll Pprocessing, TMCP) and a new generation of controlled rolling and controlled cooling process (New Ggeneration TMCP, NG-TMCP), in rolling Most of the steel billets are cooled in the air, so that the control method of the structure in hot rolling is relatively simple; at the same time, the temperature gradient in the thickness direction of the billet is small, and the deformation is difficult to penetrate deep into the core, which makes it difficult to guarantee the performance of the core of the thick steel plate

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