Production method for low-alloy medium-thick steel sheet

Abstract

The invention discloses a production method for a low-alloy medium-thick steel sheet. A process path comprises a converter steelmaking step, an external refining step, a continuous casting step, a heating step, a rolling step and an acceleration cooling step. The steel comprises the following components in percentage by weight: 0.15-0.17 percent of C, 0.20-0.40 percent of Si, 0.55-0.65 percent of Mn, not more than 0.020 percent of P, not more than 0.020 percent of S, 0.020-0.040 percent of Al, 0.014-0.016 percent of Nb and not more than 0.30 percent of CEV (Carbon Equivalent Volume). According to the production method disclosed by the invention, the microscopic structure characteristics of P plus F of a traditional Q345B steel plate are still maintained; in the design of steel plate components, the content of Mn is reduced by 0.9 percent, the content of Nb is increased by 0.015 percent and the cost of a ton-steel alloy is reduced; the Nb microalloying treatment technology is matched with a TMCP (Thermal Mechanical Control Processing) process, so that the requirement of the steel sheet on performance is met, the elongation percentage is improved by 2-3 percent and the impact ductility is improved by about 100J; the CEV of the steel sheet is reduced below 0.30 percent, and thus the welding performance of the steel sheet is greatly improved; and due to the adoption of measures of greatly reducing the alloy, removing a process path of a ladle furnace, direct hot charge rolling (DHCR) of a hot casting blank and the like, the production cost of the steel sheet is greatly reduced.

Description

technical field [0001] The invention belongs to the steelmaking technology, and relates to a production method of a low-alloy medium-thick steel plate. Background technique [0002] The Q345C steel plate with a thickness specification below 16mm can basically be mass-produced with a modern hot rolling mill and the economy is good, but the production economy of the medium-thick plate with a thickness specification of 16-60mm is poor, especially the national standard GB After the promulgation of / T 1591-2008, the lower limit of Mn content of Q345c steel in the standard is cancelled, and steel mills can produce qualified Q345C medium-thick steel plates by proposing suitable components and TMCP process according to their own process equipment production conditions. [0003] The national standard GB / T 1591-2008 has specific requirements for the chemical composition and performance of 16-60mm Q345C medium-thick steel plates produced by the TMCP process; the recommendation issued b...

AI Technical Summary

Problems solved by technology

[0026] In summary, the main defects of the low-alloy medium-heavy plate produced by the TMCP process in the prior art are: the low-alloy medium-heavy plate produced by the TMCP process has a high Mn content, the center segregation of the continuous casting slab is serious, and there are local defects in the rolled steel plate. Delamination, segregation of the center line of the steel plate often forms martensite or bainite structure, resulting in unqualified impact; in order to ensure the quality of continuous casting slabs, molten steel must be refined outside the furnace

After entering the ladle furnace, desulfurization and temperature adjustment are carried out, which increases the production cost; the high Mn content causes the steel plate to have a high carbon equivalent and poor welding performance; each steel mill is equipped with a modern medium and heavy plate rolling mill, and its capacity cannot be fully utilized, wasting production resource

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