Production method for low-alloy medium-thick steel plate

Abstract

The invention discloses a production method for a low-alloy medium-thick steel plate. The process route comprises the following stages in turn: converter steelmaking, external refining, continuous casting, heating, rolling, and accelerated cooling. Steel comprises the following components by weight percent: 0.15-0.17% of C, 0.20-0.40% of Si, 0.55-0.65% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.020-0.040% of Al, 0.014-0.016% of Nb, and less than or equal to 0.30% of CEV. The (P+F) micro-structural feature of the traditional Q345D steel plate is maintained by the steel plate; according to the design of the components of the steel plate, the Mn is reduced by 0.9%, no Ni is added and 0.015% of Nb is increased, so that the cost per ton of steel alloy is reduced; the Nb micro-alloying treatment is supplemented with TMCP (Thermo Mechanical Control Process) technology, so that the demand on the performance of the steel plate is met, the percentage elongation is increased by 2%-3% and the impact toughness is increased by about 90J; the CEV of the steel plate is reduced to below 0.30% and the welding property of the steel plate is greatly improved; and the measures, such as, the great reduction of the alloy, the eliminating of ladle furnace process route, the Direct Hot Charging Rolling (DHCR) of hot casting blank, and the like, are taken, so that the production cost of the steel plate is greatly lowered.

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 Q345D 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 Q345D steel in the standard is cancelled, and steel mills can produce qualified Q345D 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 the 16-60mm Q345D medium-thick steel plate produced by the TMCP process; the recommendation issue...

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

Images