Research And Application Of Low-Cost Q345Wide And Heavy Steel Plate Production Process

In the current, iron and steel industry requires producing low-cost, high property and saving-type products under the background of construction of economical society. As a result, more and more iron and steel enterprise pay attention to the reduced rolling process.The work of this dissertation were carried out integrating with the project of "Research on Reduced Rolling Process of High Toughness Low Alloy Heavy Plate", which were supported by a research and development center on wide and heavy steel plate. The industrial trials of20mm-60mm gauge Q345heavy steel plate were conducted by using reasonable two-stage TMCP process which were based on the research of the austenite deformation behavior at high temperature and phase transformation during continuous cooling conditions. And Mn element content was cutted down by0.2%-0.4%. Meanwhile,100mm-160mm gauge Q345B ultra-heavy steel plate was successfully realized in industrial production by optimizing RCR+ACC processes. The main work involved as follows:(1) Regarding the Q345steel as the research object, the influence of the deforming temperature, deforming degree and deforming rate to the stress of the steel was researched by single-pass compression. At the same time, the mathematical model of resistance of deformation and hot working equation was established. The behavior of static recrystallization during constant temperature after the hot deformation of the steel was studied by double-pass compression method. The softening rate curve of the steel to be tested was drawn. The activation energy of static recrystallization was180.73kJ/mol and the dynamic model of static recrystallization was set up.(2) According to the research of the austenite phase transformation during continuous cooling conditions, the results were shown as follows:deformation promots the transformation from austenite to ferrite; higher deformation temperature increases the critical cooling rate of bainite; the transformation temperatures of ferrite and bainite decrease with the increase of the Mn content.(3) The industrial trials of20mm-60mm gauge low-cost Q345heavy steel plate were conducted by using reasonable two-stage TMCP process. The microstructure and properties of the products were good. In the industrial trials, Mn element content was cutted down by0.2%-0.4%, as a result, the cost of steel per ton decreased by20Yuan-30Yuan.(4) According to the production characteristics of ultra-heavy steel plate,100mm-160mm gauge Q345B ultra-heavy steel plate was successfully realized in industrial production by using recrystallization control rolling and accelerated cooling (RCR+ACC) processes with non-microalloyed continuous cast slabs. The RCR+ACC processes were conducted through developing equipment potentialities and control process system strictly. Comparing with the TMCP process, the RCR+ACC processes can improve the good interior quality, short the rolling cycle and increase production efficiency.