A method for preparing a superfine-grained ferritic low-alloy steel thick plate

Abstract

The invention provides a manufacturing method of a low alloy steel thick plate with surface-layer ultra-fine grain ferrite, and belongs to the technical field of low alloy steel production. According to the control technical parameters, the manufacturing method comprises the technological steps that the reheating temperature of a plate blank processed before rolling ranges from 1050 DEG C to 1200 DEG C; in the rough rolling stage, the rolling temperature ranges from the austenite recrystallization final temperature Tnr DEG C to (Tnr+100) DEG C; accelerated cooling is conducted on the surface of an intermediate blank at the speed ranging from 6 DEG C / s to 33 DEG C / s so that the temperature of the surface of the intermediate blank can range from Ar3 to Ms, the rolling temperature of each pass of finish rolling ranges from (Ac1+40) DEG C to A3 DEG C, and the average strain rate of the passes ranges from 0.2s<-1> to 6s<-1>; and after rolling is finished, the steel plate is quickly cooled at the speed ranging from 6 DEG C / s to 24 DEG C / s, the re-reddening temperature of the steel plate ranges from 600 DEG C to 420 DEG C, and then air cooling is conducted. The manufacturing method has the advantages that tempered martensite, bainite structures and deformation ferritic structures easily formed on the surface of the thick steel plate in the temperature return rolling technology utilization process can be avoided, or the quantities of the tempered martensite, the bainite structures and the deformation ferritic structures can be reduced, and therefore the negative influence of the tempered martensite, the bainite structures and the deformation ferritic structures on the crack arrest toughness and the overall combination property of the thick steel plate with surface-layer ultra-fine grains is reduced.

Description

technical field [0001] The invention belongs to the technical field of low-alloy steel thick plate production, in particular to a method for preparing a surface-layer ultrafine-grained ferrite low-alloy steel thick plate. Background technique [0002] Among the various strengthening mechanisms of steel, microstructure refinement is the only method that can simultaneously improve the strength and toughness of steel plates. For thick steel plates, affected by the deformation conditions and cooling conditions of the steel plate along the thickness direction, it is very difficult to obtain a uniform ultra-fine structure from the surface to the center of the thick steel plate, but it is necessary to achieve ultra-fine structure within a certain thickness of the surface layer. possible. Research in recent years has shown that the ferrite structure with ultra-fine grain size has good low temperature toughness and high strength level, and the thick steel plate with ultra-fine grain...

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Problems solved by technology

The above three patents describe the control of temperature, deformation, etc. in the tempering rolling process in the preparation method, which will affect the strain accumulation, recrystallization or phase transformation of austenite or ferrite during the deformation process, and then affect the An important process parameter for the formation of ultrafine grains on the surface - strain rate is not described

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