Preparation of normalizing weldable fine grain steel plate with a yield strength of 420MPa

Abstract

The invention provides a method for preparing normalized weldable fine-grain steel plates with the yield strength of 420 MPa, which belongs to the technical field of manufacturing medium thick steel plates. A production process comprises the following steps: a continuous casting billet is heated to be between 1,200 and 1,250 DEG C, and the heat is preserved for 4 to 5 hours; hot rolling is performed after heat preservation; rolling is divided into two stages, namely recrystallization zone rolling and non-recrystallization zone rolling; intermediate temperature waiting thickness is controlled to be between 2.5 and 4.0 times the thickness of a finished product; the initial rolling temperature of a non-recrystallization zone is controlled between 850 and 880 DEG C; the final rolling temperature is controlled between 810 and 830 DEG C; water cooling is performed after hot rolling; the final cooling temperature is controlled between 650 and 740 DEG C, and cooling rate is controlled between 5 and 8 DEG C per second; and the steel plates are normalized at a temperature between 880 and 910 DEG C and then are thermally insulated for 5 to 20 minutes. The method has the advantages that the steel plates are excellent in mechanical properties; the mechanical property of the steel plate can stably reach over 420 MPa; the tensile strength of the steel plates can stably reach over 550 MPa; and the V-type notched impact energy of the steel plates at 50 DEG C below zero can stably reach over 140 J.

Description

technical field [0001] The invention belongs to the technical field of medium-thick steel plate manufacturing, and in particular provides a preparation method of a normalizing weldable fine-grained steel plate with a yield strength of 420 MPa. This steel plate is prepared by controlled rolling + normalizing process, and has good welding performance. Background technique [0002] 420MPa normalizing weldable fine-grain steel plate is specially used for heavy-duty parts of welded structural parts under low temperature conditions, such as: bridges, flood gates, storage tanks, water supply tanks, etc. Since the steel plate is normalized, its strength requirement is high. At the same time, in order to ensure the good welding performance of the steel plate, the carbon equivalent of the steel plate should be reduced as much as possible; at the same time, it is required to have better low temperature impact toughness. These performance characteristics put forward higher requirements...

AI Technical Summary

Problems solved by technology

Due to the addition of a large amount of precious micro-alloying elements such as Mo, Cu, etc., the economic cost of the production unit has been increased; at the same time, the smelting and microstructure control of low-carbon steel (C≤0.06%) is difficult, and the production cost has always been high.

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