Method for producing ultra-fine grains on surface layer of thick/ultra-thick low-alloy steel plate

Abstract

The present invention involves a manufacturing method of a low -alloy steel plate. Specifically, it is a manufacturing method for the super fine crystal of low -alloy steel thick plates / extra thick plates; as follows: 1. Uniform heating plate blank 30-60min is released;2. Reduce the surface temperature of the middle blank at ≥10 ℃ / s to 350-550 ° C, wait for the return of red; 3. When the temperature of the surface layer of the middle blank is red to 850-960 ° C, multiple secondary rolling is performed.During the secondary track, the surface temperature of the board is quickly reduced to below AR1 at 10 ~ 80 ° C / s. After waiting for the return to red, the next rolling temperature is 780 ~ 850 ° C;20 ° C / s Fast cooling board blank, wait for the return of red to 250-400 ° C after returning to red, and stack cold; this method does not significantly increase the existing rolling load, make full use of the accumulated storage energy in the middle of the thick steel plate, control multiple times many times, and repeatedly control it.Cold the rolling and control the surface of the surface of the surface of the surface.

Description

technical field [0001] The invention relates to a method for manufacturing a low-alloy steel plate, in particular to a method for manufacturing ultra-fine crystals on the surface of a low-alloy steel thick plate / extra-thick plate. Background technique [0002] Steel structure refinement is an important method to ensure high strength and high toughness of steel plate; structure refinement: on the one hand, the austenite grains are refined, which provides more places for subsequent ferrite nucleation, so that ferrite On the other hand, rolling is carried out in a temperature region close to the two-phase region, so that the structure undergoes deformation and induces ferrite phase transformation, thereby refining the ferrite structure; in the production of steel plates, controlled rolling and controlled rolling are generally used. The cold method refines the microstructure of steel. However, for thick plates / extra-thick plates, due to their own thickness effects and production...

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Problems solved by technology

[0002]Steel structure refinement is an important method to ensure high strength and high toughness of steel plate; The ferrite nucleation provides more places, so that the ferrite grains are refined. On the other hand, rolling is carried out in a temperature region close to the two-phase region, so that the structure is deformed and the ferrite phase transformation is induced, so that the ferrite Microstructure refinement; In the production of steel plates, controlled rolling and controlled cooling methods are generally used to refine the microstructure of steel products. However, for thick plates / extra thick plates, due to their own thickness effects and production process characteristics, it is difficult to meet large deformation and Due to the high cooling rate and other conditions, it is difficult to achieve full-thickness microstructure refinement; therefore, it is feasible to only superfine microstructure on the surface of the steel plate and rationally refine microstructure in the center of the steel plate; The super-thick plate with crystal can hinder the crack propagation, has good surface toughness at low temperature, crack resistance and fatigue resistance, and has a good application prospect; search and find, patent publication number: CN101906519A "Low yield is lower than the surface ultrafine grain The manufacturing method of the carbon steel thick plate "and the patent publication number: CN102828116A " based on the TMCP process superfine grain high-strength steel plate and its manufacturing method" The patent discloses the superfine grain manufacturing method of the surface layer, all adopt the cooling after the rough rolling mill The device quickly cools the intermediate billet + warms up the process to achieve the refinement of the surface structure; this method has a certain effect on the refinement of the surface structure of the steel plate, but the refinement effect is not very obvious; especially for the steel plate with a finished thickness ≥ 40mm , because the middle billet is thicker and has a lot of heat in the core, it is difficult to achieve ultra-fine surface structure by a water spray cooling + reheating process for the middle billet

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