Quenching machine accelerated cooling method for improving strength of normalized steel plate with thickness specification of being greater than or equal to 50 mm

Abstract

The invention discloses a quenching machine accelerated cooling method for improving the strength of a normalized steel plate with the thickness specification of being greater than or equal to 50 mm. The quenching machine accelerated cooling method comprises the following steps: the normalized steel plate enters a quenching machine along a quenching machine roller way after being discharged from a quenching furnace to be subjected to water cooling, four or six low-pressure sections are confirmed to be opened according to steel varieties and specifications, and the opening degrees, the upper and lower opening degree ratios and the roller way speeds of the areas of the low-pressure sections are adjusted, so that the steel plate is naturally cooled after the 'self-tempering' temperature reaches 580-630 DEG C, wherein the water yield control parameters are as follows: the opening degree of a flow control valve at the 15 area of the low-pressure sections is 30-40%, and the opening degree of a flow control valve at the 16 area of the low-pressure sections is 35-50%; the opening degree of a flow control valve at the 17 area of the low-pressure sections is 40-50%, and the opening degree of a flow control valve at the 18 area of the low-pressure sections is 45-60%; the opening degree of a flow control valve at the 19 area of the low-pressure sections is 60-70%, and the opening degree of a flow control valve at the 20 area of the low-pressure sections is 65-80%; the steel plate cooling speed is controlled to be 8-10 DEG C / S. The water cooling uniformity is good, the plate form after the cooling is good, and the strength of the normalized steel plate can be greatly improved through water cooling.

Description

technical field [0001] The invention belongs to the technical field of normalizing and cooling control for wide and thick plates, and in particular provides an accelerated cooling method for a quenching machine for increasing the strength of normalizing steel plates with a thickness ≥ 50 mm. Background technique [0002] Low-alloy high-strength steel plates generally refer to structural steel plates with a yield strength of 460MPa and below. Steel plates with specifications ≥ 50 mm are usually delivered in a normalized state. After normalizing, the steel plate has little strength margin, especially the yield strength. It is close to or lower than the lower limit of the standard; in addition, for steel plates with specifications ≥50mm that are produced by controlled rolling (controlled cooling) technology, if the plate shape does not conform, it is difficult to save the plate shape through the straightening process, and the normalizing process is usually used to save it. The ...

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Problems solved by technology

[0006] The object of the present invention is to provide a quenching machine accelerated cooling method for improving the strength of the normalized steel plate with a thickness ≥ 50 mm, which solves the problem of low strength of the steel plate after normalizing, and the steel plate is under the condition of multiple batches of low-pressure sections and large water volumes. The uniformity of water cooling is good, and the shape of the plate after cooling is good. At the same time, water cooling increases the ferrite nucleation rate, inhibits the growth of grains, achieves the purpose of refining grains, and improves the strength of normalized steel plates.

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