Method for controlling medium-thick plate Q345 steel flaw detection defects

Abstract

The invention discloses a method for controlling medium-thick plate Q345 steel flaw detection defects. The method comprises the steps that the component weight ratio of Q345 steel is optimized, the method is applicable to the steel Q345B / C / D, the thickness H is smaller than or equal to 30 mm, and the steel is prepared from, by weight, 0.16 of C, 0.30 of Si, 1.15 of Mn, 0-0.018 of P, 0-0.008 of S, 0.025 of Al, 0.015 of Ti and 0.0020 of Ca; the [MnS] impurities in steel are controlled, the technological process comprises molten iron desulphurization, 120t revolving furnace, LF-slab continuous casting-heating furnace, medium plate rolling and ACC-collection, wherein the sulphur content [S] in molten iron is reduced to be smaller than 0.002% through molten iron desulphurization pretreatment, and the revolving furnace tapping [N] content is smaller than 0.002%; 2, the molten steel temperature and component accuracy are improved through the revolving furnace, and the revolving furnace tapping temperature is larger than 1620 DEG C; 3, LF slagging and desulfurization are carried out to remove impurities, AL-Ca refining agent is added in LF refining, 200 kg of AL-Ca refining agent is added after revolving furnace tapping, the LF refining final slag Al2O3 content is larger than 30%, the power supply time is controlled to be within 15 min, and the molten steel nitrogen content is smaller than 0.0040%; and 4, continuous protection casting is carried out, and the tundish molten steel temperature is controlled to be 1535-1515 DEG C during continuous casting.

Description

technical field [0001] The invention relates to a method for controlling flaw detection defects of medium-thick plate material Q345 steel. Background technique [0002] With the development of national economic construction, users have put forward higher and higher requirements for the mechanical properties and internal and external quality of steel plates. This requires that the P / S / gas (N / H / O) and inclusion content of the steel are low, that is to say, the steel has good purity and high density. The flaw detection test can macroscopically reflect the purity and density of steel. Steel plates that require flaw detection inspection and delivery are generally used to manufacture important structural parts in industries such as pressure vessels, power station projects, ships, bridges, military industries, high-rise buildings, and petrochemical industries. Flaw detection steel is a high value-added steel, which can bring considerable economic benefits to enterprises compared ...

AI Technical Summary

Problems solved by technology

[0006] Due to the segregation of carbon and manganese in the center, bainite structure appears in the center of the steel plate. Under the action of thermal stress and bainite structure stress, the steel plate produces cracks, which leads to failure of flaw detection.

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