Production method for controlling fault detection defect of medium thick plate Q345 steel

Abstract

The invention provides a production method for controlling fault detection defect of medium thick plate Q345 steel. The composition design is: 0.15-0.18% of C, 0.25-0.35% of Si, 1.1-1.2% of Mn, equal to or less than 0.018% of P, equal to or less than 0.008% of S, 0.025-0.04% of Al, 0.015-0.02% of Ti, and 0.002-0.004% of Ca; an Al-Ca refining agent is added during LF refining, the Al-Ca reining agent is began to feed into a steel ladle when the temperature reaches 1530 DEG C, and the addition amount is 0.5-1.0kg / t steel; the S content of the pretreated molten iron is 0.001-0.002%, and the tapping temperature of a converter is kept at 1620 DEG C to 1630 DEG C; the Al2O3 content of refined slag of an LF refining furnace is 30-35%, the delivery of current is 10min to 15min, and the final molten steel nitrogen content is 0.002-0.004%; and the molten steel liquid level of a casting pot is controlled to be 500mm to 550mm, and the steel ladle long nozzle is protected by argon seal, thus the nitrogen content of the continuous casting molten steel is enhanced by 0.0003-0.0008%, and the molten steel continuous casting temperature is 1525 DEG C to 1535 DEG C.

Description

technical field [0001] The invention relates to steelmaking and smelting and slab pouring technology, and the determined steel chemical composition and process route are especially suitable for reducing the flaw detection defects of Q345 and ensuring the qualified flaw detection of Q345 steel plates. 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 ...

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Problems solved by technology

[0004] In order to meet the flaw detection standards of different countries, the existing technologies at home and abroad are concentrated on the production of pure steel, which puts forward strict requirements on the quantity of P / S, gas and inclusions in the steel, and also requires Ca treatment for inclusions, Make the denaturation of sulfide inclusions achieve spheroidization control, add VD / RH / VOD vacuum refining equipment to the steelmaking equipment, and adopt the process of converter (electric furnace) + refining + vacuum degassing (LD+LF+VD / RH), reaching the inner quality of pure steel, which can meet the requirement of 97% flaw detection pass rate; but due to the increase in the cost of adding a vacuum degassing treatment process, the iron and steel enterprises are also in a dilemma

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