Method for controlling cracking of low-carbon aluminum-containing cold forging steel continuous rolled billets

Abstract

The invention discloses a method for controlling cracking of low-carbon aluminum-containing cold forging steel continuous rolled billets. A converter ladle and alloy are roasted, and the effect that raw materials do not adsorb moisture is ensured; foaming slag is manufactured through LF refining, and submerged-arc heating is conducted; sealing between the ladle and a gas hood and the reducing atmosphere in a converter are ensured, micro-positive pressure operation is adopted, and nitrogen is increased by less than 0.0005% in the refining process; desulfurization treatment is conducted in the condition that Mn / S ranges from 80-100; the content of H2O of mold flux for continuous casting and a tundish covering agent is less than or equal to 0.4%, argon blowing protection is achieved on sliding plates between a long nozzle and a submerged nozzle in the casting process, argon flow is 4-6 L / min, TO is controlled to be less than 0.0015%, N of tundish molten steel is less than 0.0060%, and H of tundish molten steel is less than 0.0004%; straightening is conducted when the surface temperature of the cast billets is higher than the brittle area temperature of the steel, the specific water flow is 0.8-0.9 L / kg, and the straightening temperature is higher than 950 DEG C; and the heating time of a heating furnace is prolonged by 25-35 min, and the heating temperature is increased by 45-55 DEG C. Surface defects of the continuous rolled billets caused by cast billet map cracking can be removed or burnt, the polishing rate of the continuous rolled billets is lowered by 5%, the rejection rate is lowered, and the surface quality of steel plates is improved.

Description

technical field [0001] The invention belongs to the technical field of metallurgical technology, in particular to a method for controlling cracks in continuous rolling slabs of low-carbon aluminum-containing cold heading steel Background technique [0002] Aluminum-containing cold heading steel is mainly used to manufacture bolts, screws, rivets and pins, not only has excellent cold drawing performance, but also has good cold forging and cold extrusion performance. At present, most domestic enterprises refer to the Japanese Industrial Standards. For example, the grades are SWRCH12A and SWRCH622A, and the aluminum content is generally required to be 0.03-0.06%. Typical production process of aluminum-containing cold heading steel: molten iron—converter—refining—continuous casting—slab inspection—heating furnace heating—blooming and continuous rolling—slab grinding—high-end hot-rolled wire rod—finished product inspection— storage. After the molten steel is roughly smelted in ...

AI Technical Summary

Problems solved by technology

This process does not comprehensively consider the refining control of molten steel, the temperature control of the secondary cooling zone, etc., and cannot completely eliminate the network cracks on the surface of the continuous casting slab, let alone solve the crack defects of the continuous rolling slab