A control method for reticular cracks in continuous casting billet of low-carbon aluminum-containing cold heading steel

Abstract

The invention provides a low carbon aluminum containing cold heading steel continuous casting billet net-shaped crack control method. According to a smelting process, molten iron desulphurization pretreatment, converter smelting, LF furnace refining and continuous casting are sequentially carried out, and steel ladle and alloy baking is carried out; in the LF refining process, foaming slag is prepared, submerged arc heating is carried out, micro-positive pressure operation is carried out, the increase nitrogen is smaller than 0.0005%, and the [Mn] / [S] ratio is controlled to range from 80 to 100; continuous casting protective slag and a tundish covering agent H2O are smaller than or equal to 0.4%, tundish cover argon blowing is carried out before pouring starting, argon blowing protection is carried out on sliding plates of a long nozzle and a submersed nozzle in the pouring process, the argon flow is 4 L / min to 6 L / min, and the T[O] is controlled to be smaller than 0.0015%; [N] in tundish molten steel is smaller than 60 ppm, the precipitation amount and the precipitation size of AlN in a casting billet are reduced, and [H] is smaller than 0.0004%; and straightening is carried out with the casting blank surface temperature higher than the steel ball brittleness zone temperature, the specific water flow is controlled to range from 0.8 L / kg to 0.9 L / kg. By means of the low carbonaluminum containing cold heading steel continuous casting billet net-shaped crack control method, the surface quality of the low carbon aluminum containing cold heading steel continuous casting billetcan be improved, the occurrence rate of a net-shaped crack is effectively controlled, the depth of the net-shaped crack is reduced, and the polishing cost of the casting billet is reduced.

Description

technical field [0001] The invention belongs to the technical field of continuous casting, and in particular relates to a method for controlling reticular cracks of a continuous casting billet of low-carbon aluminum-containing cold heading steel. Background technique [0002] Low-carbon aluminum-containing cold heading steel is mainly used to manufacture bolts, screws, rivets and pins. It 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 SWRCH18A and SWRCH22A, and the aluminum content is generally required to be 0.03-0.06%. The typical production process of low-carbon aluminum-containing cold heading steel is: molten iron—converter—refining—continuous casting—slab inspection—slab opening, continuous rolling—slab grinding—high-end hot-rolled wire rod—finished product inspection—into library. The productio...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to control the [Mn] / [S] ratio in the steel, the moisture content in the mold flux, the total amount of [N]+[O]+[H] in molten steel and reduce the specific water in the secondary cooling zone, thereby Solving the problem of reticular cracks in low-carbon aluminum-containing cold heading steel continuous casting billets