Method for preventing surface cracks of thick plates in direct hot charge rolling

Abstract

Provided is a method for preventing surface cracks of thick plates in direct hot charge rolling. For the two types of steel AH32 and AH36, Nb of AH32 is controlled to be within 0.03%-0.04%, Nb of AH36 is controlled within 0.04%-0.05%, Ti of AH32 and Ti of AH36 are controlled within 0.010%-0.015%, S of AH32 and S of AH36 are controlled to be smaller than or equal to 0.03%, and H of AH32 and H of AH36 are controlled to be smaller than or equal to 0.0002%; a casting blank discharged out of a crystallizer is subjected to weak cooling, the surface temperature of the casting blank discharged out of a straightening segment is 920-950 DEG C, the casting blank discharged out of the straightening segment is subjected to air cooling and primary and secondary cutting sizing and then directly fed into a heating furnace, the surface temperature of the casting blank is higher than or equal to 800 DEG C before the casting blank is fed into the heating furnace, and the reduction rate of the first rolling pass is 15%-20%. According to another scheme, the casting blank discharged out of a casting machine is subjected to forced cooling on the basis of the previous treatment, the cooling rate of a forced cooling segment is 35-40 DEG C/min, and the cooling time is 10 min. According to the method, the surface cracks, generated after intermediate rolling of AH32 and AH36, of the finished plates are avoided, and the quality passing percent of the thick plates is increased; meanwhile, heat energy of the casting blank is recycled, energy consumption of the heating furnace can be greatly reduced, production continuity can be improved, and production cost can be lowered.

Description

technical field [0001] The invention belongs to the technical field of metallurgical technology, and in particular relates to a method for preventing surface cracks of AH32 and AH36 steel grades produced by a slab direct-loading process for shipbuilding thick plates. Background technique [0002] A shipbuilding steel such as AH32 and AH36 thick slab cast slabs in a steel factory, when the direct loading process is adopted, cracks appear on the surface of the thick plate to varying degrees, which directly affects the surface quality pass rate of the thick plate, and has become a problem for the application of the direct loading process. problem. In order to meet the surface quality requirements of the steel plate, all shipbuilding steel had to be stacked and cooled before being sent to the heating furnace instead of direct loading, which limited the direct loading process. In the prior art, there are few direct-loading processes of thick steel plates for shipbuilding, and mo...

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Problems solved by technology

[0003] In the literature, the research is carried out in combination with the temperature of the slab before entering the furnace and the control of the metallographic structure, and seldom studies from the perspective of steel composition. Even if there is a solution, it is mostly analyzed from the perspective of hot delivery, and seldom mentions the direct solution of surface cracks in loaded and rolled thick plates, therefore, it is necessary to study