Cause Analysis and Improvement Measures of Surface Crack of Q355B Steel Thick Plate
Aiming at the surface crack problem of q355b steel plate in a steel plant,this paper analyzes the main reason for the surface crack of q355b steel plate by taking samples from the crack defect location for metallographic inspection and peeling inspection of the slab,and analyzes that the main reason for the surface crack of q355b steel plate is that the third brittleness temperature range of Nb strengthened slab is higher than that of Ti,and the pouring speed is reduced by 0.2 mgmin.When the slab is straightened,the surface temperature is just in the third brittleness temperature range,which is prone to crack.The bil-lets are directly heated and charged to the heating furnace.The precipitated ferrite and the precipitated second phase particles at the austenite grain boundary can not be fully re dissolved during the heating process,and cracks are easy to occur during the rolling process.In this paper,some measures are taken to reduce the probability of slab surface crack,such as optimizing the alloy,improving the cooling intensity of slab,appropriately increasing the pouring speed and slow cooling of slab.
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