The causes of surface cracks on continuous casting billet were investigatedContinuous casting is equipped with good molten steel refining ladle to rotary tabl
The causes of surface cracks on continuous casting billet were investigated
Continuous casting is equipped with good molten steel refining ladle to rotary table, and then turn to the pouring position, after the molten steel into the tundish and steel tundish again by the gate will be assigned to each crystal fitting, but notable is, cracks on slab surface will, it will affect the end ^ quality, must find out why.
Causes of continuous casting billet crack:
1, the temperature of molten steel is too high or too fast drawing speed is the main cause of longitudinal crack. Because it is difficult to cool the mold evenly, stress is always present. High temperature of molten steel, the billet shell is thin, low strength, small stress will tear the billet shell, causing longitudinal crack, high tensile speed and high temperature is the same reason.
2. The water inlet of tundish is misaligned with the water inlet of crystal fittings or the water inlet of casting is deformed, and the steel flow is offset. Close to the steel flow side, the growth of the billet shell slows down, the billet shell is thinned, resulting in cracks, and even steel flow directly scour the billet shell causing steel leakage.
3. The cooling water of crystal parts is insufficient, the water flow rate is low, the cooling water is partially boiling or the water flow is uneven, which will cause the cooling uneven crack.
4, crystal accessories use too long, copper tube damage, wear and deformation serious. In particular, the inverted taper becomes smaller, the air gap between the shell and the wall increases, the heat transfer is blocked, and it is easy to crack.
At the same time, it should also be noted that the fluidity of molten steel decreases rapidly with the decrease of temperature. The low temperature and high viscosity of molten steel make it easy for steel condensation to occur at the nozzle of the crystallizer, resulting in nozzle freezing and blockage. This kind of nozzle blockage mostly occurs in the first batch of cold tundish, large ladle replacement and large ladle table waiting for too long pouring time.
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