Causes and improvement measures of surface cracks in stainless steel continuous casting slabs

During the continuous casting process, the crystal strength of the slab pulled out from the mold is very small at the solidification interface. When the external force (thermal stress, bulging force, pull roller pressure, straightening force) on the slab exceeds the critical value, cracks are generated on the solid-liquid surface and expand along the columnar crystals until the solidified shell can resist external force.
There are several types of surface cracks: cracks traverse the thickness direction of the cast slab, and cracks in the central equiaxed grain area are curved along the grain boundaries. During the continuous casting process, the cast slab pulled out from the mold has a crystal strength at the solidification interface. Very small. When the external force (thermal stress, bulging force, roller pressure, straightening force) on the cast slab exceeds the critical value, cracks will occur on the solid-liquid surface and expand along the columnar crystals until the solidified shell can resist the external force. until.

There are several types of surface cracks: cracks traverse the thickness direction of the cast slab, cracks in the central equiaxed grain area are curvilinear and fine cracks along the grain boundaries, cracks on the inner arc side are generally linear cracks and cracks on the outer arc side are generally Intergranular cracks. Cracks along grain boundaries are stress cracks, while crack cracks are destructive cracks across grains and are the result of external forces.

Improvement measures are as follows:
(1) Improve the arc alignment accuracy of the casting machine, avoid excessive stress on the solid-liquid interface in the early stage of solidification, and prevent cracks along the grain boundary;
(2) Use methods such as appropriately accelerating the casting speed, increasing the cooling water volume within a certain range, increasing the water flow rate, and lowering the water temperature to achieve forced cooling;
(3) Strictly control the steel composition, especially the carbon content;
(4) Increase electromagnetic stirring in continuous casting and control the superheat of molten steel in the middle package below 40C.