What measures should be taken to prevent continuous casting billet from turning off at high drawing speed　　The rhombotropy is caused by the uneven coolin

　　What measures should be taken to prevent continuous casting billet from turning off at high drawing speed

　　The rhombotropy is caused by the uneven cooling of four sides of mold. Due to the constraints of the mold wall, before the mold comes out, the cast billet shell is square, the thickness of the single billet shell is not uniform, and the corner with strong cooling forms an acute Angle, while the corner with weak cooling forms an obtuse Angle. When spraying water for cooling in the secondary cooling zone, even if the four surfaces are cooled evenly, the temperature caused by the uneven thickness of the billet shell is inconsistent, resulting in the uneven shrinkage of the billet shell. At high drawing speed, the thickness of billet shell is reduced and it is easier to cause rhombohedral change. The following measures should be taken to prevent rhombotropy under high drawing speed:

　　1. Choose appropriate mold taper and inner cavity shape, such as parabolic mold taper, with appropriate protection slag, improve the contact state between the blank shell and the mold wall.

　　2. Optimize process parameters, such as thickness of copper tube of mold, pressure of cooling water, width of water seam and uniformity of four sides of water seam, upper and lower uniformity, flow rate and water quality, so as to improve the growth environment of green shell.

　　3. Support and alignment of the lower mouth of the crystallizer: the foot roller or multistage crystallizer is used to effectively support the billet and make it evenly cooled to obtain the billet shell of uniform thickness to prevent rhomboid change (off square).

　　4. Secondary cooling: reasonable setting of nozzle and secondary cooling system, such as weak cooling at the corner, can prevent rhombotrin (off).

　　5, low temperature casting, reduce the superheat of molten steel.