Bearing steel billet center segregation by the molten steel of overheat, drawing speed, electromagnetic stirring and temperature of the secondary cooling zone and continuous casting machine equipment condition and other factors. So the prevention measures for:
1. The steel water of overheat control in the middle
Liquid steel superheat determines the inner quality of continuous casting billet continuous casting and macrostructure of the billets, when the internal cracks of macroscopic defects such as steel, the drain hole and shrinkage cavity appear, can through the rolling process of large compression ratio to improve and eliminate. So the heat appeared on the high side, production instability, should be small continuous casting and rolling specifications steel to be able to solve the problem.
SKF Bearings Construction steel casting process, on the premise of guarantee molten steel casting can be, and should use low superheat casting, usually bearing steel superheat control in 10-20 ?.
2. The control of carbon, phosphorus, sulphur
Carbon, phosphorus, sulfur, the segregation coefficient of three kinds of elements were higher. Sulfur in steel on the high side, in particular, will increase the brittleness of steel, cause the center segregation and inner crack of slab, greatly reduce the sulfur content, which reduced the steel hot brittleness, also is helpful to reduce the defects such as center segregation and inner crack.
3. The secondary cooling control
Bearing steel crack sensitivity is strong, if increase the intensity of secondary cooling zone, and increased the temperature gradient inside the slab cross section, increase the center segregation and cracking tendency. Therefore, the use of weak secondary cooling water distribution process, and guarantee the secondary cooling water distribution uniformity, can achieve the goal of reducing center segregation and crack.
4. Speed stability
System, formulate the right temperature speed by reducing steel superheat, casting speed, stable read and stabilize the liquid core length, reduce caused by drawing speed unstable casting billet insufficient liquid core steel liquid feeding, usually drawing speed control in 0.60 0.70 m/min, the control center segregation effect is obvious.
5. Using mold electromagnetic stirring and end
In the continuous casting billet, the higher the equiaxial crystal, the lighter the segregation. Mold electromagnetic stirring and the end of the electromagnetic stirring can effectively reduce the liquid steel superheat on the solidification of slab tissue, the effect of improving continuous casting equiaxial crystal of billet. Both the common use, and is good for reduce the center of the casting billet segregation.