Defects Cause And Control Of Continuous Casting Billet In Longsteel

According to Longsteel practical production, this research is based on the analysis of quality defects and influencing factors of continuous casting billets. By using system analysis technique, producing alignment-free method and macroscopic test, the converter smelting and tundish metallurgy process, mold parameters, casting temperature, secondary cooling water, casting speed and the adjusting of the arc and water-jet's accuracy in the billet are studied. The results showed that:The major factors of the breaking-off in Longsteel are the mould copper pipe wearing and assembling accuracy. The following factor is the safety of secondary water cooling system. The casting temperatures, casting speeds and injection flow deflection have a little effect on the breaking off.The major factors of the inner crack are the billet casting temperature and the casting speed. The reduction of casting speed is favor of preventions of inner crack. The casting speed should be 2.6～3.2m/min in the test. The reduction of overheating temperature in the tundish could eliminate the inner crack. The overheating temperature in the tundish is below 45℃.。The main factors of transverse crack are taper and material of the copper pipe for mould. But, the vibration parameters, temperature straightening of casting billet, molten steel composition have almost no effect on transverse crack.The main influential factor of billet inclusions is the link of smelting, and the liquid heightin tundish and the form of liquid in ladle lashed area also have significantly effects on inclusions. The billet inclusions could descend significantly after heightening 150mm to the tundish height and raising 150mm to the steel liquid level and using the current regulator in ladle lashed area.Through the research of the above items and the implement of the control measures, the billet breaking-off rate is less than 0.03%, the inclusions level reduced one grade, the transverse cracks are basically eliminated in the surface, and the qualified rate of the continuous casting billet in Longsteel reached to 99.93%.