CONTINUOUSLY CAST BILLET HAVING SUPERIOR CRACK SENSITIVITY AND ELIMINATING SOAKING AND DIFFUSION TREATMENT

摘要

PURPOSE:To obtain the titled continuously cast billet by restricting the space factor of a part having a specified concn. or above of segregated P in the total area of a sample having a restricted area taken out of the central part of a continuously cast billet. CONSTITUTION:A desired area 12 which is in a cross section of a continuously cast billet 10 in the lateral direction and includes the final solidification position 11 in the direction of the thickness is used as a sample. The area of the sample 12 is =0.04% of the cross-sectional area of the billet 10 in the lateral direction. The sample 12 is taken out and analyzed all over the surface. The space factor of a part contg. =0.1% P in the total area of the sample is restricted to =1%. The space factor of a part having =0.1% concn. of segregated P exerts considerable influence on HAZ cracking characteristics and wire breaking rate, so the desired billet can be obtd. by restricting the space factor as mentioned above.