MANUFACTURE OF SEAMLESS STEEL TUBE AND MANDREL MILL USED THEREFOR

• Main Author: OCHI SHIGEHARU
• Format: Patent
• Language: English
• Published: 15.08.1995
• Edition: 6
• Subjects: MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVINGMATERIAL; PERFORMING OPERATIONS; PUNCHING METAL; ROLLING OF METAL; TRANSPORTING

PURPOSE:To provide a method for manufacturing a seamless steel tube excellent in the accuracy of outside diameter without generating defective biting and roll mark and mandrel mill used therefor in rolling technique using a two-roll mill of plural stands and four-roll mill of the stand of the final stage. CONSTITUTION:A tube stock is successively rolled with the two-roll mills for rolling of >=2 stands in which mandrel bars having the same diameter are used and which are continuously arranged in 90 deg. phase and next, shaping rolled with the two-roll mill for shaping from the direction inclined by 90 deg. to the rolling direction of the final stand of the two-roll mill for rolling. At last, the finished thickness of the steel tube is changed by rolling the tube stock with the four-roll mill from four directions that are inclined by 45 deg. to the rolling direction of the two-roll mill of the final stand and changing the rolling reduction in the two-roll mill and four-roll mill. Since the spreading of the steel tube is corrected into a circle with the two-roll mill for shaping on the inlet side of the four-roll mill, defective biting and roll mark are not generated and the steel tube excellent in the accuracy of outside diameter is obtained.