MANUFACTURE OF SQUARE STEEL TUBE

PURPOSE:To manufacture of square steel tubes of a large sectional size by abutting the top end of a succeeding steel tube on the rear end of a preceding steel tube to provide a propelling force for the preceding tube by a pushing force of the succeeding tube. CONSTITUTION:A square steel tube rolling stand group 2 is composed of two front stage rolling stands No.1 and No.2 which restraint a tube whose sectional shape is still round and four rear stage stands No.3-No.6. A steel tube 1 introduced into a square steel tube rolling process is provided with a propelling force by being carried by the front stage stands No.1 and No.2 with the sectional shape of the tube 1 round and is rolled and formed into a square shape sequentially by the rear stage stands. In that time, the rear end 10 of the preceding tube 1 is abutted on the top end 10' of the succeeding tube 1' and is fully driven and propelled by the propelling force of the succeeding tube 1'. In this method, a driving and propelling force is given in the case of manufacture of large sectional size square steel tubes, so that those tubes can be manufactured.