PURPOSE: To ensure quality equal to that of products by mandrel rolling and to improve rolling efficiency by constituting a rolling mill train of a 2-roll type and 4-roll type rolling mills as an alternative rolling method of an existing plug mill.
CONSTITUTION: A mandrel bar 4 whose axial center is made to coincide with the center of the pass line is provided on the inlet side of a rolling line and a 1st and 2nd rolling stands 14, 15 are arranged at the rear of it. The 1st stand 14 is taken as the 2-roll type rolling mill consisting of two opposite rolls 1 having an elliptic groove to improve the biting property of a material 3 to be rolled at the 2nd stand 15 and the 2nd stand 15 is taken as the 4-roll type rolling mill having two set of circularily grooved roll pairs 5, 6 to ensure rolling- reduction of a degree equal to that of the plug mill and prevent fin flaws from the opening of roll. During rolling, the mandrel bar 4 which is inserted through the material 3 to be rolled is moved inversely to the rolling direction with a retainer 10 and detached from the material 4 at the time of completing rolling.
HAMAUZU SHUICHI
FURUKAWA TSUNEHISA
YAMAMOTO SHUJI
NARASAKI KOJI
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