| 摘要 |
PURPOSE:To eliminate a welding crack at roll forming time and a crack near welding zone and to improve the yield by performing a roll expanding after heating and cutting a seamless steel pipe. CONSTITUTION:The seamless steel pipe 1 having the ratio t/D of the thickness (t) of the pipe to the outer diameter D being 2-3% is first manufactured. The seamless steel pipe 1 is then heated at 900-1,100 deg.C by a high frequency induction heating device at heating stage. A cylindrical body 2 is made by cutting in specific length by a cutter at cutting stage the seamless steel pipe 1 heated at specific temp. and this cylindrical body is rolled at its pipe wall thickness by a roll expander device at rolling stage to form a rim blank stock 3 having t/D=0.6-1.3% necessary as the rim for wheel. Then after removing the surface scale of the rim blank stock 3 by pickling, etc., the corner is rounded off by cutting the edge of both end faces or squeezing by a roller 4 and after making the edge in rounded shape, the rim member 9 having a rim flange part 6, bead seat part 7 and well part 8 is finished by a roll forming machine 5 at forming stage.
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