PURPOSE: To obtains a pipe stock, used for a cylinder liner, of high quality, in high yield and high productivity, by rolling a stock of Cr-steel slab of specific composition, etc. into a round billet and forming it into a long-sized hollow tubular material by skew rolling, and successively cutting it into a prescribed length before increasing the wall thickness of one end of the unit tubular material by upset forging.
CONSTITUTION: A stock of Cr-steel slab or billet containing, by weight %, ≤0.5% C, ≤1.5% Si, ≤2.0% Mn, and 2W14% Cr, is hot rolled into a round billet, to pierce a hole in it by a piercer; then the billet is reduced in diam. and wall thickness by a mandrel mill and is further radially reduced by a stretch reducer. In this way, the billet, formed into a long-sized tubular material, is cut into an unit tubular material, which is formed into a titled pipe stock by heating its one end to increase the wall thickness thereof by upsetting. In this manner, many said pipe stocks free from defects such as a pin hole are manufactured from a single tubular material, and the cutting amount in the final machining is reduced to improve the yield of material.
NISHI HIROSHI
TERADA TOSHIHIRO
OTSUBO HIROSHI
TAKADA ISAO
DOI TAKEO
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