PURPOSE: To dispose a build-up hardened layer in a required part by constituting a barrel part sleeve hollowed with a caliber of an upper layer ring and a lower layer ring, forming the build-up hardened layer on the outer periphery of the lower layer ring and forming the caliber to the build-up hardened layer from the upper layer ring to the lower layer ring.
CONSTITUTION: The barrel part sleeve 2 is constituted of the upper layer ring 3 and the lower layer ring 4 and the build-up hardened layer 5 having excellent wear resistance is formed in the recess on the outer periphery of the lower layer ring 4. The caliber 6 for rolling a steel pipe is hollowed to the build-up hardened layer 5 from the upper layer ring 3 to the lower layer ring 4. The bottom of the caliber for which the wear resistance is particularly requested is, therefore, formed to the build-up hardened layer and the upper part of the caliber where the wear resistance is not so much required is formed to the upper layer ring 3 formed of a proper roll material. Since the build-up hardened layer 5 is formed only in the lower layer ring 4, the roll is economical and is advantageously used.
YOSHINO SUETARO
NAKAI YUTAKA
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