PURPOSE: To improve adhesion between steel material and concrete by forming scale of specific thickness on the surface of a PC steel material in which respective contents of C, Si, Mn, Ni, Cr, and N are specified.
CONSTITUTION: This non-magnetic steel material for prestressed concrete has a composition consisting of, by weight, 0.01-0.29% C, ≤1.0% Si, 8.0-20% Mn, 0.1-7.0% Ni, 10-25% Cr, 0.01-0.50% N, and the balance Fe with inevitable impurities. By subjecting this steel, e.g. to bluing in the air at about 400°C, a scale layer of ≥1μm thickness is formed on the surface of the steel material. By this method, a degree of adhesive stress of concrete equal to that of a ordinary PC steel stranded wire can be obtained. It is preferable to control bluing temp. to ≤550°C because excessively high bluing temp. causes too much reduction in strength or precipitation of carbides in grain boundaries and resulting deterioration in ductility of material.
YASUMATSU MAKOTO
IGARASHI MASAAKI
YAMAMOTO TAKASHI
KOYAMA SEIICHI
