STEEL BAR OR STEEL WIRE FOR PRESTRESSED CONCRETE, HAVING HIGH STRENGTH AND HIGH WELDABILITY, AND PRODUCTION THEREOF

摘要

PURPOSE: To produce a steel bar or a steel wire for prestressed concrete having high strength and high weldability and excellent in mechanical properties by subjecting a steel bar or a steel wire, having a specific composition containing small amounts of Mo, etc., to hardening and tempering under respectively specified temp. conditions. ;CONSTITUTION: A carbon steel, which has a composition containing, by weight, 0.15≥0.40% C, 0.3-2.0% Si, 0.4-1.6% Mn, and 0.08-0.35% Mo or further containing 0.01-0.05% Ti and 0.0005-0.005% B and satisfying Si+4Mo≥1%, is used. After a pattern for increasing the adhesion of concrete is applied, if necessary, to the surface of a bar or wire of the above carbon steel, this bar or wire is heated, within 20sec, to 850-1050°C and hardened by quenching by means of water quenching. Successively, this bar or wire is heated rapidly within 25sec to a tempering temp. of 400-550°C and subjected, after the application of ≤3% bending strain if necessary, to rapid cooling to undergo heat treatment. By this method, the steel bar or the steel wire, having a fine structure of austenite crystalline particle size No. ≥9, increased in strength, reduced in high temp. relaxation value, and excellent in weldability, can be produced.;COPYRIGHT: (C)1996,JPO