HEAT TREATMENT OF PC STEEL BAR OR STEEL WIRE

摘要

PURPOSE:To improve uniform elongation markedly without degrading strength by quickly cooling a PC steel bar or steel wire contg. specific ratios of C, Si, Mn, Cr down to specific temps. and holding the same at these temp. until bainite transformation ends. CONSTITUTION:A PC steel bar or steel wire contg. 0.30-0.80% C, 0.50-2.00% Si, 0.3-2.00% Mn, and 0.30-2.00% Cr as essential components is quickly cooled from an austenite area to temps. above the martensite formation temp. and = 550 deg.C. Here, the rate of quick cooling is set about =20 deg.C/sec. After the quick cooling, it is held in the bainite area above the Ms point until bainite structure is completed, and =550 deg.C is preferable. It is then cooled as it is or, further it is tempered. In the case of increasing deoxidation, strength and toughness, 1 or =2 kinds of Al, Mo, Ni, V, Nb, Ta, Ti, B are contained at about 0.01-0.50%.