低炭素鋼線材のひずみ時効におよぼすTi添加の影響

抄録

A study has been made on the effect of the addition of titanium to reduce strain aging of low-carbon steel wire rod during cold forming. The effects of the conditions of wire rod rolling and subsequent cooling on the precipitation behavior of TiC and also the effect of the reduction of strain aging on both flow stress and work hardening have been investigated by adding titanium to low-carbon steels of carbon contents of 0.005 and 0.02 mass%. The results obtained are as follows.
(1) The precipitation rate of TiC in ferrite phase is highest at approximately 1 073K. The precipitates observed are pure TiC and the complex precipitates of TiC nucleated on Ti₄C₂S₂ or Ti₂S precipitates.
(2) When a small amount of titanium is added to the low-carbon steel wire rod, the strength of the wire rod is increased by the precipitation hardening caused by TiC.
(3) In the case of ordinary rolling, the minimum amount of titanium for the prevention of strain aging is over three times more than the stoichiometric amount for 0.005 mass% carbon steels, and is approximately twice as much as the stoichiometric amount for 0.02 mass% carbon steels. The minimum amount of titanium is remarkably reduced by controlled rolling.
(4) The amount of work hardening by wire drawing and flow stress in the high-speed compression test were reduced by approximately 27% and 15%, respectively, by the prevention of strain aging.