Abstract: A heat treatment method of heat-treating a steel tube provides the steel tube with satisfactory workability and high pressure resistance capable of coping with a recent increasing trend of pressure dealt with by a recent common rail type fuel injection system. A steel tube of a desired size is formed by drawing a material of a steel containing at least vanadium. The steel tube is processed for normalizing by holding the steel tube at high temperatures between 950 and 1000° C. for a predetermined time and slowly cooling the steel tube at a predetermined cooling rate. Then, the steel tube is processed for tempering by heating the steel tube at a temperature between 500 and 700° C. and cooling the steel tube to an ordinary temperature at an optional cooling rate.

Abstract: A heat treatment method of heat-treating a steel tube provides the steel tube with satisfactory workability and high pressure resistance capable of coping with a recent increasing trend of pressure dealt with by a recent common rail type fuel injection system. A steel tube of a desired size is formed by drawing a material of a steel containing at least vanadium. The steel tube is processed for normalizing by holding the steel tube at high temperatures between 950 and 1000° C. for a predetermined time and slowly cooling the steel tube at a predetermined cooling rate. Then, the steel tube is processed for tempering by heating the steel tube at a temperature between 500 and 700° C. and cooling the steel tube to an ordinary temperature at an optional cooling rate.