High-strength steel tube and heat treatment method of heat-treating the same

A high-strength steel tube heat-treating method of processing a steel tube to improve the mechanical properties of the steel tube, the heat treatment method comprising the steps of:

• forming a steel tube of a desired size by drawing a material of a steel alloyed with alloyants consisting of a C content of 0.22% by weight or below, a Si content of 0.55% by weight or below, a Mn content of 1.60% by weight or below, and a V content between 0.10 and 0.30% by weight;
• normalizing the steel tube by holding the steel tube at a temperature and for a time effective to cause V in the material to dissolve and precipitate in a solid solution such that, upon subsequent tempering, the steel tube can be formed with a bainite structure as its principal metallographic structure and with improved strength;
• slowly cooling the steel tube at a cooling rate between 20 and 200° C/min;
• and
• tempering the steel tube by heating the steel tube at a temperature between 500 and 700° C. and cooling to form the steel tube with a bainite structure as its principal metallographic structure.