The weld seam is normalized and heat treated using a high-frequency induction heating machine. How to choose the holding time?

When a high-frequency induction heating machine is used for induction heating and normalizing heat treatment of welds, there are many factors that affect the normalizing effect, such as normalizing heating temperature, normalizing and holding time, etc. Today, the editor will tell you how to choose the normalizing and holding time for induction heating of welds.

Quenching, solid solution, and normalizing treatments are all heat treatment methods that heat the steel to the austenitizing temperature and then cool it at different cooling rates. From the perspective of the purpose of austenitizing, the three treatment methods are the same. The author conducted experiments to cancel the austenitization holding time for induction heating of low alloy steel quenching and solution treatment of austenitic heat-strength steel. The results show that as long as the induction heating quenching and solution temperatures are higher than the traditional treatment temperatures After 50-100℃, the same heat treatment effect can be achieved without holding time, the solid solution amount of strengthening elements is consistent, and the room temperature and high temperature mechanical properties after tempering and aging treatment are higher than those of traditional treatment processes. It can be seen that canceling the holding time during the induction heating normalizing treatment will not affect the subsequent heat treatment effect. The following table shows the mechanical properties of the 10-steel welded pipe after induction heating and annealing without holding time.

Effect of induction heating annealing on mechanical properties of 10 steel weld metal

In summary, for low-alloy hypoeutectoid steel, as long as the induction heating normalizing temperature is appropriately selected and the weld heating temperature is uniform, the normalizing and holding time can be completely canceled without affecting the heat treatment effect. Because, considering the phase transformation rate of the metal structure, temperature plays a decisive role, and the effect of temperature is far greater than the time factor. Trading temperature for time is a characteristic of induction heating rapid heat treatment.