Rapid Spheroidization Annealing Technique of Structural Steel Wire Rod
1983 Volume 69 Issue 10 Pages 1296-1302
Details
1983 Volume 69 Issue 10 Pages 1296-1302
A new rapid spheroidization annealing (RASA) method of wire rod has been developed to complete spheroidization within about 16 minutes. This method consists of two steps. The first step comprises heating rapidly up to a maximum temperature (TM) and cooling down to a temperature below A1 (TH) In the second step, the wire rod is held about 15 minutes at temperature TH. It has been revealed that there is an optimum combination of temperatures TM and TH for each steel to obtain a sufficiently spheroidized structure. The mechanism of RASA method is the same as that of conventional spheroi-dization. There are three different points between the two methods which cause the difference in duration time. First, the new method adopts rapid heating and cooling. Second, temperature TM of the new method is higher than that of the conventional method so as to shorten the austenitizing time. Thirdly, the holding time at temperature TH is shortened to suppress the total time within 16 minutes.
The strand heat treatment is suitable for this method, because the precise control of wire temperature is essential. The trial of RASA treatment adopting the strand treatment has been performed using gas furnace and induction furnace, and the good upsettability of treated wire has been confirmed.
Furthermore, the trial production of hexagon headed bolts using RASA treated wire has been done.
