Abstract
It is a well known fact that a steel containing over 0·5% of copper may have surface cracks when it is heated above 1, 100°C and subsequently forged. With increase of the copper content above 0·8%, the surface cracks will increase in number and size.
In order to prevent this defect of copper-bearing steels, the following methods were adopted.
1) Addition of a small amount of nickel.
2) Lowering the forging temperature below 1, 090°C.
For the experiment, 34 kinds of low carbon steel ingots, each of 6kg in weight and with various contents of copper and copper-nickel, were made with a high frequency induction furnace.
They were heated above 1, 200°C and forged to 20mm square bars with a forging ratio approximately 1/10. The bars were bent in both the hot and cold conditions and tested for surface cracks at the bent portion. The results of the experiment are summerized as follow;
1) The addition of 0·2-0·5% nickel to the copper-bearing steel (0·3-1·5% Cu) is effective for the prevention of heating of forging cracks in the steel, and the higher the copper content is, the greater the addition of nickel should be.
2)The lowering of the forging temperature below 1, 090°C inhibits the formation of heating or forging cracks in copper-bearing steel e.g.a steel containing 2·0% copper and 0·5% nickel which may crack in forging at 1, 200°C can be forged without cracking at 1, 050°C.
