An Assessment of Maraging Steel for Aircraft Applications

Extract

Mr. Haynes in his contribution to the Symposium, and also in previously published papers, has very adequately described the general development, advantages and characteristics of the maraging steels. However, as much of the information which he has given relates to the work done in the laboratories of International Nickel, and because we have only been able to find relatively little information available relating to production experience, we at Dowty Rotol set out to investigate the problems of steel making, forging, and resultant mechanical properties to be obtained under more normal production conditions. As landing gear manufacturers, our prime interest lies in the production of relatively large forgings of somewhat complex shape, and we were therefore particularly anxious to investigate first of all that our normal steel suppliers could produce material to the correct composition, that the material would forge as easily as conventional material, and that the subsequent forgings possessed adequate trans-verse properties, particularly insofar as ductility is concerned. In this latter connection, we had heard of certain difficulties encountered in the USA relating to inadequate ductility in large forgings, which they had concluded was related to the carbon and sulphur content of the steel: i.e. that it was essential to eliminate brittle intermetallic compounds such as titanium carbo-nitrides and titanium sulphides from the steel.