The New Technique of Steel Selection for Automotive Applications 650518
In steel for high hardness applications, heat to heat variation and inclusion character are more important to fatigue test results than relatively large variations in test temperature, analysis, or heat treating practice. This places’ the principal responsibility for performance of such steel parts with the steelmaker.
The two important types of inclusions in steel which adversely affect performance of fully heat treated parts in service are discussed. The presence of silicates in the heat of steel, combined with the aluminum added for grain size control, is indicated as the major single cause of harmful inclusions.
Elimination of the aluminum as a grain size control addition is strongly recommended, not only because it is the principal factor in forming crack nucleating refractory type inclusions but because of its adverse effect on sulfide inclusions.
The substitution of vanadium for aluminum as the grain size control addition is suggested. The resulting product is claimed to provide a step forward in both performance and overall economics.