Alloy Steels and Their Application in the Automotive Industry 280058

AFTER outlining the progress of research in the development of the alloy steels, the author says that alloys of steel containing nickel, chromium, and nickel and chromium, are the most important to the automotive industry, which is especially interested in alloys containing up to 5.0 per cent of nickel and up to approximately 1.5 per cent of chromium, with the carbon content ranging from 0.10 to 0.50 per cent. The additions of these amounts do not materially change the nature of the metallographic constituents, but the elements exert their influence on the physical properties largely by altering the rate of the structural changes.
In straight carbon-steel, especially of large sections, it is not possible by quenching to retard the austenite transformation sufficiently to produce as good physical properties as are desired. The addition of a small percentage of the alloying elements under consideration makes it possible to retard the transformation more effectively and hence to produce better physical properties. Steels of these types show only slightly better non-corrosive properties than straight carbon-steels, and the reason for their wide use is the high physical-properties which will be brought about by heat-treatment. A detailed discussion of a so-called high-carbon Krupp type of steel containing about 1.5 per cent of chromium, 4.0 per cent of nickel and 0.30 per cent of carbon is given.
By increasing the content of nickel, the transformation range is finally lowered to a point below normal atmospheric temperature. Not even the change from austenite to martensite will take place, and the alloy steel will, therefore, be comparatively soft. About 25 per cent of nickel is required to produce the desired effect, and steels are produced which are not used exclusively because of their physical properties, but on account of their non-corrosive, non-scaling and heat-resisting qualities. Similar properties are found in silicon-chromium steels, in chromium steels of high nickel-content, in chromium-tungsten steels, and in the high-chromium steels, the last mentioned being called stainless steel. It is stated also that the alloy steel to select is in many cases determined wholly by price, and in other cases with regard to what physical properties are desired together with the so-called stainless properties. Finally, consideration must be given to the corrosive agents with which the alloy steel will come into contact. Details concerning the mechanism of corrosion are given, and an explanation of why it is that certain types of alloy steel are more stain resisting than others is made.
Technical details relating to transverse and bending tests, and to the corrosive and non-corrosive properties of the alloy steels, are the main topics of the discussion which follows the paper.


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