Cast Iron in Its Relation to the Automotive Industry 270024
CAST iron is purchased on a basis of price instead of quality, according to the author, who says that this has depreciated the qualities of the material generally and caused engineers to look askance at its application. Combined with such factors is the influence of misinformation about cast iron that has been widely broadcast. Questions regarding the design of patterns and cheaper raw-materials have involved the foundrymen in controversial discussion concerning the influence of various elements to the detriment of the economic condition of the iron industry as well as that of the consumer of castings.
Due to the lessening of the consumption of cast iron, the foundry world has inaugurated research to better the quality of cast iron, not only through investigations of raw materials but also by improvement in melting practice. Although the accomplishment thus far attained has been small, the future outlook is that, due to the application of the results of research or by the use of alloys, the field for cast iron will become broadened. Then the engineer can obtain the material suitable for his needs and the foundryman will have a metal with the requisites suitable for foundry work.
The work of the metallurgists-microscopic, chemical and physical-has resulted in data which may help in overcoming previous prejudices. Some of the undesirable elements have been eliminated to overcome difficulties in casting, and yet this has been to the detriment of the physical qualities of cast iron; but when their proper relativity has been determined these elements will find their way back into the iron and better qualities will result.
The data presented tend to prove that true hardness is not measurable by any known test. Further, that the present hardness-test is not a function of machinability or of wear and that combined carbon bears little relation to any of these three factors. The governing features seem to be the forms of carbon, structure of the iron and quality of the materials used.
The method used in determining quality of material is that of dilatation. This test showed that the expansion of the casting is related to the expansion of the material used. It is felt that continual experimentation with this method will enlighten the many unanswerable questions which arise concerning cast iron at present.
Points brought out in the discussion of the paper include references to the variation in degree of “expansion” of cast iron, the effect of reheating and of high phosphorus-content on “growth,” the effect of lowering the content of silicon, and considerations regarding hardness. The influence of carbon is discussed also, as to the total amount present, the amount of carbon in its combined state and its micrographie structure. The inadequacy of checking the quality of cylinder-block castings by the physical properties of a test-specimen is stated, and the reasons are cited.