Metallurgy Of Cast Iron

CHAPTER XXXIII.
EFFECT OF VARIATIONS IN TOTAL CARBON IN IRON.
By utilizing the twin shaft cupola shown on page 241, the author has made comparative tests in several different ways, in an effort to discover the effect o£ changes in the total carbon in iron, all other elements being held fairly constant. This is a most difficult factor to determine, owing to the difficulty of adding" carbon to iron as can be done with silicon and manganese. The author can now only present opinions founded on what might be called indirect tests. These tests, in brief, lead the author to say that an increase in the total carbon, with all other elements remaining fairly constant, increases the life or heat of molten metal, softens the iron, increases deflection and. decreases its strength. Where high carbon exists it may cause a kish or scum to rise, which may often be the means of producing dirty or porous castings. Such results can often be remedied by lowering the carbon in mixtures, by the addition of low carbon pig metal or steels, etc.
It has been suggested that more interest should be taken in utilizing the changes in the percentages of carbon to effect changes in the grade of an iron, than in variations of silicon, as commonly practiced. This is an impractical proposition, for the reason that changes brands of iron exceed 2.00 per cent, in silicon. This iron was obtained from the Jefferson Iron Co., Jefferson, Texas. The charcoal iron in heats Nos. 7 and 9 was kindly donated by the Seaman-Sleeth Co., Pitts-burg, Pa. Further information on the effects of manganese is found on pages 213 to 215.ng. All the bars poured with the iron .having manganese added in the cupola showed this effect to a greater or less degree. No doubt this is the cause of some castingsos. 4, 5, and 6, However, when we get to low silicon irons, as to.n. in ladle 1,772 Ibs. .100" -326 " I.IOO .242 3