═══════════════════╤═══════════╤══════════╤═════════╤══════════ │ Silicon │Manganese │ Sulphur │Phosphorus │ │ │ │ ───────────────────┼────┬──────┼────┬─────┼───┬─────┼────┬───── │Wt. │ Vol. │Wt. │Vol. │Wt.│Vol. │Wt. │Vol. ───────────────────┼────┼──────┼────┼─────┼───┼─────┼────┼───── Gray Cast Iron │2.50│=10.0=│ .70│ =.7=│.09│=.36=│ .75│=3.2= Semi-Steel │1.75│ =7.0=│1.00│=1.0=│.10│=.40=│ .35│=1.5= Malleable Cast Iron│ .70│ =2.8=│ .50│ =.5=│.15│=.60=│ .17│ =.7= Cast Steel │ .30│ =1.2=│ .50│ =.5=│.05│=.20=│ .04│=.17= Mild Steel │ .05│ =.2=│ .40│ =.4=│.04│=.16=│ .03│=.13= Open-hearth Iron │ .03│ =.1=│ .02│=.02=│.01│=.06=│ .01│=.06= Wrought Iron │1.20│ =5.0=│ .08│=.08=│.01│=.04=│ .15│=.65= ───────────────────┴────┴──────┴────┴─────┴───┴─────┴────┴───── ═══════════════════╤═══════════╤═══════╤══════════ │ Total │Iron[5]│ Total │ Carbon │ │Metalloids ───────────────────┼────┬──────┼───────┼───┬────── │Wt. │ Vol. │ Wt. │Wt.│ Vol. ───────────────────┼────┼──────┼───────┼───┼────── Gray Cast Iron │3.45│=12.1=│ 92.5 │7.5│=26.4= Semi-Steel │3.20│=11.2=│ 93.6 │6.4│=21.1= Malleable Cast Iron│2.75│ =9.6=│ 95.7 │4.3│=14.3= Cast Steel │ .35│ =1.2=│ 98.8 │1.2│ =3.3= Mild Steel │ .10│ =.35=│ 99.4 │ .6│ =1.2= Open-hearth Iron │ .02│ =.07=│ 99.9 │ .1│ =.3= Wrought Iron │ .05│ =.17=│ 97.7 │2.3│ =5.9= ───────────────────┴────┴──────┴───────┴───┴────── Footnote 5: These alloys contain small amounts of other elements so these percentages of iron are a little high, though approximately correct. Note the purity (high percentage of iron) of the open-hearth iron. 6. In the cast irons, the carbon occurs not in one only but in two different forms; i.e., as graphitic carbon, commonly called graphite (Gr. C.) and the combined form (C. C.). The sum of these is usually between 3.00 per cent and 3.50 per cent. It is not so much the total amount of the carbon that causes the differences in structure and physical properties which have been noted in 1 and 2 and in 16 and 17 above, as it is the _relative proportions_ in which these two varieties occur. [Illustration: EXHIBITION CASE SHOWING FOUR WELL-KNOWN IRON ALLOYS WITH THEIR METALLOIDS ]