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18 Reduction of area, per cent 50 The usual heat treatment is to quench in oil from 1,650 deg.F. and temper or draw at 1,100 to 1,200 deg.F. One valve manufacturer stated that valves of this steel are hardened by heating the previously annealed valves to 1,650 deg.F. and cooling in still air. This treatment gives a scleroscope hardness of about 50. In addition to use in valves this steel should prove very satisfactory for shafting for water-pumps and other automobile parts subject to objectionable corrosion. TABLE 2.--COMPARISON OF PHYSICAL PROPERTIES FOR HIGH-CHROMIUM STEELS OF DIFFERENT CARBON CONTENT -------------------------------------------------------------------------- | C 0.20 | C 0.27 | C 0.50 | Mn 0.45 | Mn 0.50 | | Cr 12.56 | Cr 12.24 | Cr 14.84 -----------------------------------------|----------|----------|---------- Quenched in oil from degrees Fahrenheit | 1,600 | 1,600 | 1,650 Tempered at degrees Fahrenheit | 1,160 | 1,080 | 1,100 Yield point, pounds per square inch | 78,300 | 75,000 | 91,616 Tensile strength, pounds per square inch | 104,600 | 104,250 | 123,648 Elongation in 2 in., per cent | 25.0 | 23.5 | 14.5 Reduction of area, per cent | 52.5 | 51.4 | 33.5 -------------------------------------------------------------------------- TABLE 3.--COMPARISON OF PHYSICAL PROPERTIES BETWEEN AIR, OIL AND WATER-HARDENED STEEL HAVING CHEMICAL ANALYSIS IN PERCENTAGE OF ------------------------------------------------------------------------- Carbon 0.24 Manganese 0.30 Phosphorus 0.035 Sulphur 0.035 Chromium 12.85 Silicon 0.20 ------------------------------------------------------------------------- | Hardened | | Elastic | Tensile | | Hardening| from, | Tempered | limit, |strength,|Elongation|Reduction medium | degrees |at, degrees| per lb. |lb. Per | in 2 in. |of area, |Fahrenheit|Fahrenheit | sq. in. | sq. in. | per cent |per cent ---------|----------|-----------|---------|---------|----------|--------- | | 930 | 158,815 | 192,415 | 13.0 | 40.5 | | 1,100 | 99,680 | 120,065 | 21.0 | 59.2
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