A Treatise On The Principles And Practice Of Dock Engineering

IRON AND STEEL. 135 concise statement of its influence is given by Mr. White, of the Bethlehem Iron and Steel Co., U.S. A.:—* “ The tensile strength and elastic limit of nickel iron alloys and nickel steel rise with increasing proportions of nickel, reaching a maximum at about 20 per cent. Passing this they begin to fall, and elongation increases abnormally up to 30 per cent. The hardening effect of quench- ing ceases at about 10 per cent., but is quite marked in the lower per- centages. In this case the effect is heightened by the manganese, but with -06 per cent, manganese it is still decided. Between 10 and 20 per cent, nickel, neither quenching nor annealing exerts any decided effect. Above 20 per cent., quenching produces a softening effect, which is decided at 30 per cent. Perhaps it would be better to call it a weakening effect, as the tensile strength and elastic limit are mach lowered, the elongation inereased, but the cutting properties shown by turning in a lathe are not perceptibly changed. “ These results refer to alloys of nickel and iron containing carbon from •06 to 1 per cent., which practically can be considered carbonless alloys, as it is impracticable to make them lower. The manganese ranged between 06 and -1 per cent. “ Tliere are many difficulties to be overcome in handling nickel steel as commercially made. It is very susceptible to changes of temperature when containing the usual amounts (-2 to -9 per cent.) ot carbon and manganese, requiring considerable care in heating and working to bring out its best qualities.” The question of alloys is a very wide one, and, in view of the extensive range of modern cliemical research, the student will do well to consult technical literature for a more complété and detailed statement of the behaviour of the various products. It would be out of place here to enter into the subject seriously, and we must dismiss other known combinations witli the briefest possible notice. Tungsten and chromium have the effect of hardening steel and increasing its tenacity. Copper and antimony, on the other hand, produce brittleness. Titanium increases the ductility. The following constituents are usually accounted impurities :— Silicon produces brittleness in iron and is generally excluded as slag. It is not detrimental to steel when present in a very minute quantity, as it tends to repress agitation and bubbling during the process of cooling. Its effect on cast iron is somewhat similar to that of carbon. Phosphorus hardens cast iron, makes it more fusible, and lessens its ductility. Steel is deteriorated by a very small quantity, say, -08 per cent. Wrought iron is rendered more weldable by -01 per cent., but above that limit the metal becomes brittle and “cold short”—i.e., it cracks if bent cold. Sulphur makes wrought iron “red short,” or brittle, at high tempera- tures. It renders both steel and cast iron more fusible and more brittle. * Min. Proc. Inst. C.E., vol. cxxxviii., p. 53.