. Transactions. ic, and troosto-martensitic zones between the pearlitic andmartensitic areas and of a martenso-austenitic zone between the martensitic andaustenitic areas. For of this note, however, the existence of thesetransition-conditions may be ignored. NOTE ON THE CASE-HARDENING OF SPECIAL STEELS. 423 should be possible to cause pearlitic nickel-steel to absorb thenecessary amount of carbon to become martensitic, or even, ifdesired, austenitic. It should therefore be possible to manu-facture case-hardened objects of nickel-steel and of some otherspecial steels having pearliti
. Transactions. ic, and troosto-martensitic zones between the pearlitic andmartensitic areas and of a martenso-austenitic zone between the martensitic andaustenitic areas. For of this note, however, the existence of thesetransition-conditions may be ignored. NOTE ON THE CASE-HARDENING OF SPECIAL STEELS. 423 should be possible to cause pearlitic nickel-steel to absorb thenecessary amount of carbon to become martensitic, or even, ifdesired, austenitic. It should therefore be possible to manu-facture case-hardened objects of nickel-steel and of some otherspecial steels having pearlitic, and consequently soft and tough,cores, and troosto-martensitic, martensitic, martenso-austeniticor austenitic cases, without recourse to the quenching-bath. InFig. 1, for instance, the point A represents a steel containing cent, of carbon and 3 per cent, of nickel. By increasingthe carbon-content to per cent, its composition shifts fromA to J3 and the metal becomes martensitic. Increasing its car-. PER CENT. CARBON Fig. 1. —Constitutional Diagram of Kigkel-Steel (Guillet). l)on to per cent, would make it austenitic, since its compo-sition would now be represented by the point C. A pearliticsteel containing the same amount of carbon ( per cent), butmore nickel, say 5 per cent., would require a smaller additionof carbon to become martensitic or austenitic, since by shiftingits composition from A to B when it contains per cent,of carbon it fails within the martensitic area. It is evident thatthe nearer the composition of pearlitic steel to the boundary-line LO the less carbon will it require to make it test the practicality of the manufacture of case-hardened VOL. XLIV.—26 424 NOTE ON THE CASE-HARDENING OF SPECIAL STEELS. articles of the description referred to, a number of nickel-steelsof varying compositions were subjected to the case-hardeningtreatment, and no difficulty was experienced in producing mar-t
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