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Steel MakingThe Modern Hardening RoomA hardening room of today means a very different place from ... Hardening High-speed Steel In forging use coke for fuel in the forge. Heat steel slowly ... Chrome-nickel Steel Forging heat of chrome-nickel steel depends very largely on ... Detrimental Elements Sulphur and phosphorus are two elements known to be detrimen... Annealing ANNEALING can be done by heating to temperatures ranging from... Heat-treating Department The heat-treating department occupies an L-shaped building. ... Silicon Silicon prevents, to a large extent, defects such as gas bubb... Hardening Steel is hardened by quenching from above the upper critical.... Alloying Elements Commercial steels of even the simplest types are therefore p... Correction By Zero Adjustment Many pyrometers are supplied with a zero adjuster, by means ... Drop Forging Dies The kind of steel used in the die of course influences the he... Suggestions For Handling High-speed Steels The following suggestions for handling high-speed steels are ... Correction For Cold-junction Errors The voltage generated by a thermo-couple of an electric pyrom... Heat Treatment Of Axles Parts of this general type should be heat-treated to show the... Composition And Properties Of Steel It is a remarkable fact that one can look through a dozen tex... Impact Tests Impact tests are of considerable importance as an indication ... Annealing Alloy Steel The term alloy steel, from the steel maker's point of view, r... Optical System And Electrical Circuit Of The Leeds & Northrup Optical Pyrometer For extremely high temperature, the optical pyrometer is lar... Hardening Carbon Steel For Tools For years the toolmaker had full sway in regard to make of st... Compensating Leads By the use of compensating leads, formed of the same materia... |
Case-hardening Treatments For Various SteelsCategory: CASE-HARDENING OR SURFACE-CARBURIZING Plain water, salt water and linseed oil are the three most common quenching materials for case-hardening. Water is used for ordinary work, salt water for work which must be extremely hard on the surface, and oil for work in which toughness is the main consideration. The higher the carbon of the case, the less sudden need the quenching action take hold of the piece; in fact, experience in case-hardening work gives a great many combinations of quenching baths of these three materials, depending on their temperatures. Thin work, highly carbonized, which would fly to pieces under the slightest blow if quenched in water or brine, is made strong and tough by properly quenching in slightly heated oil. It is impossible to give any rules for the temperature of this work, so much depending on the size and design of the piece; but it is not a difficult matter to try three or four pieces by different methods and determine what is needed for best results. The alloy steels are all susceptible of case-hardening treatment; in fact, this is one of the most important heat treatments for such steels in the automobile industry. Nickel steel carburizes more slowly than common steel, the nickel seeming to have the effect of slowing down the rate of penetration. There is no cloud without its silver lining, however, and to offset this retardation, a single treatment is often sufficient for nickel steel; for the core is not coarsened as much as low-carbon machinery steel and thus ordinary work may be quenched on the carburizing heat. Steel containing from 3 to 3.5 per cent of nickel is carburized between 1,650 and 1,750 deg.F. Nickel steel containing less than 25 points of carbon, with this same percentage of nickel, may be slightly hardened by cooling in air instead of quenching. Chrome-nickel steel may be case-hardened similarly to the method just described for nickel steel, but double treatment gives better results and is used for high-grade work. The carburizing temperature is the same, between 1,650 and 1,750 deg.F., the second treatment consisting of reheating to 1,400 deg. and then quenching in boiling salt water, which gives a hard surface and at the same time prevents distortion of the piece. The core of chrome-nickel case-hardened steel, like that of nickel steel, is not coarsened excessively by the first heat treatment, and therefore a single heating and quenching will suffice. Next: Carburizing By Gas Previous: Refining The Grain
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