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| >> GLOSSARY OF TERMS |
| M |
| M B GRADE A term applied to Open-Hearth steel wire if the .45/75 carbon range either hard drawn or oil tempered. Oil tempered wire of M B and W M ?B types are the most widely used of all spring wired. Oil tempered wire is more ?suitable to precision forming and casting operations than hard drawn wire, ?because of close control of tensile strength and superior straightness. |
| MACROETCH TEST Consists of immersing a carefully prepared section of the steel in hot acid and of examining the etching surface to evaluate the soundness and homogeneity of the product being tested. |
| MACROGRAPH A photographic reproduction of any object that has not been magnified more than ten times. |
| MACROSCOPIC Visible either with the naked eye or under low magnification (as great as about ten diameters). |
| MACROSTRUCTURE The structure of metal as revealed by macroscopic examination. |
| MALLEABILITY The property that determines the ease of deforming a metal when the metal is subjected to rolling or hammering. The more malleable metals can be hammered or rolled into thin sheet more easily than others. |
| MALLEABILIZING A process of annealing white cast iron in such a way that the combined carbon is wholly or partly transformed to graphitic or free carbon or, in some instances, part of the carbon is removed completely. |
| MAlT OR MATTE FINISH (Steel) - Not as smooth as normal mill finish. Produced by etched or mechanically roughened finishing rolls. |
| MANGANESE (Chemical symbol Mn.) - Element No. 25 of the periodic system; atomic weight 54.93. Lustrous, reddish-white metal of hard brittle and, therefore, non-malleable character. The metal is used in large quantities in the form of Spiegel (See) and Ferromanganese (See) for steel manufacture as well as in manganese and many copper-base alloys. Its principal function is as an alloy in steel making: (1) It is ferrite-strengthening and carbide forming element. It increases hardenability inexpensively, with a tendency toward embrittlement when too high carbon and too high manganese accompany each other. (2) It counteracts brittleness from sulfur. |
| MARTENSITE A distinctive needlelike structure existing in steel as a transition stage in the transformation of austenite, It is the hardest constituent of steel of eutectoid composition. It is produced by rapid cooling from quenching temperature and is the chief constituent of hardened carbon tool steels. Martensite is magnetic. |
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