Macro Etch Test: A test for visual evaluation of the homogeneity and soundness of an ingot, bloom, billet, or bar. It involves pickling a disc or cross section in strong acid until deep etching displays the steel's macro structure.
Macrograph: A photographic reproduction of any object that has not been magnified more than ten times.
Macrostructure: The structure of a metal as revealed by examination of the etched surface at a magnification not exceeding ten diameters.
Magnetic-Particle Inspection: A nondestructive method of inspection for determining the existence and extent of possible defects in ferromagnetic materials. Finely divided magnetic particles, applied to the magnetized part, are attracted to and outline the pattern of any magnetic-leakage fields created by discontinuities.
Magnetism: Commonly expressed as permeability which is the ratio of the magnetic induction to the magnetic intensity. The important factor to remember is that the permeability increases as the material becomes more magnetic. The 300 series stainless is non magnetic in the annealed condition. However, as these grades become increasingly cold worked, they become more magnetic. Annealing will restore the non-magnetic condition.
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.
Mandrel: A metal bar around which other metal may be bent.
Martempering: Quenching an austenitized ferrous alloy in a medium at a temperature in the upper part of the martensite range, or slightly above that range, and holding it in the medium until the temperature throughout the alloy is substantially uniform. The alloy is then allowed to cool in air through the martensite range.
Martensite: A hard constituent in all steels which is a transformation product of austenite. In stainless steels it can be formed from austenite by high-temperature heat treatment (i.e. 410, 420, 440) or by cold-working (i.e. 301, 302, 304); method depends on chemistry balance.
Martensitic Stainless Steels: (400 SERIES WHICH HAVE HIGH CARBON). These grades of stainless have chromium in the range of 11% to 17% as the sole major alloying addition. This is the same as the ferritic grades. However, carbon is added in amounts from 0.10 % to 0.65% to radically change the behavior of the martensitic alloys. The high carbon enables the material to be hardened by heat treatment.
McQuaid-Ehn Test: A special test for revealing grain size when the steel is heated above the critical range. The test sample is immersed in a carbonaceous medium, heated to 1700°F for a designated period of time and the allowed to cool. The treatment causes the grains of the steel to be outlined sharply when polished, etched, and viewed under a microscope. There are eight standard McQuaid-Ehn grain sizes, ranging from No. 8, the finest, to No. 1, the coarsest.
Mechanical Properties: Those properties that reveal the reaction, either elastic or plastic, of a metal to an applied stress. Tensile strength, yield strength, elongation, reduction of area, hardness, impact strength, and bend ability are mechanical properties.
Mechanical Working: Plastic deformation or other physical change to which metal is subjected, by rolling, hammering, drawing., etc. to change its shape, properties or structure.
Medium-Carbon Steel: Contains from 0.30% to 0.60% carbon and less than 1.00% manganese. May be made by any of the standard processes.
Melting Range: The range of temperature in which an alloy melt; that is the range between solidus and liquidus temperatures.
Metallic Elements: In general these elements are distinguished by their luster, malleability, conductivity, and ability to form positive ions. Iron, Chromium, Nickel, Molybdenum, Cobalt, Titanium among others are metallic. Carbon, Sulfur, Phosphorus, Nitrogen, etc. are nonmetallic.
Metallography: Science concerning the constitution of metal and alloys as revealed by the microscope.
Metallurgy: The art and science which deals with the extraction of metals from their ores and the adaptation and application of these metals to the uses for which they are intended.
Micro hardness: A hardness test employed to check light-gauge metals and alloys. Ulbrich employs the test on all flat-rolled product .010" or under in thickness.
Micro structure: The internal structure of metals as viewed at high magnification (usually 100 diameters or more) under the microscope.
Mill Edge: The normal edge of steel produced in hot rolling and does not conform to any definite contour. Mill edge products may contain some edge imperfections, the more common of which are checked edges, thin edges (feather) and damaged edges due to handling or processing.
Mirror Finish: A highly reflective finish obtained by polishing with successively finer abrasive and buffing extensively free of grit lines. Finish is used most for architectural applications. A comparable finish produced by cold-rolling is Ulbrich's UlbraBright, which currently is not being produced.
Modulus of Elasticity (tension): Force which would be required to stretch a substance to double its normal length, on the assumption that it would remain perfectly elastic, i.e., obey Hooke's Law throughout the twist. The ratio of stress to strain within the perfectly elastic range.
Ms Temperature: The temperature at which a martensitic transformation starts during cooling after austenitization.