Machinability
The capability of being machined. It is controlled through the composition and rate of cooling, but often must be sacrificed for some more essential property, such as strength or toughness.

Machine Straightening
Straightening by reeling, speening or other mechanical means.

Magnesite
Naturally occurring magnesium carbonate (MgCO3) containing small amounts of silica, alumina and iron oxide, and is used in making banks and bottom of a basic furnace, as well as during its fettling.

Magnetite
The iron oxide, having the composition Fe3O4, corresponding to 72.36% of iron and 27.64% of oxygen, specific gravity 5.16 to 5.18, occurring in nature in igneous, metamorphic, and sedimentary rocks and associated with varying amounts of impurities.

Magnetite Taconite
The rock name applied to bedded sedimentary iron formations in which the principal iron mineral is magnetite. It is a hard, dense, compact, fine-grained rock, commonly containing from 40 to 55% silica and 15 to 35% iron in the form of magnetite. Magnetite taconite ores are concentrated by magnetic methods after fine grinding.

Magnet Steels
These are an example of alloy electrical steels. The outstanding property of these steels is their retentivity or ability to retain magnetism. Cobalt, chromium, and tungsten are the alloying elements commonly used to enhance this characteristic.

Malleability
Capacity for undergoing deformation in all directions, usually cold deformation by hammering or squeezing, without fracture.

Malleable Iron
The term usually means malleable cast iron but it is sometimes applied to wrought iron also.

Malleablizing
Annealing white cast iron so that some or all of the combined carbon is transformed into graphite or, in some instances, so that part of the carbon is removed completely.

Mandrel
A round bar, usually slightly tapered, inserted through the forging and not supported at the ends, and around which a tube, ring or drum is forged between the upper & lower tools of the hammer or press. The mandrel governs the internal diameter.

Man-Hours Per Ton
This is a measure of labor efficiency i.e. the ratio of total hours worked by steel employees to the tons shipped for a given period of time. Changes in the inventory level and work that is contracted out will affect the reported measurement.

Martempering
1. A hardening procedure in which an austentized ferrous material is quenched into an appropriate medium at a temperature just above the martensite start temperature of the material, held in the medium until the temperature is uniform throughout, although not long enough for bainite to form, then cooled in air. The treatment is frequently followed by tempering.
2. When the process is applied to carburized material, the controlling martensite start temperature is that of the case. This variation of the process is frequently called marquenching.

Martensitic
Small category of stainless steel characterized by the use of heat treatment for hardening and strengthening. Refers to a particular grain structure of steel which is extremely hard and consists of iron oxide precipitates in a ferrite matrix. Martensitic stainless steels are plain chromium steels with no significant nickel content. They are utilized in equipment for the chemical and oil industries and in surgical instruments. The most popular martensitic stainless steel is type 410 (a grade appropriate for non-severe corrosion environments requiring high strength).

Material Safety Data Sheets (MSDS)
Sheets that document safety issues associated with various materials used.

Matte Finish
A dull or grit surface appearance achieved by rolling on rolls which have been roughened by mechanical, chemical, or electrical means to various degrees of surface texture.

Matte Surface
A dull surface appearance on a tin plate product; non-reflowed tinplate. See Reflowed Surface.

Mechanical Galvanizing
A batch process used to produce a zinc coating on manufactured steel items by shot peening. Small iron and steel parts are coated with zinc by drum-tumbling with a mixture of promoter chemicals, zinc powder, and glass beads. The tumbling action peens the zinc powder onto the part.

Mechanical Properties
Those properties of a material that reveal the elastic and inelastic reaction when force is applied, or that involve the relationship between stress and strain; for example, the modulus of elasticity, tensile strength, and fatigue limit. These properties have often been designated as "physical properties," but the term "mechanical properties" is much to be preferred. These are determined by mechanical methods involving destruction or deformation or both, such as tensile test, bend test, impact test and hardness test.

Mechanical Shaping
Permanent deformation of metal with the objective usually of production of a specific shape or size.

Medium-Carbon Steel
Carbon steel containing generally minimum of 0.30% carbon and maximum 0.60% carbon.

Melt
A stage in the steel making process when all the scrap charged has been melted. This term is also synonymous with cast, blow or heat.

Merchant Bar
1. A group of commodity steel shapes that consist of rounds, squares, flats, strips, angles, and channels, which fabricators, steel service centers and manufacturers cut, bend and shape into products. Merchant products require more specialized processing than reinforcing bar.
2. A trade term for black bar.

Metallizing
A process used to produce a zinc coating on manufactured steel items by metal spraying. Zinc metal wire or powder is fed into a spray gun where it is melted and sprayed onto the part to be coated. Melting is accomplished either by combustion in an oxygen-fuel gas flame or an electric arc. Combustion gases and/or auxiliary compressed air provide the necessary velocity to spray the liquid metal onto the part.

Metallography
The science dealing with the condition and structure of metals and alloys as revealed to the unaided eye or by using such tools a low-power magnification, optical microscopy, electron microscopy, and diffraction or x-ray techniques.

Microcleanliness
Removal of undesirable non-metallics, primarily oxides and sulphides.

Microvalve
A control valve used to control the hydraulic pressure to the clutch plates on the winch drive.

Middling
Forging the middle of an ingot or billet as a first operation; into finishing the middle of a forging before either end.

Mild Drawn Wire (Soft Drawn Wire)
Wire drawn from the rod or annealed base with a reduction of area of less than 10%.

Mill Edge
The edge as obtained from the normal practice of rolling without the use of edge rolls. This replaces the old term, band edge.

Mill Finish
The surface finish on sheets corresponding to the ground finish of rolls used.

Mill Scale
Oxide layer (scale) formed during heating of the bar, which is dislodged at the mill and collected.

Mild Steel
Carbon steel containing generally less than 0.30% carbon.

Mini-Mills
Normally defined as steel mills that melt scrap metal to produce commodity products. Although the mini-mills are subject to the same steel processing requirements after the caster as the integrated steel companies, they differ greatly in regard to their minimum efficient size and product markets. See Integrated Mills.

Minimized Spangle
A dull Hot-Dipped Galvanized surface appearance in which the normal zinc formation has been suppressed; achieved by applying water droplets or some other nucleating agent to the zinc surface after the bath but before the zinc solidifies to suppress the growth of spangle.

Minimum Triple Spot Average Coating
The average of three coating weights test results obtained from a full width sample of a galvanized (or any other coated) coil: 2 inches from each end and dead center.

Misting
A coating defect consisting of a condition encountered, primarily on D & I high speed beverage can coating machines, which appears as many fine spots of coating.

Mist Cooling
A cooling process used in secondary cooling section of steel melting shop in place of conventional water sprays. The mist is produced by an atomized nozzle in which cooling water and compressed air are premixed; the mist is discharged through a slit outlet from a pressure chamber. This improves heat transfer, resulting in significantly lower water volumes and greater cooling uniformity.

Mixer
A large refractory lined cylindrical or rectangular vessel, provided with tilting arrangement, and is used for storage of molten iron, and in some cases, for pertly refining the stored metal (active mixer used in open hearth shops). Apart from storage, it offers considerable latitude towards the intake of 'off standard' hot iron, and aims in bringing about some uniformity in the supply of hot iron for steel making.

Mixer Metal
Molten iron from the blast furnace which has been stored in a mixer preparatory to conversion to steel.

Modulus of Elasticity
The number which represents the relative "springness" of a given type of metal. All steels have the same modulus of elasticity or "springiness" regardless of the tensile or yield strengths. That is, until the yield point is reached they all stretch the same amount for a given load. Aluminum, on the other hand, is more elastic than steel and thus will stretch more than steel under the same loading.

Molybdenum (Mo)
An alloying element used as a raw material for some classes of stainless steel. Molybdenum in the presence of chromium enhances the corrosion resistance of stainless steel.

Monkey
(See Slag Notch.)

Months of Inventory
Ratio of the end-of-period inventory to average monthly level of sales for the period.

Mould Dressing
Materials (such as varnish, lacquor, tar, etc.) applied to the inner faces of moulds for better ingot surface.

M Sections (Bantam BeamsTM , Junior BeamsTM)
Light footweight beams primarily used in the construction of pre-engineered housing. These beams are produced in lighter footweights, usually six to 10 pounds per foot, than traditional structural products.

Muck Bar
Semi-finished bar produced in the forge.

Mud Gun
It consists of a hollow, cylindrical barrel and a plunger that pushes the refractory clay out through a nozzle into the tap hole of a blast furnace to plug it after the cast has been completed.

Mult
A "mult" is the term used to describe the slitting of a coil into multiple smaller strips. If a coil is slit into strips less than 9", each strip is referred to as a "mult" and does not receive an individual IPM number. Mults are not removed from the line individually, but as a whole coil unit. For reasons pertaining to customer orders, however, they may be separated and packaged with "mults" from other coils for shipping.

Multiple Lengths
Length from which a given number of pieces of specific lengths can be cut with minimum waste.

Multi Stage Pumps
Pumps that are designed to put out different amounts of water pressure by changing the speed of the pump by opening up different ports on the turbine of the pump.