found 20 matching terms.
| Term |
Definition |
| Machinability |
Simply defined as a measure of the ease with which a metal can be machined satisfactorily. |
| Macrostructure |
The general crystalline structure of a metal and the distribution of impurities seen on a polished or etched surface by either the naked eye or under low magnification of less than x10. |
| Magnetic Crack Detection |
The bar or component to be tested is magnetised by passing a heavy current through it or by making it the core of a coil through which a heavy current is passed. Cracks or inclusions cause the magnetic flux to break the surface forming free magnetic poles. When the component is sprayed with a suspension of finely divided magnetic particles they collect at the free poles to visibly show the presence of defects. |
| Malleability |
It can be defined as the property of a metal to be deformed by compression without cracking or rupturing. The load may be applied slowly or suddenly and will determine whether the material will be suitable for forging or rolling into thin sheet. |
| Manganese |
One of the most important constituents of steel in which it fulfils a number of functions. It acts as a mild de-oxidising agent. It combines with the sulphur present to form globular inclusions of Manganese Sulphide which are beneficial to machining. It increases tensile strength and the hardenability of steel. |
| Martempering |
A heat treatment involving austenitisation followed by step quenching, at a rate fast enough to avoid the formation of ferrite, pearlite or bainite to a temperature slightly above the Ms point. Soaking must be long enough to avoid the formation of bainite. The advantage of martempering is the reduction of thermal stresses compared to normal quenching. This prevents cracking and minimises distortion. |
| Martensite |
The hard constituent produced when steel is cooled from the hardening temperature at a speed greater than its critical cooling rate. Martensite is an acicular phase when seen in the microstructure of steel. |
| Mass Effect |
A term used to signify the effect of size and shape during heat treatment, since it is the rate of cooling of a piece of steel which determines the properties resulting from the hardening and quenching process. |
| Matrix |
The mass or principal constituent (e.g. iron in the case of steel) in which other constituents are embedded. |
| Maximum Stress |
In the testing of the strength of steel a sample is machined into a standard test piece and is stretched in a tensile testing machine until it breaks. The results are expressed in N/mm2 and is the value of the maximum load reached in the test divided by the original cross sectional area of the specimen. |
| McQuaid EHN Grain Size Test |
A method of assessing grain size. It consists of a test piece at 927oC for 8 hours by slow cooling and subsequent microscopical examination. The grain size is measured at x100 magnification and compared to standard charts, the figures range from No. 1 - very coarse, to No. 8 - very fine. |
| Meehanite |
A trade name applied to a certain type of cast iron. |
| Melting Point |
The temperature at which a solid begins to liquefy. |
| Mg |
Chemical symbol for Magnesium. |
| Micron |
A unit of length equal to one millionth of a metre (0.001mm). |
| Microstructure |
The structure that is observed when a polished and etched specimen of metal is viewed in an optical microscope at magnifications in range of approximately x25 to x1500. |
| Mn |
Chemical symbol for Manganese. |
| Mo |
Chemical symbol for Molybdenum. |
| Modulus of Elasticity |
When a material is subjected to an external load it becomes distorted or strained. With metals, provided the loading is not too great, they return to their original dimensions when the load is removed, i.e. they are elastic. Within the limits of elasticity, the ratio of the linear stress to the linear strain is termed the modulus of elasticity or more commonly known as Young's Modulus. |
| Molybdenum |
Its use as an alloying element in steel increases hardenability and in low alloy steels reduces the risk of temper brittleness. When added to stainless steels it increases their resistance to corrosion. It is also used in high speed steels. |
