| Abrasive Wear | (english) The displacement and / or detachment of metallic particles from a surface as a consequence of being exposed to flowing fluids or gases. |
| Abrasive Wheels | (english) Wheels of a hard abrasive, such as Carborundum used for grinding. |
| Ac1 | (english) The temperature at which austenite begins to form on heating. |
| Ac3 | (english) In hypoeutectoid steel, the temperature at which transformation of ferrite into austenite is completed upon heating. |
| Accordion Reed Steel | (english) Hardened, tempered, polished and blued or yellow flat steel with dressed edges. Carbon content about 1.00. Material has to possess good flatness, uniform hardness and high elasticity. |
| ACCUMULATOR | (english) A vessel, normally cylindrical, which is used to store fluid and gas for future release of the energy in the compressed fluid and gas. Normally contains a diaphragm or piston between the fluid (liquid) and gas chambers. Fluid is normally introduced at one end and the gas at the opposite end. |
| Accurate | (english) Conforms to a standard or tolerance. |
| Acid | (english) 1) A solution or liquid with a pH less than 7, 2) term applied to slags, refractors, and minerals containing a high percentage of silica. |
| Acid Brittleness (Pickling Brittleness) | (english) Brittleness resulting from pickling steel in acid; hydrogen, formed by the interaction between iron and acid, is partially absorbed by the metal, causing acid brittleness. |
| Acid Process 1 | (english) A process of making steel, either Bessemer, open-hearth or electric, in which the furnace is lined with a siliceous refractory and for which low phosphorus pig iron is required as this element is not removed. |