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| Pearlite |
| A microstructural constituent of steel. It is a mixture of ferrite and cementite which normally exists in lamellar form and results from the eutectoidal transformation of cooling of austenite. |
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| PH Value |
| A measure of the relative acidity or alkalinity of a solution. It is the reciprocal of the logarithm of the hydrogen-ion activity in the solution. The pH values range from 0 to 14. A value of 7 is taken as neutral with values of decreasing magnitude below this indicating acidity and with values of increasing magnitude above this indicating increasing alkalinity. |
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| Phosphorous (P) |
| Its presence in steel is nominally limited to below 0.05% because of its embrittling effect. It is a powerful solid solution hardening agent. It is important to be aware phosphorous, especially in combination with silicon, can influence the control of post-galvanising. It is used as a deliberate alloy addition ( typically 0.07%)in low carbon free-cutting steel. |
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| Pickling |
| The removal of surface oxides from metals by chemical or electrochemical reaction. |
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| Pig Iron |
| The high carbon iron produced from the blast furnace and cast into 'pig'. |
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| Pinch Pass |
| The pass of sheet metal, at room temperature, through rolls to effect a very small reduction in thickness. (Typically 0.7 - 1.2%.) On low-carbon annealed steel sheet this is carried out in order to prevent the occurrence of stretcher strain markings on subsequent shaping of the sheet. |
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| Pipe |
| When used to describe a defect in a metal this term is used either to indicate: (i) The central cavity formed by contraction during soldifiation in the top of ingot stock or (ii) An imperfection seen in wrought material resulting from this cavity. |
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| Plate and Cylinder Rolling |
| The cold shaping of plate and sheet using rollers to produce cylinders or other rounded shapes, e.g. dished ends |
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| Poisson's Ratio |
| The absolute value of the ratio of the transverse (lateral) strain to the longitudinal strain when a material is being stressed elastically. |
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| Powder Metallurgy |
| The technology of producing metals in powder form and of using this powder in the production of useful objects, compaction and sintering. |
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| Pre-Heating |
| The heating of metal stock prior to some further thermal or thermomechanical treatment. |
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| Press Blanking |
| Press blanking is process in which (shaped) blanks are pressed out of strip feeding continuously into the press blanking machine. |
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| Profiles |
| With respect to steels this term covers two types of products: (i) Shapes cut by flame, plasma or laser from steel sheet, plate or slab. (ii) Steel sheet cold roll formed or pressed to different profiles for use, for example, as cladding for buildings. It could also refer to the variation in gauge across the width of a flat rolled product. |
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| Profiling |
| The flame, plasma or laser cutting of shapes from sheet, plate or slab. |
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| Projection Welding |
| A resistance welding procedure in which the welds made between the parts to be joined are localised at performed projections (embossments) on the parts. |
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| Proof Stress |
| The stress which will cause a specified small and permanent extension of a given material. It is normally quoted as the stress to obtain a 0.1%, or a 0.2%, extension in the material, the values being obtained from a tensile test. |
