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| Salt Bath |
| A bath of molten salt, the composition of which is varied according to the temperature and treatment required, in which steels are thermally or thermo-chemically treated. |
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| Scale |
| The thick oxide skin that forms on a steel when it is exposed to an oxidising environment for any length of time at high temperature. |
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| Scarfing |
| The cutting out of surface defects on steel with the use. |
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| Scrap |
| Discarded metallic material, arising from processing, from use or at the end of life. It is usually reclaimed by remelting and refining to produce new material. Steel is the most recycled material on earth. |
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| Seams |
| Numerous shallow grooves, cracks or striations, continuous or intermittent on the surface of wrought steel, the surfaces on which when viewed microscopically are generally heavily oxidised and decarburised. They result from the elongation during working of trapped gas pockets, blowholes or cracks that formed during the casting of the steel. |
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| Selenium (Se) |
| Can be added to improve the machinability of certain grades of stainless steel. |
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| SG Iron |
| An abbreviation for Spheroidal Graphite Cast Iron. This type of cast iron is produced by adding small amounts of ST cerium or magnesium to a molten iron, which normally solidifies to give a flake graphite iron. The spheroidal rather than the flake morphology of the graphite gives a measurable degree of ductility to the cast iron. |
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| Shearing |
| Cutting of sheet or strip to size using shear blades, as in a guillotine. |
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| Shearing Test |
| Direct shear tests can be used to determine the shear strength of bar, plate or rivet stock. For a bar a portion of the test piece is clamped while the remaining portion extends over an open die. A load is applied, to this latter portion, at right angles to the specimen axis and increased until it shears through the specimen. The maximum load applied, divided by the area subjected to the shearing force gives the average shear strength of the material tested. |
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| Sheets |
| Flat rolled steel product with a width of 600mm and a thickness of up to 3mm. |
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| Shot |
| A round steel abrasive used in the blast cleaning process. |
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| Silicon (Si) |
| Used as a deoxidiser in steelmaking, and also as a strengthening agent. An alloy addition in spring steels (~1.5%), in heat resisting steel (1.5 - 3.5%) and in steel sheet for transformer cores (>3%). It is important to be aware silicon can influence the control of post-galvanising, especially in combination with phosphorous. |
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| Slitting |
| The cutting of wide strip into narrower strip usually carried out using rotary cutters. The strip is normally decoiled before it is slit. |
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| Slotting |
| In sheet this involves the punching of elongated holes, (slots), through the steel using a punch and die. It is also applied to the cutting of a narrow aperture or groove in thicker material with a reciprocating tool cutter, broach or grinding wheel. |
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| Spinning |
| The forming of a seamless hollow metal part by forcing a rotating sheet metal blank to conform to the shape of a mandrel that is rotating concentrically with the blank. |
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| Spot Welding |
| A method of joining two pieces of overlapping sheet metal together in which the welded region is limited to a 'spot' of approximately circular cross section. This localised weld is nominally made by a resistance welding technique but can also be made using an arc. |
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| Spring Steel |
| Steel used for the manufacturer of springs. Depending on the type and application of the spring the steel composition can vary from a plain carbon type, to C-Si, to any of a range of alloy steels and if necessary to the use of a martensitic or austenitic stainless steel grade. Spring steels are characterised by a high yield strength and a high YS/TS ratio. |
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| Stabilisation |
| A term used in a number of different contexts: (i) A thermal treatment to stabilise the microstructure, mechanical properties or dimensions of a metal. (ii) The addition of the elements Ti or Nb in certain grades of austenitic stainless steel, to prevent intragranular corrosion. (iii) The effect of the addition of Al to deep drawing sheet steel to prevent it from ageing. (iv) The addition of Ti and/or Nb to interstitial free steels to prevent ageing, by combining the C and N. |
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| Stainless Steel |
| An iron-based alloy containing 10.5%, or more, of chromium. By the addition of other alloying elements to this basic ferritic alloy, such as Ni, C, N and Mo, a variety of different grades of stainless steel, namely austenitic, martensitic duplex and precipitation-hardened can be produced. |
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| Steel |
| An iron-based alloy in which the carbon content is less than its solubility limit in austenite. This limit is approximately 2.0% in a non-alloy steel but may be higher in certain alloy steels. |
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| Strain Ageing |
| The changes in ductility, yield strength and tensile strength that can occur with time in certain steels when they are stored after they have undergone plastic deformation by cold working. |
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| Strain Hardening |
| The increase in strength and hardness that occurs when a metal is plastically deformed under such conditions that softening does not take place i.e. below the recrystalisation temperature. Also known as work hardening. |
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| Stress Relieving |
| Although a degree of stress relaxation (stress relief) may occur at room temperature, this term normally implies a heat treatment in which the material is heated up and soaked at a suitable temperature before being control cooled back to room temperature. Stress relief occurs by creep, so the degree of relief achieved is both time and temperature dependent. |
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| Stress-Strain Curve |
| A graphical plot of data obtained from a tensile test, in which the stress on the metal being tested (the force causing the specimen to deform divided by the original cross-sectional area of the gauge length) is plotted against the resulting strain (the extension of the gauge length divided by its original length). |
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| Subcriticial Annealing |
| An annealing heat treatment carried out as a temperature below the critical temperature of the steel. |
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| Sulphur (S) |
| Normally kept as low as possible in steels as it has a detrimental effect on hot and cold formability, ductility, fatigue properties and on weldability. It is beneficial, through the form of manganese sulphide particles, on the machinability of steel and up to ~0.35% can be present in free-cutting steels. |
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| Surface Hardening |
| A generic term covering several processes, such as carburising, nitriding, flame and induction hardening, that can be used to produce a surface layer, on a specific type of steel, that is harder than the core of the steel. |
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| Surface Profile |
| Roughness of surface profile blast cleaning. |
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| Surface Quality |
| Cleanliness of material surface following blast cleaning |
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| Swaging |
| A process in which by hot or cold working the cross-sectional area of metal stock in the form of bar, rod, wire or tube is progressively reduced along its length by forging, hammering or squeezing. Ina rotary swage the reduction is achieved by rapid impact blows from revolving dies. |
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| Swarf |
| The chips and other particles of metal that are removed from the work-piece during a machining operation. |
