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| Bainite |
| An acicular aggregate of ferrite and carbide particles formed when austenite is transformed on cooling at temperatures in the intermediate (200-450C) range, ie above the martensite and below the pearlite range. |
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| Bake Hardenable Steel |
| Bake hardenable steels are so constituted that after press forming and stoving (baking) through the paint curing process they age, ie they increase in strength. In this way, good formability is combined with added stiffness in the finished component, which frequently is an automotive body panel in which enhanced dent resistance is a desirable attitude. |
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| Balanced Steel |
| This is made by controlling the oxygen content of the liquid steel prior to ingot casting so that the amount of gas evolved during solidification balances the contraction, so minimising the formation of pipe. (NB. The majority of steels are now produced via the concast route.) |
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| Basic Oxygen Steelmaking |
| Basic oxygen steelmaking is the process by which molten iron from a blast furnace is refined by the near total removal of carbon, silicon, manganese, phosphorus and sulphur to a point from which, by the addition of appropriate ferro-alloys and aluminium, the required grade of steel can be made. The process involves the injection of high volumes of oxygen at very high pressure into a vessel which originally will have contained a charge comprising approximately 20% selected ferrous scrap and 80% molten iron. The refractory lining of the vessel is basic, as opposed to acidic in nature, and basic fluxes are also added with the aim of creating a slag into which the impurities are driven. The capacity of vessels is very variable, but typically can range from around 200 tonnes to in excess of 350 tonnes. A cast of steel can be produced in less than 20 minutes. With modern refractories, a vessel is expected to be capable of producing in excess of 1000 heats before it needs to be relined. |
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| Batching |
| The grouping together of parts to achieve an economic use of the process. |
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| Bend Test |
| A form of mechanical testing used to assess the ductility of a piece of steel. In carrying out such a test it will often be necessary to follow a detailed procedure which may cover the form, selection and preparation of the test specimen and exactly how the specimen is to be bent and the result assessed and reported, eg see BS1639: 1964. The results are normally expressed as a minimum bend diameter in the form nT, where n is a number (sometimes a decimal fraction), and T is the thickness of the steel. |
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| Billet |
| A semi-finished long product, sometimes of rectangular but more usually of square cross-section, with radiused corners. It can be produced from the hot-rolling of a bloom, which has in turn been hot-rolled from ingot stock, or it can be produced directly by continuous casting. Square billet has sides between 50-120mm, whereas rectangular billet has a cross-sectional area between 2500 and 14400mm2 and has a width to thickness ratio greater than 1:1 and less than 2:1. In practice, sizes up to 160mm square are often referred to as billet. |
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| Bismuth |
| Added at a level of 0.1-0.2% as a direct replacement for lead, (it is more expensive, but there are not the toxicity problems associated with making lead additions), or at a lower level of 0.05-0.1% in combinations with sulphur, lead and tellurium, to improve the machinability of steel. |
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| Blast Furnace |
| A tall, 60-70m high, refractory lined furnace of circular cross-section (diameter at the base - 12m) from the bottom of which liquid cast pig iron it tapped periodically. This is produced by feeding in a solid mixture of iron ore, limestone and coke at the top and by blowing in pre-heated air, and usually fuel, at the bottom. |
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| Bloom |
| A semi-finished long product, sometimes of rectangular but more generally of square cross-section, with radiused corners. It can be produced from the hot-rolling of ingot stock or by continuous casting. Its size is larger than that of billet; a square bloom has sides generally greater than 120mm, whereas a rectangular bloom has a cross-sectional area greater than 14400mm2 and has a ratio of width to thickness greater than 1:1 and less than 2:1. |
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| Boron Steels |
| Steels that contain additions of boron, generally between 0.002-0.003%, which is added to increase the hardenability of the steel. |
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| Brazing |
| A method for joining steel parts together by melting a layer of a lower melting point alloy, usually brass, between the adjoining steel surfaces. The heat used is not sufficient to melt the steel and a flux is used to ensure flow of the brazing alloy between the steel surfaces. |
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| Bright Annealing |
| An annealing heat treatment carried out using either a specially controlled atmosphere or a vacuum, thus preventing oxidation and so keeping the surface of the steel being heat-treated bright and shiny. |
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| Bright Drawing |
| The process of drawing steel, which is initially at room temperature, in bar or coil form through a die in order to produce a product with close dimensional tolerances, with changed mechanical properties, ( higher strength and lower ductility and toughness) and a bright surface finish. Prior to the drawing operation the steel surface may need to be prepared by pickling or shot blasting in order to produce a satisfactory initial surface condition. See also Cold Drawing. |
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| Brinell Hardness Test |
| A test in which a hardened steel ball, usually 10mm in diameter, is pressed into the surface of the steel for a set time using a load of 3000kgf. The steel ball indenter is then removed and the diameter of the indentation is measured and used to determine the Brinell Hardness Number, HB, of the steel by reference to standard tables. |
