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Brass swarf and scrap commands a premium price making brass a cost-effective engineering material. |
| Introduction | |
| Machined parts and stampings | |
| Special purpose alloys | |
| Sheet, strip and wire | |
| Conclusion |
Most people recognise the high price commanded by brass scrap. Indeed many of us, after a DIY project such as installing a new kitchen or bathroom, collect together the old brass taps and fittings and sell them to our local scrap merchant in an attempt to recoup some of our expenditure. The reason such a premium price is paid for brass scrap is because it is essential to the economics of the brass industry.
Brass for extrusion and hot stamping is normally made from a basic melt of scrap of similar composition – adjusted by the addition of small amounts of virgin copper or zinc as required to meet the specification before pouring. The use of brass scrap bought at a significantly lower price than the metal mixture price means that the cost of the fabricated brass is considerably less than it might otherwise be. How many designers consider this when designing new products or seeking cost savings in existing products.
Brass machined parts and stampings
Free machining 60/40 brass with small additions of lead is particularly cost-effective and environmentally friendly when used for the manufacture of machined parts and stampings. Firstly, the swarf produced as a result of high speed machining (typically metal removal rates are two to three times those of mild steel) can be sold as scrap. Secondly, when brass components reach the end of their long and useful life they too can be readily recycled. The stamping temperatures for brasses are lower than those required for ferrous alloys making it an energy efficient process; the low stamping temperature also gives an increased die life. Stamping is a near-net-shape process but the small amount of swarf produced by machining is again recyclable. Brass is also cost-effective and kind to the environment because it does not normally need plating or painting to prevent corrosion.
Brass swarf arising from machining operations can be economically remelted but it should be substantially free from excess lubricant, especially those including organic compounds that cause unacceptable fumes during remelting. The presence in brass of some other elements such as lead is often required to improve machinability so such scrap is frequently acceptable. Besides the common free-machining brasses, there are many others made for special purposes with properties modified to give extra strength, hardness, corrosion resistance or other attributes, so strict segregation of scrap is essential.
When brass is remelted, there is usually some evolution of the more volatile zinc. This is made up in the melt to bring it back within specification. The zinc is evolved as oxide that is drawn off and trapped in a baghouse and recycled for the manufacture of other products.
The 70/30 brass to be made into sheet, strip or wire form must be significantly free of harmful impurities in order to retain ductility when cold. It can then be rolled, drawn, deep drawn, swaged, riveted, spun or cold formed. It is normal therefore to make it substantially from virgin copper and zinc, together with process scrap arising from processing that has been kept clean, carefully segregated and identified.
Brass is a cost-effective engineering material ideally suited for the manufacture of machined and stamped items. The need for plating or painting to prevent corrosion in normal circumstances is eliminated, but when required for cosmetic purposes or to give additional protection against corrosion it is easily plated. Brass is readily recycled without loss of properties and the infrastructure to do so has been proven over many years.