Why is Copper Added to Some Stainless Steels?

Stainless steel is an alloy, which means that it is a mixture of elements. Selectively combining elements gives the finished stainless steel different qualities to suit different applications, which makes the alloy extremely useful and versatile. 

The base metal used to create stainless steel is iron. The iron is alloyed with chromium, which is in fact the crucial element; to be considered as a stainless steel, the alloy must contain 10.5% chromium at an absolute minimum. Many other elements are commonly added to the mix, such as nickel, molybdenum, manganese and more. A lesser-known alloying element used in the manufacture of stainless steel is copper, which is in most cases only found in residual amounts. 

One of the key effects of adding copper to a stainless steel alloying mix is that it decreases its rate of work hardening while providing a simultaneous increase in its ductility. This improvement in ductility allows for a reduction in the amount of machining forces required; this minimises the stress (and subsequent wear and tear) on tools and also allows machining speeds to be increased, improving productivity. During operations like staking, swaging and cold forming, this increased ductility reduces the potential of the alloy cracking. 

Adding copper to stainless steel reduces the final alloy's magnetic permeability. The addition of the element has been shown to reduce magnetic permeability by 30%, making it useful for certain specific applications.  

Perhaps the most well-known property of stainless steel is its corrosion resistance and this important quality can be enhanced further with the addition of copper. This is especially useful in applications where the stainless steel will be exposed to acidic, oxidising media. Exposure causes the copper to form a film on the stainless steel's surface, giving the metal improved protection that helps to prevent the occurrence of pits and crevices. 

Stainless steel wire is one of the components that especially benefits when it contains added copper. Cold heading wire is an extremely versatile product and the copper-containing grade is in fact the industry standard in the manufacture of various fastenings and fixings such as self tapping screws and light machine screws. 

BS Stainless can supply superior cold heading wiremade using specialist stainless steel of 302HQ grade, which contains 3% copper. We also supply profiled wire in the 304 Cu copper-containing grade. For further information about these products, along with our complete collection of stainless steel wire, please browse our website or contact our expert team.