if a metal is cold worked it can develop a surface hardness. Shot blasting is a method of producing surface hardness that consists of hitting the surface of a component with many hardened steel balls. Expansion and contraction of copper piping, used for steam, can also lead to a hardness and brittleness that has to be removed by annealing. Lifting tackle such as shackles, Chains, etc., can develop surface hardness and brittleness due to cold working, hence they have to be annealed at regular intervals (as laid down by the MCA working in close co-ordination with the Health and Safety Executive).