There are many commonly used materials for metal shrapnel, such as manganese steel, brass, stainless steel, phosphorus bronze, etc. The specific selection depends on factors such as the usage environment. For example, for general hardware shrapnel, simply use cold plate nickel plating to achieve good results and low cost. The hardware spring of brass has significantly better embroidery resistance in humid environments than other materials, but the cost is higher. Of course, there are other factors to consider, such as whether to weld or not, and how to measure the resistance.