Fasteners are mainly made of carbon steel, stainless steel, and copper, and carbon steel is the most commonly used.
          Carbon steel is divided into low carbon steel, medium carbon steel, high carbon steel and alloy steel according to the carbon content. the
        1. Low-carbon steel (C%≤0.25%) is mainly used for products without hardness requirements such as grade 4.8 bolts, grade 4 nuts, and small screws.
2. Medium carbon steel (0.25%<C%≤0.45%) No. 35 and No. 45 steel are mainly used for grade 8 nuts and grade 8.8 bolts.
3. High carbon steel (C%>0.45%) is rarely used due to its high hardness and poor processing performance.
         4. Alloy steel: Add alloy elements (such as Mn, Cr, Mo, etc.) to ordinary carbon steel to increase some special properties of steel.
      
       Generally, 35 steel and 45 steel are commonly used for grade 8.8 bolts; 35CrMo; 40Cr for grade 10.9 bolts; 35CrMo and 42CrMo for grade 12.9 bolts.