Carbon steel nuts are mainly made of low-carbon steel (such as A3, Q235) and medium-carbon steel (such as No. 35, No. 45). High-grade bolts may use alloy steel (such as 40Cr). They are low in cost and have a wide strength range. Surface treatment is usually required to improve rust resistance and aesthetics, such as galvanizing (blue-white/color zinc), blackening, and phosphating. They are suitable for most general machinery, steel structures, and equipment assembly applications where strength and corrosion resistance requirements are not stringent. They are the most mainstream nuts in industry.
