4.8 grade carriage bolt: Its minimum tensile strength is 400MPa, and the ratio of yield strength to tensile strength is 0.8, so the minimum yield strength is 320MPa. These types of bolts are generally made of low-carbon steel and undergo a simple heat treatment process, resulting in relatively low strength. They are suitable for situations where strength requirements are not high, such as ordinary furniture connections and less important mechanical component connections.
8.8 grade carriage bolt: The minimum tensile strength is 800MPa, the ratio of yield strength to tensile strength is 0.8, and the minimum yield strength is 640MPa. It is usually made of medium carbon steel and undergoes quenching and tempering treatment. Its strength and hardness are higher than those of grade 4.8, and it can withstand large loads. It can be used for connecting key parts of transportation vehicles such as cars and tractors, as well as in situations where strength is required in some industrial equipment.
10.9 grade carriage bolt: The minimum tensile strength is 1000MPa, the ratio of yield strength to tensile strength is 0.9, and the minimum yield strength is 900MPa. Made of medium carbon alloy steel and subjected to stricter heat treatment processes, it has high strength and good toughness, making it suitable for high-strength connection applications such as heavy machinery, bridges, steel structure buildings, etc., where bolts are required to withstand large tensile and shear forces.
