What kind of steel is 45# steel and what is the difference between it and other grades?

45# steel is a high-quality carbon structural steel widely used in machinery manufacturing. It offers excellent mechanical properties and is relatively inexpensive.

C45 (1.0503) is a high-strength, medium-carbon, high-quality steel. C45, a UNI standard steel from Italy, is generally used in the normalized state due to its poor hardenability. When higher mechanical properties are required, it is tempered. Its cold deformation plasticity is moderate, and its machinability after annealing and normalizing is better than after tempering. C45 is the DIN designation, known as 45 steel in the national standard, S45C in the JIS standard, and 1045,080M46 in the ASTM standard. It is used to manufacture parts requiring high strength, such as gears, shafts, and piston pins, as well as machined parts, forgings, stampings, bolts, nuts, and pipe fittings subject to low loads.

High-quality carbon structural steel is carbon steel with a carbon content of less than 0.8%. This steel contains less sulfur, phosphorus, and non-metallic inclusions than carbon structural steel, and exhibits superior mechanical properties.

China GB Standard Steel Grade 45; Japan JIS Standard Steel Grades S45C/S48C; German DIN Standard Material Steel Grade 1.0503; German DIN Standard Steel Grade C45; British BS Standard Steel Grade IC45/080A47; French AFNOR Standard Steel Grade CC45; French NF Standard Steel Grade C45; Italian UNI Standard Steel Grade C45; Belgian NBN Standard Steel Grade C45-1; Swedish SS Standard Steel Grade 1650; Spanish Standard Steel Grade F.114; American AISI/SAE Standard Steel Grade 1045; International Organization for Standardization ISO Standard Steel Grade C45E4. C45 Implementation Standard: EN 10083/2-1991

Normalizing at 850°C; Quenching at 840°C; Tempering at 600°C.

Carbon (C): 0.42-0.50%, Silicon (Si): ≤0.40%, Manganese (Mn): 0.50-0.80%, Sulfur (S): ≤0.045%, Phosphorus (P): ≤0.045%, Chromium (Cr): ≤0.40%, Nickel (Ni): ≤0.40%, Molybdenum (Mo): ≤0.10.

Aside from carbon (C) and a certain amount of alloying elements (generally not exceeding 0.40%) and manganese (Mn) (generally not exceeding 0.80%, but can reach up to 1.20%) for deoxidation, the steel contains no other alloying elements (except residual elements). This type of steel must meet both chemical composition and mechanical properties. The sulfur (S) and phosphorus (P) impurity content is generally controlled below 0.035%. If this is controlled below 0.030%, it is called high-grade steel, and the grade is followed by "A," for example, 20A. If P is controlled below 0.025% and S is controlled below 0.020%, it is called special-grade steel, and the grade is followed by "E" to distinguish it. The content of other residual alloying elements introduced into the steel from the raw materials, such as chromium (Cr), nickel (Ni), and copper (Cu), is generally controlled to Cr ≤ 0.25%, Ni ≤ 0.30%, and Cu ≤ 0.25%. Some grades contain manganese (Mn) content as high as 1.40%, and are called manganese steel.

Tensile strength σb (MPa): ≥600(61), yield strength σs (MPa): ≥355(36), elongation δ5 (%): ≥16, cross-sectional shrinkage ψ (%): ≥40, impact energy Akv (J): ≥39, impact toughness value αkv (J/cm2): ≥49(5), hardness: unheat treated, ≤229HB; annealed steel, ≤197HB.

Widely used in various industries such as aerospace, power, petrochemical, shipbuilding, machinery, electronics, and environmental protection.