Analysis and comparison of 42CrMo and 45 steel

Both 42CrMo and 45 steel are commonly used types of steel, but they differ significantly in composition, properties and applications.

Chemical Composition of 42CrMo(%)

Element	Content Range
Carbon (C)	0.38 – 0.45
Silicon (Si)	0.17 – 0.37
Manganese (Mn)	0.50 – 0.80
Phosphorus (P)	≤ 0.035
Sulfur (S)	≤ 0.035
Chromium (Cr)	0.90 – 1.20
Molybdenum (Mo)	0.15 – 0.25

Chemical Composition of 45 Steel (%)

Element	Content Range
Carbon (C)	0.42 – 0.50
Silicon (Si)	0.17 – 0.37
Manganese (Mn)	0.50 – 0.80
Phosphorus (P)	≤ 0.035
Sulfur (S)	≤ 0.035
Chromium (Cr)	——
Molybdenum (Mo)	——

42CrMo: This is a high-strength alloy structural steel containing chromium (Cr) and molybdenum (Mo), which are alloying elements that help improve the steel’s wear resistance, corrosion resistance, and heat resistance.

45 steel: A high-quality carbon structural steel, mainly composed of iron and carbon, and also contains small amounts of silicon (Si), manganese (Mn), phosphorus (P), and sulfur (S). Its high carbon content gives the steel a certain strength and hardness.

Mechanical properties

42CrMo: It has high tensile and compressive strengths, and its performance can be further improved after proper heat treatment. It exhibits good toughness and fatigue resistance, and is suitable for use in high-load and impact environments.

45 steel: Although it also has good strength and toughness, its strength and hardness are relatively lower than 42CrMo. However, 45 steel has good plasticity and machinability, and its properties can be adjusted through heat treatment processes such as quenching.

Processing performance

42CrMo: Due to the high degree of alloying, it is usually more difficult to process than 45 steel, but it has good comprehensive mechanical properties and is suitable for manufacturing parts that bear heavy loads.

45 steel: Easy to cut and process, suitable for making parts with complex shapes.

Corrosion resistance

42CrMo: Generally has better corrosion resistance than 45 steel, especially in environments containing chemicals.

45 steel: It is easy to rust in a humid environment, so protective measures need to be taken to prevent corrosion.

Application areas

42CrMo: Due to its high strength and excellent durability, it is often used to manufacture key components such as ships, petrochemicals, and machinery manufacturing, including bearings, bolts, connecting rods, crankshafts, etc., as well as gears that require high reliability.

45 steel: Widely used in general machinery manufacturing, such as manufacturing shaft parts, gears, pins, etc., it is more suitable for occasions where the surface hardness requirements are not high or the required hardness can be achieved through surface hardening treatment.

If the gear needs to maintain high performance under complex working conditions, such as heavy loads, high-speed operation, or high wear resistance requirements, then 42CrMo may be a better choice. For some gears under normal working conditions, 45 steel may be given priority due to its cost-effectiveness.