1. 45 Steel - High-Quality Carbon Structural Steel

Core Characteristics

• It exhibits excellent comprehensive mechanical properties, striking a good balance between strength and toughness, which makes it suitable for parts bearing moderate loads.
• However, it has low hardenability. When water quenching is adopted (a heat treatment process to improve hardness), the material is prone to cracking due to uneven internal stress.
• For heat treatment: Small-sized workpieces are recommended to undergo quenching and tempering treatment (to optimize comprehensive performance), while large-sized workpieces are more suitable for normalizing treatment (to refine grains and reduce internal stress, avoiding cracking).

Application Examples

2. Q235A Steel (A3 Steel) - The Most Commonly Used Carbon Structural Steel

Core Characteristics

• It has high plasticity and toughness, which means it is not easy to break under external force and can undergo a certain degree of deformation, making it suitable for forming processes.
• It possesses excellent weldability and cold stamping performance. It can be easily welded into various structural parts, and can also be processed into different shapes through cold stamping (such as stamping into washers or brackets).
• While it has a certain level of strength to meet general load requirements, its strength is lower than that of medium-carbon steels like 45 Steel. Additionally, it has good cold bending performance, and no cracks will occur when bent at a specified angle.

Application Examples

3. 40Cr Steel - The Most Widely Used Alloy Structural Steel

Core Characteristics

• After quenching and tempering treatment, it has outstanding comprehensive mechanical properties, along with good low-temperature impact toughness (it can still maintain toughness in low-temperature environments) and low notch sensitivity (not prone to stress concentration and cracking at notches).
• It has good hardenability. When oil quenching is used (slower cooling rate than water quenching), it can obtain higher fatigue strength (resistant to damage under cyclic loads), which is beneficial for improving the service life of parts. However, if water quenching is adopted for complex-shaped parts, cracking may still occur due to rapid cooling.
• Its cold bending plasticity is moderate. After tempering or quenching and tempering, it has good machinability (easy to be processed into precise shapes through turning, milling, etc.).
• A key note: Its weldability is poor. Welding without preheating is likely to cause cracks. Therefore, the workpiece must be preheated to 100~150°C before welding.
• It has strong process adaptability: In addition to being used in the quenched and tempered state, it can also be subjected to carbonitriding (to improve surface hardness and wear resistance) and high-frequency surface quenching (to enhance surface strength while keeping the core tough).

Application Examples

Conclusion