AISI4140 Alloy Seamless Steel Pipe for machining DN10 - DN400 SCH160 XXS

4140 steel is a versatile low-alloy steel that contains chromium, molybdenum, and manganese. Its composition imparts excellent hardenability, making it suitable for heat treatment processes. This steel alloy exhibits high tensile strength, good fatigue resistance, and exceptional toughness, making it ideal for applications that require durability and reliability.

4140 Steel Chemical Compositions

The chemical composition of 4140 steel typically includes the following elements:

• Carbon (C): 0.38-0.43%
• Chromium (Cr): 0.80-1.10%
• Manganese (Mn): 0.75-1.00%
• Silicon (Si): 0.15-0.35%
• Phosphorus (P): ≤0.035%
• Sulfur (S): ≤0.040%
• Molybdenum (Mo): 0.15-0.25%

Heat Treatment Methods

1. Annealing: Annealing is the first step in the heat treatment process. It involves heating the steel to a specific temperature (around 800-850°C) and then slowly cooling it to room temperature. This process relieves internal stresses, refines the grain structure, and improves machinability.
2. Normalizing: Normalizing is performed after annealing to further refine the microstructure. The steel is heated to a temperature slightly above the critical range (around 870-900°C) and then air-cooled. Normalizing enhances the steel’s strength and hardness while maintaining good ductility.
3. Quenching: Quenching is a rapid cooling process that involves immersing the heated steel into a quenching medium, such as oil, water, or polymer. This step hardens the steel by transforming the austenite phase into martensite, a hard and brittle structure. The quenching process must be carefully controlled to prevent cracking or distortion.
4. Tempering: Tempering is the final step in the heat treatment process. The quenched steel is reheated to a specific temperature (typically between 150-600°C) and then cooled in still air. Tempering reduces the brittleness of the steel, improves its toughness, and relieves residual stresses.