40C8 Mechanical Properties

40C8 Carbon Steel is valued for its high strength, good toughness, and excellent resistance to wear. These mechanical characteristics make it suitable for manufacturing components that must withstand continuous mechanical loads while maintaining dimensional stability.

Property	Metric	Imperial
Ultimate Tensile Strength	660 MPa	95,700 psi
Yield Strength	560 MPa	81,200 psi
Bulk Modulus	140 GPa	20,300 ksi
Shear Modulus	80 GPa	11,600 ksi
Elastic Modulus	190–210 GPa	27,557–30,458 ksi
Poisson’s Ratio	0.27–0.30	0.27–0.30
Elongation at Break	10%	10%
Reduction of Area	40%	40%
Brinell Hardness	197 HB	197 HB
Knoop Hardness	219	219
Rockwell Hardness (B)	92	92
Rockwell Hardness (C)	13	13
Vickers Hardness	207	207
Machinability	55% (Compared to AISI 1212)	55%

Hardness

40C8 Carbon Steel offers a balanced level of hardness that helps improve resistance to abrasion and surface wear without sacrificing machinability. With an approximate Brinell Hardness of 197 HB, it is well suited for engineering components exposed to moderate and heavy mechanical loading.

Heat Treatment

Heat treatment plays an important role in enhancing the overall performance of 40C8 Carbon Steel. Depending on the intended application, different heat treatment processes can improve hardness, toughness, wear resistance, and fatigue strength, allowing the material to perform efficiently in demanding industrial environments.

Hardening

The hardening process involves heating the steel to its recommended hardening temperature before rapidly cooling it in an appropriate quenching medium. This treatment significantly increases surface hardness and improves wear resistance, making the material suitable for high-load engineering applications.

Tempering

Tempering is carried out after hardening to reduce internal stresses and improve toughness. Heating the steel between 550°C and 660°C provides a better balance of strength, hardness, and ductility while minimizing the possibility of brittleness.

Forging Properties

40C8 Carbon Steel demonstrates good forging characteristics when processed within the recommended temperature range. Forging generally begins at approximately 1050°C and should be completed before the temperature falls below 850°C. Controlled cooling after forging helps preserve the steel’s mechanical properties and reduces internal stress.

Stress Relieving

Stress relieving is performed after machining or fabrication to reduce residual stresses that may develop during manufacturing. The material is typically heated to 680°C–700°C, held until the temperature becomes uniform throughout the component, and then cooled naturally in still air. This process improves dimensional stability and reduces the possibility of distortion.

Normalizing

Normalizing is commonly used to refine the grain structure and achieve more uniform mechanical properties. During this process, the steel is heated to approximately 830°C–860°C and then cooled in air. This treatment improves toughness and prepares the material for further machining or heat treatment.

Annealing

Annealing is performed to soften the material and improve its machinability. The steel is heated to approximately 680°C–710°C and then cooled slowly inside the furnace. This process reduces internal stresses and makes machining operations smoother and more efficient.

Density

40C8 Carbon Steel has an approximate density of 7.85 g/cm³, providing an excellent balance of strength, durability, and structural reliability for a broad range of industrial and engineering applications.

Machinability

One of the key advantages of 40C8 Carbon Steel is its good machinability, especially in the annealed condition. It can be turned, milled, drilled, and threaded with ease, enabling manufacturers to produce precision components with excellent dimensional accuracy and surface finish.

Welding

Although 40C8 Carbon Steel can be welded using conventional welding techniques, proper welding procedures should always be followed. Depending on the component size and application, preheating and post-weld heat treatment may be recommended to reduce residual stresses, improve weld integrity, and maintain the desired mechanical properties.