Case hardening and through hardening

Case hardening and through hardening are two metal heat treatment techniques commonly used by MCC.
Each method is employed for different purposes and follows distinct processes.

Case Hardening

Case hardening is primarily used to increase the surface hardness of low carbon steel/low carbon alloy steel.
The process includes the following steps:

Heating: The workpiece is heated to the carburizing temperature range and placed in a carbon-rich environment (such as gas, liquid, or solid medium).

Carburizing: Carbon atoms diffuse into the surface of the steel, forming a high-carbon hardened layer, which significantly increases surface hardness after quenching.

Quenching: The workpiece is rapidly cooled in water or oil, forming a hardened surface layer while the interior remains softer to maintain toughness.

Tempering: After quenching, the workpiece undergoes low-temperature tempering to reduce internal stress and enhance toughness.

The purpose of case hardening is to give the workpiece a high-hardness surface while maintaining toughness in the interior,making it suitable for parts that require high wear resistance, such as pins, bushings, and rollers.

Through Hardening

Through Hardening is a comprehensive heat treatment method aimed at enhancing the overall mechanical properties of the steel.

The process includes:

Heating: The steel is heated to above its critical temperature, transforming it into an austenitic structure.

Quenching: The workpiece is rapidly cooled in water or oil, transforming it into a martensitic structure, which results in overall hardening of the material.

Tempering: After quenching, the workpiece undergoes a medium-temperature tempering process to reduce internal stress and enhance both strength and toughness.

The purpose of through hardening is to provide the workpiece with high strength and toughness,making it suitable for components such as chain plates and pins that need to withstand chain tension.

Differences in Roller Chain Applications

Category	Case Hardening	Through Hardening
Applied Parts	- Pin - Bushing - Roller (wear-resistant surface)	- Pin (high tensile strength) - Chain Plate (excellent               fatigue resistance)
Primary Purpose	Increase surface hardness and enhance wear resistance	Improve overall strength and toughness, capable of withstanding high loads and fatigue stress
Treatment Results	High surface hardness and strong wear resistance	High overall strength, toughness, capable of withstanding tensile and impact stresses

Between the Two Treatments and Roller Chains

In summary, Case Hardening and Through Hardening play complementary roles in the manufacturing of industrial roller chains.

Case hardening enhances the surface hardness of components like pins, bushings, and rollers,providing excellent wear resistance and ensuring the chain's long-term durability in high-wear environments.

On the other hand, Through Hardening improves the overall strength and toughness of chain plates and pins, allowing the chain to withstand heavy loads and impact stresses during repetitive operations. The combination of these heat treatment methods ensures that industrial roller chains are both durable and reliable, maintaining stable performance in demanding industrial conditions.