The life of the headset bearing is not only determined by personal operation and use, but also determined by the forging process. The addition of different materials during production will affect the final product life. So what are the material factors that affect the product life? This is what we will explain in this issue.
1. Martensite in quenched steel
Quenching of high carbon chromium steel original structure pearlite quenching + low temperature tempering: The carbon content in quenched martensite M significantly affects the mechanical properties of steel. The carbon content of GCr15 steel quenched M is 0.5% to 0.56%, which can obtain the strongest comprehensive mechanical properties against invalidation. M: cryptocrystalline martensite, the measured carbon content is the average carbon content.
2. Residual austenite in quenched steel
After normal quenching, the high carbon chromium steel can contain 8% to 20% Ar (residual austenite) for customized mountain bike headset bearing products. Ar in bearing parts has both advantages and disadvantages. The Ar content is as high as possible. The Ar%↑ strength and touch fatigue life increase accordingly. It is beneficial to reduce Ar after reaching the peak. Ar is in a stable state. If it spontaneously transforms into martensite, the toughness of the steel will decrease sharply and become brittle.
Bearing load is small: Ar deformation not only reduces the stress peak, but also strengthens the deformation Ar processing and stress strain, leading to martensite changes and strengthening. The impact of Ar increase on touch fatigue life, reducing bearing load: Ar large plastic deformation and substrate will partially produce stress and crack, thereby reducing service life
3. Insoluble carbides in quenched steel
The total number, appearance and specifications of insoluble carbides in quenched steel are affected by the chemical composition of the steel and the original organization before quenching. Customized products of road bike headset bearings are affected by the requirements of austenitization. Load (especially carbides are non-spherical) will cause stress and cracks, thereby reducing toughness and fatigue resistance.
Quenching undissolved carbides affect the performance of steel, affect the carbon content and carbon content Ar content and distribution of quenched martensite, and thus have an additional impact on the performance of steel.
Too much quenching undissolved carbides is harmful to the comprehensive mechanical properties and ineffective resistance of steel. A small amount of insoluble carbides after quenching is necessary for wear resistance. Fine-grained cryptocrystalline martensite requires insoluble carbides to be few (small number), small (small size), uniform (small size difference, uniform distribution), and round (each carbide is spherical).
The price of bowl set bearing manufacturers is very high, so appropriately reducing the carbon content of bearing steel is one of the ways to increase the service life of the product.
