Bearing steels — typical material selection Ball bearings are usually manufactured from which steel to provide high hardness, fatigue strength, and wear resistance?

Introduction / Context:
Balls and races in rolling-element bearings require materials with high hardness, cleanliness, and fatigue strength. The industry standard is a high-carbon chromium steel (often designated as 52100 or SUJ2), colloquially called “chrome steel”.

Given Data / Assumptions:

• Application: rolling-contact fatigue under high Hertzian stresses.
• Desirable properties: high hardness (typically 60–66 HRC), fine carbides, and high cleanliness to reduce spalling.
• Controlled heat treatment and finishing are applied.

Concept / Approach:
Chrome steel (high carbon ~1% and chromium ~1.5%) develops a martensitic matrix with fine dispersed carbides after quench and temper, yielding excellent wear resistance and contact-fatigue life. Low or medium carbon steels cannot reach the required hardness; austenitic stainless lacks the necessary high hardness in standard conditions.

Step-by-Step Solution:
Identify property requirements for bearings: hardness + fatigue strength.Match material: high-carbon chromium steel meets these goals.Exclude other carbon ranges that cannot achieve sustained hardness/wear resistance.Therefore select “chrome steel”.

Verification / Alternative check:
Manufacturer datasheets and standards (e.g., AISI 52100) confirm widespread use for bearing balls and races.

Why Other Options Are Wrong:
Low/medium carbon steels lack attainable hardness; generic “high carbon steel” is incomplete without chromium additions; austenitic stainless is typically non-hardenable by quench and temper.

Common Pitfalls:
Confusing corrosion resistance priorities with bearing fatigue needs; stainless may be used in special environments but usually in martensitic grades specifically designed for hardness.

Final Answer:
chrome steel