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The Influence of Each Element on Bearing Steel

Bearing steel is a grade of steel used to manufacture rolling elements such as balls and rollers, as well as inner and outer rings for rolling bearings. It can also be employed in the production of precision measuring instruments, cold‑heading dies, machine tool leadscrews, and precision mating components for diesel fuel pumps. During operation, bearings endure extremely high pressures and friction; therefore, bearing steels must exhibit high, uniform hardness and wear resistance, along with a high elastic limit.

Bearing steel is used to manufacture the balls, rollers, and inner and outer rings of rolling bearings. Steel grades designated for bearing applications can also be used to manufacture precision measuring instruments, cold‑heading dies, machine‑tool leadscrews, and precision mating components for diesel‑engine fuel pumps. During operation, bearings endure extremely high pressures and friction; therefore, bearing steels must exhibit high, uniform hardness and wear resistance, as well as a high elastic limit. Stringent requirements are imposed on the chemical‑composition uniformity of bearing steels, the content and distribution of nonmetallic inclusions, and the morphology and distribution of carbides, making them among the most demanding steel grades in all steel production.

Carbon ( C) — The higher the carbon content, the greater the yield strength and tensile strength, and the higher the hardness; however, ductility and impact toughness decrease, and carbon increases the steel’s cold brittleness and age‑sensitivity.

Manganese (Mn) — Manganese is an excellent deoxidizer and desulfurizer. It forms solid solutions with iron, enhancing the hardness and strength of both ferrite and austenite in steel and refining the pearlite microstructure. It also indirectly increases the strength of pearlitic steels. Furthermore, manganese’s ability to stabilize the austenitic structure significantly improves the hardenability of the steel.

Silicon (If)---- Silicon is soluble in both ferrite and austenite, thereby enhancing the hardness and strength of steel. It also increases the elastic limit, yield strength, and yield ratio of steel. (σs/σb), as well as fatigue strength and the fatigue ratio (σ-1/σb), among others. It also reduces the anisotropy of the crystal structure and enhances the steel’s oxidation resistance at elevated temperatures.

Sulfur (S)---- It can improve the machinability of steel. . Because its chips are brittle, it can produce a very smooth surface. Sulfur originates from the ores used in steelmaking and from the fuel coke. It is a harmful element in steel. Sulfur exists in steel in the form of iron sulfide (FeS). During hot working, the presence of FeS can cause cracking in the workpiece; this phenomenon is known as “hot shortness.”

Phosphorus (P)----It significantly reduces the steel’s ductility and toughness, with this effect being particularly pronounced at low temperatures; this phenomenon is known as cold brittleness. Sulfur and phosphorus have similar effects, making the material easier to chip during machining, which is beneficial for improving machinability. Phosphorus is the most effective element in strengthening ferrite and promotes recrystallization.

Molybdenum (Mo) — In steel, it enhances hardenability and high-temperature strength, prevents temper embrittlement, and improves tempering stability, allowing components to be tempered at elevated temperatures. This more effectively relieves (or reduces) residual stresses and increases ductility. Additionally, in the carburized layer, it diminishes the tendency of carbides to form a continuous network along grain boundaries, reduces retained austenite, and correspondingly enhances the wear resistance of the surface layer; however, it can also promote decarburization.

Nickel ( Ni) — It can enhance the strength and toughness of steel and improve its hardenability. At high levels, it can significantly alter certain physical properties of steels and alloys, thereby increasing the steel’s corrosion resistance. Nickel also boosts the strength of steel while maintaining good ductility and toughness.

High strength, high toughness, excellent hardenability, and superior corrosion resistance; however, it will reduce the hardness of the quenched layer.

Copper ( Cu) — enhances atmospheric corrosion resistance, particularly when used in combination with phosphorus; improves strength and toughness, and increases the stability of austenite in steel, thereby enhancing hardenability and quenchability; strengthens ferrite; however, it can induce age-hardening, which may adversely affect bearing accuracy.

Chromium (Cr) — Chromium enhances the hardenability of steel and exhibits a secondary hardening effect. It can increase the hardness and wear resistance of high-carbon steels without compromising their toughness; it also improves both strength and hardness. Furthermore, chromium elevates the high-temperature mechanical properties of steel. Steels containing chromium exhibit high hardness, high strength, a high yield point, and excellent wear resistance, while exerting only minimal adverse effects on ductility and toughness, along with superior oxidation resistance and corrosion resistance.

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