GCr15 Bearing Steel
GCr15 Bearing Steel, namely GCr15 bearing steel, is introduced in detail as follows:
Basic Information
Definition: GCr15 is a high-carbon chromium bearing steel with low alloy content, excellent performance, and wide application.
Corresponding Standards: It complies with China’s GB standard, equivalent to AISI 52100 in the United States, DIN 100Cr6 in Germany, etc.
Chemical Composition
Carbon (C): Generally 0.95%-1.05%. High carbon content helps improve the hardness and strength of the steel and enhance wear resistance, but it also reduces the toughness of the steel.
Manganese (Mn): 0.25%-0.45%. It can improve the strength and hardness of the steel and optimize its hot working performance.
Silicon (Si): 0.15%-0.35%. It enhances the strength and hardness of the steel and improves its oxidation resistance and corrosion resistance.
Sulfur (S): ≤0.025%. Sulfur is a harmful element that reduces the toughness and fatigue strength of the steel, so its content must be strictly controlled.
Phosphorus (P): ≤0.025%. Phosphorus is also a harmful element, which reduces the toughness and plasticity of the steel and causes cold brittleness.
Chromium (Cr): 1.40%-1.65%. Chromium is the main element that improves the hardenability, hardness, and wear resistance of the steel. It also enhances oxidation resistance and corrosion resistance.
Molybdenum (Mo): ≤0.10%. It can improve the strength and hardness of the steel and optimize its high-temperature performance.
Nickel (Ni): ≤0.30%. It enhances the toughness and corrosion resistance of the steel.
Copper (Cu): ≤0.25%. Excessive Cu content deteriorates the hot working performance of the steel. Meanwhile, it is specified that Ni + Cu ≤ 0.50%.
Physical Properties
Density: Approximately 7.85 g/cm³.
Elastic Modulus: Approximately 210 GPa.
Thermal Expansion Coefficient: Approximately 11.7×10⁻⁶/℃ in the range from room temperature to 100℃.
Mechanical Properties
High Hardness: After quenching and low-temperature tempering, the hardness can reach 62-66 HRC, providing good wear resistance and deformation resistance, enabling it to withstand high pressure and friction during bearing operation.
High Strength: The compressive strength is ≥2400 MPa, and the bending strength is ≥2000 MPa, allowing it to bear large loads and ensuring the stability of bearings under high-speed rotation and heavy load conditions.
High Contact Fatigue Strength: The contact fatigue life L10 is ≥1×10⁷ cycles (under a load of 4 GPa). It can withstand repeated cycles of contact stress and is less prone to failure modes such as fatigue spalling, thus extending the service life of bearings.
Good Toughness: The impact energy is ≥12 J (for unnotched specimens). While having high hardness and strength, it also has certain toughness, preventing brittle fracture of bearings when subjected to impact loads.
Processing Performance
Hot Working Performance: The hot working temperature range of GCr15 steel is generally 205-538℃. Hot working within this temperature range can give the steel good structure and performance.
Cold Working Performance: In the annealed or normalized state, conventional cold working methods such as cold drawing, cold extrusion, and cold rolling can be used.
Machinability: Machinability is moderate. After spheroidizing annealing, its machinability can be improved, reducing cutting force and enhancing the surface quality of processed parts.
Weldability: Weldability is poor. Welding is prone to defects such as cracks and pores, so welding is generally not used for connection in practical applications.
Heat Treatment Process
Spheroidizing Annealing: Heating to 790-810℃, holding for a certain time, and then cooling with the furnace. This process obtains a spheroidal pearlite structure, reduces hardness, improves machinability, and prepares the structure for subsequent quenching.
Quenching: Usually heated to 830-850℃ and quenched in oil. This process enables the steel to obtain a martensitic structure, improving hardness and strength, but the steel has high internal stress and brittleness after quenching.
Tempering: Low-temperature tempering is generally carried out at 150-180℃ to eliminate quenching internal stress, reduce brittleness, and maintain high hardness and wear resistance; high-temperature tempering at 650-700℃ can achieve better comprehensive mechanical properties.
Application Fields
Bearing Manufacturing: It is the main material for manufacturing rolling bearings, such as balls, rollers, and bearing rings. It is widely used in rotating components of various mechanical equipment, including motors, automobiles, machine tools, aerospace, and other fields.
Tool Manufacturing: It can be used to make various measuring tools such as calipers, micrometers, and gauge blocks, as well as molds such as cold stamping dies and wire drawing dies, and some cutting tools such as drills and reamers.
Other Fields: It can also be used to manufacture mechanical parts requiring high hardness, high wear resistance, and high fatigue strength, such as camshafts, gears, piston pins, and valve lifters.