GCr15 Steel | 52100

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GCr15 steel is a widely used high-carbon chromium bearing steel and is also considered a low-alloy cold work mold steel. It is a representative grade among high-carbon chromium-bearing steels. This steel can be either water or oil quenched, depending on the application and desired properties.

1. Chemical Composition(GB / T 18254—2002)

CSiMnCrPSV
0.95 ~ 1.050.15 ~ 0.350.25 ~ 0.451.40 ~ 1.65≤0.025≤0.025—

2. GCr15 Steel Critical Point Temperature

Critical PointAc1AccmAr1Ms
Temperature (Approx. Value)/°C745900700246

3. GCr15 Steel Forging Process Specification

ItemHeating Temperature/°CInitial Forging Temperature/°CFinal Forging Temperature/°CCooling
Steel Ingot1150 ~ 12001100 ~ 1150800 ~ 880First air-cool to 700°C, then pit-cool
Steel Billet1080 ~ 11201050 ~ 1100800 ~ 850First air-cool to 700°C, then pit-cool

4. GCr15 Steel Heat Treatment Process Specification

4.1 Preheating

Preliminary Heat Treatment PlanProcess Parameters
Isothermal Annealing after ForgingSlowly heat to 770 ~ 790°C, hold for 1 ~ 2h; furnace cool to 680 ~ 700°C, hold for 3 ~ 4h, then furnace cool to below 550°C and air cool. Hardness: 180 ~ 229HBW.
High-Temperature TemperingHeating temperature: 600 ~ 700°C, hold for 2 ~ 3h; furnace cool or air cool. Hardness: 187 ~ 229HBW. Mainly used to eliminate machining stress before quenching.
NormalizingHeating temperature: 930 ~ 950°C, air cool. Hardness: 302 ~ 388HBW. Used to refine the grains of overheated steel and eliminate network carbides.
Quenching and TemperingQuenching temperature: 840 ~ 860°C, oil cool; tempering temperature: 660 ~ 680°C, furnace cool or air cool. Hardness: 197 ~ 217HBW.

4.2 Quenching

Quenching Process PlanProcess Parameters
Conventional Quenching ProcessHeating temperature: 830 ~ 850°C, oil cool. Hardness: 62 ~ 65HRC.
Isothermal Quenching ProcessHeating temperature: 830 ~ 850°C, isothermal quenching at 240 ~ 300°C. Tempering temperature: 180 ~ 200°C. Hardness: 58 ~ 62HRC.

Note: To save energy and time, the residual heat from forging can be used for the isothermal quenching process to replace spheroidizing annealing.

Ultra-fine processing of carbides.

Carbide Super-refinement Process

Heat Treatment ProcessProcess Parameters
Super-refinement TreatmentSolution temperature is 1050°C, followed by isothermal treatment in a salt bath at 300 ~ 350°C to obtain a lower bainite structure. The tempering temperature is around 720°C with a holding time of 2h, but the hardness is too high, leading to difficult machining. An alternative is a short-time spheroidizing process: heat to 720°C and hold for one hour, then raise the temperature to 780°C and hold for one hour, then cool back to 720°C and hold for another one hour. Finally, in furnace cooled to 500°C before removing. This process can obtain ultra-fine spheroidized carbides.

4.3 Tempering

Tempering Process Specification

Heating Temperature/°CCooling MethodHardness HRC
150 ~ 190Oil cool or air cool58 ~ 62

Tempering Temperature and Hardness

Tempering Temperature/°CUntempered200300400500550600650
Hardness HRC6261564940363128

Note: Oil quenched at 830°C, tempered for two hours.

GCr15
GCr15 steel

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5. Mechanical Properties

GCr15 is a special steel for bearings. It has good hardenability, hardness, and wear resistance, high contact fatigue strength, and good dimensional stability during quenching and tempering. Tools and molds made with it have high toughness and wear resistance after low-temperature tempering, which can significantly extend their service life.

Relationship between Quenching Temperature, Microstructure, and Performance

Quenching Temperature/°CMass Fraction of Carbon in Martensite (%)Retained Austenite Content (volume fraction, %)Hardness HRCBending Strength σbb/MPaImpact Toughness αK /(J/cm²)
8200.41, Mainly lath martensite—62.832346.67
8350.49, Mainly lath martensite10.4063.727245.19
8450.52, Mixture of lath and acicular martensite14.7064.134205.19
8550.55, Mixture of lath and acicular martensite—64.932633.53
8650.59, Mixture of lath and acicular martensite16.9065.129603.43
8750.67, Mainly acicular martensite21.2065.427392.55
8850.67, Mainly acicular martensite—65.324502.45

Note: Tempered at 160°C.

6. Applications

  • Bearings: Its primary and most widespread application is in the manufacturing of various types of bearings, including races, steel balls, tapered rollers, cylindrical rollers, spherical rollers, and needles.
  • Molds and Dies (Cold Work): It is frequently used for cold stamping dies, cold heading dies, drawing dies, extrusion dies, and cutting dies/blades. It’s also suitable for plastic molds, especially those requiring high wear resistance, strength, and ability to handle high loads, and for other molds like rolling dies and powder metallurgy dies.
  • Precision Measuring Tools: GCr15 is a preferred material for precision measuring instruments such as gauge blocks, plug gauges, and thread ring gauges.
  • Machine Parts: It’s utilized in various machine components, including guide pillars and guide bushings, diesel engine injectors, and precision lead screws.
  • Other Applications: It’s also used for spring collets and as a material for general cutting tools.

7. Equivalent Material

  • AISI/SAE: 52100
  • DIN (German): 100Cr6 (or 1.3505)
  • JIS (Japanese): SUJ2
  • ISO: 100Cr6

FAQ

What is GCr15 material?

GCr15 steel is a high-carbon chromium bearing steel and a low-alloy cold work mold steel. It is widely used due to its excellent hardness, wear resistance, and high contact fatigue performance after heat treatment.

What is the hardness of GCr15 in HRC?

After quenching, GCr15 steel typically achieves a hardness of ≥62 HRC, 61-65 HRC, or ≥63 HRC. After standard low-temperature tempering (150-190°C), its hardness generally ranges from 58-62 HRC to 61-65 HRC. For instance, GCr15, when oil quenched from 845°C and tempered at 150°C, can reach 61-65 HRC.

What is the difference between GCr15 and 52100?

GCr15 and 52100 steel are essentially the same material, serving as direct equivalents under different international standards. GCr15 is the Chinese designation, while 52100 is the American ASTM (American Society for Testing and Materials) designation.

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