High carbon chromium bearing steel

      What are the grades, uses and characteristics of high carbon chromium bearing steels? The bearing network will be introduced in detail for everyone.

       High carbon chromium bearing steels have high contact fatigue strength and wear resistance. Many grades are fully hardened steels such as GCr15 GCr15SiMn, GCr15SiMo, and GCr18Mo. However, since some bearings require good toughness in the core and high hardness on the surface, a hardened bearing steel such as GCr4 has been developed.

       1 GCr15 (fully hardened steel) GCr15 is a typical steel grade of high carbon chromium bearing steel, which has high hardness, wear resistance and contact fatigue strength after quenching and tempering. Its hot workability and workability are good, the hardenability is moderate, but the weldability is poor. GCr15 has a large white point sensitivity, but this defect can be eliminated in bearings that are vacuum degassed. It is used to manufacture rolling bearing rings with wall thickness ≤12mm and diameter ≤250mm, or to manufacture cones, cylinders, spherical rollers and all sizes of needles with diameter ≤22mm. It can also be used to make molds, gauges and woodworking tools as well as mechanical parts with high elastic limit and high fatigue strength.

       2 GCr15SiMn (highly hardened steel) improves the content of silicon and manganese on the basis of GCr15 steel, so the hardenability, elastic limit and wear resistance are better than GCr15. The rolling bearing parts produced therefrom should not be used above 180 °C. It is used for the manufacture of rolling bearing rings with wall thickness >12mm, outer diameter >120mm, steel balls with diameter >50mm and cones, cylinders, spherical rollers and all sizes of needles with diameter >22mm. Other uses are the same as GCr15.

       3 GCr15SiMo (highly hardened steel) increases the silicon content based on GCr15 and adds molybdenum. It has high hardenability, good wear resistance, high fatigue strength and good overall performance. It is suitable for the manufacture of rolling bearing rings and steel balls, rollers and the like in a large size range.

       4 GCr18Mo (high-hardenable steel) adds molybdenum with a mass fraction of 0.15%~0.25% on the basis of GCr15, and increases the content of each, so the hardenability and wear resistance are improved. The lower bainite austempering can be performed to achieve hardness and wear resistance similar to martensite quenching, and the impact, fracture toughness and flexural strength of the steel are improved, thereby improving the overall mechanical properties and life of the steel. A rolling bearing ring with a wall thickness of up to 20 mm can be produced, and the size range of the rolling bearing member is also expanded.

       5 GCr4 (restricted hardened steel) GCr4 is a low-hardenability rolling bearing steel. It has the properties of GCr15 fully hardened bearing steel and low carbon alloy carburized steel after being heated by volumetric tip and surface quenched and tempered. After quenching, the surface hardness is high, the surface resistance is good, the fatigue resistance is good, the core hardness is only 35~40HRC, and the toughness is good and impact resistant. It is mainly used to manufacture rolling bearing rings and rollers of various sizes and loads.https://www.supplyforever.com/

Characteristics, chemical composition, heat treatment process and application of GCr15 steel

Core Tip: Focus on China Bearing Network and learn more about bearing. This article will take you to understand the characteristics, chemical composition, heat treatment process and application of GCr15 steel.
 Pay attention to China Bearing Network and learn more about bearing. This article will take you to understand the characteristics, chemical composition, heat treatment process and application of GCr15 steel.
1. Characteristics of GCr15 steel
GCr15 steel is developed by adding Cr element mainly on the basis of T10A steel. The characteristics of GCr15 steel are as follows:
(1) The addition of Cr element to GCr15 steel is mainly to improve the hardenability of steel, and to dissolve in the matrix to strengthen the matrix structure. In addition, the dissolution of Cr element into Fe3C to form a composite (Fe, Cr) 3C can increase its hardness and increase the hardness and wear resistance of the steel.
(2) Due to the addition of a single weak carbide forming element Cr in steel, the mechanical properties, wear resistance, hardenability and quenching deformation of GCr15 steel are inferior to those of CrWMn steel.
2. The main chemical components of GCr15 steel
0.95%~1.05%C, 0.25%~0.45%Mn, 1.40%~1.65%Cr, 0.15%~0.35%Si, ≤0.025%P, ≤0.025%S.
3. Heat treatment process of GCr15 steel
The phase transition point of GCr15 steel is: AC1745 °C, Accm900 °C, Ar1700 °C, Ms235 °C.
GCr15 steel has an initial forging temperature of 1050~1100 °C, a final forging temperature of 800~850 °C, and air cooling to 700 °C after forging, cooling in sand or cooling in the pit.
Common heat treatment process for GCr15 steel
Heat treatment process Process parameters Hardness requirements Process characteristics
Incomplete annealing Heating 770~790°C, after cooling, the furnace is cooled to below 550 °C and air-cooled 187~229HBS Ac1745°C, Accm900°C, heating temperature should be between Ac1~ Accm
Isothermal spheroidizing annealing heating 770 ~ 790 ° C, 680 ~ 700 ° C isothermal after cooling with the furnace to 550 ° C below the air cooling 187 ~ 229HBS heating temperature should be between Ac1 ~ Accm, the isothermal temperature should be lower than Ar1700 ° C line 20 ° C, to Obtaining granular pearlite structure
Stress relief annealing Heating 600~700°C, heat preservation, air cooling 187~229HBS Eliminate residual stress and eliminate work hardening
Normalizing Heating 930~950°C, heat preservation, air cooling 302~388HBS Heating temperature is higher than Accm, eliminating segregation, band structure, network structure, grain refinement
Quenching heating 830~850 °C, heat preservation, oil cooling 62~65HRC Quenching heating temperature between Ac1~ Accm, dissolution of Cr element, improve hardenability, improve tempering stability, and also reduce Ms point, there are many residues Austenite
Lower bainite austempering plus 830 ~ 850 ° C, 240 ~ 300 ° C salt bath bath isothermal, after the bath air cooling 58 ~ 62HRC Ms 202 ° C, austempered quenching structure for lower bainite + carbide + a small amount of martensite + pole A small amount of retained austenite, small quenching deformation, high strength and good toughness
Tempering heating 150~190°C, heat preservation for 2h, furnace cooling 58~~62HRC Emphasizing the lower limit of hardness, emphasizing the upper limit of toughness
Quenching and quenching: heating 840~860 °C, oil cooling; tempering: heating 660~680 °C, furnace cooling or air cooling after heat preservation 197~217HBS high temperature quenching can eliminate carbide structure defects, high temperature tempering to get fine tempering Soxhlet Body tissue, prepared for re-quenching, improves strength while improving strength. Quenching: heating temperature 820~840 °C, oil cooling
Double refining treatment Quenching heating 1050 ° C, heat preservation, 320 ° C isothermal 2 h air cooling. Tempered and heated at 710 ° C for 2 h. Re-quenching and heating at 820 ° C, heat preservation, oil cooling. Reheating and heating at 230 ° C, holding 2 h 62 HRC to obtain extremely fine quenched structure, improve the toughness of steel
Solid boronizing Boronizing is heated at 920 ° C, kept for 5 h, and oil-cooled. Infiltration agent: 3% B4C + 5% KBF4 + 5% (NH2) 2CO + 87% SiC 1500 ~ 1700HV The surface is obtained with a high hardness boride layer, and the core is a quenched structure. Layer thickness 0.145mm
Liquid chromizing heating 950 ° C, heat preservation 4h, oil cooling, infiltration agent: 15% Cr2O3 + 2.5% rare earth silicon magnesium + 72.5% borax 1665HV thickness of the layer: 0.01056mm. Improve surface impermeability, wear resistance and corrosion resistance
The liquid is infiltrated with vanadium and heated at 950 ° C for 4 h; the temperature is lowered at 860 ° C for 2 h; the temperature is raised at 950 ° C for 4 h, and the oil is cooled. Infiltration agent: 90% BaCl2+7% V2O5+3% Na2B4O7+Al powder 2500HV0.1 Infiltration layer thickness: 0.020mm. Improve surface hardness and wear resistancehttps://www.supplyforever.com/