CN105239017A - Carburization bearing steel and preparing method thereof - Google Patents

Abstract

The invention discloses carburization bearing steel. The surface of the carburization bearing steel is a compound organization composed of low-temperature bainite and martensite, and the core part of the carburization bearing steel is the low carbon martensite organization. The carburization bearing steel comprises, by weight percentage, 0.20%-0.25% of C, 1.20%-1.50% of Si, 0.20%-0.40% of Mn, 1.35%-1.75% of Cr, 2.20%-2.60% of Ni, 0.25%-0.35% of Mo, smaller than or equal to 0.010% of S, smaller than or equal to 0.015% of P, smaller than or equal to 0.0008% of O, smaller than or equal to 0.003% of Ti, smaller than or equal to 0.00015% of H, and the balance Fe and normal impurities. A manufacturing method of the carburization bearing steel comprises the steps that conventional carbonization treatment is carried out on the surface of a machined bearing blank, the surface carbon content ranges from 0.85wt.% to 1.05 wt.% after carburization, and then spheroidizing annealing treatment is carried out; and finally, final thermal treatment is carried out, the austenitizing temperature of 840-860 DEG C is achieved through heating, then, isothermal quenching is carried out, the isothermy temperature is the sum of the temperature of an Ms surface layer and the value in the range of 30 DEG C and 60 DEG C, and subzero treatment and tempering treatment of 150-200 DEG C are carried out. The tenacity of the surface layer is improved while the surface hardness of the steel bearing can be guaranteed, and the carburization bearing steel is suitable for manufacturing large wind and power bearings, rolling mill bearings and other large heavy load mechanical equipment.

Description

A kind of carburizing bearing steel and preparation method thereof

Technical field the invention belongs to field of material technology, particularly a kind of bearing steel and preparation method thereof.

Background technology bearing is the key foundation component in mechanical means, and its service condition is very complicated and severe, requires that bearing not only will have excellent wear resistance, also will have high anti-rolling contact fatigue performance simultaneously.And for heavy duty equipment as the bearing such as rolling machinery, mine excavator, large-scale wind driven generator, larger impact load is also subject in its military service process, therefore except requiring that surface has except high-wearing feature, contacting fatigue resistance, also require that heart portion has certain toughness and enough intensity and hardness, therefore select carburizing bearing steel making.

The most frequently used carburizing bearing steel of tradition is G20Cr2Ni4A steel, and this steel obtains martensitic stucture after secondary quenching and temper, and therefore have high rigidity, excellent wear resistance and rolling contact fatigue performance, heart portion has high toughness simultaneously.But Ni content high in G20Cr2Ni4A steel, makes the manufacturing cost of bearing higher.In the standard GB/T3203-1982 carburizing bearing steel technical qualification of China and JB/T8881-2001 bearings parts carburizing heat treatment technics condition, also has G20CrMo, G20CrNiMo, G20CrNi2Mo, G10CrNi3Mo, the carburizing bearing steels such as G20Cr2Mn2Mo, specify in standard that the Final Heat Treatment Process of these converted steel is secondary quenching and temper, finally obtain martensite bearing.

In recent years, novel carburizing bearing steel is at development, as patent ZL201110156392.7 discloses a kind of tough carburizing bearing steel of height and preparation method of overlength contact fatigue life, the chemical composition of its bearing steel is C:0.16 ~ 0.24, Si≤0.1, Mn≤0.1, Cr:0.3 ~ 1.5, Ni:1.50 ~ 4.50, Mo:0.3 ~ 1.5, Nb:0.02 ~ 0.10, V:0.3% ~ 0.9, by smelting in conjunction with super clean and grain refining control techniques raising material property, final thermal treatment process is that oil quenching adds low-temperaturetempering process.Patent CN102653843A discloses a kind of carburizing bearing steel, and its main chemical compositions is C:0.10 ~ 0.16, Si:0.15 ~ 0.40, Mn:0.40 ~ 0.90, Cr:1.3 ~ 1.8, Ni:3.10 ~ 3.80, Mo:0.02 ~ 0.09, Al:0.015 ~ 0.04.Patent CN104694847A discloses a kind of containing Ni carburizing bearing steel, and its Final Heat Treatment Process is quenching temperature 800-900 DEG C, tempering temperature 150-170 DEG C.The final thermal treatment process of these carburizing bearing steels all have employed secondary quenching and temper, and final bearing is also martensitic stucture.The high carbon martensite on top layer organizes hardness high, but toughness is very low, and the toughness improving bearing top layer is also conducive to the work-ing life of improving bearing.

Summary of the invention the object of the present invention is to provide a kind of can ensure bearing steel surface hardness while improve top layer toughness be suitable for manufacture large-scale heavy duty mechanized equipment carburizing bearing steels such as large-scale wind electricity bearing, rolling mill bearing and preparation method thereof.The present invention mainly reduces the content of noble metal element Ni, suppress Carbide Precipitation by adding Si alloying element in bearing steel starting material simultaneously, low temperature isothermal transformation is taked to obtain the Low Temperature Bainitic Microstructure with high-strong toughness, take sub-zero treatment subsequently, reduce remained austenite content, ensure the dimensional stability in bearing military service process, thus improve the service life of bearing.

Technical scheme of the present invention is as follows:

The complex tissue that carburizing bearing steel of the present invention is a kind of surface is low temperature bainite, martensite forms, heart portion are the bearing steel of low-carbon martensite, its chemical composition mass percent is: C0.20 ~ 0.25, Si1.20 ~ 1.50, Mn0.20 ~ 0.40, Cr1.35 ~ 1.75, Ni2.20 ~ 2.60, Mo0.25 ~ 0.35, S≤0.010, P≤0.015, O≤0.0008, Ti≤0.003, H≤0.00015, and all the other are Fe and normal impurities.

The manufacture method of above-mentioned carburizing bearing steel:

(1) adopt converter smelting molten steel, by molten steel through external refining and Fruit storage, adopt protection of inert gas cast to obtain high cleanliness ingot casting, carry out hot-work subsequently and be cold worked into blank bearing;

(2) carry out conventional carburizing treatment to the blank bearing surface after step (1) processing, carburizing rear surface carbon content is 0.85-1.05wt.%;

(3) carry out Spheroidizing Annealing process to the blank bearing after step (2) carburizing, Heating temperature is 620-680 DEG C, insulation 4-8 hour, and air cooling is to room temperature subsequently;

(4) by after step (3) bearing heating to 650-700 DEG C of insulation 1-2h, continue to be heated to 840-860 DEG C of insulation 0.5-1h, then carry out isothermal quenching, isothermal temperature is M _{s top layer}+ (30 ~ 60) DEG C, isothermal time 4-8h, the cryostat putting into-120 DEG C ~-170 DEG C is subsequently incubated 1-2h, carries out sub-zero treatment, and after being finally incubated 1-2h at 150-200 DEG C, air cooling is to room temperature.

The present invention compared with prior art tool has the following advantages:

(1) high in starting material Si content can suppress Carbide Precipitation in bainitic transformation process effectively, obtain the Low Temperature Bainitic Microstructure of high-strong toughness, high Si content can also improve the hardening capacity of material simultaneously, makes this carburizing bearing steel be suitable for manufacturing large size bearing;

(2) bearing surface has higher residual compressive stress, improves the anti-contact fatigue life of rolling of bearing;

(3) residual austenite content of bearing is low, ensure that the dimensional stability in bearing military service process.

Figure of description

Fig. 1 is the Electronic Speculum figure on the carburizing bearing steel top layer that the embodiment of the present invention 1 obtains.

Fig. 2 is the transmission electron microscope picture on the carburizing bearing steel top layer that the embodiment of the present invention 1 obtains.

Embodiment

Embodiment 1

Adopt converter smelting molten steel, by molten steel through external refining and Fruit storage, adopt protection of inert gas cast to obtain high cleanliness ingot casting; the chemical composition (wt.%) of steel is: C0.23; Mn0.28, Si1.47, Ni2.53; Cr1.43; Mo0.32, O0.00056, P0.011; S0.008, H0.00004, Ti0.0022 all the other be Fe.Steel ingot is carried out thermoplasticity processing, move back the processing of pry-rolling ring, be cold worked into blank bearing; Carry out carburizing treatment to above-mentioned blank bearing, the carbon content on carburizing rear bearing surface is 0.92wt.%, M _{s top layer}it is 142 DEG C, by air cooling after bearing heating to 650 DEG C insulation 6h to room temperature, continue to be heated to 850 DEG C after being again heated to 680 DEG C of insulation 1.5h subsequently and carry out austenitizing process, put into 200 DEG C of salt baths after insulation 40min and carry out isothermal quenching, isothermal time 4h, put into the cryostat inside holding 1.5h of-150 DEG C subsequently, finally at 180 DEG C of tempering 1h.As depicted in figs. 1 and 2, in Fig. 1, black needle-like is Low Temperature Bainitic Microstructure to process rear bearing surface structure, and white is spherical is carbide, and light colour position is martensitic stucture, can see lath of bainite and twin crystal martensite tissue in Fig. 2, and retains carbide.Surface hardness is HRC60.5, and the intensity apart from 12.5mm position, top layer is 1376MPa, impelling strength a _kufor 122J/cm ², hardness is HRC38.

Embodiment 2

Adopt converter smelting molten steel, by molten steel through external refining and Fruit storage, adopt protection of inert gas cast to obtain high cleanliness ingot casting; the chemical composition (wt.%) of steel is: C0.20; Mn0.35, Si1.34, Ni2.26; Cr1.57; Mo0.28, O0.00063, P0.010; S0.005, H0.00002, Ti0.0021 all the other be Fe.Steel ingot is carried out thermoplasticity processing, move back the processing of pry-rolling ring, be cold worked into blank bearing; Carry out carburizing treatment to above-mentioned blank bearing, the carbon content on carburizing rear bearing surface is 0.85wt.%, M _{s top layer}it is 152 DEG C, by air cooling after bearing heating to 630 DEG C insulation 8h to room temperature, continue to be heated to 840 DEG C after being again heated to 660 DEG C of insulation 2h subsequently and carry out austenitizing process, put into 185 DEG C of salt baths after insulation 1h and carry out isothermal quenching, isothermal time 8h, put into the cryostat inside holding 1h of-130 DEG C subsequently, finally at 200 DEG C of tempering 1h.The weave construction on process rear bearing surface is similar to Example 1, surface hardness HRC60, and the intensity apart from 12.5mm position, top layer is 1435MPa, impelling strength a _kufor 95J/cm ², hardness is HRC41.

Embodiment 3

Adopt converter smelting molten steel, by molten steel through external refining and Fruit storage, adopt protection of inert gas cast to obtain high cleanliness ingot casting; the chemical composition (wt.%) of steel is: C0.25; Mn0.26, Si1.43, Ni2.60; Cr1.39; Mo0.33, O0.00065, P0.010; S0.008, H0.00002, Ti0.0019 all the other be Fe.Steel ingot is carried out thermoplasticity processing, move back the processing of pry-rolling ring, be cold worked into blank bearing; Carry out carburizing treatment to above-mentioned blank bearing, the carbon content on carburizing rear bearing surface is 1.03wt.%, M _{s top layer}it is 148 DEG C, by air cooling after bearing heating to 670 DEG C insulation 4h to room temperature, continue to be heated to 860 DEG C after being again heated to 700 DEG C of insulation 1h subsequently and carry out austenitizing process, put into 190 DEG C of salt baths after insulation 0.5h and carry out isothermal quenching, isothermal time 6h, put into the cryostat inside holding 2h of-160 DEG C subsequently, finally at 160 DEG C of tempering 2h.The weave construction on process rear bearing surface is similar to Example 1, surface hardness HRC62, and the intensity apart from 12.5mm position, top layer is 1426MPa, impelling strength a _kufor 108J/cm ², hardness is HRC40.5.

Claims (2)

1. a carburizing bearing steel, it is characterized in that: the complex tissue that it is a kind of surface is low temperature bainite, martensite forms, heart portion are the bearing steel of low-carbon martensite, its chemical composition mass percent is: C0.20 ~ 0.25, Si.20 ~ 1.50, Mn0.20 ~ 0.40, Cr1.35 ~ 1.75, Ni2.20 ~ 2.60, Mo0.25 ~ 0.35, S≤0.010, P≤0.015, O≤0.0008, Ti≤0.003, H≤0.00015, and all the other are Fe and normal impurities.

2. the preparation method of carburizing bearing steel according to claim 1, is characterized in that:

(1) adopt converter smelting molten steel, by molten steel through external refining and Fruit storage, adopt protection of inert gas cast to obtain high cleanliness ingot casting, carry out hot-work subsequently and be cold worked into blank bearing;

(2) carry out conventional carburizing treatment to the blank bearing surface after step (1) processing, carburizing rear surface carbon content is 0.85-1.05wt.%;

(3) carry out Spheroidizing Annealing process to the blank bearing after step (2) carburizing, Heating temperature is 620-680 DEG C, insulation 4-8 hour, and air cooling is to room temperature subsequently;

(4) by after step (3) bearing heating to 650-700 DEG C of insulation 1-2h, continue to be heated to 840-860 DEG C of insulation 0.5-1h, then carry out isothermal quenching, isothermal temperature is M _{s top layer}+ (30 ~ 60) DEG C, isothermal time 4-8h, the cryostat putting into-120 DEG C ~-170 DEG C is subsequently incubated 1-2h, carries out sub-zero treatment, and after being finally incubated 1-2h at 150-200 DEG C, air cooling is to room temperature.