CN104232869A - Hot-processing production technology of bearing steel pipe - Google Patents

Abstract

The invention discloses a hot-processing production technology of a bearing steel pipe. The hot-processing production technology reduces a production cost and can produce finished bearing steel pipes which have smooth and flat inner surfaces and outer surfaces, have no defects such as cracks, fold and scab, have small crystalline grains and compact microstructures, contain fine and uniformly-dispersed carbides, have inner and outer wall decarburized-layer thickness of 0.5mm satisfying GB/T18254-2002 standards, do not produce cracks after bending and flattening tests and satisfy the GB/T246 standards.

Description

A kind of hot-work production technique of Steel Pipe For Bearing

Technical field

The present invention relates to a kind of technical field of producing of steel pipe, especially a kind of hot-work production technique of Steel Pipe For Bearing.

Background technology

At present, known Steel Pipe For Bearing generally adopts solid pole forging stock or strip plate, is heated to 1160 ~ 1180 DEG C, and perforated is produced as hot-rolled tube; Or after hot-rolled tube Spheroidizing Annealing, then produce specification less and cold rolling, drawn tube that precision is higher through cold rolling, cold-drawing technology.Solid cast base is when cross piercing, and the flow of metal of hollow billet internal surface is violent, if its interior tissue is bad, then easily cracks, the defect such as infolding.Employing forging stock, strip plate can improve casting blank inner organization, improve plasticity, eliminate the defect of internal surface during perforation, but in turn increase production cost undoubtedly.

Summary of the invention

The object of the invention is the hot-work production technique being to provide a kind of Steel Pipe For Bearing, it is bright and clean smooth that reduction production cost processes production tube surfaces externally and internally, defects such as not occurring crackle, fold, scab; Crystal grain is tiny, dense structure, and carbide is tiny and disperse even, and inside and outside wall practical decarburized depth is all less than 0.5mm, meets GB/T18254-2002 standard-required, through bending, squeezing test, does not occur crackle, meets the Steel Pipe For Bearing of GB/T246 standard.

The present invention adopts following technical scheme for completing foregoing invention object:

The preparation of a, centrifugal blank: rotary casting flow process is that alloy melting → pipe die heating → coating pipe die → overhead gage → molten steel cast → pipe die cools → tear open baffle plate → tube drawing → scarfing cinder → processing, the preparation process of centrifugal blank and main points: wherein heat pipe die with flame from outer wall, be preheated to 200 ~ 260 DEG C, at pipe die internal surface spraying liquid coating, paint thickness 1.8 ~ 2.2mm, improve speed of rotation to the 750 ~ 800r/min of pipe die, cast aluminium alloy, teeming temperature 1530 ~ 1560 DEG C, and in whole casting process, ensure that in die cavity, the moment is full of shielding gas;

B, oblique roll process: hollow billet coefficient heat-up time is 0.4 ~ 0.6min/mm, Heating temperature is 1130 ~ 1160 DEG C, before top, draft is about 5%, reduce the distance once biting into blank contact top, simultaneously, adopt the little ovality of 1.06 ~ 1.08mm, 12 ° of feed angles, reduce the rotation times of pipe in distorted area, the transverse spreading of restriction metal, reduces the horizontal tensile stress of pipe central section, increases and axially extends, the repeated stress that hollow billet is born reduces greatly, and employing roll speed is 0.2 ~ 0.3m/s;

C ,the tissue of hot rolling normalizing state and hardness: the finishing temperature of GCr15 weldless steel tube is 790 ~ 840 DEG C;

D, carbide annealing process: carbide annealing process is heated to 790 ~ 810 DEG C, insulation 4 ~ 5h, then close stove, furnace cooling to about 500 DEG C, air cooling of coming out of the stove;

E, Q-tempering technique: quenching technology is heated to 830 ~ 840 DEG C, insulation 40min, oil quenching, quenching structure is martensite+granular carbide+retained austenite, and low-temperaturetempering technique is heated to 165 ~ 175 DEG C, insulation 3 ~ 4h, air cooling of coming out of the stove.

Therefore, compared with prior art, apply technical scheme of the present invention, there is following beneficial effect: reduce production cost, process production tube surfaces externally and internally bright and clean smooth, flawless, folding, scab defects, crystal grain is tiny, dense structure, carbide is tiny and disperse is even, inside and outside wall practical decarburized depth is all less than 0.5mm, through bending, squeezing test, does not occur the Steel Pipe For Bearing of crackle.

Accompanying drawing explanation

Fig. 1 is centrifugal casting process schematic; In figure: 1, connect shielding gas, 2, tundish, 3, cast end-stopping plate, 4, pipe die, 5, non-cast end-stopping plate, 6, shielding gas.

Embodiment

The preparation of centrifugal blank: rotary casting flow process is that alloy melting → pipe die heating → coating pipe die → overhead gage → molten steel cast → pipe die cools → tear open baffle plate → tube drawing → scarfing cinder → processing.The preparation process of centrifugal blank and main points: 1. start whizzer, make pipe die rotary motion.2. heat pipe die with flame from outer wall, be preheated to 200 ~ 260 DEG C.3. at pipe die internal surface spraying liquid coating, paint thickness 1.8 ~ 2.2mm.4. continue, to pipe die heating, to impel the moisture in coating to evaporate completely.5. with baffle plate, pipe die two ends are blocked, form the annular die cavity closed.6. speed of rotation to the 750 ~ 800r/min of pipe die is improved.7. argon gas is blown into pipe die, removes the air that the inside exists, reduce oxidation, pore tendency.8. pour into a mould aluminium alloy, teeming temperature 1530 ~ 1560 DEG C, and in whole casting process, ensure that in die cavity, the moment is full of shielding gas.9. after casting complete, treat that molten steel evenly spreads out, open chilled water unit, impel molten steel rapid solidification, form centrifugal blank, centrifugal casting process as shown in Figure 1.Molten steel all solidifies rear stopping cooling, and closes centrifugal device.The baffle plate at pipe die two ends is opened, pipe is released in pipe die, remove the slag blanket of internal surface of bloom, after Spheroidizing Annealing, pipe surfaces externally and internally is processed, to remove the casting flaw of surfaces externally and internally, be prepared into pipe needed for rolling.

Oblique roll process: adopt the hollow bloom that centrifugal casting explained hereafter goes out, dense internal organization, performance exceedes general slush casting pipe, according to the feature of rotary casting hollow billet, can set suitable process program and produce.Deformation program adopts twice pierced billet sizing flow process, and first time pierced billet sizing adopts less deformation ratio, for improving centrifugal blank as-cast structure, improves plasticity.Second time pierced billet sizing adopts large deformation ratio, for the production of going out qualified production tube.There is not the resistance that secondary is nipped during hollow billet perforation, not easily there is front card phenomenon in suitable draught.Position, top can be got greatly, and before top, draft is about 5%, reduces the distance once biting into blank contact top.Simultaneously, adopt the little ovality of 1.06 ~ 1.08mm, 12 ° of feed angles, reduce the rotation times of pipe in distorted area, the transverse spreading of restriction metal, reduce the horizontal tensile stress of pipe central section, increase and axially extend, the repeated stress that hollow billet is born reduces greatly, and adopt less roll speed, be generally 0.2 ~ 0.3m/s, ensure the homogeneity that flows in pass of metal, stopped that hollow billet inwall cracks, infolding defect.In production process, the surface quality of tool and mould must be guaranteed, check at any time, strengthen lubrication, guarantee that steel tube surface can not cause the defects such as tube surface scuffing, pit because of tool and mould steel bonding or projection.Open high-pressure water descaling before sizing mill, pressure is 14 ~ 15MPa, eliminates oxide skin, the pit of outer wall.The each stand stretch amount of sizing mill is distributed will evenly, and initial frame reducing rate wants less, and work housing reducing rate is maximum, and expansion frame reducing rate diminishes gradually from maximum value.The coefficient of tension between each frame also wants properly distributed, with frame sizing reduction feature, large from little change, more minimum from maximum change, be out of shape tempo class seemingly with frame reducing rate, guarantees the uniform and stable of metal axial flowing and transverse flow, prevents inhomogeneity of wall thickness.Adopt little deformation ratio, rotary casting blank is after wearing for the first time, roll, determining, and original structure state improves, die break, and dense structure's property improves, and pierced billet plasticity is greatly improved, and carries out second time pierced billet sizing operation subsequently.

The tissue of hot rolling normalizing state and hardness: the finishing temperature of GCr15 weldless steel tube is 790 ~ 840 DEG C.In rolling process of cooling, first secondary cementite separates out along austenite grain boundary, and carbide is the netted of small and dispersed distribution, and austenitic transformation is the tiny perlite that cementite is alternate with ferrite lamella subsequently.Finishing temperature is lower, and carbide network is broken, and the austenite crystal of distortion has little time recrystallize, and crystal grain is more tiny, and it is tiny that distribution of carbides gets over disperse, rolls rear air cooling and is organized as tiny perlite+cementite+fine mesh carbide.Organization decided performance, tiny perlite causes hot rolling and air cooling state bearing steel to have higher hardness, larger fragility, and during aligning, pipe produces brittle rupture, and hardness value is as shown in table 1.Table 1 hot rolled steel tube hardness (HRC)

。

Tissue, performance after carbide annealing process and nodularization: (1) carbide annealing process and organize the Spheroidizing Annealing of bearing steel to cool to adopt in two ways: a class is with stove continuous coo1ing after insulation, speed of cooling 30 ~ 35 DEG C/h, be cooled to 500 ~ 600 DEG C, air cooling of coming out of the stove; Another kind of is be cooled fast to about 720 DEG C after insulation, then is incubated 2 ~ 4h, and stove is as cold as 500 ~ 600 DEG C, air cooling of coming out of the stove.This test adopt the first type of cooling, carbide annealing process: be heated to 790 ~ 810 DEG C, insulation 4 ~ 5h, then close stove, furnace cooling to about 500 DEG C, air cooling of coming out of the stove.(2) spherical carbide is evenly distributed on ferrite matrix, and nodularization effect is good, is the performance after checking nodularization, carry out sampling from the pipe of Spheroidizing Annealing state to detect, get total wall thickness, wide 25mm, long 150mm batten, be placed on pressure testing machine, inwall pressurized, angle of bend is 90 °.After bending, do not occur crackle, the pipe ring getting 65mm long carries out squeezing test, and after flattening, sample ring does not occur crackle.(3) after nodularization, hardness is got the pipe after nodularization and is measured its Brinell hardness, and result is as shown in table 2.Steel pipe hardness (HBW) after table 2 spheroidizing

Can find out, uniform spherodized structure significantly reduces hardness, is conducive to machining, improves the plasticity of pipe, is conducive to the thermal treatment of production tube, not easily causes superheating phenomenon during quenching, is beneficial to the consistence ensureing production tube performance, for quenching structure is prepared.

Q-tempering technique: (1) quenching technology is heated to 830 ~ 840 DEG C, insulation 40min, oil quenching, quenching structure is martensite+granular carbide+retained austenite.In rich carbon, Cr-rich zone, martensite point is lower, and the martensite of formation is stablized, and is not easily corroded, in white distribution, and needle-like.At poor carbon, Cr depletion zone, martensite start temperature is high, and the martensite of formation is easily corroded, and distributes in black.(2) low-temperaturetempering technique is heated to 165 ~ 175 DEG C, insulation 3 ~ 4h, air cooling of coming out of the stove.Through the tissue of tempering, white area is in the cotton-shaped distribution of group, and after tempering, martensite decomposes, and cryptocrystalline martensite changes to tempered martensite.Low-temperaturetempering is organized as tempered martensite+undissolved carbide+retained austenite, and black area is lath martensite is main cryptocrystalline martensite, and white area is the cryptocrystalline martensite based on twin.Steel pipe hardness comparatively brilliant idea table 3 after quenching, steel pipe hardness (HRC) after table 3 quenching and tempering

Processing mode	Point 1	Point 2	Point 3	Mean value
					Oil quenching	64	63.7	66.5	64.7
Oil quenching+low-temperaturetempering	63.5	64.3	64.7	64.2

There is excellent wear resistance.

Claims (1)

1. a hot-work production technique for Steel Pipe For Bearing, is characterized by and adopt following technical scheme:

The preparation of a, centrifugal blank: rotary casting flow process is that alloy melting → pipe die heating → coating pipe die → overhead gage → molten steel cast → pipe die cools → tear open baffle plate → tube drawing → scarfing cinder → processing, the preparation process of centrifugal blank and main points: wherein heat pipe die with flame from outer wall, be preheated to 200 ~ 260 DEG C, at pipe die internal surface spraying liquid coating, paint thickness 1.8 ~ 2.2mm, improve speed of rotation to the 750 ~ 800r/min of pipe die, cast aluminium alloy, teeming temperature 1530 ~ 1560 DEG C, and in whole casting process, ensure that in die cavity, the moment is full of shielding gas;

B, oblique roll process: hollow billet coefficient heat-up time is 0.4 ~ 0.6min/mm, Heating temperature is 1130 ~ 1160 DEG C, before top, draft is about 5%, reduce the distance once biting into blank contact top, simultaneously, adopt the little ovality of 1.06 ~ 1.08mm, 12 ° of feed angles, reduce the rotation times of pipe in distorted area, the transverse spreading of restriction metal, reduces the horizontal tensile stress of pipe central section, increases and axially extends, the repeated stress that hollow billet is born reduces greatly, and employing roll speed is 0.2 ~ 0.3m/s;

C ,the tissue of hot rolling normalizing state and hardness: the finishing temperature of GCr15 weldless steel tube is 790 ~ 840 DEG C;

D, carbide annealing process: carbide annealing process is heated to 790 ~ 810 DEG C, insulation 4 ~ 5h, then close stove, furnace cooling to about 500 DEG C, air cooling of coming out of the stove;

E, Q-tempering technique: quenching technology is heated to 830 ~ 840 DEG C, insulation 40min, oil quenching, quenching structure is martensite+granular carbide+retained austenite, and low-temperaturetempering technique is heated to 165 ~ 175 DEG C, insulation 3 ~ 4h, air cooling of coming out of the stove.