CN111394686B - Heat treatment method of small module gear - Google Patents

Heat treatment method of small module gear Download PDF

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Publication number
CN111394686B
CN111394686B CN202010259360.9A CN202010259360A CN111394686B CN 111394686 B CN111394686 B CN 111394686B CN 202010259360 A CN202010259360 A CN 202010259360A CN 111394686 B CN111394686 B CN 111394686B
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bevel gear
zone
flow rate
temperature
carburization
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CN111394686A (en
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李锐
田瑞
王亮
王小丛
王浩爽
孙健
权太保
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Nanyang Haofan Auto Part Co ltd
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Nanyang Haofan Auto Part Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02—Pretreatment of the material to be coated
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/28—Normalising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising
    • C23C8/22—Carburising of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
    • C23G1/19—Iron or steel

Abstract

The invention provides a heat treatment method of a small module gear, the small module gear comprises a driving bevel gear and a driven bevel gear matched with the driving bevel gear, the driven bevel gear is carburized by adopting a single-row continuous furnace, the period is 30 +/-5 min in a single row, and the method comprises the following steps: (1) pre-treating; (2) heating a zone; (3) an initial carburization carbon region; (4) a strong carburization three area; (5) four zones of diffusion carburization; (6) and a fifth quenching and carburizing zone. The invention reduces the stress of tissue transformation, shortens the material pushing period of a product by 4min, ensures the tooth profile precision within 8 levels, controls the plane deformation within 0.1mm and controls the inner hole deformation within 0.08 mm.

Description

Heat treatment method of small module gear
Technical Field
The invention relates to the technical field of gear machining, in particular to a heat treatment method for a small module gear.
Background
The small module gear is a key part of a drive axle of equipment such as agricultural machinery, a speed reducer, precision machinery and the like, and is a key part of a rear drive axle for realizing torque transmission, torque increase, torque transmission direction change, rotating speed reduction and the like. The speed reduction and the force transmission direction change are realized through a group of gear pairs, and the gear pairs comprise a driving bevel gear and a driven bevel gear which are meshed with each other to transmit power. The low noise, high transmission efficiency, high precision, high bearing capacity and low cost are the development trend of the small module gear, the current national small module gear manufacturing industry has the output value of more than 100 million yuan per year, the proportion occupied in the manufacturing industry is larger and larger, and the small module gear manufacturing industry has good growth along with the development trend of the precision, the miniaturization and the automation of mechanical products.
The small module gear can receive great impact load and surface wear at the transmission moment of torsion in-process of transaxle, and the deformation control in the carburization heat treatment process makes the gear more steady in transmission process, and the noise is littleer, makes the gear can high accuracy meshing transmission to can reduce the wearing and tearing of gear flank of tooth, increase its life, and can effectual guarantee gear better play a role in transmission process.
The existing carburizing heat treatment process is generally divided into 3 stages, for example, CN103710714A discloses a heat treatment method for carburizing and quenching a gear of an automobile transmission, wherein the carburizing process comprises increasing the temperature from room temperature to 900 ± 5 ℃ to carburize, the carburizing process is divided into an initial stage, a strong carburizing stage and a diffusion stage, the initial stage is 0.95 ± 0.03C% of carbon potential CP, the strong carburizing stage is 1.06 ± 0.03C% of CP, and the diffusion stage is 0.85 ± 0.03C%. In addition, CN106119507B discloses a heat treatment process for reducing deformation of key grooves of gear shafts, wherein the carburizing step comprises: the temperature is kept at 830 +/-5 ℃ for 20 +/-1 min, and the CP is 0.60 +/-0.025 ℃; the temperature is kept at 900 plus or minus 5 ℃ for 60 plus or minus 1min, and the CP is 0.95 plus or minus 0.025 ℃; the temperature is kept at 880 +/-5 ℃ for 40 +/-1 min, and the CP is 0.80 +/-0.025 ℃; the temperature is kept at 830 +/-5 ℃ for 35 +/-1 min, and the CP is 0.65 +/-0.025 percent. The design of the carburizing process steps and parameters cannot meet the requirement that the small-module gear prepared by using the 20CrMnTiH material reduces the structure transformation stress when the small-module gear reaches the specified metallographic structure standard.
Disclosure of Invention
The invention provides a heat treatment method of a small module gear, which reduces the tissue transformation stress, shortens the material pushing period of a product by 4min, ensures the tooth profile precision within 8 levels, controls the plane deformation within 0.1mm and controls the inner hole deformation within 0.08 mm.
The technical scheme of the invention is realized as follows: the heat treatment method of the small module gear comprises the following steps that the small module gear comprises a driving bevel gear and a driven bevel gear matched with the driving bevel gear, the driven bevel gear is subjected to carburizing treatment by adopting a single-row continuous furnace, and the period is 30 +/-5 min in a single row:
(1) pretreatment: placing the driven bevel gears on a material tray frame, and conveying the material tray frame to a pretreatment furnace, wherein the temperature of the pretreatment furnace is 460 +/-10 ℃, and the material level of the material tray frame of the pretreatment furnace is 3;
(2) heating a first zone: the driven bevel gear enters a first heating area along with the material tray frame, the temperature of the first heating area is 860 +/-5 ℃, the flow rate of methanol is 20 +/-5 ml/min, and the material positions of the material tray frame of the first heating area are 5;
(3) initial carburization carbon region: the driven bevel gear enters a carburizing zone along with a material tray frame, the temperature of the carburizing zone II is 870 +/-5 ℃, the carbon potential is 0.95 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material positions of the material tray frame of the carburizing zone II are 3;
(4) a strong carburization three-zone: the driven bevel gear enters a three-zone carburization zone along with a material tray rack, the temperature of the three-zone carburization zone is 880 +/-5 ℃, the carbon potential is 1.05 +/-0.05 percent, the flow of methanol is 30 +/-5 ml/min, the flow of acetone is 20 +/-3 ml/min, and the material positions of the material tray rack of the two-zone carburization zone are 5;
(5) four zones of diffusion carburization: the driven bevel gear enters a four carburizing zone along with a material tray rack, the temperature of the four carburizing zone is 870 +/-5 ℃, the carbon potential is 0.88 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3The material positions of the material tray racks in the four carburizing zones are 5;
(6) a quenching and carburizing five zone: the driven bevel gear enters a five carburization zone along with a material tray frame, the temperature of the five carburization zone is 830 +/-5 ℃, the carbon potential is 0.8 +/-0.05 percent, the flow rate of methanol is 20 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3And h, the material level of the tray frame in the five carburization areas is 3.
Further, after the carburization in the step (6) is finished, the driven bevel gear is subjected to quenching and tempering treatment, and the method comprises the following steps:
1) quenching: the medium is Y15-II rapid quenching oil, the temperature is 80 +/-10 ℃, and the quenching time is 8 min;
2) cleaning: the driven gear enters an alkaline water tank after quenching, the temperature of the alkaline water tank is 80 +/-10 ℃, the driven gear is soaked and washed for 10min, and then the driven gear enters a clear water tank, the temperature of the clear water tank is 80 +/-10 ℃, and the driven gear is sprayed for 8 min;
3) tempering: the temperature is 180 +/-5 ℃, and the tempering time is 5 h.
Further, before the driven bevel gear is carburized, isothermal normalizing treatment is carried out, and the method comprises the following steps:
a. placing the driven bevel gear on a material tray frame, and feeding the material tray frame into an isothermal normalizing furnace for heating, wherein the heating temperature is 940 +/-10 ℃, and the heating time is 120-150 min;
b. then, air cooling is carried out on the driven bevel gear, the air cooling time is 2-4min, and the temperature is reduced from 940 +/-10 ℃ to 640 +/-10 ℃;
c. and (3) carrying out isothermal heating for 200-250min on the driven bevel gear subjected to air cooling at the temperature of 640 +/-10 ℃, and finally carrying out air cooling.
Further, the charging tray frame comprises a bottom plate, vertical positioning barrels are symmetrically arranged at the upper end of the bottom plate, a round base plate is sleeved on each positioning barrel, positioning holes for sleeving the positioning barrels are formed in the round base plate, chutes are formed in the upper end of the round base plate at intervals along the circumferential direction, one end of each chute is located at the corresponding positioning hole, the other end of each chute extends downwards along the radial direction to the side wall of the round base plate, a plurality of communicating grooves are formed in the upper end of the round base plate between every two adjacent chutes, and the adjacent chutes are communicated with each other through the communicating grooves.
Further, the driving bevel gear is carburized by adopting a double-row continuous furnace, the period is double rows of 30 +/-5 min, and the method comprises the following steps:
(1) pretreatment: placing a driving bevel gear on a material rack, and conveying the driving bevel gear to a pretreatment furnace, wherein the temperature of the pretreatment furnace is 460 +/-10 ℃, and the material level of the material rack of the pretreatment furnace is 3;
(2) heating a first zone: the driving bevel gear enters a first heating area along with the material rack, the temperature of the first heating area is 870 +/-5 ℃, the flow rate of methanol is 20 +/-5 ml/min, and the material level of the material rack in the first heating area is 10;
(3) initial carburization carbon region: the driving bevel gear enters a carburizing zone along with a material rack, the temperature of the carburizing zone is 885 +/-5 ℃, the carbon potential is 0.95 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material level of the material rack in the carburizing zone is 6;
(4) a strong carburization three-zone: the driving bevel gear enters a three carburizing zone along with a material rack, the temperature of the three carburizing zone is 900 +/-5 ℃, the carbon potential is 1.05 +/-0.05 percent, the flow rate of methanol is 30 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material rack material level of the carbon infiltration zone is 10;
(5) four zones of diffusion carburization: the driving bevel gear enters a four carburizing zone along with a material rack, the temperature of the four carburizing zone is 880 +/-5 ℃, the carbon potential is 0.88 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3The material level of the material rack in the four carburizing zones is 10;
(6) a quenching and carburizing five zone: the driving bevel gear enters a five carburization area along with a material rack, the temperature of the five carburization areas is 820 +/-5 ℃, the carbon potential is 0.8 +/-0.05 percent, the flow rate of methanol is 20 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3And h, the material level of the material rack in the five carburization areas is 6.
The invention has the beneficial effects that:
by adopting the heat treatment method, the tooth profile precision of the small-modulus gear after heat treatment is ensured to be within 8 levels, and the gear grinding, the matching inspection noise, the contact area and the transmission stability are all qualified by 100%; after the small module gear is subjected to heat treatment, the plane deformation is controlled within 0.1mm, the inner hole deformation is controlled within 0.08mm, and the qualification rate of the driven bevel gear product is improved from 79.2% to 94.1% by measuring the large plane warpage and the inner hole ovality of the driven bevel gear.
The isothermal normalizing treatment process is adopted, so that the strip shape is ensured to be 0-2 grade, the structural stress after subsequent carburizing and quenching is greatly improved, and the gear deformation is reduced; the fine and uniform austenite grain size has special contribution to the strength and the toughness of parts, and the method has important significance for improving the fracture toughness of the gear and improving the brittle failure resistance of the gear, controls the hardenability bandwidth within 4HRC, has smaller product deformation under the carburizing process under the same condition, and has better surface and internal tissues obtained after heat treatment.
The carburizing and hot quenching treatment process reduces the structure transformation stress when reaching the specified metallographic structure standard, obtains better internal structure after quenching, shortens the material pushing period of the product by 4min, reduces the stress deformation, and improves the qualification rate of the driven bevel gear product from 79.2 percent to 94.1 percent by measuring the large plane warpage and the inner hole ovality of the driven bevel gear.
The charging tray frame provided by the invention has the advantages that the oil leakage hole is eliminated, the deformation of the charging tray frame in heat treatment is reduced, the straight groove is changed into the inclined groove, the inclined groove is favorable for oil discharge, and the adjacent inclined grooves are communicated through the communicating groove, so that the circumferential uniform oil discharge is favorably realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic view of a driven bevel gear according to the present invention;
FIG. 2 is a process diagram for isothermal normalizing of a driven bevel gear;
FIG. 3 is a metallographic view of a pearlite structure after isothermal normalizing in example;
FIG. 4 is a diagram of an internal grain phase of a driven bevel gear after an isothermal normalizing according to an exemplary embodiment;
FIG. 5 is a schematic structural view of a drive bevel gear;
FIG. 6 is a gold phase diagram of a carbide structure of the tooth tips of a driven bevel gear according to an embodiment;
FIG. 7 is a gold phase diagram of the austenite and martensite structures of the tooth surface of a driven bevel gear according to an embodiment
FIG. 8 is a metallographic view showing a core ferrite structure inside a driven bevel gear according to an embodiment;
FIG. 9 is a schematic structural view of a circular pad;
FIG. 10 is a cross-sectional view A-A of FIG. 9;
FIG. 11 is a schematic structural view of a tray rack;
fig. 12 is a top view of a tray frame.
Circular backing plate 1, locating hole 2, chute 3, intercommunication groove 4, bottom plate 5, location bucket 6, driven bevel gear 7.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.
The heat treatment method of the small module gear adopts the material of 20CrMnTiH, and the mass percentages of the chemical components of the 20CrMnTiH are shown as follows:
Figure BDA0002438711490000051
non-metallic inclusions of 20 CrMnTiH:
Figure BDA0002438711490000052
bag (bag)
Compared with the specification of the technical conditions of the steel for the CGMA001-2004 vehicle gear, the 20CrMnTiH disclosed by the invention has the advantages that the oxygen percentage content is reduced, the lower limit of the S percentage content is limited, the size, the number and the like of non-metallic inclusions are reduced, the oxide inclusions are fatigue crack sources, the oxygen content is reduced, the content of the non-metallic inclusions is reduced, and the impact toughness of the steel and the fatigue strength of the gear are improved.
The small module gear comprises a driving bevel gear and a driven bevel gear matched with the driving bevel gear, the driven bevel gear is carburized by adopting a single-row continuous furnace, the furnace pressure (water column height difference) is 6-10mm, and the period is single-row 30 +/-5 min, and the method comprises the following steps:
(1) pretreatment: placing the driven bevel gears on a material tray frame, and conveying the material tray frame to a pretreatment furnace, wherein the temperature of the pretreatment furnace is 460 +/-10 ℃, and the material level of the material tray frame of the pretreatment furnace is 3; the pretreatment is carried out to remove water stains, grease and the like on the surface of the product, and the product is preheated to reduce the temperature difference between the product and the main furnace and reduce the deformation of the product;
(2) heating a first zone: the driven bevel gear enters a first heating area along with the material tray frame, the temperature of the first heating area is 860 +/-5 ℃, the flow rate of methanol is 20 +/-5 ml/min, and the material positions of the material tray frame of the first heating area are 5;
(3) initial carburization carbon region: the driven bevel gear enters a carburizing zone along with a material tray frame, the temperature of the carburizing zone II is 870 +/-5 ℃, the carbon potential is 0.95 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material positions of the material tray frame of the carburizing zone II are 3;
(4) a strong carburization three-zone: the driven bevel gear enters a three-zone carburization zone along with a material tray rack, the temperature of the three-zone carburization zone is 880 +/-5 ℃, the carbon potential is 1.05 +/-0.05 percent, the flow of methanol is 30 +/-5 ml/min, the flow of acetone is 20 +/-3 ml/min, and the material positions of the material tray rack of the two-zone carburization zone are 5;
(5) four zones of diffusion carburization: the driven bevel gear enters a four carburizing zone along with a material tray rack, the temperature of the four carburizing zone is 870 +/-5 ℃, the carbon potential is 0.88 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3The material positions of the material tray racks in the four carburizing zones are 5;
(6) a quenching and carburizing five zone: the driven bevel gear enters a five carburization zone along with a material tray frame, the temperature of the five carburization zone is 830 +/-5 ℃, the carbon potential is 0.8 +/-0.05 percent, the flow rate of methanol is 20 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3And h, the material level of the tray frame in the five carburization areas is 3.
And (6) processing time of each stage is the number of material trays and the number of material frames multiplied by cycle time.
In the first embodiment, the steps (3) to (6) are adopted, acetone is adopted, more activated carbon atoms are generated under the high-temperature cracking of the acetone compared with propane, the impurity atmosphere is less, and the carbon potential in the furnace is controlled by controlling the flow rate, so that the carbide content and the depth of a carburized layer are ensured.
And (5) controlling the acetone flow and the air flow, increasing the acetone flow when the carbon potential is lower according to the carbon potential in the furnace, closing an air valve, stopping introducing the acetone when the carbon potential is higher, opening the air valve and diluting the carbon concentration.
After the carburization in the step (6) is finished, the driven bevel gear is quenched and tempered, and the method comprises the following steps:
1) quenching: the medium is Y15-II rapid quenching oil, the temperature is 80 +/-10 ℃, and the quenching time is 8 min;
2) cleaning: the driven gear enters an alkaline water tank after quenching, the temperature of the alkaline water tank is 80 +/-10 ℃, the driven gear is soaked and washed for 10min, and then the driven gear enters a clear water tank, the temperature of the clear water tank is 80 +/-10 ℃, and the driven gear is sprayed for 8 min;
3) tempering: the temperature is 180 +/-5 ℃, and the tempering time is 5 h.
After the driven bevel gear is quenched and tempered, strong shot blasting is carried out, shot blasting is carried out by mechanical centrifugal shot blasting equipment, ceramic shot is adopted as the shot material, the microhardness of the shot is 660HV-750HV, the diameter of the shot is 0.25-0.75mm, the distance from a nozzle to a driven bevel gear is 120-150mm, the shot blasting flow is 1.0-2.5kg/min, the shot blasting time is 6-7min, and the injection angle theta is 40-65 degrees. By adopting the strong shot blasting process, the arc height value of the shot blasting strength is 0.5-0.6mmA and the surface coverage rate is more than or equal to 200 percent when the strong shot blasting of the driven bevel gear is tested. A strong shot blasting process is adopted to flatten sharp corners of cutting tool marks, so that tooth surfaces are smoother, meanwhile, compressive stress generated by shot blasting reduces tensile stress generated by tooth surface structure transformation, fatigue fracture resistance and stress corrosion fracture resistance of the gear are improved, and as a result, the reliability and durability of the gear are improved.
Examples one to four driven bevel gears used 20CrMnTiH had the chemical composition in mass percent as shown in the following table:
Figure BDA0002438711490000071
examples one to four non-metallic inclusions of 20 CrMnTiH:
Figure BDA0002438711490000072
the driven bevel gear prepared by the heat treatment process of the embodiment I is subjected to the following detection: the surface hardness and the core hardness are detected by a Rockwell hardness tester (HR-150DT), the metallographic structure is detected by a metallographic microscope (WY-C), and the metallographic structure diagram of the first example is shown in FIGS. 6-8.
Figure BDA0002438711490000073
The hardening depth of example one was examined using a microhardness tester (H1/S-1000), and was 0.9 mm.
Comparative example 1
This embodiment is substantially the same as the first embodiment, except that: the mass percentage of 20CrMnTiH oxygen is
Figure BDA0002438711490000081
Non-metallic inclusions of 20 CrMnTiH:
Figure BDA0002438711490000082
the period is single row 34 +/-5 min, step (3) starts a carbon infiltration and precipitation zone: the temperature of the carbon infiltration carbon zone is 860 +/-5 ℃; step (4), strong carburization three-zone: the temperature of a carburization three-zone is 870 +/-5 ℃; and (5) diffusion carburizing four areas: the temperature of the four carburization zones is 865 +/-5 ℃.
Compared with the first comparative example, the carburization treatment process provided by the embodiment of the invention has the advantages that by controlling the oxygen percentage content and the nonmetallic inclusion, the structural stress is smaller before even the temperature is increased in the carburization process, and the deformation condition of the product after heat treatment is obviously improved compared with the first comparative example; meanwhile, the carburizing time is reduced due to the fact that the carburizing temperature is increased. The product pushing period is shortened by 4min, the deformation is reduced to a certain extent, and the qualification rate of the driven bevel gear product is improved from 79.2% to 94.1% by measuring the large plane warpage and the inner hole ovality of the driven bevel gear.
EXAMPLE five
Before the driven bevel gear described in the first to fourth embodiments is carburized, isothermal normalizing is performed, and the method includes the following steps:
a. placing the driven bevel gear on a material tray frame, and feeding the material tray frame into an isothermal normalizing furnace for heating, wherein the heating temperature is 940 +/-10 ℃, the heating time is 120-fold for 150min, and the step is used for heating the driven bevel gear and homogenizing austenite;
b. then, air cooling is carried out on the driven bevel gear, the air cooling time is 2-4min, and the temperature is reduced from 940 +/-10 ℃ to 640 +/-10 ℃;
c. and (3) carrying out isothermal heating for 200-250min on the driven bevel gear subjected to air cooling at the temperature of 640 +/-10 ℃, and finally carrying out air cooling.
The isothermal normalizing furnace adopts periodic material pushing, the working period is 16min, 120-150min is the time length from the time when the driven bevel gear enters the furnace chamber to the time when the driven bevel gear enters the air cooling, and compared with a common normalizing process, the isothermal normalizing process can achieve uniform and consistent microstructures and hardness, and can reliably obtain good cutting processing performance and stable quenching deformation rules.
After the driven bevel gear is subjected to isothermal normalizing treatment, a Bush hardness tester is used for hardness detection, a metallographic microscope is used for metallographic structure and grain size detection, the specific detection results are as follows, and a metallographic structure and grain size metallographic diagram in the first embodiment is shown in the following tables in FIGS. 3 and 4:
Figure BDA0002438711490000091
example one has a macrostructure rating of
Figure BDA0002438711490000092
The deformation condition of a hot product is directly determined by the banded structure of the normalized driven bevel gear, and the isothermal normalizing treatment process disclosed by the fifth embodiment is adopted, so that the banded 0-2 level is ensured, the structural stress after subsequent carburizing and quenching is greatly improved, and the gear deformation is reduced; the fine and uniform austenite grain size has special contribution to the strength and the toughness of parts, and the method has important significance for improving the fracture toughness of the gear and improving the brittle failure resistance of the gear, controls the hardenability bandwidth within 4HRC, has smaller product deformation under the carburizing process under the same condition, and has better surface and internal tissues obtained after heat treatment.
EXAMPLE six
First to four embodiment the charging tray frame include bottom plate 5 and circular backing plate 1, be equipped with coaxial locating hole 2 on the circular backing plate 1, the upper end of circular backing plate 1 is equipped with chute 3 along circumference interval, 3 one ends of chute are located locating hole 2 department, the other end along radial slope downwardly extending to the lateral wall of circular backing plate 1, circular backing plate 1 upper end between the adjacent chute 3 is provided with 3 curved intercommunication grooves 4 from inside to outside, communicate with each other through intercommunication groove 4 between the adjacent chute 3.
The upper end of bottom plate 5 is fixed with vertical location bucket 6, and location bucket 6 includes 2, and the symmetry is fixed in the upper end of bottom plate 5. The round base plate 1 is sleeved on the positioning barrel 6 through the positioning hole 2 and is arranged at the upper end of the bottom plate 5. The thickness of the circular cushion plate is 30mm, and the diameter of the excircle is 250 mm.
The application method of the embodiment comprises the following steps: the round base plate 1 is sleeved on the positioning barrel 6 through the positioning hole 2, the lower end of the round base plate 1 is arranged at the upper end of the bottom plate 5, and then the driven bevel gears 7 are vertically sleeved on the positioning barrel 6. Oil is discharged through the inclined grooves 3, and the communicating grooves 4 are communicated with the connected inclined grooves 3, so that uniform oil discharge in the circumferential direction is facilitated; when in use, the base plate is placed on the bottom plate 5, and the driven bevel gear is placed on the base plate.
The base plate of the existing driven bevel gear feed plate rack usually adopts a universal basin tooth base plate, the contact surface is provided with a straight-through flat groove and an oil leakage hole, the inner hole of the base plate is larger due to the need of considering a plurality of products, and the oil leakage hole on the base plate can cause the base plate to deform in the heat treatment process. And the driven bevel gear has small disc loading quantity, which is not beneficial to the heat treatment of the driven bevel gear on a large scale. The circular base plate of the third embodiment omits an oil leakage hole, reduces the deformation of the charging tray frame during heat treatment, changes a straight groove into an inclined groove, facilitates oil discharge by the inclined groove, is communicated with an adjacent inclined groove through a communicating groove, facilitates circumferentially uniform oil discharge, ensures that a product has enough supporting surface during heat treatment and can be cooled in time during quenching; the thickness of the circular cushion plate is 30mm, the diameter of the outer circle is 250mm, two stacks of the circular cushion plate can be symmetrically placed on the bottom plate, the tray loading amount is doubled compared with that of the conventional tray rack, the strength of the circular cushion plate is guaranteed, and deformation is avoided.
EXAMPLE seven
The drive bevel gear of the first to fourth embodiments adopts a double-row continuous furnace for carburizing treatment, the furnace pressure (water column height difference) is 6-10mm, the period is double rows for 30 +/-5 min, and the method comprises the following steps:
(1) pretreatment: placing a driving bevel gear on a material rack, and conveying the driving bevel gear to a pretreatment furnace, wherein the temperature of the pretreatment furnace is 460 +/-10 ℃, and the material level of the material rack of the pretreatment furnace is 3;
(2) heating a first zone: the driving bevel gear enters a first heating area along with the material rack, the temperature of the first heating area is 870 +/-5 ℃, the flow rate of methanol is 20 +/-5 ml/min, and the material level of the material rack in the first heating area is 10;
(3) initial carburization carbon region: the driving bevel gear enters a carburizing zone along with a material rack, the temperature of the carburizing zone is 885 +/-5 ℃, the carbon potential is 0.95 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material level of the material rack in the carburizing zone is 6;
(4) a strong carburization three-zone: the driving bevel gear enters a three carburizing zone along with a material rack, the temperature of the three carburizing zone is 900 +/-5 ℃, the carbon potential is 1.05 +/-0.05 percent, the flow rate of methanol is 30 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material rack material level of the carbon infiltration zone is 10;
(5) four zones of diffusion carburization: the driving bevel gear enters a four carburizing zone along with a material rack, the temperature of the four carburizing zone is 880 +/-5 ℃, the carbon potential is 0.88 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3The material level of the material rack in the four carburizing zones is 10;
(6) a quenching and carburizing five zone: the driving bevel gear enters a five carburization area along with a material rack, the temperature of the five carburization areas is 820 +/-5 ℃, the carbon potential is 0.8 +/-0.05 percent, the flow rate of methanol is 20 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3And h, the material level of the material rack in the five carburization areas is 6.
And (6) processing time of each stage is the number of material trays and the number of material frames multiplied by cycle time.
After the carburization in the step (6) is finished, the driving bevel gear is quenched and tempered, and the quenching and tempering method comprises the following steps:
1) quenching: the medium is Y15-II rapid quenching oil, the temperature is 80 +/-10 ℃, and the quenching time is 8 min;
2) cleaning: the driven gear enters an alkaline water tank after quenching, the temperature of the alkaline water tank is 80 +/-10 ℃, the driven gear is soaked and washed for 10min, and then the driven gear enters a clear water tank, the temperature of the clear water tank is 80 +/-10 ℃, and the driven gear is sprayed for 8 min;
3) tempering: the temperature is 180 +/-5 ℃, and the tempering time is 5 h.
Comparative example No. two
This embodiment is substantially the same as embodiment seven except that: the mass percentage of 20CrMnTiH oxygen is
Figure BDA0002438711490000111
Non-metallic inclusions of 20 CrMnTiH:
Figure BDA0002438711490000112
the period is double rows of 34 +/-5 min, and the step (3) is a carbon infiltration carbon region: the temperature of the carbon infiltration zone is 880 +/-5 ℃; (4) a strong carburization three-zone: the temperature of a carburization three-zone is 890 +/-5 ℃; (5) four zones of diffusion carburization: the temperature of the four carburization areas is 870 +/-5 ℃;
compared with the comparative example II, the cycle time is shortened, the production efficiency is improved, the rod part bounce of the driving bevel gear is obviously reduced after the carburizing heat treatment, the rod part straightening workload of the driving bevel gear after the carburizing heat treatment is reduced, and the metallographic structure can be below 2 grade.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (5)

1. The heat treatment method of the small module gear comprises a driving bevel gear and a driven bevel gear matched with the driving bevel gear, wherein the small module gear is made of 20CrMnTiH, and is characterized in that: the driven bevel gear is carburized by adopting a single-row continuous furnace, the period is 30 +/-5 min in a single row, and the method comprises the following steps:
(1) pretreatment: placing the driven bevel gears on a material tray frame, and conveying the material tray frame to a pretreatment furnace, wherein the temperature of the pretreatment furnace is 460 +/-10 ℃, and the material level of the material tray frame of the pretreatment furnace is 3;
(2) heating a first zone: the driven bevel gear enters a first heating area along with the material tray frame, the temperature of the first heating area is 860 +/-5 ℃, the flow rate of methanol is 20 +/-5 ml/min, and the material positions of the material tray frame of the first heating area are 5;
(3) initial carburization carbon region: the driven bevel gear enters a carburizing zone along with a material tray frame, the temperature of the carburizing zone II is 870 +/-5 ℃, the carbon potential is 0.95 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material positions of the material tray frame of the carburizing zone II are 3;
(4) a strong carburization three-zone: the driven bevel gear enters a three-zone carburization zone along with a material tray rack, the temperature of the three-zone carburization zone is 880 +/-5 ℃, the carbon potential is 1.05 +/-0.05 percent, the flow of methanol is 30 +/-5 ml/min, the flow of acetone is 20 +/-3 ml/min, and the material positions of the material tray rack of the two-zone carburization zone are 5;
(5) four zones of diffusion carburization: the driven bevel gear enters a four carburizing zone along with a material tray rack, the temperature of the four carburizing zone is 870 +/-5 ℃, the carbon potential is 0.88 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3The material positions of the material tray racks in the four carburizing zones are 5;
(6) a quenching and carburizing five zone: the driven bevel gear enters a five carburization zone along with a material tray frame, the temperature of the five carburization zone is 830 +/-5 ℃, the carbon potential is 0.8 +/-0.05 percent, the flow rate of methanol is 20 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3And h, the material level of the tray frame in the five carburization areas is 3.
2. The method for heat-treating a small module gear according to claim 1, wherein: after the carburization in the step (6) is finished, the driven bevel gear is quenched and tempered, and the method comprises the following steps:
1) quenching: the medium is Y15-II rapid quenching oil, the temperature is 80 +/-10 ℃, and the quenching time is 8 min;
2) cleaning: the driven gear enters an alkaline water tank after quenching, the temperature of the alkaline water tank is 80 +/-10 ℃, the driven gear is soaked and washed for 10min, and then the driven gear enters a clear water tank, the temperature of the clear water tank is 80 +/-10 ℃, and the driven gear is sprayed for 8 min;
3) tempering: the temperature is 180 +/-5 ℃, and the tempering time is 5 h.
3. The method for heat-treating a small module gear according to claim 1, wherein: before the driven bevel gear is carburized, isothermal normalizing treatment is carried out, and the method comprises the following steps:
a. placing the driven bevel gear on a material tray frame, and feeding the material tray frame into an isothermal normalizing furnace for heating, wherein the heating temperature is 940 +/-10 ℃, and the heating time is 120-150 min;
b. then, air cooling is carried out on the driven bevel gear, the air cooling time is 2-4min, and the temperature is reduced from 940 +/-10 ℃ to 640 +/-10 ℃;
c. and (3) carrying out isothermal heating for 200-250min on the driven bevel gear subjected to air cooling at the temperature of 640 +/-10 ℃, and finally carrying out air cooling.
4. The method for heat-treating a small module gear according to claim 1, wherein: the charging tray frame comprises a bottom plate, vertical positioning barrels are symmetrically arranged at the upper end of the bottom plate, a round base plate is sleeved on each positioning barrel, positioning holes for sleeving the positioning barrels are formed in the round base plate, chutes are formed in the upper end of the round base plate at intervals along the circumferential direction, one end of each chute is located at the corresponding positioning hole, the other end of each chute extends downwards along the radial direction to the side wall of the round base plate, a plurality of communicating grooves are formed in the upper end of each round base plate between every two adjacent chutes, and the adjacent chutes are communicated with each other through the communicating grooves.
5. The method for heat-treating a small module gear according to claim 1, wherein: the drive bevel gear is carburized by adopting a double-row continuous furnace, the period is double rows of 30 +/-5 min, and the method comprises the following steps:
(1) pretreatment: placing a driving bevel gear on a material rack, and conveying the driving bevel gear to a pretreatment furnace, wherein the temperature of the pretreatment furnace is 460 +/-10 ℃, and the material level of the material rack of the pretreatment furnace is 3;
(2) heating a first zone: the driving bevel gear enters a first heating area along with the material rack, the temperature of the first heating area is 870 +/-5 ℃, the flow rate of methanol is 20 +/-5 ml/min, and the material level of the material rack in the first heating area is 10;
(3) initial carburization carbon region: the driving bevel gear enters a carburizing zone along with a material rack, the temperature of the carburizing zone is 885 +/-5 ℃, the carbon potential is 0.95 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material level of the material rack in the carburizing zone is 6;
(4) a strong carburization three-zone: the driving bevel gear enters a three carburizing zone along with a material rack, the temperature of the three carburizing zone is 900 +/-5 ℃, the carbon potential is 1.05 +/-0.05 percent, the flow rate of methanol is 30 +/-5 ml/min, the flow rate of acetone is 20 +/-3 ml/min, and the material rack material level of the carbon infiltration zone is 10;
(5) four zones of diffusion carburization: the driving bevel gear enters a four carburizing zone along with a material rack, the temperature of the four carburizing zone is 880 +/-5 ℃, the carbon potential is 0.88 +/-0.05 percent, the flow rate of methanol is 25 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3The material level of the material rack in the four carburizing zones is 10;
(6) a quenching and carburizing five zone: the driving bevel gear enters a five carburization area along with a material rack, the temperature of the five carburization areas is 820 +/-5 ℃, the carbon potential is 0.8 +/-0.05 percent, the flow rate of methanol is 20 +/-5 ml/min, the flow rate of acetone is 0-10ml/min, and the air flow rate is 0-1m3And h, the material level of the material rack in the five carburization areas is 6.
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