CN117721387A - Steel for harmonic reducer flexspline and heat treatment method thereof - Google Patents
Steel for harmonic reducer flexspline and heat treatment method thereof Download PDFInfo
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- 238000010438 heat treatment Methods 0.000 title claims abstract description 79
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 67
- 239000010959 steel Substances 0.000 title claims abstract description 67
- 239000003638 chemical reducing agent Substances 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 35
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 15
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 10
- 238000000638 solvent extraction Methods 0.000 claims abstract description 10
- 239000000126 substance Substances 0.000 claims abstract description 10
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 8
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 7
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 7
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 5
- 238000001816 cooling Methods 0.000 claims description 75
- 229910001566 austenite Inorganic materials 0.000 claims description 27
- 238000011282 treatment Methods 0.000 claims description 24
- 238000000137 annealing Methods 0.000 claims description 19
- 238000005242 forging Methods 0.000 claims description 18
- 230000002411 adverse Effects 0.000 abstract description 7
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 229910045601 alloy Inorganic materials 0.000 abstract description 5
- 239000000956 alloy Substances 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 4
- 230000002829 reductive effect Effects 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 22
- 239000011572 manganese Substances 0.000 description 9
- 239000002994 raw material Substances 0.000 description 9
- 238000004458 analytical method Methods 0.000 description 8
- 239000012496 blank sample Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 238000004321 preservation Methods 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 238000013329 compounding Methods 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 6
- 230000007547 defect Effects 0.000 description 6
- 238000001514 detection method Methods 0.000 description 6
- 230000000717 retained effect Effects 0.000 description 6
- 238000005275 alloying Methods 0.000 description 5
- 239000010936 titanium Substances 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 239000000306 component Substances 0.000 description 4
- 229910000734 martensite Inorganic materials 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 230000003068 static effect Effects 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- 238000005261 decarburization Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 230000033764 rhythmic process Effects 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses steel for a harmonic reducer flexible gear and a heat treatment method thereof, wherein the steel comprises the following chemical components in percentage by mass: 0.42 to 0.48 percent of C, 1.6 to 2.0 percent of Si, 2.0 to 2.5 percent of Mn, 0.03 to 0.07 percent of Al, less than or equal to 0.002 percent of S, less than or equal to 0.002 percent of P, less than or equal to 0.10 percent of Cr, less than or equal to 0.10 percent of Mo, less than or equal to 0.01 percent of Ti, less than or equal to 0.002 percent of O, more than or equal to 0.010 percent of N, more than or equal to 3.0 percent of Al/N, and the balance of Fe and unavoidable impurities. The steel does not need to use alloy elements such as Cr, mo and the like which are unfavorable to the banded structure, so that the manufacturing cost is reduced, the adverse effect of the alloy elements on the banded structure is avoided, the good matching of a flexible gear product on high strength and high toughness is met, and the product quality is improved. The method adopts a one-step quenching-partitioning heat treatment process to obtain good matching of high strength and high toughness.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to steel for a harmonic reducer flexible gear and a heat treatment method thereof.
Background
The flexible gear is a core component of the industrial robot harmonic reducer, the service working condition of the flexible gear is complex and severe, the flexible gear material and the performance of the flexible gear are strictly required, and the flexible gear is a core technology in the field of industrial robot manufacturing. The toughness, the band structure and the grain size control level and the inclusion control level of the material are key factors for limiting the service life of the flexible gear of the harmonic reducer. At present, the flexible gear product of the high-end harmonic reducer in the markets at home and abroad is widely monopolized by Japanese enterprises. Compared with the advanced level abroad, the domestic flexible wheel has obvious differences in mechanical property, microstructure control, service life and the like due to technical blockage.
40CrNiMoA (Japanese SNCM 439) is a main stream material for preparing the harmonic reducer flexible gear at home and abroad, and isothermal normalizing and tempering heat treatment are the first heat treatment processes after the flexible gear blank is forged. The 40CrNiMoA has good strength and hardenability, but as a harmonic reducer flexspline material, there are inherent disadvantages to be solved: because of the addition of Cr, mo and other alloy elements, defects such as banded structure, center segregation and the like in the steel are difficult to effectively control; meanwhile, the process window of the heat treatment is narrow, if the heating temperature or the heat preservation time is controlled improperly, the defect of coarse grains easily occurs, and the toughness is further adversely affected. The tempering heat treatment process after forging the flexible gear blank also has the problem that crystal grains are easy to coarsen. Therefore, the development of the steel for the harmonic reducer flexspline and the heat treatment process of the steel are different from the traditional materials such as 40CrNiMoA and the like, and the steel is an effective way for improving the quality of the flexspline.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the steel for the harmonic reducer flexspline, which has high strength and high toughness and is well matched; the invention also provides a heat treatment method of the steel for the harmonic reducer flexspline.
In order to solve the technical problems, the invention adopts the following technical scheme: the chemical components of the composition by mass percent are: 0.42 to 0.48 percent of C, 1.6 to 2.0 percent of Si, 2.0 to 2.5 percent of Mn, 0.03 to 0.07 percent of Al, less than or equal to 0.002 percent of S, less than or equal to 0.002 percent of P, less than or equal to 0.10 percent of Cr, less than or equal to 0.10 percent of Mo, less than or equal to 0.01 percent of Ti, less than or equal to 0.002 percent of O, more than or equal to 0.010 percent of N, more than or equal to 3.0 percent of Al/N, and the balance of Fe and unavoidable impurities.
Further, the residual austenite content of the steel for the harmonic reducer flexible gear is controlled to be 3-5%, the grain size of original austenite is more than or equal to 10 levels, the banded structure is less than or equal to 0.5 level, the hardness is more than or equal to 48HRC, the yield strength is more than or equal to 1500MPa, and the elongation after break is more than or equal to 12%.
The invention relates to a component design idea of steel for a flexible gear, which comprises the following steps:
a medium carbon component system is adopted to ensure the strength required by the steel for the flexible gear; proper amounts of Mn and Si are utilized to promote the subsequent quenching-partitioning process and obtain residual austenite, so that the plasticity and toughness required by the steel for the flexible gear are ensured; simultaneously adding Al and N elements, controlling the Al/N ratio to be 3.0 or more, and separating out AlN particles in steel to achieve the effects of refining grains and improving yield ratio; the content of elements such as Cr, mo and the like which are unfavorable to the band-shaped structure is strictly controlled, the content of impurity elements such as Ti, O, S, P and the like which are easy to form inclusion or harmful to performance is strictly controlled, and a foundation is laid for ensuring the performance of the flexible gear finished product.
The design idea of each component of the invention is as follows:
c: carbon is the most basic element in steel, and is one of the main factors affecting hardness and strength, and also plays a role in quenching-partitioning. In general, the higher the carbon content in the steel, the higher the strength thereof after various heat treatments. In order to ensure that the hardness of the flexible gear after heat treatment is more than or equal to 48HRC and the yield strength is more than or equal to 1500MPa, the carbon content of the flexible gear material is at least 0.42% under the condition of strengthening without using elements such as Cr, mo and the like, otherwise, the strength, the hardness and the wear resistance of the flexible gear material after heat treatment are difficult to meet the requirements. On the other hand, if the carbon content is too high and exceeds 0.48%, carbide is easily precipitated in the flexspline material during heat treatment, and the risk of quench cracking is also easily increased, thereby adversely affecting the fatigue performance of the flexspline.
Mn: manganese is the most basic element in steel and is also one of the important alloying elements used in the present invention. Manganese can stabilize austenite and reduce the critical quenching rate of steel, thereby improving hardenability of the material and helping to retain sufficient retained austenite during the quench-partitioning process. In the present invention, in order to achieve the object of increasing hardenability and retaining retained austenite, particularly, in the case of improving hardenability without using elements such as Cr, mo, etc., the manganese content needs to be at least 2.0%. On the other hand, if the manganese content exceeds 2.5%, the risk of cracking of the flexspline material during forging will be significantly increased. Therefore, the manganese content should be controlled within the range of 2.0 to 2.5%.
Si: silicon is the most basic element in steel and is also one of the important alloying elements used in the present invention. The main function of silicon is to inhibit the precipitation of carbide during the quenching-partitioning heat treatment, thereby retaining enough retained austenite. In the present invention, the silicon content should be maintained at least above 1.6% for the purpose of retaining the retained austenite during the quenching-partitioning heat treatment. On the other hand, if the silicon content is too high and exceeds 2.0%, the surface quality after forging will be affected. Therefore, the manganese content should be controlled within the range of 1.6 to 2.0%.
N: nitrogen is one of the important alloying elements employed in the present invention. Nitrogen and aluminum are used simultaneously, so that AlN particles can be separated out in the heat treatment process of the steel for the flexible gear, and the growth of crystal grains is inhibited. In the invention, the nitrogen content should reach more than 0.010 percent, so that the effect of obviously refining the grains can be achieved.
Al: aluminum is one of the important alloying elements employed in the present invention. Aluminum can form AlN particles to precipitate and inhibit crystal grain growth, and can inhibit carbide precipitation in the quenching-partitioning heat treatment process, so that enough residual austenite is reserved. The ratio of Al and N in AlN particles is about 2.0, and additional aluminum in a solid solution state is required to stabilize the retained austenite, so that the Al/N is more than or equal to 3.0 and the corresponding aluminum content is at least 0.03 percent in the invention. However, if the aluminum content is too high and exceeds 0.07%, the risk of cracking of the flexspline material during forging will be significantly increased. Therefore, the aluminum content should be controlled within the range of 0.03 to 0.07%.
Cr, mo: the impurity element belongs to the present invention. If the content of any one element of Cr and Mo exceeds 0.10%, the band structure in the steel for flexspline exceeds 2.0 grade, and the performance of flexspline is adversely affected. Therefore, the content of Cr and Mo should be controlled to 0.10% or less.
Ti: the impurity element belongs to the present invention. In the case of using N as an alloying element, if the Ti content exceeds 0.01%, tiN grain inclusions having a diameter of 1.0 μm or more will appear in the steel, thereby adversely affecting the performance of the flexspline. Therefore, the titanium content needs to be controlled to 0.01% or less.
O: oxygen is an impurity element in steel, and the higher the oxygen content is, the quantity and the size of B-class, C-class and D-class inclusions in the steel are increased, so that the performance of the flexspline is adversely affected. Therefore, the lower the oxygen content, the better, and the actual production is generally controlled to 0.002% or less.
S: sulfur is an impurity element in steel, and if the sulfur content is too high, not only the number and size of class a inclusions in steel but also the tendency of hot shortness of steel increases. Therefore, the lower the sulfur content, the better, and the actual production is generally controlled to be 0.002% or less.
P: phosphorus is an impurity element in steel, and if the content of phosphorus is too high, the comprehensive mechanical properties of the steel, particularly impact toughness, are seriously damaged. Therefore, the lower the phosphorus content, the better, and the actual production is generally controlled to be 0.002% or less.
The method comprises the steps of homogenizing annealing before forging a flexible gear blank, isothermal normalizing after forging and quenching-proportioning;
the quenching-partitioning: heating the flexible gear blank subjected to isothermal normalizing treatment to 850-920 ℃, slowly cooling to 790-860 ℃ at the speed of 2-5 ℃/s for the first time, rapidly cooling to 360-400 ℃ at the speed of more than or equal to 40 ℃/s, slowly cooling to 310-350 ℃ at the speed of 2-5 ℃/s for the second time, and finally cooling to be more than or equal to 20 ℃/s.
Further, the homogenizing annealing: the steel is heated to 1100-1200 ℃ and kept for 6-8 hours, and then cooled along with the furnace.
Further, the isothermal normalizing adopts twice isothermal normalizing: heating the forged flexible gear blank to 940-980 ℃ and preserving heat for 90-120 min, then cooling to 840-880 ℃ in a furnace and preserving heat for 40-70 min, and finally air-cooling;
and (3) carrying out secondary isothermal normalizing, heating the flexible gear blank subjected to the primary isothermal normalizing to 890-930 ℃ and preserving heat for 60-90 min, then cooling to 840-880 ℃ in a furnace and preserving heat for 40-70 min, and finally carrying out air cooling.
The design idea of the method is as follows:
before forging a flexible gear blank, carrying out homogenizing annealing on the raw material, further eliminating micro segregation in the raw material, and controlling the banded structure below 1.0 level; after forging, sequentially carrying out twice isothermal normalizing treatment on the flexible gear blank, refining the austenite grain size and eliminating the mixed crystal defect, so that the austenite grain size is controlled to be more than 10 levels; and finally, quenching and distributing the flexible gear blank to obtain martensite and residual austenite structures with high strength and high toughness and good matching.
The design idea of each step of the method is as follows:
the homogenizing annealing: heating the harmonic reducer flexible gear to 1100-1200 ℃ by using steel, then preserving heat for 6-8 h, and cooling to room temperature along with a furnace. The steel for the flexible gear is heated to above 1100 ℃ and is kept for at least 6 hours, namely the micro segregation in the raw material can be effectively eliminated, and the banded structure is stably controlled below 1.0 level. However, if the heating temperature exceeds 1200 ℃ or the heat preservation time exceeds 8 hours, the grains in the steel can be obviously coarsened; if the heating temperature is less than 1100 ℃ or the heat preservation time is less than 6 hours, the functions of eliminating micro segregation and reducing the level of the banded tissue are difficult to be achieved; if the homogenizing annealing is performed after forging the flexspline blank, serious oxidation and decarburization of the surface of the blank can occur.
First isothermal normalizing after forging of flexible gear blank: heating the forged flexible gear blank to 940-980 ℃ and preserving heat for 90-120 min, then cooling to 840-880 ℃ in a furnace and preserving heat for 40-70 min, and finally cooling to normal temperature in air, wherein the purpose is to primarily refine the austenite grain size and eliminate mixed crystal defects. After the first isothermal normalizing, the austenite grain size can be stabilized above grade 8, and no mixed crystal defect exists. If the heating temperature is too high, the cooling end temperature in the furnace is too high, or the heat preservation time is too long, austenite grains can be coarsened, and oxidation and decarburization on the surface of the blank can be aggravated; if the heating temperature is insufficient or the heat preservation time is too short, it is difficult to thoroughly eliminate the mixed crystal defect.
The second isotemperature normalizing: heating the flexible gear blank subjected to the first isothermal normalizing treatment to 890-930 ℃ and preserving heat for 60-90 min, then cooling to 840-880 ℃ in a furnace and preserving heat for 40-70 min, and finally cooling to normal temperature in air. The adopted heating and heat preservation temperature and heat preservation time are lower than those of the first isothermal normalizing, so that austenite grains are further refined, and the austenite grain size is stabilized above 10 levels.
The quenching-compounding treatment: the method is a key step of the heat treatment process of the steel for the flexible gear, the temperature-time system is shown in figure 1, and the static CCT curve of the steel for the flexible gear is shown in figure 2. According to a static CCT curve, heating the flexible gear blank subjected to twice isothermal normalizing treatment to 850-920 ℃, wherein the heating rate is not limited, then slowly cooling to 790-860 ℃ at the rate of 2-5 ℃/s for the first time, rapidly cooling to 360-400 ℃ at the rate of more than or equal to 40 ℃/s, slowly cooling to 310-350 ℃ at the rate of 2-5 ℃/s for the second time, and finally cooling to normal temperature at the rate of more than or equal to 20 ℃/s for the final cooling to finish heat treatment. In the whole heating and cooling process, the traditional heat preservation stage is not needed, so that the production rhythm is quickened, and continuous production is facilitated. Heating to 850-920 ℃, then slowly cooling to 790-860 ℃ at the speed of 2-5 ℃/s for the first time, and finishing austenitizing the material; after slow cooling, rapidly cooling to 360-400 ℃ at a speed of more than or equal to 40 ℃/s, wherein the material completes the quenching process and undergoes martensitic transformation to obtain a martensite and retained austenite structure, and 40 ℃/s is the critical cooling speed shown by a static CCT curve of the material, so that the rapid cooling speed needs to reach the value; after quick cooling, slowly cooling to 310-350 ℃ for the second time at the speed of 2-5 ℃/s, and finishing the carbon distribution process of the material, wherein the residual austenite is stabilized; at last, the cooling to normal temperature at the speed of more than or equal to 20 ℃/s can avoid the decomposition of the residual austenite in the cooling process, and the residual austenite is reserved to the greatest extent.
The beneficial effects of adopting above-mentioned technical scheme to produce lie in: according to the invention, alloy elements such as Cr, mo and the like which are commonly used in traditional materials such as 40CrNiMoA and the like and are unfavorable to the banded structure are not required to be used, so that the manufacturing cost is reduced, the adverse effect of the alloy elements on the banded structure is avoided, the good matching of a flexible gear product on high strength and high toughness is satisfied, and the product quality is improved.
The method adopts a one-step quenching-partitioning heat treatment process to obtain good matching of high strength and high toughness; after heat treatment, the microstructure of the steel for the flexible gear mainly comprises martensite and residual austenite, the content of the residual austenite is controlled to be 3-5%, the grain size of the prior austenite is more than or equal to 10 levels, the band-shaped structure is less than or equal to 0.5 level, the hardness is more than or equal to 48HRC, the yield strength is more than or equal to 1500MPa, and the elongation after fracture is more than or equal to 12%, so that the steel has good comprehensive mechanical properties.
Drawings
The invention will be described in further detail with reference to the drawings and the detailed description.
FIG. 1 is a schematic diagram of a temperature-time regime employed in the quench-batch process of the present invention;
fig. 2 is a static CCT graph of the steel for the harmonic reducer flexspline of the present invention.
Detailed Description
Example 1: the steel for the harmonic reducer flexspline and the heat treatment method thereof are specifically described below.
(1) The chemical composition and the mass percentage of the steel material for the flexible gear are shown in table 1.
(2) And (3) heat treatment: before forging a flexible gear blank, carrying out homogenizing annealing on the raw materials; the forged flexible gear blank is subjected to twice isothermal normalizing and then quenching-distributing.
The homogenizing annealing: and heating the harmonic reducer flexible gear to 1100 ℃ by using steel, then preserving heat for 6 hours, and cooling to room temperature along with a furnace.
The first isothermal normalizing: the forged flexspline blank was heated to 940 c and held for 90 minutes, then cooled in a furnace to 840 c and held for 40 minutes, and finally cooled in air to ambient temperature.
The second isotemperature normalizing: the flexible gear blank after the first isothermal normalizing treatment is heated to 890 ℃ and kept for 60 minutes, then cooled to 840 ℃ in a furnace and kept for 40 minutes, and finally cooled to normal temperature in air.
The quenching-compounding treatment: and heating the flexible gear blank subjected to twice isothermal normalizing treatment to 850 ℃, slowly cooling to 790 ℃ at the speed of 2 ℃/s, rapidly cooling to 360 ℃ at the speed of 40 ℃/s, slowly cooling to 310 ℃ at the speed of 2 ℃/s, and finally cooling to normal temperature at the speed of 20 ℃/s to finish heat treatment.
(3) The microstructure analysis results and the mechanical property detection results corresponding to the flexspline blank sample obtained in this example are shown in table 2 and table 3.
Example 2: the steel for the harmonic reducer flexspline and the heat treatment method thereof are specifically described below.
(1) The chemical composition and the mass percentage of the steel material for the flexible gear are shown in table 1.
(2) And (3) heat treatment: before forging a flexible gear blank, carrying out homogenizing annealing on the raw materials; the forged flexible gear blank is subjected to twice isothermal normalizing and then quenching-distributing.
The homogenizing annealing: and heating the harmonic reducer flexible gear to 1200 ℃ by using steel, then preserving heat for 8 hours, and cooling to room temperature along with a furnace.
The first isothermal normalizing: the forged flexspline blank was heated to 980 ℃ and incubated for 120 minutes, then cooled in a furnace to 880 ℃ and incubated for 70 minutes, and finally cooled in air to ambient temperature.
The second isotemperature normalizing: and heating the flexible gear blank subjected to the first isothermal normalizing treatment to 930 ℃ and preserving heat for 90 minutes, then cooling to 880 ℃ in a furnace and preserving heat for 70 minutes, and finally cooling to normal temperature in air.
The quenching-compounding treatment: and heating the flexible gear blank subjected to twice isothermal normalizing treatment to 920 ℃, slowly cooling to 860 ℃ at the speed of 5 ℃/s, rapidly cooling to 400 ℃ at the speed of 50 ℃/s, slowly cooling to 350 ℃ at the speed of 5 ℃/s, and finally cooling to normal temperature at the speed of 25 ℃/s to finish heat treatment.
(3) The microstructure analysis results and the mechanical property detection results corresponding to the flexspline blank sample obtained in this example are shown in table 2 and table 3.
Example 3: the steel for the harmonic reducer flexspline and the heat treatment method thereof are specifically described below.
(1) The chemical composition and the mass percentage of the steel material for the flexible gear are shown in table 1.
(2) And (3) heat treatment: before forging a flexible gear blank, carrying out homogenizing annealing on the raw materials; the forged flexible gear blank is subjected to twice isothermal normalizing and then quenching-distributing.
And (3) homogenizing annealing: and heating the harmonic reducer flexible gear to 1150 ℃ by using steel, then preserving heat for 6 hours, and cooling to room temperature along with a furnace.
The first isothermal normalizing: the forged flexspline blank was heated to 960 ℃ and held for 120 minutes, then cooled in a furnace to 860 ℃ and held for 70 minutes, and finally cooled in air to ambient temperature.
The second isotemperature normalizing: and heating the flexible gear blank subjected to the first isothermal normalizing treatment to 900 ℃ and preserving heat for 90 minutes, then cooling to 860 ℃ in a furnace and preserving heat for 70 minutes, and finally cooling to normal temperature in air.
The quenching-compounding treatment: and heating the flexible gear blank subjected to twice isothermal normalizing treatment to 890 ℃, slowly cooling to 820 ℃ at the speed of 3 ℃/s, rapidly cooling to 380 ℃ at the speed of 45 ℃/s, slowly cooling to 330 ℃ at the speed of 3 ℃/s, and finally cooling to normal temperature at the speed of 22 ℃/s to finish heat treatment.
(3) The microstructure analysis results and the mechanical property detection results corresponding to the flexspline blank sample obtained in this example are shown in table 2 and table 3.
Example 4: the steel for the harmonic reducer flexspline and the heat treatment method thereof are specifically described below.
(1) The chemical composition and the mass percentage of the steel material for the flexible gear are shown in table 1.
(2) And (3) heat treatment: before forging a flexible gear blank, carrying out homogenizing annealing on the raw materials; the forged flexible gear blank is subjected to twice isothermal normalizing and then quenching-distributing.
The homogenizing annealing: and heating the harmonic reducer flexible gear to 1150 ℃ by using steel, then preserving heat for 8 hours, and cooling to room temperature along with a furnace.
A first isothermal normalizing is obtained: the forged flexspline blank was heated to 960 ℃ and held for 90 minutes, then cooled in a furnace to 860 ℃ and held for 40 minutes, and finally cooled in air to ambient temperature.
The second isotemperature normalizing: and heating the flexible gear blank subjected to the first isothermal normalizing treatment to 900 ℃ and preserving heat for 60 minutes, then cooling to 860 ℃ in a furnace and preserving heat for 40 minutes, and finally cooling to normal temperature in air.
The quenching-compounding treatment: and heating the flexible gear blank subjected to twice isothermal normalizing treatment to 910 ℃, slowly cooling to 840 ℃ at the speed of 5 ℃/s, rapidly cooling to 380 ℃ at the speed of 50 ℃/s, slowly cooling to 320 ℃ at the speed of 5 ℃/s, and finally cooling to normal temperature at the speed of 25 ℃/s to finish heat treatment.
(3) The microstructure analysis results and the mechanical property detection results corresponding to the flexspline blank sample obtained in this example are shown in table 2 and table 3.
Example 5: the steel for the harmonic reducer flexspline and the heat treatment method thereof are specifically described below.
(1) The chemical composition and the mass percentage of the steel material for the flexible gear are shown in table 1.
(2) And (3) heat treatment: before forging a flexible gear blank, carrying out homogenizing annealing on the raw materials; the forged flexible gear blank is subjected to twice isothermal normalizing and then quenching-distributing.
The homogenizing annealing: the harmonic reducer flexspline is heated to 1100 ℃ by steel, then is insulated for 7 hours, and is cooled to room temperature along with a furnace.
The first isothermal normalizing: the forged flexspline blank was heated to 960 ℃ and held for 115 minutes, then cooled in a furnace to 860 ℃ and held for 40 minutes, and finally cooled in air to ambient temperature.
The second isotemperature normalizing: and heating the flexible gear blank subjected to the first isothermal normalizing treatment to 900 ℃ and preserving heat for 70 minutes, then cooling to 860 ℃ in a furnace and preserving heat for 50 minutes, and finally cooling to normal temperature in air.
The quenching-compounding treatment: and heating the flexible gear blank subjected to twice isothermal normalizing treatment to 850 ℃, slowly cooling to 790 ℃ at the speed of 3 ℃/s, rapidly cooling to 400 ℃ at the speed of 40 ℃/s, slowly cooling to 350 ℃ at the speed of 3 ℃/s, and finally cooling to normal temperature at the speed of 25 ℃/s to finish heat treatment.
(3) The microstructure analysis results and the mechanical property detection results corresponding to the flexspline blank sample obtained in this example are shown in table 2 and table 3.
Example 6: the steel for the harmonic reducer flexspline and the heat treatment method thereof are specifically described below.
(1) The chemical composition and the mass percentage of the steel material for the flexible gear are shown in table 1.
(2) And (3) heat treatment: before forging a flexible gear blank, carrying out homogenizing annealing on the raw materials; the forged flexible gear blank is subjected to twice isothermal normalizing and then quenching-distributing.
The homogenizing annealing: and heating the harmonic reducer flexible gear to 1200 ℃ by using steel, then preserving heat for 7 hours, and cooling to room temperature along with a furnace.
The first isothermal normalizing: the forged flexspline blank was heated to 980 ℃ and held for 100 minutes, then cooled in a furnace to 850 ℃ and held for 60 minutes, and finally cooled in air to ambient temperature.
The second isotemperature normalizing: and heating the flexible gear blank subjected to the first isothermal normalizing treatment to 920 ℃, preserving heat for 80 minutes, then cooling to 870 ℃ in a furnace, preserving heat for 60 minutes, and finally cooling to normal temperature in air.
The quenching-compounding treatment: and heating the flexible gear blank subjected to twice isothermal normalizing treatment to 870 ℃, slowly cooling to 840 ℃ at the speed of 5 ℃/s, rapidly cooling to 370 ℃ at the speed of 45 ℃/s, slowly cooling to 330 ℃ at the speed of 4 ℃/s, and finally cooling to normal temperature at the speed of 20 ℃/s to finish heat treatment.
(3) The microstructure analysis results and the mechanical property detection results corresponding to the flexspline blank sample obtained in this example are shown in table 2 and table 3.
Table 1: chemical composition and content (wt%) of Steel for harmonic speed reducer flexspline in examples 1 to 6
In table 1, the balance is Fe and unavoidable impurities.
Table 2: microstructure analysis results of harmonic speed reducer flexspline blank samples obtained in examples 1 to 6
Table 3: mechanical property analysis results of harmonic reducer flexspline blank samples obtained in examples 1 to 6
。
Claims (5)
1. The steel for the harmonic reducer flexspline is characterized by comprising the following chemical components in percentage by mass: 0.42 to 0.48 percent of C, 1.6 to 2.0 percent of Si, 2.0 to 2.5 percent of Mn, 0.03 to 0.07 percent of Al, less than or equal to 0.002 percent of S, less than or equal to 0.002 percent of P, less than or equal to 0.10 percent of Cr, less than or equal to 0.10 percent of Mo, less than or equal to 0.01 percent of Ti, less than or equal to 0.002 percent of O, more than or equal to 0.010 percent of N, more than or equal to 3.0 percent of Al/N, and the balance of Fe and unavoidable impurities.
2. The steel for harmonic reducer flexspline according to claim 1, characterized in that: the residual austenite content of the steel for the harmonic reducer flexible gear is controlled to be 3-5%, the original austenite grain size is more than or equal to 10 levels, the banded structure is less than or equal to 0.5 level, the hardness is more than or equal to 48HRC, the yield strength is more than or equal to 1500MPa, and the elongation after breaking is more than or equal to 12%.
3. The heat treatment method of steel for harmonic reducer flexspline according to claim 1 or 2, characterized by: comprises the steps of homogenizing annealing before forging a flexible gear blank, isothermal normalizing after forging and quenching-proportioning;
the quenching-partitioning: heating the flexible gear blank subjected to isothermal normalizing treatment to 850-920 ℃, slowly cooling to 790-860 ℃ at the speed of 2-5 ℃/s for the first time, rapidly cooling to 360-400 ℃ at the speed of more than or equal to 40 ℃/s, slowly cooling to 310-350 ℃ at the speed of 2-5 ℃/s for the second time, and finally cooling to be more than or equal to 20 ℃/s.
4. A heat treatment method of steel for harmonic reducer flexspline according to claim 3, characterized in that said homogenizing annealing: the steel is heated to 1100-1200 ℃ and kept for 6-8 hours, and then cooled along with the furnace.
5. The heat treatment method of steel for harmonic reducer flexspline according to claim 3 or 4, characterized in that the isothermal normalizing is carried out twice: heating the forged flexible gear blank to 940-980 ℃ and preserving heat for 90-120 min, then cooling to 840-880 ℃ in a furnace and preserving heat for 40-70 min, and finally air-cooling;
and (3) carrying out secondary isothermal normalizing, heating the flexible gear blank subjected to the primary isothermal normalizing to 890-930 ℃ and preserving heat for 60-90 min, then cooling to 840-880 ℃ in a furnace and preserving heat for 40-70 min, and finally carrying out air cooling.
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