CN116949354A - Steel for motorcycle engine gear and manufacturing method thereof - Google Patents
Steel for motorcycle engine gear and manufacturing method thereof Download PDFInfo
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- CN116949354A CN116949354A CN202310655585.XA CN202310655585A CN116949354A CN 116949354 A CN116949354 A CN 116949354A CN 202310655585 A CN202310655585 A CN 202310655585A CN 116949354 A CN116949354 A CN 116949354A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 131
- 239000010959 steel Substances 0.000 title claims abstract description 131
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 49
- 238000005096 rolling process Methods 0.000 claims abstract description 40
- 238000000034 method Methods 0.000 claims abstract description 24
- 229910052742 iron Inorganic materials 0.000 claims abstract description 22
- 238000001816 cooling Methods 0.000 claims abstract description 18
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 18
- 238000007670 refining Methods 0.000 claims abstract description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 15
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 12
- 230000023556 desulfurization Effects 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 8
- 238000005266 casting Methods 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 239000000126 substance Substances 0.000 claims abstract description 3
- 239000004576 sand Substances 0.000 claims description 23
- 238000004321 preservation Methods 0.000 claims description 20
- 238000007872 degassing Methods 0.000 claims description 17
- 230000008569 process Effects 0.000 claims description 14
- 229910052717 sulfur Inorganic materials 0.000 claims description 14
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 13
- 239000011593 sulfur Substances 0.000 claims description 13
- 239000002245 particle Substances 0.000 claims description 10
- 239000003795 chemical substances by application Substances 0.000 claims description 9
- 230000003009 desulfurizing effect Effects 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 9
- 238000009749 continuous casting Methods 0.000 claims description 8
- 238000003723 Smelting Methods 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 238000001556 precipitation Methods 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 229910000604 Ferrochrome Inorganic materials 0.000 claims description 3
- 229910000616 Ferromanganese Inorganic materials 0.000 claims description 3
- 229910001309 Ferromolybdenum Inorganic materials 0.000 claims description 3
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 3
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 claims description 3
- 238000010907 mechanical stirring Methods 0.000 claims description 3
- 239000011819 refractory material Substances 0.000 claims description 3
- 238000009413 insulation Methods 0.000 claims 1
- 238000010273 cold forging Methods 0.000 abstract description 8
- 238000009849 vacuum degassing Methods 0.000 abstract description 2
- 238000005272 metallurgy Methods 0.000 abstract 1
- 229910001566 austenite Inorganic materials 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 239000011572 manganese Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 239000011651 chromium Substances 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- 239000010703 silicon Substances 0.000 description 5
- 238000009628 steelmaking Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- QIJNJJZPYXGIQM-UHFFFAOYSA-N 1lambda4,2lambda4-dimolybdacyclopropa-1,2,3-triene Chemical compound [Mo]=C=[Mo] QIJNJJZPYXGIQM-UHFFFAOYSA-N 0.000 description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- 229910039444 MoC Inorganic materials 0.000 description 3
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 229910052804 chromium Inorganic materials 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 238000004781 supercooling Methods 0.000 description 2
- 238000009489 vacuum treatment Methods 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—Dephosphorising or desulfurising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
-
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The application relates to steel for a gear of a motorcycle engine and a manufacturing method thereof, belonging to the field of metallurgy. The steel for the motorcycle engine gear comprises the following chemical components, by mass, 0.18-0.25% of C, less than or equal to 0.05% of Si, 0.60-0.90% of Mn, 0.90-1.25% of Cr, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.12-0.20% of Mo, 0.018-0.042% of Al and N:0.0090-0.0180%, and the balance Fe and unavoidable impurities. The steel for the gear of the motorcycle engine is manufactured through the process steps of molten iron pre-desulfurization, converter primary refining, vacuum degassing, casting, heating, rolling, cooling after rolling and the like. The structure is fine and uniform ferrite and pearlite, and the sizes of the ferrite and the pearlite are preferably 20-55um; the hardness of the steel is less than or equal to 80HRB; the depth of cracks on the surface of the steel is less than or equal to 0.10mm; the grain size in the surface carburized layer after carburization of the steel is more than or equal to 7.0 grade; meets the requirement of cold forging processing.
Description
Technical Field
The application belongs to the technical field of gear steel, and particularly relates to steel for a motorcycle engine gear and a manufacturing method thereof.
Background
The gear of the motorcycle engine is an important mechanical component responsible for the transmission of the motorcycle, and the gears realize high-efficiency transmission through mutual meshing. The manufacturing cost of the motorcycle gear made of steel for the common gear is relatively high, and the service life is short. Aiming at the steel requirement of the motorcycle engine gear, the application develops a steel product which has simple manufacturing flow and lower manufacturing cost and can be used for manufacturing the motorcycle engine gear by a cold forging processing method.
Disclosure of Invention
The application discloses steel for a gear of a motorcycle engine and a manufacturing method thereof, which are used for meeting the requirements of the steel for the gear of the motorcycle engine. The structure of the steel is fine and uniform ferrite and pearlite, the sizes of the ferrite and the pearlite are less than or equal to 60um, and the sizes of the ferrite and the pearlite are more preferably 20-55um; the hardness of the steel is less than or equal to 80HRB; the depth of cracks on the surface of the steel is less than or equal to 0.10mm; after carburization (e.g. 10 hours at 920 ℃) of the steel, the grain size in the surface carburized layer is more than or equal to 7.0 grade. The gear steel is more suitable for cold forging processing.
The application solves the problems by adopting the following technical scheme: the steel for the motorcycle engine gear comprises, by weight, 0.18-0.25% of C, less than or equal to 0.05% of Si, 0.60-0.90% of Mn, 0.90-1.25% of Cr, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.12-0.20% of Mo, 0.018-0.042% of Al and N:0.0090-0.0180%, and the balance Fe and unavoidable impurities.
The main functions and design basis of the steel are as follows:
carbon is the most important element for ensuring certain strength and hardenability of steel. However, too high carbon content can lead to higher hardness of the steel after cooling, increase cold brittleness of the steel, and is unfavorable for cold forging of gear parts of motorcycle engines. The application adopts low-carbon design, and the carbon content selection range is 0.18-0.25%.
Si is that the steel grade of the application belongs to steel for cold forging, and the silicon element can lead to cold work hardening in the cold forging process. The application adopts low silicon design, and the silicon content selection range is less than or equal to 0.05 percent.
Mn, mn is a better deoxidizer and can obviously improve hardenability. Manganese and iron form solid solution, so that the hardness and strength of ferrite and austenite in steel are improved; meanwhile, carbide forming elements enter cementite to replace part of iron atoms, and finally fine pearlite is formed. However, too high a manganese content reduces the toughness of the steel and increases the cold brittleness of the steel. The manganese content of the application is selected to be 0.60-0.90%.
Cr, cr and Cr can raise the strength and hardness of steel obviously while reducing the plasticity and toughness of steel. The chromium content of the application is selected to be 0.90-1.25%.
P is a harmful element in the steel of the present application, which increases the cold brittleness of the steel, so that the cold forging property of the steel is deteriorated. The steel of the application needs to strictly control the phosphorus content, and the P is less than or equal to 0.012 percent.
S, sulfur belongs to harmful elements in the steel, so that the steel generates hot brittleness, and the ductility of the steel in a high temperature state is reduced. The application adopts the design of low sulfur component, and is not easy to generate cracks in the continuous casting withdrawal and straightening process and the casting blank rolling deformation process. The sulfur content of the steel is strictly controlled, and S is less than or equal to 0.005%.
Mo is a medium-strength carbide forming element, molybdenum carbide can be formed in steel, and the molybdenum carbide is dispersed in a matrix to play a role in refining the steel structure, so that the uniformity of the structure is improved. However, as the molybdenum content increases, the amount of molybdenum carbide increases, and the fracture effect of carbide distributed at grain boundaries on the matrix increases, resulting in a decrease in toughness of the steel. The molybdenum content of the application is selected to be 0.12-0.20%.
Al is a strong deoxidizing element, and a small amount of Al is added into the steel, so that a better deoxidizing effect can be achieved. Meanwhile, aluminum can also play a role in refining austenite grain size. The aluminum content of the application is selected to be in the range of 0.018 to 0.042%.
And N is nitrogen element is added in the steelmaking process after the deoxidation of the molten steel is finished, and is combined with the residual aluminum element in the steel to form AlN particles. AlN particles can be fully separated out and dispersed in a steel matrix by matching with a reasonable rolling process. The nitrogen content of the application is selected to be in the range of 0.0090-0.0180%.
The steel for the motorcycle engine gear and the manufacturing method thereof comprise the following process steps:
(1) In the steelmaking process, molten iron pre-desulfurization, converter primary refining, refining by a refining furnace and vacuum circulation degassing equipment are adopted for degassing, a mechanical stirring method is adopted for pre-desulfurization, a cross stirring paddle formed by casting refractory materials is inserted into molten iron for rotation after baking, the stirring speed is 120r/min, then a granular desulfurizing agent is added into a vortex of the molten iron, and the desulfurizing agent is preferably particles with the diameter less than or equal to 3mm, so that the desulfurizing agent and sulfur in the molten iron are subjected to desulfurization reaction in continuous stirring until the final sulfur content of the molten iron is less than or equal to 0.002%. The self-produced scrap steel is preferably added into the pretreated molten iron in the primary smelting process of the converter, and the sulfur content of the self-produced scrap steel is less than or equal to 0.005 percent. And sequentially adding ferromanganese, ferrochrome, ferromolybdenum and ferrosilicon alloy in the refining process, adjusting the components to target values, and then feeding aluminum wires to deoxidize molten steel. The vacuum circulation degassing treatment capacity is more than or equal to 100t, the larger molten steel amount can ensure that the molten steel has better thermal stability, the pressure of a vacuum chamber of the vacuum circulation degassing equipment is controlled to be 40-50 Pa, after 2 cycles, (when the molten steel in the ladle is sucked into the vacuum chamber with low pressure along a rising pipe along with the continuous decline of the pressure of the vacuum chamber, the molten steel is in a fountain shape because of leaving the rising pipe, so that the degassing area of the molten steel is obviously increased, the degassed molten steel flows back into the ladle along the falling pipe under the action of gravity, all the molten steel in the ladle is sucked into the vacuum chamber for 1 cycle, each cycle is 3min, the total 6min is used for rapidly degassing treatment, and the temperature drop of the molten steel in the whole degassing process is controlled to be less than or equal to 10 ℃. And hoisting the molten steel subjected to the vacuum treatment to a continuous casting platform for casting.
(2) Heating the cast continuous casting blank to 1200 deg.c in a heating furnace, initial rolling at 1.6-1.8m/min, intermediate rolling at 2.3-2.5m/min, final rolling at 1050-1100 deg.c, finish rolling at 4.1-4.3m/min, and final rolling at 975-975 deg.c. The final rolling temperature of the steel is ensured by controlling the rolling speed and temperature of the initial rolling, the intermediate rolling and the finish rolling of the steel. The AlN particles in the steel material start to be separated out once under the final rolling temperature interval through the observation of a laboratory scanning electron microscope, and the AlN once separation rate in the final rolling temperature interval is higher, so that the effect of better refining the carburized grain size of the steel material is achieved.
(3) The rolled high-temperature steel is put into an online heat preservation furnace for heat preservation, the temperature setting range of the heat preservation furnace is 820-845 ℃, the optimal peak temperature of AlN precipitation in the steel is 820-845 ℃, heat preservation is carried out for a period of time at the temperature, a large amount of AlN secondary precipitation is facilitated, the effect of AlN particles precipitated secondarily and AlN precipitated primarily is overlapped, the austenite grain size of the steel can be more effectively refined, the heat preservation time of the steel is 1h, and the single austenite structure in the steel is enabled to be finer and more uniform. The temperature of the heat preservation furnace is not set to be too high, and the too high furnace temperature can cause austenite grains to grow so as to obtain coarse ferrite and pearlite tissues after cooling; too low furnace temperature can not precipitate a large amount of AlN particles for a second time in a short time (1 hour) so as to achieve the aim of evenly refining the austenite structure. The steel after heat preservation is immediately buried in a sand tank, the temperature of sand in the sand tank is 100-110 ℃ so as to ensure enough dryness of the sand, the water content of the sand is less than or equal to 0.2%, the temperature is higher, the cooling speed of the steel can be reduced by the dried sand, the cooling speed of the steel in the sand tank is less than or equal to 15 ℃/h, and the steel is slowly cooled to below 200 ℃ and then discharged out of the sand tank for air cooling. The cooling process of the steel is sufficiently slow, the pearlite transformation of the austenitic structure can be ensured under the condition of lower supercooling, otherwise, the pearlite structure with larger size can be obtained due to larger supercooling degree, the higher-hardness of the steel can be caused by the existence of the pearlite structure with larger size in the steel, and the uniform and fine pearlite and ferrite structure (the size is less than or equal to 60um, and the preferable size is 20-55 um) can ensure the hardness of the steel to be less than or equal to 80HRB, thereby being beneficial to improving the cold forging and cutting performance of the steel. The method can also greatly reduce the structural stress and the thermal stress in the cooling process of the steel by a reasonable slow cooling mode, and effectively prevent the stress cracking phenomenon in the cooling process, thereby ensuring that the crack depth of the surface of the steel is less than or equal to 0.10mm.
Compared with the prior art, the application has the advantages that:
the application adopts low carbon, low silicon, low phosphorus and low sulfur design, adds a small amount of molybdenum element in steel, and cooperates with reasonable steelmaking, rolling and cooling processes.
The steel for the motorcycle engine gear, which is produced according to the method, has fine and uniform ferrite and pearlite of steel structure, wherein the sizes of the ferrite and the pearlite are less than or equal to 60um, and more preferably the sizes of the ferrite and the pearlite are 20-55um; the hardness of the steel is less than or equal to 80HRB; the depth of cracks on the surface of the steel is less than or equal to 0.10mm; the grain size of the carburized steel is more than or equal to 7.0 grade.
Drawings
FIG. 1 is a metallographic structure of a gear steel according to example 1 of the present application;
FIG. 2 shows the metallographic structure of the gear steel according to example 2 of the present application.
Detailed Description
The application is described in further detail below in connection with the following examples, which are exemplary and intended to illustrate the application, but are not to be construed as limiting the application.
Example 1 and example 2:
a steel for a gear of a motorcycle engine and a manufacturing method thereof are provided in two embodiments: KR method desulfurization, primary refining of a 100t converter, refining of a 100t refining furnace, vacuum circulation degassing of an RH furnace, continuous casting of billets (the sizes of billets are 200mm by 200 mm), heating of a heating furnace, control of rolling speed and final rolling temperature, isothermal of a post-rolling heat preservation furnace and slow cooling of a buried sand tank.
In the steelmaking process, molten iron KR is adopted for pre-desulfurization, a BOF converter is adopted for primary refining, an LF refining furnace is adopted for refining, an RH furnace is adopted for vacuum degassing, a KR mechanical stirring method is adopted for pre-desulfurization, a cross stirring paddle formed by pouring refractory materials is inserted into molten iron for rotation after baking, the stirring speed is 120r/min, then a granular desulfurizing agent is added into a molten iron vortex, the particle diameter of the desulfurizing agent is less than or equal to 3mm, the desulfurizing agent and sulfur in the molten iron are subjected to desulfurization reaction in continuous stirring, and the final sulfur of the molten iron is 0.001% (example 1) and 0.001% (example 2). Self-produced scrap steel with the sulfur content of 0.003 percent (example 1) and 0.004 percent (example 2) is added into the pretreated molten iron in the primary smelting process of the converter. And sequentially adding ferromanganese, ferrochrome, ferromolybdenum and ferrosilicon alloy in the refining process, adjusting the components to target values, and then feeding aluminum wires to deoxidize molten steel. The vacuum circulation degassing treatment capacity is 121t (example 1) and 118t (example 2), the larger molten steel amount can ensure that the molten steel has better thermal stability, the pressure of a vacuum chamber of the vacuum circulation degassing equipment is controlled to be 40-50 Pa, the total 6min of each circulation is subjected to rapid degassing treatment after 2 circulation for 3min, and the molten steel temperature drop in the whole degassing process is controlled to be 9 ℃ (example 1) and 6 ℃ (example 2). And hoisting the molten steel subjected to the vacuum treatment to a continuous casting platform for casting.
Heating the cast continuous casting blank to 1200 ℃ in a heating furnace, and performing initial rolling, intermediate rolling and finish rolling on the heated continuous casting blank, wherein the initial rolling speed and the temperature of the full-section billet are controlled to be 1.61m/min, 1109-1141 ℃ (example 1), 1.79m/min and 1115-1145 ℃ (example 2) respectively; the rolling speed of the middle rolling and the temperature of the full-section billet are respectively controlled to be 2.32/min, 1058-1091 ℃ (example 1), 2.49/min (example 2) and 1055-1088 ℃; the finish rolling speed and the temperature of the full-section billet are controlled to be 4.12m/s, 976-1037 ℃ (example 1), 4.28m/s and 988-1049 ℃ (example 2) respectively; the steel product finishing temperatures were 956 ℃ (example 1), 971 ℃ (example 2).
The rolled high-temperature steel is put into an online heat preservation furnace for heat preservation, the temperature of the heat preservation furnace is set to 845 ℃ (example 1) and 820 ℃ (example 2), and the heat preservation time of the steel is 1h. The steel after heat preservation is immediately buried in a sand tank, the temperature of sand in the sand tank is 100-110 ℃ so as to ensure enough dryness of the sand, the water content of the sand is less than or equal to 0.2%, the temperature is higher, the cooling speed of the steel can be reduced by the dried sand, the cooling speeds of the steel in the sand tank in the embodiment 1 and the embodiment 2 are less than or equal to 15 ℃/h, and the steel is slowly cooled to below 200 ℃ and then discharged out of the sand tank for air cooling.
The chemical compositions of the steels obtained in examples 1 and 2 are shown in Table 1.
TABLE 1 (wt%)
| C | Si | Mn | Cr | P | S | Mo | Al | N | |
| Example 1 | 0.19 | 0.04 | 0.65 | 0.93 | 0.010 | 0.002 | 0.12 | 0.025 | 0.0112 |
| Example 2 | 0.24 | 0.05 | 0.85 | 1.21 | 0.011 | 0.002 | 0.18 | 0.039 | 0.0176 |
The steel products obtained in examples 1 and 2 were 20-55um in both ferrite and pearlite sizes. See in particular figures 1 and 2.
The hardness, surface crack maximum depth, grain size after carburization of examples 1 and 2 are shown in table 2.
TABLE 2
| Hardness of | Maximum depth of surface crack | Grain size after carburization | |
| Example 1 | 75.3HRB | 0.07mm | Grade 7.5 |
| Example 2 | 79.6HRB | 0.05mm | 8.0 level |
The application adopts low carbon, low silicon, low phosphorus and low sulfur design (C: 0.18-0.25%, si: less than or equal to 0.05%, P: less than or equal to 0.012%, S: less than or equal to 0.005%), and adds a small amount of molybdenum element into steel, and cooperates with reasonable steelmaking, rolling and cooling processes.
Claims (6)
1. A steel for a gear of a motorcycle engine is characterized in that: the steel comprises the chemical components of, by weight, 0.18-0.25% of C, less than or equal to 0.05% of Si, 0.60-0.90% of Mn, 0.90-1.25% of Cr, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.12-0.20% of Mo, 0.018-0.042% of Al, and N:0.0090-0.0180%, and the balance Fe and unavoidable impurities.
2. The steel for a gear of a motorcycle engine according to claim 1, wherein: the metallographic structure of the steel is ferrite and pearlite, and the sizes of the ferrite and the pearlite are less than or equal to 60 mu m; the hardness of the steel is less than or equal to 80HRB; the depth of cracks on the surface of the steel is less than or equal to 0.10mm; the grain size in the surface carburized layer after carburization of the steel is more than or equal to 7.0 grade.
3. The steel for a gear of a motorcycle engine according to claim 2, wherein: the sizes of ferrite and pearlite are 20-55um.
4. A method of manufacturing the steel for a motorcycle engine gear according to claim 1, characterized in that: the steps include
Molten steel smelting
The molten steel smelting process comprises the steps of molten iron pre-desulfurization, converter primary smelting, refining and vacuum circulation degassing which are sequentially carried out,
in the stage of molten iron pre-desulfurization, a mechanical stirring method is adopted to pre-desulfurize, a cross stirring paddle formed by casting refractory materials is inserted into molten iron for rotation after baking, and then a granular desulfurizing agent is added into a vortex of the molten iron, so that the desulfurizing agent and sulfur in the molten iron are subjected to desulfurization reaction in continuous stirring until the final sulfur content of the molten iron is less than or equal to 0.002%; smelting molten iron and steel together in the primary smelting stage of the converter, sequentially adding ferromanganese, ferrochrome, ferromolybdenum and ferrosilicon in the refining process, adjusting the components to target values, and then feeding an aluminum wire to deoxidize the molten steel; the treatment capacity of vacuum circulation degassing is more than or equal to 100t, the pressure of a vacuum chamber of vacuum circulation degassing equipment is controlled to be 40-50 Pa, after 2 circulation, molten steel is completely sucked into the vacuum chamber from a ladle to be 1 circulation, each circulation is controlled within 3min, the total time is controlled within 6min, the rapid degassing treatment is carried out, and the temperature drop of the molten steel in the whole degassing process is controlled to be less than or equal to 10 ℃;
casting
Casting molten steel into a steel billet;
heating and rolling
Heating the billet to above 1200 ℃, performing initial rolling, intermediate rolling and finish rolling on the heated continuous casting billet, wherein the initial rolling speed is 1.6-1.8m/min, the total section temperature of the billet is controlled to be 1100-1150 ℃ in the initial rolling process, the intermediate rolling speed is 2.3-2.5m/min, the total section temperature of the billet is controlled to be 1050-1100 ℃ in the intermediate rolling process, the finish rolling speed is 4.1-4.3m/min, the total section temperature of the billet is controlled to be 975-1050 ℃ in the finish rolling process, the finish rolling temperature of the steel is 955-975 ℃, and AlN particles in the steel are separated out once in the finish rolling temperature interval;
thermal insulation cooling
The rolled high-temperature steel is put into an online heat preservation furnace for heat preservation, the temperature of the heat preservation furnace is set to be 820-845 ℃, the temperature is the optimal peak temperature of AlN precipitation, alN is subjected to secondary precipitation in the heat preservation stage, alN particles subjected to secondary precipitation are overlapped with AlN effect subjected to primary precipitation, and the heat preservation time of the steel is more than 1 h; the steel after heat preservation is immediately buried in a sand tank, the cooling speed of the steel in the sand tank is less than or equal to 15 ℃/h by controlling the temperature and the water content of sand, and the steel is slowly cooled to below 200 ℃ and then discharged out of the sand tank for air cooling.
5. The method for manufacturing steel for motorcycle engine gears according to claim 4, wherein: in the stage of pre-desulfurization of molten iron, the stirring speed of molten iron is more than 120r/min, and the particle diameter of the desulfurizing agent is less than or equal to 3mm.
6. The method for manufacturing steel for motorcycle engine gears according to claim 4, wherein: in the heat preservation and cooling stage, the temperature of sand in the sand tank is 100-110 ℃, and the water content is less than or equal to 0.2%.
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