Forming process of automobile half-shaft bevel gear
阅读说明：本技术 一种汽车半轴锥齿轮的成型工艺 (Forming process of automobile half-shaft bevel gear ) 是由 吴先洋 张海英 周煊 王佳佳 陈楚文 于 2021-07-27 设计创作，主要内容包括：本发明公开一种汽车半轴锥齿轮的成型工艺,包括以下步骤：获得坯料；在室温下对所述坯料进行预锻得到预锻件；对所述预锻件进行退火处理；在室温下对经退火处理后的所述预锻件进行终锻得到终锻件；对所述终锻件进行正火处理得到锻坯；其中,所述预锻和所述终锻均采用闭式锻模。本发明通过采用闭式冷锻工艺成型得到汽车半轴锥齿轮锻坯,一方面,通过在室温下进行预锻和终锻,无需在预锻和终锻前对工件加热,对设备要求低,能源消耗少；另一方面,通过采用闭式锻模进行闭式锻造工艺,相比于开式锻造工艺,材料利用率高,后续机加工余量减少,生产成本低。(The invention discloses a molding process of an automobile half-shaft bevel gear, which comprises the following steps: obtaining a blank; pre-forging the blank at room temperature to obtain a pre-forged piece; annealing the pre-forging piece; performing finish forging on the pre-forged piece subjected to annealing treatment at room temperature to obtain a final forged piece; normalizing the finish forging to obtain a forging stock; wherein, the preforging and the finish forging both adopt closed forging dies. According to the invention, the forging stock of the automobile half-shaft bevel gear is obtained by adopting the closed cold forging process, on one hand, the pre-forging and the final forging are carried out at room temperature, so that the workpiece is not required to be heated before the pre-forging and the final forging, the requirement on equipment is low, and the energy consumption is low; on the other hand, the closed forging process is carried out by adopting the closed forging die, compared with the open forging process, the material utilization rate is high, the subsequent machining allowance is reduced, and the production cost is low.)
1. A molding process of an automobile half-shaft bevel gear is characterized by comprising the following steps:
obtaining a blank;
pre-forging the blank at room temperature to obtain a pre-forged piece;
annealing the pre-forging piece;
performing finish forging on the pre-forged piece subjected to annealing treatment at room temperature to obtain a final forged piece;
normalizing the finish forging to obtain a forging stock;
wherein, the preforging and the finish forging both adopt closed forging dies.
2. The process for molding an automotive half shaft bevel gear according to claim 1, wherein said pre-forged piece has a face angle corresponding to the pitch angle of said forging stock, said face angle of said pre-forged piece being equal to the pitch angle of said forging stock; and/or the presence of a gas in the gas,
the pre-forging piece is provided with a positioning hole corresponding to the mounting hole of the forging stock, and the depth of the positioning hole of the pre-forging piece is 2-3 mm; and/or the presence of a gas in the gas,
the pre-forging piece is provided with a first end corresponding to the small end of the forging stock, the first end of the pre-forging piece is arranged in a cylindrical shape, and the diameter of the first end of the pre-forging piece is set to beD1Setting the diameter of the small end of the forging stock to be D2，2mm≤D2-D1≤3mm。
3. The process for forming automotive half shaft bevel gears according to claim 1 wherein the step of annealing the pre-forged part comprises:
and (3) placing the pre-forging piece at the temperature of 920-950 ℃, cooling the pre-forging piece in a furnace after heat preservation treatment, and then placing the pre-forging piece after furnace cooling at the temperature of 650-680 ℃ for heat preservation treatment.
4. The molding process of the automobile half-shaft bevel gear according to claim 3, wherein the heat preservation treatment is carried out for 3 to 4 hours at a temperature of 920 to 950 ℃; and/or the presence of a gas in the gas,
the furnace cooling time is 1-3 minutes; and/or the presence of a gas in the gas,
and carrying out heat preservation treatment for 6-7 hours at the temperature of 650-680 ℃.
5. The molding process for an automotive half shaft bevel gear according to claim 1, characterized in that the step of subjecting the final forged part to normalizing treatment to obtain a forged blank comprises:
and (3) placing the final forging piece at the temperature of 900-920 ℃, carrying out heat preservation treatment, air cooling, and then placing the air-cooled final forging piece at the temperature of 620-650 ℃ for heat preservation treatment.
6. The molding process of the automobile half-shaft bevel gear according to claim 5, wherein the heat preservation treatment is carried out for 3-4 hours at the temperature of 900-920 ℃; and/or the presence of a gas in the gas,
the air cooling time is 2-3 minutes; and/or the presence of a gas in the gas,
and carrying out heat preservation treatment for 6-7 hours at the temperature of 620-650 ℃.
7. The molding process of the automobile half-shaft bevel gear according to claim 6, wherein the final forging is subjected to heat preservation treatment at 900-920 ℃, air cooling is performed, then the air cooled final forging is subjected to heat preservation treatment at 620-650 ℃, the heat preservation treatment is performed in a mixed gas of nitrogen and propane, and the carbon potential value of the mixed gas is less than or equal to 0.15% wtC.
8. The process for molding an automotive half shaft bevel gear according to claim 1, wherein after the step of annealing the pre-forged part and before the step of finish-forging the annealed pre-forged part at room temperature to obtain a final forged part, the process further comprises:
performing shot blasting treatment on the pre-forged piece after annealing treatment;
and carrying out phosphorization and saponification treatment on the pre-forged piece after the shot blasting treatment.
9. The process for forming half shaft bevel gears for automobiles according to claim 1, wherein the step of obtaining the blank comprises:
providing a drawing of a bevel gear forging;
obtaining the quality of the forged piece according to the drawing of the bevel gear forged piece;
and blanking to obtain the blank according to the quality of the forged piece.
10. The process for forming an automotive half shaft bevel gear according to claim 1, further comprising, after said step of obtaining a blank, before said step of preforging said blank at room temperature to obtain a preforged piece:
performing shot blasting treatment on the blank;
and carrying out phosphorization and saponification treatment on the blank subjected to shot blasting treatment.
Technical Field
The invention relates to the technical field of metal plastic forming, in particular to a forming process of an automobile half-shaft bevel gear.
Background
The automobile half-shaft bevel gear is used as one of important component parts of an automobile differential, is mainly used for realizing a mechanism for rotating automobile driving wheels at different rotating speeds, and has high requirement on part precision. At present, the main forming process of a forged blank (a blank product which is not subjected to deep processing after forging) of the automobile half-shaft bevel gear adopts open type hot forging and cold finishing, and the open type die forging and hot forging process is adopted in the process, so that the subsequent machining allowance of the automobile half-shaft bevel gear is large, the material utilization rate is low, the equipment requirement is high, the energy consumption is large, and the production cost is high.
Disclosure of Invention
The invention mainly aims to provide a molding process of an automobile half-shaft bevel gear, and aims to solve the problems of large subsequent machining allowance, low material utilization rate, high equipment requirement, large energy consumption and high production cost of the existing molding process.
In order to achieve the purpose, the invention provides a molding process of an automobile half-shaft bevel gear, which comprises the following steps:
obtaining a blank;
pre-forging the blank at room temperature to obtain a pre-forged piece;
annealing the pre-forging piece;
performing finish forging on the pre-forged piece subjected to annealing treatment at room temperature to obtain a final forged piece;
normalizing the finish forging to obtain a forging stock;
wherein, the preforging and the finish forging both adopt closed forging dies.
Optionally, the pre-forging has a cone face angle corresponding to the pitch cone angle of the forging stock, the cone face angle of the pre-forging being equal to the pitch cone angle of the forging stock; and/or the presence of a gas in the gas,
the pre-forging piece is provided with a positioning hole corresponding to the mounting hole of the forging stock, and the depth of the positioning hole of the pre-forging piece is 2-3 mm; and/or the presence of a gas in the gas,
the pre-forging piece is provided with a first end corresponding to the small end of the forging stock, the first end of the pre-forging piece is arranged in a cylindrical shape, and the diameter of the first end of the pre-forging piece is set to be D1Setting the diameter of the small end of the forging stock to be D2，2mm≤D2-D1≤3mm。
Optionally, the step of annealing the pre-forging includes:
and (3) placing the pre-forging piece at the temperature of 920-950 ℃, cooling the pre-forging piece in a furnace after heat preservation treatment, and then placing the pre-forging piece after furnace cooling at the temperature of 650-680 ℃ for heat preservation treatment.
Optionally, carrying out heat preservation treatment for 3-4 hours at the temperature of 920-950 ℃; and/or the presence of a gas in the gas,
the furnace cooling time is 1-3 minutes; and/or the presence of a gas in the gas,
and carrying out heat preservation treatment for 6-7 hours at the temperature of 650-680 ℃.
Optionally, the step of normalizing the finish forging to obtain a forging stock includes:
and (3) placing the final forging piece at the temperature of 900-920 ℃, carrying out heat preservation treatment, air cooling, and then placing the air-cooled final forging piece at the temperature of 620-650 ℃ for heat preservation treatment.
Optionally, carrying out heat preservation treatment for 3-4 hours at the temperature of 900-920 ℃; and/or the presence of a gas in the gas,
the air cooling time is 2-3 minutes; and/or the presence of a gas in the gas,
and carrying out heat preservation treatment for 6-7 hours at the temperature of 620-650 ℃.
Optionally, the final forging piece is placed at the temperature of 900-920 ℃, heat preservation treatment is carried out, air cooling is carried out, then the air-cooled final forging piece is placed at the temperature of 620-650 ℃, the heat preservation treatment is carried out in a mixed gas of nitrogen and propane, and the carbon potential value of the mixed gas is less than or equal to 0.15% wtC.
Optionally, after the step of annealing the pre-forging, and before the step of finish-forging the annealed pre-forging at room temperature to obtain a final forging, the method further includes:
performing shot blasting treatment on the pre-forged piece after annealing treatment;
and carrying out phosphorization and saponification treatment on the pre-forged piece after the shot blasting treatment.
Optionally, the step of obtaining a blank comprises:
providing a drawing of a bevel gear forging;
obtaining the quality of the forged piece according to the drawing of the bevel gear forged piece;
and blanking to obtain the blank according to the quality of the forged piece.
Optionally, after the step of obtaining a blank and before the step of pre-forging the blank at room temperature to obtain a pre-forging, the method further includes:
performing shot blasting treatment on the blank;
and carrying out phosphorization and saponification treatment on the blank subjected to shot blasting treatment.
According to the technical scheme, the forged blank of the automobile half-shaft bevel gear is obtained by adopting a closed cold forging process, on one hand, pre-forging and finish forging are carried out at room temperature, a workpiece does not need to be heated before pre-forging and finish forging, the requirement on equipment is low, and the energy consumption is low; on the other hand, the closed forging process is carried out by adopting the closed forging die, compared with the open forging process, the material utilization rate is high, the subsequent machining allowance is reduced, and the production cost is low.
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 related drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic flow chart of one embodiment of a process for forming an automotive half shaft bevel gear in accordance with the present invention;
FIG. 2 is a schematic flow chart of another embodiment of the process for forming an automotive half shaft bevel gear in accordance with the present invention;
FIG. 3 is a cross-sectional view of a pre-forged part resulting from the forming process of the present invention;
FIG. 4 is a cross-sectional view of a forged blank obtained by the forming process of the present invention.
The reference numbers illustrate:
reference numerals
Name (R)
Reference numerals
Name (R)
10
Preforged part
21
Mounting hole
11
Locating hole
22
Small end
12
First end
23
Big end
20
Forging stock
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
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 derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
At present, the main forming process of a forged blank (a blank product which is not subjected to deep processing after forging) of the automobile half-shaft bevel gear adopts open type hot forging and cold finishing, and the open type die forging and hot forging process is adopted in the process, so that the subsequent machining allowance of the automobile half-shaft bevel gear is large, the material utilization rate is low, the equipment requirement is high, the energy consumption is large, and the production cost is high.
In view of the above, the invention provides a molding process of an automobile half-shaft bevel gear, which is characterized in that an automobile half-shaft bevel gear forging stock is obtained by adopting a closed cold forging process, on one hand, pre-forging and finish forging are carried out at room temperature, a workpiece does not need to be heated before the pre-forging and the finish forging, the requirement on equipment is low, and the energy consumption is low; on the other hand, the closed forging process is carried out by adopting the closed forging die, compared with the open forging process, the material utilization rate is high, the subsequent machining allowance is reduced, and the production cost is low. Fig. 1 and 2 illustrate an embodiment of a molding process of a half-shaft bevel gear for an automobile according to the present invention.
Referring to fig. 1 and 2, a molding process of a half-shaft bevel gear of an automobile comprises the following steps:
step S10, a blank is obtained.
In order to ensure the smooth operation of the closed cold forging in the later period, a blank with a proper size is needed. Specifically, referring to fig. 2, in this embodiment, a blank with a suitable size is selected through a drawing of a bevel gear forging, and step S10 includes:
step S11, providing a bevel gear forging drawing, obtaining forging quality according to the bevel gear forging drawing, and blanking to obtain the blank according to the forging quality.
The method comprises the steps of firstly calculating to obtain reasonable forging quality according to a provided bevel gear forging drawing, selecting a bar with a proper diameter, then determining the length of the bar, and blanking by adopting a circular saw according to the length of the bar to obtain a blank with a proper size. Therefore, through accurate and proper blank size, smooth proceeding of closed cold forging in the later period can be guaranteed, and meanwhile, material cost is saved.
In addition, referring to fig. 2, after step S10 and before step S20, the method further includes:
and step S12, performing shot blasting treatment on the blank.
By performing shot blasting treatment on the blank, scale and attachments on the surface of the blank are removed, so that the blank is lubricated. The invention does not limit the shot blasting equipment, and specifically, referring to fig. 2, in this embodiment, a drum type shot blasting machine is used to perform shot blasting on the blank. The drum-type shot blasting machine has good surface treatment effect and convenient use and maintenance, and is favorable for improving the production efficiency.
And step S13, carrying out phosphorization and saponification treatment on the blank after shot blasting treatment.
Specifically, referring to fig. 2, in this embodiment, a phosphorization and saponification production line is used to perform phosphorization, cleaning, saponification and drying on the blank after shot blasting treatment in sequence. And (3) phosphorizing the blank subjected to shot blasting to form a phosphorized film, cleaning, saponifying to attach the saponified film to the surface, and drying to further increase the lubricity of the surface of the blank.
And step S20, pre-forging the blank at room temperature to obtain a pre-forged piece.
The blank is pre-forged at room temperature, no additional heating is needed for the blank, the requirement on equipment is low, and the energy consumption is low. And the pre-forging process adopts a closed forging die, the blank is subjected to closed forging by the closed forging die, the material utilization rate is high, the subsequent machining allowance is reduced, and the production cost is low. It should be noted that, the blank is preforged at room temperature to obtain a preforged part by using a mechanical press.
Fig. 3 is a sectional view of a pre-forged part obtained by the forming process of the present invention, fig. 4 is a sectional view of a forged blank obtained by the forming process of the present invention, and referring to fig. 3 and 4, the pre-forged part 10 has a taper angle a corresponding to a pitch angle δ of the forged blank 20, and the taper angle a of the pre-forged part 10 is equal to the pitch angle δ of the forged blank 20. The pitch cone angle is the intersection angle of a pitch cone line of the bevel gear and a gear center line, and the forging stock 20 is obtained by the molding process of the automobile half-shaft bevel gear, mainly machining and molding the gear teeth of the bevel gear, and the molded forging stock 20 is consistent with the pitch cone angle of the bevel gear. Correspondingly, the pre-forging 10 has a conical surface angle a corresponding to the pitch angle δ of the forging blank 20, and the subsequent finish forging forming is facilitated by making the conical surface angle a of the pre-forging 10 equal to the pitch angle δ of the forging blank 20. Fig. 3 and 4 show specific embodiments of the pre-forging 10 and the forging stock 20, and as shown in fig. 3 and 4, the taper angle a of the pre-forging 10 and the pitch angle δ of the forging stock 20 are both 50 °.
Furthermore, the pre-forging 10 has a positioning hole 11 corresponding to the mounting hole 21 of the forging stock 20, and the depth L of the positioning hole 11 of the pre-forging 1012-3 mm. The bevel gear is conical and is provided with a small end (small diameter) and a large end (large diameter) which are oppositely arranged, correspondingly, the forging stock 20 is also provided with a small end 22 and a large end 23 which are oppositely arranged, the mounting hole 21 of the forging stock 20 is a counter bore which is positioned at the large end 23 in the forging stock 20, and the mounting hole 21 of the forging stock 20 is used for mounting and positioning in post machining. Setting the depth L of the positioning hole 11 of the pre-forging 101The thickness of the positioning hole is 2-3 mm, so that a positioning hole is formed in advance during pre-forging, the positioning hole can be used as a counter bore foundation of the mounting hole 21 of the forging stock 20 during subsequent finish forging to improve the forming efficiency, and an auxiliary positioning can be provided for subsequent annealing treatment, finish forging and other processes. Specifically, referring to fig. 3, in the present embodiment, the depth L of the positioning hole 11 of the pre-forging 10 is greater than the depth L of the positioning hole 111Is 3 mm.
Further, the pre-forging 10 has a first end 12 corresponding to the small end 22 of the forging stock 20, the first end 12 of the pre-forging 10 is disposed in a cylindrical shape, and the diameter of the first end 12 of the pre-forging 10 is set to be D1Setting the diameter D of the small end 22 of the forging stock 202，2mm≤D2-D1Less than or equal to 3 mm. Wherein the small end 22 of the forging stock 20 corresponds to the small end of a bevel gear. Such that the diameter D of the first end 12 of the pre-forging 101With the diameter D of the small end 22 of the forging stock 202The difference of (A) is in the range of 2mm to 3mm, which contributes to the reduction of the deformation resistance during finish forging molding.In the embodiment of fig. 3 and 4, D1＝32.2mm，D2＝34.2mm，D2-D1＝2mm。
It should be noted that, in the arrangement of the three related technical features, namely, the taper angle a of the pre-forging 10, the positioning hole 11 of the pre-forging 10, and the first end 12 of the pre-forging 10, one of the three related technical features may exist, two of the three related technical features may exist, or both the two related technical features may exist. Obviously, when the three materials exist simultaneously, the effect is optimal, the deformation resistance during finish forging forming is greatly reduced through the synergistic effect of the three materials, and the finish forging with complete filling is obtained under lower load.
Step S30, annealing the pre-forged part.
The performance of the pre-forging piece is improved by annealing the pre-forging piece, and smooth closed cold forging in the later-stage finish forging is ensured. Specifically, referring to fig. 2, in the present embodiment, the annealing treatment is preferably performed by an isothermal annealing method, and step S30 includes:
and S31, placing the pre-forging piece at the temperature of 920-950 ℃, cooling the pre-forging piece in a furnace after heat preservation treatment, and then placing the pre-forging piece cooled in the furnace at the temperature of 650-680 ℃ for heat preservation treatment.
Through the isothermal annealing treatment, the hardness of the pre-forged piece is reduced, so that the forming pressure during finish forging is reduced, and the filling effect is improved.
In practical application, the heat preservation treatment is carried out for 3-4 hours at the temperature of 920-950 ℃, and the heat preservation effect of the high-temperature section is ensured by treating for 3-4 hours at the high-temperature section (920-950 ℃). The furnace cooling time is 1-3 minutes, and the cooling effect during furnace cooling is ensured. The heat preservation treatment is carried out for 6-7 hours at the temperature of 650-680 ℃, and the heat preservation effect of the isothermal section is ensured by treating for 6-7 hours at the isothermal section (650-680 ℃). In the invention, the isothermal annealing treatment is preferably performed on the pre-forging by using a continuous push rod type heating furnace, and the furnace cooling time is 1 minute, so that the efficiency of the isothermal annealing treatment is improved on the premise of ensuring the effect of the isothermal annealing treatment.
It should be noted that, in the above three settings of the three related technical features of heat preservation treatment at 920-950 ℃ for 3-4 hours, furnace cooling time for 1-3 minutes, and heat preservation treatment at 650-680 ℃ for 6-7 hours, one of them may exist, two of them may exist, or both of them may exist. It is clear that the effect is optimal when both are present.
Furthermore, referring to fig. 2, after step S30 and before step S40, the method further includes:
and step S32, performing shot blasting treatment on the pre-forged piece after annealing treatment.
Since the oxide scale and the attachment inevitably exist on the surface of the pre-forging after the annealing treatment, the shot blasting treatment of the pre-forging helps to remove the oxide scale and the attachment on the surface of the pre-forging for lubrication. It should be noted that the invention does not limit the shot blasting equipment, and the invention preferably adopts a drum type shot blasting machine to perform shot blasting treatment on the pre-forged piece after annealing treatment. The drum-type shot blasting machine has good surface treatment effect and convenient use and maintenance, and is favorable for improving the production efficiency.
And step S33, carrying out phosphorization and saponification treatment on the pre-forged piece after shot blasting treatment.
Specifically, referring to fig. 2, in this embodiment, a phosphorization and saponification production line is used to successively perform phosphorization, cleaning, saponification and drying on the pre-forged piece after shot blasting. And phosphorizing the pre-forged piece after shot blasting treatment to form a phosphorized film, cleaning, saponifying to attach the saponified film to the surface, and drying to further increase the lubricity of the surface of the pre-forged piece.
And step S40, performing finish forging on the pre-forged piece after annealing treatment at room temperature to obtain a finish forged piece.
The pre-forged part formed by the above-described pre-forging process has a shape close to the final dimensional requirements, but is subjected to finish forging to obtain a finish forged part satisfying the dimensional requirements. According to the invention, the pre-forging piece is subjected to finish forging at room temperature, the pre-forging piece does not need to be additionally heated, the requirements on equipment are low, the energy consumption is low, and meanwhile, the cold forging mode is also beneficial to improving the tooth shape and tooth direction precision of the wheel tooth part of the finish forging piece. And the finish forging process also adopts a closed forging die, and the closed forging die is used for performing closed forging on the pre-forged piece, so that the material utilization rate is further improved, the subsequent machining allowance is reduced, and the production cost is reduced. And the finish forging is preferably carried out on the pre-forging piece after the annealing treatment by adopting a mechanical press and a floating die.
And step S50, normalizing the finish forging to obtain a forging stock.
The finish forged part after the closed cold forging process has residual stress on the surface after the cold forging process, and needs to be normalized. Specifically, referring to fig. 2, in this embodiment, the normalizing process is preferably performed in an isothermal normalizing manner, and step S50 includes:
and S51, placing the final forging piece at the temperature of 900-920 ℃, carrying out heat preservation treatment, air cooling, and then placing the air-cooled final forging piece at the temperature of 620-650 ℃ for heat preservation treatment.
In practical application, the heat preservation treatment is carried out for 3-4 hours at the temperature of 900-920 ℃, and the heat preservation effect of a high-temperature section (900-920 ℃) is ensured. The air cooling time is 2-3 minutes, and the cooling effect during air cooling is guaranteed. And (3) carrying out heat preservation treatment for 6-7 hours at the temperature of 620-650 ℃, and ensuring the heat preservation effect of the isothermal section (620-650 ℃). The isothermal normalizing treatment method preferably uses the controllable atmosphere continuous push rod type heating furnace to perform isothermal normalizing treatment on the pre-forged piece, the air cooling time is 2 minutes, and the efficiency of isothermal normalizing treatment is improved on the premise of ensuring the effect of isothermal normalizing treatment.
It should be noted that, in the three settings of the three related technical features of heat preservation treatment for 3 to 4 hours at the temperature of 900 to 920 ℃, air cooling time for 2 to 3 minutes, and heat preservation treatment for 6 to 7 hours at the temperature of 620 to 650 ℃, one of the three related technical features may exist, two of the three related technical features may exist, or both the two related technical features may exist. It is clear that the effect is optimal when both are present.
Further, step S51 is performed in a mixed gas of nitrogen and propane, and the carbon potential value of the mixed gas is 0.15% or less wtC. Therefore, non-oxidation isothermal normalizing treatment is realized in the atmosphere of nitrogen and propane, residual stress generated by cold forging is eliminated under the condition of ensuring no decarburization through the non-oxidation isothermal normalizing treatment, the structure of a finish forging is homogenized, the subsequent mixed crystal defect is avoided, and the final forging stock is ensured to meet the performance requirement.
Wherein, the preforging and the finish forging both adopt closed forging dies. Closed forging dies are devices commonly used by those skilled in the art and are not described in detail herein.
The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
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