Carburizing and quenching process of thin-wall gear and clamping tool of thin-wall gear

Abstract

The invention discloses a carburizing and quenching process of a thin-wall gear and a clamping tool of the thin-wall gear. The carburizing and quenching process comprises process parameters of temperature, time, flow, carbon potential, cooling speed and the like in stages of pre-cleaning, pre-oxidation, preheating, strong carburizing, diffusion, cooling, quenching, tempering and the like. It needs to be explained that in the technical process, the purpose of reducing the heat treatment deformation quantity of the thin-wall gear is achieved by optimizing the hanging and clamping mode of the thin-wall gear and improving the temperature and time parameters during carburizing and quenching in the scheme. Besides, a clamping tool suitable for the process is designed in the scheme, so that the clamping stability of the thin-wall gear during carburizing and quenching treatment is improved, and the heat treatment deformation quantity of the thin-wall gear is further reduced.

Description

Technical Field

[0001] The invention relates to a heat treatment process for a thin-wall gear, in particular to a carburizing and quenching process for a thin-wall gear and a clamping tool for the thin-wall gear. Background Art

[0002] Ring gears play a vital role in the power transmission and performance optimization of automobiles, and are an important component to ensure driving safety and comfort. As the requirements for automobile weight reduction become higher and higher, the wall thickness of ring gears is getting thinner and thinner, and the ratio of diameter to wall thickness is getting larger and larger. The requirements for dimensional accuracy and deformation are becoming more and more stringent, and the requirements for heat treatment are also getting higher and higher. If the traditional heat treatment process is still used in existing production, the yield rate of thin-walled gears will be significantly lower than that of traditional gears, and even less than 90% of the yield rate will occur, and the production cost of enterprises will increase sharply. Therefore, how to ensure the deformation qualification rate of heat treatment processing of such products is an important issue. Summary of the invention

[0003] The object of the present invention is to provide a clamping tool for thin-walled gears and a carburizing and quenching process using the clamping tool, so as to improve the yield rate of carburizing and quenching of thin-walled gears.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A carburizing and quenching process for thin-walled gears using a clamping tool, comprising:

[0006] S1: Pre-cleaning treatment is performed on the surface of the processed thin-walled gear to remove impurities such as cutting fluid, oil spots, iron filings, etc. remaining during the processing of the thin-walled gear surface;

[0007] S2: Hang the thin-walled gear vertically on the hanging rod of the clamping tool. When hanging the thin-walled gear, it is necessary to ensure that the inner ring of the thin-walled gear has two supporting points symmetrical to the midline and in contact with the hanging rod, and the span W between the two supporting points is between 66.7% and 80% of the inner diameter D of the thin-walled gear ring;

[0008] S3: Surface pre-oxidation. During the surface pre-oxidation treatment, the pre-oxidation temperature is 450°C ± 10°C and the time is 60 ± 5 minutes.

[0009] S4: Carburizing the pre-oxidized thin-walled gear, which is divided into the following stages:

[0010] S41: preheating treatment, during which the methanol flow rate is maintained at: 1.5-2.0 L / h, the nitrogen flow rate is maintained at: 1.7-2.2 L / h, the temperature during the preheating treatment is 880°C ± 10°C, and the time is 75±5 minutes;

[0011] S42: Strong permeation treatment, during which the methanol flow rate is 1.4-1.8L / H, and the nitrogen flow rate is 1.6-2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9~1.0±0.05%, the temperature during the strong penetration treatment is 900℃±10℃, and the time is 130±5 minutes;

[0012] S43: Diffusion treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, carbon potential is selected as 0.8±0.05%, the temperature during diffusion treatment is 900℃±10℃, and the time is 60±5 minutes;

[0013] S44: Cooling treatment, during which the methanol flow rate is 1.5-2.0L / H, and the nitrogen flow rate is 1.7-2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.75±0.05%, the temperature during the cooling treatment is 840±10℃, and the time is 90±5 minutes;

[0014] S5: quenching treatment, during which the quenching oil is slow quenching oil, the quenching oil temperature is 80℃~150℃, the stirring speed is 300~800rpm, and the cooling time is 8±1 minute;

[0015] S6: Tempering treatment, during which the tempering temperature is selected to be 170±10℃ and the tempering time is 180±30 minutes.

[0016] Preferably, in step S42, the strong permeation treatment is divided into a first stage of strong permeation and a second stage of strong permeation. The methanol flow rate of the first stage of strong permeation is 1.4-1.8 L / H, and the nitrogen flow rate is 1.6-2.0 m / h. 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H; the carbon potential is 1.0±0.5%, the temperature is 900℃±10℃, and the time is 75±5 minutes; the methanol flow rate of the second stage of the strong permeation is 1.4~1.8L / H, and the nitrogen flow rate is 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9±0.5%, the temperature is 900℃±10℃, and the time is 60±5 minutes.

[0017] A clamping tool used in the carburizing and quenching process of a thin-walled gear, comprising:

[0018] Base;

[0019] The column is vertically inserted on the base;

[0020] There are multiple adjustment sleeves, and the number of adjustment sleeves arranged on each column is adjusted according to the required height of the gear when it is suspended;

[0021] The supporting rod has two ends which are slidably mounted on the upright posts and are raised by an adjusting sleeve mounted on the upright posts;

[0022] A suspension rod, wherein two suspension rods form a group, and a spacing is left between the two suspension rods, so that after the thin-walled gear is suspended on the two suspension rods, the span of the two contact points between the inner ring of the thin-walled gear and the two suspension rods is 66.7-80% of the diameter of the inner gear ring of the thin-walled gear;

[0023] The card plate is inserted into the two suspension rods in a leaping manner.

[0024] Preferably, both ends of the hanging rod are also provided with card slots respectively, and after the hanging rod is mounted on the supporting rod, the supporting rod is inserted into the card slots.

[0025] Preferably, the upper and lower surfaces of the support rod are respectively provided with racks extending along the length direction, and both ends of the suspension rod are provided with latching teeth that can be snapped into the racks.

[0026] Preferably, the suspension rod is an H rod.

[0027] Preferably, the clamping plate is M-shaped to form a positioning groove into which the upper edge of the suspension rod is clamped.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This solution changes the placement of thin-walled gears from the traditional horizontal placement of gears to vertical suspension by designing a fixture that can be used to suspend gears vertically, thereby reducing the axial force on the end face of the gear during heat treatment, thereby reducing the end jump value of the thin-walled gear after heat treatment. In addition, during carburizing, the corresponding heat treatment temperature is also improved to further improve the problem of easy deformation of thin-walled gears during heat treatment, greatly improving the compliance rate of various values ​​of thin-walled gears, reducing the margin required for processing, and greatly reducing the difficulty of subsequent workpiece processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a state diagram of the clamping tool in the present invention when clamping a thin-walled gear and performing carburizing and quenching heat treatment.

[0031] Figure 2 for Figure 1 A front view of

[0032] Figure 3 It is a structural schematic diagram of the clamping tool;

[0033] Figure 4 for Figure 3 Exploded diagram of

[0034] Figure 5 is a schematic diagram of the structure of the support rod;

[0035] Figure 6 It is a structural schematic diagram of the pallet;

[0036] Figure 7 It is a process diagram of the present invention.

[0037] Figure numerals: 1. base 2. column 3. adjustment sleeve 4. support rod 41. rack 5. hanging rod 51. latching tooth 52. latching groove 6. latching plate 61. positioning groove. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] The thin-walled gears used in this implementation plan require the outer diameter of the gear ring to reach 170mm, the inner diameter to reach 130mm, the wall thickness range to be 12±2mm, the ratio of the inner diameter to the wall thickness to be greater than or equal to 13:1, and the material of the thin-walled gears can be low-carbon alloy steel such as 20MnCr5. This plan implements the following specific carburizing and quenching process for the thin-walled gears that meet the above requirements.

[0042] Example 1

[0043] The gear used has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0044] A carburizing and quenching process for thin-walled gears using a clamping tool, comprising:

[0045] S1: Place the thin-walled gear in a basket, and then use a cleaning agent (alkaline solution or pickling) to rinse and soak the surface of the thin-walled gear to clean the residual cutting fluid, oil spots, iron filings, etc. on the surface of the thin-walled gear, and then rinse, soak and neutralize the surface of the thin-walled gear with clean water. After the treatment is completed, dry the surface of the thin-walled gear to prevent the surface of the thin-walled gear from rusting again;

[0046] S2: The dried thin-walled gear is mounted on the hanging rods of the clamping tool. The hanging rods are arranged in groups of two and are placed with a gap. After the thin-walled gear is mounted on the two hanging rods, its inner ring is suspended by the two hanging rods in the form of point contact or line contact, and the vertical relationship between the two end faces of the thin-walled gear and the horizontal plane is maintained. It should be noted that the gap between the two hanging rods as a group in the clamping tool needs to be appropriately adjusted according to the value of the inner ring diameter D of the mounted thin-walled gear to ensure that the span W between the two contact points of the two hanging rods on the inner ring of the thin-walled gear is 66.7% of the inner diameter D of the supported thin-walled gear ring.

[0047] S3: Surface pre-oxidation, the thin-walled gear hanging on the clamping tool is sent into the carburizing furnace together with the clamping tool. The temperature in the carburizing furnace is uniformly increased to 450℃±10℃ and maintained at this temperature for 60±5 minutes, so that a layer of oxide film that can promote the carburizing speed is generated on the surface of the thin-walled gear. It should be noted that compared with the traditional pre-oxidation temperature of 400℃, the basic temperature of 450℃ in this scheme has a better pre-oxidation effect when processing gears of materials such as 20MnCr5, and the formation of the oxide film is more uniform, and the later carburizing effect is also improved.

[0048] S4: After the thin-walled gear is pre-oxidized, the temperature in the carburizing furnace is further raised to a suitable temperature for carburizing. It should be noted that the carburizing process can be divided into four major stages, namely S41: preheating stage, S42: strong carburizing stage, S43: diffusion stage and S44: cooling stage. Among them:

[0049] S41: preheating treatment, during which the carburizing furnace maintains a methanol flow rate of 1.5-2.0 L / h, a nitrogen flow rate of 1.7-2.2 L / h, and a temperature of 880°C±10°C, and the preheating treatment time is maintained at 75±5 minutes.

[0050] S42: In the strong permeation stage, the methanol flow rate is 1.4-1.8L / H, and the nitrogen flow rate is 1.6-2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected to be 0.9~1.0±0.05%, the temperature during the strong penetration treatment is 900℃±10℃, and the time is 135±10 minutes.

[0051] As the core step of carburizing the workpiece surface, the temperature and carbon potential of the carburizing process determine the carburizing effect of the workpiece. It should be understood that the optimal carburizing temperature of conventional 20MnCr5 workpieces is usually 930±10℃, while the carburizing temperature used in this scheme is 900℃±10℃, which is significantly lower than the optimal carburizing temperature. At this temperature, the carburizing efficiency will be reduced by about 30% compared to 930±10℃. To this end, this scheme increases the carburizing cycle time to achieve the desired carburizing effect, specifically, from the conventional time of 100±10 minutes to the existing processing time. It should be noted that the reason for adopting this carburizing temperature is that the thin-walled gear has a low strength at high temperature and is easily affected by its own gravity and slightly deformed. By reducing the temperature of the thin-walled gear during the carburizing process, the strength of the gear during the carburizing process can be effectively guaranteed, and the deformation of the thin-walled gear in a high temperature state during the carburizing process can be reduced.

[0052] S43: Diffusion treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.8±0.05%, the temperature during diffusion treatment is 900℃±10℃, and the time is 60±5 minutes.

[0053] S44: Cooling treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.75±0.05%, the temperature during the cooling treatment is 840±10℃, and the time is 90±5 minutes;

[0054] S5: Quenching treatment, during which the quenching oil is slow quenching oil, the quenching oil temperature is 80℃~150℃, the stirring speed is 300~800rpm, and the cooling time is 8±1 minutes. ;

[0055] S6: Tempering treatment, during which the tempering temperature is selected to be 170±10℃ and the tempering time is 180±30 minutes.

[0056] On the basis of the above implementation, this embodiment can also be optimized as follows. It should be noted that in the stage of strong carburization on the surface of thin-walled gears, in order to improve the carburizing efficiency, it can be specifically divided into two stages, namely the first stage of strong carburization and the second stage of strong carburization. Among them, the role of the first stage of strong carburization is to make the surface of the thin-walled gear quickly reach a high carbon concentration. Therefore, in this stage, the methanol flow rate is selected to be 1.4~1.8L / H, and the nitrogen flow rate is selected to be 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H; the carbon potential is 1.0±0.5%, the temperature is 900℃±10℃, and the time is 75±5 minutes; in the second stage of strong penetration, the carbon potential needs to be appropriately reduced to avoid the obstruction effect caused by excessive carbon concentration on the surface of thin-walled gear parts, that is, the surface carburizing concentration is too high, resulting in the inability of activated carbon to effectively penetrate into the workpiece. For this reason, in the second stage of strong penetration, the methanol flow rate is 1.4~1.8L / H, and the nitrogen flow rate is 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9±0.5%, the temperature is 900℃±10℃, and the time is 60±5 minutes.

[0057] In addition, the present invention also discloses a clamping tool used when a thin-walled gear is subjected to a carburizing and quenching process, so as to cooperate with the clamping method of the thin-walled gear during the carburizing and quenching heat treatment to ensure the stability of the gear state during the heat treatment.

[0058] Specific as Figures 1 to 6 A clamping tool used in the carburizing and quenching process of thin-walled gears includes a metal base 1, which is rectangular and has four columns 2 vertically inserted on the four corners of the base. It should be noted that the four columns all extend vertically upward.

[0059] like Figure 3 As shown, two adjacent columns form a group, and a support rod 4 is installed on the two columns in the same group. The support rods on the two groups of columns are kept horizontal and arranged in parallel, so that a hanging rod 5 for clamping thin-walled gears can be set on the two support rods.

[0060] It should be noted that, in order to facilitate the connection between the two ends of the support rod and the column, the two ends of the support rod are sleeve structures. When installing the support rod on the column, it is only necessary to make the sleeves at both ends slide and fit on one of the corresponding columns. At this time, the two ends of the support rod are constrained by the column, and it will also remain horizontally erected. At the same time, it should be noted that in order to make full use of the space in the carburizing furnace, the height of the column in this scheme is usually high (greater than 0.7m) to ensure that a group of mounting tools can be mounted on multiple layers of thin-walled gears. For this reason, an adjustment sleeve 3 is also sleeved on the column, and these adjustment sleeves are arranged below the two ends of the support rod to prop up the support rod. By increasing or decreasing the number of adjustment sleeves on each column to adjust the height of the support rod, it is ensured that the height difference between adjacent support rods is greater than the outer ring diameter of the gear, so as to avoid surface contact between the upper and lower layers of gears during heat treatment, and to ensure that during heat treatment, the activated carbon can smoothly pass through the surface of each gear, and each gear can be evenly carburized.

[0061] like Figures 1 to 3 As shown, the suspension rods 5 mounted on the two support rods are grouped in two to implement the suspension clamping of the gear. Figure 2As shown, after the two ends of the two support rods are mounted on the support rods, a spacing is left between them to ensure that when the thin-walled gear is mounted on the two suspension rods, the span W between the support points where its inner ring contacts the suspension rod is 66.7% of its own inner ring diameter D. It should be noted that because the gear is a metal part, after a large number of thin-walled gears are mounted on the two suspension rods, the suspension rods will be subjected to the force exerted by the thin-walled gears toward the center of the thin-walled gears. Under the component of this force, the two suspension rods tend to approach each other. During carburizing or quenching treatment, if the support points are unstable and changeable, the force distribution of the thin-walled gears will inevitably be destroyed, resulting in a large change in the roundness of the gear. In order to prevent the two suspension rods from relative displacement with each other during heat treatment, a clamping plate 6 is also installed between the two suspension rods 5. For details, see. Figure 3 As shown, there are at least two clamping plates 6 fixed at both ends of the two suspension rods between the two suspension rods. It should be noted that, in order to facilitate the clamping plate to fix the two suspension rods, the two ends of the clamping plate are inserted into the two suspension rods in a leaping manner to prevent the two suspension rods from approaching or moving away from each other.

[0062] It should be noted that, in the actual production process, even if the distance between two suspension rods in a group is stable, there is still a situation where the suspension rod is displaced on the support rod, or even one end slides off the support rod when the clamping tool with the gear mounted on it is sent into the carburizing furnace. For this reason, a card slot 52 is respectively provided at both ends of the suspension rod, and the width of the card slot is the width of the support rod. When the suspension rod is mounted on the support rod, the support rod is inserted into the card slot 52. Preferably, in the above scheme, the card slot can be symmetrically provided up and down, so that the upper and lower surfaces of the support rod do not have directional differences.

[0063] It should also be noted that in order to prevent the suspension rod with the thin-walled gear from sliding in the length direction of the support rod during transportation, a rack 41 extending along the length direction of the support rod is provided on the surface of the support rod. At the same time, latching teeth 51 that can be snapped into the rack are provided at both ends of the suspension rod. When the suspension rod is mounted on the support rod, the latching teeth snap into the teeth of the rack to prevent the suspension rod from sliding on the support rod due to the shaking of the gear during transportation. Preferably, the rack is provided on the upper and lower surfaces of the support rod, and can be of different specifications of tooth spacing to achieve adjustment of different spacings.

[0064] In addition, it should be noted that in the above scheme, the suspension rod is an H-shaped rod with an H-shaped cross section. The H-shaped structure is better than a round rod in terms of load-bearing and bending resistance, has higher stability during carburizing and quenching, and avoids the problem of deformation expansion of thin-walled gears by reducing its own deformation.

[0065] On the basis of adopting the H-rod, the card plate can be an M-shaped structure. Under this structure, the card plate forms a positioning groove 61 into which the rib plate on one side of the suspension rod can be inserted, so that the card plate can limit the two suspension rods more accurately and stably.

[0066] Compared with cylindrical structures, H-type suspension rods and M-type pallets are lighter in weight, absorb less heat at high temperatures, and save energy. In addition, the wall thickness of the H-type suspension rod is relatively uniform, and there is no distinction between the outside and the core of the round rod. During the heat treatment process, its own temperature rises evenly, and the thermal expansion and contraction form is stable and uniform. After the gear is placed on the H-type suspension rod, it will not be skewed by the thermal expansion of the suspension rod (when the inner ring of the gear is uneven, skewness often occurs), ensuring the stability of the contact between the inner wall of the gear and the suspension rod during heat treatment, that is, the state of each gear during heat treatment is unified, thereby effectively ensuring the consistency of the state of thin-walled gears in a batch after heat treatment, facilitating quality control.

[0067] Example 2

[0068] The gear used has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0069] The difference between this embodiment and embodiment 1 is that in step S2 of this solution, the span W between the two contact points of the two suspension rods on the inner ring of the thin-walled gear is 72% of the inner diameter D of the supported thin-walled gear ring.

[0070] Example 3

[0071] The gear used has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0072] The difference between this embodiment and embodiment 1 is that in step S2 of this solution, the span W between the two contact points of the two suspension rods on the inner ring of the thin-walled gear is 75% of the inner diameter D of the supported thin-walled gear ring.

[0073] Example 4

[0074] The gear used has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0075] The difference between this embodiment and embodiment 3 is that in step S2 of this solution, the span W between the two contact points of the two suspension rods on the inner ring of the thin-walled gear is 80% of the inner diameter D of the supported thin-walled gear ring.

[0076] Comparative Example 1

[0077] The gear used has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0078] The difference between this embodiment and embodiment 3 is that in step S2 of this solution, the span W between the two contact points of the two suspension rods on the inner ring of the thin-walled gear is 60% of the inner diameter D of the supported thin-walled gear ring.

[0079] Comparative Example 2

[0080] The gear used has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0081] The difference between this embodiment and embodiment 3 is that in step S2 of this solution, the span W between the two contact points of the two suspension rods on the inner ring of the thin-walled gear is 85% of the inner diameter D of the supported thin-walled gear ring.

[0082] Comparative Example 3

[0083] The thin-walled gear used in this scheme has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0084] The difference between this comparative example 3 and embodiment 1 is that step S1 and step S2 are specifically as follows:

[0085] S1: Place the thin-walled gear in a basket, and then use a cleaning agent (alkaline solution or pickling) to rinse and soak the surface of the thin-walled gear to clean the residual cutting fluid, oil spots, iron filings, etc. on the surface of the thin-walled gear, and then rinse, soak and neutralize the surface of the thin-walled gear with clean water. After the treatment is completed, dry the surface of the thin-walled gear to prevent the surface of the thin-walled gear from rusting again;

[0086] S2: Place the thin-walled gear horizontally on the parts rack.

[0087] It should be noted that the heat treatment form of the thin-walled gears in this scheme is to place them horizontally on a placement rack. During the heat treatment process, the end face will be subjected to the axial force caused by its own weight, which will make the end runout value of the thin-walled gears after heat treatment reach the standard rate in a relatively low range (the qualified rate in a batch is less than 70%).

[0088] S3: Surface pre-oxidation: The thin-walled gear placed flat on the rack is sent into the carburizing furnace together with the rack. The temperature in the carburizing furnace is uniformly increased to 450℃±10℃ and maintained at this temperature for 60±5 minutes to form an oxide film on the surface of the thin-walled gear that can promote the carburizing speed.

[0089] S4: After the thin-walled gear is pre-oxidized, the temperature in the carburizing furnace is further raised to a suitable temperature for carburizing. It should be noted that the carburizing process can be divided into four major stages, namely S41: preheating stage, S42: strong carburizing stage, S43: diffusion stage and S44: cooling stage.

[0090] S41: preheating treatment, during which the carburizing furnace maintains a methanol flow rate of 1.5-2.0 L / h, a nitrogen flow rate of 1.7-2.2 L / h, and a temperature of 880°C±10°C, and the preheating treatment time is maintained at 75±5 minutes.

[0091] S42: In the strong permeation stage, the methanol flow rate is 1.4-1.8L / H, and the nitrogen flow rate is 1.6-2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9~1.0±0.05%, the temperature during the strong carburizing treatment is 900℃±10℃, and the time is 135±10 minutes. Among them, the strong carburizing stage on the surface of thin-walled gears can be specifically divided into two stages, namely the first stage of strong carburizing and the second stage of strong carburizing, in order to improve the carburizing efficiency. Among them, the role of the first stage of strong carburizing is to make the surface of the thin-walled gear quickly reach a high carbon concentration. Therefore, in this stage, the methanol flow rate is selected as 1.4~1.8L / H, and the nitrogen flow rate is selected as 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H; the carbon potential is 1.0±0.5%, the temperature is 900℃±10℃, and the time is 75±5 minutes; in the second stage of strong penetration, the carbon potential needs to be appropriately reduced to avoid the obstruction effect caused by excessive carbon concentration on the surface of thin-walled gear parts, that is, the surface carburizing concentration is too high, resulting in the inability of activated carbon to effectively penetrate into the workpiece. For this reason, in the second stage of strong penetration, the methanol flow rate is 1.4~1.8L / H, and the nitrogen flow rate is 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9±0.5%, the temperature is 900℃±10℃, and the time is 60±5 minutes.

[0092] S43: Diffusion treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.8±0.05%, the temperature during diffusion treatment is 900℃±10℃, and the time is 60±5 minutes.

[0093] S44: Cooling treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.75±0.05%, the temperature during the cooling treatment is 840±10℃, and the time is 90±5 minutes;

[0094] S5: Quenching treatment, during which the quenching oil is slow quenching oil, the quenching oil temperature is 80℃~150℃, the stirring speed is 300~800rpm, and the cooling time is 8±1 minutes. ;

[0095] S6: Tempering treatment, during which the tempering temperature is selected to be 170±10℃ and the tempering time is 180±30 minutes.

[0096] Comparative Example 4

[0097] The thin-walled gear used in this scheme has an outer diameter of 170mm, an inner diameter of 130mm, a wall thickness of 10mm, and is made of 20MnCr5.

[0098] The difference between this comparative example 4 and embodiment 1 lies in step S4, which is specifically:

[0099] A carburizing and quenching process for thin-walled gears using a clamping tool, comprising:

[0100] S1: Place the thin-walled gear in a basket, and then use a cleaning agent (alkaline solution or pickling) to rinse and soak the surface of the thin-walled gear to clean the residual cutting fluid, oil spots, iron filings, etc. on the surface of the thin-walled gear, and then rinse, soak and neutralize the surface of the thin-walled gear with clean water. After the treatment is completed, dry the surface of the thin-walled gear to prevent the surface of the thin-walled gear from rusting again;

[0101] S2: The dried thin-walled gear is mounted on the hanging rods of the clamping tool. The hanging rods are arranged in groups of two and are placed with a gap. After the thin-walled gear is mounted on the two hanging rods, its inner ring is suspended by the two hanging rods in the form of point contact or line contact, and the vertical relationship between the two end faces of the thin-walled gear and the horizontal plane is maintained. It should be noted that the gap between the two hanging rods as a group in the clamping tool needs to be appropriately adjusted according to the value of the inner ring diameter D of the mounted thin-walled gear to ensure that the span W between the two contact points of the two hanging rods on the inner ring of the thin-walled gear is 66.7% of the inner diameter D of the supported thin-walled gear ring.

[0102] S3: Surface pre-oxidation: The thin-walled gear placed flat on the rack is sent into the carburizing furnace together with the rack. The temperature in the carburizing furnace is uniformly increased to 450℃±10℃ and maintained at this temperature for 60±5 minutes to form an oxide film on the surface of the thin-walled gear that can promote the carburizing speed.

[0103] S4: After the thin-walled gear is pre-oxidized, the temperature in the carburizing furnace is further raised to a suitable temperature for carburizing. It should be noted that the carburizing process can be divided into four major stages, namely S41: preheating stage, S42: strong carburizing stage, S43: diffusion stage and S44: cooling stage.

[0104] S41: preheating treatment, during which the carburizing furnace maintains a methanol flow rate of 1.5-2.0 L / h, a nitrogen flow rate of 1.7-2.2 L / h, and a temperature of 880°C±10°C, and the preheating treatment time is maintained at 75±5 minutes.

[0105] S42: In the strong permeation stage, the methanol flow rate is 1.4-1.8L / H, and the nitrogen flow rate is 1.6-2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9~1.0±0.05%, the temperature during the strong carburizing treatment is 930℃±10℃, and the time is 100±10 minutes. Among them, the strong carburizing stage on the surface of thin-walled gears can be specifically divided into two stages, namely the first stage of strong carburizing and the second stage of strong carburizing, in order to improve the carburizing efficiency. Among them, the role of the first stage of strong carburizing is to make the surface of the thin-walled gear quickly reach a high carbon concentration. Therefore, in this stage, the methanol flow rate is selected to be 1.4~1.8L / H, and the nitrogen flow rate is selected to be 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H; the carbon potential is 1.0±0.5%, the temperature is 930℃±10℃, and the time is 55±5 minutes; in the second stage of strong penetration, the carbon potential needs to be appropriately reduced to avoid the obstruction effect caused by excessive carbon concentration on the surface of thin-walled gear parts, that is, the surface carburizing concentration is too high, resulting in the inability of activated carbon to effectively penetrate into the workpiece. For this reason, in the second stage of strong penetration, the methanol flow rate is 1.4~1.8L / H, and the nitrogen flow rate is 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9±0.5%, the temperature is 930℃±10℃, and the time is 45±5 minutes.

[0106] S43: Diffusion treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.8±0.05%, the temperature during diffusion treatment is 900℃±10℃, and the time is 60±5 minutes.

[0107] S44: Cooling treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.75±0.05%, the temperature during the cooling treatment is 840±10℃, and the time is 90±5 minutes;

[0108] S5: Quenching treatment, during which the quenching oil is slow quenching oil, the quenching oil temperature is 80℃~150℃, the stirring speed is 300~800rpm, and the cooling time is 8±1 minutes. ;

[0109] S6: Tempering treatment, during which the tempering temperature is selected to be 170±10℃ and the tempering time is 180±30 minutes.

[0110] It should be noted that, in the process of strong infiltration, the control example 4 adopted the conventional treatment temperature of 930℃±10℃, which resulted in a higher material temperature of the thin-walled gear during strong infiltration and reduced deformation resistance of the material. During heat treatment, the roundness of the gear will be reduced due to the thermal deformation of the thin-walled gear, resulting in a lower compliance rate (the qualified rate in one batch is less than 80%).

[0111] Table 1 shows the roundness and end jump values ​​of various embodiments and control examples before and after heat treatment.

[0112]

[0113] Table 2 shows the metallographic detection data before and after heat treatment of each embodiment and control example.

[0114]

[0115]

Claims

1. A carburizing and quenching process for thin-walled gears using a clamping tool, characterized in that: include S1: Pre-cleaning treatment is performed on the surface of the processed thin-walled gear to remove impurities such as cutting fluid, oil spots, iron filings, etc. remaining during the processing of the thin-walled gear surface; S2: Hang the thin-walled gear vertically on the hanging rod of the clamping tool. When hanging the thin-walled gear, it is necessary to ensure that the inner ring of the thin-walled gear has two supporting points symmetrical to the midline and in contact with the hanging rod, and the span W between the two supporting points is between 66.7% and 80% of the inner diameter D of the thin-walled gear ring; S3: Surface pre-oxidation. During the surface pre-oxidation treatment, the pre-oxidation temperature is 450°C ± 10°C and the time is 60 ± 5 minutes. S4: Carburizing the pre-oxidized thin-walled gear, which is divided into the following stages: S41: preheating treatment, during which the methanol flow rate is maintained at: 1.5-2.0 L / h, the nitrogen flow rate is maintained at: 1.7-2.2 L / h, the temperature during the preheating treatment is 880°C ± 10°C, and the time is 70±5 minutes; S42: Strong permeation treatment, during which the methanol flow rate is 1.4-1.8L / H, and the nitrogen flow rate is 1.6-2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected to be 0.9-1.0%, the temperature during the strong penetration treatment is 900℃±10℃, and the time is 135±10 minutes; S43: Diffusion treatment, methanol flow rate is 1.5~2.0L / H, nitrogen flow rate is 1.7~2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, carbon potential is selected as 0.8±0.05%, the temperature during diffusion treatment is 900℃±10℃, and the time is 60±5 minutes; S44: Cooling treatment, during which the methanol flow rate is 1.5-2.0L / H, and the nitrogen flow rate is 1.7-2.2m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.75±0.05%, the temperature during the cooling treatment is 840±10℃, and the time is 90±5 minutes; S5: quenching treatment, during which the quenching oil is slow quenching oil, the quenching oil temperature is 80℃~150℃, the stirring speed is 300~800rpm, and the cooling time is 8±1 minute; S6: Tempering treatment, during which the tempering temperature is selected to be 170±10℃ and the tempering time is 180±30 minutes.

2. A carburizing and quenching process for thin-walled gears using a clamping tool as claimed in claim 1, characterized in that: In step S42, the strong permeation treatment is divided into a first stage of strong permeation and a second stage of strong permeation. The methanol flow rate of the first stage of strong permeation is 1.4-1.8 L / H, and the nitrogen flow rate is 1.6-2.0 m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H; the carbon potential is 1.0±0.5%, the temperature is 900℃±10℃, and the time is 75±5 minutes; the methanol flow rate of the second stage of the strong permeation is 1.4~1.8L / H, and the nitrogen flow rate is 1.6~2.0m 3 / H, propane flow rate is 0~0.5m 3 / H, the process air flow rate is 0~0.5m 3 / H, the carbon potential is selected as 0.9±0.5%, the temperature is 900℃±10℃, and the time is 60±5 minutes.

3. A clamping tool used in the carburizing and quenching process of a thin-walled gear, characterized in that: include Base (1); A column (2) is vertically inserted on the base (1); An adjustment sleeve (3), wherein the adjustment sleeve (3) is provided in plurality, and the number of the adjustment sleeves (3) mounted on a column (2) is adjusted according to the required height of the gear when it is suspended; The supporting rod (4) has two ends which are slidably mounted on the upright column (2) and are raised by an adjusting sleeve (3) mounted on the upright column (2); A suspension rod (5), wherein two suspension rods (5) form a group, and a spacing is left between the two suspension rods (5), so that after the thin-walled gear is suspended on the two suspension rods, the span between the two contact points between the inner ring of the thin-walled gear and the two suspension rods (5) is 66.7-80% of the diameter of the inner gear ring of the thin-walled gear; A card plate (6) is inserted into two suspension rods (5) in a leaping manner.

4. The clamping tool used for carburizing and quenching thin-walled gears according to claim 3, characterized in that: Both ends of the hanging rod (5) are also provided with clamping grooves (52), and after the hanging rod (5) is mounted on the supporting rod (4), the supporting rod (4) is clamped into the clamping grooves (52).

5. The clamping tool used for carburizing and quenching thin-walled gears according to claim 4, characterized in that: The upper and lower surfaces of the support rod (4) are respectively provided with racks (41) extending along the length direction, and both ends of the suspension rod (5) are provided with latching teeth (51) capable of being latched into the racks (41).

6. The clamping tool used for carburizing and quenching thin-walled gears according to claim 5, characterized in that: The hanging rod (5) is an H rod.

7. The clamping tool used for carburizing and quenching thin-walled gears according to claim 6, characterized in that: The clamping plate (6) is M-shaped to form a positioning groove (61) into which the upper edge of the hanging rod (5) is clamped.

Images