Thin-walled cylinder part and machining method thereof

Abstract

The invention belongs to the technical field of machining, and particularly discloses a thin-walled cylinder part and a machining method thereof.The machining method of the thin-walled cylinder part comprises the steps of bar material preparing, rough machining, hardening and tempering, semi-finish machining, finish machining, gear shaping, nitriding, grinding and finished product obtaining, and the machining method is characterized in that stabilizing treatment is further included between gear shaping and nitriding. And stabilizing treatment is added before nitriding, the nitriding deformation is very small and does not exceed 0.05 mm, and deformation out-of-tolerance does not occur during grinding.

Description

Technical Field

[0001] The invention belongs to the field of mechanical processing, and in particular relates to a thin-walled tube-type part and a processing method thereof. Background Art

[0002] Thin-walled cylindrical parts are complex parts with long processing steps and high precision requirements. They are very easy to deform during nitriding and grinding. Nitriding deformation and grinding deformation can easily lead to batch scrapping of parts, resulting in large cost losses and difficulties in controlling production progress.

[0003] Currently, the solutions to this problem are:

[0004] (1) Control the nitriding process, ensure the sealing performance of the equipment, and heat and regenerate the desiccant in the drying tank for a long time to improve the drying capacity of the ammonia gas entering the furnace for nitriding, reduce the water content, and avoid unqualified and uneven organization, but it will still deform after grinding.

[0005] (2) Optimize the grinding process and divide the grinding process into rough grinding, alignment and fine grinding. Reduce the grinding feed and strictly control it. After clamping the parts with tooling, carefully check the clamping conditions to avoid squeezing and drying. However, this will not only reduce production efficiency, but also cause unsatisfactory deformation after grinding.

[0006] Therefore, how to provide a treatment method that can prevent thin-walled cylindrical parts from deforming after nitriding and grinding is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0007] In view of this, the present invention discloses a method for processing thin-walled tube parts. The deformation problem of thin-walled tube parts is effectively controlled by the method of the present invention.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for processing thin-walled cylindrical parts, the processing steps of the thin-walled cylindrical parts are: bar material - rough machining - tempering - semi-finishing - finishing - gear shaping - nitriding - grinding - finished product, and stabilization treatment is also included between gear shaping and nitriding.

[0010] Preferably, the process parameters of the stabilization treatment are as follows: heating temperature is 560°C ± 10°C, keeping warm for 3h to 4h and then cooling to below 60°C before taking out of the furnace.

[0011] Preferably, the vacuum degree of the stabilization treatment heating and cooling process is no more than 1.33Pa.

[0012] Preferably, a cleaning agent should be used to clean the surface oil, dirt, etc. before the stabilization treatment to prevent defects such as soft spots and uneven structure of the parts.

[0013] Preferably, during the stabilization treatment, adjacent parts are spaced at least 10 mm apart to ensure uniform heating.

[0014] Preferably, the heating rate of the stabilization treatment is 130-150°C / h and should be as gentle as possible to avoid reaching the set temperature too quickly.

[0015] Preferably, the quenching and tempering are performed to make the hardness of the parts reach 30-37.

[0016] Preferably, the nitriding is performed by a two-stage nitriding method.

[0017] The thin-walled tube-like parts processed by the above processing method are gear sleeves. This type of part belongs to the thin-walled tube-like parts, and although chamfering is performed after gear shaping, there are still many stress concentration areas.

[0018] After systematic analysis, it was found that the deformation was mainly caused by the excessive residual stress of forging and machining. The present invention combed through the existing process routes and found that there is a stress relief process after rough machining, which can largely eliminate the residual stress of forging and rough machining. However, there is still a large amount of material surplus to be removed in the subsequent mechanical processing process, and even includes processes such as gear shaping that will generate great stress. There is no stress relief process until the finishing and semi-finishing process before nitriding. The high residual stress is retained until the nitriding and final outer grinding process, and deformation is caused. Stabilization treatment is added before nitriding, and the nitriding deformation is very small, not exceeding 0.05mm, and no deformation out-of-tolerance occurs during grinding.

[0019] This method is mainly suitable for thin-walled cylindrical parts and parts with right angles or sharp angles that are prone to stress concentration and cause deformation of parts during the nitriding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0021] Figure 1 This is a schematic diagram of the dimensions of thin-walled tubular parts in Example 1. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0023] Example 1

[0024] The bar material is 38CrMoAl, bar - rough machining - tempering - semi-finishing - finishing - gear shaping - stabilization treatment - nitriding - grinding - finished product.

[0025] Rough machining: Turning Form the approximate shape of the part

[0026] Quenching and tempering: 940℃ quenching and 620℃ tempering to make the parts hardness reach 30 to 37, preparing for subsequent finishing and nitriding.

[0027] Semi-finishing and finishing: CNC equipment ensures Figure 1 shape.

[0028] Gear shaping: Gear shaping equipment ensures the number of teeth: 78; pressure angle: 30°; tooth profile tolerance: 0.025; tooth direction tolerance: 0.03 and other gear shaping requirements.

[0029] Stabilization steps:

[0030] 1) Check whether the vacuum heating equipment is operating normally.

[0031] 2) Use a cleaning agent to clean the parts to remove surface oil stains, dirt, cutting coolant and metal shavings, etc., to ensure that it does not hinder the heating and cooling of the parts, does not affect the purity of the medium and atmosphere, and prevents defects such as soft spots and uneven structure on the parts.

[0032] 3) Place the parts on the tray, leaving gaps between each part to reduce mutual shielding during heating and ensure heating rate and uniform heating. Use a cart to send the tray into the vacuum heating equipment and close the furnace door.

[0033] 4) Set the process parameters, start the equipment, and the vacuum pump will work to draw the vacuum degree of the furnace to below 1.33Pa, and heating will start automatically.

[0034] 5) After the vacuum heating equipment is heated from room temperature to 560°C at a heating rate of 140°C / h, the temperature is maintained at 560°C for 3.5h, and then the heating is stopped, and the vacuum degree of the furnace is maintained below 1.33Pa.

[0035] 6) The furnace will slowly cool down to 60°C, then be inflated and open the furnace door to take out the parts.

[0036] Nitriding: Two-stage nitriding at 540℃ and 525℃.

[0037] Grinding: The size is ground to 214.8, with an upper difference of 0 and a lower difference of 0.03; Grinding guarantees an upper tolerance of 0 and a lower tolerance of 0.03.

[0038] According to the above method, three parallel furnace groups are set up. The deformation conditions of parts in the three furnaces are shown in Tables 1, 2, and 3 respectively: the furnace number is arranged in combination with the specific production task during the test.

[0039] Table 1 Deformation of parts in the first furnace

[0040]

[0041] Table 2 Deformation of parts in the second furnace

[0042]

[0043]

[0044] Table 3 Deformation of parts in the third furnace

[0045]

[0046] Comparative Example 1

[0047] The difference from Example 1 is that the stabilization treatment is added before gear shaping instead of before nitriding, and the method of stabilization treatment is the same as that of Example 1.

[0048] Table 3 Deformation of parts in comparative example 1

[0049]

[0050] Comparative Example 2

[0051] The difference from Example 1 is that the stabilization treatment before nitriding is changed to stress relief treatment after nitriding, and the process parameters of the stress relief treatment are: heating temperature is 490℃±10℃, keeping warm for 3.5h and then cooling to below 60℃ before taking out of the furnace, and the vacuum degree of the heating and cooling process is not greater than 1.33Pa.

[0052]

[0053] The comparative effects of the present invention by adding stabilization treatment before gear shaping, adding stress relief treatment after nitriding, and adding stabilization treatment before nitriding are as follows:

[0054] 1) When stabilization treatment is added before gear shaping, nitriding deformation basically meets the requirements, but deformation after grinding still occurs from time to time.

[0055] 2) Adding stress relief treatment after nitriding is beneficial to control the deformation after grinding to meet the design requirements, but it cannot change the situation of excessive deformation after nitriding. There is a situation where the nitriding deformation is too large to be corrected by grinding.

[0056] 3) After adding stabilization treatment before nitriding, the nitriding deformation basically does not exceed 0.05mm. After 6 consecutive furnaces, stress relief treatment was added after nitriding, and no deformation exceeded the tolerance during grinding.

[0057] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for processing thin-walled cylindrical parts, wherein the processing steps of the thin-walled cylindrical parts are: bar material - rough machining - quenching and tempering - semi-finishing - finishing - gear shaping - nitriding - grinding - finished product, characterized in that: A stabilization treatment is also included between the gear shaping and the nitriding.

2. A method for processing thin-walled tube parts according to claim 1, characterized in that: The process parameters of the stabilization treatment are as follows: the heating temperature is 560°C ± 10°C, the temperature is kept for 3h to 4h, and then the furnace is cooled to below 60°C and then taken out of the furnace.

3. A method for processing thin-walled tube parts according to claim 1, characterized in that: The vacuum degree of the stabilization treatment heating and cooling process is no more than 1.33Pa.

4. A method for processing thin-walled tube parts according to claim 1, characterized in that: Before the stabilization treatment, a cleaning agent is used to clean the surface oil and dirt.

5. A method for processing thin-walled tube parts according to claim 4, characterized in that: During the stabilization treatment, adjacent parts are spaced at least 10 mm apart.

6. A method for processing thin-walled tube parts according to claim 4, characterized in that: The heating rate of the stabilization treatment is 130-150° C. / h.

7. A method for processing thin-walled tube parts according to claim 1, characterized in that: The quenching and tempering process makes the hardness of the parts reach 30-37.

8. A method for processing thin-walled tube parts according to claim 1, characterized in that: The nitriding is carried out by a two-stage nitriding method.

9. A thin-walled tubular part processed by the processing method according to any one of claims 1 to 8.

10. The thin-walled tube-like part according to claim 9, characterized in that: The thin-walled tube-like parts are gear sleeves.

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