A large-length-diameter-ratio shaft part machining manufacturing method

Abstract

The application belongs to the technical field of metal heat treatment, and relates to a machining manufacturing method of a large-length-diameter-ratio shaft part. By reducing the quenching deformation range of the large-length-diameter-ratio shaft part, the problem that the high waste rate is caused by the fact that the axial part area of the large-length-diameter-ratio shaft part still has insufficient machining allowance is solved. The spatial distortion deformation of the large-length-diameter-ratio shaft part after quenching is greatly improved, the quenching deformation amount can be effectively removed in the subsequent machining sequence after the part is quenched, and the product manufacturing precision and the product qualification rate are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of metal heat treatment technology, and mainly focuses on the processing and manufacturing of shaft parts with a length ≥ 0.40 m and a length-to-diameter ratio ≥ 20:1. It relates to a method for processing and manufacturing shaft parts with a large length-to-diameter ratio. Background Technology

[0002] Mechanical transmission systems extensively utilize shafts, primarily for connecting and transmitting torque. Some shafts, influenced and limited by service conditions, employ a large length-to-diameter ratio design; to further reduce weight, some even utilize hollow structures. These shafts exhibit high deflection and poor rigidity, making machining difficult. After quenching and intense cooling, the shafts exhibit axial twisting and radial warping; the larger the length-to-diameter ratio and the longer the shaft, the greater the quenching deformation.

[0003] Shafts with a length ≥ 0.40m and a length-to-diameter ratio ≥ 20:1 exhibit severe deformation during the quenching process. Although cold straightening can improve the degree of deformation, the improvement is limited. After straightening, some parts still lack sufficient machining allowance in certain areas, resulting in an extremely high scrap rate. This problem has been a persistent issue for the entire industry and has yet to be effectively resolved. Summary of the Invention

[0004] Purpose of the invention

[0005] The purpose of this invention is to provide a method for machining and manufacturing shaft parts with a large length-to-diameter ratio, mainly targeting the machining and manufacturing of shaft parts with a shaft length ≥ 0.40m and a shaft length-to-diameter ratio ≥ 20:1. By reducing the quenching deformation range of shaft parts with a large length-to-diameter ratio, the problem of excessively high scrap rate caused by insufficient machining allowance in the axial part of the shaft parts with a large length-to-diameter ratio is solved.

[0006] Technical solution

[0007] A method for machining and manufacturing shaft-type parts with a large length-to-diameter ratio includes the following steps:

[0008] Step one: First, before quenching shaft parts with a large length-to-diameter ratio, determine the configuration of the shaft part before quenching. Determine the axial midpoint position and extend outwards from both end faces of the shaft by (1 / 16 to 1 / 4) of the shaft length. The radius R of the determined axial region is increased by (5 to 50)%R based on the original radius. The specific area for increasing the axial radius is shown below. Figure 1 As shown.

[0009] Step two: For the axial non-thickened area, a straightening machining method is adopted to minimize the shoulder step structure. Before quenching, an appropriate machining allowance is added to one end of the shaft and an external thread is machined. A matching internally threaded sleeve tooling with a hanging upper part is manufactured. Before quenching and heating in the furnace, the internally threaded sleeve tooling is tightened to the external thread at one end of the shaft. After tightening, the shaft is suspended and transferred to the quenching furnace for quenching and heating. During the heating process, the shaft is kept in a free suspension state.

[0010] Step 3: When selecting rapid quenching oil, the quenching temperature should be the upper limit of the process temperature, and the quenching oil temperature should be set to (40~90)℃, preferably (60~90)℃. During shaft quenching, a hoist should be used to lift one end of the shaft to ensure that the shaft is always in a free-suspension state when immersed in the oil.

[0011] Furthermore, in step one, the axial thickness of shaft parts with a large length-to-diameter ratio is increased as needed.

[0012] Furthermore, in step one, when the radius is thickened by cylindrical rotation, the shoulder formed by the cylindrical rotation and the original shaft diameter is smoothly transitioned.

[0013] Furthermore, in step one, after the radius increases, the region of radius increase follows a spindle rotation pattern, as shown below. Figure 2 As shown.

[0014] Furthermore, in step one, after the radius is increased, the region of radius increase is a curved surface rotation mode, as shown below. Figure 3 As shown.

[0015] Furthermore, in step three, the deflection changes after shaft quenching and tempering are appropriately corrected, and the thickness of the middle part of the shaft is adjusted in combination with the value and method of thickening, thereby further improving the quenching deformation range of shaft parts with large length-to-diameter ratio.

[0016] Furthermore, when the shaft-type parts with a large length-to-diameter ratio are hollow shafts, aluminum silicate fiber felt is used to block both ends before quenching heating to prevent quenching oil from seeping into the hollow shaft during the quenching process.

[0017] Furthermore, in step three, when isothermal quenching oil is selected, the quenching oil temperature is set to 70℃~230℃.

[0018] Furthermore, the quenching oil temperature is specifically 130℃~220℃.

[0019] The beneficial effects of this application are as follows:

[0020] For shaft parts with a length ≥ 0.40m and a length-to-diameter ratio ≥ 20:1, the original machining methods often result in severe axial warping and circumferential rotation after the quenching process due to the excessive length-to-diameter ratio. This creates a twisted, spiral-like spatial distortion that cannot be completely eliminated during subsequent machining, frequently leading to part scrap. Even increasing the machining allowance between quenching processes along the axial direction cannot remove the deformation due to the spatial distortion.

[0021] This method significantly improves the spatial distortion deformation of shaft parts with large length-to-diameter ratios after quenching. The quenching deformation can be effectively removed in subsequent machining processes, resulting in a substantial increase in manufacturing precision and product yield. This technology can also be applied to the machining and manufacturing of non-rotationally symmetric shaft parts with large length-to-diameter ratios. Attached Figure Description

[0022] Figure 1 Schematic diagram of increasing the radius of the axial central region by cylindrical rotation;

[0023] Figure 2 Schematic diagram of increasing the radius of the axial mid-region by spindle rotation;

[0024] Figure 3 A schematic diagram illustrating the method of increasing the radius of the axial mid-region by surface rotation;

[0025] Figure 4 Schematic diagram of the structure of a slender shaft with a large aspect ratio before quenching;

[0026] Figure 5 Schematic diagram of configuration optimization of a slender shaft with a large aspect ratio before quenching;

[0027] Figure 6 The diagram shows a hanging internal threaded sleeve fixture in rainy weather. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments. The following description represents only a portion of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0029] The present invention will be further described below with reference to embodiments:

[0030] Shaft length 0.87m, maximum diameter A slender shaft with a large length-to-diameter ratio, made of 40CrNiMoA, with shoulder structures at both ends. A structural diagram is shown below. Figure 4As shown. The quenching temperature was 860℃ (process temperature range 840~860℃), the quenching oil was conventional rapid quenching oil, and the quenching oil temperature was (60±5)℃. During quenching, the part was supported by tooling and was in a vertical position. After quenching, the shaft exhibited "twisting" in the radial direction and "warping" in the axial direction. The axial roundness change was >3.00mm, far exceeding the process requirement of 0.35mm roundness. Although correction measures were taken, the radial "twisting" could not be effectively corrected due to the excessive length-to-diameter ratio, making the part unsuitable for subsequent machining and resulting in its scrap.

[0031] To improve the quenching deformation range of this slender shaft and in conjunction with the cold process, the pre-quenching configuration was optimized. The optimization results are shown below. Figure 5 As shown.

[0032] Synchronous use Figure 6 The free-suspension fixture shown connects to and tightens the slender shaft via a threaded connection. Then, auxiliary fixtures are used to ensure the slender shaft remains in a free-suspension state throughout the quenching and heating process. With the part self-suspended, the quenching temperature is set to 840℃, and isothermal quenching oil is selected. To ensure the hardness value after quenching, the quenching oil temperature is set to 150℃. After quenching and tempering, the roundness of the slender shaft part is between 0.40 and 0.65 mm. After appropriate correction, the roundness is reduced to ≤0.35 mm, meeting the subsequent machining allowance requirements and significantly improving the product qualification rate.

[0033] When the axial mid-section gyration radius thickening is less than 8mm, although the radial "twist" decreases significantly after quenching, the axial "warping" still exceeds tolerance, resulting in insufficient machining allowance. When the axial mid-section gyration radius thickening exceeds 8mm, the axial machining removal increases, raising manufacturing costs. When the midpoint of the shaft extends outwards by more than 0.20mm to both sides, although the part deformation is improved, the machining allowance increases. When the midpoint of the shaft extends outwards by less than 0.20mm to both sides, the improvement in part stiffness is limited, and the problem of "warping exceeding tolerance" still exists.

[0034] The process methods and parameters selected in this case study result in high cost-effectiveness in parts production.

[0035] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for machining and manufacturing shaft-type parts with a large length-to-diameter ratio, characterized in that, A large length-to-diameter ratio specifically refers to shaft parts with a shaft length ≥ 0.4m and a length-to-diameter ratio ≥ 20∶1, and includes the following steps: Step 1: Before quenching, determine the configuration of the shaft part and select a region extending from the midpoint of the shaft part to both ends as the region for increasing the axial radius. Based on the original radius R, increase the radius by 5%R to 50%R. Step two: For the axial non-thickened areas of shaft parts, a straightening machining method is adopted to minimize the shoulder step structure. A machining allowance is added to one end of the shaft, and an external thread is machined. A matching internal threaded sleeve tooling with a hanging structure is manufactured. Before the shaft part enters the furnace, the internal threaded sleeve tooling is tightened to the external thread at one end of the shaft part. Then, the tightened shaft part is suspended and transferred to the quenching furnace for quenching heating. During the heating process, the shaft part remains in a free-suspension state. Step 3: Select isothermal quenching oil and set the quenching oil temperature to 70℃~230℃. During quenching, use a crane to lift one end of the shaft part to ensure that the shaft part is always in a free suspension state when it is immersed in the quenching oil.

2. The method as described in claim 1, characterized in that, The specific quenching oil temperature is 130℃~220℃.

3. The method as described in claim 1, characterized in that, In step one, when the radius is increased by rotating a cylinder, the shoulder formed by the increased axial radius area and the original shaft diameter is smoothly transitioned.

4. The method as described in claim 1, characterized in that, In step one, after the radius is increased, the region with the increased radius takes the form of a spindle-shaped body of revolution or a curved body of revolution.

5. The method as described in claim 1, characterized in that, When the shaft-type parts with a large length-to-diameter ratio are hollow shafts, aluminum silicate fiber felt is used to block both ends before quenching and heating to prevent quenching oil from seeping into the hollow shaft during the quenching process.

6. The method as described in claim 1, characterized in that, In step three, rapid quenching oil is selected, the quenching temperature is the upper limit of the process temperature, and the quenching oil temperature is set to 40℃~90℃.

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