Manufacturing method of lightweight hollow shaft

Abstract

The invention belongs to the field of shaft machining, and particularly relates to a manufacturing method of a lightweight hollow shaft. The invention provides a manufacturing method of a light-weight hollow shaft. The manufacturing method comprises the steps that S1, a bar and a pipe are straightened; s2, the bars and the pipes are subjected to blanking and saw cutting; s3, the bar and the pipe are welded into an integrated blank shaft crude product through friction welding; s4, performing heat treatment on the blank shaft crude product to obtain a blank shaft; and S5, the blank shaft is machined according to a drawing, and the lightweight hollow shaft is obtained. The lightweight hollow shaft prepared by the invention is light in weight, has excellent mechanical properties, and has remarkable economic benefits and social benefits.

Description

Technical Field

[0001] The present invention belongs to the field of shaft processing, and particularly relates to a manufacturing method for a lightweight hollow shaft. Background Art

[0002] In the field of mechanical transmission, shaft parts, as key mechanical basic parts, mainly function to rotate and transmit torque. Under the rotating working conditions of shaft parts, the stress distribution shows obvious non-uniformity. Through in-depth mechanical analysis, it can be known that when the shaft transmits torque, the stress on its surface is the most concentrated, while the stress on the core is relatively small. This stress distribution characteristic provides potential possibilities for the structural optimization of the shaft.

[0003] According to the theory of bending and torsion resistance characteristics in material mechanics, by reasonably designing the cross-sectional shape of the shaft, the inside of the shaft can be appropriately hollowed out on the premise of ensuring that the strength and stiffness of the shaft meet the usage requirements. Research shows that only by moderately increasing the outer diameter of the shaft, the hollow shaft can be comparable to the solid shaft in terms of torque transmission capacity while significantly reducing the weight. However, in the actual design and manufacturing of shaft parts, since the ends of the shaft usually need to be processed with splines, gears and other structures to realize the assembly with other components, there are large differences in the dimensions between these parts and the shaft body, resulting in the inability to directly use steel pipes for the overall processing of the shaft. Therefore, the traditional manufacturing of shaft parts still mainly uses solid bars for processing.

[0004] There are many disadvantages in using solid bars to process shaft parts. On the one hand, the weight of the solid shaft is relatively heavy, which not only causes waste of materials but also increases the energy consumption during the operation of the machine. On the other hand, the large self-weight of the shaft will cause an increase in the deflection of the shaft body, and then generate a large radial runout level when the shaft rotates, leading to mechanical vibration and large noise, seriously affecting the running stability and transmission accuracy of the machine. In addition, excessive deflection may also cause problems in the fit between the shaft and other components, reducing the service life and reliability of the machine. The hollow shaft is lighter in weight and can effectively avoid the technical problems brought by the solid shaft. However, correspondingly, due to the lightweight of the material, the torsional strength of the product will be affected to a certain extent. For example, Chinese Patent Application CN116517869A mainly discloses a hollow shaft for a pump, but does not disclose the corresponding mechanical property values of the shaft. Therefore, it is of great practical significance to develop a manufacturing method that can effectively reduce weight, improve material utilization rate, has excellent mechanical properties and does not affect the performance of shaft parts. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a manufacturing method for a lightweight hollow shaft, including:

[0006] S1. Straighten the bar and the pipe.

[0007] S2. Cut the bars and tubes by sawing;

[0008] S3. Use friction welding to weld the bars and tubes into a rough blank shaft;

[0009] S4. Heat-treat the rough blank shaft to obtain a blank shaft;

[0010] S5. Machine the blank shaft according to the drawing to obtain a lightweight hollow shaft.

[0011] As an implementable case, in the straightening process, the straightness of the bars and tubes is not greater than 1.5 mm / m.

[0012] The straightening process can ensure that the straightness of the bars and tubes meets the requirement of not greater than 1.5 mm / m, thus providing a good foundation for subsequent processing operations. Through straightening, processing errors caused by the bending of raw materials can be avoided, ensuring that the final product meets the dimensional requirements of the design drawing, and improving the processing accuracy and assembly accuracy. In addition, the straightened bars and tubes can ensure good contact during friction welding, avoiding problems such as false welding and poor welding, and ensuring the welding quality. At the same time, the straightened raw materials can withstand a more uniform load distribution during subsequent machining and use, avoiding stress concentration, thereby improving the mechanical properties of the hollow shaft and extending its service life. Since the bars and tubes may be bent due to external forces during production, transportation or storage, the straightening step can eliminate the bending defects of the raw materials and meet the high-precision machining requirements of the hollow shaft.

[0013] As an implementable case, the bars and tubes are made of the same material.

[0014] Furthermore, the materials of the bars and tubes include one of 42CrMo, 40Cr, Q235, Q345, Q390 or Q420.

[0015] As an implementable case, the end face cutting slope of the cutting by sawing is not greater than 1.5 mm.

[0016] Cut the bars and tubes by sawing according to the designed length on the drawing, and control the end face cutting slope to not greater than 1.5 mm, in order to accurately match the product design dimensions and ensure the welding quality at the same time. If the end face cutting slope is too large, it will lead to insufficient contact and uneven pressure during welding, resulting in false welding, and thus affecting the overall strength and reliability of the hollow shaft. Controlling the cutting slope within a reasonable range can ensure that the end faces of the bars and tubes are closely fitted during friction welding, which helps to form a high-quality welded joint, improve the mechanical properties such as the torsional strength and torsional stiffness of the hollow shaft, and meet the actual working conditions requirements.

[0017] As an implementable case, the axial pressure of the friction welding is 15,000 - 30,000 kN, the rotational speed is 500 - 1200 rpm, the friction time is 3 - 8 s, the upsetting pressure is 10,000 - 20,000 kN, and the upsetting speed is 300 - 600 mm / s.

[0018] As an implementable case, the height of the welding flash of the friction welding is 1.5 - 10 mm.

[0019] Butt - welding the bar / tube into a blank shaft by friction welding and controlling the height of the welding flash within 1.5 - 10 mm is crucial for ensuring the quality of the hollow shaft. Controlling the height of the welding flash within a reasonable range can ensure that the welded parts fit closely, form a high - quality welded joint, improve the torsional strength and torsional stiffness of the hollow shaft, and ensure its mechanical properties. Excessive or too small flash height will affect the welding quality, material utilization rate, and balance of the hollow shaft; too small flash height usually means insufficient energy provided during the welding process, resulting in insufficient plasticization of the material at the end of the welded part, which will cause poor metallurgical bonding between the welded parts, there will be a phenomenon of false welding, seriously affecting the bearing capacity and reliability of the hollow shaft. Excessive flash may cause large deformation and stress concentration areas at the end of the welded part, which are likely to become crack sources during subsequent use, reducing the fatigue life of the hollow shaft. Reasonably controlling the flash height can not only avoid false welding or lack of fusion, ensure the connection strength, but also reduce material waste, ensure the weight balance and dimensional accuracy of the hollow shaft, and meet the design requirements.

[0020] As an implementable case, the heat treatment includes overall quenching and tempering heat treatment or weld normalizing heat treatment; for quenched and tempered steels, such as 42CrMo or 40Cr, overall quenching and tempering heat treatment is adopted; for non - quenched and tempered steels, such as Q235, Q345, Q390 or Q420, weld normalizing heat treatment is adopted.

[0021] As an implementable case, the overall quenching and tempering heat treatment includes quenching and high - temperature tempering.

[0022] Furthermore, the quenching process includes heating, holding, and cooling; the heating temperature is 800 - 900 °C, the holding time is 1 - 2 min, and the cooling is water quenching and oil cooling.

[0023] Furthermore, the high - temperature tempering process includes tempering heating, holding, and cooling; the tempering heating temperature is 500 - 700 °C, the holding time is 1 - 2 h, and the cooling is air cooling.

[0024] Furthermore, in the weld normalizing heat treatment, the weld normalizing heating zone should cover a distance of more than 300 mm outward from the weld.

[0025] Beneficial effects

[0026] (1) By adopting a hollow shaft design, compared with the traditional solid shaft, this application can significantly reduce the weight by about 40% while ensuring the same performance. The lightweight design not only reduces the material usage and production cost, but also significantly reduces the overall weight of the mechanical system, which helps to improve the operating efficiency of the machine and reduce energy consumption.

[0027] (2) In this application, the shaft body uses tubing and the shaft head uses bar stock. After being friction welded into a rough blank shaft and then subjected to overall heat treatment, the overall performance of the hollow shaft is ensured. Since friction welding can achieve good metallurgical bonding of materials, the overall heat treatment further optimizes the microstructure of the shaft, making it have no obvious weak areas. Compared with the traditional welding process, the hollow shaft after friction welding combined with overall heat treatment has higher strength and toughness and can better withstand complex loads and stresses.

[0028] (3) Through precise blanking, straightening and welding processes, this application makes the most of raw materials and reduces material waste. During the blanking process, the lengths of the bar stock and tubing are precisely controlled to maximize the material utilization rate; the straightening process ensures the straightness of the raw materials and avoids processing errors and rejects caused by material bending; the welding process reduces excessive material consumption by controlling the height of the welding flash within a reasonable range, significantly improving the material utilization rate and reducing raw material waste during the production process.

[0029] (4) The manufacturing method provided by this application does not require complex processing equipment and processes, and has a high material utilization rate, thus reducing the production cost and improving the production efficiency. The traditional manufacturing method of solid shafts usually requires a large amount of cutting processing, resulting in serious material waste, long processing cycles, low production efficiency, and high requirements for processing equipment. The manufacturing method of the present invention mainly includes processes such as blanking, straightening, welding and heat treatment, with simple processes, easy to operate, and low dependence on equipment.

[0030] (5) The manufacturing method provided by this application reduces the material usage, energy consumption and waste emissions, meeting the environmental protection requirements. Detailed implementation mode

[0031] Example 1

[0032] This example provides a manufacturing method for a lightweight hollow shaft, specifically as follows:

[0033] S1. Straighten a 40Cr bar stock with a diameter of 85 mm and a 40Cr tubing with dimensions of 85 (length) × 16 (width) mm to ensure a straightness of 1 mm / m;

[0034] S2. Cut the bar and pipe according to the designed length on the drawing. The cutting length is 2.1 m, and the end face cutting slope is 0.8 mm.

[0035] S3. Use friction welding to weld the bar and pipe into a rough blank shaft. Among them, the axial pressure of friction welding is 20000 kN, the rotation speed is 800 rpm, the friction time is 6 s, the upsetting pressure is 12000 kN, the upsetting speed is 360 mm / s, and the welding flash height is 4 mm.

[0036] S4. Perform overall quenching and tempering heat treatment on the rough blank shaft to obtain the blank shaft.

[0037] Among them, the overall quenching and tempering heat treatment is quenching and high-temperature tempering. The quenching process is heating, holding and cooling. The heating temperature is 900 °C, the holding time is 2 min, and the cooling is water quenching and oil cooling.

[0038] The high-temperature tempering process is tempering heating, holding and cooling. The tempering heating temperature is 600 °C, the holding time is 1 h, and the cooling is air cooling.

[0039] S5. Machine the blank shaft according to the drawing to process it into a splined solid shaft with a maximum outer diameter of 82 mm and a weight of 55 kg, that is, the lightweight hollow shaft is obtained.

[0040] The lightweight hollow shaft prepared in this example has passed the 18000 N·m torque test, and the shaft body is not damaged. If it is designed as a solid shaft of the same volume, the product quality is 90 kg.

[0041] Example 2

[0042] This example provides a manufacturing method for a lightweight hollow shaft, specifically:

[0043] S1. Straighten the bar of 42CrMo with a diameter of 60 mm and the pipe of 42CrMo with a size of 60 (length) × 12 (width) mm to ensure the straightness is 1 mm / m.

[0044] S2. Cut the bar and pipe according to the designed length on the drawing. The cutting length is 1.5 m, and the end face cutting slope is 1 mm.

[0045] S3. Use friction welding to weld the bar and pipe into a rough blank shaft. Among them, the axial pressure of friction welding is 20000 kN, the rotation speed is 800 rpm, the friction time is 6 s, the upsetting pressure is 12000 kN, the upsetting speed is 360 mm / s, and the welding flash height is 6 mm.

[0046] S4. Perform overall quenching and tempering heat treatment on the rough blank shaft to obtain the blank shaft.

[0047] Among them, the overall quenching and tempering heat treatment is quenching and high-temperature tempering; the quenching process is heating, holding and cooling, the heating temperature is 860 °C, the holding time is 2 min, and the cooling is water quenching and oil cooling;

[0048] The high-temperature tempering process is heating, holding and cooling, the tempering heating temperature is 630 °C, the holding time is 1 h, and the cooling is air cooling.

[0049] S5. Machine the blank shaft according to the drawing to a solid shaft with a maximum outer diameter of 54 mm and a weight of 15 kg, thus obtaining the lightweight hollow shaft.

[0050] The lightweight hollow shaft prepared in this example has passed the 8000 N·m torque test, and the shaft body is not damaged. If it is designed as a solid shaft of the same volume, the product quality is 39 kg.

[0051] Comparative Example 1

[0052] The specific implementation of this example is the same as that of Example 1, the difference is that the height of the welding flash of friction welding is 1 mm; due to the too low height of the welding flash, the phenomenon of virtual welding occurs, and the virtual welding fails to form a good metallurgical bond between the welded parts, and the connection strength at the weld is greatly reduced. In actual use, the hollow shaft cannot bear the design load, and when subjected to a large torque or bending moment, the weld is prone to cracking or even breaking, resulting in the failure of the entire structure and causing safety accidents.

Claims

1. A manufacturing method of a lightweight hollow shaft, characterized in that, Including: S1. Straighten the bars and tubes; S2. Cut the bars and tubes by sawing; S3. Weld the bars and tubes into a rough blank shaft by friction welding; S4. Heat-treat the rough blank shaft to obtain a blank shaft; S5. Machine the blank shaft according to the drawing to obtain a lightweight hollow shaft.

2. The manufacturing method of the lightweight hollow shaft according to claim 1, characterized in that, In the straightening process, the straightness of the bars and tubes is not greater than 1.5 mm / m.

3. The manufacturing method of the lightweight hollow shaft according to claim 1, characterized in that, The bars and tubes are made of the same material.

4. The manufacturing method of the lightweight hollow shaft according to claim 3, characterized in that, The material of the bars and tubes includes one of 42CrMo, 40Cr, Q235, Q345, Q390 or Q420.

5. The manufacturing method of the lightweight hollow shaft according to claim 1, characterized in that, The end cutting slope of the sawing is not greater than 1.5 mm.

6. The manufacturing method of the lightweight hollow shaft according to claim 1, characterized in that, The axial pressure of the friction welding is 15000 - 30000 kN, the rotational speed is 500 - 1200 rpm, the friction time is 3 - 8 s, the upsetting pressure is 10000 - 20000 kN, and the upsetting speed is 300 - 600 mm / s.

7. The manufacturing method of the lightweight hollow shaft according to claim 1, characterized in that, The height of the welding flash of the friction welding is 1.5 - 10 mm.

8. The manufacturing method of the lightweight hollow shaft according to any one of claims 1-7, characterized in that, The heat treatment includes overall quenching and tempering heat treatment or weld normalizing heat treatment; for quenched and tempered steel, overall quenching and tempering heat treatment is adopted; for non-quenched and tempered steel, weld normalizing heat treatment is adopted.

9. The manufacturing method of the lightweight hollow shaft according to claim 8, characterized in that, The overall quenching and tempering heat treatment includes quenching and high-temperature tempering.

10. The manufacturing method of the lightweight hollow shaft according to claim 9, characterized in that, The quenching process includes heating, holding and cooling. The heating temperature is 800 - 900 °C, the holding time is 1 - 2 min, and the cooling is water quenching and oil cooling; The high-temperature tempering process includes heating, holding and cooling. The tempering heating temperature is 500 - 700 °C, the holding time is 1 - 2 h, and the cooling is air cooling.