High-wear-resistance bearing bush and preparation method thereof

Abstract

The invention discloses a high-wear-resistance bearing bush and a preparation method thereof, and belongs to the technical field of new energy automobile driving motor bearing bush materials. The bearing bush comprises the following chemical components in percentage by weight: 2.5-3.7% of C, 1.6-2.8% of S i, 0.5-1.0% of Mn, less than or equal to 0.2% of P, less than or equal to 0.15% of S, less than or equal to 1.0% of Cr, less than or equal to 2.0% of N i and the balance of Fe. In a matrix structure, ferrite precipitation amount is less than or equal to 1%, carbide is less than 1%, and phosphorus eutectic is less than or equal to 1%. Through centrifugal metal mold casting, cutting into small blank sections, high-temperature annealing treatment and processing into the size required by a product, the lining is used for replacing a steel lining which is subjected to thermal refining of 45 # steel and used in the current mainstream market, and meanwhile, the lining has high abrasion resistance of the annealed 45 # steel and excellent cutting machining performance of a cast iron material, and the service life of the lining is prolonged. And the cutting tool consumption of the bushing after die casting (casting) can be greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of bearing bushing materials for drive motors of new energy vehicles, and particularly relates to a highly wear-resistant bearing bushing and a preparation method thereof. Background Art

[0002] Bearings are important supporting components in machinery. For many machines such as metal cutting machine tools, steam turbines, electric motors, generators, internal combustion engines, etc., their main bearings directly restrict the movement, function, role, and efficiency of the machinery, and directly determine the quality and lifespan of the machine. A bearing bushing is a part in a bearing and is a commonly used mechanical moving component. With the booming development of the new energy vehicle industry, the requirements for the rotational speed and acceleration performance of drive motors are getting higher and higher, resulting in an increasingly harsh working environment for the bearings. Since the bearing and the bearing housing are in clearance contact, there will be relative friction between the outer ring of the bearing and the bearing housing. Therefore, many oil-cooled water motors use bushings die-cast (poured) on the housing to improve the wear resistance of the bearing housing.

[0003] Traditional bearing bushings are mainly prepared from powder metallurgy iron-based materials. In the field of bearing materials for drive motors of new energy vehicles, the currently mainstream market selects 45# steel material. After thermoplastic stamping it into a profile, it is die-cast (poured) into molten aluminum after being processed into semi-finished products. After die-casting (pouring) is completed, final size precision turning is carried out, and the turning allowance is basically about 1 mm on each side. However, it has a large wear amount during the processing and poor turning performance. Therefore, there is an urgent need for a highly wear-resistant bearing bushing and a preparation method thereof to solve the above problems. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a highly wear-resistant bearing bushing to solve the problems in the prior art that the turning performance of bearing bushing materials is poor and the processing wear amount is large;

[0005] Another purpose of the present invention is to provide a preparation method of a highly wear-resistant bearing bushing.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] In the first aspect, the present invention provides a highly wear-resistant bearing bushing, which includes the following chemical components by weight percentage: C: 2.5 - 3.7%, Si: 1.6 - 2.8%, Mn: 0.5 - 1.0%, P ≤ 0.2%, S ≤ 0.15%, Cr ≤ 1.0%, Ni ≤ 2.0%, and the rest is Fe;

[0008] The precipitation amount of ferrite in the matrix structure of the bearing bushing is ≤ 1%, the carbide is < 1%, and the phosphide eutectic is ≤ 1%.

[0009] Second aspect, the present invention provides a preparation method of a highly wear-resistant bearing bushing, comprising the following steps:

[0010] Step 1: Weigh each raw material according to the proportion, and use the centrifugal casting method to pour into a tubular blank and then cut it out of the mold;

[0011] Step 2: Place the blank in a heat treatment furnace and keep it warm and calcined to obtain a semi-finished alloy cast iron bearing bushing;

[0012] Step 3: Machine the semi-finished alloy cast iron bearing bushing on a CNC lathe to obtain a highly wear-resistant bearing bushing.

[0013] As a further solution of the present invention, in the step 1, the centrifugal casting method is metal mold centrifugal casting. During the centrifugal casting process, it can be calculated and determined by the Konstantinov formula according to the casting size, and those skilled in the art can design according to the actual situation.

[0014] As a further solution of the present invention, the rotation speed of the metal mold centrifugal casting is 1200 - 1400 r / min.

[0015] As a further solution of the present invention, the pouring temperature of the metal mold centrifugal casting is 1500 - 1550 °C.

[0016] As a further solution of the present invention, the pouring speed of the metal mold centrifugal casting is 4 - 5 kg / s.

[0017] As a further solution of the present invention, in the step 1, the temperature of the blank out of the mold > 780 °C to ensure that the blank structure is in the pearlite state.

[0018] As a further solution of the present invention, in the step 2, the heat preservation and calcination temperature is 480 - 550 °C, and the heat preservation and calcination time is 1.5 - 2.5 h. Through annealing treatment, the casting stress inside the blank can be further eliminated, and at the same time, its hardness and wear resistance can be enhanced.

[0019] As a further solution of the present invention, in the step 3, the tool model for CNC lathe machining is NTKSNGN120412.

[0020] As a further solution of the present invention, in the step 3, the CNC lathe performs a turning process, and the cutting parameters are: spindle speed S = 1800 r / min, single-pass machining feed F = 0.2 mm, and single-pass machining amount 0.5 mm.

[0021] Compared with the prior art, the beneficial effects of the present invention:

[0022] 1. The present invention provides a highly wear-resistant bearing bushing. Through material replacement and then processing to the required product dimensions, it is used to replace the steel bushings treated by quenching and tempering of 45# steel currently used in the mainstream market. It simultaneously has high wear resistance after annealing of 45# steel, with a material hardness of 29 - 30 HRC, and excellent machining performance of cast iron materials, greatly reducing the cutting tool consumption after die casting (casting). The machining tool consumption cost is reduced to more than 60%, and it can replace the application of 45# steel in the bearing bushings of new energy vehicle drive motors, providing a reliable alternative solution for factories to reduce costs and increase efficiency.

[0023] 2. In the present invention, carbon is the basis for forming graphite, and silicon is a strong element promoting graphitization. Through the metal centrifugal casting method, in the graphite structure of the material, the total proportion of A-type and E-type graphite is 50%. A-type graphite presents in flakes, is evenly distributed and has no directionality, improving the toughness of the casting; E-type graphite is in a star shape or directional arrangement, which may improve the casting performance or may have an adverse effect; through reasonable process control and material design, a total proportion of 50% of A-type and E-type graphite can effectively improve the performance of the casting, thereby effectively eliminating the adverse effects of E-type graphite. A high carbon content (2.5 - 3.7%) in cast iron helps to form a graphitized structure, thereby improving the wear resistance and shock absorption of the material; the graphite morphology and distribution in cast iron have an important impact on wear resistance and antifriction. By controlling the carbon and silicon content, the graphite morphology can be optimized to make its distribution more uniform, thereby improving the wear resistance and antifriction of cast iron. Due to its graphite structure and lower hardness, the tool wears slowly during machining of cast iron and the tool life is longer; while due to its high hardness and brittleness, the tool wears quickly during machining of cast steel and the tool life is shorter. The present invention can further reduce tool wear and improve production efficiency by optimizing machining parameters, selecting suitable materials, and improving the process flow.

[0024] 3. The present invention utilizes that manganese elements help to improve the strength and hardness of cast iron, and at the same time form MnS inclusion particles with part of sulfur, reducing the influence of sulfur on graphitization. The addition of chromium and nickel can improve the corrosion resistance of cast iron. Chromium can form a stable oxide film to protect cast iron from corrosion. Nickel can increase the electrode potential of the material and reduce the dissolution current density in the passivated state, thus passivating in advance. Controlling the carbide content can reduce the hard and brittle phases in cast iron, reduce the brittleness of the material, and improve its toughness and impact resistance. The control of phosphide eutectic can reduce the non-metallic inclusions in the casting, further reduce brittleness, and improve the comprehensive performance of the material.

[0025] 4. In the preparation process of the high wear-resistant bearing bushing of the present invention, the metal mold centrifugal casting process is adopted, which can reduce the segregation of phosphorus and the formation of eutectic. Through the heat preservation and calcination process, the blank is heat-treated in a heat treatment furnace, which can further eliminate the casting stress inside the blank and enhance its hardness and wear resistance at the same time. After comparison, the hardness of the blank after heat treatment can be increased to more than 29 HRC, reaching the same level as the bushing made of the existing 45# steel material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings.

[0027] Figure 1 is the graphite metallographic picture of the bearing bushing semi-finished product in Embodiment 1 of the present invention;

[0028] Figure 2 is the matrix structure metallographic picture of the bearing bushing semi-finished product in Embodiment 1 of the present invention;

[0029] Figure 3 is the physical picture of the bearing bushing semi-finished product prepared in Embodiment 1 before rough turning in Comparative Example 2 of the present invention;

[0030] Figure 4 is the physical picture of the bearing bushing semi-finished product prepared in Embodiment 1 after rough turning in Comparative Example 2 of the present invention;

[0031] Figure 5 is the physical picture of the 45# steel material bushing semi-finished product before rough turning in Comparative Example 2 of the present invention;

[0032] Figure 6 is the physical picture of the 45# steel material bushing semi-finished product after rough turning in Comparative Example 2 of the present invention;

[0033] Figure 7 is the picture of the cutting edge wear of the alloy cast iron bearing bushing semi-finished product after rough turning during turning in Group ①;

[0034] Figure 8 is the picture of the cutting edge wear of the 45# steel material bushing semi-finished product after rough turning during turning in Group ①;

[0035] Figure 9 is the picture of the cutting edge wear of the alloy cast iron bearing bushing semi-finished product after rough turning during turning in Group ②;

[0036] Figure 10 is the picture of the cutting edge wear of the 45# steel material bushing semi-finished product after rough turning during turning in Group ②;

[0037] Figure 11 is the picture of the cutting edge wear of the alloy cast iron bearing bushing semi-finished product after rough turning during turning in Group ③;

[0038] Figure 12 It is a picture of the cutting edge wear of the semi-finished bushing made of 45# steel material after rough turning in Group ③. Specific implementation manners

[0039] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiment 1

[0041] A method for preparing a semi-finished alloy cast iron bearing bushing, comprising the following steps:

[0042] Step 1: Weigh each raw material according to the following proportions: C: 3.0%, Si: 2.1%, Mn: 0.8%, P: 0.15%, S: 0.1%, Cr: 0.8%, Ni: 1.5%, and the rest is Fe;

[0043] Melt each raw material into molten iron, and adopt metal mold centrifugal casting. The pouring temperature for centrifugal casting is 1520°C, the rotation speed is 1300 r / min, the pouring speed is 4.5 kg / s. Pour the molten iron into a tubular blank, and the temperature when it comes out of the mold is 800°C. Cut the tubular blank into small pieces by a cutting machine;

[0044] Step 2: Concentrate and pack the blanks and place them in a heat treatment furnace. Keep them calcined at 500°C for 2 h to obtain a semi-finished alloy cast iron bearing bushing.

[0045] Embodiment 2

[0046] A method for preparing a semi-finished alloy cast iron bearing bushing, which is different from Embodiment 1 in that the raw material components are weighed according to the following proportions: C: 2.6%, Si: 2.5%, Mn: 1.0%, P: 0.1%, S: 0.1%, Cr: 1.0%, Ni: 1.8%, and the rest is Fe;

[0047] Melt each raw material into molten iron, and adopt metal mold centrifugal casting. The pouring temperature for centrifugal casting is 1520°C, the rotation speed is 1300 r / min, the pouring speed is 4.5 kg / s. Pour the molten iron into a tubular blank, and the temperature when it comes out of the mold is 800°C. Cut the tubular blank into small pieces by a cutting machine;

[0048] Step 2: Concentrate and pack the blanks and place them in a heat treatment furnace. Keep them calcined at 500°C for 2 h to obtain a semi-finished alloy cast iron bearing bushing.

[0049] Embodiment 3

[0050] The preparation method of the semi-finished alloy cast iron bearing bushing is different from that of Example 1 in that the raw material components are weighed according to the following proportions: C: 3.6%, Si: 1.7%, Mn: 0.5%, P: 0.18%, S: 0.05%, Cr: 0.5%, Ni: 1.4%, and the rest is Fe;

[0051] Melt each raw material into molten iron, and use metal mold centrifugal casting. The pouring temperature for centrifugal casting is 1520 °C, the rotational speed is 1300 r / min, the pouring speed is 4.5 kg / s. Pour the molten iron into a tubular blank, and the temperature when it exits the mold is 800 °C. Cut the blank into small segments with a cutting machine;

[0052] Step 2: Concentrate and pack the blanks and place them in a heat treatment furnace. Keep them calcined at 500 °C for 2 h to obtain the semi-finished alloy cast iron bearing bushing.

[0053] Comparative Example 1

[0054] The preparation method of the semi-finished alloy cast iron bearing bushing includes the following steps:

[0055] Step 1: Weigh each raw material according to the following proportions: C: 3.0%, Si: 2.1%, Mn: 0.8%, P: 0.15%, S: 0.1%, Cr: 0.8%, Ni: 1.5%, and the rest is Fe;

[0056] Melt each raw material into molten iron, and use metal mold centrifugal casting. The pouring temperature for centrifugal casting is 1520 °C, the rotational speed is 1300 r / min, the pouring speed is 4.5 kg / s. Pour the molten iron into a tubular blank, and the temperature when it exits the mold is 800 °C. Cut the blank into small segments with a cutting machine to obtain the semi-finished alloy cast iron bearing bushing.

[0057] Perform heat treatment crystal phase and hardness tests on the semi-finished alloy cast iron bearing bushings prepared in Examples 1 to 3 and Comparative Example 1. The test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] Among them, the graphite metallographic picture of the semi-finished alloy cast iron bearing bushing in Example 1 under 100-fold magnification is as Figure 1 shown, and the matrix structure metallographic picture is as Figure 2As shown, it can be seen from Table 1 that the semi-finished alloy cast iron bearing bushing prepared according to the raw material ratio provided by the present invention meets the bearing bushing material specifications, and the ferrite precipitation amount ≤ 1%, the carbide < 1%, and the eutectic phosphorus ≤ 1%; in addition, by performing heat preservation calcination annealing treatment on the blank, the casting stress inside the blank can be eliminated, and at the same time, its hardness and wear resistance can be enhanced.

[0061] Example 4

[0062] Wear resistance experiments were respectively carried out on the semi-finished alloy cast iron bearing bushing and the semi-finished bushing of 45# steel material prepared in Example 1. The semi-finished bearing bushings were respectively nested on the right bearings of the P1 motor shaft and the P3 motor shaft, simulating the motor driving process, detecting the change in the inner diameter size of the semi-finished product, and monitoring the wear amount. The test results of the semi-finished alloy cast iron bearing bushing prepared in Example 1 are shown in Table 2;

[0063] Table 2

[0064]

[0065] The test results of the semi-finished bushing of 45# steel material are shown in Table 3.

[0066] Table 3

[0067]

[0068]

[0069] It can be seen from Table 2 that the wear amounts of the semi-finished alloy cast iron bearing bushings in the right bearings of the P1 motor shaft and the P3 motor shaft meet the dimensional requirements and can completely replace the bushings of 45# steel material.

[0070] Example 5

[0071] The semi-finished alloy cast iron bearing bushing prepared in Example 1 was processed on a CNC lathe. The model of the CNC lathe is CNC lathe (processing B107). The specific processing process is as follows: (1) Rough turning, turning the outer circle of the semi-finished bushing to make it round. The physical drawing of the semi-finished alloy cast iron bearing bushing before turning is as Figure 3 shown, and the physical drawing of the semi-finished bushing after turning is as Figure 4 shown, and the outer circle needle prick is turned off; (2) Make marks with a paint pen and perform turning processing; cut 5 semi-finished bushings for each cutting edge, and each bushing is cut 8 times; set 3 groups of cutting edges in parallel for comparison, with 5 semi-finished bushings in each group. The tool model is NTK SNGN120412, and the turning parameters are: spindle speed S = 1800 r / min, single-pass machining feed F = 0.2 mm, single-pass machining amount 0.5 mm.

[0072] Comparative Example 2

[0073] The semi-finished bushing made of 45# steel material is processed on a CNC lathe. The model of the CNC lathe is CNC lathe (processing B107). The specific processing process is as follows: (1) Rough turning, turning off the anti-rotation groove on the outer circle of the semi-finished bushing. The physical diagram of the semi-finished bushing made of 45# steel material before rough turning is as shown in Figure 5 shown, and the physical diagram of the semi-finished bushing made of 45# steel material before rough turning is as shown in Figure 6 shown; other processing steps and parameters are the same as those in Example 5.

[0074] The relevant parameters of the bushing in the turning process in Example 5 and Comparative Example 2 are shown in Table 4. Since the semi-finished bushing made of 45# steel material has a relatively deep anti-rotation groove, it needs to be turned into a complete circle before the turning performance experiment can be carried out. Since the outer diameters are different after being turned into a complete circle, the tool wear amount is converted to the tool wear amount per unit area for comparison.

[0075] Table 4

[0076]

[0077] Among them, the picture of the cutting edge wear of the semi-finished alloy cast iron bearing bushing after rough turning in Group ① is shown in Figure 7 , and the picture of the cutting edge wear of the semi-finished bushing made of 45# steel material after rough turning is shown in Figure 8 ; the picture of the cutting edge wear of the semi-finished alloy cast iron bearing bushing after rough turning in Group ② is shown in Figure 9 , and the picture of the cutting edge wear of the semi-finished bushing made of 45# steel material after rough turning is shown in Figure 10 ; the picture of the cutting edge wear of the semi-finished alloy cast iron bearing bushing after rough turning in Group ③ is shown in Figure 11 , and the picture of the cutting edge wear of the semi-finished bushing made of 45# steel material after rough turning is shown in Figure 12 .

[0078] It can be seen from Table 4 and Figures 7 to 12 that under the working conditions of using the same CNC machining machine tool, tool and machining parameters, the further machining wear amount of the semi-finished alloy cast iron bearing bushing prepared by the present invention is 64% lower than that of the semi-finished bushing made of 45# steel material. This shows that the raw material ratio and preparation process in the present invention can greatly reduce the tool wear. Under the condition of having the same hardness and wear resistance as the existing 45# steel material, replacing the bushing material with the bushing material prepared by the present invention can reduce the processing tool consumption cost to more than 60%, providing a reliable alternative solution for the factory to reduce costs and increase efficiency.

[0079] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0080] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high wear-resistant bearing bushing, characterized in that: In terms of weight percentage, it includes the following chemical components: C: 2.5-3.7%, Si: 1.6-2.8%, Mn: 0.5-1.0%, P≤0.2%, S≤0.15%, Cr≤1.0%, Ni≤2.0%, and the rest is Fe; The ferrite precipitation amount in the bearing bushing matrix structure is ≤1%, the carbide is <1%, and the phosphorus eutectic is ≤1%.

2. A method for preparing a high wear-resistant bearing bushing according to claim 1, characterized in that: The following steps are involved: Step 1, weighing each raw material according to the proportion, using the centrifugal casting method, casting into a tubular blank and then cutting it out of the mold; Step 2, placing the blank in a heat treatment furnace, and calcining it at a heat preservation temperature to obtain a semi-finished alloy cast iron bearing bushing; Step 3: Processing the semi-finished alloy cast iron bearing bushing on a CNC lathe to obtain a bearing bushing.

3. The method for preparing a high wear-resistant bearing bushing according to claim 2, characterized in that: In the step 1, the centrifugal casting method is metal mold centrifugal casting.

4. The method for preparing a highly wear-resistant bearing bushing according to claim 3, characterized in that: The rotation speed of the metal mold centrifugal casting is 1200-1400r / min.

5. The method for preparing a highly wear-resistant bearing bushing according to claim 3, characterized in that: The pouring temperature of the metal mold centrifugal casting is 1500-1550°C.

6. The method for preparing a highly wear-resistant bearing bushing according to claim 3, characterized in that: The pouring speed of the metal mold centrifugal casting is 4-5 kg / s.

7. The method for preparing a highly wear-resistant bearing bushing according to claim 2, characterized in that: In the step 1, the temperature of the blank leaving the mold is greater than 780°C.

8. The method for preparing a highly wear-resistant bearing bushing according to claim 2, characterized in that: In the step 2, the calcination temperature is 480-550° C., and the calcination time is 1.5-2.5 hours.

9. The method for preparing a highly wear-resistant bearing bushing according to claim 2, characterized in that: In step 3, the tool model of the CNC lathe is NTK SNGN120412.

10. The method for preparing a high wear-resistant bearing bushing according to claim 2, characterized in that: In step 3, the cutting parameters of the CNC lathe are: spindle speed S=1800r / min, single processing feed F=0.2mm, and single processing amount 0.5mm.

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