Cast iron shaft sleeve and its processing technology

Abstract

The application relates to the field of transmission accessories, in particular to a cast iron shaft sleeve and a processing technology thereof, which comprises the following steps: S1, adding graphite into iron powder to smelt an iron alloy; S2, centrifugal casting the shaft sleeve; S3, pressure casting the shaft sleeve; S4, sintering; S5, machining; and S6, vacuum oil immersion of the shaft sleeve. Through the above technical scheme, the shaft sleeve contains oil in the porous structure on the surface, and the oil content of the shaft sleeve is not less than 15%. The shaft sleeve has reduced material cost and labor cost, and is more suitable for mass production; the shaft sleeve has good wear resistance and anti-bite property; and the shaft sleeve has a low expansion coefficient, and can keep long-term high-precision movement.

Description

TECHNICAL FIELD

[0001] The application relates to the field of transmission accessories, in particular to a cast iron shaft sleeve and a processing technology thereof. BACKGROUND

[0002] The shaft sleeve is a cylindrical mechanical part sleeved on a rotating shaft and used for rotating relative to the rotating shaft. The shaft sleeve on an existing injection molding machine guide rod is generally made of a copper alloy shaft sleeve or a zinc alloy shaft sleeve in order to ensure that no obvious friction marks are left on the surface of the shaft sleeve when the mold is used for 1 million times.

[0003] However, the copper alloy shaft sleeve and the zinc alloy shaft sleeve are high in material cost and are not suitable for mass production. SUMMARY

[0004] In order to save cost and be more suitable for mass production under the premise of meeting the service life,

[0005] In one aspect, the application provides a processing technology for a cast iron shaft sleeve, which adopts the following technical scheme:

[0006] The processing technology for the cast iron shaft sleeve comprises the following steps,

[0007] S1, proportioned iron alloy is added to a smelting furnace for smelting, the iron alloy comprising iron powder and graphite, wherein the percentage of carbon in the iron alloy is less than 1% by weight;

[0008] S2, the metal casting mold is heated in the process of raising the furnace temperature, and the shaft sleeve is centrifugally cast after the mold is loaded, and the shaft sleeve is taken out from the mold after cooling and forming;

[0009] S3, the iron alloy powder is pressed by an oil press according to the composition of the above-mentioned iron alloy, so that a porous structure is formed on the surface of the shaft sleeve;

[0010] S4, the shaft sleeve after pressing and forming is sintered;

[0011] S5, the shaft sleeve is machined according to the shape requirement, and the porous structure is exposed on the surface of the shaft sleeve;

[0012] S6, the shaft sleeve is immersed in lubricating oil by vacuum impregnation during the growth period of the shaft sleeve, so that the porous structure on the surface of the shaft sleeve contains oil, and the oil content rate of the shaft sleeve is not less than 15%.

[0013] By adopting the above technical scheme, the specific gravity of the iron alloy is less than that of the copper alloy, and the price of the iron alloy is about 30%-40% cheaper than that of the copper alloy; the specific gravity of the iron alloy is close to that of the zinc-based alloy, but the price of the iron alloy is 15%-25% cheaper than that of the zinc-based alloy, thereby reducing the material cost and being more suitable for mass production.

[0014] By adding graphite in the iron alloy, carbon is added to the cast iron to cause the growth phenomenon. The reason for the growth of the cast iron is that the internal oxidation occurs when the oxidizing gas penetrates into the cast iron along the graphite sheet boundary or crack. The cementite in the casting decomposes to form graphite with small density and large volume at high temperature, and the volume change of the cast iron matrix structure occurs during the heating and cooling process. Under the action of high temperature and load, the casting will eventually deform, warp, crack, and even break due to oxidation and growth. Therefore, in daily life, the growth phenomenon is not conducive to product quality.

[0015] However, in this application, after machining the bushing, the bushing is immersed in oil under negative pressure, so that the porous interior of the bushing formed by the growth phenomenon is immersed in lubricating oil. The OILES characteristic of the cast iron structure is changed during the growth of the casting. Therefore, the entire friction surface of the bushing is immersed in lubricating oil during use, and the wear resistance of any direction, especially small movement, has very good performance. Therefore, the service life of the bushing is improved. Even if the casting is made of iron powder as the main material, it can also meet the requirement of 1 million service life.

[0016] At the same time, the bushing is formed by the method of centrifugal casting and pressure casting. Centrifugal casting can obtain castings without shrinkage, porosity, and slag, and the structure is fine and the mechanical properties are good. When casting a circular hollow part, the core can be omitted. However, the inner hole of the cylindrical part cast by centrifugal casting has a rough free surface and large size error. Pressure casting can make the casting have excellent size accuracy. However, it is only suitable for small quality pressure casting products because the metal flow is realized by pressure casting to achieve plasticity.

[0017] By the method of centrifugal casting and then pressure casting, the first aspect can make the casting have excellent size accuracy, the second aspect can ensure the fineness of the entire casting structure, and the third aspect can also save cost. It is more suitable for mass production.

[0018] Finally, compared with the copper alloy body, the bushing is made of cast iron material, and the linear expansion coefficient is very low, less than 1 / 2, which can effectively reduce the size change of the base caused by friction heat and maintain long-term high-precision movement.

[0019] Optionally, the weight percentage of the iron alloy is as follows: C is less than 1%, S is less than 1%, and Cu is greater than 2% to less than 5%.

[0020] By adopting the above technical scheme, the product density is controlled in the range of greater than or equal to 7.0 g / cm3, and the strength of the bushing is ensured as much as possible. At the same time, the cost is also controlled.

[0021] Optionally, the bushing molded in step S2 is first subjected to density detection; if the density of the bushing is greater than or equal to 7.0 g / cm3, the surface of the bushing is dried, and then subjected to pressing in step S3; if the density of the bushing is less than 7.0 g / cm3, the bushing is remelted and recast.

[0022] By adopting the above technical solution, if the density of the original blank is not enough during pressing, the original blank will be affected. If the final production is completely finished and then quality inspection is performed, subsequent process time and materials will be wasted. The application first performs density detection, thereby ensuring the yield of products as much as possible and reducing waste.

[0023] Optionally, the machining system is used for machining in step S4, and the vacuum oil immersion machine is used for oil immersion in step S6, and a conveying mechanism is arranged between the discharging end of the machining system and the feeding end of the vacuum oil immersion machine, and after the machining system finishes machining the bushing, the bushing falls from the discharging end of the machining system to the conveying mechanism and is conveyed into the vacuum oil immersion machine for oil immersion.

[0024] By adopting the above technical solution, manual participation is further reduced, and labor cost is reduced. After machining is finished, the product can be directly conveyed to the oil immersion station for oil immersion treatment, and manual careful carrying operation is no longer needed.

[0025] Optionally, the conveying mechanism comprises a guide rail and a power source, a guide groove is formed in the guide rail, a projection of the discharging end of the machining system in the vertical direction falls in the guide groove, the discharging end of the guide groove receives the feeding end of the vacuum oil immersion machine, the guide groove is filled with lubricating oil with a density greater than that of the bushing, and the power source is used to provide power for the lubricating oil flowing from the machining system to the vacuum oil immersion machine, and the bushing moves with the lubricating oil.

[0026] By adopting the above technical solution, since the lubricating oil is used for buffering, the bushing after machining directly falls into the lubricating oil and will not be deformed or even broken due to direct impact on a rigid part. Since the density of the lubricating oil is greater than that of the bushing, the bushing will float up and move towards the vacuum oil immersion machine under the movement of the lubricating oil driven by the power source, thereby being smoothly conveyed. No manual operation and complex conveying equipment are needed in the middle. Meanwhile, the bushing is pre-impregnated with oil and cooled during conveying, thereby further improving the efficiency of subsequent processing of the bushing.

[0027] Optionally, the vacuum oil immersion machine comprises an oil immersion tank, an oil storage tank and a vacuum pump, a first connecting pipe and a second connecting pipe are arranged between the oil immersion tank and the oil storage tank for connecting the two, the first connecting pipe is connected to the lower end of the side wall of the oil immersion tank and the lower end of the side wall of the oil storage tank respectively, and a first valve is arranged on the first connecting pipe, the second connecting pipe is connected to the upper end of the oil immersion tank and the upper end of the oil storage tank respectively, the upper end of the oil storage tank is provided with an exhaust hole connected to the outside, the vacuum pump is installed on the second connecting pipe, and the oil immersion tank is provided with an inlet for the outlet end of the guide rail to enter, and a second valve for opening and closing the inlet is arranged on the inlet.

[0028] By adopting the above technical scheme, the shaft sleeve enters the oil immersion tank through the inlet, and then the inlet is closed by the second valve. The oil and air in the oil immersion tank are sucked into the oil storage tank by the vacuum pump, so that negative pressure is achieved in the oil immersion tank, and then the vacuum pump is closed. The first valve is opened, and under the action of pressure, the oil in the oil storage tank enters the oil immersion tank to immerse the shaft sleeve, and the oil immersion work is completed.

[0029] Optionally, the power source is located at the end of the guide rail away from the oil immersion tank, and a return pipe for returning the oil in the oil immersion tank to the inlet end of the guide rail is connected to the lower end of the oil immersion tank, the first return pipe is connected to the liquid inlet end of the power source, and a third valve is arranged on the return pipe.

[0030] By adopting the above technical scheme, before the vacuum pump pumps air and liquid, the third valve can be opened first, so that the lubricating oil entering the oil immersion tank with the shaft sleeve from the inlet is discharged from the return pipe and flows back into the guide groove of the guide rail, and the oil is fully utilized. At the same time, when the power source pumps the oil in the return pipe to the guide rail, it also gives the oil in the guide groove a certain flow power, so that the shaft sleeve moves forward with the oil.

[0031] Optionally, the return pipe comprises a vertical section and an inclined section, one end of the vertical section is connected to the power source and the other end is located below the power source, one end of the inclined section is connected to the lower end of the vertical section, and the other end is inclined upward and connected to the lower side of the side wall of the oil immersion tank, and the third valve is installed at the end of the inclined section close to the oil immersion tank.

[0032] By adopting the above technical scheme, the oil can flow back into the guide groove of the guide rail more smoothly.

[0033] Optionally, the machining system comprises a lathe, the lathe comprises a lathe bed and a three-jaw chuck for clamping the shaft sleeve, the length direction of the lathe bed is perpendicular to the length direction of the guide rail, a through groove is formed in the lathe bed, and the through groove is located directly below the three-jaw chuck and connected to the upper side of one end of the guide rail; when the three-jaw chuck releases the shaft sleeve, the shaft sleeve falls into the guide groove of the guide rail along the through groove.

[0034] By adopting the technical scheme, the manual participation steps are further reduced. After the machining is completed, the shaft sleeve does not need to be manually cancelled and thrown into the guide rail, but only needs to be loosened from the three-jaw chuck, so that the shaft sleeve can be automatically dropped into the guide rail, and the operation is convenient. The length direction of the machine base is perpendicular to the length direction of the guide rail, so that the guide rail does not affect the operation of the lathe by workers.

[0035] In another aspect, the application provides a cast iron shaft sleeve, which adopts the following technical scheme:

[0036] A cast iron shaft sleeve is made by a machining process for cast iron shaft sleeves.

[0037] By adopting the technical scheme, the shaft sleeve has good wear resistance and anti-seizure, low expansion coefficient, and can maintain long-term high-precision movement. At the same time, the shaft sleeve needs to be lubricated less frequently during use.

[0038] In summary, the application includes at least one of the following beneficial technical effects:

[0039] 1. Reducing material cost and labor cost, more suitable for mass production;

[0040] 2. Good wear resistance and anti-seizure;

[0041] 3. Low expansion coefficient, can maintain long-term high-precision movement. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a structural schematic diagram of example 1.

[0043] Figure 2 is a structural schematic diagram of example 1 for realizing an oil groove.

[0044] Figure 3 is a structural schematic diagram of example 2.

[0045] Figure 4 is a structural schematic diagram of a lathe in example 2.

[0046] Figure 5 is a sectional view of example 2.

[0047] Figure 6 is a sectional view of a vacuum oil immersion machine in example 2.

[0048] Explanation of reference numerals: 1, shaft sleeve; 2, shaft sleeve body; 3, oil groove; 4, vacuum oil immersion machine; 5, lathe; 6, conveying mechanism; 7, machine base; 8, three-jaw chuck; 9, turning tool assembly; 10, through groove; 11, oil immersion tank; 12, oil storage tank; 13, vacuum pump; 14, first connecting pipe; 15, second connecting pipe; 16, first valve; 17, exhaust hole; 18, guide rail; 19, power source; 20, return pipe; 21, feed inlet; 22, second valve; 23, drive cylinder; 24, closure plate; 25, guide groove; 26, vertical section; 27, inclined section; 28, material taking door; 29, oil inlet pipe; 30, third valve. DETAILED DESCRIPTION

[0049] The following description will be made in conjunction with the accompanying drawings. Figures 1-6 The present application is further described in detail.

[0050] Example 1

[0051] With reference to Figure 1 and Figure 2 Example 1 of the present application discloses a cast iron shaft sleeve, which comprises a shaft sleeve body 2. An oil groove 3 is formed in the inner wall of the shaft sleeve body 2, and the oil groove 3 can have a shape of "8", an egg shape, a waist groove, a straight groove, a ring groove, etc. The shaft sleeve body 2 is made of cast iron metallurgy. The chemical composition of the shaft sleeve body 2 (in terms of weight percentage) is as follows: C: <1.0%, S: <1.0%, Cu: 2%-5%, Fe: balance, and unavoidable impurities.

[0052] The specific gravity of the cast iron shaft sleeve 1 is less than that of copper alloy, and the price of the cast iron shaft sleeve 1 is about 30%-40% cheaper than that of copper alloy. The specific gravity of the cast iron shaft sleeve 1 is close to that of zinc-based alloy, but the price of the cast iron shaft sleeve 1 is about 15%-25% cheaper than that of zinc-based alloy, thereby reducing the material cost. The cast iron shaft sleeve 1 is more suitable for mass production.

[0053] In order to ensure the service life, the shaft sleeve body 2 is immersed with lubricating oil through negative pressure. Compared with copper alloy shaft sleeve 1 and zinc-based alloy shaft sleeve 1, the frequency of oil supply can be greatly reduced because the lubricating oil is contained. The shaft sleeve 1 of the present application has excellent wear resistance and anti-seizure due to the high compatibility and oil film retention of the organizational structure. Since the shaft sleeve body 2 is made of cast iron material, the expansion coefficient is very low compared with the copper alloy shaft sleeve 1, which can effectively reduce the size change of the base caused by friction heat and maintain long-term high-precision movement. Compared with the solid lubricant inlaid type shaft sleeve 1, the shaft sleeve 1 of the present application has very good performance in wear resistance for any direction of friction, especially for small movements.

[0054] Example 2

[0055] Example 2 of the present application discloses a machining device for processing a cast iron shaft sleeve, which is used for processing the shaft sleeve in Example 1. With reference to Figure 3A machining device for machining cast iron bushing includes a machining system, a vacuum oiling machine 4 and a conveying mechanism 6. The machining system includes a lathe 5. The lathe 5 is used for machining the cast iron bushing 1. The vacuum oiling machine 4 is used for oiling the machined bushing 1. The conveying mechanism 6 is used for conveying the bushing 1 from the discharge end of the lathe 5 to the vacuum oiling machine 4.

[0056] Specifically, referring to Figure 4 and Figure 5 , the lathe 5 includes a lathe bed 7, a three-jaw chuck 8 for clamping the bushing 1 and a turning tool assembly 9 for machining. A through slot 10 is formed in the lathe bed 7, which is directly below the three-jaw chuck 8. During machining, the bushing 1 is clamped by the three-jaw chuck 8, and the bushing 1 is machined by the turning tool assembly 9.

[0057] Referring to Figure 5 and Figure 6 , the vacuum oiling machine 4 includes an oiling tank 11, an oil storage tank 12 and a vacuum pump 13. A first connecting pipe 14 and a second connecting pipe 15 are arranged between the oiling tank 11 and the oil storage tank 12 for connecting the two. The first connecting pipe 14 is connected to the lower end of the side wall of the oiling tank 11 and the lower end of the side wall of the oil storage tank 12 respectively, and a first valve 16 is arranged on the first connecting pipe 14. The first valve 16 can be an electronic valve or a butterfly valve. The first valve 16 is used to control the opening and closing of the first connecting pipe 14. The second connecting pipe 15 is connected to the upper end of the oiling tank 11 and the upper end of the oil storage tank 12 respectively, and the vacuum pump 13 is installed on the second connecting pipe 15. An exhaust hole 17 is arranged at the upper end of the oil storage tank 12 for connecting to the outside.

[0058] During machining, the first valve 16 is closed, the bushing 1 is placed in the oiling tank 11, the air in the oiling tank 11 is pumped into the oil storage tank 12 by the vacuum pump 13, and then is discharged to the outside through the exhaust hole 17. At this time, the oiling tank 11 is in a negative pressure state. Then the vacuum pump 13 is closed and the first valve 16 is opened. Under the action of air pressure, the lubricating oil in the oil storage tank 12 enters the oiling tank 11, and the bushing 1 is oiled. The lubricating oil is generally mechanical oil of HJ-20 brand specified in GB443-64.

[0059] Referring to Figure 5 and Figure 6 , the conveying mechanism 6 includes a guide rail 18, a power source 19 and a return pipe 20. The guide rail 18 is used to guide the movement of the bushing 1 from the lathe 5 to the oiling tank 11 under the action of the power source 19.

[0060] The guide rail 18 is connected with the lathe 5 and the vacuum oiling machine 4. The length direction of the guide rail 18 is perpendicular to the length direction of the machine base 7. One end of the guide rail 18 is located below the machine base 7 and is aligned with the through slot 10, and the other end penetrates into the oiling tank 11. The oiling tank 11 is provided with an inlet 21 for the guide rail 18 to enter from the outlet end, and the guide rail 18 abuts against the inner wall of the inlet 21. The inlet 21 is provided with a second valve 22 for opening and closing the inlet 21. The second valve 22 comprises a closing plate 24 and a driving cylinder 23 for driving the closing plate 24 to move up and down, and the driving cylinder 23 is fixedly installed on the oiling tank 11.

[0061] A guide groove 25 is formed in the guide rail 18, the guide groove 25 is formed along the length direction of the guide rail 18, and the bottom surface of the guide groove 25 is inclined downward towards the oiling tank 11. The projection of the through slot 10 in the vertical direction falls within the guide groove 25. The guide groove 25 is filled with lubricating oil with a density greater than that of the shaft sleeve 1. When the second valve 22 opens the inlet 21, the shaft sleeve 1 can enter the oiling tank 11 along with the lubricating oil in the guide groove 25.

[0062] Referring to Figure 5 and Figure 6 , the return pipe 20 comprises a vertical section 26 and an inclined section 27. One end of the vertical section 26 is connected to the power source 19 and the other end is located below the power source 19. One end of the inclined section 27 is connected to the lower end of the vertical section 26, and the other end is inclined upward and connected to the lower side of the side wall of the oiling tank 11. A third valve 30 is installed at the end of the inclined section 27 close to the oiling tank 11, and the third valve 30 is used to control the opening and closing of the inclined section 27.

[0063] In order to prevent the shaft sleeve 1 entering the oiling tank 11 along with the lubricating oil from directly falling onto the bottom surface of the oiling tank 11, the end of the inclined section 27 connected to the oiling tank 11 is slightly higher than the bottom surface of the oiling tank 11. This allows a certain amount of oil to be stably stored in the oiling tank 11.

[0064] Referring to Figure 5 , the power source 19 is an oil pump. The inlet end of the oil pump is connected to the vertical section 26, and the outlet end of the oil pump is directed towards the vacuum oiling machine 4 along the length direction of the guide rail 18.

[0065] The implementation principle of the machining equipment for machining the cast iron shaft sleeve 1 according to the embodiment 2 is as follows:

[0066] 1. The lathe 5 completes the machining of the shaft sleeve 1 blank, the three-jaw chuck 8 loosens the shaft sleeve 1, and the shaft sleeve 1 falls into the oil in the guide groove 25 along the through slot 10;

[0067] 2. Under the action of the power source 19, the oil moves towards the oiling tank 11, and the shaft sleeve 1 moves towards the oiling tank 11 along with the oil, and enters the oiling tank 11 through the inlet 21; in this process, the shaft sleeve 1 is pre-oiled and cooled by the oil in the guide groove 25;

[0068] 3、Close the inlet 21 by the second valve 22, open the third valve 30, due to the power given by the oil pump, the lubricating oil in the oil tank 11 returns to the guide groove 25 of the guide rail 18 from the return pipe 20, then close the third valve 30;

[0069] 4、Open the vacuum pump 13, pump the oil tank 11, and discharge the oil into the oil tank 12, the oil mixed in the air enters the oil tank 12 for storage and use, the air is discharged from the oil tank 12 through the exhaust hole 17, so that the oil tank 11 reaches a negative pressure close to vacuum, and the air pressure in the oil tank 12 remains at atmospheric pressure;

[0070] 5、Close the vacuum pump 13, open the first valve 16, under the action of air pressure, the lubricating oil in the oil tank 12 enters the oil tank 11, and the shaft sleeve 1 is immersed in oil, and the processing is completed.

[0071] Refer to Figure 3 In order to facilitate taking materials, the oil tank 11 is provided with a material taking door 28 on one side wall, and the processed shaft sleeve 1 can be taken by opening the material taking door 28. In order to ensure that the oil tank 12 has sufficient oil, the oil tank 12 is further connected with an oil inlet pipe 29.

[0072] Embodiment 3

[0073] The embodiment 3 discloses a processing technology for cast iron shaft sleeve, which is used for processing the shaft sleeve in the embodiment 1 by using the equipment in the embodiment 2.

[0074] A processing technology for cast iron shaft sleeve, comprising the following steps

[0075] S1, the matched iron alloy is added to the smelting furnace, the refining purifying agent is added when the furnace temperature is controlled at 1120 DEG C, the refining purifying agent is 1.1% of the furnace charge, the stirring time is 30 minutes, the furnace temperature is increased to 1360 DEG C after 60 minutes of static setting, the metal liquid is separated from the slag, the slag is removed, the covering agent is added, the total amount of the covering agent is 0.3% of the furnace charge, and the slag is removed again after 30 minutes of static setting;

[0076] S2, in the process of increasing the furnace temperature, the metal mold is heated to 100 DEG C-150 DEG C, the shaft sleeve 1 is centrifugally cast after the mold is assembled, the shaft sleeve 1 is taken out from the mold after cooling and forming; the formed shaft sleeve 1 blank is first detected for density; if the density of the shaft sleeve 1 is greater than or equal to 7.0 g / cm3, the surface of the shaft sleeve 1 is dried, and the next step is performed; if the density of the shaft sleeve 1 is less than 7.0 g / cm3, the shaft sleeve 1 is remelted and recast;

[0077] S3, the iron alloy powder is pressed by using a 500T-800T oil press according to the above iron alloy composition;

[0078] S4, the bushing 1 after press forming is sintered by a mesh belt straight-through sintering, the sintering temperature is 1030-1100℃, the bushing 1 surface has a porous structure;

[0079] S5, the bushing 1 is machined by a machining system, after machining, the bushing 1 is transported to the vacuum oil immersion machine 4 by the transport mechanism 6; the machined bushing 1 should have a uniform metal luster, and cracks, inclusions and rust defects are not allowed;

[0080] S6, during the bushing 1 growth phenomenon, the bushing 1 is immersed in oil for 4-8h under negative pressure by the vacuum oil immersion machine 4, so that the oil is contained in the porous structure of the bushing 1 surface.

[0081] During the growth phenomenon of cast iron, a porous structure is formed, at this time, the bushing 1 is immersed in lubricating oil, which can change the OILES characteristics of the cast iron organization during the growth phenomenon of the bushing 1. After the oil immersion is completed, the oil content of the bushing 1 is greater than 15%, the oil density is 5.7-6.5g / cm3, the radial crushing strength is greater than 3.5MPa, and the hardness HB is 50-80.

[0082] According to the process, the bushing produced by the process is tested for 3 million times, and the results are as follows:

[0083] Test item Bushing Surface temperature No obvious abnormality Dimensional change No obvious change Visual inspection of the surface finish of the pull rod Shiny with oil traces Visual inspection of the wear inside the bushing No obvious friction marks

[0084] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made according to the structure, shape and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A machining process for cast iron bushings, characterized in that: The process includes the following steps: S1. The proportioned ferroalloy is added to the melting furnace and melted. The ferroalloy includes iron powder and graphite, wherein the carbon weight percentage in the ferroalloy is less than 1%; S2. During the process of raising the furnace temperature, the metal casting mold is heated. After the mold is installed, the bushing (1) is centrifugally cast. After cooling and forming, the bushing (1) is removed from the mold; S3. Ferroalloy powder is prepared according to the above ferroalloy composition and pressed by a hydraulic press to form a porous structure on the surface of the bushing (1); S4. The pressed bushing (1) is sintered; S5. According to the shape requirements, the bushing (1) is machined to expose the porous structure on the surface of the bushing (1); S6. During the growth period of the bushing (1), the bushing (1) is impregnated with lubricating oil by vacuum impregnation so that the porous structure on the surface of the bushing (1) contains oil and the oil content of the bushing (1) is not less than 15%. The weight percentage of the iron alloy is as follows: C less than 1%, S less than 1%, Cu greater than 2% to less than 5%. The bushing (1) formed in step S2 is first tested for density. If the density of the bushing (1) is greater than or equal to 7.0 g / cm3, its surface is dried and then pressed in step S3. If the density of the bushing (1) is less than 7.0 g / cm3, the bushing (1) is remelted and recast.

2. The machining process for cast iron bushings according to claim 1, characterized in that: In step S4, machining is performed using a machining system. In step S6, oil immersion is performed using a vacuum oil immersion machine (4). A transport mechanism (6) is provided between the discharge end of the machining system and the feed end of the vacuum oil immersion machine (4). After the machining system finishes machining the bushing (1), the bushing (1) falls from the discharge end of the machining system onto the transport mechanism (6) and is transported by the transport mechanism (6) into the vacuum oil immersion machine (4) for oil immersion.

3. The machining process for cast iron bushings according to claim 2, characterized in that: The transport mechanism (6) includes a guide rail (18) and a power source (19). A guide groove (25) is provided on the guide rail (18). The projection of the discharge end of the machining system in the vertical direction falls into the guide groove (25). The discharge end of the guide groove (25) receives the feed end of the vacuum oil impregnation machine (4). The guide groove (25) is filled with lubricating oil with a density greater than that of the bushing (1). The power source (19) is used to provide power for the lubricating oil to flow from the machining system to the vacuum oil impregnation machine (4). The bushing (1) moves with the lubricating oil.

4. The machining process for cast iron bushings according to claim 3, characterized in that: The vacuum oil immersion machine (4) includes an oil immersion tank (11), an oil storage tank (12), and a vacuum pump (13). A first connecting pipe (14) and a second connecting pipe (15) are provided between the oil immersion tank (11) and the oil storage tank (12) to connect the two. The two ends of the first connecting pipe (14) are respectively connected to the lower end of the side wall of the oil immersion tank (11) and the lower end of the side wall of the oil storage tank (12), and a first valve (16) is provided on the first connecting pipe (14). The two ends of the second connecting pipe (15) are respectively connected to the upper end of the oil immersion tank (11) and the upper end of the oil storage tank (12). The upper end of the oil storage tank (12) is provided with an exhaust hole (17) communicating with the outside. The vacuum pump (13) is installed on the second connecting pipe (15). The oil immersion tank (11) is provided with a feed inlet (21) for the material outlet of the guide rail (18) to enter. The feed inlet (21) is provided with a second valve (22) for opening and closing the feed inlet (21).

5. The machining process for cast iron bushings according to claim 4, characterized in that: The power source (19) is located at the end of the guide rail (18) away from the immersion tank (11). The lower end of the immersion tank (11) is connected to a return pipe (20) for returning the oil in the immersion tank (11) to the feed end of the guide rail (18). The first return pipe (20) is connected to the liquid inlet end of the power source (19). A third valve (30) is provided on the return pipe (20).

6. The machining process for cast iron bushings according to claim 5, characterized in that: The return pipe (20) includes a vertical section (26) and an inclined section (27). One end of the vertical section (26) is connected to the power source (19) and the other end is located below the power source (19). One end of the inclined section (27) is connected to the lower end of the vertical section (26), and the other end is inclined upward and connected to the lower side of the side wall of the immersion tank (11). The third valve (30) is installed on the inclined section (27) near the end of the immersion tank (11).

7. The machining process for cast iron bushings according to claim 3, characterized in that: The machining system includes a lathe (5), which includes a base (7) and a three-jaw chuck (8) for holding the bushing (1). The length direction of the base (7) is perpendicular to the length direction of the guide rail (18). A through groove (10) is provided on the base (7). The through groove (10) is located directly below the three-jaw chuck (8) and connected to one end of the guide rail (18). When the three-jaw chuck (8) releases the bushing (1), the bushing (1) falls into the guide groove (25) of the guide rail (18) along the through groove (10).

8. A cast iron bushing, characterized in that, It is manufactured using any one of the machining processes for cast iron bushings as described in claims 1-7.

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