Highly lubricious bearing journal surface structure and method of obtaining same

Abstract

The application relates to a high-lubricity bearing journal surface structure and a method for obtaining the same, wherein the friction surface of the bearing journal is uniformly staggered with hardened areas of protrusions and relatively recessed journal base material softening areas, the hardness of the hardened areas is 15-25 HRC higher than that of the journal base material, and the protrusion height of the hardened areas is 5-30 mu m. The friction surface with the alternately soft and hard and staggered high and low areas is wear-resistant, improves bearing elasticity, reduces vibration load, can improve the oil capacity of the journal surface, increase the lubricating oil film thickness under low-speed and high-speed conditions, reduce the friction coefficient, improve the lubricating performance, and prolong the journal fatigue life. The journal structure is realized through an electrolytic plasma local heat treatment method, the manufacturing process can be automated, the process is energy-saving, environment-friendly and efficient, and the risk of overall deformation of large journal parts is eliminated.

Description

Technical Field

[0001] This invention belongs to the field of sliding bearing design technology, and particularly relates to a high-lubricity bearing journal surface structure and its method of obtaining it. Background Technology

[0002] In industrial production, sliding bearing components are widely used. The journal is the component on the shaft used to mount the bearing. It is subjected to pressure loads and sliding loads for a long time. When it is under heavy load, the journal and the bearing bush will not get stuck if most of the load is transmitted through the lubricating medium in the form of liquid or semi-liquid friction. At low sliding speeds, the journal surface and the bearing bush surface are closer together, the lubricant is squeezed out, the metal contact area increases, and the possibility of sticking on the friction surface increases, which can easily cause journal wear and even journal breakage in severe cases.

[0003] Comparing patent 1: RU2613129 "Liquid Friction Bearing", this patent proposes a liquid friction bearing with multiple oil holes on its journal surface for supplying oil to the surface gap between the journal and the bushing to maintain the lubrication layer. The disadvantages of this device are that the journal surface has low hardness, and because its journal surface is a smooth cylindrical surface, it reduces the fluid lubrication effect of the lubricating oil, making the surface extremely prone to wear during use. Furthermore, the presence of oil holes on the journal surface leads to stress concentration and reduced strength, thus limiting its application areas.

[0004] Compare this to patent 2: RU2598121 "Sliding Bearing," which proposes a sliding bearing for ship shafts with anti-friction plate segments arranged alternately in the following order: a plate made of solid lubricating material (lubricant) is located at the bottom center, and plates made of durable material are located on the left and right sides. This bearing can improve the reliability of propeller shaft support, increase load-bearing capacity, and improve vibratory acoustic characteristics. The disadvantage is that its structure is assembled using prefabricated components, and there are grooved and segmented stress concentration areas, which reduces the bearing's load-bearing capacity and limits its application areas.

[0005] Comparing patent 3: RU2139765 "Liquid Friction Bearing," this patent proposes a liquid friction bearing for rolling mill rolls, comprising a bearing bush with hydrodynamic grooves and holes for supplying lubricating fluid. This invention can be used in roll stands for plate mills, section mills, and wire rod mills, increasing load-bearing capacity and bearing speed. The disadvantage of this bearing device is that its smooth sliding surface reduces the slow-speed fluid lubrication effect of the lubricating oil, resulting in low efficiency in forming a lubricating layer during mill start-up and shutdown, and easily causing wear.

[0006] Comparing patent 4: RU2366560 "Method and Equipment for Surface Hardening of Parts," this patent proposes a method and equipment for surface hardening of bearing parts. This patent uses a plasma welding torch and a rod-shaped deformation element to heat and plastically deform the surface of the sliding bearing journal, thereby obtaining a journal surface with alternating hardness and raised areas. These raised areas enable fluid lubrication at low speeds. Its disadvantage is that the raised areas on the journal surface are formed through deformation, resulting in low hardness and irregular shape. This leads to reduced wear and hydrodynamic lubrication efficiency, limiting its application.

[0007] Improvements are needed to address the aforementioned technical issues. Summary of the Invention

[0008] Based on the problems of the aforementioned comparative technologies, this invention provides a high-lubricity bearing journal surface structure and its method for obtaining a high-lubricity bearing journal surface structure that exhibits high strength, good wear resistance, and excellent lubrication efficiency under both low and high-speed sliding conditions under high load. The designed bearing journal surface features uniformly distributed, interlaced high-hardness raised hardened zones that form a uniform wave pattern with the journal substrate, increasing the oil capacity of the journal surface and improving low-speed lubrication performance. The journal structure proposed in this invention is achieved through localized heat treatment, resulting in an energy-saving and efficient manufacturing process.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is: a high-lubricity bearing journal surface structure, which is the friction surface of the bearing journal, the friction surface including multiple raised hardened areas and recessed softened areas of the journal substrate; the multiple raised hardened areas are evenly and alternately arranged, and the friction surface formed by the raised areas of the hardened areas and the journal substrate has a wave-like texture.

[0010] In a preferred embodiment of the present invention, the diameter of the hardened zone is 10-50 mm, the depth is 2-8 mm, and the spacing between adjacent hardened zones is 10-40 mm.

[0011] In a preferred embodiment of the present invention, the surface shape of the hardened area is rectangular, rhomboid, circular, or elliptical, and the surface area of ​​a single hardened area is 60~2000 mm². 2 .

[0012] As a preferred embodiment of the present invention, the hardness of the center of the hardened zone is 15-25 HRC higher than that of the journal substrate.

[0013] As a preferred embodiment of the present invention, the radius of the high point envelope circle of the hardened zone is 5~30μm larger than the radius of the envelope circle formed on the surface of the journal substrate, that is, the friction surface of the bearing journal has a wave of 5~30μm.

[0014] A method for obtaining a highly lubricating bearing journal surface structure includes the following specific steps:

[0015] Step 1: Install the untreated bearing journal onto the journal fixture, and adjust and fix the bearing journal using the bracket and adjusting screws arranged on the bracket;

[0016] Step 2: Fix the electrolytic plasma heat treatment equipment using a bracket, so that the nozzle of the electrolytic plasma heater is aligned with the position on the bearing journal surface to be subjected to hardening heat treatment, and there is a discharge gap between the nozzle of the electrolytic plasma heater and the bearing journal surface.

[0017] Step 3: Supply electrolyte to the electrolytic plasma heat treatment equipment through the electrolyte pipeline to fill the electrolytic tank;

[0018] Step 4: Use a power source to pass electricity between the anode and the bearing journal to generate current in the electrolyte, and then induce plasma discharge at the surface of the bearing journal to be treated to achieve heating of the bearing journal surface;

[0019] Step 5: Periodically increase and decrease the power supply voltage to achieve a hot and cold cycle on the bearing journal surface above and below the phase transformation temperature. The martensitic phase transformation causes the local surface volume to expand, forming a raised hardened zone. Then turn off the power supply.

[0020] Step 6: Use the journal clamp to rotate or move the bearing journal so that the nozzle of the electrolytic plasma heater is aligned with the next position to be treated on the surface of the bearing journal. Repeat steps 4 and 5 to complete the heat treatment hardening of that position.

[0021] Step 7: Repeat step 6 to complete the treatment of the entire bearing journal friction surface in sequence, and finally obtain a bearing journal surface structure with high lubricity.

[0022] In a preferred embodiment of the present invention, in step 5, when the voltage is increased to make the temperature of the bearing journal surface to be treated 50-100°C higher than the temperature of Ac1 (hypereutectoid steel) or Ac3 (hypoeutectoid steel), the voltage is reduced and the bearing journal surface to be treated is placed in the electrolyte to rapidly reduce its temperature to 50-100°C lower than the martensitic transformation initiation temperature (Ms). The above operation is repeated to complete 1-20 thermal cycles.

[0023] As a preferred embodiment of the present invention, in addition to the bearing journal, the friction surfaces of sliding friction parts such as shafts and planar guide rails can also adopt a structure with uniformly staggered distribution of raised hardened areas and relatively recessed journal substrate softened areas.

[0024] As a preferred embodiment of the present invention, the bearing journal is made of carbon steel, stainless steel or cast iron.

[0025] As a preferred embodiment of the present invention, in step 2, an electrolytic plasma heat treatment equipment and an electrolytic plasma heater nozzle of appropriate specifications are selected according to the process requirements and the size of the bearing journal.

[0026] As a preferred embodiment of the present invention, the journal clamp is equipped with a two-axis or multi-axis motion mechanism, so that the bearing journal and the electrolytic plasma heat treatment equipment can move relative to each other according to a program.

[0027] The beneficial effects of this invention are:

[0028] 1. The bearing journal friction surface proposed in this invention has all protrusions in a high-hardness state, which increases its wear resistance. The relatively soft journal substrate outside the high-hardness area improves the elasticity of the structure under load, reduces vibration load, and improves fatigue life.

[0029] 2. The bearing journal surface structure proposed in this invention is obtained through multiple local heat treatments. The surface area of ​​a single hardened zone is 60~2000mm2 and the depth is 2~8mm. The large volume hardened zones that are evenly and interspersed generate compressive stress on the surface layer of the bearing journal. This compressive stress state also increases the strength of the journal and its ability to withstand cyclic loads.

[0030] 3. The bearing journal manufacturing method proposed in this invention, which uses electrolytic plasma heat treatment, is achieved by performing multiple local heat treatments on the friction surface of the bearing journal. This eliminates the need for overall heat treatment of the bearing journal, thereby eliminating the risk of overall thermal deformation, reducing manufacturing difficulty, and saving energy. Especially for large products, such as heavy crankshafts, compared with overall nitriding hardening, the electrolytic plasma local heat treatment method can reduce energy consumption by more than 95%.

[0031] 4. The electrolytic plasma heat treatment method proposed in this invention can obtain a deeper hardened layer with a hardening depth of 2-8 mm, while the hardened layer depth using the furnace nitriding method does not exceed 1 mm.

[0032] 5. This invention proposes a method for obtaining a highly lubricating bearing journal surface structure. The proposed method uses electrolytic plasma heat treatment. Based on consistent system design and stable equipment specifications, it can obtain a hardened zone with regular shape and uniform size. The shape, size and arrangement interval of the hardened zone can be set in advance, resulting in good process repeatability. The regular shape and uniform arrangement of the hardened zone can reduce the wear of the friction surface and improve the hydrodynamic lubrication efficiency. Attached Figure Description

[0033] Figure 1 This is a cross-sectional view of the bearing journal proposed in this invention;

[0034] Figure 2 This is a partially enlarged view of the bearing journal section proposed in this invention;

[0035] Figure 3 The present invention provides an unfolded view, an unfolded sectional view, and a corresponding hardness distribution curve of the bearing journal friction surface.

[0036] Figure 4 This invention provides a localized electrolytic plasma heat treatment device for the surface of bearing journals.

[0037] Figure 5 The curves showing the variation of lubricating oil film thickness on the bearing journal surface with sliding speed for bearings with different hardening zone protrusion heights;

[0038] Figure 6 The curves showing the change in friction coefficient of bearing journal surfaces with sliding speed for different hardened zone protrusion heights;

[0039] The attached figures are labeled as follows: 1. Bearing journal; 2. Journal clamp; 3. Electrolytic plasma heat treatment equipment; 4. Support; 5. Adjusting screw; 6. Bracket; 7. Anode; 8. Electrolyte; 9. Power supply; 10. Electrolyte pipeline; 11. Electrolytic plasma heater nozzle; 12. Hardened zone; 13. Journal substrate. Detailed Implementation

[0040] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] like Figure 1-3 As shown, a high-lubricity bearing journal surface structure is provided. This bearing journal surface structure is the friction surface of the bearing journal 1. The friction surface of the bearing journal 1 has uniformly and alternately distributed raised hardened areas 12 and relatively recessed softened areas of the journal substrate 13. The hardness of the center of the hardened area 12 is 15-25 HRC higher than that of the journal substrate 13. The friction surface formed by the raised hardened area 12 and the journal substrate 13 has a wavy texture. The radius of the envelope circle of the high point of the raised hardened area 12 is 5-30 μm larger than the radius of the envelope circle formed by the surface of the journal substrate 13, that is, the friction surface of the bearing journal 1 has a wavy texture of 5-30 μm. The diameter of the hardened area 12 is 10-50 mm, the depth is 2-8 mm, and the spacing between adjacent hardened areas 12 is 10-40 mm.

[0043] The equipment used in the method for obtaining the high-lubricity bearing journal surface structure proposed in this invention is as follows: Figure 4 As shown, it includes the following steps:

[0044] Step 1: Install the untreated bearing journal 1 onto the journal fixture 2, and adjust and fix the bearing journal 1 using the bracket 4 and the adjusting screws 5 arranged on the bracket 4;

[0045] Step 2: Fix the electrolytic plasma heat treatment equipment 3 using bracket 6, so that the electrolytic plasma heater nozzle 11 is aligned with the position on the bearing journal 1 surface to be subjected to hardening heat treatment, and there is a discharge gap between the electrolytic plasma heater nozzle 11 and the bearing journal 1 surface.

[0046] Step 3: Supply electrolyte 8 to the electrolytic plasma heat treatment equipment 3 through electrolyte pipeline 10 to fill the electrolytic cell;

[0047] Step 4: Power is applied between the anode 7 and the bearing journal 1 using the power supply 9 to generate current in the electrolyte. Then, plasma discharge is induced at the surface of the bearing journal 1 to be treated, thereby heating the surface of the bearing journal 1.

[0048] Step 5: Periodically increase and decrease the voltage of power supply 9 to achieve hot and cold cycles on the surface of bearing journal 1 at the phase transformation temperature. The martensitic phase transformation causes the volume of this local surface to expand, forming a raised hardened area 12. Then, turn off power supply 9.

[0049] Step 6: Use the journal clamp 2 to rotate or move the bearing journal 1 so that the electrolytic plasma heater nozzle 11 is aligned with the next position to be treated on the surface of the bearing journal 1. Repeat steps 4 and 5 to complete the heat treatment hardening of that position.

[0050] Step 7: Repeat step 6 to complete the friction surface treatment of the entire bearing journal 1 in sequence, and finally obtain the high lubricity bearing journal surface structure as described in claim 1.

[0051] In this embodiment, the surface shape of the hardened region 12 in the high-lubricity bearing journal surface structure can be rectangular, rhomboid, circular, or elliptical, and the surface area of ​​a single hardened region is 60~2000 mm². 2In step 5 of the method for obtaining a high-lubricity bearing journal surface structure, the voltage is increased so that the temperature of the bearing journal 1 to be treated is 50-100°C higher than Ac1 (hypereutectoid steel) or Ac3 (hypoeutectoid steel). Then, the voltage is reduced and the surface of the bearing journal 1 to be treated is placed in the electrolyte 8 so that its temperature is rapidly reduced to 50-100°C below the martensitic transformation initiation temperature (Ms). The above operation is repeated to complete 1-20 thermal cycles. In addition to the bearing journal, the friction surfaces of sliding friction parts such as shafts and planar guides can also adopt a structure of uniformly staggered raised hardened areas and relatively recessed journal substrate softened areas. The bearing journal 1 is made of carbon steel, stainless steel, or cast iron. According to the process requirements and the size of the bearing journal, an appropriate specification of electrolytic plasma heat treatment equipment and electrolytic plasma heater nozzle are selected. The journal clamp 2 can be configured with a two-axis or multi-axis motion mechanism so that the bearing journal 1 and the electrolytic plasma heat treatment equipment 3 can move relative to each other according to the program.

[0052] Figure 5 The curves show the variation of lubricating oil film thickness with sliding speed on the bearing journal surface with different hardening zone protrusion heights, where: 1-no protrusion (surface roughness is 0.6), 2-protrusion 10μm, 3-protrusion 12μm, 4-protrusion 14μm, 5-protrusion 16μm.

[0053] Figure 6 The curves show the variation of the friction coefficient of the bearing journal surface with sliding speed for different hardened zone protrusion heights, where: 1-no protrusion (surface roughness is 0.6), 2-protrusion 10μm, 3-protrusion 12μm, 4-protrusion 14μm, 5-protrusion 16μm.

[0054] The bearing journal surface structure proposed in this invention is simple, with high hardness and raised hardened areas evenly distributed on the friction surface. The surface waviness of 5~30μm can improve the oil capacity of the journal surface. Figure 5 The figure shows the curve of the thickness of the lubricating oil film on the surface of the bearing journal with the same height of the hardened zone as a function of sliding speed. It can be seen that when there is no protrusion and the waviness is 0, the thickness of the lubricating oil film is almost zero when the sliding speed is less than 4m / s. However, when the protrusion heights are 10μm, 12μm, 14μm and 16μm respectively, there is a lubricating oil film with a thickness of at least 2μm on the surface even when the sliding speed is zero. Moreover, the oil film thickness increases with the increase of the protrusion height and the sliding speed. Figure 6The curves showing the coefficient of friction of bearing journal surfaces with varying hardening zone protrusion heights as a function of sliding speed reveal that the coefficient of friction is highest when there are no protrusions and the waviness is zero, meaning the journal is most prone to wear in this state. When the protrusion heights are 10μm, 12μm, 14μm, and 16μm, the coefficient of friction decreases by 50-150% compared to when there are no protrusions, with a particularly significant decrease at low sliding speeds. In summary, the bearing journal surface structure proposed in this invention enables the formation of a stable lubricating film on the journal surface during service, maintaining a liquid friction mode even at low speeds, thus improving low-speed lubrication performance and increasing the efficiency of the sliding bearing.

[0055] Depend on Figures 5-6 It can be seen that the high-lubricity bearing journal surface structure proposed in this invention can increase the oil capacity of the journal surface by the wavy shape formed by the protrusion of the surface hardening zone, increase the thickness of the lubricating oil film under low and high speed conditions, reduce the coefficient of friction, and improve lubrication performance.

[0056] The journal structure proposed in this invention is achieved through local heat treatment by electrolytic plasma, which is energy-saving, environmentally friendly, and efficient, and eliminates the risk of overall deformation of large journal components. The resulting alternating soft and hard friction surfaces are not only wear-resistant but also improve load-bearing elasticity, reduce vibration loads, and increase fatigue life. The large-volume hardened zone distribution generates compressive stress on the surface layer, which also improves the journal strength and the ability to withstand cyclic loads.

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

[0058] Although this document uses numerous reference numerals from the figures, such as bearing journal 1, journal clamp 2, electrolytic plasma heat treatment equipment 3, bracket 4, adjusting screw 5, support 6, anode 7, electrolyte 8, power supply 9, electrolyte pipeline 10, electrolytic plasma heater nozzle 11, hardened zone 12, and journal substrate 13, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would be contrary to the spirit of the invention.

Claims

1. A method for obtaining a highly lubricating bearing journal surface structure, characterized in that, The highly lubricating bearing journal surface structure is the friction surface of the bearing journal (1). This friction surface includes multiple raised hardened areas (12) and a recessed softened area of ​​the journal substrate (13). The multiple raised hardened areas (12) are evenly and alternately arranged, and the friction surface formed by the raised areas (12) and the journal substrate (13) has a wave-like texture. The specific steps are as follows: Step 1: Install the untreated bearing journal (1) onto the journal fixture (2), and adjust and fix the bearing journal (1) using the bracket (4) and the adjusting screws (5) arranged on the bracket (4). Step 2: Fix the electrolytic plasma heat treatment equipment (3) using the bracket (6) so that the electrolytic plasma heater nozzle (11) is aligned with the position on the bearing journal (1) where hardening heat treatment is to be performed, and there is a discharge gap between the electrolytic plasma heater nozzle (11) and the bearing journal (1) surface. Step 3: Supply electrolyte (8) to the electrolytic plasma heat treatment equipment (3) through the electrolyte pipeline (10) to fill the electrolytic cell; Step 4: Using the power supply (9), current is passed between the anode (7) and the bearing journal (1) to form a current in the electrolyte. Then, plasma discharge is induced at the surface of the bearing journal (1) to be treated, thereby heating the surface of the bearing journal (1). Step 5: Periodically increase and decrease the voltage of the power supply (9) to achieve a hot and cold cycle on the surface of the bearing journal (1) at the phase transformation temperature. The martensitic phase transformation causes the volume of the local surface to expand, forming a raised hardened area (12). Then turn off the power supply (9). Step 6: Use the journal clamp (2) to rotate or move the bearing journal (1) so that the nozzle (11) of the electrolytic plasma heater is aligned with the next position to be treated on the surface of the bearing journal (1). Repeat steps 4 and 5 to complete the heat treatment hardening of that position. Step 7: Repeat step 6 to complete the friction surface treatment of the entire bearing journal (1) in sequence, and finally obtain a bearing journal surface structure with high lubricity.

2. The method for obtaining a high-lubricity bearing journal surface structure according to claim 1, characterized in that: The diameter of a single hardened area (12) is 10~50mm and the depth is 2~8mm. The distance between adjacent hardened areas (12) is 10~40mm.

3. The method for obtaining a high-lubricity bearing journal surface structure according to claim 1, characterized in that: The surface shape of the hardened area (12) is rectangular, rhomboid, circular, or elliptical, and the surface area of ​​a single hardened area is 60~2000 mm². 2 .

4. The method for obtaining a high-lubricity bearing journal surface structure according to claim 1, characterized in that: The hardness of the center of the hardened zone (12) is 15-25 HRC higher than that of the journal substrate (13).

5. The method for obtaining a high-lubricity bearing journal surface structure according to claim 1, characterized in that: The friction surface of the bearing journal (1) has a wave pattern of 5~30μm.

6. The method for obtaining a high-lubricity bearing journal surface structure according to claim 1, characterized in that: In step 5, when the voltage is increased so that the temperature of the bearing journal (1) to be treated is 50~100°C higher than the temperature of Ac1 or Ac3, the voltage is reduced and the bearing journal (1) to be treated is placed in the electrolyte (8) so that its temperature is rapidly reduced to 50~100°C lower than the martensitic phase transformation start temperature. The above operation is repeated to complete 1~20 thermal cycles.

7. The method for obtaining a high-lubricity bearing journal surface structure according to claim 1, characterized in that: The bearing journal (1) is made of carbon steel, stainless steel or cast iron.

8. The method for obtaining a high-lubricity bearing journal surface structure according to claim 1, characterized in that: In step 2, an appropriate electrolytic plasma heat treatment equipment (3) and an electrolytic plasma heater nozzle (11) are selected according to the process requirements and the size of the bearing journal (1).

9. The method for obtaining a highly lubricating bearing journal surface structure according to claim 1, characterized in that: The journal clamp (2) is equipped with a two-axis or multi-axis motion mechanism, so that the bearing journal (1) and the electrolytic plasma heat treatment equipment (3) can move relative to each other according to a program.

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