Slurry pump piston with self-lubricating nested leather cup and preparation method of slurry pump piston

Abstract

The invention belongs to the technical field of pistons, and discloses a slurry pump piston with a self-lubricating nested leather cup and a preparation method of the slurry pump piston. The slurry pump piston with the self-lubricating nested leather cup comprises a piston core, an inner-layer leather cup and an outer-layer leather cup, the lower end of the piston core is a plug crown of a columnar structure, the middle of the plug crown protrudes upwards to form a plug rod of a rod-shaped structure, and the plug crown and the plug rod are coaxially arranged. The inner-layer leather cup and the outer-layer leather cup are both of an annular structure coaxial with the plug rod and are sequentially arranged outside the plug column in a matched and sleeved mode from inside to outside, and the lower end faces of the inner-layer leather cup and the outer-layer leather cup make close contact with the upper end face of the plug crown. And the outer-layer leather cup is made of a self-lubricating material. The slurry pump piston has the excellent self-lubricating characteristic, and when the outer-layer leather cup generates groove scratches due to abrasion, lubricating oil can be released, so that friction loss is further reduced, heat generation is reduced, and the service life of the leather cup and the service life of the piston are remarkably prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of pistons, and in particular relates to a mud pump piston with a self-lubricating nested leather cup and a preparation method thereof. Background Art

[0002] The oil drilling mud pump is one of the indispensable and important equipment in oil drilling projects, and the piston is the core component of the mud pump. The main function of the mud pump is to transport the drilling fluid to the bottom of the well and carry the cuttings at the bottom of the well to the surface. At the same time, it plays the role of driving drilling, cleaning drilling tools, and cooling the drill bit. However, the piston of the mud pump is easily damaged during operation and requires regular maintenance and replacement, which seriously affects the drilling efficiency and project progress.

[0003] According to the drilling records of mud pumps and cylinder liners of 180 oil wells in January and February 2012 of a drilling company of Daqing Petroleum Administration Bureau (Yuan Huijuan, Guo Jianying, Su Zimei, et al. Research on the Reliability of Friction Pairs of Piston and Cylinder Sleeves of Domestic Drilling Mud Pumps [J]. China Mechanical Engineering, 2013, 24(11): 1425-1430.), the piston was replaced at an average depth of 1300 m and the cylinder liner was replaced at an average depth of 2600 m (the working life is characterized by the drilling depth). It can be seen that the piston cup of the mud pump is very easy to be damaged and the damage frequency is too high. On the one hand, it is a huge maintenance and installation cost, and on the other hand, the progress of the project is delayed due to piston damage. Extending the service life of the piston cup is of great value. Lanzhou Petroleum Machinery Research Institute once pointed out in the article "Reciprocating Pumps in Oil Fields" (Zhang Yong. Research on Evaluation Methods of Piston Life of Drilling Mud Pumps [D]. Zhejiang University, 2004.): "When heavy mud (ρ=2.24 g / cm 3 ) and clean water as drilling fluid, it was found that the service life of the piston using heavy mud as the working medium is 1 / 10 of that of the piston using clean water as the working medium, which also shows that the sand content is an important factor affecting the service life of the piston cup. Therefore, it is necessary to develop a long-life piston.

[0004] When the piston makes a rapid reciprocating motion in the cylinder sleeve, it will rub against the cylinder sleeve and generate heat. Reducing the friction coefficient of the piston is the key to improving its service life. Wang Lan et al. applied fiber fabric composite materials to the outer surface of the mud pump piston, thereby reducing the friction coefficient of the piston lip and reducing the friction wear of the piston (Wang Lan. Research and Development of High-Pressure Mud Pump Piston for Engineering Machinery [J]. Special Rubber Products, 2010, 31(06): 48-50.). Wang Yi et al. found that coolants containing chlorine and copper sulfate are beneficial to improving the wear degree of the friction pair. The coolant contains chlorine, which forms a layered chloride film on the metal surface, which will reduce the friction coefficient of the contact surface and reduce the wear of the friction pair (Wang Yi. Development of Mud Pump and Piston Optimization Research [J]. China Petroleum and Chemical Standards and Quality, 2012, 33(16): 63.). Although the above method can reduce the friction coefficient of the friction pair surface, in actual production, facing the complex conditions of high temperature and high pressure, this wear reduction effect is very ineffective compared to abrasive wear. Therefore, a new method for reducing the friction coefficient of the cylinder liner-cup friction pair is needed. Summary of the invention

[0005] The object of the present invention is to provide a mud pump piston with a self-lubricating nested leather cup and a preparation method thereof, so as to solve the problem that the current piston leather cup fails due to abrasive wear.

[0006] The mud pump piston with a self-lubricating nested leather cup of the present invention comprises a piston core, an inner leather cup and an outer leather cup; The lower end of the piston core is a plug crown with a columnar structure, the middle part of the plug crown is convex to a plug rod with a rod-like structure, and the plug crown and the plug rod are coaxially arranged; The inner leather cup and the outer leather cup are both annular structures coaxial with the plug rod, and are sequentially fitted onto the outside of the plug rod from the inside to the outside, with their lower end surfaces in close contact with the upper end surface of the plug crown; the outer leather cup is made of self-lubricating material.

[0007] The radial thickness of the inner leather cup is 25-30 mm; the radial thickness of the outer leather cup is 2-3 mm.

[0008] Preferably, the inner leather cup is made of the following materials and cast into a mold and sleeved onto the outside of the plug rod: Liquid polyurethane rubber prepolymer, 3,3'-dichloro-4,4'-diphenylmethanediamine (MOCA), zinc oxide, stearic acid, antioxidant and carbon fiber.

[0009] Furthermore, the above raw materials are composed of the following in parts by mass: Liquid polyurethane rubber prepolymer 100-150 parts, MOCA 10-20 parts, zinc oxide 0.5-1 part, stearic acid 0.5-1 part, antioxidant 0.5-1 part, carbon fiber 0.5-2 parts.

[0010] Among them, the liquid polyurethane rubber prepolymer is a product of Dongguan Polymer Rubber Products Co., Ltd., the product name is "polyurethane prepolymer", and the NCO mass content is about 2%.

[0011] Preferably, the outer leather cup is made of the following raw materials and cast into a mold and sleeved onto the outer side of the inner leather cup: Liquid polyurethane rubber prepolymer, MOCA, porous carbon-lubricant powder, zinc oxide, stearic acid, antioxidant and graphite oxide.

[0012] Furthermore, the above raw materials are composed of the following in parts by mass: Liquid polyurethane rubber prepolymer 100-150 parts, MOCA 10-20 parts, porous carbon-lubricating oil powder 5-10 parts, zinc oxide 0.5-1 part, stearic acid 0.5-1 part, antioxidant 0.5-1 part, graphite oxide 0.5-2 parts.

[0013] Among them, the liquid polyurethane rubber prepolymer is a product of Dongguan Polymer Rubber Products Co., Ltd., the product name is "polyurethane prepolymer", and the NCO mass content is about 2%.

[0014] The method for preparing a mud pump piston with a self-lubricating nested leather cup of the present invention comprises the following steps: Step 1: Mix liquid polyurethane rubber prepolymer, MOCA, zinc oxide, stearic acid, antioxidant and carbon fiber evenly, cast and mold them onto the outside of the plug rod and mature them.

[0015] Step 2: Add the porous carbon into the lubricating oil and mix and stir to allow the porous carbon to fully absorb the lubricating oil.

[0016] Step 3: Place the porous carbon adsorbed with lubricating oil into an aqueous solution of polyvinyl alcohol (1788), stir, and spray dry to obtain porous carbon-lubricating oil powder.

[0017] Step 4: Mix the liquid polyurethane rubber prepolymer, MOCA, zinc oxide, stearic acid, antioxidant, graphite oxide and porous carbon-lubricating oil powder evenly, cast and mold them at 100°C, and sleeve them on the outside of the inner leather cup, and then perform pre-ripening and aging molding in sequence.

[0018] In step 1, the raw materials are composed of 100-150 parts by mass of liquid polyurethane rubber prepolymer, 10-20 parts of MOCA, 0.5-1 parts of zinc oxide, 0.5-1 parts of stearic acid, 0.5-1 parts of antioxidant, and 0.5-2 parts of carbon fiber.

[0019] In step 1, the mixing speed is set to 300-400 rpm, the mixing temperature is 100°C, and the mixing time is 20-30 min; the aging temperature is 120°C, and the aging time is 0.5 h.

[0020] In step 2, the raw materials are composed of 10-15 parts of porous carbon and 20-30 parts of lubricating oil in terms of mass fractions.

[0021] In step 2, during the mixing and stirring process, the rotation speed is set at 120-150 rpm and the stirring time is 30-40 min.

[0022] In step 3, the raw materials are composed of 10-15 parts by mass of porous carbon for absorbing lubricating oil, 2 parts of polyvinyl alcohol (1788), and 100 parts of water.

[0023] In step 3, the stirring speed is 80-100 rpm, the time is 15-20 min, and the spray drying temperature is 180-200°C.

[0024] In step 4, the raw materials are composed of 100-150 parts by mass of liquid polyurethane rubber prepolymer, 10-20 parts of MOCA, 0.5-1 parts of zinc oxide, 0.5-1 parts of stearic acid, 0.5-1 parts of antioxidant, 0.5-2 parts of graphite oxide, and 5-10 parts of porous carbon-lubricating oil powder.

[0025] In step 4, the mixing speed is set to 300-400 rpm, the mixing temperature is 100°C, and the mixing time is 20-30 min; the pre-aging temperature is 120°C, and the pre-aging time is 0.5 h; the aging temperature is 90°C, and the aging time is 10 h.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention designs a new type of self-lubricating nested leather cup. The double-layer leather cup together gives it excellent performance. On the one hand, the inner leather cup of the piston contains carbon fiber reinforcement filler, which gives the inner leather cup of the piston high strength and high modulus performance. On the other hand, the outer leather cup of the piston contains two lubricating substances, graphite oxide and porous carbon-lubricating oil powder, which helps to reduce the friction coefficient between the piston and the inner wall of the cylinder sleeve, thereby reducing heat generation. Since the lubricating oil is adsorbed in the porous carbon, it has a slow release function. Therefore, this mud pump piston with a self-lubricating nested leather cup can greatly increase its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The schematic diagram of the structure of the mud pump piston with self-lubricating nested leather cup is shown in the figure: 1 piston core, 2 inner leather cup, 3 outer leather cup. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with specific embodiments, but the described embodiments are only 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention. Embodiment 1:

[0029] In this embodiment, a mud pump piston with a self-lubricating nested leather cup is prepared according to the following steps: 1. Add 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 1 part of carbon fiber into a reaction container and stir them at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, cast and mold it onto the outside of the piston rod and keep it at 120°C for 0.5 h to obtain a piston with a semi-matured inner leather cup.

[0030] 2. Weigh 20 parts of lubricating oil according to the formula and put it into the container. Then weigh 10 parts of porous carbon powder with uniform particle size and put it into the container. Use a mechanical stirring device with the speed set at 120 rpm to fully mix the porous carbon and the lubricating oil so that the porous carbon can fully absorb the lubricating oil. The stirring time is 30 min.

[0031] 3. Dissolve 2 parts of polyvinyl alcohol 1788 in 100 parts of water, then add 10 parts of porous carbon for adsorbing lubricating oil, mix and stir evenly at a speed of 100 rpm, and then use spray drying to obtain porous carbon-lubricating oil powder at a drying temperature of 180-200°C.

[0032] 4. Add 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.5 parts of graphite oxide, and 5 parts of porous carbon-lubricating oil powder into a reaction vessel and stir at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, it is cast and molded onto the outside of the inner leather cup. It is kept warm at 120°C for 0.5 h and then matured at 90°C for 10 h to obtain a piston with inner and outer nested leather cups. Embodiment 2:

[0033] This embodiment adopts the same method as that of Embodiment 1 to prepare a mud pump piston with a self-lubricating nested leather cup, except that: in step 4, 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.5 parts of graphite oxide, and 5 parts of porous carbon-lubricating oil powder are replaced with 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.25 parts of graphite oxide, and 5 parts of porous carbon-lubricating oil powder. Embodiment 3:

[0034] This embodiment adopts the same method as that of Embodiment 1 to prepare a mud pump piston with a self-lubricating nested leather cup, except that: in step 4, 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.5 parts of graphite oxide, and 5 parts of porous carbon-lubricating oil powder are replaced with 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.5 parts of graphite oxide, and 10 parts of porous carbon-lubricating oil powder. Embodiment 4:

[0035] This embodiment adopts the same method as that of Embodiment 1 to prepare a mud pump piston with a self-lubricating nested leather cup, except that: in step 4, 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 1 part of carbon fiber are changed to 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 0.5 parts of carbon fiber. Comparative Example 1:

[0036] 1. Add 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 1 part of carbon fiber into a reaction container and stir them at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, cast and mold it onto the outside of the piston rod and keep it at 120°C for 0.5 h to obtain a piston with a semi-matured inner leather cup.

[0037] 2. Weigh 20 parts of lubricating oil according to the formula and put it into the container. Then weigh 10 parts of porous carbon powder with uniform particle size and put it into the container. Use a mechanical stirring device with the speed set at 120 rpm to fully mix the porous carbon and the lubricating oil so that the porous carbon can fully absorb the lubricating oil. The stirring time is 30 min.

[0038] 3. Dissolve 2 parts of polyvinyl alcohol 1788 in 100 parts of water, then add 10 parts of porous carbon for adsorbing lubricating oil, mix and stir evenly at a speed of 100 rpm, and then use spray drying to obtain porous carbon-lubricating oil powder at a drying temperature of 180-200°C.

[0039] 4. Add 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 5 parts of porous carbon-lubricating oil powder into a reaction vessel and stir them at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, pour and mold them onto the outside of the inner leather cup, keep them warm at 120°C for 0.5 h, and then mature them at 90°C for 10 h to obtain a piston with inner and outer nested leather cups. Comparative Example 2:

[0040] 1. Add 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, and 0.5 parts of antioxidant into a reaction container and stir at high speed in advance. Set the speed to 300 rpm and the temperature to 50°C. After being completely and evenly mixed, cast and mold it onto the outside of the piston rod and keep it at 120°C for 0.5 h to obtain a piston with a semi-matured inner leather cup.

[0041] 2. Weigh 20 parts of lubricating oil according to the formula and put it into the container. Then weigh 10 parts of porous carbon powder with uniform particle size and put it into the container. Use a mechanical stirring device with the speed set at 120 rpm to fully mix the porous carbon and the lubricating oil so that the porous carbon can fully absorb the lubricating oil. The stirring time is 30 min.

[0042] 3. Dissolve 2 parts of polyvinyl alcohol 1788 in 100 parts of water, then add 10 parts of porous carbon that absorbs lubricating oil, mix and stir evenly at a speed of 100 rpm, and then use a spray drying method at a drying temperature of 180-200°C to remove excess moisture on the surface of the porous carbon that absorbs lubricating oil to obtain porous carbon-lubricating oil powder.

[0043] 4. Add 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.5 parts of graphite oxide, and 5 parts of porous carbon-lubricating oil powder into a reaction vessel and stir at high speed in advance. The speed is set to 300 rpm and the temperature is set to 50 °C. After being completely and evenly mixed, pour and mold it onto the outside of the inner leather cup, keep it warm at 120 °C for 0.5 h, and then mature it at 90 °C for 10 h to obtain a piston with inner and outer nested leather cups. Comparative Example 3:

[0044] 1. Add 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 1 part of carbon fiber into a reaction container and stir them at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, cast and mold it onto the outside of the piston rod and keep it at 120°C for 0.5 h to obtain a piston with a semi-matured inner leather cup.

[0045] 2. Add 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 0.5 parts of graphite oxide into a reaction vessel and stir them at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, cast and molded, sleeved on the outside of the inner leather cup, and kept at 120°C for 0.5 h. Then, matured and molded at 90°C for 10 h to obtain a piston with inner and outer nested leather cups. Comparative Example 4:

[0046] 1. Add 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 1 part of carbon fiber into a reaction container and stir them at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, cast and mold it onto the outside of the piston rod and keep it at 120°C for 0.5 h to obtain a piston with a semi-matured inner leather cup.

[0047] 2. Add 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.5 parts of graphite oxide, and 5 parts of lubricating oil into a reaction vessel and stir at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, pour and mold it onto the outside of the inner leather cup, keep it warm at 120°C for 0.5 h, and then mature it at 90°C for 10 h to obtain a piston with inner and outer nested leather cups. Comparative Example 5:

[0048] 1. Add 100 parts of liquid polyurethane rubber prepolymer, 13 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, and 1 part of carbon fiber into a reaction container and stir them at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, cast and mold it onto the outside of the piston rod and keep it at 120°C for 0.5 h to obtain a piston with a semi-matured inner leather cup.

[0049] 2. Dissolve 2 parts of polyvinyl alcohol 1788 in 100 parts of water, then add 10 parts of porous carbon, mix and stir evenly at a speed of 100 rpm, and then use spray drying to obtain porous carbon powder at a drying temperature of 180-200°C.

[0050] 3. Add 100 parts of liquid polyurethane rubber prepolymer, 12 parts of MOCA, 0.5 parts of zinc oxide, 0.5 parts of stearic acid, 0.5 parts of antioxidant, 0.5 parts of graphite oxide, and 5 parts of porous carbon powder obtained in step 2 into a reaction container and stir at high speed in advance. The speed is set to 300 rpm and the temperature is set to 100°C. After being completely and evenly mixed, pour and mold it onto the outside of the inner leather cup, keep it warm at 120°C for 0.5 h, and then mature it at 90°C for 10 h to obtain a piston with inner and outer nested leather cups.

[0051]

[0052] *The tensile strength of the cup material is tested according to the national standard GB / T 528-2009; **Piston service life is the average value of field trial results; ***The friction coefficient is tested according to the national standard GB / T 40721-2021.

[0053] It can be seen from the data in the above table that compared with Example 1, Example 2 reduces the content of graphite, resulting in a certain increase in the friction coefficient. Compared with Example 1, Example 3 increases the content of porous carbon-lubricating oil powder, reduces the friction coefficient and increases the service life. Compared with Example 1, Example 4 reduces the content of carbon fiber, resulting in a decrease in the tensile strength of the inner cup material. The above results show that graphite and porous carbon-lubricating oil powder can play a role in reducing the friction coefficient between the cylinder liner and the cup friction pair; carbon fiber can improve the mechanical properties of the cup.

[0054] Compared with Example 1, in Comparative Example 1, no graphite was added, and the friction coefficient was improved to a certain extent, indicating that adding graphite to the outer leather cup can reduce the friction coefficient.

[0055] Compared with Example 1, in Comparative Example 2, no carbon fiber was added, and the tensile strength of the inner leather cup was reduced, indicating that adding a certain amount of carbon fiber can improve the mechanical properties of the inner leather cup.

[0056] Compared with Example 1, in Comparative Example 3, no porous carbon-lubricating oil powder was added, the friction coefficient reached the maximum, and the service life was the lowest, indicating that the porous carbon-lubricating oil powder was the main factor playing a role in the cylinder liner-cup friction pair.

[0057] Compared with Example 1, in Comparative Example 4, no porous carbon-lubricating oil powder was added, but only lubricating oil was added as the lubricating medium, the friction coefficient increased to a certain extent, and the service life decreased.

[0058] Compared with Example 1, in Comparative Example 5, no porous carbon-lubricating oil powder is added, but only porous carbon is added as a lubricating medium. The friction coefficient is greatly improved, and the service life is also significantly reduced. Comparative Examples 4 and 5 both show that the effect of adding lubricating oil or porous carbon as a lubricating medium is not good, and the effect of the two together in extending the service life of the piston is far less good.

[0059] The above results show that designing the mud pump piston with a self-lubricating nested leather cup can significantly improve its self-lubricating ability and extend the service life of the piston.

Claims

1. A mud pump piston with a self-lubricating nested leather cup, characterized in that: The mud pump piston with self-lubricating nested leather cup comprises a piston core, an inner leather cup and an outer leather cup; The lower end of the piston core is a plug crown with a columnar structure, the middle part of the plug crown is convex to a plug rod with a rod-like structure, and the plug crown and the plug rod are coaxially arranged; The inner leather cup and the outer leather cup are both annular structures coaxial with the plug rod, and are sequentially fitted onto the outside of the plug rod from the inside to the outside, with their lower end surfaces in close contact with the upper end surface of the plug crown; the outer leather cup is made of self-lubricating material.

2. The mud pump piston with self-lubricating nested leather cup according to claim 1, characterized in that: The inner leather cup is processed and casted with the following raw materials and is sleeved on the outside of the plug rod: liquid polyurethane rubber prepolymer, MOCA, zinc oxide, stearic acid, antioxidant and carbon fiber.

3. The mud pump piston with self-lubricating nested leather cup according to claim 1, characterized in that: The outer leather cup is cast and molded with the following raw materials and is sleeved on the outside of the inner leather cup: liquid polyurethane rubber prepolymer, MOCA, porous carbon-lubricating oil powder, zinc oxide, stearic acid, antioxidant and graphite oxide.

4. A method for preparing a mud pump piston with a self-lubricating nested leather cup as claimed in any one of claims 1 to 3, characterized in that The following steps are involved: Step 1: mixing liquid polyurethane rubber prepolymer, MOCA, zinc oxide, stearic acid, antioxidant and carbon fiber uniformly, casting and molding, sleeved on the outside of the plug rod and ripening; Step 2: Add the porous carbon into the lubricating oil and mix and stir to allow the porous carbon to fully absorb the lubricating oil; Step 3: placing the porous carbon adsorbing the lubricating oil into an aqueous solution of polyvinyl alcohol, stirring, and spray drying to obtain porous carbon-lubricating oil powder; Step 4: Mix the liquid polyurethane rubber prepolymer, MOCA, zinc oxide, stearic acid, antioxidant, graphite oxide and porous carbon-lubricating oil powder evenly, cast and mold them at 100°C, and sleeve them on the outside of the inner leather cup, and then perform pre-ripening and aging molding in sequence.

5. The preparation method according to claim 4, characterized in that: In step 1, the raw materials are composed of 100-150 parts by mass of liquid polyurethane rubber prepolymer, 10-20 parts of MOCA, 0.5-1 parts of zinc oxide, 0.5-1 parts of stearic acid, 0.5-1 parts of antioxidant, and 0.5-2 parts of carbon fiber.

6. The preparation method according to claim 4, characterized in that: In step 1, the aging temperature is 120° C. and the aging time is 0.5 h.

7. The preparation method according to claim 4, characterized in that: In step 2, the raw materials are composed of 10-15 parts of porous carbon and 20-30 parts of lubricating oil in terms of mass fractions.

8. The preparation method according to claim 4, characterized in that: In step 3, the raw materials are composed of 10-15 parts of porous carbon for absorbing lubricating oil, 2 parts of polyvinyl alcohol, and 100 parts of water in terms of mass fraction.

9. The preparation method according to claim 4, characterized in that: In step 4, the raw materials are composed of 100-150 parts by mass of liquid polyurethane rubber prepolymer, 10-20 parts of MOCA, 0.5-1 parts of zinc oxide, 0.5-1 parts of stearic acid, 0.5-1 parts of antioxidant, 0.5-2 parts of graphite oxide, and 5-10 parts of porous carbon-lubricating oil powder.

10. The preparation method according to claim 4, characterized in that: In step 4, the pre-aging temperature is 120°C, and the pre-aging time is 0.5 h; the aging temperature is 90°C, and the aging time is 10 h.

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