Method for controlling uniformity of high-temperature-resistant graphite-based solid lubricating coating of diesel engine piston skirt

Abstract

According to the uniformity control method for the high-temperature-resistant graphite-based solid lubricating coating of the diesel engine piston skirt, according to the rule of the thickness and the spraying quality of the high-temperature-resistant graphite-based solid lubricating coating of the piston skirt, the uniformity of the high-temperature-resistant graphite-based solid lubricating coating is controlled on the premise that the equipment cost is not increased and the production efficiency and the machining quality are guaranteed. The sand blasting process before the high-temperature-resistant graphite-based solid lubricating coating of the piston skirt and the surface control after the high-temperature-resistant graphite-based solid lubricating coating is cured are comprehensively analyzed, and the sand blasting process before the high-temperature-resistant graphite-based solid lubricating coating is sprayed and the surface flatness after the high-temperature-resistant graphite-based solid lubricating coating is cured are controlled; the problem of uniformity of the high-temperature-resistant graphite-based solid lubricating coating on the surface of the piston skirt of the diesel engine is solved, spraying of the high-temperature-resistant graphite-based solid lubricating coating of the piston skirt is achieved, and product quality is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of diesel engines, and particularly relates to a method for controlling the uniformity of a high-temperature-resistant graphite-based solid lubricating coating on a piston skirt of a diesel engine. Background Art

[0002] As one of the most important components in a diesel engine, the piston is connected to the connecting rod during operation. Through reciprocating motion, it transmits power to the crankshaft to achieve power transmission. Therefore, the piston is called the heart of the diesel engine, and a piston with good performance is a prerequisite for the normal operation of the diesel engine. Appropriate surface treatment of the piston surface - coating with a high-temperature-resistant graphite-based solid lubricating coating can significantly improve the service life and performance stability of the piston, especially beneficial for the initial running-in of the diesel engine and effectively avoiding the phenomenon of cylinder scoring.

[0003] The conventional spraying method is as follows: After liquid sandblasting the piston skirt, a high-temperature-resistant graphite-based solid lubricating coating is sprayed. Different diesel engine pistons have different requirements for the thickness of the high-temperature-resistant graphite-based solid lubricating coating. For pistons with higher film layer requirements, the film layer uniformity of the piston skirt is better, but there are high points on some surfaces; for pistons with lower film layer requirements, the film layer uniformity of the piston skirt is poor, and when the thickness requirements are met for most areas, individual surfaces expose the metal surface. Unqualified coating uniformity leads to an increased risk of cylinder scoring of parts, poorer stability, and affects the service life of the diesel engine. Therefore, in view of the above problems, it is necessary to make improvements. Summary of the Invention

[0004] The technical problem solved by the present invention: Provide a method for controlling the uniformity of a high-temperature-resistant graphite-based solid lubricating coating on a piston skirt of a diesel engine. According to the law of the thickness of the high-temperature-resistant graphite-based solid lubricating coating on the piston skirt and the spraying quality, without increasing equipment costs and ensuring production efficiency and processing quality, a comprehensive analysis is carried out on the sandblasting process before the high-temperature-resistant graphite-based solid lubricating coating on the piston skirt and the control of the surface after the high-temperature-resistant graphite-based solid lubricating coating is cured. By controlling the sandblasting process before the spraying of the high-temperature-resistant graphite-based solid lubricating coating and the surface flatness after curing, the problem of the uniformity of the high-temperature-resistant graphite-based solid lubricating coating on the surface of the piston skirt of the diesel engine is solved, the spraying of the high-temperature-resistant graphite-based solid lubricating coating on the piston skirt is realized, and the quality of the product is ensured.

[0005] The technical solution adopted by the present invention: A method for controlling the uniformity of a high-temperature-resistant graphite-based solid lubricating coating on a piston skirt of a diesel engine, comprising the following steps:

[0006] 1) Cleaning: After the piston skirt is completely processed, the surface of the piston skirt is cleaned with alcohol or acetone;

[0007] 2) Protection before sandblasting: The cleaned piston skirt is adaptively connected to a protective tooling, and the non-spraying parts on the piston skirt are protected by the protective tooling;

[0008] 3) Liquid sandblasting: Determine the surface roughness of the piston skirt according to the target thickness of the high-temperature resistant graphite-based solid lubricant coating on the piston skirt, and perform surface liquid sandblasting on the spraying part of the piston skirt according to the determined roughness;

[0009] 4) Water rinsing: Rinse the piston skirt after liquid sandblasting to wash away the sand grains remaining on the piston skirt (5) to ensure that there are no sand grains remaining on the surface-roughened piston skirt;

[0010] 5) Drying: Blow dry the moisture of the piston skirt, and then wipe and clean the surface of the dried piston skirt with acetone;

[0011] 6) Spraying: Spray the high-temperature resistant graphite-based solid lubricant coating on the surface of the piston skirt to make it reach the target spraying thickness;

[0012] 7) Curing: Remove the protective tooling, let the piston skirt dry naturally for 2 h, then put the piston skirt into an aging furnace with a rated temperature of 300 °C and a furnace temperature uniformity of ±5 °C, and raise the furnace temperature to 150 ± 10 °C at a heating rate of ≤5 °C / min, keep it warm for 5 h and then cool it with the furnace to ensure that the heating and cooling of the piston skirt are relatively uniform;

[0013] 8) Polishing: If there are high points on the surface of the piston skirt after curing and taking out of the furnace, use 300 - 600# metallographic sandpaper to clean it on the premise of ensuring not to damage the coating, and polish off the coarse grains on the surface of the coating to make it flat, uniform and smooth.

[0014] In the above step 2), the protective tooling includes a support and two baffles respectively arranged at both port positions of the pin holes of the piston skirt. The upper end surface of the support is provided with a protective groove, and the non-spraying working outer ring at the lower end of the piston skirt is adapted to the protective groove. The cross-sectional shape of the baffle is a T-shaped structure with a positioning convex ring arranged at the outer edge position. The inner end of the baffle is adapted to the pin hole port position, and the positioning convex ring at the outer end of the baffle contacts and positions with the pin hole edge. And under the fit connection of the long screw passing through the two baffles and the locking nut outside the baffle, the two baffles protect the pin holes.

[0015] In the above step 3), when the target thickness of the high-temperature resistant graphite-based solid lubricant coating of the piston skirt is 0.025 mm - 0.045 mm, the surface roughness of the piston skirt after liquid sandblasting is controlled at Ra3.5 - 5.0; and when the target thickness of the high-temperature resistant graphite-based solid lubricant coating of the piston skirt is 0.015 mm - 0.030 mm, the surface roughness of the piston skirt after liquid sandblasting is controlled at Ra3.0 - 4.0.

[0016] Furthermore, the specific liquid sandblasting process when the surface roughness of the piston skirt is controlled at Ra 3.5 - 5.0 is as follows: First, add 60# emery / white fused alumina and water, and perform sandblasting on the surface of the piston skirt with the ratio of 60# emery / white fused alumina to water being 1:2 - 1:1. After sandblasting one or two pieces, add 46# sand, and the additional amount is 4.5 - 5.5 Kg / 2 pieces;

[0017] When the surface roughness of the piston skirt is controlled at Ra 3.0 - 4.0, the specific liquid sandblasting process is as follows: First, add 80# emery / white fused alumina for sandblasting. After sandblasting one or two pieces, add 60# sand, and the additional amount is 2.5 - 3.5 Kg / 2 pieces.

[0018] Advantages of the present invention compared with the prior art:

[0019] 1. According to the law of the thickness and spraying quality of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt, this technical solution comprehensively analyzes the sandblasting process before the high-temperature resistant graphite-based solid lubricating coating on the piston skirt and the control of the surface after the curing of the high-temperature resistant graphite-based solid lubricating coating without increasing equipment costs and ensuring production efficiency and processing quality. By controlling the sandblasting process before the spraying of the high-temperature resistant graphite-based solid lubricating coating and the surface flatness after curing, the problem of the uniformity of the high-temperature resistant graphite-based solid lubricating coating on the surface of the diesel engine piston skirt is solved, the spraying of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt is realized, and the quality of the product is guaranteed;

[0020] 2. According to the relationship between the target thickness and surface roughness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt, this technical solution optimizes the liquid sandblasting steps, thereby appropriately roughening the surface of the piston skirt, improving the adhesion between the surface of the piston skirt and the high-temperature resistant graphite-based solid lubricating coating, and ensuring the uniformity of the coating on the surface of the piston skirt;

[0021] 3. By adding a polishing process to the surface of the coating after curing, this technical solution polishes off the coarse grains on the surface of the coating without damaging the coating, making it flat, uniform, and smooth, achieving the effect of reasonably and effectively controlling the surface quality of the piston skirt and improving the product quality. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the protection tooling of the present invention. Detailed Embodiments

[0023] Next, in combination with the Figure 1 in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] It should be noted that in this article, unless otherwise stated, it should be understood that: the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0025] In this article, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation. The element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0026] Method for controlling the uniformity of a high-temperature resistant graphite-based solid lubricating coating on a diesel engine piston skirt, comprising the following steps:

[0027] 1) Cleaning: After the piston skirt 5 is completely machined, the surface of the piston skirt 5 is cleaned with alcohol or acetone to ensure that the surface of the piston skirt 5 is clean and free of dust before sandblasting;

[0028] 2) Protection before sandblasting: As Figure 1 shown, the cleaned piston skirt 5 is adaptively connected to the protection tooling, and the non-spraying parts on the piston skirt 5 are protected by the protection tooling;

[0029] Specifically, the protection tooling includes a support 4 and two baffles 1 respectively arranged at both ends of the pin holes 5-1 of the piston skirt 5. The upper end surface of the support 4 is provided with a protection groove 6, and the non-spraying working outer ring at the lower end of the piston skirt 5 is adapted to the protection groove 6. The cross-sectional shape of the baffle 1 is a T-shaped structure with a positioning convex ring arranged at the outer edge position. The inner end of the baffle 1 is adapted to the orifice position of the pin hole 5-1, and the positioning convex ring at the outer end of the baffle 1 contacts and positions with the edge of the pin hole 5-1. Under the condition that the long screw 3 passing through the two baffles 1 is adaptively connected to the locking nut 2 outside the baffle 1, the two baffles 1 protect the pin hole 5-1;

[0030] Adopt the structure that two baffles 1 are adaptively connected with a locking nut 2 through a long screw 3 to seal both ends of the pin hole 5-1 on the piston skirt 5, achieving effective and reliable protection for the pin hole 5-1 at the spraying part. The protection structure is simple and the disassembly and assembly are convenient and fast. At the same time, the non-spraying working outer ring at the lower end of the piston skirt 5 is adapted to the protection groove 6, and the support 4 protects the outer circumferential wall of the non-spraying working outer ring. The protection structure is simple and the protection effect is good.

[0031] 3) Liquid sandblasting: According to the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5, determine the surface roughness of the piston skirt 5, and perform surface liquid sandblasting on the spraying part of the piston skirt 5 according to the determined roughness.

[0032] The three embodiments here are specifically as follows:

[0033] Embodiment 1

[0034] When the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5 is 0.03 mm, the surface roughness of the piston skirt 5 after liquid sandblasting is controlled at Ra3.8; when the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5 is 0.018 mm, the surface roughness of the piston skirt 5 after liquid sandblasting is controlled at Ra3.2.

[0035] The specific liquid sandblasting process when the surface roughness of the piston skirt 5 is controlled at Ra3.8 is as follows: First, add 60# carborundum / white fused alumina and water, so that the ratio of 60# carborundum / white fused alumina to water is 1:2 to 1:1, and perform sandblasting on the surface of the piston skirt 5. After spraying one or two pieces, add 46# sand, and the added amount is 4.8 Kg / 2 pieces.

[0036] The specific liquid sandblasting process when the surface roughness of the piston skirt 5 is controlled at Ra3.2 is as follows: First, add 80# carborundum / white fused alumina for sandblasting. After spraying one or two pieces, add 60# sand, and the added amount is 2.8 Kg / 2 pieces.

[0037] Embodiment 2

[0038] When the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5 is 0.035 mm, the surface roughness of the piston skirt 5 after liquid sandblasting is controlled at Ra4.2; when the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5 is 0.024 mm, the surface roughness of the piston skirt 5 after liquid sandblasting is controlled at Ra3.5.

[0039] The specific liquid sandblasting process when the surface roughness of the piston skirt 5 is controlled at Ra4.2 is as follows: First, add 60# emery / white fused alumina and water, and use a ratio of 60# emery / white fused alumina to water of 1:2 to 1:1 to sandblast the surface of the piston skirt 5. After sandblasting one or two pieces, add 46# sand, and the additional amount is 5 Kg / 2 pieces;

[0040] The specific liquid sandblasting process when the surface roughness of the piston skirt 5 is controlled at Ra3.5 is as follows: First, add 80# emery / white fused alumina for sandblasting. After sandblasting one or two pieces, add 60# sand, and the additional amount is 3 Kg / 2 pieces;

[0041] Example 3

[0042] When the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5 is 0.040 mm, the surface roughness of the piston skirt 5 after liquid sandblasting is controlled at Ra4.8; while when the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5 is 0.028 mm, the surface roughness of the piston skirt 5 after liquid sandblasting is controlled at Ra3.6;

[0043] The specific liquid sandblasting process when the surface roughness of the piston skirt 5 is controlled at Ra4.8 is as follows: First, add 60# emery / white fused alumina and water, and use a ratio of 60# emery / white fused alumina to water of 1:2 to 1:1 to sandblast the surface of the piston skirt 5. After sandblasting one or two pieces, add 46# sand, and the additional amount is 5.2 Kg / 2 pieces;

[0044] The specific liquid sandblasting process when the surface roughness of the piston skirt 5 is controlled at Ra3.6 is as follows: First, add 80# emery / white fused alumina for sandblasting. After sandblasting one or two pieces, add 60# sand, and the additional amount is 3.2 Kg / 2 pieces;

[0045] Through daily production, the relationship between the target thickness of the high-temperature resistant graphite-based solid lubricating coating on the piston skirt 5 and the surface roughness is obtained, so as to optimize the liquid sandblasting steps, thereby appropriately roughen the surface of the piston skirt 5, improve the adhesion between the surface of the piston skirt 5 and the high-temperature resistant graphite-based solid lubricating coating, and ensure the uniformity of the surface coating of the piston skirt 5;

[0046] 4) Water rinsing: Rinse the piston skirt 5 after liquid sandblasting to wash away the sand grains remaining on the piston skirt 5, and ensure that there are no sand grains remaining on the piston skirt 5 after surface roughening;

[0047] 5) Drying: Blow dry the moisture of the piston skirt 5, and then wipe and clean the surface of the piston skirt 5 after drying with acetone to ensure that the surface of the piston skirt 5 is dry before spraying;

[0048] 6) Spraying: Spray the high-temperature resistant graphite-based solid lubricating coating on the surface of the piston skirt 5 to make it reach the target thickness of spraying;

[0049] 7) Solidification: Remove the protective tooling, allow the piston skirt 5 to dry naturally for 2 h, then place the piston skirt 5 into an aging furnace with a rated temperature of 300 °C and a furnace temperature uniformity of ±5 °C, and raise the furnace temperature to 150 ± 10 °C at a heating rate of ≤5 °C / min. After holding for 5 h, cool it with the furnace to ensure that the temperature rise and fall of the piston skirt 5 are relatively uniform;

[0050] 8) Polishing: If there are high points on the surface of the piston skirt 5 taken out of the furnace after solidification, through a large number of production practices, it has been proved that polishing with 300 - 600# metallographic sandpaper has a good effect. Therefore, use 300 - 600# metallographic sandpaper to clean it on the premise of not damaging the coating, polish off the coarse grains on the coating surface to make it flat, uniform and smooth; by adding the polishing process of the coating surface after solidification, polish off the coarse grains on the coating surface while ensuring not to damage the coating to make it flat, uniform and smooth, achieving the effect of reasonably and effectively controlling the surface quality of the piston skirt 5 and improving the product quality.

[0051] According to the law of the thickness and spraying quality of the high-temperature resistant graphite-based solid lubricant coating on the piston skirt, without increasing the equipment cost and ensuring the production efficiency and processing quality, this technical solution comprehensively analyzes the sandblasting process before the high-temperature resistant graphite-based solid lubricant coating on the piston skirt and the control of the surface after the solidification of the high-temperature resistant graphite-based solid lubricant coating. By controlling the sandblasting process before the spraying of the high-temperature resistant graphite-based solid lubricant coating and the surface flatness after solidification, the problem of the uniformity of the high-temperature resistant graphite-based solid lubricant coating on the surface of the diesel engine piston skirt is solved, the spraying of the high-temperature resistant graphite-based solid lubricant coating on the piston skirt is realized, and the product quality is ensured;

[0052] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0053] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for controlling the uniformity of a high temperature resistant graphite-based solid lubricating coating on a diesel engine piston skirt, characterized in that The following steps are involved: 1) Cleaning: After the piston skirt (5) is completely processed, the surface of the piston skirt (5) is cleaned with alcohol or acetone; 2) Protection before sandblasting: the cleaned piston skirt (5) is connected to the protective tooling, and the protective tooling is used to protect the non-spraying parts of the piston skirt (5); 3) Liquid sandblasting: according to the target thickness of the high temperature resistant graphite-based solid lubricating coating on the piston skirt (5), the surface roughness of the piston skirt (5) is determined, and the spraying part of the piston skirt (5) is subjected to surface liquid sandblasting according to the determined roughness; 4) Water flushing: flushing the piston skirt (5) after liquid sandblasting, flushing away the sand grains remaining on the piston skirt (5), and ensuring that no sand grains remain on the piston skirt (5) after the surface roughening; 5) Drying: Dry the piston skirt (5) by air, and then scrub the dried piston skirt (5) surface with acetone; 6) Spraying: spraying a high temperature resistant graphite-based solid lubricating coating on the surface of the piston skirt (5) to achieve a target spraying thickness; 7) Curing: Remove the protective tooling and allow the piston skirt (5) to dry naturally for 2 hours. Then place the piston skirt (5) in an aging furnace with a rated temperature of 300°C and a furnace temperature uniformity of ±5°C, and raise the temperature in the furnace to 150±10°C at a heating rate of ≤5°C / min. Keep the temperature for 5 hours and then cool it with the furnace to ensure that the heating and cooling of the piston skirt (5) are relatively uniform. 8) Polishing: If there are high spots on the surface of the piston skirt (5) after curing, use 300-600# metallographic sandpaper to clean it without damaging the coating, and polish away the coarse particles on the surface of the coating to make it flat, uniform and smooth.

2. The method for controlling uniformity of high temperature resistant graphite-based solid lubricating coating on diesel engine piston skirt according to claim 1, characterized in that: In the above step 2), the protective tooling comprises a support (4) and two baffles (1) respectively arranged at the two end positions of the pin hole (5-1) of the piston skirt (5); the upper end surface of the support (4) is provided with a protective groove (6), and the non-sprayed working outer ring at the lower end of the piston skirt (5) is adapted to the protective groove (6); the cross-sectional shape of the baffle (1) is a T-shaped structure with a positioning convex ring at the outer edge position; the inner end of the baffle (1) is adapted to the position of the pin hole (5-1) hole mouth, and the positioning convex ring at the outer end of the baffle (1) is contacted and positioned with the edge of the pin hole (5-1), and the long screw (3) passing through the two baffles (1) is adapted to be connected with the locking nut (2) outside the baffle (1), so that the two baffles (1) can protect the pin hole (5-1).

3. The method for controlling uniformity of high temperature resistant graphite-based solid lubricating coating on diesel engine piston skirt according to claim 1, characterized in that: In the above step 3), when the target thickness of the high temperature resistant graphite-based solid lubricating coating of the piston skirt (5) is 0.025 mm to 0.045 mm, the surface roughness of the piston skirt (5) after liquid sandblasting is controlled within the range of Ra3.5 to 5.0; and when the target thickness of the high temperature resistant graphite-based solid lubricating coating of the piston skirt (5) is 0.015 mm to 0.030 mm, the surface roughness of the piston skirt (5) after liquid sandblasting is controlled within the range of Ra3.0 to 4.

0.

4. The method for controlling uniformity of high temperature resistant graphite-based solid lubricating coating on diesel engine piston skirt according to claim 3, characterized in that: When the surface roughness of the piston skirt (5) is controlled at Ra3.5-5.0, the specific liquid sandblasting process is as follows: first, add 60# corundum / white corundum and water, so that the ratio of 60# corundum / white corundum to water is 1:2-1:1, and then sandblast the surface of the piston skirt (5). After each one or two pieces are sprayed, add 46# sand, and the amount of additional sand is 4.5-5.5 kg / 2 pieces; When the surface roughness of the piston skirt (5) is controlled at Ra3.0-4.0, the specific liquid sandblasting process is as follows: first add 80# corundum / white corundum for sandblasting, and then add 60# sand after each one or two pieces are blasted, with the additional amount being 2.5-3.5 kg / 2 pieces.

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