Piston type aero-engine main connecting rod inner hole surface strengthening treatment method

Abstract

The invention discloses a surface strengthening treatment method for an inner hole of a main connecting rod of a piston type aero-engine. The surface strengthening treatment method comprises the following steps that S100, the main connecting rod is subjected to oil removal treatment; s200, performing waxing treatment on the non-plated surface on the main connecting rod to form an insulating protection layer; s300, weak corrosion activation treatment is conducted on an inner hole of the main connecting rod; s400, a tool clamp is used for installing and hanging the main connecting rod, then a lead and tin plating solution is poured into an inner hole of the main connecting rod for out-groove electroplating treatment, and the lead and tin plating solution comprises 110 g / L to 275 g / L of lead fluoroborate, 30 g / L to 65 g / L of stannous fluoroborate, 1 g / L to 2 g / L of hydroquinone and 1.5 g / L to 2.0 g / L of oxhide gelatin; and S500, the main connecting rod is detached from the tool clamp and then subjected to wax removal and cleaning treatment, and then whether the lead-tin layer is qualified or not is checked. According to the surface strengthening treatment method for the inner hole of the main connecting rod of the piston type aero-engine, the uniformity of a plating layer can be improved, the tin content in a lead-tin layer is increased, and the wear-resisting and lubricating capacity is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of piston aero-engine, in particular, to a piston aero-engine main connecting rod inner hole surface strengthening treatment method. BACKGROUND

[0002] In the piston aero-engine, the main connecting rod is a key core component for transmitting power, and its working environment is extremely harsh, and it needs to withstand high-frequency and high-load reciprocating impact and friction for a long time. The inner hole of the connecting rod is an important contact surface cooperating with the crankshaft, and its wear resistance, anti-seizure and dimensional stability directly affect the overall performance, operation reliability and service life of the engine. At present, for the strengthening treatment of the surface of the main connecting rod inner hole, the industry often adopts the process of electroplating wear-resistant lead-tin alloy, which uses the good wear resistance, wear resistance and corrosion resistance of lead-tin alloy to improve the surface quality of the main connecting rod inner hole. However, when disassembled and inspected after the aero-engine runs for 2000h, it is found that the lead-tin layer of the main connecting rod inner hole often appears wear and peeling and exposes the matrix, and the service life is short, which is affected by the following factors: (1) Poor uniformity of plating layer: the traditional electroplating lead-tin method in the groove of the main connecting rod is affected by the distance of the anode plate and the depth of the inner hole during electroplating, and the electroplating current density is not uniform, which easily causes large thickness deviation of the plating layer at different positions of the inner hole, and the uniformity of the plating layer can only reach ±10um, affecting the dimensional accuracy, and the wear resistance of the plating layer is difficult to meet the long-term high-strength operation requirements of the aero-engine; (2) Poor wear resistance: the tin content in the traditional wear-resistant lead-tin layer is relatively low, and the wear resistance is poor. The tin content in the wear-resistant lead-tin layer is generally required to be 6% to 10%. The current mainstream method for controlling the tin content in the lead-tin layer is to control the ratio of lead fluoroborate and stannous fluoroborate in the plating solution and the current density, but this method has no obvious effect on improving the tin content, and the highest tin content reached is only about 6%. SUMMARY

[0003] The present application provides a piston aero-engine main connecting rod inner hole surface strengthening treatment method to solve the technical problem that the lead-tin layer formed by the existing electroplating lead-tin method cannot meet the high-strength use requirements of the piston aero-engine main connecting rod.

[0004] According to one aspect of the present application, a piston aero-engine main connecting rod inner hole surface strengthening treatment method is provided, comprising the following steps: S100: immerse the main connecting rod as a whole in a water-based oil removal solution for oil removal treatment, then clean and dry the main connecting rod; S200: wax coating treatment is performed on the non-plating surface of the main connecting rod to form an insulating protective layer; S300: weak etching activation treatment is performed on the inner hole of the main connecting rod; S400: using the fixture to clamp the main connecting rod, then pouring the lead-tin plating solution into the inner hole of the main connecting rod to perform the out-of-slot electroplating treatment, the composition of the lead-tin plating solution includes lead fluoroborate: 110g / L-275g / L, stannous fluoroborate: 30g / L-65g / L, hydroquinone: 1g / L-2g / L, and gelatin: 1.5g / L-2.0g / L; S500: after the main connecting rod is clamped from the fixture, wax removal and cleaning treatment are performed, then it is checked whether the lead-tin layer is qualified, if qualified, the main connecting rod is immersed in the rust-proof oil for rust-proof treatment, so that the whole surface is covered with an oil film; if unqualified, the lead-tin layer on the main connecting rod is removed, and steps S100-S400 are performed again.

[0005] Preferably, the fixture includes a main frame, an insulating bottom plate arranged at the bottom of the main frame, and two fastening screws arranged at opposite sides of the main frame and above the insulating bottom plate, an inner cavity of the main frame is used to place the main connecting rod and support the main connecting rod through the insulating bottom plate, and the fastening screws are used to tightly abut the upper surface of the main connecting rod and tightly fix the main connecting rod on the insulating bottom plate.

[0006] Preferably, the fixture further includes an anode rod matched with the inner hole of the main connecting rod, the diameter of the anode rod gradually increases from both ends to the middle, and the anode rod is used to connect with the electroplating equipment and is arranged in the inner hole of the main connecting rod to perform the electroplating operation.

[0007] Preferably, the insulating bottom plate is provided with a limiting groove matched with the end structure of the main connecting rod, and the fixture further includes a flexible gasket embedded in the limiting groove and matched with the edge of the inner hole of the main connecting rod.

[0008] Preferably, step S200 specifically includes: preheating the main connecting rod to 40-60℃, then immersing the main connecting rod in the wax liquid with a temperature higher than 95℃ for wax immersion treatment, repeating the wax immersion treatment at least twice, and finally scraping off the wax layer in the inner hole of the main connecting rod and cleaning the inner hole surface of the main connecting rod with an organic solvent.

[0009] Preferably, after step S200, it further includes: immersing the main connecting rod in a flowing cold water tank for cleaning, then taking out the main connecting rod from the water surface after cleaning, checking the oil removal and cleaning quality, and observing whether the water film on the inner hole surface of the main connecting rod can be continuously maintained for 30s, if not, using a decontamination powder to remove the oil on the inner hole surface of the main connecting rod.

[0010] Preferably, before the wax removal and cleaning treatment in step S500, the main connecting rod is further immersed in a neutral solution with weak alkalinity for neutralization, so as to avoid the corrosion of the main connecting rod caused by the residual acid on the surface of the main connecting rod, and the neutral solution comprises 5g / L-30g / L potassium dichromate and 5g / L-30g / L sodium carbonate, and the neutralization is performed at room temperature for 1-5 minutes.

[0011] Preferably, in step S500, the checking of whether the lead-tin layer is qualified specifically comprises: placing the main connecting rod into a heating furnace for heating treatment, the heating temperature is 140-200 DEG C, the heating time is greater than or equal to 2 hours, then air cooling to room temperature, and then checking whether the lead-tin layer on the main connecting rod is foamed and / or peeled.

[0012] Preferably, before step S100, the pin hole on the inner hole surface of the main connecting rod is further chamfered, the chamfer radius R is 0.4-0.8mm, and then the chamfer structure is smoothed, so as to reduce the sharp end effect at the pin hole during the lead-tin plating.

[0013] Preferably, after step S500, the inner hole of the main connecting rod and the matching part of the crankshaft are coated with aviation oil, and then the assembly of the main connecting rod and the crankshaft is performed, so as to avoid the problem that the lead-tin layer is damaged due to the insufficient lubrication between the main connecting rod and the crankshaft during the first start of the aero-engine.

[0014] The present application has the following advantages: In the piston aero-engine main connecting rod inner hole surface strengthening treatment method, the main connecting rod is first cleaned completely, so as to ensure the subsequent waxing treatment and electroplating treatment effect, then the non-plating surface of the main connecting rod is coated with wax to form an insulating protective layer, compared with the method of pasting protective adhesive tape on the non-plating surface, the protective treatment time can be effectively shortened and the protection effect can be improved, the plating leakage problem caused by poor adhesive tape protection can be avoided, then the inner hole of the main connecting rod is subjected to weak corrosion activation treatment, the adhesion between the lead-tin layer and the substrate after the electroplating of lead-tin is improved, then the main connecting rod is fixed by using a tool clamp and the outer slot electroplating treatment is performed on the main connecting rod, compared with the traditional in-tank electroplating method, the problem of poor plating uniformity can be effectively solved, more importantly, the tin content is effectively improved by adding cowhide glue into the lead-tin plating solution, in the prior art, for the fluoroborate lead-tin plating system, the main role of the organic glue is to improve the cathode polarization, make the crystal fine, and improve the dispersion ability, and there is no any data showing that the tin content in the electroplated lead-tin layer can be increased by adjusting the composition of the organic glue, the tin content in the lead-tin layer is successfully adjusted by adding cowhide glue into the lead-tin plating solution, the problem of low tin content in the traditional wear-resistant lead-tin plating layer is solved, and the wear-resistant and lubricating ability of the inner hole of the main connecting rod is effectively improved.

[0015] In addition to the above-described objects, features and advantages, the present application has other objects, features and advantages. The present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which form a part of this application, are intended to provide further understanding of the application and are incorporated herein in their entirety, and they show by way of example the preferred embodiments of the application in which: Fig. 1 The step diagram of the piston aero-engine main connecting rod inner hole surface strengthening treatment method provided by the embodiment of the present application; Fig. 2 The structure schematic diagram of the main connecting rod suitable for the piston aero-engine main connecting rod inner hole surface strengthening treatment method provided by the embodiment of the present application; Fig. 3 The structure schematic diagram of the tool fixture in the piston aero-engine main connecting rod inner hole surface strengthening treatment method provided by the embodiment of the present application.

[0017] LEGEND 100, main connecting rod; 101, inner hole; 200, tool fixture; 201, main body frame; 202, insulating bottom plate; 203, fastening screw; 204, anode rod; 205, flexible gasket. DETAILED DESCRIPTION

[0018] The embodiments of the present application will be described in detail below with reference to the accompanying drawings, but the present application can be implemented in various different ways as defined and covered below. The examples of the embodiments are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are used only to explain the present application, and cannot be interpreted as limiting the present application.

[0019] Those skilled in the art can understand that, unless specifically stated, the word "comprise" used in the specification of the present application means that the features, integers, steps, operations, components and / or assemblies are present, but does not exclude the presence or addition of one or more other features, integers, steps, operations, components, assemblies and / or combinations thereof. It should be understood that when we say that a component is "connected" to another component, it can be directly connected to the other component or connected through an intermediate component. The word "and / or" used herein includes all or any unit and all combinations of the associated listed items. The terms "first" and "second" and the like in the specification and claims of the present application are used to distinguish different objects, not to describe a specific order.

[0020] Figs. 1 to 3The piston aero-engine main connecting rod inner hole surface strengthening treatment method provided by the embodiment of the application is used for carrying out lead-tin layer electroplating strengthening treatment on the inner hole surface of the main connecting rod of the piston aero-engine, and compared with the traditional electroplating process, the uniformity of the plating layer and the tin content in the lead-tin layer can be effectively improved, so that the wear-resistant lubricating capacity of the main connecting rod inner hole is enhanced.

[0021] Specifically, the piston aero-engine main connecting rod inner hole surface strengthening treatment method comprises the following steps: Step S100: the main connecting rod 100 is immersed in a water-based oil removal solution for oil removal treatment, and then the main connecting rod 100 is cleaned and dried; S200: waxing treatment is carried out on the non-plating surface of the main connecting rod 100 to form an insulating protective layer; S300: weak etching activation treatment is carried out on the inner hole 101 of the main connecting rod 100; S400: the main connecting rod 100 is hung by using the tool clamp 200, and then the lead-tin plating solution is poured into the inner hole 101 of the main connecting rod 100 for out-of-slot electroplating treatment, the composition of the lead-tin plating solution comprises lead fluoroborate: 110g / L-275g / L, stannous fluoroborate: 30g / L-65g / L, hydroquinone: 1g / L-2g / L, and oxhide glue 1.5g / L-2.0g / L; S500: after the main connecting rod 100 is detached from the tool clamp 200, wax removal and cleaning treatment are carried out, and then it is checked whether the lead-tin layer is qualified, if the main connecting rod 100 is qualified, the main connecting rod 100 is immersed in the rust-proof oil for rust-proof treatment, so that the oil film covers the whole surface; if the main connecting rod 100 is unqualified, the lead-tin layer on the main connecting rod 100 is removed, and then steps S100-S400 are carried out again.

[0022] In the piston aero-engine main connecting rod inner hole surface strengthening treatment method, the main connecting rod 100 is cleaned as a whole first, the subsequent wax coating treatment and electroplating treatment effect are ensured, then the non-plating surface on the main connecting rod 100 is treated with wax coating, an insulating protective layer is formed, compared with the way of sticking protective adhesive tape on the non-plating surface, the protective treatment time can be effectively shortened and the protection effect is improved, the plating leakage problem caused by poor adhesive tape protection is avoided, then the inner hole 101 of the main connecting rod 100 is subjected to weak corrosion activation treatment, the adhesion between the lead-tin layer after electroplating lead-tin and the matrix is improved, then the main connecting rod 100 is fixed by using a tool clamp 200 and the main connecting rod 100 is subjected to out-of-slot electroplating treatment, compared with the traditional in-slot electroplating method, the problem of poor plating layer uniformity can be effectively solved, more importantly, by adding cowhide glue to the lead-tin plating solution, the tin content is effectively improved, in the prior art, for the fluoroborate lead-tin plating system, the main role of the organic glue is to improve the cathode polarization, make the crystal fine, and improve the dispersion ability, and there is no material indicating that the tin content in the electroplated lead-tin layer can be increased by adjusting the composition of the organic glue, the present application successfully adjusts the tin content in the lead-tin layer by adding cowhide glue to the lead-tin plating solution, solves the problem of low tin content in the traditional wear-resistant lead-tin plating layer, and effectively enhances the wear-resistant and lubricating ability of the inner hole 101 of the main connecting rod 100.

[0023] Because the cowhide glue molecule has a large number of polar groups (amino, carboxyl, etc.), it will be preferentially adsorbed on the active site of lead ion reduction in the electroplating process, hindering the reduction reaction of lead ions, and the reduction potential of tin is more negative than that of lead, and the increase of polarization has a more significant inhibitory effect on lead deposition, so adding cowhide glue can increase the tin content in the lead-tin layer. It has been verified through experiments that when the content of cowhide glue in the lead-tin plating solution changes, the change of the tin content in the lead-tin layer formed by electroplating is as shown in Table 1: Table 1 Correspondence between the content of cowhide glue in the lead-tin plating solution and the tin content in the lead-tin layer

[0024] Specifically, when the content of gelatin in the lead-tin plating solution is 0.5 g / L, the tin content in the lead-tin layer can only be controlled in the range of 0.1% to 2% by adjusting the content of other components and the current density during electroplating; when the content of gelatin in the lead-tin plating solution is 1 g / L, the tin content in the lead-tin layer can be controlled in the range of 3% to 6% by adjusting the content of other components and the current density during electroplating; when the content of gelatin in the lead-tin plating solution is 1.5 g / L, the tin content in the lead-tin layer can be controlled in the range of 6% to 8% by adjusting the content of other components and the current density during electroplating; when the content of gelatin in the lead-tin plating solution is 2 g / L, the tin content in the lead-tin layer can be controlled in the range of 10% to 14% by adjusting the content of other components and the current density during electroplating; when the content of gelatin in the lead-tin plating solution is 2.5 g / L, the tin content in the lead-tin layer can be controlled in the range of 16% to 20% by adjusting the content of other components and the current density during electroplating. It can be seen that the tin content in the lead-tin layer can be obviously improved by adjusting the content of gelatin in the lead-tin plating solution, and different tin content requirements can be flexibly met.

[0025] It is worth noting that the mainstream method for regulating the tin content in the lead-tin layer generally controls the ratio of lead fluoroborate to stannous fluoroborate in the plating solution and the current density, but this method has no obvious effect on improving the tin content, and the highest tin content achieved is only about 6%, while the tin content in the wear-resistant lead-tin layer is generally required to be 6% to 10%. By controlling the content of gelatin to be 1.5 g / L to 2.0 g / L, the tin content in the lead-tin layer can be stably controlled in the range of 9% to 10% according to the present application, which effectively improves the wear resistance of the lead-tin layer and meets the high-strength use requirements of the piston aero-engine.

[0026] Further, the components of the lead-tin plating solution also include free fluoroboric acid (HBF4): 50 g / L to 100 g / L. By adding free fluoroboric acid, the hydrolysis of divalent tin can be inhibited, the stability of the plating solution can be maintained, and the passivation of the anode (lead-tin alloy anode) can be inhibited to ensure efficient dissolution of the anode. It should be understood that the remaining components of the lead-tin plating solution are water.

[0027] Please refer to Fig. 2 and Fig. 3 , the tool clamp 200 includes a main frame 201, an insulating bottom plate 202 arranged at the bottom of the main frame 201, and two fastening screws 203 arranged on opposite sides of the main frame 201 and located above the insulating bottom plate 202. The inner cavity of the main frame 201 is used to place the main connecting rod 100 and support the main connecting rod 100 through the insulating bottom plate 202, and the fastening screws 203 are used to tightly abut the upper surface of the main connecting rod 100 and fix the main connecting rod 100 tightly on the insulating bottom plate 202.

[0028] Specifically, the main body frame 201 is adapted to the end structure of the main connecting rod 100 to be electroplated, and the opposite sides of the main body frame 201 are inwardly bent to form a flange structure, and two fastening screws 203 are correspondingly screwed on the two flange structures, so that the fastening screws 203 are arranged in the vertical direction towards the insulating bottom plate 202. After the end structure of the main connecting rod 100 to be electroplated is positioned by the cooperation of the main body frame 201 and the insulating bottom plate 202, the main connecting rod 100 is pressed down by the fastening screws 203, so that the locking and fixing of the main connecting rod 100 are realized, and the inner hole 101 of the main connecting rod 100 can be stably subjected to the out-of-slot electroplating treatment, ensuring the uniformity of the plating layer, and the positioning structure is simple and efficient, and convenient and fast to disassemble and assemble.

[0029] Preferably, the tool clamp 200 further comprises an anode rod 204 adapted to the inner hole 101 of the main connecting rod 100, the diameter of the anode rod 204 gradually increases from both ends to the middle part, and the anode rod 204 is used to connect with the electroplating equipment and is arranged in the inner hole 101 of the main connecting rod 100 for electroplating operation. The special anode rod 204 can further improve the electroplating effect and the uniformity of the plating layer, and since the middle part of the anode plate 204 is consumed faster, the diameter of the anode rod 204 gradually increases from both ends to the middle part, which can improve the use effect and service life of the anode plate 204, and avoid the middle part from being recessed.

[0030] Preferably, the insulating bottom plate 202 is provided with a limiting groove adapted to the end structure of the main connecting rod 100, and the tool clamp 200 further comprises a flexible gasket 205 embedded in the limiting groove and adapted to the edge of the inner hole 101 of the main connecting rod 100. The flexible gasket 205 seals the bottom of the inner hole 101 of the main connecting rod 100, preventing the lead-tin plating solution from flowing out, and the limiting groove and the flexible gasket 205 can also be used for high-precision positioning of the main connecting rod 100.

[0031] Further, in step S400, the out-of-slot electroplating treatment operation specifically includes: using the tool clamp 200 to hang the main connecting rod 100, then connecting the anode rod 204 to the positive pole of the power supply and connecting the main connecting rod 100 to the negative pole of the power supply, pouring the lead-tin plating solution into the inner hole 101 of the main connecting rod 100, and then opening the power supply to perform electroplating operation, with a current density of 1.5A / dm²-2.5A / dm², an electroplating temperature of room temperature, and an electroplating time of 15min-30min, so that the lead-tin layer reaches 20um-25um.

[0032] Preferably, the step S200 specifically comprises: preheating the main connecting rod 100 to 40-60°C, so as to facilitate the full flow of the wax liquid on the surface of the main connecting rod 100 and then solidification, ensure uniform waxing, then immerse the main connecting rod into the wax liquid with a temperature higher than 95°C for waxing treatment, repeat the waxing treatment at least twice, ensure the wax layer has a certain thickness, finally use a low-hardness scraping sheet such as wood sheet or plastic sheet to scrape off the wax layer in the inner hole of the main connecting rod, and use a clean cotton cloth or scouring pad dipped with organic solvent such as gasoline or acetone to carefully scrub the copper sleeve surface of the inner hole 101 of the main connecting rod 100, ensure that the residual wax layer on the surface of the inner hole 101 is removed clean.

[0033] Preferably, after the step S200, it further comprises: immerse the main connecting rod 100 into a flowing cold water tank for cleaning, after cleaning, take out the main connecting rod 100 from the water surface, check the oil removal and cleaning quality, observe whether the water film on the surface of the inner hole 101 of the main connecting rod 100 can be kept continuous for 30s, if not, use a detergent to remove the oil on the surface of the inner hole 101 of the main connecting rod 100, realize enhanced oil removal and decontamination, ensure that the surface of the inner hole 101 of the main connecting rod 100 is cleaned.

[0034] Further, after the main connecting rod 100 is cleaned, the surface of the inner hole 101 is weakly etched and activated, the weak etching solution is 80-350g / L sulfuric acid solution, the weak etching time is 0.5-5min, which can improve the adhesion between the lead-tin plating layer and the substrate.

[0035] Preferably, before the wax removal and cleaning treatment in the step S500, it further comprises: immerse the main connecting rod 100 into a weakly alkaline neutralizing solution for neutralization, avoid the residual acid liquid on the surface of the main connecting rod 100 causing part corrosion, the neutralizing solution comprises 5-30g / L potassium dichromate and 5-30g / L sodium carbonate, neutralize for 1-5min at room temperature, ensure the neutralization treatment effect.

[0036] Preferably, in the step S500, the checking whether the lead-tin layer is qualified specifically comprises: put the main connecting rod 100 into a heating furnace for heating treatment, the heating temperature is 140-200°C, the heating time is ≥2h, then air cool to room temperature, and then check whether the lead-tin layer on the main connecting rod 100 appears blistering and / or peeling phenomenon.

[0037] Currently, the existing lead-tin layer adhesion inspection methods include visual method, grid method, bending method and thermal shock method. The non-destructive inspection methods only include visual method and thermal shock method. The main connecting rod 100 is a component of copper alloy and structural steel. Due to the thermal expansion and cold shrinkage characteristics of different materials, the thermal shock method cannot be used for inspection. Therefore, in the prior art, the lead-tin layer adhesion can only be inspected by the normal temperature visual method. If the plating layer surface has no peeling and blistering, it is determined that the lead-tin layer adhesion is qualified. However, since the maximum working temperature of the inner hole 101 of the main connecting rod 100 of the aero-engine is greater than 100℃ when the aero-engine is working, the visual method cannot prevent the plating layer from peeling off when it cannot withstand high temperature during work.

[0038] In the embodiment, the plating layer adhesion is inspected by the heating inspection method. The main connecting rod 100 is heated at a preset temperature and for a preset time, then air-cooled to room temperature, and then the lead-tin layer of the inner hole 101 of the main connecting rod 100 is inspected to see if there is blistering, peeling and the like. It can be ensured that the qualified lead-tin layer meets the high temperature working requirements of the aero-engine.

[0039] Preferably, before step S100, it also includes chamfering the pin hole on the surface of the inner hole 101 of the main connecting rod 100, the chamfering radius R is 0.4mm-0.8mm, and then smoothing the chamfering structure to reduce the sharp end effect of the pin hole during lead-tin plating. Specifically, there are two pin holes in the surface of the inner hole 101 of the main connecting rod 100. Due to the sharp end effect of electroplating, there is a rough plating layer at the chamfering part of the pin hole, which causes the lead-tin layer at this part to wear the most. The present application increases the chamfering of the pin hole, so that the chamfering radius R is 0.4mm-0.8mm, and before the bronze bushing of the inner hole 101 of the main connecting rod 100 is bored, a triangular scraper is used to smooth the pin hole, effectively reducing the roughness of the lead-tin layer at this part and reducing the risk of scratching and grinding.

[0040] Preferably, after step S500, it also includes smearing aviation oil on the fitting part of the inner hole 101 of the main connecting rod 100 and the crankshaft (not shown in the figure, the same below) before assembling the main connecting rod 100 and the crankshaft, to avoid the problem that the insufficient lubrication between the main connecting rod 100 and the crankshaft causes excessive instantaneous circumferential friction and damages the lead-tin layer when the aero-engine is started for the first time.

[0041] Since the oil has not flowed through the connecting rod and crankshaft gap when the aero-engine is started for the first time, the main connecting rod bushing and the crankshaft gap are not sufficiently lubricated, which causes the lead-tin layer to have excessive load when the aero-engine is started, affecting the service life. The present application effectively improves the lubrication effect between the main connecting rod 100 and the crankshaft by smearing 4060 aviation oil before assembling the main connecting rod 100, thereby avoiding the above problems.

[0042] Further, the step S100 specifically comprises: immersing the main connecting rod 100 as a whole into a special water-based oil removal solution, and turning on an ultrasonic device, and the water-based oil removal time is greater than 5 minutes; if the oil removal time is not enough, the wax cannot be effectively attached to the non-plating surface of the part after the wax is air-dried, resulting in non-plating of the part. After the oil removal treatment, the main connecting rod 100 is immersed into a flowing water washing tank for cleaning, and clean compressed air or hot air is used to dry the surface of the main connecting rod 100 after water washing.

[0043] The preferred embodiments of the present application have been described above with the aid of drawing figures, and are not intended to limit the present application, and for those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of surface hardening the bore of a piston aeroengine main connecting rod, characterised in that, The method comprises the following steps: S100: the main connecting rod is immersed in a water-based oil removal solution for oil removal treatment, and then the main connecting rod is cleaned and dried; S200: the non-plating surface of the main connecting rod is subjected to waxing treatment to form an insulating protective layer; S300: the inner hole of the main connecting rod is subjected to weak corrosion activation treatment; S400: the main connecting rod is hung by using a tool clamp, and then a lead-tin plating solution is poured into the inner hole of the main connecting rod for slot-out electroplating treatment, the composition of the lead-tin plating solution comprises 110 g / L-275 g / L of lead fluoroborate, 30 g / L-65 g / L of stannous fluoroborate, 1 g / L-2 g / L of hydroquinone, and 1.5 g / L-2.0 g / L of gelatin; S500: after the main connecting rod is removed from the tool clamp, the main connecting rod is subjected to wax removal and cleaning treatment, and then it is checked whether the lead-tin layer is qualified, if the lead-tin layer is qualified, the main connecting rod is immersed in a rust-proof oil for rust-proof treatment so that the whole surface of the main connecting rod is covered with an oil film, and if the lead-tin layer is unqualified, the lead-tin layer on the main connecting rod is removed, and then the steps S100-S400 are performed again.

2. The method of claim 1, wherein, The tool clamp comprises a main frame, an insulating bottom plate arranged at the bottom of the main frame, and two fastening screws arranged on opposite sides of the main frame and above the insulating bottom plate, an inner cavity of the main frame is used for placing the main connecting rod and supporting the main connecting rod through the insulating bottom plate, and the fastening screws are used for abutting against the upper surface of the main connecting rod and fixing the main connecting rod on the insulating bottom plate.

3. The method of claim 2, wherein, The tool clamp further comprises an anode rod matched with the inner hole of the main connecting rod, the diameter of the anode rod gradually increases from the two ends to the middle part, and the anode rod is used for being connected with an electroplating device and penetrating into the inner hole of the main connecting rod for electroplating operation.

4. The method of claim 2, wherein, The insulating bottom plate is provided with a limiting groove matched with the end structure of the main connecting rod, and the tool clamp further comprises a flexible gasket embedded in the limiting groove and matched with the edge of the inner hole of the main connecting rod.

5. The method of treating the bore surface of a piston aeroengine main rod according to claim 1, characterized in that, The step S200 specifically comprises: preheating the main connecting rod to 40-60 DEG C, then immersing the main connecting rod in a wax liquid with a temperature higher than 95 DEG C for waxing treatment, repeating the waxing treatment at least twice, and finally scraping off the wax layer in the inner hole of the main connecting rod and cleaning the inner hole surface of the main connecting rod by using an organic solvent.

6. The method of treating the bore surface of a piston aeroengine main rod according to claim 5, characterized in that, After the step S200, the main connecting rod is further immersed in a flowing cold water tank for cleaning, the main connecting rod is taken out of the water surface after cleaning, the oil removal and cleaning quality are checked, and it is observed whether the water film on the inner hole surface of the main connecting rod can be continuously maintained for 30 s, if not, the inner hole surface of the main connecting rod is subjected to oil removal treatment by using a detergent powder.

7. The method of treating the bore surface of a piston aeroengine main rod according to claim 1, characterized in that, Before the wax removal and cleaning treatment in the step S500, the main connecting rod is further immersed in a weakly alkaline neutralizing solution for neutralization, so as to avoid the problem of part corrosion caused by residual acid liquid on the surface of the main connecting rod, and the neutralizing solution comprises 5 g / L-30 g / L of potassium dichromate and 5 g / L-30 g / L of sodium carbonate, and the neutralization is performed at room temperature for 1-5 min.

8. The method of treating the bore surface of a piston aeroengine main rod according to claim 1, characterized in that, The step S500 includes: putting the main connecting rod into a heating furnace for heating treatment, the heating temperature is 140-200 ℃, the heating time is greater than or equal to 2 hours, then air cooling to room temperature, and then checking whether the lead-tin layer on the main connecting rod appears bubbling and / or peeling phenomenon.

9. The method of treating the bore surface of a piston aeroengine main rod according to claim 1, characterized in that, Before the step S100, the method further includes: chamfering the pin hole on the inner hole surface of the main connecting rod, the chamfering radius R is 0.4-0.8 mm, then smoothing the chamfering structure, and reducing the sharp end effect of the pin hole during lead-tin plating.

10. The method of treating the bore surface of a piston aeroengine main rod according to claim 1, characterized in that, After the step S500, the method further includes: smearing aviation oil on the matching part of the inner hole of the main connecting rod and the crankshaft, then assembling the main connecting rod and the crankshaft, avoiding the problem that the insufficient lubrication between the main connecting rod and the crankshaft during the first start of the aero-engine causes the instantaneous circumferential friction to be too large and damages the lead-tin layer.

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