Method for repairing damage to inner wall of beryllium bronze piston part

Abstract

The invention relates to the technical field of remanufacturing, in particular to a beryllium bronze piston part inner wall damage repairing method which comprises the following specific steps: S1, defect inspection; s2, preparing an electrode bar; s3, electric spark coating repair is carried out; s4, remelting by a cold welding machine; s5, heat treatment; s6, honing an inner hole; s7, repairing and verifying; according to the method, a method of electric spark coating repairing and cold welding composite repairing is adopted, the problem that an electric spark coating repairing layer is not compact is solved, the problem that wire feeding is difficult in the cold welding inner hole repairing process is solved, the problem that an overlong electrode bar rotating at a high speed shakes in the electric spark coating repairing process is solved by adopting the specially-made electrode bar, and the welding quality is improved. The metallographic phase of the repair layer does not have cracks and incomplete fusion defects, the repair layer is metallurgically bonded with the substrate, and the hardness of the repair layer reaches more than 90% of that of the substrate of the plate.

Description

Technical Field

[0001] The present invention relates to the technical field of remanufacturing, and specifically to a method for repairing the inner wall damage of a beryllium bronze piston part. Background Art

[0002] Beryllium bronze has excellent properties such as high strength, hardness, wear resistance, corrosion resistance, and elastic limit, and is widely used in the fields of aerospace and electronics.

[0003] The beryllium bronze piston part is used for the telescopic actuating component of an aviation equipment to transmit hydraulic power. After long-term service, the inner wall of this part is worn and damaged by repeated friction of the plunger.

[0004] The inner diameter of the beryllium bronze piston part is 20 - 30 mm, and it cannot be repaired by conventional means. For example, when using the laser inner hole repair process, limited by the technical bottleneck of the miniaturization of the inner hole laser head, this type of equipment can only extend into inner holes above 30 mm. For beryllium bronze piston parts with an aperture less than 30 mm, the laser inner hole repair equipment has no repair ability. When using conventional inner hole welding, the beryllium on the surface of beryllium bronze is prone to react with oxygen to generate beryllium oxide with high volatility, which affects the welding forming quality, generates a large number of defects, and the wire feeding for inner hole welding is also very inconvenient. In addition, a large heat input can cause the part to deform and become unusable. When using the electrospark cladding process, the formed repair layer has a large number of defects and cannot meet the use requirements.

[0005] There is no relevant research on the repair of the inner wall damage of beryllium bronze piston parts. Summary of the Invention

[0006] In order to solve the above problems, the present invention proposes a method for repairing the inner wall damage of a beryllium bronze piston part.

[0007] A method for repairing the inner wall damage of a beryllium bronze piston part, the specific steps are as follows:

[0008] S1. Defect inspection:

[0009] Visually inspect the beryllium bronze piston part to find the damaged part. There is a small hole at the bottom of the beryllium bronze piston part;

[0010] S2. Preparation of the electrode rod;

[0011] Heat-treat the hot-rolled QBe2 beryllium bronze rod, and prepare the electrode rod by turning the heat-treated rod. The electrode rod consists of a coating section, a middle diameter fixing section, a thick diameter fixing section, and a clamping section;

[0012] S3. Electrospark cladding repair:

[0013] Clamp the clamping section of the prepared electrode rod on the welding torch of the electro-discharge surfacing welding machine, and use the electro-discharge surfacing welding machine to repair the damaged part of the inner hole by electro-discharge coating. Measure the wall thickness of the repaired part with an external groove vernier caliper. When the wall thickness of the repaired part is greater than the part thickness by 100 μm, stop the electro-discharge coating repair;

[0014] S4. Cold welding remelting:

[0015] Use a cold welding machine. Insert the welding torch of the cold welding machine into the damaged part of the inner wall repaired by electro-discharge coating, and remelt the damaged part to obtain a dense repair layer;

[0016] S5. Heat treatment:

[0017] Put the part processed in step S4 into a vacuum heat treatment furnace for heat treatment. After evacuating to below 1 Pa, fill it with argon to 0.1 MPa for heat treatment, and take it out after cooling to room temperature in the furnace;

[0018] S6. Inner hole honing:

[0019] Hone the inner hole to remove the protruding part at the repaired position of the inner wall;

[0020] S7. Repair verification:

[0021] Use a plate made of the same material and in the same heat treatment state as the beryllium bronze piston part. After the electro-discharge coating repair in step S3 and the cold welding remelting in step S4, detect the metallography and hardness of the repaired part:

[0022] a. If no cracks and lack of fusion defects are found in the metallography, observe that the repair layer and the plate substrate are metallurgically bonded, and detect the hardness of the repair layer and the plate substrate;

[0023] b. If the hardness of the repair layer reaches 90% of the plate substrate, it is determined that the beryllium bronze piston part repaired in steps 1 to 6 is qualified.

[0024] The heat treatment process of step S2 is: keep warm at 770 °C - 790 °C for 1 - 2 h and then water-cool, and then keep warm at 310 °C - 320 °C for 2 - 4 h and air-cool.

[0025] The electrode rod in step S2 is a rotary body. The diameter of the coating section is 2 - 4 mm, the diameter of the middle diameter fixed section is 4.5 - 6.5 mm, the diameter of the thick diameter fixed section is 6 - 8 mm, and the diameter of the clamping section is 3 - 6 mm. The transition between each section is a 45° chamfer.

[0026] The process of the electro-discharge coating repair in step S3 is that the rotation speed of the electric shock rod is 1000 - 2500 r / min, the power is 500 W - 1300 W, the voltage is 60 V - 80 V, the frequency is 280 - 500 HZ, and the argon flow rate of the electro-discharge coating equipment is 5 - 8 L / min.

[0027] Before electro-discharge cladding, the argon gas pipe provides argon gas for no less than 20 s, and during the electro-discharge cladding process, argon gas is continuously provided in the argon gas pipe.

[0028] After the argon gas protection environment is formed in step S3, the argon gas flow rate in the argon gas pipe is 4 - 6 L / min.

[0029] During the remelting in step S4, the welding current parameter is 5 - 15 A and the welding time parameter is 70 - 90 ms.

[0030] The heat treatment temperature in step S5 is 280 - 300 °C and the heat preservation time is 3 - 4 h.

[0031] The beneficial effects of the present invention are as follows: Compared with the prior art:

[0032] 1. The electrode rod is prepared by turning after heat treatment of the QBe2 beryllium bronze rod, which improves the strength of the electrode rod material, avoids the plastic deformation of the electrode rod caused by the centrifugal force generated by the high-speed rotation of the electrode rod during the electro-discharge cladding repair process, and reduces the jitter of the electrode rod caused by the high-speed rotation of the electrode rod during the electro-discharge cladding repair process; In addition, the electrode rod is designed as a cylinder with a variable cross-sectional diameter. In particular, the diameters of the coating section, the middle-diameter fixed section, and the thick-diameter fixed section increase in sequence, which will increase the structural stability of the long electrode rod during the high-speed rotation in the electro-discharge cladding repair process and reduce the jitter of the electrode rod; Setting the diameter of the coating section to be the smallest will reduce the contact area between the electrode rod and the damaged area during the electro-discharge cladding repair process, so as to facilitate the precise repair of the damaged area.

[0033] 2. Before electro-discharge cladding repair, argon gas is provided through the argon gas pipe into the inner cavity through the small hole at the bottom of the beryllium bronze piston part to form an inert gas protection environment, and argon gas is continuously provided in the argon gas pipe during the electro-discharge cladding process, reducing the oxidation of the copper alloy during the electro-discharge cladding process; The electro-discharge cladding repair can prefabricate a repair layer that is tightly combined with the part substrate.

[0034] 3. The cold welding machine has a small heat input during remelting, will not cause macroscopic deformation of the beryllium bronze piston part, and during the remelting process, a solid phase → liquid phase → solid phase transformation occurs, which can eliminate cracks and lack of fusion defects formed during the electro-discharge cladding repair process, reduce porosity defects, and form a metallurgical bond between the repair layer and the part substrate.

[0035] 4. Vacuum heat treatment can avoid the oxidation of the surface of the beryllium bronze piston part. At this heat treatment temperature, it will not cause changes in the structure and properties of the beryllium bronze piston part substrate, and can improve the hardness of the material in the repair area.

[0036] 5. The method of electro-discharge cladding repair + cold welding composite repair is adopted, which not only solves the problem of non-dense electro-discharge cladding repair layer, but also solves the problem of difficult wire feeding during the cold welding inner hole repair process.

[0037] 6. Verify the repair effect through test pieces, avoiding damage to the repaired parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below in conjunction with the drawings and embodiments.

[0039] Figure 1 Schematic structural diagram of a damaged beryllium bronze piston part of the present invention;

[0040] Figure 2 Schematic structural diagram of the electrode rod of the present invention;

[0041] Figure 3 Schematic structural diagram of the electric spark cladding repair of the present invention;

[0042] Figure 4 Schematic diagram of the remelting of the cold welding machine of the present invention;

[0043] Reference numerals: 1. Beryllium bronze piston part; 2. Damaged part; 3. Small hole; 4. Electrode rod; 5. Coating section; 6. Medium-diameter fixing section; 7. Thick-diameter fixing section; 8. Clamping section; 9. Argon gas pipe; 10. Electric spark surfacing welding torch; 11. Cold welding machine torch. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below.

[0045] As Figures 1 to 4 shown, a method for repairing the inner wall damage of a beryllium bronze piston part specifically comprises the following steps:

[0046] S1. Defect inspection:

[0047] Visually inspect the beryllium bronze piston part 1 to find the damaged part 2. There is a small hole 3 at the bottom of the beryllium bronze piston part 1;

[0048] S2. Preparation of the electrode rod;

[0049] Heat-treat the hot-rolled QBe2 beryllium bronze bar, and prepare the electrode rod 4 by turning the heat-treated bar. The electrode rod 4 consists of a coating section 5, a medium-diameter fixing section 6, a thick-diameter fixing section 7, and a clamping section 8;

[0050] Heat-treating the QBe2 beryllium bronze bar will increase the strength of the prepared electrode rod, avoid plastic deformation of the electrode rod caused by the centrifugal force generated by the high-speed rotation of the electrode rod during the electric spark cladding repair process, and reduce the jitter of the electrode rod caused by the high-speed rotation of the electrode rod during the electric spark cladding repair process;

[0051] An electrode rod with a variable cross-sectional diameter is adopted. In particular, the diameters of the coating section 5, the middle-diameter fixed section 6, and the thick-diameter fixed section 7 increase in sequence, which will increase the structural stability of the high-speed rotation of the electrode rod during the electrospark coating repair process and reduce the jitter of the electrode rod.

[0052] Setting the diameter of the coating section 5 to be the smallest will reduce the contact area between the electrode rod and the damaged area during the electrospark coating repair process, so as to facilitate the precise repair of the damaged area.

[0053] S3. Electrospark coating repair:

[0054] An argon gas pipe 9 is externally connected at the position of the small hole 3, and argon gas is transported by the argon gas pipe 9. The argon gas enters the inner cavity of the beryllium bronze piston part 1 through the small hole 3 to form an argon gas protection environment. The argon gas pipe 9 provides argon gas for 30 s before the electrospark coating. During the electrospark coating process, the argon gas pipe 9 continuously provides argon gas, and the argon gas flow rate in the argon gas pipe 9 is 6 L / min. The clamping section 8 of the prepared electrode rod is clamped on the welding torch 10 of the electrospark surfacing welding machine, and the electrospark surfacing welding machine is used to repair the damaged part 2 of the inner hole by electrospark coating.

[0055] An external groove vernier caliper is used to measure the wall thickness of the repaired part. When the measured wall thickness of the repaired part is greater than the part thickness by 110 μm, the electrospark coating repair is stopped.

[0056] Before the electrospark coating repair, argon gas is provided through the argon gas pipe into the inner cavity through the small hole at the bottom of the beryllium bronze piston part to form an inert gas protection environment, and the argon gas pipe continuously provides argon gas during the electrospark cladding process, which will better provide inert gas protection for the repair process and reduce the oxidation of the copper alloy during the repair process. The electrospark coating repair can prefabricate a repair layer that is tightly combined with the part substrate.

[0057] S4. Cold welding machine remelting:

[0058] A cold welding machine is adopted. The welding torch 11 of the cold welding machine is inserted into the inner wall damaged part 2 repaired by electrospark coating to remelt the damaged part 2 to obtain a dense repair layer.

[0059] The heat input during the cold welding machine remelting is small and will not cause macroscopic deformation of the beryllium bronze piston part. Moreover, during the remelting process, a solid phase → liquid phase → solid phase transformation occurs, which can eliminate the cracks and lack of fusion defects formed during the electrospark coating repair process, reduce the porosity defects, and make the repair layer form a metallurgical bond with the part substrate.

[0060] S5. Heat treatment:

[0061] The parts processed in step S4 are put into a vacuum heat treatment furnace for heat treatment. After evacuating to below 1 Pa, argon is filled to 0.1 MPa. The heat treatment temperature is 300 °C, the holding time is 3 h, and they are taken out after furnace cooling to room temperature. Vacuum heat treatment can avoid the oxidation of the surface of the beryllium bronze piston parts. At this heat treatment temperature, it will not cause changes in the hardness of the matrix of the beryllium bronze piston parts, and can improve the hardness of the repaired area material;

[0062] S6. Inner hole honing:

[0063] Hone the inner hole to remove the protruding parts at the repaired position on the inner wall to meet the dimensional usage requirements;

[0064] S7. Repair verification:

[0065] Use plates of the same material and the same heat treatment state as the beryllium bronze piston parts. The plate material is QBe2, and the heat treatment system is holding at 780 °C for 2 h and water cooling, followed by holding at 320 °C for 3 h and air cooling. After the same process treatment as step 3 electric spark cladding and step 4 cold welding remelting, the metallography and hardness of the repaired part are detected. No cracks and lack of fusion defects are seen in the metallography, and it is observed that the repaired layer and the plate matrix are metallurgically bonded. Detect the hardness of the repaired layer and the plate matrix. The hardness of the repaired layer is 361 HV, 365 HV, 367 HV, 372 HV, 368 HV, and the matrix hardness is 380 HV, 384 HV, 387 HV, 385 HV, 384 HV. The average hardness of the repaired layer reaches 95.9% of the average hardness of the plate matrix, and it is determined that the beryllium bronze piston parts repaired in steps 1 to 6 are qualified. The heat treatment process of step S2 is: holding at 780 °C for 2 h and water cooling, followed by holding at 320 °C for 3 h and air cooling.

[0066] The electrode rod 4 in step S2 is a rotating body, where the diameter of the coating section 5 is 3 mm, the diameter of the middle diameter fixed section 6 is 5 mm, the diameter of the thick diameter fixed section 7 is 7 mm, and the diameter of the clamping section 8 is 5 mm. The transition between each section is with a 45° chamfer.

[0067] The process of electric spark cladding repair in step S3 is that the rotation speed of the electric shock rod is 1500 r / min, the power is 950 W, the voltage is 70 V, the frequency is 400 HZ, and the argon flow rate of the electric spark cladding equipment is 7 L / min.

[0068] Continuously supplying argon in the argon pipe 9 during the electric spark cladding process will better provide inert gas protection for the repair process and reduce the oxidation of the copper alloy during the repair process. Electric spark cladding repair can prefabricate a repair layer that is tightly bonded to the part matrix.

[0069] During the remelting in step S4, the welding current parameter is 10 A and the welding time parameter is 80 ms. The cold welder has a small heat input during remelting, which will not cause macroscopic deformation of the beryllium bronze piston parts. Moreover, during the remelting process, the transformation of solid phase → liquid phase → solid phase occurs, which can eliminate the cracks and lack of fusion defects formed during the electrospark cladding repair process, reduce the porosity defects, and enable the repair layer to form a metallurgical bond with the part substrate.

[0070] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for repairing damage to the inner wall of a beryllium bronze piston part, characterized in that: The specific steps are as follows: S1. Defect inspection: Visually inspect the beryllium bronze piston part (1) to find a damaged part (2), and a small hole (3) is present at the bottom of the beryllium bronze piston part (1); S2, electrode rod preparation; A hot-rolled QBe2 beryllium bronze bar is heat-treated, and the heat-treated bar is turned to prepare an electrode bar (4), wherein the electrode bar (4) comprises a coating section (5), a medium diameter fixing section (6), a thick diameter fixing section (7), and a clamping section (8); S3, Electric spark coating repair: An argon pipe (9) is externally connected to the position of the small hole (3), and argon is transported by the argon pipe (9). The argon enters the inner cavity of the beryllium bronze piston part (1) through the small hole (3), forming an argon protection environment; the prepared electrode rod clamping section (8) is clamped on the welding gun (10) of the electric spark cladding welding machine, and the electric spark cladding welding machine is used to perform electric spark coating repair on the damaged part (2) of the inner hole, and the wall thickness of the repaired part is measured by an external groove vernier caliper. When the wall thickness of the repaired part is greater than 100 μm of the part thickness, the electric spark coating repair is stopped; S4, cold welding machine remelting: Using a cold welding machine, inserting a cold welding machine torch (11) into the damaged portion (2) of the inner wall that has been repaired by electric spark coating, remelting the damaged portion (2) to obtain a dense repair layer; S5. Heat treatment: The parts processed in step S4 are placed in a vacuum heat treatment furnace for heat treatment. After the parts are evacuated to below 1 Pa, argon gas is filled to 0.1 MPa for heat treatment. The parts are taken out after the furnace is cooled to room temperature. S6, inner hole honing: Honing the inner hole to remove the protrusions at the repair location of the inner wall; S7. Repair verification: Using a plate made of the same material and heat-treated state as the beryllium bronze piston part, after the repair by electric spark coating in step S3 and remelting by cold welding in step S4, the metallographic structure and hardness of the repaired part are tested: a. If no cracks or unfused defects are found in the metallographic structure, observe that the repair layer and the plate substrate are metallurgically bonded, and test the hardness of the repair layer and the plate substrate; b. If the hardness of the repaired layer reaches 90% of the plate substrate, the beryllium bronze piston parts repaired through steps 1 to 6 are deemed qualified.

2. A method for repairing inner wall damage of a beryllium bronze piston part according to claim 1, characterized in that: The heat treatment process of step S2 is: keeping at 770°C to 790°C for 1 to 2 hours and water cooling, followed by keeping at 310°C to 320°C for 2 to 4 hours and air cooling.

3. A method for repairing inner wall damage of a beryllium bronze piston part according to claim 1, characterized in that: The electrode rod (4) in step S2 is a rotating body, wherein the diameter of the coating section (5) is 2 to 4 mm, the diameter of the medium diameter fixed section (6) is 4.5 to 6.5 mm, the diameter of the large diameter fixed section (7) is 6 to 8 mm, and the diameter of the clamping section (8) is 3 to 6 mm, and each section has a chamfer transition of 45°.

4. A method for repairing inner wall damage of a beryllium bronze piston part according to claim 1, characterized in that: The process of the electrospark coating repair in step S3 is as follows: the electric rod speed is 1000-2500r / min, the power is 500W-1300W, the voltage is 60V-80V, the frequency is 280-500HZ, and the argon flow rate of the electrospark coating equipment is 5-8L / min.

5. A method for repairing inner wall damage of a beryllium bronze piston part according to claim 4, characterized in that: The argon gas pipe (9) provides argon gas for no less than 20 seconds before the electrospark coating, and the argon gas pipe (9) continuously provides argon gas during the electrospark coating process.

6. A method for repairing inner wall damage of a beryllium bronze piston part according to claim 5, characterized in that: After the argon protective environment is formed in step S3, the argon flow rate in the argon pipe (9) is 4 to 6 L / min.

7. A method for repairing inner wall damage of a beryllium bronze piston part according to claim 1, characterized in that: During the remelting in step S4, the welding current parameter is 5-15A, and the welding time parameter is 70-90ms.

8. The method for repairing inner wall damage of a beryllium bronze piston part according to claim 1, characterized in that: The heat treatment temperature of step S5 is 280-300° C., and the heat preservation time is 3-4 hours.

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