Method for locally plating chromium on metal surface of part

Abstract

According to the method for locally plating the chromium on the metal surface of the part, the metal surface of the part comprises a surface B needing to be plated with the chromium and a surface A which is adjacent to the surface B and does not need to be plated with the chromium, and a groove is formed between the surface B and the surface A to separate the surface B and the surface A; before electroplating, a non-ferrous metal sheet is tightly bonded to the A face through insulation paste so that the A face can be shielded by the non-ferrous metal sheet, and insulation protection is conducted on the other non-plated faces needing to be protected through insulation protection materials; and the surface B is soaked in electroplating liquid, and electroplating treatment is conducted after electrification. According to the method, non-plating surface protection is achieved, the current density distribution condition of the chromium plating surface is improved, the obtained chromium plating surface is smooth and fine, and the edge is free of the wavy defect; compared with a traditional insulating material, the tool clamp is low in cost, easy and convenient to operate and high in manufacturing qualification rate.

Description

Technical Field

[0001] The invention relates to a parts processing technology, in particular to a method for local chromium plating on a metal surface. Background Art

[0002] The hard chrome plating layer has a high hardness (usually >HV750), which can significantly improve the wear resistance of the part surface and reduce wear caused by frequent deformation or friction. It is suitable for high-load, high-frequency vibration applications, such as aircraft engine elastic components and automotive shock absorbers. In such applications, to maintain the characteristics of the substrate and avoid affecting the performance of non-working areas, only the parts that need to withstand friction and wear are locally electroplated with hard chrome, such as the elastic support bearing assembly surface, shock absorber piston rod, cylinder expansion ring, etc. The thickness of the electroplated hard chrome layer after grinding is usually 20μm to 50μm.

[0003] When hard chrome is applied to a part's surface, insulation protection is typically applied to all surfaces except the chrome-plated surface. Then, anodes are assembled and the entire part is immersed in the hard chrome plating solution for hard chrome plating. The process generally follows: pre-drying inspection → stress relief → degreasing with an organic solvent → protective mounting → manual degreasing → hard chrome plating → cleaning → cleaning → dehydrogenation → rust prevention. For parts with grooves at the edges of the chrome-plated surface and requiring a thicker chrome layer (greater than 500μm) before grinding, the "edge effect" can easily lead to unevenness such as thickened edges and burrs, reducing product qualification rates. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for local chromium plating on the metal surface of a part with a smooth coating.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows: a method for locally chrome plating a metal surface of a part, wherein the metal surface of the part includes a B surface to be chrome-plated and an A surface adjacent to the B surface that does not need to be chrome-plated, wherein a groove is formed between the B surface and the A surface to separate the two surfaces, and the groove serves as a transition zone that can be chrome-plated or not;

[0006] Before electroplating, insulating glue is used to tightly adhere the non-ferrous metal sheet to surface A so that surface A is shielded by the non-ferrous metal sheet, and insulating protection material is used to insulate and protect the remaining non-plated surfaces that need protection; after the parts enter the electroplating tank, the surface B is immersed in the electroplating solution; a current of 0.2 to 0.8 times the working current is used for treatment for 20 seconds to 60 seconds; then a current of 1 to 2.5 times the working current is used for treatment for 40 seconds to 160 seconds; the current is gradually reduced to the working current, and the electroplating process is carried out at the working current for 4 to 8 hours; then the current is increased by 2% to 15% per hour until the current reaches 1.1 to 1.6 times the working current.

[0007] Preferably, the metal surface material of the part is low alloy medium carbon steel or austenitic stainless steel.

[0008] Preferably, the non-ferrous metal sheet is lead sheet and / or aluminum sheet.

[0009] Preferably, the thickness of the non-ferrous metal sheet is 0.5 mm to 0.8 mm.

[0010] Preferably, the insulating protective material includes one or more of plastic tape, high-temperature wax, electroplating protective glue, and insulating paint.

[0011] Preferably, the soaking time is 3 minutes to 8 minutes.

[0012] Preferably, the anode device for electroplating uses a lead-antimony alloy.

[0013] Preferably, the electroplating solution comprises: 200 g / L to 250 g / L of chromic anhydride and 2 g / L to 2.5 g / L of sulfuric acid.

[0014] Preferably, the temperature of the electroplating solution is 50°C to 60°C.

[0015] Preferably, before the part enters the electroplating tank, the state of surface B is that the water film on the surface remains intact for more than 30 seconds after washing.

[0016] Preferably, the parts are also heated to relieve stress prior to electroplating.

[0017] Preferably, after the part enters the electroplating tank, the B side is immersed in the electroplating solution; treated with a current of 0.3 to 0.6 times the working current for 30s to 40s; then treated with a current of 1.05 to 2 times the working current for 60s to 120s; the current is gradually reduced to the working current, and the electroplating process is carried out at the working current for 5.5 to 7h; then the current is increased by 3% to 10% per hour until the current reaches 1.2 to 1.5 times the working current.

[0018] Preferably, the groove between surface A and surface B is a grinding wheel overtravel groove.

[0019] Preferably, the part is a bearing elastic support, and surface B is the inner hole surface of the part.

[0020] More preferably, surface A is an adjacent surface of surface B on a side close to the rib.

[0021] More preferably, the part is an elastic support of a turboshaft aircraft engine compressor bearing.

[0022] The present invention has the following beneficial effects:

[0023] (1) The present invention not only achieves non-plated surface protection, but also improves the current density distribution of the chrome-plated surface. The obtained chrome-plated surface is smooth and delicate, with no "wavy" defects at the edge;

[0024] (2) Compared with the use of traditional insulating materials, the fixture of the present invention is low-cost, easy to operate, and has a high manufacturing qualification rate.

[0025] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 This is a photo of the actual coating effect after partial chrome plating using existing technology;

[0028] Figure 2 This is the actual effect of the coating after local chrome plating using existing technology and grinding;

[0029] Figure 3 This is a photo of the actual coating effect obtained by partial chrome plating in Example 1 of the present invention;

[0030] Figure 4 This is a photo of the actual coating effect obtained by partial chrome plating in Example 2 of the present invention;

[0031] Figure 5 This is a photo of the actual coating effect obtained by partial chrome plating in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, scheme and beneficial technology of the present invention clearer, the present invention is further described in detail below with reference to the embodiments and drawings. It should be noted that the embodiments described in this specification are only for explaining the present invention and are not intended to limit the present invention.

[0033] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and similarly, any upper limit can be combined with any other upper limit to form an unspecified range. In addition, although not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value can serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0034] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and the "multiple" in "one or more" means two or more, and the "multiple" in "one or more" means two or more.

[0035] An embodiment of the present invention provides a method for partially chrome plating a metal surface of a part, wherein the metal surface of the part includes a B surface to be chrome-plated and an A surface adjacent to the B surface that does not require chrome plating. A groove is formed between the B surface and the A surface to separate the two surfaces. The groove is a transition zone that can be chrome-plated or not.

[0036] Before electroplating, insulating glue is used to tightly adhere the non-ferrous metal sheet to surface A so that surface A is shielded by the non-ferrous metal sheet, and insulating protection material is used to insulate and protect the remaining non-plated surfaces that need protection; after the parts enter the electroplating tank, the surface B is immersed in the electroplating solution; a current of 0.2 to 0.8 times the working current is used for treatment for 20 seconds to 60 seconds; then a current of 1 to 2.5 times the working current is used for treatment for 40 seconds to 160 seconds; the current is gradually reduced to the working current, and the electroplating process is carried out at the working current for 4 to 8 hours; then the current is increased by 2% to 15% per hour until the current reaches 1.1 to 1.6 times the working current.

[0037] like Figure 1 As shown in the figure, for parts with grooves at the edge of the chrome-plated surface, the chrome layer at the edge after plating appears "wavy". The thickness of the coating at the trough is thin, and it is easy to have local unground phenomenon after grinding. The stress is concentrated at the peak, and it is easy to cause local collapse of the chrome layer during grinding. Figure 2 As shown in the figure, the chrome-plated surface has localized chipping at both ends. The upper end chipped, leaving the remaining plating unground, while the lower edge has "jagged" burrs caused by the chipping. Grinding this "wavy" chrome surface is difficult, resulting in frequent chrome layer repairs and low manufacturing yields. This is due to the high cathode current density at the edge of the chrome-plated surface, adjacent to the groove, and the proximity of this area to the transition zone, which causes large fluctuations in the growth rate of the chrome layer.

[0038] In the embodiment of the present invention, the non-ferrous metal sheet not only replaces the traditional insulating material to play a shielding role; as the chromium layer grows, the chromium layer in the groove area contacts and conducts with the non-ferrous metal sheet, so that the non-ferrous metal sheet forms an auxiliary cathode, thereby improving the current density distribution on the chromium plating surface; on the other hand, as the chromium layer deposited on the non-ferrous metal sheet increases, the area of ​​the non-ferrous metal sheet serving as the auxiliary cathode increases, thereby increasing the working current to offset the adverse effects caused by the excessive area of ​​the auxiliary cathode; ultimately, a smooth, delicate plating layer with no "wavy" edges is obtained.

[0039] The operating current is set conventionally based on the part's condition and plating requirements; the plating time is set conventionally based on the target coating thickness. Once the chromium coating reaches the required thickness, the part is removed from the tank, all protective devices are removed, and standard cleaning, hydrogen removal, and rust prevention procedures are performed.

[0040] The method for local chrome plating on a metal surface of a part provided by the embodiment of the present invention has the following advantages:

[0041] (1) The embodiment of the present invention not only achieves non-plated surface protection, but also improves the current density distribution of the chrome-plated surface. The obtained chrome-plated surface is smooth and delicate, with no "wavy" defects at the edge.

[0042] (2) Compared with the use of traditional insulating materials, the fixture has low cost, easy operation and high manufacturing qualification rate.

[0043] In an embodiment of the present invention, the metal surface material of the part is low alloy medium carbon steel or austenitic stainless steel.

[0044] In an embodiment of the present invention, the non-ferrous metal sheet is lead and / or aluminum. Lead and aluminum have excellent corrosion resistance and good plasticity, making them suitable for thin sheeting for use in the present invention. Other non-chrome-plated surfaces can also be shielded using the non-ferrous metal sheet to prevent them from being affected by electroplating.

[0045] In an embodiment of the present invention, the thickness of the non-ferrous metal sheet is 0.5 mm to 0.8 mm.

[0046] In an embodiment of the present invention, the insulating protective material includes one or more of plastic tape, high-temperature wax, electroplating protective glue, and insulating paint.

[0047] In some embodiments of the present invention, before performing insulation protection, the surface of the component is wiped with an organic solvent to remove all oil stains.

[0048] In an embodiment of the present invention, the soaking time is 3 minutes to 8 minutes. The soaking allows the B surface to contact with the electroplating solution and plays a role of preheating.

[0049] In an embodiment of the present invention, the anode device of the electroplating adopts a lead-antimony alloy.

[0050] In an embodiment of the present invention, the electroplating solution comprises: 200 g / L to 250 g / L of chromic anhydride and 2 g / L to 2.5 g / L of sulfuric acid. The electroplating solution may be a conventional hard chromium electroplating solution.

[0051] In an embodiment of the present invention, the temperature of the electroplating solution is 50°C to 60°C.

[0052] In the embodiment of the present invention, before the part enters the electroplating tank, the state of the B side is that the water film on the surface remains intact for more than 30 seconds after washing. To ensure that the B side state meets the requirements, it is necessary to remove all surface oil stains. This can be done by using cotton yarn or a brush dipped in detergent powder and repeatedly scrubbing the surface.

[0053] In an embodiment of the present invention, the parts are also heated to relieve stress before electroplating.

[0054] In some embodiments of the present invention, parts are stress relieved by oven heating and / or immersion heating in a dehydrogenating oil bath prior to electroplating.

[0055] In some embodiments of the present invention, the entire part is immersed in a dehydrogenation oil tank at a temperature of 180° C. to 200° C. for more than 3 hours before electroplating to eliminate stress.

[0056] In an embodiment of the present invention, after the part enters the electroplating tank, the B surface is immersed in the electroplating solution; it is treated with a current of 0.3 to 0.6 times the working current for 30s to 40s; then it is treated with a current of 1.05 to 2 times the working current for 60s to 120s; the current is gradually reduced to the working current, and the electroplating process is carried out at the working current for 5.5 to 7h; then the current is increased by 3% to 10% per hour until the current reaches 1.2 to 1.5 times the working current.

[0057] In some embodiments of the present invention, the electroplating anode device is a lead-antimony alloy with a lead content of 82% to 94%; and a sandblasting activation treatment is performed before use.

[0058] In an embodiment of the present invention, the groove between surface A and surface B is a grinding wheel overtravel groove.

[0059] In an embodiment of the present invention, the part is a bearing elastic support, and the B surface is the inner hole surface of the part.

[0060] The elastic support of the bearing plays a role in reducing bearing vibration and ensuring the stability and reliability of the bearing system. For the inner hole of the elastic support of the bearing, there are grooves (overrun grooves) on both sides of the chrome-plated surface, so in the present invention, the adjacent surfaces on both sides of the chrome-plated surface are "A surfaces"; in the currently common electroplating hard chrome method, a cover plate made of insulating material (plastic, rubber, ceramic, etc.) is used to overlap the adjacent surfaces of the chrome-plated surface (one or two A surfaces) when protecting the non-plated surface; the cover plate is a circular plate that covers the A surface to divide the inner hole of the part into two, isolating the chrome-plated surface from the non-chrome-plated surface on the side of the rib; to ensure the protective effect of the cover plate, the edge of the cover plate is precisely matched with the overrun groove, with almost no matching gap. After chrome plating, the chrome-plated surface forms a "wavy" chromium layer near the A surface and the edge of the cover plate. The wave peak grows inward, which blocks the cover plate, making it difficult to remove the cover plate normally. It can only be removed in a destructive way, and the cost of the fixture is high. For elastic bearing supports, the chromium plating method of the present invention is adopted, which not only has a smooth coating, a high pass rate, and simple grinding processing, but also avoids the cost increase caused by fixture loss.

[0061] In some embodiments of the present invention, surface A is the adjacent surface of surface B close to the rib. The non-ferrous metal sheet bonded to surface A can imitate the cover plate to separate the chrome-plated surface from the non-chrome-plated surface on the rib side.

[0062] In some embodiments of the present invention, the component is an elastic support of a turboshaft aircraft engine compressor bearing.

[0063] Example

[0064] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight. Unless otherwise stated, all reagents used in the examples are available through conventional commercial sources or synthesized according to conventional methods and can be used directly without further processing. Unless otherwise stated, all instruments used in the examples are available through conventional commercial sources.

[0065] Example 1

[0066] The part that needs to be partially chrome-plated on the surface in this embodiment is called elastic support, the material grade is 15CrMnMoVE, the hardness is HR15N76.5~79.5, and the area of ​​the plated surface is 0.3dm 2 The inner hole surface (side B) is required to be chrome plated, and the remaining surfaces are protected. The thickness of the chrome plating layer is ≥ 200μm. Side A is the adjacent surface of side B close to the rib. Chrome is allowed in the groove between the A and B surfaces.

[0067] The chrome plating process of this embodiment is as follows: pre-drying inspection → stress relief → organic solvent degreasing → protective hanging → manual degreasing → hard chrome electroplating → cleaning → cleaning → hydrogen removal → rust prevention; the details are as follows:

[0068] Step 1. Measure and record the dimensions of the chrome-plated parts before plating.

[0069] Step 2. Stress relief: Immerse the entire part in a dehydrogenation oil tank at a temperature of 190°C ± 10°C for ≥ 3 hours.

[0070] Step 3. Degreasing with organic solvents: Wipe the surface of the parts with white cotton gauze soaked in a small amount of organic solvent to remove all oil stains.

[0071] Step 4. Protection 1: Use aluminum sheet (thickness 0.5mm) to fit tightly against surface A, use insulating glue to bond it, and stick plastic tape on the side close to the ribs to strengthen the aluminum sheet.

[0072] Step 5. Protection 2: After the parts are assembled with the anode device, use tape, aluminum foil, and perchlorethylene paint to protect the other non-chrome-plated surfaces of the parts.

[0073] Step 6. Manually degrease the chrome-plated surface. Use cotton yarn or a brush dipped in detergent powder and repeatedly scrub the surface until all the oil is removed. After scrubbing, rinse the part with running cold water and check the continuity of the water film. The water film on the part surface should remain unbroken for at least 30 seconds after the cold water rinse. If not, repeat the manual degreasing step.

[0074] Step 7. Based on the part's condition and plating requirements, set the operating current to 20A. The plating solution contains 220g / L chromic anhydride and 2.5g / L sulfuric acid. Preheat the part after placement in the bath for 8 minutes at a plating solution temperature of 55°C. Then, perform an anodic etching process using an 8A current for 40 seconds. Immediately after the anodic etching process, apply a 26A current for 120 seconds. After the current is applied, slowly reduce the current to the operating current of 20A. Continue plating at 20A for 6 hours, then begin adjusting the current by increasing it by 1A per hour until it reaches 26A, at which point no further adjustments will be made.

[0075] Step 8: After the plating reference time is reached, the post-plating dimensions are measured and the coating thickness is calculated based on the pre-plating dimensions recorded in Step 1. If the coating thickness is acceptable, the next step begins. If the thickness is unacceptable, re-plating is continued until the thickness is acceptable. The final plating time is 24 hours.

[0076] Step 9. After leaving the tank, the parts are cleaned in the recovery tank and the flowing cold water tank respectively.

[0077] Step 10. Cleaning: Clean the surface protection of the parts and blow dry the parts with compressed air.

[0078] Step 11. Dehydrogenation: This should be carried out in a dehydrogenation oil tank within 10 hours after plating. The temperature is 190°C ± 10°C and the time is ≥ 4 hours.

[0079] Step 12. Rust prevention: Apply ZYS-991(36) anti-rust oil to the entire surface of the parts and check the parts. The surface oil film should be complete.

[0080] The actual coating of the plated parts in this embodiment is as follows Figure 3 As shown, it can be seen that the coating is smooth and there are no ripples at the edges. Compared with the use of traditional insulating materials, the fixture of this embodiment is low-cost, easy to operate, and has a high manufacturing qualification rate.

[0081] Example 2

[0082] The part that needs partial chrome plating is named X-shaped spring, made of 40CrNiMoA material, with a hardness of HRC36-40, and a plating area of ​​0.4dm 2 The inner hole surface (side B) is required to be chrome plated, and the remaining surfaces are protected. The thickness of the chrome layer is ≥ 180μm. Side A is the adjacent surface of side B close to the rib. Chrome is allowed in the groove between the A and B surfaces.

[0083] The chrome plating process of this embodiment is as follows: pre-drying inspection → stress relief → organic solvent degreasing → protective hanging → manual degreasing → hard chrome electroplating → cleaning → cleaning → hydrogen removal → rust prevention; the details are as follows:

[0084] Step 1. Measure and record the dimensions of the chrome-plated parts before plating.

[0085] Step 2. Stress relief: Immerse the entire part in a dehydrogenation oil tank at a temperature of 190°C ± 10°C for ≥4 hours.

[0086] Step 3. Degreasing with organic solvents: Wipe the surface of the parts with white cotton gauze soaked in a small amount of organic solvent to remove all oil stains.

[0087] Step 4. Protection 1: Use lead sheet (thickness 0.8mm) to fit tightly against surface A, use insulating glue to bond it, and stick plastic tape on the side close to the rib to strengthen the lead sheet.

[0088] Step 5. Protection 2: After the parts are assembled with the anode device, use tape, lead sheet, and perchlorethylene paint to protect the other non-chrome-plated surfaces of the parts.

[0089] Step 6. Manually degrease the chrome-plated surface. Use cotton yarn or a brush dipped in detergent powder and repeatedly scrub the surface until all the oil is removed. After scrubbing, rinse the part with running cold water and check the continuity of the water film. The water film on the part surface should remain unbroken for at least 30 seconds after the cold water rinse. If not, repeat the manual degreasing step.

[0090] Step 7. Set the operating current to 26A based on the part's condition and plating requirements. The plating solution contains 250g / L chromic anhydride and 2g / L sulfuric acid. Preheat the part after placement in the bath for 6 minutes at a plating solution temperature of 55°C. Anodic etching is then performed at a current of 12A for 40 seconds. Immediately after anodic etching, apply a surge current of 33A for 110 seconds. After the surge current is applied, slowly reduce the current to the operating current of 26A. After 6 hours of plating at 26A, begin adjusting the operating current by increasing it by 1A per hour until it reaches 32A, at which point no further adjustments are required.

[0091] Step 8: After the plating reference time is reached, the post-plating dimensions are measured and the coating thickness is calculated based on the pre-plating dimensions recorded in Step 1. If the coating thickness is acceptable, the next step begins. If the thickness is unacceptable, re-plating is continued until the thickness is acceptable. The final plating time is 24 hours.

[0092] Step 9. After leaving the tank, the parts are cleaned in the recovery tank and the flowing cold water tank respectively.

[0093] Step 10. Cleaning: Clean the surface protection of the parts and blow dry the parts with compressed air.

[0094] Step 11. Dehydrogenation: This should be carried out in a dehydrogenation oil tank within 10 hours after plating. The temperature is 190°C ± 10°C and the time is ≥ 4 hours.

[0095] Step 12. Rust prevention: Apply ZYS-991(36) anti-rust oil to the entire surface of the parts and check the surface of the parts. The oil film should be complete.

[0096] The actual coating of the plated parts in this embodiment is as follows Figure 4 As shown, it can be seen that the coating is smooth and there are no ripples at the edges. Compared with the use of traditional insulating materials, the fixture of this embodiment is low-cost, easy to operate, and has a high manufacturing qualification rate.

[0097] Example 3

[0098] The part that needs partial chrome plating in this embodiment is X-shaped bearing spring, made of 1Cr11Ni2W2MoV, with a hardness of HRC30 and a plating area of ​​0.2dm 2 The inner hole surface (side B) is required to be chrome plated, and the remaining surfaces are protected. The chrome plating thickness is ≥ 400μm. Side A is the adjacent surface of side B close to the rib. Chrome is allowed in the groove between the A and B surfaces.

[0099] The chrome plating process of this embodiment is as follows: pre-drying inspection → stress relief → organic solvent degreasing → protective hanging → manual degreasing → hard chrome electroplating → cleaning → cleaning → hydrogen removal → rust prevention; the details are as follows:

[0100] Step 1. Measure and record the dimensions of the chrome-plated parts before plating.

[0101] Step 2. Stress relief: Immerse the entire part in a dehydrogenation oil tank at a temperature of 190°C ± 10°C for ≥ 3 hours.

[0102] Step 3. Degreasing with organic solvents: Wipe the surface of the parts with white cotton gauze soaked in a small amount of organic solvent to remove all oil stains.

[0103] Step 4. Protection 1: Use lead sheet (thickness 0.7mm) to fit tightly against surface A, use insulating glue to bond it, and stick plastic tape on the side close to the rib to strengthen the lead sheet.

[0104] Step 5. Protection 2: After the parts are assembled with the anode device, use tape, lead sheet, and perchlorethylene paint to protect the other non-chrome-plated surfaces of the parts.

[0105] Step 6. Manually degrease the chrome-plated surface. Use cotton yarn or a brush dipped in detergent powder and repeatedly scrub the surface until all the oil is removed. After scrubbing, rinse the part with running cold water and check the continuity of the water film. The water film on the part surface should remain unbroken for at least 30 seconds after the cold water rinse. If not, repeat the manual degreasing step.

[0106] Step 7. Set the operating current to 10A based on the part's condition and plating requirements. The plating solution contains 225g / L chromic anhydride and 2.5g / L sulfuric acid. Preheat the part after placement in the bath for 7 minutes at a solution temperature of 56°C. Then, perform an anodic etching process using a current of 6A for 35 seconds. Immediately after the anodic etching process, apply a surge current of 18A for 100 seconds. After the surge current is applied, slowly reduce the current to the operating current of 10A. After 6 hours of plating at 10A, begin adjusting the operating current by increasing it by 1A per hour until it reaches 14A, at which point no further adjustments will be made.

[0107] Step 8: After the plating reference time is reached, the post-plating dimensions are measured and the coating thickness is calculated based on the pre-plating dimensions recorded in Step 1. If the coating thickness is acceptable, the next step begins. If the thickness is unacceptable, re-plating is continued until the thickness is acceptable. The final plating time is 32 hours.

[0108] Step 9. After leaving the tank, the parts are cleaned in the recovery tank and the flowing cold water tank respectively.

[0109] Step 10. Cleaning: Clean the surface protection of the parts and blow dry the parts with compressed air.

[0110] Step 11. Dehydrogenation: This should be carried out in a dehydrogenation oil tank within 10 hours after plating. The temperature is 190°C ± 10°C and the time is ≥ 4 hours.

[0111] Step 12. Rust prevention: Apply ZYS-991(36) anti-rust oil to the entire surface of the parts and check the parts. The surface oil film should be complete.

[0112] The actual coating of the plated parts in this embodiment is as follows Figure 5 As shown, it can be seen that the coating is smooth and there are no ripples at the edges. Compared with the use of traditional insulating materials, the fixture of this embodiment is low-cost, easy to operate, and has a high manufacturing qualification rate.

Claims

1. A method for local chrome plating on the metal surface of a part, characterized in that: The metal surface of the part includes a B surface that needs to be chrome-plated, and an A surface that is adjacent to the B surface and does not need to be chrome-plated. A groove is formed between the B surface and the A surface to separate the two surfaces. The groove is a transition zone that can be chrome-plated or not. Before electroplating, the non-ferrous metal sheet is tightly bonded to surface A with insulating glue so that surface A is shielded by the non-ferrous metal sheet, and the remaining non-plated surfaces that need protection are insulated and protected with insulating protective materials; after the part enters the electroplating tank, the surface B is immersed in the electroplating solution; and the treatment is carried out for 20s to 60s with a current of 0.2 to 0.8 times the working current; Then use a current of 1 to 2.5 times the working current for 40s to 160s; gradually reduce the current to the working current, and perform electroplating processing at the working current for 4 to 8 hours; then increase the current by 2% to 15% per hour until the current reaches 1.1 to 1.6 times the working current.

2. The method for local chromium plating on the metal surface of a part according to claim 1, characterized in that: The metal surface material of the part is low alloy medium carbon steel or austenitic stainless steel; the non-ferrous metal sheet is lead and / or aluminum; the thickness of the non-ferrous metal sheet is 0.5mm to 0.8mm.

3. The method for local chromium plating on the metal surface of a part according to claim 1, characterized in that: The insulating protective material includes one or more of plastic tape, high temperature wax, electroplating protective glue, and insulating paint.

4. The method for local chromium plating on the metal surface of a part according to claim 1, characterized in that: The soaking time is 3 minutes to 8 minutes.

5. The method for local chromium plating on a metal surface of a part according to any one of claims 1 to 4, characterized in that: The electroplating anode device adopts lead-antimony alloy; the electroplating solution comprises: 200g / L-250g / L of chromic anhydride and 2g / L-2.5g / L of sulfuric acid; the temperature of the electroplating solution is 50-60°C.

6. The method for local chromium plating on a metal surface of a part according to claim 1, characterized in that: Before the parts enter the electroplating tank, the state of side B is that the water film on the surface remains intact for more than 30 seconds after washing.

7. The method for local chromium plating on a metal surface of a part according to claim 1 or 6, characterized in that: The parts are also heated for stress relief before plating.

8. The method for local chromium plating on a metal surface of a part according to any one of claims 1 to 7, characterized in that: After the part enters the electroplating tank, the B side is immersed in the electroplating solution; it is treated with a current of 0.3 to 0.6 times the working current for 30 seconds to 40 seconds; then it is treated with a current of 1.05 to 2 times the working current for 60 seconds to 120 seconds; the current is gradually reduced to the working current, and the electroplating process is carried out at the working current for 5.5 to 7 hours; then the current is increased by 3% to 10% per hour until the current reaches 1.2 to 1.5 times the working current.

9. The method for local chromium plating on a metal surface of a part according to any one of claims 1 to 4, characterized in that: The groove between surface A and surface B is the grinding wheel overtravel groove; the part is elastically supported by the bearing, surface B is the inner hole surface of the part; surface A is the adjacent surface of surface B close to the rib side.

10. The method for local chromium plating on a metal surface of a part according to claim 9, characterized in that: The part is an elastic support for a turboshaft aircraft engine compressor bearing.

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