Alkaline cyanide-free cadmium plating process for ultrahigh-strength steel parts

Abstract

The invention discloses an alkaline cyanide-free cadmium plating process for an ultrahigh-strength steel part. The alkaline cyanide-free cadmium plating process comprises the steps of oil removal, stress elimination, electrolytic oil removal, flowing water washing, weak corrosion, flowing cold water washing, copper pre-plating, flowing cold water washing, alkaline cyanide-free cadmium plating, flowing water washing, hydrogen removal, aftertreatment, drying and inspection. In order to avoid the situation that the metal surface of the workpiece is passivated in a plating tank, the pretreatment process is adopted, a cyanide-free copper electroplating layer is pre-plated on the surface of the workpiece, the surface of the part is adjusted, the surface activity is improved, and then the binding force of a base body and the plated cadmium is improved; according to the method, a stress eliminating process and a long-time hydrogen removing process after plating are adopted before plating, so that the hydrogen embrittlement risk is reduced, the process steps are simple, and the implementation is high.

Description

Technical Field

[0001] The invention belongs to the field of electroplating surface treatment, and more specifically, relates to an alkaline cyanide-free cadmium plating process for ultra-high strength steel parts with a tensile strength of 1480Mpa to 2350Mpa. Background Art

[0002] Electroplating cadmium has excellent anti-corrosion performance and stable electrochemical properties, and can provide effective protection for base metals in a variety of harsh environments. It is especially commonly used to prevent corrosion of low-alloy steel in humid, salt-fog environments. Some load-bearing parts in aircraft engines are made of ultra-high-strength steel, such as material grades 50CrVA, 60Si2MnA, 70, 65Mn, etc. The tensile strength of the processed parts can reach 1480MPa to 2350MPa. The above materials have poor corrosion resistance, and considering their use in marine environments, cadmium plating protection is required.

[0003] The current efficiency of alkaline cyanide-free cadmium plating is 45.2%. During the cadmium electroplating process, while the coating is formed, there is a side reaction of hydrogen evolution. There are two problems in the high-concentration alkaline cadmium plating of ultra-high strength steel;

[0004] 1. Compared with low-strength steel parts, ultra-high-strength steel parts have more serious hydrogen evolution, which leads to the passivation of the metal surface of the parts during the electroplating process. The subsequent cadmium plating has poor bonding strength, the parts are prone to blistering, and the appearance is as follows: Figure 2 As shown;

[0005] 2. At present, there is more than 50% hydrogen evolution reaction in alkaline cadmium plating. Hydrogen penetration is a potential source of damage to high-strength steel and ultra-high-strength steel. The distribution of hydrogen in the metal is uneven, and the concentration on the surface is much higher than the concentration in the center of the part. High concentration of hydrogen on the surface will migrate to the stress concentration area under the action of stress during the hydrogen penetration process. Hydrogen weakens the internal bonding force of the steel in some way. When enough hydrogen accumulates, cracks may form, and high stress moves to the crack tip. This process continues until it causes brittle fracture of the metal material. This brittle fracture phenomenon is called hydrogen embrittlement. High-strength steel itself has high strength and relatively low toughness, and is more sensitive to hydrogen embrittlement. As shown in the attached Figure 3 As shown in the figure, under the same stress load, the higher the strength, the shorter the fracture time of the test bar. Ultra-high strength steel has high tensile strength and is extremely sensitive to hydrogen embrittlement. Accidents caused by hydrogen embrittlement fracture are very serious.

[0006] CN118727073A discloses a method for low hydrogen embrittlement cadmium plating of spring parts. The scheme is to reduce the hydrogen content of spring parts in the process of electroplating cadmium. For electrolytic degreasing, there are two methods: anodic degreasing and cathode degreasing. Since there is a risk of hydrogen absorption when only cathode degreasing is used, for spring parts, cathode degreasing is not allowed, and anodic degreasing is required; for strong corrosion, in order to avoid a large increase in hydrogen content in spring parts during strong corrosion, weak corrosion and dust removal steps are designed to replace the strong corrosion steps of the conventional electroplating cadmium process; for the cadmium plating step, the cadmium plating time determines the amount of hydrogen absorption. In order to avoid the increase of hydrogen absorption due to too long electroplating time, during the electroplating process, the electroplating time is strictly controlled, and the thickness is measured once every two minutes. When the thickness does not meet the requirements, the power is turned on to continue electroplating cadmium until the thickness meets the requirements. However, the process steps of this scheme are cumbersome, and the cadmium plating process is complicated; corrosion and dust removal steps are used after degreasing, which increases the infiltration of hydrogen content. At the same time, the thickness is measured every two minutes during the electroplating process, which poses a risk of blistering in the coating. This is because the surface of the part should be a dry surface when measuring the thickness. This measure does not comply with the requirement of GJB480A-1995 "Quality Control Requirements for Metal Plating and Chemical Covering Processes" that "drying is not allowed between wet processing steps during metal plating". When cadmium is re-plated, foreign matter such as surface contamination and surface oxidation will affect the bonding of subsequent coatings. Summary of the invention

[0007] The invention provides an alkaline cyanide-free cadmium plating process for ultra-high-strength steel parts to solve the problem of hydrogen evolution in the cadmium plating of existing ultra-high-strength steel parts and to avoid the passivation of the parts in the cadmium plating bath, thereby reducing the bonding force between the substrate and the cadmium plating layer.

[0008] The present invention is achieved through the following technical solutions:

[0009] An alkaline cyanide-free cadmium plating process for ultra-high strength steel parts comprises the following steps:

[0010] S1. Degreasing: Use organic solvent to clean the oil stains on the surface of the workpiece;

[0011] S2. Stress relief: heat to 190℃±10℃, keep warm for ≥4h;

[0012] S3, electrolytic degreasing: using 50-60g / L sodium hydroxide, 50-60g / L sodium phosphate, 50-60g / L sodium carbonate, 5-10g / L sodium silicate, current density 0.5-5A / dm 2 ;

[0013] S4, running water washing;

[0014] S5, weak corrosion: using sulfuric acid (98%wt) 60-70mL / L, the bath temperature is room temperature, the corrosion time is 2-3min;

[0015] S6, washing with running cold water;

[0016] S7, Pre-copper plating: Use copper plating solution containing 15-20g / L copper ion content, bath temperature 40℃~60℃, cathode current density 0.5A / dm 2 ~3A / dm 2 , electroplating time 5min~10min;

[0017] S8, washing with running cold water;

[0018] S9. Alkaline cyanide-free cadmium plating: Use an alkaline cyanide-free cadmium plating solution containing 40-50 g / L cadmium sulfate and 95-105 g / L potassium hydroxide, the bath temperature is 35°C-45°C, and the cathode current density is 1A / dm 2 ~4A / dm 2 , deposition rate 5μm / h~7.5μm / h.

[0019] S10, running water washing;

[0020] S11, dehydrogenation: temperature is 190℃±10℃, insulation time is ≥23h;

[0021] S12, post-processing;

[0022] S13, drying;

[0023] S14. Inspection.

[0024] Furthermore, the organic solvent in the degreasing step in S1 is washing gasoline or a high flash point hydrocarbon cleaning agent.

[0025] Furthermore, the temperature of the S3 electrolytic degreasing tank liquid is 80-90° C., and the degreasing time is 10 min-20 min.

[0026] Furthermore, the S7 pre-copper plating bath liquid temperature is 40° C. to 60° C., and the electroplating time is 5 min to 10 min.

[0027] Furthermore, the interval between the step S9 of alkaline cyanide-free cadmium plating and the step S11 of dehydrogenation is ≤4h.

[0028] Furthermore, in steps S4 and S10, the running water washing adopts running hot water at 70-80°C for 1-3 min, and then uses running cold water not exceeding 40°C for 1-3 min; and in steps S6 and S8, the running cold water washing adopts running cold water not exceeding 40°C for 1-3 min.

[0029] Furthermore, the activation treatment is performed by placing the workpiece in a 20-30 g / L sulfuric acid solution for activation for 10-15 seconds.

[0030] Furthermore, the polishing treatment is performed by placing the workpiece in a 150-160 g / L chromic anhydride solution for 10-15 ss.

[0031] Furthermore, the passivation treatment is performed by placing the workpiece in a solution of 20 to 35 g / L sodium dichromate, 15 to 20 g / L sodium sulfate and 10 to 15 g / L nitric acid for light passivation for 20 to 25 seconds.

[0032] Furthermore, the S14 inspection includes inspecting the coating appearance, thickness, bonding strength, corrosion resistance, and hydrogen embrittlement.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1) In order to avoid the metal surface passivation of the workpiece in the plating tank, the present invention adopts a pre-treatment process to pre-plate a copper coating on the surface of the workpiece, adjust the surface of the part, improve the surface activity, and further improve the bonding strength between the substrate and the coating.

[0035] 2) The process steps of the present invention are simple, and a stress elimination process is adopted before plating and a long-term hydrogen removal process is adopted after plating, thereby reducing the risk of hydrogen embrittlement and having strong feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A process flow chart of alkaline cyanide-free cadmium plating for ultra-high strength steel parts;

[0037] Figure 2 It is the appearance of blistering on the coating on the surface of the part caused by hydrogen evolution reaction;

[0038] Figure 3 It is a sensitivity curve of different strength levels to hydrogen embrittlement;

[0039] Figure 4 This is the appearance diagram of the spring coating in Example 1;

[0040] Figure 5 This is the metallographic microstructure diagram of the spring coating in Example 1;

[0041] Figure 6 This is the appearance diagram of the spring coating in Example 2;

[0042] Figure 7 This is the appearance picture of the spring coating in Example 3. DETAILED DESCRIPTION

[0043] The following is further explained and illustrated in conjunction with the examples, but the specific examples do not limit the present invention in any form. If not specifically stated, the methods and equipment used in the examples are conventional methods and equipment in the art, and the raw materials used are all conventional commercially available raw materials.

[0044] Example 1

[0045] A certain type of engine spring (material 50CrVA) is used. Figure 1 The process is alkaline cyanide-free cadmium plating.

[0046] The process steps are as follows:

[0047] S1. Degreasing: Use high flash point hydrocarbon cleaning agent to clean the oil stains on the workpiece surface;

[0048] S2. Stress relief: In order to reduce the residual stress caused by machining, cold forming, cold straightening and other processes, and to prevent cracking during chemical and electrochemical treatments, the spring is placed in an oven and heated to 180°C for 4 hours;

[0049] S3, electrolytic degreasing: using 50g / L sodium hydroxide, 50g / L sodium phosphate, 50g / L sodium carbonate, 5g / L sodium silicate, current density 0.5A / dm 2 ; Temperature 80℃, degreasing time 20min;

[0050] S4, running water washing: first use 70℃ running hot water to wash for 1min and then use running cold water not exceeding 40℃ to wash for 1min;

[0051] S5, weak corrosion: using 60mL / L sulfuric acid (98%wt), the bath temperature is room temperature, and the corrosion time is 2min;

[0052] S6. Wash with running cold water: Wash with running cold water not exceeding 40℃ for 1 minute;

[0053] S7, Pre-copper plating: Use LD-5101M 950mL / L copper plating solution, copper ion content is 15g / L, bath temperature is 40℃, cathode current density is 0.5A / dm 2 , electroplating time 10min;

[0054] S8, running cold water washing: use running cold water not exceeding 40℃ to wash for 1 minute;

[0055] S9. Alkaline cyanide-free cadmium plating: Use alkaline cyanide-free cadmium plating solution containing 40g / L cadmium sulfate, 95g / L potassium hydroxide, 500mL / L LD-5032Mu, 12-14mL / L LD-5032A, LD-5032B, and 8mL / L LD-5032C. The bath temperature is 35°C and the cathode current density is 1A / dm 2, deposition rate 5 μm / h;

[0056] S10, running water washing: first use 70℃ running hot water to wash for 1min and then use running cold water not exceeding 40℃ to wash for 1min;

[0057] S11, dehydrogenation: dehydrogenation is carried out within 4 hours after electroplating, the temperature is 180℃, and the holding time is 23 hours;

[0058] S12, post-treatment: Post-treatment includes removing the oxides produced by the cadmium layer of the parts after hydrogen removal, which requires activation treatment and light treatment, and passivation treatment to improve the corrosion resistance of the cadmium plating layer. The specific process is as follows:

[0059] Activation treatment was performed with 20 g / l sulfuric acid solution for 10 s;

[0060] Use 150g / l chromic anhydride solution for 10s of light treatment;

[0061] Use 20g / l sodium dichromate, 15g / l sodium sulfate and 10g / l nitric acid solution for 20s passivation treatment. The time of activation, light emission and passivation is adjusted according to the temperature of the tank solution;

[0062] S13, drying: use a hot air dryer at 60°C for 30 minutes;

[0063] S14. Inspection:

[0064] 1) Appearance: The crystals of cadmium plating should be uniform and fine. The passivated cadmium plating should be golden yellow with rainbow colors. After metallographic section inspection, the plating and the substrate are closely combined without separation. Figure 5 shown.

[0065] 2) Thickness: The coating thickness meets the design requirements.

[0066] 3) Adhesion: The cross-cut method specified in GB / T 5270 "Review of test methods for adhesion strength of electrodeposited and chemically deposited metal coatings on metal substrates" was used to test the parts. The coating did not peel or fall off after the test.

[0067] 4) Corrosion resistance: Low alloy steel test pieces (test piece size 100mm×50mm×4mm, test piece cadmium plating thickness 8μm~12μm, test piece quantity: 3 pieces) were used for neutral salt spray test according to GB / T 10125. After 96h salt spray test, no white corrosion products appeared. After the test was continued for 360h, no red corrosion products appeared.

[0068] 5) Hydrogen embrittlement: Six 30CrMnSiA hydrogen embrittlement test bars with notch tensile strength of 1930.7 MPa were used to carry out hydrogen embrittlement test according to HB 5067.1 "Hydrogen embrittlement test for coating process Part 1: Mechanical method". After 201 hours, the test bars did not break.

[0069] Example 2

[0070] Using a certain type of engine spring (material 70) Figure 1 The process is alkaline cyanide-free cadmium plating.

[0071] The process steps are as follows:

[0072] S1. Degreasing: Use organic solvent to clean the oil stains on the surface of the workpiece;

[0073] S2. Stress relief: In order to reduce the residual stress caused by machining, cold forming, cold straightening and other processes, and to prevent cracking during chemical and electrochemical treatments, place the spring in an oven and heat it to 200℃±10℃ for 4h;

[0074] S3, electrolytic degreasing: using 60g / L sodium hydroxide, 60g / L sodium phosphate, 60g / L sodium carbonate, 10g / L sodium silicate, current density 5A / dm 2 ; Temperature 90℃, degreasing time 20min;

[0075] S4, running water washing: first use 80℃ running hot water to wash for 3min and then use running cold water not exceeding 40℃ to wash for 3min;

[0076] S5, weak corrosion: using sulfuric acid (98%wt) 70mL / L, the bath temperature is room temperature, the corrosion time is 3min;

[0077] S6. Wash with running cold water: Wash with running cold water not exceeding 40℃ for 3 minutes;

[0078] S7, Pre-copper plating: Use LD-5101M 950mL / L copper plating solution, copper ion content is 20g / L, bath temperature is 60℃, cathode current density is 3A / dm 2 , electroplating time 5min;

[0079] S8, running cold water washing: use running cold water not exceeding 40℃ to wash for 3 minutes;

[0080] S9. Alkaline cyanide-free cadmium plating: Use alkaline cyanide-free cadmium plating solution containing 50g / L cadmium sulfate, 105g / L potassium hydroxide, 500mL / L LD-5032Mu, 12-14mL / L LD-5032A, LD-5032B, and 8mL / L LD-5032C. The bath temperature is 45°C and the cathode current density is 4A / dm 2, deposition rate 7.5μm / h;

[0081] S10, running water washing: first use 70℃ running hot water to wash for 1-3min and then use running cold water not exceeding 40℃ to wash for 3min;

[0082] S11, dehydrogenation: dehydrogenation is carried out within 4 hours after electroplating, the temperature is 200℃, and the holding time is 23 hours;

[0083] S12, post-treatment: Post-treatment includes removing the oxides produced by the cadmium layer of the parts after hydrogen removal, which requires activation treatment and light treatment, and passivation treatment to improve the corrosion resistance of the cadmium plating layer. The specific process is as follows:

[0084] Activation treatment was performed with 30 g / l sulfuric acid solution for 15 s;

[0085] Use 160g / l chromic anhydride solution for 15s of light treatment;

[0086] Use 35g / l sodium dichromate, 20g / l sodium sulfate and 15g / l nitric acid solution for 25s passivation treatment. The time of activation, light emission and passivation is adjusted according to the temperature of the tank solution;

[0087] S13, drying: use a hot air dryer at 60°C for 30 minutes;

[0088] S14. Inspection:

[0089] 1) Appearance: The crystallization of cadmium plating should be uniform and fine. The passivated cadmium plating should be golden yellow with iridescence. Figure 6 shown.

[0090] 2) Thickness: The coating thickness meets the design requirements.

[0091] 3) Adhesion: The cross-cut method specified in GB / T 5270 "Review of test methods for adhesion strength of electrodeposited and chemically deposited metal coatings on metal substrates" was used to test the parts. The coating did not peel or fall off after the test.

[0092] 4) Corrosion resistance: Low alloy steel test pieces (test piece size 100mm×50mm×4mm, test piece cadmium plating thickness 8μm~12μm, test piece quantity: 3 pieces) were used for neutral salt spray test according to GB / T 10125. After 96h salt spray test, no white corrosion products appeared. After the test was continued for 360h, no red corrosion products appeared.

[0093] 5) Hydrogen embrittlement: Six 30CrMnSiA hydrogen embrittlement test bars with notch tensile strength of 1930.7 MPa were used to carry out hydrogen embrittlement test according to HB 5067.1 "Hydrogen embrittlement test for coating process Part 1: Mechanical method". After 201 hours, the test bars did not break.

[0094] Example 3

[0095] A certain type of engine spring (material 60Si2MnA) is used. Figure 1 The process is alkaline cyanide-free cadmium plating.

[0096] The process steps are as follows:

[0097] S1. Degreasing: Use washing gasoline to clean the oil stains on the surface of the workpiece;

[0098] S2. Stress relief: In order to reduce the residual stress caused by machining, cold forming, cold straightening and other processes, and to prevent cracking during chemical and electrochemical treatments, the spring is placed in an oven and heated to 190°C for 5 hours;

[0099] S3, electrolytic degreasing: using 55g / L sodium hydroxide, 55g / L sodium phosphate, 55g / L sodium carbonate, g / L sodium silicate, current density 2.5A / dm 2 ; Temperature 85℃, degreasing reference time 15min, the time can be adjusted according to the oil pollution on the surface of the parts;

[0100] S4, running water washing: first use 75 ℃ running hot water to wash for 1.5 min and then use running cold water not exceeding 40 ℃ to wash for 1.5 min;

[0101] S5, weak corrosion: using 65mL / L sulfuric acid (98%wt), the bath temperature is room temperature, and the corrosion time is 1.5min;

[0102] S6. Wash with running cold water: Wash with running cold water not exceeding 40°C for 1.5 minutes;

[0103] S7, Pre-copper plating: Use LD-5101M 950mL / L copper plating solution, copper ion content is 17g / L, bath temperature is 50℃, cathode current density is 1.5A / dm 2 , electroplating time 7min;

[0104] S8, running cold water washing: use running cold water not exceeding 40℃ to wash for 1 to 3 minutes;

[0105] S9. Alkaline cyanide-free cadmium plating: Use alkaline cyanide-free cadmium plating solution containing 45g / L cadmium sulfate, 100g / L potassium hydroxide, 500mL / L LD-5032Mu, 12-14mL / L LD-5032A, LD-5032B, and 8mL / L LD-5032C. The bath temperature is 40°C and the cathode current density is 2.5A / dm 2 , deposition rate 6μm / h;

[0106] S10, running water washing: first use 75 ℃ running hot water to wash for 1.5 min and then use running cold water not exceeding 40 ℃ to wash for 1.5 min;

[0107] S11, dehydrogenation: dehydrogenation is carried out within 4 hours after electroplating, the temperature is 190℃, and the insulation time is 24 hours;

[0108] S12, post-treatment: Post-treatment includes removing the oxides produced by the cadmium layer of the parts after hydrogen removal, which requires activation treatment and light treatment, and passivation treatment to improve the corrosion resistance of the cadmium plating layer. The specific process is as follows:

[0109] Activation treatment was performed with 25 g / l sulfuric acid solution for 10 s;

[0110] Use 155g / l chromic anhydride solution for 10s of light treatment;

[0111] Use 25g / l sodium dichromate, 17g / l sodium sulfate and 13g / l nitric acid solution for 23s passivation treatment. The time of activation, light emission and passivation is adjusted according to the temperature of the tank solution;

[0112] S13, drying: use a hot air dryer at 60°C for 30 minutes;

[0113] S14. Inspection:

[0114] 1) Appearance: The crystallization of cadmium plating should be uniform and fine. The passivated cadmium plating should be golden yellow with iridescence. Figure 7 shown.

[0115] 2) Thickness: The coating thickness meets the design requirements.

[0116] 3) Adhesion: The cross-cut method specified in GB / T 5270 "Review of test methods for adhesion strength of electrodeposited and chemically deposited metal coatings on metal substrates" was used to test the parts. The coating did not peel or fall off after the test.

[0117] 4) Corrosion resistance: Low alloy steel test pieces (test piece size 100mm×50mm×4mm, test piece cadmium plating thickness 8μm~12μm, test piece quantity: 3 pieces) were used for neutral salt spray test according to GB / T 10125. After 96h salt spray test, no white corrosion products appeared. After the test was continued for 360h, no red corrosion products appeared.

[0118] 5) Hydrogen embrittlement: Six 30CrMnSiA hydrogen embrittlement test bars with a notch tensile strength of 1930.7MPa were used to conduct hydrogen embrittlement testing in accordance with HB 5067.1 "Hydrogen embrittlement test for plating process Part 1: Mechanical method".

[0119] After 201h, the test rod did not break.

[0120] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A process for alkaline cyanide-free cadmium plating of ultra-high strength steel parts, characterized in that: The following steps are involved: S1. Degreasing: Use organic solvent to clean the oil stains on the surface of the workpiece; S2. Stress relief: heat to 190℃±10℃, keep warm for ≥4h; S3, electrolytic degreasing: using 50-60g / L sodium hydroxide, 50-60g / L sodium phosphate, 50-60g / L sodium carbonate, 5-10g / L sodium silicate, current density 0.5-5A / dm 2 ; S4, running water washing; S5, weak corrosion: using sulfuric acid (98%wt) 60-70mL / L, the bath temperature is room temperature, the corrosion time is 2-3min; S6. Wash with running cold water: Wash with running cold water not exceeding 40℃ for 1 to 3 minutes; S7, Pre-copper plating: Use copper plating solution containing 15-20g / L copper ion content, bath temperature 40℃~60℃, cathode current density 0.5A / dm 2 ~3A / dm 2 , electroplating time 5min~10min; S8, Wash with running cold water: Wash with running cold water not exceeding 40℃ for 1 to 3 minutes; S9. Alkaline cyanide-free cadmium plating: Use an alkaline cyanide-free cadmium plating solution containing 40-50 g / L cadmium sulfate and 95-105 g / L potassium hydroxide, the bath temperature is 35°C-45°C, and the cathode current density is 1A / dm 2 ~4A / dm 2 , deposition rate 5μm / h~7.5μm / h; S10, running water washing; S11, dehydrogenation: temperature is 190℃±10℃, insulation time is ≥23h; S12, post-processing: including activation treatment, light extraction treatment and passivation treatment; S13, drying; S14. Inspection.

2. The alkaline cyanide-free cadmium plating process for ultra-high strength steel parts according to claim 1, characterized in that: The organic solvent in the degreasing step in S1 is washing gasoline or a high flash point hydrocarbon cleaning agent.

3. A process for alkaline cyanide-free cadmium plating of ultra-high strength steel parts, characterized in that: The temperature of the S3 electrolytic degreasing tank liquid is 80-90° C., and the degreasing time is 10-20 minutes.

4. A process for alkaline cyanide-free cadmium plating of ultra-high strength steel parts, characterized in that: The S7 pre-copper plating bath has a liquid temperature of 40° C. to 60° C. and a plating time of 5 min to 10 min.

5. The alkaline cyanide-free cadmium plating process for ultra-high strength steel parts according to claim 1, characterized in that: The interval between the step S9 of alkaline cyanide-free cadmium plating and the step S11 of dehydrogenation is ≤4h.

6. The alkaline cyanide-free cadmium plating process for ultra-high strength steel parts according to claim 1, characterized in that: In steps S4 and S10, the running water washing adopts running hot water at 70-80°C for 1-3 minutes, and then uses running cold water not exceeding 40°C for 1-3 minutes; in steps S6 and S8, the running cold water washing adopts running cold water not exceeding 40°C for 1-3 minutes.

7. The alkaline cyanide-free cadmium plating process for ultra-high strength steel parts according to claim 1, characterized in that: The activation treatment is performed by placing the workpiece in a 20-30 g / L sulfuric acid solution for 10-15 seconds.

8. The alkaline cyanide-free cadmium plating process for ultra-high strength steel parts according to claim 1, characterized in that: The light treatment is performed by placing the workpiece in a 150-160 g / L chromic anhydride solution for light exposure for 10-15 seconds.

9. The alkaline cyanide-free cadmium plating process for ultra-high strength steel parts according to claim 1, characterized in that: The passivation treatment is performed by placing the workpiece in a solution of 20 to 35 g / L sodium dichromate, 15 to 20 g / L sodium sulfate and 10 to 15 g / L nitric acid for light passivation for 20 to 25 seconds.

10. The alkaline cyanide-free cadmium plating process for ultra-high strength steel parts according to claim 1, characterized in that: The S14 inspection includes inspection of coating appearance, thickness, bonding strength, corrosion resistance, and hydrogen embrittlement.

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