High-strength steel hydrogen embrittlement-free barrel aluminum plating method capable of being repeatedly loaded and unloaded

Abstract

The invention belongs to the technical field of high-strength steel coatings, and discloses a high-strength steel hydrogen embrittlement-free barrel aluminum plating method capable of being repeatedly assembled and disassembled. Step 2, physically removing an oxidation film; 3, the sand blasting base material is cleaned; step 4, activating; step 5, barrel plating aluminum; step 6, cleaning with a plating solution; and 7, passivating and sealing. A water-free, acid-free, alkali-free and atmosphere-isolated process is adopted, the problem of hydrogen embrittlement fracture of the high-strength steel caused by the processes of electroplating pretreatment, electroplating, electroplating aftertreatment and the like is avoided or solved, the barrel plating process is adopted, and batch production can be achieved. The prepared aluminum coating is low in hardness, good in ductility and high in binding force, can play a self-lubricating role in the loading and unloading process, is good in workpiece loading and unloading performance, is not prone to falling off and the like, and can be self-repaired after being scratched or scratched.

Description

Technical Field

[0001] The invention belongs to the technical field of high-strength steel plating, and in particular relates to a high-strength steel hydrogen-embrittlement-free aluminum rolling plating method that can be repeatedly loaded and unloaded. Background Art

[0002] The service life of high-strength steel is closely related to the bonding strength, porosity, corrosion resistance, hardness and other properties of the surface protective coating. Different coating properties are suitable for different application scenarios. When the workpiece needs to be loaded and unloaded repeatedly or multiple times during use, such as the use of high-strength steel bolts, nuts, gaskets, etc., the coating is required to have a strong bonding strength with the substrate to ensure that the coating does not fall off during loading and unloading. Secondly, the coating must have good mechanical properties and can improve or not affect the assembly performance of the workpiece during assembly and disassembly. Finally, the coating must still play a good protective role on the high-strength steel substrate after repeated loading and unloading, and will not affect the normal service life of the workpiece.

[0003] During the traditional aqueous electroplating process of cadmium, zinc, nickel, copper and other protective coatings on high-strength steel, hydrogen penetrates into the high-strength steel matrix, causing hydrogen embrittlement and fracture of the workpiece during subsequent use, and the current dehydrogenation process cannot completely solve this problem. Currently, high-strength steel fasteners generally use the Dacromet coating process, but the Dacromet coating is made of flaky zinc and aluminum coatings that are solidified on the surface of the workpiece. The bonding strength between the coating and the matrix is ​​poor, and the coating has strong corrosion resistance when not loaded or unloaded or bumped. The coating falls off during loading and unloading or use, and the corrosion resistance is significantly reduced, which significantly weakens the protective effect on high-strength steel. Summary of the invention

[0004] The object of the present invention is to provide a method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement and aluminum rolling, so as to solve the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the specific technical scheme of the high-strength steel hydrogen-embrittlement-free aluminum rolling plating method that can be repeatedly loaded and unloaded of the present invention is as follows: A method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement by rolling aluminum plating comprises the following steps: Step 1: Degreasing: Degreasing the high-strength steel workpiece using organic solvent ultrasonic cleaning; Step 2: Physical removal of oxide film: For high-strength steel workpieces that do not have high requirements for brightness, sandblasting is used to remove the oxide film on the surface of the spring; for high-strength steel workpieces with high requirements for appearance, magnetic polishing and vibration polishing are used to remove the oxide film; Step 3: Sandblasting substrate cleaning: Use organic solvent ultrasonic cleaning to remove the dirt remaining on the surface during the physical removal of the oxide film; Step 4: Activation: The high-strength steel workpiece is hung on the hanger and activated in the activation liquid in the activation chamber. After activation, it is placed in a drum filled with barrel plating materials to prepare for barrel aluminum plating; Step 5: Roll aluminum plating: Add an electroplating additive to the ionic liquid composed of AlCl3: halogenated imidazole salt in the electroplating chamber as a roll plating solution to roll aluminum plating on the activated high-strength steel workpiece; Step 6: Plating solution cleaning: After barrel plating, ultrasonic cleaning is performed in the cleaning solution in the equipment cleaning chamber to remove the ionic liquid; Step 7: Passivation and sealing: The barrel aluminum coating is subjected to chromate passivation treatment.

[0006] Furthermore, in the step 1, an organic solvent with strong oil removal ability is used for cleaning 2-4 times, and each cleaning lasts 5-20 minutes.

[0007] Furthermore, when sandblasting is used to remove the oxide film on the surface of the spring in step 2, the sandblasting pressure is 0.05MPa-0.4MPa, the sandblasting particles are 100-300 mesh silica sand and alumina sand, and the distance between the spray gun and the workpiece is 3-20cm.

[0008] Furthermore, in step 3, the ultrasonic cleaning is performed 2-4 times, and the ultrasonic cleaning time is 3-5 min / time. After the cleaning is completed, it is immediately blown dry and placed in the ionic liquid electroplating equipment cabin.

[0009] Furthermore, in step 4, the activation time is 5-30min, the activation temperature is 20-100°C, the steel balls with a diameter of 2-5mm as the roller plating material are pickled and activated before electroplating, the water content and oxygen content in the activation chamber where the activation liquid is located are less than 50ppm, an inert gas is introduced as a protective gas, and the positive pressure state in the chamber is maintained.

[0010] Furthermore, in step 5, a 0.02-2 g / L nitrogen phenanthroline derivative electroplating additive is added to an ionic liquid prepared by AlCl3: halogenated imidazolium salt in a molar ratio of 1-2:1 as a barrel plating solution, and the bath temperature is controlled at 10-80°C during barrel plating, and the barrel plating current density is 0.01-1 A / dm 2 , the roller plating speed is 1-15 rpm, the pure aluminum plate is used as the anode, the water content and oxygen content of the plating solution are less than 50ppm, inert gas is introduced as protective gas, and the positive pressure in the electroplating cabin is maintained.

[0011] Furthermore, in step 6, the cleaning is repeated 4 times, each time for 2-5 minutes, the workpiece is taken out of the chamber, and ultrasonically cleaned with deionized water for 3 times, each time for 2-4 minutes.

[0012] Furthermore, the passivation conditions of step 7 are as follows: a passivation temperature of 20-30° C., a pH range of 1.3-1.8, a passivation time of 30-180 s, a drying temperature of 50-100° C., and a drying time of 5-25 min.

[0013] Furthermore, step 8 includes a loading and unloading performance test: the high-strength steel bolts and nuts with rolled aluminum are repeatedly loaded and unloaded many times according to the loading and unloading conditions during normal use, and then the loaded and unloaded bolts and nuts are matched and placed in a neutral salt spray test box for corrosion resistance testing.

[0014] The invention discloses a method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement rolling aluminum plating, which has the following advantages: the method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement rolling aluminum plating adopts a set of water-free, acid-free, alkali-free and atmosphere-isolated processes, which avoids or solves the problem of hydrogen embrittlement fracture of high-strength steel caused by electroplating pre-treatment, electroplating and electroplating post-treatment, and adopts a rolling plating process, which can achieve mass production. The prepared aluminum coating has low hardness, good ductility and strong bonding force, can play a self-lubricating role in the loading and unloading process, has good loading and unloading performance of the workpiece, and is not easy to fall off. In addition, the aluminum coating has low porosity, has a strong anodic protection effect on high-strength steel, and has a strong self-repairing ability after chromate passivation, which still plays a strong protective role on high-strength steel after repeated loading and unloading. And the aluminum coating can self-repair after being scratched or abraded. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the SEM structure of the barrel-plated aluminum surface of the bolt in Example 1; Figure 2 This is a schematic diagram of the SEM structure of the bolt cross section of Example 2; Figure 3 This is the bolt and nut diagram after 5 loading and unloading tests; Figure 4 Figure 1104h of neutral salt spray test after 5 loading and unloading tests. DETAILED DESCRIPTION

[0016] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a high-strength steel hydrogen-embrittlement-free aluminum rolling plating method that can be repeatedly loaded and unloaded in conjunction with the accompanying drawings.

[0017] A method for repeatedly loading and unloading high-strength steel hydrogen-embrittlement-free aluminum rolling plating. In order to obtain good repeated loading and unloading performance of hydrogen-free aluminum plating coating, the high-strength steel is degreased with organic solvent, physically deoxidized, and then activated in an activation chamber to ensure good bonding between the aluminum coating and the substrate. Subsequently, aluminum is rolled in the electroplating chamber, and the coating is made densely crystalline, low in porosity, and well uniform through the effect of electroplating additives. Finally, through the self-repairing effect of the chromate passivation film, the aluminum coating still maintains a high corrosion resistance after repeated loading and unloading. The specific process steps are as follows: Step 1: Degreasing Use organic solvent ultrasonic cleaning to remove oil from high-strength steel workpieces to avoid the risk of hydrogen embrittlement during the degreasing process. When degreasing, use an organic solvent with strong degreasing ability to clean 2-4 times, each cleaning lasting 5-20 minutes.

[0018] Step 2: Physical removal of oxide film In order to avoid hydrogen embrittlement caused by the pickling and rust removal process, when the appearance of the high-strength steel workpiece does not require high brightness, sandblasting is used to remove the oxide film on the surface of the spring. The sandblasting pressure is 0.05MPa-0.4MPa, the sandblasting sand particles are 100-300 mesh silica sand and aluminum oxide sand, and the distance between the spray gun and the workpiece is 3-20cm. When the appearance of the high-strength steel workpiece is required to be high, magnetic polishing, vibration polishing and other methods are used to remove the oxide film.

[0019] Step 3: Sandblasting substrate cleaning Use organic solvent ultrasonic cleaning to remove the dirt remaining on the surface during the physical removal of the oxide film. The ultrasonic cleaning frequency is 2-4 times, and the ultrasonic cleaning time is 3-5 minutes / time. After cleaning, blow dry immediately and put it into the activation chamber of the ionic liquid electroplating equipment.

[0020] Step 4: Activation The high-strength steel is hung on the hanger and activated in the activation liquid in the activation chamber. The activation time is 5-30 minutes and the activation temperature is 20-100℃. After activation, it is placed in a drum with barrel plating materials to prepare for barrel aluminum plating. The steel balls with a diameter of 2-5mm for barrel plating materials are acid-washed and activated before electroplating. The water content and oxygen content in the chamber where the activation liquid is located are less than 50ppm. Inert gases such as argon and nitrogen are introduced as protective gases, and the positive pressure state in the chamber is maintained. There is no hydrogen evolution, decomposition and waste discharge during use, and long-term stable and green activation can be achieved.

[0021] Step 5: Aluminum Roll Plating In the electroplating chamber, a 0.02-2 g / L nitrogen phenanthroline derivative electroplating additive is added to the ionic liquid composed of AlCl3: halogenated imidazolium salt in a molar ratio of 1-2:1 as a barrel plating solution. During barrel plating, the bath temperature is controlled at 10-80°C and the barrel plating current density is 0.01-1 A / dm 2 , the roller plating speed is 1-15 rpm, and the pure aluminum plate is used as the anode. The water content and oxygen content of the plating solution must be less than 50ppm, and inert gases such as argon and nitrogen are introduced as protective gases, and the cabin is maintained in a positive pressure state.

[0022] Step 6: Plating solution cleaning After barrel plating, the ionic liquid is removed by ultrasonic cleaning in the cleaning liquid in the equipment cleaning chamber, and the cleaning is repeated 4 times, each time for 2-5 minutes. The workpiece is taken out of the chamber and ultrasonically cleaned 3 times with deionized water, each time for 2-4 minutes.

[0023] Step 7: Passivation and sealing In order to obtain better repeated loading and unloading performance, the barrel aluminum coating is subjected to chromate passivation treatment to obtain a better self-repairing passivation film and reduce the low corrosion resistance caused by coating scratches. The passivation conditions are passivation temperature 20-30℃, PH range 1.3-1.8, passivation time 30-180 s, drying temperature 50-100℃, and drying time 5-25min.

[0024] Step 8: Loading and unloading performance test The high-strength steel bolts and nuts that were rolled aluminum were loaded and unloaded repeatedly for 5 times according to the loading and unloading conditions during normal use. The loaded and unloaded bolts and nuts were then matched and placed in a neutral salt spray test box for corrosion resistance testing. Example

[0025] Step 1: 10 pieces of M16*80mm half-thread high-strength steel bolts were ultrasonically cleaned with acetone for 10 minutes, ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove oil, and cleaned twice.

[0026] Step 2: Each M16 bolt is sandblasted at a pressure of 0.4 MPa for 5 minutes, and then sandblasted at a pressure of 0.2 MPa for 2 minutes. The sand grains used are 200 mesh alumina sand, and the distance between the spray gun and the workpiece is 3-20 cm.

[0027] Step 3: Ultrasonic cleaning with anhydrous ethanol for 3 times, 4 minutes each time, and after drying, place it in the activation chamber of the ionic liquid electroplating equipment.

[0028] Step 4: Load 2kg of 3mm steel balls into the drum, activate them in the pickling activation chamber of the production line for 15 minutes, clean them 3 times, and transfer them to the hydrogen embrittlement-free activation chamber of the equipment.

[0029] After the bolts are installed, activate them in the activation solution for 10 minutes at a temperature of 50°C. After activation, put the bolts into the drum and transfer them to the barrel plating chamber.

[0030] Step 5: Add 0.5 g / L of nitrogen phenanthroline derivative electroplating additive to the AlCl3: halogenated imidazolium salt ionic liquid with a molar ratio of 2:1, roll plate for 600 min at a current of 3 A and a plating solution temperature of 40°C.

[0031] Step 6: After barrel plating, clean the workpiece in the cleaning chamber of the equipment with cleaning solution for 4 times, each time for 2 minutes. Take the workpiece out of the cleaning chamber and ultrasonically clean it in deionized water for 3 times, each time for 2 minutes.

[0032] Step 7: Use chromate passivation for 1 minute, the passivation temperature is 25°C, the passivation solution pH value is 1.5, and the temperature is 65°C for 15 minutes.

[0033] The surface morphology of barrel-plated aluminum bolts is as follows Figure 1As shown in the figure, the coating is dense, smooth, uniform and continuous. Under the same conditions, the bolts of aluminum barrel plating were directly subjected to neutral salt spray test after chromate passivation and then subjected to neutral salt spray test after 5 loading and unloading tests. The appearance of the bolts after loading and unloading tests is as follows: Figure 3 As shown, no problems such as coating shedding occurred during the loading and unloading process. Due to the soft aluminum coating and passivation film, there were coating scratches at the bite position. The bolts under both conditions did not show red rust until 1000 hours after the neutral salt spray test, and there was no significant difference in the corrosion resistance of the bolts after the loading and unloading test and before the loading and unloading test. Under the same test conditions, white rust appeared on the Dacromet bolts after 96 hours of corrosion when not loaded and unloaded, and no red rust appeared after 1000 hours. White rust appeared 24 hours after the loading and unloading test, and red rust appeared after 500 hours, and the corrosion resistance was significantly reduced. The neutral salt spray test results of the rolled aluminum bolts and Dacromet bolts after the loading and unloading test are as follows Figure 4 shown. Example

[0034] Step 1: 50 pieces of M16 high-strength steel nuts were ultrasonically cleaned with acetone for 15 minutes and then ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove oil.

[0035] Each M16 nut was sandblasted at a pressure of 0.3 MPa for 2 minutes and then sandblasted at a pressure of 0.2 MPa for 1 minute. The sand grains used were 250 mesh alumina sand, and the distance between the spray gun and the workpiece was 3-20 cm.

[0036] Step 2: Ultrasonic cleaning with anhydrous ethanol for 3 times, 4 minutes each time, and after drying, place it in the activation chamber of the ionic liquid electroplating equipment.

[0037] Step 3: Load 1.5kg of 5mm steel balls into the drum, activate them in the pickling activation chamber of the production line for 15 minutes, clean them 3 times, and transfer them to the hydrogen embrittlement-free activation chamber of the equipment.

[0038] Step 4: After the nuts are installed, activate them in the activation solution for 12 minutes at a temperature of 40°C. After activation, place the bolts in the drum and transfer them to the barrel plating chamber.

[0039] Step 5: Add 1 g / L of nitrogen phenanthroline derivative electroplating additive to the AlCl3: halogenated imidazolium salt ionic liquid with a molar ratio of 1.8:1 in the electroplating chamber, roll plate for 360 min at a current of 5 A and a bath temperature of 25°C.

[0040] Step 6: After barrel plating, clean the workpiece in the cleaning chamber of the equipment with cleaning solution for 4 times, each time for 2 minutes. Take the workpiece out of the cleaning chamber and ultrasonically clean it in deionized water for 3 times, each time for 2 minutes.

[0041] Step 7: Use chromate passivation for 50 seconds, the passivation temperature is 28°C, the passivation solution pH value is 1.3, and the temperature is 65°C for 15 minutes.

[0042] Electroplated nut coating cross section Figure 2 As shown in the figure, the coating thickness is 10-20μm. Under the same conditions, the aluminum-plated nuts were matched with bolts, and then tested with bolts for 5 times of loading and unloading, and then subjected to neutral salt spray test. Figure 3 As shown, there are scratches on the coating at the bite position, but the coating has good bonding strength and ductility, and there is no problem of coating shedding. The nuts under both conditions did not show red rust until 1000 hours after the neutral salt spray test, and there was no significant difference in the corrosion resistance of the nuts after the loading and unloading test and before the loading and unloading test. Under the same test conditions, white rust appeared on the Dacromet bolts after 96 hours without loading and unloading, and no red rust appeared after 1000 hours. White rust appeared 24 hours after the loading and unloading test, and red rust appeared after 500 hours, and the corrosion resistance was significantly reduced. The neutral salt spray test results of the rolled aluminum bolts and Dacromet bolts after the loading and unloading test are as follows Figure 4 shown.

[0043] In summary, the ionic liquid electroplated aluminum coating has strong bonding strength, low porosity, and strong protective effect of the sacrificial anode. The aluminum coating has low hardness (30-35Hv) and good ductility. It can play a self-lubricating role during loading and unloading, and can effectively replace the electroplated cadmium coating. In addition, the ionic liquid electroplated aluminum plating solution is a room temperature molten salt formed by AlCl3 and halogenated imidazole salts. There is no problem of hydrogen evolution during the electroplating process, and electroplating can be carried out at room temperature. The electroplating process will not affect the organization and performance of high-strength steel.

[0044] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement by rolling aluminum, characterized in that: The steps include: Step 1: Degreasing: Degreasing the high-strength steel workpiece using organic solvent ultrasonic cleaning; Step 2: Physical removal of oxide film: For high-strength steel workpieces that do not have high requirements for brightness, sandblasting is used to remove the oxide film on the surface of the spring; for high-strength steel workpieces with high requirements for appearance, magnetic polishing and vibration polishing are used to remove the oxide film; Step 3: Sandblasting substrate cleaning: Use organic solvent ultrasonic cleaning to remove the dirt remaining on the surface during the physical removal of the oxide film; Step 4: Activation: The high-strength steel workpiece is hung on the hanger and activated in the activation liquid in the activation chamber. After activation, it is placed in a drum filled with barrel plating materials to prepare for barrel aluminum plating; Step 5: Roll aluminum plating: Add an electroplating additive to the ionic liquid composed of AlCl3: halogenated imidazole salt in the electroplating chamber as a roll plating solution to roll aluminum plating on the activated high-strength steel workpiece; Step 6: Plating solution cleaning: After barrel plating, ultrasonic cleaning is performed in the cleaning solution in the equipment cleaning chamber to remove the ionic liquid; Step 7: Passivation and sealing: The barrel aluminum coating is subjected to chromate passivation treatment.

2. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: In the step 1, an organic solvent with strong oil removal ability is used for cleaning 2-4 times, and each cleaning takes 5-20 minutes.

3. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: When the oxide film on the surface of the spring is removed by sandblasting in step 2, the sandblasting pressure is 0.05MPa-0.4MPa, the sandblasting particles are 100-300 mesh silica sand and alumina sand, and the distance between the spray gun and the workpiece is 3-20cm.

4. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: In the step 3, the ultrasonic cleaning is performed 2-4 times, and the ultrasonic cleaning time is 3-5 min / time. After the cleaning is completed, the mixture is immediately blown dry and placed in an activation chamber of the ionic liquid electroplating equipment.

5. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: In step 4, the activation time is 5-30min, the activation temperature is 20-100°C, the steel balls with a diameter of 2-5mm are used as the roller plating material, and are acid-washed and activated before electroplating. The water content and oxygen content in the cabin where the activation liquid is located are less than 50ppm, an inert gas is introduced as a protective gas, and the positive pressure state in the cabin is maintained.

6. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: In step 5, a 0.02-2 g / L nitrogen phenanthroline derivative electroplating additive is added to an ionic liquid prepared by AlCl3: halogenated imidazolium salt in a molar ratio of 1-2:1 as a barrel plating solution, and the plating solution temperature is controlled at 10-80 °C during barrel plating, and the barrel plating current density is 0.01-1 A / dm 2 , the roller plating speed is 1-15 rpm, the pure aluminum plate is used as the anode, the water content and oxygen content of the plating solution are less than 50ppm, inert gas is introduced as protective gas, and the positive pressure state in the electroplating cabin is maintained.

7. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: Step 6: Repeat the cleaning for 4 times, each time for 2-5 minutes, take the workpiece out of the chamber, and use deionized water for ultrasonic cleaning for 3 times, each time for 2-4 minutes.

8. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: The chromate passivation conditions in step 7 are as follows: a passivation temperature of 20-30° C., a pH range of 1.3-1.8, a passivation time of 30-180 s, a drying temperature of 50-100° C., and a drying time of 5-25 min.

9. The method for repeatedly loading and unloading high-strength steel without hydrogen embrittlement aluminum barrel plating according to claim 1, characterized in that: Including step 8 loading and unloading performance test: the high-strength steel bolts and nuts with aluminum plating are repeatedly loaded and unloaded many times according to the loading and unloading conditions during normal use, and then the loaded and unloaded bolts and nuts are matched and placed in a neutral salt spray test box for corrosion resistance testing.

Images