The electrical properties, appearance quality and micromorphology of copper foil after laser cladding repair of pits on the surface of TA1 titanium plate were studied by using eddy current conductivity meter, scanning electron microscope (SEM) and high current density copper plating test simulating actual production conditions. The results show that after the pit defects of TA1 titanium plate were repaired by laser cladding process, the conductivity of cladding zone, fusion zone, heat affected zone and substrate zone was slightly different, and the average difference was within 5%, but the appearance quality and micromorphology of copper foil plated in each area were almost the same. The use of laser cladding technology to repair defects such as pits on the surface of cathode titanium roller is expected to achieve green repair and remanufacturing of titanium roller.

The foil machine is one of the most important production equipment in the manufacturing process of electrolytic copper foil, and the cathode titanium roller is the highest value and most critical component in the foil machine. Its electrical properties will affect the electrodeposition behavior of copper ions in the foil production process. Its surface quality (including roughness, uniformity, etc.) will be copied or inherited to the rough surface of copper foil during the foil production process, thereby determining the surface quality of the rough surface of copper foil. When the titanium roller is physically injured or burned by an arc during service, pit defects will be left on its surface, which will be copied or inherited to the copper foil during operation, causing defects such as mottled, color difference, pinholes or copper powder on the copper foil, which will adversely affect the surface quality of the copper foil. However, the repair of pits on the surface of titanium rollers has always been one of the problems that plague copper foil manufacturers and titanium roller manufacturers. The cathode titanium roller is made of TA1, which is either made by strong spinning or welded from rolled plates. Its grain size is fine, and its grain size is generally between 6 and 12 levels.

At present, the industry generally uses a grinder to grind a layer of titanium roller to remove the pits for shallow titanium roller pit defects. For pit defects that are slightly deeper and close to the edge of the titanium roller, the pits are generally repaired by argon arc welding. However, after repair, the repaired area is prone to copper nodules during high current density copper plating production, and the copper nodules are easy to fall off and fall into the electrolyte, which may cause a short circuit failure of the cathode and anode of the raw foil system, which may further damage the equipment and affect production. For pit defects that are deep and close to the middle of the titanium roller, there is no way to deal with them temporarily. At this time, the titanium roller can only be scrapped, resulting in material waste and huge economic losses [4]. Laser cladding technology uses the heat of the laser beam to melt the surface of the substrate to be repaired and the metal powder passing through to form a molten pool. The two materials diffuse and solidify into one, achieving the purpose of repairing parts and molds. It has the advantages of fast heating speed, fast cooling speed, small heat-affected zone, metallurgical bonding between the cladding layer and the substrate, dense structure, less residual stress in the cladding layer, and fewer defects such as cracks. Laser cladding technology can be used to repair various types of pit defects on cathode titanium rollers, and it is expected to achieve green remanufacturing and restoration of titanium rollers [58. Therefore, in order to obtain the electrical properties and copper plating effect of the cathode titanium roller pit defect after laser cladding repair, this study prepared a sample of TA1 titanium plate pit repaired by laser cladding technology, and tested the conductivity of different parts of the sample using a conductivity meter. By simulating the service condition of the cathode titanium roller, the repaired TA1 titanium plate was subjected to a high current density copper plating test. The research results can provide reference for the laser cladding remanufacturing repair of the cathode titanium roller.

1 Experimental materials and methods

1.1 Experimental materials

The test selected a rolled TA1 titanium plate with the same material as the cathode titanium roller, with a size of 160mmx45mmx6mm (length×width×thickness), to simulate the cathode titanium roller. A groove of 80mmx6mmx2mm (length×width×depth) was opened on its surface to simulate the pit defect on the titanium roller. The bottom of the groove was designed as a transition fillet with a radius of 6mm, as shown in Figure 1. The cladding material used commercial TA1 pure titanium powder, the appearance of which is shown in Figure 2. The powder particles have good sphericity and a diameter of 50~100μm.

1.2 Test method

The laser cladding test was completed using a 3kW flexible fiber laser cladding system. The system consists of a LaserlineLDF60-3000 semiconductor fiber laser, an ABB six-axis robot, a ZF annular cladding head, a CWFL water cooling device, and an RC-PGF-D-2 double-bin negative pressure powder feeder. Argon with a purity (mass fraction) of 99.9% was used as the carrier gas and shielding gas. The coaxial powder feeding mode was adopted in the light, and the cladding was carried out in a longitudinal (marked in Figure 1) “bow path” with a 50% overlap rate. After repeated tests, the selected laser cladding process parameters are shown in Table 1.

The FD-102 digital portable eddy current conductivity meter was used to measure the conductivity of different positions of the sample at an ambient temperature of 25°C. A homemade small-scale raw foil testing machine was used to carry out the copper plating test of the repaired titanium plate. The specific configuration of the copper plating solution was: copper ion (Cu2+) 90g/L, sulfuric acid (H,SO4) 120g/L, chloride ion (CI) 20mg/L, Several additives. The copper plating solution temperature is 55°C, and the current density during copper plating is 60A/dm². An ordinary optical microscope was used to observe the macroscopic morphology of the titanium plate sample cladding layer and the copper foil plated on the titanium plate. A ZEISSEVO18 scanning electron microscope was used to observe the microscopic morphology of the copper foil plated on the test titanium plate.

2 Results and Discussion

2.1 Electrical Conductivity

Figure 3 shows the macroscopic morphology and electrical conductivity test positions of the laser cladding area of ​​the titanium plate. Positions 1 and 7 in Figure 3 are the base material area, which is not affected by the laser cladding, positions 2 and 6 are the heat-affected zones, which are affected by the heat of the laser cladding, positions 3 and 5 are the fusion zones, and position 4 is the cladding zone. It can be seen that the laser cladding area has a uniform appearance, good overlaps between each pass, and a smooth transition between the cladding area and the base metal, without defects such as pores, oxidized welding slag, cracks, and spatter. After machining the clad test titanium plate, the electrical conductivity of each area in Figure 3 was tested, as shown in Figure 4. It can be seen that the electrical conductivity of the cladding area of ​​the test titanium plate is the lowest, while the electrical conductivity of the heat-affected zone is the highest. The differences in electrical conductivity between the cladding zone and the heat-affected zone at positions I and II are 3.06% and 7, respectively. .96%, the conductivity of each area at II is quite different. This is because the test titanium plate is in a rolled state, and the heat-affected zone has recovered to a certain extent under the impact of laser cladding heat, and the stress, dislocation, distortion and other defects in the matrix that are unfavorable to the conductivity have been eliminated to a certain extent, so the conductivity of the heat-affected zone of the test titanium plate is the highest. The lowest conductivity in the cladding zone is because the powder will inevitably introduce a small amount of impurity elements after melting under the input of laser energy, which is unfavorable to the conductivity. In addition, since II is more affected by the heat of laser cladding than I, the conductivity of each area is slightly different. However, in general, the average value of the conductivity difference of each area is about 5%, indicating that the conductivity of each area of ​​the test TA1 titanium plate after laser cladding is slightly different.

2.2 Copper plating effect

Figure 5 shows the morphology of the cladding layer of the titanium plate sample after machining and the morphology of the plated copper foil. It can be seen that the cladding zone, fusion zone, heat-affected zone and substrate of the titanium plate sample after machining are almost the same in the macroscopic sense, and the copper foil plated in each area is almost unobservable in the macroscopic sense.

Figure 6 is the SEM microscopic morphology of the copper foil plated in different areas of the test titanium plate. There are no obvious differences in the morphology, size, uniformity, etc. of the copper foil plated in each area. It can be concluded that during the high current density copper plating process, the deposition behavior of copper ions in each area of ​​the test titanium plate is almost the same. Combined with the conductivity test analysis results, it can also be inferred that although the conductivity of each area of ​​the test TA1 titanium plate after laser cladding is slightly different, these differences will hardly affect the copper plating effect of the test titanium plate. Therefore, it can be further inferred that the laser cladding technology is used to repair defects such as pits on the surface of the titanium roller. The copper plating effect of the cladding area, fusion area and heat-affected zone repaired by laser cladding on the titanium roller is basically the same as that of other areas on the titanium roller.

3 Conclusion

The use of laser cladding technology to repair defects such as pits on the surface of the cathode titanium roller is expected to achieve green repair and remanufacturing of titanium rollers.

After the pit defects of TA1 titanium plate were repaired by laser cladding, the conductivity of the cladding zone, fusion zone, heat-affected zone and substrate zone was slightly different, and the average difference was within 5%, but the appearance quality and micromorphology of the copper foil plated in each area were almost the same.