How To Repair Chrome Plating On Piston Rods
The piston rod is one of the important parts of the hydraulic cylinder, especially in large crane equipment, because of the large size, it will inevitably cause surface damage such as strains, bruises, and peeling of the chrome plating layer during use. Once the surface of the chrome plating piston rods is damaged, it may leak oil, or damage the oil seal, causing the hydraulic cylinder to fail to operate normally.
According to the manufacturer’s use regulations, all piston rods must be updated in this case. Due to the relatively high price of these larger piston rods, how to maximize the service life through repair has become a problem worthy of attention.
We have used tin hanging repairs, brazing coating and other methods to repair, but because the strength of tin is too low, the tin layer is quickly worn away. However, due to the large heat-affected zone of welding copper, the chrome-plated layer around the weld is often peeled and peeled off, resulting in greater damage. Later, manual arc welding with stainless steel or cast iron electrodes received better results. Since then, this method has been adopted and a certain amount of experience has been accumulated. The following describes this process.
Step 1: Clean up welding parts of the chrome plating piston rods.
- Remove all oil stains, oxide layers, and burrs from the damaged part to expose the metal color, and be careful not to scratch the undamaged part.
- Clean the welding parts, dry them, and proceed to the next process.
Step 2: Welding repair.
- Welding rod selection. Generally, low-carbon and medium-carbon steel can use Ao-137 low-hydrogen electrode and dry it at 100-150°C for 1.5 hours to prevent welding seam pores, slag inclusion, and other defects caused by the wet electrode.
- Polarity selection of welding machine. DC reverse connection, high electrode temperature, and low working temperature during reverse welding, the heat-affected zone is relatively small.
- Selection of welding current. The current is 20% lower than that of ordinary carbon steel welding. Choose the appropriate electrode diameter for long-term welding and repair parts. Generally finer than coarser.
- Use the straight-line transportation method. Cover the non-welded surface during operation to prevent damage to the surface that does not need to be repaired. The current should not be too large to prevent weld undercut. One welding time should not be too long to avoid deformation caused by thermal influence. Continue welding when the weld metal temperature drops below 80°C.
Step 3: Trimming and shaping.
After all repair welding is completed, file it with a rough file. When the machining allowance remains 0.3-0.5mm, use fine files for grinding. Finally, leave a margin of 0.03-0.05mm and use sandpaper or metallographic sandpaper of 240 mesh or more for polishing and polishing with cloth wheels.