Polishing methods for stainless steel seamless pipes

Stainless steel seamless pipes, unless intended for deep underground use, typically require polishing to ensure a bright and aesthetically pleasing surface. The commonly used polishing methods include mechanical polishing, chemical polishing, and electrochemical polishing. This article will talk about the polishing methods for stainless steel seamless pipes.

1. Mechanical Polishing

Mechanical polishing uses a polishing wheel or polishing belt to process the surface of stainless steel seamless pipes. The abrasives in the polishing agent facilitate the polishing process, resulting in a smooth, polished surface.

- Surface Quality:

Mechanical polishing can achieve a mirror-bright finish with a roughness of less than 0.4μm.

- Polishing Techniques:

Simple-shaped parts can be polished using hard polishing wheels or polishing tapes.

Complex-shaped parts are polished with soft polishing wheels.

Large quantities of small parts can be polished in batches using methods such as drum polishing, vibration machine polishing, centrifugal polishing, and rotational polishing.

- Grinding Process:

The mechanical polishing process minimally removes material, making it unsuitable for rough surfaces.

Pre-polishing processes include rough grinding, medium grinding, and fine grinding using polishing paste.

Additional treatments like sandblasting, shot peening, and wire wheel brushing can be used for specific requirements like scale removal, deburring, and welding slag removal.

2. Chemical Polishing

Chemical polishing involves immersing the stainless steel seamless pipes in a suitable solution. The solution dissolves the protruding parts on the pipe surface faster, leading to a flattened and polished surface.

- Efficiency:

Chemical polishing is less labor-intensive and time-consuming compared to mechanical polishing and can handle the inner surfaces of small parts.

- Limitations:

Chemical polishing has a weak polishing ability and slightly improves brightness.

It increases surface activity, requiring post-polishing passivation to ensure corrosion resistance.

It is more suitable for pre-polishing due to its fast polishing speed but poor finish quality.

3. Electrochemical Polishing

Electrochemical polishing enhances the reflective properties of stainless steel seamless pipes, improves corrosion resistance, reduces surface hardness, and decreases the friction coefficient by reducing surface roughness. It is also effective in removing burrs.

- Advantages over Mechanical Polishing:

Electrochemical polishing forms a passivated surface on stainless steel, enhancing corrosion resistance.

It has higher production efficiency.

- Substrate Requirements:

Requires a uniform metallographic structure for an even polished surface.

Cannot effectively polish deep scratches.

- Current Density:

The surface current density must remain uniform for consistent brightness.

Adequate contact area between the fixture and the pipe is necessary to prevent local overheating and burnout.

- Material Specificity:

Processes suitable for polishing austenitic stainless steels may not be appropriate for martensitic stainless steels due to the risk of corrosion.