Which factors will affect the surface roughness of stainless steel seamless pipes after polishing

Which factors will affect the surface roughness of stainless steel seamless pipes after polishing? 

The factors influencing the surface roughness of stainless steel seamless pipes after polishing mainly include polishing process parameters, equipment and abrasive material characteristics, pipe material, and operational standardization. The details are as follows: 

1. Polishing Process Parameters

Rotational speed of the polishing wheel

If the rotational speed is too high, it will cause local temperature rise, surface melting or burning, and roughness increase; if the rotational speed is too low, the polishing efficiency will be insufficient and residual scratches will remain. 

Polishing pressure

If the pressure is too high, it may cause surface scratches, deformation or excessive grinding, resulting in coarse lines; if the pressure is too low, it will not be able to effectively remove the traces from the previous process. 

Polishing time

If the time is too short, the roughness from the previous process (such as grinding) will not be completely eliminated; if the time is too long, excessive polishing may cause the surface to become "orange-peel-like" (with increased microscopic undulations). 

II. Characteristics of Abrasives and Polishing Materials

Abrasive grit size

Coarse abrasives (such as 80-240 mesh) are used to remove obvious defects but will leave deeper scratches; fine abrasives (such as 800-2000 mesh) are used for fine polishing. The finer the grit size, the smoother the surface.

The hardness of the abrasive needs to match that of stainless steel: if the hardness is too high, it will scratch the surface; if it is too low, the grinding efficiency will be low. 

Polishing liquid / paste components

The insufficient lubricity and cooling property of the polishing liquid will cause abrasive particles to accumulate or local overheating, which will affect the roughness; if the concentration of the polishing paste containing abrasive particles is too high or the distribution is uneven, scratches may occur. 

Material of polishing wheels

Rigid polishing wheels (such as wool wheels) are suitable for fine polishing, while flexible wheels (such as cloth wheels) are adaptable to complex surfaces, but improper pressure control may lead to unevenness. 

III. Pipe Material and Pre-treatment

Material Hardness

Harder stainless steel (such as martensitic stainless steel) requires stronger grinding force. If the abrasive or pressure is insufficient, it is prone to leaving processing marks; soft materials (such as austenitic stainless steel) are easily over-polished, resulting in deformation. 

Original surface condition

The welding spatter, oxide scale, burrs, etc. have not been ground smooth in advance, which will increase the difficulty of polishing and result in uneven surface roughness. 

Organizational structure

If the grains are coarse or the structure is uneven (such as forging defects), the grinding speed in different areas during polishing is inconsistent, which affects the surface flatness. 

IV. Equipment and Operating Factors

Equipment Precision

The main shaft vibration of the polishing machine and the insufficient coaxiality of the fixture will cause uneven contact between the polishing wheel and the pipe material, resulting in local over-polishing or under-polishing. 

Operation techniques

During manual polishing, the pressure is uneven and the movement speed is unstable, which can lead to inconsistent surface roughness; during mechanical polishing, the feed speed is too fast and the abrasive material does not have sufficient effect. 

Abrasive replacement and cleaning

If the abrasive is used for too long and becomes worn or contaminated with impurities, not replacing it in time will reduce the polishing effect; and the leftover grinding debris from the previous process on the equipment and fixtures will cause the mixing and contamination of different grit abrasive. 

V. Environmental Factors

Temperature and Humidity: In high-temperature environments, the polishing solution is prone to evaporate, resulting in a decline in lubrication effect; in humid environments, it may cause the abrasive to clog or the surface of the pipe to rust, thereby affecting the polishing quality. 

Summary: To effectively control the surface roughness after polishing, it is necessary to optimize process parameters (rotation speed, pressure, time), select appropriate abrasives and equipment, control the quality of material pre-treatment, and standardize operations.