Grinding marks on the surface of imported bearings during precision grinding

Grinding marks on the surface of imported bearings during precision grinding 

During the precision grinding of imported bearings, due to high requirements for surface roughness, the grinding marks on the working surface can often be observed with the naked eye. The surface grinding marks can be categorized as follows:

1. Crossed spiral lines: This phenomenon is mainly caused by the poor straightness of the grinding wheel's axis, resulting in unevenness. During the grinding process, only a partial contact occurs between the grinding wheel and the workpiece. After multiple reciprocating movements, crossed spiral lines can be observed on the workpiece surface.

The pitch of these spiral lines is related to the workpiece table speed, workpiece rotational speed, as well as the alignment of the grinding wheel's axis and the worktable guide.

Causes of the formation of spiral lines:

1. Poor rigidity of the V-shaped guide rail, resulting in grinding wheel offset, with only the edge of the grinding wheel contacting the work surface.
2. Unstable reversing speed and low accuracy of the worktable during dressing of the grinding wheel, resulting in slightly less dressing on one edge of the grinding wheel.
3. Poor rigidity of the workpiece itself.
4. Presence of broken or peeled abrasive grains on the grinding wheel and iron chips generated during the grinding process, which should be removed by rinsing or brushing the dressed grinding wheel with coolant water.
5. Poor dressing of the grinding wheel, resulting in local protrusions, etc.

Main causes of the formation of spiral lines:

1. Poor dressing of the grinding wheel, unrounded edges and corners, and failure to use coolant during dressing.
2. Excessive lubricating oil on the worktable guide rails, causing the worktable to float.
3. Poor precision of the machine tool.
4. Excessive grinding pressure, etc.

Additionally, the following issues related to imported bearings were mentioned:

1. Bearing burning: The presence of large-sized alloy abrasive particles and black metal oxides in the iron spectrum.
2. Micro-dynamic wear on the back of the bearing: Abnormal iron concentration in the spectral analysis, presence of sub-micron-sized iron wear particles, abnormal moisture content and acid value of the lubricating oil.
3. Corrosion on the surface of the bearing journal: Abnormal iron element concentration in the spectral analysis, presence of sub-micron-sized iron particles in the iron spectrum, exceeding the standard for water content or acid value of the lubricating oil.
4. Peeling on the bearing surface: Discovery of fatigue-peeled alloy abrasive particles and layered abrasives in the iron spectrum.
5. Surface scratches on the bearing: Presence of cutting abrasive particles in the iron spectrum, with the abrasive composition being non-ferrous metals.
6. Corrosion on the bearing surface: Abnormal concentration of non-ferrous metal elements in the spectral analysis, the presence of sub-micron-sized wear particles of non-ferrous metal components in the iron spectrum, and exceeding the standard for water content or acid value of the lubricating oil.
7. Surface scratches on the bearing journal: Presence of iron-based cutting abrasive particles or black oxide particles in the iron spectrum, and the presence of tempering colors on the metal surface.

Please note that the translation may not capture the entire context accurately, and it's advisable to refer to the original text for precise understanding.