This is a kind of high-speed precision steel ball made from GCr15 vacuum degassing refining bearing steel, by a series of operations like forming, burnishing, heat treatment, polishing, surface reinforcing, initial lapping, flaw detection, precision lapping, cleaning, rust prevention, and packaging. The ball forming involves 2 steps: lightly pulling the raw material, and cutting & cold heading automatically. Compression ratio of the raw material is controlled between 1.9 and 2.5 during cold heading. After forming, the precision balls will show little or no rings and poles. The finished steel balls feature high precision, no noise, stable quality, and no surface defect. Specifications of our steel balls range from 3.9688 to 15.0812, including 3.9688, 4.7625, 5.9531, 6.35, 6.7469, 7.144, 7.9375, 8.7312, 9.525, 11.1125, 11.5094, 11.9062, 12.0000, 12.3031, 12.7000, 13.4938, 14.2875, and 15.0812. Zhengang steel balls are mainly applied in appliances, automobile, engine, bearings, bicycle, etc.

Manufacturing

Inspection Standards

1. The standards regulate the inspection requirements and quality appraisal for GCr15G steel ball cold heading process.
2. The cold heading process will be detected according to “ZG/QW05-01-2009 Steel Ball Cold Heading Process Technical Requirements”.
3. Quality assurance is needed for hot rolling process apart from the cold heading technical requirements.
4. We test the measuring tools, testing methods, number of sampling (N), and unqualified counting number (C) by self-test or sample test according to Table 1.

5. Details of quality appraisal standards
5.1. Steel balls whose cold heading detection results meet the standards are left to be processed
5.2. Balls whose diameter tolerance and pressure deviation are in line with Table 2 are left to be processed
5.3. Steel balls with the burrs, cracks less than 1/2 of the sided allowance can be seen as qualified, those with the flaws less than 2/3 are treated as unqualified.
5.4. For those balls do not comply with 5.3, or whose diameter tolerance and pressure deviation are in line with Table 2, we retain them if the unqualified balls account for less than 2% of the total number, else we report as worthless.
5.5. Steel balls with the ball amount for each 1kg weight fail to reach our standards will be left for further process.

5.6. Unqualified treatment will be given the steel balls if there are unqualified items in the hot rolling quality assurance.

Quality Inspection