Differences between surface polishing and fine grinding of red copper balls and analysis of applicability of high-pressure valves

I. Core differences between polishing and fine grinding
Surface polishing and fine grinding of red copper balls are both processes to improve their surface quality, but there are significant differences in technical paths, goals and applicable scenarios:

Process principles and goals

Polishing: Removal of surface micro-protrusions through mechanical or chemical action, mainly relying on the friction and dissolution of soft polishing wheels or polishing liquids (such as copper chemical polishing liquids), the goal is to reduce the surface roughness to Ra≤0.1μm, forming a mirror effect, while reducing surface micro-defects (such as scratches, micropores).
Fine grinding: Use hard abrasives (such as diamond or silicon carbide) to cut the surface in a directional manner, and through step-by-step grinding of multi-grade abrasives (such as G100-G1000 grades), the goal is to control the surface roughness within Ra 0.2~0.4μm, and achieve strict matching of geometric accuracy (such as spherical degree ±0.001mm).
Material removal mechanism

Polishing is mainly based on "micro plastic flow", which softens the surface metal and fills the concave area to form a continuous and smooth surface; grinding is mainly based on "micro cutting", and the material is uniformly removed through mechanical scraping of abrasive particles.

Surface performance influence

The surface oxide film of the polished copper ball is denser and the corrosion resistance is improved (such as 72 hours without rust in a neutral salt spray environment), but the hardness may decrease due to excessive softening (HV 80→70).

The surface after grinding retains a certain micro texture, which can enhance the friction adaptability with the sealing material, but it needs to be matched with passivation treatment (such as copper passivation liquid T401) to prevent oxidation.

2. Special requirements for the surface treatment of copper balls for high-pressure valves

High-pressure valves (such as oil and gas pipeline ball valves) need to operate stably for a long time under working conditions (pressure>10MPa, medium containing sulfur or acidic impurities), and the following core requirements are put forward for the surface performance of copper balls:

Sealing: The surface roughness must be ≤0.2μm to reduce the risk of medium leakage.
Wear resistance: It needs to withstand high-frequency friction between the valve seat and the ball, and the surface hardness is recommended to be ≥HV 90.
Corrosion resistance: In oil and gas media containing H₂S or CO₂, the surface passivation film must have the ability to resist chemical penetration.
Dimensional stability: The G1000-level precision tolerance must be controlled within ±0.001mm to avoid deformation under high temperature and high pressure.

III. Process optimization suggestions
Grinding control points:

Use abrasives with different particle sizes (such as G200→G1000) to avoid abrasive embedding caused by high ductility of red copper (lubricants such as soapy water or polishing paste are required).
Perform passivation treatment immediately after grinding to prevent the thickening of the oxide layer from affecting dimensional accuracy.
Polishing process upgrade:

For high-purity red copper (Cu≥99.9%), chemical mechanical polishing (CMP) technology is used in combination with cerium dioxide polishing liquid to achieve nano-level finish of Ra≤0.05μm while avoiding lattice deformation caused by mechanical stress.