Valve grinding, in the valve manufacturing process is the sealing surface of a common method of finishing. Grinding can make the valve seal surface to obtain a very high dimensional accuracy, geometric shape accuracy and surface roughness, but can not seal the surface of the interface between the accuracy of the position. After grinding the sealing surface of the valve can usually reach the dimensional accuracy of 0.001mm~0.003mm, geometric shape accuracy (such as roughness) of 0.001mm. In the lapping project, the grinding tool is fitted together with the surface of the sealing ring, and the lapping process is made with complex grinding motion along the fitting surface. The grinding agent is placed between the surface of the sealing ring and the surface of the seal circle, while the grinding material in the grinding agent slides or rolls with the surface of the sealing ring, and the thin layer of metal on the surface of the sealing ring is cut off.

The convex peaks on the surface of the seal ring are first milled and then gradually reached the required geometrical shape. Grinding is not only the abrasive of the metal machining process, but also chemical action.

The grease in the abrasive can be the surface formed by the oxide film, thus accelerating the grinding process.

Principle of grinding valve sealing surface

The basic principle of the sealing surface grinding includes five aspects, such as lapping process, lapping movement, lapping speed, grinding pressure and grinding allowance.

1. Grinding process The grinding fixture is well fitted with the surface of the sealing ring, and the lapping is done with a complex abrasive movement along the surface of the fitting. The grinding agent is placed between the surface of the sealing ring and the surface of the seal circle, while the grinding material in the grinding agent slides or rolls with the surface of the sealing ring, and the thin layer of metal on the surface of the sealing ring is cut off.

The convex peaks on the surface of the seal ring are first milled and then gradually reached the required geometrical shape. Grinding is not only the abrasive of the metal machining process, but also chemical action.

The grease in the abrasive can be the surface formed by the oxide film, thus accelerating the grinding process.

2. Abrasive movement When the grinding tool is relative to the surface of the sealing ring, each point on the surface of the seal ring should be the same as the relative sliding distance of the grinding tool. Furthermore, the direction of relative motion should be constantly changed. The continuous change in the direction of the movement so that each abrasive particles will not be on the surface of the seal to repeat their own movement trajectory, so as to avoid the obvious scratches and increase the surface roughness of the seal ring.

In addition, the moving direction of the constant change can also make the abrasive distribution more evenly, thereby more evenly cut off the surface of the seal ring metal. Despite the complexity of the grinding movement, although the direction of movement in the change, but the grinding movement is always along the grind with the surface of the sealing ring on the surface of the fitting.

Whether it is hand-lapping or mechanical grinding, the geometrical precision of the sealing ring surface is mainly influenced by the geometry precision and lapping motion of the grinding tool.

3. Grinding speed The faster the lapping movement, the higher the efficiency of the grinding.

Grinding speed, in the unit time of the workpiece surface through more abrasive grains, cutting away more metal. The grinding speed is usually 10m/min~240m/min. Grinding accuracy requires a relatively high workpiece, grinding speed is generally not more than 30m/min.

The grinding speed of valve sealing surface is related to the material of sealing surface, the grinding speed of copper and cast iron sealing surface is 10m/min~45m/min, hardened steel and cemented carbide sealing surface is 25m/min~80m/min, austenitic stainless steel sealing surface is 10m/min~25m/min.

4. Grinding pressure The grinding efficiency increases with the increase of the grinding pressure, and the grinding pressure cannot be too large for 0.01mpa~0.4mpa. The grinding pressure is 0.1mpa~0.3mpa when grinding the sealing surface of cast iron, copper and austenitic stainless steel materials, and hardened steel and cemented carbide sealing surface are 0.15mpa~0.4mpa.

Coarse research to take a larger value, when the smaller value.

5. Grinding allowance Due to the grinding Liang Mian finishing process, the cutting volume is very small. The size of the grinding allowance depends on the machining accuracy and surface roughness of the process.

The smaller the grinding allowance is, the better it is to ensure the removal of the machining marks and correction of the geometrical shape error of the seal ring. The sealing surface is usually polished before grinding. After finishing the sealing surface can be directly acquired, the minimum grinding allowance is: the diameter allowance is 0.008mm~0.020mm; The plane allowance is 0.006mm~0.015mm. Manual grinding or high hardness of materials to take a small value, mechanical grinding or low hardness of materials to take large values.