Grinding is a commonly used finishing method for the sealing surface of valves in the manufacturing process. Grinding can make the valve sealing surface obtain high dimensional accuracy, geometric shape roughness and surface roughness, but it cannot improve the mutual position accuracy between the surfaces of the sealing surface. The dimensional accuracy of the ground valve sealing surface is usually 0.001~0.003mm; the geometric shape accuracy (such as unevenness) is 0.001mm; the surface roughness is 0.1~0.008.
The basic principle of sealing surface grinding includes five aspects: grinding process, grinding movement, grinding speed, grinding pressure and grinding allowance.
1. Grinding process
The grinding tool and the surface of the sealing ring are well combined, and the grinding tool makes complex grinding movements along the joint surface. Abrasives are placed between the lapping tool and the surface of the sealing ring. When the lapping tool and the surface of the sealing ring move relative to each other, part of the abrasive grains in the abrasive will slide or roll between the lapping tool and the surface of the sealing ring. layer of metal. The peaks on the surface of the sealing ring are first ground away, and then the required geometry is gradually achieved.
Grinding is not only a mechanical process of abrasives on metals, but also a chemical action. The grease in the abrasive can form an oxide film on the surface to be processed, thus accelerating the grinding process.
2 . grinding movement
When the grinding tool and the surface of the sealing ring move relative to each other, the sum of the relative sliding paths of each point on the surface of the sealing ring to the grinding tool should be the same. Also, the direction of relative motion should be constantly changing. The constant change of the direction of motion prevents each abrasive grain from repeating its own trajectory on the surface of the sealing ring, so as not to cause obvious wear marks and increase the roughness of the surface of the sealing ring. In addition, the continuous change of the direction of motion cannot make the abrasive more evenly distributed, so that the metal on the surface of the sealing ring can be cut more evenly.
Although the grinding movement is complicated and the direction of movement changes greatly, the grinding movement is always carried out along the bonding surface of the grinding tool and the surface of the sealing ring. Whether it is manual grinding or mechanical grinding, the geometric shape accuracy of the sealing ring surface is mainly affected by the geometric shape accuracy of the grinding tool and the grinding movement.
3. grinding speed
The faster the grinding movement, the more efficient the grinding. The grinding speed is fast, more abrasive particles pass through the surface of the workpiece per unit time, and more metal is cut off.
The grinding speed is usually 10~240m/min. For workpieces requiring high grinding precision, the grinding speed generally does not exceed 30m/min. The grinding speed of the sealing surface of the valve is related to the material of the sealing surface. The grinding speed of the sealing surface of copper and cast iron is 10~45m/min; the sealing surface of hardened steel and hard alloy is 25~80m/min; the sealing surface of austenitic stainless steel 10~25m/min.
4. grinding pressure
The grinding efficiency increases with the increase of the grinding pressure, and the grinding pressure should not be too high, generally 0.01-0.4MPa.
When grinding the sealing surface of cast iron, copper and austenitic stainless steel, the grinding pressure is 0.1~0.3MPa; the sealing surface of hardened steel and hard alloy is 0.15~0.4MPa. Take a larger value for rough grinding and a smaller value for fine grinding.
5. Grinding allowance
Since grinding is a finishing process, the amount of cutting is very small. The size of the grinding allowance depends on the machining accuracy and surface roughness of the previous process. Under the premise of ensuring the removal of the processing traces of the previous process and correcting the geometric error of the sealing ring, the smaller the grinding allowance, the better.
The sealing surface should generally be finely ground before grinding. After fine grinding, the sealing surface can be directly lapped, and the minimum grinding allowance is: the diameter allowance is 0.008~0.020mm; the plane allowance is 0.006~0.015mm. Take a small value when manual grinding or material hardness is high, and take a large value when mechanical grinding or material hardness is low.
The sealing surface of the valve body is inconvenient to be ground and processed, so fine turning can be used. After finish turning, the sealing surface must be rough ground before finishing, and the plane allowance is 0.012~0.050mm.
Tianjin tanggu water-seal valve Co.,ltd was specilized in manufacture resilient seated butterfly valve, gate valve, Y-strainer, balancing valve, wafer check valve, etc.
Post time: Jun-25-2023