Equipment protection technology: When the engine is working, the valve seat and valve are always in high temperature, high pressure and dry friction conditions, and receive a large reciprocating impact load. Through the use of a period of time, there will be scenes such as increased valve subsidence and poor sealing. Together, the valve and the valve seat are ground into groove steps, resulting in poor intake and exhaust, severely affecting the engine's power and economy. Sex. At this time, the valve and valve seat should be repaired. There are four questions to be aware of when repairing the valve seat.

   (1) Determine the repair method. For the amount of wear, the valve seat with ablation only can be corrected by grinding; for the valve seat with large wear and tight seal, but the valve subsidence is within the allowable range, it can be milled and ground; If the amount of valve subsidence exceeds the allowable value, the demand is fitted with a valve seat.

   (2) Select the valve seat data. Suitable materials should be ductile iron, alloy cast iron or austenitic steel.

   (3) Matching scale and processing. The dimensions of the valve seat are determined primarily by the dimensions of the valve seat and the valve, and must be sufficiently tight, suitable for height and inner diameter. Normally, the valve seat ring should be 2.5-3.0mm below the cylinder head surface, the thickness is 0.10-0.15 times its inner diameter, the height is 0.16-0.20 times its outer diameter, and the interference during cold setting is usually 0.10- 0.15mm, the interference during hot setting is usually 0.20-0.25mm. When machining the seat ring, the circular runout of the inner and outer circle to the center line should be no more than 0.05mm, and the surface roughness parameter value Ra should be no more than 3.2μm.

   (4) Milling process. Milling uses a special alignment, and the force is even, not back, otherwise it will easily form valve tilt and partial milling. Different sizes of milling cutters should be selected according to the size of the valve subsidence and the orientation and width of the contact ring.