Valve grinding process and tool selection

1. Valve grinding inspection

During the grinding process, the inspection stage is always run through. The purpose is to keep abreast of the grinding situation at any time, to be aware of the situation, and to achieve the technical requirements of the grinding quality. It should be noted that different valves should use grinding tools suitable for various sealing surface forms to improve the grinding efficiency and ensure the grinding quality.

Valve grinding is a very meticulous work that requires constant experience, exploration, and improvement in practice. Sometimes the grinding is very good, but after installation, it still leaks steam and water. This is because of the imagination of grinding in the grinding process. The grinding rod is not vertical, skewed, or the size and angle of the research tool are deviated.

Because the abrasive is a mixture of abrasive and grinding fluid, the grinding fluid is only general kerosene and engine oil. Therefore, the most critical part of choosing the right abrasive is to choose the right abrasive.

2. How to choose the valve abrasive correctly

Alumina (AL2O3) Alumina, also known as corundum, has high hardness and is widely used. Generally used for grinding workpieces of cast iron, copper, steel and stainless steel.

Silicon Carbide (SiC) Silicon carbide is available in green or black, and its hardness is higher than that of alumina. Green silicon carbide is suitable for grinding cemented carbide; black silicon carbide is used for grinding brittle and soft materials, such as cast iron and brass.

Boron carbide (B4C) is second only to diamond powder in hardness and harder than silicon carbide. It is mainly used to replace diamond powder to grind cemented carbide and grind hard chrome-plated surfaces.

Chromium oxide (Cr2O3) Chromium oxide is a kind of high hardness and extremely fine abrasive. Chromium oxide is often used in the hardening of hardened steel, and it is generally used for polishing.

Iron oxide (Fe2O3) Iron oxide is also a very fine valve abrasive, but its hardness and grinding effect are inferior to chromium oxide, and its use is the same as chromium oxide.

Diamond powder is crystal crystallization C, which is the hardest abrasive with good cutting performance, and is especially suitable for grinding cemented carbide.

In addition, the thickness of the abrasive particle size (abrasive particle size) has a significant effect on the grinding efficiency and the surface roughness after grinding. When rough grinding, the surface roughness of the valve workpiece is not high. To improve the grinding efficiency, it is appropriate to use coarse-grained abrasives; when fine grinding, the grinding allowance is small, and the requirements of the workpiece surface roughness are high. Fine-grained abrasives can be used.

The abrasive grain size is generally 120#～240# when the sealing surface is rough grinding; W40～14 is the fine grinding.

Valves are formulated with abrasives, usually by adding kerosene and engine oil directly to the abrasive. Abrasives blended with 1/3 kerosene plus 2/3 engine oil and abrasive are suitable for rough grinding; abrasives blended with 2/3 kerosene and 1/3 engine oil and abrasive can be used for lapping.

When grinding workpieces with high hardness, the effect of using the above abrasives is not ideal. At this time, three parts of abrasives and one part of heated lard can be blended together, and after cooling, a paste is formed. When using, add some kerosene or gasoline to mix thoroughly.

3. Selection of grinding tools

The sealing surfaces of the valve disc and valve seat cannot be directly researched due to the different degrees of damage. Instead, first use a certain number and specifications of fake valve flaps (that is, grinding heads) and false valve seats (that is, grinding seats) that are specially made in advance to the valve. The seat and disc are polished.

The grinding head and grinding seat are made of ordinary carbon steel or cast iron, and the size and angle should be equal to the valve flap and valve seat placed on the valve.