How to improve the service life of high pressure valve?

The main failure reasons of ultra-high pressure valve are cavitation and erosion wear, and there are many factors affecting cavitation and erosion, mainly mechanical properties of materials, hydrodynamics factors and environmental influence. A number of methods can be used to improve valve resistance to cavitation and erosion wear.

1. Material selection

In order to improve the ability of ultra-high pressure valve to resist erosion wear, corrosion resistant materials are usually selected:

1, high hardness of materials

2. Materials with acid corrosion resistant protective film

3. Materials with high yield point and good stability

4. Materials with high fatigue strength

To improve the properties of materials, one is to use alloying, the other is to use appropriate heat treatment. Alloying method is to develop new materials with special properties by changing the chemical composition of steel. Heat treatment method does not change the chemical composition of steel, but imposes different heating, heat preservation and cooling on steel in solid state, in order to change the structure of steel and improve the performance of materials.

Heat treatment and surface hardening treatment 1, vacuum heat treatment

It does not produce oxidation, decarbonization and other corrosion during heating, and has the effect of purifying the surface and removing grease. In vacuum, hydrogen, nitrogen, oxygen and other gases absorbed in the smelting process can be removed, improving the quality and performance of the material. For example, after vacuum heat treatment of the ultra-high pressure needle valve made by W18Cr4V, the impact toughness of the needle valve is effectively increased, and the mechanical properties and service life are also improved.

2. Surface strengthening treatment

Such as surface hardening (flame heating, high frequency heating surface hardening, in contact with electrical heating surface hardening, electrolyte heating surface hardening, laser beam heating surface quenching, etc.), carburizing, nitriding, cyanide, boronizing, metal seeping method (TD), laser hardening, chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma chemical vapor deposition (PC) VD method), plasma spraying, etc.

3, using new engineering materials

When choosing the material of ultra-high pressure valve flow parts, the different flow rate (maximum service pressure) and weight loss should be considered.

Below relatively high pressure (above 400MPa), choose material with high hardness and red rigidity, be like tool steel or hard alloy.

At lower pressure (100 ~ 400MPa), the material is required to have good plasticity and toughness, and high hardness. For example, the ultra-high pressure needle valve of HIP company in the United States, the working pressure of 690MPa is made of austenitic 316 stainless steel, and the working pressure of 1034MPa is made of Martensite precipitated hardened stainless steel 17-4pH. In foreign countries, martensitic stainless steel and tool steel are used for component materials, disc and seat to withstand cavitation, while chrome-aluminum steel and stainless steel are used for seat base.

With the successful development of industrial ceramic technology, also appeared ceramic valve. Ceramic material has high erosion resistance at low impact Angle, but due to the reduction of needle taper, its end strength also decreases, needle and valve seat support force is also reduced, affecting the reliability of the seal. Therefore, in the selection of ceramic materials to make valve needle, not only to consider the size of the taper, but also to consider its strength.