Mechanical seal for kettle How to select the matrix material of

The sealing performance and service life of mechanical seals are related to the mechanical shaft seal materials of all parts, especially the end seal (friction pair) materials, auxiliary seal materials and spring materials.

1、 Material of friction pair of end face seal

Friction pair materials include graphite, ceramics, hardfacing carbide, tungsten carbide, SiC, filled with PTFE, tin bronze, steel bonded hard mechanical seal specification alloy, stainless steel, phenolic plastic, nylon, etc. The properties of commonly used materials are as follows:

1. Tungsten carbide alloy is metal carbide produced by mechanical seal manufacturers with high hardness and melting point, such as tungsten carbide and titanium carbide. It is pressed and sintered by means of powder metallurgy with adhesive. The advantage is high hardness and strength. Wear resistance, high temperature resistance, corrosion resistance, low coefficient of linear expansion, the disadvantage is brittle and difficult to process. Tungsten carbide is a widely used end face sealing material, which is mostly used as the static ring of medium and low speed mechanical seals and the dynamic ring of high speed mechanical seals.

2. Graphite graphite has the advantages of good corrosion resistance and self lubrication, small friction coefficient, good heat shock resistance and easy processing. The disadvantages are low mechanical strength and porosity. These two shortcomings of graphite can be improved by impregnation and carburization. Impregnated graphite can be divided into resin impregnated graphite and metal impregnated graphite. Resin impregnated graphite has good corrosion resistance, but is not resistant to high temperature (about 170-200 ℃); Impregnated metal graphite has good temperature resistance (high temperature resistance of bronze, aluminum, lead, etc. can reach 400~500 ℃), but poor corrosion resistance. Graphite is a widely used non-metallic material, which is used as the dynamic ring of medium and low speed mechanical seals and the static ring of high speed mechanical seals. Good graphite is dense to the naked eye, and it does not take off powder or darken when touched by fingers.

3. The advantages of ceramic ceramics are good corrosion resistance, high hardness, and good wear resistance. The disadvantages are high brittleness and high hardness, which make it difficult to machine. Alumina ceramics and cermets are widely used. Ceramics are mostly used in corrosive media, medium and low speed situations.

4. Hard alloy surfacing Hard alloy surfacing on the sealing surface of carbon steel, chromium steel and chromium nickel steel has the advantages of high hardness, good wear resistance, good temperature resistance (below 500 ℃), good corrosion or cavitation resistance, and the disadvantages of easy to produce pores, slag inclusion and uneven surface hardness.

2、 Material of auxiliary seal ring

The requirements for auxiliary sealing materials are good elasticity, small friction coefficient, good wear resistance, heat resistance and low temperature resistance, resistance to medium corrosion, dissolution and aging, etc. In addition, good residual deformation after compression and in long-term use is also required. The commonly used auxiliary sealing ring materials are rubber and polytetrafluoroethylene, in addition to soft PVC.

1. Polytetrafluoroethylene Polytetrafluoroethylene has the advantages of excellent chemical stability, oil resistance, dissolution resistance, moisture resistance, low friction coefficient, and is suitable for various corrosive media. Its disadvantage is that it is less elastic than rubber and easy to deform.

2. Rubber rubber has good elasticity, buffering, vibration absorption, heat resistance and corrosion resistance. The rubber sealing ring has good sealing effect and is most widely used. Common rubbers include silicone rubber, nitrile rubber, neoprene rubber and fluororubber.

3、 Elastic element material

1. The requirements of spring materials for spring materials are: good elasticity and medium corrosion resistance. Common spring materials include stainless spring steel (1Cr18Ni9Ti, etc.), chromium steel (3Cr13, 4Cr13, etc.), carbon cord spring steel (60si2Mn, etc.) and phosphor bronze.

2. The requirements of corrugated pipe materials for corrugated pipe materials are: good welding performance, greater elasticity, and certain corrosion resistance. The commonly used corrugated pipe materials include iron base, copper base, nickel base alloy and titanium materials. Generally, nickel chromium austenitic strip in titanium base is the main material, especially 1Cr18Ni12Mo2Ti. High nickel elastic alloy is considered to be an ideal material for making bellows, and aluminum containing materials will encounter difficulties when using general welding technology. At present, AM350 (similar to Cr16Ni45MnMo3N) is a kind of solid solution with low strength, low hardness and high elongation, which is widely used abroad.