Mechanical seal performance and seal life, and all parts of the material, in particular in face seal (Friction) of materials, auxiliary materials, seal and spring materials.
First, seal Friction materials
Friction materials are graphite, ceramics, welding alloy, carbide alloy, SiC, PTFE, bronze, steel bonded carbide, stainless steel, Bakelite and nylon. The nature of the material used are as follows:
1, graphite
The advantages of graphite corrosion resistance and good self-lubricating, low friction coefficient, good thermal shock resistance and easy processing, drawback is the low mechanical strength, have pores. These two shortcomings can be graphite impregnated and carburization of the ways to improve. Resin impregnated graphite dipping and dipping can be divided into two kinds of metal. Baptist resin graphite corrosion resistance is good, but not high temperature (temperature of about 170 ~ 200 ℃); impregnated metal graphite temperature is good (Baptist bronze, aluminum, lead and high temperature up to 400 ~ 500 ℃), but poor corrosion resistance . Graphite is the most widely used non-metallic materials, for low speed Mechanical seal ring and high-speed mechanical seal stationary ring. Good graphite, the naked eye appears to compact powder off fingers feel that he does not, not Black fingers.
2, ceramic
Ceramic has the advantage of good corrosion resistance, high hardness, good wear resistance, disadvantage is brittleness and hardness is too high and hard to process. Application of alumina ceramic is more, there are metal-ceramic. Ceramics are used for corrosive medium, medium and low speed situations.
3, surfacing alloy
In carbon steel, chrome steel and chrome-nickel steel alloy welding sealing surface, the advantage of high hardness, good wear resistance, good heat resistance (500 ℃ or less), anti-corrosion or cavitation is good, disadvantage is easy to produce porosity, inclusions, and uniform surface hardness.
4, tungsten carbide alloy
By the tungsten carbide, titanium carbide and other high hardness and high melting point metal carbide is a powder metallurgy method of adding binder, pressing sintering. Advantage of the hardness, strength are high, wear, high temperature, corrosion resistance, low coefficient of linear expansion, disadvantage is brittle, difficult process. Tungsten carbide is the most widely used end-sealing materials, and more for the low-speed Mechanical sealstationary ring, high-speed mechanical seal ring.
Second, the material supporting ring
The requirements of the secondary sealing material is a good elasticity, friction, wear, heat and low temperature, good resistance to media corrosion, dissolution and aging, also called compression and good long-term use of residual deformation. Supplementary material is commonly used in rubber and PTFE seals, in addition to the soft PVC.
1, rubber
Rubber has good elasticity, buffer, absorber, heat resistance, corrosion resistance. Rubber ring sealing effect, the most widely used. Commonly used are silicone rubber, NBR, chloroprene rubber and fluorine rubber.
2, PTFE
PTFE has the advantage of chemical stability, oil resistance, dissolution, excellent moisture resistance, low coefficient of friction for a variety of corrosive media, elastic than rubber disadvantage is poor, easy to produce permanent deformation.
3, elastic element material
1, Spring Material
Of the spring material requirements are: good elasticity, resistance to media corrosion. Commonly used material is stainless spring steel spring (1Cr18Ni9Ti, etc.), chrome steel (3Cr13, 4Cr13, etc.), carbon spring steel (60Si2Mn etc.) and phosphor bronze.
2, bellows material
Of bellows material requirements are: good welding performance; greater flexibility; some corrosion resistance. Bellows materials commonly used are iron, copper and nickel based alloys and titanium, etc.. Generally iron-based nickel-chromium austenite in the main strip, especially 1Cr18Ni125MnMo2Ti used most. High nickel alloy is considered to produce flexible bellows better materials, aluminum material with the general welding technique, are difficult. Most used in foreign countries, bellows material is AM350 (approximate Cr16Ni45MnMo3N) are solid solutions, low strength, low hardness, high elongation.