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How To Choose The Matrix Material Of The Mechanical Seal?
Apr 16, 2018

How to choose the matrix material of the mechanical seal?

Brief introduction of mechanical seals

The sealing performance and service life of mechanical seals are related to the material of each of the zero mechanical seals, especially the material of the end seal (friction pair), the auxiliary seal material and the spring material.

First, the material of the end seal friction pair

Friction materials include graphite, ceramics, hardfacing alloys, tungsten carbide alloys, SiC, filled PTFE, tin bronze, steel cemented carbide, stainless steel, phenolic plastics, and nylon. The properties of common materials are as follows:

1. tungsten carbide alloy Tungsten carbide, titanium carbide and other high hardness, high melting point of metal carbide, is the use of binder powder metallurgy method, press sintering molding. The advantages are high hardness and strength. Wear resistance, high temperature resistance, corrosion resistance, low coefficient of linear expansion, the disadvantage is brittle, difficult processing. Tungsten carbide is the most widely used end face seal sub-material, mostly used as a stationary ring for mechanical seals in medium and low speeds, and as a moving ring for high-speed mechanical seals.


2. Graphite Graphite has the advantages of good corrosion resistance and self-lubrication, low friction coefficient, good thermal shock resistance and easy processing. The disadvantages are low mechanical strength and porosity. These two disadvantages of graphite can be improved by impregnation and carburizing. Impregnated graphite can be divided into impregnated resin and impregnated metal. The impregnated graphite has good corrosion resistance, but it is not resistant to high temperatures (temperature resistance is about 170-200°C); impregnated metal graphite has good temperature resistance (impregnated bronze, aluminum, lead, etc. can withstand high temperatures up to 400-500°C), but corrosion resistance Poor sex. Graphite is the most widely used non-metallic material, used as a ring and high-speed mechanical seal for medium and low-speed mechanical seals.

Sealed static ring. A good graphite is dense to the naked eye, and the fingers do not touch the powder, and it is not very black.

3. ceramics The advantages of ceramics are good corrosion resistance, high hardness, good wear resistance, the disadvantages are brittle and high hardness and difficult to process. More applications are alumina ceramics, as well as metal ceramics. Ceramics are mostly used in corrosive media, in low to medium speed applications.

4. surfacing hard alloy in the carbon steel, chromium steel and chromium nickel steel sealing surface surfacing hard alloy, the advantages are high hardness, good wear resistance, good temperature resistance (below 500 °C), corrosion resistance or The cavitation is good, the disadvantage is that it is easy to produce pores, slag inclusions and uneven surface hardness.

Second, the auxiliary seal material

The requirements for auxiliary sealing materials are good elasticity, low friction coefficient, good wear resistance, heat resistance and low temperature resistance, resistance to media corrosion, dissolution and aging, etc. In addition, residual deformation is required after compression and long-term use. The commonly used auxiliary seal material is rubber and PTFE, in addition to soft polyvinyl chloride.

1. PTFE Polytetrafluoroethylene advantages are chemical stability, oil resistance, resistance to dissolution, excellent moisture resistance, low friction coefficient, suitable for a variety of corrosive media, the disadvantage is that the elasticity is less than rubber, easy to produce permanent deformation.

2. rubber Rubber has good elasticity, cushioning, vibration absorption, heat resistance, corrosion resistance. Rubber seals have a good sealing effect and are used most widely. The commonly used rubbers are silicone rubber, nitrile rubber, neoprene rubber and fluororubber.

Third, the elastic component material

1. the spring material The spring material requirements are: good elasticity, resistance to media corrosion. Commonly used spring materials are stainless spring steel (1Cr18Ni9Ti, etc.), chrome steel (3Cr13, 4Cr13, etc.), carbon cable spring steel (60si2Mn, etc.) and phosphor bronze.

2. Bellows materials The requirements for bellows materials are: good welding performance, large elasticity, and certain corrosion resistance. Commonly used bellows materials are iron-based, copper-based and nickel-based alloys, and titanium materials, and are generally based on nickel-chromium austenitic strips in titanium-based materials, especially 1Cr18Ni12Mo2Ti. High-nickel-elastic alloys are considered to be ideal materials for making bellows, and aluminum-containing materials encounter difficulties with general welding techniques. At present, the most commonly used foreign material for the bellows is AM350 (approximately Cr16Ni45MnMo3N) which is a solid solution, low strength, low hardness, and high elongation.

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Susie Ding


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