AS-C402 Customized Single Cartridge Mechanical Seal

AS-C402 is customized single seal in cartridge form made as per client's drawing

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Background Knowledge：

The cemented carbide in the materials which are used in making mechanical seals
Welding a layer of hard alloy on the surfaces of the sealing rings of the mechanical seals can improve their wear resistance and corrosion resistance , and this action’s prices are low, so it is a common practice. The hard alloys used for surfacing include chromium-based No. 1, cobalt-based No. 1 and cobalt-based No. 2.

The chrome-based No. 1 surfacing layer has good cavitation resistance and corrosion resistance; the Co-based No. 1 surfacing layer has high hardness and good acid resistance; the Co-based No. 2 surfacing layer has high temperature resistance and and high hardness at high temperature. Although surfacing hard alloy has certain corrosion resistance, it is not resistant to strong acid and hot alkali corrosion. Besides，its hardness is not high, & its thermal crack resistance is poor, and the surfacing welding process poses quite high requirements, so it is not suitable for mechanical seals whose sealed medium are granular and mechanical seals at high-speed. For the above-mentioned two cases，the heat treatment requirements before and after surfacing welding are relatively strict, and defects such as pores and cracks are prone to occur in this process.

A new type of hard alloy for surface welding has been developed in China. It is F e-Cr-C series, the models are EDZCr55-1 and EDZCr-60, and it is a welding electrode for surfacing welding with high wear resistance, good toughness and crack resistance. The hardness of EDZCr55-1 after surfacing is HRC55, and the impact toughness can reach more than 10N.m/c㎡; the hardness of EDZCr-60 is HRC60, but the toughness is slightly worse. This hard alloy has a simple surfacing process, and both AC and DC welding machines can be used.The preheating temperature of this cemented carbide before welding only needs to be about 200°C, no heat tracing is needed during the welding process, and it needs to be covered with insulating materials after welding only. The electrode is low in price and is a promising hard alloy for surfacing.

In order to solve the shortcoming of the shrink-fit sealing ring（a kind of mechanical seal structure） loosening, a kind of cemented carbide that can be welded has emerged in China.It is a chromium carbide cemented carbide (Cr3-C2-Ni) with nickel as the binder phase, and the grade is CN15. Compared with YG6, it has the advantages of light weight (specific gravity 7~7.5), corrosion resistance and oxidation resistance. Because the coefficient of linear expansion (10.2x10¯6 1/°C below 500°C) is similar to that of stainless steel, and the alloy composition belongs to Cr-Ni base, it can be directly welded to the ring seat. When welding, clean the ring seat and the hard alloy ring, and lay a layer of Ni-based powder between them, then place them in a vacuum resistance furnace, sinter at a high temperature of 1100 ° C, keep warm and cool with the furnace, and then process them after tempering to the required size.

What are the characteristics of cobalt-based cemented carbide
Cobalt-based tungsten carbide is the most widely used cemented carbide for mechanical seals. It is made of extremely hard tungsten carbide (WC) plus cobalt (Co) or other iron group metals as a binder, and is pressed and sintered by powder metallurgy. Its biggest feature is high hardness, high thermal conductivity and low linear expansion coefficient. Hard phases such as WC in cemented carbide have strong corrosion resistance and are very stable in corrosive media such as acid and alkali. However, the corrosion resistance of the bonding metal is poor, and the sealing medium of mechanical seals often corrodes the bonding metal first, so that the hard phase WC and the like are isolated and lost, and are quickly worn away in relative friction.So WC-Co cemented carbide is not suitable for corrosive occasions. However, it has strong corrosion resistance in media such as sulfuric acid at ordinary temperatures and caustic soda below the boiling point. WC-Co material has low impact toughness and high brittleness, and the machining cost is expensive.

What are the characteristics of steel bonded carbide？
Steel bonded carbide is a commonly-used material in producing mechanical seals. What are their characteristics？
Steel-bonded cemented carbide is a cemented carbide with steel as the binder phase and titanium carbide as the hard phase. It has high wear resistance and rigidity (high modulus of elasticity), as well as high strength, hardness and certain toughness. Due to the small specific gravity of TiC, it is lighter in weight; at the same time, the TiC particles are round, the friction coefficient is greatly reduced, and it has better self-lubricating properties. The alloy also has good thermal shock resistance and can be used in situations where the temperature changes drastically. Its outstanding feature is that it has good processing technology and can be heat treated. After heat treatment, the dimensional change is small, and the deformation is within the range of dimensional error. In addition, it has good weldability and malleability. The corrosion resistance of steel-bonded carbide varies with the type of steel base. They have good corrosion resistance in seawater and alkali solution