Since the use of aluminium cylinder heads was intro- duced, the importance of valve seat inserts has increased dramatically. Together with the valves, they serve to seal off the combustion chamber of the cylinder head. The valve seat insert prevents the valve from knocking/ digging into the cylinder head. It absorbs part of the combustion heat that is transferred to the valve.

The valve seat insert passes this heat on to the cylinder head. In order to respond to the different conditions to which a valve seat is subjected, the best combination of materials for its production must be found. Not only the operating conditions in the engine have to be taken into account, but the ability of the engine reconditioner to work with the material as well.

Material
Valve seat inserts made of sintered material (powder metallurgy process) are used in the latest generations of engines produced by well known automotive manufacturers. The increasing extreme thermal and mechancial strain placed on the valve seat inserts in the combustion chamber can scarcely be accommodated by materials manufactured by the conventional casting process. For this reason KS offers sintered valve seat inserts, among other items, made of two different combinations of material to cover the entire range of uses for the engines of the future.

Sintered Metal Seat Inserts:

HM-Series Semi Finished (Standing for High Machinability)
This combination of material is characterised by its excellent machinability. The sintered HM valve seat insert is composed of tungsten carbide embedded in alloy steel, balanced exactly to the demands placed on it. This way previously impossible combinations of material properties such as extreme toughness and very good machinability can be brought together. In addition, the HM series possesses a very good resistance to wear and heat. This very machinable material is designed for naturally aspirated and turbocharged engines in the light to upper duty range.

HT-Series Semi Finished (High Temperature Resistance)
This combination of materials is charcterised by its high resistance to wear which can endure even at extremely high temperatures. The sintered HT valve seat insert approximates a cermaic tool steel made of tungsten carbide with properly balanced, high-temperature-resistant additives embedded in its matrix. Due to the large quantity of permanently embedded lubricants, these inserts are especially suitabled for "dry" fuels such as propane, LPG or natural gas. They prevent the "microwelding" of the valve seat insert to the valve.

Steel Seat Inserts:

ST Series Finished (Chrome – Nickel – Steel)
The ST series consists of a high quality steel alloy with chrome and nickel additives. The have a wide range of application and were developed for the exhaust area of trucks. They can be used in extreme conditions and at high temperatures.

G1 series finished (high-temperature resistant)
The G1 series is made of a hightempera ture cast iron alloy with chromium and molybdenum additives . The G1 series has been developed for a wide range of applications and is mainly used in utility vehicles. This valve seat insert with its composition of annealed martensite and well-shaped carbide net is perfectly adapted to intense wear. Consequently, this valve seat insert is highly resistance to strain and high temperature.

G2 series finished (high-wear resistant)
The G2 series is made of a high-wear resistant cast iron alloy with high proportions of molybdenum and vanadium. This material combination is renowned for its high wear resistance which endures even at very high tempe ratures. It is a high-alloy material with a well shaped, closed grid of mixed and special carbides in a martensitic matrix and evenly distributed solid lubricant portions. This material has been developed for dry fuels, such as CNG, LPG and Flex Fuel.

The selection of engine part specifications must be checked carefully by the engine reconditioner. Extreme operating conditions, such as heavy stress on the respective engine, must be taken into account and are the responsibility of the engine reconditioner.