EGR Coolers
An EGR (Exhaust Gas Recirculation) cooler is a heat exchanger that cools the exhaust prior to recirculation back to the engine in order to reduce NOX (Nitrous Oxide) emissions. NOX is formed at higher temperatures and by recirculating the exhaust in to the combustion chamber the amount of available oxygen is reduced and the combustion temperature is lowered. In order to minimise the loss of power the exhausts have to be cooled before entered into cylinder.
While various heat exchanger technologies are used, tube and shell are the most common types used today. Engine size and emission legislation are two factors that influence the required size of the heat exchangers.
High corrosion resistance and heat resistance are two major requirements of the brazing filler metal for EGR cooler applications. When brazing the components of an EGR cooler, the melting point of the brazing filler metal should be as low as possible. Brazing at too high temperatures deteriorates the base metal and also produces an adverse effect on corrosion resistance due to precipitation of chromium carbide (Cr3C2).
Corrosion of the brazing filler metal is caused by exhaust gas condensation as it is circulated in the EGR system. As condensate contains sulfuric acid, corrosion may be caused to the brazing filler metal and the diffused part as a result.
Höganäs products are able to combine low brazing temperatures with high corrosion- and oxidation resistance. This makes them very suitable for applications such as EGR coolers.