The Brazing Technics Of The EGR Cooler And The Study On The Corrosion Resistance Of The Brazed Joint

To meet future NO, diesel emissions standards, exhaust gas recircuIation(EGR) technology is likely to be used. To improve fuel economy and further lower emissions, the recirculated exhaust gas needs to be cooled, with the possibility that cooling of the exhaust gas may form sulfuric acid condensate in the EGR cooler. This corrosive condensate can cause EGR cooler failure and consequentially result in severe damage to the engine. The core of the EGR cooler can be made by vacuum brazing. The brazing technics of the EGR cooler and corrosion resistance of the joint, with three brazing filler metal - copper, BNi-2, BNi-7 brazing 316L stainless steel, is discussed in this paper. The main conclusions are as follows:1. The optimum technics of brazing 316L stainless steel with copper is: brazing temperature 1145℃, heat rate 8℃/min, heat time 8min.The corrosion rate of the brazed joint after dipped in the 5% II..S0,, 100℃ for 6 hours is 4.12mm/a. Fe, Ni, Cr, Mo Mn is corroded by liquid spectroscopic analysis of the solution, in which Fe 9.73 ppm/cm2, Ni 3.46 ppm/cm2. Cr 1.73 ppm/cm2, Mo 1.67 ppm/cm2, Mn 0.39 ppm/cm2.2. The optimum technics of brazing 316L stainless steel with BNi-2 is: brazing temperature 1030℃, heat rate 8℃/min, heat time 3min. The corrosion rate of the brazing joint after dipped in the 5% H2SO4, 100℃ for 6 hours i s 4.95mm/a. Fe, Ni Cr, Mo, Mn is corroded by liquid spectroscopic analysis of the solution, in which Fe 9.78 ppm/cm2, Ni 3.85 ppm/cm2. Cr 2.34 ppm/cm2. Mo 0.84 ppm/cm2. Mn 0.33 ppm/cm2.3. The optimum technics of brazing 316L stainless steel with BNi-7 is: brazing temperature 1030℃, heat rate 8℃/min, heat time 3min. The corrosion rate of the brazing joint after dipped in the 5% II..S0,, 100℃ for 6 hours is 8.44mm/a. Fe, Ni, Cr, Mo, Mn is corroded by liquid specroscopic. analysis of the solution, in which Fe 18.87 ppm/cm2, Ni 8.39 ppm/cm2, Cr 6.11 ppm/cm2, Mo 1.80 ppm/cm2,Mn 0.62 ppm/cm2.