Nocolok Brazing Aluminum Heat Exchangers

Nocolok^® flux brazing is becoming widely accepted as the principal manufacturing process for brazed aluminum heat exchangers in the automotive industry. This paper summarizes brazing profiles, production results, and quality control details about the Nocolok^® flux brazing process in relation to its use with heavy duty heat exchangers and oil coolers. The results presented suggest that Nocolok^® flux brazing is a relatively forgiving process. Acceptable products were brazed using heat rates and temperatures beyond standard requirements suggesting manufacturers will have more flexibility to braze large size heavy duty heat exchangers with the Nocolok^® process. Pre-brazed gaps of 0.2 mm could be tolerated in the joining of parts while in some cases, gaps up to 0.5 mm were satisfactorily brazed by applying filler alloys such as Al-Si in paste or sheet form to the joint gaps. Material selection and failure modes are discussed in detail as well as relationships between process parameters and scrap rates. The results suggest that component cleanliness and flux loads are critical parameters in the control of production quality and scrap rates.