Eng. Seyyed Ali Akbar Hashemi Milani, Dr. Reza Tavangar, Dr. Maziyar Azadbeh, Eng. Ibrahim Kahinpoor, Eng. Hossein Sadeghi-Nasab,
Volume 10, Issue 4 (12-2020)
Abstract
Drying temperature of the flux at normal atmosphere has a crucial role in brazing quality in automotive aluminum-based heat exchangers. Over the course of this research, NOCOLOK® flux consists of two phases of K2AlF5.H2O and KAlF4 with melting point around 580 °C was used. A flux slurry was applied on the base metal, and dried at 220, 300 and 380 °C in air. Mechanical assessment revealed that when flux dried at 300 °C, the joint withstands maximum shear stress of 44 MPa with complete bonding. At 220 °C and 380 °C, joint shear stresses are 34 MPa, 30 MPa respectively. 380 °C dry-off temperature under nitrogen gas improved shear strength to 39 MPa. Taking dry-off temperature as 300 °C the amount of defective heat exchangers was reduced from 6% to 2% on a daily basis.
