TWI Industrial Member Report Summary 149/1981
By N R Stockham
A programme of work was carried out to investigate the effect on tensile properties of varying bonding parameters when joining cold-drawn mild steel (EN3B to BS 910 : 1955). Butt joints 12.5mm diameter were produced in a small vacuum diffusion bonding unit. The parameters studied were the bonding temperature (710 to 1200°C), time at temperature (0.06ksec (1min) to 7.7ksec (128min), bonding load (1 to 20N/mm2) and the effect of using an interlayer. It was found that a wide range of bonding conditions could be used to pmduce joints with tensile strength equal to that of the annealed parent metal, but the range was more restricted if failure away from the interface was taken as the ruling criterion. Batch to batch variations in composition resulted in differences in joint properties and in the mlnimum bonding conditions required. The introduction of an interlayer (even mild steel) was found, in some instances, to aid bonding.