A Study of Weld Crackings in Nickel and Nickel alloys (Report 1)

Effect of aluminum and titanium

Abstract

A small amount of aluminum and titanium are generally added, so as to avoid the porosity in weld metals and improve their mechanical properties, to the nickel and monel welding electrodes.
Such addition of aluminum and titanium, however, it may be promoted the possibility of crack occurrence of the weld metals, because the content of silicon in the weld metals shall increase by reducing reaction of the aluminum and titanium to the silicates of coating flux.
The authors investigated on the effect of aluminum and titanium in nickel and monel welding electrodes on weld crackings of nickel and monel weld metals.
The results are summerized as follows.
1) In nickel weld metals, hot crackings are remarkably observed with increasing aluminum and titanium in the welding electrodes.
This is considered that some low melting substances are formed in austenite grain-boundaries with the reducing reaction of aluminum and titanium to the silicates.
On the contrary, in monel weld metals such a phenomenon was not observed.
2) Amount of aluminum and titanium in nickel weld metals was increased with aluminum and titanium contents in the welding electrodes and such elements were considered to be cause of the decrease of oxygen in the weld metals.
Therefore, micro crackings with decreasing ductilities (refers as micro crackings) in multitude nickel weld metals were remarkably decreased as the increase of aluminum and titanium in the welding electrodes.
Meanwhile, the effect of aluminum and titanium on micro crackings of monel weld metals was less than it of nickel weld metals.
The occurrence of micro crackings of monel weld metals, however, was promoted by a small amount of aluminum in the welding electrodes.