Abstract
This is a report on the effects of welding variables in mash seam welding of cold rolled and annealed low carbon rimmed steel sheets of lmm thickness on joint thickness, Erichsen value and tensile elongation along the weld line.
Throughout the investigation, welding current and electrode force were varied in the wide range, while the rest of the condition were kept constant as follows:
Welding speed 1m/min,
weld time and cool time 4 _??_ and 2 _??_,
and jointoverlap 1.5mm.
The results obtained are as follows:-
1. When the welding condition is properly chosen, the Erichsen value of over 10.0 and the tensile elongation of 30% along the weld line are obtained.
2. In the range of the condition investigated. The electrode force of 600-700Kg and the welding current of 9000A may be recommended to obtain the best ductility of the weld.
3. Ductility of weld decreases with the increase of welding current, and the lower becomes the electrode force, the higher is the decrease rate, but too low current results in the incomplete bond and very poor ductility.
4. Joint thickness decreases with the increase of welding current and electrode force, but the effect of electrode force is not so distinct as that of current.
5. The microstructure of the weld section at the time when ductility is the best presents recrystalized ferrite grains and small islands of bainite and martensite surrounding cementite, and there is no regions of fine ferrite and pearlite or columnar dendritic nugget which show the temperature has risen above the critical or melting limits.
