How does Peak current and Base current affect the properties of weldments?

The current levels are only two of the parameters determining weld quality. To understand parameters function, the period can be broken down into several parts:

1. Ramp up rate increase stiffens the arc, reducing the arc column size and increasing the propelling force throwing molten drops detached from the electrode,
2. Overshoot, an instantaneous current increase above the peak current level, necessary to overcome the influence of inductance, variable with cable length,
3. Peak current level directly controls penetration: the higher the peak current, the deeper the penetration,
4. Peak Time or Peak Duration influences the width of the bead shape,
5. Tail-out drop time, speed of change and shape controls energy addition to the molten droplet, directly influencing puddle fluidity and penetration,
6. Sudden current drop down to background level, reduces the tendency for fine droplet spatter,
7. Background Current, the low-level current needed to maintain the arc,
8. Frequency or Repetition Rate shapes the weld bead by narrowing the arc cone with increased frequency.

DC AC arc Welding Plant

• DC or AC arc welding plant shall be used Instruments, cables and the accessories shall conform to the requirements of the relevant Indian Standards wherever available


• Their capacity shall be adequate for the Welding procedure laid down. All welding plants shall be maintained in good working order.

• The arc shall be struck on the points/crossing and then the electrodes shall be progressively advanced by maintaining the arc using uniform movement.

• Means for measuring the current (tong tester) shall be available in addition to the current setting panel integrated with the welding plant.

• The actual output of welding current may not be equal to the current as set on the control panel in many cases, specially when the plant becomes old.

• The current range as recommended by the manufacturer for the particular brand of electrode selected for welding shall be used.

• All electrical appliances required with the welding plant shall be properly earthed.

• The points and crossings shall be pre-heated by oxyacetylene films to a temperature between 250 degree centigrade to 300 degree centigrade before welding.

• This temperature shall be maintained throughout the welding operation.

• If welding is to be interrupted for some reason, then the portions to be reclaimed subsequently shall be pre-heated again to the above temperature range before welding as continued.

• The pre-heating and inter pass temperature shall be measured either by contact type pyrometer or tempil stick. No post heat-treatment is required after welding.