Arc Length, Weld Speed and Welding Current
Every commercial welder will tell you that the arc length, also called arc gap, is the distance between the part that has to be welded and the electrode tip. The arc length depends on the arc stability, the weld current and the concentricity of the part. The task of the commercial welder here is to keep the electrode at a certain distance from the surface so that there is enough place to avoid stubbing out. In general, the arc length is 0.10 inch and this measurement is taken as a base. One half of the weld penetration is combined with the base measurement and this results in the arc length for a certain amperage.
The weld speed that the commercial welder has to choose is the speed of travel of the torch ad it is dependent on the flow rate of the material that has to be welded and also on the thickness of the material that needs to be welded. In general the commercial welders should weld as quickly as possible for them to secure a weld that is of good quality. The weld speed in an important factor when defining the result from the welding process that has been done.
For example, the tube mill welding speed should be between 3 inches to 60 feet per minute, the lathe welding speed should be 5 to 60 inches per minute and the orbital welding equipment weld speed should be 4 to 10 inches per minute. In general, the starting welding speed for the parts that are rotated under the welding torch, the speed on the tungsten surface needs to be between 10 and 20 inches per minute. Slow speeds are applied to parts with heavy thickness and faster speeds are applied to parts with thinner walls.
The welding current that the commercial welders use in general corresponds to the amount of the heat that is applied to the part that will effect the weld. The welding current depends on the material that has to be welded and on its thickness, the welding speed itself, the shield gas.
The aim here is to get welds that have no defects with the right kind of penetration. As a rule the welders start with 1 amp of the welding current that corresponds to 0.001 inch of the thickness of the material. In general, if the material is 0.030 inch thick, the average current of the weld should be around 30 amps. In circular parts there might be a heat building up, which could be compensated with multiple weld current levels. The number of the welding current that are needed depend mainly on the welding application and on the welding speed.