Arc blow can cause a number of welding problems, including excessive spatter, incomplete fusion, porosity and lower quality.
What is it and how can it be prevented?
we will examine arc blow and discuss ways to troubleshoot and eliminate this phenomenon to create a better weld.
Arc blow occurs in DC arc welding when the arc stream does not follow the shortest path between the electrode and the work piece and is deflected forward or backward from the direction of travel or, less frequently, to one side.
First, let's examine some of the terms associated with arc blow. Back blow occurs when welding toward the work piece connection, or the end of a joint, or into a corner. Forward blow is encountered when welding away from the work piece connection, or at the starting end of the joint. Forward blow can be especially troublesome with SMAW iron-powder electrodes or other electrodes that produce large slag coverings, where the effect is to drag the heavy slag or the crater forward and under the arc.
Magnetic Arc Blow
Magnetic arc blow is caused by an unbalanced condition in the magnetic field surrounding the arc. This unbalanced condition results from the fact that at most times; the arc will be farther from one end of the joint than another and will be at varying distances from the work piece connection. Imbalance also exists because of the change in direction of the current as it flows from the electrode, through the arc, and into and through the work piece.
Thermal Arc Blow
We've already examined the most common form of arc blow, magnetic arc blow, but what other forms might a welder encounter? The second type is thermal arc blow. The physics of the electric arc require a hot spot on both the electrode and plate to maintain a continuous flow of current in the arc stream. As the electrode is advanced along the work, the arc will tend to lag behind. This natural lag of the arc is caused by the reluctance of the arc to move to the colder plate. The space between the end of the electrode and the hot surface of the molten crater is ionized and, therefore, is a more conductive path than from the electrode to the colder plate. When the welding is done manually, the small amount of "thermal back blow" due to the arc lag is not detrimental, but it may become a problem with the higher speeds of automatic welding or when the thermal back blow is added to magnetic back blow.
What is it and how can it be prevented?
we will examine arc blow and discuss ways to troubleshoot and eliminate this phenomenon to create a better weld.
Arc blow occurs in DC arc welding when the arc stream does not follow the shortest path between the electrode and the work piece and is deflected forward or backward from the direction of travel or, less frequently, to one side.
First, let's examine some of the terms associated with arc blow. Back blow occurs when welding toward the work piece connection, or the end of a joint, or into a corner. Forward blow is encountered when welding away from the work piece connection, or at the starting end of the joint. Forward blow can be especially troublesome with SMAW iron-powder electrodes or other electrodes that produce large slag coverings, where the effect is to drag the heavy slag or the crater forward and under the arc.
Magnetic Arc Blow
Magnetic arc blow is caused by an unbalanced condition in the magnetic field surrounding the arc. This unbalanced condition results from the fact that at most times; the arc will be farther from one end of the joint than another and will be at varying distances from the work piece connection. Imbalance also exists because of the change in direction of the current as it flows from the electrode, through the arc, and into and through the work piece.
Thermal Arc Blow
We've already examined the most common form of arc blow, magnetic arc blow, but what other forms might a welder encounter? The second type is thermal arc blow. The physics of the electric arc require a hot spot on both the electrode and plate to maintain a continuous flow of current in the arc stream. As the electrode is advanced along the work, the arc will tend to lag behind. This natural lag of the arc is caused by the reluctance of the arc to move to the colder plate. The space between the end of the electrode and the hot surface of the molten crater is ionized and, therefore, is a more conductive path than from the electrode to the colder plate. When the welding is done manually, the small amount of "thermal back blow" due to the arc lag is not detrimental, but it may become a problem with the higher speeds of automatic welding or when the thermal back blow is added to magnetic back blow.
