Welding is a process that involves joining two pieces of metal or plastic, and this is done by melting the pieces of metal.
The heat produced provides a strong joint between the two joined pieces of metal or plastic.
Two popular types of current are used in the welding process. These are Alternating current (AC) and Direct current (DC).
Welding cannot often be done on all types of metals; for instance, stainless steel is often prone to distortion and cracking when exposed to high heat.
On the other hand, alloys cannot be exposed to high amounts of heat due to the chemical composition of the metal.
Therefore, considering the type of metal you want to work with is critical.
Changes periodically (positive and negative)
Constant (positive or negative)
Aluminum, thicker steel
Steel, stainless steel, thinner metals
Deeper penetration, more splatter, less control
Smoother weld, less splatter, more control
General fabrication, aluminum welding, thick metals
Precision welding, thinner metals, stainless steel
How Electrical Current Affects Welding Processes
The type of current used affects arc stability, penetration depth, and the ease of starting the arc. AC welding helps remove the oxide layer on materials such as aluminum due to its current reversal. On the other hand, DC welding provides greater control, making it the preferred choice for accuracy tasks.
What is Alternating Current (AC)?
Alternating current is a type of electric current that often switches its direction in a back-and-forth motion, bringing about a reverse in voltage due to the change in the current direction.
AC is known to change its polarity 120 times per second, and a reversed polarity in the AC causes a deeper penetration to the object undergoing welding. The alternating current frequency is often 50Hz to 60Hz, depending on the country of residence.
Long-distance transmissions are often done within high voltages, thus reducing current and loss in transmission. The alternating current also allows a convenient shift from one voltage to another, which is made possible because the current often switches its direction in a back-and-forth motion.
Advantages of AC Welding
AC welding is suitable for materials inclined to magnetic interference and can be more cost-effective due to lower maintenance requirements. They are universal and can handle magnetic materials and environments where electrical conductivity varies.
Disadvantages of AC Welding
The fluctuating nature of AC can cause difficulty in controlling the arc, leading to increased spatter and making it challenging to perform proper welds.
Ideal Applications for AC Welding
This welding process is suitable for ferrous metals and high arc stability, such as in outdoor conditions where the electrical supply may fluctuate.
What is Direct Current (DC)?
Direct current is a type of electric current which flows in one direction. The current may either be positive or negative.
Direct current is often used in batteries and low-voltage devices such as remote controls, mobile phones, aircraft applications, automotive applications, and solar panels. The frequency of direct current is often zero and is not influenced by the country of residence.
Direct current likewise makes it possible to transmit power over long distances. If alternating current is available, it can easily be converted to direct current for transmission.
However, direct current is considered more efficient, especially when the transmission distance is less than 100 feet. Working with direct current also reduces the risk of hazards often brought about by shocks.
This is made possible because the voltage produced is below 48 volts, thus making it safe for individuals handling the electrical equipment.
Advantages of DC Welding
DC welding produces smoother welds with less spatter, providing accurate control over the welding process. This makes it ideal for tasks requiring high accuracy.
Disadvantages of DC Welding
Due to the constant direction of current flow, the main drawbacks include higher equipment costs and limitations in welding certain types of metals effectively.
Ideal Applications for AC Welding
DC welding is highly effective for precision welding tasks, especially for thin metals where control and a smooth finish are essential.
Difference Between AC Welding and DC Welding
AC welding is ideal for welding magnetic metals, which cannot be done by DC welding.
AC welding welds down heavy plates and aluminum TIG with high frequency and fast fills. The primary advantage of AC welding compared to DC welding is that it allows the welder to weld magnetized materials.
The current changes in direction in AC current are not affected by magnetism. Therefore, it is easier to control the arc as it remains stable.
AC welding is a commonly preferred method in seam welding, which is often used in shipbuilding. This is because the current settings are much higher than those used in DC welding.
Therefore, much deeper penetration of the metal is achieved. It is also used in TIG welding aluminum since AC supports welding at higher temperatures.
Old Machinery often has rusty areas, which may be a concern due to the amount of heat the Machinery will be exposed to.
AC welding promotes a higher heat penetration than DC welding, thus ensuring that it does not affect the piece of Machinery.
DC welding is best suited for single carbon brazing, cutting tap, stainless steel TIG welding, overhead welding, and hard-facing.
Aside from AC welding, DC welding is also preferred in some circumstances.
This is because it can weld much thinner pieces of metal compared to AC welding. Machines often using DC welding are also deemed less expensive than AC welding.
DC welding produces smoother welding, with fewer chances of spatter due to the direct current produced. It also has a stable and constant arc, making it more reliable and easier to handle than AC welding.
Therefore, it is vital for a welder or the individual handling the welding equipment to conduct extensive research on the materials to be used and their current condition to choose whether alternating or direct current is ideal for the task at hand.
This is because using incorrect current may result in a lack of arc control, overheating, excessive splatters, and, at the same time, quick burning of electrodes.