Table of Contents
- 1 What Is Welding?
- 2 AC Welding
- 3 DC Welding
- 4 What Is Better – AC or DC?
- 5 Which Electrode To Use?
- 6 Conclusion
AC / DC may arguably be one of the greatest bands of all time, however, here it is something completely different. When it comes to welding, we are referring to the difference between alternating current (AC) and direct current (DC) welding.
Typically, DC stick welding is a more popular option but there are certain circumstances where AC stick welding may offer a better solution. Below we will explore the difference between the two and help you to understand when it is the best time to use each.
What Is Welding?
Wikipedia describes Welding as “the fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal. (1)
A power supply will create and maintain an electric arc between an electrode and the base material to melt metals at the welding point. They can use either direct current (DC) or alternating current (AC), and consumable or non-consumable electrodes. There is often a filler material that is used to join the two materials. When the base metal has melted the weld pool will cool to form the join.
When it comes to AC Welding, the electron flow keeps changing directions as it moves back and forth. The polarity can be change up to 120 times a second. As this flows from negative to positive, the output has a zero amperage for a fraction of a second. This period with of zero output can cause the arc to be extinguished. Look for electrodes that are specifically for AC welding to minimise this problem. They also have a special coating that ignites the arc.
One of the main benefits of AC is that it will transmit power transfer over long distances. This current can typically be found in household outlets and equipment in high voltage systems. When it comes to welding, is typically a secondary option. There are, however, a few situations in which AC welding is favored.
Welding Processes That Use AC
It is better suited to TIG aluminium welding. Aluminium is a special metal with a durable oxide coating. When the reverse current is active, it helps to dissolve the oxide layer and clean the air.
In fact, the electric flow reversely can connect periodically which can allow high-temperatures for welders. An electric current that flows in one direction is adopted in most soldering techniques. TIG aluminium equipment uses an electric current that periodically reverses, however systems that use alternating voltage and direct voltage are now also available. These MIG- or stick- and TIG-Soft Aluminium are usually multi-processing devices.
AC Welding Applications
As AC welding is better for higher temperatures it is preferred for welding aluminium and other non-ferrous metals. The welding of magnetized metals is another major use of AC welding.
Advantages of AC Welding
- TIG Aluminium welding as AC facilitates soldering at higher temperatures
- If deeper penetration of platform metals is needed, i.e. shipbuilding
- For welding materials with a magnetized field
- Is often more affordable and portable
Disadvantages of AC Welding
- The arc can be more difficult to control
- Can potentially create more spatter
- The weld is often not as smooth as a DC weld
In this type of electrical voltage, the electricity flows in one direction. Therefore, the polarity is continuous and can be positive or negative. This is applied in low voltage devices including computers, remote controls, etc.
It tends to be smoother when welding, leading to the rapid melting of the electrode. The polarity can be positive or negative, as stated previously. Often called line, the negative polarity of the electrodes is faster than the positive polarity of the electrodes.
Negative polarity, however, results in less heat than the positive electrode. This is suitable for welding thinner wire electrodes.
Types of Welding Processes That Use DC
It is used to a greater degree than AC. Nearly all soldering processes are based on this direct electric flow. The key welding processes which use direct voltage are stick welding and MIG welding.
DC Welding Applications
In stick weld applications, direct voltage is also applied. This means that it is excellent for weld applications including overhead or vertical weld. Direct flow is often used because AC is not as suitable for finer metals weld.
While AC is used particularly when cutting aluminium for TIG cutting applications, DC is used for TIG stainless steel welding. In single carbon brazing, DC is also used.
Advantages of DC Welding
- This produces a cleaner and smoother weld
- Keeps a smooth arc which makes it simpler to use than AC
- Is often a lot easier to start
- Is a god fit for use on thinner metals
- Great for vertical and overhead work
Disadvantages of DC Welding
- It does not work well when high intensity heat is required
- Often more expensive than AC machines
- Can have arc blow problems
What Is Better – AC or DC?
When it comes down to AC vs DC welding it is best to think about what is better for the type of metal and workpiece that you will be working on. It is also important to remember that to achieve a strong weld you need to have the correct polarity, current and electrode. Let’s look at which electrode to use.
Which Electrode To Use?
When it comes to AC, the arc can be easily extinguished. You want to look for AC specific electrodes, these will have elements in their coating that are made to function on AC polarity which helps to keep the arc ignited.
Check electrode 6010 for DC welding. This is only planned for immediate use. The sodium film is high in cellulose. It provides increased penetration and various field applications.
The arc appears to go out and then has to be re-established when welded with reverse electric flow polarity. Using electrodes with other elements in their layer to help hold the arc lit, for reverse electric flow. This alternating current rod includes 6011, 6013, 7018, and 7024 plates.
The 6011 has a potassium-like high-cellulose shell. It can be used for cutting in both places. These also perform well on rusty and dusty metals and even under windy weather when soldering outdoors.
The clean sheet metal is welded with the rods 6013. We reduce penetration and avoid metal fire.
The rods of 7018 are usually for connecting directly when soldering but are also compatible with when you have a reverse current. They deliver solid welds to a decent bead.
The 7024 rods are ideal for high current applications. For flat horizontal welds, they operate well on a reverse current. These rods are often used where a higher deposition rate is required for general manufacturing.
As we stated earlier it is not so much which is better in terms of AC vs DC, it is more to do with the material and even what sort of workspace you have. Although DC welding typically has more advantages, both AC and DC have their pros and their cons. It is important to research the materials that you will be working on to know the best fit for the specific job.
Keep in mind that you must use the correct polarity, current and electrode to achieve a good welding result. Incorrect current can lead to poor arc control, excessive splatter and poor beading.