For MIG welding it depends on the wire size. As a rule of thumb…….for every .001 inch of wire you want to use 1 amp of output. For .125 inches of wire, you’ll need to use 125 amps.
However, for more detail, choosing the amperage and polarity depends on the welding electrode, base metal, and welding process. This determines the level of penetration and amount of electricity flowing per second, as well as the quality of the bead when you’re welding.
It can be kind of intimidating to understand the digital readouts and dials on a welding machine. The controls on a TIG machine are going to be more complex than those on a stick welding machine. Top end TIG machines can have up to 20 knobs for controlling a number of settings.
All welding types (TIG, Stick, and MIG) have a number of controls that are all on front of the machine. These controls are in place to control the amount of current used to perform a weld.
The question you may be asking is what voltage or welding amperage setting do you put the machine at?
There are a few variables that come into play when you’re setting the amperage on a MIG, TIG, or Stick welding machine such as electrode, welding process, base material, and application.
Once these 3 main variables are determined, one can set the welding machine and begin laying their bead. In the article, one will discuss each of these variables in depth, while also receiving a few tips.
Base material and welding application
We’ll discuss base material, welding application, and how these things apply to the selection of amperage on the welding machine.
Base Material
Base material’s category is very broad. With that in mind, we’re going to talk about a couple of areas in the base material category. These 2 categories are thickness and type.
Each of these 2 areas are strongly correlated with choosing the correct amperage on the welding machine.
How does the type of material affect the selection of amperage?
The material used in a number of welding applications varies with each weld, jobsite, and welding technology.
Before you even begin to think of the amperage you set your welder to, you have to ask yourself what kind of metal will be welded.
The material types that standard welding methodologies can actually meld together are aluminum, carbon steel, and stainless steel. All of these types of material need a different selection of amperage on the machine that will be doing the welding. The biggest difference is between non-ferrous and ferrous materials such as between aluminum versus steel.
Some materials need lower or higher amperage settings based on the material’s raw melting point. This is apparent when one looks at aluminum. Since aluminum’s melting point is around 1,200 degrees Fahrenheit.
Choosing amperage when you’re welding aluminum
When you’re welding aluminum materials, the current has to typically be switched from direct current to alternating current. In addition to this, the amperage has to be turned up to make up for aluminum’s higher melting temperature.
When TIG welding aluminum take note of the fact that AC current is utilized due to its relative cleanness. This is mainly because of the fact that the weld current is alternating directions.
Once one strikes the arc in aluminum TIG weld beads and the puddle for the weld is formed, the operator has to move the bead fairly quick. This is because the aluminum base material tends to soak up the high amperage heat and may warp the base materials.
Welding amperage for different thicknesses of steel
Adjustments made to compensate for the thickness of steel is similar to the processes one does to compensate for the material thickness in a MIG welder.
Welders that are stick have a control knob on the machine’s front that adjusts the level of amperage as you turn your wrist. Much like the stick welder, MIG welders tend to have the same functionality, something that comes in handy when one wants to switch from workpieces that’re thick to thin ones.
Welding Application
The application the welding is used for directly correlates with the amperage that’s going to be used for the weld.
Laser beam and micro TIG welding are similarly applied whereas TIG welding’s amperage is fairly low. In the case of laser welding however, there is no amperage since there is no electrical current in the workpiece. In contrast Stick and MIG welding use very high amperage settings so they achieve optimal penetration into the material.
An example of this is that a highly technical TIG weld on helicopter exhaust manifolds have drastically different amperage needs than for things such as oil pipelines. The main difference is between welding thin, exotic materials and welding 3 ft diameter pipe to the next sequenced pipe.
In a few applications, one selects amperage for convenience.
ie. you may want to MIG weld sheets of metal to other pieces of metal in the workshop, so you may be inclined to turn the amperage up so you can get the weld bead laid as fast as possible.
That isn’t to say that you should rush through welds, but it isn’t bad to speed up a weld bead in non-critical applications.
MIG welding
For this article’s purposes, the variable voltage settings will be used instead of the amperage settings which are used by other welders typically.
Voltage settings on standard MIG welders determine the amount of power that will be used while the MIG welder is being operated. There will always be a necessary balance between wire feed speed and voltage. Mainly because the wire feed speeds have to increase as the voltage increases or the weld puddle won’t be adequately fed with filler material.
Thin materials have to start at the lowest possible voltage setting, thicker materials are already consistent as the base materials don’t have much need to change. Welding operators may have a MIG welder at a certain setting for years of they don’t change the type of material they use.
Stick welding
Stick welding has the most significant correlative relationship between weld amperage and weld application.
Stick welding operators may use an amperage setting on one day while they are welding steel plating for a structure and use another setting on a different day while they are surface welding a backhoe bucket.
Some good news about stick welding is there are charts that one can find online that are good at predicting the necessary amperage for certain welding thickness as well as the accompanying stick welding electrode.
TIG welding
Generally speaking, TIG welding is reserved for those who have high hand-eye coordination since a great deal of TIG welders require foot, hand, and eye coordination – much like driving a vehicle.
A unique characteristic of TIG welding is that the foot pedal on the TIG welder has control over the amperage used based on the person’s input.
Foot pedals start at 0 amps while resting and will gradually increase as the operator presses down on it. The foot pedal’s amperage control is limited by the machine’s amperage capabilities and the settings installed on the machine.
A few TIG welders have a peak amperage feature placed on the control panel that should be set to around 40 to 50 percent above the desired amperage range that’s going to be used in the weld.
A few TIG welders have different amperage controls like the background amperage or allow fine adjustments to the amperage when AC current is used. These adjustments will not be discussed in this paper though.
The electrode
The only process of welding that has a significant correlation between amperage and the electrode or SMAW. This method of stick welding and the amperage is so dependent on one another in this category, which explains how this topic made it into the top three amperage selection factors.
MIG and TIG welding processes use electrodes by definition, however, TIG uses semi-consumable tungsten rods and MIG makes use of highly consumable wire, each of which are of little significance when discussing amperage selection.
There are a few types of electrodes one could use for stick welding; each one has a specific use. An example of this would be that electrodes are different based on the thickness of the base material.
There are also different because of the overhead, horizontal, and vertical positions. Each of these different properties are represented in the 4-to-6-digit number that’s printed on each stick electrode.
Each of these numbers tell the user which tensile strength, power supply, weld position, and penetration the electrode is designed to be used for.
Typical electrodes that can be found on market are 7018, 6010, and 6013. Each of these electrodes are found normally in the industry because of their flexibility in use.
The 6013 electrode is designed for less penetration while the 6010 is designed for high penetration. To make the weld look best one should use the 7018 electrodes.
Once one selects a welding electrode, they should read the side of the electrode container so they can see if the manufacturer of the electrode has a recommended welding amperage. To be specific amperage depends on the electrode’s diameter.
An example of this would be, a 1/8th diameter electrode welds near perfectly between 75 to 125 amps. On the other hand, a 5/32 diameter electrode welds great ay 220 amps.
A great way to know the optimal amperage one should use is for them to test the welding electrode on scrap pieces of metal and see what the result is. If it appears acceptable and the penetration rate is good, go with it.
Make sure to consider when you’re changing the amperage on the SMAW machine is its duty cycle.
Duty cycle is the length of time the welding machine can weld in a 10-minute time frame. There are machines that are more heavy-duty than others.
An example of this would be, some machines used at construction sites will likely be of a heavier duty and longer duty cycles than a machine used by a hobby welder in their garage.
Duty cycle has the inverse proportion to welding amperage. As the amperage increases, the duty cycle will decrease in minutes.
