Types of Welding Rods
Firstly, carbon electrodes are usually used in arc welding and cutting; they are made of carbon graphite and may be left bare or coated with a layer of copper. In contrast with many other types of welding, the AWS (American Welding Society) does not provide any specifications for carbon electrodes, but the military has given a list of guidelines for optimum sizes based on the job requirements.
Secondly, tungsten electrodes are the type of non-consumable electrode used in TIG welding. They are either made from pure tungsten (which is marked in green), tungsten with 1% thorium (which is marked in yellow), tungsten containing 2% thorium (which is marked in red) and tungsten with a 0.3-0.5% zirconium content (which has brown markings).
Pure tungsten electrodes are usually used on lighter welding applications. The reason for this is twofold: it doesn’t have the same strength and durability of alloys, and it isn’t suitable for welding with a high current.
Tungsten electrodes containing 0.3-0.5% zirconium can provide great results when using an alternating current, but otherwise, it is generally considered that they are more effective than pure tungsten, but less effective than those containing thorium.
Tungsten electrodes which contain 1 or 2 percent thorium are the most common types of non-consumable electrodes because they are more resistant and last longer than other types. They can be used with higher currents than pure tungsten electrodes, they’re easier to start, and they provide better control of the arc while welding.
When it comes to using tungsten electrodes, you’ll have to use the maximum possible current if they’re kept in a standard cylindrical shape, otherwise, it will be too difficult to maintain the arc. To make your life easier and regain control of the arc, grind the electrodes to a point – but bear in mind that if you do so, you should opt for touch-starting rather than using direct current welding machines. If you do decide to touch-start your TIG welding with tapered tungsten electrodes, those combined with thorium and zirconium will have longer lives than pure tungsten welding rods.
Welding rod classification
Now that you understand the basics of different welding rod types, it’s possible to look in closer detail at the welding rod classification system. This applies to stick electrodes and considers their diameter, material used for the coating, tensile strength, the welding position for which they are most suited, and the percentage of iron powder in the electrode.
Consumable electrodes cannot be thicker than the metals which you’re welding; 3/32 inch is the diameter which you’ll come across most often, but the sizes can range from as small as 1/16 inch to as much as five times larger.
With regards to the tensile strength, this refers to the amount of force which the weld can withhold. In order for the join to remain secure and durable, the weld needs to be stronger than the materials which you’ve used, which means that the materials used within the electrode must also be stronger than the metals. If you use an electrode which contains weaker materials than the metal, it will be almost impossible to create a strong, durable weld joint in a neat, clean, smooth way.
The percentage of iron powder in the wire is important because it will be turned into steel when heated up during welding. As a result, more iron powder means that there will be more molten metal which you can use in the weld. You should always be aware of the iron powder content, but bear in mind that you’re unlikely to find a percentage higher than 60.
With those points in mind, we can now consider the fact that many electrodes will bear a code starting with the letter ‘E’, followed by 4 or 5 digits (such as E6010). This is far more than just a code: break down the different elements to classify any welding rod.
For starters, the letter ‘E’ stands for ‘electrode’. Take note of this, just to make sure that you’re using the right piece of kit for the job!
Moving on to the numbers, the first 2 digits (or 3, if the entire code contains 5 digits) give an indication of the material’s tensile strength. If the number is 60, it means that it can withstand 60,000 pounds per square inch; if the number is 70, the weld will be able to withstand 70,000 pounds per square inch.
The penultimate digit in the code will either be a 1 or a 2, and it signifies the positions in which you can use the welding rod. If you see the number 1, you’ll know that you have an all-position rod – it can be used for flat, vertical, horizontal and even overhead welds. However, if you see the number 2, your welding rod can only be used in flat and horizontal positions.
The final digit should be read in conjunction with the second-to-last number: together, these will tell you which type of coating has been used on the welding rod, and so which welding current to use. See the table below for a full list.
The thought of all the possible permutations and combinations is enough to make you balk, but you’ll be pleased to know that there is only a small number of commonly used welding rods. The electrodes which you’re most likely to come across are E6010, E6011, E6013, E7018, and E7024.
If you come across an electrode which has the letter ‘R’ at the end of its classification, it will be more resistant to moisture than any electrode that does not have this suffix.