One of the problems you may encounter when welding high-strength steel is cracking caused by hydrogen contamination. Your best bet will be to use a low hydrogen electrode to avoid this problem. Question is, which low hydrogen electrode should you use?
You could opt for the 7018, but it isn’t easy to perform an open root weld on a pipe with it. Fortunately, another low hydrogen electrode is perfect for such a task. The 7016 welding rod is a low hydrogen electrode with a potassium-based coating.
What makes the 7016 rods better for open root welding than the 7018 or any other low hydrogen rod?
Mechanical properties of E7016
70 ksi (550 MPa)
58 ksi (460 MPa)
low hydrogen and sodium
welding parameters of 7016 welding rod
deposit composition of E- 7016 as per AWS A5.5 requirements
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Characteristics and features of the 7016 welding rod
To answer the above question, we have to look at the chemical properties of this electrode. Unlike the 7018, the 7016 rod has a potassium-coated flux that is low on iron powder. The rod has chromium, manganese, silicon, sulfur, and phosphorus
It can be welded on both AC and DC. However, the stability of the weld puddle is better when using DC. And as you might have guessed from its name, the rod can be used in all positions.
The amperage you set when using this rod will depend on the diameter. The rod can use an amperage of as low as 50 to as high as 260 amps. A 2.0 mm thick rod will require between 50 to 80 amps.
On the flip side, thicker rods of about 5.8 mm thick will require an amperage of 230 to 260 amps. As with most other low hydrogen electrodes, it has prone to damage when exposed to water. As such, it is recommended to dry it at a temperature of 350 degrees Celsius before use.
What is the 7016 used for?
- Used to world low alloy steels and carbon steel
- Used in shipyards to weld grades A, B, D, and E steel
- Used in the construction of pressure vessels, boilers, and other steel structures
- Used in the repair of pipelines
- Used to weld highly restrained joints
- Used in general repair and fabrication works
E7016 vs. E7018
The 7016 and 7018 welding rods are relatively common, and both are similar in some aspects. The first is that both are low hydrogen electrodes that can be used in all positions. However, they do differ in some regards.
One notable difference is in the coating. The 7016 has a potassium coating, while the 7018 has an iron powder coating. This results in the appearance of their slag. The 7018 slag is more liquid.
On the other hand, the 7016 slag has a glassy slag that is easy to identify. As a result, the 7016 is easier to use for downhill welding compared to the 7018. Also, the 7016’s arc can be buried right in the weld pool without it being snuffed out.
This makes the 7016 a better choice for welding in awkward positions. In terms of the weld bead, both are pretty similar. In fact, you would find it difficult to differentiate a weld done using a 7016 from one done with the 7018.
Though the 7018 seems to have slightly more spatter, it is easy to remove. I think the 7018 beats the 7016 in the handling of dirty or rusted surfaces—the 7018 burns right through paints, oils, and dirt.
And while the 7016 can weld dirty or rusted surfaces, you will have to use a whipping motion to get it to burn through. So for dirty surfaces, I would pick the 7018 rods over the 7016. Also, the 7018 has a slightly faster deposition rate.
So which one should you pick between the two? Well for most general-purpose work, the 7016 seems to be a better choice. The 7018 has its advantages and can be a good rod, but the 7016 is more versatile.
What is the root pass, and how does it differ from a hot pass
You will hear two terms used in the welding world: root pass and hot pass. These two terms vary in their definition. The root pass is the first pass you make when welding. This is typically the first weld bead where the welding process requires more than one pass.
As for the hot pass can be described as the second pass made after the root pass. However, in stove-pipe welding, this term is used to describe the process of cleaning up slag. This process entails first cleaning the weld bead with a grinder and following this with a hot pass.
The purpose of this hot pass is to burn out the slag trapped between the bead and the pipe wall. This slag is often referred to as wagon tracks. And the term hot pass came from the second pass needing to be hot enough to burn the trapped slag deposits. Overall, the hot pass is usually used to refer to the second pass made after the root pass.
7016 root welding technique and tips
For overhead welding using the 7016-rod, use a 90 degrees angle. Use a drag motion to weld through the pipe joint. One thing you will have to do is to feather your tacks and grind before restarting.
This allows for complete melting and the weld to blend nicely without a crater left. After each stop when welding, you will see a crater grinding is important to remelt the parts of the crater.
DCEN polarity works best with the 7016 and is what you will want to use for root welding pipes. The 7016 is different from the 6010, which is another rod commonly used to weld pipes.
The 7016 in some industries is preferred over the 6010 because of its low hydrogen properties that minimize the risk of hydrogen-induced cracking. And thanks to its lighter slag, it is also ideal for downhill welding. It is considerably slow to weld with compared to the 6010 and 7018.
This is something to note if you plan to use this rod overall, though it is a versatile rod that can be used in different weld applications.