We are often asked questions like “is X wire comparable in strength to Y welding rods?”.
In this article we compare the typical strength of Stick vs MIG vs Gasless welding consumables for steel, to assist with chosing the most suitable products for your application.
Different measurements of strength
Welding wire and electrode standards typically require testing for various aspects of strength and toughness, and the outcome of each test to meet either a minimum value or to be within a specific range. These tests include:
Tensile Strength (TS): The maximum load that a material can withstand before breaking, when being pulled or stretched. Measured in terms of the force divided by the original cross-sectional area of the material.
Yield Strength (YS): Indicates the maximum load that a material can withstand without producing permanent (or ‘plastic’) deformation. Indicates the elasticity of a material, or the ability to withstand stress and then return to it’s original shape/form.
Elongation (EL%): Percentage of stretch (change in length) from the original length of the material to the point of failure. This indicates how ductile the material is – the capability to be stretched without becoming weaker or more brittle in the process.
Impact Toughness (CVN): This is a measure of how much energy (joules) a material can absorb when a load is suddenly applied to it. The Charpy (CVN) method is used to impact metals. This involves striking a specimen with a weighted pendulum to cause it to fracture, and measuring the energy absorbed during fracture (how far the pendulum swings after it has struck the specimen). This is often performed at various low temperatures typically ranging from -20c to -50c.
Globally, there are various standards for welding filler metals, including AWS, EN, ISO, AS/NZS, etc. In this article we will refer to AWS (American Welding Society) standards, which are arguably the most commonly / widely used standards across the USA / Asia Pacific / Australasian regions.
A Quick Comparison
Here is a comparison of the AWS requirements for common welding consumables for steel.
|Low Hydrogen Rods||E7016||>420||500-640||>22||>47 @ -20c|
|Solid MIG Wire||ER70S-6||>400||>480||>22||>27 @ -30c|
|Gasless MIG Wire||E71T-11||>390||490-660||>20||n/a|
Comparing the above data, we can observe that:
Gasless Wire vs GP Rods: Gasless wire has higher higher Yield and Tensile requirements (eg YS 390 vs 330 Mpa). AWS does not require impact testing, indicating these are expected to be used in ‘general purpose’ applications where impact toughness is not critically important – for example the welded components are not likely to be subject to impacts, blows or sudden load stress.
Solid Wire vs Gasless Wire: Similiar in terms of Yield and Tensile requirements.
Solid Wire vs Low Hydrogen Rods: Low-hydrogen rods have higher Yield and Tensile requirements. Both have impact requirements indicating suitability for use where impact or sudden loads may occur.
Consider the purpose, not just the material
Let’s use Railway iron as an example.
A question that is often asked is: I understand that railway iron is strong/harder than mild steel. So should I be using low-hydrogen electrodes or a high-strength wire to weld it?
Railway Iron is often used (or re-used) for general construction/fabrication and applications such as gates, fences, livestock yards, and the like. In these applications, the weld joint is unlikely to be subject to high-impact load and therefore general-purpose consumables – such as GP rods, Gasless wire or Solid Wire – are usually more than ample for the purpose.
Where it may become necessary, or an advantage, to use low-hydrogen consumables is where a particular weld joint will be subject to high load, impact, or sudden stress. For example, a tow-hitch component on a tractor implement.
Other Factors & FAQs
Correct use of Low-Hydrogen Rods:
One factor that is often overlooked is that low-hydrogen electrodes should be dried/warmed immediately before use, to remove any atmospheric moisture absorbed by the flux coating. If this is not done then the low-hydrogen status can be compromised – becuase moisture/water (H2O) contains hydrogen – and as a result the weld strength or toughness may not be much different to regular GP electrodes.
Benefits of Gasless Wire:
Just because gasless wire (E71T-11 grade) is not technically ‘low hydrogen’, does not mean that it is not capable of a high-quality weld in the right application.
With a high-quality gasless wire such as Weldclass Platinum GL-11, good penetration is often achieved thanks to cleaning action of the flux – especially on dirty and rusty materials where some other consumables are not as tolerant.
Also, because the likes of GL-11 wire is both all-positional and very user-friendly, this can allow the operator to achieve the best possible result / weld quality even when conditions are not ideal – for example site and field applications where the workpiece is not in a perfect welding position and/or condition.
These attributes can be a major benefit when it comes to strength, as many weld joints fail at the point where the weld joins the parent material (rather than in the weld metal itself).
Is there a low-hydrogen Gasless Wire?
Yes, with some catches! E71T-8 grade gasless wire is a low-hydrogen product for high-strength and critical applications – tensile and yield strength requirements are very similiar to standard gasless wire (E71T-11), however E71T-8 is required to meet impact testing (>27j @ -30c).
The catch is that E71T-8 wire is intended for use in heavy industry and for welding heavy material, is available only in larger sizes 1.4mm-2.0mm, and is more challenging to use / operate (especially compared to the very user-friendly Weldclass Platinum GL-11). For this reason E71T-8 is not an option for the likes of general fabrication and maintenance, welding thinner materials, or use with single-phase/portable welders.
Post time: Sep-11-2023