Gotcha…I might have typed the numbers wrong on that wire. I meant what is comparable in class to the Lincoln E71T-11 MP211 innershield wire that I have on my MM215 at present.
I’m open to your explanation of the difference, and apologize for the mistake. I am here to learn, and very much appreciate you and others taking a moment or two to help me, and steer me in the right course of this welding thing! Most here are way more experienced, and way more knowledgeable than I am! Thanks, Louie!
To further expand on what Louie said:
E71T-1/E71T-1M are both electrodes designed to use an external shielding gas to protect the weld puddle which forms a protective slag covering to protect the solidified weld. This is why they are commonly called dual shield flux core electrodes. They can be used to make single or multi-pass welds and when used with Argon or Argon mixes they create higher strength weld deposits than CO2 shielding gas alone. Some of the elements in the flux for this type of electrode gets transferred across the arc and into the puddle to add silicon and manganese to the weld deposit. These are called alloying elements and they act to strengthen the weld metal. Although if oxygen is present in the puddle (such when welding over rust or using 100% CO2) they will act as a deoxidizer instead of strengthening the weld.
E71T-11 is a self shielded electrode which requires an atmosphere of oxygen and nitrogen (normal air) to produce sound welds. The flux is now providing the protective atmosphere for the weld metal when it reacts with air instead of enhancing the alloy content like a dual shield electrode. The main difference for this flux compared to dual shield is it uses aluminum and magnesium to remove oxygen and nitrogen in the weld. These elements are transferred across the arc where they react with any free oxygen and nitrogen in the puddle and form part of the slag. They do not provide any strengthening of the weld like silicon and manganese do but they are much stronger at removing oxygen and nitrogen. This means there is less room in the wire for the manufacturer to add alloying elements that would strengthen the weld. This electrode is also usually limited to a single pass weld up to 3/4" thick steel since there's not enough alloying elements present to prevent dilution of the weld metal with multiple passes and thicker material would cool the weld too fast. The extra deoxidizers in the flux can also accumulate over multiple passes and further weaken the welds.
While multiple electrodes may all have the same ultimate tensile strength (70,000 psi in this case), that does not mean they have the same notch toughness, elongation %, yield strength or final weld composition. Tensile strength is not the end all be all of determining weld metal performance.
The fumes generated by flux core is also a health concern when using self shielded electrodes indoors because of how much gets generated by the reaction between the flux and the air. I wouldn't weld indoors with self shielded without a good fume extractor or respirator, dual shield you probably don't need to worry unless the weld area is pretty small.
