Welding Tips and Tricks

Hi all, so this is my first post, and I thought it would be fitting to post my questions here rather on the introduction section. To explain my situation, I am a mechanical engineer student and we got this mechanical shop class where I recently did a report about arc welding. We haven't done any form of welding yet in class so I had to rely on the internet for information. After my report, the professor gave me some questions that he wants answered by next meeting. The problem is, I can't seem to answer two of his questions. Here they are:

1.Is the tensile strength value written on the welding electrode refer to the welding electrode before welding or after welding (the welding bead)?
2.Why does the metal (I think he was referring to the electrode core wire?) melts first during welding and the coating remains to cover the core wire?

Well, for the first question, I think it refers to after welding because I think that would make much more sense. While for the second one, I think the metal melts first because the heat is concentrated there and not on the coating. However, I am still not sure about these answers and haven't welded firsthand yet and would like to ask the help of some experienced welders out there. I also tried looking up the internet but haven't found any luck and I do not know any welders near my home. Many thanks for reading it up to here.

1. The Electrode tensile rating is for the strength the weld bead will produce.
2. The “coating” is called flux and it is there to shield the arc during the process. Depending upon which process is used, and whether you are electrode positivie or negative, the electrode is actually short circuited against the parent metal.

https://www.millerwelds.com/resources/a ... electrodes

Also the tensile indication on the box is considered the minimum. For actual "as welded" tested results, you must refer to the manufacturers spec sheet.

Here's one for a typical er-70s6

http://www.lincolnelectric.com/assets/g ... /c4105.pdf

cj737 wrote:2. The “coating” is called flux and it is there to shield the arc during the process.

Also, in many rods, most notably 7018, iron powder in the coating melts and becomes a part of the weld deposit.

http://www.esabna.com/euweb/awtc/lesson3_13.htm

As I've been told, the same metal rods go into each electrode and the flux coating is what changes the properties if the weld. Is this also true?

Farmwelding wrote:As I've been told, the same metal rods go into each electrode and the flux coating is what changes the properties if the weld. Is this also true?

Not entirely sure but here's a >guess<: that is probably true for electrodes within the same class, such as 6010, 6011, 6013. Probably less true for electrodes in different tensile strengths: 7018, 8018, 11018. And definitely not true if you compare aluminum, stainless, and cast iron electrodes.

Depends strictly to the individual electrode. There are lots of high chrome rods that the wire inside is just mild steel. So you can’t just knock the flux off and tig with any rod.

[no input needed on this]

You have to know ahead of time what metal the base rod is made of , but yes 7018 and 7014 have the same rod in the center and in a pinch you can. Or you can Texas tig as you stick weld with one rod and use a second with the flux knocked off to add filler when you need to. It would be pretty hard to make an X-ray quality weld doing this, but not everything needs to be X-rayed.

[no input needed on this]

If in fact you are a student, flux is designed to shield the hot arc, and deposit filler metal from atmosphere. A component of that shielding is to physically form a barrier, around the most reactive part of the arc, as it is consumed, barrier gasses are formed to displace air.

Tensile strength speaks to the strength of the weld it produces. For obvious reasons it is possible to F**K up a good weld and yield strength would be less.

Yield strength is always going to be less than tensile. Yield strength simply refers to the amount of stress the metal can take before it "yields" --- in other words, where it won't spring back to its original size/shape/position. Yield strength refers to how much stress it takes to strain it permanently.

If you pull on a wire of steel until it permanently stretches (and thins as a result), you've reached its yield strength. If you kept pulling on it, stretching it like a piece of fishing line, until it broke, you would have reached its tensile strength.

Wow, thank you all everyone for the helpful and very informative replies.