Welding Tips and Tricks

So if I tig steel using ER70S-2, lets say I make a 1" weld on a properly designed Widget, does that mean it can withstand a 70K load?

The 70 is 70k pounds per sq in of pressure at the max and if done with no deformities or weld errors? (Might be wrong but that is my understanding.)

LtBadd wrote:So if I tig steel using ER70S-2, lets say I make a 1" weld on a properly designed Widget, does that mean it can withstand a 70K load?

Sure it does. I lift 70k all the time...doesn't everybody?

exnailpounder wrote:

LtBadd wrote:So if I tig steel using ER70S-2, lets say I make a 1" weld on a properly designed Widget, does that mean it can withstand a 70K load?

Sure it does. I lift 70k all the time...doesn't everybody?

K mean pounds-not ounces or fluid volume...understand now

Farmwelding wrote:The 70 is 70k pounds per sq in of pressure at the max and if done with no deformities or weld errors? (Might be wrong but that is my understanding.)

HUH? 70 K is tensile strength. Try again

The 70K is the tensile strength of the filler metal. Your base metal may not be that strong, and the join between the filler metal and the base metal may not support that load. That's only the filler metal/electrode strength.

exnailpounder wrote:

Farmwelding wrote:The 70 is 70k pounds per sq in of pressure at the max and if done with no deformities or weld errors? (Might be wrong but that is my understanding.)

HUH? 70 K is tensile strength. Try again

That's why I said that's my understanding and I may be wrong...so I thank you all for straightening it out-happy to be proven wrong. You still can't lift 70k though

Farmwelding wrote:

exnailpounder wrote:

Farmwelding wrote:The 70 is 70k pounds per sq in of pressure at the max and if done with no deformities or weld errors? (Might be wrong but that is my understanding.)

HUH? 70 K is tensile strength. Try again

That's why I said that's my understanding and I may be wrong...so I thank you all for straightening it out-happy to be proven wrong. You still can't lift 70k though

Can too!

I need proof-video would suffice

Farmwelding wrote: K mean pounds-not ounces or fluid volume...understand now

K in the context of 70k means 70,000

The units of pounds or ounces or grams is separate.

So 70kpsi means 70,000 psi.

LtBadd wrote:So if I tig steel using ER70S-2, lets say I make a 1" weld on a properly designed Widget, does that mean it can withstand a 70K load?

In my opinion, your question is much too vague.

But I think the spirit of your question would be answered: no, unless your 1" weld has a cross sectional area of 1 square inch and the load is putting that weld in tension through that cross section.

Keep in mind, I'm not an engineer so that's about as close as I can get without further study

MinnesotaDave wrote: In my opinion, your question is much too vague.

But I think the spirit of your question would be answered: no, unless your 1" weld has a cross sectional area of 1 square inch and the load is putting that weld in tension through that cross section.

Keep in mind, I'm not an engineer so that's about as close as I can get without further study

Thanks MDave, I understand

https://www.rolledalloys.com/technical- ... -ductility

Tensile strength is how hard it is to pull apart. Like Idbtx said it truly only applies to the filler wire. It's also relative to the size of the cross section.

I think Richard was just putting out some bait to see what he could catch..Kill 'em and grill 'em

exnailpounder wrote:I think Richard was just putting out some bait to see what he could catch..Kill 'em and grill 'em

Now THAT is a load!!

If the original question is to be taken at face value then a linear inch of weld of unknown cross section will not hold 70k in any joint configuration but if you took 2 pieces of inch square bar & did a cantered V prep butt on them & welded full penetration root from one side - back grind & weld alternate sides to reduce internal stress - then once the cap is dressed flush & if the parent metal has a high enough tensile strength itself then yes you should achieve 70k if you have a machine capable of measuring it - or you could use a smaller piece & scale expected results on cross section - I've not done this since college along with hours of macro polishing by hand on wet & dry ( don't miss it either ! ) tearing stuff apart with the old " Dennison " was quite fun though.

noddybrian wrote:If the original question is to be taken at face value then a linear inch of weld of unknown cross section will not hold 70k in any joint configuration but if you took 2 pieces of inch square bar & did a cantered V prep butt on them & welded full penetration root from one side - back grind & weld alternate sides to reduce internal stress - then once the cap is dressed flush & if the parent metal has a high enough tensile strength itself then yes you should achieve 70k if you have a machine capable of measuring it - or you could use a smaller piece & scale expected results on cross section - I've not done this since college along with hours of macro polishing by hand on wet & dry ( don't miss it either ! ) tearing stuff apart with the old " Dennison " was quite fun though.

This is my take on it as well.

Although I've never done any of that kind of testing - would be interesting for a while.
...minus the polishing...lol

My post was me trying to get an idea of how to interpret, or think about what the 70K meant. I realize (now) such questions need to be specific, and mine wasn't, this is an area I don't have any real world experience in.

Thanks for the replies

I don't know a whole lot about material testing so what kind of test do you need to do to test the tensile strength on a joint like this or test its breaking point.

Farmwelding wrote:I don't know a whole lot about material testing so what kind of test do you need to do to test the tensile strength on a joint like this or test its breaking point.

You pull it apart, Google tensile test or see the link in Josh's post above

I had some coupons go through tensile test recently (for procedure qualification).

1/4" 304l SS. TIG coupon, two tensiles, and MIG coupon, two tensiles. Both passed. The result you want to see is under "Failure mode", and should read, "Ductile--Weld"

All four coupons tested to an average of 90KSI, 20K stronger than 7018 is rated for. The range was 88.7 to 93.4 KSI.

I still don't understand two root fails from the MIG coupon that tested this high on tensile with the desired ductile failure. A fresh coupon is out for test now.

Steve

Well the way I see it is Mig is the hardest process to get 100% root penetration & if I understand the qualifying process across the pond you may have put in 2test pieces at either end of the accepted parameters so that anything in between & allowing some real world variations will pass - if there is even a microscopic line of root LOF seen by X ray it will usually fail - on a bend test even a few thou depth LOF ( or undercut ) will generally give a point that the weld breaks from which shows enough that it fails the test - on a tensile however that few thou at the root effects the cross sectional area of the total being tested so little that the results will not show any difference from a weld that passes all other inspections - the exact point of failure on a tensile will vary each test & the so will the exact figure - we used to see this in college where you had like 25 guys pulling welds apart every time we were in metallurgy class - I think the point of the different types of test are to catch not always the fact a given weld shows adequate strength one time - it's over time & cyclic loading / temperature cycling / unexpected bending forces etc that a small defect in say the root does'nt become the source of a crack later in it's life - we had locally an elevated walkway collapse that was part design flaw but weld defects that went unseen was the biggest issue - cost several lives so I do see why weld tests seem kinda harsh sometimes - the testers don't know the welds purpose - just if they find anything less than 100% it's going to fail as the it could later come back to haunt them.

Ive seen an all weld metal tensile test welded. (not tested though) A test plate 50mm thick was welded with a big prep, maybe 25 degrees... then the weld is cut out with and a sample that comes from the centre of the specimen, this is machined into a sample that is totally weld metal, see pic.

Yes - done similar at school many years ago - but the only reason was the machine doing the testing was very small with limited available force & holding ability - it was'nt used much as there were sample pieces kept on display with it for common materials used in the coursework - the big Denison at college was huge & would tear most stuff apart - had huge taper grip jaws that bit deeper the harder it pulled - only needed to measure pieces for cross section prior to testing to quantify results which was'nt that big a deal as it was more how & where the piece broke rather than the tonnage.