A general question fusion verses penetration

[AdrianH]

I am asking this as I am unsure on what people generally think regarding this. I was reading a post in the mig section of welding were Bede was looking to get greater penetration in a weld. People posting ideas to get greater depth of penetration even on stringers.

Now I could not understand the point so could not see the reasoning behind it. To me if you have melted the base metal with the weld metal you have as much strength as there is. Now please do not get me wrong, I can understand getting full penetration on a but weld, grooved and small face to ensure the weld metal has melted into all surfaces, or, on a fillet weld getting slightly into the metal under the vertical piece to get a bit more melted metal in there. But on the stringers, weaves etc. apart from ensuring there are no voids and you have fusion why try to go 4 or 5 mm when say 1.5 to 2mm will do?


I have found an article on a Lincon web page that seems to suggest one does not!
http://www.lincolnelectric.com/en-u...heory/Pages/weld-fusion-weld-penetration.aspx

I will not copy it here as I am sure there would be copyright issues.

There are always counter positions and I am willing to learn.

Adrian

 

[TechnicAl]

As far as the thread you refer to Bede was getting inconsistent penetration. Sometimes enough but sometimes not or borderline.

I think in most cases you dont need excessive penetration. Some fillets can be specified by throat thickness so the deeper the penetartion the less "visible" weld. In some applications this is wanted. Wheels are one such case.

 

[Richard.]

Good penetration on the initial 1st run in the corner of the fillet and good side wall fusion with the base is going to improve the strength of the joint as is the throat thickness and well blended toes. Filling and capping runs just need to be well sequenced and have good interun fusion with the other beads

 

[AdrianH]

So it was just to get increased penetration on the root, I must have read the post and possibly pictures wrong.

Live and learn.

Adrian

 

[J.B. Welding]

Its worth considering where the load is coming from with regards to a full pen weld or a multi run fillet. For example a tab that attaches a tensioned cable and is subject to a constant straight pulling force in my opinion a full pen weld is as strong as it can get. Building up the fillets on each side with the multi runs adds no real benefit and could promote cracking of the tab due to excess heat or Hydrogen around the weld causing embrittlement (so I believe). Where the material is very thick I gouge and chamfer to get most or all the weld 'right in there'. Its good whilst learning to do destructive testing to really get a feel of why and what kind of welds fail. The better at welding you get the bigger the hammers and presses you need!

 

[Richard.]

Good pen in the root and good fusion in the side walls

 

[AdrianH]

Question and not trying to be smart but asking.

I imagine these types of welding jobs would be spec'ed first so one has to follow a procedure, bit like the ISO thread, or is it a case of down to welders experience and go and weld it, then do a load test afterwards.

I have never done anything like this type of current, well once when playing with a 400 amp set but that was xx years ago for about 5 mins to attached sky hooks!

I will say that my chances of doing this type of work are slim to non existent so have to generally ask or read about it.

I must get a press to test some of my hobby stuff one day could be interesting.

Adrian

 

[J.B. Welding]

I remember reading on here a chap wrote about migging at 500amps in spray and feeding in a 5mm piece of bright bar, tig style, into the pool. That to me is the best of both worlds, Pen and filler all at once. I've still not tried it out, I'm saving up for the leccy..

 

[TechnicAl]

Question and not trying to be smart but asking.

I imagine these types of welding jobs would be spec'ed first so one has to follow a procedure, bit like the ISO thread, or is it a case of down to welders experience and go and weld it, then do a load test afterwards.

I have never done anything like this type of current, well once when playing with a 400 amp set but that was xx years ago for about 5 mins to attached sky hooks!

I will say that my chances of doing this type of work are slim to non existent so have to generally ask or read about it.

I must get a press to test some of my hobby stuff one day could be interesting.

Adrian

Usually........but you need to develop the procedure in the first place............which I believe is what Bede is doing

 

[Richard.]

^^^ exactly this.
You need to develop the procedure first which is why he is etching the samples and noting the conditions. When he has his desired penetration and fusion levels he said it's going to be put under a 12 ton load which no doubt will be a lot more than it's required to hold in service. When all this is done he may even send those test peices out with his conditions to an approval bodie (Zurich for example) and get an approved wps/wpqr for that job.