While typos are standard part of writing on this form, I gotta love the liquid metal embroilment (you mean embrittlement) -metal cooked in liquid metal.
uclesyd I've been trying to get rid of that stupid galvanized backer since I got on this project, but it's not going away. We do prep the backer by grinding it to remove some of the galvanized first and we are usuing a root pass and cover pass weld.
The cracks are only in the weld and they are mostly running transverse. I've seen as many as 4 in one 5' section of weld. And what really concerns me is that these are showing up approx 2 to 4 days after being tested clean at the initial process point using mag particle.
My theory is rapid cooling following the initial process is causing stresses to form and giving me these cracks.
QSRW4;
If what you describe is correct, these transverse cracks are more probably caused by delayed cracking from hydrogen in the weld. I would use low hydrogen electrodes immediately and if necessary, increase preheat and clean the weld joint before welding.
In reference to the post by meteng I would open a new can of electrodes to use for testing.
Normally cooling or restraint cracking will split the weld.
I can get them to throw a new spool of the metal core wire on the machine for this but since all that stuff is packaged in cardbord I don't think one wheel is going to differ that much from another. And since the welds I'm having cracks in are welded by diffrent opporators on diffrent machines I'm not sure a new spool of wire will help much.
And no worries I give my spell checker a real work out. I've even had to update it with words after checking them online first. I can mis-spell anything if you catch me at the right time.
QSRW4:
You may need to replace this shipment of weld wire and purchse wire with the suffix designator H4, for low hydrogen. As an alterate approach conduct a post weld bake at 500-550 deg F for 30 minutes, immediately after welding and see if this helps.
I doubt that the base material was originally tempered at or below 600 deg F. So, I would not see any adverse effects on base material properties with a post weld bake to remove hydrogen.
I'll look into that, but due to our application there is a lot of skittishness about any high heat applications. I did confirm that our weld wire is the equivalent of H4.
If it's metal-cored, it shouldn't be all that hygroscopic and the cardboard cartons are probably ok, so that's probably not it. Not that I have anything useful to add about what probably *is* it.
QSRW4;
What does equivalent mean? Either you purchase the solid core wire as low hydrogen with a suffix designator or you don't. By the way, I have rejected solid core wire on several occasions because of excessive dissolved hydrogen content from manufacture.
The designator K4 according to TriMark is the same as a H4 designator. It has the same Hydrogen dissolution rate of less than 4ml/100g. Sorry I guess I stated that wrong in my previous post. I should have stated that the K4 designator on our weld wire is = to H4.
Sorry I want to make sure I understand this, you mean you've rejected the raw wire or did you reject products built with it due to bad welds caused by the use of this type of wire? And if you rejected the wire, do you mind me asking who the manufacturer was? If it's the same one we use I'll have an easy time of convincing the weld group to test the wire stock.
My next question, the current theory of our tiger team is that insufficent removal of tack welds is the main cause of the tranverse cracks. What do you think of this theory?
K4 is not equivalent to H4. K4 is a reference to the alloy forumulation. H4 is an independent part of the designation that would get tagged on to the end. So either it's EC110-K4-H4, or it's just plain EC110-K4. The manufacturer's cert should say which.
I just looked at their typicals online, and it's interesting that their CWB designation includes H4 but their AWS designation doesn't. Typically a company won't include the H4 designation if they don't consistently get test results below 4 ml/100g; I've seen certs with a one-time diffusible hydrogen result of 3.8 and an H8 designation.
I'll have to get someone to get me a copy of the certs. The tacks were made by the same wire. I'm really not happy to hear that the results of some of the test were higher than the 4 ml/100 g that they claim in the MSDS. I was hoping we were already using the right wire.
