I'm new on this forum but i've been reading up for some time now. I'm a self taught fabricator and Weldingtipsandtricks has been a huge help. Recently I've been experiencing some problems on the start of my welds. I've been struggling with it for some time now but I cant figure out what i'm doing wrong.
The link shows the machine I'm using
The material I'm welding is 2 mm thick square steel tube
In the past I've used cheap machines with no pre flow, so the solution was to hit the switch off the work piece to start the gas, then go to start the weld with the gas flowing nicely.
Pre flow is set to 4 seconds and gas is indeed flowing. flowmeter shows 7L/min if I'm not mistaking the is about 30 cfh.The surface is grinded bright and clean. The thing I cant figure is why I haven't got this issue in the past. Could it be a gas leak?. I've checked the torch on an identical machine. No problems there.
I guess it was just the blurry pic that made it look like mill scale. 4 secs is a bit much for mild steel. I typically keep mine set at half a sec unless I have a need to flood the area first. Porosity like that is either gas coverage or contamination. I doubt with a 4 sec preflow that gas is to blame. You can try cleaning the area with acetone. You may have contaminates on your grinder wheel that are eing left behind. Just an idea.
Interesting sticker on that machine - at first glance it looks like an Everlast - does this happen on just that piece of metal or is it on everything - I've had various pieces of steel that will exhibit similar porosity on start - despite adequate cleaning but it's in the material itself & boils out until you add enough filler that the silicon / de-oxidizers do their job - free machining steels & bright drawn types are notorious for it - hot rolled once the scale is taken off rarely does it enough to worry - sure others with more Tig experience tan me will chime in on this - good luck.
TNX a lot for the reactions. I's always amazing to see that someone you don't actually know from half way around the world is willing to help. I would be so screwed without the internet.
I't happens on some materials and not on others. The example is welded steel square 30x30x2mm tube DIN 2395 S235 JRG2. I don't know if this is an US standard as well. Tried it on a few pieces out of different batches. All the same result.
Machine set to 90 Amp. Tomorrow I'll get some new grinding disc's and try those.
What noddybrian suggests about the boiling out is indeed happening. When i grind of the weld i can see inclusions under the filler metal over the length of the weld. Thats what worry's me.
Tested the same settings on a piece of stock 100x100x40 mm on 150 Amp no problem. Super clean weld.
In Europe Everlast is only sold in Finland. I think the machine is sold globally under a lot of different names. Basically its made in China. I The Netherlands its sold by a company called Freetech.
You don't have a clear laquer on that steel do you? I've had that with some steel purchased from "retail" outlets and it makes a mess if you don't clean it right off first.
Lero,
We've had quite a few post with the same problem as you're having. It's been blamed on gas coverage, torch angle, cleaning, grinding, you name it. I've found that it comes from the steel itself. I finally changed steel suppliers because they only carried steel from China and it seemed to be the worst. I'm not one to bash China or any other country out of hand, but that's what I found.
I used up the old steel that I had on hand and it welded just fine, when it ran out and I had to make my last few sections out of the Chinese stuff it went right back to the same thing you're finding.
If you're penetrating all the way through the metal, the contaminates could just as easily be coming from the backside. I had a problem awhile back with zinc coated parts. Didn't matter how much I cleaned it I could see the bubbles forming as I was movin along. Turns out that zinc from the backside and the higher silicon 70S-6 filler were reacting with each other. I switched to 70S-2 and the prob went away.
Given that it's the whole length of the weld and not just the start, an air leak is a real possibility as well.
Pre flow is set to 4 seconds and gas is indeed flowing. flowmeter shows 7L/min if I'm not mistaking the is about 30 cfh.The surface is grinded bright and clean. The thing I cant figure is why I haven't got this issue in the past. Could it be a gas leak?. I've checked the torch on an identical machine. No problems there.
While it could be the steel I personally doubt it. I would think if the steel was bad the whole weld would show signs of contamination. One thing that was not cought onto was the 30cfh. This is WAY to much gas for your application. Try 10-15cfh and see how that works. I believe you are in fact siphoning in atmosphere at the start of your weld caused by the sudden gas pressure surge. This can be especially true I'd you are holding your torch at a angle to the work piece. Another thought can be a leak in the torch but I doubt that as well as the rest of your weld looks fine.
Go back and grind that entire weld out and as you go, see if there is porosity throughout. If so than go with the bad steel, if not than it is something else.
Also you mentioned switching the torch with another machine. That is a good test. We're the settings on that machine identical?
What size cup and tungsten are you using for curiosity sake?
-Jonathan
When I was living in Ga. learning how to TIG weld for the company I was working for I did come across bad steel. No matter what I did porosity was always present..............so it does happen!
Thank you for the input. It seems the problem was a leak in the regulator valve. Noticed that the bottle was losing 2 Bar/hour when i was not working. Switched out the valve. All seems to work as it should.
