[James1000]

Hi All

I Mig weld mild steel tubes, flat bars and I beams. Whatever I weld I always put the current high enough to make a penetration weld. Is this always the best thing to do?

Best regards

James

[Rick_H]

Welcome to the forum James...

I'm assuming your talking a full penetration weld. It all depends on the joint configuration but not all welds will be full pen nor do they need to be . Full pen welds are most often found on open root pipe or sanitary pipe with a backpurge.

How are you prepping for full pen welds on your joints? What type of joints?

[Mike]

Welcome to the forum James1000.

[James1000]

Thanks Rick H and Heavy Hitter!

For example if I am welding two 10 mm flat bars together, I will grind the edges of the two flat bars I am going to weld together to 45 degree angles.I will grind the flat bars around the area I am going to weld them ,to clean the flat bars so my weld doesn't have gaps in it, then I will turn the welding machine high enough so that when I weld the one side of my two flat bars together, they have two parallel blue lines showing through on the other side i.e; the weld has burned through.

My steps;

1. Grind edges to 45 degrees
2. Clean material
3. Do a full penetration Mig weld.
4. Grind weld

Is there any harm in always doing full penetration welds?

Best regards James

Cape Town, South Africa

[weldin mike 27]

If you are always grinding the weld off, it is good to have the most amount of penetration possible . If you are always welding heavy stuff, ie 8mm + hot is best. If you occasionally weld thinjer stuff, you need to find a happy medium between the to. so you dont alwsys have to fight undercut and burn thru.

Mick

[James1000]

Thanks Mick for the information! We are always grinding the welds.

Best regards James

[weldin mike 27]

No worries , hope it helps.
I have seen jobs where there is a mixture of thick and thin, and some welders leave the welder set hot for all of it. Makes a mess. Fine to turn the welder down, but it takes skill and a keen eye to ensure fusion to the thick material at a lower setting . This is what makes a good tradesman . Soon i will take a photo to aid my explaination.

Mick

[AKmud]

I do a lot of 1/4" and smaller stuff. Not much of what I do would be considered structural so I don't typically worry about full penetration. If someone could get hurt from one of my welds failing I will take more time to prep and make sure I get as deep as I can. I rarely grind anything.

[weldin mike 27]

Hey,

Here is the picture I promised.

It is of a M12 mm nut and a threaded "boss" welded to a piece of 10mm plate, as per a job at work. (The plate is normally wider)

I cut it in half and had it etched to examine the penetration.

The reason I did this is because I took over the job from a bloke who was "not the sharpest tool in the shed" and I was told he had his welder set too hot, leading to undercut and ugly welds. In order to find a good setting and technique i did this weld and another similar one which I beat the hell out of with a hammer and the parts were completely destroyed but didnt break the weld.

The setting was slightly less wire and making sure the arc bit into the plate, led to a bit of spatter but a small managable fillet with no under cut. (welding inspector happy)

Mick

[Arizona SA200]

I'm not sure what the criteria is for becoming a weld inspector is in Australia but in the US there are pretty much two types of inspectors. The first being the good ones that have done their time as actual welders in the trade and the second being the ones that went to "school" to be an inspector. I have had problems with both but still met the weld requirements at hand. They don't know it all and neither do i but if im welding on a job i know what my requirements are.

[weldin mike 27]

Hey,

I do believe you have to have a trade background to become an inspector, at least at my work. However there have been ones who were crap at their jobs and got "off the tools" as soon as possible, and are often hard to deal with.

Mick

[Arizona SA200]

I was a foreman on a structural job years back and had an inspector flag a weld for a small amount if undercut on one of my guys welds. She was a previous diver/welder/inspector and i must say she new her stuff about all that. It was a simple d1.1 job and she was nitpicking the job to death. I made a call to the inspection company about it and apparently i was not the only one. I have dealt with them a lot since and found out she was fired for it. I didn't intend for that to happen but wanted her to inspect by the code at hand. Sometimes you have to inspect the inspectors, know the code that you are dealing with. I don't recommend confronting them as this just adds to complications but you can ask for another inspection to be done by another person.