Jim Davey
R H Davey Welding Supplies Ltd
- Messages
- 5,736
- Location
- Southampton
Are you sticking the tungsten out about 5-6mm or are you using it almost flush? Too short a stickout will overheat the ceramic massively as the arc is just too close to the hot tungsten and weld pool. You don't mention filler rod size bit at that thickness I'd be at least on 2.4mm, in the past I've noticed thinner filler rod can be overheated while adding it to the pool if it's too thin.
As for amperage, 160-180 could well be fine but it depends entirely how much heat you have managed to get into the metal before you attempt to add filler. If you go pedal to the metal and get 180 amps on 8mm thick material and try to get it to take filler immediately you will get nowhere. If the part has got up to 150-200 degrees all over then you will be away immediately. You aren't cleaning your metal enough, it's obvious from your picture it need more, and in doing so you will be able to fun 5-15 more neg polarity which will help penetration no end. I would be on at least 8 LPM flow with a ceramic like that and I'd either use an oven to get the part hot enough or hang around with the torch in a few spots round the pipe with the arc going to get some heat into the part.
You are looking at a fillet and the front edge of the puddle forms a 'C' shape, the edges that form the two pints of the C will wet first as they are closer to the arc but the bit you need to watch and wait for it to 'wet out' is the bottom of the U shaped part of the C as it were. This is the root of the fillet and it will eventually melt and join nicely to the two sides. It's very important no to rush and bury this with filler, the weld will look outwardly ok, but fusion will be flawed and the weld will be weak with a lot of inbuilt stress and likely to crack. This is why preheat is useful if you don't have enough excess power to overcome the ally's ability to pull heat away from the arc faster than you can put it in before the whole job heats up enough to stop this happening. If you had a 300-350 you could in theory light up on 10mm and blast a weld in from cold, but it's always nicer if the job can heated to some degree before you start, although on bigger pieces this isn't always possible or practical.
As for amperage, 160-180 could well be fine but it depends entirely how much heat you have managed to get into the metal before you attempt to add filler. If you go pedal to the metal and get 180 amps on 8mm thick material and try to get it to take filler immediately you will get nowhere. If the part has got up to 150-200 degrees all over then you will be away immediately. You aren't cleaning your metal enough, it's obvious from your picture it need more, and in doing so you will be able to fun 5-15 more neg polarity which will help penetration no end. I would be on at least 8 LPM flow with a ceramic like that and I'd either use an oven to get the part hot enough or hang around with the torch in a few spots round the pipe with the arc going to get some heat into the part.
You are looking at a fillet and the front edge of the puddle forms a 'C' shape, the edges that form the two pints of the C will wet first as they are closer to the arc but the bit you need to watch and wait for it to 'wet out' is the bottom of the U shaped part of the C as it were. This is the root of the fillet and it will eventually melt and join nicely to the two sides. It's very important no to rush and bury this with filler, the weld will look outwardly ok, but fusion will be flawed and the weld will be weak with a lot of inbuilt stress and likely to crack. This is why preheat is useful if you don't have enough excess power to overcome the ally's ability to pull heat away from the arc faster than you can put it in before the whole job heats up enough to stop this happening. If you had a 300-350 you could in theory light up on 10mm and blast a weld in from cold, but it's always nicer if the job can heated to some degree before you start, although on bigger pieces this isn't always possible or practical.
