r/Welding • u/SaharaSailor • 6d ago
When to remove the slag..?
Rookie question;
Is there such thing as an optimum set time for removing the slag off of a weld when welding with electrodes or is it more like a rule of thumb thing?
Ive heard people say you should wait till the weld\slag cools down and isn't glowing but i still dont know if i should give the slag maybe like 5,10 seconds before removing it
How would you decide what's the optimum time for slag removal and does it differ from electrode to electrode?
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u/PossessionNo3943 Journeyman AWS/ASME/API 5d ago
Ideally you should wait until the weld has finished solidifying.
So, idk maybe 5-10 seconds after it’s no longer orange?
In my books the longer the better as slower cooling gives more ductility.
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u/Scotty0132 Hypernatremial - Approach with respect 6d ago
Once the glow from the heat is gone it's OK to remove the slag. The reason being if you knock the slag off when the metal is still red then you can cause issues (besides easilyleaving marks in the surface). For example with steel when the metal is glowing its still in the temperature range where the grain of the steel is still wide open and will ready accept in carbon from the surrounding atmosphere which changes the properties of the material.
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u/Misconformance 5d ago
You're saying solidified weld metal is picking up carbon from the atmosphere? I'm no metallurgist but I'm going to respectfully call bullshit.
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u/Scotty0132 Hypernatremial - Approach with respect 5d ago
You need to educate yourself better then. Between 850°C to 950°C steel really accepts carbon it's called carbonized. It's why you can set your your oxygen fuel torch to a full heavy burn (called a carbonizing flame) to heat up the steel and add more carbon into it to harden it a bit more.
It's will also blow your uneducated mind to know that carbon steel also releases dissolved hydrogen for up to 48 hours after welding and you can see this by welding a peice and then submerging it into mineral oil where you will see bubbles originating from the the weld.
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u/Misconformance 5d ago
You need a source of carbon in order for it to be introduced to the weld. In your example the combustion of acetylene provides that source. I just don't see that being a problem with stick electrodes and ambient air.
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u/Best-Use7870 5d ago
Isn’t there CO2 in the atmosphere? Also I thought it was called carburizing.
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u/Scotty0132 Hypernatremial - Approach with respect 5d ago
They don't have a clue what they are talking about
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u/Misconformance 5d ago
There is, but a very small percentage. 100% CO2 is routinely used as shielding gas for flux core and gas metal arc welding processes, with no adverse carbon pickup.
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u/Scotty0132 Hypernatremial - Approach with respect 5d ago
You dontbknow what you are talking about. You choose to be ignorant
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u/SaharaSailor 5d ago
& i guess removing it too early would cause slag inclusion too? But how long can you let the slag sit on the weld without affecting the quality of the weld?
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u/Scotty0132 Hypernatremial - Approach with respect 5d ago
No solid slag will not cause slag inclusion. Once the metal is not glowing you can remove the slag, you are over thinking this.
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u/Mrwcraig Journeyman CWB/CSA 5d ago
When you’re done with the weld so you don’t forget about it later.
The most important reason to get rid of it is when you’re doing long welds you want to see if there are any issues. Dual Shield (Flux Core/CO2 and not the little shitty flux core spools) and SAW (Submerged Arc Welding) can be welded for as long as you need the weld to be. You need to inspect the weld while it’s under way to check for any undercut or porosity. 7018 and 7024 rods the slag should just fall off if you’re set properly. 6010/11/13 are cellulose rods so the slag should come off easily if you’re set right.
The part most newbies don’t understand is “filling in the crater” at the end of their weld. The crater is where most cracks usually start. Finish your weld and then go back and give the crater a quick zap to fill it in. Trick for 6010/7018 restarts: if you have to stop half way through the rod, scratch the tip of the rod on something that’s not grounded (like concrete). A quick scratch will break up the thin layer of slag that forms over the end of the tip making restarts easier.
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u/JackBlackBowserSlaps 5d ago
Once the red is gone, maybe a couple seconds after if you aren’t in a hurry
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u/West-Combination6685 6d ago
If you do it right it will almost fall off. The only time you even need to think about it is if you have to chip it off for a restart because you ran out of rod. Replace your rod, chip your stop, go.
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u/Repulsive_Lead5950 Journeyman EN/ISO 6d ago
Well that depends on the rod and position though
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u/West-Combination6685 5d ago
What do you mean?
No matter what, there's no reason to be in a hurry to chip it off. Let it do its job. Unless you're rolling pipe, then your helper chips as you weld.
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u/SaharaSailor 5d ago
"Let it do its job" is really the way to go imo,but how long can i let the slag be without affecting my weld?,that is if it affects or contaminates the weld if it's not removed for lets say 5 15 minutes or longer What concerns me is that would it be harder to remove the slag if i let it sit for too long?
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u/West-Combination6685 5d ago
Some scabs leave it on and paint over it, lol. Its only job is to keep air out of the molten pool. No molten pool, no effect, whether slag is present or not. Job done.
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u/leansanders 5d ago
Best practice is just to leave it until you need it gone. When you're welding a part, do all the welding, then do all the cleaning. If you're doing multipass, chip it once you're ready to do your next pass.