Pre-heat for stick weld?

[jake98]

Do I need to? Is there a rule of thumb?
Thanks.

 

[k0ua]

Let me start by saying I am not an expert, and there are people on here who are, but I have only heard of pre-heating for stick welding cast iron, and more importantly post heating, (letting it cool very slowly) so it does not crack. But just welding mild steel, with a stick I say just start in and git-r-done. Perhaps others with more experience will weigh in here.

James K0UA

 

[Shield Arc]

A lot of variables to this question, like material thickness, carbon content, etc, etc. Good rule of thumb, yes at least 50, 60 degrees.
Here is the back side of a Lincoln preheat and interpass calculator.

 

[jake98]

A lot of variables to this question, like material thickness, carbon content, etc, etc. Good rule of thumb, yes at least 50, 60 degrees.
Here is the back side of a Lincoln preheat and interpass calculator.

Shieldarc, 50-60 degrees above the surrounding metal? or total? what's interpass? (you probably saw this comming.. ) Thanks.
Oh, and is there a way to determine carbon content?

 

[Shield Arc]

Interpass temperature goes hand in hand with preheat. In simple terms, don't weld too fast, or too much and overheat the material.
What I usually do is take a propane weed burner and take the moisture out of the material. Within a few seconds you'll see the moisture come to the surface.
Might be easier to just state what you're building.

Couple very good books for any weldor to have on hand.

 

[davygp38]

I am no pro, but my dad was, he always tried to get the metal warm in the winter time. I can remember him setting up a salamander under a tractor trailer that he was going to weld on. he also got the area as clean as possible. I just do it, because I saw him do it. He would also keep the heat on the welded area for a while after.

 

[Shield Arc]

I am no pro, but my dad was, he always tried to get the metal warm in the winter time. I can remember him setting up a salamander under a tractor trailer that he was going to weld on. he also got the area as clean as possible. I just do it, because I saw him do it. He would also keep the heat on the welded area for a while after.

Sounds like a very smart man! :thumbsup:

 

[notme]

thinner steel its not really nescesary the heat of the arc will chase the moisture out of the steel, if u get into bigger stuff like 3/4 plate or bigger and put a torch on it u will actually see the moisture roll out of it!

 

[jake98]

Interpass temperature goes hand in hand with preheat. In simple terms, don't weld too fast, or too much and overheat the material.
What I usually do is take a propane weed burner and take the moisture out of the material. Within a few seconds you'll see the moisture come to the surface.
Might be easier to just state what you're building.

Couple very good books for any weldor to have on hand.

I'm welding some 1/4" angles to some 5/16" angles to alter a carry-all into a bedder wheel holder attachment. It's been really cold in the shop so I'll warm them up with the torch first. I've seen that 'flash over' but didn't know it was the moisture.. Thanks again.
Recently got an ac/dc tombstone, so I'm anxious to see the dc difference over the ac unit. (not anxious enough to go out there today tho )

 

[notme]

especially with low hydrogen rod u wanna get rid of that extra moisture (7018,7024) thats why those rods are kept in an oven to keep dry