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

 

[Shield Arc]

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 )

As notme says, you won't have any problems.

Let us know what you think of DC!

 

[jake98]

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

I just bought some new rods but I keep them in a case (rod guard?) What's the symptom of damp rods, splattering?

 

[Soundguy]

i have (pre-heated/peened/slow cooled) before welding cast iron.. but for mild steel.. no.

i'm not a pro welder.. I OWN a welder and use it often for my tractor projects..

soundguy

 

[westcliffe01]

When you pre-heat steel with a propane torch, what you will initially see is water vapor from the burning propane condensing on the steel surface.... :laughing::laughing::laughing::laughing:
When condensation will no longer form on the steel, it is probably hot enough.

The higher the carbon content, the more prone to cracking on cooling, this obviously includes cast iron.

 

[Shield Arc]

I think the last thing I built where I was concerned about preheat, is when I built my ripper / counterweight for my tractor. 5-inch x 5-inch solid square stock. Water really boiled out of this material!

 

[slowzuki]

I never preheat for mild steel of any thickness. I always do for high carbon steels/cast iron.

 

[jimmysisson]

I think the last thing I built where I was concerned about preheat, is when I built my ripper / counterweight for my tractor. 5-inch x 5-inch solid square stock. Water really boiled out of this material!

5x5? How much did that puppy weigh? Probably helps it dig, too!
Jim

 

[jake98]

I think the last thing I built where I was concerned about preheat, is when I built my ripper / counterweight for my tractor. 5-inch x 5-inch solid square stock. Water really boiled out of this material!

That thing is amazing. What did you use to pre-heat it?

 

[Gary Fowler]

For most of the plate and shapes using A-36 grade material, you can get by without preheating. 7018 rods will get less porosity in them if you do warm the surface to at least 50F, above that temp you dont get much benefit from warming. 60xx series rods will weld without preheat in most instances till your get above .750" at which point all qualified welding procedures require preheating with reduces the stress that is put into the steel when welding. Again, mostly if you are building Ag equipment, you can likely skip the preheat as long as it is above 50F and you are not working on material that is more than or = to 3/4" thick. If you are using a light duty welder especially MIG machines, preheating to about 200F will allow you to weld at lower amperage and still get good tie-in with your weld when working on material more than 1/8" thick

 

[Shield Arc]

5x5? How much did that puppy weigh? Probably helps it dig, too!
Jim

Jim I never thought to weigh it. I think that square stock is around 85-pounds per foot. I think the ripper is 5-feet wide. When I revamped a skidsterr grapple to fit my tractor I felt as I needed a little more counterweight, so I doubled up on it.

That thing is amazing. What did you use to pre-heat it?

Jake when pre heating material I like to use the weed burner, but when heat shrinking, or heating material to bend, I like the oxygen acetylene torch / rosebud.