[fdude64]

I have a job coming up soon that will require me to weld outside in below freezing temperatures, will I need to warm up the base metals before welding?

[Otto Nobedder]

That depends a great deal on what you're welding.

I've built powerplants and ethanol plants in the freezing cold and never needed to preheat anything. Carbon steel and most 300-series stainless steels won't care if you preheat, and I've done them MIG, TIG, and stick, at down to 22 below.

Aluminum depends on the thickness and the power you have available, but preheat is always good with aluminum, even in warm weather.

The job should have a WPS for the welds. If preheat is not specified, it's not needed.'

Where and what's the job? (State is fine, if you can't post the specific job)

Steve S

[fdude64]

actually finishing a job I started a couple weeks ago. I am welding a dump truck hoist saddle together on the frame, I have already welded the bed to the frame a couple weeks ago. there is no garage to work in and it is in Ohio.

[Otto Nobedder]

For that kind of welding, all carbon steel (7018, I presume?) preheat is not an issue. For carbon steel, the difference between 100* and 10* is meaningless.

Steve S

[fdude64]

ok thank you and yes 7018 3/32 for root passes and 7018 1/8 for cover passes

[Otto Nobedder]

I will say this...

If they'll "let" you pre-heat, it's more comfortable in cold weather...

Steve S

[fdude64]

well there will be some torch cutting before the welding so I will weld it before it cools completely. thanks again

[Braehill]

The welds will be fine but your work boots will need a preheat though.

Len

[fdude64]

boots are very well insulated so not too much worry there,but thanks for the info on the welds

[JDIGGS82]

http://www.basspro.com/ThermaCELL-Heate ... 13014/this will help the cold feet issue lol

[fdude64]

Those are cool but not $130.00 cool

[jwmacawful]

many years ago i was working on a high rise and the welding inspector required me to preheat. not knowing any better i asked him why this was necessary. he took the propane heating torch out of my hands lit it and ran it quickly once or twice over the column i was getting ready to splice. the water that ran off and beaded up on the surface surprised me even though it wasn't visible.

[Otto Nobedder]

many years ago i was working on a high rise and the welding inspector required me to preheat. not knowing any better i asked him why this was necessary. he took the propane heating torch out of my hands lit it and ran it quickly once or twice over the column i was getting ready to splice. the water that ran off and beaded up on the surface surprised me even though it wasn't visible.

On cold steel, all that condensation came from the flame itself. The vapor from that propane flame is CO2 and H2O (water vapor), and the water instantly condenses on the cold steel. You didn't melt some invisible film of ice. He impressed a young you with his demonstration, and you did it his way.

The only stuff I've seen preheated (other than ice/snow removal), even in a record cold IA winter, was the high-chrome steel and the aluminum.

Steve S

[jwmacawful]

many years ago i was working on a high rise and the welding inspector required me to preheat. not knowing any better i asked him why this was necessary. he took the propane heating torch out of my hands lit it and ran it quickly once or twice over the column i was getting ready to splice. the water that ran off and beaded up on the surface surprised me even though it wasn't visible.

On cold steel, all that condensation came from the flame itself. The vapor from that propane flame is CO2 and H2O (water vapor), and the water instantly condenses on the cold steel. You didn't melt some invisible film of ice. He impressed a young you with his demonstration, and you did it his way.

The only stuff I've seen preheated (other than ice/snow removal), even in a record cold IA winter, was the high-chrome steel and the aluminum.

Steve S

it was summer.

[jwmacawful]

column pre-heat. summertime.

[Otto Nobedder]

Pass your cutting torch closely over some 100* steel, and see the band of water droplets on each side of your path. My point is, the water didn't come out of the steel, it came from the flame.

Steve S

[jwmacawful]

steel retains moisture during climate change. it's called dew point. preheat removes this.

[MinnesotaDave]

steel retains moisture during climate change. it's called dew point. preheat removes this.

Strange statement jwmacawful.

"The dewpoint temperature is the temperature at which the air can no longer "hold" all of the water vapor which is mixed with it, and some of the water vapor must condense into liquid water. The dew point is always lower than (or equal to) the air temperature"
http://www.weatherquestions.com/What_is ... rature.htm

It is my understanding that the water droplets on the surface of steel do not come from the steel itself.
The water condenses on the surface much like it does on a pop can.

The water can come from the torch, the air, or a combination of both.

Never seen a moisture meter to check if the steel is "waterlogged."

Preheat temps and interpass temps are about the way steel grain structure behaves during welding.
I'm not a science genius, so I'll leave the technical explanation to others.
http://www.aisc.org/bookstore/itemredir ... x?id=14870

[Nils]

I was preheating some 1/2 inch alum plate prior to TIG welding it when I notice moisture forming on it. I was wondering where in the hell that came from? Now I know. That's funny.

[Otto Nobedder]

jwmacawfull,

A water molecule is simply too large to work it's way in to steel. To make steel, you have to heat it to extreme temperatures to get it to accept carbon atoms.

I detect vacuum leaks by finding where Helium atoms, one of the smallest things in "normal" nature can pass. I can often temporarily plug these leaks with water, because it can't pass through.

Steel is not porous to water. Someone pulled your leg once, to get you to do it his way.

Steve S

[jwmacawful]

jwmacawfull,

A water molecule is simply too large to work it's way in to steel. To make steel, you have to heat it to extreme temperatures to get it to accept carbon atoms.

I detect vacuum leaks by finding where Helium atoms, one of the smallest things in "normal" nature can pass. I can often temporarily plug these leaks with water, because it can't pass through.

Steel is not porous to water. Someone pulled your leg once, to get you to do it his way.

Steve S

oddo nobetter/steve
who said the water was inside the steel?? this is SURFACE water that is called condensation. it is the same principal as putting cold beer in a warm glass. the droplets that form on the outside of the glass isn't beer. the glass isn't leaking. same principal. raising the temp of the steel above the dew point prevents the water that is on the surface of that steel from condensing. the only one pulling my leg is you. what a joker you are!!

[Otto Nobedder]

You're enjoying this WAY to much.

That tells me I'm probably being teased here.



Steve S

[jwmacawful]

You're enjoying this WAY to much.

That tells me I'm probably being teased here.



Steve S

simple physics. but if you have to be right you gotta expect to be teased for it.

[Otto Nobedder]

The condensation on your beer glass came out of the air, not the glass, to use your analogy

That was fun. And I don't mind being challenged. I've been wrong once or twice .

Steve S

[jwmacawful]

The condensation on your beer glass came out of the air, not the glass, to use your analogy

That was fun. And I don't mind being challenged. I've been wrong once or twice .

Steve S

now you got it. the same way the water is condensing on the steel. from the air. i knew if i used beer.....