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3/4 to 1/2 T Joint tips?

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3/4 to 1/2 T Joint tips?

Postby Nickw33 » Wed Feb 08, 2017 12:14 am

Hi, I was hoping to get a few tips on making a T joint weld on 3/4 to 1/2. I've welded lots of half and under but never above half inch. I'll be welding with a miller bobcat 225, I currently have 5/32 7018, 5/32 6010 & 1/8 7018. I've cleaned up both areas to be joined real well, my plan was to make a root pass with the 6010, cover with mulitpass stringer beads 7018 to achieve a fillet 1/2 in. Does this sound acceptable? Do I need to preheat? Any tips? What am I forgetting?
Thank you in advance.
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Re: 3/4 to 1/2 T Joint tips?

Postby PeteM » Wed Feb 08, 2017 7:09 pm

Pre-heat probably isn't required, but it is nice to hit the metal with a torch and sweat out any moisture. Depending on where and how long it has been stored there can be quite a bit.

A 6010 root isn't exactly necessary, but if there isn't anything saying whether you should or shouldn't, it's up to you. For the sake of simplicity, I'd probably just go with 7018 through out. Just be mindful of the effects of heat. It may be bigger/thicker, but it will still move and distort.
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Re: 3/4 to 1/2 T Joint tips?

Postby Nickw33 » Wed Feb 08, 2017 7:40 pm

Thank you Pete. Would you use the 5/32 or just the 1/8 7018?
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Re: 3/4 to 1/2 T Joint tips?

Postby PeteM » Wed Feb 08, 2017 8:55 pm

Since they're on hand, the 5/32. That will help the weld move along a little quicker.
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Re: 3/4 to 1/2 T Joint tips?

Postby MinnesotaDave » Wed Feb 08, 2017 9:43 pm

PeteM wrote:Pre-heat probably isn't required, but it is nice to hit the metal with a torch and sweat out any moisture. Depending on where and how long it has been stored there can be quite a bit.


I would respectfully have to disagree with your statement.
Steel does not absorb moisture during storage and then need to be heated to get it out.
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Re: 3/4 to 1/2 T Joint tips?

Postby PeteM » Wed Feb 08, 2017 10:47 pm

MinnesotaDave wrote:
PeteM wrote:Pre-heat probably isn't required, but it is nice to hit the metal with a torch and sweat out any moisture. Depending on where and how long it has been stored there can be quite a bit.


I would respectfully have to disagree with your statement.
Steel does not absorb moisture during storage and then need to be heated to get it out.


How do I have that wrong or in some way mixed up?

I've sweated a lot of steel pre-weld, and a good bit of moisture comes out.
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Re: 3/4 to 1/2 T Joint tips?

Postby Otto Nobedder » Wed Feb 08, 2017 11:03 pm

No, Pete, it doesn't.

You're using a torch who's primary by-product is H2O on a metal surface whose temperature is well below the dewpoint of your gas flame, so you get instant condensation which doesn't disappear until the metal is nearing 212F.

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Re: 3/4 to 1/2 T Joint tips?

Postby PeteM » Wed Feb 08, 2017 11:21 pm

Oh? I always just took for granted that there was moisture in the metal. I guess that makes sense though.

Sorry for dispensing bad info. :oops: If you think its a good idea, I'll edit that part about sweating it out.
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Re: 3/4 to 1/2 T Joint tips?

Postby weldin mike 27 » Thu Feb 09, 2017 5:21 am

This is how we judge our lower preheat temp. Apply flame and watch the condensation form and then evaporate and that's reasonably close to the required temp.
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Re: 3/4 to 1/2 T Joint tips?

Postby Otto Nobedder » Thu Feb 09, 2017 9:01 pm

weldin mike 27 wrote:This is how we judge our lower preheat temp. Apply flame and watch the condensation form and then evaporate and that's reasonably close to the required temp.


Exactly. This is good practice any time one is welding metal below 50F, and advisable on any metal to be sure it's above the local dew-point and is dry.

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