Short #82 - Brazing Temperature

HVAC School - For Techs, By Techs

Bryan Orr

Careers, Business, Self-improvement, Education

4.9 • 1K Ratings

🗓️ 3 December 2019

⏱️ 12 minutes

🔗️ Recording | iTunes | RSS

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Summary

In this short podcast episode, Bryan talks a bit about brazing temperature. He also covers how to heat your copper to the proper temperature. You can use torches with oxyacetylene or air-acetylene tips.

Joining two metals with an alloy above 840 degrees classifies as brazing; anything that uses an alloy to join two metals below 840 degrees is technically soldering. When you join two similar metals by melting the base material (not using an alloy), that's welding.

Another temperature of interest is 500 degrees; oxygen rapidly bonds to copper at temperatures above 500 degrees, so we will want to flow nitrogen while brazing to prevent cupric oxide (black scale) from forming on the copper. (We always recommend flowing nitrogen even if you are soldering below 500 degrees.)

When brazing with a 15% silver alloy (with a phosphorus fluxing agent), you will want to reach a temperature of 1100-1200 degrees. Solidus is when the rod gets a putty-like consistency. However, we want liquidus, which is when the alloy can flow freely into the joint. The color of the copper will be either dark or medium cherry. To be clear, you DO want to see redness when brazing; the color shouldn't be very bright red or orange, but a dark or medium red is ideal. The brazing indicators hold true for copper-to-steel and copper-to-grass brazing as well.

Aluminum brazing should stay below 1200 degrees; aluminum also doesn't have the same color indicators as copper, steel, and brass. Steel is complicated because it has a lower melting temperature, but it has much lower thermal conductivity than steel, so it will take longer to heat up and may heat unevenly.

You also CANNOT use an alloy with a phosphorus fluxing agent when brazing steel or brass; you need a silver alloy with a separate flux.

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Transcript

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0:00.0	Well, hey, this is a short episode of the H.Vac School Podcast, which makes sense because I'm sure you
0:08.5	you meant to click the H.Vac school podcast. If you didn't, if you meant to be listened to this American life or radio lab or 99% invisible,
0:18.0	that I don't know why you typed in HVAC school.
0:20.0	Those are all good podcasts, by the way, but this is H.C. School, the
0:23.0	podcast that helps you remember some things you forgot along the way as well as helps you
0:26.0	remember some things you forgot in the first place. This is a short episode
0:28.7	and if I would stop wasting time. And this short episode is about braising temperature.
0:33.1	We're going to talk a little bit about the temperatures of braising.
0:36.0	Hopefully it'll be helpful.
0:37.5	But before we do that, let's thank our sponsors and our sponsors are carrier and carrier
0:41.0	dot com.
0:42.2	We use a heck of a lot of carrier green speed and five-stage inverter driven systems in our contracting business.
0:50.0	Our customers love them and like anything we had to figure out a few things along the way to make everything work better. But now we've got all those details figured out, we really have great results with those units. If you want to find out more about being a dealer of carrier equipment go to carrier.
1:04.1	com. Navac and Navac Global.com. Navac is definitely a booth you're going to want to check out at
1:09.5	AHR. Which speaking of AHR go to H-G-A- a c r school dot com forward slash a h a hr and sign up but when you go to a hr the a hr conference in
1:19.5	Orlando you're gonna want to go to the navvac booth because they're going to be showing off some really
1:24.6	awesome new products, really neat tools that will help make your job better.
1:29.0	Navvac makes some of the best vacuum and recovery tools as well as some of the best tools for working with tubing and piping
1:35.5	out there so that's kind of part and parcel to the brasing we're talking about today.
1:39.1	Go take a look at navfat global.com Field Peace and Field Peace.
1:42.6	Come, great partner for HVEC School.
1:45.2	Goodway, goodway.com, goodway recently on the podcast and
	...

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