Brazing Copper to Steel with Gasflux C-04 Nickel Bronze

While researching something else the other day, I came across a few people wondering how to join copper and steel.  I had to do this once and had great success using this method, so much so that I've used it a few times since.


I use Gasflux C-04 nickel bronze in 3/32" diameter, along with their Type B blue paste flux. These should be available through Airgas on the East Coast. Low-fuming bronze from the local welding store is not at all the same thing.

Copper, being much more thermally conductive than steel, quickly sucks heat away from the joint. So if the copper you're brazing is connected to more copper, be prepared to heat up the whole mess, which can take a lot of heat.

Conversely, steel is slow to disperse heat, so you may want to preheat the steel to avoid overheating the copper, especially if there's a lot of steel and not so much copper. By the time the steel comes up to temp, the copper may be hot enough to flow brazing filler, just from being around the steel.

All that said, this is not a very hard joint to braze. If you've done blacksmithing or basic MIG or stick welding, this would be a lot easier to learn than TIG.  A quick practice joint or two would suffice for training.

There are other ways to join copper and steel, like silver soldering, but this method may create a stronger joint than silver, especially in a tee or butt joint. Bronze fillers (like C-04) are better for filling gaps than silver fillers.

This method works especially well for brazing copper tube passing through a hole in sheet steel. The hole need not have a perfect clearance fit around the pipe, and the tube need not be perfectly centered in the hole.

As in all brazing operations, freshly-sanded, clean, oil-free parent metals are highly recommended.

If the copper gets too hot, it'll open up a hole, which would likely mean replacing the copper, so watch out for that.

Discoloration of the copper is normal and can be easily removed with abrasives like Scotch-Brite and emery roll.

Copper anneals at temperatures well below brazing temperatures.  Be prepared for the copper to soften considerably.

I've always used oxy-acetylene, but oxy-propane would surely work.

UPDATE: Here's an example.

Not my absolute best work, but good enough.  Flux was applied to the steel only in a small circle, hence the black oxidation everywhere.

What Obama Could Say to Students

Later today, the President will make a "Back to School" speech to America's K-12 students. The White House released the text of his remarks earlier.

The speech mentions several careers to which students might aspire:
Maybe you could be a good writer – maybe even good enough to write a book or articles in a newspaper – but you might not know it until you write a paper for your English class. Maybe you could be an innovator or an inventor – maybe even good enough to come up with the next iPhone or a new medicine or vaccine – but you might not know it until you do a project for your science class. Maybe you could be a mayor or a Senator or a Supreme Court Justice, but you might not know that until you join student government or the debate team.
And no matter what you want to do with your life – I guarantee that you’ll need an education to do it. You want to be a doctor, or a teacher, or a police officer? You want to be a nurse or an architect, a lawyer or a member of our military? You’re going to need a good education for every single one of those careers. You can’t drop out of school and just drop into a good job. You’ve got to work for it and train for it and learn for it. [Emphasis mine.]
Generally, a fine message. But it doesn't jive with Obama's desire to reinvigorate the American manufacturing sector. In naming Ron Bloom as his senior counselor on manufacturing policy on Monday, he said Bloom is "going to help us craft the policies that will create the next generation of great manufacturing jobs." [Emphasis mine.]

What about the next generation of great manufacturing workers? Tomorrow's machinists, carpenters, welders?

As it turns out, welders are in short supply in this country. The American Welding Society reports the average age of American welders is in the mid-fifties. AWS anticipates a potential shortage of 200,000 welders by 2010. That figure excludes self-employed welders.

Compare this with the oft-reported nursing shortage, which a recent Johns Hopkins Magazine article reports is gone but will return soon. According to a nursing professor at Vanderbilt, the average American nurse is 43.8 years old. Buerhaus predicts a shortage of 260,000 nurses by 2025.
The average welder is more than 10 years older than the average nurse, and we'll need more welders sooner.

In fact, few of the careers Obama mentions are among those in short supply. In May 2009, Manpower, Inc. released the results of its fourth annual Talent Shortage Survey.

The top 10 jobs American employers are having difficulty filling:
1. Engineers
2. Nurses
3. Skilled Trades*
4. Teachers
5. Sales Representatives
6. Technicians
7. Drivers
8. IT Staff
9. Laborers
10. Machinists/Machine Operators

Worldwide, it's a similar picture:
1. Skilled Trades*
2. Sales Representatives
3. Technicians (primarily production/operations, engineering or maintenance)
4. Engineers
5. Management/Executives
6. Accounting & Finance Staff
7. Laborers
8. Production Operators
9. Secretaries, PAs, Administrative Assistants & Office Support Staff
10. Drivers

* Manpower notes:
In this survey, Skilled Trades refers to a broad range of job titles that require workers to possess specialized skills, traditionally learned over a period of time as an apprentice. Examples of skilled trades jobs are: electricians, bricklayers, carpenters, cabinetmakers, masons, plumbers, welders, etc.
Of course Obama is right to encourage students to follow the careers they're drawn to. And I don't expect him to mention only the jobs that are in high demand amongst employers.

But Obama is missing an opportunity. He could have started to remove the stigmas that help shroud manufacturing careers from today's brightest students: that training in the trades is "just something to fall back on"; that welding is dirty work, unfit for an educated young person; that there's no future in being a plumber or an electrician.

Obama says students will need the "problem-solving skills [they] learn in science and math to cure diseases like cancer and AIDS". He could have also mentioned the problem-solving skills required to, say, plumb a house, or diagnose engine trouble.

There's much work to be done to revive the manufacturing sector, especially small manufacturers. Expanding the MEP would be a great start.

But if this is to be "a country where things are made" in the next twenty years, I hope it's today's kids who'll be doing the making.

Conversation with a Shop Teacher

I was talking to a welding teacher earlier tonight. He teaches high schoolers all day, then adult students like me at night.
I've talked to a lot of shop teachers. This one said something especially frank.
"It's hard to get anyone to take me seriously around here. Even the administration."
He explained that this was why he'd gotten a Master's, and he said it in a way that made me empathize.
His tone belied a contentious relationship with his colleagues, one that found him fighting for resources, for funds, for respect for being a Teacher, dammit, not the ringmaster of some sooty circus.