Brazing PH Materials 2

[tc7]

We have tried and failed at an attempt to qualify a TIG weld procedure on joining PH13-8Mo to itself. Rather than try again with new advice sought and rec'd on this fine Forum, the designers have altered the configuration to eliminate all but one welded joint. The single joint is for an indexing tab to be attached to the main body of the component(both pieces are still 13/8)and this tab will experience very, very low operating loads. The indexing tab will most likely be added with a butt type joint.

The idea of manual brazing this butt joint with as much of a fillet reinforcement as can be achieved is winning favor, but can brazing be done on a PH material? Ultimately the item needs to be Condition H1050 or H1100, so I forsee brazing the joint in this final condition. Any recommendations on type of filler, gas, etc. What about post braze heat treatment - if I braze on H1050 material, will a some type of stress relief be necessary?

I should add that in service, the item will only see environmental temp conditions and be used in coastal salt atmosphere environments.

All advice eagerly sought.Thankyou.

 

[tomwalz]

Looks like it.

Try a google search for "brazing PH13-8Mo"

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

 

[EdStainless]

Can you find a braze alloy that brazes at 1050F? Then you could braze in your age cycle, or right after it and not change properties.

If the tab loads are that low why not use 312 for the tab? Then you weld prior to heat treatment and not worry about the ductility of your weld.

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http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[metengr]

http://www.handyharmancanada.com/thebrazingbook/section 3/Part 14.htm#Precipitation

 

[tc7]

tomwalz-

I did that before I posted here and didn't find much. You would be interested to know that my first search led me to your website and I immediately bookmarked it for future reference.

When you are brazing saw blade teeth, do you place the tip in intimate contact with the blade? or do you provide a clearance, or root opening? if so, how much clearance is suggested? What about surface finish on the opposing parts? Do you post heat treat your carbides in any way? Come on Tom, give it up!!! Thanks.

 

[tc7]

Met-
That Handyharman and their Lucas-Milhaupt(?) partner are good folks to deal with aren't they? It just so happens I have some of their Easy-Flo 3 onhand, which according to your link, is the recommendation for 17/4. I'll check with them to be sure it is applicable to 13/8 also.

Ed-
We did consider the idea of welding a 312 or 308 tab, but I am running into much opposition about qualifying ANY new weld procedure of any kind. This is how the brazing suggestion came about - there is a belief that a brazing procedure would be exempt from formal testing under the criteria set in the scope of work. However, I will do a local tension and torsion test on production samples.

I believe the Easy-Flo 3 that I mentioned to Met does run at about 1100-1200 degrees, so I think you are suggeting that the brazing will not have an adverse affect on the final condition of 13/8?

Thanks.

 

[tomwalz]

Sorry – I just read the original question as to the theoretical possibility. You’re correct, there’s not much there.

BAG-3 is 1170 – 1270 F, AWS Bag-1 is 1125F – 1145F. (They both have Cadmium.) Figure maybe 50F over that. Don’t know why. NASA uses it and it seems to work well in actual practice.

Depending on what we are brazing we try for a joint of .003” to .005” as a trade off between maximum strength (maybe .0005”) and maximum cushioning (roughly the thicker the better up to maybe .015” at a guess with a sandwich shim.)

Put a pretinned tip next to the steel and heat the assembly. At temperature move the tip out just a bit and let the capillary attraction of the molten metal suck the tip back in. This release any trapped flux.

Cleaning – we like caustic cleaners. We use Easy Off oven cleaner in the lab. Cleans, saponifies and rises well. I have a few other preparations for other materials and large batches. (See patents for some idea of our approach.)

We like a slightly rough surface since we want both a physical and a chemical (creation of an intermetallic such as silver tungstate).

We don’t heat treat the carbide but the brazing temp is high enough to affect the steel so tempering after brazing is recommended depending on the thickness of the saw plate.

We like brazing in a notch if you can. Put flux coated wire in a notch and set the carbide on top then heat until the wire metals. Wiggle the carbide just enough to break the surface tension and allow the trapped gas to escape.

I have a couple hundred pages about this in Braze Failure Analysis and Building Superior Brazed Tools. You can buy those at CaféPress.com.

There is a lot of free stuff on our web sites. Try newsletters at CS4U.org.

I’m not one of those experts who know everything or who even get everything right all the time. It is not unusual for me to finish a speech and have practitioners suggest effective methods different than mine.

We pretin carbide, sell braze alloy and carbide. I started on this because everybody is happier if the customer can use my product successfully.

If you go to the thread “Discoloration of 347SS parts in brazing cycle” you will see opinions other than mine and you will see Unclesyd, for one, add considerations that I hadn’t mentioned.

If someone really wants to know how to braze I will take them to one of a couple customers close by for demonstration of good practice with equipment we don’t use.

So anyway, I am happy to share information as long as it is clear that all I am doing is sharing what I have seen work.

Now I am going to go back and work on a speech I have given maybe too many times where I try to convince people to buy the right material for their use.

Thanks for the break and feel free to call if you wish.

Tom



Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

 

[Kanuk]

You tried and failed at an attempt to qualify a TIG weld procedure on joining PH13-8Mo to itself. May I ask what was the problem with the TIG weld ?

 

[tc7]

Kanuk-
I don't precidely know, I wasn't here at the time. My best guess after reviewing the info I do have on file is that the PWHT may not have been completed correctly.

The latest decision was to forget about the brazing idea and revisit getting the welding procedure qualified with the 13-8 filler.