Clearing threaded nuts of hot dip galvanized coating 2

[intimidator3]

This is a follow-up on my problem on welding galvanized A588 steel,and DEANC has peeked my interest for a solution.
Is there a effeciant way to remove the zinc coating from the thread area of the nuts to make them useable if we were to attach them prior to hot dipping?
My research on this has said to "heat the thread area moderatly,not enough to destroy the thread, and use a wire brush or similar tool to remove the zinc.Running a hand tap through may be required".
Is this true?

 

[metengr]

intimidator3;
To remove all of the zinc in the threads will require you to heat the entire nut above 1650 deg F (1650 deg F is the temperature that zinc vaporizes). Metal temperatures above 1300 deg F will affect the mechanical properties of the steel nut( A 588) upon cooling- so the bottom line is that heating the threads to vaporize the zinc would be very risky. This operation would have to be performed under very controlled heating conditions (like a furnace)with temperature monitoring and controlled cooling to avoid altering the specified mechanical properties of the steel.

If you can allow the zinc vapor to escape into atmosphere instead of being absorbed by the weld metal, this will result in success. Some additional information - you might want to use weld rod that contains a maximum of 0.85% Si (too much silicon will cause zinc to penetrate the weld puddle). Also, Hobart makes a flux cored wire called "Galvacore" - you might want to try this as an option.


Another option is to investigate grit blasting or possibly chemically stripping the zinc plating on the nuts.

 

[unclesyd]

Heating Zn is quite hazardous to ones health and extremely bad on certain metals. Don't heat the nuts.

When you vaporize Zn metal it has to condense somewhere, all over the equipment and possibly in one's lungs.

What was the specification for these nuts and how many are you talking about? Plateed,Mechanical, or HDG.

Some ways to get out from under the problem
Get new nuts.
Tap the nut.
Have the plater strip the zinc.

 

[intimidator3]

Metengr,
Thanks again for your input concerning this ongoing problem.
It would appear removing the zinc coating will not be a option due to cost concerns.
Currently, we are using 6010, production is 40% lower.
I was not aware that there was a wire called Galvacore available,and I try to keep up on things. Thanks again! I will order some ASAP. I'll let you know how we make out.
Thanks again for the input.

 

[IFRs]

If you did remove the zinc, you would find that the bolts are too loose. The threads are cut differently for galvanized bolts and nuts, to provide room for the HDG. Start with new bolts!!

 

[JTMcC]

What size of 6010 rod are you using?
If you are using smaller sizes you might want to look into 3/16" and 7/32" to speed up production.

As far as production being 40% lower, that's not true. Before you were making faulty welds, now you are (we assume) making proper welds. You could put a drop of super glue on each nut and probably increase production by several hundred percent, but that's not a true increase because your product is faulty, just like it was with those poor welds.

JTMcC.

 

[intimidator3]

To JTMcC,
It's funny you mention Super Glue, it's the running joke of the shop,i.e. " you want me to glue it on?"
Seriously tho,we are using 5/32 6010 and producing a sound weld that passes independent inspection. It's just too slow, and I need to speed things up. We are 360 pcs. into an order of 3800.
I totaly agree with your "production assessment",and we will not allow a faulty product to be shipped. The products that need attention are still in my shop.I have sent the independently approved pcs.
The un-approved pcs. are being re-worked.
Thanks for the input!

 

[IFRs]

Why not use a stud welder?

 

[JTMcC]

5/32" is pretty small rod for what you are doing. I still suggest 3/16" or 7/32". You will see an increase in production. There might be a learning curve for the welders if they are unfamiliar with 6010. But faster it will be!

JTMcC.