How to Harden a Fabricated, Mild Steel 1018 Nut

In practice no. There is insufficient carbon to transform to martensite and if the section thickness is too much, even the surface won't harden.

If you had a lab furnace (1700 F) you could always try to carburize the surface by packing in carbon and quenching, but that will only give surface hardness not toughness. thread pullout prevention needs toughness.

Higher carbon gives you increased toughness- 1045, 1050, but then you can't weld easily.

milo

its always a heads or tails thing with strength and welding...

Thanks Milo, that is what I kinda figured. I guess I could try it as is and see how it goes. For all I know, the original nut is mild steel too. On the plus side, I have learned a lot about steel grades and properties

I'm curious did the original nut have any markings on it to indicate the grade? There maybe be lines or dots on one face.

No markings, I have a pic so you can see better what I am talking about.

I think you're going to be alright with the nut you've machined and at some time in the future it too will need replacement.

Heat the nut and the area to be welded cherry red before and after welding

Hello. if you have the clearance you could make a thicker nut with more threads. Or make the nut to where you could use an insert like helicoil. Charles metalSmiths

Hi tbone8,

Welcome to CR4. It's always nice to see that there are still craftsmen out there.

In case you should wonder why no one else responds to your post, the #1 expert in the field on CR4, (in my opinion) has already answered the question.

Cheers and stick around. It's addicting.

I have used a product called Kasenit that is made for low carbon steel on several projects. It works very good. The maker of Kasenit does not have a website, but by doing a Google search you should come up with several places that sell it in the 1 pound cans. It can sometimes be found at your local welding supply shops. To use it you just clean and heat up the item you wish to case harden, the dip the item in the powder. After the initial dipping, you have to heat the item again......then you are done. By repeating the process you can attain additional hardness. The items to be case hardened have to be bare clean metal with no plating on it. Always be careful of heating metal that has zinc, cadmium, or other protective coatings. These are very hazardous to breathe in. Another product you can Google for is called Cherry Red which is just another brand similar to Kasenit.

Sometimes when I am worried about fasteners that may be damaged due to any push/pull forces that may be applied to them, I put some red Thread Locker on the threaded area. This will help as long as the vibration or push/pull forces are not too great. To remove a fastener that has had the red thread locker applied to it will require some heat (approx 500 degrees) applied to it.............good luck with your project.

Try this link.:https://www.instockfasteners.com/PRODUCTS/squarenuts.asp

Square nuts of all sizes.Yours looks to be a 3/4"- 10 thd or a 7/8"- 9 thd.

No sense reinventing the wheel.

HTRN

try this link: https://www.instockfasteners.com/PRODUCTS/squarenuts.asp

Plenty of square nuts, all sizes.

Your looks like a 3/4"-10 thread or 7/8" 9 thread nut on a lift arm of a Farmall or Allis Chambers tractor.

HTRN

They don't have 1 3/8"-6 thread nuts...

Got the nut bored, just need to thread it...

Instead of using 1018, consider using 4130 alloy steel, You should still be able to weld it using 7018 electrodes but the strength will be much higher due to the higher carbon (5o-60 ksi min. yield vs 36-38 ksi for 1018 depending on the section thickness). For 4130 you'll need to pre-heat the nut and then immediately wrap it with a asbestos blanket after welding and let it cool back down slowly to prevent cracking. Even 8620 which should not require pre/post heating would get you 55ksi, and would respond very well to case hardening.

Milo is indeed the expert here. He is correct that case hardening/carbourizing the part will only result in higher surface hardness, not in overall strength or toughness. it would be good for wear, and may be a good idea for that reason alone, but it won't prevent the threads from stripping one iota.

I wanted to thank all who posted on this. Its a strange application for this nut, it has a threaded eye bolt that rotates with the lift arm limiters. I think it wore out due to dirt in the threads and corrosion. I will try my mild steel nut and see how it works, pics to follow!

Thanks,
Tom

if the issue is wear from grit in the threads, then you should seriously consider case hardening the threads as commented upon earlier. you might also want to consider crossdrilling into the threaded area and tapping in a grease zerk and keeping the area greased to prevent grit from getting in there.