Welding a Disc Blade.

[BufordBoone]

I broke a disc off Saturday. Replacements are about $20, if I remember correctly. However, I want to fix things when I can.

I'm trying to learn welding so I welded it up and thought all was good. Then I noticed I had missed welding on the crack in a few spots. Damn. Welded more, making sure I was all over the crack. All good. I went about putting stuff away and heard a loud pop.

Looked at the disc and, damn, there is a crack just beside my most recent weld.

A friend has said he thinks it it "Cast" and that I should try a "55 Nickle Rod".

Any advise (other than getting better at welding) from any of you would certainly be appreciated.

 

[lpakiz]

Disc blades are "spring" steel and are not very weldable. Sometimes you can pre-heat and weld spring steel using multiple passes. The subsequent passes serve to "anneal" the spring steel, making it softer so it doesn't crack as easily. But, you destroy the hardness of it.
Nickel rod would do better than 6013 or 7018. Still no guarantee, tho.
As with cast iron, pre-heat and slow cooling help.
i used to annual hard stuff like truck king pins by heating them red hot overnight in the wood furnace, then pick them out with channel lock pliers and putting it in the ash drawer for a day. Soft as mild steel, and easily machined on my lathe. It would work the same for bearings, leaf springs, pretty much anything ferrous and hard.

 

[BufordBoone]

Disc blades are "spring" steel and are not very weldable. Sometimes you can pre-heat and weld spring steel using multiple passes. The subsequent passes serve to "anneal" the spring steel, making it softer so it doesn't crack as easily. But, you destroy the hardness of it.
Nickel rod would do better than 6013 or 7018. Still no guarantee, tho.
As with cast iron, pre-heat and slow cooling help.
i used to annual hard stuff like truck king pins by heating them red hot overnight in the wood furnace, then pick them out with channel lock pliers and putting it in the ash drawer for a day. Soft as mild steel, and easily machined on my lathe. It would work the same for bearings, leaf springs, pretty much anything ferrous and hard.

So, "Buy another disc blade and forget fixing this one" is what you're saying?

If so, that is why I ask in this forum. Lots of knowledge here.

I'd have never guessed.

Thanks!

 

[lpakiz]

Oh, and peening it also might help. A small ball peen hammer, medium blows, and lots of them for several minutes as it cools.
This helps relieve shrinkage stress as it cools.

In the case of that disc blade, I would try it, if you can source a couple nickel rods. Heck, it's good experience and you may be able to get it to hold where you welded/annealed, but still preserve the hard outer rim.
I suspect the disc might bend and start to wobble at your (annealed) weld, but you won't have much invested to see if you can pull it off.

 

[MtnViewRanch]

I'll say one thing. This is a learning experience, when you are done, you will have leaned to just get a replacement disk.

 

[BufordBoone]

I'll say one thing. This is a learning experience, when you are done, you will have leaned to just get a replacement disk.

And, let's not forget that I've gotten a whole bunch of practice at unsticking a welding rod.

That is why they call it "Stick" welding, right?

 

[lpakiz]

Yeah, and where else can you learn this much for the price of a couple nickel rod?

 

[Raul-02]

If so, that is why I ask in this forum. Lots of knowledge here.

there's no such thing as "spring steel."
There are dozens of tool steels that can be heat treated to about 48 Rockwell which is spring temper. I don't know of any tool steel that is not weldable. Some like 4140 and 4150 ya gotta pre heat and ramp down slowly or the welds will crack, they will still be strong but cracks no one will pay for.
I'd use a 6011 or 6010 rod and go for it. What's the worst that can happen? Welding will distemper any heat-treated steel in the area of the weld. So the disks my just bend like pretzels afterward.
If you have access to a tig welder friend ask him to do it and try to use as little heat as possible for that purpose, might save the disk

 

[lpakiz]

Well, you name it whatever you want, but when I see a disc blade or a leaf spring, I'm gonna call it spring steel.
And I guarantee that if you weld spring steel and make it hold, it will no longer be "springy" but "bendy"
Thats my story and I'm sticking to it.

 

[Raul-02]

And I guarantee that if you weld spring steel and make it hold, it will no longer be "springy" but "bendy"
Thats my story and I'm sticking to it.

This is correct