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Welding To Hardened Steel?


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#1 IamSherwood OFFLINE  

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Posted November 04, 2012 - 08:15 AM

How is that done? What welding rod should be used?
I'm trying to weld a piece of mild steel, to a hardened shaft.

#2 caseguy OFFLINE  

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Posted November 04, 2012 - 08:27 AM

Will the mild steel be in a wear or stress situation? Mild steel can be welded to hardened steel, but deep penetration is a necessity. The right rod is important too. I generally use a 7014 when welding anything with a temper, but 11018 is a low alloy rod that is better suited to actual shaft applications (i.e. welding shaft steel to shaft steel) Personally I'd say that 7014 would be better for welding shaft steel to mild steel.
If you are extending the shaft, and it will be in a wearing or high stress situation, I would recommend using a raw (not been heat treated yet) shaft material (1130 is common in automotive applications and 4140C is another shaft material, but it's more expensive). Heavily bevel the ends to be joined, preheat the steel to 400 F and weld it up in layers, being sure to thoroughly clean the welds in between layers, allow it to cool slowly to under 600 F in between passes as well (to avoid tempering it unevenly at the weld site). Many also recommend a close fitting overlaying sleeve welded on both ends. Have the shaft heat treated when you're through.
And now it's time for the disclaimer. This is not recommended for high speed highway applications...period! If you're planning high stress use (such as plowing or other ground engaging work) it will also be a weak point no matter how it's done. Shaft steel is often forged and hardened at the factory. You will not be able to duplicate the original strength of the part.
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#3 olcowhand ONLINE  

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Posted November 04, 2012 - 08:55 AM

Steve, please correct me if I've been doing wrong, but here on our farm, we've always used 7018 on such welding jobs. It's always held well.

#4 IamSherwood OFFLINE  

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Posted November 04, 2012 - 09:04 AM

Thanks Steve.
Yes, it's in a stress stuation.

I like the disclaimer. I promise I'll go slow, when I cross the highway.

So, how do I go about checking the temp in the preheating/cooling process?

#5 caseguy OFFLINE  

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Posted November 04, 2012 - 09:24 AM

Steve, please correct me if I've been doing wrong, but here on our farm, we've always used 7018 on such welding jobs. It's always held well.


7018 is a good choice and for most applications it will do a fine job, especially if it's what you have. I recommend 7014 because it has a higher deposition rate and thus will allow less heat transfer and possible loss of strength. The "70" part of the number is the tensile strength, so the two rods are equivalent in that respect.

...So, how do I go about checking the temp in the preheating/cooling process?


You could pick up one of these:

infrared thermometer.jpg

Harbor freight has on available for about $35 Here. I'll bet that you could get one at Princess auto too.
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#6 mjodrey OFFLINE  

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Posted November 04, 2012 - 09:39 AM

7018 would be my choice ,although the 7014 should do the trick as well.
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#7 ol' stonebreaker ONLINE  

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Posted November 04, 2012 - 10:20 AM

Would help to have more detail of what your plans are for this. Definitely preheat, if you have one,an air chisel will work well to peen each weld pass, which will help relieve stress in the HAZ(heat affected zone). If you don't have an air chisel, then prolonged hammering w/ chipping hammer will work. Peen the weld until it no longer looks like a weld. I concur w/ using 7018, 7018AC if you don't have a DC welder. The peening will help greatly no matter what rod you use.
Mike
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#8 Cvans ONLINE  

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Posted November 04, 2012 - 10:27 AM

Another option that I used a number of times was a Rod called Missile Weld. It's a Stainless alloy that you can weld high strength or tool steel with. I've used it to repair or make custom leaf springs and have not had one break. Used to repair leaf springs on fork lifts and Jeeps. Other springs would break but not the repaired ones. Your mileage may vary though :smilewink:
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#9 ducky OFFLINE  

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Posted November 04, 2012 - 10:55 AM

Chris that is some amazing rod. Have used it before and never a failure.
Also nice disclaimer there as well:-)
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#10 IamSherwood OFFLINE  

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Posted November 04, 2012 - 06:47 PM

My plan was to weld that stub coupling into the splined clutch output shaft (hardened).
I've changed my mind now, because as it turns out, I have enough space to allow me to have a
bolt together connection there. It'll be much better, for future possible service situations.
Now, the plan is to weld a flange on the stub, that mates/bolts to the splined shaft flange.

But, thanks for the info guys. I learned a few things, and next time I'm faced with this type
of situation, I'll be better prepared.

P1010104.JPG




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