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i need to weld a grade 8 bolt to a cast iron diff pumkin, i think i need to use nickel rod right?, and i also think i have to preheat the cast iron...if so how hot do i get it...red hot?... then weld it? well somone has to know, and also do i heat the bolt up to?
adam <IMG SRC="smilies/confused.gif" border="0">
 

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I've been told you need to get it at least 400 degrees, I tried to weld a spring perch w/out heating it up and it was nasty, i ended up just burning through the steel and making the cast look uglier.
 

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There are specific rods made to weld on cast and your local welding supplier should carry some and they'll give their recomendations as far as preheat (they're usually high nickel). Just from past experience, if you hear a funny ping after your done and it's cooling, you'll have to start over. Some reccomend post heat in hot sand.
 

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Hard to explain...

I was told and saw how to weld on a pumpkin without having to preheat it. Ask someone who knows how to do it <IMG SRC="smilies/wink.gif" border="0">

If you are welding on the edge of the housing you dont have to pre heat, since it will expand and wont tend to break while it cools off, but if you weld on the center of the pumpkin you do have to preheat...

Thats the theory I LEARNED from a guy who does suspensions and WELDS quite a lot on them with no problems.. check into that, ask someone who fabs suspensions,

hth
 

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Originally posted by BIGA$$YJ:
<STRONG>ohh ya is red hot atleast 400 degrees? <IMG SRC="smilies/confused.gif" border="0"></STRONG>
im thinking red hot metla will be over or close to 1000 deg.
 

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Welding on cast iron is always a PITA. If the joint is subject to shearing stress, it will be very difficult to make an adequate joint by simple electric welding even with preheating and nickel rod. We learned in welding school that when joint strength is critical, first drill and tap the cast iron piece with a grid of holes and install "stitching pins" and then weld the steel piece to the stitching pins.
Check it out: http://www.locknstitch.com/CastIronWelding.htm
 

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I welded a spring perch on the diff of my waggy d44 front axle. I just heated up the cast with a torch then just started welding with a gasless mig. It layed out some pretty welds and there strong as hell! Never had any problems with it. <IMG SRC="smilies/skull.gif" border="0"> <IMG SRC="smilies/skull.gif" border="0"> <IMG SRC="smilies/skull.gif" border="0">
 

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I used nickel rod to weld a traction bar mount on the top of my pumpkin. It worked great, but I used about 2 1/2 sticks per side. I have heard that the 9inch pumpkin is cast steel, but have also heard it's iron. Nickel rod is the way to go. I don't know about the preheat. As soon as you strike an arc it will be hot enough in my opinion.
 

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I welded a shock mount to the top of my 44 for a traction bar mount. I preheated the cast with a torch, not red hot, that's too much. Just heat it for about 2 minutes or so in a circular pattern, that should be good enough. I welded with pure nickel rod and about 135 - 150 amps out of my AC/DC Lincoln. I only welded about a 1/2 inch at a time and covered it with aluminum foil to help slow the cool down. Took me a little while, I think I repeated the process about 5 times, but so far so good.

I had welded it previously with 7018 and no pre-heat and broke it off on the first run.
 

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9" housings are stamped steel so normal welding works on them.

There are a couple of reasons for preheat.
1. is to drive out any impurities in the area. Due to cast irons pourous structure oils, gas etc get trapped and can affect the weld quality.

2. to eliminate the weld and the base metal cooling at different temps thus creating internal stress on the part and usual cracking right beside the weld.

The main problem is people sometimes only heat up the immediate area and the cracking just moves. The whole part needs to be heated to 400-500 deg. F (ovens work for this but the smell can be aweful!)

you can get away without preheating just clean the area really well either by heating to around 500 deg and then letting it cool or by grinder and sander. Then run short cool passes with a sheilded MIG welder. allowing the weld to cool to the touch in between.

If you can pick up a wrecked housing or something to practice on it helps alot.

Have fun! <IMG SRC="smilies/biggrin.gif" border="0">
 

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You can buy a temp. stick at a welding shop, it will melt at whatever temp the stick is rated at...

I'm not sure a grade 8 bolt is still gonna be grade 8 after you weld it to something.

I weld to diff housings and knuckles with a mig and plain steel wire and I have no
problems. Preheat to 400 weld it and let it cool slowly.
 

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9" housings are stamped steel so normal welding works on them.
There are a couple of reasons for preheat.
1. is to drive out any impurities in the area. Due to cast irons pourous structure oils, gas etc get trapped and can affect the weld quality.

2. to eliminate the weld and the base metal cooling at different temps thus creating internal stress on the part and usual cracking right beside the weld.

The main problem is people sometimes only heat up the immediate area and the cracking just moves. The whole part needs to be heated to 400-500 deg. F (ovens work for this but the smell can be aweful!)

you can get away without preheating just clean the area really well either by heating to around 500 deg and then letting it cool or by grinder and sander. Then run short cool passes with a sheilded MIG welder. allowing the weld to cool to the touch in between.

If you can pick up a wrecked housing or something to practice on it helps alot.

Have fun!
I agree with everything he said. The big problem you are dealing with is that the base metal is brittle, and you can't change that. If you do it all correctly, it will just tend to break some distance from the weld. And there is not point in using a GRADE 8...It won't be grade quality after the weld, and something softer (GRADE 5?) will weld easier, be more maleable. Hope this isn't going to see much stress....
<IMG SRC="smilies/rolleyes.gif" border="0">
 
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