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dewat
12-24-2006, 10:00 AM
I have a little HF flux core wire feed and little welding experience. If I'm in a hurry I'll quench the part shortly after welding which makes for some REAL hard weld, too hard to drill or mill, other than that are there other problems with quenching.

Thanks Jim

pntrbl
12-24-2006, 10:32 AM
It's been my experience a weldment is harder than the parent material even if you don't quench it. Just recently I was modifying a steel workbench and the un-quenched welds ate sawzall bades pretty good. If I missed the weld the surrounding steel was like butter.

SP

Evan
12-24-2006, 10:44 AM
It makes the weld brittle. It will crack more easily. It is why gas welding is used for welding 4130 aircraft tubing on aircraft fuselages.

rockrat
12-24-2006, 11:10 AM
At the place where I work, all weldments are required to be fully annealed before machining. This reduces the internal stresses that welding can create, plus it softens up the weld if we need to put a hole at a welded joint or machine part of the weld.

At home, if the item is small enough, I toss it into a box of kitty litter to slowly cool. But man do the cats get ticked off when they find that stinky thing in there! :eek:

dewat
12-24-2006, 11:25 AM
Thanks for the replies, which brings up another question, if I weld 3/8 x 2" round CRS to 1/4 x 1/2 CRS and then case harden the whole part should it hold up to say 10 to 15 pounds of pressure.

JCHannum
12-24-2006, 01:15 PM
I am not sure what pressure you are describing. Case hardening adds surface hardness, but in most cases will not increase the strength of the material.

Welding causes intense, localized heating. The heatsink of a large part can act to quench the area, creating hard spots in the weld area. Heating to anneal or normalize the part with slow cooling will remove most of the problems.

Your Old Dog
12-24-2006, 02:02 PM
At the place where I work, all weldments are required to be fully annealed before machining. This reduces the internal stresses that welding can create, plus it softens up the weld if we need to put a hole at a welded joint or machine part of the weld.

At home, if the item is small enough, I toss it into a box of kitty litter to slowly cool. But man do the cats get ticked off when they find that stinky thing in there! :eek:

I worked at GATX (General American Tank Company) and they anneal each and every railroad tank car the make as one of the last steps to relieve stress. I don't quench anything unless I'm ready run the risk of it being too brittle for the intended use. Sometimes if I'm bending stuff i'll quench in the snow.

Tin Falcon
12-24-2006, 04:32 PM
The only time you should quench is for hardening. When is was in welding school we quenched the welds. This was so the insructor would not be hanling hot metal. We were told to never quench in the"Real world' it builds up strsses in the weld area and can cause cracks.
Tin

Bill in Ky
12-24-2006, 05:41 PM
I always thought that there had to be carbon in the steel in order to harden it.
Is case hardening different? How do you case hardon mild (crs) steel?

Mcgyver
12-24-2006, 06:23 PM
iirc the superheated metal leeches carbon out the surrounding material.

wierdscience
12-24-2006, 06:37 PM
iirc the superheated metal leeches carbon out the surrounding material.

But only if that surrounding metal or the filler contains greater than .02% carbon.

When a weld cools it contracts,when you quench that weld it contracts faster than it would with air cooling.This can lead to internal cracks or the weld cracking out of the base metal.The effect is also aggrevated by not gapping the parts being welded,when it cools,quenched or not there is nowhere for the contraction stress to go and the joint cracks.

Allowing the part to cool naturally allows the weld and the surrounding area time to mormalize to a degree,retarding the cooling using flux,sand,or kitty litter adds to the effect.

Pre-heating the joint before welding helps counter some of the effects of contraction stresses too.

WJHartson
12-24-2006, 06:43 PM
The higher the carbon content in the steel the more likely it is to crack if you quench the weld right after it is welded. When you get up to about 40 points of carbon and above it is recommended that you pre heat and post heat to help avoid cracking the weld.

Joe

dewat
12-24-2006, 07:28 PM
http://i81.photobucket.com/albums/j218/dewat/Copyoflinkerloader003.jpg

Sorry this isn't a good pic, my camera ate my last batteries. On the far right there is an eye bolt, through the eye is a piece of 3/8 round CRS welded to it is a piece of 1/4 x 1/2 CRS, thats it with the shoulder bolt through it, there is an overlap of about 3/8 where its welded on both sides ( this is a ratchet mechanism). My concern was that after I case hardened the part that it would cause the weld to be too brittle, so I just made another one of these double heat treated it and did a destructive test on it by clamping the round part in a vise and bolting a piece of 1/2 sq. onto the flat piece, I bent the hell out it and the weld held so I guess for now its not too brittle LOL. There isn't that much pressure on the part but I wanted to make sure it wouldn't fail. Those are some pretty ugly welds I do better on the production model (hopefully).:D

Swarf&Sparks
12-25-2006, 12:16 AM
FWIW, I was taught always to quench stainless (minimize chromium carbide precipitation) and never to quench any other steel.
Rgds, Lin

Mike W
12-25-2006, 12:40 AM
I have filed, drilled and tapped mig welds made with ER70S6. I can't see how they would get hard unless you were welding metal that had enough carbon in it to affect the weld.

dewat
12-25-2006, 02:07 AM
Mike, I'm using E71T-GS, if I quench it it will round off the corners of end mills (good ones too) and break drills & taps, but its ok if I just let it cool on its own.
I'm just using hot and cold rolled steel.

pntrbl
12-25-2006, 03:21 AM
I used to test my welds on concrete walls back in my stock car days. Had a few tubes tear right next to a weld, but that's about as good as it gets.

The crazy one was the night I side slapped the wall going backwards. Probably still had my foot in it! LOL! Anyway, the rear axle had to suddenly change rotation from "wall friction" and my welded spider gears didn't stand up for that. It musta been like an explosion in there because I didn't find a single piece of the resulting shrapnel that had more than 2 teeth.

Nothing's indestructable.

SP

Scishopguy
12-25-2006, 06:40 PM
At home, if the item is small enough, I toss it into a box of kitty litter to slowly cool. But man do the cats get ticked off when they find that stinky thing in there! :eek:

Careful Rock,

The kitty will get even by taking a dump in you can of oil dry!!!

Merry Christmas