Carbon Steel Mild Steel cracks.

IMHO: welds can crack due to :

moving the rod to fast in the seam,( staying to long in one spot , bigger hole to fill now )

having the wrong material as your welding rod...

have the surface area being contaminated...

sounds as though the students have learned the art of welding very well...

to induce conditions that facilitate a failure...

as the techniques for a good weld are known.......

could it be that difficult to see where to introduce the " culprit " .?

We don't really let the students weld. We just teach them various methods on how to detect "cracks". I'm interested in makeing cracks that are fun to find.

uhmm... stress cracks..? place the piece in a vise grab the 90 o arm . bend till , bent the other way till..repeat as required?

i dunno knowww

gl..

You must be very strong...

manpower is never an issue..... ..that's the least of the materials that's in short supply

here in the us.. there's a beer ad for a mexican beer.." the most interesting man in the world "..really very funny..

but in the spot..is a line " bulls , flat out , refuse to fight him "

in response to your signature...

and luck is the residue of design

Try welding onto manganese steel without pre- and post-weld stress relief. Martensite rules, OK?

This is a dangerous method to try and induce weld cracks, so please use all the personal protection (safety glasses, leather gloves, etc.). After the plate has been welded and it's good and hot, toss it into a container of liquid nitrogen. The shock alone should do the trick.

If you try welding 1144 resulfurized steel you should get cracks.

Heat 4140 alloy steel to austenitizing temperature then water quench.

we always made our set up bars fro our rototesters by machining very fine grooves. also we could make them various depths.

milo

Another method:

Weld with wet electrodes. Weld steel with a high carbon content. Hydrogen gnerated during the welding disolves readily in the molten metal but is much less soluable in the cold metal, the pressure generated internally in the steel by the hydrogen gas phase results in cracking of the hard metal.

Chama

I have done that to students in a welding class to drive home the point that electrodes that hate moisture must be kept dry. Dip them (electrodes not the students) in water for a few minutes then set the on the bench to dry over night. The next day is great.

Try welding cast iron to chromoly steel or chromoly to black pipe without CO2 or preheating using #5118

Spray (flush) them with water on one side only. If you quench them, there is a chance the plates will cool evenly. As far as when to spray, try different temperatures (delays), as the transformation stress will offset the thermal stress around 1400 F (red hot).

You will not get mild steel to crack by quenching it in water, it does not have enough carbon content. You need to get a higher carbon content steel and do not pre or post weld heat treat and it should crack fine. Dosing rods with water will not usually cause cracks but will however cause plenty of porosity due to the water vapor displacing the protective vapor(smoke) from the flux or shielding gas and letting oxygen in the air contaminate the molten puddle. One way to get mild steel to crack is by welding a circular flush patch continuously in one direction and the stress will cause the adjacent tacks to crack. Another way to do this is to weld one bead on one side of a Tee joint as cold as you can possibly make a decent weld and then turning the machine up and running several beads on the other side. With mild steel the only way I know to cause a crack is by introducing heavy uneven stresses to a weld joint. One other thing you might try is to weld a open butt weld joint while you have vibration. I know that many times I have welded objects in the field when vibration from a motor or some other source the weld will tend to crack.

Once again Pipewelder has beat me to the punch line. To get the kinds of cracks you want for training purposes, you need to design a highly restrained joint that will be the weak link in an assembly and then do everything wrong while welding that joint. My best suggestion would be to weld either a T-1 (514, 517) or an HY series steel cold, with cold 11018 electrodes that have been sitting out for a day or two. Let rest for a minimum of 72 hours and Viola!, transverse cracks.