Welding 4140 to mild steel

SNIP

Shouldn't be a problem. The load should be evenly spread across the surface.

Not many jobs will require the full 75T capacity of the press.. I'd expect most jobs to be significantly lower.

I'm no metallurgist, but a piece of steel that can be bent without snapping will just deform under stress/tension. There could possibly be some reason for concern if working with work hardening stainless alloys.

Unless you try pressing endmills or other hard cutting tool steel into other parts, there should be no shattering, or flying bits breaking away from the workpieces.

As you describe it there will be essentially no force on the weld as the ram will press against the mild steel which will press against the work (if I read your description correctly :-)

Ignoramus3543 fired this volley in news:e82dnbEpGbfNmQrMnZ2dnUVZ snipped-for-privacy@giganews.com:

What's to fail? The ram pushes on the plate, not the tube. The tube is only providing positioning and retention for the plate.

Were I you, I'd nix the rag between plate and ram. You can put three setscrews around the tube to hold the plate in place. The rag consitutes "cushion", as you noted. Anything that can absorb energy and spring back suddenly when released is bad to have around hydraulic presses.

Lloyd

I agree with Lloyd but for somewhat different reasons. I think you will get some distortion in the ram anyway and having a close fit will make it hard to take your weldment offi So I would put some set screws in the tube. I would only put in two set screws spaced about

60 degrees apart. And drill a slight bit into the ram where the set screws contact the ram so the set screws will not distort the ram and make it hard to remove. When you put it together put some wax in the hole so the ram and tube will not rust. And make sure the ram is not a close fit in the tube.

It would be better if the plate was 4140 and the tube was mild steel. The force will almost all on the plate.

Dan

And that is why my fit is far from close, and exactly why I use a rag, to fill a space with soft material, keep the nose in place, and provide minimal cushioning.

I thought a lot about Lloyd's comment about cushioning providing some undesirable spring action, but, I think, a rag should not be able to store any significant energy.

Yes. The cylinder is double acting, so I think that I will be able to pull it out of the nose piece, if I ever need to.

As for set screws, I am afraid that they will get damaged by the pressing action and "play".

I agree with that, I used what I had available, not saying that it is the best selection.

i

One thing I just thought of, Are the faces of both sides of the plate parallel? You don't want the face to be angled in any direction while your using the press. Not a good thing for precise work.

Yes, the plate was cut out from a hot rolled plate, it looks like.

i

Cool. :)

Prob'ly 100% right too! :)

Spark test it and you'll know-more. ;)

I was given some hot rolled steel that's new-old-stock VascoWear. (type 421 tool steel, type 420 = A2)

Bought some hot rolled steel that was D2 Tool steel.

Igno, I know you from the blacksmithing newsgroup, please learn how to spark test?

Please? ;)

All you need are a few known samples.

Alvin in AZ

Normally, to weld 4140 to Mild steel you would use a stronger rod, like

8018. You should also have preheated the whole piece to around 500 degF before welding and allow to slow cool under sand or some other insulator.

I doubt anything will explode. All the force is on the mild steel, however your welds will likely crack eventually. No big deal. Just grind out the cracks and reweld.

The rag will likely decompose over time and pressure into powder.

Ernie, thanks a lot, I will be using it and will reweld as necessary.

i

If it's not cracked yet, you can post weld heat treat the assembly at 1150F and that will reduce the potential for delayed hydrogen cracking. A post weld soak at 350 - 450 would work almost as well. The 7018 rod is fine as it matches the mild steel side of the joint and as long as the rod was dry (like in fresh out of the can or always protected in a rod oven) you should be fine. The medium carbon alloy steel is very susceptible to delayed cra cking and both the higher the strength of the rod and the greater the stren gth of the weld (i.e., size) the greater the chances of cracking. Crackin g will mostly happen due to residual stresses from welding. Service loads shouldn't be a problem unless the weld is undersized and then you'll get w eld metal cracking.

good luck.

j

i do have a screen on my press, check the picture above

IMHO, ANY heavy press should be equipped with a substantial screen which is permanently attached to the press frame and can be positioned to prevent any flying shrapnel from striking any persons or property. The screen should be able to be moved aside (or up) to load the work into the press then easily positioned to contain any possible shrapnel caused by the failure of the press, its attachments or jigs or of the work. The positioning of the screen should be done before ANY substantial pressure is applied.

Some would suggest that the screen should be equipped with a micro switch that prevents application of substantial pressure without the screen being locked into place, but most workplaces just have a sign requiring the use of the screen. I suspect that a screen is a requirement of OH&S / OSHA.

"Protect yourself at all times" is not just for boxers.

Good Luck, YMMV