For the metallurgists here.

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I know a man who worked at a plant that produced large I beams. This guy was assigned to straighten any of those that warped. These beams were apparently suspended by cables, I am not sure, but he would have them heated red hot, either in a strategic area, or all of the beam, again I am assuming, then they would be pointed in such a manner as to self straighten due to natural magnetic attraction. Is this possible? If so, in your opinion, would it apply to blade quenching at all, or in part. Please forgive my lack of details, it has been years since I have had contact with this person.
 
Magnetic attraction ?No .Mild steel may be straightened by heating with a torch to red heat on one side .Perhaps they did that while it was suspended. Maybe Joe Marsillo the steel worker can tell you !!!..The beams they use on our new bridge are made of Cor-Ten steel and the flanges are welded to the web .They're 8' high and at least 40' long .You wouldn't want to heat Cor-Ten to straighten.
 
I'll bet he and the guys at the plant had a good laugh over that story.
The weight of the beam could create a sag to straighten the warp.
The heating and cooling could create a reverse warp.
Lots of ways of straightening out a long object with the right heat and the right pressure.
Using the earths magnetic lines of flux is Not one of them.

On knives true north and magnetism only apply if you are Mark Williams, and doing HT at midnight on a full moon.
Stacy
 
bladsmth said:
I'll bet he and the guys at the plant had a good laugh over that story.
The weight of the beam could create a sag to straighten the warp.
The heating and cooling could create a reverse warp.
Lots of ways of straightening out a long object with the right heat and the right pressure.
Using the earths magnetic lines of flux is Not one of them.

On knives true north and magnetism only apply if you are Mark Williams, and doing HT at midnight on a full moon.
Stacy
Click to expand...

Hey now! You're not says it DOESN'T work are you??

Someone might be making up a little 'bladsmth' voodoo doll right now to use in a secret forge-purification ceremony!:eek:
 
I imagine the suspension was to keep it laterally neutral while trying to straighten it with heat... the heating on one side and consequent cooling changes the internal stresses and will straighhten a bent beam if done on the correct side or bend a straight beam. This is usually done at a few locations along one side so the curve is straightened gradually.. the more you do the more gradual it is, but then your heating would need to be less.

It is a very similar issue for blades, with unsymmetric cooling of the blade that causes it to warp. (among other factors). Unfortunately reheating one side to straighten it will ruin the hardening. Magnetism in both the above cases has much affect as the tooth fairy.
 
I have a bit of experience with this from building drilling derricks, skids for the gas compression industry, and structural fab.

Beam straightening is as much an art as a science. Knowing where to heat, how wide an area to heat, and how much heat to use takes a thorough knowledge of steel. You have to factor in material thickness, the amount of heat sink in the member (cooling rate), as well as knowing which way the material will expand and shrink from heating and cooling. The journeyman who taught me how to do it did everything by eye and marked out the areas he wanted to heat with a soapstone beforehand. Overheat the beam, or heat it in the wrong spot or sequence and you're screwed. I would stress that this will only work well on mild steel. Alloy steel shapes (stainless or wear-resistant / chrome-moly bearing steels) can have inherent stress in the material from the HT / tempering / manufacturing process and can warp unexpectedly with heat.

From what I understand of it at this point, blade warp in quench is caused by uneven cooling which causes uneven stress in the material (faster cooling in one area causes more stress in that side/area) similar to the bimetallic strip in your thermostat.

There are no dumb questions, but magnetism is a property of steel - not a method of working it.

Nathan
 
I am mainly a pipe fitter and have worked with pipe for many years. I have heard that if you lay joints of pipe out with the ends north to south and leave it set for a few years it will pick up a bit of magnetism and then be harder to weld. I am not sure of this one way or the other. I do know for sure that guys in the steel related industries love to pull a guys leg:eek:
 
Havn't read everythig, only the first few posts.

I don't think it would work. Red hot steel is not even magnetic.
 
You have to be patient - let the magnetic field work while you go for the bucket of steam !!
 
ib2v4u said:
I am mainly a pipe fitter and have worked with pipe for many years. I have heard that if you lay joints of pipe out with the ends north to south and leave it set for a few years it will pick up a bit of magnetism and then be harder to weld. I am not sure of this one way or the other. I do know for sure that guys in the steel related industries love to pull a guys leg:eek:
Click to expand...

If you want to get the field parallel to the pipe, in Seattle, you would have to point the pipe 17° East of North and stand it up to 69.3° above horizontal.

That would not line up the magnetic axes of the steel, however. To do that efficiently, you would have to heat to non-magnetic (above the Curie Temperature for the steel) and hold it right at the transition for many centuries.

If you could subject the pipe to a strong enough field, it could become magnetized, but the Earth's field intensity is orders of magnitude too weak.

There are many old wives (smiths?) tales about steel and the Earth's magnetic field.
 
Hey, cool trick for any of you with a TIG. A great trick I heard about and used recently. You can use it just like an OA torch to heat metal. In fact, I think it is better because it is more concentrated and has foot control. So the next time you need to heat the hell out of something (such as heat drawing a bend) grab the TIG. Seriously, I couldn't believe how well it works. This is with Argon, not Helium.

For y'all with no idea what I mean by "heat draw":

When you heat one side, it expands and softens. The soft expanded metal (now under compressive forces) yields a bit in this state. As it cools and shrinks to normal size, it pulls past where it started, straightening the bend. So to straighten a bend, heat the outside of the bend then let it cool. As said above, it is a bit of an art form.
 
And Nathan, don't try that with hardened tool steel. It was a 12"x20"x1" tool steel plate warped in HT. They tried the torch thing and got TWO 12"x20"x1/2" pieces !!! Never saw that type of failure before or since !!!
 
mete said:
And Nathan, don't try that with hardened tool steel. It was a 12"x20"x1" tool steel plate warped in HT. They tried the torch thing and got TWO 12"x20"x1/2" pieces !!! Never saw that type of failure before or since !!!
Click to expand...


That's a neat trick. It might be really useful if you could do it more then once, eh? Do you think there was a defect in the bar?

I once made some beautiful go/no-go gages in O1. Perfectly round and perfectly smooth. Pulled them out of the oil and sat them on the work bench. One fell over. Hadn't been tempered yet. Cracked cleanly straight through the middle. Feh.
 
ib2v4u said:
I am mainly a pipe fitter and have worked with pipe for many years. I have heard that if you lay joints of pipe out with the ends north to south and leave it set for a few years it will pick up a bit of magnetism and then be harder to weld. I am not sure of this one way or the other. I do know for sure that guys in the steel related industries love to pull a guys leg:eek:
Click to expand...

Creation of magnetic fields in steel during welding has nothing to do with magnetic north. It has everything to do with physics, namely the magnetic fields induced by an electrical current travelling through the workpiece in one direction (DC - direct current). These magnetic fields disrupt the transfer of weld metal between the electrode and the workpiece through the arc, causing arc blow (wandering, erratic arc) and lots of spatter. You can get rid of it by switching polarity while using DC to either electrode negative or positive, switching to AC current (current switches polarity (direction) about 60 times/sec which doesn't allow a mag. field to form), or by moving your ground clamp to a different location (different path of electrical travel).
 
mete said:
You have to be patient - let the magnetic field work while you go for the bucket of steam !!
Click to expand...

Damn you beat me to the bucket of steam :D Maybe a left handed smoke shifter will help :D

If you want a cool example of magnetic field while welding coil up some of the electrode lead in a pile of grinding dust and watch the steel dance as the arc burns (You gotta find a way to entertain yourself when your an apprentice)
 
Nathan, we had etchants to find grinding damage. I etched the plate and found obvious indications that a torch had been passed over both sides, showing up as a series of stripes !! The only defect was the torch man. There wasn't just one fracture origin but about a dozen , truly strange.
 
Mete,

That sounds similar to some of the longitudinal cracking I've seen in welds because of lack of preheat on thick material. The edges of the weld cool too fast because of the heat being drawn out into the parent metal too quickly. If they only heated the surface of the material on both sides, the cool area in the center of the plate could crack because of the material shrinking towards the heated surface, especially if the heated areas (say 1/4" on either side leaving 3/8-1/2" of cooler material in the middle) were quenched to try to speed up the process (common practice on mild steel).

Nathan
 
Yes I have seen a lot of examples of magnetism and welding. You often get a weird effect in tight corners. Another thing that can help if a few wraps of the lead around the material.

On the splitting things. When I first started making knives I decided to take a power hack saw blade (about 1 1/4" wide 1/16" and about a ft long) and weld stripes of different rod down the sides and leave the edge alone. That way I would thicken the blade and have some interesting lines when I etched it. After th first pass PING and it split in 2 length wise and both curved back. LOL another failed experiment. I keep thinking about tryin again on some annealed stuff like 15N20
 
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