Welding Question

I'd grind the edges so that I have V's inside and out for the bead. Then make a short pass inside, followed by a short pass directly opposite it on the outside. It'd be like tack welding it. The less heat you can out into the work piece the less it will warp.

Also, if you're rolling it with a three roll machine, you could finish the welds flush and throw it back in the roller to take out any warpage.

Try it.

Exactly, alternate your passes (side to side), keep them short and you will limit any possible warping. But as i noticed another reader post you could cut it out of pipe as long as its the 6" I.D. that's important, not the outside Diameter as well. Being as you want an O.D. Pipe will probably not work as it is based upon the I.D.

Not really an answer to your question, but how about a ring cut from pipe?

Are your dimensions critical enough to justify a special order? These guys sell 6" OD steel tube, wall thickness .250". According to their service information, you can probably get them to slice the rings, too.

I am assuming these are parts for your train wheels. How many will you need?

I think it depends on the the size of "appreciable". I don't know your situation. I'd be tempted to try it, and if I was particularly concerned about maintaining circularity, I'd apply heat to anneal it before removing from the form and clamps.

Fusion welding will always create some distortion. A narrow weld such as a resistance or electron beam weld will result in less distortion than a torch or arc weld. Unless your tolerances are tight, the difference may not be important.

Welding causes stress in metal. The way to make sure ´that its not going to be a problem is to "stress relieve", usually by heating to some specific temperature and letting it cool down.

Look here:-

http://www.aws.org/wj/sept01/cullison.html

for the full article that I took the following from:-

Welding, in particular, because of the rapid thermal expansion and contraction created along a very localized area, is a prime source of residual stress. A very high heat source is applied to a small area relative to the cooler surrounding area. That point where the arc is directed is rapidly heated from ambient temperature to temperatures that can be in excess of 3000°F. The metal expands as it is brought to a molten state. As the molten weld pool solidifies along the joint, there is resistance to its shrinkage by the already solidified weld metal and the unmelted base metal adjacent to the weld. This resistance creates a tensile strain in the longitudinal and transverse directions of the weld. Distortion is often the result, and if the stress is excessive, buckling, stress corrosion cracking, and shortened fatigue life are possible.

All welds will have some residual stress, and it will never be totally reduced to zero strain. But the level of stress can be very high depending on certain conditions. Heat input, base metal thickness, cooling rate, restraint of the weldment, and welding process play roles in the level of residual stress induced into a weldment.

Thermal or Nonthermal
There are two major approaches to stress relieving: thermal and mechanical. A major difference between the two is thermal treatment, which in addition to relieving stress, will also effect metallugical changes in the metal. A postweld heat treatment entails uniform heating of the weldment, holding at temperature, and then a controlled cooling.

As metal becomes hotter, it becomes weaker. Once a certain temperature is reached, there is a reduction in yield strength from the rated property of the steel. The residual stress decreases to that of the lower yield strength, and it is thereby relieved. The effect sometimes visibly manifests itself in the straightening of a distorted material.

For carbon and low-alloy steels, stress relieving is commonly performed in the range of 1100° to 1350°F. The time at which the weldment is held at temperature is dependent on the thickness of the workpiece and its chemical composition.

There is plenty of info about this on the internet.

I hope this helps.

As metal becomes hotter, it becomes weaker.

Yes, this is for the train wheels. My original thought was to use rings cut from pipe or tube, but the welded ring idea was also on the table. I can accept a small amount of distortion due to welding since I will be final machining on the lathe.

I look upon this as a classic product design which combines low cost and high quality. Although I may only make 12 of these wheels, the potential will be there to mass produce them if anyone would be interested. Right now, I am doing this as a hobby; too old to hold a 9-5 job, but engineering and technology always holds my interest.

I am quite the boring fellow. I prefer to read machine and fastener catalogs than watch football or soap operas.

Rolled rings are commonly welded, ground, and re-rolled, to obtain circularity.

Given a good tradesman, you're hard pressed to find the join.

My question would be; but what of the flange? ^{_{(as in train wheels)}}

The flange would be machined after the strip is in the form of a ring.

i want to know how.

To roll a ring to these dimension is not impossible but, very difficult. When rolling any type of ring you have at both ends of the stock a flat section that does not roll round. This is caused by the roller spacing and where it contacts metal to begin the shaping process. In order to make a round ring the steel is then calculated out to a longer dimension to account for this flat area. Rings are then cut at the properly rolled area to make round ring. I only bring this up due to the sizes you are suggesting for use. As one of the others have mentioned, you would be better off at 6" OD getting steel tubing and slicing the sections off. You had mentioned that some machining can be tolerated. So to me this would make better sense to produce this way from a cost stand point.

Good point. This is why I suggested putting the ring back through the rolling process after welding.

'...or assuming the rings shape is held with a form and clamps...'

Although forms/jigs are very useful in set up and tacking of a workpiece, these should generally be removed prior to welding. Restricting the thermal expansion/contraction of a workpiece during welding typically results in far greater distortion and internal stresses than would occur in the workpiece had the movement not been restricted with a form.

The suggestion of making equal passes inside and outside is good advice.

TIG welding with a pulser will certainly provide better potential for low distortion than MIG or stick.

You might consider brazing or perhaps braze welding for a lower heat, lower distortion option.

....in the bigger picture, I can't help feeling like you are looking in the wrong part of the shop. Lathes are much better at making circles than welding machines....

GA for some good tpical tips. I prefer brazing in many situations, or even silver soldering....if the "contact" areas are correctly designed, the strength of the connection can be radically improved without the stress of welding....

With a cross section of .250" x .750", would I use a butt joint or a lap joint using brazing or silver solder? By a butt joint, I don't know the name for the joint, but a long bevel is ground on the ends and then lapped over each other. (skeved???)

I suspect you are over-thinking the problem. If you fusion weld the rolled ring, there will be no stress, only slight distortion that can be machined out on a lathe. If you fusion weld while restraining the ring on a circular mandrel, there will be some stress, but less distortion (strain). It's true that brazing or silver soldering will provide lower stress/distortion, but it will also give lower strength and force you into thinking about how to increase the bond area by using a skived joint. If this item were fabricated from difficult to weld steel, there would be additional concerns, but as this is low carbon cold rolled, I recommend you just weld it.