Annealing steel parts after welding?

[Edster]

I make parts for actuators that are made from tube that I cut a shoulder on and cut to length. I press stamped washers on the shoulder then I weld the washers on to the tube. I have to bore out the tube to .7575 +/- .0025. It seems like the parts are getting hardened slightly near the welds and It's affecting my dimensions. The part is perfect except it's a few thou smaller on the very end near the weld. The tube is 1018 DOM and the steel is cold roll. I'm tig welding these with no filler metal, just fusing them together. I'd like to anneal them somehow, but I don't know anything about annealing. I used to swage these parts together with a BFH, but sometimes the parts would come apart in the cnc. Welding seems like the way to go. I have a few thousand of these to make a month and I need to figure out how hot to go for how long and how long to cool. Any help would be appreciated.

[Bowman]

Hmmm. No welding expert here but I have been down the street. Do you think the issue could be because you aren't using a filler material to join the washer to the tube? I would think that using the push the puddle technique and using the material from the pieces your trying to weld together as the filler may be causing lose of material in one spot as it flows to another spot. Are you welding this around the external seem or internal or both? Give it a try using some filler materiel and then just turn/bore down the excess to the desired dimension and see if that works. To anneal heat till red hot and quick quench in water that should re-align the atoms and make it softer to work with. Like I said I am no expert on this subject but I did stay in a Holiday Inn last night.. ohh and took a few classes on this way back when in college...

Hope you work it out.

Bowman

[Geof]

Possibly what you should be considering is stress relieving not annealing. This is done at a lower temperature so it does not affect the properties of the steel as much. If you did anneal DOM you might find it difficult to get a good machined surface because the machining properties are not as good as in the work hardened state. One thing I suggest you try is preheating the piece before welding; the effect you are getting is largely due to the metal being heated in a small area which is then chilled rapidly by the surrounding material as the weld moves on. You should not need much preheat to reduce the chilling effect.

[Bowman]

True Geof.. Pre-heating is always a good practice.. And I should have mentioned that a full anneal will make the metal much softer until its either work hardened or heat treated. Stress relieving is also a good option but I am not sure what type of constant temperature levels you may have to maintain or time lengths you might be looking at. It all depends on the metal and thickness etc.

I remember my first demo of annealing when we took a basturd file and annealed it till it was easy to bend, then heat treated it back to full hardness to the point it would shatter if you tried to bend it back. Ahhhh metal is wacky weird wild stuff lol..

[motomitch1]

The parts are heated and held at the austenitic temperature for one-half to one hour per inch of thickness to allow the part to stabilize throughout as austenite. The steel is then cooled very slowly.

[Edster]

I just tried heating the parts with a rosebud till the were barley red hot and letting them cool to room temp naturally. It seems to work good. The finish is good, and it doesn't sound like a helicopter when i bore through that area like it use to. The size is also good. The parts need to be plated after machining and I'm not sure if using o/a will affect that. I really would like a small oven to do this in. Which get's me back to, how hot do I need to get these parts. I saw a small electric oven that went to around 1000 deg f, but I don't want to get it to find out it won't go hot enough. I'm definitly willing to experiment with time and temp etc. I just don't want to buy the wrong oven.

[WhiteTiger]

Annealing range for 1018 is 1575-1650 F. Time at temp 1/2 hr for small section (13 mm or less), 1 hr for 25mm section.

Recommended furnace cooling rate of 50F/hr over range from 1575 to 1300 for HB 111-149.

(from metals handbook)


Tiger

[NC Cams]

To add to Tiger's input:

After you weld, you can do high temp stress relieve at 1250 for 1-1.5 hr per inch of material thickness, 1 hour min as opposed to a true anneal. Furnace cool if possible.

After we weld low carbon steel (under 0.25 carbon) we usually normalize which helps "homogonize" the material. Anneal then normalize is called "double draw" and is REAL good to do if you'll carburize or do some other H/T later. Helps keep stuff from moving around.

We find that stuff stays REAL stable (distortion free) after doing the high temp stress relieve mentioned above...

[Edster]

I bought a small oven and I've got some experimenting to do.
Thanks for all the help!

[Edster]

600F for 1 hour is working pretty good.

Here are a few pics if anyone is interested.

http://www.ewwenterpriseinc.com/images/DSCF0001.JPG

http://www.ewwenterpriseinc.com/images/DSCF0002.JPG

http://www.ewwenterpriseinc.com/images/DSCF0003.JPG

http://www.ewwenterpriseinc.com/images/DSCF0004.JPG