Heat Treating Parts.

I got grates from Meyers. The instructions state to heat then 5 times to 600 and cool them. So they harden. Can I just heat them in my oven and throw them in the snow or do I have to slow cool them.

Slow cool them or they will crack if they cool too fast. Cast likes SLOW changes.

That seems a little odd, never heard of heat treating cast iron, maybe tempering it. I wouldnt cool it rapidly.
ray

You want to cool them slowly. I worked in a heat treat for 5 yrs. I never worked with cast but the principle should be the same. If you cool them quickly they will lose their temper and make them brittle. By cooling them slowly, what your doing is stress relieving them.

Jeff

Just received my new front grill for the Vermont Casting yesterday, from Woodmanspartsplus.com. The directions said to season it with five small kindling fires, or put it in the oven starting at 325 and every half hour rise the temp by 25 deg. till the oven is maxed out, then let cool. This should extend the life of cast parts used in stoves.

It sounds to me that the foundrys that are making these parts are by-passing a important part of the process, hopefully they at the very least passed the savings on down (yea sure) but I just don`t believe you could get the proper heat treating out of a domestic oven.

It is not heat treating the way you would temper steel. Cast iron doesn't have enough carbon to be tempered per say. As ceccil said, it is only a stress relief process and does work. Steel parts used on stoves are a low carbon mild steel.

The casting process has a lot of steps from the prehesting of the sand to the amount of time before demolding & finishing, not all parts are put into the ovens after grinding for stress relief but apparently if the supplier feels this needs to be done then IMO it should have been done beforehand, cast iron needs a much higher temp. than steel.

samhill wrote: if the supplier feels this needs to be done then IMO it should have been done beforehand

I agree, why would you sell a product that is not ready to use. Also what happens if it's not done properly? Are they going to honor any warrenty?

Jeff

No doubt a time and cost issue. The public wants a $1500 stove. How many are willing to buy a $3000 stove? (small exaggeration) but point made. Carbon steel and iron have near the same melting point. We aren't talking about bringing the cast parts to cherry red for stress relief. 600 deg. is recommended. My oven hit 575. A few low temp burns would have worked also.
A small precaution I would recommend for any new stove owner to follow, burn a few small fires before trying to see how hot the stove will run.
It's akin to breaking in the motor on your new car.

Diesel wrote:I got grates from Meyers. The instructions state to heat then 5 times to 600 and cool them. So they harden. Can I just heat them in my oven and throw them in the snow or do I have to slow cool them.

This is done to normalize the casting, if you don't do it they can bend or crack much easier over the life of the grate from the heat. Its purpose is to relieve stresses inherent in cast products due to the nature of the grain. This would be pointless for something that never gets heated, but coal fires tend to heat grates up pretty good so it is recommended and will extend the life of the grate considerably. Allow them to cool slowly as posted previously, throwing them in the snow is the last thing you want to do. You will wind up with grate-lets.

coaledsweat wrote: grate-lets.

Thats funny!!

Jeff

Diesel wrote:I got grates from Meyers. The instructions state to heat then 5 times to 600 and cool them. So they harden. Can I just heat them in my oven and throw them in the snow or do I have to slow cool them.

In my opinion this is a total load of crap. Your grates are most likely a grey iron casting.

You didn't say if it's 600 F or 600 C but I'd guess it is 600 F.

At that low of a temperature, you aren't doing much of anything to grey cast iron. You then go on to say Meyers said this process is to harden the parts? Sorry, no way. To harden grey iron, you have to first heat it to around 1660F, quench it and them temper. Tempering has a range of between 400 and 1000 F depending upon what you want as an end product. Your grates are going to be in a fire sitting at temps well above 1000 F so any kind of heat treatment would get obliterated anyway so that would make no sense. They can't send you quenched parts because there is a time constraint between quenching and tempering, wait to long and the parts crack just sitting there. So a tempering step is not the answer.

Stress relief? Well maybe. But grey iron is usually stress relieved at higher temps - like 900 to 1100 F. Also, if stress relief is the desire, then both heating and cooling rates are specified, especially cooling rates. Grey iron prefers slow temperature changes.

If you wanted to be nice to your new grates, I'd suggest you put them in your oven cold. Turn it on to it's highests setting - probably about 550 F - let it fully warm up with the grates in the oven and then let them sit like that for about 30 minutes to an hour then turn the oven off. Don't open the door and just let the whole oven and grates cool down slowly.

Just for general information - cast irons have higher carbon contents that steels. A rule of thumb is steels run up to about 2% carbon content. Cast irons run from about 2% carbon content through about 4%.

dj

Made me have to look that up. I stand corrected. I was thinking of pure iron which has little to no carbon, thus can't be hardened and tempered. 1.5%-2.5% carbon=white cast 2.5%-4%= grey cast.
I think they should still be tempered for stress relief. At least by letting cool between a few low temp fires before running full out.

I still stand behind my first thought, if you buy a object for an intended purpose it should be ready to be put to use for that purpose. Would you buy a new car if they tell you you`ll have to tow it home & put all the fluids in & tune it up before you can drive it. Unless they are deeply discounting those grates I think they are ripping people off, if they are letting them go out the foundry door without being stress reliefed then what other shortcuts are they taking.