Coating to Prevent Warping

[RyanMark]

Is anyone familiar with coating a piece to be heat treated with clay, sand, or something to prevent warping during the process?  If so, please elaborate.  Thank you!

[SoCal Dave]

Wouldn't a coating also change the heat treating process?  

[ThomasPowers]

Coating usually increases warping unless you can guarantee exact thicknesses everywhere---look at japanese swords they go into heat treat straight and are coated and quenched to produce the curve!

[Rich Hale]

If you are forging blades,,normalizing as a part of the whole heat treat process, may prevent warping,,,so can the way youi put the steel at the correct temperature into the correct quench that is also at the correct temp.

And if it is blades,,there is a whole knifemaking sectiion farther down the home page  here that has a wealth of information,,If youi choose to loook!

[Richard Furrer]

There is an adage "if you can not straighten a blade you can not make a blade".

 

Most of the time industry moves to higher alloy and less severe quenches to avoid cracking, warpage and other heat treat issues. Air hardening steel for example.

 

I know of no coating that prevents the detrimental occurrences of volume change/stress in heat treating.

 

What you can do is make a form to support the work. For steel blades it can be as simple as a thick flat steel bar with a clamp.

For other metals of odd shapes....such as say ...drum kit cymbals....then a top and bottom form of aluminum or copper cooled with water cooling channels or having holes to allow for water to get in/out may be in order. Or the same top/bottom press mold idea to be the step following a quench to force the item back into shape.

 

Ric

[RyanMark]

Cymbals, Ric?  How'd you guess? :) 

 

I have read a few references to such a coating from one cymbal manufacturer.  But, I'm thinking the coating is actually to help prevent excessive oxidization and tin sweat.   I figured if there was such a coating then you guys would know about it, thanks!

[Richard Furrer]

I would agree about the oxidation issue...any oxide prevented means more metal and less pickling to remove.

Liquid tin may be an issue with temp more than surface oxide.

 

There are several coatings I use made by Advanced Technical Products in Cincinnati, OH 513-851-6858

They may have one for bronze/coppers.

Using salt pots may be a good idea as well depending upon volume of production.....a pot large enough for a full cymbal would be, well, big.

 

Ric

[SagebrushBlades]

I clay coat every blade I make, and will be demonstrating my techniques at the Shenandoah Valley Blacksmiths Guild meeting in July...

That said, I will second what most others have already said, with one addition.

 

Claying steel prior to the quench can limit warpage or it can induce warpage, depending on how and where you apply it.

Japanese Katana are clayed prior to heat treat in a manner intended to protect the spine from hardening in the quench, giving a tougher overall blade for a given edge hardness.  I believe the curvature induced was an unintended side effect of that goal that became a symbol of a quality blade.

 

For something like a cymbal, protection from oxidation seems much more likely the goal since uneven hardness may distort sound quality.

It will also slow the quench and result in a tougher but softer structure than a direct quench.

 

I use a rough 50/50 mix of natural clay and fireplace ash for my coating, but a premixed fireplace cement works well also.  Just make sure to cure the coating before attempting to bring the item up to full hardening temp.

 

Bottom line is fiddle with it and see what works for your purpose.

[Steve Sells]

not sure how many steels are cymbol quailty, please explain?  most I have seen are a copper and some a silver alloy and a quenching will aneal those.  to harden we allow most metals to air cool so a clay coating will confuse things more, but you did not post this in the non ferous HT section,  So I may assume we are dealing with a steel alloy, a non hardened part IE the clay covered section, will mess up the ring, as that needs a constant grain matrix to ring, interupting that lattice would intorduce a deadening effect wouldnt it ?

[Nobody Special]

Not sure about how clay hardening would affect it, but varying hardness would not necessarily be completely undesirable in a cymbal unless it affected structural integrity.

 

It would definitely affect a "ring" by limiting vibration and production of overtones over entire surface (i.e. a deadening effect), but would be desirable for producing different overtones during the "clash/crash", much as in playing on the edge or center of a commercially produced brass cymbal, or the differing tension spots in a drum head. 

 

It's not uncommon for brass cymbals to become "work hardened" over certain parts over time, usually leading to the inevitable cracked cymbals after a strong hit.

 

Would think that  steel cymbals, since stiffer, would be more prone to produced long wave, standing overtones (a cleaner ring) than a crash.

 

Also depends how it's to be played, striking two together by hand? By mechanical action? One suspended by center and struck by stick? Or two and a stick, like a gong.

 

And besides, less vibration by no means indicates that it will be quiet. Horn's not as hard as the rest of the anvil, but it still rings. Former music major, out!

[RyanMark]

I didn't realize or forgot there was a non-ferrous HT section, sorry. 

 

Thank you all for your answers.

[Steve Sells]

as I mentioned most iron Iron work is the the opposite of most other metals and their alloys. so the information will be a lot different. Its relocated now :)