heat tempering music wire after brazing

I've made up several very nice control horns using some laser cut uprights and 1/8 mw and 3/32 mw. In order to do a good job of brazing with the silver the wire must reach over red hot temperatures. The parts are very strong and seem more than "enough". I'm very happy with the brazing strength and appearance.

The question then is; is it necessary to re-temper the mw? If it is preferred then how do you do it? I don't want it so hard that it becomes brittle.

As it is they are tweakable, and can endure some significant torque without taking a set. So, the other question is are they good as is?

What say the metalurgists?

Bruce

Do not just get them red and dunk them. Very extremely brittle, I tried that one.

Hi Bruce:

I've always left mine soft. ie as they are when done brazing or silver soldering.

You can quench them to get them brittle hard again but the problem is then annealing them down so they dont break. Without a real well controlled annealing oven, your chances are iffy at best. BEst to leave them tweakable soft IMHO.


BTW.. the way we do this on plane blades and chisels is to polish the edge so one can see the discoloration on heating, then heat until one "draws" the temper color desired (blue, straw, etc to the proper position on the edge. Problem is with the wire, its really hard to do this accurately and repeatably. Thus the need for a temp controlled oven.


FWIW
Curt

>BTW.. the way we do this on plane blades and chisels is to
>polish the edge so one can see the discoloration on heating,
>then heat until one "draws" the temper color desired
>(blue, straw, etc to the proper position on the edge. Problem
>is with the wire, its really hard to do this accurately and
>repeatably. Thus the need for a temp controlled oven.
>
>
>FWIW
>Curt

yep, straw is what you want, just don't apply heat to where you plan on tempering otherwise you gonna have a mess. let the straw come down and everything is in the hay then.

I remember a great thread from several years back in which Tom Morris described his brazing and tempering technique. Unfortunately that thread has been lost.

Ron Burn stepped up and provided this advice: http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=82455&mesg_id=82455&listing_type=search

Derek

Bruce ...to re-temper the wire after brazing. Heat the wire to a cold blue stage about 400-500 hold temp for a few seconds (10max)...The wire will change color. IF you can get a hold of a "TEMP STICK" and buy one of 400-500 degrees you can re-temper your landing gear, horns and ECT. ALSO Charley Bruce is a good contact. Maybe someone can help with that...

A temp stick is a crayon type wax material that melts at given temperatures when you touch the material being heated a must for metal dudes and us welders.

I do a lot of silv-brazing…

Hope to see you soon............OHHHH I also heat treat mine! with "kasnet"

Just put them in your oven @ 500 deg. for about an hour, take them out and let air cool,"Do Not"!! quench in water as this will cause brittlness.

TOOLMAKER...is right. IT'S a simple thing. Don't over think.

Bruce,

You do not want to temper the wire. You want it to remain annealed. There is no force of nature that a control line plane will encounter(other than a non-conforming air-to-ground interface) that will cause a 1/8" flap or elevator horn to bend even in this softer state.

Should you decide to temper the wire there are no known forces in this or any parallel universe that would allow you to adjust the horn after installation.

If you do decide to go the "quench" method, remember to use premium chocolate milk as the liquid.


Kim.

Perhaps a final thought would be to use 4130 instead of music wire to begin with.

Curt

Finally had a little time to add a bit to this one! There seems to be a bit of info here which is confusing to some of us. Firstly, when we give technical info, it's best to give ALL info rather than presume.

Due to the fact the forum is followed worldwide, I feel that when we give temperatures, we should give the units we are working in.............. believe me it can make a difference! An example only last week was my wife, bless her soul, made a cake from an old recipe. Yes, the good book said 375 deg so the stove got set to 375 deg and after 30 minutes, the aroma was more like that of a crematorium. You see the stove is in Celsius and her book was in F!

The temps given here in reference to the wire doesn't give us what units we are working in.

Secondly, there seems confusion regarding HARDNESS, TEMPER and ANNEALING.

If we heat the wire to the temperature required for the silver brazing which is a red heat, the wire at that point would have ALL the hardness drawn by TEMPERING and would be in it's ANNEALED state ( as near as we can have for the purpose here). With this we can't simply heat it to a temperature under the critical range to regain hardness (described in another post as temper). If we need this, the steel has to be HARDENED again which would be at a temperature (maybe say 760 C not knowing the ingredients of the spring steel) which is above that of the silver brazing which means the horn will fall apart at the joint! After we HARDEN the steel, that's when it is heated to the temps mentioned in a post above which I presume is F deg for tempering or reducing the hardness/brittleness so the steel doesn't fracture under load such as when we "tweek" the horn for adjustment/alignment.

I think Ron B has explained actual metalurgy on soft/hard metals elswhere here recently so do a search on that to find explanation.

With all of this said, when we silver braze the horns, you will generally find that about 8mm each side of the horn has been tempered quite a bit (depending on the size of the flame envelope)but may not be back to it's full annealed state. The mass of the wire beside the heated section may be enough to quench a small portion back towards the horn. As mentioned also in another post, leave it as is and use it in it's tweekable state. It's strong enough.

HH

If the material has enough carbon content the wire will "air harden" and should be tempered. One never knows for sure the carbon content of the wire we use,especially if if came from China. All brazed horns should be temperd as a percaution even if you can tweek them. If you can set your home oven at 375 C thats one #### of an oven.

If you can set your home oven at 375 C thats one #### of an oven.

Bakes a chicken in fifteen seconds!

Are we all referring to either carbon steel or carbon laced stainless when we refer to "music wire"? If I remember correctly, pure stainless does not have carbon and will not temper.

George

>Finally had a little time to add a bit to this one! There
>seems to be a bit of info here which is confusing to some of
>us. Firstly, when we give technical info, it's best to give
>ALL info rather than presume.
>
>Due to the fact the forum is followed worldwide, I feel that
>when we give temperatures, we should give the units we are
>working in.............. believe me it can make a difference!
> An example only last week was my wife, bless her soul, made a
>cake from an old recipe. Yes, the good book said 375 deg so
>the stove got set to 375 deg and after 30 minutes, the aroma
>was more like that of a crematorium. x( You see the stove is
>in Celsius and her book was in F!
>
>The temps given here in reference to the wire doesn't give us
>what units we are working in.
>
>(1)Secondly, there seems confusion regarding HARDNESS, TEMPER and
>ANNEALING.>
>If we heat the wire to the temperature required for the silver
>brazing which is a red heat, the wire at that point would have
>ALL the hardness drawn by TEMPERING and would be in it's
>ANNEALED state ( as near as we can have for the purpose here).
> With this we can't simply heat it to a temperature under the
>critical range to regain hardness (described in another post
>as temper). If we need this, the steel has to be HARDENED
>again which would be at a temperature (maybe say 760 C not
>knowing the ingredients of the spring steel) which is above
>that of the silver brazing which means the horn will fall
>apart at the joint! After we HARDEN the steel, that's when
>it is heated to the temps mentioned in a post above which I
>presume is F deg for tempering or reducing the
>hardness/brittleness so the steel doesn't fracture under load
>such as when we "tweek" the horn for
>adjustment/alignment.
>
>I think Ron B has explained actual metalurgy on soft/hard
>metals elswhere here recently so do a search on that to find
>explanation.
>
>With all of this said, when we silver braze the horns, you
>will generally find that about 8mm each side of the horn has
>been tempered quite a bit (depending on the size of the flame
>envelope)but may not be back to it's full annealed state. The
>mass of the wire beside the heated section may be enough to
>quench a small portion back towards the horn. As mentioned
>also in another post, leave it as is and use it in it's
>tweekable state. It's strong enough.
>
>HH
>
>


Ron B.
F4Fguy

(1) There's also a great deal of confusion in the difference between "strength" and "stiffness". All steels have essentially the same "stiffness", or resistance to deformation, the material modulus. Changing the shape of the part, or the nature of the loading, whether tensile, compression, or torsional, may affect the bending resistance, but changing the steel alloy will not.

"Strength" can be changed dramatically by alloying or heat treating or both, this does not change the stiffness. As long as the loads are within the elastic limits (the stress level below which the material returns to its original shape when unloaded), the force to deflect to a given position is the same for all steels. The BIIIGG difference comes in the bending distance reqired to achieve the elastic limit. The stronger the steel, or the harder it is after heat treatment,the farther it can be deflected without "taking a set". This is true even to the point of breakage in a part that is very hard and not tempered or annealed.

Soft, low alloy, low carbon steels are easily bent and are, for "tweakable" parts, ideal. If music wire is used it should be drawn as much as possible or, ideally, annealed.

In an earlier post on this subject, I recommended drill rod. I still do. This is an alloyed tool steel which is supplied fully annealed. It may air harden locally at the braze joint (although I seriously doubt it gets to transformation temperature), but it will remain soft and tweakable over most of it's length,and it's toughness will allow many adjustments without breaking.

I know, long and boring ZZZZZZZZZZZZZZZZZZZZZ, but it's the least technical I can see to make it, and I'm still not satified that it really says it all.

Ron B.

>In an earlier post on this subject, I recommended drill rod. I
>still do. This is an alloyed tool steel which is supplied
>fully annealed. It may air harden locally at the braze joint
>(although I seriously doubt it gets to transformation
>temperature), but it will remain soft and tweakable over most
>of it's length,and it's toughness will allow many adjustments
>without breaking.
>
>I know, long and boring ZZZZZZZZZZZZZZZZZZZZZ, but it's the
>least technical I can see to make it, and I'm still not
>satified that it really says it all.
>
>Ron B.

Ron,
I think you did an admirable job in the context of this discussion.
The discussion of stiffness vs strength came up at the flying field here in Tucson one day and after about half an hour trying to give some understanding of the subject to the nontechnical folks there, most just walked away shaking their heads.
Guess I didn't do so well at explaining it.

Randy C

>>If you can set your home oven at 375 C thats one #### of an oven.

Bakes a chicken in fifteen seconds!<<

Not sure on the actual max temp on the old kitchen oven as I can't find the book and the setting marks have gone so the stated degrees are only a guess! . The part about cremating the cake is true as she read the book as number rather than C or F and so on The main point I was making there was to put into our tech info the units etc which we are working in.

Thanks to Ron B for finding that bit for me and adding it into the post.

Off topic...... thanks for the thoughts Ron with our fires down south in Victoria, OZ. There have been at least 180 odd people confirmed dead with expectations it could go as high as 300. Some small mountain towns are completely gone. Last reports were some 1800 homes lost in Victoria as of last night. One 39 year old firebug arrested over one of the blazes. Should give him a free ride in one of the water bomber helis.

Back on topic! Yes, as a toolmaker of many years as well as a teacher of engineering I do understand heat treatment of steels but we try to keep it in simple terms here for all to understand. Give me alloy steels used in toolmaking and heat treatment info and controlled furnaces and all is sweet. Here we have unknown quality spring steel which we have heated to an unknown temperature (we can only guess) during the silver brazing.

If we heat the spring steel again to a temperature BELOW the critical or transformation range it can't increase the hardness. It'll just give it "a perty colour" .... straw, purple or whatever turns us on. What it will do is temper or lower the hardness the whole length of the wire if we place the unit in an oven rather than a section of it as has been done during the silver brazing operation.

As Ron states above, if we use "drill rod" or as we know it "Downunder", Silver Steel, the material most likely doesn't get to the transformation temperature and wouldn't harden. The ASSAB or Bohler Silver Steel which was commonly used here had a transformation temperature of 790 - 810 Deg C and was an oil quenching steel. If cooled in still air there was no hardening taking place. If my memory is correct, this steel has around 0.9% carbon so not an over high content but other alloying elements give the results we need.

A usefull link below. Download the chart from Bohler-Udderholm, print it off and hang it on the workshop wall. A great refference chart.

http://www.buau.com.au/english/files/Temperature_Guide.pdf

Hope this helps answer a bit more.

HH

Well said Herb, and a new chart for my wall!
I would think that the "Piano Wire" we get these days would be a plain, high carbon steel with some heat treatment as it is drawn. The temperature range used for silver soldering (silver brazing) could easily get to 350 C or more, depending on the flame, and water, or oil, quenching will increase the hardness and therefore the brittleness - which is what we want to avoid! Try it sometime, heat some 1/8" wire to a dark red then quench and try to bend, it will certainly shatter, try to file it and then throw the file away.
Only slow air cool after silver brazing, then try flexing the wire to make sure it has not hardened and become brittle. Only use enough heat to just melt the silver, any more and it will oxidize both surfaces and you will end up with a dry joint. (ask me how I know!)

Off topic and again well said Herb, many thanks to everyone for their kind thoughts re the bushfires - and floods,
From a very soggy Coffs Harbour

Hi Dave, hope you dry out soon! Maybe the general spring steel we get is the cheaper silicon manganese stuff rather than the chrome/vanadium etc.

Temperature varies for silver brazing depending on silver etc content. It's up above the 600 deg C at least so that's a dull rd heat ..............still well under the temperature for hardening but where the problem arises is that we don't usually do our work in a dimly lit room so chances are that the temp is in the high 700 deg C so can be a problem if quenched in any way.

Anyone who has access to "Machinery's Handbook" can check the info there on all this stuff. A real handy reference book.

What many don't realise is that the other steel mentioned through this subject, drill rod or "silver steel" is actually a good quality tool steel used in blanking dies and punches. Also good in the soft state for horns and belcranks if you get the flat stock known as "gauge plate" due to being that bit harder with the 0.9% carbon content and a bit of tungsten!!

HH

Agreed Herb, can't imagine any fancy steels these days, we both remember the real 12swg wire that was better than the current 1/8" stuff. Anyway, the gen is that you can't (quench and) temper this wire without a proper furnace, and it is not necessary anyway for our purposes.
But, don't fall into the trap of trying to break the flux away by cooling quickly, cool slowly and chip the flux off.
I have tried a crude tempering but ended up with a brittle failure, which makes me think it is probably a Silicone/Manganese with a high carbon content.
BTW, has anybody done a proper analysis of the loads on a control horn? do we really need 1/8" wire when 3/32" is so much lighter and easier to adjust? could something else work as well, remember the old kits that used a small strip of hardwood between the elevators?
cheers

Do they make wire any bigger than 3/32" Dave?? Well I did actually use the old 12 swg Brit stuff (0.104" dia from memory) for horns but that was to the early 70s at the latest. Not sure on 3/32" for the 75 size model though. Will go to 1/8" for that one.

I should have sent the little muffle furnace off from work when I had a chance Dave! Still a part timer with TAFE so have use of it all still. Makes it easy with controlled temperatures but still can do ok with my mate oxy/acet.

HH

You never know what you need until you retire Herb,
A good reference for metals is www.matweb.com, all sorts of good stuff!, including ASTM A228 Spring steel music wire: Cold drawn. High tensile strength and uniform mechanical properties
Hardness; 41 - 60 Rockwell C (Bl...y hard)
Ultimate tensile strength 1590 - 2750 MPa (Bl...y strong)
Carbon 0.7 - 1.0% (High!, making it more brittle)
Manganese 0.2 - 0.6%
But the important point is "Maximum service temperature in air 120C", in other words, any heating can cause changes to it's properties.
So, in answer to the original query, No, it is not possible, nor is it necessary to carry out any heat treatment, other than cooling slowly.
Having never built a model with a 75 (apart from a Mills .75) I wouldn't know what is really needed.
Cheers

G'day Herb

An old Lysaght Referee tells me that 12 SWG is indeed, 0.104" dia.

Not bad for an old bloke.

Cheers, Geoff

>Hi Dave, hope you dry out soon! Maybe the general spring
>steel we get is the cheaper silicon manganese stuff rather
>than the chrome/vanadium etc.
>
>Temperature varies for silver brazing depending on silver etc
>content. It's up above the 600 deg C at least so that's a
>dull rd heat ..............still well under the temperature
>for hardening but where the problem arises is that we don't
>usually do our work in a dimly lit room so chances are that
>the temp is in the high 700 deg C so can be a problem if
>quenched in any way.
>
>Anyone who has access to "Machinery's Handbook" can
>check the info there on all this stuff. A real handy
>reference book.
>
>What many don't realise is that the other steel mentioned
>through this subject, drill rod or "silver steel" is
>actually a good quality tool steel used in blanking dies and
>punches. Also good in the soft state for horns and belcranks
>if you get the flat stock known as "gauge plate"
>due to being that bit harder with the 0.9% carbon content and
>a bit of tungsten!!
>
>HH


Ron B.
F4Fguy

Dallas,

Here, in the US, music wire is (usually) 1080 or 1095 plain carbon steel. A large part of the hardness is from the work hardening of drawing it into wire. As you will note, a different kind of "drawing" than in the heat treatment context. If heated above transformation temp and quenched, it gets very hard and brittle. unless fully annealed, it will be subject to fracture due to almost "0" elongation. If drawn to an acceptable level of toughness it will be very difficult to "tweak". It really needs to be fully annealed. This is only possible, in a small mass like this, if the whole part is heated to lower critical temp ≈ 1330°F, then furnace cooled to well below critical. Otherwise it is quite possible to air quench if the braze area was overheated. That's the real beauty of using drill rod. If it hardens locally it really doesn't matter a great deal. it still has enough toughness to meet the purpose. This especially true if torch brazing is used, as you needn't worry too much about local hardening.

Hope this makes some kind of sense,

Ron B.

Had some of the 3/32" K & S music wire some time back Ron and was so hard it needed more than the general minimum bend radius to prevent fracture. The whole length was the same. Needed tempering to get it to work properly. I've got a good supply of various sizes of spring steel wire (well actually the "old work" has it ) from around 0.014" but all is in coil form. The small stuff is good for wrist pin circlips if I had a need for a few hundred thousand of them!! Now Dave will want some next time I see him [photo not recovered: sipcof.gif]

Hope all of our ramblings have been useful.

HH

Of course he will Herb, actually, we have a piano tuner near us, we should go and pay him a visit, I'll bet he has real piano wire!, even it is coiled it must straighten, ever seen a cylindrical piano?

Had the same problem with 1/8" K & S, ended up chucking a whole length out, brittle failure with a 1.5mm bend radius, if it was going to fail like that you would not want to put your (model's) life on it.
Batten down the hatches, the rain is heading your way!