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Strange rolling problem


#1

Hi,

I’ve worked for two weeks on a strange problem in my workshop and
now I’ve run out of ideas.

The problem occurred when a claw in a basket mount came loose. The
solder joints were bad.

I then discovered that when I hard solder a sterling silver wire to
a sterling silver plate, the solder flows and looks good but
afterwards the wire can be pulled off and the solder stays on the
plate with a perfect imprint of the wire.

I started an investigation and in order to judge the quality of the
soldering process I made a standard layout: wires are numbered and
placed on a 0,5 mm silver sheet, the wires protruding a bit from the
plate. If they tend to roll, I separate them with small stiches in
the plate. Unknown wires are tested in pair together with a bad and a
good wire. They are soldered with hard solder and pickled. To test
the strength I take a pair of pliers and pull. If a wire is good, it
should not be possible to remove it from the plate.

I have replaced everything in the soldering process with new stuff;
charcoal, solder, tweezers, solder, flux, gas. I’ve ruled out the
silver, the amount of solder, the cleaning procedure, the heating
technique, the acid, the draw plate, the mineral oil for drawing
wire, the water quality, the size of the wire.

There is two things left to test, the brick I use to anneal on (not
likely the problem since I use it when drawing wire) and my 2 years
old Durston 100 Minimill combo. Purchased untreated wire works
perfectly and the same goes if I draw the wire but if I roll the wire
it doesn’t work, it won’t solder.

The rolling process works good and I anneal and pickle after 50%
size reduction. I occasionally get some flaking or thin hairs along
the edges of the wire which I remove by sanding. The rolled silver
wire look ok but has a greyish color that I do not remember having
seen before. I’ve clean the rolls with acetone but there was no
difference. I do not know if I’ve had this problem before because I
have not tried to pull off a soldered wire.

Now I am out of ideas for further testing and I hope that any of you
have any suggestions to what I can do.

Thanks,
Eva Nedergard
Atelje 54


#2

Eva

You just have uneven heating properties. Tin solder your wire first
then heat up the larger piece using conduction soldering techniques
moving your flame back and forth until solder runs from wire to
major object.


#3

Hi Eva,

Weird. Deeply weird.

Just to make sure I understand your issue correctly, you’re having
trouble with rolled wire pulling loose from a solder joint that runs
along the length of the rolled wire, correct?

I understand that you have removed all the obvious variables, and
all that remains is the fact that rolled wire has this problem but
unrolled wire doesn’t. Correct?

My first thought was oil or crud on the rolls, but you said you’d
cleaned them with acetone. That should get them down to bare metal,
and head off any trouble.

My next thought was to be suspicious of the wire itself. Are you
sure it isn’t the new ‘silver filled’ stuff? (Very heavy plate) That
would have an issue with pulling loose from that type of solder
joint if the plate had been thinned by rolling.

What confuses me is that you said it worked OK if you draw it,
rather than rolling. But that’s still my best guess. Where did you
get the wire?

If you take a new (unrolled) piece of it, and cut/file a long
diagonal taper on it, (just one side taper, not a long skinny cone).
If you then heat that (gently) you may see a little color difference
between the exposed core of the wire and the outside skin. (The goal
is just until it just barely starts to oxidize. No need to go to red
heat.) If you see two-tone wire, that’s your culprit right there.

Alternately, if you have any Ferric Chloride copper etching
solution, dump the tapered wire bit in there, and see what happens.

The Ferric Chloride will go after the brass core, and just plate
brown gunk onto the silver skin. Should be pretty obvious if there’s
a difference.

For whatever that was worth,
Brian

Ps. > you can avoid getting the little fins on your rolled wire by
rotating it 90 degrees between passes through the mill.

Personally, I roll twice in each groove, rotating 90 between the
first and second passes. Stops that problem.


#4

Thanks for advice Alberic, you understood me correctly. I only work
with solid sterling silver and yes I do rotate the wire when rolling.
And thanks Russ but in the standardized test I heat the plate from
below to treat all wires in the same way and always include a
positive and a negative control wire.

All my data says that the rolling process impairs the quality of the
silver - but that’s not true?

If I solder an untreated wire, the wire will stick to the plate
after soldering.

If I take wire from the same lot and draw it, the wire will stick to
the plate after soldering.

If I take wire from the same lot and run through the mill, the wire
will NOT stick to the plate after soldering

  • it can be pulled off with a pair of pliers but in some cases it
    sits so loose I could pull it off with my hands.

This result repeats itself every time.

Please, is there any more parameter you can think of?

Thanks
Eva


#5

To eliminate the mill being the culprit, flatten the wire with a
hammer and see if you get the same results as with the mill.

Paf Dvorak


#6

Hi Eva,

I’m still really suspicious of the wire itself. How thick is it?
(Dia) and where did you get it? Have you got other (old, differently
sourced) sterling wire you can test with, to see if that wire has
the same issue?

There’s no reason on earth that rolling should change the color (or
post-soldering mechanical properties) of sterling wire in any
significant fashion.

It’s a giant, mechanical rolling pin. Pie crust doesn’t suddenly
become jello when you roll it out. Neither should sterling change
drastically when you squish it a bit. (For the true pedants out
there, yes, obviously there will be microstructural changes, but not
anything drastic enough to cause what she’s describing.)

On the other hand, if it isn’t pure sterling, and especially if
it’ssome sort of a plate job, then it will have a skin that can be
pulled off, just like you’re describing.

Have you tried heating up a filed chunk of it? Did you see any color
differences? I don’t suppose you have a set of gold testing acids do
you? An acid kit would spot a plate job too.

Wait a sec: how hot are you heating it when you anneal? If you heat
the hell out of it, and hold it at heat for too long, you can
generate a fairly thick oxide skin. The copper of which gets
dissolved away in the pickle, creating a fine silver skin that can
separate like a plate job, if it’s really, really, really bad.
Alternately, if you overheat your solder joint, the solder will fail
easily, but having good joints right next to the bad ones would seem
to rule that out.

What’s your annealing surface made out of? I can’t imagine that’s
it, but it’s worth knowing what it is, just as a rule-out.

What kind of torch are you using? When you anneal, how do you
determine ‘hot enough’? and how long do you hold it at heat?

Deeply puzzled,
Brian


#7
If I take wire from the same lot and run through the mill, the
wire will NOT stick to the plate after soldering 

Given that the metal is the same type, and the only difference is
which is the last tool to affect the surface of the metal, then logic
says that something the tool does, makes the difference. And that
difference will be to the surface affecting soldering. Structural
differences in the silver from working can be discounted, as that
would be internal, not affecting soldering, plus are not that
different between drawing and rolling. What’s left then, is
something on the surface impairing soldering, and for me, that pretty
much isolates the problem to something left ON the surface of the
metal. Classically, one key thing we’re all taught about soldering is
that the metal must be clean. Dirt, oxides, etc, all will impair
soldering. In this case, it needs to be something that will survive
the heat of soldering in a way that still impairs joining, yet is
not easily visible (unlike most dirt, carbon deposits, tarnish,
oxides, etc). I will assume you’re rolls look clean, so depositing of
iron oxides on the surface seems unlikely (if you’re rolls are rusty,
then fix that, and try again). So what’s left? How about, how do you
lubricate or clean or maintain your rolls? One material comes to mind
that survives heating, and will easily get in the way of good solder
joins. Silicone lubes. Petroleum lubes will also get in the way, but
are easier to wash off. They interfere simply by rejecting the
liquid flux’s ability to wet the surface, so you’re soldering without
flux if there’s oil on the metal. But unlike petroleum oils, which
burn off, silicones are heat resistant (as easily demonstrated by the
fact you can pour lower melting metals like pewter into a silicone
rubber mold without damage to the rubber). Even small amounts can
survive a bit on the metal surface, enough to get in the way of flux
and soldering Do you use a lubricant, such as WD-40 type sprays
(WD-40 itself doesn’t have silicone, as I recall, but many similar
appearing lubricants do) to clean or lubricate the rolls? If so, then
you’ll find that not only will these allow the rolls to leave a thin
film of the stuff on the silver, but it may actually be somewhat
difficult to get it off with just simple rinsing or washing in water.
Take your rolled metal, and scrub it clean with a bit of pumice
powder until plain water from the tap flows smoothly on it, wetting
it evenly without pulling away. That’s a clean surface. I’ll bet if
you then flux and solder that metal, it will solder well, and if so,
you’ve just demonstrated that it’s a surface contaminant, such as I
suggest, to blame, not the metal itself. Try it and see. More
thorough cleaning of the metal, perhaps with an ultrasonic cleaner or
more aggressive detergent, may help. If not, use a suitable solvent
(alcohol, acetone, etc) to very thoroughly clean the rolls so they
are clean and dry before rolling your silver. See if that helps. And
in keeping your rolls clean and rust free, use something that when on
the metal, will easily wash off your silver, like simple machine or
motor oil.

Peter


#8

I think you need a much more reactive flux, like Johnson Matthey
stainless steel grade. For really difficult soldering theres nothing
stronger, its reactive enough to even dissolve copper oxide fire
stain out of sterling metal. Tho you need to use a lot of it to do
this.

This flux will ensure thet the solder and silver are clean enough
for the intermatallic bond of soldering to take place.

Im in the UK and I can buy this flux at any welding supply house.

It comes in 1lb plastic tubs as a white powder with screw top lids.

You may have to chase up all local welding shops, who might let you
have a thimblefull to try.


#9

Just to add to what Peter said " like simple machine or motor oil".
One Thing to be careful of is motor oil for a car or truck engine is
no longer a “simple motor oil”. This is a common problem that home
shop machinists run into. ‘ordinary’ 5W30 oil contains detergents and
additives that will tend to over time attract moisture and form a
type of varnish. In addition semi synthetic and synthetic oils have
Teflon or silicone based additives that are HELL to remove if you
want to do cold bluing etc.

It can be hard to find but I would suggest either a plain
NON-detergent 10 weight oil (use 30 weight oil for long term storage)
or even better “way oil” for metal cutting lathes.

Kay