Silver Soldering

[Peter Miller]

"Gliders" do blade type joiners in various sizes. and as they specialise in glider they know what they are doing.

[Erfolg]

Steve

Think about the warren girder and the shear web, and think parallel axis

Regards

Erfolg

[ROY DAVIES]

Hello Peter

 A few more tips on silver soldering. Don't use more than is necessary. I cut a piece that is quite small but hopefully enough for the job, a matchhead size piece is more than big enough to join two U/C wires together. Use a decent side cutter and watch the bit doesn't fly as it's quite hard.How to get it on to the job? I use powder flux, put a few spots of water on a tin lid ( preffered ) and mix to a stiff cream/paste. If you're only making a minute amount spittle works equally well. Warm/Heat the joint and apply a little of the paste and it should coat it. Using a piece of thin wire with a tiny amount of flux paste on it pick up your piece of solder. Heat the joint untill the flux melts and apply the solder and wait untill it flows then take the flame away.This method prevents too much heat at the joint,  and you are not heating up the solder stick as most of the time it can be bigger than the job which means you overheat the wire getting it up to temp'  together with too much solder and an ugly joint. When the joint has cooled pour boiling water over it to clean off the flux, if the flux is left it goes hard and it will be  as hard as glass and just as sharp when you chip it off. BE AWARE MOST SIVER SOLDER FLUXES ARE POISONESS so no biting your fingernails.     Re, soft solder. Lead solder is now banned and tin alloys will replace them an exception where  I work is that Defence equipment is exempt and it can be used for repair work on in service equipment.       Keep your eyes open for cheap solder stations as the new ones required for the new regs'  operate at a much higher temparature range and aresuper exspensive - 100s of £                   

         

[Former Member]

[This posting has been removed]

[ROY DAVIES]

Yes Eric you are correct. The new legislation means that no equipment made from the implementation date is allowed to use lead based solder, and as you say it is still readily available even from the big boys, e,g, Farnell, R,S. and others. Peter has mentioned Bakers fuid, if  any of you buy some to use don't get it under your nails or in even a small cut, or it will make you dance some! I have not used it myself for years. A more user friendly flux is LA-CO' Comes in a back plastic pot in a small and large size. The other even better product is, Fry's Easyflow ? in a yellow pot. Both are available, in plumbers supply centres. The Fry's flux is that good you do not have to clean copper or brass tube first , dip it in and apply  heat and it cleans before your eyes, But I do clean piano wire. The fumes produced by these products are all nasty so use in a well ventilated space.

[Erfolg]

As I have said before, silver soldering/brazing will remove alot of the benefits from the  "processing history" of the  piano wire. The grain structure which had been distorted and elongated along the length of the wire etc, will become relatively coarse, loosing the directional alignment. In short the wire will tend to bend in the heat effected zone, where cross sectional area is small relative to the joint.

I would only consider hot processess if there was no other way or I can ensure that the resulting fabrication is adequate. 

[Former Member]

[This posting has been removed]

[ROY DAVIES]

 Nice one Eric I fell for that. Actually I need to correct the name. It is Fry's Powerflow, obtainable in three sizes. starts at around £4 for the smallest.Now if that was chocolate I could do with some right now as its benefits are sorely needed. A lot of you are reminiscing about your youth so here's is my three P's worth. In the '50s I was given the EAGLE BOOK of BALSA MODELS I plowed through a few and needed a moddel to use my Jetex 50 on, I decided to make the ROCKET. It would slide along a wire on paper hooks for many hundred yards (It did) so the blurb said. So- I had a coil of pin making wire hundreds of yards of it, I stretched it across the valley where I live ( Wales) so we have few,  250 yards or so.                  I crossed via a bridge. A friend and I tied it off on railings and we were in business. It worked perfectly ran out of fuel so time to wrap up.--- Unfortunately--- The wire snapped!  and fell across power cables and put out half the village! And believe it or not nobody knew who did it, they were completely in the dark!!! I used to make 'cannons' from pram tubing and the powder from Mighty Atom bangers. Flatten the tube one end stuff a ball bearing in a rag and use a resistance wire fuse and fire at telegraph poles, they used to boom and the wires would sing. It was quite good. All down to Errol Flynn and too many pirate films I think. Then I nearly grew up and went to fix 'planes for the Queen just like Peter Miller. Talking of flattening tube. If you can't get your head around silver soldering use tube sleeves and soft solder, there are various sizes of Microbore copper tube ask a plumber for some off cuts. Anneal it, = heat it up and quench it and there you are, brass tube will do the same but they both work harden so if it's a tricky job you may have to do it again   

[ROY DAVIES]

 Erflog re piano wire,Can you explain this. Long ago our wire was tinned in some kits and consequently was easy to solder, I also remember wire breaking when it was bent, the breaks were often like dowel snapping leaving sharp striations. You could see the grain as you mentioned in your post. I know I had a few nasty cuts this way. the wire did not have to be bent to a sharp radius for this to occur. Was this due to some chemical reaction with the tin coating ? I know we have had a problem at work with high tensile screws with the heads coming off due to Hydrogen embritlement after the passivation process - electro zinc plating. 

[Erfolg]

Piano wire is steel is iron (Fe or ferrite and  C, carbon between 0.2 and 2.04 %), but I guessed you knew that. It is often comes with additional alloying elements to further modify the properties. The important aspect for modellers is that material can exist in two solid phaces FCC (face centred cubic )and (body centred cubic) at room temperature. Scientists will oftren talk of energetically preffered condition. For steel that is FCC but above approx 900C it is BCC. By controlling tempertures carbon content and cooling the state of the material can be altered.

The hardness of the steel is affected by the C solubility in the steel, which I have hinted at. There are a large number of conditions that the steel can exist in, which you may have heard of Cementite, pearlite etc. The first people to make use of these effects knew nothing of the above (probably), but managed with mixed results  to produce swords, armour etc. Often to get consitant results religion was used (Japenese Monks) or Medeival Gilds, often not really knowing what mattered, but the whole ritual if adhered to got results.

The other thing which is pertinant to us is dislocations and grain size. As I have mentioned steel has specific atomic strucures FCC etc. But the structures lack long distance range. This is due to cooling which causes nucli of grains to form at many sites in the material, where these grains meet there are areas of disorder (weak areas). Ohh did I mention slip planes?

Anyway back to our materials in genral, if we process the material, the structure will change. If we draw wire for instance the grains distort, if done at room temperature in particular. These distortions give directional properties, very apparent in wire. By repeated drwing at temperature or cold (room temerature) the material can become very different to the intial start condition.

However provide energy (say heat) and the material will try and achieve its intial condition, rounder grains, disloctions moving to a lower energy arrangements, Softer, more ductile, less directional. Put more energy in say by bending then the disloctions can/will slip (along slip planes) until so called tangles occur, where the stress is graeter than the grain or boundary strength, the material fails. In the case of wire the a charateristic brittle type failure.

This has been a vey simplified explanation. Although we now know a lot and calculate a lot, much of the above was postulated up to about 20-30 years ago. But with Spectrograhic technigues etc, structrures have been seen at ataomic level, disloction movement observed and the precise ultimate strength of materials calculated (yet we are still far from achieving, these values in normal production).

We really need a young materials engineer to continue the thread, who can get into the effects cooling velocities, body aginst surface effects of stress distibutions, in a consice and pertinant form. I have tried to give an idea of

• what steel is
• it having potentially many structures
• heat effects on structures
• processing effects

What I have ommited are such issues of loading rates (very important on polymers), effects of temperture (not important to our wire, but are for bridges) and the list goes on.

Heat has a tremendous impact on steel structures, even after processing. Most of us think it only matters in tempering.

Erfolg

[Erfolg]

Roy

I have suddenly remember the hydrogen enbriitlement, part to your post.

A I stated earlier you really need a materials engineer.

From the Mendelev table, hydrogen is the first elemnt, with its isotopes of Dueteruim, Tritium. Normally i believe it is diatromic gas  (two bonded to each other by single bond,  H2), increadibly common, found in plastics, wood, nearly everything you look at etc. I cannot remember its precise atomic structure but seem to remember that their is a nuclis of a Proton with an electron in orbit, more give the isotopes (some one will correct me). Any way it is small.

Being small it will diffuse through many materials quite easily, in the case of steel, which has carbon it can bond with the carbon or get trapped interstially. In each case either by being a bigger molecule, or filling space can induce stress or block slippage, there by reducing ductility.

Anyway that is what I was taught, twenty five or so years ago. If my memory does not fail me again. At this rate I will go in the atic and get my text books.

Although I am sure some young turk will tell me that is not quite true. I used to believe that the electrons did whirl round in there nice decrete shells. in perfect ordrer. Only to be told and showed a photograph (Image) which was a fussy mess which I was told was a real atom with structure, and that was the first time an Image had been produced.

Erfolg

[ROY DAVIES]

Thank you for that reply, I can follow a lot of what you mean in my own simplistic way.You mention the crystaline structure in fractures etc. When I was a boy I worked at the local steelworks in the slab yard. The slabs were anything from 6" to 12" thick up to 13' long and sometimes were 4 or so feet wide of differing grades fit for their purpose. The yard was where the stocks were sorted and repairs to blemishes made before re- rolling. The case in point. We rolled a grade called COR - TEN this was for the sheet 'iron' core of transformers, immediately it was rolled and in the yard, they would roll about !00 tons of 'Trostre' grade { for the car indusrtry } as it was called this was to muffle the Cor -ten to keep it better than 'black hot' all the time it was in the yard. The 'Trostre' was changed at regular intervals as its temp' went down. All had to be perfect, if there was a hiccup in the rolling  and storage there was a serious problem. When there was a slowdown in the system the  cranes would up lift Cor - Ten that was by then down to black hot and often it would snap in half all 30 tons of it and fall to the floor. Now that was crystalization. As an aside as most of this post is. It was always easy to warm one's tin of beans or Fray Bentos pie on a black hot slab, 3 min's I remember, the crane drivers would as a prank lower a full load of glowing slabs within an inch of your tin and carbonise your food. It was after this job I went to fix planes for HMQ's airline .