Member postings for Keith Hale

Hi Steve,

You are correct - Silverflo 55 flux does not exist!

You have a flux that has been used in the past with silverflo 55.

It could be either a low temperature short life flux or a higher temp long life flux. Not knowing your brazing requirements, it is impossible to suggest the best alternative either EF flux or HT5.

Sorry Neil,

but both have a long shelf life made longer by the addition of a little detergent and water to make a yoghurt consistency paste. When this dries out (and it will) it can be reconstituted with a little more water.

No need to throw it away when it dries as hard as a brick!

Keith

Hi Nick,

Probably the best approach is a two stage one.

Use a medium temperature alloy like 438 for the first joints. Follow up with low temperature 455 The latter joints will be made without fear of melting the first ones.

Both alloys can be used successfully with either EF or HT5 flux.

All materials readily available.

Keep your costs down by having small joint gaps (0.1 - 0.15mm) and joint length 3 - 4 x material thickness. Then use the thinnest rod practical to you.

Change subject

Cyclone burners as mentioned above are available up to 10kw

Keith

Edited By CuP Alloys 1 on 24/04/2015 10:15:18

Hi Nick,

If you are going to Harrogate next month you can see the range of Sievert burners on the CuP Alloys stand. You will be able to discuss your requirements, see the burners lit and be able to make an informed decision.

For information on silver solders visit http://www.cupalloys.co.uk

Keith

Edited By CuP Alloys 1 on 22/04/2015 07:22:29

Edited By CuP Alloys 1 on 22/04/2015 07:25:40

KWIL is correct. But check on the grade of silver solder. Low silver content alloys (as favoured by most DIY stores because they are cheaper) have higher melting points and are more difficult to use.

Alternatively, when heating, place the components on lightweight refractory bricks or insulation blanket to improve your heating efficiency.

Keith

And you will find the flux mixes easier and sticks better to your components.

Keith

To prolong the useful life of powder flux ..............

Add a couple of drips of the wifes' washing up liquid to the powder.

Mix to yoghurt consistency with water.

If it dries out in the future (and it will!) you will be able to remix it easily by adding more water. The absence of any detergent makes the re-mixing a bit of a chore.

Keith

Use C103 or C106

For more info cupalloys.co.uk/best-practice/

keith

Alloy not flowing is normally down to three factors.

1) flux exhaustion (so use a longer life flux eg HT5)

2) incorrect joint gap or and more commonly

3) cold spots in the joint. If the whole of the joint is not at a temperature above the melting point of the alloy. The alloy will simply freeze and stop flowing.

How do I know if the joint is hot enough - watch the flux. Make your flux into a paste. (use water or meths if you prefer). Apply to the joint and heat.

When it has turned molten and itself is flowing the joint is hot enough. That is the whole of the joint.

Apply the alloy. It will flow by capillary action and fill the joint.

I am not a fan of "hot-rodding" ie dipping a warm rod into flux powder to apply flux unless it is used as a means of adding extra flux. In my experience relying on hot-rodding tends to promote a welding technique of heating, - that of heating the rod not the joint. This can lead to cold spots in the joint and is common in assemblies with a less thermally conductive steel component.

For more information see **LINK**

Keith

Western Steam - Burnham on Sea, Cheddar Valley Steam? Both just off the M5.

Googling (?) will find them

Keith

Hydrogen embrittlement of copper can be caused by any gas flame be it oxy-acetylene or propane /air. If the burner gets too close to the work the oxygen in the copper is converted to steam which causes the cracking.

You will see when these conditions prevail because the copper will shine like a mirror.

Work outside the blue zone of your flame.

If you are experiencing difficulty in obtaining oxygen free copper ask a professional boiler maker for your requirements.

Regards

Keith

I can't talk about JM products but they do not talk about them on forums either!

Why not use 440 from CuP or even 438. Yes there is a potential danger from the differential rates of expansion between the brass and steel but that is there no matter which silver older you use.

Having made a joint, and upon cooling, the brass contracts more than the steel. That puts the joint under a tensile stress. Minimize the effect by having a slightly larger joint gap (say 0.2mm) and set out to create a thicker joint than usual (more alloy to absorb the stress).

Do not overheat the joint. Watch the flux. Get the whole of the joint hot. Ideally use a propane torch with a burner suitable to achieve the heating you require.

Of course there would be no problem if the tubes were steel and the plate copper!

Allow the joint to cool slowly. Cover the joints perhaps with an insulation blanket. At about 350 degrees C the silver solder becomes less ductile but on further cooling ductility returns. This phenomenon is called "hot shortness".

Brass fittings into a steel shell was/is commonplace. 40 years ago, It was a standard production technique in the manufacture of fire extinguishers.

Keith

Lets clear something up from square 1

The 2%, 5% and 15% silver alloys are not "silver solders". They are copper (Cu) phosphorus (P) alloys for the fluxless brazing of copper in air.

The 45% silver alloy is a silver solder that contains copper, zinc and possibly cadmium or tin.

Generally, increasing silver contents lowers the effective liquidus (temperature at which a joint can be made) and improves the ductility of the alloy itself.

It makes very little difference to the solidus (temperature at which the alloy freezes)

Data from the International Standard for Brazing Materials ISO 17672 shows the following melting ranges:

2% 645 - 825 or 643 - 788 dependent on the phosphorus content. Ductility 5%

5% 645 - 815 or 643 - 771 dependent on the phosphorus content Ductility 6%

15% 645 645 - 800 Ductility 25%

The ductility figures are as stated by manufacturers.

The 2%, 5% and 15% alloys can be used to join copper alloys but need an external flux. Use a suitable silver solder flux to suit the heating cycle.

In reality it makes little difference to the joint ductility for the model engineer because the copper is fully annealed at brazing temperature and as usual the parent material will fail first.

A word of caution.

DO NOT USE THESE ALLOYS TO JOIN COPPER OR ITS ALLOYS TO NICKEL OR FERROUS ALLOYS. They form brittle inter-metallic compounds in the parent materials that will lead to catastrophic joint failure.

DO NOT USE THESE ALLOYS IN HOT SULPHUROUS ATMOSPHERES eg COAL FIRED BOILERS. The sulphur will go through the joint like a hot knife through butter!

Keith

Hi Brian,

Presumably you do not anticipate handling it with asbestos gloves!

Soft solder it.

Keith

Skamollex bricks and kaowool blanket readily available. **LINK**

Ian,

I do not believe that there is an adaptor to suit your needs. If such an animal existed it would have to be fitted upstream of the low pressure fixed regulator. That would involve dis-assembling your current cylinder!

Another cylinder is required.

Equate the gas consumption (kg/hour) of the burners. you intend to use, to the available cylinder sizes. You may find that you do not need a heavy cylinder to suit your needs. A smaller, more compact, lighter one may suffice.

Burning 80gms/hr will produce  approx 1 kw of heat

Keith

Edited By CuP Alloys 1 on 29/12/2014 08:40:25

Hiya,

Try not letting the rod get too short say 3 - 4 inches.

Butt it against the next rod and fuse the two together with a fine flame.

Regards

Keith

PS Merry Christmas to you all

1) Lead bearing soft solders are readily available as solid or flux cored wire.

2) Citric acid pickle turns blue due to the formation of copper citrate during the cleaning. Copper citrate is blue.

3) The remelt temperature of silver solder is due to mainly

a) the silver solder dissolving copper/zinc/iron from the parent materials so changing the composition or

b) to a lesser extent the loss of cadmium during heating

Regards

Keith

Silver Steel was supplied by Stubs of Warrington.

They relocated to Oldbury and subsequently took up the name of their parent company - Bohler UK.

A look at their website indicates they still sell silver steel.

Keith

Hi Brian,

See email.

Keith

Hello Jason

In the post I take it up from the "plumbing"

Taking it from the start ....

If the decision is to use soft solders then the 3938 burner should cope. If not put on a slightly larger burner eg 3939.

Use soft solders with different melting ranges if it helps. Alloys available with temperatures between 145 and 305 degC

If the decision is to use silver solder the 3938 will struggle.

As I understand it. the jury is out on the filler metals to be used. One of the considerations of burner selection is the melting point of the materials.

Keith