Cup Alloys - Model Engineering - www.cupalloys.co.uk

 

UK Silver Price
28th Mar 2017

£463.61/kg
£14.42/oz

  Model Engineering

  

Silver Solder

Due to European legislation you are now compelled to buy cadmium free silver solder alloys.

The most popular silver solders are 455, 445, 438, 434, 430 and 424.
All will produce strong, leak tight joints with small neat fillets. 
All will join copper, brass, bronze, mild and stainless steel, nickel alloys in any combination.
Most importantly, they will still give you what you want.

You will make your choice considering the melting temperature or colour or alloy content or price of the silver solder. 
It will not be based on joint strength. If used properly, all will produce joints stronger than the parent materials.
If you feel that this range of alloys does not quite fit your requirements please contact on the details below. We can normally arrange something to suit. For flux details and prices visit "silver solder fluxes"

Use all silver solders in well ventilated areas. Do not overheat the alloy or flux.
Refer to the section on Silver Soldering Tips and Health & Safety.

424
24% Silver Brazing alloy for the joining of dis-similar metals - e.g. copper, brass and steel. Produces a high strength, leak free joint.
It is often used in the first operation of step brazing when several joints are made in close proximity. 
Brazing Temperature Range: 740 - 780°c
Its high melting point often requires the use of oxyacetylene heating. It is available as rod 1.5mm dia. Use it with our HT5 flux

430
30% Silver Brazing alloy for the joining of dis-similar metals - e.g. copper, brass and steel. Produces a high strength, leak free joint.
Conforms to ISO 17672 Ag 130
Brazing Temperature Range: 665 - 755°c

438
38% Silver Brazing alloy for the joining of dis-similar metals - e.g. copper, brass and steel. Produces a high strength, leak free joint.
Although it contains more silver, it offers considerable advantages in that it can be more readily melted with a propane torch and you can use the ordinary conventional flux. No duplication.
It is used as either the second of three or first of a two stage brazing operation.
Conforms to ISO 17672 Ag 138
Brazing Temperature Range: 650 - 720°c
It is available as rod 1.0mm, 1.5mm, 2.0mm, 2.5mm dia.

445
45% Silver Brazing alloy for the joining of dis-similar metals - e.g. copper, brass and steel. Produces a high strength, leak free joint.
It has reasonable fluidity, produces small neat fillets.
Offers more "invisible" joints on polished brass.
Conforms to ISO 17672 Ag 145
Brazing Temperature Range: 640 - 680°c

455
55% Silver Brazing alloy for the joining of dis-similar metals - e.g. copper, brass and steel. Produces a high strength, leak free joint. It has the lowest melting range, good fluidity and produces small neat fillets 
It offers a reasonable colour match on stainless steel and is the most popular silver solder.
Conforms to IS0 17672 Ag 155
Brazing Temperature Range: 630 - 660°c.
It is available as 0.5mm dia wire and rod 1.0, 1.5, 2.0, 2.5mm dia, rings, foil and paste.

Silver Solder Fluxes
"The silver solder melts - but it won't flow - it just goes into a ball and falls off" 
There is nothing wrong with the silver solder. You have a flux problem! 
The flux to be used with any silver solder  is decided by three considerations all of which must be satisfied. These are a) the melting range of the silver solder b) the parent materials. c) the heating cycle 

Silver Solder Flux
Generally speaking, 99% of all silver solder joints can be successfully made using one of two basic fluxes. They behave in exactly the same way as the solder. They flow into the joint gap by capillary flow prior to the alloy melting removing the oxides and keeping the joint "clean" at temperature. 

EF Flux 
By far the most popular flux used with silver solder is this low melting point flux based on alkali floro-borates. It melts at approx 550°c, has excellent cleansing and capillary flow characteristics (essential for successful brazing) and stays active for a reasonable length of time. The active life of EF "Easy Flowing Flux" is sufficient to cope with most silver soldering heating cycles. The flux residues are readily soluble in warm water perhaps with the help of a soft nylon brush. Or use a bath of citric acid 20 grams salts/litre of water. EF flux will enable joints to be made between the common parent materials. These are copper and its alloys (e.g. brasses & bronzes), mild steel and cast iron. The exceptions involve prolonged heating or joining aluminium bronze containing more than 2% aluminium and stainless steel. These exceptions will be dealt with later. 

HT5 Flux 
HT5 contains metaborates that offers a longer life at higher temperatures than EF flux and is recommended for longer heating cycles. It is also more aggressive and is capable of removing the oxide of chromium and as such is suitable for stainless steel. Use with higher melting point silver solder or during protracted heating cycles. The flux residues are more "glassy" and are more difficult to remove. Use 10% caustic soda solution or elbow grease.
Both fluxes are available in 50grm sachets, 250grm and 500grm containers.

Hint 1
Both these fluxes become fully molten and working at a temperature of about 560°C. This is an excellent guide to the joint temperature. Apply the silver solder only when the flux has melted. To do so beforehand leads to a tendency to heat the rod, it melts but the joint is cold and freezes the brazing alloy. The result is a superficial joint with no penetration.
Hint 2 
When mixing the powder into a paste add a few drops of detergent. It helps make the powder into a smooth paste, it helps the paste "stick" onto the parent materials. and if the paste dries out a little (and it will!) it allows the paste to be reconstituted by simply adding a little more water.
Hint 3
Brazing Aluminium Bronze with up to 10% aluminium? Add 20% by weight of table salt to the flux powder. The increase in chloride ions helps to remove the aluminium oxide.

Lead Bearing Soft Solders have not been banned 
The use of lead bearing solders has been restricted in those products associated with the food and drink industries. This is on health and safety grounds. Their use has also been restricted on environmental grounds.Manufacturers and suppliers are responsible for the safe disposal of their product. To avoid the mass return of their production, manufacturers have switched to lead free solders. These regulations apply to electric motors, PCB’s, white goods.The restrictions do not apply to model making nor to the production of any product on a non-commercial basis. They do not apply to the activities of the model engineer.

CuP Alloys offer a range of soft solders. Look at the temperature ranges, there are combinations that facilitate "step soldering."
Generally speaking, if the melting temperature is above 250°c, heating is best achieved with a small butane flame, otherwise a soldering iron can be used.
For best results, the joint must be free of any grease. Clean the components with a stiff wire brush or wool. Do not use emery clothes as they can leave a deposit that prevents the flux working. Follow the guidelines in the "Best Brazing Practice" section.
The principles are exactly the same - it's only the temperature that varies.

 

General purpose free flowing 2/62/36 silver-tin-lead
Conforms to BS 219 KP
Melting Temperature: 187°c
Available as flux cored wire in 1 metre lengths or 0.5 kg reels and paint.
Wire diameters 1.0mm and 1.5mm
We also supply a 62/38 alloy paste whose flux residues are non-corrosive. Ideal for the model boat builder.

General purpose 40/60 tin-lead
Conforms to BS 219 G
Melting Temperature Range: 180 - 220°c
Available as flux cored wire 1 metre lengths or 0.5 kg reels.
Wire diameters 1.0mm and 1.5mm

2207 4% silver tin alloy - for stainless steel
ComSol has excellent fluidity and produces neat fillets.
It offers an excellent colour match on stainless steel and silver.
Use with conventional soft solder fluxes
Conforms to BS 219 96S Melting Temperature Range: 220 - 225°c
Available as solid or flux cored wire in 1 metre lengths or 0.5 kg reels. Wire diameters 1.0mm and 1.5mm

Comsol Silver-Tin-Lead 1.5% silver tin lead
Can be used in the first of two-stage soldering operations. 
Melting Temperature: 295°c.
Conforms to BS 219 5S
Available as solid or flux cored wire in 1 metre lengths or 0.5 kg reels.
Wire diameters 1.0mm and 1.5mm

Alusol - Silver tin lead wire
A solder for joining aluminium and copper aluminium alloys.
The wire is cored with a suitable flux for ease of soldering. 
Melting Temperature Range: 178 - 270°c
Available as flux cored wire in 1 metre lengths or 0.5 kg reels.
Wire diameter 0.9mm and 1.5mm

LT145 - 40% tin
Contains 42% lead and 18% cadmium.
Its low melting temperature makes it suitable for repairing zinc based materials e.g. die cast models.
Melting Temperature: 145°c
Available as solid wire in 1 metre lengths or 0.5 kg reels.
Wire diameter 1.0mm and 1.5mm dia.
Ironically cadmium has not been banned in soft solders!

The model engineer is best served by three liquid fluxes depending on the parent materials.
The most common is ComSol flux. It is used readily with tin-lead solders on copper, brass and mild steel.
Stainless steel and aluminium alloys require a more active flux. Use STAYCLEAN Stainless Steel grade or Aluminium grade as appropriate.
The residues of all are corrosive and should be removed, which is easily done with water.
All three fluxes are corrosive and should be kept in a cool dry area, well away from children and pets.

Pre-order for exhibitions and save the carriage costs.

Technoweld
Not really a solder, but is a very versatile method of joining/repairing all types of aluminium alloy. Visit www.technoweld-fusion.com to see a series of videos of it being used.

 

Copyright CuP Alloys (Metal Joining) Ltd 2017