Solder Question

[fredrosse]

I have noticed some marketers advertising "silver solder" that melts at 450F/230C. This stuff only has 1-2% silver, and is really a soft solder used for plumbing. This stuff is not to be used on anything involving steam or high pressure.

Real silver solder (typically 45-55% silver) melts in the ranges of 1100F/600C or higher, and requires a borax based flux. Welding supply houses usually have this flux, or brazing flux (for brass based brazing) flux which works OK too. This type of flux melts on the surface of the metals to be joined, and looks like melted glass on the hot surfaces.. After the joint cools, it is like solidified glass (or hard candy), and must be chipped away from the joint, or submerged in water and dissolved overnight.

Make a silver soldering flux using just borax and salt.
Measure 1 tbsp. of borax with a measuring spoon. Pour the borax into a mixing bowl.
Add 1 tsp. of salt to the borax in the mixing bowl.
Grind the mixture into a fine powder.
Mix the dry ingredients with just enough water to form a paste.

[johnp]

Hey Fred

Sent you a pm and email

[Lopez Mike]

I watched an outboard motor repairman in Baja some years ago do very nice welds using a home made welder that ran straight from a 120v outlet with a carbon resistor made from a big flashlight battery center and an inductor made from a great big bundle of 20p nails with 12 gauge house wire wrapped around them.

What was even more astounding was that he made his own welding rod. He started with a runny solution of salt and borax just as Fred describes. He soaked old newspaper in the solution overnight and then wrapped the paper around old mild (very mild) steel coat hangers. Then set it out in the sun to dry. His mask was a welders glass held in his left hand.

I do marginal welds with a fancy $1800 wire feed machine. Very humbling.

Mike

[fredrosse]

Another improvised arc welder, three automotive batteries connected in series (36 volts) with jumper cables. If you don't have the borax, just wrap the coat hanger (welding rod) with a piece of ordinary cotton (NOT POLYESTER) cloth.

These improvised welding methods probably would not meet any engineering specifications, but they do melt steel and make real welds.

[gondolier88]

This type of flux melts on the surface of the metals to be joined, and looks like melted glass on the hot surfaces.. After the joint cools, it is like solidified glass (or hard candy), and must be chipped away from the joint, or submerged in water and dissolved overnight.

Catering grade Citric Acid makes a great acid bath to remove flux from components that are difficult to clean, our large areas. Just put it into hot water and bathe the soldered item into it overnight. This also removes any grease/oxidation if further soldering/engineering processes need to be undertaken on the item.

Greg