93 I need to solder some sheet metal, and my soldering iron won't melt the solder onto the metal.
Description
This article is from the Antique Radios And Phonographs FAQ, by Hank van Cleef vancleef@netcom with numerous contributions by others.
93 I need to solder some sheet metal, and my soldering iron won't melt the solder onto the metal.
The soldering process for electronics work is conceptually the same
as for sheet metal, but uses small irons, mild fluxes, and eutectic
solder (63/37 or 60/40), which melts from solid to liquid state very
quickly.
For sheet metal work, there are several processes that are used,
depending on the metals to be joined and the strength needed. These can
be divided into three categories:
a. Soft solder, using pewter (tin-lead alloys). Requires use
of a large soldering iron or a flame such as a propane torch. May
require strong fluxes and use of 50/50 or 37/63 solder, which has a
mushy state and can be worked with paddles or a damp rag. Most radio
sheet metal work is done with cadmium plated parts, which will solder
with rosin flux.
b. Brazing, which is a similar process, but uses copper or
silver alloys and a much higher temperature than soft soldering.
Requires an oxy-acetylene torch and appropriate fluxes. The principal
difference between brazing and soldering is that non-pewter alloys and
much higher temperatures are used. Silver brazing is often called
"silver soldering."
c. Welding, which involves melting the metal of the parts and
using a similar alloy as a filler to join the parts together. This
requires use of high temperatures to melt the metal. Principal
methodologies are oxy-acetylene "gas" welding, traditional electric
"arc" welding, and inert gas electric welding, such as "MIG" or "TIG."
There are other electrical processes such as resistance, or "spot"
welding.
I mention all of these because you need to recognize where these
processes were used in original manufacture. For radio work, soft
soldering on sheet metal parts generally involves lead attachment, and
is best done with a 75-100 watt iron, using radio solder and rosin flux.
Don't attempt to repair brazed or welded parts with soft solder if any
strength is required. While brazing and gas welding are conceptually
simple, most hobbyists do not purchase the equipment necessary, and both
require some experience to do well, particularly on small work.
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