Can someone explain what is the different between resistance
soldering machine and spot welding machine? both seems to work
similar but they are not the same.
The fundamental difference between welding and soldering (or
brazing) is that in welding the two pieces of metal to be joined are
locally melted and the liquid zones (in spot welding called the
"weld nugget") fuses together, making the two one on cooling. The
crystal structure of the metals is continuous across the join.
In soldering or brazing the workpieces are not melted, nor do they
come near to melting. The workpieces are heated and some other,
lower melting point alloy is added which melts, flows and coats the
contacting surfaces of the work. On cooling this lower melting
solder or braze solidifies and sticks to the workpieces, gluing them
together. However there is a definite physical surface between the
work and the solder, and the two workpieces will not actually be
touching each other, they are held apart (and together) by a thin
layer of solder.
Welding tends to be stronger, soldering tends to be easier to do and
usually requires fewer safety precautions.
can somebody tell me what is the different between the two
Other than the fundamental difference between welding and soldering,
I cannot tell you the difference, because I'm not familiar with
resistance soldering (or possibly do not know it by that name).
and why in spot welding sometimes there is not need of flux to
avoid oxide in metals like stainless steel and titanium.
Because the initial flash of heat drives air and contaminants out
from between the workpieces and there is then a clamping force that
holds the work surfaces firmly together so that air cannot reach the
main molten part of the weld nugget, only a small ring around the
also I need to know where can I buy a small spot welding units
since it looks like they work better than resistance machines..
Which is "better" depends on what you want to do. There are
applications for which soldering is right and applications for which
welding is right. Also some metals just wont solder/braze easily and
some wont weld.