Hard and Soft Copper...
Question...
-If you solder stranded copper wire, it loses it's flexibility and
-becomes brittle.
-If you solder solid copper wire, it becomes more flexible, though not as
-much changed as the stranded wire changes.
Copper in (solid) cables is cold-drawn down to diameter through a series of dies. This "work hardens" the metal. Work hardening occurs when a metal is strained beyond the yield point, passing from elastic to plastic deformation. An increasing stress is required to produce additional plastic deformation and the metal apparently becomes stronger and more difficult to deform. Heating the metal "anneals" it, relaxing the stresses within. Copper is thoroughly annealed by bringing it to red heat, but the heat of soldering is sufficient to partially relax the internal stresses.
Most metals will work harden, indeed, the process is commonly used for hardening low-carbon steels that cannot be heat-treated. Planishing Copper and Silver, for example, (as well as making all those little rounds that are so pretty...) renders it so hard and brittle that the work-piece has to be regularly annealed during fabrication, or else it will crack. Another method, used in industry, is "shot peening", where the metal is surface-hardened by blasting it with hard metal beads. Some low-melting point metals, such as Indium, cannot be work-hardened; at room temperature they are already at annealing temperature. Indium is used for vacuum gaskets in fancy lab equipment, because it stays soft. The rest of us get greased leather...
When the strands of flexible flex are soldered they behave as if they were a solid wire; the strands can no longer slide over each other. This will make the assembly stiffer. The biggest problem is at the junction between solid and stranded, and it is here that the wire will break. In sea-going electrical work it is good practice to solder connections and then enclose the join with heat-shrink sleeving to relieve the stress. Good quality sleeving has hot-melt glue inside, which also prevents water from entering the cables by capillarity.
-If you solder stranded copper wire, it loses it's flexibility and
-becomes brittle.
-If you solder solid copper wire, it becomes more flexible, though not as
-much changed as the stranded wire changes.
Copper in (solid) cables is cold-drawn down to diameter through a series of dies. This "work hardens" the metal. Work hardening occurs when a metal is strained beyond the yield point, passing from elastic to plastic deformation. An increasing stress is required to produce additional plastic deformation and the metal apparently becomes stronger and more difficult to deform. Heating the metal "anneals" it, relaxing the stresses within. Copper is thoroughly annealed by bringing it to red heat, but the heat of soldering is sufficient to partially relax the internal stresses.
Most metals will work harden, indeed, the process is commonly used for hardening low-carbon steels that cannot be heat-treated. Planishing Copper and Silver, for example, (as well as making all those little rounds that are so pretty...) renders it so hard and brittle that the work-piece has to be regularly annealed during fabrication, or else it will crack. Another method, used in industry, is "shot peening", where the metal is surface-hardened by blasting it with hard metal beads. Some low-melting point metals, such as Indium, cannot be work-hardened; at room temperature they are already at annealing temperature. Indium is used for vacuum gaskets in fancy lab equipment, because it stays soft. The rest of us get greased leather...
When the strands of flexible flex are soldered they behave as if they were a solid wire; the strands can no longer slide over each other. This will make the assembly stiffer. The biggest problem is at the junction between solid and stranded, and it is here that the wire will break. In sea-going electrical work it is good practice to solder connections and then enclose the join with heat-shrink sleeving to relieve the stress. Good quality sleeving has hot-melt glue inside, which also prevents water from entering the cables by capillarity.
posted by Simeon Lapinbleu at 18:08
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