Banging Metal (Forging, Hammering)
* Mechanism: The impact of the hammer creates stress waves that travel through the metal. These waves cause the metal's atoms to vibrate more intensely. This vibration can cause the metal to deform (change shape) by breaking and re-forming bonds between atoms.
* Atomic Changes:
* Bonding: The metal's bonds are broken and then re-formed, but the original atoms within each piece of metal remain largely unchanged.
* Structure: The impact can cause crystals within the metal to realign, resulting in a change in the metal's grain structure. This can make the metal stronger.
* Heat: Some heat is generated due to friction and the internal movement of atoms, but the temperature isn't high enough to melt the metal.
Melting-Welding
* Mechanism: Heat is applied to the metal, causing the atoms to vibrate so violently that they overcome the forces holding them in a solid structure. The metal melts into a liquid state. When the melted metal from both pieces cools and solidifies, it forms a single continuous piece.
* Atomic Changes:
* Bonding: Atoms from both pieces of metal intermix and form new bonds.
* Structure: The melted metal typically cools and solidifies into a different crystal structure than the original pieces, known as the weld bead. This structure is often stronger than the original metal.
* Heat: This process requires a high temperature, enough to break the bonds between atoms and melt the metal.
In Summary
* Banging: Re-arranging existing bonds by mechanical force, no melting or atom mixing.
* Welding: Breaking bonds, melting, and forming new bonds between atoms from different pieces of metal.
Important Note: Both forging and welding can significantly alter the properties of the metal, like its strength, hardness, and ductility. The specific process used will impact the final properties of the metal.
