How did hammer welding allow old iron tools to be reused?

Hammer welding was a vital process for recycling iron because of the unique material properties of wrought iron. Unlike metals that were typically recovered in a molten state, iron was historically reduced to a spongy aggregate that required consolidation through heat and pressure.1

A key advantage of wrought iron is the ease with which multiple pieces can be united by hammering while the metal is at a high temperature. When iron tools reached the end of their useful life, they were not discarded as waste. Instead, blacksmiths could collect these worn-out implements and weld the scrap metal together into a new, compact blank. This consolidated mass could then be forged into a new tool, a process functionally similar to melting down copper or bronze scrap to cast new items. This ability to repurpose material was essential for maintaining the supply of iron tools, as it allowed for the efficient recovery and reuse of the metal.1