Which procedure involves molten metal?

The procedure that involves molten metal is casting. In casting, metal is heated until it reaches a liquid state and then poured into a mold where it cools and solidifies into the desired shape. This process is fundamental in manufacturing because it allows for complex shapes and structures to be formed that might be difficult or impossible to achieve through other methods.

Casting is widely used in various industries for producing parts ranging from small components to large structural items. It typically involves a series of steps, including melting the metal, pouring it into a mold, and then allowing it to cool and solidify, after which the mold is removed to reveal the final product.

The other procedures mentioned do not involve molten metal:

• Rolling is a process where metal is deformed into thin sheets or other shapes by passing it between rollers, working with the metal in a solid state.

• Piercing is a deformation process where a hole is created in a solid material using a punch or similar tool.

• Coring is often associated with creating holes or cavities within a material, which again involves working with solid materials rather than molten metal.

Thus, casting is distinctly characterized by the use of molten metal during its process.