salamander

A salamander is a mass of solidified metal, slag, and refractory material that accumulates on the hearth of a blast furnace or other high-temperature smelting vessel. Unlike the mythical creature it is named after, this salamander cannot survive fire, yet it persists in the hottest part of the furnace where molten metal flows. It forms from metal that has cooled and bonded with slag residue, ash, and fragments of the refractory lining itself, creating a hard obstruction that sits directly on the furnace floor.

Salamanders typically contain iron, manganese, or copper depending on what is being smelted, mixed with silicates from slag and oxides from the refractory brick. They range from fist-sized lumps to masses weighing several tons in large furnaces. The problem arises because a salamander obstructs the flow of molten metal and slag to the tap hole, forces operators to work around it, and if it grows large enough, must be physically broken up and removed during maintenance shutdowns. In blast furnaces, this is often done with sledgehammers and crowbars once the furnace has cooled.

Prevention is the practical concern. Keeping the hearth hot and maintaining good slag chemistry that flows freely reduces salamander formation. Using higher quality refractory materials helps, as does controlling the temperature profile in the lower furnace. Some operations add flux or adjust burden composition to keep the hearth cleaner. Operators monitor salamander growth by observing changes in tap hole behavior and metal drainage patterns; sudden slowdowns or irregularities signal that a salamander may be developing.

The name likely derives from the old belief that salamanders could live in fire. Workers gave this name to the persistent, hard lump that seemed to thrive in conditions no other material could endure. The term appears in blast furnace and foundry practice across English-speaking countries, though regional variations exist. It sits in the vocabulary of furnace maintenance alongside similar problem materials like skulls (refractory buildup in shaft furnaces) and dogs (irregular metal deposits in casting channels).