HMS stands for heavy melting scrap, and 1 & 2 are the two grades within that definition. Heavy melting steel (HMS) or heavy melting scrap, is a designation for recyclable steel and wrought iron. It is broken up into two major categories: HMS 1 and HMS 2. The difference between the two is HMS 1 does not contain galvanized and blackened steel, whereas HMS 2 does.

Both HMS 1 & 2 comprise obsolete scrap only. That is iron and steel recovered from items demolished or dismantled at the end of their life. Because both grades guarantee a minimum piece thickness – at least 1/4inch (6.3mm) for HMS 1, and 1/8in for HMS 2 – consignments have a high density. Both also have defined maximum dimensions (usually *0in x *4in), and should be prepared to facilitate handling and charging to a furnace.

This density, sizing and preparation makes for efficient furnace operation by minimising the time to charge enough scrap for a full melt. In contrast, thin mixed scrap greatly increases charging time, cutting furnace productivity.

HMS is usually traded as a blend of 1 & 2, either a premium blend (*0:*0) or lower grade mixes (*0:*0) and (*0:*0).