scope:

GENERAL

The raw materials for hollow metal doors and frames are steel coils and sheets. At the mills, steel is processed into slabs and "rolled" into coils of varying thicknesses. The thickness of the steel is controlled by adjusting the distance between the rollers through which the red-hot steel passes. As the steel is rolled, it is spooled into coils. These coils may then be further processed into other types of steels. After the final processing step, the steel is either shipped as a coil or is passed through a series of rollers (leveled) and cut into sheets of a fixed length.

Types of carbon steel commonly used in hollow metal work are as follows:

1. Hot-Rolled (HR) - reinforcement and doors and frames of thicker steel

2. Cold-Rolled (CR) - typical commercial hollow metal

3. Zinc-Coated Steel - enhanced protection against elements

4. Stainless Steel (SS) - corrosive environments or aesthetic applications

By far the most commonly used material for commercial hollow metal is cold-rolled steel. The use of hot-rolled steel is generally limited to hardware reinforcements and thicker steel doors and frames. Zinc-coated sheets, either galvannealed or galvanized are recommended to enhance corrosion protection from the elements. Various grades of stainless steel sheets, either cold-rolled finish or polished as specified, are used for applications where maximum cleanliness, severe corrosion resistance, or high degree of aesthetics are required.