| Block Off | (english) 1) Wooden separators which are used at both the bottom of a lift and between IPM's (bundles) of a lift. 2) The act of placing 4x4s between the lifts in the piler's box. |
| Block, Jo | (english) Shop name for a Johnnson gage block, a very accurate measuring device. |
| Blocker | (english) Preform die or impression, used when part cannot be made in a single operation. |
| Bloom 2 | (english) A semi-finished hot rolled product, rectangular in cross section, produced on a blooming mill. For iron and steel, the width is not more than twice the thickness, and the cross-sectional area is usually not less than 36 sq. in. Iron and steel blooms are sometimes made by forging. |
| Bloomery | (english) A primitive furnace used for direct reduction of ore to iron. |
| Blow | (english) The impact or force delivered by one workstroke of the forging equipment. |
| Blow Back | (english) A coating defect consisting of a lower coating film weight on the bottom of the coated sheet caused by high velocity air in the oven. Blow back usually occurs with high solids coatings which have little solvent to evaporate and "set" the film. |
| Blowhole | (english) A defect in a casting caused by trapped steam or gas. |
| Blue Annealing | (english) Heating hot rolled ferrous sheet in an open furnace to a temperature within the transformation range and then cooling in air, in order to soften the metal. The formation of a bluish oxide on the surface is incidental. |
| Blue Brittleness | (english) Brittleness exhibited by some steels after being heated to some temperature within the range of 300 (degrees) to 650 (degrees) F, and more especially if the steel is worked at the elevated temperature. Killed steels are virtually free of this kind of brittleness. |