| K | Chemical symbol for potassium. |
| Kaldo Process | A method of producing steel from molten iron, using an inclined rotating converter and a water cooled oxygen lance inserted through the converter mouth. Originating in Sweden, this process is no longer in use in the UK. |
| Killed Steel | The term indicates that the steel has been completely deoxidized by the addition of an agent such as silicon or aluminium, before casting, so that there is practically no evolution of gas during solidification. Killed steels are characterized by a high degree of chemical homogeneity and freedom from porosity. |
| Knoop Hardness | Microhardness determined from the resistance of metal to indentation by a pyramidal diamond indenter, having edge angles of 172°, 30°, and 130°, making a rhombohedral impression with one long and one short diagonal. |
