Magnetic Micro-probe Determination of the Condition of Maraging Steel

Microstructural and mechanical properties of precipitation-hardened maraging steel could be stated on a basis of magnetic properties of such a material. A correlation between mechanical and magnetic properties of the maraging steel is treated from the view of non-destructive testing during and after heat treatment as well as during use under unfavourable conditions at elevated operating temperatures. A group of maraging steels shows numerous technical and technological properties, which substantially differ from those of classical steels, i.e. excellent weldability, high ductility in soft state, high hardening ability and favourable suitability for EDM machining. All of those properties are extremely important in machining of technologically exacting products such as die casting dies. The selected maraging steel contains 12 % of nickel and is primarily intended for the production of hot-working dies and various machine elements exposed to heavy mechanical and thermo-mechanical loads. Non-destructive testing of maraging steels enables cheaper and more reliable production. Selected characteristic properties for testing of maraging steel after precipitation hardening are impact toughness, hardness, and residual magnetism. Supervision should be performed not only during precipitation hardening but also during the use of such a material at elevated temperatures at which additional precipitation may occur, which could lead to overaging of the micro-structure. A fast and reliable method of non-destructive testing of mechanical properties could significantly affect the time, price and quality of production as well as maintenance of products made of maraging steel.