Innovative software for steel hardness: Bochum student inspires experts!

Innovative software for steel hardness: Bochum student inspires experts!

Jakob Lensing, a student at the Chair of Materials Engineering at the Ruhr University Bochum, recently presented a significant expansion of a computer program for calculating steel hardness. On February 13, 2025, he was awarded 2nd prize in the Dörrenberg Studies Award for his study work. Lensing's research aims to predict the ideal chemical composition from the desired properties of a material. Existing software at the department can predict macroscopic properties such as hardness based on chemical composition and heat treatment.

Lensing's recent advances include the integration of the martensite starting temperature (MS) factor, a crucial metric in materials science. The martensite starting temperature defines the point at which the structure of the material changes after annealing during quenching. This restructuring in the structure leads to a significant hardness of the material, which is crucial for numerous industrial applications. The complete transformation of the structure depends heavily on this temperature.

Martensitic stainless steel and its properties

Martensitic stainless steel, which belongs to the 400 series, has a body-centered tetragonal (BCT) crystal structure. This type of stainless steel typically contains between 12-18% chromium and 0.1-1.2% carbon. Despite its high strength and hardness after heat treatment, martensitic stainless steel shows lower corrosion resistance compared to austenitic stainless steel. Applications include cutlery, surgical instruments, valves, bearings and turbine blades.

Heat treatment of martensitic stainless steel is accomplished by heating to temperatures between 925 and 1070°C, followed by rapid cooling (quenching) to achieve the desired martensitic structure. This material also has magnetic properties, which makes it applicable in various industries. The most common grades are 403, 410, 416, 420, 431, 440A, 440B, 440C and 17-4 PH. Grade 410 in particular is known for its balanced combination of corrosion resistance and high strength.

The process of martensite formation

Martensite is a metastable structure that is created through a diffusionless and athermal transformation from the original structure. The transformation occurs when the material is quickly cooled from a high-temperature phase – austenite, for example – to a low-temperature phase. It is important to ensure that the cooling occurs quickly enough to prevent diffusion processes.

Martensite formation occurs via nuclei already present in the austenite and is not limited to metals; it can also occur in ceramics and polymers. The transformation of the face-centered cubic lattice of austenite into a tetragonal body-centered lattice is a central process that depends, among other things, on the chemical composition. The changes in the structure lead to a significant increase in hardness, which is also strongly influenced by the carbon content.

In summary, Jakob Lensing's research represents an important step in materials engineering, especially in the area of ​​martensitic steels. The precise calculation of steel hardness could not only revolutionize material development, but also accelerate the application of these material engineering findings in other industrial contexts.

Ruhr University Bochum reports that Lensing has significantly improved its steel calculation method. You can find out more about martensitic stainless steel at Steel Pro Group and the overall process of martensite formation Wikipedia.