Processing Strategies for Hot-Rolled Medium-Mn Steels

The study aims at reviewing manufacturing schedules for hot-rolled and intercritically-annealed and thermomechanically processed medium-Mn sheet steels. Major differences between these two types of processing are indicated. They include initial microstructure (low-C martensite for hot-rolled products and deformed austenite for thermomechanically processed products), partitioning of alloying elements (depending on intercritical annealing or batch annealing conditions) and microstructure prior to cooling (ultrafine-grained lath mixture of ferrite and austenite for hot-rolled, intercritically annealed products and deformed austenite for directly cooled products). The comparison of typical microstructures (LM, SEM) and phase transformation behavior are presented. A role of Mn as an austenite stabilizer in a range used for medium-Mn steels is explained. Some results are provided for economic steels containing 3% and 5% Mn.

Sintering of High Mn Cemented Carbides in Mn-Rich Environment

The economic, environmental and healthcare aspects are pushing cemented carbide industry to reduce or even avoid the usage of conventional binder metals – nickel and cobalt. Commonly, austenitic Fe-Ni alloys have been preferred choice for substituting Co. Similar to Ni, manganese acts as austenite stabilizer and studies have shown that Fe-Mn alloys offer alternative binder metal to Co and Ni in cemented tungsten carbides. In addition, Fe-Mn as a binder potentially offers improved wear resistance due to the well-known wear properties of Fe-Mn-C steels. Addition of chromium to the binder composition increases corrosion performance of composite. Cemented carbides bonded with austenitic FeCrNi binder have demonstrated promising performance. In present work the possibility of achieving austenitic binder phase through substitution of nickel by manganese as an austenite stabilizer is investigated. Structure formation, phase composition and mechanical performance of WC-FeMn and WC-FeCrMn cemented carbides are discussed.

Macrosegregation Characteristics of Ferrite and Austenite Stabilizer Elements in Large Size High Strength Steel Ingot

In the present work, the segregation degrees of ferrite and austenite stabilizer alloying elements were analyzed for a high strength steel. For this, samples were taken from the surface and center of the hot-top and the upper section of a 40 MT ingot. The results showed that the positive segregation ratios for all the investigated elements were higher in the ingot center than in the surface with higher values for austenite stabilizer elements. The increase of austenite alloying element stabilizers was accompanied by the change in the primary solidification mode of the austenite phase. The obtained results are in good agreement with the observed presence of austenite, revealed by X-ray diffraction analysis, stabilized by the austenite alloying elements.

Microstructural Characterization and Properties of Microalloyed Powder Metallurgy Steels

The aim of this research is to investigate the effect of alloying elements of nickel, molybdenum, carbon and copper on hardness, density and microstructure of low alloy steel produced by powder metallurgy method. The results showed that molybdenum addition could lead to increase the density and hardness. Also, an increase in carbon content up to 1 wt. % could result in an increase in density and hardness. Copper is mainly added to increase strength as a result of solid solution hardening effect. Molybdenum is a ferrite stabilizer while Nickel is a strong austenite stabilizer. Consequently, the nickel and copper rich regions are mainly surrounded by austenite or bainite. Regions with higher amounts of alloying elements appeared to be martensitic islands. Increasing martensite and bainite volume fraction led to increase hardness.