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The present contribution concentrates on the different effects of Si and Al on the carbide precipitation and austenite decomposition during the Q&P-process and an additional galvannealing treatment of up to 560 °C. These effects have been investigated by dilatometry (derivation of relative length change) and differential scanning calorimetry (heat flow) during tempering. It was possible to show the beneficial effect of Si on retarding the carbide precipitation in tempered martensite and thereby the ability to stabilize higher amounts of retained austenite compared to Al. Furthermore, the effect on retained austenite decomposition during Q&P and subsequent galvannealing could be demonstrated. Here, Al has the benefit to increase the thermal stability of austenite during galvannealing.

Modelling and simulation of solidification processes and solid-state phase transformation have become key instruments in the field of alloy development and heat treatment optimization. Apart from equilibrium-controlled processes, also diffusion-based effects need to be considered. This contribution presents some typical approaches at the example of martensitic stainless steels. Important aspects affecting the production and properties of these steels, such as alloying limits with nitrogen, the formation of ledeburitic structures, or the retained austenite content after heat treatment, can be predicted with reasonable accuracy.

© 2022 Society of Dyers and Colourists.Sustainability, being a recent buzzword, has been given an increasing emphasis in all industry fields, especially in the textile industry, since it is one of the main contributing sectors to resource consumption and thus environmental pollution. Among them, coloration of textiles should be paid special attention due to offering enormous savings in terms of sustainability. Within all fibres, cotton, being one of the cellulosic fibres, has been the most widely used material alone or together with poly(ethylene terephthalate) (PET). Therefore, we focus on the coloration of cellulose-based fibres and its blends with PET in this review. There is only one single coloration technique at the intersection of sustainability and coloration, that is, sublimation or heat transfer printing, because it is the most eco-friendly approach for the coloration of textiles. There are many studies on this issue, in which either cellulose, that is, cotton, or the transfer paper is modified/treated. In spite of many attempts for sublimation printability of cotton and its blends with PET, they still have problems in terms of sustainability that limits its applicability. In light of ever-increasing sustainability issues such as Agenda 2030, new developments are yet to be expected for achieving sustainable coloration of cellulose-based textiles and their blends. Therefore, it is high time to revisit the sublimation printability of cellulose-based textiles, to mention the latest developments considering nanotechnological advancements, and to give a future perspective in this field.

The typical heat treatment of martensitic stainless steels comprises hardening and subsequent tempering. Depending on the application and size of the component, tempering is carried out either at low temperatures (< 300 °C) or at high temperatures (> 500 °C). In this paper, tempering at lower temperatures is examined. First, the austenitizing step is considered in greater detail and an optimized formula for the calculation of the MS temperature of such steel grades is created in order to enable to be modelled. For the calculations, the austenite composition is determined at different austenitizing temperatures using thermodynamic simulation. Furthermore, the transformation of austenite into martensite during quenching is described with the help of the Koistinen-Marburger equation. The second part deals with effects in the material at low holding temperatures. Here, the influence of different hardening temperatures and interception temperatures of the quenching procedure is investigated. There is no complete partitioning at temperatures of 300 °C. Certain tempering processes can also take place, such as the formation of transition carbides, so-called M3C carbides. A typical tempering with formation of stable Cr-rich carbides does not occur at this low temperature. Finally, the calculated results of the model correlate well with microstructural investigations (XRD, LOM). ◼

The influence of a thermal-treatment simulating a galvannealing-process (GA) on the microstructure of a 0.2C–4Mn–1.5Si and 0.2C–4Mn–1.5Al (in wt-%) medium-Mn-Q&P-steel was investigated in detail us...

The modulus of elasticity is an important parameter for an accurate prediction of the springback in sheet metal forming processes. With increasing plastic deformation, this modulus behaves nonlinearly and declines, which leads to an unpredictable springback behavior. The most cited reason for this nonlinearity is the dislocation movement during plastic deformation that especially occurs with multiphase steels. The present contribution investigates the nonlinear unloading behavior and the resulting decrease of the elastic modulus from a differently heat treated DP980 steel. The heat treatments set five different microstructures with martensite volume fractions in the range of 42 to 95 %. By means of the tensile test, a decline of the elastic modulus according to pre-strain was examined by evaluating the chord-modulus during unloading at different strain levels. In addition, a nano-hardness test was performed. It turned out that in all heat treatment conditions, a pronounced decrease in the modulus of elasticity up to 25% from the initial value occurred. With decreasing annealing temperature and lower martensite volume fraction, respectively, the martensite hardness increased, leading to higher hardness differences between the ferrite and the martensite phase in the microstructure. This led to an increase of strain hardening, i.e. to an increased formation of fresh mobile dislocations in the vicinity of the harder martensite phase during plastic deformation. As a result, the modulus of elasticity decreased more sharply. Thus, in the present contribution, an interplay between the martensite volume fraction and its hardness on the decrease of elastic modulus could be clearly manifested.

The service life of roller bearings is extremely sensitive to large and hard nonmetallic inclusions (NMIs), requesting the highest standards in their production. To determine the metallurgical possibilities, the effect of Al2O3 contents between 0 and 33 pct in the remelting slag was investigated by remelting a roller bearing steel in an experimental electroslag remelting (ESR) plant. Thereby, changes in the chemical composition of the materials (electrode vs ingots) and in the remelting slag during remelting, as well as the amount and composition of the NMIs prior to and after remelting, were investigated. Changes in the chemical composition can largely be explained by equilibrium reactions between the slag and the metal, thereby low Al contents in the remelted materials could only be achieved with the lowest Al2O3 contents in the slag. Furthermore, higher Al2O3 contents in the slag also lead to higher oxygen and sulfur contents in the steel as well as higher amounts of NMIs after remelting. The composition of the NMIs changed from alumina type for high Al2O3 contents to spinel type and other mixed MgO-SiO2 oxides for low Al2O3 contents. The results indicate solutions for the production of bearing steels with the lowest amounts of undesired large and hard NMIs.