Well-defined heat-treatment guidelines are required to achieve the target mechanical properties in high-chromium steels for forgings. Moreover, for this class of materials, the microstructure evolution during heat treatment is not clearly understood. Thus, it is particularly important to assess the steel microstructure evolution during heat treatment, in order to promote the best microstructure. This will ascertain the safe use for long-term service. In this paper, different heat treatments are considered, and their effect on a 7% Cr steel for forging is reported. Results show that, following the high intrinsic steel hardenability, significative differences were not found versus the cooling-step treatment, although prior austenite grain size was significantly different. Moreover, retained austenite (RA) content is lower in double-tempered specimens after heat treatments at higher temperatures.

AISI 904L is a super-austenitic stainless steel that is remarkable for its mechanical properties and high corrosion resistance, which strictly depend on its chemical composition and microstructural features. The recrystallization process and grain growth phenomena play key roles in achieving high levels of material quality, as often requested by customers for specific applications. In this paper, the evolution of the microstructure and hardness values after cold rolling and subsequent annealing is reported, with the aim of optimizing the thermomechanical treatment conditions and improving the efficiency of the production process. The investigation was focused on three different cold reduction ratios (50%, 70% and 80%), while combining different annealing temperatures (950, 1050 and 1150 °C) and soaking times (in the range of 20–180 s. The test results were organized using a data analysis and statistical tool, which was able to show the correlation between the different variables and the impacts of these on recrystallization and grain growth processes. For low treatment temperatures, the tested soaking times led to partial recrystallization, making this condition industrially unattractive. Instead, for the higher temperature, full recrystallization was achieved over a short time (20–40 s), depending on the reduction ratio. Regarding the grain growth behavior, it was found to be independent of the reduction ratio; for each treatment temperature, the grain growth showed a linear trend as a function of the soaking time only. Moreover, the static recrystallization kinetics were analyzed using a statistical analysis software program that was able to provide evidence indicating the most and least influential parameters in the process. In particular, taking into consideration the hardness values as output data, the temperature and soaking time were revealed to have major effects as compared with the reduction ratio, which was excluded from the statistical analysis. The prediction approach allowed us to formulate a regression equation in order to correlate the response and terms. Moreover, a response optimizer was used to predict the best solution to get as close as possible to the hardness target required by the market.

The adoption of the ultrafast heating (UFH) process has gained much attention in the last few years, as the green energy and minimization of CO₂ emissions are the main aspects of contemporary metal science and thermal treatment. The effect of ultrafast heating (UFH) treatment on carbon steels, non-oriented grain (NGO) electrical steels, and ferriticor austenitic stainless steels is reported in this review. The study highlights the effect of ultrarapid annealing on microstructure and textural evolution in relation to microstructural constituents, recrystallization temperatures, and its effect on mechanical properties. A strong influence of the UFH process was reported on grain size, promoting a refinement in terms of both prior austenite and ferrite grain size. Such an effect is more evident in medium–low carbon and NGO steels than that in ferritic/austenitic stainless steels. A comparison between conventional and ultrafast annealing on stainless steels shows a slight effect on the microstructure. On the other hand, an evident increase in uniform elongation was reported due to UFH. Textural evolution analysis shows the effect of UFH on the occurrence of the Goss component (which promotes magnetic properties), and the opposite with the recrystallization g-fiber. The recovery step during annealing plays an important role in determining textural features; the areas of higher energy content are the most suitable for the nucleation of the Goss component. As expected, the slow annealing process promoted equiaxed grains, whereas rapid heating promoted microstructures with elongated grains as a result of the cold deformation.

Plastic deformation is the most common technique adopted to manufacture complex shape pieces in the most efficient way. Even higher requirements need to be faced in the different applications. In order to target such requirement quality and compliance tests are carried out aimed to guarantee that these standards are faced. This often means a waste of material and economic resources. A far as concerns welded stainless steel pipes many criticises affecting the general trend of subsequent machining need to be considered. Such critical issues are more evident in the case of ferritic stainless steel with respect to austenitic ones. Therefore, the study of operating and geometric parameters is fundamental in the production process of ferritic stainless-steel tubes, whose use is mainly for the automotive industry. The possibility to simulate by finite element method (FEM) allows to evaluate the effect of geometric parameters and process constraints on plastic deformation tubes capability, thus allowing to properly fit the plastic deformation process to the target shape as a function of the adopted steel.

A welded stainless steel tube is a component used in several industrial applications. Its manufacturing process needs to follow specific requirements based on reference standards. This calls for a predictive analysis able to face some critical issues affecting the forming process. In this paper, a model was adopted taking into account the tube geometrical parameters that was able to describe the deformation process and define the best industrial practices. In this paper, the effect of different process parameters and geometric constraints on ferritic stainless steel pipe deformation is studied by finite element method (FEM) simulations. The model sensitivity to the input parameters is reported in terms of stress and tube thinning. The feasibility of the simulated process is assessed through the comparison of Forming Limit Diagrams. The comparison between the calculated and experimental results proved this approach to be a useful tool in order to predict and properly design industrial deformation processes.