Lightweight steel-framed (LSF) structural elements in building construction provide a wayof increasing building sustainability. These structural elements present great potentialfor recycling and reuse, allowing the conservation of natural resources and theenvironment. When compared with other materials, these construction components alsoprovide other advantages: reduced weight with simultaneous high mechanical strength;easier prefabrication, allowing modular elements and higher quality control; shorterperiods for assembling the building on-site; no dimensional variations caused by moisture;and low cost. The high thermal conductivity of steel could be a drawback, leading tothermal bridges if not well designed and executed. In the case of LSF components (e.g.walls and slabs) it is necessary to take special care with the elements’ designoptimisation, with it being essential to use continuous thermal insulation. The buildingenvelope thermal performance is crucial to provide good thermal behaviour and energyefficiency, allowing a reduction of operational energy. In this paper, the LSFconstruction system is analysed in order to show its main advantages and drawbacks. Theassessment of embodied and operational energy is essential to perform a life cycleanalysis. The reduction of both energies’ consumption is crucial to increase thesustainability label. Special focus will be given to the mitigation strategies ofoperational energy in LSF construction.

Recently, the issue of sustainable resource management has been increasingly recognized.Economic growth of human activity is associated with a rapid rise in the use of resourcesin our economy, and society has a potential environmental impact. The UNEP InternationalResource Panel (IRP) pointed out the importance of decoupling resource use and negativeenvironmental impacts from economic activity (UNEP IRP 2011). In order tooptimize the material cycles and increase resource efficiency, material flow analysis(MFA) is a powerful tool to understand the resource consumption and material cycle in thenational economy. In this study, we present the results of global material flow analysisof nickel, which is one of the important resources for reducing energy use andCO2 emission inour society, and discuss the importance and possibility of controlling its resourcelogistics. This study also introduces the challenge of identifying the land-use changes innickel mining sites by a remote-sensing technique, and knowledge to increase the resourceefficiency in metal recycling based on the metallurgical thermodynamic approach. Theresults indicated the importance of recovery of nickel in recycling policies forend-of-life (EoL) vehicles and constructions. Improvement in EoL sorting technologies andimplementation of designs for recycling/disassembly at the manufacturing phase are needed.Possible solutions include development of sorting processes for steel scrap andintroduction of easier methods for identifying the composition of secondary resources.Recovery of steel scrap with a high alloy content will reduce primary inputs of alloyingelements and contribute to more efficient resource use.

There are many examples world-wide how mining contributes to sustainable regionaldevelopment. The LKAB mining and processing of iron ore in the north of Sweden, in theArctic Region, is such an example. The definition of sustainable mining is however notclear-cut and further studies are necessary to fully understand the impacts on economy,society and environment.

Aluminium (Al) consumption growth exceeded those of all other major metals over the lastdecades. The main driver for this development is the broad range of applications for Aland Al-alloys. As the growth in consumption went along with an increase of anthropogenicstocks and flows of Al, information about material cycles became a crucial issue in termsof resource management. In this study a comprehensive material flow analysis (MFA) of theflows and stocks of Al in Austria for the year 2010 is conducted. The focus of thepresented Al balance is on data harmonization and plausibility checks, both based onextensive data and literature research. The stock of Al is derived from bottom-upcalculations indicating a total stock of about 260 kg Al per capita with an annual growthof 11 ± 3.1 kg/cap yr in 2010.Total old Al scrap generation is calculated to be 7 ± 1 kg/cap yr. For considering dataquality aspects of single input data an adopted method for uncertainty assessment has beenapplied to the different material flows. This allowed a consistent evaluation ofuncertainties within the material flow model. Due to the substantial uncertaintiesassociated with end-of-life Al flows and their significance for secondary Al production inAustria, a better data base is needed in order to evaluate and optimize national Al scraputilization in secondary production. Therefore, a dynamic MFA model will be built forAustrian Al flows and, in conjunction with the results from the static analyses, willprovide a reliable decision basis for future Al resource management.

Many materials can only be recycled a limited number of times because of physicaldegradation (paper and board), chemical degradation (plastics), or impurities (severalmetals). Management of the quality of materials is a key to high long-term recycling ratesand, hence, to the sustainable future. This key includes several elements, such as:retaining the quality of materials in the production and use of products; retaining thequality of materials in the recycling processes; and using high-quality materials onlywhen it is required. Pinch analysis is a set of methods to optimize physical flows bytaking the quality into account. It was originally developed for minimizing the energydemand in process industries. It has been adapted for optimization also of water andsolvents flows. A Japanese research group applied part of the method on flows of steelwithin Japan and globally. We present a pilot study that illustrates how all the elementsof the basic pinch approach can be applied to global systems of material flows. Ourmaterial pinch analysis (MPA) distinguishes between three categories of steelapplications, each with its own requirements on the material quality: rolled steel,sections and re-bar. Copper in wiring etc. increases the copper content of steel recycledfrom machinery and eventually restricts the recyclability of the steel in a global systemwhere steel use does not increase. This is important because an MPA is mainly relevantwhen impurities or other quality aspects restrict the recycling rate. Our quantitativeresults should not be considered accurate reflections of the reality, because the pilotstudy is to a large extent based on assumptions and crude data. However, the model gives afirst indication that the maximum recycling rate of steel is approximately 80% in apotential future when steel use does not increase, unless technology is improved. A fullMPA with more thorough data collection would more accurately define the maximum long-termrecycling rate and the minimum quantity of ore-based material. In addition, a full MPAwould give information on for what applications ore-based material should be used, andwhat scrap flows should be discarded rather than recycled. Such information can beimportant for policy-making aiming at increased resource efficiency. If it is importantfor policy-making it is also likely to be important to industrial companies that can beaffected by policies.

A model for predicting the austenite grain growth during a common heating process including continuous and isothermal heating processes in medium carbon alloy steel 42CrMo was developed. The isothermal austenite grain growth kinetics were studied with conditions involving soaking time and soaking temperature. The time exponent n in the model was obtained considering the influence of the initial grain size rather than simply utilizing Beck’s equation. The results showed that the value of the time exponent n is 3.55 ± 0.30 when the temperature is above 1000 °C, while the value is 8.33 when the temperature is below 1000 °C. When the temperature is below 1000 °C, the pinning effect of carbides contributes to the higher value of the time exponent. Based on the isothermal model and the rule of additivity, a model for predicting the grain growth occurring during continuous heating was proposed. A reasonable agreement between the calculations and experimental measurements of grain size was obtained. According to the model, the effect of the initial austenite grain size on the final austenite grain size during induction quenching was analyzed. The initial austenite grain size has a significant effect on the final austenite grain size. In order to obtain a refined quenched microstructure, it is necessary to refine the microstructure at room temperature.

In this study, the effect of titanium addition on the microstructure and wear behavior ofHadfield steel was investigated. To do so, four groups of samples with different titaniumcontents of 0, 0.2, 0.4 and 0.6 wt% were prepared. After casting, the samples wereaustenitized at 1100 °C for 3h and quenched in water subsequently for solution treatment. Themicrostructure of the samples was investigated using an optical microscope (OM) andscanning electron microscope (SEM). For more studies the carbide composition was analyzedvia energy-dispersive spectroscopy (EDX). A wear test was performed via a pin-on-disk weartesting machine. The results show that after heat treatment the microstructure of thetitanium-free sample is fully austenitic, while the other samples show an austeniticstructure with non-continuous carbide precipitates. It was also revealed that titaniumaddition improves the hardness and wear resistance of the samples. The highest wearresistance was observed in the sample with 0.6 wt% titanium content. It was also shownthat the predominant wear mechanisms are adhesive and tribo-chemical. Beyond this, theeffect of cold working via a hammering treatment was studied on the samples and revealedthat austenite-to-martensite transformation improves the hardness and wear resistancesignificantly.