Lightweight steel-framed (LSF) structural elements in building construction provide a way of increasing building sustainability. These structural elements present great potential for recycling and reuse, allowing the conservation of natural resources and the environment. When compared with other materials, these construction components also provide other advantages: reduced weight with simultaneous high mechanical strength; easier prefabrication, allowing modular elements and higher quality control; shorter periods 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 to thermal 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’ design optimisation, with it being essential to use continuous thermal insulation. The building envelope thermal performance is crucial to provide good thermal behaviour and energy efficiency, allowing a reduction of operational energy. In this paper, the LSF construction system is analysed in order to show its main advantages and drawbacks. The assessment of embodied and operational energy is essential to perform a life cycle analysis. The reduction of both energies’ consumption is crucial to increase the sustainability label. Special focus will be given to the mitigation strategies of operational 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 resources in our economy, and society has a potential environmental impact. The UNEP International Resource Panel (IRP) pointed out the importance of decoupling resource use and negative environmental impacts from economic activity (UNEP IRP 2011). In order to optimize the material cycles and increase resource efficiency, material flow analysis (MFA) is a powerful tool to understand the resource consumption and material cycle in the national economy. In this study, we present the results of global material flow analysis of nickel, which is one of the important resources for reducing energy use and CO2 emission in our society, and discuss the importance and possibility of controlling its resource logistics. This study also introduces the challenge of identifying the land-use changes in nickel mining sites by a remote-sensing technique, and knowledge to increase the resource efficiency in metal recycling based on the metallurgical thermodynamic approach. The results indicated the importance of recovery of nickel in recycling policies for end-of-life (EoL) vehicles and constructions. Improvement in EoL sorting technologies and implementation of designs for recycling/disassembly at the manufacturing phase are needed. Possible solutions include development of sorting processes for steel scrap and introduction of easier methods for identifying the composition of secondary resources. Recovery of steel scrap with a high alloy content will reduce primary inputs of alloying elements and contribute to more efficient resource use.

There are many examples world-wide how mining contributes to sustainable regional development. The LKAB mining and processing of iron ore in the north of Sweden, in the Arctic Region, is such an example. The definition of sustainable mining is however not clear-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 last decades. The main driver for this development is the broad range of applications for Al and Al-alloys. As the growth in consumption went along with an increase of anthropogenic stocks and flows of Al, information about material cycles became a crucial issue in terms of resource management. In this study a comprehensive material flow analysis (MFA) of the flows and stocks of Al in Austria for the year 2010 is conducted. The focus of the presented Al balance is on data harmonization and plausibility checks, both based on extensive data and literature research. The stock of Al is derived from bottom-up calculations indicating a total stock of about 260 kg Al per capita with an annual growth of 11 ± 3.1 kg/cap yr in 2010. Total old Al scrap generation is calculated to be 7 ± 1 kg/cap yr. For considering data quality aspects of single input data an adopted method for uncertainty assessment has been applied to the different material flows. This allowed a consistent evaluation of uncertainties within the material flow model. Due to the substantial uncertainties associated with end-of-life Al flows and their significance for secondary Al production in Austria, a better data base is needed in order to evaluate and optimize national Al scrap utilization in secondary production. Therefore, a dynamic MFA model will be built for Austrian Al flows and, in conjunction with the results from the static analyses, will provide a reliable decision basis for future Al resource management.

Many materials can only be recycled a limited number of times because of physical degradation (paper and board), chemical degradation (plastics), or impurities (several metals). Management of the quality of materials is a key to high long-term recycling rates and, 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 the quality of materials in the recycling processes; and using high-quality materials only when it is required. Pinch analysis is a set of methods to optimize physical flows by taking the quality into account. It was originally developed for minimizing the energy demand in process industries. It has been adapted for optimization also of water and solvents flows. A Japanese research group applied part of the method on flows of steel within Japan and globally. We present a pilot study that illustrates how all the elements of the basic pinch approach can be applied to global systems of material flows. Our material pinch analysis (MPA) distinguishes between three categories of steel applications, 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 recycled from machinery and eventually restricts the recyclability of the steel in a global system where steel use does not increase. This is important because an MPA is mainly relevant when impurities or other quality aspects restrict the recycling rate. Our quantitative results should not be considered accurate reflections of the reality, because the pilot study is to a large extent based on assumptions and crude data. However, the model gives a first indication that the maximum recycling rate of steel is approximately 80% in a potential future when steel use does not increase, unless technology is improved. A full MPA with more thorough data collection would more accurately define the maximum long-term recycling rate and the minimum quantity of ore-based material. In addition, a full MPA would give information on for what applications ore-based material should be used, and what scrap flows should be discarded rather than recycled. Such information can be important for policy-making aiming at increased resource efficiency. If it is important for policy-making it is also likely to be important to industrial companies that can be affected 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 of Hadfield steel was investigated. To do so, four groups of samples with different titanium contents of 0, 0.2, 0.4 and 0.6 wt% were prepared. After casting, the samples were austenitized at 1100 °C for 3 h and quenched in water subsequently for solution treatment. The microstructure of the samples was investigated using an optical microscope (OM) and scanning electron microscope (SEM). For more studies the carbide composition was analyzed via energy-dispersive spectroscopy (EDX). A wear test was performed via a pin-on-disk wear testing machine. The results show that after heat treatment the microstructure of the titanium-free sample is fully austenitic, while the other samples show an austenitic structure with non-continuous carbide precipitates. It was also revealed that titanium addition improves the hardness and wear resistance of the samples. The highest wear resistance was observed in the sample with 0.6 wt% titanium content. It was also shown that the predominant wear mechanisms are adhesive and tribo-chemical. Beyond this, the effect of cold working via a hammering treatment was studied on the samples and revealed that austenite-to-martensite transformation improves the hardness and wear resistance significantly.