Materials Science Forum Vol. 892

Abstract: Products and manufacturing processes of long-product producers are subject to constantly changing requirements, characterized by increasing demands on product quality and the efficient use of resources in production, combined with permanent cost pressures. For these reasons steel wire producers must constantly improve their innovation capacity to be able to meet increasing customer demands more flexibly and more efficiently. This awareness has been anchored at Swiss Steel AG, part of the Schmolz + Bickenbach Group, for many years and leads to more and new solutions in all corporate divisions.This article focuses on practical examples from the areas of process and product innovation. It discusses options for and the potentials and challenges of meeting current and future market needs.The successful implementation of new solutions requires an in-depth understanding as well as the application of knowledge throughout the entire process chain from development, production, sales to further processing and actual use of a product. The technical challenges are addressed as well as the opportunities presented when new approaches are sought.

Abstract: This paper examines the economic costs and benefits of the use of an ultrasonic wire or tape cleaning system. In the last years, major technology improvements made the use of power ultrasound more reasonable for the cleaning of wires. The cavitation of modern high-power ultrasonic processors serves to remove grease, oil, and other contaminations from the surface of the wire. Reduced investment costs and high performance of these ultrasonic wire cleaning systems made them not only competitive but superior to conventional cleaning methods as for example acid baths.

Abstract: The heat treatment after cold forming is used to decrease the residual stresses of springs, but the mechanical characteristics of the spring steel wires alters, too. This presentation describes the influence of the heat treatment technology (oven equipment, temperature, duration,…) to the properties and quality of helical compression springs made from oil hardened and tempered spring steel wire.

Abstract: Simulation of the rolling and controlled cooling sequence for bainitic steel rods was the general objective of the paper. The main focus was put on exploring possibility of prediction of the retained austenite occurrence in TRIP assisted bainitic steels. Existing discrete phase transformation models require long computing times and their application to optimization of industrial processes is limited. Therefore, a model based on the modified JMAK equation was proposed. The occurrence of the retained austenite was predicted by carbon distribution calculations in the austenite during bainite transformation. This model was implemented into the FE software for simulation of cooling of rods. The model was verified by comparison of results with the physical simulations during rolling in the pilot mill and during cooling. The first part of the paper contains thermal-mechanical-microstructural simulations of rod hot rolling process. The objective of this part was to determine temperature and grain size distribution at the rod cross section at the beginning of phase transformations. FE simulations of the cooling were performed next. Correlation between cooling parameters and the volume fraction of the retained austenite in rod was determined.

Abstract: Actual improvements in rod or wire production e.g. in relation to power requirements, energy consumption and final material properties demand powerful simulation tools for process optimization, pre-setting calculations or automation. The groove pass design model of TU Bergakademie Freiberg was developed and applied for this purposes. This paper gives a short review of the history of this model approaches and highlights some important stages of development.

Abstract: A constant strain hardening rate is characteristic for large strain deformation at low temperatures and often observed during wire drawing. This stage of deformation, in the following referred to as stage IV, is determined by the microstructural evolution of dislocation cells. At elevated temperatures, rapid stress saturation is typically reached and no stage IV behavior is observed. This behavior is modelled in the present work, following the concept of state-parameter based plasticity, evolving dislocation density and subgrain formation as functions of strain rate, strain and temperature. It is demonstrated that the temperature dependence of state parameters at different deformation stages is closely related. The present model is compared to a series of compression tests carried out on a Gleeble 1500 thermo-mechanical simulator. EBSD micrographs of the same material reveal the microstructural evolution during plastic deformation. It is shown experimentally that the transition from cell forming behavior to subgrain formation correlates well with the disappearance of stage IV and the overall change in the dominant mechanism for overcoming obstacles. In combination with thermally activated yield stress prediction, this model, recently implemented in the software package MatCalc, offers a powerful tool for flow-curve simulation.

Abstract: The main objective of this research was a study the simultaneous influence of cold working and particle reinforcement on mechanical properties of Al. The model composites were fabricated by cold pressing RAl1 aluminium and 5% and 10% SiC powders and hot extrusion with ratio 3.8 in isothermal conditions at 480°C with 90° die angle to 18 mm diameter. Some specimens were then cold drawn with linear velocity 1 m/min to 16% area reduction, and one specimen in 3 passes to 51% reduction in area. Mechanical properties of the near fully dense composites were determined by axial compression, bend tests and hardness measurement and their microstructures examined, showing near homogenous distribution of SiC particles in the aluminium matrix. The increase in Young’s modulus was from 67 to 74 GPa and to 82 GPa for 5% and 10% reinforcement, respectively. Drawing increased average yield strength from 70 to 100 MPa for Al, and from 74 to 110 MPa and from 80 to 115 MPa, for 5 and 10% reinforcement, respectively. The results indicate that there is a significant increase in E, in accord with the law of mixtures, through incorporation of SiC and a synergistic effect of SiC and plastic deformation during drawing on strength. An attempt is made to identify the various contributions to overall strengthening of Al by considering also Al-8.8Cu-6.3%Si-0.7Mg alloy. It appears that alloying and age-hardening have the greatest effect, but that contributions from hot, warm and cold working are not insignificant. As powder metallurgy processing is an important fabrication method, their incorporation into the processing schedule merits consideration.

Abstract: Hpulcas GmbH has developed a process of high purity nickel wire manufacturing directly from cathode plates without melting. This means significantly lower capital investments and energy costs as compared to the standard manufacturing technology by melting on the one hand and remaining of the high degree of purity on the other hand. Hpulcas wire is produced by the hot rolling of full cathode plates, slitting the plates into sticks, frontal joining and drawing.High purity nickel has such beneficial properties as microcleanliness, excellent mechanical and electrical properties and beneficial corrosion resistance. These properties have been used in batteries and fuel cell components, welding and brazing products, and sensing and controlling instruments.

Abstract: Ultrafine-grained (UFG) pure copper has been in the focus of materials scientists over the last two decades, however ultrafine-grained high-strength copper alloys have scarcely been processed or characterized so far industrially.In this contribution, UFG copper alloys, especially Cu-Ni-Si alloys, being well known as ideal materials for electromechanical connectors, springs and leadframes, are presented. Precipitation hardened Cu-Ni-Si alloys are a well established and technologically important class of materials for a wide range of applications where high strength and good conductivity are required. Yield strength and fatigue properties of metallic alloys can be significantly enhanced by severe plastic deformation methods. In contrast to other strengthening methods such as solid solution hardening, severe plastic deformation leads to a weaker decrease of electrical conductivity and is therefore a means of enhancing strength while maintaining acceptable conductivity for current bearing parts and components. Characterization of these materials after severe plastic deformation by swaging, wire drawing and subsequent aging was carried out using conductivity-, hardness-and tensile tests as well as highly-resolved microstructural characterization methods.The results reveal that UFG low alloyed copper alloys exhibit impressive combinations of properties such as strength, conductivity, high ductility as well as acceptable thermal stability at low and medium temperatures. By a subsequent aging treatment the severely plastically deformed microstructure of Cu-Ni-Si alloys can be further enhanced and thermal stability can profit from grain-boundary pinning by precipitated nanoscale nickel silicides.