Scania has experienced difficulties with large variations of the slope of the back plane after press quenching of case hardened crown wheels of especially type R780 Steg supplied from ingot cast material. This leads to that a large number of crown wheels has to be remeasured and sorted according to back slope which is time consuming for operators. Also, after sorting of the crown wheels, hard machining has to be adjusted according to the different slopes of the back plane of the crown wheels. In some cases, it also leads to scrapping of the crown wheels.This master’s thesis was divided in two parts. The aim of the first part was to confirm that the crown wheel type and casting technique that exhibits the largest variations in slope of the back plane is the R780 Steg originating from ingot cast material. The crown wheel types that were compared were the R780 Steg, R780 Slät and R885 Slät. Crown wheels manufactured from ingot cast material and from continuous cast material were compared. Hence, 6 combinations were examined. The slope of the back plane was measured with the measuring probe FARO after press quenching. The slope of the crown wheels was found to depend on both casting technique and the geometry of the crown wheel. The results confirmed that the crown wheel type and supplier combination that by far yields the largest variations in slope of the back plane is the R780 Steg supplied by Steel Plant A who uses the ingot casting technique. For this combination the variation exceeds 0,1 mm. All other combinations of crown wheels and suppliers yield acceptable variations.The second part of this master’s thesis was composed of determining if segregations in the cast ingot are the cause of the variations in slope of the back plane of the crown wheel type R780 Steg. This was done by measuring if there is a correlation between the slope of the back plane of the crown wheel after press quenching, the chemical composition and the original position of the crown wheel in the ingot. As in the first part of the study, the distortion was measured by the measuring probe FARO. The samples were sent to Degerfors Laboratorium for chemical analysis. Analyses of C, S and N were made by using combustion analyses. For As, P, B and Al optic spectrometry (spark) was used. All other elements were analysed by x-ray fluorescence. Segregations were found to be present and in combination with the geometry of R780 Steg to be the cause of the large variations in slope of the crown wheels.The results of this thesis show that, for the crown wheel type R780 Steg, Scania should not use suppliers that employ the ingot casting technique. Instead, only suppliers using the continuous casting technique should be used. However, for the other crown wheel types ingot or continuously cast material can be used.

The use of aluminum is a key factor in creating an Eco-friendlier automotive industry. The material has good properties and the ability to reuse the material. The requirement on the material in this industry is very high, due to the exposed working environments. The usage of aluminum will reduce the vehicle’s weight, which in turn will reduce emissions.    Aluminum casting is not free from obstacles. The properties can be altered with different casting methods and the design of the casting to a great extent. This master will focus on how the melt quality will have an impact on the material properties and how it is changed during the process. To fully understand what happens to the melt during the casting process, samples are received at different stages for further investigation. Different data is collected to be able to analyze what happens during the process. A quality measurement called the Quality index is used to determine the change in the quality in the different stages. With data from bifilm and density index, conclusions can be made on how and where the impurities are entering the melt and their effect. A conclusion is made that the degassing harms the quality of the melt.

No description available.

High pressure die casting (HPDC) is both a cost-efficient and high throughput method for making near-net shape castings. 7xxx series aluminum alloys are excellent candidates for manufacturing structural components for significant light-weighting opportunities in the automotive industry. This project explores the development of a new 7xxx series aluminum alloy with iron additions to improve castability. The main objective of this project is to develop an optimized heat treatment process for the new Al-Zn-Mg-Fe alloy to achieve solute homogenization in the primary Al grains. The rationale behind adding iron as an alloying element was presented, as well as an analysis of the Al-Fe intermetallic phases to show their mitigating effects on hot tearing. A detailed analysis of the casting quality was carried out, including detailed microstructural analyses of defects and defect-free castings, correlating process parameters, shot profiles, uniaxial tensile properties, and fractography. Improvements on casting conditions and parameters were suggested. Solution heat treatments were carried out between 0.25 and 24 hours and quenched with forced air. Bulk hardness measurements were obtained following solution heat treatment to determine the arrest times for the precipitation reactions during natural aging. The uniaxial tensile properties of the alloy in the F- and T4-tempers were presented. Microstructural analyses of the alloy were carried out by optical and electron microscopy (SEM), including phase identification, phase fraction, average grain size, and distribution. A predictive model for the homogenization of the solutes in the Al matrix was developed using a one-dimensional diffusion model with spherical geometry, and a MATLAB code was developed to time for complete homogenization. Electron-dispersive X-ray spectroscopy (EDX) line scans were carried out on the F and T4 samples (0.25-2h) and the concentration profiles of Zn and Mg (the diffusing solutes) were extracted and analyzed. The models were verified and validated with experiment data. / Thesis / Master of Applied Science (MASc)

Im Rahmen der Dissertation wurde eine Fertigungstechnologie entwickelt, die die Überleitung des Stahlniederdruckgießverfahrens (3CAST) in die Produktion und somit die Erzeugung des dünnwandigen Stahlgusses ermöglicht. Die konventionellen Stahlgusswerkstoffe sowie ihre Gießbarkeit und Wärmebehandlung wurden untersucht und an die Besonderheiten des neuen Verfahrens und dünnwandigen Stahlgusses angepasst. Auf der Basis von schon existierenden Gießtechnologien wurde eine Formträgertechnologie (FTTech) entwickelt, die unter Berücksichtigung ökologischer Aspekte eine hohe Gussteilqualität und Wirtschaftlichkeit des Gießverfahrens sichert. Die gewonnen Ergebnisse wurden anhand eines Formträgerprototyps unter produktionsnahen Bedingungen erfolgreich erprobt. Somit ist eine Grundlage für den bei der Fa. Evosteel GmbH geplanten Aufbau der Fertigungstechnologie zur Serienproduktion von komplexen dünnwandigen Stahlgussteilen geschaffen.

Im Rahmen der Dissertation wurde eine Fertigungstechnologie entwickelt, die die Überleitung des Stahlniederdruckgießverfahrens (3CAST) in die Produktion und somit die Erzeugung des dünnwandigen Stahlgusses ermöglicht. Die konventionellen Stahlgusswerkstoffe sowie ihre Gießbarkeit und Wärmebehandlung wurden untersucht und an die Besonderheiten des neuen Verfahrens und dünnwandigen Stahlgusses angepasst. Auf der Basis von schon existierenden Gießtechnologien wurde eine Formträgertechnologie (FTTech) entwickelt, die unter Berücksichtigung ökologischer Aspekte eine hohe Gussteilqualität und Wirtschaftlichkeit des Gießverfahrens sichert. Die gewonnen Ergebnisse wurden anhand eines Formträgerprototyps unter produktionsnahen Bedingungen erfolgreich erprobt. Somit ist eine Grundlage für den bei der Fa. Evosteel GmbH geplanten Aufbau der Fertigungstechnologie zur Serienproduktion von komplexen dünnwandigen Stahlgussteilen geschaffen.:1 Einleitung 2 Stand der Technik „Fertigung dünnwandiges Stahlgusses“ 2.1 Stahlgusswerkstoffe 2.2 Metallurgische Erzeugung 2.3 Gießtechnologie 2.3.1 Schwerkraftguss 2.3.2 Gegenschwerkraftguss 2.3.3 Druckguss 2.3.4 Schleuderguss 2.4 Formtechnologie 2.4.1 Dauerformen 2.4.2 Verlorene Formen 2.4.2.1 Tongebundene Formen 2.4.2.2 Technologie der kalthärtenden Formstoffe 2.4.2.3 Technologie der warmhärtenden Formstoffe 2.4.2.4 Feinguss 2.4.2.5 Vollformguss 2.4.2.6 Vakuumformverfahren 2.4.3 Stützschalenverfahren 2.5 Wärmebehandlung 2.6 Dünnwandiger Stahlguss 2.6.1 Erzeugung 2.6.2 Anwendungsgebiete 3 Aufgaben und Zielstellung der Arbeit 4 Werkstoffentwicklung 4.1 Werkstoffauswahl 4.2 Probenentwicklung 4.3 Untersuchung des Erstarrungs- bzw. Abkühlungsvorganges 4.3.1 Versuchsdurchführung 4.3.2 Ergebnisse der Untersuchung 4.3.3 Diskussion der Ergebnisse 4.4 Wärmebehandlung und Ermittlung mechanischer Eigenschaften 4.4.1 Versuchsdurchführung 4.4.2 Ergebnisse der Untersuchung 4.4.3 Diskussion der Ergebnisse 5 Entwicklung der Formtechnologie 5.1 Konzepterarbeitung 5.1.1 Kernpaket 5.1.2 Formträger 5.1.3 Konturnaher Formträger 5.1.4 Formträger mit Formhinterfüllung 5.2 Vorversuch 5.2.1 Versuchsdurchführung 5.2.2 Ergebnisse der Untersuchung 5.2.3 Diskussion der Ergebnisse 5.3 Entwicklung des Formträgerprototyps 5.3.1 Konstruktion des Formträgerprototyps 5.3.2 Erprobung des Formträgerprototyps 5.3.3 Ergebnisse der Untersuchung 5.3.4 Diskussion der Ergebnisse 5.4 Formstoffentwicklung 5.4.1 Untersuchungen zur Einsetzbarkeit verschiedener Formgrundstoffe 5.4.1.1 Untersuchte Formgrundstoffe 5.4.1.2 Eigenschaften der untersuchten Formgrundstoffe 5.4.1.3 Diskussion der Ergebnisse 5.4.1.4 Gießtechnologische Untersuchungen 5.4.1.5 Ergebnisse der gießtechnologischen Untersuchungen 5.4.1.6 Diskussion der Ergebnisse 5.4.2 Untersuchungen zur Einsetzbarkeit verschiedener Bindersysteme 5.4.2.1 Cold-box-Verfahren 5.4.2.2 Resol-CO2-Verfahren 5.4.2.3 Beach-Box-Verfahren 5.4.2.4 Diskussion der Ergebnisse 5.5 Entwicklung des Formstoffüberzuges 5.5.1 Laboruntersuchungen 5.5.2 Gießtechnologische Untersuchungen 5.5.3 Diskussion der Ergebnisse 5.6 Entwicklung des Formhinterfüllmateriales 5.6.1 Vorversuch mit Formträgerprototyp 5.6.2 Diskussion der Ergebnisse 5.6.3 Entwicklung des Formhinterfüllmateriales 5.6.4 Diskussion der Ergebnisse 6 Wirtschaftliche Betrachtung der entwickelten Technologie 7 Beiträge zur Verbesserung der Umweltbedingungen 8 Zusammenfassung

This master thesis had been created at the instigation of Skoda Auto. a.s. tool design department, which designed a new concept of the diecast mold. For this new concept of construction mold was requested to describe its strain-stress behaviour. The main goal of this thesis was to run s-s analysis. According to results of s-s analysis the potentially risky location had been found and the recommendation of the design improvement had been made. The problem has been solved by Finite Element Method in software ANSYS Workbench. The output of the work is mainly used as a basis for the design of high-pressure casting molds of S. A. a.s.

This diploma thesis deals with the technology of high pressure die casting and especially influences having effect on their final quality. The aim of this thesis is to design the measures to convert casting of the cylinder for chainsaw into the serial production. The thesis contains a description of the production of castings by technology of high pressure die casting, theoretical analysis of the factors with effects on their final quality and practical description of the conversion casting of cylinder for chainsaw into the serial production. The problem of converting to serial production has been solved by several samplings and final test series. Part of each sampling is analysis of defects and design of measures leading to elimination or at least minimization of such defects. On the basis of the production process has been successfully optimized and casting of the cylinder for chainsaw was successfully converted into the serial production. The results of this work also allowed for a smooth conversion into the serial production of another type of cylinder, manufactured by company MOTOR JIKOV.

After hot rolling, the presense of segregation in the center of wire-rod can lead to a nonuniform transformation, resulting in bands of martensite in the microstructure. This is considered to be a defect, called center-martensite, because it can cause cracks and breaks during wire drawing. To identify the mechanism for the formation of center-martensite in wire-rod, the structure, macrosegregation and microsegregation in unworked billets were characterized. Based on measurements of secondary dendrite arm spacings, cooling rates during solidification were estimated. It appears that the macrosegregation of carbon and manganese in the billets manifests itself as the microsegregation in wire-rod, which is an agent in forming the center-martensite. Thus, electromagnetic stirring is proposed as a means to reduce the macrosegregation in the billet and, thereby, reduce the occurrence of center-martensite in wire-rod.

Published Article / Rapid tooling (RT) in the context of this research presents the possibility of improving the traditional investment casting process by shortening lead times while still maintaining affordable costs and required quality. Various rapid prototyping processes are available that can be used to create direct metal, polymer or wooden dies for this casting technology. This paper presents results gained in an AMTS project, focusing on RT development for investment casting of light metals. One of the most widely used layer manufacturing processes available in South Africa is selective laser sintering. A machine produced by the German manufacturer EOS (process known as laser sintering) utilising this technology was selected for the study. Two of the materials that are suitable for rapid die making are used, which in tum reflects different mechanical properties and process economics. A standard benchmark part was used as a study base. Two dies were built, one in alumide and one in polyamide. A comprehensive measurement programme was conducted, followed by an appropriate statistical analysis and evaluation regarding accuracy and surface finish. A number of wax patterns were produced. The best wax patterns from each die were selected and evaluated. The subsequently produced castings in AI, Mg and TI were further examined and evaluated. Various issues concerning the reinforcement, wax injection, pattern removal, accuracy and surface finish of the dies are discussed in the paper. The research concludes that rapid tooling techniques can be successfully used for creating accurate dies in order to shorten lead times in the investment casting process chain.