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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 141-143 (July 2008), p. 695-700 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The process of thixoforming incorporates a series of forming processes in the semi-solidstate, which can be categorized between the conventional processes of forging and casting andcombines the advantages of these processes. Thixoforming of steels in the semi-solid state, requiresround, solid particles (globulites) in a liquid matrix which is deformed with low forming forces. Inorder to achieve laminar material flow and to produce segregation-free components, the materialmust fulfil diverse criteria. First, the melting interval should be as large as possible for an easytemperature regulation. Next, low solidus and liquidus temperatures are advantageous regardingtool loading. Additionally, thixoformable steels should show a melting behaviour that is finegrainedand globular. Furthermore, these steels should possess low contents of intraglobular liquidphase fractions.This paper gives a survey of the current state of steel Thixoforming and deals with the developmentof adaptive heat treatment strategies. Regarding the structure formation and the development ofsuitable heat treatment strategies, the once semi-solid state yields new structures that can be appliedin ways not previously possible with conventional hardening processes. New microstructures andup to date unknown better mechanical properties can be adjusted with an optimised heat treatmentstrategy. By this, new fields of application for thixo-materials can be entered and also advancedprocedures for special applications can be established. For example the steel X210CrW12 leads to avery hard material with high wear-resistance, which can be used at higher temperatures than theconventional hardened material. In general, new generic microstructures after thixoforming resultsin unexpected favourable mechanical properties. Problems arise with respect to segregation andpores which resulting in inhomogeneous property distributions
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 539-543 (Mar. 2007), p. 4297-4302 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Thixoforming of metals is a new forming technology, which combines the advantagesof casting and forging. This technology focuses on structural components with complex shapes,which can not be manufactured using conventional processing methods. Different components madeof aluminum and magnesium are already industrially produced. Apart from this, the use of steels inthe Thixoforming processes is still being researched and developed. During the last years it becameobvious that the Thixoforming of steels may not be a complete substitution for highly automateddie-casting or forging processes, but rather a new process route to produce special components withhigh quality and geometrical demands. Special interest lies in the development and production offiligree components, parts with voids or undercuts, integrated elements such as tubes or tube-systemsand joining pieces or products made of different materials. Beside the design of suitable toolmaterials and tool concepts, the development of homogeneous heating strategies and thedevelopment of thixoformable steels is at the center of current research. Therefore, this paper focuseson material requirements which are needed for the Thixoforming of steels and on the production ofcomponents and occurring problems. By use of a failure catalogue for Thixoforming of steels,reasons for characteristic failures and suggestions are given to avoid them, so that the quality ofthixoformed parts can be improved
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 116-117 (Oct. 2006), p. 34-43 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The semi solid forming of steel has the potential of an innovative technology, which couldopen a new possibility of metal components production. Earlier research works in the 1990s havealready shown the principal feasibility of the process but also revealed the various kinds of technicalproblems. Since then, research works on steel processing have been continuously made in severallocations in Japan, USA and Europe. Currently, the focus of these research activities is thedevelopment of suitable tool material and the achievement of high part quality, which is the key pointfor the success of the process. This paper gives an overview of the previous research works and thecurrent state of the research with an outlook on future tasks for this challenge
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 116-117 (Oct. 2006), p. 177-180 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The bearing steel 100Cr6 in the forged and hardened condition is of great importance inindustrial use. Escaping the geometry restrictions of conventional forging, the application ofsemi-solid metalworking (SSM) offers significantly increased design freedom. Using conventionallyavailable rolled feedstock material with carbide banding, however, results in a higher segregationtendency during thixoforging, and thus special attention was paid to the feedstock’s “quality”. Toachieve a fine-grained, globular microstructure in the semi-solid state, castings with and without theaddition of 100 ppm titanium were compared with the hot rolled material. With its inherent nitrogenTi forms TiN particles, which reduce grain-growth in austenite. The results indicate that TiNprecipitates strongly affect grain growth during solid state processing, but the grain size in thesemi-solid state can only be influenced for short process times. Generally the cast feedstock materialspossess smaller globulites in the semi-solid state compared to forgings, so that a reduction of thesponge effect and a minimization of the segregation in produced components are expected. Since thecast material already showed a fine-grained, globulitic microstructure, the use of TiN is notrecommended because of the possible negative influence of TiN on the dynamic mechanicalproperties
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 116-117 (Oct. 2006), p. 209-212 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: This paper deals with the examination of the steel grade X210CrW12 and its suitabilityfor Thixoforming. In the semi-solid state, the microstructure of this steel consists of a homogeneousdistribution of globular particles surrounded by liquid. Additionally, carbides are stabile up tofraction liquid contents of approximately 40%. After quenching, this steel reveals a globularaustenitic microstructure with eutectic (former liquid phase) at the grain boundaries. Compressiontests permit to determine the influence of different process parameters on the properties and thematerial behaviour in the semi-solid state. Their influence on the microstructure was investigatedbut not yet highlighted. Further investigations on this steel allow a fine-tuning to establish optimalprocess windows of the different thixoforming- and rheoforming- routes
    Type of Medium: Electronic Resource
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