Mareile Kriwall

Graduation:
Dipl.-Ing.
Function:
Manager process technology
Phone:
+49 (0)511 279 76-330
E-Mail:
kriwall@iph-hannover.de
vCard:
vCard

Publications

Hybrid compound forging of aluminum bulk parts and steel sheet metals is a combination of material lightweight design and structural lightweight design. During this process, an aluminum bulk part and a steel sheet metal are combined and formed simultaneously. A material joint is generated by deforming, using zinc as solder material. This prevents the generation of brittle intermetallic Fe-Al-Phases as well as contact corrosion. The zinc layer is applied to the aluminum bulk part by hot dipping. To create a material locking connection by forming, suitable parameters such as the forming temperature are identified in first experimental trials. Microsections showed that the zinc layer is still intact after forming. In this paper the investigation of the effects of different steps of forming and different geometries of the aluminum bulk part surface on the joint strength are described. The forming tests show that a further forming of the aluminum part, resulting in a bigger deformation, leads to a stronger connection between both joining partners. But there is a limit to the forming since the applied forces can transfer to the steel sheet leading to an unintended deformation. The generated hybrid parts are tested for their ability for further forming. Therefore, the joined hybrid parts are undertaken a deep drawing process to see if the joint withstands further forming of the hybrid part.

aluminium, hybrid forging, lightweight construction, hybrid

The aim of subproject B1 of the Collaborative Research Center (CRC) 1153 is to determine the formability of novel hybrid semi-finished products by means of incremental forming cross wedge rolling. Main aspect is the forming of hybrid semi-finished products made of steel, aluminium and hard material alloys. In order to reduce the component weight, the use of hybrid semi-finished products makes it possible to manufacture less stressed segments of a previously monolithic component from a light metal. To increase wear resistance, a component area (e.g. a bearing seat) can be coated with a hard material. In addition, process variables (e.g. temperature and force) are to be measured in contact between work piece and tool in the future. There are primarily two material arrangements for the semi-finished products used: coated (coaxial - demonstrator shaft 1) and joined at the front (serial - demonstrator shaft 3). One challenge is the heating of the semi-finished products necessary for forming, since the hybrid semi-finished product has different flow resistances due to the different materials and may have to be heated inhomogeneously in order to enable uniform forming.

cross-wedge rolling, forming, hybrid work pieces, tailored forming, hybrid semi-finished products

In order to reduce CO2 emissions, it is necessary to know the emissions of operational processes. The Institut für Integrierte Produktion Hannover gGmbH has developed a software demonstrator which shows ecological-logistic cause-effect relationships. Internal and logistical processes can be investigated with regard to CO2 emissions, costs and process duration. Comparisons of different alternatives illustrate differences and show savings potentials of CO2.

ecology, logistics, CO2

The Institute for Integrated Production Hannover develops process technologies for the simultaneous forming and joining of dissimilar materials. In the future, they should enable, for example, sheet-metal solid parts and steel-aluminum connections. This expands the possibilities for cost-efficient multi-material construction methods in the automobile.

forging, hybrid, progressive compound

The CO2 emissions of the logistics sector and the resulting environmental impact are continuously increasing. Rising costs for energy and resources, increased sensitivity of customers, changed legal bases and the impending climatic change force producing enterprises to ecologically-oriented rethink. The lack of knowledge about interdependencies, quantitative effects of actions and parameter characteristics prevents SMEs from the implementation. A holistic ecological-logistical impact model with software implementation can support SMEs reaching their potential. Requirements for the model and fundamental relationships between logistic parameters and ecological target values are presented in this publication.

SME, logistic, ecology

In lightweight automotive construction, hybrid structures made of various materials as well as solid and sheet metal elements are used. By hybrid compound forging, a sheet steel and a solid aluminium part can already be joined in a material-locking manner during the forming process. The Institut für Integrierte Produktion Hannover (IPH) gGmbH and the Institut für Schweißtechnik und Trennende Fertigungsverfahren (ISAF) of TU Clausthal are investigating how solid aluminium bolts and steel sheets can be joined in a material-locking manner. This article explains the decisive forming parameters. Furthermore, the tool design for the joining tests is presented.

lightweight construction, aluminum, compound forging

Lightweight automotive construction increasingly relies on hybrid structures made of steel and aluminium. These materials are currently joined mainly by form locking, for example by riveting. Welding and bonding are also used for joining the two materials. Hybrid composite forging allows to join the two components during the forming process. This shortens the process chain. With the help of zinc as a brazing material, the components are joined to form a material bond. This publication explains the results of the simulative parameter study. It shows how temperature, geometry and speed influence the joining result. Furthermore, first results of practical joining tests are presented.

lightweight construction, aluminum, simulative parameter study

In lightweight construction, light metals like aluminum are used in addition to high-strength steels. However, a welded joint of aluminum and steel leads to the precipitation of brittle, intermetallic phases and contact corrosion. Nevertheless, to use the advantages of this combination in terms of weight saving composite hybrid forging has been developed. In this process, an aluminum solid part and a steel sheet were formed in a single step and joined at the same time with zinc as brazing material. For this purpose, the zinc was applied by hot dipping on the aluminum in order to produce a connection via this layer in a forming process, under pressure and heat. Due to the formed intermediate layer of zinc, the formation of the Fe-Al intermetallic phases and the contact corrosion are excluded. By determining the mathematical relationships between joining parameters and the connection properties the strength of a specific joint geometry could be adjusted to reach the level of conventional joining techniques. In addition to the presentation of the joint properties, the influence of the joining process on the structure of the involved materials is also shown. Furthermore, the failure behavior under static tensile and shear stress will be shown.

lightweight construction, aluminum, joining properties

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