Einfluss der Abkühlbedingungen auf ausgewählte Eigenschaften und Eigenspannungen in warmumgeformten zylindrischen Hohlkörpern

Translated title of the contribution: Influence of cooling conditions on selected properties and on residual stresses in hot formed cylindric hollow parts

Gerd Frosch

Research output: ThesisMaster's Thesis

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Abstract

High-pressure cylinders are safety-components. In case of total failure while they are used, the effects of their burst may lead to environmental damage and injury to human beings in the surrounding areas. That’s why highest quality standards for these products are required. By ensuring optimum production conditions a failure of the cylinders due to manufacturing or material defects should be completely ruled out. Based on these demands a project dealing with possible reasons for the formation of cracks as a result of production-related cooling processes has been initiated. In the course of this thesis the theoretical basics concerning mechanical deformation and heat treatment of steel cylinders were summarized. Based on these information a test program focusing on the main influencing factors regarding crack formation was developed. Cylinders produced under different cooling conditions were tested according to selected material properties and residual stresses. The results are compared and evaluated. In the course of the tests it could be demonstrated that there is no big influence on the material properties due to a variation of the temperature of the cooling media when the transformation of the austenite has already been finished before the actual massive cooling starts. It doesn’t matter whether the cooling media has 60°C or 20°C. It is very important, that the cooling of the cylinders follows a specific time frame. In addition it has to be assured that the temperature in the cylinders wall and bottom area is on a similar level. Regardless of the type of the cylinder, the temperature has to be lower than 520°C in the bottom area before the rapid cooling takes place. The residual stresses increases by using cold water but do not become critical. Rapid cooling under the presence of high temperature gradients between bottom and wall leads to an increase of the residual stress up to ten times of the standard. During the test production of 200 steel cylinders no cracks could be enforced. Accordingly the conclusion can be drawn that the development of cracks involves a number of various factors.
Translated title of the contributionInfluence of cooling conditions on selected properties and on residual stresses in hot formed cylindric hollow parts
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Bernhard, Christian, Supervisor (internal)
  • Schneider, Reinhold, Co-Supervisor (internal)
  • Summer, Heribert, Supervisor (external), External person
Award date1 Jul 2016
Publication statusPublished - 2016

Bibliographical note

embargoed until 17-05-2021

Keywords

  • selected properties
  • hollow parts

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