Identifikation der verzugsbestimmenden Einflussgrößen beim Austenitisieren am Beispiel von Ringen aus dem Wälzlagerstahl 100Cr6

The identification of distortion relevant-factors in an overall process chain in order to describe the distortion behaviour of a regarded component is an important step in the method Distortion Engineering . In this context, the application of design of experiments (DoE) assures a systematic procedure during both experiment and distortion analysis. The distortion behaviour of the examined thin-walled bearing rings was characterised by harmonic analysis in explicit consideration of the direction of the respective shape changes. The change in roundness deviation due to heat treatment is controlled by a variation of the clamping system during machining. Based on the experimental results and additional finite element analysis, this effect is explained by local plastic deformation due to stress relief during heating of the non-uniform machining residual stress state. The variation of the supporting pattern during heat treatment induces a change in roundness and flatness deviation, respectively. The alteration in flatness deviation is also influenced by the heating rate. The distortion mechanism that is responsible for these effects could not be identified in this work. The experimental results provide an indication that creep processes during heat treatment could be an effect regarding distortion, whose importance should not be underestimated

Identification of distortion relevant-factors during austenitisation by the example of rings made from bearing steel 100Cr6

The identification of distortion relevant-factors in an overall process chain in order to describe the distortion behaviour of a regarded component is an important step in the method Distortion Engineering . In this context, the application of design of experiments (DoE) assures a systematic procedure during both experiment and distortion analysis. The distortion behaviour of the examined thin-walled bearing rings was characterised by harmonic analysis in explicit consideration of the direction of the respective shape changes. The change in roundness deviation due to heat treatment is controlled by a variation of the clamping system during machining. Based on the experimental results and additional finite element analysis, this effect is explained by local plastic deformation due to stress relief during heating of the non-uniform machining residual stress state. The variation of the supporting pattern during heat treatment induces a change in roundness and flatness deviation, respectively. The alteration in flatness deviation is also influenced by the heating rate. The distortion mechanism that is responsible for these effects could not be identified in this work. The experimental results provide an indication that creep processes during heat treatment could be an effect regarding distortion, whose importance should not be underestimated

Hydrogen Absorption during Case Hardening of Steels EN20MnCr5 (SAE5120) and EN18CrNiMo7-6 (SAE4820)

Damages to case-hardened components are often associated with the phenomenon of hydrogen embrittlement due to their specific fracture pattern. In the present work, the effects of the case hardening process on the hydrogen content in the material were investigated and the effects of hydrogen on the mechanical properties were examined. In order to determine not only the influence of the heat treatment process but also the influence of the material, the case-hardening steels EN20MnCr5 (SAE5120) and EN18CrNiMo7-6 (SAE4820) with different degrees of purity were investigated. From the results it can be deduced that the sulphidic and oxidic inclusions have no significant influence on the hydrogen content. When checking the mechanical properties, it was shown in the incremental step loading technique according to ASTM F1624 that a purely case-hardened condition only has a slight tendency to hydrogen embrittlement. However, if the material is additionally loaded with hydrogen, the material fails significantly below the maximum expected load in the incremental step loading test, which is to be interpreted as a clear indication of failure due to hydrogen embrittlement. However, the fracture patterns of these two states do not show any significant differences. Therefore, it does not seem possible to attribute damage to a case-hardened component to hydrogen embrittlement on the basis of the fracture pattern alone

Hydrogen Absorption during Case Hardening of Steels EN20MnCr5 (SAE5120) and EN18CrNiMo7-6 (SAE4820)

Damages to case-hardened components are often associated with the phenomenon of hydrogen embrittlement due to their specific fracture pattern. In the present work, the effects of the case hardening process on the hydrogen content in the material were investigated and the effects of hydrogen on the mechanical properties were examined. In order to determine not only the influence of the heat treatment process but also the influence of the material, the case-hardening steels EN20MnCr5 (SAE5120) and EN18CrNiMo7-6 (SAE4820) with different degrees of purity were investigated. From the results it can be deduced that the sulphidic and oxidic inclusions have no significant influence on the hydrogen content. When checking the mechanical properties, it was shown in the incremental step loading technique according to ASTM F1624 that a purely case-hardened condition only has a slight tendency to hydrogen embrittlement. However, if the material is additionally loaded with hydrogen, the material fails significantly below the maximum expected load in the incremental step loading test, which is to be interpreted as a clear indication of failure due to hydrogen embrittlement. However, the fracture patterns of these two states do not show any significant differences. Therefore, it does not seem possible to attribute damage to a case-hardened component to hydrogen embrittlement on the basis of the fracture pattern alone

Der Stammzellmarker LgR5 wird in einer Subpopulation proliferierender (Ki-67 pos.) Zellen im Barrett-Ösophagus sowie Barrett-assoziierter Adenokarzinome exprimiert

In order to improve the rolling contact fatigue (RCF) behavior of gear steels, a concept to increase their damage tolerance is developed alternatively to the conventional approach of improving the degree of steel cleanliness. For that purpose, Cu is used as a main alloying element in order to trigger the precipitation of nano-sized Cu precipitates which shall improve the strain-hardening rate of the martensitic matrix of Cu-alloyed 18CrNiMo7-6 steel surrounding a non-metallic inclusion during plastic deformation. In this way, early component failure may be avoided and the maintenance costs of, e.g., wind energy converters may be kept low. The experimental analysis shows that nano-sized Cu precipitates influence the material's strength, ductility, and strain-hardening behavior under tension, depending on their coherence. Among others, the latter is related to strain-induced martensitic transformation of coherent Cu. The structure of the Cu precipitates is studied by TEM and SANS analysis. The Cu-alloyed steel also shows an increased hardening-exponentCHT studied by cyclic hardness test (CHT) PHYBALCHT. Fatigue tests of specimens with coherent precipitates show cyclic hardening until a critical stress amplitude. Above that, stress amplitude cyclic softening is detected. An increased damage tolerance could be obtained for a 1 mass-% Cu-alloyed 18CrNiMo7-6 steel