The Largest Inclusions in a Piece of Steel

Fatigue properties of steels are strongly influenced by the presence of microscopic particles of oxides or foreign material known as inclusions. The size of the largest inclusion is an important determinant of fatigue strength. This paper studies the problem of estimating the sizes of large inclusions from measurements made on a two-dimensional section of the steel. The approach combines traditional stereological ideas with more recent extreme value modeling. It is shown that both classical likelihood and Bayesian approaches are useful in the inference.     

Combining TEM and APFIM techniques to study the microstructure of steels and hardmetals

This paper describes the benefits of combining transmission electron microscopy (TEM) and atom probe field ion microscopy (APFIM) techniques to study the microstructure of steels and hardmetals. In addition to energy dispersive X-ray spectrometry (EDS), recent experience of electron energy loss spectroscopy (EELS) and energy filtered TEM (EFTEM) is treated. Topics covered are: phase composition (APFIM, TEM/EDS and TEM/EELS); precipitate size distribution (EFTEM); precipitate volume fraction (APFIM); and compositional gradients (APFIM, EFTEM and SEM). Examples given include precipitate composition and size distribution in creep resistant 9–12% chromium steels, phase distribution and composition in nitrogen containing hardmetals (cermets) after sintering and heat treatment, and boron grain boundary segregation in austenitic stainless steels.     

非调质钢35MnVN强化状态的磨粒磨损性能研究

利用销－盘式ＭＬ－１０型磨粒磨损试验机，对非调质钢３５ＭｎＶＮ强化状态（淬火＋低温回火）的磨粒磨损性能进行了试验研究．结果表明，非调质钢３５ＭｎＶＮ强化状态的硬度虽然比调质处理的４０Ｃｒ钢和４５＃钢的都低，但因其显微组织中的沉淀相对提高耐磨性十分有益，而且晶粒细化也有利于提高耐磨性，所以在同样的试验条件下，非调质钢３５ＭｎＶＮ强化状态的耐磨粒磨损性能与４０Ｃｒ钢及４５＃钢调质处理后强化态的耐磨粒磨损性能基本相当，可以替代后二者在磨粒磨损工况下使用     

Crystallographic variant selection of martensite at high stress/strain

The phenomenological theory of martensitic transformation is well understood that the displacive phase transformations are mainly influenced by the externally applied stress. Martensitic transformation occurs with 24 possible Kurdjomov-Sachs (K-S) variants, where each variant shows a distinct lattice orientation. The elegant transformation texture model of Kundu and Bhadeshia for crystallographic variant selection of martensite in metastable austenite at various stress/strain levels has been assessed in this present research. The corresponding interaction energies have also been evaluated. Encouraging correlation between model prediction and experimental data generation for martensite pole figures at many deformed austenite grains has been observed at different stress/strain levels. It has been investigated that the mechanical driving force alone is able to explain the observed martensite microtextures at all stress/strain levels under uniaxial tensile deformation of metastable austenite under low temperature at a slow strain rate. The present investigation also proves that the Patel and Cohen’s classical theory can be utilized to predict the crystallographic variant selection, if it is correctly used along with the phenomenological theory of martensite crystallography.     

Spark ablation as sample introduction device for ICP-AES: Analysis of free cutting steels

A method for ICP analysis of free cutting steels after spark ablation is presented. The partial removal of the nonconductive inclusions by etching with hydrochloric acid leads to a sufficient conductivity of the sample surface and achieves a high efficiency of the presparking process. This is essential for the analytical evaluation of the spark. The etching time of 30 s enables removal of the sulfides in a layer smaller than the one concerned by the presparking process. The reproducibility of the measurements is within 2–5% depending on the element. After etching of the standard samples no significant differences in the results achieved by spark ablation-ICP and spark emission were observed. They were also in good agreement with the ICP analysis of solutions of the corresponding samples.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

新试剂3,5-二溴-4-氨基苯基荧光酮的合成及其应用研究

本文提供了新显色剂3,5-二溴-4-氨基苯基荧光酮的合成方法,较详细的研究了在表面活性剂增溶下,在盐酸介质中,试剂与锆(Ⅳ)的分光光度性质及反应条件,建立了分光光度法测定锆(Ⅳ)的高灵敏高选择性的新方法,并成功地用于铝锆合金中微量锆的测定。     

Obtaining confidence limits for safe creep life in the presence of multi batch hierarchical databases: An application to 18Cr–12Ni–Mo steel

The creep and creep rupture properties of 18Cr–12Ni–Mo steel tubes have been analysed using the Wilshire equations. The observed behaviour patterns are then briefly discussed in terms of the dislocation processes governing creep strain accumulation. A suitable statistical framework for analysing both the single and multi batch data available on this material is then specified. It is shown that ignoring the hierarchical nature present in many creep data bases, which has been the approach used until now when using the Wilshire equations, leads to a serious and significant underestimate of the predicted safe life for this material. The model allows accurate predictions, with associated levels of confidence, of long-term properties by extrapolation of short-term test results for this steel.     

Bestimmung der Homogenität von Legierungen mittels Autoradiographie and Aktivierungsanalyse

An für Konstruktionselemente verwendente verwendete Legierungen werden in Abhängigkeit von ihrer Verwendung folgende Anforderungen gestellt: hole Festigkeitskoeffizienten, erhöhte Temperaturbeständigkeit, erhöhte Korrosionbeständigketi gegen Chemikalien, erhöhte Verschleißbeständigkeit u. a. Chemische Heterogenität ist Ursache für Korrosionserscheinungen, Einleitung ungünstiger Reaktionen sowie Herabsetzung der örtlichen Reibfestigkeit und bewirkt damit eine Erniedrigung der Güteeigenschaften der Legierung. Einer der grundsätzlichen Wege, diesen Erscheinungen vorzubeugen, ist ein möglichst hoher Homogenitätsgrad der Legierung.     

Autoradiographische Untersuchungen der Erstarrung von Schmiedeblöcken

Es wurde der Erstarrungsverlauf an zwei 11 und 12 t schweren, in eine achteckige (älterer Typ) und eine zwölfeckige Kokille abgegossenen Blöcken des Stahls St 35 verglichen. Die Untersuchungen mit Hilfe des Radioisotops ^110m Ag umfaßlen den Bereich des gesamten Blocks.

Ermittelt wurde der Verlauf der Kristallisationsfront im Block in exakt festgelegten Zeitabständen von 20, 60 und 120 Minuten nach Fütlung der Kokille sowie des Wachstums der Blockhaut in horizontaler und senkrechier Richtung als Funktion-der Zeit.

Die Koeffizienten für die Erstarrung der Blöcke in horizontaler Richtung sowie die Volumina des flüssigen Stahls nach 20, 60 und 120 Minuten nach Abschluß des Gießens wurden berechnet.