Mechanical properties and microstructure of powder metallurgy Ti–xNb–yMo alloys for implant materials

Vegetable oils and animal oils have been used as quenchants for metals for thousands of years; however, it hasn’t been until relatively recently that their cooling properties have been studied in a thorough, quantitative manner. This review will focus on the published data relating to the use of triglycerides from various animal and vegetable sources to quench-harden steels. Particular focus will be on the traditional selection and use of different vegetable and animal oils for steel hardening applications and the cooling time-temperature behavior of these fluids to characterize their quenching performance. This information has not been previously reviewed in this manner.

Use of Vegetable Oils and Animal Oils as Steel Quenchants: A Historical Review—1850-2010

Characterisation and modelling of tempering during multi-pass welding

Surface layer modification charts for gear grinding

In der vorliegenden Arbeit wird die Entwicklung der Software SimCarb QuenchTemp fur das computergestutzte Einsatzharten beschrieben, die die Simulationsaufgabe lost, in welcher Weise sich eine bestimmte, nach dem Aufkohlen erreichte Kohlenstofftiefenverteilung material-, werkstuck- und prozessabhangig auf die nach dem Abschrecken bzw. weiteren Anlassen resultierenden Harteprofile und die Gefugezusammensetzung ubertragt. Hierfur werden ein empirisches und ein thermophysikalisches Modell formuliert und implementiert.
Im empirischen Modell werden Jominy-Stirnabschreckkurven mit einer in der Literatur vorgeschlagenen Formel anhand der chemischen Zusammensetzung und der Austenitkorngrose des verwendeten Stahls berechnet. Die Auswertung dieser Stirnabschreckkurven findet am masgeblichen Stirnflachenabstand statt. Die Werkstuckgeometrie wird durch einen reprasentativen Zylinderdurchmesser charakterisiert. Die Kuhlwirkung des Abschreckmittels beschreibt der Grossman’sche Abschreckintensitatsfaktor. Zur Berechnung der Anlass- aus der Abschreckharte werden von der Kohlenstoffkonzentration abhangige Abminderungsfaktoren verwendet.
Im thermophysikalischen Modell wird eine zeitliche Temperaturverteilung fur die unendlich lange Vollzylinderprobe wahrend des Abschreckprozesses simuliert. Hierzu wird eine modifizierte Fourier’sche Temperaturleitungsgleichung mithilfe einer expliziten Finite-Differenzen-Methode gelost. Bei der Simulation werden temperaturabhangige Warmeubergangs- und Warmeleitkoeffizienten angewendet. Zur Bestimmung der tiefenabhangigen Gefugeausbildung und Harteverteilung werden die betreffenden Abkuhlkurven der simulierten Temperaturverteilung mit Abkuhlkurven aus kontinuierlichen Zeit-Temperatur-Umwandlungsschaubildern verglichen. Diese Abkuhlkurven werden zuvor fur handelsubliche Einsatzstahle berechnet und in SimCarb QuenchTemp programmiert. Die Anlassharte wird im thermophysikalischen Modell abhangig von der Abschreckharte aus Hollomon-Jaffe-Parametern berechnet. 
In the present thesis, the development of the software SimCarb QuenchTemp for computer aided case hardening is described that solves the simulation task, in which way a certain carbon depth distribution obtained by carburizing is transferred to the resulting hardness profile and microstructure composition respectively after quenching and subsequent tempering, depending on the material, workpiece and process. For this purpose, an empirical and a thermophysical model are formulated and implemented.
In the empirical model, Jominy end quench curves are calculated from a formula proposed in the literature by means of the chemical composition and the austenite grain size of the used steel. The evaluation of these end quench curves occurs at the applicable distance from the end face. The workpiece geometry is characterized by a representative cylinder diameter. The cooling capability of the quenchant is described by the Grossman quench severity. For the calculation of the tempering from the quenching hardness, diminution factors depending on the carbon concentration are applied.
in the thermophysical model, a time distribution of the temperature is simulated for the infinitely long solid cylinder during the quenching process. For this purpose, a modified Fourier temperature conduction equation is solved by means of an explicit finite difference method. Temperature dependent coefficients of heat transfer and conduction are used in the simulation. To determine the depth dependent microstructure development and hardness distribution, the relevant cooling curves of the simulated temperature distribution are compared with cooling curves of continuous cooling transformation diagrams. Theses cooling curves are computed beforehand for customary case hardening steels and programmed in SimCarb QuenchTemp. Depending on the quenching hardness, the tempering hardness is calculated from Hollomon-Jaffe parameters in the thermophysical model.

Vorhersage des Einsatzhärtungsergebnisses aus dem Aufkohlungsprofil und den Abschreck- und Anlassbedingungen

The results of the stress relieving and tempering processes are dependent on the temperature and time of the process, which may be correlated using a parameter such as Holloman's (Holloman-Jaffe) parameter or the Larsen-Miller parameter. These parameters are a measure of the thermal effect of the process on the metallurgical transformation of the steel during tempering. The processes that exhibit the same tempering parameter are expected to exhibit the same effect (such as hardness). However, these more traditional numerical expressions assume isothermal tempering processes which seldom exist in production tempering ovens due to the heat-up period prior to soaking

A historical overview of steel tempering parameters

Currently, ASTM cooling curve analysis standards ASTM D6200 “Standard Test Method for Determination of Cooling Characteristics of Quench Oils by Cooling Curve Analysis,” D6482 “Standard Test Method for Determination of Cooling Characteristics of Aqueous Polymer Quenchants by Cooling Curve Analysis with Agitation,” and D6549 “Standard Test Method for Determination of Cooling Characteristics of Quenching by Cooling Curve Analysis with Agitation (Drayton Unit),” describe the experimental methodology for cooling curve data acquisition but leave the analysis of the resulting time-temperature cooling data up to the user. Therefore, it is of interest to provide an overview of the various methodologies that may be used by the user of these standards for data analyses and reporting. This is important in order to assess the impact of quench severity on resulting metallurgical properties of various steel alloys. The objective of this paper is to provide a general overview of approaches used to quantify not only the time-temperature behavior, but also a general quantitative assessment of relative quench severity exhibited by the various quenching media being analyzed. Methods for characterizing and interpreting cooling time-temperature curves are reviewed and the reasons for their utilization are discussed.

Quenchant Characterization by Cooling Curve Analysis

History And Advances In Tempering Parameter Development

The residual stresses and distortion induced by quenching in an eccentric ring were investigated in this study with finite element method. The ring was made of AISI 52100 steel. A fully coupled 3D temperature-displacement analysis was performed to simulate heat transfer, phase transformations and mechanical stresses and strains during the heating and subsequent quenching processes. Commercial FEA package ABAQUS/Standard 6.4 was used for the analyses along with user subroutines developed by the authors to model the thermal and mechanical constitutive behaviour. The eccentric ring was subjected to three stress analysis in response to temperature, martensitic transformation and transformation plasticity, respectively. Simulation results indicated that thermal stress leaves the surface in compressive and the core in tensile. Martensitic transformation dilation in the surface pushes the compressive stress to a higher level in the early stage of quenching, but the subsequent dilation in the core nearly counteracts the tensile stress there. The quenching residual stresses change the signs with the addition of transformation plasticity, which also induces significant plastic strains during quenching. Quenching distortion experiments are in accordance with the simulation results which take transformation plasticity into consideration.

Xin Yao

Papers

A historical overview of steel tempering parameters

Quenchant Characterization by Cooling Curve Analysis

History And Advances In Tempering Parameter Development

A fully coupled material constitutive model for steel quench analysis

Quenching of Titanium Alloys