CCI Valve Technology AB is a company located in Säffle, Sweden, that manufactures and installs bypass valves. Due to requirements outside normal standards on the valve's hardness values, some measurements have had difficulties meeting such requirements. During this thesis work, tests were carried out to determine how to overcome the difficulties. The experiments focused on five different areas that may affect the components hardness, welding method, soaking temperature during post weld heat treatment, measuring procedure, component thickness and number of heat treatment cycles. The Grade 91 steel specimens that were examined consisted of five solid cylinders and three various pipes that were welded together by using shielded metal arc welding (SMAW) or gas tungsten arc welding (GTAW). Each pipe was sawed apart into three equal parts. All specimens were hardness tested and eight of the specimens' microstructure was studied with an optical microscope. The hardness measurement instruments used, LECO V-100-C2 and GE-MIC 10, are Vickers hardness testers, one stationary and the other one portable. The measuring results contain a vast number of different hardness measurement data. From the analyzed data, the conclusions were drawn that the most suitable soaking temperature during post weld heat treatment were 750° C, that the SMAW method creates a more stable hardness profile than the GTAW method, and that one heat treatment cycle is more beneficial than two or more.

by Yeung Ching Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 69-71). / Text in English; abstract also in Chinese. / by Yeung Ching Chung. / Table of contents --- p.i / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- General overview --- p.1 / Chapter 1.2 --- The present study --- p.3 / Chapter Chapter 2 --- Sample preparation and characterization / Chapter 2.1 --- Sample preparation / Chapter A. --- General description --- p.5 / Chapter B. --- The thermal pulse furnace --- p.7 / Chapter C. --- The substrates --- p.9 / Chapter D. --- Sample preparation --- p.10 / Chapter 2.2 --- Sample characterization / Chapter A. --- Micro Raman system --- p.11 / Chapter B. --- Rutherford backscattering spectrometry (RBS) --- p.12 / Chapter C. --- X-ray powder diffraction --- p.13 / Chapter D. --- AFM. SEM and Surface Profiler --- p.13 / Chapter Chapter 3 --- Results and discussion / Chapter 3.1 --- The surface morphology / Chapter A. --- General description --- p.15 / Chapter B. --- The as-deposited amorphous film --- p.15 / Chapter C. --- The crystalline Ge film --- p.16 / Chapter D. --- The alloy film --- p.17 / Chapter E. --- The role of a-Si layer --- p.22 / Chapter 3.2 --- The depth profile (RBS) / Chapter A. --- General description --- p.24 / Chapter B. --- Peak temperature dependence --- p.27 / Chapter C. --- Heating rate dependence --- p.30 / Chapter 3.3 --- The near surface composition measured by Raman scattering / Chapter A. --- General description --- p.33 / Chapter B. --- Peak temperature dependence --- p.43 / Chapter C. --- Heating rate dependence --- p.45 / Chapter 3.4 --- Preferred growth direction / Chapter A. --- General description --- p.47 / Chapter B. --- Peak temperature dependence --- p.48 / Chapter C. --- Heating rate dependence --- p.51 / Chapter 3.5 --- Discussion / Chapter A. --- The particle size --- p.55 / Chapter B. --- The participation of Si substrate --- p.58 / Chapter C. --- The alloy formation --- p.58 / Chapter D. --- The abnormally fast interdiffusion --- p.63 / Chapter Chapter 4 --- Conclusion --- p.65 / Appendix --- p.67 / References --- p.69

"The thesis includes fundamental work in the following, · Development of materials database which includes the main parameters of the various heat transfer models · Validation and testing of the system capability and accuracy by means of various case studies A computer aided heat treatment planning system (CAHTPS) is developed to assist the heat treatment process. The temperature distribution inside the furnace and the temperature of the various parts in the load can be determined. The various models for the heat treatment are analyzed and the various parameters in the equations are classified. The majority of the equations parameters were properties of various metals and non metals. Hence an extensive database is developed so as to assist the models. The remaining physical conditions dependent parameters of the models were analyzed and the effects due to change in the conditions and these parameters are tested and studied by various case studies. The change in the loading pattern effects and change in the load quantity effects for the various cases are presented. The thesis work establishes the system’s application scope and the accuracy to be used in the current heat treatment industries."

M.S. / Materials Science and Engineering / The most fundamental step in the development of a predictive model for microstructure and residual stress distribution in steels is the accurate representation of the transient temperature field. Three constituents of a database of thermophysical properties, namely the thermal conductivity, volumetric specific heat capacity and convective heat transfer coefficient, were isolated and their effects quantified on the accuracy of temperature field predictions using finite element analysis (FEA). The most critical parameter in the heat transfer process was ultimately identified to be the temperature dependent convective heat transfer coefficient. It was determined using an inverse heat transfer method, which was successfully applied to accurately establish the thermal boundary conditions for an arbitrary 3D steel geometry. The temperature dependency of the volumetric specific heat capacity in the transformation range of temperatures has to be known a priori, for which a reliable model describing alloy dependent reaction kinetics has to be developed first. Thermal conductivity and its dependency on temperature have secondary effects on the accuracy of FEA predictions. The impact of the outcome of this study lies in its relevance to the heat treatment industry.

No description available.

No description available.

The objective of this research was to develop and verify a mathematical model that enables the prediction of the effects of heat treatment on cast aluminum alloy components. The model, which uses the commercially available software (ABAQUS), predicts dimensional changes, distortion, and residual stresses in heat treated components. An extensive database is developed for an example aluminum alloy (A356) and includes the mechanical, physical, and thermal properties of the alloy all as functions of temperature. The database is obtained through calculations and measurements made on A356 alloy specimens. In addition, boundary conditions ¨C in the form of heat transfer coefficients for each of the heat treatment steps - are obtained from measurements performed with a special quenching system developed at the Center for Heat Treating Excellence at WPI. The database and boundary conditions were used in the software to predict the dimensional changes, distortions, and residual stresses that develop in a commercial A356 cast component that is subjected to a standard commercial heat treating cycle. In order to verify the accuracy of the software predictions, the predictions were compared to their measured counterparts, where dimensional changes and distortion were measured with a coordinate measuring machine, and residual stresses were measured with x-ray diffraction.

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

The effect of heat treatment of milk on whey proteins, sulphydryl (reactive and total), disulphide groups, half cystine, volatile sulphur compounds and sensory properties was studied in order to relate changes in the flavour of milks to changes in chemical composition. The degree of heat denaturation of whey proteins increased generally in the following order: HTST treatment, direct UHT treatment, indirect UHT treatment, and the severest was laboratory heat treatment where milks were held at temperatures below 1000 C for several minutes. At the same heating temperature and holding time indirect UHT treatment was found to result in more whey protein denaturation compared with direct UHT treatment. The sensitivity of whey proteins to denaturation was confirmed to be In decreasing order: serum albumin, S-lactoglobulin B, S-lactoglobulin A and a-lactalbumin. Laboratory heat treatment resulted in a peak of reactive sulphydryl groups, followed by a decrease, as the heating time is prolonged. HTST treatment and UHT treatments (direct and indirect) increased reactive sulphydryl groups from nearly zero in raw milk to values dependent on the heating temperature. Generally, heat treatment caused a decrease in concentration of total sulphydryl groups, disulphide groups and half cystine. Hydrogen sulphide and dimethyl sulphide were identified in heat-treated milks. Dimethyl sulphide was found to be present in raw milk as well as in heat treated milks. The increase in concentration of each of the volatile sulphur compounds was found to parallel the intensity of heating to the extent that they appeared to be linearly related. Volatile sulphur compounds decreased rapidly during storage at 22°C compared with~slower decrease during storage at 4oC. The panel was unable to detect differences between direct UHT milk and pasteurised milk. On the other hand, most panelists could detect differences between indirect UHT milk and pasteurised milk. The panelists were not able to distinguish between milks processed, respectively, at 77oc, 830 C and 890 C for 20 seconds using HTST treatment. A significant number of correct judgments w~s observed Wl+~ 940 C milk. The statements describing the difference were: heated taste, strong flavour, sulphurous, burnt flavour and very pronounced cooked flavour. All these statements are related to the cooked flavour. A good linear correlation was clearly observed between reactive sulphydryl groups and the whey proteins very sensitive to heat treatment, eg S-lactoglobulin A, S-lactoglobulin B and serum albumin. There was also a good linear correlation between reactive sulphydryl groups and mean whey protein denaturation. It was found that hydrogen sulphide concentration increased with increasing concentration of reactive sulphydryl groups, and with decreasing concentration of total sulphydryl groups, disulphide groups and half cystine respectively. There was also a good correlation between hydrogen sulphide and S-lactoglobulin A, S-lactoglobulin B and serum albumin. The degree of cooked flavour, the degree of whey protein denaturation, the concentration of reactive sulphydryl groups, the concentration of half cystine and the concentration of hydrogen sulphide show good correlation and similar dependence upon the severity of heat treatment. The data also suggest that the cooked flavour threshold corresponds to: a) 59 per cent denaturation of S-lactoglobulin (A + B); b) reactive sulphydryl group concentration of 0.037 mmole per litre of milk; c) half-cystine concentration of 1.082 mmole per litre of milk; d) hydrogen sulphide concentration of 3.4~g per litre of milk.

No description available.