Bibliography: leaves 191-198. / xxi, 201 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the mechanisms controlling the dilution, geometry and wear performance of weld- deposited high-chromium white iron surface layers. Focuses on layers deposited by mechanised flux-cored-arc welding, as this process achieves higher deposition rates than manual-metal-arc welding and affords a greater degree of control over individual welding variables. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999

Thesis (M.Eng.)--University of Wollongong, 2007. / Typescript. Includes bibliographical references: leaf 94-98.

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Dissimilar metals joining have been used in many industry fields for various applications due to their technique and beneficial advantages, such as aluminum-steel and magnesium-steel joints for reducing automobile weight, aluminum-copper joint for reducing material cost in electrical components, steel-copper joints for usage in nuclear power plant, etc. The challenges in achieving dissimilar joints are as below. (1) Big difference in physical properties such as melting point and coefficient of thermal expansion led to residual stress and defects. (2) The miscibility issues resulted in either brittle intermetallic compound layer at the welded interface for miscible combinations (such as, aluminum-steel, aluminum-copper, aluminum-titanium, etc.) or no metallurgical bonding for immiscible combinations (such as magnesium-copper, steel-copper, etc.). For metallurgical miscible combinations, brittle intermetallic compounds formed at the welded interface created the crack initiation and propagation path during deformational tests. (3) Stress concentration appeared at the welded interface region during tensile testing due to mismatch in elastic properties of dissimilar materials. In this study, different combinations of dissimilar metals were joined with friction stir welding. Lap welding of 6022-T4 aluminum alloy/galvanized mild steel sheets and 6022-T4 aluminum alloy/DP600 steel sheets were achieved via friction stir scribe technology. The interlocking feature determining the fracture mode and join strength was optimized. Reaction layer (intermetallic compounds layer) between the dissimilar metals were investigated. Butt welding of 5083-H116 aluminum alloy/HSLA-65 steel, 2024-T4 aluminum alloy/316 stainless steel, AZ31/316 stainless steel, WE43/316 stainless steel and 110 copper/316 stainless steel were obtained by friction stir welding. The critical issues in dissimilar metals butt joining were summarized and analyzed in this study including IMC and stress concentration.

This study was an evaluation of thermite rail welding with the goal of the development of welds with improved mechanical properties. The first part of the study involved an in-depth evaluation of 14 thermite rail welds produced by the Department of Transportation using current production practices. These welds were produced using CrMo, CrV and Cr alloy rails, AREA CC rails (i.e., standard rails) and head-hardened rails which were welded with weld metal produced by the aluminothermic reaction of "standard" and "alloy" thermite charges. Temperature at various locations was measured during welding for both the rails and the weld metal. After welding, mechanical properties, macro- and microstructure, inclusion levels and residual stresses induced by the welding operation were all determined. Low impact properties and ductility (2-6 percent reduction in area) were observed in the thermite rail weld metal. These low properties were attributed to microstructure and, to a lesser extent, inclusion content. In order to improve the process by reducing the inclusion content, attempts were made to filter the molten thermite steel by passing it through zirconia/mullite filters. This was included in the second part of the study in which 9 plate welds we made using "standard" thermite charges. Filtering, at best, was only partly successful. However, it was observed that a 30 percent increase in yield strength and hardness was achieved in weld metal containing approximately 0.55 percent carbon and 0.06 percent vanadium. Normalization of the plate welds resulted in a significant improvement in the tensile ductility of as-cast weld metal. Weld metal of 0.55 percent carbon and 0.06 percent vanadium had ductilities in the range of 10-20 percent when the cooling rate exceeded 37 K(DEGREES)/min. through the transformation range. At cooling rates of four times this level, tensile properties equivalent to those of the "alloy" weld metal were obtained along with the enhanced tensile ductility. It was concluded that it is possible to produce a thermite weld with both improved strength and ductility by the judicious control of composition, the addition of microalloying elements and the application of an appropriate post-weld heat treatment, such as normalization.

The problem was to study the effectiveness of four instructional techniques of teaching arc welding at the university level.

In this master thesis different overlay welding methods suitable for boiler application has been investigated. The purpose of this project is to define advantages and disadvantages for each overlay welding methods and suggest some evaluation criteria on some commercial and experimental alloys aimed for overlay welding material. Many components in a boiler are made of low alloy steel and the atmosphere in the furnace region can be very complex; therefore many different types of corrosion can occur. Weld overlay is a process where one or multiple layers of corrosion resistant material are applied to a base material. The two overlay welding methods investigated in this study were Tungsten Inert Gas welding and Metal Inert/Active Gas welding. Tests were performed with FeCrAl alloys (Kanthal A, Kanthal D and some experimental alloys). FeCrAl alloys in general are ferritic iron-based steels with a typical concentration of 20-23 wt. % chromium and ~5 wt.% aluminum. Different overlay welding evaluation was made; visual examination, dye penetrant inspection, macro/micro examination, side bend test and short term corrosion test (~50hours). Conclusion of this thesis is that MIG welding is a more productive method than TIG, but more defects such cracks and lack of fusion can be produced for MIG welding. These defects can be “fixed” if welding parameters is optimized. If repairing a certain place TIG welding is a better option. A conclusion about number of layers; one layer with MIG welding is almost as thick as three layers with TIG welding with welding wire Ø 1mm. Three welding evaluation that is really important is visual examination, dye penetrant testing and corrosion test in order to choose which overlay welding method is suitable in boiler application. / I detta examensarbete har olika påsvetsningsmetoder som är lämpliga för en pannapplikation undersökts. Syftet med denna studie var att undersöka både för- och nackdelar med påsvetsningsmetoderna och föreslå några utvärderingskriterier på vissa kommersiella och experimentella legeringar som lämpar sig för påsvetsningsmaterial. Många komponenter i en panna är tillverkade av låg legerat stål och miljön där förbränningen sker kan vara väldigt komplex, därför kan det ske korrosion. Påsvetsning är en process där ett eller flera skikt av ett mer korrosionsbeständigt material appliceras på ett basmaterial. De två olika svetsmetoderna som undersöktes i denna studie var TIG-svetsning och MIG-svetsning. Testerna utfördes med FeCrAl legeringar (Kanthal A, Kanthal D och vissa experimentella legeringar). FeCrAl legeringar är i allmänhet ferritiska järnbaserade stål med 20-23% krom och ~5% aluminium. De utvärderingsmetoderna som undersöktes var: visuell undersökning, penetrantprovning, makro/ mikroundersökning, sidobockprovning och korttidskorrosionstest (~50 timmar). Slutsatsen av detta examensarbete är att MIG-svetsning är en mer produktiv metod än TIG, men fler defekter såsom bindfel och sprickor uppkom för MIG-svetsning. Dessa defekter kan ”fixas” genom optimering av svetsparametrar. Om man bara ska reparera ett specifikt område är TIG-svetsning ett bättre alternativ. En slutsats om antal lager är att ett lager med MIG-svetsning är nästan lika tjockt som tre lager med TIG-svetsning med Ø 1mm svetstråd. Tre svetsutvärderingar som är viktiga är visuell undersökning, penetrantprovning och korrosionstest för att välja vilken påsvetsmetod som är lämpligast i pannapplikation.

The ultrasonic welding of Cu110, electrolytic tough pitch copper sheet to electroless plated laminate circuit board was experimentally investigated within the range of 20 kHz. The effects of machine parameters; energy, amplitude and pressure as well as material characteristics such as surface roughness, gauge, temper, and silver and gold plating schemes were compared through pull tests and analysis of microstructure. Evidence was discovered which attributes plastic deformation, mechanical interlocking, and acoustic softening to the mechanism of weld formation. It was further determined that ultrasonic welding of Cu110 sheet to silver immersion laminate circuit boards as means of electrical termination is a robust process. Therefore it was the goal of this thesis to understand the mechanism of ultrasonic welding and determine if ultrasonic welding to laminate circuit boards is an alternative to soldering electrical terminations.

Electric arc welding is the most prevalent welding type in industry. It creates two main groups of health hazards for workers; fumes and gases, and radiant energy. Shielded Metal Arc (SMA) welding is the most widely used welding method in industrial plant welding shops. The main chemical health hazards associated with this type of welding are fumes. Fumes are particles formed when the electrode and base metal constituents are vaporized and condensed in the welding area. Potential health problems can be anticipated by measuring the concentration of fumes in the welding space and comparing these data to established exposure standards. If high concentrations of these fumes are present, control measures should be undertaken to reduce the potential toxic effect to workers. Most of the studies have been done on mild (carbon) steel welding where it is generally necessary to monitor only the total amount of fumes. Stainless steel welding differs from carbon steel welding in that it generates considerable fume concentrations of chromium and nickel, which are suspected human carcinogens. The first part of this study evaluated the health risks posed to workers exposed to chromium and nickel fumes from routine stainless steel welding procedures. All the welding was performed in an industrial plant welding shop by one experienced welder. The welded piece was a three-part stainless steel cylinder. The whole period of welding lasted almost three weeks, although the actual welding was done in eleven days during that period. All sampling was performed with filter cassettes connected to personal air pumps. Sampling was performed in welder's breathing zone, in the general area (background sample), and at conveniently located points outside the breathing zone for evaluation of ratios of chromium and nickel to total fumes. The results indicated that at this particular industrial plant, exposure levels did not exceed the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs) and the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs). The results also indicated that it was not necessary to monitor the general area because of very low concentrations of chromium and nickel fumes. Rather, it is suggested that the monitoring focuses on the welder's breathing zone where it is important to sample hexavalent chromium (chromates) because of its proven carcinogenic effect and therefore very low TLV. Also, it was found that if TLV for chromates is not exceeded, then levels of total chromium and nickel are also likely to be below limits. The second part of the study sought to devise a simplified method of monitoring of welding operations. The results suggested that it is not always necessary to sample for all the components (total fumes, total chromium, chromates, and nickel) when estimating worker's exposure. Rather, it is possible to simplify the process by establishing the ratios of fume constituents during a period of heavy welding, thus enabling the industrial hygienist to make a reasonable estimate of exposure that occurs at other times. The estimate can be made by sampling either the main constituent (chromates) or total fumes, and predicting the exposure to remaining constituents of interest from these data. In addition, and in contrast to previous studies, it has been concluded that when fume concentrations are low, a welder's helmet does not provide any additional protection against fumes. Additional protection can be provided with the use of proper local ventilation, such as with a flexible hose, to reduce exposure well below suggested limits. / Graduation date: 1994

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