 January 2006FEATURES Managing Thermite Weld Quality for Railroads The most common defects found in the rails of typical metro mass rapid-transit systems are cracks in the heat-affected zone (HAZ), flaking, pitting, gauge corner crack, wheel burns, shelling, turnouts, corrugations, and lipping/depression. These defects are initiated and aggravated by the contact stresses caused by the nonconformities between the rail and wheel interfaces - Fig. 1. Some typical examples of surface rail defects formed by rail-wheel contact stresses are shown in Fig. 2. Thermite welding is commonly used to repair these surface and subsurface defects. The performance of the welded joints, which are generally weaker than the rails bae metal, is of great concern since the joints generally account for most of the defects detected in rail track systems. F. T. Lee How to Build a 'Lean' Team The steel manufacturing industry must recognize that its employees are the most important asset it has. As such, it is important that companies ensure that they have the right employees in the right numbers with the right skills at the right time to perform their jobs. As we strive for continuous improvement in our production lines, we need to understand that the improvements we make are only as good as the people on the line. If the people do not have the necessary skills to accomplish the tasks at hand, then no process improvement will be successful. J. C. Barto III and A. D. Robertson Guide to Joint Design for Welding Ship Hulls The first all-welded ships were built just before World War II. More than 4000 welded ships were constructed during the war. When some of those ships experienced major structural failures relating to brittle cracking, most notably the Liberty Ships, government and industry undertook immediate and extensive investigation and research into the problem. Most major failures started either in a defective groove weld in the deck or bottom shell or at a sharp structural intersection, or some other abrupt change in structural cross section. As a result of this research, steels with superior notch-toughness were developed and design details were improved. Essen Welding Fair Abounds with Technology What is striking about the Essen Welding Fair is the sheer number of welding and cutting equipment manufacturers whos products are needed to fill the demand of a global manufacturing community. Technology from 44 countries was displayed by 1043 exhibitors, and viewed by 61,100 attendees. Those are the statistics of Schweissen & Schneiden 2005 (Welding and Cutting) held this past September in Essen, Germany. Organized by Messe Essen GmbH and sponsored by the German Society for Welding and Allied Processes (DVS), this every-four-year event is the stalwart exposition of the welding community. The exhibitions filled 17 halls, and a special USA Pavilion was organized for the Welding Equipment Manufacturers' Committee (WEMCO) by the American Welding Society. A. Cullison Hybrid EBS Process Joins Heavy-Duty Impellers The electron beam welding (EBW) process has been used to accomplish many critical joining applications over the past 40 years (Refs. 1, 4). But because the use of computer numerical control (CNC) on electron beam welding machines did not become common practice until the 1980s, the majority of parts designed for EBW prior to the mid-1980s had joints that were either straight line or circular (so that they could readily be welded with semi-manually operated x-y tables and/or rotary fixtures). However, since the use of CNC on electron beam welding machines has become fairly standard, current part designs can take full advantage of its capacity to simultaneously control both the weld path motion and electron beam parameters. One recent application of CNC/EBW that employed all capabilities of the process, and even required development of additional features, is the final assembly welding of covers onto integral bladed impeller disks used in turbo compressors. These advanced compressor impellers have complex computer-aided design generated geometries involving covers of varying thicknesses and blades of convoluted shapes that exhibit variations in both height and width. G. LaFlamme et al. WELDING RESEARCH SUPPLEMENT *A Novel Edge Feature Correlation Algorithm for Real-Time Computer Vision-Based Molten Weld Pool Measurements (.pdf) A potentially more efficient control scheme compared to traditional open loop systems is investigated C. Balfour et al. *Predicting
and Reducing Liquation-Cracking Susceptibility Based on Temperature vs.
Fraction Solid (.pdf)
*Fatigue
Behavior of Welded Joints Part 2: Physical Modeling of the Fatigue
Process (.pdf) |
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