Laser Beam and Laser-Arc Hybrid Welding of Aluminium Alloys

Aluminium alloys are widely used in many industries due to their high strength-to-weight ratios and resistance to corrosion. Due to their specific thermophysical properties and intricate physical metallurgy, these alloys are challenging to weld. Work-hardened alloys may experience strength loss in heat-affected zones (HAZ). The strength of precipitation-hardened alloys is severely damaged in both HAZ and weld metal due to coarsening or full dissolution. The high thermal conductivity and reflectivity of aluminium causes lower laser beam absorptivity with lower processing efficiency. Weld imperfections such as porosity, humping, and underfills are frequently formed due to the low melting point and density promoting high liquidity with low surface tension. Porosity is the most persistent imperfection and is detrimental for mechanical properties. In this work, extensive review was made on laser beam and laser-arc hybrid welding of aluminium alloys. Solidification cracking, evaporation of alloying elements, porosity and keyhole stability, and other challenges are studied in detail. The current development of laser welding of aluminium alloys is not so mature and new discoveries will be made in the future including the use of newly developed laser systems, welding consumables, welding methods, and approaches.

Manufacturing Status of JT-60SA Vacuum Vessel and the Related Technology of Welding

JT-60SA is a fully superconducting coil tokamak upgraded from the JT-60U, and this paper focuses on the vacuum vessel (VV, 150 tons) design concept with the related technology of welding and its manufacturing status. The design concept is developed from the ASME Boiler and Pressure Vessel Code Section VIII Division 2, and the damage tolerant concept is adopted into the welding part hardly inspected. These weld joints are treated as a partial penetration and residual strength is evaluated in the design process. Consequently, accuracy of VV weld structure is enhanced due to reduction of the welding heat input and also less process of weld work is achieved. The vacuum vessel has been manufactured since Nov. 2009. Welding technology related to the VV is surveyed and developed in three stages; element test, 1-m size trail and 20-degree upper half mock-up manufacture. The welding methodologies are selected from element tests, and then the typical vessel segments as a 1-m size are tested. The welding conditions to control its quality and the distortion are evaluated, and the lower heat input condition is additionally researched. On the basis of these results, the manufacturing sequences are established through the large size trial of the mock-up manufacturing.

The Man-Hour Calculation Model for Multi-Stage Manufacturing System Based on Primitive Decomposition and Web Service

To solve the problems that basic man-hour data scarcity and avoid the difficulties in establishing man-hour, a man-hour calculation model for multi-stage manufacturing system based on primitive decomposition and Web Service is presented. The model consists of two modules. Aiming at a five-stage manufacturing system contained machine work, punching work, weld work, electrophoresis work and assembly work, the first module analyzed the characteristic of each manufacturing system, proposed the definition and decomposition rule of the primitive operation and founded the man-hour calculation model based on primitive decomposition. In order to use the relevant information about man-hour and provide decision-making and plan-making departments with the distributed manhour data, the second module applied Web Service technique in the enterprise Intranet to achieve the information share in the enterprise. The presented model system simplifies the man-hour establishing process and provides an effective theory model which establishes the man-hour rapidly and accurately. Finally, the products man-hour establishing example in an enterprise shows the feasibility and the good performance of the presented model.