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AWS - D3.7:2004

Guide for aluminum hull welding

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Organization: AWS
Publication Date: 1 January 2004
Status: inactive
Page Count: 86
ICS Code (Hulls and their structure elements): 47.020.10
ICS Code (Welding, brazing and soldering in general): 25.160.01
ISBN (print): 0-87171-690-9
scope:

This standard makes sole use of U.S. Customary Units. Approximate mathematical equivalents in the International System of Units (SI) are provided for comparison in parentheses or in appropriate columns in tables and figures This guide provides information on proven processes, techniques, and procedures for welding aluminum hulls and related ship structures. The information presented applies chiefly to the welding of aluminum hulls that are over 30 ft (9 m) in length and made of sheet and plate 1/8 in. (3.2 mm) thick and greater. Thin-gage aluminum welding usually requires specific procedures in the area of fixturing, welding sequence, and other techniques for distortion control that are not necessarily applicable to thick plates. Similarly, the choice of welding process or applicable process conditions, or both, also differs according to thickness. 1.2 Welding Processes. The inert gas shielded welding processes have been employed as the principal joining method for the majority of aluminum naval and merchant ship structures built since the early 1950s. In their basic forms, these processes employ two distinct types of electrodes, although both use a protective shield of inert gas to prevent oxidation of the hot metal in the weld zone. 1.2.1 Gas Tungsten Arc Welding (GTAW).1 Thefirst inert gas welding process to be developed was gas tungsten arc welding which is sometimes referred to as TIG welding. Introduced in 1941, this process uses a nonconsumable tungsten electrode. Inert gas is fed through the welding torch while filler metal, when required, is added into the weld pool separately by hand or machine. 1.2.2 Gas Metal Arc Welding (GMAW).2 The second process, gas metal arc welding, which is sometimes1. Refer to AWS C5.5/C5.5M, Recommended Practices for Gas Tungsten Arc Welding, and the Welding Handbook, Vol. 2,8th Ed. 73-108. 2. Refer to AWS C5.6, Recommended Practices for Gas Metal Arc Welding, and the Welding Handbook, Vol. 2, 8th Ed. 109-156. referred to as MIG welding, is employed for over 90% of the joining in a welded aluminum hull because it is muchfaster than GTAW. This process also uses an inert gas shield, but employs a continuous aluminum wire electrode that provides filler metal as it is fed mechanically through a welding gun. Introduced in 1948, GMAW is suitable for production welding of aluminum of 1/16 in. (1.6 mm) thickness and greater. 1.3 Comparison of Welding Processes. The gas shielded arc welding processes GMAW and GTAW offer speed, good weld strength, and ease of operation in all positions on a wide range of aluminum thicknesses and joint types. Inert gas shielded arc welded joints in aluminum alloys, generally recommended for marine use, retain a high percentage of the original base metal strength. Similarly, properly made welded joints, produced with the correct filler metals have virtually the same corrosion resistance as the base metal. Oxyfuel gas and shielded metal arc welding are not suitable for aluminum ship structures because weld quality is inadequate, and the residual chlorides from the flux must be removed. 1.4 Serviceability of Welded Aluminum Hulls. Service records of welded aluminum craft and other marine structures are excellent. Maintenance and repair cost records of hulls, which have been in service for 20 years or more, are impressive. In many respects, preparation of aluminum hull plate for welding is simpler and more flexible than preparation of steel plate. Portable routers and radial saws, operating at relatively high speeds, and plasma arc cutting are widely used to advantage in cutting aluminum. Machining operations to provide the required joint geometry for sound welds usually can be done with the same equipment employed for steel, but the cutting tools should be designed for aluminum. Shipyards already equipped with plate milling and planing machines, for example, employ the equipment for aluminum edge preparation using tools properly shaped for cutting aluminum. for sound aluminum welds and should be more precise than that normally required for welded steel construction. For most ship structures, no root opening in the joint is preferred. However, where base metal thickness or other conditions demand, proper root openings are well defined. Aligning procedures generally follow those used in steel practice. Many shipyards have discovered that the best fitters for aluminum construction come from carpentry shops. This is due primarily to the fact that most aluminum cutting is done with similar mechanical equipment. A workman with woodworking experience is more likely to follow the cutline more accurately than is a worker versed in steel ship construction where moderately loose fits may be tolerated. 1.6 Sources of Information. Data and opinions presented in this manual are based on the experience of shipyards, aluminum producers, naval architects and engineers, and welding equipment suppliers. The following subjects are covered in sufficient detail to provide reliable and practical guidelines: (1) Marine aluminum alloy, temper, and shape availabilities (2) Edge preparations (3) Forming (4) Cleaning for welding (5) Welding processes (6) Welder training and qualification (7) Fitting, aligning, and assembling (8) Types of joints and assemblies (9) Welding procedures (10) Stress relief (11) Inspection and testing of welds (12) Repair of welds Additional information is available from the aluminum producers as well as from various comprehensive publications covering structural data, specifications, welding, and related subjects. A number of applicable publications are available from the Aluminum Association, American Welding Society, Society of Naval Architects and Marine Engineers, American Bureau of Shipping, and U.S. Naval Ship Systems Command. These and other organizations of interest are listed in Annex A, together with pertinent codes, specifications, and regulations.

abstract:

This guide provides information on the welding of sea going aluminum hulls and other structures in marine construction. Included are sections on hull materials, construction preparation, welding... View More

Document History

D3.7:2004
January 1, 2004
Guide for aluminum hull welding
This standard makes sole use of U.S. Customary Units. Approximate mathematical equivalents in the International System of Units (SI) are provided for comparison in parentheses or in appropriate...
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