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Welding-designIssue of Knowledge and Expertise.Solutions with Effective, Practical AdviceCorrect Welding-design: is it essential for good Weldments? You bet! However important, this is not always self-evident even to Designers, possibly because their standard preparation generally lacks involvement in aspects of welding that are essential to successful Welding design.
Welding design cannot be good in general. You cannot make an excellent Design once, and then copy it as much as you wish. NO! Welding Design must be service specific. Operating conditions and application requirements are essential elements of suitable design. Both safety and service life depend upon good Welding-design for stability and functionality. Welding-design satisfactory for a certain application may not be adequate for a different one, depending on service conditions. Modern trends indicate a growing need in Welding-design team activity, to satisfy requirements covering different disciplines that cannot possibly be mastered by a single individual. At minimum, the chief designer should make sure to seek advice from expert professionals for their Welding-design review.
Individuals responsible for Welding-design should dedicate time and study to learn and assimilate at least basic principles of the different subjects intervening in establishing effective weldments, in order to be receptive to the input available from welding specialists. Conversely welding experts should familiarize themselves with Welding-design to the point of understanding construction and manufacturing requirements even if it is not their piece of cake, and developing an effective communication language to make their points clear without generating resistance or hostility. We would like to call our readers' attention to an article we published on this subject and available online at An Article on Surface Impact Improvement Treatments was published in Issue 42 of Practical Welding Letter for February 2007. An Article on Materials Selection for Product Design (2)
was published in Issue 48 of Practical Welding Letter for August 2007.
To receive each issue of PWL as it is published, please Subscribe. There is no substitute for experience. Welding-design should be based on experience, as distilled in quality examples of successful cost effective realizations. It is an iterative process, by this meaning that it may start as an approximate idea or sketch of what is needed, and then refined and detailed as necessary, exploring alternative solutions and finally selecting the most appropriate in terms of functionality, economy and building time. Stability is traditionally assured by calculation of the applied loads or forces, those deriving by the weight of the structure itself and by environmental conditions (wind, snow etc.), and those produced by the activation of the intended functions. Loads, configuration and dimensions define stresses and strains operating on the structural elements and on the joints. It is the designer's responsibility to verify that these are well within acceptable limits for safe operation. It should be understood that properties and characteristics of materials are influenced and changed by welding processes, and therefore at the Welding-design stage one must specify the required process while taking into account its consequences on integrity and stability. Excellent sources to gain a lot of experience from, are books on Failure Analysis of which the following one is a recommended example. ASM Handbook Volume 11: It may be the difference between success and failure. Material selection is a complex procedure which has to consider, besides standard mechanical properties and manufacturing constraints, also requirements for resistance to corrosion or weathering agents, need for protection, finishing and ease of maintenance, as well as availability and economy of production. Ease of manufacturing and of welding, if applicable, should also be taken into account. Projected savings in maintenance along the planned life of the structure may suggest the selection of a more resistant material even if more expensive at purchase time. This concept is sometimes called the Total Life cost, including the proceeds from selling the scrap. For mechanized and robot Welding-design one should pay particular attention to set realistic joint tolerances, especially for sheet metal parts. Although not restricted to Welding-design only, a most complete reference is ASM Handbook Volume 20: Metallurgy and weldability are essential considerations, especially when it appears that special procedures have to be implemented for successful welding. If weight is at premium (for high rise constructions or for transport), higher properties may permit weight reduction and savings, even if more expensive materials are selected. When considering Welding-design involving the use of aluminum alloys, it is important to remember that the strongest alloys are not weldable, as explained briefly in another page, reachable by clicking on Materials and that only specific processes can be used to preserve those high properties, as can be seen on a different page by clicking on Aluminum Welding. Some of the items to be considered in Welding-design are: materials weldability as mentioned, function, stability, accessability (of the joint by the welder), maintainability, inspectability (that is design for easy inspection access), manufacturability, transport, design for quality, and cost calculated on the base of practical weld deposition rates. Individuals involved with Welding-design should become familiar with the following publications covering several aspects of the matter. AWS ARE-5 Joint configurations must be specified on drawings by use of accepted weld symbols as described in: AWS A2.4-98 For a limited, unofficial information on symbols, one can consult a short page available on the Internet at: Good Welding-design of joints, besides a thorough knowledge of important features of welding processes, needs familiarity with terminology. Basic essential information is found in the following: ANSI/AWS A3.0:2001 Good Welding-design is an essential condition for obtaining acceptable Quality, as shown in a different page reachable by clicking on the above link. But Design must also comply with all requirements of applicable Welding Codes. For interpretation of Code requirements, the following book may be invaluable, as it was written to help with all question related to Welding-design regulated by welding Codes: Welding Codes, Standards, and Specifications A short list of Codes may include the following: ANSI/API 1104 AWS API-M:2006 ASME Section IX ANSI/AWS D1.1/D1.1M-2006
ANSI/AWS D1.6-99 ANSI/AWS D1.2/D1.2M:2003 Material thickness and process selected define the edge preparations required which are illustrated in figures displayed in the following Handbooks: AWS Welding Handbook ASM Handbook : Welding, Brazing & Soldering
Other influencing factors to be evaluated are heat flow, residual stresses and distortion. Weldability and properties of the selected materials determine the strength of welded joints. Standard calculation of weld size required for static loading should be applied. Size of fillet joints can be dimensioned using In certain cases of perceived danger, suitable control should be specified in drawings and implemented during welding to avoid brittle fracture. Unacceptable defects should be established by design as well as limits for acceptable discontinuities detected by visual and other non destructive inspection methods, each technique with its specific requirements. When using radiography (X-Ray inspection), reference is usually made to the volumes of Reference Radiographs (see in Welding Inspection), according to materials and thickness: the designer has to select the maximum size and density of defects that is acceptable for the service conditions of the item on hand, and establish on the drawing a note to this effect. If resistance to fatigue straining is an issue, then the assessment of the relative fatigue life of welds should be researched and, if applicable, fatigue life improvement (i.e. shot peening) methods should be implemented. Most books on Engineering Design reserve only a limited place to the description of popular welding processes. A good course in Welding-design would provide important insight to the students if detailing and discussing proven quality examples of successful implementation of the basic principles briefly introduced in this presentation. Dedicated courses are available at A journal dedicated to practical aspects is: Which instructions should be included in the welding drawing?
In conclusion, Design for Welding is a most complex subject, because it involves knowledge and experience in a lot of disciplines that cannot be possibly found in a single individual, however brilliant and thorough. The best provision to ensure adequate accomplishment would be to involve in the task a small team of excellent professionals.
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