Need a book? Engineering books recommendations...
Re: Welds[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)seaoc.org
- Subject: Re: Welds
- From: "Ron Hamburger" <roh(--nospam--at)eqe.com>
- Date: Mon, 30 Dec 1996 15:19:49 PST
- Priority: normal
On 12/30 Tom Harris wrote: > There is an interesting L.A. Times article on welds today ( Mon, > 12-30-96) on the front page and two other pages ( 2 1/2 page article ). It > says Mr. Fisher warned against using E70T-4 electrodes at a L.A. seaoc > conference in Sept. '94 but i can't remember it. If E70T-4 is what has mainly > been used in the past and is not recommended, then what is recommended in its > place? Engineers should not call out specific electrodes for their projects. The selection of an electrode is really the fabricator/erector's responsibilty. Selection depends on the weld process to be utilized (e.g. SMAW, FCAW, SAW, etc.), the procution conditions, the position that welding will be done in, the materials being welded, and the qualifications of the welders who will do the work. Much of this information is available to the engineer. Instead, the engineer should specify welds on a performance basis. Specifically, strength (as given by the ultimate tensile of the deposited metal - 70ksi is usually specified for building structural purposes), toughness (if required) in terms of a rated Charpy V-notch value for the deposited metal at a specified temperature (20 ft-bl at 0 deg. F should be considered for critical applications in most building applications). The engineer should require that the Fabricator/Erector provide a Welding Procedure Specification for approval, prior to performing any work. The WPS will call out the electrode type, as well as the various welding variables including - position, voltage, current, interpass temperature, preheat temperature, etc. required to acheive the requried performance. The WPS should be accompanied by the product data for the proposed electrode, which will indicate the rated performance of the deposited material, and the variables for which this performance can be obtained. For more information on this please refer to the SAC-FEMA-267 Interim Guidelines document. You will find Chapter 8 particularly helpful. Also, SAC is about to publish a volume of Background Reports that includes a 120 page paper on structural welding. It will tell you all you wanted to know about welding, but were afraid to ask. By the way, there is currently ongoing litigation, pertaining to use of E70T4 electrodes. The L.A. times article was spurred on by this litigation and an attempt by one side in the case to press its point. All "technical" information presented in the article should be read with that knowledge in mind. However, the fact is that E70T4 material does typically result in very low toughness. The use of low toughness metal is not recommended by SAC for welds subjected to large cyclic demands, such as the full penetration welds of moment connections. Ronald O. Hamburger Project Director for Product Development SAC Joint Venture
- Prev by Subject: Welds
- Next by Subject: Re: What does T-4 stands for?
- Previous by thread: Welds
- Next by thread: Test message please delete