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Fwd: Re: Lincoln Arc[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: wai(--nospam--at)euken.com
- Subject: Fwd: Re: Lincoln Arc
- From: rlewis(--nospam--at)techteam.org (Richard Lewis)
- Date: 05 Aug 1997 15:31:00 GMT
Tom- In response: The "Lincoln Rod Problem" is not specifically a "Lincoln" problem. The "problem" is that a specific electrode used in FCAW, specifically, the E70-T4 electrode, produces low toughness weld metal, with typical Charpy V-Notch values on the order of 5ft-lb at 70deg. F or less. Low toughness metal (weld or base) is quite vulnerable to brittle fracture. Fracture initiates as a result of stress exceeeding the ultimate tensile strength of the material. Usually, steel and weld metal behave in a ductile manner, meaning that fracture occurs after large deformation. In brittle fracture, failure occurs without large deformation and progresses rapidly through and across the section. Brittle fracture is common in low toughness materials and can be initiated by stress concentrations at notches. The stress concentration essentially raises the stress very locally, above the ultimate tensile strength. This produces a small fracture. The small fracture, in turn, increases the notch effect. This increases the stress concentration - producing more fracture - essentially resulting in a runaway reaction. Stress concentrations (notches) can occur from many causes. - Geometry of a joint - for example- the basic "T" joint produces stress concentrations, unless the joint is rounded at the fillet. Metallurgical changes in the material can produce notch effects - e.g. an arc strike on the steel can prdouce local deposits of martensite, which because of its different properties, can be a fracture initiation point. Also - almost all welds have slight imperfections (if they are too large they are called defects) that in low toughness material - can lead to initiation of brittle fracture at elastic stress levels. Now back to the "Lincoln" problem. The E70-T4 electrode was developed by Lincoln in the 1960s and they started marketing it in the late 1960s. Because of the speed of welding with this electrode, compared to other available consumables, it rapidly caught on and by the early 1970s, nearly all field welding of large volume welds were performed using this electrode. Obviously a great product like this is going to be imitated and other manufacturers of electrodes also produced and sold T4. In addition to the low toughness problem, the T4 electrode can be easily abused by allowing welders to place metal too rapidly, in too large a bead size. These welds are susceptible to slag inclusions, poor fusion and other defects. This is all accentuated by the low toughness. You can find out much more information - First obtain a copy of FEMA-267 Interim Guidelines - Welded Steel moment Frames, produced by FEMA in 1995. It is available free from FEMA - You can get the phone number to order this at 1-800-480-2520. FEMA is also producing a publication FEMA-288 that has more than 400 pages of information on Fracture Mechanics and welding processes (as well as other items of interest). You may find it useful. You can order this at the same number. The L.A. Times is not a particularly good place to research this information. The articles that appeared on this topic were not technical in nature and were highly slanted by one side in litigation to present facts only that favor a particular position in the litigation. Ronald O. Hamburger Project Director, Product Development SAC Joint Venture; Member - AWS D1.1 Subcommittee on Welding for Seismic Applications Member - AISC TC-115 on Structural Shapes --- Internet Message Header Follows --- Received: from server1.seaoc.org (bqe.com [220.127.116.11]) by host1.texramp.net (8.8.5/8.8.5) with SMTP id JAA13190 for <rlewis(--nospam--at)techteam.org>; Fri, 21 Mar 1997 09:28:10 -0600 (CST) Received: from eqe.com by server1.seaoc.org (NTList 3.02.10) id qa010260; Fri, 21 Mar 1997 07:15:59 -0800 Received: from eqe-1.eqe.com by eqe.com via ESMTP (951211.SGI.8.6.12.PATCH1502/951211.SGI) id HAA07864; Fri, 21 Mar 1997 07:13:06 -0800 Received: from EQE-1/SpoolDir by eqe-1.eqe.com (Mercury 1.21); 21 Mar 97 07:18:09 +1100 Received: from SpoolDir by EQE-1 (Mercury 1.21); 21 Mar 97 07:17:38 +1100 From: "Ron Hamburger" <roh(--nospam--at)eqe.com> Organization: EQE International To: tomlong(--nospam--at)silcom.com Date: Fri, 21 Mar 1997 07:17:25 PST MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Re: Lincoln Arc CC: seaoc(--nospam--at)seaoc.org, sacsteel(--nospam--at)eerc.berkeley.edu Priority: normal In-reply-to: <199703201747.JAA01956(--nospam--at)beach.silcom.com> X-mailer: Pegasus Mail for Windows (v2.52) Message-ID: <11CD505647F(--nospam--at)eqe-1.eqe.com> Reply-To: seaoc(--nospam--at)seaoc.org Error-To: seaoc-ad(--nospam--at)seaoc.org X-Loop: seaoc(--nospam--at)seaoc.org X-Info: [SEAOC] Owner: seaoc-ad(--nospam--at)seaoc.org X-POP3-Rcpt: seaoc-ad(--nospam--at)seaoc.org X-Sender: seaoc-ad(--nospam--at)seaoc.org Precedence: list X-ListMember: rlewis(--nospam--at)techteam.org [seaoc(--nospam--at)seaoc.org] __________________________________________________ Richard Lewis, P.E. Missionary TECH Team rlewis(--nospam--at)techteam.org The service mission like-minded Christian organizations may turn to for technical assistance and know-how.
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