Self-shielded electrodes help contractor weld to FEMA specifications
March 25, 2004
New construction abounds all over the U.S., and Seattle is not immune to this trend. In 2002 an open-looking courthouse was completed, rising 387 feet above the city skyline.
This $215 million federal courthouse was needed both because the city had outgrown the previous building and because of new Federal Emergency Management Agency (FEMA) specifications that require buildings in seismic areas to be built to withstand earthquakes.
Seattle may be in earthquake territory, but that didn't mean that designers wanted to make the new courthouse look like a fortress just so it could withstand seismic activity. This was a challenge for designers.
What designers came up with was a structural system that uses a "hybrid shear wall" core that combines steel plate, braces, and beams in cells guarded at the corners by giant steel cans filled with concrete.
Adam Jones, owner and president of structure builder The Erection Company of Arlington, Wash., calls the system "the thing of the future" for high seismic zones, despite some fit-up difficulties, including sometimes troublesome coordination problems between concrete and steel work.
What makes this system so futuristic is the FEMA welding specifications required for steel buildings. Currently only 50 percent of the buildings in the area are following these specifications for high seismic activity. In the future, everyone will have to follow the FEMA specifications.
A lot of welding was required; 25 employees welded exclusively, using almost 2,400 lbs. of filler metal each week. Before welders were hired to do the job, they had to be tested and were required to weld a joint according to FEMA procedures. Part of this test required that the welder learn how to weld with a copper backing bar. The welder then was tested on this technique before being hired.
"At one point we had 15 welders joining 5 1/2-in. flanges, using more than 1,200 lbs. of electrode per day," Jones said.
The amount of welding was not the only challenge, however. FEMA specifications required preheating of the iron before welding, and in some cases, gouging was required after the weld was completed. The Erection Company tackled this challenge when it qualified the procedure. This was all done as part of the company's process of bidding on the job.
The Erection Company tested four different filler metals when it qualified the procedure. It found that most of the electrodes required the use of a steel backing bar, which required more postweld work for the welders.
"After the weld was completed, you went under the bottom flange of the I beam and gouged it out and finished it with an overhead welding rod," said Gino Saccon, weld technician.
Another problem with some of the wires the company tested was the failure rate. Almost all of the tests the company performed resulted in cracked welds. One wire that did not require extra postweld effort was Coreshield® from ESAB Welding & Cutting Products.
The Erection Company found that Coreshield 6 and 8 self-shielded, flux-cored filler metals worked satisfactorily in a range of arc voltages, which helped simplify welding training and qualification. These combined factors helped produce a lower rate of rejects and repairs in actual construction.
The electrodes were designed for FEMA specifications. Their Charpy V-notch toughness values meet FEMA 353, especially for construction in seismic areas, according to ESAB. The company also describes the electrodes' characteristics as suitable for meeting strength and toughness requirements of American Welding Society (AWS) A5.20. Coreshield 8 has been approved by the American Bureau of Shipping (ABS) 3SA, 3YSA (H10), Det Norske Veritas III YMS (H-10), and Bureau Veritas SA3YM HH, according to the manufacturer.
Dwight Myers, product business manager for ESAB, said he feels that although several manufacturers' filler metals meet the increasingly strict needs of buildings being constructed today to withstand natural phenomena, such as earthquakes, ESAB's goal was to not only meet the requirements of the end user, but also to improve operator appeal and usability. FEMA specifications, such as those for high heat and low heat input in welding structures, are spelling out these types of building requirements.
"FEMA is relatively new but is taking hold when designers are designing new buildings," Myers said.
By using the filler metals, Saccon reported that the company completely eliminated weld failures, which was a top priority for this project. Slag removal improved 100 percent, and no root passes cracked, he reported.
In addition, Saccon said, the welders could use a copper backing bar with this filler metal instead of steel. The copper backing bar fell out after welding, eliminating the need for gouging. This eliminated much of the extra work that would have been required, increasing production by 20 percent.
Saccon also said that a welder didn't have to be an expert to lay a good weld bead. Myers commented, "You have to meet the needs of the people using your products to make their job easier than it was before. If you look at the industry, self-shielded wires are good for higher productivity where you don't have gas to shield the wire."
ESAB Welding & Cutting Products, Filler Metals Division, 801 Wilson Ave., P.O. Box 517, Hanover, PA 17331, 717-637-8911, fax 717-637-9859, www.esabna.com.