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Winning Welds

01.02.2012
Category: application stories

“ESAB came up with a simple solution and an incredible delivery time.” Owen Steel Co. saves critical minutes with customized cutting and welding machines.

In a welding shop, half the battle is the application of weld into joints and the other half is finding ways to reduce the amount of weld in those joints,” says Stacey Oxendine, production engineering manager for Owen Steel Co. Inc.

The Columbia, S.C., company has been fabricating steel for more than 75 years. Its knowledge and experience with complex structural metal puts Owen Steel in a class of its own and allows the company to provide customers with a complete range of steel contracting services. When Owen Steel was awarded a job to construct box columns from high strength steel for one of the towers being built at the World Trade Center site, the project’s design criteria presented engineers with a difficult problem, Oxendine says.

“The thickness of the plate (2 in. to 4 in.) and the sizes, 24 in. to 40 in. square, meant we couldn’t purchase ready made shapes,” he says. “We had to build the box columns from scratch out of four pieces of steel approximately 35 ft. long or the height of two floors. Specifications called for a full penetration weld the length of the column to join the four plates into a box shape. The amount of welding needed to meet that criterion was astronomical. We knew based on scheduled delivery time frames and available manpower that we had to come up with a way to reduce our welding time.”

Innovative approach

Owen Steel worked closely with the project’s engineer of record and came up with a creative alternative. The fabricator could save time without sacrificing quality by performing a complete joint penetration weld at floor level and a partial joint penetration weld between floor levels. The ability to make full penetration welds in just two zones saved time but posed other challenges.

“The steel had to be stripped and beveled to prep the plate for welding,” says Oxendine. “Instead of the simple cut dictated by the original weld approach, the alternative weld method meant we ended up with a very complex cut—a bevel that needed to change depth over the length of the column. When you are dealing with thick plate, it has a tendency to move during cutting. You also have the potential for distortion due to the heat generated by the cutting process. To minimize distortion and help keep the plate straight, we needed to cut both sides at the same time and we needed equipment that could meet those requirements.”

Traditional CNC machines can be mounted with multiple torches and programmed to follow a complex shape, but the torches will move in the same orientation. “We needed an equal but opposite reaction, a machine equipped with torches that could be programmed to move in a mirror fashion but in opposite directions,” says Oxendine.

After talking with several CNC equipment manufacturers, Owen Steel selected ESAB Welding & Cutting Products, Florence, S.C. “ESAB came up with a simple solution and an incredible delivery time,” says Oxendine. In addition to an Avenger X CNC burning table with a cutting area 16 ft. wide and 72 ft. long, Owen Steel purchased a Mechtrac gantry welding system with a PEK controller and automated tracking system. The equipment was installed in September 2011.

Oscar Kjellberg established ESAB in 1904. Today, the company leads the industry in welding and cutting as an international supplier and manufacturer of equipment and accessories for nearly all welding and cutting applications.

“ESAB has a long history of experience with bevel cutting for heavy fabrication industries,” says Steve Zlotnicki, North American regional product line manager for cutting at ESAB. “We adapted our standard method of moving torch stations across the beam to allow the two torches to move in opposite directions on one axis while making a cut down the length of the plate. We also modified the torch stations to float along the top of the plate instead of riding up and down powered by a motor. Torch height above the material is critical because it affects bevel geometry and part size. To ensure accurate cutting height, we developed a special plate riding system that allowed the torch to use the top surface of the material as a cutting guide or reference point.”

For the first step in fabricating the box column, the Avenger X was used to cut through approximately 6 in. of material to achieve a 45 degree bevel. The amount of cleanup, the next step, depends on the cut quality.

“Full penetration welds undergo very strict quality control testing requirements, and a good cut helps to optimize weld quality,” says Oxendine. “We achieved a very good cut quality, which greatly minimized our touch up work.”

Once structural steel fitters form the four pieces of plate into a box, the column is tack welded to prep it for the next stage of welding. Owen Steel prefers submerged arc welding when faced with large weld volumes on structural steel. With the Mechtrac, the fabricator was able to perform submerged arc welding using two wires (about the size of a coat hanger) instead of the standard one wire in the weld puddle. This meant Owen Steel could shave time by running faster while still managing heat input to minimize distortion.

“The Mechtrac’s PEK controller monitors heat or kilojoules input,” says Scott Brockman, regional sales manager, southeast region at ESAB. The control allows Owen Steel to find premium parameters for heat input then set minimum and maximum limits, which ensures the welder stays within specification—a critical factor when it comes to minimizing distortion.”

Oxendine also is able to use the PEK to gather data intelligence about his production processes. “The control is very operator friendly, and because it is constantly calculating the different facets of the weld, like how much filler metal we used on a job, we gain information that helps me improve internal production planning.”

Running faster

GMH tracking on the welding system gives Owen Steel an automation advantage. “We want to fill void as fast as possible but that also means using more heat and running faster,” says Oxendine. “Conventional welding systems require you to physically watch the placement of the weld and manually make adjustments to the weld head. Mechtrac’s automated seam tracking allows me to position the weld head where I want it then automatically makes adjustments to maintain that position and give me a consistently placed bead of weld.”

Once welding is complete and passes testing, the fabricator performs secondary assembly work before the box columns are shipped to the construction site.

Owen Steel is fabricating 150 of the box columns. The cutting and welding system has helped his shop substantially reduce the amount of time required to weld each joint, which is critical to meeting shipping schedules, according to Oxendine. “Our engineer came up with the idea, but ESAB made it happen,” he says.

Shorter welds also mean less testing for Owen Steel. As operators become more familiar with the equipment, the cutting and welding machines have opened up creative avenues for the team to explore ways to apply welds differently, Oxendine says.

The partnership with ESAB has given Owen Steel more than just an equipment solution to perform a tough job.

“As a company, we here at Owen Steel are extremely proud of the fact that we were able to work on a project of this magnitude,” Oxendine says. “Its importance to the City of New York, families who lost loved ones in the attacks, the service members defending our freedoms overseas, those who have given the ultimate sacrifice in that defense and the nation as a whole is always on our minds and hearts as we fabricate each piece. We all take pleasure in the hope that when people see our steel being erected at the World Trade Center site, they know those that tried to hurt us could not keep us down and will not keep this country from moving forward in growth and prosperity.” FFJ

 

As seen in the February 2012 issue of FFJournal

Oxy-Fuel Bevel Cutting at Owen Steel.

Owen Steel uses an Avenger X to cut the weld preparation on both sides of the steel at the same time.