Anniston Army Depot's weld lab ensures proper environment for tests
November 10, 2011
ANNISTON ARMY DEPOT, Ala. -- The building may be small and unimposing, compared to the much taller buildings that surround it, but Anniston Army Depot's welding lab makes a large impact on the installation.
Each welder working on the depot must certify in the lab for the forms of welding they perform.
"Anniston Army Depot is like a job shop -- different vehicle or artillery programs have different requirements and we set testing parameters to meet those requirements," said Brian Anderson, chief of the Directorate of Engineering and Quality's Fabrication and Repair Division.
The weld test facility has five bays used to create test plates. Here, depot welders' skills are checked against standards set for the type of welding required.
"We have, at times, had 10 different weld process certification tests to administer," said Chris Downing, mechanical engineering technician.
Currently, the most challenging test is administered to welders who work on Stryker vehicles. Those welders must retest annually and complete several test plates during the certification phase.
"The Stryker welding test is probably one of the hardest tests we give," said Downing. "When we first started administering the test, it took six weeks to complete the entire Stryker test. Now, we have it down to two and a half weeks."
Each weld must be tested before the welder can be certified. Each plate is checked by the lab's x-ray before it is sent to the materials lab for further testing.
As each weld is radiographed, it is checked against a standard showing the amount of porosity and lack of fusion allowed for the type of material.
"If the weld shows too much porosity or lack of fusion when x-rayed, it has to be redone," said Downing, showing dark spots on the radiograph film that indicate a poorly executed weld.
The quality of the radiograph is important and comes, in part, from the film itself, which must meet a density standard between 2.0 and 4.0.
"We can shoot through about five inches of steel and get a quality radiograph," said Downing.
Radiographs are kept at least five years, though the records in the weld lab go back much farther and newly implemented standards require the lab to keep radiographs of all active welders on the installation.
Once a test weld passes the radiograph test, it is sent to the depot's materials lab.
In the materials lab, the plates are root and face bend tested, according to Phillip Coleman, engineering technician for DEQ. If the weld does not break, but forms a uniform curve, the test plate passes. If the weld breaks, it fails.
Fracture testing is also commonly performed. The weld is put under stress until the piece breaks. It is then examined for defects.
That examination may include microstructure testing, where small particles from the weld are examined for cracks.
A Vickers hardness test may also be performed on welded material. Hardness tests are used to provide generic information on the material properties -- primarily toughness and strength.
In addition to welding certification tests, the weld lab assists with test welds for new welding procedures.
"If I want to try a new welding process or wire combination from researching published literature, I get it performed in the weld lab," said Bob Stockton, a welding engineer for DEQ. "Not only does that ensure a more controlled environment, I am also able to receive feedback on the new procedure from the welders."