United States Department of Transportation
i
Gas Pressure Welds and Hollink Slot Welds Testing at the Facility for Accelerated Service Testing [Research Results]
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2008-12-01
[PDF-152.96 KB]
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Abstract:In 2006, two new weld tests were installed in the High Tonnage Loop (HTL) at the Facility for Accelerated Service Testing (FAST) located at the Transportation Technology Center (TTC) in Pueblo, Colorado. Two rail strings containing a total of 10 gas pressure welds (GPWs) were installed in Section 3 at FAST in January, and in June, the Holland Company sent one of its Hollink slot weld vehicles to make several robotic gas-metal-arc railhead repair welds for in-track testing in a 5-degree curve with a 4-inch superelevation. A total of 14 slot welds were installed in Section 3 at FAST for testing. The primary objective of these tests was to improve field weld performance under heavy axle load cars. As of June 2007, the GPW test accumulated 263 million gross tons (MGT). Three of the welds required maintenance at 84 MGT due to weld batter (approximately 0.065 inch). Rails adjacent to the welds were taper-ground to minimize impacts on the welds. Three additional welds failed due to subsurface shells that broke out on the gage face at 150, 193, and 216 MGT. Another weld failed at 165 MGT due to web cracking which originated at a rail manufacturers stamp located in the weld heat affected zone. The GPW test outlived both the first and second generation of thermite welds used for the test in track. The heat-treated process needs to be improved further. Currently, the Jinzhou Institute in China is improving and automating a welding process to produce a product suitable for North American railroads. The Hollink slot weld equipment was not capable of performing slot welds in a 5-degree curve with a 6-inch superelevation because of the physical limitations of the weld dam consumables. One plant weld was successfully slot welded. Two welds experienced horizontal fractures that originated at the weld fusion line in the railhead at 124 and 127 MGT. A third weld failed due to shelling of the gage corner at 171 MGT. As of June 2007, the slot weld test accumulated 192 MGT.
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