I had heard about this two part video from some other folks but hadn't thought much about it until I was able to watch the process. Thermite welding is generally used to fix railroad lines as each 1 to 3 inch section can be fixed in 45 minutes to an hour. The process is a high energy mix of materials which are created by a heat generating reaction of iron oxide and aluminum with additional high carbon alloy metals added to produce the molten mixture used to fuse the rail line back together. After seeing this and I have mucho respect for the back breaking work the railroad guys go through to fix these lines and keep our commerce flowing. For a more indepth look into the process of thermite welding here are a few links, along with the videos from youtube:
Thermite Welding - Wikipedia
Weld Procedures - Thermite Welding
