Titanium is a wonderful metal that is strong, beautiful, and often times is sought after. You find titanium in industrial projects, stovepipes, and even sold as wedding rings for couples who want their rings to last for eternity. Yet even though it is becoming more and more common to use titanium in welding projects, many welders face a lot of challenges when they try to weld titanium. It sometimes warps, cracks, or even turns blue, all serious problems that can have a welder give up in frustration.
Take for example the case of a welding shop that created stovepipes. In this particular case, the stovepipe hat assembly kept turning blue and warping. In order to get it to fit into the next assembly, it had to be hand fitted and a lot of muscle used – which ended up cracking or breaking parts. The raw material itself was shiny and clean. The welders had ground the edges, the shop itself was clean, and the parts were treated with a solution treatment and aged before they were welded. So why was it cracking and turning blue?
Colors are caused when the atmosphere during the heat treatment is off. If it's off by just a couple parts per million (PPM) then the color will not show up right away, even though the oxide is already sitting on the surface of the metal. When the metal is welded, the oxide becomes heated again and grows, changing from clear to enough thickness that the surface is colored with iridescent colors. If you have organics like oil and grease they tend to show up as a stain and while that is easy to fix it can contaminate every piece in the furnace, coating them all with a layer of oxides.
Cleanliness of the shop is very important. If you are going to be welding titanium, it's a good idea to prevent water and oil from blowing out of the grinder head. Air compressors also tend to leak oil and often do not filter out the moisture like they should. If you have old compressors that aren't going to be replaced in a while, make sure to use them to avoid oil and water coming through the hand grinder head. Dual-stage, self cleaning filters are the best idea.
If a lot of titanium tends to be ground at a shop, then that shop should use downdraft booths, as these control the dust and make sure it doesn't turn into a fire hazard. If the shop can't afford to do something like this, then grinding the titanium in a separate room is a good alternative. Welding curtains can also help and certainly protect passersby and control air currents, but dust still has a way of finding a path above or through the curtains. Exhaust filters need to be carefully monitored with titanium dust to ensure they aren't clogged and any dust on the floor swept up as soon as possible.
Something to remember when welding titanium – it doesn't conduct heat well. It takes longer to heat than other metals do. Many welders will heat an inch of bead on one side of the part and then skip to another side. Because of the way titanium is, this means that the welder is working with cold metal throughout the process. It's like tightening the lug nuts on a tire – best to keep all sides equal, with no side more stressed than another. An idea in the case of the stovepipe would be a five-step star pattern, as this would help prevent cracking and warping when the pipe is welded to a plate.
These steps would help the shop avoid blue pipes, cracking, and warping. Theses tips should be kept in mind for any welder that works with titanium. Clean all the parts before you put them in the furnace and try to keep the atmosphere as clean as possible. When grinding, do it a good distance away from the area that you are planning to weld in, so that the dust can't interfere. Soon after grinding, weld in a clean area.
Other Tips & Resources for Welding Titanium