Triangular steel tubing? I'm looking for 3-sided steel...tubing is the closest word I can think...

I'm looking for 3-sided steel...tubing is the closest word I can think of. Ideally, it would own all 3 sides of equal breadth, about 3-4". The steel wants to be hard. The interior channel should be large satisfactory to snugly fit a steel pipe around 1" - 1 1/4" O.D.