Round steel pipe or square steel pipe

It seems like lots of steel pipes used in project are round and there are rare square one. Why? What’s the difference when we choose the round one and square one, like the seamless steel pipe?

Here are some introduction for it:

Production process: Round steel pipe is generally circular in finished pipe and they would be added the base and column cap composition; While square column is generally a combination of columns, which is assembled from steel.

Fore taking difference: There is difference for pressure taking due to the different production process. Their composition determines their force's different. Round steel pipe is generally bearing axial stress or eccentric force in smaller parts. However, square steel column would take the pressure in one direction larger cross-section, this decides that it can be used for large eccentric stress places.

Thus, we can tell that lots of steel pipe has the function of transportation so that we can see them often instead of the square steel pipe.