但是，圆管也有一定的局限性，如在受平面弯曲的条件下，圆管就不如方、矩形

However, there are some limitations tube, as at the receiving plane bending, not as good as square tube, rectangular tube large flexural strength, the skeleton of some farm machinery, steel and wood furniture on common square, rectangular pipe. The use of different shaped pipe should also have other cross-sectional shapes.

However, the round tube also has certain limitations, such as in the condition of plane bending, the round tube is not as strong as square, rectangular tube anti-bending strength, some agricultural tools skeleton, steel and wood furniture on the common square, rectangular tube. Special steel pipes with other cross-sectional shapes are also required for different uses.

However, the circular pipe has some limitations, such as under the condition of plane bending, the bending strength of the circular pipe is not as strong as that of the square and rectangular pipes, and the square and rectangular pipes are commonly used in the framework of some agricultural machines and tools, steel and wood furniture, etc. According to different uses, there are also other cross-section shapes of special-shaped steel pipes.<br>