D型鋼按鋼管截面形狀尺寸的不同又可分為等壁厚D型管(代號為D)、不等壁厚無縫異型鋼管(代號為BD)、變直徑無縫異型鋼管(代號為BJ)。D型管廣泛用于各種結(jié)構(gòu)件、工具和機械零部件。和圓管相比，D型管一般都有較大的慣性矩和截面模數(shù)，有較大的抗彎抗扭能力，可以大大減輕結(jié)構(gòu)重量，節(jié)約鋼材。

D-shaped steel can be divided into D-shaped steel pipe with equal wall thickness (code D), seamless special-shaped steel pipe with different wall thickness (code BD) and seamless special-shaped steel pipe with variable diameter (code BJ) according to the shape and size of steel pipe section. D-tube is widely used in various structural parts, tools and mechanical parts. Compared with circular tubes, D-shaped tubes generally have larger inertia moment and section modulus, and have greater flexural and torsional resistance, which can greatly reduce the weight of the structure and save steel. D型管一般是根據(jù)斷截面來區(qū)分的，按材料來說又可分為無縫鋼管D型管，鋁合金D型管，塑料D型管。下面主要介紹一下鋼管D型管。

D-type pipe is generally distinguished according to the broken section. According to material, it can be divided into seamless steel D-type pipe, aluminum D-type pipe, plastic D-type pipe. The following is a brief introduction of the D-shaped steel pipe.

鋼管異型管可分為橢圓形異型鋼管、三角形異型鋼管、六角形異型鋼管、菱形異型鋼管、八角形異型鋼管、半圓形異型鋼圓，不等邊六角形異型鋼管、五瓣梅花形異型鋼管、雙凸形異型鋼管、雙凹形異型鋼管、瓜子形異型鋼管、圓錐形異型鋼管、波紋形異型鋼管。

The special-shaped steel pipe can be divided into elliptical, triangular, hexagonal, rhombic, octagonal, semi-circular, unequal hexagonal, five-petal plum-blossom, double convex, double concave, melon-shaped, conical and corrugated special-shaped steel pipes.