外径表示数学中的直径。一般也用字母d来表示。外径和内径是相对的. 就比如一根焊管,外围的那个最大圆的直径是外径,管里面那个圆的直径是内径. 它的外径=内径+2*焊管的厚度 就是两个同心圆,外径是焊管大圆的直径,内径是焊管小圆的直径. 外径和内径都属于直径,只是分别又有特指.
The outer diameter represents the diameter in mathematics. The letter D is also commonly used. For example, in a welded pipe, the outer diameter of the largest circle is the outer diameter, and the inner diameter of the circle is the inner diameter. Its outer diameter = the inner diameter + 2* is two concentric circles, the outer diameter is the diameter of the larger circle of the welded pipe, and the inner diameter is the diameter of the smaller circle of the welded pipe. 下面说下直缝焊管的最新外径标准参数介绍
Following is the introduction of the latest external diameter standard parameters of longitudinal welded pipe
DN600- ф 630mm
DN15- ф 22mm DN20- ф 27mm
DN25- ф 34mm DN32- ф 42mm
DN40- ф 48mm DN50- ф 60mm
DN65- ф 76 73 mm DN80- ф 89mm
DN100- ф 114mm DN125- ф 140mm
DN150- ф 168mm DN200- ф 219mm
DN250- ф 273mm DN300- ф 324mm
DN350- ф 360mm DN400- ф 406mm
DN450- ф 457mm DN500- ф 508mm
其中DN表示公称直径： DN是公称通径，公称通径(或叫公称直径),就是各种管子与管路附件的通用口径。同一公称直径的管子与管路附件均能相互连接，具有互换性.它不是实际意义上的管道外径或内径，虽然其数值跟管道内径较为接近或相等； ф表示外径。
Among them, DN denotes nominal diameter: DN is nominal diameter, nominal diameter (or nominal diameter), which is the general diameter of all kinds of pipes and pipeline accessories. Pipes and pipe accessories of the same nominal diameter can be interconnected and interchangeable. It is not the actual outside diameter or inside diameter of the pipeline, although its numerical value is close or equal to the inside diameter of the pipeline; indicates the outside diameter.
