折叠和麻面是nd钢管常见的表面缺陷类型，容易造成成材报废，影响nd钢管的金属收得率，需要分清表面质量缺陷的类型及分析其成因，并采取行之有效的控制措施。对于两者的常见情况及控制措施为：
Folding and hemp surface are common surface defects of ND steel pipe, which easily lead to scrap of finished products and affect metal yield of ND steel pipe. It is necessary to distinguish the types of surface quality defects and analyze their causes, and take effective control measures. The common situations and control measures are as follows: 1折叠。
1 fold.

折叠指nd钢管的表面沿轧制方向成直线状或锯齿状裂纹。情况为：连续或断续出现在nd考登钢管局部或全长，深浅不一，内有氧化铁皮的横断面上经扭转呈折面翘起。直线状的折叠与法裂、划痕相似，通过挫平断面或作扭转实验可以区别。
Folding refers to the straight or serrated cracks on the surface of ND steel pipe along the rolling direction. Circumstances are as follows: continuous or intermittent appearance in part or full length of ndkauden steel pipe, varying in depth, with iron oxide scales in the cross section of the torsion is folded upward. Linear folding is similar to normal cracking and scratches. It can be distinguished by frustrating the section or doing torsion experiments.

控制措施为：精细操作，防止各道孔型出现耳子，造成后续折叠；认真检查辊环、轧槽的使用情况，及时更换；严格检验原料质量，对缺陷必须彻底清理后才可入炉。
The control measures are as follows: fine operation to prevent ears from appearing in each pass and subsequent folding; careful inspection of the use of roll rings and rolling grooves, timely replacement; strict inspection of raw material quality, and thorough cleaning of defects before entering the furnace.

2麻面。
2 pock.

麻面指nd钢管表面上有许多细小凹点组成的片状粗糙面。情况为：在nd考登钢管的全长连续或周期出现。
The hemp surface refers to the flaky rough surface formed by many small concave points on the surface of ND steel pipe. The situation is as follows: the whole length of ndkauden steel tube appears continuously or periodically.