折疊和麻面是nd鋼管常見的表面缺陷類型，容易造成成材報廢，影響nd鋼管的金屬收得率，需要分清表面質量缺陷的類型及分析其成因，并采取行之有效的控制措施。對于兩者的常見情況及控制措施為：
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折疊。
1 fold.

折疊指nd鋼管的表面沿軋制方向成直線狀或鋸齒狀裂紋。情況為：連續或斷續出現在nd考登鋼管局部或全長，深淺不一，內有氧化鐵皮的橫斷面上經扭轉呈折面翹起。直線狀的折疊與法裂、劃痕相似，通過挫平斷面或作扭轉實驗可以區別。
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.

控制措施為：精細操作，防止各道孔型出現耳子，造成后續折疊；認真檢查輥環、軋槽的使用情況，及時更換；嚴格檢驗原料質量，對缺陷必須徹底清理后才可入爐。
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鋼管表面上有許多細小凹點組成的片狀粗糙面。情況為：在nd考登鋼管的全長連續或周期出現。
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.