nd鋼管的外層鐵皮主要有（yǒu）四大類組成，分別是（shì）一次氧化鐵皮，二次氧化鐵（tiě）皮，三（sān）次氧化鐵（tiě）皮和紅（hóng）色氧化鐵皮（pí）。nd鋼管每一層的氧化鐵皮由於其生產工藝（yì）和具體的材質（zhì）不同而進行劃分，最終四種鐵皮組合（hé）後變成nd鋼管的外層（céng）結構。對於四種外層（céng）鐵皮，我們來（lái）進行一（yī）些簡單的（de）了解。一次氧化鐵皮：鋼在熱軋前，往往要在１１００～１３００℃加熱和保溫。在此溫度下，鋼表麵於高溫（wēn）爐氣接觸發生氧化反應，生成１～３ｍｍ厚的一次鱗以及由粗軋（zhá）側壓（yā）不充分、除鱗不徹底所致。該一次鱗也稱為一次氧化鐵皮（pí）。一次鱗的內部（bù）存在（zài）有較大的空穴，nd鋼管一次氧化鐵皮為灰黑色鱗層，呈（chéng）片狀（zhuàng）覆蓋在鋼板表麵。
The outer iron sheet of ND steel pipe mainly consists of four kinds: primary oxide sheet, secondary oxide sheet, tertiary oxide sheet and red oxide sheet. Each layer of iron oxide scale is divided according to its production process and specific material. Finally, four kinds of iron scale are combined to form the outer structure of ND steel pipe. For four kinds of outer iron sheets, we have a simple understanding. Primary scale: Before hot rolling, steel is often heated and kept warm at 1100 - 1300 (?) At this temperature, oxidation reaction occurs on the steel surface in contact with high temperature furnace gas, resulting in a primary scale 1-3 mm thick, as well as inadequate side pressure during rough rolling and incomplete descaling. The primary scale is also called primary iron oxide scale. There are large holes in the primary scale. The primary oxide scale of ND steel pipe is grey-black scale, which covers the surface of steel plate in sheet form. 鱗層主要成分由磁鐵（Ｆｅ３Ｏ４）組成。二次氧化鐵（tiě）皮：熱軋鋼坯從加熱爐出來後，經高壓水除去一次鱗後，即表麵氧（yǎng）化鐵皮脫落，進行粗軋。在短（duǎn）時間的粗軋過程中鋼坯表麵與水和空氣接（jiē）觸，鋼（gāng）坯表麵產生了二次鱗，nd鋼管也稱為一次氧化（huà）鐵皮（pí）。
The scales are mainly composed of magnets (Fe3O4). Secondary oxide scale: After hot-rolled billet comes out of the heating furnace, the scales are removed by high-pressure water, that is, the oxide scale on the surface falls off and rough rolling is carried out. During short roughing process, the surface of billet contacts with water and air, and the surface of billet produces secondary scale. The ND steel pipe is also called primary oxide scale.
二次（cì）鱗受水（shuǐ）平軋製的影響厚度較薄，鋼坯與鱗的界（jiè）麵應力小，nd鋼管所以剝離性差。如果噴射高壓水不能完全（quán）除去二次鱗，鱗殘留在鋼板表麵的情況下進行精軋，產品表麵就（jiù）會出現缺陷。
The thickness of secondary scale affected by horizontal rolling is thin, the interface stress between billet and scale is small, and the stripping property of ND steel pipe is poor. If spraying high-pressure water can not completely remove the secondary scale, and the scale remains on the surface of the steel plate for finishing rolling, defects will appear on the surface of the product.
二次（cì）氧化鐵皮為紅色鱗層，nd鋼管呈明顯的長條（tiáo）、壓入狀，沿軋製方向帶狀分布，鱗層主要成分由方鐵（tiě）礦（ＦｅＯ）、赤鐵礦（Ｆｅ２Ｏ３）等微粒組成。
The secondary oxide scale is red scale. The ND steel pipe is obviously long and pressed, and distributes in strip along rolling direction. The scale is mainly composed of iron ore (FeO), hematite (Fe2O3) and other particles.
nd鋼管三（sān）次氧化鐵皮：
Third-order oxide scale for ND steel pipe:
熱軋精軋過程中，帶鋼進入每架軋機時都將產生（shēng）表（biǎo）麵氧化鐵皮層。軋製後通過最終的除鱗或在每架軋機之間時還將再次產生氧化鐵皮。因此，軋輥（gǔn）作用下的（de）帶鋼表麵條件將取（qǔ）決於進入各架軋機前形成的氧化鐵（tiě）皮的數量和特性（xìng）。這時的氧化鐵皮稱為三次氧化鐵皮，因為它是在除（chú）鱗之後。nd鋼管進入（rù）精軋（zhá）機之前形成（chéng）的。
In the process of hot rolling and finishing, iron oxide coating will be produced on the surface of strip when it enters each rolling mill. Iron oxide scale will be produced again after rolling through final descaling or between each rolling mill. Therefore, the strip surface conditions under the action of rolls will depend on the number and characteristics of oxide scales formed before entering each stand of rolling mill. At this time, the scale of iron oxide is called tertiary scale, because it is after descaling. ND steel pipe formed before entering finishing mill.
三次氧化鐵皮缺陷肉眼可見：
The third iron oxide defect is visible to the naked eye.
黑褐色、小舟狀。相對密集、細小、散沙狀地分布在（zài）缺陷帶鋼表麵，細摸有手感，酸洗後在帶鋼表麵（miàn）缺陷處留下深淺不一的針孔狀小（xiǎo）麻坑，它們在正常熱軋帶鋼（gāng）的表麵上是看不（bú）見的。
Black-brown, boatlike. Relatively dense, fine and scattered sand distributes on the surface of defective strip steel, which has a fine feel. After pickling, pinhole pits with different depths are left on the surface of defective strip steel, which are invisible on the surface of normal hot rolled strip steel.
紅色氧化鐵皮：
Red oxide scale:
紅（hóng）色氧化鐵皮僅發生在高矽（guī）含量等特定的鋼種上（shàng），主要由於（yú）在鋼坯加熱過程中，表麵氧（yǎng）化物與基體金屬強烈齧合所致。無明顯深度，呈不規則片狀（zhuàng）。
The red oxide scale only occurs on special steel grades such as high silicon content. It is mainly due to the strong meshing between surface oxide and matrix metal during billet heating. No obvious depth, irregular sheet.
紅色（sè）氧化鐵皮分兩種：
There are two kinds of red oxide scales:
一種在板寬方向非均勻分（fèn）布，主（zhǔ）要分布在中間（jiān），偏向（xiàng）操作側，nd鋼管紅（hóng）色與蘭（lán）色處（chù）有明顯水印，在鋼板長度方向（xiàng）上也（yě）不（bú）均勻，個別部位稍輕些。這（zhè）種（zhǒng）紅色氧化鐵皮較厚，矯直時可崩起，可用高壓風吹去，殘餘（yú）紅色很易擦下色，此紅色氧化鐵皮稱紅鏽較貼切。
A kind of non-uniform distribution in the direction of plate width, mainly distributed in the middle, biased to the operation side, ND steel pipe red and blue have obvious watermarking, in the direction of steel plate length is not uniform, some parts are slightly lighter. The red oxide scale is thicker and can collapse when straightening. It can be blown away by high pressure wind. The residual red color is easy to rub off. This red oxide scale is called red rust.
另一種紅色氧化鐵皮沿板（bǎn）寬分布比較均勻（yún），一般靠邊部１００ｍｍ內稍重些，nd鋼管（guǎn）卷外部比內（nèi）部重些。這（zhè）種（zhǒng）紅（hóng）色氧化鐵皮較薄，不（bú）易擦下色，鋼板越厚紅（hóng）色越重。nd鋼管這種紅色氧化鐵皮其他一些鋼種也存在，具有一定的普（pǔ）遍性。
Another kind of red oxide sheet distributes evenly along the width of the sheet, which is slightly heavier within 100 mm on the edge and heavier outside than inside of ND steel tube coil. This kind of red iron oxide scale is thin and difficult to rub off the color. The thicker the steel plate, the heavier the red. The red oxide scale of ND steel pipe also exists in some other steels, which has certain universality.
