nd鋼管的外層（céng）鐵皮主要有四大類組成（chéng），分別是一次氧化鐵皮，二次氧化鐵皮，三次氧化鐵皮和紅色氧化（huà）鐵皮。nd鋼管每一層的氧化鐵皮由於其生（shēng）產工藝（yì）和具（jù）體的材質不同而進行劃分，最終四種鐵（tiě）皮組合（hé）後變成（chéng）nd鋼管的外層結構（gòu）。對於四種外（wài）層鐵皮，我們來進行一些簡單的了解。一次氧化鐵皮：鋼在熱軋（zhá）前，往往要在（zài）１１００～１３００℃加熱和保（bǎo）溫。在（zài）此溫度（dù）下（xià），鋼表麵於高溫爐氣接觸發生氧化反應，生成１～３ｍｍ厚的一次鱗以及由粗軋側壓不充分、除鱗不徹底所致。該一次鱗也稱為（wéi）一次氧化鐵皮。一次鱗的內（nèi）部存在有較大的空穴，nd鋼管一次氧化鐵皮為灰黑（hēi）色鱗層，呈片狀覆蓋在鋼板（bǎn）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（lín）層主要成分由磁鐵（Ｆｅ３Ｏ４）組（zǔ）成。二次氧化（huà）鐵皮：熱軋鋼坯從加熱爐出來後，經（jīng）高壓水除去一次鱗後，即表麵氧化鐵皮脫落，進行粗軋。在短時間的粗軋過程中鋼坯表麵與水和空氣接觸，鋼坯表（biǎo）麵產生了二次鱗，nd鋼管也稱為一次（cì）氧化鐵皮。
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.
二次鱗受水平軋製的影響厚度較薄，鋼坯與鱗的（de）界麵應力小，nd鋼管所以剝離性差。如果噴射高壓水不能完全除去二次鱗，鱗（lín）殘留（liú）在鋼板表麵的（de）情（qíng）況下進行精軋，產品表麵就會出（chū）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（èr）次氧化鐵（tiě）皮為紅色（sè）鱗層，nd鋼管呈明顯的長（zhǎng）條、壓入狀，沿軋製方向帶狀分布（bù），鱗（lín）層主要成（chéng）分由（yóu）方鐵礦（kuàng）（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（gāng）管三次（cì）氧化鐵皮：
Third-order oxide scale for ND steel pipe:
熱（rè）軋精軋過程中，帶鋼進入每架軋機時都（dōu）將產生表麵氧化（huà）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，軋輥作（zuò）用下的帶鋼表麵條件將取決於進入各架軋機前形成的（de）氧化鐵皮的數量和特性。這時的氧化鐵皮稱為（wéi）三次氧化鐵皮，因為它是在除鱗之後。nd鋼管進入精（jīng）軋機之（zhī）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（hè）色、小舟狀。相（xiàng）對密集（jí）、細小、散沙狀地分布在缺陷帶鋼表麵，細摸有手感，酸洗後在（zài）帶鋼表麵缺陷（xiàn）處留下深淺（qiǎn）不一的（de）針孔狀小麻坑，它們在正常熱軋帶鋼的表麵上是看不見的。
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:
紅色氧化鐵皮僅（jǐn）發生（shēng）在（zài）高矽含（hán）量等特（tè）定的（de）鋼種上，主要由於在鋼坯加熱過程（chéng）中，表麵氧化物與基（jī）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.
紅色氧化鐵皮分（fèn）兩（liǎng）種：
There are two kinds of red oxide scales:
一（yī）種在板寬方向非均勻分布，主要分布在（zài）中（zhōng）間，偏向操作側（cè），nd鋼管紅色與蘭色處有明顯水印，在鋼板長度方向上也不均勻，個別部位稍輕（qīng）些。這種紅色氧化鐵皮較厚，矯直時可崩起，可用高壓風吹（chuī）去，殘餘（yú）紅色（sè）很易擦下（xià）色（sè），此紅色氧化鐵皮稱（chēng）紅鏽較（jiào）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（fèn）布比較（jiào）均勻，一般靠邊部１００ｍｍ內（nèi）稍重些，nd鋼（gāng）管卷外部比內部重些。這種紅色氧化鐵皮（pí）較薄，不易擦下（xià）色，鋼板越厚（hòu）紅色越重。nd鋼管這種紅色氧化鐵皮其他一（yī）些鋼種也存在，具有一定的普遍性。
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.
