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热镀锌的加工工艺应该注意哪些?

来源:http://www.jnxxjm.com

【 发布于:2018-12-20 16:08:38 】


热镀锌也叫热浸锌和热浸镀锌:是一种有效的金属防腐方式,主要用于各行业的金属结构设施上。是将除锈后的钢件浸入500℃左右融化的锌液中,使钢构件表面附着锌层,从而起到防腐的目的。热镀锌工艺流程:成品酸洗-水洗-加助镀液-烘干-挂镀-冷却-药化-清洗-打磨-热镀锌完工。热镀锌是由较古老的热镀方法发展而来的,自从1836年法国把热镀锌应用于工业以来,已经有一百七十多年的历史了。近三十年来,伴随着冷轧带钢的飞速发展,热镀锌工业得以大规模发展。

Hot-dip galvanizing is also called hot-dip galvanizing and hot-dip galvanizing: it is an effective way of metal corrosion protection, mainly used in the metal structure facilities of various industries. It is to immerse the steel parts after rust removal into the molten zinc solution melting at about 500 C, so that the surface of the steel components is adhered to zinc layer, so as to achieve the purpose of anti-corrosion. Hot-dip galvanizing process: finished product pickling-washing-adding bath-drying-hanging galvanizing-cooling-medication-cleaning-grinding-hot-dip galvanizing. Hot-dip galvanizing is developed from the older method of hot-dip galvanizing. It has been more than 170 years since France applied hot-dip galvanizing to industry in 1836. In the past 30 years, with the rapid development of cold-rolled strip, hot-dip galvanizing industry has been developed on a large scale.

热镀锌原理:热镀锌也称热浸镀锌,是钢铁构件浸入熔融的锌液中获得金属覆盖层的一种方法。随高压输电、交通、通讯事业迅速发展,对钢铁件防护要求越来越高,热镀锌需求量也不断增加。

Hot-dip galvanizing principle: Hot-dip galvanizing, also known as hot-dip galvanizing, is a method of obtaining metal coating by immersing steel components in molten zinc solution. With the rapid development of high-voltage power transmission, transportation and communication, the protection requirements for steel parts are getting higher and higher, and the demand for hot-dip galvanizing is also increasing.

防护性能

Protective performance

通常电镀锌层厚度5~15μm,而热镀锌层一般在35μm以上,甚至高达200μm。热镀锌覆盖能力好,镀层致密,无有机物夹杂。众所周知,锌的抗大气腐蚀的机理有机械保护及电化学保护,在大气腐蚀条件下锌层表面有ZnO、Zn(OH)2及碱式碳酸锌保护膜,一定程度上减缓锌的腐蚀,这层保护膜(也称白锈)受到破坏又会形成新的膜层。

Generally, the thickness of galvanized layer is 5-15 & mu; m, while that of hot-dip galvanized layer is generally 35 & mu; m or above, even up to 200 & mu; M. Hot-dip galvanizing has good covering ability, compact coating and no organic inclusions. It is well known that the anti-atmospheric corrosion mechanism of zinc is mechanical protection and electrochemical protection. Under atmospheric corrosion conditions, zinc layer surface has zinc oxide, zinc (OH) 2 and basic zinc carbonate protective film, which to some extent slows down the corrosion of zinc, and this protective film (also known as white rust) will be damaged and form a new layer.

当锌层破坏严重,危及到铁基体时,锌对基体产生电化学保护,锌的标准电位-0.76V,铁的标准电位-0.44V,锌与铁形成微电池时锌作为阳极被溶解,铁作为阴极受到保护。显然热镀锌对基体金属铁的抗大气腐蚀能力优于电镀锌。

When the zinc layer is seriously damaged and endangers the iron matrix, zinc produces electrochemical protection. The standard potential of zinc is -0.76V, the standard potential of iron is -0.44V. When zinc and iron form micro-batteries, zinc is dissolved as an anode and iron as a cathode is protected. It is obvious that the atmospheric corrosion resistance of hot-dip galvanizing is better than that of galvanizing.

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镀锌层形成过程

Formation Process of Galvanized Coating

热镀锌层形成过程是铁基体与最外面的纯锌层之间形成铁-锌合金的过程,工件表面在热浸镀时形成铁-锌合金层,才使得铁与纯锌层之间很好结合,其过程可简单地叙述为:当铁工件浸入熔融的锌液时,首先在界面上形成锌与α铁(体心)固熔体。这是基体金属铁在固体状态下溶有锌原子所形成一种晶体,两种金属原子之间是融合,原子之间引力比较小。因此,当锌在固熔体中达到饱和后,锌铁两种元素原子相互扩散,扩散到(或叫渗入)铁基体中的锌原子在基体晶格中迁移,逐渐与铁形成合金,而扩散到熔融的锌液中的铁就与锌形成金属间化合物,沉入热镀锌锅底,即为锌渣。当工件从浸锌液中移出时表面形成纯锌层,为六方晶体。其含铁量不大于0.003%。

The formation process of hot-dip galvanizing layer is the process of forming iron-zinc alloy between iron base and the outermost pure zinc layer. The iron-zinc alloy layer is formed on the surface of workpiece during hot-dip galvanizing, which makes the iron and pure zinc layer combine well. The process can be simply described as: when the iron workpiece is immersed in molten zinc solution, first zinc and alpha are formed on the interface; iron (core) solid melt is formed. This is a kind of crystal formed by dissolving zinc atoms in solid state of matrix metal iron. The two metal atoms are fused, and the attraction between atoms is relatively small. Therefore, when zinc saturates in the solid melt, the two elements of zinc and iron atoms diffuse into (or infiltrate into) the iron matrix. The zinc atoms diffuse into (or infiltrate into) the matrix lattice and gradually form alloys with iron. The iron diffused into the molten zinc solution forms intermetallic compounds with zinc and sinks into the bottom of the hot-dip galvanizing pot, which is called zinc slag. When the workpiece is removed from the zinc dipping solution, a pure zinc layer is formed on the surface, which is a hexagonal crystal. Its iron content is less than 0.003%.

与冷镀锌的区别:热镀锌抗腐蚀能力远远高于冷镀锌(又称电镀锌)。热镀锌在几年里都不会生锈,冷镀锌在三个月内就会生锈。

The difference between hot galvanizing and cold galvanizing is that the corrosion resistance of hot galvanizing is much higher than that of cold galvanizing (also known as galvanizing). Hot galvanizing will not rust in a few years, cold galvanizing will rust in three months.

冷镀锌工艺用于保护金属防止腐蚀,为此利用了锌填料的涂料,在利用任何一种涂敷的方法将其涂在被保护表面,干燥之后形成锌填料涂层,在干燥涂层中具有含量的锌(达到95%)。钢铁在冷却的条件下在表面镀锌,而热镀锌是钢管在热浸的条件下对表面镀锌,它的附着力很强,不容易脱落,热镀锌管虽然也出现锈蚀的现象,但在很长的周期可以满足技术、卫生要求。

Cold galvanizing process is used to protect metals from corrosion. For this reason, zinc filler coatings are used, which are coated on the protected surface by any coating method. After drying, zinc filler coatings are formed, which contain zinc (up to 95%) in the dry coatings. Iron and steel are galvanized on the surface under cooling conditions. Hot-dip galvanizing is a kind of galvanizing on the surface of steel pipes under hot-dip conditions. It has strong adhesion and is not easy to fall off. Although hot-dip galvanized pipes are also corroded, it can meet the technical and sanitary requirements in a long period.





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