Generally speaking, in dry main gas and indoor use, the thickness of galvanized coating is only 6-12μm, but under poor environmental conditions, the thickness of galvanized coating is 20μm, can reach 50μm. Therefore, environmental factors should be considered when choosing the thickness of galvanized layer. Galvanized layer after passivation treatment, can naturally form a layer of bright, beautiful color passivation film, can obviously improve its protective function, decorative.
Good galvanized wire, plating thickness of 3- 4 mm, zinc adhesion should be less than 460 grams/m, that is, the average thickness of zinc layer is not less than 65 microns. When the thickness of plated parts is greater than 4 mm, the zinc adhesion should not be less than 610 g/m, that is, the average thickness of zinc layer should not be less than 86 microns. Standard galvanized wire coating must be uniform, galvanized layer basically uniform with copper sulfate solution test etching five times no dew iron. For standard galvanized wire coating adhesion requirements, the zinc layer of plated parts should be firmly combined with the basic metal and have enough adhesion strength, after hammer test does not fall off, not convex.
The material of steel structure will affect the organization and thickness of hot dip galvanized film. For example, high tension steel containing silicon, carbon content is high, easy to react with molten zinc quickly, the result of excessive growth of alloying, will cause a grayish black appearance, but does not affect its corrosion resistance. Or heat treated steel, if its tensile strength exceeds 90kg/mm2, after hot dip operation, easy to reduce its strength, etc.
Zinc is a silver-white metal, brittle at room temperature, soluble in acid and alkali, known as amphoteric metal. Pure zinc is more stable in dry air, and small in humid air or water containing carbon dioxide and oxygen. A thin film layer of basic zinc carbonate will be formed on the surface, which can delay the corrosion rate of zinc layer. The corrosion resistance of galvanized layer in aqueous solution of acid, alkali and sodium chloride is relatively strong. It is also not resistant to corrosion in atmospheres containing carbon dioxide and hydrogen sulfide and in Marine atmospheres; In high temperature and high humidity air and containing organic acid atmosphere is small, galvanized layer is also easy to be corroded.
The duration of the protective effect of galvanized layer on large roll galvanized wire is closely related to the coating thickness. Generally speaking, in the dry main gas and indoor use, the thickness of galvanized layer only 6-12μm, and in the environment is more severe conditions, galvanized layer thickness needs 20μm “to be up to 50μm”. Therefore, the influence of environment should be considered when choosing the thickness of galvanized layer.
When galvanized wire out of the light plating should be carried out light treatment. The bath temperature of galvanized wire should be controlled well. Galvanized wire, also known as hot dip zinc and hot dip galvanized, is an effective way of metal corrosion prevention, mainly used in various industries of metal structure facilities. It is to immerse the steel parts after rust removal into the molten zinc liquid at about 500℃, so that the surface of the steel member is attached with zinc layer, so as to play the purpose of anticorrosion.
The welding core is the metal core of the electrode. In order to ensure the quality of the weld, there are strict regulations on the content of various metal elements in the weld core. In particular, there are strict restrictions on harmful impurities (such as sulfur and phosphorus), and the quality of the weld core metal should be better than that of the base metal. Arc welding cannot be carried out on a smooth rod without a coating. This is because the arc stability is very poor, splashing is very large, and the weld is not well formed. After long-term practice, it is gradually found that the performance of the electrode is greatly improved by coating the welding core with some mineral raw materials (i.e. electrode coating). (1) Ensure stable arc combustion, so that the welding process is normal. (2) Using the gas produced after the drug skin reaction, protect the arc and the molten pool, prevent the harmful gases in the air (such as nitrogen, oxygen, etc.) from invading the molten pool, such as these gases will cause cracks and pores in the welding material, so that the welding can not achieve the ideal effect. (3) After the drug skin is melted, slag is formed, which covers the weld surface to protect the weld metal, make the weld metal slowly cool, help the gas escape, prevent the generation of pores, and improve the structure and performance of the weld. (4) After melting, various metallurgical reactions will be carried out, such as deoxygenation, sulfur removal, phosphorus removal, etc., so as to improve weld quality and reduce alloying element burning loss.
