During the reheating process of steel, oxidation reactions are highly likely to occur on the surface of the steel, which is a widespread phenomenon that poses significant challenges to product quality and production efficiency. This article will delve into the causes of oxidation reactions, the two main consequences they bring, and why it is necessary to apply antioxidant coatings to address this issue.
The mechanism of oxidation reactions
The fundamental cause of the oxidation reaction lies in the fact that during the high-temperature reheating stage, the iron (Fe) on the surface of the steel comes into contact with oxygen (O₂) in the atmosphere and undergoes a chemical reaction to form ferric oxide (Fe₂O₃), that is, iron phosphorus (rust). Its chemical reaction formula can be simplified as: Fe + O₂ → Fe₂O₃.
The two main forms of oxidation reactions and their hazards
Oxidation reactions mainly manifest in two forms, causing varying degrees of damage to steel:
Severe surface oxidation (formation of iron scales)
Oxidation forms a thick, map-like layer of iron oxide scale on the steel surface. Thinner scales may peel or wash off. This not only directly wastes metal but also significantly reduces the final yield.What’s more troublesome is that the thicker oxide scale will firmly adhere to the surface of the steel. During the subsequent rolling process, these hard oxide scales will be pressed into the steel substrate by the rolls, forming pits or pockmarks of various sizes, which seriously damage the surface quality of the steel.
Deep oxidation
When the oxide scale on the surface peels off, tiny holes and spots are sometimes exposed beneath it, which is the result of deep oxidation. Deep oxidation means that oxidation has eroded beneath the surface layer of the steel. To fix these defects, the steel must be ground and polished. Grinding away the defective layer wastes a considerable thickness of steel. This waste of high-quality material, such as iron filings, slashes output. In extreme cases, severe deep oxidation can scrap the entire product, resulting in massive financial loss.
Conclusion: The necessity of antioxidant coatings
In conclusion, reheating oxidation undermines production on three fronts: it cuts yield, compromises quality with defects, and drives up processing costs—even to the point of scrapping. Therefore, in the heat treatment process, it is crucial to take effective protective measures.
Applying antioxidant coatings is precisely an efficient and crucial solution. This type of coating can form a dense protective film on the surface of steel, effectively isolating oxygen from direct contact with high-temperature steel, thereby inhibiting the occurrence of oxidation reactions from the source. By preventing the formation of iron scales and the erosion of deep oxidation, antioxidant coatings can:
Significantly increase the metal yield (yield rate).
It greatly improves the surface quality of steel and reduces or even eliminates defects such as pits and pockmarks.
Reduce or even eliminate the grinding and polishing processes for defect repair, saving production costs and time.
Reduce the scrap rate caused by oxidation and enhance the overall production efficiency.
Therefore, in modern steel production, the application of high-performance anti-oxidation coatings has become one of the important technical means to improve product quality, control production costs, and enhance market competitiveness.
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