How to clean iron oxide scale?

AUTHOR: admin       TIME:2021-12-29       READER:

There is an oxide film on the surface of the stainless steel tube. This oxide film is thin and dense, and it is not easy to fall off. Under normal conditions, the stainless steel billet will produce an oxide scale of 0.2-0.3mm in the heating furnace. As the scale is removed, if the defects are not within this range, the surface defects on the billet, if not treated, will inevitably be carried into the final product. The stainless steel billet usually cannot be cleaned by flame to clean the surface defects of the billet. Flame cleaning will cause changes in the composition and crystal phase composition of the cleaned area of the billet, which will affect the corrosion resistance of stainless steel pipe products. Therefore, mechanical cleaning is a common and effective means of stainless steel surface treatment.

 The general cleaning methods include iron oxide scale cleaning machine treatment, water blasting, and shot blasting machine cleaning.

1. Treatment of scale cleaning machine: The scale cleaning machine is mainly composed of steel brush roller, driving device, high pressure water system, cooling water system and clamping device. Two rollers with steel wires (called steel brush rollers) are installed on the roller table seat. The steel brush rollers rotate at high speed along the opposite direction of the slab running, and use the steel wire to wash the surface of the slab to remove the oxidation attached to the surface of the stainless steel tube. tin. The scale cleaning machine is suitable for many types of steel, but the cleaning of scale is not thorough enough.

2. Water explosion pool: The water explosion pool uses normal temperature circulating water as the cooling medium, puts the high temperature cast billets into the water pool, and uses "water explosion" to remove the iron oxide scale on the surface of the stainless steel tube. The principle is that when the water encounters the high-temperature casting billet, it vaporizes instantly, and a "water explosion" occurs, producing a large amount of high-pressure steam, and the impact force of the steam acts on the surface of the casting billet to peel off the iron oxide scale. At the same time, the cast slab and the iron oxide scale on its surface are rapidly cooled by water at high temperature to generate shrinkage stress. Due to the difference in stress between the cast billet and the iron oxide scale on its surface, the iron oxide scale breaks and falls off. The water explosion pool has low investment, less maintenance, and low production and operation costs. However, there are few applicable steel grades, and it is only suitable for some austenitic stainless steels, such as 301, 304 and other steel grades.

3. Shot blasting machine cleaning: Shot blasting machines are often used to clean the iron oxide scale on the surface of stainless steel pipes. The shot blasting machine is mainly composed of a shot blasting chamber, a blasting head, a shot blasting conveying system, a shot cleaning device, a shot replenisher, a dust removal system, a lubrication system and an electrical control system.

Its working principle is to use the high-speed steel shot thrown by the shot blasting machine to impact the iron oxide scale on the surface of the slab to make it fall off. The shot blasting machine has a high operating rate, the cleaning speed can reach 3m/min, and it is suitable for many types of steel. The removal effect of iron oxide scale is better, but the shot blasting machine cannot handle high-temperature casting billets. Generally, the casting billet temperature is required to be lower than 80°. Therefore, the use of shot blasting machine to clean the cast billet scale cannot be performed online, and the casting billet needs to be cooled to below 80°. Then carry out the shot blasting operation.



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