Foshan Runtian New Material Technology Co.,Ltd
Oxidation method of 304 stainless steel pipe Nov 17, 2021

The oxide film on the surface of stainless steel pipe fittings 304 is thin and dense, and it is not easy to fall off. Generally, 304 stainless steel pipe fittings will produce an oxide layer of 0.2~0.3mm in the heating furnace. The casting defects within this range can be removed with the oxide scale. Outside of this range, if the defects on the surface of the cast slab are not treated, they will be brought into super-final parts. 304 stainless steel pipe cannot be cleaned by flame, which will change the composition and crystal phase composition of the billet cleaning area, and affect the corrosion resistance of stainless steel products. Therefore, mechanical cleaning is an effective method for surface treatment of stainless steel. The general methods include scale cleaning machine treatment, water explosion, and shot blasting machine cleaning.

The first type, the treatment of scale cleaning machine

The scale cleaning machine is mainly composed of steel brush roller, drive 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. The steel brush rollers rotate at a high speed in the opposite direction of the casting billet, and use the steel wire to wash the cast billet surface to remove the oxidation attached to the cast billet surface Iron sheet.

The second type, water burst pool

The water explosion pool uses circulating water at room temperature as the cooling medium, puts the high-temperature cast slab into the pool, and uses "water explosion" to remove the oxide scale on the surface of the cast slab. The principle is that when water encounters a high-temperature cast slab, it vaporizes instantly, causing a "water explosion" and a large amount of high-pressure steam is generated. The impact force of the steam acts on the surface of the cast slab to peel off the oxide scale. At the same time, the cast slab and the oxide scale on its surface are rapidly cooled in high temperature conditions to produce shrinkage stress. Due to the difference in stress between the cast slab and the oxide scale on the surface, the oxide scale breaks and falls off.

The third type, shot blasting machine cleaning

The grinder is usually used to clean the iron oxide on the surface of the cast slab. Shot blasting machine is mainly composed of shot blasting chamber, shot head, shot blasting conveying system, shot cleaning device, shot replenisher, dust removal system, lubrication system and electrical control system. Its working principle is to use the high-speed steel shot thrown by the shot blasting machine to impact the oxide scale on the surface of the cast slab, causing it to fall off. The shot blasting machine has a high working rate, and the cleaning speed is up to 3m/min. There are many types of applicable steels. Iron oxide has a good removal effect. However, the shot blasting machine cannot handle high-temperature cast slabs. Generally, the temperature of the cast slab is required to be lower than 80°. Therefore, the use of a shot blasting machine to clean the cast slab oxide scale cannot be performed online. The cast slab needs to be cooled to below 80° before performing the shot blasting operation.

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