There is an oxide layer on the stainless steel duplex pipe. The layer is thin and dense, and it is not easy to fall off. Under normal conditions, the stainless steel slab will produce a layer of 0.2 to 0.3 mm in the heating furnace. The impurities in it can be removed. Otherwise it must be brought into the final product.
Stainless steel slabs can not be cleaned with fire, it will cause the composition and crystal phase composition of the cleaning area, which will affect the corrosion resistance of the stainless steel pipe products. Mechanical cleaning is a common and effective method of stainless steel surface treatment.
The general cleaning methods are oxide scale cleaning machine processing, water brust and shot blasting machine cleaning.
Scale cleaning machine: scale cleaning machine is mainly composed of steel brush roller, driving device, high pressure water system, cooling water system and clamping device.
Two steel wire rollers (steel brush rollers) are installed on the roller table. The steel brush rollers rotate at high speed in the opposite direction of the slab. The steel wire is used to wash the surface of the casting slab to remove the oxide coating attached to the stainless steel pipe surface. This method is suitable for more steel types, but it is not thorough enough.
Water brust: water brust pool uses normal temperature circulating water as the cooling medium, puts the high temperature casting slab into the pool, and uses "water explosion" to remove the oxide layer on duplex pipe.
The principle is that when water meets a high-temperature casting slab, it instantaneously vaporizes, and a "water burst" occurs, generating a large amount of high-pressure steam. The impact force of the steam acts on the surface of the casting slab to peel off the oxide coating. This method is easy maintenance, and has low production and operating costs.
However, there are few applicable steel grades, only applicable to some austenitic stainless steels, such as 301, 304 and other steel grades.
Shot blasting machine cleaning: Shot blasting machine is often used to clean the oxide coating on the surface.
The shot blasting machine is mainly composed of a shot blasting chamber, a head, a shot blasting conveying system, a pellet cleaning device, a pellet supplement, a dust removal system, a lubrication system and an electrical control system.
It is using the high-speed steel shot thrown by the shot blaster to impact the oxide coating on the surface of the slab to make it fall off. It has a high operating rate, the cleaning speed can reach 3m / min, and it is suitable for many steel types. Its removal effect is better, but also disadvantages: the machine can not handle high-temperature slab, so it required temperature is lower than 80 °C.