The oxide film on the surface of stainless steel billet is thin and dense, which is not easy to fall. Normally, the stainless steel billet will produce 0.2 ~ 0.3 mm oxide skin in the heating furnace. The billet defects within this range can be removed with the oxide skin. If the defects are not within this range, the surface defects on the billet will inevitably be brought into the final product if they are not disposed. Generally, flame cleaning can not be used to clear the surface defects of stainless steel billets. The composition and crystal phase composition of the clearing area of stainless steel billets will change after flame cleaning, which will affect the corrosion resistance of stainless steel products. Therefore, mechanical liquidation is a common and effective means of stainless steel surface treatment. Common methods include iron oxide scale clearing machine, water explosion and shot blasting machine< br>
1. Iron oxide scale clearing machine disposal
The iron oxide scale clearing machine is mainly composed of steel brush roller, drive installation, high-pressure water system, cooling water system and clamping installation. Two rollers with steel wires (called steel brush rollers) are installed on the roller bed. The steel brush rollers rotate at a high speed along the opposite direction of slab operation, and the iron oxide scale attached to the slab surface is removed by scouring the slab surface with steel wires. The iron oxide scale clearing machine is applicable to many steel types, but the iron oxide scale clearing is not thorough enough< br>
2. Water explosion pool
The water blasting pool uses normal temperature circulating water as the cooling medium, puts the high-temperature slab into the pool, and uses "water blasting" to remove the iron oxide scale on the surface of the slab. The principle is that when the water encounters the high-temperature slab, it vaporizes instantly, and a "water explosion" occurs, producing a large amount of high-pressure steam. The impact of the steam acts on the slab surface to peel off the iron oxide scale. At the same time, the iron oxide scale on the slab and its surface rapidly cools with water under high temperature, resulting in shrinkage stress. Due to the different stress between the slab and its surface, the iron oxide scale is broken and scattered. The water explosion pool has low investment, less maintenance and low consumption and operation cost. However, it is only applicable to local austenitic stainless steels, such as 301, 304 and other steels< br>
3. Shot blasting machine clearing
Shot blasting machine is often used to clear the iron oxide scale on the surface of casting slab. The shot blasting machine is mainly composed of shot blasting room, throwing head, shot blasting escort system, shot cleaning and installation, shot replenisher, dust removal system, smoothing system and electrical control system. Its working principle is to use the high-speed steel shot thrown by the shot blasting device to impact the iron oxide scale on the surface of the casting slab to make it scattered. The operation rate of shot blasting machine is high, and the clearing speed can reach 3 m/min. Applicable to many types of steel. The removal effect of iron oxide scale is good. However, the shot blasting machine can not handle high-temperature billets. Generally, the temperature of billets is required to be lower than 80 °. Therefore, the on-line operation cannot be carried out by using the shot blasting machine to clear the scale of billets. The shot blasting operation shall be stopped after the billets are cooled to below 80 °.