How to remove the oxide scale on the surface of stainless steel pipe?
There is an oxide scale on the surface of the stainless steel tube. This oxide scale is thin and dense, and it is not easy to fall off. Normally, the stainless steel cast billet will produce 0.2～0.3mm oxide scale in the heating furnace. The cast billet defects in this range can be As the scale is removed, if the defects are not within this range, the surface defects on the cast slab will inevitably be brought into the final product if it is not treated. Stainless steel casting billets generally cannot be cleaned by flame cleaning the surface defects of the casting billets. Flame cleaning will cause changes in the composition and crystal phase composition of the cleaned area of the cast billets, which will affect the corrosion resistance of stainless steel pipe products. Therefore, mechanical cleaning is a common and effective method for surface treatment of stainless steel.
The general cleaning methods include scale cleaning machine treatment, water explosion, shot blasting machine cleaning.
Treatment of the iron oxide scale cleaning machine
The iron oxide 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. 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 surface of the stainless steel pipe. Iron sheet. The scale cleaning machine is suitable for many steel types, but the scale cleaning is not thorough enough.
Water explosion pool
The water explosion pool uses circulating water at room temperature as the cooling medium, puts the high temperature casting billet into the pool, and uses “water explosion” to remove the oxide scale on the surface of the stainless steel pipe. The principle is that when water encounters a high-temperature cast slab, it vaporizes instantaneously, causing a “water explosion” to produce a large amount of high-pressure steam, and the impact 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 with water at high temperatures 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 water explosion pool has low investment, low maintenance and low production and operation costs. However, there are fewer suitable steel grades, and only suitable for 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 surface oxide scale of stainless steel pipe. 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 operating rate, the cleaning speed can reach 3m/min, and it is suitable for many kinds of steel. The iron oxide scale removal effect is better, but 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 shot blasting machine to clean the cast slab oxide scale cannot be operated online, and the cast slab needs to be cooled to below 80° Perform shot blasting again.