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Surface Preparation
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
Sa 2, known as thorough or commercial blast cleaning, removes almost all the mill scale, rust, rust scale, paint and foreign matters by means of abrasives. Contaminants that are firmly attached and adhering to the metal surface will not remain on the surface after SA 2 blast cleaning. Commercial blasting is not typically acceptable in the NORSOK M-501 standard, as it does not provide an excellent or perfect metal surface. But we can say that some degree of cleanliness is achieved. This type of surface preparation could be applied prior to coating in non-corrosive environments and atmospheres. After applying abrasive blasting, the surface is cleaned with a vacuum cleaner, dry compressed air or a clean brush. Mill scale, often just called scale, is a type of iron oxide that is formed on the surface of steel during the hot metalworking process. To sum up, all loosely adhering materials, tightly adhering materials and 65%–66% of stains, streaks and shadows are removed from the metal surface after Sa 2 metal surface cleaning. Sa 2 has a grayish color, unlike Sa 1, which has a black and reddish color due to the presence of rust and foreign matters. Figure 2.44 compares Sa 1 and Sa 2 metal surface abrasive cleaning.
Structural Steel
Published in Fiona Cobb, Structural Engineer’s Pocket Book, 2020
Hot rolled structural steelwork (in mild steel) leaves the last rolling process at about 1000°C. As it cools, its surface reacts with the air to form a blue-grey coating called mill scale, which is unstable, will allow rusting of the steel and will cause problems with the adhesion of protective coatings. The steel must be degreased to ensure that any contaminants which might affect the coatings are removed. The mill scale can then be removed by abrasive blast cleaning. Typical blast cleaning surface grades are:
Process of Sintering
Published in Ram Pravesh Bhagat, Agglomeration of Iron Ores, 2019
Mill Scale: Mill scale is a major waste generated during rolling of steel. It constitutes 1–2 wt.% of the steel rolled. It is very high iron and low in impurity product. About 90 wt.% of the mill scale generated is of a coarser category, whereas the remaining 10 wt.% is oily mill sludge. The coarser (and non-oily) variety of mill scale is porous and flat in shape. It mainly consists of wustite and magnetite.
EUROCORR 2020: ‘Closing the gap between industry and academia in corrosion science and prediction’ Part 2
Published in Corrosion Engineering, Science and Technology, 2021
D. J. Mills, D. Nuttall, L. Atkin
N. Lyu (Shou Gang Research Institute of Technology, Beijing, China) reported on ‘High temperature oxidation behaviour of low carbon sulphur free (S = 0.3–0.5%) cutting steel’. Low carbon sulphur free-cutting steel is mainly used for manufacturing components, requiring high dimensional accuracy. Occasionally, the mill scale is inadequately removed, leading to surface defects. In the laboratory, samples of the steel were heated between 900 and 1100°C in Argon for 0.5–4 h with the following additions: (a) 2% O2; (b) 0.5% SO2 and (c) 2% SO2. It was concluded that in sulphur-containing atmospheres, the scale is loose and porous comprising a FeS–FeO liquid phase between the scale and metal. Nearer the metal, sulphur compositions were higher, confirming inward diffusion of sulphur.
Mill scale as a potential additive to improve the quality of hematite ore pellet
Published in Mineral Processing and Extractive Metallurgy Review, 2018
Y. Rajshekar, Jagannath Pal, T. Venugopalan
Mill scale is a by-product generated during casting and rolling process, chiefly composed of magnetite and it is almost free of any silica or alumina-type gangue. Therefore, use of mill scale can also reduce the proportional amount of alumina and silica in the pellet. In this connection, it is worthy to be mentioned that several investigators have used alternative binders such as corn starch, lignin, molasses, dextrin, and bitumen (Halt and Kawatra 2017), to replace bentonite for reduction of alumina and silica input in pellet. However, use of mill scale in pellet is also an important aspect. Pal et al. (2014b) used mill scale as in situ heat source in their Pellet-Sinter Composite Agglomerates (PSCA) and found good strength improvement. Ahmed et al. (1997) observed low drop numbers in complete mill scale pellets which was increased with the addition of lime as binder. Umadevi et al. (2009) added mill scale in iron ore pellets containing carbon and reported that with the addition of 10% mill scale addition, the properties of pellets were satisfactory. Harp et al. (2007) mentioned that increased use of mill scale is limited in sinter as it is found to raise the FeO content of sinter lowering its productivity.
Performance of subgrade soil stabilised with by-product recycled mill scale and cementitous materials
Published in International Journal of Pavement Engineering, 2022
Samer Rababah, Hussein Aldeeky, Hisham Qasrawi, Omar Al Hattamleh
Besides slag, mill scale (iron oxides) is another waste being generated. The mill scale (mainly magnetite) is formed during the reheating and hot rolling process as a flaky surface of the rolled steel. The oxidisation of the steel surface during the scale formation resulted in high content of iron oxides with varying amounts of other oxides, elements, and trace compounds. Since large quantities of mill scale are generated daily, mill scale represents about 2% of the steel produced (Bagatini et al.2011), the disposal of such large quantities is problematic for both the factories and the environment (Qasrawi et al.2009).