Study of Oxidation of Stainless Steel in Hot rolling
Background
Studies on the oxidation of stainless in hot rolling have obtained much attention during the last few decades where the finishing temperature ranges from 850-1100 °C.
Oxidation is the formation of oxide rich scale that slows down further oxidation when formed. In stainless steels at elevated temperatures (up to 1100°C), this oxide scale is necessary as it is predominantly chromium rich and prevents further oxidation. On the other hand the metal lost in the formation of oxide will reduce the effective strength of the steel section [1].
According to the British Stainless Steel Association [2], it is obvious that the oxidation resistance depends mainly on temperature, gas composition and moisture level and steel grade (mainly chromium level). Then, understanding each of these factors and their influence on the oxidation process of stainless steel plays a big role in determining the scope of this research.
In other words, the alloying element affects the temperature of which the oxide scale forms and its behaviour is at higher elevation temperature as well as gas composition and moisture level [3].
Aim
The aim of this study is to observe, understand and draw conclusions on the formation of the oxide scale of the selected stainless steel at high rolling temperature and its associated factors.
Objectives
• Investigate the tested steel materials and its effective alloying elements in the oxidation process
• Test the oxide scale thickness versus time at different humid conditions
• Try to achieve more uniform and thin oxide scale at elevating high temperature
• Evaluate the results and determine whether the selected steel grade is viable in meeting Objective 3
Method
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Combined with corrosion fatigue” (“Silver”).
Stainless steel, especially, Austenitic stainless steel, because of their high corrosion resistance and customizable mechanical properties has become an indispensable part of the regularly evolving modern day technology. Stainless steels of various grades find applications in numerous fields starting from the household to the nuclear reactors; from food and beverage cans to construction of different automobile parts. The formation of impervious oxide layer on the surface makes it suitable for use in adverse environments such as sea water.
-Developed and implemented strip casting overseas to eliminate a step in the steel making process
The stainless steel columns seem to have been made by casting and then polished to achieve their current look. Casting is an artistic manufacturing process by which hot liquid materials are poured into a mould and allowed to sit until cooled and solidified. Then the Mould is taken off of the art piece or broken off the art in some cases. This method is used because of the difficulty that would arise from having to figure out how to manipulate materials such as steel or aluminum that are very hard to work
The process which consists of heating the hardened components to a temperature between 100°C and 700°C, holding at this temperature for specific period and cooling to room temperature, usually by air is called as „tempering‟.
The behaviour of the parental material is completely changed. Among them few behaviours are listed down like wear rates, damping, friction behaviour etc. In this process the most beneficial material is casted material. The cast metals also exhibit chemical behaviour but in very low quantity. These behaviours depend upon the cooling rate of the liquid
"Using GMAW-P with Aluminum and Stainless Steel." - TheFabricator.com. Kodi Welch, 05 Nov. 2013. Web. 28 Apr. 2014.
The Company’s product portfolio consists of steel products, including hot and cold rolled sheets and coils, galvanized sheets, electrical sheets, railway products, plates, bars and rods, stainless steel and other alloy steels.
Some of the data of losses due to corrosion follows. In the United Kingdom the Paint Research Association has estimated that metallic corrosion costs developed countries some up to four per cent of gross national product (GNP) annually. In the UK this would equal about £30 billion. In the United States, various reports put the cost of corrosion slightly higher at four to five per cent, equating in that country to about US $300 billion, of which it is claimed that around one-third could be prevented. In India approximately 5% of the GDP is lost due to corrosion, of which again it is claimed that around one-third could be prevented.
Corrosion is the deterioration and undesirable scale formation in metal by either chemical attack or reaction with its environment. Corrosion control of metals involves technical, economical, environmental, and aesthetical significance. The use of corrosion inhibitors constitutes one of the most economical ways to protect metal surfaces against corrosion and preserve industrial facilities [1, 2]. The study of corrosion of mild steel is a subject of incredible theoretical and practical interest and as such has established a considerable amount of attention. Industrial acid cleaning, acid descaling, acid pickling and oil well acidizing widely require acid solutions. The use of corrosion inhibitors is very necessary in order to restrain corrosion attack of acid solutions on metallic materials. A corrosion inhibitor is a chemical substance which, when added in small
Rust is a coating of iron oxide that is formed by oxidation on an iron alloy. When a person sees rusting, it is a form of corrosion. Rust is found more often when there is lots of moisture around the iron or iron alloy. Iron oxide is formed when the iron alloy is mixed with oxygen. According to howstuffworks.com, ‘when a drop of water hits an iron object, two things begin to happen almost immediately. First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid, an even better electrolyte. As the acid is formed and the iron dissolved, some of the water will begin to break down into its component pieces -- hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the process
This study is intended to investigate the effects of heat treatment particularly quenching on the mechanical properties of mild steel especially on its strength using different quenching medium.
All metals can corrode but the speed of corrosion is different from a metal to another. Pure iron, corrode quickly while stainless steel which has iron and other alloys in its structure is slower to corrode and that’s why used more frequently. While other metals such as copper, silver, platinum and gold never corrode.
Iron: It reduces cathodic protection characteristics by increasing pitting corrosion because it forms FeAl3, when present at higher concentrations. But this effect can be reduced by addition of 1.25% manganese. The presence of iron (max. of 0.1%) is beneficial, especially in improving the galvanic efficiency in case of Al-Zn-In alloys. It forms a coarse constituent with aluminium and other alloying elements such as copper, nickel, manganese and silicon thus reducing ductility. It also reduces the strength and impairs corrosion resistance and fatigue resistance properties.
The lubrication also deeply affects the heat transfer and has a key role for the process robustness. The interfacial slag layer between the solidifying steel shell and the mould wall dominates resistance to heat removal and thus, controls mould heat transfer in the CC mould [3]. The rate of heat transfer across the shell-mould gap depends on the slag layer thickness and its thermal properties.