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
Th...
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[11] CEMEF, Pierre Montmitonnet, accessed on the 25th of april, http://www.cemef.mines-paristech.fr/cemef/sections/cemef/annuaire/chercheurs/chercheurs-cemef/pierre-montmitonnet
[12] Alibaba, Stainless steel surface defects caused by sticky roller, accessed on the 24th of april, http://resources.alibaba.com/topic/800012182/Stainless_steel_surface_defects_caused_by_sticky_roller.htm
[13] Alibaba, Hot rolled steel in the iron oxide scale broadband solutions generated, accessed on the 26th of april, http://resources.alibaba.com/topic/800012307/Hot_rolled_steel_in_the_iron_oxide_scale_broadband_solutions_generated.htm
[14] Liu, J. (2013). "Effect of diffusion annealing on interface microstructure of hot rolled high boron alloyed stainless steel composite plate". Transactions of Materials and Heat Treatment (1009-6264), 34 (4), p. 90.
-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
If work-hardening is performed at elevated temps it is said to be hot-worked. In contrast cold-working is done right around room temperature. In both situations the work hardening increases the strength and hardness because of plastic deformation. This causes atoms in a crystal to become disordered, which means that the atoms have moved into a disordered structure. This then raises the strength and hardness by impairing the easy movement of dislocations. Cold working was done at first along with harness testing, once familiarized with all of this testing relationships between hardness, microstructure, and degree of work hardening of brass were
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.
Corrosion may be defined as the deterioration of a material due to a reaction with the environment around it. Metals corrode because we use them in environments that are chemically unstable. Very few metal are found in nature in their metallic state such as copper, gold and silver . All other metals are processed from minerals or ores into metals which are innately unstable in their environments. These unstable metals have a tendency to revert to their more stable mineral forms. Some metals form protective ceramic films (passive films) on their surfaces and these prevent, or slow down, their corrosion process. We can prevent corrosion by using metals that form naturally protective passive films, but these alloys are usually expensive, so we have developed other means of corrosion control. That are discussed later in this paper.
Corrosion is the electrochemical deterioration of a metal because of its chemical reaction with the surrounding environment. While new and better materials are continuously being developed, this progress is offset, in part, by a more aggressive operational environment. This problem is compounded by the fact that corrosion is a complex phenomenon. It can take many different forms and the resistance of materials to corrosion can drastically change with only a small environmental change.
Weight loss studies on mild steel in 1 mol L-1 HCl solution in the absence and presence of different concentrations of GAI gum for various immersion periods (1, 2, 4, 6, 12 h) at temperature range from 303-323K were performed. After specific time of immersion, each coupon is washed using double distilled water to remove the corrosion product, rinsed with acetone, dried and reweighed. From the average weight loss results, the corrosion rate (CR), the inhibition efficiency (IE) and surface coverage (θ) were determined using the following known equations (1-3).
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.
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.
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.
Grey cast iron is the most widely used foundry alloy in the world due to its wide range of achievable mechanical properties, good castability, excellent wear resistance and damping properties, high thermal conductivity as well as low cost (20-40% less than steel) (Xu et al., 2005). It is used in such diverse applications as cookware and musical instruments to auto parts and heavy machineries. Microstructure of grey cast iron is characterized by dispersion of graphite flakes in a ferrous matrix. It has been evidently shown that the size, morphology and distribution of graphite flakes greatly affect the physical and mechanical properties of grey cast irons and that these characteristics depend mainly on the chemical composition of the alloy, the foundry practice adapted such as inoculation treatment used and the cooling conditions during solidification (Bartocha et al., 2005; Xu et al., 2005;
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.
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.