Introduction
We all agree on the fact that we use the word ‘steel’ several times during our day. We even use so many steel products such as tiffin boxes, water bottles, utensils, and so on. Our mother packs our lunch box with that tasty puff or roll in a steel tiffin every morning. Also, during extreme cold or summer, we pick up a steel bottle to keep either warm water or cool water respectively. Our lunch and dinner are served to us in steel plates and bowls. And also, our crockery set consists of beautiful steel spoons.
But have you ever tried to go into the depths of the word ‘steel’? What are its different types and how to differentiate among the several types of steel? Well, there is an answer to all these questions. Many types of steel are available in the market. But we’ll look into two of its types, i.e., one is aluminized steel and the other is stainless steel.
Aluminized Steel vs. Stainless Steel
While we are shopping, whatever products we purchase from the market, we just look for their strength and durability. The major difference between aluminized steel and stainless steel is in their different strengths. Stainless steel is stronger than aluminized steel. It is also the more durable of the two. If we consider the issue of rusting, then stainless steel does not rust because of the presence of chromium in it. On the contrary, aluminized steel can corrode once its aluminium coat breaks down (S, n.d.).
Difference Between Aluminized Steel and Stainless Steel in Tabular Form
| Parameters of Comparison | Aluminized Steel | Stainless Steel |
| Strength | It is less strong and durable. | It is stronger and more durable. |
| Rusting | It can get corroded. | It doesn’t rust easily. |
| Thermal Conductivity | It has higher thermal conductivity. | It has lower thermal conductivity. |
| Thermal Expansion Coefficient (ability to change shape when exposed to excessive heat) | It has a lower thermal expansion coefficient. | It has a higher thermal expansion coefficient |
| Aesthetic Beauty | It cannot be used as aesthetic beauty. | Stainless steel has aesthetic beauty and that’s why it’s used even in buildings. |
| Products Made | Products such as water heaters, furnaces, space heaters, and grills are made from aluminized steel. | Products such as kitchen utensils, cookware, and storage tanks, are made from stainless steel. |
What is Aluminized Steel?
The steel that has been coated with the help of hot-dip on both sides with aluminium-silicon alloy is called Aluminized steel. In this process, there exists a strong metallurgical bond between the steel sheet and its aluminium coating that produces an exceptionally unique material that contains special properties. Such unique properties are not possessed by either aluminium or steel alone. An alloy is a metal that has been made by the combination of two or three metallic elements to give the final product greater strength. Steel has great strength and hardness, whereas aluminium has a great property of corrosion resistance.
Aluminizing is a surface treatment process that is done to simple and ordinary steel to satisfy the needs of manufacturing sectors such as transportation, construction, aerospace, automotive, and shipbuilding industries.
Types of Aluminized Steel
There are two types of Aluminized steel, Type 1 and Type 2. The Type 1 consists of aluminium-silicon alloy. On the other hand, Type 2 consists of pure aluminium.
Type 1
This type of aluminized steel is made by a bath consisting of 5-11% of balanced silicon and aluminium. The silicon plays a vital role as it ensures the proper formation of the brittle intermetallic layer (between the outer aluminium coat and the inner base metal). Next, the silicon is added in order to control or slow the growth of the intermetallic layer. This enhances the workability of the finished material as well as improves heat resistance.
Uses
This Type 1 aluminized steel is typically useful for making industrial equipment such as furnaces, burners, and heat exchangers.
Type 2
The Type 2 Aluminized steel is completely made from pure aluminium and steel only. These are generally used only in conditions wherein the primary or the major requirement is corrosion resistance from the atmosphere.
Uses
These are involved in common structural materials such s sewage piping, enclosures, and corrugated roofing.
Advantages of Aluminized Steel
There are many advantages of using Aluminized Steel. Aluminized Steel provides protection against any sort of direct chemical attack and any electrochemical action. The direct chemical attack indicates dry corrosion, whereas, the electrochemical attack indicates wet corrosion. Both types of corrosion are present in most of the industrial environments.
Furthermore, Aluminized Steel has the capacity to work in temperatures up to 700-degree Celsius. This maximum temperature is variable and is based on the type of aluminium coating and the carbon and steel base.
Moreover, Aluminized Steel also has the property to reflect infrared radiations. The infrared radiations are the most common form of heat source in burners and furnaces. Aluminized Steel can actually reflect 80% of the incoming radiation approximately.
Other Important Characteristics
Apart from being a great corrosion-resistant material, Aluminized Steel has some other notable properties as well. Some of these properties are as follows:
- Toughness- Aluminium actually maintains its great Toughness usually at lower temperatures. Low temperature makes the metals become brittle. In general, the mechanical properties of aluminium are almost constant at most temperatures.
- Resilience- Aluminium has the ability to absorb sudden shocks or forces and can easily handle dynamic loads.
- Reflectivity- Aluminium has one of the highest reflectivity capacities. Its reflectivity falls under the 200-400 nm range which is considered to be much better than even gold and silver metals.
Aluminium coatings are applied to the glass to make mirrors. Depending on its final finishing, aluminium can reflect even 90% of the light (across different wavelengths that come under the visible spectrum).
Moreover, in its pure or even alloy form, aluminium doesn’t produce any sort of sparks. This quality of aluminium makes it suitable for making tools that are used in explosive or flammable environmental conditions (Aluminized Steel, n.d.).
What is Stainless Steel?
Stainless steel is an alloy of iron and chromium. Generally, the stainless steel must have at least 10.5% of chromium in it, but it highly depends on the requested grade and the intended usage of the steel.
Some other common additive requirements include:
- Carbon
- Manganese
- Nickel
- Sulfur
- Silicon
- Copper
- Nitrogen
- Molybdenum
The reasons for the addition of some gases and the above-mentioned other metals to a Stainless Steel alloy are as follows-
- It provides high-temperature and even low-temperature resistance.
- It also helps to improve overall strength.
- It enhances formability.
- It even leads to better corrosion resistance.
- It also leads to a better performance of weldability.
Process of Making Stainless Steel
Step-1- Melting the Requirements
The process of making stainless steel begins with the melting of scrap metals in an electric arc furnace. With the help of high-power electrodes, the electric arc furnace heats the metals (for many hours) and creates a molten and fluid mixture.
Step-2-Reducing Excessive Carbon Content
The carbon-metal actually enhances the strength and hardness. Still, excessive carbon or too much carbon can cause some problems such as carbide precipitation during the time of welding. So, the excessive carbon is removed by following either Argon Oxygen Decarburization or the process of Vacuum Carbon Decarburization. In the Argon Oxygen Decarburization method, an argon gas mixture is injected into the molten fluid mixture (molten steel) which leads to the removal and reduction of extra carbon particles. On the other hand, in the Vacuum Carbon Decarburization method, oxygen is injected into the molten steel, and heat is applied. Then a vacuum removes the vented gases, thereby reducing the carbon content.
Step-3- Tuning It
After reducing carbon, there comes the step of tuning and balancing the temperature and chemistry. This step ensures the high quality of the stainless steel. The samples are then sent for testing and further analysis. Certain changes and some adjustments are made until the mixture meets the needs of the required standard.
Step-4- Forming or Providing Shapes
After all these protocols, there arrives the final step of shaping the molten steel into desired forms. Some of the common shapes include tubes, slabs, billets, blooms, and rods. These different forms are then marked with an identifier to track the batch as it goes through the several processes to follow.
From here, the steps might differ as they would depend on the intended grade and the final product or the function that it has to serve. For example, slabs would become plates, then sheets and strips. The billets and blooms would turn into wires and bars. (WHAT IS STAINLESS STEEL AND HOW IS IT MADE?, n.d.).
Main Differences Between Aluminized Steel and Stainless Steel In Points
After gathering all of this basic knowledge about Aluminized Steel and Stainless Steel, let’s discuss some of their major differentiating factors in a bit more detail. These points would help in understanding information about the Aluminized Steel and Stainless Steel in a better manner. Apart from the things discussed above, there exist some more differentiating points between the two, which are as follows:
- Aluminium is composed of many desirable characteristics such as corrosion resistance, conductivity, and toughness. On the other hand, stainless steel is known for its commendable strength (the ability to withstand loads without deformation or any environmental rusting) (What are Properties of Stainless Steels-Characteristics-Definition, n.d.).
- The electrical conductivity of aluminium is greater (around 61% more than copper). The electrical conductivity of stainless steel is much lower than that of aluminium.
- The melting point of Stainless Steel is around 1400-1450 degrees Celsius. On the contrary, the melting point of aluminized steel is around 660 degrees Celsius.
- The density of Stainless Steel is about 7.93 g/cm3. The density of aluminized steel is about 2.7 g/cm3.
- Aluminized Steel is less lustrous than Stainless Steel. That’s why Stainless Steel is also known for its shining and gleaming surface.
- If we look at the economical aspect, then the cost of production of Stainless Steel is much higher than the cost of production of Aluminized Steel.
- Aluminium is paramagnetic in nature. On the other hand, steel is ferromagnetic in nature. Paramagnetism means the ability of some metals to get weakly attracted by a magnetic field. Ferromagnetism is the mechanism by which some materials form permanent magnets or get strongly attracted to magnets.
- Any acidic solution can damage the protective coating of the Aluminized Steel and can lead to blemishes. Stainless Steel doesn’t have any such problem and that’s why it’s more preferred and more used in the blowers.
- If we compare the weight of Aluminized Steel and the Stainless Steel, then Stainless Steel is much heavier than Aluminized Steel. This happens because of the greater strength of Aluminized Steel (Difference Between Aluminized Steel and Stainless Steel (With Table), n.d.).
Conclusion
In today’s world, most of the alloys and metals have a tendency to disintegrate due to the action of heat, moisture, and other environmental factors. However, the pace and the rate of their deterioration depend on their daily usage and maintenance. Corrosion of the equipment used in the industries is a common problem. That’s why the industries and the experts should search for stronger and corrosion-free or rusting-free alloys for increasing the durability of their machinery. By understanding the details about Aluminized Steel and Stainless Steel, people will become more aware of their usage or advantages and also their disadvantages in daily life. This awareness will eventually be useful for the manufacturing industries and also for technological advancements. By using the Aluminized Steel in the right place, the cost of production of many materials such as furnaces, burners, heat exchangers, etc can be reduced to a great extent. Similarly, by using the gleaming and shining property of stainless steel, it could be used for decorating purposes as well. Hence, it becomes extremely vital to know in detail about the major differentiating points between the Aluminized Steel and Stainless Steel.
References
- Aluminized Steel. (n.d.). Retrieved from iqsdirectory.com: https://www.iqsdirectory.com/articles/steel-service-center/aluminized-steel.html
- What are Properties of Stainless Steels-Characteristics-Definition. (n.d.). Retrieved from material-properties.org: https://material-properties.org/what-are-properties-of-stainless-steels-characteristics-definition/
- WHAT IS STAINLESS STEEL AND HOW IS IT MADE? (n.d.). Retrieved from UNIFIED ALLOYS: https://www.unifiedalloys.com/blog/what-is-stainless-steel
