Are you conversant with stainless steel and the properties of different types? It makes sense to know what you can about this alloy metal.
This article discusses what it is, the different types, its advantages, etc.
If you’re ready, let’s dive in!
What is Stainless Steel?
Stainless steel is an alloy produced via the combination of iron and other elements. In most cases, the actual alloy referred to as ‘stainless steel’ has a minimum of 10.5 percent chromium content by mass and a maximum of 1.2 percent carbon content by mass.
Some of the other elements used in making stainless steel include austenite, molybdenum, silicon, nitrogen, manganese, and nickel. The alloy is much more resistant to corrosion than plain iron or regular steel, i.e., a combination of iron and carbon.
The elements used in making stainless steel – as well as other additives – provide that passive oxide layer that gives the alloy its shiny and reflective surface. This passive oxide layer is also responsible for resisting the formation of rust.
Its shiny surface is somewhat difficult to tarnish, especially when compared to plain steel. Hence the name ‘Stainless Steel.’ This alloy metal can be considered as a strong material and can be utilized for the purpose of construction in the form of Stainless Steel Angle Iron, beams, pipes, etc.
How Stainless Steel is Made
To make this alloy, the manufacturer has to, first of all, determine the type required. This is crucial since the grade of stainless steel produced may affect the ratio of stainless steel materials – such as carbon, iron ore, molybdenum, etc. – present in the mixture.
These ratios are often not always precise. They are often on a range due to the inevitable risk of variance in the overall purity of every element in the mix. Moreover, the ratio of iron to other elements or materials can affect how strong the protective oxide layer is.
It also determines how resistant the alloy is to specific corrosives in addition to several mechanical properties, e.g., melting point, hardness, shear modulus, etc. The components of these different ratios result in the production of different types of stainless steel alloys.
Every unique combination of elements is referred to as a ‘grade’ of stainless steel. Examples are grade 304 stainless, grade 420, etc.
The different raw materials are placed in an electric furnace and heated until melting points. This process may take up to 12 hours.
Then excess carbon is removed after placing the molten material in an AOD (argon oxygen decarburization) or VOD (vacuum oxygen decarburization) system. The amount of carbon removed determines the quality of the stainless steel produced.
Fine-tuning the quality of the final product requires stirring the molten steel in order to remove or distribute specific stainless steel components within the mixture. This ensures the product is of uniform quality and meets the end-user’s specifications.
As the molten stainless steel cools, it undergoes several forming processes, including hot rolling while the mixture is still above its crystallization temperature. The steel is put in rough shape and may be used for creating blooms of metal or billets.
Relieving internal stress and altering the stainless steel’s mechanical properties involves annealing, i.e., heating and cooling the material under controlled conditions. The steel is descaled – if annealed – to prevent compromising the protective oxide layer.
The steel further undergoes several cutting and shaping processes – after the annealing procedure – in order to create a perfect final product for a particular application. The specific techniques may vary depending primarily on the shape and size of the bloom/billet as well as the final product.
Before shipping them to other manufacturers, some manufacturers apply different surface finishes to their stainless steel blooms, wires, or billets. The finish used varies, depending on the stainless steel’s intended use.
The Types
Different types of stainless steel exist today, each with its upsides and downsides. But they are generally categorized into 4 groups:
1. Austenitic
This is the most common type on the market today. It has exceptionally high nickel content as well as high amounts of molybdenum, chromium, and nitrogen.
Austenitic is well renowned for its malleability and weldability. They are generally used for storage components and kitchen cutlery. They are also very strong and possess high resistance-to-corrosion properties.
2. Duplex
This type is basically a combination of austenitic and ferritic steel. It is stronger than austenitic and ferritic stainless steel as it possesses less nickel content. It is also less expensive than austenitic steel.
Duplex is heavily employed in the underwater oil industry due to its corrosion-resistant properties. These allow it to withstand the corrosive nature of saltwater over extended periods.
3. Ferritic
This type has low amounts of carbon, i.e., approximately .10 percent. The primary mineral is chromium, and the common additive is molybdenum. Other minerals can also be added to these steels.
Ferritic is magnetic and generally used to resist stress corrosion cracking. Common examples of ferritic steel are alloys 430 and 434.
4. Martensitic
This type shares structural similarities with ferritic stainless steel. The only difference is their carbon content. The carbon content in martensitic stainless steel hovers around 1 percent, while ferritic stainless steel is below 0.1o percent.
Martensitic is used in environments that call for high strength but have average corrosion resistance. Examples of this type include alloy 431 and 420S45.
The Characteristics
The following are the characteristics:
- Temperature resistant
- High tensile strength
- Corrosion-resistant
- Highly attractive appearance
- Highly durable
- Easy fabrication and formability
- Low maintenance
- Environmentally friendly, i.e., recyclable
The Advantages
Here are several advantages:
- Enhanced Durability
Superior industry-leading durability, i.e., it is strong and retains its shape. It is highly resistant to structural damage and impact. The rigidity of stainless steel is highly preserved with a broad temperature range, up to 1400 degrees Fahrenheit.
- Preserved Resale Value Over Time
It holds highly substantial resale value, making it a reasonably safe investment. Its aesthetic appeal is primarily responsible for this, i.e., its attractive appearance.
- Resistant to Corrosion
It is incredibly resistant to corrosion and widely suitable for various environments and applications.
- Equipment Stays Clean for Longer Periods
It retains its even and smooth surface efficiently, especially if maintained properly. This minimizes the opportunity for dirt, dust, or oil capture. Bacteria also have zero chances of growing and thriving on hidden areas on the material.
- Ease of Fabrication
Modern steel-manufacturing technology/techniques allow stainless steel to be machined, cut, fabricated, and formed almost as readily as conventional steels.
The long-term value that its long useful life cycle creates often yields the least expensive material option.
- Hygienic Surface
Cleaning and maintaining the surface is relatively easy. This is why it is used in strict hygiene environments such as kitchens, hospitals, abattoirs, etc. This implies that any food in direct contact with such surfaces will not attract germs or dirt.
The Uses
Stainless steel is used to make a wide variety of products. Here are some of them:
- Metallic Valve Parts
The highest grade is used to manufacture an entire range of metallic compressor valve plates and rings for air and process gas compressors, refrigeration, PET industries, etc.
The stress-free steel compressor valve components are manufactured using state-of-the-art laser profiling equipment.
After cutting the metallic parts, i.e., the highest grade 20 stainless steel, they undergo a series of proprietary procedures. Finally, they pass quality control tests to ensure consumers get the highest quality metallic compressor parts.
Stainless steel is used for the production of the following metallic compressor valve parts:
- Valve plates
- Wafer plates
- Valve rings
- Spring plates
- Damping and cushion plates
- Lentoid rings
Conclusion
Stainless steel is one of the most valuable materials in nearly every facet of life. Different types exist, and each has specific properties that make it suitable for a particular use.
The benefits are numerous, and it has found worldwide use in many industrial applications.