Look around you, and you will find stainless steel everywhere. It is a vital element, from manufacturing kitchen appliances to large automotive parts. But not all stainless steel is equal. It varies in strength, resistance, composition, and universal standards. One such stainless steel is SUS. But what is SUS material, and how does it differ from other stainless steel?
This question is worth discussing before diving into the world of metals. Knowing the properties of SUS helps you choose the right material for your projects. Moreover, it will also enable you to understand why it stands out in the world of stainless steel. So, are you curious to learn more? This article is all about exploring SUS material in the simplest possible way. Let’s get started!
What is SUS Material?
SUS stands for “Steel Used Stainless Steel”. It is a specialized stainless steel that follows Japanese Industrial Standards (JIS). It is an alloy primarily made of iron, carbon, nickel, sulfur, and chromium. However, the percentage content of each element varies in SUS.
In simple words, SUS is a simple stainless steel, but it follows strict Japanese rules. Different countries set standards for various materials. For example, AISI is a common standard that classifies stainless steel in America. Europ follows the EN( European Norm) standards. In this way, SUS is the Japanese way of naming stainless steel grades.
Observing this term, you may wonder: Is SUS different from regular stainless steel? The answer is YES! SUS contains the same composition elements as regular stainless steel. However, it is tested according to strict Japanese guidelines. Its mechanical properties and production methods vary from stainless steel used in other regions.
For example, AISI 316 stainless steel is equivalent to SUS 316. But their specifications are not always the same. For instance, AISI 316 contains slightly higher sulfur content than SUS 316. This slight difference makes them suitable for different regions and applications. Manufacturing industries rely on these standards to ensure quality.
Properties of SUS Material
Have you ever wondered why SUS stainless steel stays strong for decades? The reason is more than just strength. So, let’s dive in and explore some common properties of SUS material that make it top-notch.
1- Corrosion Resistance
Corrosion resistance is one of the most defining properties of SUS material. It has an excellent ability to resist rust and moisture for a long time. But what makes it able to resist corrosion? The answer lies in the chromium layer. As you know, stainless steel contains higher chromium content. It develops an oxide layer when exposed to air or rust. This layer acts as a protective shield and prevents the surface from further corrosion.
2- High Strength and Durability
Strength and durability are other dominating properties of SUS material. HOW? First, its composition involves nickel, manganese, and chromium. These elements provide flexibility and enhance their tensile strength. This means SUS stainless steel can withstand heavy stress without breaking. Moreover, low carbon content makes it harder and stiffer. You can adjust this stiffness by controlling the amount of carbon.
3- Heat and Fire Resistance
SUS material has excellent thermal resistance. It means it can withstand high temperatures without melting. However, keep in mind that this property varies from grade to grade. WHY? Because each grade has its distinct melting point. For example, SUS grade 316 has an M.P. of 925°C, which is higher than SUS 304. Moreover, SUS stainless steel does not expand when heated but retains its shape and volume. This makes it ideal for a fire-prone environment.
4- Easy Maintenance and Hygiene
Manufacturers often prefer materials that offer easy maintenance. In this regard, SUS stainless steel stands out. HOW? First of all, it has a self-healing protective layer. As I said above, stainless steel develops a chromium layer. This layer repairs itself automatically after some time, which reduces regular polishing. Moreover, SUS material has a non-porous surface. This surface does not allow bacteria to penetrate and keep the material hygienic. Lastly, this material does not stain easily. However, if smudges appear, you can clean them with regular soap.
5- Aesthetic Appeal
Beyond easy maintenance, SUS material offers a sleek and modern look. Basically, this material has shiny surfaces that enhance the overall look of the art. Moreover, SUS material comes in various finishes. For example, you can apply a mirror-like, matte, or brushed finish to provide a premium look. As I said above, SUS stainless steel resists smudges and stains. So it can maintain its aesthetics for a long time. Lastly, this material can be textured with different patterns to create unique visual effects.
6- Recyclability and Sustainability
Sustainability is a significant concern for manufacturers. However, SUS material stands as one of the most eco-friendly materials. HOW? As you know, this material has a long life span. So it does not quickly deteriorate or end up in landfills, which decreases pollution. Moreover, you can recycle SUS stainless steel several times. This directly reduces energy consumption for remanufacturing and the need for new resources.
Type of SUS Material
SUS stainless steel is not just one material. It comes in various types that vary in many aspects. So, let’s dive in and explore some common types of SUS stainless steel in this section.
1- Austenitic Stainless Steel (SUS Series: 200 & 300)
Austenitic is the most widely used type of SUS material. The word “Austenitic” came from “austenite,” a phase of iron that remains stable at high temperatures. It means this material does not harden when exposed to heat. Moreover, austenitic material contains a higher chromium content of about 16-26%. This higher content makes them more corrosion-resistant. HOW?
When chromium is exposed to air or moisture, it forms an oxide layer. This layer acts as a protective shield and prevents the material from further corrosion. Furthermore, austenitic stainless steel shows non-magnetic properties. The reason lies in the paired electrons of iron. However, during cold welding, these materials become slightly magnetic.
2- Ferritic Stainless Steel( SUS Series: 430&409)
Ferritic stainless steel is another common type of SUS material. This type is known for its higher magnetic properties. Actually, the internal structure of Ferritic stainless steel is body-centred cubic(BCC). This allows it to interact with magnetic fields. Besides, the presence of unpaid electrons also enhances magnetism.
This magnetic property makes it suitable for electrical appliances and transformers. If we discuss its composition, ferritic contains higher chromium content but lack nickel. This makes it less expensive with higher corrosion resistance. Moreover, ferritic stainless steel has a high melting point. This means that it can handle higher temperatures without losing its structural integrity.
3- Martensitic Stainless Steel (SUS series: 420 & 440)
Martensitic stainless steel is the strongest type of SUS material. WHY? It contains a higher carbon content. When heat-treated, it becomes harder and stiffer. This makes it suitable for applications that require cutting, impact resistance, and durability. For example, it hardens at 950-1050°C. After that, it cools rapidly and increases its strength.
However, you can adjust its toughness and flexibility at low temperatures. Moreover, it contains little to no nickel and low chromium content. That’s why it is moderately corrosion-resistant compared to other types. Therefore, Martensitic stainless steel is not suitable for harsh conditions. In terms of magnetism, it shows magnetic properties due to the BCC structure.
4- Duplex Stainless Steel (SUS Series: 2505 & 2507)
It is a unique SUS material type that combines austenitic and ferritic stainless steel. This material contains features of two materials; thus, it is called a “Duplex.” For example, it is as strong as ferritic stainless steel but also corrosion-resistant like austenitic. This makes it useful for marine applications, for which both features are crucial.
Moreover, it contains the perfect balance of toughness. Unlike ferritic and martensitic, it is not brittle. It means that duplex stainless steel can withstand heavy loads without breaking. This higher tensile strength makes its machinability and weldability effortless. Furthermore, its magnetic properties are also moderate. It is less magnetic than ferritic but higher than austenitic.
Applications of SUS Material
As I said above, SUS materials follow strict Japanese industrial standards. So, they impart unique properties, including durability and strength. This material is mainly used in Japan and Asia. Let’s find out the typical applications of SUS material across various industries.
1- Construction and Architecture
SUS stainless steel is known for its durability and tensile strength. So, it is the backbone of the construction industry. For example, you can see it has railings and balconies to provide a sleek and modern look. In high-rise buildings, SUS material maintains a polished and aesthetic appearance. Many architects also use it for underground construction due to its moisture absorption.
2- Automotive and Aerospace Industry
SUS stainless steel has a higher strength-to-weight ratio. So, the aerospace industry uses it to make body frames and panels for aircraft. As you know, this material also has higher temperature resistance. As a result, the automotive industry uses them in exhaust systems and mufflers. Lastly, the corrosion resistance of SUS helps handle fuel transportation in vehicles.
3- Medical and Healthcare Industry
I discussed earlier that SUS stainless steel has a non-porous surface, preventing contamination. Thus, it is a vital material used in the healthcare industry because of its non-reactive nature. For example, it is used in making surgical instruments to ensure sterility. Moreover, braces and dental implants also contain SUS to prevent corrosion.
4- Energy and Power Generation
SUS material is highly resistant to heat and chemicals, so it is widely used in power generation systems to resist high heat. For example, it handles radiation and pressure in nuclear reactors. Further, it prevents corrosion in wind turbines. Due to its non-reactive nature, oil and gas pipelines also use this material to transport fuels.
5- Marine and Shipbuilding Industry
The marine environment is known for its harsh, salty conditions. In such situations, regular materials can not withstand. Therefore, SUS has become a must-have for the shipbuilding industry. It can resist corrosion and salt, so it is used in making ship parts such as hulls and decks. Moreover, submarines also use this material to handle the high pressure of the deep sea.
Frequently Asked Questions
Which is better, SUS304 or SUS 316?
In my opinion, SUS 316 is far better than 304. The reason lies in its higher corrosion resistance due to its higher chromium content. Moreover, it is slightly more rigid than SUS 304. But keep in mind that SS316 is expensive. So first, understand your requirements and choose the one.
Is SUS stainless steel expensive?
Yes, SUS stainless steel is more expensive than regular stainless steel. As you know, it follows strict Japanese standards to ensure quality. The higher quality means a longer life span and more properties. Moreover, it does not require regular maintenance and replacements. So, SUS stainless proves cost-effective in the long run.
What is the lifespan of SUS stainless steel?
On average, SUS stainless steel lasts for 20 to 50 years. However, its life span varies from grade to grade. For example, SUS 304 decays more quickly in normal conditions. Upper grades, such as 316 and 430, last for a long time due to improved corrosion resistance. Moreover, with proper maintenance, you can enhance its lifespan.
Conclusion
SUS is a specialized stainless steel classified under Japanese industrial standards. This stainless steel itself is an alloy containing iron, nickel, and chromium. However, it follows the Japanese standards to ensure high quality. This makes it a popular choice among several manufacturers. In its distinct properties, SUS is highly corrosion and heat-resistant.
However, these properties vary with grades. For example, SUS 316 contains more chromium than 304. This makes them different for different industries. SUS is used in shipbuilding, healthcare, and automotive industries. In this article, I have covered everything about SUS in detail. I hope you have a deep understanding of this material.