Stainless steel is a versatile and widely used alloy known for its durability, corrosion resistance, and strength. It plays a crucial role in various industries, from kitchenware to medical instruments and industrial equipment. One of the most commonly used types of stainless steel is 18/8 stainless steel. Due to its excellent properties and cost-effectiveness, 18/8 stainless steel is found in numerous everyday products and industrial applications.
In this article, we will explore 18/8 stainless steel composition, properties, advantages, disadvantages, and applications, as well as compare it with other types of stainless steel.
What is 18/8 Stainless Steel?
18/8 stainless steel is a type of stainless steel that contains 18% chromium (Cr) and 8% nickel (Ni). These two elements are the key to its unique properties.
The name “18/8” refers to the percentage of chromium and nickel in the alloy. It is one of the most commonly used grades of stainless steel, particularly in the food, medical, and manufacturing industries.
Chemical Composition of 18/8 Stainless Steel
The composition of 18/8 stainless steel is relatively simple but effective, contributing to its overall performance. The table below shows the typical chemical composition of 18/8 stainless steel:
Element | Percentage (%) |
Chromium (Cr) | 18% |
Nickel (Ni) | 8% |
Manganese (Mn) | 2% |
Carbon (C) | ≤ 0.08% |
Phosphorus (P) | ≤ 0.045% |
Sulfur (S) | ≤ 0.03% |
Iron (Fe) | 70-75% |
The combination of chromium and nickel gives 18/8 stainless steel its desirable characteristics, including excellent corrosion resistance, strength, and aesthetic appeal.
Physical Properties of 18/8 Stainless Steel
Property | Value |
Density | 7.93 g/cm³ |
Melting Point | 1400 – 1450 °C |
Thermal Conductivity | 16.2 W/m·K |
Electrical Resistivity | 0.72 µΩ·m |
Specific Heat | 500 J/kg·K |
Coefficient of Thermal Expansion | 16.5 × 10⁻⁶ /°C |
Magnetic Properties | Non-magnetic |
18/8 has a high density, a relatively high melting point and low thermal conductivity. So it performs well in high-temperature environments.
Mechanical Properties of 18/8 Stainless Steel
Property | Value |
Tensile Strength | 520 – 720 MPa |
Yield Strength | 215 MPa (minimum) |
Elongation | 40 – 50% |
Hardness (Rockwell B) | 80 – 90 HRB |
Modulus of Elasticity | 193 GPa |
Poisson’s Ratio | 0.30 |
Fatigue Strength | 240 MPa |
18/8 stainless steel has good tensile strength and ductility. Meanwhile, it has a relatively high hardness and is suitable for a variety of structural applications.
Properties of 18/8 Stainless Steel
18/8 stainless steel is known for its outstanding properties, making it suitable for a wide range of applications. Some of its key properties include:
Corrosion Resistance
One of the primary reasons 18/8 stainless steel is widely used is its excellent resistance to corrosion. The chromium in the alloy forms a protective oxide layer on the surface, which prevents rust and oxidation. This makes 18/8 stainless steel ideal for use in environments exposed to moisture, heat, and chemicals.
Strength and Durability
18/8 stainless steel is strong and durable, capable of withstanding significant wear and tear. Its high tensile strength makes it suitable for applications that require long-term reliability and stability.
Formability
This type of stainless steel is highly formable, meaning it can be easily molded or shaped into different forms without losing its strength. This makes it a popular choice in manufacturing processes that involve bending, stamping, or welding.
Temperature Resistance
18/8 stainless steel can withstand high temperatures without losing its structural integrity. It is commonly used in kitchenware and industrial equipment where it is exposed to heat for long periods, such as in ovens or food processing machines.
Aesthetic Appeal
The shiny, smooth surface of 18/8 stainless steel gives it a modern and attractive appearance. This makes it a popular choice for products where appearance is important, such as in kitchen utensils, medical tools, and consumer goods.
Advantages of 18/8 Stainless Steel
There are several key advantages to using 18/8 stainless steel:
Cost-Effective
Compared to other types of stainless steel, such as 18/10 stainless steel, 18/8 stainless steel is more affordable. It strikes a good balance between performance and price, making it an excellent choice for both industrial and consumer applications.
Long-Term Durability
Due to its excellent corrosion resistance and high strength, 18/8 stainless steel is highly durable. Products made from this material can last for many years with minimal maintenance.
Ease of Maintenance
The smooth surface of 18/8 stainless steel makes it easy to clean and maintain. It resists dirt and stains, which is especially important for products like kitchenware and medical instruments that need frequent cleaning.
Versatility
18/8 stainless steel is incredibly versatile. It is used in a wide range of applications, from household products to industrial machinery, due to its balance of strength, corrosion resistance, and ease of manufacturing.
Disadvantages of 18/8 Stainless Steel
While 18/8 stainless steel is an excellent material, it does have some disadvantages:
Lower Corrosion Resistance than 18/10 Stainless Steel:
18/8 stainless steel is slightly less corrosion-resistant compared to 18/10 stainless steel, which has 10% nickel. However, the difference is usually not significant for most applications.
Limited Acid Resistance
Although 18/8 stainless steel is resistant to most acids, it has limited resistance to highly corrosive acids, such as concentrated sulfuric acid or hydrochloric acid. In environments where these substances are present, the material may degrade over time.
Prone to Scratching
The smooth, shiny surface of 18/8 stainless steel can be prone to scratching, especially when exposed to hard or sharp objects. While this does not affect its performance, it can impact the appearance of products, especially over time.
Welding Challenges
Welding 18/8 stainless steel can be challenging due to its high chromium content, which can lead to heat-affected zone (HAZ) issues. Special welding techniques are required to ensure the strength and quality of welded joints.
Applications of 18/8 Stainless Steel
18/8 stainless steel is used in a wide variety of industries and products, thanks to its excellent properties. Some common applications include:
Kitchenware:
Due to its corrosion resistance, heat resistance, and ease of cleaning, 18/8 stainless steel is commonly used in kitchen products such as cookware, cutlery, and kitchen utensils. It is a preferred material for high-quality pots, pans, knives, and other kitchen tools.
Medical Instruments
In the medical field, 18/8 stainless steel is used for manufacturing surgical instruments, needles, and medical tools. Its resistance to corrosion and smooth surface make it ideal for products that require high hygiene standards and frequent sterilization.
Industrial Equipment
18/8 stainless steel is also widely used in the food processing, chemical, and pharmaceutical industries. Its resistance to corrosion, high strength, and ability to withstand extreme temperatures make it a reliable material for industrial machinery and equipment.
Consumer Goods
18/8 stainless steel is commonly used in high-end consumer products such as watches, jewelry, and other accessories. Its shiny appearance and durability make it an attractive option for luxury items.
Architectural Applications
In architecture, 18/8 stainless steel is used for decorative elements, stair railings, window frames, and more. Its modern appearance and resistance to environmental factors make it ideal for both indoor and outdoor applications.
Comparison with Other Stainless Steel Types
18/8 stainless steel is often compared to other common types of stainless steel, such as 18/10 and 316 stainless steel.
18/10 stainless steel has 10% nickel compared to 8% in 18/8 stainless steel. As a result, 18/10 stainless steel offers better corrosion and oxidation resistance, making it ideal for high-end kitchenware and medical applications.
316 stainless steel contains molybdenum (Mo) and has better corrosion resistance, particularly in marine and chemical environments. However, 18/8 stainless steel is more cost-effective and still offers great performance in most applications.
How Can Manek Help
At Manek, we offer our clients a series of customized services specifically for stainless steel and other metals, including investment casting, sand casting, die casting, CNC machining, sheet metal fabrication as well as various surface treatments.
We also provide a variety of other manufacturing capabilities. You can get quotations for free, such as 3D printing, plastic injection molding and powder coating.
18/8 stainless steel, with its excellent balance of corrosion resistance, strength, and cost-effectiveness, is one of the most commonly used materials in both industrial and consumer applications. It is versatile, durable, and easy to maintain, making it ideal for products ranging from kitchenware to medical tools and industrial equipment. While it has some limitations, such as lower acid resistance compared to 18/10 stainless steel, its overall performance makes it a popular choice across many industries. Whether for home use or industrial applications, 18/8 stainless steel remains a reliable and affordable option.
