18/8 stainless steel is stainless steel grade containing 18% chromium and 8% nickel, also known as 304 stainless steel. It is known for its excellent corrosion resistance, and good heat resistance and is suitable for use in a variety of applications, including kitchenware and medical equipment. 18/8 stainless steel has good room-temperature processing properties such as deep drawing and bending, and does not harden after heat treatment. However, it is important to note that while it is resistant to impregnation by most food processing media, corrosion may occur at elevated temperatures, especially in environments containing concentrated acid and chloride components. In addition, 18/8 stainless steel is resistant to organic compounds, dyes, and a wide range of inorganic compounds.
18/8 Stainless Steel Composition
The numbers “18” and “8” in 18/8 refer to the percentages of Chromium and Nickel alloying elements in the stainless steel composition:
18% Chromium (Cr)
Chromium is the primary alloying element in stainless steel that provides corrosion resistance. The high chromium content forms a passive oxide layer on the surface of the steel, which helps protect it from oxidation and corrosion.
8% Nickel (Ni)
Nickel enhances the stainless steel’s resistance to corrosion and adds to its overall strength. The nickel content also contributes to the steel’s ability to maintain its austenitic structure at various temperatures.
Other Elements
In addition to chromium and nickel, 18/8 stainless steel may contain small amounts of other elements, such as carbon, manganese, silicon, and other trace elements. These elements help fine-tune the steel’s properties for specific applications. The specific chemical composition is defined by the product standard. The common industry judgment is that as long as the Ni content is greater than 8 percent and the Cr content is greater than 18 percent.
Chemical Composition Chart
| Standard | Grade | C | Mn | P | S | Si | Cr | Ni | N |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A240 | 304 | ≤0.08 | ≤2.00 | 0.045 | 0.030 | 0.75 | 18-20 | 8.0-11 | ≤0.10 |
| ASTM A240 | 304L | ≤0.03 | ≤2.00 | 0.045 | 0.030 | 0.75 | 18.0-20.0 | 8.0-12 | ≤0.10 |
| ASTM A240 | 304H | 0.04-0.10 | ≤2.00 | 0.045 | 0.030 | 0.75 | 18-20 | 8.0-10.5 | – |
| ASTM A240 | 304N | ≤0.08 | ≤2.00 | 0.045 | 0.030 | 0.75 | 18-20 | 8.0-10.5 | 0.10-0.16 |
| ASTM A240 | 305 | ≤0.12 | ≤2.00 | 0.045 | 0.030 | 0.75 | 17.0-19.0 | 10.5-13.0 | – |
Mechanical Properties Chart
| Standard | Grade | Yield Point | Tensile Strength | Elongation | Hardness | Hardness |
|---|---|---|---|---|---|---|
| MPa | MPa | % | HRB | HB | ||
| ASTM A240 | 304 | ≥ 205 | ≥ 515 | ≥ 40 | ≤ 92HRB | ≤ 201 |
| ASTM A240 | 304L | ≥ 170 | ≥ 485 | ≥ 40 | ≤ 92HRB | ≤ 201 |
| ASTM A240 | 304H | ≥ 205 | ≥ 515 | ≥ 40 | ≤ 92HRB | ≤ 201 |
| ASTM A240 | 304N | ≥ 240 | ≥ 550 | ≥ 30 | ≤ 95HRB | ≤ 217 |
| ASTM A240 | 305 | ≥ 170 | ≥ 485 | ≥ 40 | ≤ 88HRB | ≤ 183 |
18/8 Stainless Steel Characteristics
- Excellent corrosion resistance, 18/8 Stainless Steel is composed of 18% chromium and 8% nickel, which is where it gets its name. It also contains around 50% iron and 0.8% carbon. The chromium in the steel can bond with oxygen, which helps to prevent rust and corrosion.
- Durability, the nickel content is what gives stainless steel its durability. Generally speaking, the more nickel that Stainless Steel contains, the more durable it will be.
- Versatility, it is one of the most widely used stainless steel due to its excellent properties.
- The non-magnetic, structure of 18/8 stainless steel is austenitic at room temperature in the solution annealed condition, which makes it non-magnetic.
- Hardenable by cold working.
- It can resist most types of corrosion, but it can be damaged by salt water.
- Food-grade stainless steel.
18/8 Stainless Steel Applications
18/8 stainless steel is the combination of corrosion resistance, strength, and ease of fabrication making it a popular choice for many applications where exposure to moisture, chemicals, and harsh environments is a concern.
Chromium can improve the strength and corrosion resistance of stainless steel, nickel has high brightness and corrosion resistance—application products such as corrosion-resistant containers, cutlery, household, railings, and medical equipment.
304 vs 18/8 stainless steel
18-8 stainless steel is an alloy containing approximately 18% chromium and 8% nickel, and the addition of other elements such as carbon and manganese. The most common grade of 18-8 stainless steel is 304, which is known for its excellent corrosion resistance, durability, and ease of fabrication. The name ‘18-8’ refers to the percentage of chromium and nickel in the alloy, which contributes to its rust-free properties.
Stainless Steel 304 is the most widely used grade of stainless steel in the world. It also contains 18 percent chromium and 8per cent nickel, similar to 18-8 stainless steel. In addition, it contains small amounts of carbon and manganese. This grade has excellent corrosion resistance, can withstand high temperatures, and is suitable for a wide range of applications, including kitchen utensils, food processing equipment, and industrial applications.
18-8 stainless steel and 304 stainless steel may look the same, 18-8 stainless steel and 304 have the same chemical composition in chromium and nickel. The grade or name 18-8 indicates its composition, which is 18 percent chromium and 8 percent nickel. However, it is important to note that ‘18-8’ is often used interchangeably with 304, but not all 18-8 steel is 304. Some 18-8 stainless steels may have different compositions, resulting in slightly different properties. Therefore, while they are closely related, they are not identical.
18/8 vs 18/10 Stainless Steel
The main difference between 18/8 stainless steeland18/10 stainless steel is the difference in nickel content, 18/8 stainless steel has a nickel content of 8 percent, while 18/10 stainless steel has a nickel content of 10 percent. The difference in nickel content determines the grade and properties of the stainless steel. Simply put, the higher the nickel content, the less likely the stainless steel is to rust and corrosion resistance.
The main composition of both 18/8 stainless steel and 18/10 stainless steel are iron, chromium and nickel. 18/8 stainless steel is represented by 304 stainless steel, while 18/10 stainless steel is 316 stainless steel. 304 stainless steel is widely used in household appliances and food processing equipment, while 316 stainless steel is used for more advanced, corrosion-resistant requirements. It is used in more advanced and higher corrosion resistance requirements, such as medical equipment.
In terms of application, 18/8 stainless steel has been able to meet most of the needs of daily use, such as cooking pots and pans. While 18/10 stainless steel is usually considered more suitable for medical grade, such as surgical tools, due to its higher corrosion resistance and higher nickel content. Therefore, if a higher standard of corrosion resistance and purity is required, 18/10 stainless steel is a better choice.
FAQ
18/8 stainless steel is safe, it has good resistance to acid, alkali, salt and other chemicals at room temperature, not easily rust. it does not contain harmful substances and will not cause harm to human health to food-grade standards, it is able to withstand a certain range of high-temperature liquids without releasing harmful substances.
18/8 stainless steel is non-magnetic. The standard composition of 18/8 stainless steel is 18 percent chromium plus 8 percent nickel, a composition that makes it non-magnetic.