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A Comprehensive Guide to 304 Stainless Steel
Stainless steel is a group of alloys that consists of iron, carbon, and at least 10.5% chromium. The different types of stainless steel grades include martensitic, duplex, ferritic, austenitic, and precipitation hardening, each with distinct grades based on their chemical composition.
Of these types, 304 stainless steel is the most commonly used in the austenitic series. It has excellent resistance to corrosion and is suitable for a wide range of applications. This article will explore the chemical composition, physical and mechanical properties, unique characteristics, and applications of 304 stainless steel.
The Origins
In the late 19th century, a French metallurgist named Pierre Berthier created a new type of iron-chromium alloy called “acier inoxydable”. This new alloy is now commonly known as stainless steel. By the 1930s, the new alloy development led to the creation of the first grade of stainless steel, known as Type 304. This grade was specifically designed for its high resistance to corrosion and heat and has since become a popular choice for many industrial and food-processing applications.
Definition of 304 Stainless Steel
304 stainless steel(18/8 stainless steel) is an austenitic alloy containing 18% chromium and 8% nickel. It also contains minor quantities of carbon, manganese, silicon, and phosphorus, which combine to give 304 stainless steel unique properties.
304 stainless steel rod
Chemical Composition of 304 Stainless Steel
| Element | Percentage |
| Sulfur | 0%–0.02% |
| Phosphorus | 0%–0.04% |
| Carbon | 0.04%–0.08% |
| Nitrogen | 0%–0.1% |
| Silicon | 0%–1% |
| Manganese | 0%–2% |
| Nickel | 8%–11% |
| Chromium | 17%–20% |
| Iron | Balance (66.76%–75%) |
Aisi 304 is a highly durable material that owes its strength and corrosion resistance to a combination of elements. Chromium is the critical component that confers excellent corrosion resistance to 304 stainless steel. Nickel is another important element that enhances oxidation resistance and improves stability at high temperatures. Carbon increases the alloy’s strength and hardness, while Manganese helps maintain the steel’s austenitic structure. Silicon prevents oxidation and scaling, and phosphorus and sulfur are carefully controlled to ensure better weldability.
The Properties of 304 Stainless Steel
Physical Properties of 304 Stainless Steel
| Property | Value |
| Density | 8.0g/cc（0.289 lb/in3） |
| Electrical Resistivity | 0.072 x 10-6 Ω .m |
| Electrical Conductivity | 1.25% IACS |
| Magnetism | Nonmagnetic (Austenitic) |
| Note: 304 stainless steel is generally nonmagnetic but may display limited magnetic properties after cold rolling. | |
Mechanical Properties of 304 Stainless Steel
| Property | Value |
| Hardness | 123(Brinell) /138(Knoop）/ 70(Rockwell)/ 129(Vickers） |
| Tensile Strength( Ultimate) | 505 MPa（73200 psi） |
| Tensile Strength(Yield) | 215 MPa（31200 psi） |
| Elongation at Break | 70% |
| Modulus of Elasticity | 193 GPa（28000 ksi） |
| Poissons Ratio | 0.29 |
| Shear Modulus | 77.0 GPa（11200 ksi） |
Thermal Properties of 304 Stainless Steel
| Property | Value |
| Melting Point | 2,550ºF-2,651ºF (depending on the exact composition) |
| Rate of Linear Thermal Expansion | 17.3 µm/m-°C |
| Specific Heat Capacity | 0.500 J/g-°C |
| Thermal Conductivity | 16.2 W/m-K |
| Thermal Expansion | 17.2 x 10-6 /K |
Some other Properties of 304 stainless steel
Corrosion Resistance
SUS 304 is widely known for its exceptional resistance to corrosion in a broad range of environments., including humid atmospheric conditions and mild chemical environments. The credit goes to chromium, which creates a protective oxide coating on the surface, halting the alloy from further oxidation and corrosion. Consequently, 304 stainless steel is ideal for use in corrosive environments like chemical processing plants or coastal areas.
Heat Resistance
SS 304 is renowned for its outstanding heat resistance properties. It can maintain its strength and structural integrity at high temperatures without undergoing significant scaling or deformation, even up to 870°C (1600°F). Heat exchangers and exhaust systems benefit from this resilience.
Cold Working
SUS 304 stainless steel is also well-known for its significant work-hardening properties, which can make it more challenging to shape during the fabrication process. Therefore, performing an intermediate annealing stage is often essential when using cold working methods. This intermediate annealing process helps to reduce the effects of work hardening, which minimizes the risk of material tearing or cracking.
Hot Working
For hot-working fabrication methods, such as forging, it is crucial to ensure that the SS 304 stainless steel is heated uniformly within a temperature range of 1149-1260°C (2100-2300°F). This uniform heating process guarantees that the material is malleable and workable during the hot-working process.
After completing hot working, it is essential to cool the fabricated parts rapidly to ensure high corrosion resistance.
Machinability
Material 304 stainless steel is very machinable and can be cut, drilled, and shaped easily using standard machining practices. The property mentioned helps in simplifying the manufacturing process and reduces the overall production costs. The following guidelines should be followed to optimize machining: Maintain sharp cutting edges to prevent work hardening; Cuts should be deep but not too heavy as to ride on the surface of the material; Chip breakers should be used to ensure the swarf remains clear of the work; Heat accumulates at the cutting edges because austenitic alloys have low thermal conductivity. This necessitates using coolants and lubricants, which should be used in large quantities.
Weldability
Stainless steel ss 304 is easily weldable using fusion techniques such as GTAW/TIG, GMAW/MIG/MAG, MMAW/stick and SAW without preheat post heat or interpass temperature control. To maintain both corrosion resistance and strength, it is recommended to use common austenitic filler metals like grades 308, 308L, 309, 309L, 316, or 316L (or their silicon-containing versions). Grades 308 and 308Si are prequalified weld metals to AS1554.6:1994 for welding grade 304 to itself or to most other austenitic grades.
304 stainless steel tubing
Equivalent Forms of 304 Stainless Steel
The following are equivalent forms of SS304. Note that some chemical compositions may not be an exact match but are the nearest equivalent:
| Country | Equivalent Grade |
| China | 0H18N9 |
| Russia | 08KH18N10 |
| Japan | SUS304 |
| France | X5CrNi18-10 |
| Italy | X5CrNi18-10 |
| UK | 304S15; 304S31 |
| Germany | X5CrNi18-9 |
| USA | 304304N |
| EU | X5CrNi18-10 |
Common Forms of 304 Stainless Steel
Sheet
304 stainless steel is a material commonly available as sheet metal. The product is available for purchase in specific thicknesses from 0.018″ to 0.250″. 304 ss sheet metal is often used to make bodywork and panels for different types of machinery. Additionally, it is frequently used to create various household items such as grills, sinks, cookers, pots, and pans.
Plate
Any 304 stainless steel plate will have a thickness greater than 0.25″. These 304 stainless plates can be used in the food industry for food processing equipment or architectural cladding.
Bar
The bar form of 304 stainless steel is utilized in structural applications where high corrosion resistance is essential. It can come in various geometries, such as circular and tubular.
Pipe
304 Stainless Pipe is highly formable and can be welded using standard methods.304 ss pipes have a wide range of applications in fabrication projects exposed to various environments, including chemical, acidic, and seawater.
304 stainless steel pipe
Manufacturing Methods of 304 Stainless Steel
If you are looking to manufacture 304 stainless steel, there are several processing options available:
Drawing
This process improves the strength, hardness, and wear resistance of shaping stainless 304 by pulling it through a die.
Hot Rolling
Hot rolling reduces material thickness by passing it through two rollers after it has been heated to a specific temperature.
Cold Rolling
This process involves reducing material thickness by passing it between two rollers with a decreasing gap.
Annealing and Pickling
The material’s surface is cleaned to improve its corrosion resistance by heating it to a specific temperature and then immersing it in an acid solution.
Polishing
The 304 stainless steel undergoes polishing to create a sleek and visually appealing surface finish with a smooth texture.
Passivation
Steel is passivated by being dipped into an acid solution during the manufacturing process to withstand harsh environments.
Laser Cutting
Laser cutting is the ultimate solution for precise and rapid stainless steel cutting. With the accuracy of a laser beam, cutting stainless steel has never been easier.
304 Stainless Steel Finishes
There are various finishes available for Aisi 304 stainless steel to achieve different aesthetics. Whether you’re after an elegant, rustic, or industrial look, this selection offers something. Look at the different finishes available to find the perfect one for your project.
Polished
It is a sleek and glossy surface that reflects light exceptionally well.
Mirror
A mirror is a surface that reflects light with a highly reflective finish, resulting in a bright and clear reflection.
Satin
“Satin” is a type of finish with a smooth, non-shiny texture. To achieve this, a fine abrasive is used during the manufacturing process.
Sandblasted
Sandblasted is a textured finish that blasts the surface with fine abrasive material. This process results in a roughened surface that can be used to create various interesting visual effects.
Electropolished
Electropolishing is a process used to remove surface impurities and create a smooth and shiny surface.
Painted
One can apply paint or powder coating to achieve a painted finish on a surface.
Anodized
The anodized finish is a protective coating created through an electrochemical process on the surface.
Applications of 304 Stainless Steel
The applications of stainless ss304 are wide-ranging and impact various industries. Some common applications include:
- Architectural hardware
- Food processing equipment
- Chemical processing equipment
- Pharmaceutical equipment
- Heat exchangers
- Kitchen appliances
- Automotive components
- Oil and gas industry equipment
Advantages & Disadvantages
Advantages:
- It is an exceptionally corrosion-resistant alloy, making it ideal for use in chemical, food, and shipbuilding industries, among others. Compared to most other metals, its superior resistance to rust and oxidation makes it a good choice for these industries.
- 304 stainless steel is incredibly durable and can withstand harsh environments and extreme temperatures.
- The material is low-maintenance and ideal for projects that require minimal upkeep.
- 304 stainless steel is a cost-effective option for various applications due to its lower cost compared to other metals.
Disadvantages:
- SS304 stainless steel is susceptible to stress corrosion cracking in high chloride solutions.
- Its low tensile strength makes it more likely to deform and crack than other metals.
- 304 stainless steel has a slight magnetic property due to high chromium and low nickel content, which can be problematic in some applications.
- Due to its high carbon content, steel can be susceptible to intergranular corrosion, especially when exposed to high temperatures like during welding.
Comparison
304 Stainless Steel & 201 Stainless Steel
If you’re trying to decide between 304 and 201 stainless steel, it’s essential to consider the differences to determine which is best for your particular needs.
201 stainless steel contains 16-18% chromium and 3-5% nickel. Although it is a more affordable option, it is less resistant to corrosion than 304 stainless steel. However, if you need a material for freshwater environments, 201 stainless steel is a good choice since it is less likely to rust or corrode in this setting.
304 SS is composed of 18-20% chromium and 8-10.5% nickel. It is the most commonly used material for outdoor use because it resists corrosion and withstands various kinds of weather.
304 stainless steel exhibits superior corrosion resistance compared to 201 stainless steel. Therefore, it is better for projects exposed to acids and other corrosive elements. On the other hand, 201 SS is more suitable for indoor projects where the risk of corrosion is relatively low.
304 Stainless Steel & 18/10 Stainless Steel:
18/10 stainless steel, also known as type 304, is named after its 18% chromium and 10% nickel content. It’s important to differentiate between type 304 and 304-grade steel due to their different compositions. The significant difference is that a protective layer forms on the surface of 304 SS, which helps mitigate corrosion. However, 18/10 lacks this safeguard, making it more susceptible to corrosion. Additionally, the surface finish of 18/10 stainless steel tends to be shinier, making it more appropriate for decorative applications compared to 304 stainless steel.
304 Stainless Steel & 316 Stainless Steel:
It can be challenging to differentiate between 304 and 316 stainless steels as they look similar but have slight chemical differences that set them apart. Consider these differences before choosing a grade.
In terms of composition, 304 SS contains 18% chromium and 8% nickel, while 316 SS contains 16% chromium, 10% nickel, and 2% molybdenum. The higher molybdenum content in 316 SS gives it more excellent resistance to corrosion than 304 SS, making it a superior choice for projects that may be exposed to saltwater or other chemical compounds.
Regarding mechanical properties, 316 SS has better tensile and yield strength than 304 SS, making it more suitable for structural applications. Additionally, 316 SS has higher creep resistance, which can benefit applications where temperatures may rise over time.
Cost is an essential factor when choosing between 316 and 304 SS. The 316 SS is generally more expensive than the 304 SS, but its higher cost is justified by its superior corrosion-resistant properties. In some cases, the 316’s long lifespan can outweigh its additional cost, making it a more cost-effective option in the long run.
Summary
Overall, 304 stainless steel is a versatile material with excellent corrosion resistance. It is durable and robust, making it ideal for various items such as cutlery, kitchen appliances, and architecture.
One drawback to using 304 is its relatively high cost and need for regular maintenance. However, proper upkeep can provide a durable and reliable solution for any project.
If you are looking for a stainless steel parts supplier, don’t hesitate to get in touch with us for a fast quote
