Type 304 stainless steel is one of the most ubiquitous steel grades on the market. Renowned for its excellent corrosion resistance, grade 304 serves a multitude of purposes, from household to industrial applications. Although it may be replaced with 316 stainless steel in extremely corrosive environments–especially when severe pitting and crevice corrosion are an issue–304 stainless remains a go-to solution for engineers and manufacturers worldwide.
Specifying 304 Stainless steel
304 is the SAE International grading for the composition initially branded as Staybrite 18/8; those figures derive from the ratio of chromium and nickel in the alloy. That terminology has persisted, so some still refer to 304 stainless steel as 18/8 steel. However, the content of both chromium and nickel can vary upwards by about 2%. These same general principles apply to other global certifications, so though there’s some variation in vernacular, the different certifications agree on the chemical composition. Hence the 304 stainless steel is equivalent to EN 1.4301 and SU304.
Chemical Composition
| UNS No | S30400 |
| EN | 1.4301 |
| AISI | 304 |
| Carbon (C) | 0.07 |
| Silicon (Si) | 0.75 |
| Manganese (Mn) | 2.00 |
| Phosphorus (P) | 0.045 |
| Sulphur (S) | 0.030 |
| Chromium (Cr) | 17.50 – 19.50 |
| Molybdenum (Mo) | |
| Nickel (Ni) | 8.00 – 10.50 |
| Nitrogen (N) | 0.10 |
304 stainless steel’s composition promotes good resistance to corrosive media, inhibiting both corrosion and oxidation. The low corrosivity of type 304 is largely due to the high chromium content, which forms a protective passivation layer–or patina–on the alloy’s surface. All stainless steel products have this protective layer which self-heals through oxidation, preventing oxidation of the internal structure. Yet grade 304’s higher chromium content increases its durability in the presence of oxidizing agents, meaning 304 stainless steel is unlikely to rust.
Mechanical Properties
| Proof Stress 0.2% (MPa) | 205 |
| Tensile strength (MPa) | 515 |
| Elongation A5 (%) | 40 |
| Hardness | HB: 201HRB: 92 |
Some of the standard mechanical properties of 304 stainless steel are shown in the table above, but we will look into the tensile strength, elongation A5, hardness and yield strength in more detail in the following section.
304 Stainless Steel Tensile Strength
The tensile strength of a property describes the maximum amount of stress the steel can withstand before fracturing or breaking. The tensile strength of 304 stainless steel is at a minimum of 515 MPa and can typical reach 625 MPa as a maximum.
304 Stainless Steel Yield Strength
The yield strength of 304 stainless steel is at 205 MPa. When the steel is placed under stress at 205 MPa or higher it will become permanently deformed. It is therefore important to know this measurement to avoid causing irreversible damage to a steel.
Different Types of 304 Stainless Steel
There are different grades of 304 stainless steel and the two key grades we will cover in this section are 304L and 304H. The L and H grades relate to the carbon content of the 304 forms of steel, each of which has its own benefits and drawbacks.
304L is the low carbon version and has a maximum of 0.3% carbon. When used in temperatures above 425oC, 304L is not as likely to result in carbide precipitation, unlike 304H. It is often used to improve weldability in heavy gauge components.
304H is the high carbon form with a carbon content between 0.04 and 0.1%. 304H stainless steel is often used in the food industry for a number of applications. These include cooking pots, cutlery, kitchen appliances and sinks because of its resistance to corrosion and high tolerance for extreme temperatures. (500 to 800oC)
What is 304 Stainless Steel Used for?
304 stainless steel is used in a variety of applications because of its flexibility and versatility. However, manufacturers might need to make a decision between steel types 304L or 304H depending on the properties they require.
Typical applications for 304 steel are:
- Bolts, screws and springs: Especially in industrial and marine applications where corrosion resistance is important.
- Chemical processes in petroleum refineries: 304H is frequently used to manufacture high-temperature processing equipment and pressure vessels because of its long and short-term strength and ability to withstand extreme temperatures. Additional reasons for using 304H in refineries are its resilience in hydrogen-rich environments and resistance to naphthenic acid attacks.
- Cookware and cutlery: 304L is commonly typically used in cookware and kitchens because of its strong resistance to corrosion and high temperatures. This includes other applications such as sinks, splashbacks, worktops and more. 304H can also be used for larger appliances and sinks.
- Dairy and food production equipment: 304L is used for food processing equipment because of its corrosion resistant properties and ability to withstand high temperatures. It reduces harmful interaction between food products and equipment.
Other applications include:
- Architectural panelling
- Building fascias in the construction industry
- Heat exchangers in the brewing industry
- Tubing
304L stainless steel is most commonly used in applications that present extremely corrosive conditions and operate under high temperatures. Other avantages include rapid hardening after cold forming and resistant to aggressive organic acids. Because of the aforementioned advantages, 304L is a popular choice for manufacturing industry components such as beams, pipe tubes, sheet plates and more.
304H stainless steel is a preferred choice in architectural and industrial processing applications because of it’s durability, high strength properties and reduced need for maintenance. It is especially suited for manufacturing heat exchangers in petroleum refineries.
304 vs 316 Stainless Steel?
The 300 series of stainless steel contain two of the most widely used austenitic stainless steels: 304 and 316. These steels arepopular in the building, food production and pharmaceutical industries because of their lower carbon content, have a austenitic crystalline structure and provide outstanding forming and welding properties.
The differences between these 304 and 316 stainless steels are quite simple in that 304 is made up of 18% chromium and 8% nickel whereas 316 is made up of 16% chromium, 10% nickel and 2% molybdenum. Another difference is their applications.
304 is typically used in food processing environments, including beer brewing and milk and wine processing as well as in petrochemical industries. It is highly resistant to corrosion and common acids and is easily moulded into desired shapes. Due to its good appearance and long service life, 304 can also be used in architectural applications. However, 304 should not be used in marine environments due to its weakness to chloride solutions and saline.
For industrial and marine applications and high-saline environments, 316 is the more appropriate steel. It is robust and can strong withstand powerful acids and chemicals that could cause corrosion. Additionally, 316 is used to manufacture equipment in the pharmaceutical industry, where cleanliness is paramount.
Looking for Stainless Steel Products?
As a stainless steel supplier, Masteel provides a wide range of products that can be delivered worldwide to suit your application and requirements. Our available steels include the 300 series, which encompasses grades 304 (L and H), 316 (L and H), 321, and 410, and the UNS series of stainless steel.
For more information about our products or to request a quote, please don’t hesitate to contact us.