304 Stainless Steel Castings: A Detailed Analysis of Properties and Practical Uses

304 Stainless Steel Castings are stainless steel casting components produced through casting methods such as investment casting or sand casting. Grade 304, also known as CF8 (the cast equivalent) is a type of austenitic stainless steel offering excellent corrosion resistance, decent strength and ductility. SS304 is one of the most popular grades of stainless steel, used in a wide range of industrial and everyday applications, including automotive, marine, and food processing.

Although it is not as effective in terms of corrosion resistance and performance compared to grade 316, AISI 304 is generally considered more prevalent than AISI 316 due to its cost-effectiveness. Taiyuan Simis Investment Casting Co., Ltd. is a professional investment casting manufacturer in China. With over 40 years of metal casting and general engineering experience, we offer comprehensive stainless steel casting services, including fully optimized options for various stainless steel grades. In this article, you will learn everything about 304 stainless steel castings, including international equivalents, chemical composition, mechanical properties, physical properties, casting processes, and their common applications.

International Equivalents and Standards

304 stainless steel, widely recognized under the Unified Numbering System (UNS) as S30400, is known by several other standards around the world.

International Standard	Designation	Description
AISI	304	Common American standard for industrial use
EN	1.4301	Widely used European standard
JIS	SUS 304	Standard Japanese designation
BS	304S15	British standard for stainless steel
SAE	30304	Automotive and aerospace standard in the USA
ASTM	A276	Specification for stainless steel bars and shapes
DIN	1.4301	German standard, synonymous with European EN 1.4301

Chemical Composition of 304 Stainless Steel

The chemical makeup of 304 stainless steel is balanced to provide a harmonious mix of high corrosion resistance with good strength and formability. The primary elements are iron, chromium, and nickel, but it also contains small amounts of manganese, silicon, carbon, and sometimes molybdenum to enhance certain properties.

Element	Percentage (%)
Chromium (Cr)	18.0 – 20.0
Nickel (Ni)	8.0 – 10.5
Manganese (Mn)	2.0 max
Silicon (Si)	1.0 max
Carbon (C)	0.08 max
Phosphorus (P)	0.045 max
Sulfur (S)	0.03 max
Iron (Fe)	Balance

• Chromium (Cr): Provides stainless steel with its stainless quality, enhancing the material’s corrosion resistance by forming a passive layer of chromium oxide on the steel’s surface when exposed to oxygen.
• Nickel (Ni): Adds ductility and toughness to the stainless steel, which is particularly important for the forming and manufacturing of products.
• Manganese (Mn) and Silicon (Si): Serve as deoxidizers during the steelmaking process and enhance the strength and hardness of the steel when present in small amounts.
• Carbon (C): Increases strength but decreases ductility. The low carbon content in 304 helps maintain a balance between strength and ductility.
• Phosphorus (P) and Sulfur (S): Typically kept to a minimum as they can lead to harmful inclusions in the steel, affecting its mechanical properties and corrosion resistance.

Mechanical Properties

The mechanical properties of 304 stainless steel are crucial for its performance in structural and pressure-containing applications.

Property	Value
Tensile Strength	505 – 860 MPa
Yield Strength	215 MPa (min)
Elongation	50 – 60%
Hardness	82 HRB (max)
Modulus of Elasticity	193 – 200 GPa

• Tensile Strength: 304 stainless steel has a tensile strength range from 505 to 860 MPa, which varies based on the specific form and treatment of the steel.
• Yield Strength: It typically has a minimum yield strength of 215 MPa, ensuring that it can withstand significant stress before deforming.
• Elongation: The elongation rate of 50-60% showcases its excellent ductility, allowing it to stretch significantly before it breaks.
• Hardness: The maximum Rockwell hardness for 304 stainless steel is 82 HRB, balancing machinability with durability.
• Modulus of Elasticity: The modulus of elasticity, ranging from 193 to 200 GPa, illustrates the steel’s ability to resist deformation under load.

Casting Processes

304 stainless steel can be cast using investment casting and sand casting. Both methods have their unique benefits and are suitable for different requirements, such as size, weight, dimensional tolerance, structure, and design.

Investment Casting

The investment casting process is most commonly used for casting 304 stainless steel. This process offers unparalleled precision and surface smoothness, unmatched by other casting methods. At Simis, we achieve very high dimensional tolerances (CT4 – CT7) and use ceramic cores for casting parts with complex internal structures in 304 stainless steel. Another significant benefit of this method is the ability to reduce secondary processing such as machining, which can cut production costs.

However, a major drawback of investment casting for 304 stainless steel is the weight limit. Compared to sand casting, investment casting can only handle weights up to 100 kg or slightly above without encountering defects. Another limitation of using this process for 304 stainless steel is the potential for longer lead times due to the many steps involved.

Sand Casting

Sand casting is another viable process for casting 304 stainless steel, typically used for larger components, especially for parts and components weighing up to several tons. In comparison to investment casting, sand casting offers faster turnaround times.

Surface Treatments for 304 Stainless Steel Castings

Several common surface treatments can be applied to 304 stainless steel castings to enhance corrosion resistance, environmental protection, and aesthetic appeal, including passivation, electropolishing, mirror polishing, sandblasting, phosphating, anodizing, and powder coating.

Passivation

Passivation is a treatment that enhances the natural corrosion resistance of stainless steel. The process involves treating the steel with a mild oxidant, such as citric acid or nitric acid, to remove free iron from the surface and promote the formation of a thin, protective oxide layer. This treatment can further prevent rust and maintain the integrity of the stainless steel in corrosive environments.

Electropolishing

Electropolishing is a process that smooths and refines the microscopic surface of a metal object. For 304 stainless steel castings, this method not only improves the aesthetic and cleanability of the surface but also increases its corrosion resistance. Electropolishing is greatly beneficial for stainless steel parts that require a high level of sanitation, such as those used in the food processing, pharmaceutical, and surgical industries, as it enhances both the material’s resistance to bacterial growth and its overall durability.

Mirror Polishing

Mirror polishing provides a highly reflective surface on stainless steel. This process involves sequential polishing with increasingly fine abrasives and then finally using a buffing compound. Mirror polishing is sought after for decorative applications and for components where aesthetic appearance is needed, such as in architectural and consumer castings. The smooth and shiny finish not only looks appealing but helps in reducing the adhesion of dirt and bacteria as well, making the surface easier to clean.

Phosphating

Phosphating is a chemical process that provides a phosphate conversion coating to metals. It is used to enhance the corrosion resistance of the steel and to provide a foundation for subsequent coatings or painting. Phosphating results in a matte finish that can also improve the adhesion of lubricants in metal forming processes.

Anodizing

Anodizing is typically used more for non-ferrous metals like aluminum, but it can be applied to stainless steel for certain specialized applications. It uses an electrochemical process that converts the metal surface into a durable, corrosion-resistant, anodic oxide finish. Anodizing for stainless steel can enhance the aesthetics of the metal while providing a surface that is resistant to wear and erosion.

Powder Coating

Powder coating applies a free-flowing, dry powder that is typically cured under heat to form a skin-like polymer layer on the surface of the casting. This coating is much thicker and more durable than conventional liquid paints. For 304 stainless steel, powder coating provides superior corrosion resistance, impact resistance, and aesthetic qualities. It is ideal for applications in environments that demand high durability and where a vibrant, lasting color is necessary.

Applications of 304 Stainless Steel Castings

304 stainless steel castings are widely used across various industries due to their excellent corrosion resistance, durability, and versatility. Common applications of 304 stainless steel in several key industries include automotive, railway, oil & gas, marine, food processing, chemical processing, and hydroelectricity.

Automotive

In the automotive industry, 304 stainless steel is used for manufacturing exhaust systems such as exhaust outlets, intake manifolds and other components that require good corrosion resistance and durability. SS304 castings’ ability to withstand harsh environments and maintain structural integrity makes them ideal for parts exposed to moisture and road salts.

Railway

For railway applications, 304 stainless steel is used in a variety of components such as tankers, refrigeration units, and carriage parts. The material’s resistance to corrosion and its strength ensure that these components can withstand the rigors of long-term exposure to the elements and mechanical stress.

Oil & Gas

In the oil and gas industry, 304 stainless steel castings are used for parts that require resistance to corrosion from water, salt, and chemicals. Common uses include MLE clamps, tube clamps, valves and pumps, storage tanks, mechanical seal rings and pipe fittings which all benefit from the material’s durability and resistance to a variety of chemical environments.

Marine

The marine environment is particularly challenging due to its high salinity. 304 stainless steel is used for a wide range of marine applications, including fittings, bollards, hawse pipes, various deck equipment and hull construction parts. 304 Stainless Steel Castings provide excellent resistance to corrosion from salt water and therefore suitable for marine applications.

Food Processing

304 stainless steel is extensively used in the food processing industry due to its resistance to oxidation and corrosion, as well as its ease of cleaning. It is commonly used for making kitchen appliances, food handling equipment, and food processing machine components, all of which require strict hygiene standards. You can also see this article here for a complete guide to stainless steel castings for the food processing industry.

Chemical Processing

The chemical processing industry relies on 304 stainless steel for equipment like reactors, piping, and housings. Its corrosion resistance is crucial for handling a wide range of chemicals and acidic materials, ensuring long-lasting performance and safety.

Hydroelectricity

In hydroelectric power plants, 304 stainless steel is used for turbine blades, pelton wheels and other structural components exposed to water. Its excellent corrosion resistance helps prevent the deterioration of parts that are in constant contact with water, thus enhancing the efficiency and lifespan of the equipment.

I’ve listed a few common applications of 304 stainless steel castings. For detailed information about stainless steel investment casting applications, here you check out our article on stainless steel investment casting.

Conclusion

304 stainless steel castings are indispensable across a broad spectrum of industries due to their exceptional corrosion resistance, strength, and versatility. From critical components in automotive and railway applications to essential equipment in the harsh environments of oil & gas and marine sectors, 304 stainless steel stands out for its durability and performance.

As I’ve previously mentioned, Simis can provide stainless steel casting services for various grades, including AISI 304, AISI 316, 2205 and other grades such as AISI 347. We also offer custom investment casting services to meet your exact specifications and special designs, including logos, markings, designs, tolerances, treatments, and machining. Contact us now to discuss your casting project requirements.