304 stainless steel is a standard and classic Chrome 18 – Nickel 8 Austenitic stainless steel, It is the most familiar and frequently used alloy in the stainless steel family, Its composition contains iron, carbon, chromium, nickel, and other elements, and it is a food-grade stainless steel grade, the composition of 304 grade provides excellent overall properties, 304 Stainless Steel has excellent formability, and excellent forming and welding characteristics thanks to its austenitic structure, which enables it to be severely deep drawn and fabricated without intermediate annealing, It is non-magnetic stainless steel in the annealed condition, It has a higher corrosion resistance than regular steel. Stainless Steel 304 is commonly available in many product forms and dimensions. It can be supplied with a wide range of functional and aesthetic surface finishes, these characteristics make 304 grade widely used in many applications.
304 is also known as
- AISI 304, is defined following the American Iron and Steel Institute (AISI).
- TP 304, is for tube and pipe products material in 304 grade.
- SUS304, is defined by Japanese Industrial Standards.
- UNS S30400, is UNS No. in the unified numbering system.
- 1.4301, is EN steel No., the EN 10088 equivalent grade.
- SS304 is the abbreviation of stainless steel 304, the “SS” stands for stainless steel, and can be also 304SS.
Table of Content
- 304 Stainless Steel Composition
- 304 Stainless Steel Mechanical Properties
- 304 Stainless Steel Physical Properties
- 304 Stainless Steel Equivalent
- Corrosion Resistance
- Heat Resistance
- Heat Treatment
- Welding
- Machining
- 304 Stainless Steel Magnetic
- 304 Stainless Steel Specifications
- 304 Stainless Steel Forms
- Benefits of 304 Stainless Steel
- 304 Stainless Steel Used For
- 304 Stainless Steel vs 304L
- 304 Stainless Steel vs 316
304 Stainless Steel Composition
the chemical composition of 304 Stainless Steel is composed of 18-20% chromium and 8-10.5% nickel, combined with a maximum of 0.07% carbon, 2% manganese, 1% silicon, 0.11% nitrogen, 0.045% phosphorus, and 0.03% sulfur. chromium and nickel are important elements to improve the corrosion resistance and oxidation resistance of stainless steel, chromium can form a layer of stable passivation film on the surface, to protect the steel from external erosion, and nickel can enhance the stability and ductility of the passivation film to improve the plasticity and toughness of stainless steel, these elements on the mechanical properties and processing performance of stainless steel has a certain impact.
ASTM 304 stainless steel and EN 1.401 composition comparison.
| 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 A312 | TP 304 | ≤0.08 | ≤2.00 | 0.045 | 0.030 | 1.00 | 18.0-20.0 | 8.0-11 | ≤0.10 |
| EN 10088-2 | 1.4301 | ≤0.07 | ≤2.0 | 0.045 | 0.030 | 1.00 | 17.5-19.5 | 8.0-10.5 | ≤0.10 |
| EN 10088-3 | 1.4301 | ≤0.07 | ≤2.00 | 0.045 | 0.030 | 1.00 | 17.5-19.5 | 8.0-10.5 | ≤0.10 |
304 Stainless Steel Mechanical Properties
- Tensile strength: ≥515MPa.
- Yield strength: ≥205MPa.
- Elongation: ≥40%.
- Hardness: ≤201HB.
ASTM 304 and EN 1.4301 mechanical properties comparison.
| Standard | Grade | Yield Point | Tensile Strength | Elongation | Hardness | Hardness |
|---|---|---|---|---|---|---|
| MPa | MPa | % | HRB | HB | ||
| ASTM A240 | 304 | ≥ 205 | ≥ 515 | ≥ 40 | ≤ 92HRB | ≤ 201 |
| EN 10088-2 | 1.4301 | ≥ 230 | 540-750 | ≥ 35 | ≤ 215 |
304 Stainless Steel Physical Properties
| Physical Properties | Metric | Imperial |
|---|---|---|
| Density | 7.93 g/cm3 | 0.286 lb/in3 |
| Melting point | 1400-1450 °C | 2550-2650 °F |
| Specific heat capacity | 500 J/kg·K at 20 °C | 0.12 Btu/lb ·°F at 68 °F |
| Electrical resistivity | 0.72 μΩ·m at 20 °C | 28.35 μΩ·in. at 68 °F |
| Conductivity, %, IACS | 2.5 | – |
| Magnetic permeability | 1.02 (Approximate) | – |
| Elastic modulus (Modulus of Elasticity) | 193 GPa | 28 x 106 psi |
| Thermal diffusivity | 3.84 mm2/s | 0.006 in2/s |
| Thermal conductivity | 16.2 W/m·K at 100 °C | 9.4 Btu/ft·h·°F at 212 °F |
| 21.5 W/m·K at 500 °C | 12.4 Btu/ft·h·°F at 932 °F | |
| Coefficient of thermal expansion (CTE) | 17.2 10-6/K at 0-100 °C | 9.6 μin./in.·°F at 32-212 °F |
| 17.8 10-6/K at 0-315 °C | 9.9 μin./in.·°F at 32-600 °F | |
| 18.4 10-6/K at 0-538 °C | 10.2 μin./in.·°F at 32-1000 °F |
304 Stainless Steel Equivalent
- AISI UNS S30400
- DIN 1.4301
- JIS SUS304
- GB 0Cr18Ni9
- EN 08KH18N10
Corrosion Resistance
304 stainless steel is excellent in a wide range of atmospheric environments and many corrosive media. It is subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above 60 °C (approximate). Grade 304 is considered to be resistant to potable water up to approximately 200 mg/L chlorides at ambient temperatures, reducing to approximately 150 mg/L at 60 °C.
AISI 304 is highly corrosion-resistant to most oxidizing acids. However, corrosion can occur in environments containing chlorides. 304 is not as corrosion-resistant as 316 stainless steel.
Heat Resistance
Grade 304 has good oxidation resistance in intermittent service to 870 °C and in continuous service to 925 °C. Continuous use of 304 in the 425-860 °C range is not recommended if subsequent aqueous corrosion resistance is important. Grade 304L is more resistant to carbide precipitation and can be heated into this temperature range.
Heat Treatment
304 stainless steel annealing temperature can be from 1010 °C to 1120 °C and then cooled rapidly. 304 grade cannot be hardened by thermal treatment.
Welding
Grade 304 has excellent weldability by all standard fusion methods, both with and without filler metals. it is suitable for the full range of conventional welding methods (like MMA, MIG, MAG, TIG, SAW, LBW, or RSW), except gas welding. Post-weld heat treatment is generally not required. In special cases where there is a high risk of stress corrosion cracking or fatigue, stress relief treatment may be considered.
304/1.4301 has about 50% higher thermal expansion and lower heat conductivity than carbon steel. This means that larger deformation and higher shrinkage stresses may result from welding.
To fully restore the corrosion resistance of the weld seam, the weld discoloration should be removed by pickling and passivation.
Machining
Due to their high toughness and work-hardening behavior austenitic steels are more difficult to machine than carbon steels but are still comparatively easier than more highly alloyed stainless steel grades. It requires higher cutting forces than carbon steel, shows resistance to chip breaking, and has a high tendency to build up edge formation.
304 Stainless Steel Magnetic
304 stainless steel is not magnetic under heat treatment conditions but may be slightly magnetic after cold working. 304 SS is austenitic stainless steel whose organization may undergo a phase transformation from austenite to martensite or ferrite under certain temperature and stress conditions. This phase transformation will change the properties of 304 grade and make it produce a weak magnetic property. For example, if 304 stainless is after cold working, such as stretching, stamping, bending, etc., its organizational structure will be transformed to martensite, the greater the degree of cold working deformation, the more martensite transformation, the greater the magnetic properties of steel. In addition, if 304 stainless is after welding treatment, its weld part may also appear as martensite or ferrite, thus generating magnetism. In some special environments, such as high temperature, high humidity, acid and alkali salts, etc., this passivation film may be damaged or reduce the effect, resulting in oxidation of the surface of 304 SS. This oxidized layer may contain some iron elements, which makes the surface of 304 material produce weak magnetism.
304 Stainless Steel Specifications
| Product Forms | ASTM | ASME |
|---|---|---|
| Plate, Sheet And Strip | A 240 | SA-240 |
| Seamless And Welded Pipe | A 249/A 249M TP304. A 554 MT304 | SA-249/SA-249M |
| Plate, Sheet, And Strip | A 312/A 312M, A 409/A 409M | SA-312/SA-312M, SA-409/SA-409M |
| Bar, Wire | A 276, A478, A479/A 479M, | SA-479/SA-479M |
| Billet, Forgings | A 314, A473 | |
| Flanges, Fittings | A 182/A 182M, A 403/A 403M | SA-182/SA-182M, SA-403/SA-403M |
304 Stainless Steel Forms
304 Stainless Steel Plate
304 stainless steel plate according to the method of hot-rolled and cold-rolled two kinds, including the thickness of 0.02-4 mm thin cold plate and 4.5-100 mm hot rolled plate. To ensure that the yield strength, tensile strength, elongation and hardness of 304 plate mechanical properties are in line with the requirements of the steel plate before delivery must be annealed, solution treatment, aging treatment and other heat treatments. The stainless steel plate has a smooth surface, high plasticity, toughness and mechanical strength, and is resistant to corrosion by acid, alkaline gases, solutions and other media.
304 Stainless Steel Pipe
304 stainless steel pipe is divided into two categories: seamless steel pipe and welded steel pipe. The shape of the cross-section can be divided into round and shaped pipe, widely used is round steel pipe, but there are also some square, rectangular, semi-circular, hexagonal, equilateral triangle, octagonal, and other shaped steel pipes. Stainless Steel Seamless Tubes are made from steel ingots or solid billets that are pierced to make a blank tube, which is then hot-rolled, cold-rolled, or cold-dialed. The size of the pipe is expressed in millimeters of outer diameter and wall thickness. 304 stainless steel welded pipe, commonly used steel or steel strip through the unit and mold roll forming after welding made of steel pipe. The welded steel pipe production process is simple, with high production efficiency, more varieties and specifications, and less investment in equipment, but the general strength is lower than seamless steel pipe.
304 Stainless Steel Strip
304 Stainless Steel Strip is a 304 steel strip material with a width of 600mm and below, also known as 304 stainless steel strip or 304 steel strip. It is actually a calendered material, usually produced by stainless steel calendering manufacturers, or from 304 stainless steel coils as raw material by slitting and processing into stainless steel strip of the required width. With its unique physical properties and chemical properties, this material plays an irreplaceable role in many fields. 304 stainless steel strip also performs well. It is easy to machine and shape and can be processed through a variety of processes such as cutting, bending, and welding. Its moderate hardness allows for efficient cutting and drilling without damaging equipment.
Other 304 material shapes include bar, fitting, angle, tube, sheet, coil, etc.
Benefits of 304 Stainless Steel
- Corrosion resistance: AISI 304 contains 18% chromium and 8% nickel, which gives it excellent corrosion resistance against most chemical media, including acids, alkalis and salts.
- High-temperature resistance: AISI 304 has high-temperature resistance, can maintain structural stability and mechanical properties in high-temperature environments, suitable for use in high-temperature working conditions.
- Processability: AISI 304 is easy to process into a variety of shapes, including plates, tubes, profiles, etc. It can be shaped by cold working and hot working methods, and it is easy to weld, cut, and process into shape.
- Strength and toughness: AISI 304 has high strength and toughness at room temperature, and can withstand a certain degree of tensile, bending and impact loads, which ensures its reliability and safety in a variety of engineering applications.
- Surface finish: AISI 304 has a smooth and uniform surface, with excellent decorative and aesthetic properties, suitable for applications with high requirements for appearance.
- Antioxidant performance: AISI 304in the air surface forms a dense layer of oxide film, has good antioxidant properties, can effectively prevent metal oxidation and rust, and prolongs service life.
- Non-toxic and health and safety: AISI 304 material does not contain heavy metal elements that are harmful to the human body, in line with health and safety standards, it can be safely used in food processing, medical equipment and other fields.
- Environmental sustainability: AISI 304is a recyclable material, environmentally friendly, in line with the concept of sustainable development, and helps to reduce resource waste and environmental pollution.
304 Stainless Steel Used For
- Household products
- Auto parts
- Medical equipment
- Building materials
- Chemicals
- Food process
- Agriculture
- Ship parts
- Heat exchanger
304 vs 304L Stainless Steel
The key difference between 304 and 304L stainless steel is the carbon content, 304 contains max 0.08% carbon content while 304 has max 0.03%, generally, 304L is considered as low carbon as 304, other alloy elements are the same proportion, low carbon content gives 304L better property to resist corrosion, of course, there are slight differences in mechanical properties.
Type 304L is the low-carbon version of 304. It is used in heavy gauge components for improved weldability. Some products such as plates and pipes may be available as “dual certified” material that meets the criteria for both 304 and 304L, these items have chemical and mechanical properties complying with both 304 and 304L.
304 vs 316 Stainless Steel
Grade 304 is a basic austenitic stainless steel. It contains a high level of nickel and chromium, with chromium ranging from 18 to 20% by weight and nickel weighing in at between 8 and 10.5%. Grade 304’s other alloying elements include silicon and manganese with iron comprising the remaining chemical composition.
316 stainless steel has the same material composition as 304 stainless steel. However, in addition to high amounts of chromium and nickel, it also holds silicon, carbon, and manganese, with a huge portion comprising iron. Grade 316 stainless steel has a denser chemical composition. It holds a significant amount of molybdenum of about 2-3% in weight compared to the traces found in 304. The higher molybdenum in 316 results in higher corrosion resistance than in 304. 316 stainless steel does well in salty water, making it ideal for marine applications.
304 and 316 stainless steel are the first and second most used stainless steel grades respectively, they naturally draw comparisons, but they are different. It is not easy to judge which grade is better, it depends on some conditions, such as cost, application, and lifetime.
FAQ
316 is more expensive due to more Molybdenum and Nickel content added, generally, the price of 316 material is about USD 1450 per tonne higher than that of 304 material, in the market, the price difference between products made of 316, such as plates, tubes and bars, reflects this price difference.
304 stainless steel is relatively soft compared to some 400 series grades, which are more suitable materials for knives, like 410, 420, and 430, and lower cost.
304 stainless steel possesses excellent properties in corrosion and heat resistance, it is unsuitable material as a cutting tool material. In the selection of knife materials, we prefer to choose those with high hardness, good wear resistance and excellent impact resistance, such as some specialized tool steel or high-performance alloys, to ensure sharpness, durability, and reliability.
Although 304 stainless steel has overall excellent corrosion resistance, however, 304 stainless steel is not recommended to use in salt water or marine use, it will not withstand corrosion for very long and rust very quickly, 316/316 or 2205 grade is the better choice.
304 stainless steel will not rust under normal circumstances but may rust under certain conditions. 304 stainless steel is a commonly used stainless steel material with excellent corrosion resistance and good machinability. At room temperature, it has good corrosion resistance to oxidants, water vapor and a wide range of chemical media such as acids and alkalis. However, in certain environments, such as high humidity, high salinity, or environments containing corrosive chemicals, 304 stainless steel may corrode and rust. In addition, if there are scratches, grooves, or other mechanical damage on the surface and it is not repaired or protected in time, it may also lead to rusting. Especially in coastal areas or areas with poor water quality, the surface of 304 stainless steel may appear floating rust or mold spots, and so on. Therefore, to avoid the rust problem of 304 stainless steel, it should try to avoid contact with corrosive chemicals, high temperature, high humidity environments, and factors that may cause surface damage, and at the same time, pay attention to the maintenance and timely cleaning of surface stains in the process of use. Although 304 stainless steel will not rust under normal conditions, it may rust under specific conditions. Therefore, it is very important to use and maintain 304 stainless steel products correctly to extend their service life.
304 stainless steel is considered a food-grade stainless steel material, 304 stainless steel has good corrosion resistance in most common food and beverage environments and can resist corrosive substances such as acids, alkalis, and salts in food. It is Non-toxic and a low lead and cadmium material that contains very small amounts of harmful metallic substances, this makes it compliant with food safety requirements as it does not release toxic substances when in contact with food. 304 stainless steel has a smooth surface, no holes, and is not easy to adhere to bacteria, dirt and other substances, making it easy to clean and hygienically maintain. This makes it widely used in food processing equipment, kitchen utensils and other fields.
Related References
- ASTM A240/ASME SB240, Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
- ASTM A480, Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip
- EN 10088-2, Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion-resisting steels for general purposes
- EN 10088-3, Stainless steels. Technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products of corrosion-resisting steels for general purposes
- EN 10088-4, Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion-resisting steels for construction purposes
- EN 10088-5, Stainless steels. Technical delivery conditions for bars, rods, wire, sections and bright products of corrosion-resisting steels for construction purposes
- ASTM A249, Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes
- ASTM A213, Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes
- ASTM A312, Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes
- ASTM A276, Standard Specification for Stainless Steel Bars and Shape
- World Stainless