304 stainless steel is a common material in stainless steel, with a density of 7.93 g/cm³; it is also called 18/8 stainless steel in the industry, meaning it contains more than 18% chromium and more than 8% nickel; high-temperature resistance of 800 ℃, with good processing performance, With the characteristics of high toughness, it is widely used in industry and furniture decoration industry and food and medical industry. However, it should be noted that food-grade 304 stainless steel has stricter content indicators than ordinary 304 stainless steel. For example, the international definition of 304 stainless steel is 18%-20% of chromium and 8%-10% of nickel, but food-grade 304 stainless steel is 18% of chromium and 8% of nickel, which is allowed to fluctuate within a certain range, and the Limit the content of various heavy metals. In other words, 304 stainless steel is not necessarily food grade 304 stainless steel.
Common labeling methods on the market include 06Cr19Ni10 and SUS304, of which 06Cr19Ni10 generally means national standard production, 304 generally means ASTM standard production, and SUS 304 means Japanese standard production.
304 is general-purpose stainless steel that is widely used to make equipment and parts that require a good combination of properties (corrosion resistance and formability). To maintain the inherent corrosion resistance of stainless steel, the steel must contain more than 18% chromium and more than 8% nickel. 304 stainless steel is a grade of stainless steel produced according to the American ASTM standard.
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Physical properties
Tensile strength: σb (MPa)≥515-1035
Conditional yield strength: σ0.2 (MPa)≥205
Elongation: δ5 (%)≥40
Area shrinkage: ψ (%)≥?
Hardness: ≤201HBW;≤92HRB;≤210HV
Density: (20℃, g/cm³): 7.93
Melting point: (℃): 1398~1454
Specific heat capacity: (0~100℃, KJ·kg-1K-1): 0.50
Thermal conductivity: (W·m-1·K-1): (100℃) 16.3, (500℃) 21.5
Linear expansion coefficient: (10-6·K-1): (0~100℃) 17.2, (0~500℃) 18.4
Resistivity: (20℃, 10-6Ω·m2/m): 0.73
Longitudinal elastic modulus: (20℃, KN/mm2): 193
Product Standards
For 304 stainless steel, the Ni element in its composition is very important, which directly determines the corrosion resistance of 304 stainless steel and its value.
The most important elements in 304 are Ni and Cr, but they are not limited to these two elements. Specific requirements are specified by product standards. The common judgment in the industry is that as long as the Ni content is greater than 8% and the Cr content is greater than 18%, it can be considered 304 stainless steel. This is why the industry calls this type of stainless steel 18/8 stainless steel. The relevant product standards have very clear regulations for 304, and these product standards have some differences for different shapes of stainless steel.
ASTM A276, ASTM A240, JIS G4305, and JIS G4303 are several common standards. ASTM and JIS mention more than 304 standards. Each standard has different requirements for 304, so to determine whether a material is 304, the accurate expression should be whether it meets the 304 requirements in a product standard.
Scope of application
System description: 304 stainless steel is the most widely used chromium-nickel stainless steel. As a widely used steel, it has good corrosion resistance, heat resistance, low-temperature strength, and mechanical properties; good hot workability such as stamping and bending, and No heat treatment hardening phenomenon (use temperature -196 ℃ ~ 800 ℃). Corrosion resistance in the atmosphere, if it is an industrial atmosphere or heavily polluted area, it needs to be cleaned in time to avoid corrosion. Suitable for food processing, storage, and transportation. Has good processability and weldability. Plate heat exchangers, bellows, household products (Class 1 and 2 tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs), auto parts (windshield wipers, mufflers, molded products), medical appliances, building materials, chemicals, food industry, agriculture, ship parts, etc. The 304 stainless steel whose content is strictly controlled can also be called food grade 304 stainless steel.
Most of the usage requirements are to maintain the original appearance of the building for a long time. When determining the type of stainless steel to choose, the main considerations are the required aesthetic standards, the corrosiveness of the local atmosphere, and the cleaning system to be used. However, other applications increasingly seek only structural integrity or water impermeability. For example, roofs and side walls of industrial buildings. In these applications, the owner’s construction cost may be more important than aesthetics, and the surface is not very clean. 304 stainless steel works reasonably well in dry indoor environments. However, to maintain its appearance outdoors in rural and urban areas, frequent cleaning is required. In heavily polluted industrial and coastal areas, the surface can be very dirty and even rust.
However, for an aesthetic effect in an outdoor environment, nickel-containing stainless steel is required. Therefore, 304 stainless steel is widely used in curtain walls, side walls, roofs, and other construction purposes, but in severely corrosive industrial or marine atmospheres, 316 stainless steel is preferred. Stainless steel sliding doors, people have fully realized the advantages of using stainless steel in structural applications. 304 and 316 stainless steels are included in several design guidelines. Because the “duplex” stainless steel 2205 combines good atmospheric corrosion resistance with high tensile and elastic strengths, this steel is also included in European guidelines. Product Shapes Stainless steel is actually manufactured in a full range of standard metal shapes and sizes, and many special shapes are also available. The most commonly used products are made from sheets and strips, but also special products are produced from medium and heavy plates, for example, in the production of hot-rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular, and hexagonal welded or seamless pipes and other forms, including profiles, bars, wires, and castings.
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