304 is a general-purpose stainless steel, which is widely used in the production of equipment and parts that require good overall performance (corrosion resistance and formability). In order 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。

Product Standards

For 304 stainless steel, the Ni element in its composition is very important, which directly determines the corrosion resistance and value of 304 stainless steel.

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 situation 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 as 304 stainless steel. This is why the industry calls this type of stainless steel 18/8 stainless steel. In fact, the relevant product standards have very clear regulations on 304, and these product standards have some differences for different shapes of stainless steel. Below are some common product standards and tests.

To determine whether a material is 304 stainless steel, it must meet the requirements of each element in the product standard. As long as one of them does not meet the requirements, it cannot be called 304 stainless steel.

ASTM A276 (Standard Specification for Stainless Steel Bars and Shapes)

ASTM A240(Chromium and Chromium-Nickel Stainless Steel Plate,Sheet, and Strip for Pressure essels and for General Applications)

JIS G4305 (cold-rolled stainless steel plate, sheet and strip)

The above four standards are just a few common standards. In fact, there are more than these standards mentioned in ASTM and JIS. Each standard actually has different requirements for 304, so if you want to determine whether a material is 304, the accurate expression should say whether it meets the 304 requirements in a certain product standard.

Application range

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; it has good hot workability such as stamping and bending. , no heat treatment hardening phenomenon (use temperature -196 ℃ ~ 800 ℃). Corrosion-resistant in the atmosphere, if it is an industrial atmosphere or a 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, corrugated pipes, household products (category 1 and 2 tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs), auto parts (windshield wipers, mufflers, molded products), medical appliances, building materials, chemistry, 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 use requirements are to maintain the original appearance of the building for a long time. When determining the type of stainless steel to be selected, the main considerations are the required aesthetic standards, the corrosiveness of the local atmosphere, and the cleaning system to be adopted. Increasingly, however, other applications simply seek structural integrity or impermeability. For example, roofs and side walls of industrial buildings. In these applications, the owner's cost of construction may be more important than aesthetics, and the surface is not very clean. The effect of using 304 stainless steel in a dry indoor environment is quite good. However, to maintain its appearance outdoors in both the country and the city, frequent washing is required. In heavily polluted industrial areas and coastal areas, the surface will be very dirty and even rusted.