Stainless Steel 304

Stainless Steel 304 is one of the most common stainless steel materials, with a density of 7.93 g/cm³. It is also known in the industry as 18/8 stainless steel, indicating a composition of ≥18% chromium (Cr) and ≥8% nickel (Ni). Due to its higher nickel content compared to chromium-based steels, it offers superior corrosion and heat resistance, along with excellent physical properties such as: High-temperature resistance (up to 800°C), Excellent workability (easy to machine and form), and high toughness. It is widely used to manufacture equipment and mechanical components that require good comprehensive performance (corrosion resistance and formability), and is commonly applied in industries such as industry, furniture decoration, and food and medical sectors.

Physical Properties

Surface Treatment

● Brushing

● Bead Blasting

● Powder Coating

● Silkscreen

● Laser Marking

Applications

Stainless steel 304 is the most widely used chromium-nickel stainless steel. As a versatile grade, it offers excellent corrosion resistance, heat resistance, low-temperature strength, and mechanical properties. It has good hot workability such as stamping and bending, shows no heat treatment hardening (service temperature: -196℃ to 800℃), and provides good processing performance and weldability.

Suitable for food processing, storage, and transportation. Applications include plate heat exchangers, bellows, household products (class 1 and 2 tableware, cabinets, indoor piping, water heaters, boilers, bathtubs), automotive parts (windshield wipers, mufflers, molded components), medical instruments, building materials, chemical industry, food industry, agriculture, and ship components. Stainless steel 304 with a strictly controlled composition can also be referred to as food-grade 304 stainless steel.

Reasons for The Rusting of Stainless Steel 304

The occurrence of rust on stainless steel 304 may be due to the following reasons:

Chloride ions

Chloride ions are widely present, such as in table salt, sweat, seawater, sea breeze, soil, and so on. Stainless steel corrodes rapidly in environments containing chloride ions, sometimes even more quickly than ordinary low-carbon steel. Therefore, stainless steel requires specific usage environments and needs to be wiped regularly to remove dust and keep it clean and dry.

Solution treatment

The alloying elements have not dissolved into the matrix, resulting in a low alloy content in the matrix and poor corrosion resistance.

Intergranular corrosion

This material, which does not contain titanium or niobium, tends to suffer from intergranular corrosion. The addition of titanium and niobium, combined with stabilization treatment, can reduce intergranular corrosion. Stainless steel is a high-alloy steel that can resist corrosion in air or chemical corrosive media. It has an attractive surface and good corrosion resistance, without requiring additional surface treatments such as plating, allowing its inherent surface properties to be fully utilized. Common examples include 13% chromium steel and 18-8 chromium-nickel steel, among other high-alloy steels.

From a metallurgical perspective, the chromium in stainless steel forms a very thin chromium oxide film on the surface, which acts as a barrier against oxygen penetration from the steel and provides corrosion resistance. To maintain the inherent corrosion resistance of stainless steel, the steel must contain more than 12% chromium. For applications requiring welding, a lower carbon content minimizes the formation of carbides in the heat-affected zone near the weld. The precipitation of carbides can lead to intergranular corrosion (weld decay) in certain environments.

Surface Marks

Surface marks refer to linear or dot-like indentation defects that appear on the surface of stainless steel 304 after deep processing or grinding of the product.

Cause: Foreign particles on the surface or mold surface, and scratches on the edge pressing pad.

Countermeasure: Remove foreign particles and scratches before processing, and orange peel can also be eliminated through thorough grinding.

Orange peel refers to the phenomenon where the surface of stainless steel 304 formed products develops a texture resembling the surface of an orange, occurring during grinding or other processes.

Causes: Insufficient grinding, with more severe orange peel occurring during greater processing; coarse-grained raw materials; and softening due to heat treatment.

Countermeasures: Thoroughly grind deep-processed products, select appropriate heat treatment conditions, and control the grain size of the raw materials.