A Brief Overview of the Main Applications of Several Common Stainless Steel Grades

Stainless steel is subject to numerous variables that characterize the corrosive environment—namely, the chemical agents and their concentrations, atmospheric conditions, temperature, and exposure time. Consequently, without a thorough understanding of the medium’s exact properties, selecting and specifying appropriate materials can be quite challenging. Below is a brief overview of several common types of stainless steel:

Type 304 A widely used material. In construction, it withstands ordinary corrosion and resists attack by food-processing media (though it may corrode under high‑temperature conditions in the presence of concentrated acids or chlorides). It also resists organic compounds, dyes, and a broad range of inorganic substances. Type 304L (low‑carbon) exhibits excellent resistance to nitric acid and is suitable for sulfuric acid at moderate temperatures and concentrations. It is extensively employed in liquid‑gas storage tanks, cryogenic equipment (304N), household appliances and other consumer products, kitchen equipment, hospital furnishings, transportation vehicles, and wastewater‑treatment systems.

Type 316 It contains slightly more nickel than Type 304 and 2%–3% molybdenum, offering superior corrosion resistance compared to Type 304, particularly in chloride environments prone to pitting. Type 316 has been developed for use in sulfite pulp mills due to its excellent resistance to sulfuric acid compounds. Moreover, its applications have expanded to include the handling of numerous chemical products in the processing industry.

Type 317 It contains 3%–4% molybdenum (also among the highest levels in this series) and a higher chromium content than Type 316, resulting in superior resistance to pitting and crevice corrosion.

Type 430 It has a lower alloy content than Type 304, and is used for highly polished decorative applications in mild atmospheric conditions; it can also be employed in nitric acid‑resistant and food‑processing equipment.

Type 410 Among the three commonly used grades of stainless steel, it has the lowest alloy content and is selected for high‑strength components that require both strength and corrosion resistance, such as fasteners. Grade 410 exhibits good corrosion resistance in mild atmospheric conditions, in humid environments, and in many moderately aggressive chemical media.

Type 2205 It is superior to grades 304 and 316, as it exhibits excellent resistance to chloride‑induced stress corrosion cracking and possesses roughly twice the strength.

The differences among HB, HR, and HV hardness values for stainless steel

I. Introduction to Hardness:

Hardness refers to a material’s ability to resist the penetration of a harder object into its surface. It is one of the key mechanical properties of metallic materials. Generally, the higher the hardness, the better the wear resistance. Commonly used hardness scales include Brinell hardness, Rockwell hardness, and Vickers hardness.

1. Brinell Hardness (HB) A hardened steel ball of a specified size (typically 10 mm in diameter) is pressed into the material’s surface under a fixed load (usually 3,000 kg), held for a certain period, and then removed. The Brinell hardness value (HB) is calculated as the ratio of the applied load to the area of the resulting indentation, expressed in kilogram-force per square millimeter (N/mm²). 2)。

2. Rockwell Hardness (HR) When the HB value exceeds 450 or the specimen is too small, the Brinell hardness test cannot be used and the Rockwell hardness test should be employed instead. This method involves pressing a diamond cone with a vertex angle of 120° or a steel ball with a diameter of 1.59 mm or 3.18 mm into the surface of the material under a specified load, and determining the material’s hardness from the depth of the resulting indentation.

Depending on the hardness of the test material, three different scales are used for representation:

HRA ： It is a hardness value obtained using a 60 kg load and a diamond indenter, intended for extremely hard materials such as cemented carbides.

HRB: It is the hardness determined using a 100 kg load and a 1.58 mm diameter hardened steel ball, and is used for materials with relatively low hardness, such as annealed steel and cast iron.

HRC: It is a hardness value obtained using a 150 kg load and a diamond indenter, intended for very hard materials such as quenched steel.

3. Vickers Hardness (HV) A diamond square pyramid indenter with a vertex angle of 136° is used to indent the material surface under a load not exceeding 120 kg. The Vickers hardness HV value (in kgf/mm²) is obtained by dividing the area of the indentation by the applied load. 2)。