There are many volatile factors in stainless steel that represent the characteristics of corrosive media, namely, chemicals and their concentration, atmospheric state, temperature, and time. Therefore, if you do not understand the correct properties of the media, it is difficult to use and select materials. The following is a brief introduction to several common stainless steel materials:

Type 304 is a widely used material. "In buildings, it can withstand general corrosion, resist corrosion by food processing media (but corrosion may occur at high temperatures containing concentrated acids and chlorides), and resist organic compounds, dyes, and a wide variety of inorganic compounds.". Type 304L (low carbon), with good resistance to nitrate and acid, and durability for sulfuric acid at medium temperatures and concentrations, is widely used as liquid gas storage tanks, low-temperature equipment (304N), appliances, and other consumer products, kitchen equipment, hospital equipment, transportation tools, and wastewater treatment devices.

Type 316 contains slightly more nickel than type 304, and contains 2% to 3% molybdenum. It has better corrosion resistance than type 304, especially in chloride media that tend to initiate corrosion. The Type 316 has been developed as a sulfite pulp machine because it is durable with sulfuric acid compounds. Moreover, its use has expanded to handle many chemicals in the processing industry.

Type 317 contains 3% to 4% molybdenum (also a higher level obtained in this series), and contains more chromium than Type 316, providing higher resistance to spot and crack corrosion.

"Type 430 has a lower alloy content than Type 304, and is used for high polish decorative purposes in mild atmospheres. It can also be used as nitric acid and food processing equipment.".

Type 410 has the lowest alloy content among the three general purpose stainless steels, and is selected for high load-bearing components that require a combination of strength and corrosion resistance, such as fasteners. Type 410 is resistant to corrosion in mild atmospheres, water vapor, and many mild chemical product media.

The 2205 type is superior to the 304 and 316 types because it has a high resistance to chloride stress corrosion cracking and has approximately twice the strength.

Differences in hardness HB, HR, and HV of stainless steel

1、 Introduction to hardness:

Hardness indicates the ability of a material to resist hard objects pressing into its surface. It is one of the important performance indicators of metal materials. Generally, the higher the hardness, the better the wear resistance. The commonly used hardness indicators include Brinell hardness, Rockwell hardness, and Vickers hardness.

1. Brinell hardness (HB) Press a hardened steel ball of a certain size (typically 10 mm in diameter) into the surface of the material under a certain load (typically 3000 kg), maintain it for a period of time, and after unloading, the ratio of the load to the indentation area is the Brinell hardness value (HB), in kilogram force/mm2 (N/mm2).

2. Rockwell hardness (HR) When HB>450 or the sample is too small, the Brinell hardness test cannot be used instead of Rockwell hardness measurement. It uses a diamond cone with a tip angle of 120 ° or a steel ball with a diameter of 1.59 or 3.18 mm to press into the surface of the material under test under a certain load, and calculates the hardness of the material from the depth of the indentation.

According to the hardness of the test material, there are three different scales to represent:

HRA: The hardness obtained using a 60 kg load and a diamond cone press is used for materials with extremely high hardness (such as cemented carbide).

HRB: The hardness obtained using a 100kg load and a 1.58mm diameter hardened steel ball is used for materials with lower hardness (such as annealed steel, cast iron, etc.).

HRC: The hardness obtained using a 150kg load and a diamond cone press is used for materials with high hardness (such as hardened steel, etc.).

3. The Vickers hardness (HV) value (kgf/mm2) is obtained by dividing the surface product of the indentation pits in the material by the load value, using a diamond square cone indenter with a tip angle of 136 ° and a load within 120 kg.