The ability of a metal material to resist indentation by a hard object is called hardness. According to different test methods and application ranges, the hardness standards of sanitary stainless steel precision tubes can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness and microhardness.
1. What are the characteristics of high hardness pipes of sanitary stainless steel precision pipes?
Quenching, tempering and annealing can be used for high hardness pipes. As hardness increases, tensile strength and yield strength increase, while elongation, cross-sectional shrinkage, and impact energy decrease. In addition, the corrosion resistance of high-hardness pipes mainly depends on the chromium content, and the carbon in the steel indirectly affects the corrosion resistance of the steel due to the formation of stable chromium carbide with chromium. Therefore, the lower the carbon content, the higher the corrosion resistance, and the order of corrosion resistance and strength is reversed. Therefore, when processing high-hardness products, in order to improve the strength and hardness of sanitary stainless steel precision tubes, the carbon content will increase, resulting in reduced product plasticity and corrosion resistance. Therefore, the corrosion resistance of products processed from sanitary stainless steel precision tubes is poor.
2. What is high hardness stainless steel material?
High hardness stainless steel materials are usually martensitic stainless steel and precipitation hardening stainless steel. Standard martensitic stainless steels are: 410, 414, 416, 416(SE), 420, 431, 440A, 440b and 440C, which are magnetic. Type 440 can obtain high yield strength after proper heat treatment, and its hardness can reach 58hrc, which is one of the hardest stainless steels. Typical materials for precipitation hardening stainless steels include 0Cr17Ni4Cu4Nb, 0Cr17Ni 7Al, and 0cr15ni25ti2movb. After treatment, precipitation hardening steel can also reach about 40HRC.
3. What processes can be used to improve the hardness of sanitary stainless steel precision tubes?
In order to improve the hardness of ordinary stainless steel, the following three process methods can be used: quenching, carburizing and nitriding. Without changing the material, the hardness is usually increased by methods such as technology.
The purpose of quenching is to make supercooled austenite undergo martensite or bainite transformation to obtain martensite or bainite structure, and then temper at different temperatures to greatly improve the stiffness, hardness and wear resistance of steel , fatigue strength and toughness.
Carburizing is the process of infiltrating carbon atoms into the surface layer of steel. The surface layer of the low carbon steel workpiece is also made to have the surface layer of the high carbon steel. After quenching and low temperature tempering, the surface layer of the workpiece has high hardness and wear resistance, while the central part of the workpiece still maintains the toughness and plasticity of low carbon steel.
Nitriding is a chemical heat treatment process in which nitrogen atoms penetrate into the surface layer of the workpiece in a certain medium at a certain temperature. On the one hand, the nitrogen infiltrating the steel forms iron nitrides with different nitrogen contents from the outside to the inside. On the other hand, it combines with alloying elements in steel to form various alloying nitrides, especially aluminum nitride and chromium nitride. These nitrides have high hardness, thermal stability and high dispersibility, therefore, nitrided steel parts can obtain high surface hardness, wear resistance, fatigue strength, seizure resistance, atmospheric and superheated steam corrosion resistance, temper softening resistance susceptibility and reduced notch sensitivity.
