Stainless steel classification

Stainless steel is a high alloy steel material, containing a variety of alloying elements. According to the different structures, stainless steel can be divided into the Austenitic system, ferritin system, Martensite system, biphasic system, and precipitation hardening system, and other types.

Austenitic stainless steel

The market is used more austenitic stainless steel, commonly known as 304,304 is the representative of austenitic stainless steel. Austenitic stainless steel system processing, welding, and corrosion resistance are superior, accounting for the world consumption of stainless steel about 60%, very economical value, and use value, this stainless steel is not magnetic. The representative steel of the Austenitic stainless steel system is SUS304 (18CR-8NI-0.05C). SUS304 is also the most widely used stainless steel. The crystal structure is FCC (face-centered cubic), and the elongation is about 60% due to the formation of machined martensite.

In the daily living environment, it has sufficient corrosion resistance, but in order to further improve the corrosion resistance, most of Mo is added, the biggest disadvantage is that it is easy to produce stress corrosion cracks. By increasing or decreasing the content of Ni, martensite formation can be controlled and induced by processing. There are also steel types such as SUS301 (17CR-7Ni) with both high strength and high toughness. In order to reduce the C content to about 0.02%, L-type steels such as SUS304L and SUS316L were developed in order to suppress the intergranular corrosion at the welding site. In addition, in recent years, the high price of Ni raw materials, so the cost increased. Therefore, the utilization of 200 series SUS201 (17CR-4.5Ni-6.5MN-0.2N) replacing Ni with Mn and the development of high corrosion resistance iron system SUS and other resource-saving stainless steels were carried out. This 200 series is also austenitic stainless steel, also non-magnetic.

Ferritic stainless steel

And another kind more used is ferritic stainless steel, representative ferritic stainless steel system is SUS430 (16CR-0.05C), which is magnetic stainless steel, sometimes known as "stainless iron", although this stainless steel with magnetic, does not represent rust. In order to improve corrosion resistance, workability, and weldability, many kinds of ferritic stainless steels have been developed. This kind of steel basically does not contain Ni, so the price is relatively cheap, as ordinary stainless steel is widely used. Industrial production of stainless steel Cr content of 11%-30%. SUS430 exhibits a biphasic structure of α phase (ferritic phase) and γ phase (austenitic phase) in the high-temperature region of the hot rolling process. In the cold rolling annealing process, the heat treatment of the α single phase region is carried out, and the structure is ferritic single phase. Also can be through high Creation and low C, high temperature γ phase does not, in the full temperature region for α single-phase structure. The crystal structure is BCC with an elongation of about 30%. The important R-value of deep flushing is high. In order to improve the processability, low C and N (high purity) and Ti and Nb (stabilization) elements were added. Adding Ti and Nb is also effective for improving weldability. Ferrite stainless steel is used in construction, the most common in handrails, escalators, railings, etc., for eye-catching, there is also such non-corrosion steel marked with the word "304", that is false stainless steel.

Martensite system, biphasic system and precipitate hardening system and other types of stainless steel or with a slight magnetic, ferrite in the tissue, the magnetic larger.

Stainless steel pipe application

Stainless steel pipe is an economical section of steel and an essential product in the steel industry. It can be widely used in life decoration and industry. Many people in the market use it to make stair handrails, window guards, railings, furniture, etc. Two common materials are 201 and 304. It accounts for about 8% to 16% of the total amount of steel, and it is widely used in the national economy. Because the steel pipe has a hollow section, it is most suitable for conveying liquids, gases, and solids; at the same time, compared with round steel of the same weight, the steel pipe has a large section coefficient and high flexural and torsional strength, so it has become a variety of mechanical and architectural structures. important material. Structures and components made of stainless steel tubing have a greater section modulus than solid components for the same weight. Therefore, stainless steel pipe itself is economical section steel that saves metal. It is an important part of high-efficiency steel, especially in oil drilling, smelting, and transportation industries. Industry, aircraft and automobile manufacturing, boilers, medical equipment, furniture, and bicycle manufacturing, also require large quantities of various steel pipes. With the development of new technologies such as atomic energy, rockets, missiles, and aerospace industries, stainless steel pipes play an increasingly important role in the defense industry, science and technology, and economical construction.