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22/02/2016 17:31

Inox screw bolts are used in many different applications, but really shown their value in environments where corrosion is of primary concern. bolts screws with screws are varied in type, size, features high corrosion resistance is used mainly in the fields of chemical industry, automobile, ship, petroleum, machinery and equipment now.


 Stainless steel is resistant to oxidation and corrosion is very high, but the choice of the right type and their specifications to fit into each specific case is very important.
Resistant to oxidation from the surrounding air temperature of stainless steel typically is due to the ratio of chromium present in the alloy (minimum of 13% and up to 26% in the case of work in harsh working environments). Oxidized state of chromium oxide of chromium is commonly (III). When chromium alloy steel in contact with air is a very thin layer of chromium oxide III appeared on the surface of the material; This thin layer that can not be seen with the naked eye, which means that the metal surface is still shiny. However, they absolutely do not react with water and air protection should be below grade steel. This phenomenon is called oxidation engineered stainless material. Can see this phenomenon for some other metals such as aluminum and zinc in.
There are four main types of stainless steel: austenitic, ferritic, austenitic-ferritic (duplex), and martensitic.
- Austenitic stainless steel is the most common. Under this line may include the steel grade SUS 301, 304, 304L, 316, 316L, 321, 310S ... this type containing a minimum 7% nickel, 16% chromium, carbon (C) 12:08% max. Such components created for this steel has high corrosion resistance in a wide temperature range rather, not magnetized, flexible, pliable, easy to weld. This steel is used to make many household items, tanks, industrial pipes, industrial ships, exterior architecture, construction works ...
- Ferritic stainless steel is the physical properties similar to mild steel, but potentially higher corrosion resistance of mild steel (low carbon steel). Under this line may include the steel grade SUS 430, 410, 409 ... this type containing approximately 12% - 17% chromium. This category, with 12% Cr more often in architectural applications. Type containing approximately 17% chromium is used for household appliances, boilers, washing machines, the architecture of the house ...
- Austenitic-ferritic (duplex) steel This type nature "in the middle" ferritic and austenitic type collectively called DUPLEX. Under this line may include LDX 2101, SAF 2304, 2205, 253MA. Duplex steel contains less than Ni austenitic type. DUPLEX with typical characteristics are high strength and durability flexibility widely used in petrochemical industry, paper, pulp, manufactured marine vessels ... Given the escalating price of stainless steel due to the scarcity of nickel DUPLEX lines are increasingly more applications to substitute for some grades of austenitic steels such as SUS line 304, 304L, 316, 316L, 310S ...
- Martensitic this type contains about 11% to 13% Cr, bearing strength and hardness, corrosion resistance relative degree. Widely used to manufacture turbine blades, blades ...
Table chemical composition of stainless steel:

Mechanical table features:​



(1) SUS201: A type of low nickel content steel, cold-worked after magnetic, can be used as a substitute for SUS301. Bolts, screws of this type can be used in normal conditions, such as rain and car exhaust, corrosive environment of low, however, this type is less likely to withstand solvents or chemicals. This category has the lowest cost compared to other stainless steel grades
(2) SUS202: This type of high-strength, corrosion-resistant. Suitable as components in cameras, computers & office machines.
(3) SUS304: stainless steel type with low carbon and high chromium, compared with 302 the features better corrosion resistance, stainless steel is often used to produce 304 Bolts Hexagon, production of nuts and processing as well as the method of cold stamping processing, hot stamping method to do these kinds of large diameter and bolt length. Better chemical resistance are not as hard as 201 201, used in chemical plants and other industries where corrosion is a permanent concern
Like in the line of austenitic steels, the magnetic properties of 304 stainless steel is very weak and almost non-existent. But after working in an environment with low temperatures, the magnetism is very strong (this goes against the process I).
(4) SUS304L: There are more than 304 low-carbon and therefore lower bearing properties a bit. Low carbon content also increases corrosion resistance and weldability in 304L (L is the symbol for Low letters, in English means l Low)
(5) SUS304HC: suitable for use in cold-processed products, with high corrosion resistance. Typically used to produce all kinds Screw.
(6) SUS309 & 310: Nickel and Chromium There components higher than the lower grade steels, and is recommended for use in environments with high temperatures. 310 is also capable of salt corrosion resistance and other adverse environments.
(7) SUS316 & 317: corrosion resistant in sea water environment and superior chemical. They contain high levels of black lip-Mo-steels create tolerate taking better porous surfaces. These steels have higher tensile strength and excellent stability in high-temperature environments than other SUS304 alloy.
 (8) SUS316L: lower carbon loai There should SUS316 better corrosion resistance.
 (9) SUS410: There is a certain hardness higher than others, at higher temperatures it has the ability to withstand environmental and organic acid salts have low concentrations. This type is often used to produce all kinds Screws Self-cutters and corrugated stainless steel shot


According to those presented above, we can see the marks of their 4xx steel martensite and ferrite stainless steel, the steel grade 2xx and 3xx of austenite stainless steel. In theory, the original austenite steel group completely nonmagnetic (not magnet) but, according to the presentation above, austenite steel groups transformed sharply hard when cold plastic deformation due to the transition from austenite into deformation martensite (martensite phase which is magnetic). So, in fact, used magnets to distinguish the stainless steel grade, especially to distinguish the marks 2xx and 3xx, you can say is impossible. To distinguish the most accurate method can only analyze the chemical composition (but more expensive) or based on the method of identification according grinding sparks (dependent on experience).
Steel Group 4xx: because in the composition containing more Cr and Ni should hardly be formed when grinding rays and orange flowers with dark fire, end the shape of a flower blooming. Strongly magnetic than 2xx and 3xx marks
Steel Group 2xx: Partly Ni Mn should be replaced with the same thickness at the label if 3xx, breaking or bending when it feels harder. When grinding, beam bright orange, thick sparks, fire flowers much more wings (compared to 3xx)
Steel Group 3xx: When grinding, the beam with orange petals of little fire, sparks along with the flashing blip.
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