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A comprehensive presentation on stainless

I. Introduction to stainless steel

basic knowledge of 1  stainless steel

definition: stainless steel is in the air, water, acids, alkalis and salt solutions, or other corrosive chemical stability of steel in General.


                            &Nbsp;              ? weak medium such as air, steam and water corrosion resistant steel known as stainless steel;  

? to acid, alkali and salt and other corrosive medium corrosion of steel corrosion of steel or acid-proof steel.

history of 1.2   found

? 100 years ago (1904-1906) French Jiyeh (L.B.Guillet) first of Fe-Cr-Ni alloy metallurgical and mechanical properties of the groundbreaking basic research;  ?1907-1911 years, the French Portevin (A.M.Portevin) and the British Giessen (W.Giesen) were discovered Fe-Cr and Fe-Cr-Ni alloys corrosion resistance;  ? 1908-1911 German mengnaerci (P.Monnartz) revealed the principles of corrosion resistance of steel and put forward the concept of passivation.

1.4  principles of corrosion resistance of stainless steel

chromium oxide film on the surface.  

Cr  reacts with O2  in the air of chromium oxide layer that is "passive film", so that the steel body protected.

1.5 stainless steel alloying elements in  

Cr: in oxidizing medium, 100 √• Cr2O3 film formed on the surface, > antioxidant ability   of 12% more than film;

Ni: expansion of austenitic, improve abrasion resistance, high temperature toughness improvement of mechanical properties and weldability of  

c: low, or chromium carbide at grain boundary precipitates down   corrosion resistance;

Ti:TiC elimination of intergranular corrosion of austenitic            

Nb:[Ti]= ([C%]-0.02%) X5 (Ti<0.8%) the saturated solubility of 0.02%---C in steel

classification of 1.6  stainless steel

  elements impact on organizations:  

            expansion of ferritic element:  Cr, Mo, Si, Nb, Ti,... 

            expanded austenite element  :  C, N, Ni,Mn,Cu,... 

stainless steel 5:  

?  austenitic,  austenite;

?  ferritic,  iron;

?  bipolar  duplex (ferritic-austenitic)  

?  Martensitic  Martensitic 

? precipitation harden, precipitation hardening


2.  austenitic stainless steel

? 200 series  

? 300 series  

200 series stainless steel high performance:

? (1) replace carbon with nitrogen and stable austenitic, increased strength and improved corrosion resistance, such as 204,211,216; 

? (2) appropriate to add elements of Mo, Nb, improving resistance to pitting, intergranular corrosion and stress corrosion resistance properties, such as 216,223; 

? (3) copper steels cold work hardening rate, improved cold upsetting and cold forming properties, such as 204Cu,211,223. United States metallurgist, a member of ASTM yuehan·maijie, 204Cu instead of 304 study particularly encouraging.

300-series stainless steel:

?304  is a universal stainless steel, which is widely used to produce good overall performance requirements (corrosion resistance and formability) of equipment and parts.  

?301  stainless steel in the deformation process was clearly showed when hardening, high strength for a variety of occasions.  

?302  stainless steel is essentially high carbon content 304 stainless steel variants, by cold rolling to give it more strength.  

?302B  is a stainless steel with high silicon content, it has a higher resistance to high temperature oxidation.  

? 303 and 303Se  free cutting stainless steel containing sulfur and selenium are respectively used to light primarily require cutting and sheet-Ho high occasions. 303Se stainless steel is also used for making hot upsetting parts, because in such conditions, which has good thermal processing of stainless steel.  

?304L  is a variant of 304 stainless steel with low carbon content, used for welding applications. Lower carbon content makes it near the carbide precipitation in weld heat-affected zone to a minimum, and carbides can cause stainless steel intergranular corrosion in some environments (welding erosion).  

 ?304N  is a stainless steel containing nitrogen, nitrogen-enriched is to enhance the strength of steel.  

? 384  and 305 stainless steel containing high levels of nickel, its low rate of work hardening, suitable for various occasions which require high cold formability.  

?308  stainless steel for the production of welding electrodes.  

? 309, 310, 314 and 330  of stainless steel nickel and chromium content is relatively high, in order to increase the oxidation resistance at high temperature and creep strength. And 30S5 and 310S is 309 and 310 varieties of stainless steel, the difference is lower carbon content, so that the carbide precipitation near the weld to a minimum. 330 stainless steel has a particularly high degree of carburization resistance and thermal shock resistance.  

? 317  and 316 stainless steel with aluminum, marine and chemical environments of greatly superior 304 stainless steel corrosion resistance. Type 316 stainless steel variant by including low-carbon stainless steel 316L, nitrogen-containing high-strength stainless steel 316N and high sulphur free cutting stainless steel 316F.  

321, 347 and 348  respectively of titanium, niobium and tantalum, niobium stabilized steel components suitable for use at high temperatures. 348 is suitable for the nuclear power industry of stainless steel, tantalum has some limitations with the drill.  

3. ferritic stainless steel  

using predominantly State by ferrite stainless steel.  

  chromium content in 11%~30%, has a body-centered cubic crystal structure. This type of steel without nickel, sometimes containing a small amount of Mo, Ti, Nb until element, this type of steel with thermal conductivity, expansion coefficient and resistance to oxidation of good and excellent resistance to stress corrosion characteristics, used in the manufacture of air resistance, water vapour, water and oxidation of acid corrosion of parts. Like OCr13, 1Cr17, 1Cr25, 1Cr28, OCr17Ti, 1Cr25Ti etc, are property of ferritic stainless steel.  

      This type of steel is insensitive to thermal fatigue, working under the high temperature of the workpiece can be made.  

      This type of steel plastic difference, decrease in ductility and resistance to corrosion after welding and other disadvantages, thus limiting its application. Refining technology (AOD or VOD) application of gap elements such as carbon, nitrogen can be greatly reduced, thus making this type of steel is widely used.  

4.  of martensite stainless steel


? martensite stainless steel in high temperature condition as Dan Xiangao cementite can get martensite after quenching, with high strength and high hardness, mechanical properties of steel can be adjusted by heat treatment.  

?   of martensite stainless steel with moderate levels of rust.  

in?  steel with chromium content of 12~19%, 0.1~0.45% carbon content, individual carbon content in steels up to 1%. Common types are 2~4Cr13, 9Cr18, etc.  

?  Martensitic stainless steel for strength, hardness, wear resistance and cutting performance is significantly improved. Used to produce mechanical properties of high corrosion resistance of the workpiece (such as resistance to atmospheric corrosion, seawater, water vapour) widely used in tools, brakes, bearings, turbine blades, structural and wear-resistant appliances.  

5.  precipitation hardening stainless steel  

  It was developed on the basis of austenitic chromium-nickel stainless steel. As ratio of nickel, chromium, and other elements properly quenched with austenite and cold workability excellent, easy rolling gang Strip and foil, in sub-zero temperatures after cold treatment and transformed into martensite, so the steel strength can be significantly improved. The steel due to the presence of precipitation hardening effect of Mo, Cu  , Al, b elements, thus the strength can be further improved. Typical grades such as OCr17Ni4Cu4Nb (17-4PH), OCr15Ni25Ti2MoVB  , and 0Cr15Ni7Mo2Al (PH15-7Mo), OCr17Ni7Al (17-7PH) and so on. The chromium content of the steel near 17%, and contains elements such as nickel, molybdenum, therefore, in addition to sufficient stainless exterior, corrosion resistance is close to 18-8 type austenitic stainless steel. Due to the series of high-strength steel grades, can be used as a spring, washer requirements such as high strength, good elasticity of the workpiece.