Organization of stainless steel metallographic and standard introduce, how much do you know?

Introductive
Stainless steel is to point to normally be in atmosphere, water, acerbity, alkaline wait for solution with salt or other the tall alloy steel that excellent chemical stability has in corroding medium. Basis GB/T 13304.2-2008[1] " the classification of steel " and on international current method, by metallographic arrangement distinguishs distinguish stainless steel it is 5 kinds, namely ferrite stainless steel, martensite stainless steel, austenite stainless steel, austenite - stainless steel of ferrite double photograph and deposit and sclerotic stainless steel. Stainless steel has function of crackajack corrosion resistance, oxidation not merely, still have outstanding mechanical function normally (like intensity, endurance) , physical function (magnetism function, stretch) with craft function (forging, forming, heat treatment, solder) , be in consequently chemical industry, motivation, mechanical, light industrial wait for a profession to get be used extensively.

1.The metallographic of of all kinds stainless steel is arranged
1.1 ferrite stainless steel
Matrix is arranged with the ferrite of structure of crystal of body heart cubic metre (α photograph) give priority to, have magnetism, cannot pass heat treatment sclerosis normally, but cold working makes his subtle the stainless steel of aggrandizement. Contain Cr: 11~30% , passable the Mo that contains minority, Nb, Ti, basically do not contain Ni, intensity is higher, be able to bear or endure chloride stress is corroded, the function such as dot corrode, crevice corrosion is outstanding, but corrode delicacy to crystal boundary, microtherm endurance is poorer. First steel grade has 06Cr13Al, 10Cr17, 10Cr17Mo, 008Cr27Mo, 008Cr30Mo2 to wait. 900 ℃ heat preservation shows classics of this kind of steel after air is cold small arrangement is: The carbide with dispersed direction of rolling of ferrite class edge; Heat via 1200 ℃ and after water temper by dipping in water show small arrangement to be δ ferrite + low carbon martensite.
1Cr17 steel heats to be direction of rolling of ferrite ＋ edge to the arrangement with the cold air after 900 ℃ dispersed carbide

The arrangement after 1Cr17 steel quenchs is martensite of ferrite ＋ low carbon
1.2 martensite stainless steel
Matrix is martensite arrangement, have magnetism, can adjust its through heat treatment the stainless steel of mechanical function. Martensite stainless steel is austenite in the arrangement of high temperature state, after the course quenchs, austenite change is martensite, friend call his martensite stainless steel. The steel grade that martensite stainless steel sees at most has 12Cr12, 20Cr13, 30Cr13, 40Cr13, they contain carbon the volume is higher, after quenching, get martensite is arranged; Have higher intensity, hardness, wearability; Classics overheat handles the function that attainable place requests; Cutting treatment function is better. Solder the function is poor.
10Cr13 quenchs temperature: 1050 ℃ of 1000 ℃ ～ , arrangement is ferrite of δ of martensite ＋ minority

10Cr13, temper of 650 ℃ , arrangement is ferrite of ＋ of body of family name of temper all alone
1.3 austenite stainless steel
Matrix is arranged with the austenite of structure of crystal of face heart cubic metre (γ photograph) give priority to, without magnetism, first course cold working makes the stainless steel of its aggrandizement. After austenite stainless steel contains Cr 16%~25% to contain Ni 7%~20% proper heat treatment normally, onefold A arrangement is below room temperature. The steel grade that sees more has 12Cr18Ni9, 06Cr18Ni11Ti, 06Cr19Ni10, 304(18-8) , 316 etc have crackajack plasticity, endurance and be able to bear or endure corrode sex, use very extensive.
304, arrangement is onefold austenite
1.4 austenite - stainless steel of ferrite double photograph
Matrix holds austenite and ferrite two-phase arrangement concurrently, have magnetism, can make through cold working the stainless steel of its aggrandizement. Typical steel is planted have 022Cr22Ni5Mo3N, 022Cr26Ni7Mo3N. The way that to its metallographic content examines in national standard has GB/T 13305-2008[2] " the α in stainless steel - mensuration of metallographic of photograph area content " .
Iron potassium cyanide, oxyhydrogen changes potassium aqueous solution to corrode, the austenite that arrangement is white and grey black (solid for brown) ferrite, the bulk mark of ferrite is occupied about 50%
1.5 deposit and sclerotic stainless steel
Matrix is austenite or martensite arrangement, can pass deposit sclerosis (call effectiveness for a given period of time sclerosis again) make the stainless steel of its aggrandizement. Deposit and sclerotic stainless steel is martensite or half austenite arrangement after solid dissolve, final heavy integral gives martensite to arrange; Have very high strength; Be able to bear or endure profiled bar of martensite of excel of uniform corrosion ability; Shape and solder the function is crackajack. Typical steel is planted 05Cr17Ni4Cu4Nb, 07Cr17Ni7Al, 05Cr15Ni7Mo2Al waits.

Main ingredient is Cr: 17 ％ of 14 ～ , ni≤7 ％ and minority molybdenum, aluminous, copper, the arrangement after solution treatment is ferrite of austenite ＋ minority
2.The metallographic of stainless steel is checked
Of 2.1 stainless steel times lower the experimental method of arrangement and defect
Can basis GB/T 226-1991[3] " of steel times lower arrangement and law of experiment of defect acid etching " undertake. Soak a law of corrode of commonly used heat, soon sample immerses in HCl aqueous solution, be in next the corrosion product with clean and outside wash and brush of scrub of water be of use. Corrode is heated up in still can choosing HNO3 and HF aqueous solution or HCl and HNO3 aqueous solution in addition.
Times lower the appraisal of arrangement can consult GB/T 1979-2001[4] " structural steel is times lower arrangement defect grade pursues " the standard undertakes. Additional and normative GB/T1220-2007 " stainless steel club " in regulation, the cross section acerbity dip of steel bar is times lower or there must not be macroscopical shrinkage cavity, bleb, flaw on fracture surface sample, mingle, turn over skin and white spot. To more high-grade steel bar, its base is loose, normally loose, slant analyse all must not surpass 2 level; To general steel bar, its afore-mentioned grade all must not surpass 3 level.
The grade of the metalloid adulterant in 2.2 stainless steel
But according to GB/T 10561-2005[5] " of content of adulterant of metal of steel Central Africa determine method " undertake probation.
The brilliant granuality of 2.3 austenite steel is checked
But according to GB/T 6394-2002[6] " the metal is even brilliant granuality determines method " undertake probation mixing grade.
Of 2.4 stainless steel anti-corrosive function
But according to GB/T4334-2008[7] " of metal and alloy corrode stainless steel experimental method is corroded between brilliant " have experiment and grade.

Solution of glycerine of aqua fortis of; of dissolve of 1050 ℃ solid corrodes 12Cr18Ni9 steel the A that waits for an axis equably arranges; , there is twin brilliant to pursue inside brilliant 9. 12Cr18Ni9 steel dissolve of 1050 ℃ solid + aqueous solution of oxalic acid of;10% of 650 ℃ sensitize electroanalysises, vitriolic bluestone corrodes tendency experiment to discover edge brilliant is corroded

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