Organization of stainless steel metallographic and measure are allowed first

Stainless steel is to point to normally in atmosphere, water, acerbity, alkaline wait for solution with salt or other good chemistry is had in eroding medium the tall alloy steel of not random sex. According to GB/T 13304.2-2008[1] " the classification of steel " and on international current method, by metallographic the organization differentiates stainless steel it is 5 kinds, namely ferrite stainless steel, martensite stainless steel, austenite stainless steel, austenite - stainless steel of ferrite double photograph and precipitation sclerosis stainless steel. Stainless steel is had not only be able to bear or endure goodly function of aggressivity, oxidation, still have exceedingly good mechanical function normally (like intensity, tenacity) , physical function (magnetism function, stretch) with craft function (forging, forming, heat treatment, solder) , be in consequently chemical industry, the sources of energy, mechanical, light industrial wait for an industry to get applied extensively.
 
1.The metallographic of of all kinds stainless steel is organized
1.1 ferrite stainless steel
Matrix is organized with the ferrite of structure of crystal of body heart cubic metre (α photograph) give priority to, have magnetism, cannot pass heat treatment sclerosis commonly, but cold working makes its a little the stainless steel of aggrandizement. Contain Cr: 11~30% , passable contain a few Mo, Nb, Ti, basically do not contain Ni, intensity is higher, be able to bear or endure chloride stress is eroded, dot corrode, aperture is eroded etc function is good, but erode to crystal boundary sensitive, microtherm tenacity is poorer. Main steel grade has 06Cr13Al, 10Cr17, 10Cr17Mo, 008Cr27Mo, 008Cr30Mo2 to wait. This kind of steel via 900 ℃ heat preservation small tissue of empty Leng Houxian is: The carbide that direction of rolling of ferrite class edge distributings; Heat via 1200 ℃ and the microstructure after water temper by dipping in water is δ ferrite + low carbon martensite.

 
Graph 2. The organization after 1Cr17 steel quenchs is martensite of ferrite ＋ low carbon
1.2 martensite stainless steel
Matrix is martensite organization, have magnetism, can adjust its through heat treatment mechanical functionary stainless steel. Martensite stainless steel is austenite in the organization of high temperature condition, after by quenchs, austenite change is martensite, friend call his martensite stainless steel. The steel grade with martensite the commonnest stainless steel has 12Cr12, 20Cr13, 30Cr13, 40Cr13, they contain carbon the volume is higher, after quenching, get martensite is organized; Have higher intensity, hardness, wearability; Connect overheat to handle the function that attainable place asks; Cutting treatment function is better. Solder function is poor.

Graph 4. 10Cr13, temper of 650 ℃ , the organization is ferrite of ＋ of body of family name of temper all alone
1.3 austenite stainless steel
Matrix is organized with the austenite of structure of crystal of face heart cubic metre (γ photograph) give priority to, without magnetism, basically make through cold working the stainless steel of its aggrandizement. After austenite stainless steel contains Cr 16%~25% to contain Ni 7%~20% proper heat treatment commonly, single A organization is below room temperature. Common steel grade has 12Cr18Ni9, 06Cr18Ni11Ti, 06Cr19Ni10, 304(18-8) , 316 etc have good plasticity, tenacity and be able to bear or endure corrode sex, application is very wide.

Graph 5. 304, the organization is onefold austenite
1.4 austenite - stainless steel of ferrite double photograph
Matrix holds austenite and ferrite two-phase structure concurrently, have magnetism, can make through cold working the stainless steel of its aggrandizement. Typical steel is planted have 022Cr22Ni5Mo3N, 022Cr26Ni7Mo3N. The method that to its metallographic content overhauls in national measure has GB/T 13305-2008[2] " the α in stainless steel - mensuration of metallographic of photograph area content " .

Graph 6. Iron potassium cyanide, oxyhydrogen changes potassium aqueous solution to corrode, the austenite that the organization is white and grey dark look (solid for brown) ferrite, the bulk mark of ferrite is occupied about 50%
Stainless steel of 1.5 precipitation sclerosis
Matrix is austenite or martensite organization, can pass precipitation sclerosis (call effectiveness for a given period of time sclerosis again) make the stainless steel of its aggrandizement. Precipitation sclerosis is martensite or half austenite organization after dissolve of stainless steel solid, martensite of culminating precipitation separate out is organized; Have very high strength; Be able to bear or endure to eat profiled bar of ability excel martensite on average; Shape and solder function is good. Typical steel is planted 05Cr17Ni4Cu4Nb, 07Cr17Ni7Al, 05Cr15Ni7Mo2Al waits.

 
Graph 7. Main ingredient is Cr: 17 ％ of 14 ～ , ni≤7 ％ reachs a few molybdenum, aluminous, copper to wait, the organization after solution treatment is austenite ＋ a few ferrite
2.The metallographic of stainless steel is overhauled
The macrostructure of 2.1 stainless steel reachs the experiment method of blemish
Can according to GB/T 226-1991[3] " the macrostructure of steel and law of trial of blemish acid etching " undertake. Soak use hot corrode method commonly, be about to sample immerses in HCl aqueous solution, eat product in what brush of water be of use washs clean down face next. Corrode is heated up in still can employing HNO3 and HF aqueous solution or HCl and HNO3 aqueous solution in addition.
The assess of macrostructure can consult GB/T 1979-2001[4] " structural steel macrostructure blemish grade pursues " measure undertakes. Additional measure GB/T1220-2007 " stainless steel club " in delimit, the cross section acerbity dip of steel bar is times lower or there must not be macroscopical shrinkage cavity, bleb, crackle, be mingled with on section sample, turn over skin and white spot. To more advanced steel bar, its are general and inattentive, in the center of inattentive, slant analyse all must not exceed 2 level; To common steel bar, its afore-mentioned level all must not exceed 3 level.

 
Graph 8. Solution of glycerine of aqua fortis of; of dissolve of 1050 ℃ solid corrodes 12Cr18Ni9 steel the A organization that; makes the same score equal axis, 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 erodes liability trial to discover edge brilliant is eroded