Metallography Experiment Report

8/9/2019 Metallography Experiment Report

1/11

Kasırga,

Instructor: Prof. Dr. Ahmet ARAN

0

HÜSEYİN KASIRGA

03004033GR!"P

#

$A%ERIA& %ES%ING : $A'R!($I'R!


2/11

Kasırga,

%A#&E !) '!N%EN%S

I. Intro*uct+on

1. Definitionsa. Metallography

b. Microscopyc. Macroscopy

II. E,-er+ment/ Proce*ure1. Specimen Preparation

a. Grinding b. Polishingc. Etching

. Microscopical E!amination

a. "b#ecti$e b. E!periment

%. Macroscopical E!aminationa. "b#ecti$e

b. E!perimenti. S&lph&r Printingii. 'lo( )inesiii. *elded Sections

III. Dt An/s+s1. 'or Microscopical E!amination

. 'or Macroscopical E!amination

I1. Resu/ts 2 D+scuss+on !f Resu/ts1. +es&lts of Microscopical E!amination. +es&lts of Macroscopical E!amination

1. 'onc/us+on

1I. References

1II. %/es n* )+ures

1III. A--en*+,

1


3/11

Kasırga,

I. IN%R!D"'%I!N

5. DE)INI%I!NS

. $et//or-h:

Metallography is the science and art of preparing a metal s&rface for analysis bygrinding, polishing, and etching to re$eal microstr&ct&ral constit&ents. fter preparation, thesample can easily be analy-ed &sing optical or electron microscopy. silled technician isable to identify alloys and predict material properties, as (ell as processing conditions bymetallography alone. /here are t(o e!amination methods in Metallography

1. Microscopy. Macroscopy

. $+crosco-:

n microscopy, the e!amination of the prepared specimen is done (ith the opticalmicroscopes applying magnifications from 10! to 000!. /his e!amination pro$idesinformation regarding the morphology and distrib&tion of constit&ent phases as (ell as thenat&re and pattern of crystal imperfections.

c. $crosco-:

n this method the e!amination of the material 2generally metals and alloys3 is done by the &naided eye or a lo(4po(er microscope (ith a magnification &p to 10!. /hise!amination method pro$ides information abo&t the nat&re of inhomogenities, flo( lines,

segregations, and fabricating defects that cannot be e!amined by microscopy. 5o(e$er, thesedata represents the characteristics only at a partic&lar section of the material.

II. E6PERI$EN%A& PR!'ED"RE

5. SPE'I$EN PREPARA%I!N

/he p&rpose of specimen preparation is to prepare the material piece for analysis byminimi-ing mechanical s&rface damages to obtain reprod&cible res&lts. Preparation of a

metallographic specimen generally re6&ires follo(ing ma#or operations1. Grinding. Polishing%. Etching

. Gr+n*+n:

/he p&rpose of grinding is to minimi-ing the mechanical damages on specimen7ss&rface by lessening the depth of deformed metal to the point (here the last $estiges of damage can be remo$ed by series of polishing steps. /he scratch depth and the depth of cold(ored metal &nderneath the scratches decrease (ith decreasing particle si-e of abrasi$e.Grinding is done &sing a machine carrying rotating discs co$ered (ith silicon carbide paper and (ater. /here are a n&mber of grades of paper, (ith 180, 90, %0, 900, :00, 1000, 100,


4/11

Kasırga,

grains of silicon carbide per s6&are inch in the order from coarser to finer. Most grinding of metallographic specimen is performed by man&ally holding the specimen (ith its s&rfaceagainst that grinding material co$ering discs. /o establish and maintain a flat s&rface o$er theentire area being gro&nd, e6&al press&re m&st be applied on both sides of the specimena$oiding any rocing motion that (ill prod&ce a con$e! s&rface. S&ccess in grinding depends

in part on the press&re applied to the specimen. $ery light press&re remo$es ins&fficientmetal. Some(hat hea$ier press&re prod&ce polishing, (hile still hea$ier press&re brings abo&tthe desired grinding action. ;ery hea$y press&re res&lts in non&niform scratch si-e, deepgo&ges, and embedded abrasi$e particles. Generally, a medi&m to moderately hea$y press&reapplied firmly gi$es the best res&lts. /o a$oid from e!cessi$e (arm of the specimen (ater is&sed as cooler.

/he grade of the silicon carbide paper to begin the grinding operation is the coarsest paper, 180 grade. l(ays light press&re is &sed, applied at the centre of the specimen andcontin&ed grinding &ntil all the blemishes ha$e been remo$ed, the sample s&rface is flat, andall the scratches are in a single orientation. /hen the sample is (ashed in (ater and mo$ed tothe ne!t finer grades, orienting the scratches from the pre$io&s grade normal 2


5/11

Figure 1: Machine used for grinding and polishing

Kasırga,

4 >ital 2ethyl alcohol ? @ 5>"%3 iron and steel

4 lcholic 'erric Ahloride copper alloys

4 Mi!ed cids al&min&m alloys

4 Dil&te 5Al -inc alloys

Etching times $aries according to specimen, b&t a general proced&re is to obser$ethe s&rface d&ring the operation and to end the operation (hen e$idence of the grains firstappears. '&rther etching then follo(s to strengthen &p the details as re6&ired for a goodcontrast in microscopical e!amination. fter etching, the specimen sho&ld be thoro&ghly(ashed and dried (ith acetone or alcohol.

9


6/11


7/11

Kasırga,

i. Su/-hur Pr+nt+n:

/he p&rpose of this e!periment is to e!amine the imp&rities that may e!ist in steel prod&cts. /he importance of these imp&rities is beca&se of their amo&nt and distrib&tion in the

steel. /hese imp&rities degrade steel7s mechanical properties especially it7s strengthen.S&lph&r e!istence is one of these imp&rities and maes the steel brittle.S&lph&r printing is a common method to detect and record the distrib&tion of

S&lph&r in steel. /o prepare the s&rface of rail material to the e!periment it m&st be cleanedfrom the foreign matters on the s&rface by grinding and polishing. Ceca&se it is a macroscopice!amination (ith &naided eye, etching is not re6&ired. Preparing the s&rface, a special photo

paper, photographic bromide paper, is soaed in a @ a6&eo&s sol&tion of s&lph&ric acid for appro!imately %49 min. fter the paper is remo$ed from the sol&tion and allo(ed to drainfrom e!cess sol&tion, prepared s&rface of the specimen is pressed on the paper (ith a press&refor 14 min to let the chemical reactions bet(een the s&rface and acid sol&tion proceed. /henit remo$ed and the paper is placed into a photographic fi!ing sol&tion for abo&t 1B min. to fi!

it permanently. *hen fi!ation completed the paper is (ashed in r&nning (ater and dried.Presence of darly colored areas on paper indicates the presence of s&lph&r on the materialand distrib&tion of these areas pro$ides information abo&t the mechanical properties of railmaterial.

ii. )/o9 &+nes

'lo( lines are the nat&ral conse6&ences of applied mechanical (oring on material.'lo( lines pro$ide information abo&t the defects of material and e!cessi$e amo&nt of incl&sions and segregated areas as (ell as the direction of metal flo( d&ring deformation. nthis method, beca&se the elongated incl&sions of imp&rities, s&ch as o!ides and other

heterogeneo&s areas are selecti$ely attaced by etching reagent, flo( lines are made $isible.

iii. e/*e* Sect+ons:

/he p&rpose of (elded section e!periment is to find the locations of (eld sections of a (elded material. fter the s&rface of the specimen cleared from foreign matters anddeformations by grinding and polishing, prepared s&rface is etched (ith nital for 1040 sec./his operation is repeated se$eral times &ntil some relief of the macrostr&ct&re is prod&ced.'inally the specimen is rinsed in alcohol and dried.

III. DA%A ANA&YSİS5. $I'R!S'!PI'A& E6A$INA%I!N

d the a$erage grain diameter n) the n&mber of grain bo&ndaries intersected per &nit length of a test lineM magnificationA constant 2generally A1,B3

:

d An) .M


8/11

Kasırga,

I1. RES"&%S 2 DIS'"SSI!N !) RES"&%S

5. RES"&%S of $I'R!S'!PI'A& E6A$INA%I!N

5. %he S;etch !f $+crostructure:

Figure 2. Micrograph of the Microstructure of specimen.Dar colored areas indicates perlits 2F ? 'e%A 3 and other (hite areas ferrits 2F3.

. 'ron 'ontent of the Stee/:

Aontaining the compo&nd of Aarbon 2A3, the amo&nt of the dar areas, perlits 2F ?'e%' 3, per &nit area can gi$e the Aarbon content of the steel. 5o(e$er, the microstr&ct&re of the specimen in fig&re is not clear eno&gh to calc&late this content, beca&se the grain

bo&ndaries are not distinct eno&gh. /he reason of this sit&ation is inade6&ate time of theoperation for etchant to attac and resol$e details

3. A8ere Gr+n D+meter:

$erage grain diameter of a microstr&ct&re can be calc&lated (ith H)inear nterceptMethodI. n this method, the grains intercepted by a theoretical line on the specimen s&rfaceare co&nted. /he a$erage grain si-e is indicated by the in$erse of the n&mber of grain

bo&ndaries intersected per &nit length of the test line, corrected for the magnification ofmicrograph. /hen the a$erage grain diameter is gi$en by follo(ing form&la

J


9/11

Kasırga,

d the a$erage grain diameter n) the n&mber of grain bo&ndaries intersected per &nit length of a test lineM magnificationA constant 2generally A1,B3

5o(e$er, beca&se of the &nclear micrograph abo$e, the a$erage grain diameter cannot be calc&lated for this fig&re 2'ig&re .3.

. RES"&%S of $A'R!S'!PI'A& E6A$INA%I!N

. Su/-hur Pr+nt+n

5. Su/-hur Inc/us+ons +n R+/ $ter+/:

Figure 3. Sulphur Inclusions

. )/o9 &+nes

3. E,+stence of )/o9 &+nes:

'lo( lines appear as a conse6&ence of applied mechanical (oring on materials. 'or e!ample, (hen a plastic formation, for instance rolling is applied to the material, orientationsin the rolling direction are started in the microstr&ct&re of the material d&e to the mo$ement of dislocations.

'lo( lines do not e!ist in casted materials, beca&se in casting, the material in li6&idform is po&red into a mold (here it is allo(ed to solidify by cooling. /he li6&id andhomogeny form of the material pre$ents any lines inside the prod&ct (hile it cools slo(ly.

4. )/o9 &+nes n* $echn+c/ Pro-ert+es:

'lo( lines are the ind of discontin&o&sness in the constit&tion of the metals that

affects the mechanical properties of the metal. press&re applied on the metal is transmittedon the flo( lines thro&gh the metal and according to the distrib&tion and direction of the flo(

8

d An) .M

s e!plained abo$e in the s&lph&r printingsection, a conse6&ence of the chemical reaction

bet(een the s&lph&ric acid on the photographic bromide paper and the s&lphide regions of thespecimen7s s&rface, darly colored stains and arease!ist on the paper. /hat is, dar colored pointsindicate s&lph&r incl&sions of the rail material.

. D+str+ut+on of Su/-hur Inc/us+ons:

s it is seen in the fig&re %, s&lph&r incl&sions arenot distrib&ted homogeneo&sly. /hey are distrib&tedas segregated points in the material. /his distrib&tionaffects mechanical properties of the material,especially its strength. /his inhomogenic distrib&tionof s&lph&r maes the material brittle (here thes&lph&r density is higher.


10/11

Kasırga,

lines, some stress stacs appears in partic&lar sections of metal (here ha$e the ris of brittlefract&re. 2See the fig&re 9.3

c. e/*e* Sect+ons:


11/11

Kasırga,

1I. RE)EREN'ES

1L ni$ersity of Aambridge, retrie$ed from httpwww.msm.cam.ac.uk , September 8, 00:.

L D.+. seland, “The Science and Engineering Materials”, P.P Ph&le /homson P&b., Bth

edition 00:.%L *iipedia, the free encyclopedia, retrie$ed from http://en.wikipedia.org , September 8,00:.9L rnes Aorporation, retrie$ed from httpwww2.arnes.si , September

Metallography Experiment Report

Documents

Transcript of Metallography Experiment Report