3 Process and Defect

7/24/2019 3 Process and Defect

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NDT UNIT


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Metals and Alloys NDT deals with metal and alloy-important

to understand its structure

Metal comprises of atoms Each atoms is bonded together by

METALLI !"ND #hat is METALLI !"ND

Most metal ha$e few outer orbital electron Outer orbital electron o$erlapped and

totally shared by other atom formingelectron gas% act li&e glues


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C

C

C

C

C

Na Cl Na Cl

Na ClNa Cl

Na Cl Na Cl Covalent bonding

in diamond

Sodium chlorideionic bonding

BONDING

+ + + +

+ + + +

Metallic bond


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Metal and Alloy 'roperties of metal closely related to the

atomic arrangement

Electrical onductor( due to freemo$ement of electron in electrical )eld

*eat conductor( free electron cantransfer thermal energy+

M! is not speci)c-so di,erent metal canbe oined

M! is non-directional


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.#hen metal heat-atoms $ibrateincreasingly-manifest as e/pansion

.ontinuous heating cause M! to brea&at melting point% now atom free to mo$e.More heating cause more melt buttemperature remain steady% until

melting is complete 0energy is &nown aslatent heat.#hen cooled the re$erse happen.Atom begin to ta&e up a speci)cpositons to form 123TAL


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. If centre of atoms are connected wewill construct space lattice+

. The smallest $olume of space latticerepresents the positions of atomswrt each other is &nown as unit cell

.

Unit cell of most metals are !%4% he/agonal% tetragonal etc. #hat is 4% !% etc


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rystal structure of metal

BCC FCC

hexagonal

Plan

viewtetragonal


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T2'IAL 3T1E33-

3T1AIN U15E "'-LINEA1 '"1TI"N

"!E2 *""6E3 LA#

E-ELA3TI LIMIT

N"1MALL2 '7E E-U2'( 'LA3TI

DE4"1MATI"N "U1

!E2"ND U2'( E8TEN3I"N"U1 AT 1EDUED3T1E33 U' T" L2'

U( TEN3ILE 3T1EN9T*0*I9*E3T 3T1E33 T*EMETAL AN #IT*3TAND

8-41ATU1E '"INT

O

PE

UYP

YP

U

!

S"#$%N

S"#ESS

SPEC%MEN FO#"ENS%E "ES"


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'roperties of Material 'hysical properties( constants associated with

the atomic structure of materials 0e+g+ density%melting point% cohesi$e strength% etc:

Mechanical properties( properties that re$eals itelastic and inelastic beha$iour 0e+g+ modulus ofelasticity% tensile strength% elongation% etc:

hemical properties( properties that describe thereaction between a material with other materials

'rocessing properties( properties that describethe ability of a material to be processed 0e+g+weldability% castability% machinability% bending:


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'roperties of metal Elasticity( the ability of metal to strain

under load and then return to its originalsi;e and shape when unloaded

3trength( the ability of metal to resistchanging its shape or si;e when e/ternalforce is applied

*ardness( the ability of metal to resistbeing permanently deformed !rittleness( properties of metal whereby it

will not deformed plastically under load+


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'roperties of metals Ductility( a property that allows a metal to

deform permanently when loaded in tension Malleability( abilty of metal to deform

permanently when loaded under compression Notch toughness 0impact strength:( ability of

metal to resist rupture from impact loadingwhen there is a notch or stress raiser

presents+ onducti$ity( ability of metal to conduct

electricity


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9rain Under microscope metal

comprise of grain

*ow grains are formed ertain atom form a unit cell

and solidi)ed 0called crystal: "ther atoms ta&e up position

alongside this crystal+-thegrain grows 9rowth are interfered by

other grain growth-forminggrain boundary


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Alloy Metal rarely e/ist in pure form

"ther materials are added to modify

properties Alloy7pure metal


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3teel Ma&ing 'rocess

CO&E

O#E

%MES"ONE

ME"%N'

$#E$

()))OC

S$'

P%'

%#ON

S$'

*O"

$%#

P%'

%#ON

Iron ore + coke + limestone

fed to top of blast furnace

Coke burns, heat created

molten metal trickle to bottomLimestone gather impurities

to it, melts and trickle to

bottom but remain on top

called SLG

!ost slag gone but some

remain

Slag form discontinuities at a

later stage"


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3teel Ma&ing process Molten iron then poured

to mould to form PIGIRON-dirty containnonmetallic inclusion

PIG IRON is the rstproduct in the steelmaking process

Pig iron is brittle-not souseful

Other elements were

added to make betteruality steel and processdone in open hearthfurnace

some nonmetallicinclusion remain

MO"EN

%#ON

PO#OS%"Y

MOU,

%N'O"

O"*E#

M$"E#%$S


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3teel ma&ing process Inclusion rise to upper

part because it is lightersome trapped beforereaching the surface

Inclusion is irregular Normally o!ide "

sulphide inclusion #lowmelting point-harmfulduring hot working andwelding$ and brittle-can

act as stress raiser Porosity also formed as a

result of trapped gasbubble as it rises

Porosity is round

MO"EN

%#ON

PO#OS%"Y

MOU,

%N'O"

O"*E#

M$"E#%$S


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Melting

metal

a-er b- la-er

.olidi/ication

Final 0roduct with

di00ed .ur/ace"he u.e o/ hot1to0

/or .lab 0roduction

Formation o/

.hrin2age

Formation o/

0i0e"he u.e o/ hot to0 to

avoid 0i0ing

Cho00ed

here

Cho00ed bloomor billet


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1olling process 1eduction of thic&ness

of ingot by passing hotmetal through two rolls

an be done at hot0abo$e recrystalli;ationtemperature: or cold0below recrystalli;ation

temperature: 'roducts( bloom% billlet%

slab% plate% sheet

1ollingdirection

1ollers


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1olling process


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'roduct of 1olling 'rocess


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1olling Defects

1ollingdirection

1ollerslamination

seam

piping


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DE4ET3 IN 1"LLED

'1"DUT#OE#

F$""ENE,

%NCUS%ON

3OUME"#%C

%NCUS%ON

BEFO#E

#OE,

$F"E#

#OE,

SU#F$CE C#$C& BECOME

SE$M

BEFO#E

#OE,

$F"E#

#OE,

%NCUS%ON BECOME

S"%N'E# $F"E# #O%N'

P%PE BECOME ON'E# P%PE$F"E# #O%N'


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#elding 'rocess Method of fabrication

intended to obtain

physical continuitybetween two piecesto be oined

In$ol$ed rapid

heating and cooling 'roduce weld ;one%

heat a,ected ;oneand parent metal

'late =

'late >

#eldmetal

*eata,ecte

d ;one

'arentmetal >

'arentmetal =


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#elding application in

$essel manufacturing

$

$

$

$

$

$

$ $

$

B

B

B

B

B

B

C

C

C

C

C

C

,

,

,

,


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#elding method-

"/yacetylene


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#elding

method-ManualMetal Arc


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#elding

method-MI9and MA9


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#elding defects( crac&

Crater crac2

#oot crac2

"ran.ver.e

crac2ongitudinal

crac2

Underbead

crac2

"oe

crac2

Fu.ion linecrac2


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#elding defects( crac&s

"YP%C$ *$4 C#$C&%N'

Shrin2age .train


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#elding defects( lac& of

penetration

LC# O$

%&N&'('ION

SINGL&)* &LD

LC# O$ %&N&'('ION

DOBL&)* &LD

LC# O$ %&N&'('ION IN

SINGL&)- &LD


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#elding defefcts( Lac& of

fusion

ac2 o/ .idewall /u.ion

ac2 o/ root

/u.ion

ac2 o/

%nter1run /u.ion


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#elding defects( porosity

Pi0ing5wormhole*erringbone

0oro.it-

Clu.tered

0oro.it-

%O(OSI'.


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"ther welding defects

%nclu.ion

between the

bead.

%nclu.ion at the

/u.ion /ace

INCLSION

undercut

ND&(C'

#OO"

UN,E#C

U"

"OE

UN,E#CU

"


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"ther welding defects

Incompletely)lled groo$e 3hrin&agegroo$e

1oot conca$ity burnthrough


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asting process A process of

manufacturing a)nish or near-)nishproducts by pouringmolten metal intomould

#hen metal solidi)edit will be remo$edfrom the mould

Many type of casting(die casting%permanent casting%sand casting etc

mould

Moltenmetalsolidifying

'ouringofmoltenmetal


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A3TIN9 '1"E33

P$""E#N P$""E#N %N

S$N, MOU,

MO, C$3%"Y 6%"*

'$"%N' SYS"EM

COMPE"E

C$S"%N' 6%"*

$""$C*E,

'$"%N' SYS"EM

C$S"%N' OF BUE"


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asting defects

'ouring ofmetal

old shut

ight .ection

.olidi/ie. /a.ter than

heav- .ection

*ot "ear.

Formed

$rea where hot tear.

mo.t li2el- to occur

shrin&age


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4orging #or&ing of

metal intodesired shapeby repeatedlyhammering orpressing themetal while it

is hot and soft an produce

forging burstand lap Internal

burst


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4orging defect

'erfectalignment

Misalignmentcausing lap


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In ser$ice Discontinuities orrosion( Destruction or deterioration of a

material because of reaction with itsen$ironment

4atigue( Discontinuities de$eloped due torepeated application of load

3tress corrosion crac&ing( rac&s de$elopeddue to the presence of stress in corrosi$e

en$ironment Embrittlement( loss of ductility due to the

presence of element such as hydrogen in thegrain boundary


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E,ects of defect 3harp edge defects act as a stress

riser% hence a,ect mechanical

properties Defect may reduce the e,ecti$e

thic&ness of material% thus reduce

strength 3e$erity depends on types% ?uantity%

location% orientation and si;e+


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3 Process and Defect

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