API 571 Damage Mechanisms

 

API 571 Damage Mechanisms

GENERAL MECHANICAL MECHANICAL  AND META METALLUGICAL FAILURE MECHANISMS

 

Graphitizatio n

A change in the carbide phase of C/S

Strain Aging

 +he deformation and aging at

and 0.5 Mo steels after long term epos!re to

an intermediate temperat!re of older C/S and

"00# $ %&'7# C( to 1100#$ %5)*# C( temperat!res ca!sing decomposition into graphite

C,0,5 Mo loallo steels.

Brittle Fracture

apid fract!re !nder stress -ith little eidence of plastic deformation.

 

Shor t Term Short Overheating

Thermal Shock 

Softening (Spheroidizat ion)

ocali2ed oerheating

3cc!rs -hen high and non,

A change in the

ca!sing deformation and/or r!pt!re at lo- stress

!niform thermal stresses deelop oer a

microstr!ct!re of steels -here the carbide phase change

leels.

short of time. period If restrained4 stresses aboe the ield strength can occ!r.

from plate normal lie forms to spheroidal in the temperat!re range of "50#$

#

 

885 m!rittlemen t A loss of to!ghness in allos containing a ferrite phase %&00 series SS4 d!ple SS4 -ro!ght and cast SS4 -elds  oerla( d!e to epos!re to 600#$%*16#C(

"reep# Stre$$ %upture

Steam Blanketing

At high temperat!res metals deform !nder load belo- the ield stress.

A steam blanet inside a t!be ca!sed b a 8depart!re from n!cleate boiling8 that ca!ses locali2ed oerheating and deformation and/or r!pt!re.

 

to

ro$ion# ro$ion

Temper m!rittlemen

Sigma &ha$e m!rittlemen

"orro$ion

t

t

A red!ction in to!ghness in lo- allo steel d!e to long term epos!re to