PSI - Issue 14

K.C. Sahoo et.al./ Structural Integrity Procedia 00 (2018) 000 – 000

K.C. Sahoo et.al./ Structural Integrity Procedia 00 (2018) 000 – 000 t. l./ t t l I t it i ( ) . .

K.C. Sahoo et al. / Procedia Structural Integrity 14 (2019) 60–67 The creep properties are specially improved by solid solution stre gthening of nitrogen and precipitation hardening of ‘Cu’ particles and Nb (C, N) compounds [ F. Masuyama t. , 2001]. Further, small addition of boron suppresses the creep cavitation and increases the creep strength to a higher extent compared to 304SS [K. Laha etal.,2007]. Indira Gandhi Centre of Atomic Research (IGCAR) has taken up a project along with the collaboration of other organization to assess the development of materials, design and fabrication of AUSC. 304HCu SS is one of the candidate material to be used in AUSC boiler tubes. Creep tests are the requirement to qualitatively and quantitatively judge mechanical, physical and durability of the material under the required service condition. This paper presents the creep properties of indigenously developed 304HCu SS tubes. The results are presented in the form of the variations of creep life and steady state creep rate as a function of applied stress, the variations of creep ductility with rupture life, time to onset tertiary creep, damage tolerance factor with rupture life. In the other hand, creep deformation and rupture life has been predicted through FE-analysis coupled with continuum damage mechanics. The creep properties are specially improved by solid solution strengthening of nitrogen and precipitation hardening of ‘Cu’ particles and Nb (C, N) compounds [ F. Masuyama t. , 2001]. Further, small addition of boron suppresses the creep cavitation and increases the creep strength to a higher extent compared to 304SS [K. Laha etal.,2007]. Indir Gandhi C ntre of Atomic Research (IGCAR) has taken up a project along with the collaboration of other organization to assess the d velopment of materials, design and fabrication of AUSC. 304HCu SS is one of th candidat material to be used in AUSC boiler tubes. Cre p t sts are the requ rement to qualitatively and quantitatively judge mechanical, physical and durability of the material under the r quir d service condi ion. This paper presents the creep properties of indigenously developed 304HCu SS tubes. The results are presented in the for of the variations of creep life and steady state creep rate as a function of applied stress, the variations of creep ductility with rupture life, time to onset tertiary creep, damage tolerance factor with rupture life. In the other hand, creep deformation and rupture life has been predicted through FE-analysis coupled with continuum damage mechanics. T ti i ll i li l ti t t i it i it ti i ti l , . t. , . t , ll iti the cr it ti i t t t t i t t t . t l., . i i t t i t j t l it t ll ti t i ti t t l t t i l , i i ti . i t i t t i l t i il t . t t t t t lit ti l and titati l j i l, i l ilit t t i l t i i iti . i t t ti i i l l t . lt t i t t i ti li t t t t ti li t , t i ti tilit it t li , ti t t t ti , t l t it t li . t t , ti t li i t t l i l it The 304HCu SS material has been fabricated in the form of seamless tubes in collaboration with M/S MIDHANI and NFC Hyderabad. The dimension of the tube is outer diameter of 52mm, wall thickness of 9.5mm and length of 6-7m. The creep specimen fabricated from the tube with total length 120mm, gauge length 50mm and gauge diameter of 5 mm as shown in fig.1. Creep tests were carried out at 923-1023K in the stress range of 100-240MPa. All the creep tests were conducted as per the ASTM standard procedure practice E-139 and operating temperature was carefully controlled within ±2 K. The chemical composition of the steel was shown in table-1 The 304HCu SS material has been fabricated in the form of seamless tubes in collaboration with M/S MIDHANI and NFC Hyderabad. The dimension of the tube is outer diameter of 52mm, wall thickness of 9.5mm and length of 6-7m. The creep specimen fabricated from the tube with total length 120mm, gauge length 50mm and gauge diameter of 5 mm as shown in fig.1. Creep tests were carried out at 923-1023K in the stress range of 100-240MPa. All the creep tests were conducted as per the ASTM standard procedure practice E-139 and operating temperature was carefully controlled within ±2 K. The chemical composition of the steel was shown in table-1 i aterial has been fabricated in the form of seamless tubes in collaboration with M/S . i i of the tube is outer diameter of 52mm, all thickness of . l t . i i t t t it t t l l t , l t 50mm and gauge diameter of 5 mm as shown in fig.1. Creep tests were carried out at 923-1023K in the stress range of 100-240MPa. All the creep tests were conducted as per the ASTM standard procedure practice E-139 ti t t ll t ll it in ±2 K. The chemical composition of the steel wa i t l i . 2.0 EXPERIMENTAL: 2.1 Materials and Testing: 2.0 EXPERIMENTAL: 2.1 Materials and Testing: ti 2.0 . i l

61

Fig.1 Smooth specimen fabricated from the tube.

Table-1.1 Chemical composition (wt. %) of the material Element Al B C Cr Cu

Mn 0.88

Ni

Nb

N

P

Si

S

Fe

0.002

0.003

0.096

17.7

2.88

9.94

0.55

0.1

0.02

0.19

0.004

Balance

Wt%

Fig.1 Smooth specimen fabricated from the tube. f ri t fr t t . i . t i

2.2 Finite element coupled with continuum damage mechanics:

Table-1.1 Chemical composition (wt. %) of the material Element Al B C Cr Cu l - . i l iti ( t. ) f t t ri l

The governing equation used for calculating creep strain and damage rate through FE-analysis from uniaxial stress creep data has mentioned below. Continuum damage mechanics proposed by Kachanov [L. M. Kachanov., 1967] coupled with Finite element method, has been widely used to predict the deformation and damage behaviour from simple uniaxial data. (1) Mn Ni Nb N P Si S 0.002 0.003 0.096 17.7 2.88 0.88 9.94 0.55 0.1 0.02 0.19 0.004 2.2 Finit element coupled with continuum damage mechanics: The governing equation used for calculating creep strain and damage rate through FE-analysis from uniaxial stress creep data has mentioned below. Continuum damage mechanics proposed by Kachanov [L. M. Kachanov., 1967] coupled with Finite element method, has been widely used to predict the deformation and damage behaviour from simple uniaxial data. (1) t l r i i . . . . . . . .55 0.1 0.02 . . . i i l l i i i i ti l l ti t i t t l i i i l t t ti l . ti i . . ., l it i it l t t , i l t i t t ti i i l i i l t .

Fe

l

Balance

Wt% t

l