Investigation on Creep Behavior of Grade 91 Heat-Resistant Steel at 923K

2016 ◽  
Vol 853 ◽  
pp. 163-167
Author(s):  
Fa Cai Ren ◽  
Xiao Ying Tang
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Minimum Creep Rate ◽  
Resistant Steel ◽  
Creep Tests ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Grade 91

Creep deformation behavior of SA387Gr91Cl2 heat-resistant steel used for steam cooler has been investigated. Creep tests were carried out using flat creep specimens machined from the normalized and tempered plate at 973K with stresses of 100, 125 and 150MPa. The minimum creep rate and rupture time dependence on applied stress was analyzed. The analysis showed that the heat-resistant steel obey Monkman-Grant and modified Monkman-Grant relationships.

Creep Deformation Behavior and Microstructural Degradation During Creep of Pre-Strained 25Cr-20Ni-Nb-N Steel

2007 ◽  
Author(s):  
Nobuhiko Saito ◽  
Nobuyoshi Komai
Keyword(s):  
Creep Rate ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Minimum Creep Rate ◽  
Strengthening Mechanism ◽  
Creep Rupture ◽  
Microstructural Degradation ◽  
Solution Treated ◽  
Long Time ◽  
Strained Materials

The purpose of this study is to clarify the creep deformation behavior and microstructural degradation during creep of pre-strained 25Cr-20Ni-Nb-N steel (TP310HCbN), which has the highest creep strength among austenite stainless steels used for boiler tubes. The creep rupture strengths of the 20% pre-strained materials tested at 650°C under 210 MPa and 180 MPa were higher than those of solution-treated materials. However, the long time creep rupture strengths of the 20% pre-strained materials tested at 700°C and 750°C were lower than those of solution-treated materials. Thus, the creep strengths of the prestrained materials depend on test temperature and stress. Furthermore, the minimum creep rate of the 20% pre-strained materials and re-solution-treated materials tested at 650°C under 300MPa were 1.2 × 10−9 and 1.6 × 10−8 s−1, respectively. Thus, the minimum creep rate of the 20% pre-strained materials was lower than for re-solution-treated materials. The creep strengthening mechanism of the pre-strained materials at 650°C was considered to be that high-density dislocations were maintained until the late stage of creep. On the other hand, the creep rupture strengths of the 20% pre-strained materials were lower than those of solution-treated materials tested at over 700°C because of agglomeration and coarsening of precipitates and the recovery of dislocations.

Creep Deformation Analyses for Grade 91 Steels Considering Heat-to-Heat Variation

2018 ◽  
Author(s):  
Haruhisa Shigeyama ◽  
Yukio Takahashi ◽  
John Siefert ◽  
Jonathan Parker
Keyword(s):  
Creep Strain ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Power Plants ◽  
Primary Creep ◽  
Heat Resistant ◽  
Large Heat ◽  
Reasonable Prediction ◽  
Materials Used ◽  
Grade 91

In order to evaluate creep life of heat-resistant materials used in power plants, it is important to estimate variation of stress distribution caused by creep deformation appropriately. For achieving this, creep strain equations which can express the creep deformation behavior with good accuracy are indispensable. Additionally, a lot of heat-resistant steels show large heat-to-heat variations in creep properties. Therefore, it is also important to take into account of the heat-to-heat variations in the creep analyses. In this study, existing creep strain equations for Grade 91 steel were applied to six heats with a variety of creep strength and creep deformation behavior. Furthermore, some modification was made in order to obtain better agreement with test data in primary creep stage. It was found that reasonable agreements were obtained between the measured creep deformation behavior and predictions obtained by these equations only by changing creep rupture property depending on the particular heats. This suggests that reasonable prediction for creep deformation can be made even for the materials lacking the information of creep deformation as long as their rupture properties are known.

Effect of Ausforming on Creep Strength of G91 Heat-Resistant Steel

2018 ◽  
Vol 941 ◽  
pp. 400-406 ◽  
Author(s):  
Javier Vivas ◽  
Rosalia Rementeria ◽  
Marta Serrano ◽  
Eberhard Altstadt ◽  
David San Martín ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Creep Strength ◽  
Operating Temperature ◽  
Strengthening Mechanism ◽  
Processing Route ◽  
Resistant Steel ◽  
Creep Tests ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Conventional Heat Treatment

The major challenge in a heat-resistant steel is to generate thermally stable microstructures that allow increasing the operating temperature, which will improve the thermal efficiency of the power plant without diminishing strength or time to rupture. The strengthening mechanism in tempered martensitic 9Cr steels comes mainly from the combination of solid solution effect and of precipitation hardening by fine MX carbo-nitrides, which enhance the sub-boundary hardening. This work is focused on the effect of ausforming processing on MX nanoprecipitation, on both their distribution and number density, during the subsequent tempering heat treatment. The creep strength at 700 oC was evaluated by small punch creep tests. The creep results after ausforming were compared to those obtained after conventional heat treatment concluding, in general, that ausforming boosts the creep strength of the steel at 700 oC. Therefore, conventional ausforming thermomechanical treatment is a promising processing route to raise the operating temperature of 9Cr heat-resistant steels.

Hot deformation behavior of Super304H austenitic heat resistant steel

2010 ◽  
Vol 17 (2) ◽  
pp. 167-172 ◽  
Author(s):  
Shu-ping Tan ◽  
Zhen-hua Wang ◽  
Shi-chang Cheng ◽  
Zheng-dong Liu ◽  
Jie-cai Han ◽  
...  
Keyword(s):  
Hot Deformation ◽  
Deformation Behavior ◽  
Resistant Steel ◽  
Hot Deformation Behavior ◽  
Heat Resistant Steel ◽  
Heat Resistant

scholarly journals Effect of B on Microstructural Change during Creep Deformation in High Cr Ferritic Heat Resistant Steel

2002 ◽  
Vol 88 (10) ◽  
pp. 678-685 ◽  
Author(s):  
Tsukasa AZUMA ◽  
Kazuhiro MIKI ◽  
Yasuhiko TANAKA ◽  
Tohru ISHIGURO
Keyword(s):  
Creep Deformation ◽  
Microstructural Change ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant

Hot Deformation Behavior of NF709 Austenitic Heat-Resistant Steel

2014 ◽  
pp. 357-363
Author(s):  
Wang Jingzhong ◽  
Wang Kuaishe ◽  
Du Zhongze ◽  
Liu Zhengdong ◽  
Baohansheng
Keyword(s):  
Hot Deformation ◽  
Deformation Behavior ◽  
Resistant Steel ◽  
Hot Deformation Behavior ◽  
Heat Resistant Steel ◽  
Heat Resistant

Microstructure Evolution in a 3%Co Modified P911 Heat Resistant Steel under Creep Conditions

2010 ◽  
Vol 89-91 ◽  
pp. 295-300 ◽  
Author(s):  
Alla Kipelova ◽  
Rustam Kaibyshev ◽  
Andrey Belyakov ◽  
Izabella Schenkova ◽  
Vladimir Skorobogatykh
Keyword(s):  
Structural Changes ◽  
Elevated Temperatures ◽  
Second Phase ◽  
Resistant Steel ◽  
Creep Tests ◽  
Tempering Temperature ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Static Annealing ◽  
Average Size

The microstructural changes in a 3%Co modified P911 heat resistant steel were examined under static annealing and creep at elevated temperatures. The quenched steel was tempered at temperatures ranging from 673 to 1073 K for 3 hours. The temperature dependence of hardness for the tempered samples exhibits the maximum at 723 – 823 K which is associated with the precipitations of fine carbides with an average size of about 20 nm. The transverse lath size of martensitic structure is  200 nm after air quenching and remains unchanged under tempering at temperatures below 800 K. An increase in tempering temperature to 1073 K resulted in hardness drop. Coagulation of carbides and growth of martensitic laths takes place at these temperatures. The creep tests were carried out at 873 and 923 K up to rupture, which occurred after about 4.5 × 103 hours. The structural changes in crept specimens were characterized by the development of coarse laths/subgrains. The mean transverse size of which was  0.67 and  1.3 m after the creep tests at 873 and 923 K, respectively. On the other hand, an average size of second phase particles of  165 nm was observed in the samples tested at both temperatures.

scholarly journals Low-Stress Creep Deformation in Long-Term Aged Ferritic Heat-Resistant Steel

2014 ◽  
Vol 55 (5) ◽  
pp. 842-849 ◽  
Author(s):  
Shigeto Yamasaki ◽  
Masatoshi Mitsuhara ◽  
Ken-ichi Ikeda ◽  
Satoshi Hata ◽  
Hideharu Nakashima
Keyword(s):  
Creep Deformation ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant
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