Research on Welding Repair for Tee Joint Crack of Final Superheater Header of 300MW Station Boiler

2012 ◽  
Vol 235 ◽  
pp. 96-100
Author(s):  
Xiao Guang Niu ◽  
Qing Wang ◽  
Xiang Feng Zheng ◽  
Xue Xia Xu ◽  
Hui Fan ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Main Crack ◽  
Welding Residual Stress ◽  
Fusion Line ◽  
Power Station ◽  
Metallographic Examination ◽  
Small Cracks ◽  
Steam Pipe ◽  
Power Station Boiler

Through methods, such as microscope analysis, metallographic examination, the crack located nearby the fusion line between tee joint and outlet steam pipe of subcritical power station boiler final superheater header is reheat crack (the main crack occurred in the heat affected zone and extended along the fusion line and grain boundary in HAZ. There are many small cracks paralleling with main crack). The base metal material (12Cr1MoV) and excessive welding residual stress are the primary inducement of crack. In repair crack, the measures of reducing residual stress, such as lower welding heat input, reducing thickness of welding layer, hammer blowing, assigning reasonably heat treatment power ,lengthening holding time and so on, were taken. The welding repair succeeded greatly.

Failure Analysis on Tee Joint Crack of Subcritical Power Station Boiler Final Superheater Header

2011 ◽  
Vol 311-313 ◽  
pp. 615-618
Author(s):  
Xiang Feng Zheng ◽  
Yan Ting Feng ◽  
Xiao Guang Niu ◽  
Qing Wang ◽  
Xiao Jun Hao ◽  
...  
Keyword(s):  
Residual Stress ◽  
Chemical Analysis ◽  
Failure Analysis ◽  
Mechanical Analysis ◽  
Welding Residual Stress ◽  
Power Station ◽  
Metallographic Examination ◽  
Microscope Analysis ◽  
Power Station Boiler

Through methods, such as microscope analysis, mechanical analysis, chemical analysis, metallographic examination, the causes resulting in tee joint crack of subcritical power station boiler final superheater header (12Cr1MoV) have been analyzed. The result indicates the tee joint crack is reheat crack, and irrational structure and excessive welding residual stress are the primary inducement of tube joint crack.

Research on Welding Repair for Reheating Hot Pipe Elbow of 325MW Station Boiler

2012 ◽  
Vol 516-517 ◽  
pp. 414-418 ◽  
Author(s):  
Xiang Feng Zheng ◽  
Qing Wang ◽  
Yan Ting Feng ◽  
Xiao Guang Niu ◽  
Xiao Jun Hao ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Base Metal ◽  
Heat Input ◽  
Welding Residual Stress ◽  
Fusion Line ◽  
Metallographic Examination ◽  
Microscope Analysis ◽  
Metal Material ◽  
Pipe Elbow

Through methods, such as microscope analysis, metallographic examination, the crack located nearby the fusion line between reheating hot pipe elbow and blocking valve is reheat crack. The base metal material and excessive welding residual stress are the primary inducement of crack. In replacing pipe elbow, the measures of reducing residual stress, such as hammer blowing ,lower welding heat input, post welding heat treatment and so on, were taken. The welding repair succeeded greatly.

Research on Welding Repair for Tee Joint Crack of Subcritical Power Station Boiler Platen Superheater Header

2012 ◽  
Vol 628 ◽  
pp. 173-178
Author(s):  
Qing Wang ◽  
Xiang Feng Zheng ◽  
Yan Ting Feng ◽  
Xiao Guang Niu ◽  
Xiao Jun Hao ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Heat Input ◽  
Holding Time ◽  
Power Station ◽  
Microscope Analysis ◽  
Reheat Cracking ◽  
Welding Heat Input ◽  
Power Station Boiler

Through methods, such as microscope analysis, metallography examination, the causes resulting in tee joint crack of subcritical power station boiler platen superheater header have been analyzed. The result indicates the tee joint crack originated in the original defects, expanded to connect with reheat cracking and leaked finally. In repair crack, the measures of reducing residual stress, such as lower welding heat input, reducing thickness of welding layer, hammer blowing, assigning reasonably heat treatment power ,lengthening holding time and so on, were taken. The welding repair succeeded greatly.

Flaw Stability Analysis of Semi-Elliptical Surface Cracks in Canisters Under the Influence of Welding Residual Stress

2016 ◽  
Author(s):  
Jinhua Shi ◽  
Liwu Wei ◽  
Poh-Sang Lam
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Spent Nuclear Fuel ◽  
External Surface ◽  
Welding Residual Stress ◽  
Surface Cracks ◽  
Coastal Regions ◽  
Dry Storage ◽  
Induced Stress ◽  
Design Pressure

Many stainless steel canisters for the dry storage of spent nuclear fuel are located in coastal regions. Because the heat treatment for relieving the welding residual stress is not required during fabrication, these canisters may be susceptible to chloride induced stress corrosion cracking due to the deliquescence of chloride-bearing marine salts or dust that enter the overpack system and deposit on the canister external surface. The NDE techniques and the associated delivery system are being developed to conduct periodic inservice inspections. The acceptance standards are needed to disposition findings should flaw-like indications be found. The instability crack lengths and depths for these flaws in the form of semi-elliptical shape near the welds are determined with R6 procedure. The cracks are subject to the canister design pressure and handling loads as well as the estimated welding residual stresses.

Analysis on Welding Crack of Subcritical Power Station Boiler Platen Superheater Header

2012 ◽  
Vol 251 ◽  
pp. 446-449 ◽  
Author(s):  
Yan Ting Feng ◽  
Xiang Feng Zheng ◽  
Xue Xia Xu ◽  
Guo Zhen Dong ◽  
Yong Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Welding Residual Stress ◽  
Composition Analysis ◽  
Power Station ◽  
Element Analysis ◽  
Test Chemical ◽  
Welding Defects ◽  
Chemical Composition Analysis ◽  
Leakage Failure ◽  
Power Station Boiler

Welding crack analysis was carried out on tee joint crack of boiler platen superheater header (12Cr1MoV) of subcritical power station applying finite element analysis,microanalysis, mechanical properties test, chemical composition analysis, metallography examination and SEM observation etc. Results indicated that the improper structure, the original welding defects, higher welding heat input, excessive welding residual stress and improper heat treatment led to cold crack and reheat crack ,then induced to the leakage failure while operating.the welding crack originated at the original defects, connected with reheat cracks during propagation and led to leakage finally.

Effects of Post Weld Heat Treatment Residual Stress on the Creep of Elbow Welded Joint

2009 ◽  
Author(s):  
Changyu Zhou ◽  
Guodong Zhang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
High Temperature ◽  
Internal Pressure ◽  
Creep Strain ◽  
Welded Joint ◽  
Post Weld Heat Treatment ◽  
Welding Residual Stress ◽  
Creep Analysis ◽  
Boiler Tubes

It is well known that type IV crack emerges in the high temperature welded components. Although the welding residual stress will drop after post weld heat treatment (PWHT), the PWHT residual stress still remains in the welded joint. When the joint is in service at high temperature and under high pressure, the PWHT stress and pressure will induce the creep strain in the welded joint of the elbow of T91 boiler tubes. Usually, it is considered that the PWHT stress will relax at high temperature environment and is ignored by many researchers. In this paper, by the finite element analysis codes ABAQUS and the function of RESTART, a sequential coupling calculating program for creep based on welding residual stress has been developed by establishing the model of temperature field, residual stress and creep analysis. The welding residual stress and creep of elbow welded joint for T91 boiler tubes was simulated by the program. According to the finite element calculation results, the PWHT stress has a great influence on the T91tube creep. This method established the basis of calculating the effects of welding residual stress on the creep of welded joint. Firstly, the welding residual stress and the PWHT stress was simulated by ABAQUS. Based on the work, the stress distribution of the T91 tube elbow can be obtained under internal pressure and the PWHT stress. Secondly, for the elbow welded joint the creep under the internal pressure only and the creep under internal pressure and PHWT stress can be simulated by the ABAQUS codes. Then comparison of creep strain in the elbow welded joint with PWHT stress and with internal pressure is made in the paper. Although the stress induced by the PWHT and internal pressure would relax in a short time, the creep strain of the elbow welded joint is still influenced by initial stress state. The results shown that the PWHT stress can not be ignored for the creep analysis of the elbow welded joint. So it can be considered that the PWHT residual stress is one of possible failure factors for the elbow welded joint. The design of high temperature elbow welded joint need to consider the influence of the PWHT residual stress. This paper will provide a more comprehensive means for life assessment of the welded joint in service.

Mechanism Research on Residual Stress's Elimination of Aluminum Alloy Welding by Ultrasonic

2013 ◽  
Vol 690-693 ◽  
pp. 2616-2620
Author(s):  
Gao Jian Cui ◽  
Ting Ting Lv ◽  
Xue Zheng
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Aluminum Alloy ◽  
Aluminium Alloy ◽  
Welding Residual Stress ◽  
Traditional Methods ◽  
Mechanism Research ◽  
Practical Engineering

Through analysing the shortcomings of the traditional methods of eliminating residual stress, and aimed at the mechanism of eliminating residual stress, put forward the method of eliminating aluminium alloy welding residual stress by ultrasonic. Explained the superiority of using ultrasonic to eliminate aluminium alloy welding residual stress by the comparison with heat treatment and vibration processing that are the most commonly used methods in practical engineering.

Failure Analysis of Expansion Bellows Serving in Steam Pipe Network

2013 ◽  
Author(s):  
Yichang Huang ◽  
Xiaoying Tang ◽  
Houde Yu ◽  
Yaozhou Qian ◽  
Ruqing Wu
Keyword(s):  
Stress Raiser ◽  
Pipe Network ◽  
X Ray Diffraction ◽  
Metallographic Examination ◽  
Spider Web ◽  
Type 316L ◽  
Small Cracks ◽  
Steam Pipe ◽  
As Stress ◽  
Type 316L Stainless Steel

The failure of Type 316L stainless steel expansion bellows serving in steam pipe network has been analyzed. The expansion bellows cracked after approximately 4-year service in steam network at 230°C. The caustic stress corrosion cracking (caustic-SCC) resulting from a combined function of caustic concentrating, metal temperature and residual stress was responsible for the failure. Cracking initiated on the inside surface of the bellow at the peak where served as stress raiser by observation of sample taken from failed expansion bellows. The pattern of cracking was shown as a spider web of several small cracks in photomicrographs. The metallographic examination also indicated that cracks were predominantly transgranular. The oxides on the surface of cracks can be confirmed to be caustic NaOH through X-ray diffraction (XRD) examination.

Failure Analysis on Tee Joint Crack of Subcritical Power Station Boiler Platen Superheater Header

2012 ◽  
Vol 538-541 ◽  
pp. 1992-1997
Author(s):  
Yan Ting Feng ◽  
Xiang Feng Zheng ◽  
Xue Xia Xu
Keyword(s):  
Mechanical Properties ◽  
Welding Residual Stress ◽  
Composition Analysis ◽  
Power Station ◽  
Cause Analysis ◽  
Test Chemical ◽  
Welding Defects ◽  
Chemical Composition Analysis ◽  
Leakage Failure ◽  
Power Station Boiler

Failure cause analysis was carried out on tee joint crack of boiler platen superheater header (12Cr1MoV) of subcritical power station applying microanalysis, mechanical properties test, chemical composition analysis, metallography examination and SEM observation etc. Results indicated that the tee joint crack originated at the original defects, connected with reheat cracks during propagation and led to leakage finally. The improper structure, the original welding defects, overhigh welding heat input, and excessive welding residual stress resulted in the leakage failure.

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