Microcracking in multipass weld metal of alloy 690 Part 3 – Prevention of microcracking in reheated weld metal by addition of La to filler metal

Nishimoto, Kazutoshi; Saida, Kazuyoshi; Okauchi, Hironori; Ohta, Kenji

doi:10.1179/174329306x94318

Cited by 33 publications

(24 citation statements)

References 7 publications

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“…Researchers have proposed a variety of mechanisms of DDC, including impurity elements embrittlement, such as the segregation of S, P and other impurity elements at GBs, causing the loss of GBs ductility, thereby leading to DDC [17][18][19][20] , GB sliding [14,[21][22][23][24][25] , and precipitation-induced cracking (PIC), such as M 23 C 6 PIC [49] . In essence, DDC is caused by GB embrittlement [49] , and elements segregation at GBs and precipitates along GBs would affect GB embrittlement and DDC.…”

Section: Discussionmentioning

confidence: 99%

“…Filler metal composition, such as S, P, H, C, Ti, Ta, Mo, La, Ce, and Nb, has a strong effect on DDC formation in austenitic weldments. Segregation of S, P, and H to GBs is a dominant factor for DDC aggravation in Ni-base alloys, whereas Ti, Ta, Mo, La, Ce, and Nb addition to a filler metal reduces the sensitivity of DDC [13,17,20,[27][28][29][30][31] .…”

Section: Introductionmentioning

confidence: 99%

“…DDC is a solid-state hot cracking, caused by GB embrittlement at homologous temperatures that ranges from about 0.5 to 0.8 of the alloy melting points, which is observed at grain boundaries (GBs) [14,15] . DDC has been investigated extensively from various perspectives, such as chemical composition [15,16] , elements segregating at GBs [17][18][19][20] , precipitation behavior [12] , GB migration [14,[21][22][23][24][25] , peak temperature and cooling rate [26] and so on. Filler metal composition, such as S, P, H, C, Ti, Ta, Mo, La, Ce, and Nb, has a strong effect on DDC formation in austenitic weldments.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Boron on the Microstructure, Ductility-dip-cracking, and Tensile Properties for NiCrFe-7 Weld Metal

Mo,

Hu,

et al. 2015

Journal of Materials Science & Technology

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Boron on the Microstructure, Ductility-dip-cracking, and Tensile Properties for NiCrFe-7 Weld Metal

Mo,

Hu,

et al. 2015

Journal of Materials Science & Technology

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“…[7][8][9][10][11] However, in the case of heat resistant cast steels, the low ductility is intrinsically due to their characteristic microstructure, resulting from both the manufacturing process and their composition. These materials are prepared by the sand casting technique and are stabilised using an aging treatment of several hours at y950uC.…”

Section: Introductionmentioning

confidence: 99%

Method for predicting risk of cracking during weld repair of heat resistant cast steels

Duchosal¹,

Deschaux-Beaume²,

Bordreuil³

et al. 2008

Science and Technology of Welding and Joining

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Owing to their low ductility at room temperature, heat resistant cast austenitic stainless steels are very sensitive to weld cracking. Cracks are formed in brittle zones of the heterogeneous microstructure constituted by the carbide rich interdendritic spaces. In order to identify the operating factors affecting the cracking propensity of such steels during welding, a three step method, based on numerical simulation, is presented. First, the macroscopic temperature and stress fields are determined by a finite element calculation, considering a homogeneous material. In a second step, a localisation criterion is defined to identify critical zones, according to the macroscopic fields determined in the first step. Then, the heterogeneous microstructure of the cast steel is modelled in a 'representative cell', and the thermomechanical history of the critical zone previously identified is applied as boundary condition, in order to determine the local stress field. The cracking is then supposed to occur when the maximal principal stress in the interdendritic zone of the representative cell reaches the cleavage stress of the carbides, determined using SEM in situ tensile tests. This method is used to predict cracking during multipass weld repair of bulk samples, under various welding conditions. A comparison is carried out between experiment and simulation to validate the method.

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“…The authors have been reported that the primary cause of microcracking (ductility dip cracking) in alloy 690 was the reduction of hot ductility during cooling from welding attributed to the grain boundary segregation of impurity elements such as P and S. 8,9 Furthermore, the authors have also proposed an effective method for preventing microcracks in alloy 690 welds with using La added filler metals of alloy 690, and confirmed that microcracks in the multipass welds of alloy 690 could be completely prevented by using the filler metal added 0?01 mass%La. 10 Similar benefit to the hot cracking susceptibility by rare earth matel (REM) addition (0?02-0?04 mass-%) to the filler metal has been suggested in the Varestraint test of the alloy 690 weld metal. 11 On the other hand, type 316L stainless steel has been widely applied for pressurised water nuclear reactor components.…”

Section: Introductionmentioning

confidence: 93%

Microcracking susceptibility in dissimilar multipass welds of alloy 690 to type 316L stainless steel using La added filler metals

Saida¹,

Ohta²,

Nishimoto³

2007

Science and Technology of Welding and Joining

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The microcracking susceptibility in dissimilar multipass welds of alloy 690 to type 316L stainless steel was investigated by the Varestraint test and the multipass welding test using the four different stainless steels varying the amounts of impurity elements such as P and S, and using the nine different filler metals of alloy 690 varying the La content. In order to simulate the dissimilar weld metals, stainless steels were gas tungsten arc (GTA) welded using alloy 690 filler metals with varying the dilution ratio. Microcracks occurring in the reheated weld metals were classified into ductility dip, liquation and solidification cracks. The ductility dip cracking susceptibility decreased with increasing the La content in the weld metal, while the liquation and solidification cracking susceptibilities increased contrarily when the La content in the weld metal exceeded y0?03 mass-%. The relation among the microcracking susceptibility, the (PzS) and La contents in every weld pass of the multipass welding was investigated. Ductility dip cracks occurred in the compositional range (atomic ratio) of La/(PzS),0?17 and solidification/liquation cracks occurred in that of La/(PzS).0?76, while any cracks did not occur at La/(PzS) being between 0?17-0?76. The ductility dip cracking susceptibility could be improved by adding La due to the scavenging of the impurity elements. The excessive La addition to the weld metal resulted in the solidification/ liquation cracking alternatively attributed to the formation of Ni-La intermetallic compounds with low eutectic point. The optimal filler metal for the dissimilar multipass welding of alloy 690 to stainless steel was selected as La/(PzS) would be 0?17-0?76 for every weld pass. Microcracking could be completely prevented in the dissimilar multipass weld metal of alloy 690 to type 316L stainless steel by using two kinds of filler metals containing 0?03 mass-%La for the weld passes adjacent to the stainless steel base metal and containing 0?01 mass-%La for other weld passes.

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Microcracking in multipass weld metal of alloy 690 Part 3 – Prevention of microcracking in reheated weld metal by addition of La to filler metal

Cited by 33 publications

References 7 publications

Effects of Boron on the Microstructure, Ductility-dip-cracking, and Tensile Properties for NiCrFe-7 Weld Metal

Effects of Boron on the Microstructure, Ductility-dip-cracking, and Tensile Properties for NiCrFe-7 Weld Metal

Method for predicting risk of cracking during weld repair of heat resistant cast steels

Microcracking susceptibility in dissimilar multipass welds of alloy 690 to type 316L stainless steel using La added filler metals

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