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Kazuyoshi Saida - One of the best experts on this subject based on the ideXlab platform.
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Hot Cracking Susceptibility in Duplex Stainless Steel Welds
Materials Science Forum, 2018Co-Authors: Kazuyoshi Saida, Tomo OguraAbstract:The hot cracking (solidification cracking) susceptibility in the weld metals of duplex stainless steels were quantitatively evaluated by Transverse-Varestraint test with gas tungsten arc welding (GTAW) and laser beam welding (LBW). Three kinds of duplex stainless steels (lean, standard and super duplex stainless steels) were used for evaluation. The solidification Brittle Temperature ranges (BTR) of duplex stainless steels were 58K, 60K and 76K for standard, lean and super duplex stainless steels, respectively, and were comparable to those of austenitic stainless steels with FA solidification mode. The BTRs in LBW were 10-15K lower than those in GTAW for any steels. In order to clarify the governing factors of solidification cracking in duplex stainless steels, the solidification segregation behaviours of alloying and impurity elements were numerically analysed during GTAW and LBW. Although the harmful elements to solidification cracking such as P, S and C were segregated in the residual liquid phase in any joints, the solidification segregation of P, S and C in LBW was inhibited compared with GTAW due to the rapid cooling rate in LBW. It followed that the decreased solidification cracking susceptibility of duplex stainless steels in LBW would be mainly attributed to the suppression of solidification segregation of P, S and C.
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Evaluation of solidification cracking susceptibility in laser welds for type 316FR stainless steel
Welding in the World, 2016Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Kazuyoshi SaidaAbstract:Laser beam welding (LBW) transverse-Varestraint tests were performed to quantitatively evaluate the solidification cracking susceptibility of laser welds of type 316FR stainless steel with two kinds of filler metal (316FR-A and 316FR-B). This found that as the welding speed increased from 1.67 to 40.0 mm/s, the increase in the solidification Brittle Temperature range (BTR) was greater in the case of 316FR-B (from 14 to 40 K) than 316FR-A (from 37 to 46 K). Based on theoretical calculations for the Temperature range over which both solid and liquid phases coexist, for which Kurz-Giovanola-Trivedi and solidification segregation models were used, the greater increase in BTR with 316FR-B was determined to be due to a larger decrease in δ-ferrite during welding solidification than with 316FR-A. This, in turn, greatly increases the segregation of impurities, which is responsible for the greater Temperature range of solid/liquid coexistence when using 316FR-B.
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evaluation of solidification cracking susceptibility in austenitic stainless steel welds using laser beam welding transverse varestraint test
2016Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Hayato Baba, Kazuyoshi SaidaAbstract:In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of type 310S and type 316L stainless steels, the Varestraint testing system for laser beam welding (LBW transverse-Varestraint test) was newly constructed. The timing-synchronisation among the laser oscillator, welding robot and hydraulic pressure devices was established by employing high-speed camera observation together with electrical signal control among the three components. Moreover, the yoke-drop time measured by high-speed camera was compensated to prevent underestimation of the crack length. The LBW transverse-Varestraint test was conducted varying the welding speed from 10.0 to 40.0 mm/s, and the transverse-Varestraint test with gas tungsten arc welding was also performed varying the welding speed from 1.67 to 5.00 mm/s. As the welding speed increased from 1.67 to 40.0 mm/s, the solidification Brittle Temperature range (BTR) of type 310S stainless steel welds was reduced from 146 to 120 K, while the BTR enlarged from 36 to 49 K in type 316L stainless steel welds. A numerical simulation of the solid/liquid coexistence Temperature range, using solidification segregation model combined with the Kurz–Giovanola–Trivedi model, explained the mechanism of the BTR shrinkage in type 310S stainless steel welds by reduction of the solid/liquid coexistence Temperature range of the weld metal due to the inhibited solidification segregation of solute elements and promoted dendrite tip supercooling attributed to rapid solidification in the LBW process. The reason why the BTR enlarged in type 316L stainless steel welds could be clarified by the enhanced solidification segregation of solute elements (mainly P and S), corresponding to the decrement in δ-ferrite content at the solidification completion in the weld metal. It follows that the opposite tendencies on solidification cracking susceptibility with increasing the welding speed in LBW could be explained by the different solidification segregation behaviour of solute elements, closely related with the δ-ferrite content.
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development of laser beam welding transverse varestraint test for assessment of solidification cracking susceptibility in laser welds
Metals and Materials International, 2015Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Hayato Baba, Kazuyoshi SaidaAbstract:In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of type 310S stainless steel, a transverse-Varestraint testing system using a laser beam welding apparatus was newly constructed. The timing-synchronization between the laser oscillator, welding robot and hydraulic pressure devices was established by employing high-speed camera observations together with electrical signal control among the three components. Moreover, the yoke-drop time measured by the camera was used to prevent underestimation of the crack length. The laser beam melt-run welding used a variable welding speed from 10.0 to 40.0 mm/s, while the gas tungsten arc welding varied the welding speed from 1.67 to 5.00 mm/s. As the welding speed increased from 1.67 to 40.0mm/s, the solidification Brittle Temperature range of type 310S stainless steel welds was reduced from 146 to 120 K. It follows that employing the laser beam welding process mitigates the solidification cracking susceptibility for type 310S stainless steel welds.
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influence of minor and impurity elements on hot cracking susceptibility of extra high purity type 310 stainless steels
2011Co-Authors: Kazutoshi Nishimoto, Kazuyoshi Saida, K Kiuchi, Junpei NakayamaAbstract:The hot cracking behaviour of extra high-purity stainless steels was investigated with respect to type 310 stainless steel with various amounts of minor and impurity elements such as C, P, S and Mn. The purity of the type 310 stainless steels used was enhanced in the order of Type 310
Brittle Temperature range due to the suppression of solidification segregation of minor and impurity elements. The quantitative contribution of minor and impurity elements to the hot cracking susceptibility of extra high-purity type 310 stainless steels was evaluated by using lab-melted steels with different amounts of C, P, S and Mn. The essential influence on solidification cracking was the ratio of P:S:C=1:1.3:0.5, while Mn negligibly ameliorated solidification cracking in the extra low S (and P) steels. On the other hand, a molecular orbital analysis to estimate the binding strength of the grain boundary suggested that the increased ductility-dip cracking susceptibility in extra high-purity steels was caused by grain boundary emBrittlement due to the refining of beneficial elements for grain boundary strengthening such as C.
A. A. Bessarabov - One of the best experts on this subject based on the ideXlab platform.
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STRESS RELAXATION IN ZIRCONIUM CARBIDE. REPORT 1. TEST METHOD AND STRESS RELAXATION CURVES
Strength of Materials, 1994Co-Authors: P. V. Zubarev, A. B. Kuraev, A. S. Maskaev, E. V. Astakhova, A. A. BessarabovAbstract:A method of stress relaxation tests with use of four-point bending is described. Experimental data is given on pure stress relaxation in ZrC{sub 1.00} with different grain sizes (d = 6-35 {mu}m) in the area of the ductile-to-Brittle Temperature (1600-2200{degrees}C).
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Stress relaxation in zirconium carbide. Report 1. Test method and stress relaxation curves
Strength of Materials, 1994Co-Authors: P. V. Zubarev, A. B. Kuraev, A. S. Maskaev, E. V. Astakhova, A. A. BessarabovAbstract:A method of stress relaxation tests with use of four-point bending is described. Experimental data is given on pure stress relaxation in ZrC _1.00 with different grain sizes (d= 6–55Μm in the area of the ductile-to-Brittle Temperature (1600–2200‡C)
Kazutoshi Nishimoto - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of solidification cracking susceptibility in laser welds for type 316FR stainless steel
Welding in the World, 2016Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Kazuyoshi SaidaAbstract:Laser beam welding (LBW) transverse-Varestraint tests were performed to quantitatively evaluate the solidification cracking susceptibility of laser welds of type 316FR stainless steel with two kinds of filler metal (316FR-A and 316FR-B). This found that as the welding speed increased from 1.67 to 40.0 mm/s, the increase in the solidification Brittle Temperature range (BTR) was greater in the case of 316FR-B (from 14 to 40 K) than 316FR-A (from 37 to 46 K). Based on theoretical calculations for the Temperature range over which both solid and liquid phases coexist, for which Kurz-Giovanola-Trivedi and solidification segregation models were used, the greater increase in BTR with 316FR-B was determined to be due to a larger decrease in δ-ferrite during welding solidification than with 316FR-A. This, in turn, greatly increases the segregation of impurities, which is responsible for the greater Temperature range of solid/liquid coexistence when using 316FR-B.
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evaluation of solidification cracking susceptibility in austenitic stainless steel welds using laser beam welding transverse varestraint test
2016Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Hayato Baba, Kazuyoshi SaidaAbstract:In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of type 310S and type 316L stainless steels, the Varestraint testing system for laser beam welding (LBW transverse-Varestraint test) was newly constructed. The timing-synchronisation among the laser oscillator, welding robot and hydraulic pressure devices was established by employing high-speed camera observation together with electrical signal control among the three components. Moreover, the yoke-drop time measured by high-speed camera was compensated to prevent underestimation of the crack length. The LBW transverse-Varestraint test was conducted varying the welding speed from 10.0 to 40.0 mm/s, and the transverse-Varestraint test with gas tungsten arc welding was also performed varying the welding speed from 1.67 to 5.00 mm/s. As the welding speed increased from 1.67 to 40.0 mm/s, the solidification Brittle Temperature range (BTR) of type 310S stainless steel welds was reduced from 146 to 120 K, while the BTR enlarged from 36 to 49 K in type 316L stainless steel welds. A numerical simulation of the solid/liquid coexistence Temperature range, using solidification segregation model combined with the Kurz–Giovanola–Trivedi model, explained the mechanism of the BTR shrinkage in type 310S stainless steel welds by reduction of the solid/liquid coexistence Temperature range of the weld metal due to the inhibited solidification segregation of solute elements and promoted dendrite tip supercooling attributed to rapid solidification in the LBW process. The reason why the BTR enlarged in type 316L stainless steel welds could be clarified by the enhanced solidification segregation of solute elements (mainly P and S), corresponding to the decrement in δ-ferrite content at the solidification completion in the weld metal. It follows that the opposite tendencies on solidification cracking susceptibility with increasing the welding speed in LBW could be explained by the different solidification segregation behaviour of solute elements, closely related with the δ-ferrite content.
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development of laser beam welding transverse varestraint test for assessment of solidification cracking susceptibility in laser welds
Metals and Materials International, 2015Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Hayato Baba, Kazuyoshi SaidaAbstract:In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of type 310S stainless steel, a transverse-Varestraint testing system using a laser beam welding apparatus was newly constructed. The timing-synchronization between the laser oscillator, welding robot and hydraulic pressure devices was established by employing high-speed camera observations together with electrical signal control among the three components. Moreover, the yoke-drop time measured by the camera was used to prevent underestimation of the crack length. The laser beam melt-run welding used a variable welding speed from 10.0 to 40.0 mm/s, while the gas tungsten arc welding varied the welding speed from 1.67 to 5.00 mm/s. As the welding speed increased from 1.67 to 40.0mm/s, the solidification Brittle Temperature range of type 310S stainless steel welds was reduced from 146 to 120 K. It follows that employing the laser beam welding process mitigates the solidification cracking susceptibility for type 310S stainless steel welds.
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influence of minor and impurity elements on hot cracking susceptibility of extra high purity type 310 stainless steels
2011Co-Authors: Kazutoshi Nishimoto, Kazuyoshi Saida, K Kiuchi, Junpei NakayamaAbstract:The hot cracking behaviour of extra high-purity stainless steels was investigated with respect to type 310 stainless steel with various amounts of minor and impurity elements such as C, P, S and Mn. The purity of the type 310 stainless steels used was enhanced in the order of Type 310
Brittle Temperature range due to the suppression of solidification segregation of minor and impurity elements. The quantitative contribution of minor and impurity elements to the hot cracking susceptibility of extra high-purity type 310 stainless steels was evaluated by using lab-melted steels with different amounts of C, P, S and Mn. The essential influence on solidification cracking was the ratio of P:S:C=1:1.3:0.5, while Mn negligibly ameliorated solidification cracking in the extra low S (and P) steels. On the other hand, a molecular orbital analysis to estimate the binding strength of the grain boundary suggested that the increased ductility-dip cracking susceptibility in extra high-purity steels was caused by grain boundary emBrittlement due to the refining of beneficial elements for grain boundary strengthening such as C. -
Effect of Ni content on solidification cracking susceptibility of Inconel 706 Ni-base superalloy
Welding International, 1999Co-Authors: R Kayano, T Ishiguro, Kazutoshi NishimotoAbstract:Summary Inconel 706 Ni-base superalloy has been developed on the basis of Inconel 718 to confer the economic advantage of Ni content saving. The modified alloy has much the same high strength, high ductility and high-Temperature oxidation resistance as Inconel 718, while having a slightly higher hot-cracking susceptibility. The hot-cracking susceptibility of Inconel 706, however, has not yet been investigated in any great detail. The trans-varestraint test was conducted to determine the solidification cracking susceptibility of Inconel 706 depending on the base metal Ni content. Three types of Ni-base alloys with an Ni content of 44, 55, and 65mass%Ni were used. The fracture surfaces of the trans-varestraint test specimens show the typical dendrite structure. Quantitative analysis of the cracks reveals that the solidification crack length and the Temperature range in which hot-cracking occurs (Brittle Temperature range (BTR)) decreases with an increasing Ni content. Calculation of the liquidus and solidus...
P. V. Zubarev - One of the best experts on this subject based on the ideXlab platform.
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STRESS RELAXATION IN ZIRCONIUM CARBIDE. REPORT 1. TEST METHOD AND STRESS RELAXATION CURVES
Strength of Materials, 1994Co-Authors: P. V. Zubarev, A. B. Kuraev, A. S. Maskaev, E. V. Astakhova, A. A. BessarabovAbstract:A method of stress relaxation tests with use of four-point bending is described. Experimental data is given on pure stress relaxation in ZrC{sub 1.00} with different grain sizes (d = 6-35 {mu}m) in the area of the ductile-to-Brittle Temperature (1600-2200{degrees}C).
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Stress relaxation in zirconium carbide. Report 1. Test method and stress relaxation curves
Strength of Materials, 1994Co-Authors: P. V. Zubarev, A. B. Kuraev, A. S. Maskaev, E. V. Astakhova, A. A. BessarabovAbstract:A method of stress relaxation tests with use of four-point bending is described. Experimental data is given on pure stress relaxation in ZrC _1.00 with different grain sizes (d= 6–55Μm in the area of the ductile-to-Brittle Temperature (1600–2200‡C)
Eunjoon Chun - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of solidification cracking susceptibility in laser welds for type 316FR stainless steel
Welding in the World, 2016Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Kazuyoshi SaidaAbstract:Laser beam welding (LBW) transverse-Varestraint tests were performed to quantitatively evaluate the solidification cracking susceptibility of laser welds of type 316FR stainless steel with two kinds of filler metal (316FR-A and 316FR-B). This found that as the welding speed increased from 1.67 to 40.0 mm/s, the increase in the solidification Brittle Temperature range (BTR) was greater in the case of 316FR-B (from 14 to 40 K) than 316FR-A (from 37 to 46 K). Based on theoretical calculations for the Temperature range over which both solid and liquid phases coexist, for which Kurz-Giovanola-Trivedi and solidification segregation models were used, the greater increase in BTR with 316FR-B was determined to be due to a larger decrease in δ-ferrite during welding solidification than with 316FR-A. This, in turn, greatly increases the segregation of impurities, which is responsible for the greater Temperature range of solid/liquid coexistence when using 316FR-B.
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evaluation of solidification cracking susceptibility in austenitic stainless steel welds using laser beam welding transverse varestraint test
2016Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Hayato Baba, Kazuyoshi SaidaAbstract:In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of type 310S and type 316L stainless steels, the Varestraint testing system for laser beam welding (LBW transverse-Varestraint test) was newly constructed. The timing-synchronisation among the laser oscillator, welding robot and hydraulic pressure devices was established by employing high-speed camera observation together with electrical signal control among the three components. Moreover, the yoke-drop time measured by high-speed camera was compensated to prevent underestimation of the crack length. The LBW transverse-Varestraint test was conducted varying the welding speed from 10.0 to 40.0 mm/s, and the transverse-Varestraint test with gas tungsten arc welding was also performed varying the welding speed from 1.67 to 5.00 mm/s. As the welding speed increased from 1.67 to 40.0 mm/s, the solidification Brittle Temperature range (BTR) of type 310S stainless steel welds was reduced from 146 to 120 K, while the BTR enlarged from 36 to 49 K in type 316L stainless steel welds. A numerical simulation of the solid/liquid coexistence Temperature range, using solidification segregation model combined with the Kurz–Giovanola–Trivedi model, explained the mechanism of the BTR shrinkage in type 310S stainless steel welds by reduction of the solid/liquid coexistence Temperature range of the weld metal due to the inhibited solidification segregation of solute elements and promoted dendrite tip supercooling attributed to rapid solidification in the LBW process. The reason why the BTR enlarged in type 316L stainless steel welds could be clarified by the enhanced solidification segregation of solute elements (mainly P and S), corresponding to the decrement in δ-ferrite content at the solidification completion in the weld metal. It follows that the opposite tendencies on solidification cracking susceptibility with increasing the welding speed in LBW could be explained by the different solidification segregation behaviour of solute elements, closely related with the δ-ferrite content.
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development of laser beam welding transverse varestraint test for assessment of solidification cracking susceptibility in laser welds
Metals and Materials International, 2015Co-Authors: Eunjoon Chun, Kazutoshi Nishimoto, Hayato Baba, Kazuyoshi SaidaAbstract:In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of type 310S stainless steel, a transverse-Varestraint testing system using a laser beam welding apparatus was newly constructed. The timing-synchronization between the laser oscillator, welding robot and hydraulic pressure devices was established by employing high-speed camera observations together with electrical signal control among the three components. Moreover, the yoke-drop time measured by the camera was used to prevent underestimation of the crack length. The laser beam melt-run welding used a variable welding speed from 10.0 to 40.0 mm/s, while the gas tungsten arc welding varied the welding speed from 1.67 to 5.00 mm/s. As the welding speed increased from 1.67 to 40.0mm/s, the solidification Brittle Temperature range of type 310S stainless steel welds was reduced from 146 to 120 K. It follows that employing the laser beam welding process mitigates the solidification cracking susceptibility for type 310S stainless steel welds.