Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c0091009
A thick-walled tube that was weld fabricated for use as a pressure vessel exhibited cracks. Similar cracking was apparent at the weld toes after postweld stress relief or quench-and-temper heat treatment. The cracks were not detectable by nondestructive examination after welding, immediately prior to heat treatment. Multiple-pass arc welds secured the carbon-steel flanges to the Ni-Cr-Mo-V alloy steel tubes. Investigation (visual inspection, metallographic analysis, and evaluation of the fabrication history and the analysis data) supported the conclusion that the tube failed as a result of stress-relief cracking. Very high residual stresses often result from welding thick sections of hardenable steels, even when preheating is employed. Quenched-and-tempered steels containing vanadium, as well as HSLA steels with a vanadium addition, have been shown to be susceptible to this embrittlement. Manufacturers of susceptible steels recommend use of these materials in the as-welded condition.
{"title":"Stress-Relief Cracking of a Welded Alloy Steel Tube","authors":"","doi":"10.31399/asm.fach.process.c0091009","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c0091009","url":null,"abstract":"\u0000 A thick-walled tube that was weld fabricated for use as a pressure vessel exhibited cracks. Similar cracking was apparent at the weld toes after postweld stress relief or quench-and-temper heat treatment. The cracks were not detectable by nondestructive examination after welding, immediately prior to heat treatment. Multiple-pass arc welds secured the carbon-steel flanges to the Ni-Cr-Mo-V alloy steel tubes. Investigation (visual inspection, metallographic analysis, and evaluation of the fabrication history and the analysis data) supported the conclusion that the tube failed as a result of stress-relief cracking. Very high residual stresses often result from welding thick sections of hardenable steels, even when preheating is employed. Quenched-and-tempered steels containing vanadium, as well as HSLA steels with a vanadium addition, have been shown to be susceptible to this embrittlement. Manufacturers of susceptible steels recommend use of these materials in the as-welded condition.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114232450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c0047745
A 321 stainless steel radar coolant-system assembly fabricated by torch brazing with AWS type 3A flux, failed at the brazed joint when subjected to mild handling before installation, after being stored for about two years. It was revealed by visual examination of the failed braze that the filler metal had not covered all mating surfaces. Lack of a metallurgical bond between the brazing alloy and stainless steel and instead mechanical bonding of the filler metal to an oxide layer on the stainless steel surface was revealed by examination of the broken joint at the cup. It was indicated by the thickness of the oxide layer that the steel surface was not protected from oxidation by the flux during torch heating. It was concluded that the failure was caused by lack of a metallurgical bond between the brazing alloy and the stainless steel. Components made of 347 stainless steel (better brazeability) brazed with a larger torch tip (wider heat distribution) and AWS type 3B flux (better filler-metal flow) were recommended for radar coolant-system assembly.
{"title":"Failure of a Brazed Joint in a Type 321 Stainless Steel Assembly Due to Inadequate Cleaning","authors":"","doi":"10.31399/asm.fach.process.c0047745","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c0047745","url":null,"abstract":"\u0000 A 321 stainless steel radar coolant-system assembly fabricated by torch brazing with AWS type 3A flux, failed at the brazed joint when subjected to mild handling before installation, after being stored for about two years. It was revealed by visual examination of the failed braze that the filler metal had not covered all mating surfaces. Lack of a metallurgical bond between the brazing alloy and stainless steel and instead mechanical bonding of the filler metal to an oxide layer on the stainless steel surface was revealed by examination of the broken joint at the cup. It was indicated by the thickness of the oxide layer that the steel surface was not protected from oxidation by the flux during torch heating. It was concluded that the failure was caused by lack of a metallurgical bond between the brazing alloy and the stainless steel. Components made of 347 stainless steel (better brazeability) brazed with a larger torch tip (wider heat distribution) and AWS type 3B flux (better filler-metal flow) were recommended for radar coolant-system assembly.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114429827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c0046044
A rocket-motor case made of consumable-electrode vacuum arc remelted D-6ac alloy steel failed during hydrostatic proof-pressure testing. Close visual examination, magnetic-particle inspection, and hardness tests showed cracks that appeared to have occurred after austenitizing but before tempering. Microscopic examinations of ethereal picral etched sections indicated that the cracks appeared before or during the final tempering phase of the heat treatment and that cracking had occurred while the steel was in the as-quenched condition, before its 315 deg C (600 deg F) snap temper. Chemical analysis of the cracked metal showed a slightly higher level of carbon than in the component that did not crack. X-ray diffraction studies of material from the fractured dome showed a very low level of retained austenite, and chemical analysis showed a slightly higher content of carbon in the metal of the three cracked components. Bend tests verified the conclusion that the most likely mechanism of delayed quench cracking was isothermal transformation of retained austenite to martensite under the influence of residual quenching stresses. Recommendations included modifying the quenching portion of the heat-treating cycle and tempering in the salt pot used for quenching, immediately after quenching.
{"title":"Brittle Fracture of Rocket-Motor Case That Originated at Delayed Quench Cracks","authors":"","doi":"10.31399/asm.fach.process.c0046044","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c0046044","url":null,"abstract":"\u0000 A rocket-motor case made of consumable-electrode vacuum arc remelted D-6ac alloy steel failed during hydrostatic proof-pressure testing. Close visual examination, magnetic-particle inspection, and hardness tests showed cracks that appeared to have occurred after austenitizing but before tempering. Microscopic examinations of ethereal picral etched sections indicated that the cracks appeared before or during the final tempering phase of the heat treatment and that cracking had occurred while the steel was in the as-quenched condition, before its 315 deg C (600 deg F) snap temper. Chemical analysis of the cracked metal showed a slightly higher level of carbon than in the component that did not crack. X-ray diffraction studies of material from the fractured dome showed a very low level of retained austenite, and chemical analysis showed a slightly higher content of carbon in the metal of the three cracked components. Bend tests verified the conclusion that the most likely mechanism of delayed quench cracking was isothermal transformation of retained austenite to martensite under the influence of residual quenching stresses. Recommendations included modifying the quenching portion of the heat-treating cycle and tempering in the salt pot used for quenching, immediately after quenching.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114623844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c0089646
Nodular cast iron crankshafts and their main-bearing inserts were causing premature failures in engines within the first 1600 km (1000 mi) of operation. The failures were indicated by internal noise, operation at low pressure, and total seizing. Concurrent with the incidence of engine field failures was a manufacturing problem: the inability to maintain a similar microfinish on the cope and drag sides of a cast main-bearing journal. Investigation supported the conclusion that the root cause of the failure was carbon flotation due to the crankshafts involved in the failures showing a higher-than-normal carbon content and/or carbon equivalent. Larger and more numerous cope side graphite nodules broke open, causing ferrite caps or burrs. They then became the mechanism of failure by breaking down the oil film and eroding the beating material. A byproduct was heat, which assisted the failure. Recommendations included establishing closer control of chemical composition and foundry casting practices to alleviate the carbon-flotation form of segregation. Additionally, some nonmetallurgical practices in journal-finishing techniques were suggested to ensure optimal surface finish.
{"title":"Premature Engine Failure Due to Improper Surface Finish Caused by Carbon Flotation","authors":"","doi":"10.31399/asm.fach.process.c0089646","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c0089646","url":null,"abstract":"\u0000 Nodular cast iron crankshafts and their main-bearing inserts were causing premature failures in engines within the first 1600 km (1000 mi) of operation. The failures were indicated by internal noise, operation at low pressure, and total seizing. Concurrent with the incidence of engine field failures was a manufacturing problem: the inability to maintain a similar microfinish on the cope and drag sides of a cast main-bearing journal. Investigation supported the conclusion that the root cause of the failure was carbon flotation due to the crankshafts involved in the failures showing a higher-than-normal carbon content and/or carbon equivalent. Larger and more numerous cope side graphite nodules broke open, causing ferrite caps or burrs. They then became the mechanism of failure by breaking down the oil film and eroding the beating material. A byproduct was heat, which assisted the failure. Recommendations included establishing closer control of chemical composition and foundry casting practices to alleviate the carbon-flotation form of segregation. Additionally, some nonmetallurgical practices in journal-finishing techniques were suggested to ensure optimal surface finish.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114701982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c0047749
A type 321 stainless steel (AMS 5570) pressure-tube assembly that contained a brazed reinforcing liner leaked during a pressure test. Fluorescent liquid-penetrant inspection revealed a circumferential crack extended approximately 180 deg around the tube parallel to the fillet of the brazed joint. The presence of multiple origin cracks was indicated on the inside surface of a fractured portion of the crack surface. The cracks had originated adjacent to the braze joining the tube and the reinforcing liner and propagated through the wall to the outer surface. The residues on the inner surface of the tube were identified as fluorides from the brazing flux by chemical analysis. The nature of the crack, potential for corrosion due to residual fluorides and residual swaging stress in the tube prior to brazing, confirmed that failure of the tube end was due to stress-corrosion cracking. Stress relief treatment of tube before brazing and immediate cleaning of brazing residual fluorides was recommended to avoid failure.
{"title":"Stress-Corrosion Cracking of a Brazed Joint in a Type 321 Stainless Steel Pressure-Tube Assembly","authors":"","doi":"10.31399/asm.fach.process.c0047749","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c0047749","url":null,"abstract":"\u0000 A type 321 stainless steel (AMS 5570) pressure-tube assembly that contained a brazed reinforcing liner leaked during a pressure test. Fluorescent liquid-penetrant inspection revealed a circumferential crack extended approximately 180 deg around the tube parallel to the fillet of the brazed joint. The presence of multiple origin cracks was indicated on the inside surface of a fractured portion of the crack surface. The cracks had originated adjacent to the braze joining the tube and the reinforcing liner and propagated through the wall to the outer surface. The residues on the inner surface of the tube were identified as fluorides from the brazing flux by chemical analysis. The nature of the crack, potential for corrosion due to residual fluorides and residual swaging stress in the tube prior to brazing, confirmed that failure of the tube end was due to stress-corrosion cracking. Stress relief treatment of tube before brazing and immediate cleaning of brazing residual fluorides was recommended to avoid failure.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122670399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c0090974
A cast steel bracket manufactured in accordance with ASTM A 148 grade 135/125 steel failed in railroad maintenance service. Ancillary property requirements included a 285 to 331 HB hardness range and minimum impact energy of 27 J (20 ft·lbf) at -40 deg C (-40 deg F). The conditions at the time of failure were characterized as relatively cold. Investigation (visual inspection, chemical analysis, and unetched 119x and 2% nital etched 119x SEM images) supported the conclusion that the bracket failed through brittle overload fracture due to a number of synergistic factors. The quenched-and-tempered microstructure contained solidification shrinkage, inherently poor ductility, and type II Mn-S inclusions that are known to reduce ductility. The macro and microscale fracture features confirmed that the casting was likely in low-temperature service at the time of failure. The composition and mechanical properties of the casting did not satisfy the design requirements. Recommendations included exerting better composition control, primarily with regard to melting, deoxidation, and nitrogen control. Better deoxidation practice was recommended to generate the more desirable Mn-S inclusion morphology, and reevaluation of the casting design was suggested to minimize shrinkage.
{"title":"Fracture of a Cast Steel Bracket","authors":"","doi":"10.31399/asm.fach.process.c0090974","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c0090974","url":null,"abstract":"\u0000 A cast steel bracket manufactured in accordance with ASTM A 148 grade 135/125 steel failed in railroad maintenance service. Ancillary property requirements included a 285 to 331 HB hardness range and minimum impact energy of 27 J (20 ft·lbf) at -40 deg C (-40 deg F). The conditions at the time of failure were characterized as relatively cold. Investigation (visual inspection, chemical analysis, and unetched 119x and 2% nital etched 119x SEM images) supported the conclusion that the bracket failed through brittle overload fracture due to a number of synergistic factors. The quenched-and-tempered microstructure contained solidification shrinkage, inherently poor ductility, and type II Mn-S inclusions that are known to reduce ductility. The macro and microscale fracture features confirmed that the casting was likely in low-temperature service at the time of failure. The composition and mechanical properties of the casting did not satisfy the design requirements. Recommendations included exerting better composition control, primarily with regard to melting, deoxidation, and nitrogen control. Better deoxidation practice was recommended to generate the more desirable Mn-S inclusion morphology, and reevaluation of the casting design was suggested to minimize shrinkage.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122703024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c9001178
F. Naumann, F. Spies
Eight cylinderhead screws cracked after a short running time in motors. They were made of Fe-0.45C-1Cr steel, had rolled threads, were heat treated to 110 kg/sq mm tensile strength, and were electrolytically galvanized. All fractured at the root of the thread. The surfaces of fracture were fine-grained and had not spread by rubbing. Because the screws were electrolytically galvanized, failure resulted from “delayed fracture.” Experience has shown that this type of fracture is seen on production parts made of high-strength steels, which absorbed hydrogen during pickling or during a galvanic surface treatment. Such parts will rupture below the elastic limit during continuous stressing. This often occurs only after the expiration of a certain time period, and preferably at locations of stress concentrations such as changes in cross section or threads. As a rule, the hydrogen cannot be verified analytically because most of it escapes again after prolonged storage at room temperature or short heating at 100 to 200 deg C.
{"title":"Fractures of Electro-Galvanized Cylinderhead Screws","authors":"F. Naumann, F. Spies","doi":"10.31399/asm.fach.process.c9001178","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c9001178","url":null,"abstract":"\u0000 Eight cylinderhead screws cracked after a short running time in motors. They were made of Fe-0.45C-1Cr steel, had rolled threads, were heat treated to 110 kg/sq mm tensile strength, and were electrolytically galvanized. All fractured at the root of the thread. The surfaces of fracture were fine-grained and had not spread by rubbing. Because the screws were electrolytically galvanized, failure resulted from “delayed fracture.” Experience has shown that this type of fracture is seen on production parts made of high-strength steels, which absorbed hydrogen during pickling or during a galvanic surface treatment. Such parts will rupture below the elastic limit during continuous stressing. This often occurs only after the expiration of a certain time period, and preferably at locations of stress concentrations such as changes in cross section or threads. As a rule, the hydrogen cannot be verified analytically because most of it escapes again after prolonged storage at room temperature or short heating at 100 to 200 deg C.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128723400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c0047632
An air bottle, machined from a solid block of aluminum alloy 2219-T852, displayed liquid-penetrant crack indications after assembly welding. The air bottle was machined to rough shape, a 3.8 mm (0.15 in.) wall thickness cylindrical cup with a 19 mm (3/4 in.) wall thickness integral boss on one side. After annealing, hot spinning, annealing a second time, and tack welding a port fitting, the assembly was torch preheated to 120 to 150 deg C (250 to 300 deg F). The port fitting was then welded in place. Final full heat treatment to the T62 temper was followed by machining, testing, and inspection. The crack indications were found only on one side of the boss and on the lower portion of the hot-spun dome region. The metallographic specimens revealed triangular voids and severe intergranular cracks. The cracks displayed the glossy surfaces typical of melted and resolidified material. The localized cracks in the air bottle were from grain-boundary eutectic melting caused by local torch overheating used in preparation for assembly welding of a port fitting. A change in design was scheduled to semiautomatic welding without the use of preheating for the joining of the port fitting for the dome opening.
{"title":"Intergranular Cracking in an Air Bottle Because of Torch Overheating Before Welding","authors":"","doi":"10.31399/asm.fach.process.c0047632","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c0047632","url":null,"abstract":"\u0000 An air bottle, machined from a solid block of aluminum alloy 2219-T852, displayed liquid-penetrant crack indications after assembly welding. The air bottle was machined to rough shape, a 3.8 mm (0.15 in.) wall thickness cylindrical cup with a 19 mm (3/4 in.) wall thickness integral boss on one side. After annealing, hot spinning, annealing a second time, and tack welding a port fitting, the assembly was torch preheated to 120 to 150 deg C (250 to 300 deg F). The port fitting was then welded in place. Final full heat treatment to the T62 temper was followed by machining, testing, and inspection. The crack indications were found only on one side of the boss and on the lower portion of the hot-spun dome region. The metallographic specimens revealed triangular voids and severe intergranular cracks. The cracks displayed the glossy surfaces typical of melted and resolidified material. The localized cracks in the air bottle were from grain-boundary eutectic melting caused by local torch overheating used in preparation for assembly welding of a port fitting. A change in design was scheduled to semiautomatic welding without the use of preheating for the joining of the port fitting for the dome opening.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"469 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120940096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c9001194
F. Naumann, F. Spies
A seamless hot-drawn boiler tube NW 300 of 318 mm OD and 9 mm wall thickness made of steel 15Mo3 was bent with sand filling after preheating allegedly to 1000 deg C. In the process it had cracked repeatedly in the drawn fiber. The composition corresponded to specifications, but exceptionally high copper content was noticeable. Microstructural examination showed the damage was due to overheating and burning during preheating and bending. Furthermore, crack formation was promoted by precipitation of metallic copper that had penetrated into the austenitic grain boundaries under the influence of tensile stresses that arose during bending. This phenomenon is known as “solder brittleness.”
{"title":"Boiler Tube Cracked During Bending","authors":"F. Naumann, F. Spies","doi":"10.31399/asm.fach.process.c9001194","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c9001194","url":null,"abstract":"\u0000 A seamless hot-drawn boiler tube NW 300 of 318 mm OD and 9 mm wall thickness made of steel 15Mo3 was bent with sand filling after preheating allegedly to 1000 deg C. In the process it had cracked repeatedly in the drawn fiber. The composition corresponded to specifications, but exceptionally high copper content was noticeable. Microstructural examination showed the damage was due to overheating and burning during preheating and bending. Furthermore, crack formation was promoted by precipitation of metallic copper that had penetrated into the austenitic grain boundaries under the influence of tensile stresses that arose during bending. This phenomenon is known as “solder brittleness.”","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121346907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-01DOI: 10.31399/asm.fach.process.c9001150
Fred W. Tatar
A number of rotating blades in a diffuser at a sugar beet processing plant fabricated from rectangular bars cut from rolled carbon-manganese steel plate fractured brittlely. However, apparently identical blades underwent significant plastic deformation without fracture. Inspection of both fractured and bent blades revealed similar preexisting cracks at the toes of bar attachment welds. Metallographic examination of the bent and the fractured bars revealed they had been cut parallel and transverse, respectively, to the rolling direction of the steel plate. Due to the combined effects of the low fracture toughness of the plate on planes parallel in the rolling direction, the presence of the preexisting cracks, and the relatively large section thickness of the bars, the bars whose lengths were transverse to the rolling direction fractured brittlely when subjected to impact loads. Had the poor transverse properties of thick-section plate been recognized, and all the bars properly cut with respect to the rolling direction, the premature fractures would not have occurred.
{"title":"Improper Fabrication Rotating Blades Results in Premature Failure","authors":"Fred W. Tatar","doi":"10.31399/asm.fach.process.c9001150","DOIUrl":"https://doi.org/10.31399/asm.fach.process.c9001150","url":null,"abstract":"\u0000 A number of rotating blades in a diffuser at a sugar beet processing plant fabricated from rectangular bars cut from rolled carbon-manganese steel plate fractured brittlely. However, apparently identical blades underwent significant plastic deformation without fracture. Inspection of both fractured and bent blades revealed similar preexisting cracks at the toes of bar attachment welds. Metallographic examination of the bent and the fractured bars revealed they had been cut parallel and transverse, respectively, to the rolling direction of the steel plate. Due to the combined effects of the low fracture toughness of the plate on planes parallel in the rolling direction, the presence of the preexisting cracks, and the relatively large section thickness of the bars, the bars whose lengths were transverse to the rolling direction fractured brittlely when subjected to impact loads. Had the poor transverse properties of thick-section plate been recognized, and all the bars properly cut with respect to the rolling direction, the premature fractures would not have occurred.","PeriodicalId":294593,"journal":{"name":"ASM Failure Analysis Case Histories: Processing Errors and Defects","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116463175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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