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MnS inclusions
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in Mechanisms and Appearances of Ductile and Brittle Fracture in Metals
> Failure Analysis and Prevention
Published: 01 January 2002
Fig. 10 Debonding associated with a MnS inclusion in a bainitic microstructure. Loading direction indicated. Source: Ref 30
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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0089793
EISBN: 978-1-62708-235-8
... showed the main crack had propagated parallel to the fusion boundary along the subcritical HAZ and was associated with long stringers of type II manganese sulfide (MnS) inclusions. This supported the conclusion that the weld failed by lamellar tearing as a result of the high rotational strain induced...
Abstract
During the final shop welding of a large armature for a direct-current motor (4475 kW, or 6000 hp), a loud bang was heard, and the welding operation stopped. When the weld was cold, nondestructive evaluation revealed a large crack adjacent to the root weld. Investigation showed the main crack had propagated parallel to the fusion boundary along the subcritical HAZ and was associated with long stringers of type II manganese sulfide (MnS) inclusions. This supported the conclusion that the weld failed by lamellar tearing as a result of the high rotational strain induced at the root of the weld caused by the weld design, weld sequence, and thermal effects. Recommendations included removing the old weldment to a depth beyond the crack and replacing this with a softer weld metal layer before making the main weld onto the softer layer.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001780
EISBN: 978-1-62708-241-9
...Abstract Abstract A number of failures involving carbon and alloy steels were analyzed to assess the effects of inclusions and their influence on mechanical properties. Inclusions, including brittle oxides and more ductile manganese sulfides (MnS), affect fatigue endurance limit, fatigue crack...
Abstract
A number of failures involving carbon and alloy steels were analyzed to assess the effects of inclusions and their influence on mechanical properties. Inclusions, including brittle oxides and more ductile manganese sulfides (MnS), affect fatigue endurance limit, fatigue crack propagation rates, fracture toughness, notch toughness, and transverse tensile properties, and do so in an anisotropic manner with respect to rolling direction. Significant property anisotropy has been documented in the failures investigated, providing evidence that designers failed to account for it. Typical fracture morphologies observed in such cases and metallographic appearances of MnS-containing materials are illustrated.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0090974
EISBN: 978-1-62708-235-8
.... 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...
Abstract
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.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c9001489
EISBN: 978-1-62708-217-4
... frequently observed inclusions were spinel solid solutions of the type MO middot; N2O3, where M = Fe, Mn, or Mg and N = Cr or Al. The detrimental inclusions were corundum, calcium aluminates, cristobalite, and silicates. The most detrimental phases were traced on the surfaces of the specimens fractured using...
Abstract
The cause of the fatigue failure in the retaining ring of the compressor region of an aero-engine turbine was found to be the presence of a high concentration of nonmetallic inclusions. The results of chemical analysis were used to estimate the phases present. The most frequently observed inclusions were spinel solid solutions of the type MO middot; N2O3, where M = Fe, Mn, or Mg and N = Cr or Al. The detrimental inclusions were corundum, calcium aluminates, cristobalite, and silicates. The most detrimental phases were traced on the surfaces of the specimens fractured using impact loading; the comparison is being made with the polished surfaces and the tensile specimen fracture surfaces. The inclusions in the failed retaining ring were compared with the ones in a similar component obtained from a used engine. In the case of the latter, a large number of fine and elongated (Mn, Cr, Fe)S inclusions were present along with spinels. The nondeformable, rigid oxide particles are considered more undesirable than the sulfides as far as fatigue life of the component is concerned. It has been reported that the presence of sulfides may eliminate the stresses due to oxides.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001302
EISBN: 978-1-62708-215-0
... processing. Fig. 6 Optical micrographs of the spool region of failed kingpin. (a) Away from the site of the failure. This view shows MnS stringers typical of those seen in wrought steel products. Not etched. (b) Close to the site of the failure. This view shows the globular MnS inclusions associated...
Abstract
To forged AISI 4140 steel trailer kingpins fractured after 4 to 6 months of service. Fractographic and metallographic examination revealed that cracks were present in the spool-flange shoulder region of the defective kingpins prior to installation on the trailers. The cracks grew and coalesced during service. Consideration of the manufacturing process suggested that the cracks were the result of overheating of the kingpin blanks prior to forging, which was exacerbated during forging by deformation heating in the highly-strained region. This view was supported by results of two types of tensile tests conducted near the incipient melting temperature at the grain boundaries. All kingpins made by the supplier of the fractured ones were ultrasonically inspected and six more anticipated to fail were found. It was recommended that the heating of forging blanks be more carefully controlled, especially with respect to the accuracy of the optical pyrometer temperature readout. Also, procedures must be developed such that forging blanks that trigger the over-temperature alarm are reliably and permanently removed from the production line.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001037
EISBN: 978-1-62708-214-3
... stress raisers at “A” and the rough machining on surface “B.” Metallography Microstructural Analysis The core ( Fig. 3 ) had a banded microstructure of ferrite and pearlite and contained some MnS inclusions. The case ( Fig. 4 ) showed a tempered martensite matrix with a nearly continuous...
Abstract
Six wrist pins in a high-performance six-cylinder automotive engine failed after 4800 km (3000 mi) of normal operation. The pins were made of low-carbon steel that had been carburized both inside and outside. Two failed pins were examined. One had fractured into three pieces. The other had not fractured, but exhibited circumferential cracks on the surface of the central zone. Visual surface examination and metallographic and chemical analyses were performed on the specimens. Cracking was attributed primarily to poor heat treatment, resulting in a brittle grain-boundary network of cementite, and to a design that had a raised central section of the inner diameter whose fillets were locations of high stress concentration. Rough machining of the inner diameter and an excessively deep case also contributed to failure. A double type of heat treatment after carburizing and change of the design to eliminate the raised central section were recommended.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.auto.c9001256
EISBN: 978-1-62708-218-1
... a specimen was subjected to electronprobe microanalysts. The result was as given below: “The elements found to be present in the inclusion are: Mn, Si, Cr and S. No Fe was found in the inclusion. The distributions of S and Si were not uniform along the length of the inclusion. Mn content was found...
Abstract
There was a large incidence of surface defects on the crank pins and journals and other areas of crank shafts of a high power automotive engine. The steel used was a Cr-Mo type of nitriding steel. Metallographic observations conclusively proved that the defective areas were entrapment of foreign bodies, resulting from steel making/deoxidizing/teeming stages. The occasionally globular nature of the foreign particles suggested these were formed at the liquid condition of the steel. The ratio of Mn-Si as seen on electron probe microanalysis also suggested the globules high in Mn content might have resulted in deoxidizing stage. Particularly the absence of Fe in some areas in the inclusion was indicative of precipitation deoxidation by ferromanganese/ferrosilicon. The defects apparently did not have time to coalesce and rise up to the top.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.usage.c9001597
EISBN: 978-1-62708-236-5
... source of the failure and thus no continued analysis to pin down and eliminate the root cause. Continuous cast steel Induction hardening MnS inclusions Segregation Woody fracture 1548 (mod) Fatigue fracture Failure analysis has long been a special field of study for metallurgical...
Abstract
This case study involves two continuously cast steel crankshaft failures. Three parties performed their own failure analyses: (1) the engine manufacturer responsible for component design, specification, and application; (2) the steel supplier and forging supplier responsible for making the steel, forging the shape, and preliminary heat treatment; and (3) a supplier that provided induction hardening, finish machining, and inspection. An independent engineering firm was subsequently involved, but because each party had its own agenda, there was no agreement on the metallurgical source of the failure and thus no continued analysis to pin down and eliminate the root cause.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.marine.c9001141
EISBN: 978-1-62708-227-3
... inclusions in the base of the elongated depressions. Fig. 13 Fracture surface showing fern-like pattern of inclusions. The inclusions are composed mainly of Mn and S and from their flat elongated form can be identified as Type II MnS inclusions. A shear wall between two terraces is seen in Fig...
Abstract
During a refit of a twenty-year-old Naval destroyer, two cracks were found on the inside of the killed carbon-manganese steel hull plate at the forward end of the boiler room. The cracks coincided with the location of the top and bottom plates of the bilge keel. Metallurgical examination of sections cut from the cracked area identified lamellar tearing as the principle cause of the cracking. This was surprising in 6 mm thick hull plates. Corrosion fatigue and general corrosion also contributed to hull plate perforation. Although it is probable that more lamellar tears exist near the bilge keel in other ships and may be a nuisance in the future, the hull integrity of the ships is not threatened and major repairs are not needed.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001592
EISBN: 978-1-62708-228-0
... was ferrite and pearlite with numerous inclusions dispersed throughout the structure ( Fig. 5 ). The inclusions were analyzed as MnS particles. The inclusions were elongated parallel to the rod length and contained numerous micro-cracks. Additionally, the inclusions provided preferential sites for pitting...
Abstract
Sucker-rod pumps are operating in very aggressive environments in oil well production. The combined effect of a corrosive environment and significant mechanical loads contribute to frequent cases of failure of the rod string during operation. Standards and recommendations have been developed to control and avoid those failures. This study presents various failure cases of sucker rods in different applications. The heat treatment of the steel material and the resulting microstructure are an important factor in the behavior of the sucker rod. A spheroidized microstructure presents a weaker resistance to corrosion affecting the rod life. Non-metallic inclusions are a pitting preferential site leading to fatigue crack initiation. Heterogeneous microstructure as banded martensite and ferrite/pearlite decreases the ductility of the material affecting the fatigue propagation resistance.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.petrol.c9001603
EISBN: 978-1-62708-228-0
.... According to the authors, MnS inclusions act as a preferable site for the ferrite nucleation, which starts at the interface between the matrix and MnS. The volume fraction of inclusions in the vicinity of the crack (fusion zone) and away from the crack (PM) was determined to be 0.15 and 0.14...
Abstract
The genesis of failure of 6.1 mm thick electric resistance welded API 5L X-46 pipes during pretesting at a pressure equivalent to 90% of specified minimum yield strength was investigated. Cracks were found to initiate on the outer surface of the pipes in the fusion zone and propagate along the through-thickness direction. The presence of extensive decarburization and formation of a soft ferrite band within the fusion zone may have contributed to the nucleation of the cracks. Crack propagation was aided by the presence of exogenous inclusions entrapped within the fusion zone. Analysis of these inclusions confirmed the presence of Fe, Si, Ca, and O, indicating slag entrapment to be the most probable culprit.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001206
EISBN: 978-1-62708-235-8
... in a section through the end crater, Etch: nital. 50 × Fig. 6 As Fig. 5 . 200 × Fig. 7 As Fig. 5 . 500 × Fig. 8 MnS inclusions and ferrite network at the austenite grain boundaries in longitudinal section through the starting point of the weld seam, Etch: picral. 500...
Abstract
A number of seamless pipe nipples of 70 mm diam and 3.5 mm wall thickness made of steel type 35.8 were oxyacetylene welded to collectors of greater wall thickness with a round bead. X-ray examination showed crack initiation in the interior of the nipples close to the root of the weld seam. The cracks only appeared where the originally deposited bead was remelted in the regions of overlap. Given the construction and welding technique used, it would have been preferable to make the nipples of a steel lower in sulfur content. However, by taking advantage of all the potential in shaping and welding technology, it should be possible to prevent crack formation with steel type 35.8 of normal composition.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001557
EISBN: 978-1-62708-234-1
.... Fig. 3 Sub-surface discontinuous hairline cracks close to the bore surface, (as polished) at ×50 Fig. 4 Intergranular crack in the as-polished condition, at × 400 Fig. 5 Discontinuous intergranular cracks with Mn-sulphide inclusions along the path of cracking (2% Nital etched...
Abstract
A number of machined end frame steel forgings made of Cr-Si-Mn alloy showed tiny cracks during magnetic particle inspection after heat treatment. The cracks were mostly confined to base edges and fillet radius. No significant abnormality was observed in chemical composition and microstructure. SEM, optical microscopy, and gas analysis revealed that the subsurface discontinuous cracks at the bore edges and in the fillet radius of the heat-treated end frame component had occurred due to hydrogen embrittlement, and not because of faulty heat treatment. This conclusion was supported by the presence of cracklike indications in machined bore surface of the annealed part.
Series: ASM Failure Analysis Case Histories
Volume: 3
Publisher: ASM International
Published: 01 December 2019
DOI: 10.31399/asm.fach.v03.c9001820
EISBN: 978-1-62708-241-9
... the metal and those cracks that connect with the HIC cracks are able to grow more rapidly [ 7 , 8 ]. Fig. 7 SEM micrograph showing combined SSC and HIC corrosion crack growth Figure 8 shows microcracks that nucleated from an elongated FeS and extended from an acicular MnS inclusion. Stress...
Abstract
A group of control valves that regulate production in a field of sour gas wellheads performed satisfactorily for three years before pits and cracks were detected during an inspection. One of the valves was examined using chemical and microstructural analysis to determine the cause of failure and provide preventive measures. The valve body was made of A216-WCC cast carbon steel. Its inner surface was covered with cracks stemming from surface pits. Investigators concluded that the failure was caused by a combination of hydrogen-induced corrosion cracking and sulfide stress-corrosion cracking. Based on test data and cost, A217-WC9 cast Cr–Mo steel would be a better alloy for the application.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001645
EISBN: 978-1-62708-232-7
... was carried out on the failed roller-bearing and inner-race specimens in unetched condition to observe the characteristics of nonmetallic inclusions present. The roller-bearing sample showed numerous stringers of brittle angular alumina inclusions as well as sulfides with entrapped oxides. Few MnS inclusions...
Abstract
An extensive metallurgical investigation was carried out on samples of a failed roller bearing from the support and tilting system of a basic oxygen furnace converter used in the steel melting shop of an integrated steel plant. The converter bearing was fabricated from low-carbon, carburizing grade steel and had failed in service within a year of fitting to a repaired shaft. Microscopic observations of both the broken roller and inner-race samples revealed subsurface cracking and preponderance of brittle oxide and other macroinclusions. Electron probe microanalysis studies confirmed that the brittle oxides that formed stringers were alumina, and the other macroinclusions were complex silicates. Both the alumina and silicate inclusions were deleterious to contact-fatigue properties. Microstructurally, the carburized regions of the broken roller and of inner-race samples contained high-carbon tempered martensite. Microhardness measurements revealed that. Although the core hardness of the roller and the inner-race samples were similar, the surface hardness of the roller was approximately 8.5 HRC units harder than that of the inner-race. SEM observations of the roller fracture surface revealed striations indicative of fatigue, and EDS analyses corroborated a high incidence of silicate inclusions at crack sites. The study suggests that the failure of the bearing occurred because the hardness difference between the roller bearing and the inner-race surfaces resulted in wear of the inner-race. The wear led to shaft misalignment and play during service. The misalignment, coupled with the presence of inclusions, caused fatigue failure of the roller bearing.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c9001555
EISBN: 978-1-62708-217-4
... One main undercarriage axle made of high strength alloy steel (C 0.33%, Cr 1.15%, Ni 1.50%, Mn 1.05%, Si 0.96%) was subjected to simulated fatigue test for 6000 hours of service. But only after 300 hours it prematurely broke into two along the sharp radius ( Fig. 1 ). Fig. 1 Line of breakage...
Abstract
One main undercarriage axle made of high strength alloy steel was subjected to simulated fatigue test for 6000 h of service. After only 300 h it broke in two along the sharp radius. The fracture revealed a coarse, irregular, and brittle surface before final fracture by thick angular shear lip zone. The presence of micropores in the cleavage facets as well as at the grain boundaries and hairline type crack indications under SEM examination were all suggestive of hydrogen embrittlement. On the basis of investigation results and observations, it was concluded that the transverse breakage of the axle had occurred intergranularly in a brittle manner, possibly, initiated by a shallow zone of fatigue along the sharp radius acting as stress riser.
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001096
EISBN: 978-1-62708-214-3
... jagged areas) and MnS 2 inclusions (round gray spots) are visible. Unetched. 154×. Fig. 4 Higher magnification, etched view of Fig. 3 , showing crack (large black jagged area at top left), pearlite (black irregular fuzzy areas), and probably iron carbide precipitates (scattered jagged lines...
Abstract
A stud that was part of a man hole cover on an old steam boiler broke when it was dropped. The boiler was more than 100 years old, but still performed satisfactorily when fired up at regular intervals. Chemical analysis showed the steel to be a low-carbon EN2 type. Microstructural examination indicated brittle fracture caused by strain aging. Replacement of all studs on the man hole cover and examination of the boiler steel in other places were recommended.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001679
EISBN: 978-1-62708-229-7
... found in the matrix were either chromium (Cr) and manganese (Mn) rich or manganese sulfide (MnS) inclusions ( Figures 14 and 15 ). Because of problems with thinning, the particles in Figure 14 could not be identified with diffraction patterns. Since Cr is a ferrite stabilizer, it is likely...
Abstract
Several mercury diffusion pump stages in the Tritium Purification process at the Savannah River Site (SRS) have been removed from service for scheduled preventive maintenance. These stages have been examined to determine if failure has occurred. Evidence of fatigue around the flange portion of the pump has been seen. In addition, erosion and cavitation inside the throat of the venturi tube and corrosion on the other surface of the venturi tube has been observed. Several measures are being examined in an attempt to improve the performance of these pumps. These measures, as well as the noted observations, are described. Six stages [two machined (MP) and four electron beam (EB) welded] from the mercury diffusion pumps operating in the Tritium Purification process at SRS have been analyzed to determine their condition after nine months of usage. Several cracks were found around the necked region of the two MP stages. The EB welded stages, however, seemed to perform better in service; only two of four stages showed cracking. The cracking is caused by fatigue that has been enhanced by high stresses and tritium in the flange area. The EB welded stage appears to be a step in the right direction. Since the EB weld is a shrink fit, the surface is in compression, thereby eliminating crack propagation. In addition, shot peening has been employed to produce a compressive material surface since fatigue usually originates at the surface. Pitting was observed down the throat of the venturi. This pitting was caused by cavitation and erosion along the length of the venturi tube. Corrosion and pitting was seen on the exterior walls of the diffuser tubes. Stress-corrosion cracks were observed emanating from these corrosion pits. The corrosion likely occurred from the chloride ions present in the process cooling water. Shot peening is now being used in an attempt to place the outside of the diffuser tube in compression to eliminate the stress-corrosion cracking.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.steel.c9001532
EISBN: 978-1-62708-232-7
..., (c) Si x-ray map, (d) Cr x-ray map, and (e) Ni x-ray map; magnification 180× The EPMA investigations of typical NMIs present in the spalled HSM roll samples revealed the existence of both TiN- and MnS-type inclusions. The BSE and x-ray dot mapping images of a typical TiN associated MnS...
Abstract
Work rolls made of indefinite chill double-poured (ICDP) iron are commonly used in the finishing trains of hot-strip mills (HSMs). In actual service, spalling, apart from other surface degeneration modes, constitutes a major mechanism of premature roll failures. Although spalling can be a culmination of roll material quality and/or mill abuse, the microstructure of a broken roll can often unveil intrinsic inadequacies in roll material quality that possibly accentuate failure. This is particularly relevant in circumstances when rolls, despite operation under similar mill environment, exhibit variations in roll life. The paper provides an insight into the microstructural characteristics of spalled ICED HSM work rolls, which underwent failure under similar mill operating environment in an integrated steel plant under the Steel Authority of India Limited. Microstructural features influencing ICDP roll quality, viz. characteristics of graphite, carbides, martensite, etc., have been extensively studied through optical microscopy, quantitative image analysis (QIA), and electron-probe microanalysis (EPMA). These are discussed in the context of spalling propensity and roll life.