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Heat shields
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Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.usage.c9001508
EISBN: 978-1-62708-236-5
... Abstract New type 321 corrosion-resistant steel heat shields were cracking during welding operations. A failure analysis was performed. The cause was found to be chloride induced stress-corrosion cracking. Packaging was suspected and confirmed to be the cause of the chloride contamination...
Abstract
New type 321 corrosion-resistant steel heat shields were cracking during welding operations. A failure analysis was performed. The cause was found to be chloride induced stress-corrosion cracking. Packaging was suspected and confirmed to be the cause of the chloride contamination. A contributing factor was the length of time spent in the packaging, 21 years.
Image
in Failure Analysis of Gas Turbine Engine Fuel Nozzle Heat Shields
> ASM Failure Analysis Case Histories: Improper Maintenance, Repair, and Operating Conditions
Published: 01 June 2019
Image
in Failure Analysis of Gas Turbine Engine Fuel Nozzle Heat Shields
> ASM Failure Analysis Case Histories: Improper Maintenance, Repair, and Operating Conditions
Published: 01 June 2019
Image
in Failure Analysis of Gas Turbine Engine Fuel Nozzle Heat Shields
> ASM Failure Analysis Case Histories: Improper Maintenance, Repair, and Operating Conditions
Published: 01 June 2019
Image
in Failure Analysis of Gas Turbine Engine Fuel Nozzle Heat Shields
> ASM Failure Analysis Case Histories: Improper Maintenance, Repair, and Operating Conditions
Published: 01 June 2019
Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001043
EISBN: 978-1-62708-214-3
... Abstract A 76 mm (3 in.) type 304 stainless steel tube that was used as a heat shield and water nozzle support in a hydrogen gas plant quench pot failed in a brittle manner. Visual examination of a sample from the failed tube showed that one lip of the section was eroded from service failure...
Abstract
A 76 mm (3 in.) type 304 stainless steel tube that was used as a heat shield and water nozzle support in a hydrogen gas plant quench pot failed in a brittle manner. Visual examination of a sample from the failed tube showed that one lip of the section was eroded from service failure, whereas the opposite side exhibited a planar-type fracture. Sections were removed from the eroded area and from the opposite lip for microscopic studies and chemical analysis. The eroded edges exhibited river bed ditching, indicative of thermal fatigue. Microstructural analysis showed massive carbide formations in a martensite matrix and outlining of prior-austenite grains by a network of fine, white lines. These features indicated that the material had been transformed by carburization by the impinging gas. The outer surface exhibited a heavy scale deposit and numerous cracks that originated at the surface of the tube. The cracks were covered with scale, indicating that thermal fatigue (heat cracking) had occurred. Chemical analysis confirmed that the original material was type 304 stainless steel that had been through-carburized by the formation of an endothermic gas mixture. It was recommended that plant startup and shutdown procedures be modified to reduce or eliminate the presence of the carburizing gas mixture.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.aero.c9001145
EISBN: 978-1-62708-217-4
... heat shields welded inside the chamber. The configuration can be seen in the cut-away section of a chamber, Fig. 2 . The heat shields are not sealed to the exhaust port and are not pressure containing components. The volume between the heat shields and the chamber dome is initially pressurized...
Abstract
Cartridge-pneumatic starter systems are used on military aircraft. In the cartridge mode used for alert starts, the starter turbine is driven by hot gases produced through the controlled burning of a solid propellant cartridge within a closed chamber (the breech chamber/cartridge chamber assembly). Premature failures of steel breech chambers have been prevalent enough to cause serious concern. The breech chamber is fabricated from a 4340 Ni-Cr-Mo steel forging heat treated to a hardness in the range HRC 40 to 45. The failures have taken several forms, including fracture and unzipping of the chamber dome, burn-through of the dome, and shearing of bayonet locking lugs. Factors identified as significant in the failures are the pressure developed in the chamber and internal corrosion of the chamber in an environment that can produce stress-corrosion cracking. The interior configuration of the chamber and the stress distribution also have a bearing upon the failure modes. Several failures are reviewed to illustrate the problems.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0091655
EISBN: 978-1-62708-229-7
... structure in the HAZ of the Inconel 600. There were very few matrix precipitates immediately adjacent to the fusion line of the heat shield attachment weld; this condition was true of the entire HAZ near the root pass. The cracking generally initiated in the HAZ some distance away from the tip of the tight...
Abstract
Cracking occurred in an ASME SB166 Inconel 600 safe-end forging on a nuclear reactor coolant water recirculation nozzle while it was in service. The safe-end was welded to a stainless-steel-clad carbon steel nozzle and a type 316 stainless steel transition metal pipe segment. An Inconel 600 thermal sleeve was welded to the safe-end, and a repair weld had obviously been made on the outside surface of the safe-end to correct a machining error. Initial visual examination of the safe-end disclosed that the cracking extended over approximately 85 deg of the circular circumference of the piece. Investigation (visual inspection, on-site radiographic inspection, limited ultrasonic inspection, chemical analysis, 53x metallographic cross sections and SEM images etched in 8:1 phosphoric acid) supported the conclusion that the cracking mechanism was intergranular SCC. No recommendations were made.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0047645
EISBN: 978-1-62708-229-7
... to form and propagate in tension under the thermal stresses created by the repair-weld heat input. The crack resulted from contamination and embrittlement of a repair weld that had received inadequate gas shielding. Thermal stresses cracked the oxide-rich layer that formed. The gas-shielding accessories...
Abstract
An outer fan-duct assembly of titanium alloy Ti-5Al-2.5Sn (AMS 4910) for a gas-turbine fan section cracked 75 mm (3 in.) circumferentially through a repair weld in an arc weld in the front flange-duct segment. Examination of the crack with a binocular microscope revealed no evidence of fatigue. A blue etch-anodize inspection showed the presence of an alpha case along the edges of the repair weld. The alpha case, a brittle oxide-enriched layer, forms when welds are inadequately shielded from the atmosphere during deposition. The brittleness of this layer caused transgranular cracks to form and propagate in tension under the thermal stresses created by the repair-weld heat input. The crack resulted from contamination and embrittlement of a repair weld that had received inadequate gas shielding. Thermal stresses cracked the oxide-rich layer that formed. The gas-shielding accessories of the welding torch were overhauled to ensure that leak-in or entrainment of air was eliminated. Also, the purity of the shielding-gas supplies was rechecked to make certain that these had not become contaminated.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0047641
EISBN: 978-1-62708-235-8
... contamination. Contaminants Gas tungsten arc welding Heat affected zone Oxygen Stress concentration Thermal stresses Ti-6Al-4V UNS R56406 Joining-related failures A Ti-6Al-4V alloy pressure vessel failed during a proof-pressure test, fracturing along the center girth weld. The pressure vessel...
Abstract
A Ti-6Al-4V alloy pressure vessel failed during a proof-pressure test, fracturing along the center girth weld. The girth joints were welded with the automatic gas tungsten arc process utilizing an auxiliary trailing shield attached to the welding torch to provide inert-gas shielding for the exterior surface of the weld. A segmented backup ring with a gas channel was used inside the vessel to shield the weld root. The pressure vessel failed due to contamination of the fusion zone by oxygen, which resulted when the gas shielding the root face of the weld was diluted by air that leaked into the gas channel. Thermal stresses cracked the embrittled weld, exposing the crack surfaces to oxidation before cooling. One of these cracks caused a stress concentration so severe that failure of the vessel wall during the proof test was inevitable. A sealing system at the split-line region of the segmented backup ring was provided, and a fine-mesh stainless steel screen diffuser was incorporated in the channel section of the backup ring to prevent air from leaking in. A titanium alloy color chart was furnished to permit correlation of weld-zone discoloration with the degree of atmospheric contamination.
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in Assessment of Damage to Structures and Equipment Resulting from Explosion, Fire, and Heat Events
> Analysis and Prevention of Component and Equipment Failures
Published: 30 August 2021
Fig. 11 Example of melted polycarbonate light fixture shield. The material flows above approximately 155 °C (310 °F), near the upper end of heat exposure zone III.
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Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c0048154
EISBN: 978-1-62708-235-8
... of the fracture was not available, but it was assumed that a drop of molten metal landed at the origin. The degree of heating involved would lessen or eliminate the compressive stress produced by shot peening, and contraction of the surface in contact with the tightly adherent weld metal during cooling could...
Abstract
A medium-carbon helical spring was installed in a machine assembly that was welded into its final location. Weld spatter was not prevented from landing on the wire surface by any shield. An elongated drop and two tiny droplets of metal were observed a short distance from the fracture. No droplets were revealed at the origin of the fracture, but it was assumed that a drop of molten metal landed at the origin. Adherence of the spatter drop was expected to have been affected by the opening and closing of the fatigue crack. Weld spatter bead was concluded to have caused the fatigue fracture.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.conag.c0047508
EISBN: 978-1-62708-221-1
...-to-sulfur ratio and be in a normalized condition, low-hydrogen electrodes and welding practices should be used, all corners should be generously radiused, the welds should be inspected and ground or dressed to minimize stress concentrations, postweld heating is advisable, and radiographic and penetrant...
Abstract
A riveted 0.25% carbon steel oil-storage tank in Oklahoma was dismantled and reassembled in Minnesota by welding to form a storage tank for soybean oil. An opening was cut in the side of the tank to admit a front-end loader. A frame of heavy angle iron was welded to the tank and drilled for bolting on a heavy steel plate. The tank was filled to a record height. In mid-Jan the temperature dropped to -31 deg C (-23 deg F), with high winds. The tank split open and collapsed. The welding used the shielded metal arc process with E6010 electrodes, which could lead to weld porosity, hydrogen embrittlement, or both. At subzero temperatures, the steel was below its ductile-to-brittle transition temperature. These circumstances suggest a brittle condition. Steps to avoid this type of failure: For cold conditions, the steel plate should have a low carbon content and a high manganese-to-sulfur ratio and be in a normalized condition, low-hydrogen electrodes and welding practices should be used, all corners should be generously radiused, the welds should be inspected and ground or dressed to minimize stress concentrations, postweld heating is advisable, and radiographic and penetrant inspection tests should be performed.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.rail.c0048087
EISBN: 978-1-62708-231-0
.... Heat affected zone Martensite Shielded metal arc welding Vibrations Welded joints Welding parameters 1020 1050 UNS G10200 UNS G10500 Fatigue fracture Figure 1(a) shows a hoist carriage tram-rail assembly fabricated by shielded metal arc welding the leg of a large T-section 1020 steel...
Abstract
Several of the welds in a hoist carriage tram-rail assembly fabricated by shielded metal arc welding the leg of a large T-section 1020 steel beam to the leg of a smaller T-section 1050 steel rail failed in one portion of the assembly. Four weld cracks and several indefinite indications were found by magnetic-particle inspection. The cracks were revealed by metallographic examination to have originated in the HAZs in the rail section. Cracks in welds and in HAZs resulting from arcing the electrode adjacent to the weld and weld spatter were also revealed. The tram-rail assembly was concluded to have failed by fatigue cracking in HAZs. The fatigue cracking was initiated and propagated by vibration of the tram rail by movement of the hoist carriage on the rail. As a corrective measure, welding procedures were improved and the replacement rail assemblies were preheated and postheated.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.chem.c0091362
EISBN: 978-1-62708-220-4
... Intergranular corrosion of a contaminated E-Brite ferritic stainless steel weld. Electrolytically etched with 10% oxalic acid. 200× Fig. 3 Intergranular corrosion of the inside surface heat-affected zone of E-Brite stainless steel adjacent to the weld fusion line. Electrolytically etched with 10...
Abstract
A nozzle in a wastewater vaporizer began leaking after approximately three years of service with acetic and formic acid wastewaters at 105 deg C (225 deg F) and 414 kPa (60 psig). The shell of the vessel was weld fabricated from 6.4 mm (0.25 in.) E-Brite stainless steel plate and measured 1.5 m (58 in.) in diameter and 8.5 m (28 ft) in length. Investigation (visual inspection, chemical analysis, radiography, dye-penetrant inspection, and hydrostatic testing of all E-Brite welds, 4x images, 100x/200x images electrolytically etched with 10% oxalic acid, and V-notch Charpy testing) supported the conclusion that failure of the nozzle weld was the result of intergranular corrosion caused by the pickup of interstitial elements and subsequent precipitation of chromium carbides and nitrides. Carbon pickup was believed to have been caused by inadequate joint cleaning prior to welding. The increase in the weld nitrogen level was a direct result of inadequate argon gas shielding of the molten weld puddle. Two areas of inadequate shielding were identified: improper gas flow rate for a 19 mm (0.75 in.) diam gas lens nozzle, and contamination of the manifold gas system. Recommendations included changes in the cleaning and welding process.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.process.c9001647
EISBN: 978-1-62708-235-8
... to identify any gas contaminant or pressure transient that might lead to porosity. Two welds were made with increased heat input, accomplished through placing a second closure weld on top of the first weld, to maximize the likelihood of detecting any contaminant released by the heat associated...
Abstract
An unacceptable degree of porosity was identified in several closure welds on stainless steel containers for plutonium-bearing materials. The pores developed in the weld tie-in region due to gas trapped by the weld pool during the closure process. This paper describes the efforts to trace the root cause of the porosity to the geometric conditions of the weld joint and establish corrective actions to minimize such porosity.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0048814
EISBN: 978-1-62708-229-7
... with a backing strip. The backing was back gouged off, and the weld was completed from the inside with E8018-C3 electrodes by the shielded metal arc process. The weld was continuously stress relieved for 12 h at 540 °C (1000 °F). Hardness traverses on the weldments suggested that the actual heat-treatment...
Abstract
A nuclear steam-generator vessel constructed of 100-mm thick SA302, grade B, steel was found to have a small leak. The leak originated in the circumferential closure weld joining the transition cone to the upper shell. The welds had been fabricated from the outside by the submerged arc process with a backing strip. The backing was back gouged off, and the weld was completed from the inside with E8018-C3 electrodes by the shielded metal arc process. Striations of the type normally associated with progressive or fatigue-type failures including beach marks that allowed tracing the origin of the fracture to the pits on the inner surface of the vessel were revealed. Copper deposits with zinc were revealed by EDS examination of discolorations. Pitting was revealed to have been caused by poor oxygen control in the steam generators and release of chloride into the steam generators. It was concluded by series of controlled crack-propagation-rate stress-corrosion tests that A302, grade B, steel was susceptible to transgranular stress-corrosion attack in constant extension rate testing with as low as 1 ppm chloride present. It was recommended to maintain the coolant environment low in oxygen and chloride. Copper ions in solution should be eliminated or minimized.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0048331
EISBN: 978-1-62708-229-7
... corrosion. The thinned tubes were reinforced by pad welding. Type 304 stainless steel shields were welded to the stainless steel portions of the top reheater tubes and were held in place about the chromium-molybdenum steel portions of the tubes by steel bands. Coal dust Heat exchanger tubes Thinning...
Abstract
The top tube of a horizontal superheater bank in the reheat furnace of a steam generator ruptured after seven years in service. The rupture was found to have occurred in the ferritic steel tubing (2.25Cr-1Mo steel (ASME SA-213, grade T-22)) near the joint where it was welded to austenitic stainless steel tubing (type 321 stainless steel (ASME SA-213, grade TP321H)). The surface temperature of the tube was found to be higher than operating temperature in use earlier. The ferritic steel portion of the tube was found to be longitudinally split and heavily corroded in the region of the rupture. A red and white deposit was found on the sides and bottom of the tube in the rupture area. The deposit was produced by attack of the steel by the alkali acid sulfate and had thinned the tube wall. It was concluded that rupture of the tube had occurred due to thinning of the wall by coal-ash corrosion. The thinned tubes were reinforced by pad welding. Type 304 stainless steel shields were welded to the stainless steel portions of the top reheater tubes and were held in place about the chromium-molybdenum steel portions of the tubes by steel bands.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001632
EISBN: 978-1-62708-234-1
..., on the outer surface as a means for determining surface temperature during operation. In practice, the thermocouples indicated a temperature much higher than that of the surface of the window due to heating of the thermocouples and the pads by the protons and because the heat transfer path to the coolant...
Abstract
A double-walled, hemispherical metal beam exit window made of alloy 718 developed a crack during service, leading to coolant leakage. The window had been exposed to radiation damage from 800 MeV protons and a cyclic stress from 600 MPa tensile to near zero induced by numerous temperature cycles calculated to be from 400 to 30 deg C (752 to 86 deg F). The window was activated to >200 Sv/h. It was determined through analysis using remote handling techniques and hot cells that the crack initiated near a spot weld used to affix thermocouples to the window surface. In addition to analysis of the crack, some of the irradiated material from the window was used to measure mechanical properties. Hot cell techniques for preparation of samples and testing were developed to determine true operating conditions of radiation, strain, and temperature.
Series: ASM Handbook Archive
Volume: 11
Publisher: ASM International
Published: 01 January 2002
DOI: 10.31399/asm.hb.v11.a0003570
EISBN: 978-1-62708-180-1
... or induction heating), brazed-on shields of Stellite 6B, or welded-on hard facing. Helicopter rotors are made of titanium sheet laid over a structural framework and pressurized internally with nitrogen, or of fiber-reinforced composites with a polymeric foam core. Manifestations of Liquid-Droplet Erosion...
Abstract
Erosion of solid surfaces can be brought about solely by liquids in two ways: from damage induced by formation and subsequent collapse of voids or cavities within the liquid, and from high-velocity impacts between a solid surface and liquid droplets. The former process is called cavitation erosion and the latter is liquid-droplet erosion. This article emphasizes on manifestations of damage and ways to minimize or repair these types of liquid impact damage, with illustrations.
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