scholarly journals Effects of Microstructure on the Low-Temperature Toughness of an X80 × D1422 mm Heavy-Wall Heat-Induced Seamless Bend

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1055
Author(s):  
Juntai Hu ◽  
Yu Liu ◽  
Ge Wang ◽  
Qiang Li
Keyword(s):  
Electron Microscopy ◽  
Low Temperature ◽  
Crack Propagation ◽  
Outer Surface ◽  
High Angle ◽  
Surface Center ◽  
Inner Surface ◽  
Center Position ◽  
Low Temperature Toughness ◽  
The Impact

The relationship between the microstructure and the low-temperature toughness of an X80 × D1422 mm heavy-wall heat-induced seamless bend was investigated, including the influence of microstructure on crack initiation and crack propagation. Using optical microscopy, scanning electron microscopy, transmission electron microscopy, and electron backscattered diffraction, the microstructure and crystallographic orientation characteristics were studied. An instrumented impact tester was used to investigate the impact toughness. The results showed that during the hot bending process, there was a difference in the induction heating temperature and the cooling rate results in the uneven microstructure of the inner surface, center position, and outer surface of the bend. The center position was mainly composed of granular bainite and exhibited the best combination of strength and toughness. The ductile–brittle transition temperatures of the inner surface, center position, and outer surface were −88, −85, and −60 °C, respectively. In the process of impact deformation, the non-uniformly distributed strain concentration regions are likely to cause uneven distribution of plastic deformation and the nucleation of microcracks. The high ratio of high-angle grain boundaries and the smaller effective grain size of the inner surface and center position lead to higher crack growth absorption energy. The low crack propagation energy of the outer surface is attributed to the fact that the high-angle grain boundary does not effectively deviate or arrest the crack propagation, and multiple microcracks are connected to one another and cause fracture failure.

Fracture and Crack Propagation Behavior of 560 MPa Microalloyed Pipeline Steel under Different Cooling Schedules

2017 ◽  
Vol 898 ◽  
pp. 1094-1102 ◽  
Author(s):  
Jin Hua Zhao ◽  
Dong Fang Li ◽  
Guo Yuan ◽  
Xue Qiang Wang ◽  
Rui Hao Li ◽  
...  
Keyword(s):  
Grain Size ◽  
Low Temperature ◽  
Crack Propagation ◽  
Pipeline Steel ◽  
Crack Arrest ◽  
Dominant Factor ◽  
Cooling Schedules ◽  
Effective Grain Size ◽  
Mixed Microstructure ◽  
Low Temperature Toughness

Three kinds of pipeline steel with different microstructures were fabricated by varying cooling schedules during thermo-mechanical controlled processing (TMCP). Charpy impact property of the pipeline steels were obtained, and the fracture and crack-arrest mechanisms were further studied. The results indicated that the steels were classified into two kinds according to their microstructures, the mixture of acicular ferrite (AF), quasi-polygonal ferrite (QF), granular bainite (GB) and small fraction of degenerate pearlite (DP), and the mixed microstructure of AF and GB, respectively. The processed steel with microstructure of AF and GB exhibited more excellent low-temperature toughness and crack-arrest properties with upper shelf energy of ~281 J and energy transition temperature of ~-76°C. The mixed microstructure (AF + GB) possessing smaller effective grain size hindered the propagating of crack and consumed large amount of energy during fracture. The effective grain size of microstructure was the dominant factor controlling low-temperature toughness and crack-arrest properties of pipeline steel, which increased the high-angle boundary length per unit area and further increased the crack propagation energy during fracture.

Microsculpture and phylogenetic significance of the spermatheca of black flies (Diptera: Simuliidae)

2000 ◽  
Vol 78 (8) ◽  
pp. 1468-1482 ◽  
Author(s):  
Christopher L Evans ◽  
Peter H Adler
Keyword(s):  
Electron Microscopy ◽  
Outer Surface ◽  
Phylogenetic Reconstruction ◽  
Black Flies ◽  
Phylogenetic Significance ◽  
Phylogenetic Information ◽  
Character System ◽  
Single Character ◽  
Inner Surface ◽  
Scanning Electron

The highly varied spermatheca of black flies provided an under-studied character system for phylogenetic reconstruction of the Simuliidae. Scanning electron microscopy of the spermatheca of 17 simuliid species elucidated folds and spicules on the inner surface; callosities, anastomosing ridges, and minute tubercles on the outer surface; and an intricately fluted spermathecal duct. The spermatheca of Parasimulium crosskeyi, the most plesiomorphic taxon, had a slightly wrinkled inner surface and an outer surface with acutely raised polygonal ridges. Species hypothesized to be among the basal lineages of the simuliids (e.g., Helodon susanae and Prosimulium magnum) had an irregularly folded inner spermathecal surface, but their relationships were not well resolved on the basis of information about the spermatheca. More evolutionarily derived species, including a number of species in the genus Simulium, had short or filiform spicules on the inner surface of the spermatheca. Although the use of a single character system, the spermatheca, did not fully resolve relationships among Simuliidae, its utility as a rich source of phylogenetic information was demonstrated.

Effect of Rolling Parameters on the Low-Temperature Toughness and Microstructure of High-Strength Linepipe Steel

2016 ◽  
Author(s):  
C. Stallybrass ◽  
A. Völling ◽  
H. Meuser ◽  
F. Grimpe
Keyword(s):  
Electron Microscopy ◽  
Low Temperature ◽  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Processing Parameters ◽  
Small Scale ◽  
Electron Backscatter ◽  
Low Temperature Toughness ◽  
Backscatter Diffraction ◽  
Scanning Electron

In recent years, large-diameter pipe producers around the world have witnessed a growing interest to develop gas fields in arctic environments in order to fulfill the energy demand. High-strength linepipe grades are attractive for economic reasons, because they offer the benefit of a reduced wall thickness at a given operating pressure. Excellent low-temperature toughness of the material is essential under these conditions. Modern high-strength heavy plates used in the production of UOE pipes are produced by thermomechanical rolling followed by accelerated cooling (TMCP). The combination of high strength and high toughness of these steels is a result of the bainitic microstructure and is strongly influenced by the processing parameters. For this reason, the relationship between rolling and cooling parameters of heavy plate production, the low-temperature toughness and the microstructure is at the center of attention of the development efforts at Salzgitter Mannesmann Forschung (SZMF) in collaboration Salzgitter Mannesmann Grobblech (SMGB). It has been shown previously that a variation of the processing parameters has a direct influence on the microstructure and correlates with mechanical properties that are accessible via small-scale tests. Modern characterization methods such as scanning electron microscopy in combination with electron backscatter diffraction have broadened our understanding of the underlying mechanisms and have helped to define processing conditions for the production of heavy plates with optimized low-temperature toughness in small scale tests. Within the present paper, the results of a recent laboratory investigation of the effect of a systematic variation of rolling parameters on the microstructure and low-temperature toughness of as-rolled and pre-strained Charpy specimens are discussed. In these trials, final rolling temperatures above the onset of the ferrite-austenite transformation and cooling stop temperatures above the martensite start temperature were selected. The microstructure of the plates was investigated by scanning electron microscopy and electron backscatter diffraction. In a series of Charpy tests in a specific temperature range, it was found that plate material in the as-rolled condition is not strongly sensitive to variations of the selected processing parameters, whereas pre-straining the Charpy specimens made it possible to assess the potential of individual processing concepts particularly with regard to low-temperature toughness. In addition to Charpy testing, the toughness was also quantified via instrumented drop-weight tear (DWT) testing. By comparing total energy values from regular pressed-notch DWT-test specimens to J-integral values determined in drop-weight testing of pre-fatigued DWT-test specimens, the impact of variations of specimen type on material tearing resistance is shown.

Estimation of Impact Toughness Transition Temperatures of As-Quenched Steels

2018 ◽  
Vol 941 ◽  
pp. 498-503
Author(s):  
Sakari Pallaspuro ◽  
Antti J. Kaijalainen ◽  
Saara Mehtonen ◽  
Jukka I. Kömi ◽  
Zhi Liang Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Low Temperature ◽  
Impact Toughness ◽  
Yield Strength ◽  
Rolling Temperature ◽  
Transition Temperatures ◽  
Finish Rolling Temperature ◽  
Finish Rolling ◽  
Low Temperature Toughness ◽  
The Impact

High strength and sufficient toughness are key requirements for modern high-performance structural steels. In an attempt to develop a suitable estimation of impact toughness transition temperatures for as-quenched steels, we investigated the determiners of low-temperature toughness with a group of thermomechanically rolled direct-quenched steels with varying martensite contents. These were produced by altering chemical composition, finish rolling temperature and reduction below the non-recrystallization temperature, i.e. austenite pancaking, and characterised in terms of microstructural constituents, grain size distributions, texture and fractography. Provided the finish rolling temperature is high enough to avoid the formation of granular bainite on subsequent cooling, high levels of austenite pancaking yield the best combinations of low-temperature toughness and strength by effectively refining the size of the coarsest grains and randomizing the texture. While absolutely no direct correlation is found within as-quenched steels between the impact toughness transition temperatures and yield strength alone, T28J and T50 do closely follow a dynamic reference toughness, i.e. the opening stress intensity factor defined by yield strength and the size of the coarsest grains in the effective grain size distribution. This parameter reflects the transition temperatures – the lower the temperature, the lower the reference toughness needed to cause a local brittle fracture. Finally, we show that the impact toughness transition temperatures T28J and T50 of as-quenched steels can be accurately estimated, irrespective of the test specimen orientation, by utilizing just the dynamic reference toughness and the fraction of {100} cleavage planes within ± 15° of the specimen notch plane.

Effect of Heat Input on Toughness of Deposited Metal at -40οC of Self-Shielded Flux-Cored Wire

2011 ◽  
Vol 291-294 ◽  
pp. 979-983
Author(s):  
Shao Peng Song ◽  
Zhuo Xin Li ◽  
Guo Dong Li ◽  
Tian Li Zhang
Keyword(s):  
Low Temperature ◽  
Heat Input ◽  
Polygonal Ferrite ◽  
Granular Bainite ◽  
Chemical Compositions ◽  
Cored Wire ◽  
Slight Tendency ◽  
Deposited Metal ◽  
Low Temperature Toughness ◽  
The Impact

The effect of welding heat input ranging from 1.507 KJ/mm to 2.987KJ/mm on low temperature toughness of deposited metal made by self-shielded flux-cored wire has been investigated. The results showed that low temperature toughness decreased with the increase of heat input, and the impact fracture changed from ductile to cleavage fracture. In addition, the chemical compositions demonstrated a slight tendency to decrease with increasing heat input. While, heat input has little effect on inclusions of deposited metal. Higher heat input lead to grains coarsened further, reduced acicular ferrite and granular bainite, and increased polygonal ferrite, which mainly lead to toughness decreased.

A SEM and Light Microscope Study of the Epidermal Leaf Structures of the Carnivorous Plant, Sarracenia purpurea, L.

1971 ◽  
Vol 29 ◽  
pp. 358-359
Author(s):  
B. J. Panessa ◽  
J. F. Gennaro
Keyword(s):  
Methylene Blue ◽  
Toluidine Blue ◽  
Outer Surface ◽  
Microscope Study ◽  
Light Microscope ◽  
Carnivorous Plant ◽  
Sarracenia Purpurea ◽  
Inner Surface

Tissue from the hood and sarcophagus regions were fixed in 6% glutaraldehyde in 1 M.cacodylate buffer and washed in buffer. Tissue for SEM was partially dried, attached to aluminium targets with silver conducting paint, carbon-gold coated(100-500Å), and examined in a Kent Cambridge Stereoscan S4. Tissue for the light microscope was post fixed in 1% aqueous OsO4, dehydrated in acetone (4°C), embedded in Epon 812 and sectioned at ½u on a Sorvall MT 2 ultramicrotome. Cross and longitudinal sections were cut and stained with PAS, 0.5% toluidine blue and 1% azure II-methylene blue. Measurements were made from both SEM and Light micrographs.The tissue had two structurally distinct surfaces, an outer surface with small (225-500 µ) pubescent hairs (12/mm2), numerous stoma (77/mm2), and nectar glands(8/mm2); and an inner surface with large (784-1000 µ)stiff hairs(4/mm2), fewer stoma (46/mm2) and larger, more complex glands(16/mm2), presumably of a digestive nature.

Gastric Ulcers Produced by Cisplatin

1981 ◽  
Vol 39 ◽  
pp. 582-583
Author(s):  
S.K. Aggarwal ◽  
J. San Antonio
Keyword(s):  
Electron Microscopy ◽  
Single Dose ◽  
Side Effects ◽  
Antitumor Agent ◽  
Gastric Ulcers ◽  
Enzyme Cytochemistry ◽  
Intestinal Toxicity ◽  
Ovarian Cancers ◽  
Inner Surface

Cisplatin (cis-dichlorodiammineplatinum(II)) a potent antitumor agent is now available for the treatment of testicular and ovarian cancers. It is however, not free from its serious side effects including nephrotoxicity, gastro intestinal toxicity, myelosuppression, and ototoxicity. Here we now report that the drug produces peculiar bloating of the stomach in rats and induces acute ulceration.Wistar-derived rats weighing 200-250 g were administered cisplatin(9 mg/kg) ip as a single dose in 0.15 M NaCl. After 3 days the animals were sacrificed by decapitation. The stomachs were removed, the contents analyzed for pepsin and acidity. The inner surface was examined with a dissecting microscope after a moderate stretching for ulcers. Affected areas were fixed and processed for routine electron microscopy and enzyme cytochemistry.The drug treated animals kept on food and water consistently showed bloating and lesions (Fig. 1) with a frequency of 6-70 ulcers in the rumen section of the stomachs.

Low-temperature annealing of YBa2Cu3O7-x

1992 ◽  
Vol 50 (1) ◽  
pp. 88-89
Author(s):  
R.L. Sabatini ◽  
Yimei Zhu ◽  
Masaki Suenaga ◽  
A.R. Moodenbaugh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Low Temperature ◽  
Oxygen Diffusion ◽  
Diffusion Rate ◽  
Oxygen Depletion ◽  
Low Temperature Annealing ◽  
Transmission Electron ◽  
Microstructural Effects ◽  
Oxygen Diffusion Rate

Low temperature annealing (<400°C) of YBa2Cu3O7x in a ozone containing oxygen atmosphere is sometimes carried out to oxygenate oxygen deficient thin films. Also, this technique can be used to fully oxygenate thinned TEM specimens when oxygen depletion in thin regions is suspected. However, the effects on the microstructure nor the extent of oxygenation of specimens has not been documented for specimens exposed to an ozone atmosphere. A particular concern is the fact that the ozone gas is so reactive and the oxygen diffusion rate at these temperatures is so slow that it may damage the specimen by an over-reaction. Thus we report here the results of an investigation on the microstructural effects of exposing a thinned YBa2Cu3O7-x specimen in an ozone atmosphere using transmission electron microscopy and energy loss spectroscopy techniques.

Intracellular structures of rapid frozen biological samples observed by high-resolution low-temperature Scanning Electron Microscopy

1989 ◽  
Vol 47 ◽  
pp. 736-737
Author(s):  
T. Inoué ◽  
H. Koike
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Temperature ◽  
Liquid Nitrogen ◽  
Specimen Preparation ◽  
Chemical Fixation ◽  
Brown Adipose ◽  
Critical Point Drying ◽  
Temperature Scanning ◽  
Scanning Electron

Low temperature scanning electron microscopy (LTSEM) is useful to avoid artifacts such as deformation and extraction, because specimens are not subjected to chemical fixation, dehydration and critical-point drying. Since Echlin et al developed a LTSEM, many techniques and instruments have been reported for observing frozen materials. However, intracellular structures such as mitochondria and endoplasmic reticulum have been unobservable by the method because of the low resolving power and inadequate specimen preparation methods. Recently, we developed a low temperature SEM that attained high resolutions. In this study, we introduce highly magnified images obtained by the newly developed LTSEM, especially intracellular structures which have been rapidly frozen without chemical fixation.[Specimen preparations] Mouse pancreas and brown adipose tissues (BAT) were used as materials. After the tissues were removed and cut into small pieces, the specimen was placed on a cryo-tip and rapidly frozen in liquid propane using a rapid freezing apparatus (Eiko Engineering Co. Ltd., Japan). After the tips were mounted on the specimen stage of a precooled cryo-holder, the surface of the specimen was manually fractured by a razor blade in liquid nitrogen. The cryo-holder was then inserted into the specimen chamber of the SEM (ISI DS-130), and specimens were observed at the accelerating voltages of 5-8 kV. At first the surface was slightly covered with frost, but intracellular structures were gradually revealed as the frost began to sublimate. Gold was then coated on the specimen surface while tilting the holder at 45-90°. The holder was connected to a liquid nitrogen reservoir by means of a copper braid to maintain low temperature.

Sign in / Sign up

Export Citation Format

Share Document