scholarly journals ANÁLISE DA FALHA DE PARAFUSOS CLASSE 10.9 UTILIZADOS EM GUINDASTE OFFSHORE

e-xacta ◽  
2017 ◽  
Vol 10 (2) ◽  
pp. 17
Author(s):  
Rafael Gomes de Castro ◽  
Bárbara Ferreira de Oliveira ◽  
Alessandro Da Silva Rolin ◽  
Eduardo Atem de Carvalho
Keyword(s):  
Chemical Composition ◽  
Offshore Platforms ◽  
High Concentration ◽  
Technical Standards ◽  
Final Fracture ◽  
Martensitic Microstructure ◽  
Fracture Region ◽  
Metallic Inclusions ◽  
Beach Marks ◽  
Hardness Values

<p>Neste trabalho foram avaliadas as propriedades mecânicas de dois parafusos que têm como função a fixação de um guindaste utilizado nas plataformas offshore. Foram retiradas duas seções de cada elemento para a realização de análises de composição química, da fratura e microestrutural e ensaios mecânicos de dureza e de tração. Os resultados obtidos nas análises da composição química mostraram-se condizentes com as normas e que o material utilizado para fabricação dos parafusos trata-se de um aço ASTM 4140, sendo apropriado para fabricação de parafusos da classe 10.9. Através das fraturas foi possível verificar que o parafuso 1 provavelmente foi submetido a um esforço por torção, tendo uma alta concentração de tensão na região da raiz do filete, assim como a existência de marcas de catraca, o que possibilitou a criação da trinca e propagação por fadiga. No parafuso 2 foram observadas marcas de praia originadas em cavidades e uma região de fratura final pequena como indicativo de baixa tensão nominal. Identificou-se que ambos possuem uma matriz microestrutural martensítica, contudo foi encontrada a presença de austenita retida e também inclusões não metálicas, as quais apresentam maior concentração no parafuso 2, indicando que provavelmente estariam presentes nas cavidades produzidas na fratura. Os valores de dureza determinados são apropriados para os valores mínimos estabelecidos por normas técnicas. No entanto, verificou-se que o parafuso 2 não apresenta as porcentagens mínimas de ductilidade estipuladas por uma das normas técnicas analisadas.</p><p> </p><p>ABSTRACT</p><p>The purpose of this article was evaluate the mechanical properties of two bolts that has as function the fixing of a crane used at oil offshore platforms. Two specimens were removed of each bolt for analysis such of chemical composition, fracture and hardness and tensile testing. The results obtained from analysis of the chemical composition proved to be consistent with the standards and the material used to manufacture the bolts consists of a steel ASTM 4140, being appropriate for manufacturing class 10.9 bolts. Through the fractures it was found that the bolt 1 was probably subjected to a load of torsion with a high concentration of stress in the region of bolt’s root, well as the existence of ratchet marks, which enabled the creation of fatigue crack. Beach marks were observed originating from cavities and a small final fracture region indicated a low nominal stress on bolt 2. It was identified that both have the martensitic microstructure matrix, however it was found the presence of retained austenite and also non-metallic inclusions, which are more concentrated on the bolt 2, indicating that probably would be present in cavities produced in the fracture. The hardness values are appropriate to the minimum values established by technical standards. However, it was found that the bolt 2 does not show the minimum ductility percentages prescribed by technical standards analyzed.</p>

scholarly journals Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

2012 ◽  
Vol 12 (2) ◽  
pp. 129-134 ◽  
Author(s):  
M. Opiela ◽  
A. Grajcar
Keyword(s):  
Rare Earth ◽  
Chemical Composition ◽  
Rare Earth Elements ◽  
Mechanical Treatment ◽  
Induction Furnace ◽  
Microalloyed Steels ◽  
Metallurgical Process ◽  
Metallic Inclusions ◽  
Mean Size ◽  
Thermo Mechanical Treatment

Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermo-mechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and a realization of metallurgical process in vacuous conditions result in a low concentration of sulfur (0.004%), phosphorus (from 0.006 to 0.008%) and oxygen (6 ppm). The high metallurgical purity is confirmed by a small fraction of non-metallic inclusions averaging 0.075%. A large majority of non-metallic inclusions are fine, globular oxide-sulfide or sulfide particles with a mean size 17 μm2. The chemical composition and morphology of non-metallic inclusions was modified by Ce, La and Nd, what results a small deformability of non-metallic inclusions during hot-working.

scholarly journals Phytochemical Screening, Chemical Composition and Antimicrobial Activity of Cinnamon verum Bark

2020 ◽  
pp. 36-43
Author(s):  
Hamza Mohamed Ahmed ◽  
Ashraf Mahmoud Ramadhani ◽  
Ibrahim Yaagoub Erwa ◽  
Omer Adam Omer Ishag ◽  
Mohamed Bosharh Saeed
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Activity ◽  
Chemical Composition ◽  
Essential Oil ◽  
Phytochemical Screening ◽  
High Concentration ◽  
Standard Methods ◽  
Crude Extracts ◽  
Acetone Extracts

cinnamon dating from 1000 AD when it was firstly recorded in English due to its important as aroma and as herbs. The aim of this study was to investigate phytochemicals constitutes, chemical composition and antimicrobial activity of the essential oil of commercial samples of Cinnamon verum bark. The essential oil was extracted by hydrodistillation, while the crude extracts were prepared by three different solvents methanol (70%), acetone and aqueous. Phytochemical screening of crude extracts was performed using standard methods. The essential oil was subjected to GC-MS analysis and tested against Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa, Eschericchia coli and Candida albicans. The obtained results indicated the presence of alkaloids, flavonoids, coumarin, tannins, terpenoids, saponin, glycoside, anthrocyanin and phenolic compounds in the methanolic, aqoueous and acetone extracts of C. verum bark; while the major components of the extracted essential oil of C. verum bark were cinnamaldehyde (85.50%), stigmasterol (3.69%), Cadinene (1.37%), (E)-cinnamaldehyde (1.35%), alpha-amorphene (1.33%), hydrocinnamaldehyde (1.28%), alpha-cubebene (1.25) and ergosterol (1.09%) respectively. The antimicrobial activity result indicated the high activity of the extracted essential oil against all tested microorganisms at high concentration; except in S. typhimurium and C. albicans at concentrations of 25% and 12.5% no activity was noticed. Based in our obtained results the essential oil of C. verum bark had high potential as antimicrobial agent, therefore, recommended for more advanced studies to be conducted on this abundant plant as natural source of antibiotics.

Study of Hydrogen Cracking and PWHT of Dissimilar Materials for Elevated Temperature Application

2015 ◽  
Vol 754-755 ◽  
pp. 797-801
Author(s):  
Muhammad Sarwar ◽  
Mohd Amin bin Abd Majid
Keyword(s):  
Heat Treatment ◽  
Dissimilar Materials ◽  
High Hardness ◽  
Construction Sites ◽  
Gas Tungsten Arc ◽  
Martensitic Microstructure ◽  
Alloy Steels ◽  
Temperature Application ◽  
The Impact ◽  
Hardness Values

s. On construction sites many challenges and premature failures are being encountered in welded joints of creep strength-enhanced ferritic (CSEF) steels. The primary reason of these premature failures is found to be the dissimilar material joints, having strength mismatch, or improper heat treatment that is mandatorily carried out to achieve the required weld hardness. This study aims at determining the impact of post welding heat treatment (PWHT) on dissimilar alloy steels joints, between ASTM A335 Gr. P-22 and ASTM A335 Gr. P-91 steels, welded by gas tungsten arc welding (GTAW) using ER 90S-B9 filler wire. The PWHT, at 745°C for 1hr., was applied to attain the required hardness. The effect of PWHT was investigated on the weld metal and the heat affected zones (HAZ) by hardness testing. Due to the martensitic microstructure, the hardness values of HAZ of P91 steel are over 350 HV. However, the hardness value of the P22 HAZ less than 350 HV. P91 HAZ has a higher hardness value than P22 HAZ because of its higher hardenability and due to phase transformation from martensite to ferrite. The interaction between the too high hardness microstructure with hydrogen can result in the hydrogen induced cracking (HIC) initiation in the HAZ. Therefore, the PWHT is needed to reduce this high hardness HAZ.

Study on the Crack Forming during Cold Forging Process of ML25Mn Steel

2012 ◽  
Vol 184-185 ◽  
pp. 1255-1258
Author(s):  
Zhuang Li ◽  
Di Wu ◽  
Wei Lv
Keyword(s):  
Chemical Composition ◽  
Surface Quality ◽  
High Hardness ◽  
Complex Oxides ◽  
Cold Forging ◽  
Internal Defects ◽  
Forging Process ◽  
Sem Observation ◽  
Metallic Inclusions ◽  
The Matrix

The important factors that affect the formability of the cold forging steel are its surface quality and internal defects. The cracking phenomenon was taken place during cold forging of ML25Mn steel. In this study, microstructural analyses were made on around the cracked regions of the steel. The reason of cracking, which occurred during cold forging for ML25Mn steel, was investigated based on SEM observation in detail. The results have shown that the crack forming during cold forging process is not related to the chemical composition for ML25Mn steel. Cracking is not resulted from high hardness of the steel rods. There are some non-metallic inclusions in the matrix of ML25Mn steel, and the film-like inclusions are composed of MnS, CaS and complex oxides containing Mg, Al, Mn, Fe, S, Ca and O. The formation of non-metallic inclusions is the result of the deoxidation and the solidification during smelting and casting of steel.

The Colorants Effects of Fe2O3 on Borosilicate Glasses Prepared from Subbituminous Fly Ash

2015 ◽  
Vol 1119 ◽  
pp. 731-735
Author(s):  
W. Rachniyom ◽  
Y. Ruangtaweep ◽  
K. Boonin ◽  
K. Phachana ◽  
J. Kaewkhao
Keyword(s):  
Refractive Index ◽  
Fly Ash ◽  
Chemical Composition ◽  
Crystal Structures ◽  
Absorption Spectra ◽  
Borosilicate Glasses ◽  
Ferrous Ions ◽  
Melt Quenching ◽  
Hardness Values

In this work, the subbituminous fly ash (SFA) in Thailand has been investigated for their compositions and crystal structures. Borosilicate glasses were prepare from SFA , B2O3, Na2O and various concentration of Fe2O3 by melt quenching technique. The results have shown that the chemical composition comprised with SiO2, Al2O3 and Fe2O3. The crystal structures of SFA were raised of mullite and quartz phases. The density and refractive index values of glasses were found to increase with increasing of Fe2O3 concentrations. The hardness values have been decreased with increasing of Fe2O3 content. The absorption spectra are corresponding to ferric and ferrous ions in wavelength of 440 nm and 1,050 nm and the color of glasses are green to yellow.

scholarly journals Analysis of CCN activity of Arctic aerosol and Canadian biomass burning during summer 2008

2013 ◽  
Vol 13 (5) ◽  
pp. 2735-2756 ◽  
Author(s):  
T. L. Lathem ◽  
A. J. Beyersdorf ◽  
K. L. Thornhill ◽  
E. L. Winstead ◽  
M. J. Cubison ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Biomass Burning ◽  
Industrial Pollution ◽  
Physical Aging ◽  
Volume Fraction ◽  
Cloud Condensation Nuclei ◽  
Water Soluble ◽  
The Arctic ◽  
High Concentration ◽  
Air Masses

Abstract. The NASA DC-8 aircraft characterized the aerosol properties, chemical composition, and cloud condensation nuclei (CCN) concentrations of the summertime Arctic during the 2008 NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. Air masses characteristic of fresh and aged biomass burning, boreal forest, Arctic background, and anthropogenic industrial pollution were sampled. Observations were spatially extensive (50–85° N and 40–130° W) and exhibit significant variability in aerosol and CCN concentrations. The chemical composition was dominated by highly oxidized organics (66–94% by volume), with a water-soluble mass fraction of more than 50%. The aerosol hygroscopicity parameter, κ, ranged between κ = 0.08–0.32 for all air mass types. Industrial pollution had the lowest κ of 0.08 ± 0.01, while the Arctic background had the highest and most variable κ of 0.32 ± 0.21, resulting from a lower and more variable organic fraction. Both fresh and aged (long-range transported) biomass burning air masses exhibited remarkably similar κ (0.18 ± 0.13), consistent with observed rapid chemical and physical aging of smoke emissions in the atmosphere, even in the vicinity of fresh fires. The organic hygroscopicity (κorg) was parameterized by the volume fraction of water-soluble organic matter (εWSOM), with a κ = 0.12, such that κorg = 0.12εWSOM. Assuming bulk (size-independent) composition and including the κorg parameterization enabled CCN predictions to within 30% accuracy for nearly all environments sampled. The only exception was for industrial pollution from Canadian oil sands exploration, where an external mixture and size-dependent composition was required. Aerosol mixing state assumptions (internal vs. external) in all other environments did not significantly affect CCN predictions; however, the external mixing assumption provided the best results, even though the available observations could not determine the true degree of external mixing and therefore may not always be representative of the environments sampled. No correlation was observed between κorg and O : C. A novel correction of the CCN instrument supersaturation for water vapor depletion, resulting from high concentrations of CCN, was also employed. This correction was especially important for fresh biomass burning plumes where concentrations exceeded 1.5×104 cm−3 and introduced supersaturation depletions of &amp;geq;25%. Not accounting for supersaturation depletion in these high concentration environments would therefore bias CCN closure up to 25% and inferred κ by up to 50%.

Nonmetallic inclusions in rails made of electro-steel alloyed with chromium

2020 ◽  
Vol 62 (12) ◽  
pp. 936-942 ◽  
Author(s):  
A. A. Umanskii ◽  
A. V. Golovatenko ◽  
A. S. Simachev
Keyword(s):  
Hot Deformation ◽  
Ultrasonic Testing ◽  
Nonmetallic Inclusions ◽  
Relative Concentration ◽  
Metallographic Analysis ◽  
High Ductility ◽  
High Concentration ◽  
Metallic Inclusions ◽  
Significant Concentration

Type, relative concentration and size of most characteristic non-metallic inclusions for the elements of rails (head, web) from electro-steel of E79KhF and E90KhАF grades were determined on the basis of metallographic (with a microscope “OLYMPUS GX-51”) and spectral (using spectrometer “ARL iSpark” method “Spark-DAT”) analyses. It was found that the highest relative concentration of manganese sulfides (MnS) is 30.8 – 43.4 ppm. At the same time, 60 – 100 % of inclusions of this type are of small sizes (less than 4 μm), and it does not allow them to be detected using standard metallographic analysis with 100-fold magnification. The revealed high relative concentration of sulfide inclusions directly correlates with the established positive sulfur liquation in considered rail elements, which is up to 40 %. Despite the high concentration of manganese sulfides, their influence on the quality of rails can be considered not dangerous, taking into account their high ductility during hot deformation and the established prevalence of inclusions of this type with small size (less than 4 μm). Among inclusions of a silicate type, SiO2 inclusions (3.4 – 14.9 ppm) have a significant concentration. All detected inclusions of this type have a size not exceeding 4 μm. It was found that the concentration of complex inclusions containing alumina (Al2O3 – CaO – MgO, Al2O3 – CaO – MgO – CaS, Al2O3 – CaO, Al2O3 – MgO) is insignificant: in total it does not exceed 3.1 ppm and 1.6 ppm for individual types. The concentration of corundum (Al2O3) is also insignificant and does not exceed 0.3 ppm. In this case, alumina inclusions of small size (less than 6 μm) prevail. Due to the low contamination (taking into account the relative concentration and size of inclusions) with non-plastic silicate and alumina non-metallic inclusions, their influence on the quality of the rails was not significant. It is confirmed by the absence of defects detected during ultrasonic testing.

scholarly journals The Phase Transformations in Hypoeutectoid Steels Mn-Cr-Ni

2015 ◽  
Vol 60 (1) ◽  
pp. 497-502 ◽  
Author(s):  
E. RoŻniata ◽  
R. Dziurka
Keyword(s):  
Chemical Composition ◽  
Phase Transformations ◽  
Critical Points ◽  
Light Microscope ◽  
Cooling Curves ◽  
Critical Temperatures ◽  
Martensitic Microstructure ◽  
Cct Diagrams ◽  
Kinetics Of ◽  
Undercooled Austenite

Abstract The results of a microstructure and hardness investigations of the hypoeutectoid steels Mn-Cr-Ni, imitating by its chemical composition toughening steels, are presented in the paper. The analysis of the kinetics of phase transformations of undercooled austenite of steels containing different amounts of alloying elements in their chemical composition, constitutes the aim of investigations. Metallographic examinations were carried out on a Axiovert 200 MAT light microscope. Sections were etched with a 3% HNO3 solution in C2H5OH. Dilatometric tests were performed using L78 R.I.T.A dilatometer. Using dilatometer the changes of elongation (Δl) of the samples with dimensions Ø 3×10 mm as a function of temperature (T) were registered. Obtained heating curves were used to precisely determine the critical temperatures (critical points) for the tested steels, while the differentiation of obtained cooling curves allowed to precisely define the temperatures of the beginning and the end of particular transition to draw CCT diagrams. Four CCT diagrams worked out for the tested hypoeutectoid steels (for quenching of steel) are - in the majority of steels - separated by the undercooled austenitic range and are of the letter „C” shape. However, for steels with Mn and Ni the separation of diffusive transformations from the bainitic transformation by the stable austenitic range is not observed. Hardenability of four investigated hypoeutectoid steels is similar, but still not high. To obtain martensite in the microstructure of these steels, it is necessary to apply the cooling rate higher than 25°C/s. The exception constitutes the Mn - Ni steel, in which only cooling with the rate higher than 50°C/s allows to achieve the martensitic microstructure and to avoid diffusive transformations (pearlitic and ferritic).

Cleanness and Mechanical Properties of Steel after Remelting under Different Slags by ESR

2014 ◽  
Vol 635 ◽  
pp. 112-117
Author(s):  
Alena Pribulová ◽  
Peter Futáš ◽  
Marianna Bartošová
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Sulphur Content ◽  
Metallic Inclusions ◽  
Change Chemical Composition

Quality of machine production is very close-knit with quality of metallurgical semi-products and with improvement their working properties. It can be achieved first of all by decrease of sulphur and non-metallic inclusions content in metal. Improvement of working properties provide remelted processes above an electro slag remelting (ESR). The slags play very important role by ESR process. By experiments steel with next chemical composition was used: C (0,9 – 1,1%), Mn (0,30 – 0,50%), Si (0,15 – 0,35%), Cr (1,30 – 1,65%), Ni (max.0,30%), Cu (max.0,25%), P (max.0,027%), S (max.0,030%). The steel was remelted under 8 types of slags on the base of CaO, Al2O3, CaF2 and SiO2 in different ratios. The contribution deals with influence of chemical composition of slag on mechanical properties and cleannes of metal after electro slag remelting. Variation of slag chemical composition enables to change chemical composition of remelted steel, to reduce the non-metallic inclusions and sulphur content and to improve the mechanical properties of steel.

scholarly journals Vibratory Stress Relief and Vibratory Weld Conditioning of Flux cored arc welded CA6NM steel

2019 ◽  
Vol 9 (1) ◽  
pp. 32
Author(s):  
Luiz Fernando Cursino Briet de Almeida ◽  
Julio Cesar Lourenco ◽  
Maria Ismenia Sodero Toledo Faria ◽  
Decio Lima Vieira ◽  
Alain Laurent Marie Robin ◽  
...  
Keyword(s):  
Weld Metal ◽  
Welded Joint ◽  
Stress Relief ◽  
Delta Phase ◽  
Martensitic Microstructure ◽  
Hydraulic Turbines ◽  
Welding Electrode ◽  
The Individual ◽  
Ca6nm Steel ◽  
Hardness Values

ASTM A743 CA6NM steel is used in the manufacturing of hydraulic turbines components. Multipass welding is commonly used for their fabrication or repairing. In this work, two different vibratory welding procedures were studied: vibration applied during welding (VWC) and vibration applied after welding (VSR). Results have shown that in both conditions, CA6NM steel presented a martensitic microstructure, in which the VSR welded joint presented column-shaped packets and fine martensite delineating the individual beads, while VWC joint presented grain refinement. Heat affected zones (HAZ) presented &delta;-phase in small amounts for both conditions in the regions which reached higher temperatures. VSR and VWC conditions presented similar behavior in terms of hardness, HAZ hardness values being close to those of the weld metal, except for the root regions, where higher values were obtained. Charpy-V results showed that HAZs presented higher impact values than those of the weld metal. The low impact values of the weld metal were attributed to presence of inclusions from the welding electrode.

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