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Volume 67 (2020): Issue 4 (December 2020)

Volume 67 (2020): Issue 3 (September 2020)

Volume 67 (2020): Issue 2 (June 2020)

Volume 67 (2020): Issue 1 (March 2020)

Volume 66 (2019): Issue 4 (December 2019)

Volume 66 (2019): Issue 3 (December 2019)

Volume 66 (2019): Issue 2 (June 2019)

Volume 66 (2019): Issue 1 (March 2019)

Volume 65 (2018): Issue 4 (December 2018)

Volume 65 (2018): Issue 3 (September 2018)

Volume 65 (2018): Issue 2 (September 2018)

Volume 65 (2018): Issue 1 (March 2018)

Volume 64 (2017): Issue 4 (December 2017)

Volume 64 (2017): Issue 3 (September 2017)

Volume 64 (2017): Issue 2 (July 2017)

Volume 64 (2017): Issue 1 (March 2017)

Volume 63 (2016): Issue 4 (December 2016)

Volume 63 (2016): Issue 3 (September 2016)

Volume 63 (2016): Issue 2 (July 2016)

Volume 63 (2016): Issue 1 (May 2016)

Journal Details
Format
Journal
eISSN
1854-7400
First Published
30 Mar 2016
Publication timeframe
4 times per year
Languages
English

Search

Volume 65 (2018): Issue 4 (December 2018)

Journal Details
Format
Journal
eISSN
1854-7400
First Published
30 Mar 2016
Publication timeframe
4 times per year
Languages
English

Search

5 Articles
Open Access

Decarburization of the Carbon Steel C45 During Annealing in Air

Published Online: 31 May 2019
Page range: 167 - 178

Abstract

Abstract

In production it is necessary to achieve conditions that lead to the minimum decarburization of a steel product’s surfaces. In this study, the hypo-eutectoid carbon steel C45 was annealed in air in the temperature range Ta = 600–1100 °C. The annealing times were between ta = ½ h and ta = 2 h. Different decarburizations occurred in different microstructures: ferrite–pearlite (Ta = 600 °C and 700 °C, Ta < AC1, no visible decarburization); ferrite–austenite (Ta = 760 °C, AC1 < Ta < AC3, visible decarburization); austenite at the beginning, ferrite– austenite after the incubation period (Ta = 850 °C, AC3 < Ta < 912 °C, visible decarburization); and austenite (Ta= 950 °C and 1100 °C, Ta> 912 °C, visible decarburization and overheating of steel). The edges were more prone to decarburization and to overheating. Stress relieving, normalizing and annealing before quenching of the steel C45 can be carried out in air.

Keywords

  • annealing
  • hypo-eutectoid steel
  • air
  • oxidation
  • decarburization
Open Access

Wire arc additive manufacturing of mild steel

Published Online: 31 May 2019
Page range: 179 - 186

Abstract

Abstract

This paper presents an overview of additive manufacturing technologies for production of metal parts. A special attention is set to wire arc additive manufacturing (WAAM) technologies, which include MIG/MAG welding, TIG welding and plasma welding. Their advantages compared to laser or electron beam technologies are lower investment and operational costs. However, these processes have lower dimensional accuracy of produced structures. Owing to special features and higher productivity, the WAAM technologies are more suitable for production of bigger parts. WAAM technology has been used together with welding robot and a cold metal transfer (CMT) power source. Thin walls have been produced using G3Si1 welding wire. The microstructure and hardness of produced structures were analysed and measured. A research was done to determine the optimal welding parameters for production of thin walls with smooth surface. A SprutCAM software was used to make a code for 3D printing of sample part.

Keywords

  • robotic MIG/MAG weld surfacing
  • hardness
  • wire arc additive manufacturing (WAAM)
  • SprutCAM
Open Access

The Universal Kriging Mapping of the Neogene EL-markers Rs5 and Δ, Northern Croatia

Published Online: 31 May 2019
Page range: 187 - 198

Abstract

Abstract

The area of the Bjelovar Subdepression in Northern Croatia, which represents the southwestern part of Drava’s depression, has been analysed. More than 700 depth data were collected in a regular grid covering the existing structural maps of e-log markers Rs5, Z’ and Δ, with cells 2 x 2 km in size. For zonal assessment, Thiessen polygon method was used as introductory analysis preceding Kriging interpolation on regional scale. The emphasis was on OK and UK interpolation, their comparison and selection of most appropriate method for mapping. Crossvalidation results proved UK technique to be the most appropriate in mapping of e-log markers Rs5 and Δ, thus acquiring the most accurate maps so far of the analysed Neogene area.

Keywords

  • e-log markers
  • advanced mapping method
  • Universal Kriging
  • Bjelovar Subdepression
  • Croatia
Open Access

Preliminary geophysical investigation for road construction using integrated methods

Published Online: 31 May 2019
Page range: 199 - 206

Abstract

Abstract

Integrated geophysical methods have been used to investigate the competency of the subsoil. The geophysical surveys conducted involve very low-frequency electromagnetic (VLF-EM) and electrical resistivity (ER) methods (dipole-dipole). ABEM Wadi and Ohmega resistivity meter were used to acquire VLF-EM and ER data, respectively, along two traverses. Station interval of 5 m was used for the VLF-EM survey, while inter-electrode spacing for dipole–dipole was 10 m; the inter-dipole expansion factor (n) ranged from 1 to 5. KHFFILT software was used to generate VLF-EM profiles and pseudosection, while DIPRO software was used for ER. Results from the ER method revealed the pattern of resistivity variations within the study area. The low resistivity values (11–25 Ohm-m) observed at the southern part of the study area could be attributed to changes in clay contents and degree of weathering in the subsurface. The results from the VLF-EM investigation revealed the presence of near-surface linear geologic structures of varying lengths, depths and attitudes, which suggest probable conductive zones that are inimical to the foundation of the road subgrade.

Keywords

  • Electrical resistivity
  • roadway subgrade
  • subsoil competence
  • clay material
  • road failure
Open Access

Geochemical assessment of claystone deposits from the Patti Formation, Southern Bida Basin, Nigeria

Published Online: 31 May 2019
Page range: 207 - 218

Abstract

Abstract

Geochemical studies of claystone deposits from the Patti Formation in the southern Bida Basin, north-Central Nigeria, were carried out on representative samples to determine the basin’s depositional conditions, provenance and tectonic setting. The localities within the study area included Gegu, Ahoko, Ahoko-Etigi, Omu and Idu.

Semi-quantitative phase analysis using the Rietveld method and X-ray powder diffraction data revealed that the claystone samples had prominent kaolinite with other constituents such as quartz, illite–muscovite, K-feldspar, pyrite, marcasite, anatase, rutile and gorceixite.

Enrichment of Al2O3, Ba, Th, Sr, Cr and La suggests that these elements are primarily controlled by the dominant clay minerals.

Geochemical parameters such as U, U/Th, Ni/Co, V/Cr and Cu/Zn ratios strongly implied that these claystones were deposited in an oxidising environment. Provenance deducing ratios for felsic, mafic and basic igneous rocks were compared. Al2O3/TiO2 ratio suggested intermediate to felsic rocks as the probable source rocks for the claystone samples; however, Y/Ni, Cr/V, La/Sc and Th/Sc ratios suggested a felsic progenitor. The tectonic discrimination diagram showed that the samples’ plot was within the region specified for passive margin-type tectonic setting.

Keywords

  • claystone
  • geochemical
  • tectonic
  • provenance
  • paleo-oxygenation
5 Articles
Open Access

Decarburization of the Carbon Steel C45 During Annealing in Air

Published Online: 31 May 2019
Page range: 167 - 178

Abstract

Abstract

In production it is necessary to achieve conditions that lead to the minimum decarburization of a steel product’s surfaces. In this study, the hypo-eutectoid carbon steel C45 was annealed in air in the temperature range Ta = 600–1100 °C. The annealing times were between ta = ½ h and ta = 2 h. Different decarburizations occurred in different microstructures: ferrite–pearlite (Ta = 600 °C and 700 °C, Ta < AC1, no visible decarburization); ferrite–austenite (Ta = 760 °C, AC1 < Ta < AC3, visible decarburization); austenite at the beginning, ferrite– austenite after the incubation period (Ta = 850 °C, AC3 < Ta < 912 °C, visible decarburization); and austenite (Ta= 950 °C and 1100 °C, Ta> 912 °C, visible decarburization and overheating of steel). The edges were more prone to decarburization and to overheating. Stress relieving, normalizing and annealing before quenching of the steel C45 can be carried out in air.

Keywords

  • annealing
  • hypo-eutectoid steel
  • air
  • oxidation
  • decarburization
Open Access

Wire arc additive manufacturing of mild steel

Published Online: 31 May 2019
Page range: 179 - 186

Abstract

Abstract

This paper presents an overview of additive manufacturing technologies for production of metal parts. A special attention is set to wire arc additive manufacturing (WAAM) technologies, which include MIG/MAG welding, TIG welding and plasma welding. Their advantages compared to laser or electron beam technologies are lower investment and operational costs. However, these processes have lower dimensional accuracy of produced structures. Owing to special features and higher productivity, the WAAM technologies are more suitable for production of bigger parts. WAAM technology has been used together with welding robot and a cold metal transfer (CMT) power source. Thin walls have been produced using G3Si1 welding wire. The microstructure and hardness of produced structures were analysed and measured. A research was done to determine the optimal welding parameters for production of thin walls with smooth surface. A SprutCAM software was used to make a code for 3D printing of sample part.

Keywords

  • robotic MIG/MAG weld surfacing
  • hardness
  • wire arc additive manufacturing (WAAM)
  • SprutCAM
Open Access

The Universal Kriging Mapping of the Neogene EL-markers Rs5 and Δ, Northern Croatia

Published Online: 31 May 2019
Page range: 187 - 198

Abstract

Abstract

The area of the Bjelovar Subdepression in Northern Croatia, which represents the southwestern part of Drava’s depression, has been analysed. More than 700 depth data were collected in a regular grid covering the existing structural maps of e-log markers Rs5, Z’ and Δ, with cells 2 x 2 km in size. For zonal assessment, Thiessen polygon method was used as introductory analysis preceding Kriging interpolation on regional scale. The emphasis was on OK and UK interpolation, their comparison and selection of most appropriate method for mapping. Crossvalidation results proved UK technique to be the most appropriate in mapping of e-log markers Rs5 and Δ, thus acquiring the most accurate maps so far of the analysed Neogene area.

Keywords

  • e-log markers
  • advanced mapping method
  • Universal Kriging
  • Bjelovar Subdepression
  • Croatia
Open Access

Preliminary geophysical investigation for road construction using integrated methods

Published Online: 31 May 2019
Page range: 199 - 206

Abstract

Abstract

Integrated geophysical methods have been used to investigate the competency of the subsoil. The geophysical surveys conducted involve very low-frequency electromagnetic (VLF-EM) and electrical resistivity (ER) methods (dipole-dipole). ABEM Wadi and Ohmega resistivity meter were used to acquire VLF-EM and ER data, respectively, along two traverses. Station interval of 5 m was used for the VLF-EM survey, while inter-electrode spacing for dipole–dipole was 10 m; the inter-dipole expansion factor (n) ranged from 1 to 5. KHFFILT software was used to generate VLF-EM profiles and pseudosection, while DIPRO software was used for ER. Results from the ER method revealed the pattern of resistivity variations within the study area. The low resistivity values (11–25 Ohm-m) observed at the southern part of the study area could be attributed to changes in clay contents and degree of weathering in the subsurface. The results from the VLF-EM investigation revealed the presence of near-surface linear geologic structures of varying lengths, depths and attitudes, which suggest probable conductive zones that are inimical to the foundation of the road subgrade.

Keywords

  • Electrical resistivity
  • roadway subgrade
  • subsoil competence
  • clay material
  • road failure
Open Access

Geochemical assessment of claystone deposits from the Patti Formation, Southern Bida Basin, Nigeria

Published Online: 31 May 2019
Page range: 207 - 218

Abstract

Abstract

Geochemical studies of claystone deposits from the Patti Formation in the southern Bida Basin, north-Central Nigeria, were carried out on representative samples to determine the basin’s depositional conditions, provenance and tectonic setting. The localities within the study area included Gegu, Ahoko, Ahoko-Etigi, Omu and Idu.

Semi-quantitative phase analysis using the Rietveld method and X-ray powder diffraction data revealed that the claystone samples had prominent kaolinite with other constituents such as quartz, illite–muscovite, K-feldspar, pyrite, marcasite, anatase, rutile and gorceixite.

Enrichment of Al2O3, Ba, Th, Sr, Cr and La suggests that these elements are primarily controlled by the dominant clay minerals.

Geochemical parameters such as U, U/Th, Ni/Co, V/Cr and Cu/Zn ratios strongly implied that these claystones were deposited in an oxidising environment. Provenance deducing ratios for felsic, mafic and basic igneous rocks were compared. Al2O3/TiO2 ratio suggested intermediate to felsic rocks as the probable source rocks for the claystone samples; however, Y/Ni, Cr/V, La/Sc and Th/Sc ratios suggested a felsic progenitor. The tectonic discrimination diagram showed that the samples’ plot was within the region specified for passive margin-type tectonic setting.

Keywords

  • claystone
  • geochemical
  • tectonic
  • provenance
  • paleo-oxygenation

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