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Effects of South African Silica Sand Properties on the Strength Development and Collapsibility of Single Component Sodium Silicate Binders

F.C. Banganayi K. Nyembwe H. Polzin
Archives of Foundry Engineering | 2017 | vol. 17 | No 3 | DOI: 10.1515/afe-2017-0081
Keywords Inorganic binders Strength development Collapsibility
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Abstract

This study shows the results of the investigation of the strength performance, and residual strength of a single component inorganic binder

system Cast Clean S27®. The study was conducted using three different foundry sand sources in South Africa. Sample A is an alluvial

coastal sample, sample B is an alluvial riverbed sample and Sample C is a blasted sample from a consolidated quartzite rock. The binder

was also cured using three different curing mechanisms. The aim of the investigation was to determine the variation of strength

performance and residual strength between the different South African sand sources based upon the physical and chemical properties of

the sand sources. The moulding sand was prepared using three possible curing mechanisms which are carbon dioxide curing, ester curing

and heat curing. The strength measurements were determined by bending strength. Sample A and sample C sand had good strength

development. Sample B sand had inferior strength development and excellent high temperature residual strength. The study showed that

the single component inorganic binders have good strength development and low residual strength. The silica sand properties have major

contributing factors on both strength development and residual strength. The degree of influence of silica sand properties on strength

performance and residual strength is dependent on the time of curing and method of curing.

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Authors and Affiliations

F.C. Banganayi
K. Nyembwe
H. Polzin

Evaluation of Collapsibility of Selected Core Systems

T. Obzina V. Merta J. Rygel P. Lichý K. Drobíková
Archives of Foundry Engineering | 2022 | vol. 22 | No 1 | 48-52 | DOI: 10.24425/afe.2022.140216
Keywords Foundry Foundry cores De-coring Knocking-out Collapsibility
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Abstract

There are mainly two different ways of producing sand cores in the industry. The most used is the shooting moulding process. A mixture of sand and binder is injected by compressed air into a cavity (core), where it is then thermally or chemically cured. Another relatively new method of manufacturing cores is the use of 3D printing. The principle is based on the method of local curing of the sand bed. The ability to destroy sand cores after casting can be evaluated by means of tests that are carried out directly on the test core. In most cases, the core is thermally degraded and the mechanical properties before and after thermal exposure are measured. Another possible way to determine the collapsibility of core mixtures can be performed on test castings, where a specific casting is designed for different binder systems. The residual strength is measured by subsequent shake-out or knock-out tests. In this paper, attention will be paid to the collapsibility of core mixtures in aluminium castings.
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Bibliography

[1] Dietert, H.W. (1950). Core knock-out, in Foundry Core Practice, 2nd ed. Chicago: American Foundrymen’s Society.
[2] Jorstad, J.L. (2008). Expendable-mold casting processes with permanent patterns, in ASM Handbook Vol. 15 Casting, 10th ed. ASM International
[3] Almaghariz, E.S., Conner, B.P., Lenner, L., Gullapalli, R., Manogharan, G.P. (2016). Quantifying the role of part design complexity in using 3D sand printing for molds and cores. International Journal of Metalcasting. 10, 240-252. DOI: 10.1007/s40962-016-0027-5.
[4] Vykoukal, M., Burian, A., Přerovská, M., Bajer, T., Beňo, J. (2019). Gas evolution of GEOPOL® W sand mixture and comparison with organic binders. Archives of Foundry Engineering. 19(2), 49-54.
[5] Steinhäuser, T. (2017). Inorganic binders-Benefits, State of the art, Actual use. In World Cast in Africa, Innovative for Sustainability, Proceedings of the South African Metal Casting Conference, Johannesburg, South Africa, 13–17 March 2017; WFO: Johannesburg, South Africa, p. 26
[6] Ramrattan, S. (2019). Evaluating a ceramic resin-coated sand for aluminum and iron castings. International Journal of Metalcasting. 13(3), 519-527. DOI: https://doi.org/10.1007/s40962-018-0269-5
[7] Ettemeyer, F., Schweinefuß, M., Lechner, P., Stahl, J., Greß, T., Kaindl, J., Durach, L., Volk, W. & Günther, D. (2021). Characterisation of the decoring behaviour of inorganically bound cast-in sand cores for light metal casting. Journal of Materials Processing Technology. 296, 117201, ISSN 0924-0136. DOI: https://doi.org/10.1016/j.jmatprotec.2021. 117201.
[8] Dobosz, P., Jelínek, K., Major-Gabryś, K. (2011). Development tendencies of moulding and core sands. China Foundry. 8, 438-446.

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Authors and Affiliations

T. Obzina
1
V. Merta
1
ORCID: ORCID
J. Rygel
1
P. Lichý
1
ORCID: ORCID
K. Drobíková
1
  1. VSB - Technical University of Ostrava, Czech Republic

The Role of Acid Hardener on the Hardening Characteristics, Collapsibility Performance, and Benchlife of the Warm-Box Sand Cores

I. Budavári H. Hudák G. Fegyverneki
Archives of Foundry Engineering | 2023 | vol. 23 | No 1 | 68-74 | DOI: 10.24425/afe.2023.144282
Keywords Warm-box Sand cores bending strength Collapsibility Benchlife
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Abstract

The heat-cured core-making process has been applied for over 60 years to produce molds and cores for different types of castings. The following technologies can be classified into the terminology of “heat-cured coremaking process”: croning-, hot-box -, and warm-box process. The latest technology provides good workability of core mixture, good strength properties, dimensional stability, and good knockout performance of the sand cores. Despite all its advantages, the warm-box technology is less widespread in foundries due to the cost of the high quality thermosetting resin and the maintenance cost of the core box. In this study, the influence of the acid hardener content on the hardening characteristics (bending strength), collapsibility, and the benchlife of the warm-box sand cores were investigated. From the results, it can be said, that within the investigated composition range, increasing the acid hardener content will improve the bending strength of the sand cores. The increased acid hardener content results in higher thermal stability at the beginning of the thermal exposure, and smaller residual bending strength after 15 minutes of thermal loading. The acid hardener level has little effect on the benchlife of the warm-box sand cores, although the sand core mixture is very sensitive to the combined effect of the sand temperature and dwelling time.
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Authors and Affiliations

I. Budavári
1
ORCID: ORCID
H. Hudák
1
G. Fegyverneki
1
  1. University of Miskolc, Faculty of Materials Science of Engineering, Institute of Foundry, Hungry

Development of Water-Soluble Composite Salt Sand Cores Made by a Hot-Pressed Sintering Process

Xiaona Yang Long Zhang Xing Jin Jun Hong Songlin Ran Fei Zhou
Archives of Foundry Engineering | 2023 | vol. 23 | No 3 | 51-58 | DOI: 10.24425/afe.2023.146662
Keywords Water-soluble cores Hollow composite castings Salt cores Collapsibility
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Abstract

A wide variety of water-soluble cores are widely used in hollow composite castings with internal cavities, curved channels, and undercuts. Among them, the cores made by adding binders of inorganic salts in the form of aqueous solutions have excellent solubility in water. However, excellent collapsibility is often accompanied by poor moisture absorption resistance. In this study, a water-soluble core with moderate strength and moisture absorption resistance was prepared by hot pressing and sintering the core sand mixture of sand, bentonite, and composite salts, and a tee tube specimen was cast. The experimental results showed that the cores with KCl-K2CO3 as binder could obtain strength of more than 0.9 MPa and still maintain 0.3 MPa at 80±5% relative humidity for 6 hours; the subsequent sintering process can significantly improve the resistance to moisture absorption of the hot pressed cores (0.6 MPa after 24 hours of storage at 85±5% relative humidity); the water-soluble core prepared by the post-treatment can be used to cast tee pipe castings with a smooth inner surface and no porosity defects, and it is easy to remove the core.
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Authors and Affiliations

Xiaona Yang
1
Long Zhang
1
Xing Jin
2
Jun Hong
3
Songlin Ran
2
Fei Zhou
3
  1. School of Metallurgical Engineering, Anhui University of Technology, China
  2. Anhui Province Key Laboratory of Metallurgical Engineering & Resources Recycling, Anhui University of Technology, China
  3. Technical Department, Anhui Highly Precision Casting Co., Ltd, China

Resistance to Progressive Collapse Performance Analysis of Steel Open-Web Sandwich Plate Structure

Weiyi Zeng Jie Luo Jianchun Xiao
Archives of Civil Engineering | Vol. 66 | No 3 | 281-303 | DOI: 10.24425/ace.2020.134398
Keywords sensitivity analysis rod failure steel open-web sandwich plate structure progressive collapse redundancy index
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Abstract

In order to investigate the progressive collapse performance of steel open-web sandwich plate structure, the sensitivity index and the importance coefficient of the bars are analyzed by the alternate path method. The condition that the model has perimeter supports with different parameters shows the result that: the redundancy index of structure increases at the structural edge, and the redundancy index will be reduced to changing degrees at the middle structure, when the stiffness of higher ribs increases. The redundancy index has little change, when the stiffness of lower ribs or shear keys increases. The sensitivity index of the shear keys dropped significantly, but the sensitivity index of the higher ribs and lower ribs increase, when the span to depth ratio increases. The sensitivity index of the higher ribs in L1 line increases significantly, when the span to depth ratio declines. So it is advisable to strengthen the higher ribs to avoid excessive sensitivity of ribs, when the span to depth ratio declines.

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Authors and Affiliations

Weiyi Zeng
Jie Luo
Jianchun Xiao

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