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Abstract

The paper deals with the impact of technological parameters on the mechanical properties and microstructure in AlSi12 alloy

using squeeze casting technology. The casting with crystallization under pressure was used, specifically direct squeeze

casting method. The goal was to affect crystallization by pressure with a value 100 and 150 MPa. From the experiments we

can conclude that operating pressure of 100 MPa is sufficient to influence the structural characteristics of the alloy AlSi12.

The change in cooling rate influences the morphology of the silicon particles and intermetallic phases. A change of excluded

needles to a rod-shaped geometries with significantly shorter length occurs when used gravity casting method. At a pressure

of 100 MPa was increased of tensile strength on average of 20%. At a pressure of 150 MPa was increased of tensile strength

on average of 30%. During the experiment it was also observed, that increasing difference between the casting temperature

and the mold temperature leads to increase of mechanical properties.

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Authors and Affiliations

R. Pastirčák
J. Ščury
J. Moravec
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Abstract

The phenomenon of “soft zone” is occurring in the heat affected zone (HAZ) of high strength low alloy (HSLA) steels. Therefore, the process of weld metal solidification and phase transformation in HAZ is essential to understand the behaviour of the material, especially in the case where welded joints are debilitating part of the construction. The simulation program SYSWELD is powerful tool to predict solidification and phase transformation of welding joint, what correspond to the mechanical properties of the joints. To achieve relevant results of the simulation, it is necessary to use right mathematic-material model of the investigated material. Dilatometric test is the important methods to gather necessary input values for material database. In this paper is investigated physical and metallurgical properties of S960MC steel. The dilatometric curves were carried out on the laboratory machine dilatometer DIL 805L. In addition to determination of the phase transformation temperatures at eight levels of the cooling rate, the microstructure and hardness of the material are further analysed. The hardness of the samples reflects the achieved microstructure. Depending on the cooling rate, several austenitic transformation products were observed such as pearlite, bainite, martensite and many different ferritic microstructures. The differences between the transformation temperature results using the first derivation method and the three tangent method are up to 2%. The limit cooling rate was set at value 30°C/s. The microstructure consists only of bainite and martensite and the hardness reaches a value of 348HV and higher.
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Bibliography

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Authors and Affiliations

M. Málek
1
M. Mičian
1
ORCID: ORCID
J. Moravec
1

  1. Faculty of Mechanical Engineering, Technical University of Liberec, Studentská 1402/2, 461 17 Liberec I, Czech Republic
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Abstract

The paper deals with the possibility of the renovation of permanent steel molds for casting using electric arc welding technology. When casting liquid metal into permanent steel molds, there is chemical-thermo-mechanical wear of the surface of the mold cavity and the inlet system, which causes a deterioration of the surface quality and dimensional accuracy of the casting. For this reason, it is necessary to renovate the steel mold after a certain casting interval - mold life. In this case, the technology of manual electric arc welding with a coated electrode was used for the renovation. The welding renovation aims to increase the service life of the mold using carbide hardfacing welds, which after welding achieve high mechanical properties of the renovated mold parts. Two types of hardfacing coated electrodes were used for welding, namely the OK Weartrode 55HD electrode and the OK Weartrode 50T electrode. Macroscopic analysis, tribological tests as well as the measurement of the hardness of the welded layers were performed to evaluate the quality and the friction coefficients of the additional materials used. The properties of hardfacing welds were compared with the properties of the basic material of the high-alloy steel mold. The main advantage is in addition to increasing the durability and longevity of the mold, also reducing the cost of mold renovation compared to other renovation technologies.
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Bibliography

[1] Jankura, D., (2013). Wear evaluation of renovation layers based on hardfacing (Hodnotenie opotrebenia renovačných vrstiev na báze tvrdonávarov). Transfer Inovácií. 26, 126-129.
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[6] Mician, M. et al. (2018). The Repair of Foundry Defects in Steel Castings Using Welding Technology. Archives of Foundry Engineering. 18(2), 177-180. DOI: 10.24425/122524.
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[9] Pliszka, I. et al. (2018). Surface improvement by wc-cu electro-spark coatings with laser modification. In: 10th conference on terotechnology, 18-19 October 2017 (pp. 237-242). Kielce, Poland: Kielce University of Technology.
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[12] Bronček, J., Vicen, M., Fabian, P., Radek, N., 2020, Investigation of the tribological properties of the nitride layer on heat-treated steel 100Cr6, Lecture notes in mechanical engineering, 59th International Conference of Machine Design, 11-14 September 2018, (pp. 463-471). Žilina, Slovakia: University of Žilina.
[13] Mician, M. et al. (2020) Effect of the t(8/5) cooling time on the properties of S960MC steel in the HAZ of welded joints evaluated by thermal physical simulation. Metals. 10(2), 229. DOI: 10.3390/met10020229
[14] Winczek, J. et al. (2019). The Evaluation of the Wear mechanism of High-Carbon Hardfacing Layers. Archives of Metallurgy and Materials. 64 (3), 1111-1115. DOI: 10.24425/amm.2019.129502.

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Authors and Affiliations

J. Šutka
1
R. Koňar
1
J. Moravec
1
L. Petričko
1

  1. Department of Technological Engineering, University of Zilina, Univerzitna 1, 010 26 Zilina, Slovakia
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Abstract

The aim of this paper is to present the procedure test for calibration and validation of the numerical model for X22CrMoV12-1 steel multilayer welding. On the real multilayer weld was described how to arrange the whole experiment in order to obtain not only relevant input data but also verification data. Tests on a specially prepared specimen, welded with 8 beads in 4 layers, allows to determine the actual geometry of the single welded beads, registration of welding thermal cycles and the hardness distribution in successively deposited beads together with determining the heat influence of subsequent layers. The results of the real welding tests were compared with the results obtained from the numerical simulations and extended by the calculated stresses and distortions distributions of the tested specimen. A new, improved hardness prediction algorithm for high-alloy martensitic and bainitic steels was also proposed.

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Authors and Affiliations

T. Kik
ORCID: ORCID
J. Moravec
I. Novakova
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Abstract

This research is focused on the analysis of heat-affected sub-zones in 2 mm thick steel S960MC samples, with the aim of observing and evaluating the mechanical properties after exposure to temperatures corresponding to individual heat-affected sub-zones. Test samples were prepared using a Gleeble 3500 thermo-mechanical simulator. The samples were heated in the range from 550°C to 1350°C and were subsequently quickly cooled. The specimens, together with the base material, were then subjected to tensile testing, impact testing, and micro-hardness measurements in the sample cross-section, as well as evaluation of their microstructure. Fracture surfaces are investigated in samples after impact testing. The heat-affected sub-zones studied indicate high sensitivity to the thermal input of welding. There is a significant decrease in tensile strength and yield strength at temperatures around 550°C.

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Authors and Affiliations

M. Mičian
ORCID: ORCID
J. Winczek
D. Harmaniak
R. Koňár
M. Gucwa
J. Moravec

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