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Fatigue Resistance and Other Utility Properties of NiMn-Type of Austenitic Nodular Cast Iron

Vaško Alan, Uhríčik Milan, Kaňa Václav

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 2

563--569

EN

The aim of this paper is to evaluate the fatigue resistance of austenitic nodular cast iron and to compare it with other types of nodular cast irons. The austenitic nodular cast iron, used for the experiments, was alloyed by 13% nickel and 7% manganese (EN-GJSA-XNiMn13-7) to obtain an austenitic matrix. The microstructure was studied using light metallographic microscopy. Mechanical properties were investigated by tensile test, impact bending test and Brinell hardness test. Fatigue tests were carried out at sinusoidal cyclic push-pull loading at ambient temperature. The results of fatigue tests were compared with the fatigue properties of ferrite-pearlitic nodular cast iron and pearlite-ferritic nodular cast iron. Experimental results show that NiMn-type of austenitic nodular cast iron has lower tensile strength and hardness, but higher elongation and absorbed energy than the compared types of nodular cast iron. However, austenitic nodular cast iron has lower fatigue limit.

2

Precipitation of Sigma and Chi Phases in Cast Standard Duplex Stainless Steel

Myška Martin, Bořil Petr, Krutiš Vladimír, Kaňa Václav, Zádĕra Antonin

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 2

29--34

EN

This work deals with the problem of intermetallic phases in cast standard duplex steel ASTM A890 Gr 4A (generally known as 2205). The investigated steel was subjected to isothermal heat treatment in the range from 595 °C to 900 °C and in the duration from 15 minutes to 245 hours, and was also investigated in terms of anisothermal (natural) cooling after casting into the mould. The precipitation starts at grain boundaries with a consistent ferrite transformation. The work is focused on the precipitation of the sigma phase (σ) and the chi phase (χ). Examination of the microstructure was conducted using light and scanning electron microscopy. Their statistical analysis was carried out using the results of the investigations of precipitation processes in the microstructure, both within the grains and at the grain boundaries. To illustrate this impact, the surface area of precipitates was evaluated. The percentage of these intermetallic phases was calculated by measuring their area using a computer image analysis system. Based on their observations, a combined time-temperature transformation (TTT) diagram with continuous cooling transformation (CCT) curves was created.

3

Improvement of Mechanical Properties of Cast Ceramic Cores Based on Ethyl Silicate

Bořil Petr, Kaňa Václav, Myška Martin, Krutiš Vladimír

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 4

47--52

EN

The aim of the paper is experimental verification of the influence of the composition of the ceramic mixture on the mechanical properties of cast ethyl silicate cores. Cast ceramic cores have a great potential in the production of complex castings, especially in the field of hydropower. However, the disadvantage of the cast ceramic cores is their low strength during cores removing from the core box and handling with them. The research is focused mainly on the possibilities of increasing the handling strength of the cores during removal from the core box and after their ignition. The paper investigates different ways of increasing the strength of cast ceramic cores by adjusting the composition of the ceramic mixture. Further, the research verifies the possibility of increasing the strength of ceramic cores by adding synthetic fibers to the ceramic mixture. The paper also contains the results of measuring the strength of the cores after impregnation with a solution of phosphorous binder and subsequent annealing.

4

Effect of Inoculants on the Structure and Properties of Thin-Walled Ductile Iron Castings

Roučka Jaromir, Kaňa Václav, Kryštůfek T., Chýlková A.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 4

90--95

EN

In many application fields, thin-walled ductile iron castings can compete with castings made from aluminium alloys thanks as their show superior mechanical properties higher stiffness, vibrations damping as well as properties at higher temperatures. As problematic criterion in thin-walled cast-iron castings can be seen the graphitization ability and high sensitivity of the structure and the mechanical properties to the solidification rate. The tests were curried on plate castings with wall thicknesses of 3, 5, and 8 mm, using inoculants based on FeSi70 with different contents of nucleation-active elements as aluminium, calcium, zirconium and magnesium. The inoculation was made by the in-mould method. In the experiments structures were achieved, differing by the graphite dispersity, structure and mechanical properties. The experiments have proved particularly a high sensitivity of the structure and the mechanical properties to the cooling rate of the sample castings. The influence of the inoculant type is less important than the influence of solidification rate.

5

Corrosion resistance of SiMo- and SiCu-types of nodular cast iron in NaCl solution

Vaško Alan, Zatkalíková Viera, Kaňa Václav

System Safety : Human - Technical Facility - Environment

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2020

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Vol. 2, nr 1

191--198

EN

Nodular cast irons are used in a wide range of industrial applications, especially in the automotive industry. SiMo-type of nodular cast iron is suitable for high-temperature applications, for example the exhaust manifolds of the combustion engines; SiCu-type of nodular cast iron is used in various components of tribotechnical units. These automotive components often work in a corrosive environment. Therefore, the aim of this paper is to compare the corrosion resistance of two types of the nodular cast irons (SiMo-type and SiCu-type). Corrosion resistance was determined by the exposure immersion test at ambient temperature. Specimens of both types of nodular cast iron were immersed in 3.5 % NaCl solution (to simulate sea water) and gradually removed from the solution after 1, 2, 4 and 8 weeks. Subsequently, the weight loss (g) and the average corrosion rate (g m-2 day-1) were calculated. Experimental results show that nodular cast iron alloyed by Si and Mo has higher corrosion resistance than the nodular cast iron alloyed with Si and Cu. Moreover, the mechanical properties (evaluated by tensile test, impact bending test and hardness test) and fatigue properties of both types of nodular cast iron has been compared in the paper.