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Spheroidal Cast Iron for Works at Low Temperature - Requirements, Structure, Properties, Control of the Production Process

Zych Jerzy, Jurga T., Mocek Jan, Myszka Marcin, Snopkiewicz Tomasz

Archives of Metallurgy and Materials

2022

Vol. 67, iss. 3

999--1005

Two standardised grades of spheroidal cast iron determined in standard EN PN 1563-1997 as: EN-GJS-350-22LT (T=-40°C) and EN GJS 400-18LT (T=-20°C) are intended for work at low temperatures: -20 and -40°C. The main mechanical property of these cast iron grades is a high impact strength at a work temperature down to: -40°C. A series of controlled melts was performed to optimise the production technology of spheroidal cast iron, which in as-cast state is characterised by ferritic matrix (the best without any pearlite), fine precipitates of nodular graphite and high purity (without non-metallic inclusions). Variable structures of metal charges and various spheroidisation techniques (the modification methods) (slender ladle with a tight cover - Tundish technology as well as the technology with cored wire) were applied in the research. In order to obtain refinement of graphite precipitates and to achieve the ferritic matrix multistage inoculations of technologies were applied. Cast iron was subjected to refining to limit non-metallic inclusions since they decrease the impact strength. The production process of cast iron was controlled by the thermal derivative analysis at the stage of initial cast iron and after its secondary metallurgy (modification and inoculation). It was pointed out, that the reproducible production of cast iron for work at low temperatures was only possible when all elements of the technological process were strictly adhered to. It was pointed out, in the hereby paper, that: it should be strived to maintain Si content not higher than 2.50÷2.60%, which at producing spheroidal cast iron is sometimes difficult and requires using a lot of pig iron in the metal charge. For a fast assessment of the cast iron quality, concerning its impact strength, the proposed - in the hereby paper - index quality (IQu) can be applied. It is determined on the bases of measuring the cast iron hardness and propagation velocity of ultrasound wave.

Wysychanie powłok ochronnych nanoszonych na elementy form piaskowych o zróżnicowanym kształcie

Matonis Natalia, Jamrozowicz Łukasz, Zych Jerzy, Snopkiewicz Tomasz

Przegląd Odlewnictwa

2020

Vol. 70, nr 5-6

120--127

W artykule przedstawiono wyniki badań przebiegu procesu suszenia wybranych powłok ochronnych oraz jego kinetykę. Badaniom została poddana alkoholowa powłoka ochronna oraz wodna powłoka ochronna. Powłoki nakładano na powierzchnie „zewnętrzne” i „wewnętrzne” rdzeni przygotowanych z masy ze spoiwem furanowym na osnowie piasku kwarcowego o średniej wielkości ziarna . Na rdzenie nanoszono powłokę o lepkości kinematycznej: v=16 · 10-6 ; v=61 · 10-6 ; v=122 · 10-6 m2 /s; co odpowiada lepkości umownej wynoszącej 10, 20 i 30 sekund. Aby wyznaczyć kinetykę przebiegu procesu wysychania powłok ochronnych zastosowano technikę grawimetryczną. Pomiar szybkości odparowania rozcieńczalnika prowadzono w sposób ciągły i rejestrowano go na bieżąco w komputerze. Pomiary zostały przeprowadzone przy stałych warunkach temperatury (T=24°C) (wilgotności (42%) i ruchu powietrza. W toku prowadzonych badań został wyznaczony przebieg procesu wysychania wodnej i alkoholowej powłoki ochronnej nałożonej na powierzchnie „wewnętrzne” i „zewnętrzne” rdzenia. Ponadto rdzenie poddane badaniom posiadały różne wysokości (3/3 H, 2/3 H i 1/3 H) oraz kształt (kwadratowy, cylindryczny), by zbadać wpływ smukłości i kształtu rdzenia na przebieg i kinetykę procesu suszenia alkoholowego i wodnego pokrycia ochronnego. Co więcej określono czas „całkowitego” wysuszenia dla pierwszej i drugiej warstwy pokrycia i oceniono jakość wysuszonej warstwy powłoki.

Results of investigations of the courses and kinetics of drying processes of the selected protective coatings are presented in the hereby paper. The alcohol protective coating as well as the water protective coating was subjected to inve¬stigations. These coatings were deposited on 'external' and 'internal' surfaces of cores prepared of a moulding sand with a furan binder on the matrix of quartz sand of the average grain size L=0,28 mm. Coatings of a kinematic viscosities: v=16 · 10-6 ; v=61 · 10-6 ; v=122 · 10-6 m2 /s, which corresponds the conventional viscosities being 10,20 and 30 seconds, were deposited on the cores. In order to determine the kinetics of the drying process of protective coatings the gravimetric technique was applied. The evaporation rate of the diluent was continuously measured on -line by the computer. Measurements were performed at constant conditions of a temperature (T=24°C), humidity (42%) and air movement. During the performed tests the courses of drying processes of water and alcohol protective coatings deposited on 'internal'and 'external' surfaces of the core, were determined. In addition, the cores subjected to investigations had various heights (3/3 H, 2/3 H and 1/3 H) and shapes (square, cylindrical), to enable testing the influence of slenderness and shape of the core on the course and kinetics of the drying process of alcohol and water protective coatings. What's more, the time of 'complete' drying of the first and the second layer of the coating was determined and the quality of dried coating layers was assessed.