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1

The Effect of Reclaim Primary Quality on Moulding Sand Parameters and Quality of Ductile Iron Casting Surface Layer

Kamińska Jadwiga, Angrecki M., Puzio S., Stachowicz M.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 2

83--88

EN

The aim of the research was to determine the effect of the primary quality of reclaim from dry mechanical reclamation on the strength properties and service life of moulding sands based on this reclaim. Another aim was to establish the effect of the quality of reclaim, sulphur content - in particular, on the surface quality and thickness of the deformed surface layer in ductile iron castings. The research has revealed differences in the strength parameters and service life (mouldability) of sands based on the tested reclaims, depending on the type of the furfuryl resin used, including resins whose synthesis was done as part of the Żywfur project. Examinations of the structure of the surface layer of test castings poured in moulds made of loose self-hardening sands containing the addition of reclaim have confirmed the occurrence of degenerated spheroidal graphite in this part of the casting. It should be noted here that when massive castings with a long solidification time are made, the graphite degeneration effect can be more visible and the layer with the changed structure can increase in thickness. The research has clearly shown that it is necessary to control the parameters of the reclaim, including sulphur content which is transferred from the hardener and accumulates on the grains. This phenomenon has a negative impact not only on the sand strength and technological properties but also on the surface layer of castings.

2

Research on Selected Types of Lustrous Carbon Carriers After the High - Temperature Pyrolysis

Kamińska Jadwiga, Stachowicz M., Kubecki M.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 1

56--62

EN

For research purposes and to demonstrate the differences between materials obtained from the carbonaceous additives to classic green moulding sands, five lustrous carbon carriers available on the market were selected. The following carbonaceous additives were tested: two coal dusts (CD1 and CD2), two hydrocarbon resins (HR1 and HR2) and amorphous graphite (AG1). The studies of products and material effects resulting from the high-temperature pyrolysis of lustrous carbon carriers were focused on determining the tendency to gas evolution, including harmful compounds from the BTEX group (benzene, toluene, ethylbenzene and xylene). Moreover, the content of lustrous carbon (LC), the content of volatile matter and loss on ignition (LOI) of the carbonaceous additives were tested. The solid products formed during high-temperature pyrolysis were used for the quantitative and qualitative evaluation of elemental composition after the exposure to temperatures of 875oC in a protective atmosphere and 950oC in an oxidizing atmosphere. The conducted studies have indicated the necessity to examine the additives to classic green moulding sands, which is of particular importance for the processing, rebonding and storage of waste sand. The studies have also revealed some differences in the quantitative and qualitative composition of elements introduced to classic moulding sands together with the carbonaceous additives that are lustrous carbon carriers. It was also considered necessary to conduct a research on lustrous carbon carriers for their proper and environmentally friendly use in the widely propagated technology of classic green sand system.

3

Influence of Automatic Core Shooting Parameters in Hot-Box Technology on the Strength of Sodium Silicate Olivine Moulding Sands

Stachowicz M.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 1

67--72

EN

The paper presents the results of preliminary research on the application of olivine moulding sands with hydrated sodium silicate containing 1.5 % wt. of binder to perform ecological casting cores in hot-box technology using a semi-automatic core shooter. The following parameters were used in the process of core shooting: initial shot pressure of 6 bar, shot time 3 s, the temperature of the core-box: 200, 250 and 300°C and the core curing time: 30, 60, 90, 120 and 150 s. The matrix of the moulding mixture was olivine sand, and the binder of the sandmix was commercial, unmodified hydrated sodium silicate with molar module SiO2/Na2O of 2.5. In one shot of the automatic core-shooter were formed three longitudinal specimens (cores) with a dimensions 22.2×22.2×180 mm. The samples obtained in this way were subjected to the assessment of the influence of the shooting parameters, i.e. shooting time, temperature and curing time in core-box, using the following criteria: core box fill rate, mechanical strength to bending RgU, apparent density, compaction degree and susceptibility to friability of sand grains after hardening. The results of trials on the use of olivine moulding sands with hydrated sodium silicate (olivine SSBS) in the process of core shooting made it possible to determine the conditions for further research on the improvement of inorganic hot-box process technology aimed at: reduction of the heating temperature and the curing time. It was found that correlation between the parameters of the shooting process and the bending strength of olivine moulding sands with sodium silicate is observed.

4

Evaluation of the Chemical Composition, TG – DTA and Tensile Strength Tests of Commercial Gypsum Kinds for Foundry Sandmixes Application

Paduchowicz P., Stachowicz M., Baszczuk A., Hasiak M., Granat K.

Archives of Foundry Engineering

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2020

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Vol. 20, iss. 2

59--64

EN

The paper presents the preliminary results of research on determining the possibilities of using available on the market commercial gypsum kinds as a binder for foundry moulding and core sandmixes. Construction gypsum and plaster gypsum, finishing coat and jewelry casting gypsum were tested. Elemental composition of gypsum kinds were carried out using a scanning electron microscope (SEM) with EDS/EDX probe, their crystal structure and phase composition was determined by analyzing the results of X-ray diffraction measurements (XRD) and thermogravimetric studies (TG-DTA). Evaluation of the mechanical properties of selected materials was carried out at the tensile strength test of the dog-bone samples after initial hardening of gypsum mortar at 25°C for 5 h and drying at 110°C for 24 hours. The impact of the properties of the used commercial gypsum kinds on the possibility of their use as a valuable binders in the manufacture of the foundry sandmixes for moulds and cores was evaluated. Construction gypsum and finishing coat have the highest tensile strength. Plaster gypsum and finishing coat have the longest setting time. In all tested types of gypsum, the initial water loss during heating occurs at a temperature of about 200°C. The lowest valuable properties as a binder for sand moulding mixtures has jewelry casting gypsum mass.

5

Microstructure and Mechanical Properties of Braze Welded Joints of Copper with Austenitic Steel Made by CMT Method

Wojdat T., Kustroń P., Margielewska A., Stachowicz M.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 4

1411--1420

EN

This paper outlines issues associated with gas-shielded braze welding of CU-ETP copper with austenitic steel X5CrNi18-10(1.4301) using a consumable electrode. The possibilities for producing joints of this type using innovative low-energy welding methods are discussed. The paper provides an overview of the results of metallographic and mechanical (static shear test, microhardness) tests for braze welded joints made on an automated station using the Cold Metal Transfer (CMT) method. Significant differences in the structure and mechanical properties are indicated, resulting from the joint configuration and the type of shielding gas (argon, helium).

6

Wpływ sposobu nagrzewania i grubości rdzeni pomiarowych wykonanych z oliwinowych mas formierskich z krzemianem sodu na odkształcalność badaną na urządzeniu DMA Hot-Distortion

Stachowicz M., Paduchowicz P.

Prace Instytutu Odlewnictwa

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2018

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Vol. 58, no. 4

277--293

PL

W artykule podjęto tematykę wpływu podwyższonej temperatury na oliwinowe masy formierskie i rdzeniowe ze spoiwem nieorganicznym z grupy niemodyfikowanych gatunków uwodnionego krzemianu sodu. Sporządzone w warunkach laboratoryjnych masy na osnowie piasku oliwinowego formowano w kształtki prostopadłościenne do badania przemieszczenia wolnego końca rdzenia pomiarowego w warunkach otoczenia o podwyższonej temperaturze. W celu utwardzenia, wykonane z mas oliwinowych, kształtki poddawano szybkiemu nagrzewaniu mikrofalowemu w piecu z generatorem częstotliwości fali elektromagnetycznej f = 2,45 GHz i mocy wyjściowej 1000 W, w czasie 180 s. Badania przeprowadzono na kształtkach prostopadłościennych formowanych we wnęce o wymiarach: 25,9 × G × 120,4 mm, gdzie G = 6 lub 8, lub 10 mm. Pomiary przemieszczeń wolnego końca kształtek rdzeni pomiarowych przeprowadzono na zautomatyzowanym urządzeniu laboratoryjnym DMA Hot- Distortion. W trakcie pomiarów zastosowano trzy sposoby ogrzewania powierzchni prostopadłościennych kształtek spotykanych w technice pomiarowej odkształceń H-D (Hot Distortion Test): grzanie od dołu, grzanie od dołu i od góry (Modified Hot Distortion Test) oraz ogrzewanie tylko od góry. Przemieszczenie wolnego końca kształtek prostopadłościennych, w zależności od grubości oraz sposobów ogrzewania ich powierzchni, posłużyło do wstępnej oceny zachowania utwardzonych mikrofalowo mas oliwinowych z krzemianem sodu w warunkach otoczenia o podwyższonej temperaturze.

EN

The article raises the issue of the influence of increased temperature on olivine moulding and core sands with an inorganic binder from the group of unmodified kinds of hydrated sodium silicates. Produced at laboratory conditions, moulding sands with an olivine sand matrix were formed into cuboidal specimens to test the deformation of the free measuring core end at conditions of increased temperature. In order to harden, the measuring cores made of olivine moulding sands fast microwave heating was applied to which used was a furnace with an electromagnetic wave frequency generator f = 2.45 GHz and output power of 1000 W, in the time period of 180 s. Tests were carried out on cuboidal specimens moulded in a cavity with the dimensions 25.9 × G × 120.4 mm, where G = 6 or 8 , or 10 mm. Measurements of deformation of the free specimen end of the measuring cores were conducted on an automated laboratory DMA Hot-Distortion apparatus. During the measurements three techniques were used to heat the surfaces of cuboidal specimens which are applied in the Hot Distortion Test: heating from the bottom, heating from the bottom and the top (Modified Hot Distortion Test), and heating only from the top. The deformation of the free end of cuboidal specimens, depending on the thickness and heating techniques of their surfaces, served for the initial assessment of the behaviour of microwave hardened olivine moulding sands with sodium silicate at conditions of increased temperature.

7

Badania wstępne utwardzanych mikrofalowo połączeń wykonanych z klejów sporządzonych na bazie uwodnionego krzemianu sodu i piasku kwarcowego

Stachowicz M.

Prace Instytutu Odlewnictwa

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2018

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Vol. 58, no. 4

295--308

PL

W pracy podjęto próbę wyjaśnienia zjawisk towarzyszących powstawaniu i niszczeniu połączeń klejonych elementów form i rdzeni, w których jako kleje zastosowano mieszaninę niemodyfikowanego uwodnionego krzemianu sodu o module molowym 2,9 (SiO2/Na2O) i nośnika, którym był bardzo drobny piasek kwarcowy. Mieszaniny sporządzanych klejów wykonano według własnych propozycji składu i opisów patentowych. Na podstawie dostępnych danych literaturowych opracowano metodykę wytwarzania i badania wytrzymałości na rozciąganie połączeń klejonych z użyciem dzielonych kształtek ósemkowych typu dog-bone. Przeznaczone do klejenia połówki kształtek ósemkowych typu dog-bone wykonano z utwardzonej mikrofalowo kwarcowej masy z uwodnionym krzemianem sodu o module molowym 2,5 (SiO2/Na2O). Do utwardzenia klejonych połączeń również zastosowano metodę nagrzewania falą elektromagnetyczną o częstotliwości 2,45 GHz. Wyniki badań zrywania sklejonych połówek kształtek typu dog-bone, w ich najmniejszym przekroju, odniesiono do prób wytrzymałości standardowych kształtek ósemkowych oraz do połączeń klejonych znanych z opisów patentowych. Wyniki badań obciążeń krytycznych połączeń klejonych uzupełniono obserwacjami SEM po próbach rozciągania. Na podstawie przeprowadzonych badań ustalono, że wytrzymałość takich połączeń przewyższa wytrzymałość masy formierskiej, a destrukcja sklejonych kształtek ósemkowych odbywa się w strefach przy powierzchniach, na które naniesiono sporządzone nieorganiczne kleje.

EN

In this paper an attempt was made to explain the phenomena accompanying the formation and destruction of bonded elements of moulds and cores in which a mixture of unmodified hydrated sodium silicate with a molar module of 2.9 (SiO2/Na2O) and a carrier – very fine quartz sand – was used as adhesives. Mixtures of prepared adhesives were made according to own compositional proposals and patent descriptions. On the basis of available literature data, the methodology of production and tensile strength testing of bonded joints with the use of divided octagonal dog-bone shapes was worked out. Dog-bone shaped pieces intended for binding were made of microwave-cured quartz sand with hydrated sodium silicate of molar module 2.5 (SiO2/Na2O). For the curing of bonded joints the electromagnetic wave heating method of 2.45 GHz was also applied. The results of tearing off the bonded halves of dog-bone shaped pieces in their smallest cross-section were related to the tensile strength tests of standard octagonal shaped pieces and to bonded joints known from patent descriptions. The results of critical loads of bonded joints were supplemented with SEM observations after tensile tests. On the basis of the conducted tests it was found that the tensile strength of such joints exceeds the tensile strength of the moulding sand, and the destruction of the bonded octagonal shapes takes place in areas near the surfaces on which inorganic adhesives were applied.

8

Wpływ dodatku melaminy i krzemionki w dogarbowaniu skór na palność i wybrane właściwości skór naturalnych

Śmiechowski K., Stachowicz M.

Bezpieczeństwo i Technika Pożarnicza

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2018

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Vol. 51, iss. 3

68--84

PL

Cel: Określenie wpływu dodatku melaminy i krzemionki w procesie dogarbowania na wybrane właściwości skór ze szczególnym uwzględnieniem palności. Artykuł przedstawia wyniki prac związanych z obróbką skór na etapie dogarbowania. W dogarbowaniu zastosowano różne ilości krzemionki i melaminy w celu uzyskania wyższej odporności skór na palność. Metody: W pracy wykonano badania eksperymentalne, które obejmowały dogarbowanie skór naturalnych oraz badania wybranych właściwości skór otrzymanych w wyniku tego procesu. Dogarbowanie wykonano w skali laboratoryjnej. Badania skór obejmowały parametry związane z komfortem użytkowania wyrobów skórzanych takich jak miękkość i przepuszczalność pary wodnej. W zakresie palności badania przeprowadzono za pomocą specjalnie opracowanych metod. Wykonano także badania odporności skór na palenie w warunkach ograniczonego dostępu tlenu. Ponadto określono odporność hydrotermiczną otrzymanych skór. Wyniki: Skład kompozycji dogarbowującej i rezultaty badań właściwości skóry posłużyły za bazę do optymalizacji oraz określenia wpływu dodatków melaminy i krzemionki na badane właściwości skóry. Rezultaty badań właściwości dogarbowanych skór wskazują na istnienie zależności między ilością dodatków w dogarbowaniu a palnością skóry. Wnioski: Na podstawie przeprowadzonych badań stwierdzono, że: 1. Wzrost ilości użytej melaminy i krzemionki w składzie kompozycji powoduje wzrost odporności próbek skóry na przepalenie, przy czym dominujący jest wpływ melaminy. 2. Dogarbowanie zarówno z dodatkami (krzemionka i melamina), jak i bez dodatków nieznacznie tylko obniża przepuszczalność pary wodnej dla wszystkich badanych wariantów. Dogarbowanie prowadzi do wzrostu temperatury skurczu o max. 4°C. 3. Wyniki optymalizacji wskazują, że kompromisowe optimum przy założonych właściwościach skóry utrzymuje się przy dodatku melaminy i krzemionki w kompozycji dogarbowującej na poziomie 0,06–0,5% dla krzemionki i 0,35–0,65% dla melaminy w warunkach przeprowadzonych badań.

EN

Aim: The purpose of the research was to determine the effect of the addition of melamine and silica in the retanning process on selected properties of leather with particular regard to flammability. The article presents the results of work related to the processing of leather at the retanning stage. Various amounts of silica and melamine were used in retanning in order to achieve a higher resistance of leather to flammability. Methods: The work involved experimental tests, which included retanning of natural leather and testing of selected properties of the leathers obtained. Retanning was carried out on a laboratory scale. The leather testing included parameters related to the comfort of using leather goods such as softness and water vapor permeability. Flammability tests of leather were carried out using specifically developed methods. The tests of flame resistance of leather under conditions of limited access of oxygen were also carried out. In addition, the hydrothermal resistance of the resulting hides was determined. Results: The composition of a retanning mixture and the results of the leather properties tests were the basis for the optimisation and determination of the effect of melamine and silica on the examined properties of leather. The results of investigations of the properties of retanned leather show a correlation between the amount of additives in retanning and on the flammability of the leather. Conclusions: Based on the conducted tests, it was found that: 1. The increase in the amount of melamine and silica used in the composition of the mixture increases the resistance of leather samples to burning through (with the influence of melamine being the more important of the two). 2. Retanning both with additives (silica and melamine) and without additives only slightly reduces the water vapour permeability for all tested variants. Retanning leads to an increase in the shrinkage temperature by max. 4°C. 3. The results of the optimisation show that the compromise optimum with the assumed properties of the leather is obtained with the addition of melamine and silica in the retanning mixture at 0.06–0.5% for silica and 0.35–0.65% for melamine under the test conditions.

9

Modified Hot Distortion Test to Investigate the Effect of the Inorganic Binder on the High-Temperature Behaviour of Physically Hardened Moulding Sands

Stachowicz M.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 2

45--50

EN

This study is an attempt to determine by Hot Distortion Test (HDT) the impact of physical methods of hardening inorganic binders in the moulding sands on phenomena caused by influence of thermal energy from heating elements with a temperature of 900°C +/- 10°C. Medium silica sand-based moulding mixtures were densified and then hardened using two physical methods: microwave heating at a frequency of 2.45 GHz or classical drying at a temperature of 110°C. Sodium silicate bonded sand (SSBS) with five unmodified kinds of hydrated sodium silicates subjected to two different types of hardening method were assessed in terms of their behaviour in high temperature. Thermal behaviour by means of deformation measurement was carried out with a modified Hot Distortion Test (mHDT). Due to this advanced, but unstable by appropriate standards Hot Distortion Test gives an opportunity to measure thermoplastic deformations (L) in moulding sands in many aspects, such as time of annealing. Research carried out in this way exposed differences between inorganic binders with molar module ranging from 3.4 to 2.0. It was established that deformations under the influence of high temperature last the longest in SSBS containing binders with molar module ranging from 3.4 to 2.9. Similarly, for these types of moulding sands the method of hardening the binder is found to be essential for increasing/decreasing the rate of thermoplastic deformations during the annealing of samples. The samples of SSBS made with binders with molar module from 2.5 to 2.0 are found to be excessively susceptible to thermoplastic deformation as a result of heating them in high environmental temperature presence.

10

Impact of Higher Temperature on Quartz Moulding Sand with Gypsum Binders

Paduchowicz P., Stachowicz M., Granat K.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 1

81--86

EN

This paper presents initial findings from research into the possibility of using gypsum binders in quartz moulding sand that could be used in the production of casting moulds and cores. For the purposes of the research two commercial types of gypsum were used as binders: building gypsum and gypsum putty. Dry components of moulding sand i.e. medium quartz sand and gypsum were mixed in proportion of 89/11 parts by weight. In order to achieve bonding properties for the binders, 5 parts by weight of water was added to the mixture of dry components. After 24 hours of adding water and mixing all the components, the moulding sand, naturally hardened, was subjected to high temperature. The moulding sand thus produced, i.e. with cheap and environmentally-friendly gypsum binders, was eventually analysed after heating (at temperatures of 300oC, 650oC and 950oC) and cooling in order to determine changes in the following parameters: LOI – loss on ignition, chemical composition and pH. Moreover, investigated were bonding bridges, before and after the moulding sand was roasted. The research results revealed differences in the structure of bonding bridges and the occurrence of automatic adhesive destruction for both types of gypsum binders. For two types of moulding sands under the investigation of the LOI exceeded 2.59wt.% (with building gypsum) or 2.84wt.% (with putty gypsum) and pH increased to ca. 12 as a result of increasing roasting temperature from 300oC to 650oC. Next, roasting at 950oC decrease value of LOI in both types of moulding sands. Moulding sand with builoding gypsum roasted at 950oC revealed a return to the value of pH parameter measured prior to annealing.

11

Rola zagęszczenia mas formierskich ze spoiwami nieorganicznymi w kształtowaniu ich wytrzymałości osiąganych po utwardzaniu mikrofalowym

Stachowicz M.

Prace Instytutu Odlewnictwa

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2017

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Vol. 57, no. 2

103--113

PL

W pracy podjęto próbę uzupełnienia informacji na temat wpływu zagęszczenia masy formierskiej ze spoiwami nieorganicznymi na podstawowe parametry wytrzymałościowe, tj.: wytrzymałość na rozciąganie i zginanie mas formierskich z uwodnionym krzemianem sodu po procesie szybkiego nagrzewania mikrofalowego. W badaniach zastosowano świeży piasek kwarcowy średni oraz trzy gatunki handlowego niemodyfikowanego uwodnionego krzemianu sodu o module molowym (SiO2/Na2O) w przedziale od 1,9 do 3,4. Masy sporządzone z 0,5% cz. mas. wody i 1,5% cz. mas. spoiwa zagęszczano wibracyjnie tak, aby osiągnąć różną gęstość pozorną (ϱ0) masy formierskiej. Badane parametry wytrzymałościowe po utwardzeniu i ostudzeniu próbek mas odnoszono do gęstości pozornej. Wyniki badań nad wpływem zróżnicowanego zagęszczenia odnoszono do dostępnych danych literaturowych. Występowanie zależności między gęstością pozorną a wytrzymałością na rozciąganie i zginanie utwardzonych mas potwierdzono za pomocą modeli liniowych dla korzystnego nagrzewania mikrofalowego, podobnie jak to ma miejsce w dotychczas opisanych przypadkach stosowania chemicznych metod sieciowania spoiw nieorganicznych. Ponadto na podstawie wykonanych badań stwierdzono występowanie podobnych przyrostów wytrzymałości na skutek zmian gęstości pozornej mas nagrzewanych mikrofalowo do tych, które zaobserwowano w masach utwardzanych chemicznie. Wyniki badań posłużyły do oceny jakości spoiw chemicznych stosowanych w odlewnictwie według kryteriów wytrzymałości przypadających na 1% wag. spoiwa w masie. W przypadku wszystkich badanych spoiw nieorganicznych stwierdzono korzystny stosunek wytrzymałości przeliczonej na udział 1% wag. spoiwa powyżej wartości 1,20 g/cm3 gęstości pozornej mas na osnowie piasku kwarcowego średniego.

EN

The study attempts to complement the information on the effect of the density of moulding sands with inorganic binders on basic strength parameters, i.e. the tensile and bending strength of moulding sands with hydrated sodium silicate, after the process of fast microwave heating. The tests applied fresh medium quartz sand and three types of commercial non-modified hydrated sodium silicate with a molar module (SiO2/Na2O) ranging from 1.9 to 3.4. The masses made of 0.5 wt. % of water and 1.5 wt. % of binder underwent vibrational densification so as, to obtain different apparent densities (ϱ0) of the moulding sand. The examined strength parameters, after hardening and cooling of the mass samples, were compared to apparent density. The results of the studies of the effect of a diversified density were referred to in the literature data. The occurrence of relations between the apparent density and the tensile and bending strength of the hardened masses was confirmed by means of linear models for advantageous microwave heating, similarly to the previously discussed cases of the use of chemical methods of curing inorganic binders. Also, based on the performed tests, similar strength increases were established, as a result of the changes in the apparent density of the microwave heated masses to those which were observed in the chemically hardened masses. The tests results were used to evaluate the quality of the chemical binders applied in casting according to the strength criteria per 1 wt. % of binder in the mass. In the case of Poall the tested inorganic binders, an advantageous ratio of strength recalculated to 1 wt. % of binder above the value of 1.20 g/cm3 of the apparent density of the masses based on medium quartz sand, was established.

12

Impact of Density Degree and Grade of Inorganic Binder on Behavior of Molding Sand at High Temperature

Stachowicz M., Paduchowicz P., Granat K.

Journal of Casting & Materials Engineering

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2017

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Vol. 1, no. 3

64--69

EN

This paper discusses the impact of high temperatures (up to 900°C) on molding and core sand with inorganic binders selected from among the group of unmodified grades of hydrated sodium silicate (water-glass). Molding sands with medium quartz sand were made under laboratory conditions and compacted at the different energy inputs necessary for obtaining various apparent densities (ϱ0). Due to the different composition and apparent density of molding mixtures hardened via microwaves at a frequency of 2.45 GHz, it was possible to assess their deformation (L) at a high temperature above the binder’s eutectic temperature. For this purpose, an apparatus for hot distortion tests was used whose construction and equipment allows us to measure the thermoplastic deformations in molding sand in many aspects; i.e., in its time of annealing. The article proposes new possibilities of interpreting the hot distortion phenomena in comparative studies of molding materials and mixtures. The application of this new measurement method revealed the differences between molding mixtures made with five inorganic binders with a molar module ranging from 2.0 to 3.4 and apparent density ranging from 1.34 to 1.57 g/cm3. It was established that distortions under the influence of high temperatures last the longest in molding sand with a binder with the highest molar module (3.4). Research also revealed that the density of molding sand is significant for increasing/decreasing the rate of thermoplastic deformations following the heating of samples only if the molding sand includes binders with a molar module of between 3.0 to 3.4. For molding sand with binders with molar modules from 2.0 to 2.5, it was established that this is excessively susceptible to thermoplastic deformation.

13

Influence of sand base preparation on properties of chromite moulding sands with sodium silicate hardened with selected methods

Stachowicz M., Granat K., Pałyga Ł.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 1

379--383

EN

The paper presents a research on the relation between thermal preparation of chromite sand base of moulding sands containing sodium silicate, hardened with selected physical and chemical methods, and structure of the created bonding bridges. Test specimens were prepared of chromite sand - fresh or baked at 950°C for 10 or 24 hours - mixed with 0.5 wt.% of the selected non-modified inorganic binder and, after forming, were hardened with CO2 or liquid esters, dried traditionally or heated with microwaves at 2.45 GHz. It was shown on the grounds of SEM observations that the time of baking the base sand and the hardening method significantly affect structure of the bonding bridges and are correlated with mechanical properties of the moulding sands. It was found that hardening chromite-based moulding mixtures with physical methods is much more favourable than hardening with chemical methods, guaranteeing also more than ten times higher mechanical properties.

14

Effect of parameters of high-pressure die casting on occurrence of casting nonconformities in sleeves of silumin alloy EN AB 47100

Pałyga Ł., Stachowicz M., Granat K.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 1

373--378

EN

The paper presents a research on the effect of extreme - for the technology of the considered silumin EN AB 47100 - parameters of high-pressure die casting on occurrence of casting nonconformities. Considered was influence of the way of assembling the mould cooled-down to 140-160°C, non-standard for the selected casting, and pouring temperature in the range of 705 to 720°C (higher than the recommended) of non-refined alloy. The castings were prepared with use of a high-pressure casting machine made by Kirov with mould closing force of 2500 kN. Occurrence of nonconformities was evaluated on properly prepared specimens taken from the castings manufactured with various parameters of the injection piston and various multiplication pressures. The results were subjected to quantitative and qualitative analyses of casting nonconformities and distribution of major alloying elements. It was found that proper selection of working parameters of the casting machine, in spite of disadvantageous pouring conditions, makes it possible to reduce occurrence of some casting defects, like shrinkage cavities and porosity, to improve tightness of castings even when the alloy refining process is omitted.

15

Long-term Effects of Relative Humidity on Properties of Microwave Hardened Moulding Sand with Sodium Silicate

Stachowicz M., Granat K.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 3

127--132

EN

Moulding sands containing sodium silicate (water-glass) belong to the group of porous mixture with low resistance to increased humidity. Thanks to hydrophilic properties of hardened or even overheated binder, possible is application of effective methods of hydrous reclamation consisting in its secondary hydration. For the same reason (hydrophilia of the binder), moulds and foundry cores made of high-silica moulding sands with sodium silicate are susceptible to the action of components of atmospheric air, including the contained steam. This paper presents results of a research on the effect of (relative) humidity on mechanical and technological properties of microwave-hardened moulding mixtures. Specimens of the moulding sand containing 1.5 wt% of sodium water-glass with module 2.5 were subjected, in a laboratory climatic chamber, to long-term action of steam contained in the chamber atmosphere. Concentration of water in atmospheric air was stabilized for 28 days (672 h) according to the relative humidity parameter that was ca. 40%, 60% and 80% at constant temperature 20 °C. In three cycles of the examinations, the specimens were taken out from the chamber every 7 days (168 h) and their mechanical and technological parameters were determined. It was found on the grounds of laboratory measurements that moulds and cores hardened with microwaves are susceptible to action of atmospheric air and presence of water (as steam) intensifies action of the air components on glassy film of sodium silicate. Microwave-hardened moulding sands containing sodium silicate may be stored on a long-term basis in strictly determined atmospheric conditions only, at reduced humidity. In spite of a negative effect of steam contained in the air, the examined moulding mixtures maintain a part of their mechanical and technological properties, so the moulds and foundry cores stored in specified, controlled conditions could be still used in manufacture.

16

Influence of Soaking Parameters on the Segregation and Corrosion Resistance of GJS-X350NiMnCu7-3-2 Ductile Iron

Medyński D., Janus A., Stachowicz M.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 2

69--74

EN

In this paper, the effect of changes the parameters of heat treatment on the structure and the degree of elements segregation was determined, in the context of corrosion resistance of ductile iron Ni-Mn-Cu, containing 7.2% Ni, 2.6% Mn and 2.4% Cu. In the condition after casting, castings of austenitic matrix and 160HBW hardness were obtained. The achieved castings were soaked at 450, 550 and 650°C for 4, 8 and 12 hours, then cooled down at the ambient air. In most cases, the heat treatment resulted in a change in the castings matrix, had the consequence of increasing their hardness in comparison to raw castings. Increasing the temperature and prolonging soaking time resulted in increasing the degree of transformation of austenite, while reducing the degree of elements segregation. This led to the formation of slightly bigger number of pitting due to corrosion, but not so deep and more evenly distributed in comparison to raw castings. Wherein the results of corrosion tests show that heat treatment of castings did not significantly change their corrosion resistance in comparison to raw castings, in contrast to the significant increase in mechanical properties.

17

Evaluation of the Possibilities of Sodium Silicate Sands Application in Automated Hot-Box Process of Cores Shooting

Stachowicz M., Granat K., Obuchowski P.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 4

155--160

EN

The paper presents the results of preliminary research on the use of silica sands with hydrated sodium silicate 1.5% wt. of binder for the performance of eco-friendly casting cores in hot-box technology. To evaluate the feasibility of high quality casting cores performed by the use of this method, the tests were made with the use of a semiautomatic core shooter using the following operating parameters: initial shooting pressure of 6 bar, shot time 4 s and 2 s, core-box temperature 200, 250 and 300 °C and core heating time 30, 60, 90 and 150 s. Matrixes of the moulding sands were two types of high-silica sand: fine and medium. Moulding sand binder was a commercial, unmodified hydrated sodium silicate having a molar module SiO2/Na2O of 2.5. In one shot of a core-shooter were made three longitudinal samples (cores) with a total volume of about 2.8 dm3. The samples thus obtained were subjected to an assessment of the effect of shooting parameters, i.e. shooting time, temperature and heating time, using the criteria: core-box fill rate, bending strength (RgU), apparent density and surface quality after hardening. The results of the trials on the use of sodium silicate moluding sands made it possible to further refine the conditions of next research into the improvement of inorganic warm-box/hot-box technology aimed at: reduction of heating temperature and shot time. It was found that the performance of the cores depends on the efficiency of the venting system, shooting time, filling level of a shooting chamber and grains of the silica matrix used.

18

Effect of Temperature on Chromite-Based Moulding Sands Bonded with Sodium Silicate

Stachowicz M., Kamiński M., Granat K., Pałyga Ł.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 2

95--100

EN

In the paper, a research on effects of baking temperature on chromite sand base of moulding sands bonded with sodium silicate is presented. Pure chromite sand and its chromite-based moulding sand prepared with use of sodium silicate were subjected to heating within 100 to 1200°C. After cooling-down, changes of base grains under thermal action were determined. Chromite moulding sand was prepared with use of 0.5 wt% of domestic made, unmodified sodium silicate (water-glass) grade 145. After baking at elevated temperatures, creation of rough layer was observed on grain surfaces, of both pure chromite sand and that used as base of a moulding sand. Changes of sand grains were evaluated by scanning microscopy and EDS analyses. It was found that changes on grain surfaces are of laminar nature. The observed layer is composed of iron oxide (II) that is one of main structural components of chromite sand. In order to identify changes in internal structure of chromite sand grains, polished sections were prepared of moulding sand hardened with microwaves and baked at elevated temperatures. Microscopic observations revealed changes in grains structure in form of characteristically crystallised acicular particles with limited magnesium content, intersecting at various angles. EDS analysis showed that these particles are composed mostly of chromium oxide (III) and iron oxide (II). The temperature above that the a.m. changes are observed in both chromite-based moulding sand and in pure chromite sand. The observed phenomena were linked with hardness values and mass of this sand.

19

Effect of Microwave Heating on Moulding Sand Properties with Gypsum Binder

Paduchowicz P., Stachowicz M., Granat K.

Archives of Foundry Engineering

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2017

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Vol. 17, iss. 3

97--102

EN

The paper presents results of initial research on the possibility of applying microwave radiation in an innovative process of making casting moulds from silica sand, where gypsum CaSO4∙2H2O was acting as a binding material. In the research were compared strengths and technological properties of moulding mixture subjected to: natural bonding process at ambient temperature or natural curing with additional microwave drying or heating with the use of microwaves immediately after samples were formed. Used in the research moulding sands, in which dry constituents i.e. sand matrix and gypsum were mixed in the ratio: 89/11. On the basis of the results of strength tests which were obtained by various curing methods, beneficial effect of using microwaves at 2.45 GHz for drying up was observed after 1, 2 and 5 hours since moisture sandmix was formed. Applying the microwaves for hardening just after forming the samples guarantees satisfactory results in the obtained mechanical parameters. In addition, it has been noted that, from a technological and economic point of view, drying the silica sand with gypsum binder in microwave field can be an alternative to traditional molding sand technologies.

20

Wpływ dodatku zwilżającego osnowę kwarcową na parametry suszonych mas formierskich ze szkłem wodnym sodowym

Stachowicz M., Granat K., Pałyga Ł.

Prace Instytutu Odlewnictwa

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2016

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Vol. 56, no. 1

43--55

PL

W pracy podjęto próbę określenia wpływu dodatku zwilżającego powierzchnię osnowy kwarcowej, wprowadzonego dla zwiększenia efektywności utwardzania, wybraną metodą fizyczną, ekologicznych mas ze szkłem wodnym sodowym. Ocenę wpływu zwilżania wodą osnowy kwarcowej, przed wprowadzeniem w procesie mieszania niemodyfikowanych, nieorganicznych spoiw, przeprowadzono na podstawie porównania parametrów wytrzymałościowych i technologicznych mas świeżo sporządzonych i utwardzonych suszeniem w temperaturze 100°C. W badaniach zastosowano piasek kwarcowy średni oraz trzy gatunki uwodnionego krzemianu sodu: 137, 140 i 145. Stwierdzono, że modyfikacja sposobu przygotowania osnowy kwarcowej poprzez wprowadzenie dodatku wody, przed dodaniem niewielkiej, 1,5 cz. mas. spoiwa, korzystnie wpływa na osiągane po utwardzeniu parametry wytrzymałościowe i technologiczne mas. Wyniki pomiarów skonfrontowano z obserwacjami połączeń ziaren osnowy kwarcowej, przeprowadzonymi za pomocą mikroskopu skaningowego. Uzupełniono je również zdjęciami i analizą składu chemicznego powierzchni ziaren kwarcu. Na podstawie kompleksowej oceny, utwardzonych suszeniem klasycznym mas formierskich, stwierdzono pozytywny wpływ obecności dodatku zwilżającego w masach, którego najkorzystniejsza ilość powinna być dobierana w zależności od gatunku użytego spoiwa.

EN

An attempt has been made to determine the effect of the addition of an agent wetting the surface of silica sand grains, introduced in order to increase the hardening efficiency of selected physical methods applied to the ecological foundry sands bonded with sodium water glass. The effect of water used as a wetting agent of the silica sand grains, added during the mixing process prior to the introduction of unmodified inorganic binders, was evaluated by comparing the mechanical and technological parameters of green sands and sands hardened by drying at 100°C. Tests and studies were carried out on silica sand of medium grain size and on three grades of hydrated sodium silicate, i.e. 137, 140 and 145. It has been found that modification of the method of the base sand processing by adding water prior to the addition of a small amount (1.5 parts by weight) of binder has a beneficial effect on the technological and mechanical parameters of moulding sands obtained after the hardening process. The results of measurements were confronted with the SEM studies of bonds formed between the grains of silica sand. The studies were completed with photographs and chemical analysis of the surface of silica sand grains. Based on a comprehensive evaluation of moulding sands hardened by the conventional drying process, the beneficial effect of a wetting agent, added to the sand mixture in an amount optimum for a given type of binder, has been confirmed.