Archives of Foundry Engineering

The paper presents the results of studies on the development of correlation of solidification parameters and chemical composition of nickel

superalloy IN-713C, which is used i.a. on aircraft engine turbine blades. Previous test results indicate significant differences in

solidification parameters of the alloy, especially the temperatures Tliq and Tsol for each batch of ingots supplied by the manufacturer.

Knowledge of such a relationship has important practical significance, because of the ability to asses and correct the temperatures

of casting and heat treatment of casts on the basis of chemical composition. Using the statistical analysis it was found that the temperature

of the solidification beginning Tliq is mostly influenced by the addition of carbon (similar to iron alloys). The additions of Al and Nb have

smaller but still significant impact. Other alloying components do not have significant effect on Tliq. The temperature Teut is mostly

affected by Ni, Ti and Nb. The temperature Tsol is not in any direct correlation with the chemical composition, which is consistent with

previous research. The temperature Tsol depends primarily on the presence of non-metallic inclusions present in feed materials and

introduced during the melting and casting processes.

The study consisted in assessing the influence of surface and volume modification on the characteristics of high-temperature creep of

castings made of waste products of nickel-based superalloys IN 713C and the MAR-247. The results of high-temperature creep tests

performed under conditions of two variants of research were analysed. The characteristics of creep according to variant I were obtained on

the basis of earlier studies of these alloys with the parameters T=982o

C, σ=150MPa [1]. Variant II included carrying out creep tests of

alloy IN713C with the parameters T=760o

C, σ =400MPa and alloy MAR247 with the parameters: T=982o

C, σ=200MPa.Developed creep

characteristics were compared with the results of these alloys with the parameters according to variant I of the study. It was observed that

the conditions of experiments carried out depending upon the value of the creep test temperature and stress with the creep stability depends

on the size of the macrograin (I variant of the studies) or such influence was not observed (II variant of the studies). Stability of samples

with coarse structure in variant I of creep tests was significantly higher than the samples with fragmented grain. It was found that the

observed stability conditions are dependent on the dominant deformation mechanisms under creep tests carried out - diffusion mechanism

in variant I and a dislocation mechanism in variant II of the study. The conditions for the formation and growth of the cracks in the tested

materials, including the morphological characteristics of their macro-and microstructure were tested.

The investigation results of the mechanical reclamation of spent moulding sands from the Cordis technology are presented in the paper.

The quality assessment of the obtained reclaim and the influence of the reclaim fraction in a matrix on the core sand strength is given. The

reclaim quality assessment was performed on the basis of the determination of losses on ignition, Na2O content on reclaim grains and pH

values. The reclaim constituted 100%, 75% and 50% of the core sand matrix, for which the bending strength was determined. The matrix

reclamation treatment was performed in the experimental rotor reclaimer RD-6. Spent sands were applied in as-delivered condition and

after the heating to a temperature of 140 o

C. Shaped samples for strength tests were made by shooting and hardening of sands in the warmbox

technology.

The paper presents the idea of the integrated recycling system of used moulding sands with organic resins. A combination of the method of

forecasting averaged ignition loss values of moulding sands after casting and defining the range of necessary matrix reclamation

treatments in order to obtain its full recycling constitutes the basics of this process.

The results of own investigations, allowing to combine ignition loss values of spent moulding sands after casting knocking out with

amounts of dusts generated during the mechanical reclamation treatment of such sands, were utilized in the system.

The paper presents the results of studies on the development of manufacturing technologies to cast hearth plates operating in chamber

furnaces for heat treatment. Castings made from the heat-resistant G-X40CrNiSi27-4 steel were poured in hand-made green sand molds.

The following operations were performed: computer simulation to predict the distribution of internal defects in castings produced by the

above mentioned technology with risers bare and coated with exothermic and insulating sleeves, analysis of each variant of the technology,

and manufacture of experimental castings. As a result of the conducted studies and analysis it was found that the use of risers with

exothermic sleeves does not affect to a significant degree the quality of the produced castings of hearth plates, but it significantly improves

the metal yield.

Magnesium alloys are one of the lightest of all the structural materials. Because of their excellent physical and mechanical properties the

alloys have been used more and more often in various branches of industry. They are cast mainly (over 90%) on cold and hot chamber die

casting machines. One of the byproducts of casting processes is process scrap which amounts to about 40 to 60% of the total weight of a

casting. The process scrap incorporates all the elements of gating systems and fault castings. Proper management of the process scrap is

one of the necessities in term of economic and environmental aspects.

Most foundries use the process scrap, which involves adding it to a melting furnace, in a haphazard way, without any control of its content

in the melt. It can lead to many disadvantageous effects, e.g. the formation of a hard buildup at the bottom of the crucible, which in time

makes casting impossible due to the loss of the alloy rheological properties. The research was undertaken to determine the effect of an

addition of the process scrap on the mechanical properties of AZ91 and AM50 alloys. It has been ascertained that the addition of a specific

amount of process scrap to the melt increases the mechanical properties of the elements cast from AZ91 and AM50 alloys.

The increase in the mechanical properties is caused mainly by compounds which can work as nuclei of crystallization and are introduced

into the scrap from lubricants and anti-adhesive agents. Furthermore carbon, which was detected in the process scrap by means of SEM

examination, is a potent grain modifier in Mg alloys [1-3].

The optimal addition of the process scrap to the melt was determined based on the statistical analysis of the results of studies of the effect

of different process scrap additions on the mean grain size and mechanical properties of the cast parts.

The object of the experimental studies was to determine the mechanical properties of a hypoeutectic EN AC - 42100 (EN ACAlSi7Mg0,3)

silumin alloy, where the said properties are changing as a result of subjecting the samples of different types to solution

treatment. An important aspect of the studies was the use type of device for the heat treatment. As a basic parameter representing the

mechanical properties, the tensile strength of the metal (Rm) was adopted.

Small additions of Cr, Mo and W to aluminium-iron-nickel bronze are mostly located in phases κi (i=II; III; IV),and next in phase α

(in the matrix) and phase γ2. They raise the temperature of the phase transformations in aluminium bronzes as well as the casts’ abrasive

and adhesive wear resistance. The paper presents a selection of feeding elements and thermal treatment times which guarantees structure

stability, for a cast of a massive bush working at an elevated temperature (650–750°C) made by means of the lost foam technology out of

composite aluminium bronze. So far, there have been no analyses of the phenomena characteristic to the examined bronze which

accompany the process of its solidification during gasification of the EPS pattern. There are also no guidelines for designing risers and

steel internal chill for casts made of this bronze. The work identifies the type and location of the existing defects in the mould’s cast. It also

proposes a solution to the manner of its feeding and cooling which compensates the significant volume contraction of bronze and

effectively removes the formed gases from the area of mould solidification. Another important aspect of the performed research was

establishing the duration time of bronze annealing at the temperature of 750°C which guarantees stabilization of the changes in the bronze

microstructure – stabilization of the changes in the bronze HB hardness.

The modification is a widespread method of improving the strength properties of cast iron. The impact in terms of increasing amounts of

eutectic grains has been thoroughly studied while the issue of the impact on the mechanical properties of primary austenite grains has not

been studied in depth yet. The paper presents the study of both aspects. The methodology was to conduct the melting cast iron with flake

graphite, then modifying the alloy by two sets of modifiers: the commercial modifier, and a mixture of iron powder with a commercial

inoculant. The DAAS test was carried out to identify the primary austenite grains. The degree of supercooling was determined and the

UTS test was performed as well. Additionally carried out the metallographic specimen allowing for counting grains. It can be concluded

that the introduction of the iron powder significantly improved the number of austenite primary grains which resulted in an increase

in tensile strength UTS.

Austenitization is the first step of heat treatment preceding the isothermal quenching of ductile iron in austempered ductile iron (ADI)

manufacturing. Usually, the starting material for the ADI production is ductile iron with more convenient pearlitic matrix. In this paper we

present the results of research concerning the austenitizing of ductile iron with ferritic matrix, where all carbon dissolved in austenite must

come from graphite nodules. The scope of research includedcarrying out the process of austenitization at 900o

Cusing a variable times

ranging from 5 to 240minutes,and then observations of the microstructure of the samples after different austenitizing times. These were

supplemented with micro-hardness testing. The research showed that the process of saturating austenite with carbon is limited by the rate

of dissolution of carbon from nodular graphite precipitates.

Non-metallic inclusions found in steel can affect its performance characteristics. Their impact depends not only on their quality, but also,

among others, on their size and distribution in the steel volume. The literature mainly describes the results of tests on hard steels,

particularly bearing steels. The amount of non-metallic inclusions found in steel with a medium carbon content melted under industrial

conditions is rarely presented in the literature. The tested steel was melted in an electric arc furnace and then desulfurized and argonrefined.

Seven typical industrial melts were analyzed, in which ca. 75% secondary raw materials were used. The amount of non-metallic

inclusions was determined by optical and extraction methods. The test results are presented using stereometric indices. Inclusions are

characterized by measuring ranges. The chemical composition of steel and contents of inclusions in every melts are presented. The results

are shown in graphical form. The presented analysis of the tests results on the amount and size of non-metallic inclusions can be used to

assess them operational strength and durability of steel melted and refined in the desulfurization and argon refining processes.

Trials of cast steel filtration using two types of newly-developed foam filters in which carbon was the phase binding ceramic particles have

been conducted. In one of the filters the source of carbon was flake graphite and coal-tar pitch, while in the other one graphite was

replaced by a cheaper carbon precursor. The newly-developed filters are fired at 1000o

C, i.e. at a much lower temperature than the

currently applied ZrO2-based filters. During filtration trials the filters were subjected to the attack of a flowing metal stream having

a temperature of 1650°C for 30 seconds.

Characteristic of the filters’ properties before and after the filtration trial were done. It was found, that the surface reaction of the filter

walls with molten metal, which resulted in local changes of the microstructure and phase composition, did not affect on expected filter

lifetime and filtration did not cause secondary contamination of cast steel.

The investigation results of the influence of the selected parameters of the thermal reclaimer operations on the temperature changes in the

combustion chamber and the process energy consumption, are presented in the hereby paper. The analysis of the heat treatment was

performed with the application of a fresh foundry sand, since it was assumed that the dominating energy part was used for the grain matrix

heating and due to that, the energy used for burning small amounts of organic binder remained on sand grains could be omitted. Thermal

treatment processes performed under various conditions were analysed from the point of view of a gas consumption and temperatures

obtained in the experimental reclaimer. The recorded data allowed to point out the parameters having essential influence on the process of

the quartz matrix heating in the combustion chamber as a gas consumption function.

The performed examinations concerning the process of filling the plaster ceramic moulds with aluminium alloys allowed to assess the

influence of various methods of introducing the metal into the mould cavity on the macro- and microstructure of the obtained experimental

castings. The comparison was performed for castings with graded wall thickness made either of EN AC-44000 alloy or of EN AC-46000

alloy, produced either by gravity casting, or by gravity casting with negative pressure generated around the mould (according to the

Vacumetal technology), or by counter-gravity casting. It was found that the silicon crystals grow in size with an increase in wall thickness

due to the slower cooling and solidification of castings.

Simulation software dedicated for design of casting processes is usually tested and calibrated by comparisons of shrinkage defects

distribution predicted by the modelling with that observed in real castings produced in a given foundry. However, a large amount of

expertise obtained from different foundries, including especially made experiments, is available from literature, in the form of

recommendations for design of the rigging systems. This kind of information can be also used for assessment of the simulation predictions.

In the present work two parameters used in the design of feeding systems are considered: feeding ranges in horizontal and vertical plates as

well as efficiency (yield) of feeders of various shapes. The simulation tests were conducted using especially designed steel and aluminium

castings with risers and a commercial FDM based software. It was found that the simulations cannot predict appearance of shrinkage

porosity in horizontal and vertical plates of even cross-sections which would mean, that the feeding ranges are practically unlimited. The

yield of all types of feeders obtained from the simulations appeared to be much higher than that reported in the literature. It can be

concluded that the feeding flow modelling included in the tested software does not reflect phenomena responsible for the feeding processes

in real castings properly. Further tests, with different types of software and more fundamental studies on the feeding process modelling

would be desirable.

Nickel alloys belong to the group of most resistant materials when used under the extreme operating conditions, including chemically

aggressive environment, high temperature, and high loads applied over a long period of time. Although in the global technology market

one can find several standard cast nickel alloys, the vast majority of components operating in machines and equipment are made from

alloys processed by the costly metalworking operations. Analysis of the available literature and own studies have shown that the use of

casting technology in the manufacture of components from nickel alloys poses a lot of difficulty. This is due to the adverse technological

properties of these alloys, like poor fluidity, high casting shrinkage, and above all, high reactivity of liquid metal with the atmospheric air

over the bath and with the ceramic material of both the crucible and foundry mold. The scale of these problems increases with the expected

growth of performance properties which these alloys should offer to the user.

This article presents the results of studies of physico-chemical interactions that occur between theH282alloy melt and selected refractory

ceramic materials commonly used in foundry. Own methodology for conducting micro-melts on a laboratory scale was elaborated and

discussed. The results obtained have revealed that the alumina-based ceramics exhibits greater reactivity in contact with the H282 alloy

melt than the materials based on zirconium compounds. In the conducted experiments, the ceramic materials based on zirconium silicate

have proved to be a much better choice than the zirconia-silica mixture. Regardless of the type of the ceramic materials used, the time and

temperature of their contact with the nickel alloy melt should always be limited to an absolutely necessary minimum required by the

technological regime.

The paper is devoted to grain-refinement of the medium-aluminium zinc based alloys (MAl-Zn). The system examined was sand cast Zn10

wt. %. Al binary alloy (Zn-10Al) doped with commercial Al-3 wt. % Ti – 0.15 wt. % C grain refiner (Al-3Ti-0.15C GR). Basing on the

measured attenuation coefficient of ultrasonic wave it was stated that together with significantly increased structure fineness damping

decreases only by about 10 – 20%. The following examinations should establish the influence of the mentioned grain-refinement on

strength and ductility of MAl-Zn cast alloys.

Some eutectic stripes have been generated in a hexagonal (Zn) - single crystal. The stripes are situated periodically with the constant interstripes

spacing. The eutectic structure in the stripes consists of strengthening inter-metallic compound, Zn16Ti, and (Zn) – solid solution.

The rod-like irregular eutectic structure (with branches) appears at low growth rates. The regular lamellar eutectic structure is observed at

middle growth rates. The regular rod-like eutectic structure exists exclusively in the stripes at some elevated growth rates. A new

thermodynamic criterion is recommended. It suggests that this eutectic regular structure is the winner in a morphological competition for

which the minimum entropy production is lower. A competition between the regular rod-like and the regular lamellar eutectic growth is

described by means of the proposed criterion. The formation of branches within irregular eutectic structure is referred to the state of

marginal stability. A continuous transitions from the marginal stability to the stationary state are confirmed by the continuous

transformations of the irregular eutectic structure into the regular one.

Design of a compressed air system is a complex issue, involving the design of structures formed by the air sources, air receptors and

installations connecting all structure components. Another major task is to ensure the required quality of compressed air. The paper briefly

outlines the methodology of integrated and network structure design, using an objective function to find the optimal solution. In terms of

quality assurance, the technological aspects of compressed air generation, treatment and distribution are defined.

Presence of iron in Al-Si cast alloys is common problem mainly in secondary (recycled) aluminium alloys. Better understanding of iron

influence in this kind of alloys can lead to reduction of final castings cost. Presented article deals with examination of detrimental iron

effect in AlSi10MgMn cast alloy. Microstructural analysis and ultimate tensile strength testing were used to consider influence of iron to

microstructure and mechanical properties of selected alloy