|Izabela Krzak, Adam Tchórz, Zenon Pirowski, Krzysztof Jaśkowiec, Małgorzata Grudzień, Robert Purgert|
As a part of the international project carried out at the Foundry Research Institute in Krakow in cooperation with Energy Industries of Ohio, anopen induction furnace melting technology and gravity casting of nickel superalloys have been developed. These alloys have been processed plastically so far.
Quality control of Haynes 282 alloy (H282), was made with X-ray computed tomography (CT). CT is a non-destructive method that combines X-ray examinations with advanced computer technology.
Selected results of the research obtained from the X-ray computer tomograph have been presented in the paper. Research were made by using the GE Phoenix v/ tome/x l-450 tompgraph type belonging to the Foundry Research Institute equipment. All operations related to the processing of CT data were performed using the datos/x-reconstruction and VGStudio Max 2.0 software.
Keywords: X-ray computed tomography (CT), structural discontinuity, nickel superalloys, Haynes 282,
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Marcin Myszka, Jerzy Zych, Tomasz Snopkiewicz
The results of testing the tendency of light metals to forming defects from the group of discontinuities - hot cracks (W-301) , are presented in the hereby study. These are alloys of a small or moderate tendency for hot cracking. However this tendency is growing when castings are produced in metal moulds or have large dimensions. The majority of investigation methods, developed several years ago, does not provide the possibility of the total assessment of alloys. This convinced the authors to develop the new method and to build the new research set-up in the Faculty of Foundry Engineering AGH. This new set-up makes possible to perform measurements of stresses growing in the sample (casting) in the real time - during the whole period of solidification and cooling. The measurements allowed to determine the moment in which the initiation, followed by the propagation, of cracks occurs as well as to find out at what thermal stress the casting discontinuity forms. Due to this, the complete image of the defect formation is obtained. The results of investigations performed for the casting alloy AlSi7Mg (A356), which is widely applied in the automotive and aircraft industry for drive gear housings, are presented in the hereby study. This alloy is characterised by a low hot cracking tendency.
Keywords: hot cracking, discontinuity, shrinkage, research set-up,
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Viktoriya Boyko, Edward Czekaj, Małgorzata Warmuzek, Kostiantyn Mykhalenkov
Together with development of casting technology for Al-Si-Mg alloys, new groups of casting materials are undergoes its implementation into foundry practice. Al-Mg-Si casting alloys possessed several advantages such as good strength in as-cast state combined with high ductility, good corrosion resistance and castability. In both Al-Si-Mg and Al-Mg-Si systems, the range of the eutectic crystallization occurs: L → αAl + βSi and L → αAl + Mg2Si, respectively. In the hypoeutectic alloys of both system as a primary phase - dendrites of the solid solution αAl solidify. The transition elements - Ti, Zr, Sc, which provides efficient grain refinement can dissolve in this solid solution αAl causing precipitation strengthening effect. In the article the present state of the researches on the development of Al-Mg-Si casting alloys is considered together with the results of the examinations on the effect of Ti addition on the microstructure of the AlMg5Si2Mn alloy. These researches results were discussed at the annual conference on the casting of non-ferrous metals "Science and Technology" (2018) and initially presented in an shortened form in the article .
Keywords: aluminium alloys, Al-Mg-Si system, alloying addition, grain refiners, eutectic modifiers, precipitation, casting,
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Tomasz Snopkiewicz, Jerzy Zych, Marcin Myszka
Investigation results of erosion-mechanical grinding (wearing) of surfaces of foundry patterns (test samples) made of several kinds of materials are presented in the hereby paper. Investigations contained: resins, wood, painted wood and Al-Si alloys. Resistance tests were carried out on the new, author’s device, for testing abrasion-mechanical grinding, in which the abrasion material constitutes a dry foundry sand. Using the sand selected fraction makes test conditions similar to operation conditions of patterns/core boxes at producing moulds and cores. The device allows performing tests while maintaining - on the selected level - such parameters as: pressure on the surface, moving speed of abrasive material, kind of abrasive material and its parameters. Schemes and pictures of the device as well as of the tested samples, are presented in the paper. The comparison of grinding of the tested materials was performed and the results are presented graphically. On the basis of assessing the resistance for erosional grinding the stability and suitability of the given material for patterns/core boxes can be estimated. The results of the pilot investigations are presented in the paper. The new, prototype device allows performing investigations within a wide range of parameters variability and can be recommended for testing other materials operating under similar conditions as foundry patterns and core boxes. This concerns elements of devices in which the process of grain material movements on the surface of structure elements occurs (e.g. at fluidal sand transportation).
Keywords: abrasion resistance, friction moulding sand-pattern, removal of patterns from moulding sands, materials for patterns and core boxes,
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Mateusz Stachowicz, Patrycja Paduchowicz
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.
Keywords: foundry engineering, olivine moulding sand, hydrated sodium silicate, thermal deformation, microwave heating,
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Jadwiga Kamińska, Michał Angrecki, Aleksander Palma, Sabina Puzio
The increasing requirements of casting users regarding the dimensional accuracy and surface roughness of castings force the manufacturers, i.e. foundries, to use protective coatings on moulds and cores. Coatings are applied in order to protect the casting against the burn-on defects (mould material adhering to the casting surface), to reduce the surface roughness of castings, and to facilitate casting removal from the mould cavity. This paper presents the results of studies of multi-component coatings of the new generation made in accordance with the Polish Standard PN-H-11011:1997. Tests included the density of coatings, the content of dry matter, the sedimentation index and the amount of gas emitted by the coating. Melts were made to determine the impact of coating on the quality of the external surface of steel castings.
Keywords: protective coatings, moulding sands, iron alloys, surface quality of castings,
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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.
Keywords: casting, moulding and core sand, casting cores, hydrated sodium silicate, adhesive,
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The present study was created as a result of the execution of the project entitled "Technological conversion of nickel alloys working under extreme conditions". This project, contract No.: TANGO2/340100/NCBR/2017 of 28.04.2017 is realised by the Foundry Research Institute in Kraków under TANGO2 Programme. It was created on the basis of the International Non Co-financed Project No. 721/NNICKEL/2010/0 entitled "Defining the impact of the technological process on the quality of castings of nickel superalloys for the needs of the energy, chemical and automotive industries".
In the first part of the study nickel and its alloys is characterised, in short, in historical, geological, economic and ecological aspects. However, the main issue tackled are this part of the study is to classify nickel alloys both in terms of the chemical composition (the type of main alloying additives), and the application under specific exploitation conditions. IN740 and H282 alloys were selected for the research. The results of which will be discussed in the second part of the article.
Keywords: conversion, nickel alloys, resources, production, classification,
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The aim of the second part of the study was to make utility castings of refractory nickel alloys, traditionally processed plastically, intended for use in extremely difficult conditions. The related technological problems and obtained effects were discussed, both in terms of the properties of cast alloys and the quality of the castings obtained. Inconel 740 (IN740) and Haynes 282 (H282) alloys were the subject of research, which so far have been used only as plastically processed alloys. Attempts were made to melt them in an open induction furnace and gravity casting. It has been shown that mechanical properties of such alloys are comparable at high temperature and even exceed those of their counterparts processed plastically. It has been confirmed that with a well-developed technological regime it is possible to produce from these alloys of good quality castings intended for operation at temperatures significantly exceeding 760°C.
Keywords: technological conversion, refractory alloys, nickel alloys, melting, casting,
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