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1
Content available remote Mechanism of silicon influence on chills in ductile iron
100%
Górny M.
|
2009
|
tom Vol. 9, iss. 1
147-150
EN
In the present work an analytical expression that combines the susceptibility of liquid cast iron to solidify according to the Fe-C-X metastable system (also known as the chilling tendency of cast iron, CT) is proposed. A relationship between CT and several factors has been developed. In particular the CT is related to the critical wall thickness (Scr), below which the chill is formed. Theoretical calculations of Scr were made and then compared with experimental outcome for ductile iron melts. The predictions of the theoretical analysis are in rather good agreement with the experimental data.The results can be used as a guide for a better understanding of the effect of technological variables such as the melt chemistry, the holding time and temperature, the spheroidizing and inoculation practice, the resulting nodule count and the type of mold material and pouring temperature, on the resultant chill of the ductile iron.
2
Content available Thin wall ductile iron castings: technological aspects
100%
Fraś E. , Górny M. , Kapturkiewicz W.
Archives of Foundry Engineering
|
2013
|
tom Vol. 13, iss. 1
23--28
EN
The paper discusses the reasons for the current trend of substituting ductile iron castings by aluminum alloys castings. However, it has been shown that ductile iron is superior to aluminum alloys in many applications. In particular it has been demonstrated that is possible to produce thin wall wheel rim made of ductile iron without the development of chills, cold laps or misruns. In addition it has been shown that thin wall wheel rim made of ductile iron can have the same weight, and better mechanical properties, than their substitutes made of aluminum alloys.
3
Content available remote Thin Wall Austempered Ductile Iron (TWADI)
84%
Fraś E. , Górny M.
|
2009
|
tom Vol. 9, iss. 3
45-48
EN
In this paper the analysis of thin walled castings made of ductile iron is considered. It is shown that thin wall austempered ductile iron can be obtained by means of short-term heat treatment of thin wall castings without addition of alloying elements. Metallographic examinations of 2 mm thin walled castings along with casting with thicker wall thickness (20x28 mm) after different austempring conditions are presented. It has been proved that short-term heat treatment amounted 20 minutes of austenitizing at 880 oC followed by holding at 400 oC for 5 minutes causes ausferrite matrix in 2 mm wall thickness castings, while casting with thicker wall thickness remain untransformed and martensite is still present in a matrix. Finally there are shown that thin wall ductile iron is an excellent base material for austempering heat treatments. As a result high mechanical properties received in thin wall plates made of austempered ductile iron.
4
Content available remote Thermal analysis of ductile iron in thin walled casting
84%
Górny M.
|
2007
|
tom Vol. 7, iss. 4
69-72
EN
Hypereutectic ductile iron was cast in self hardening moulding sand to produce castings with the shape of Archimedes spirals and with wall thickness of 1, 2 and 3 mm. Inmould technique was used to produce thin wall ductile iron (TWDI). In this work it has been carried out thermal analysis in spiral with 3 mm wall thickness. The present work provides results of thermal analysis, that are initial temperature of metal in mould cavity, velocity of metal stream as well as solidification time. Measurement of temperature shows that there is essential its drop during filling of mould cavity and amounts 230 °C for distance 700 mm from the beginning of spiral. On the basic on first derivative of temperature versus time characteristic solidification points were distinguish, namely solidification of primary graphite, austenite dendrite and eutectic. Experimental measurements of temperature drop during filling of mould cavity along with microscopic examinations of castings structure can be used to verify computer modeling and simulation of fluid flow and thermal field in TWDI.
5
Content available remote Structural gradient in a thin wall casting of ductile iron
84%
Fraś E. , Górny M.
|
2007
|
tom Vol. 7, iss. 4
63-68
EN
In this paper a experimental and theoretical structural analysis of thin walled casting made of ductile iron is presented. The work shows that these castings posses a non-homogenous gradient structure associated with (i) the graphite nodule densities and (ii) the ferrite and cementite volume fractions. The microstructural inhomogeneities are attributed to sharp variations in the cooling rates along the length of the casting. The experimental investigations were made using of the castings with a 1.6 mm wall thickness, where the graphite nodule count, N_F and de fractions of ferrite, f_f and cementite eutectic, f_c were determined as a function of distance from the runner. It was found that the theoretical predictions were in good agreement with the experimental outcome. In particular, this work shows that it is possible to produce thin wall plate shaped castings made of nodular cast iron with wall thicknesses of 1.6 mm (without chills, cold laps, or misruns).
6
Content available remote Structure of ductile iron in thin walled castings
84%
Górny M.
|
2007
|
tom Vol. 7, iss. 4
73-78
EN
It this work it has been shown that it is possible to produce thin wall ductile iron (TWDI) castings with considerably length using Archimedes spiral with wall thickness of 1, 2 and 3 mm. Inmould technique was used to produce TWDI. It has been estimated castability and metallographic investigations were made using different moulding materials. From castability measurements result that it is possible to obtain thin wall ductile iron castings with wall thickness down to 1 mm with castability of 200 mm. Using mould with small ability to absorb heat castability increases twice. At wall thickness equal 3 mm castability reaches 1000 mm and using LDASC sand its value increases to over 1500 mm. Structure parameters for different wall thickness and moulding materials (graphite nodule count, ferrite and cementite fraction) are plotted versus distance from the beginning of spiral. It is shown strong influence of LDASC sand (material with small ability to absorb heat) on structure parameters (N_F, V_f i V_C) revealing gradient character of TWDI.
7
Content available Role of titanium in Thin Wall Vermicular Graphite Iron Castings production
84%
Górny M. , Kawalec M.
Archives of Foundry Engineering
|
2013
|
tom Vol. 13, iss. 2
25--28
EN
In this paper the effects of titanium addition in an amount up to 0.13 wt.% have been investigated to determine their effect on the microstructure and mechanical properties of Thin Wall Vermicular Graphite Iron Castings (TWVGI). The study was performed for thin-walled iron castings with 3-5 mm wall thickness and for the reference casting with 13 mm. Microstructural changes were evaluated by analyzing quantitative data sets obtained by image analyzer and also using scanning electron microscope (SEM). Metallographic examinations show that in thin-walled castings there is a significant impact of titanium addition to vermicular graphite formation. Thin-walled castings with vermicular graphite have a homogeneous structure, free of chills, and good mechanical properties. It may predispose them as a potential use as substitutes for aluminum alloy castings in diverse applications.
8
Content available remote Temperature drop of liquid iron in thin wall channels during mold filling
84%
Górny M.
|
2009
|
tom Vol. 9, iss. 1
137-142
EN
This work deals with first period of metal cooling in mold cavity. It has been performed thermal analysis of flooding metal stream in thin wall ductile iron with the shape of Archimedes spirals. It has been presented comparison of real temperature drop with predictions according to the analytical equations based on heat balance and with simulation using Fluent program. Additionally velocity decrease predicted by Fluent program is compared to the experimental data. Moreover change of cooling rate as function of spiral length of liquid metal before eutectic solidification is presented.
9
Content available remote Thin wall ductile iron casting as a substitute for aluminum alloy casting in automotive industry
84%
Górny M.
|
2009
|
tom Vol. 9, iss. 1
143-146
EN
In paper it is presented thin wall ductile iron casting (TWDI) as a substitute of aluminium alloy casting. Upper control arm made of ductile iron with wall thickness ranging from 2 - 3.7 mm was produced by inmold process. Structure, mechanical properties and computer simulations were investigated. Structural analysis of TWDI shows pearlitic-ferritic matrix free from chills and porosity. Mechanical testing disclose superior ultimate tensile strength (Rm), yield strength (Rp0,2) and slightly lower elongation (E) of TWDI in comparison with forged control arm made of aluminium alloy (6061-T6). Moreover results of computer simulation of static loading for tested control arms are presented. Analysis show that the light-weight ductile iron casting can be loaded to similar working conditions as the forged Al alloy without any potential failures.
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