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A contribution to study of processes on the steel cast–sand mould contact surface during casting
September 2000
Materials Letters 45 Ž2000. 235–240 www.elsevier.comrlocatermatlet
A contribution to study of processes on the steel cast–sand mould contact surface during casting Z. Janjusevic ˇ ´ a,) , Z. Gulisija ˇ a, S. Radosavljevic´ a, Z. Acimovic ´ ´b a
Institute for Technology of Nuclear and Other Mineral Raw Materials, Franchet d’Esperey St 86, 11000 Belgrade, YugoslaÕia b Faculty of Technology and Metallurgy, KarnegieÕa St 4, 11000 Belgrade, YugoslaÕia Received 23 August 1999; received in revised form 3 April 2000; accepted 7 April 2000
Abstract The testings involved in this paper were part of a comprehensive research project conducted to find out what complex processes were taking place at metal–mould contact surface. These investigations are of particular importance for metal casting from relatively high melting temperature, such as that of steel Žapproximately 16008C.. Steel castings, in regard to their high manufactured temperature and other specifications in pouring, need a mould mixture of such good quality. The mould mixture, used for casting steel class DIN G-X 120 Mn 12, was based on the silica sand, and with water-glass as a binder and AlKŽSO4 . 2 as an active component. This active component is, at pouring temperature of liquid steel, decomposed in the mould by thermal influence during pouring, crystallization and cooling the casting. In decomposition process of the active component, the gaseous products appear and the water-stream is generated from chemically bonded water. These processes are influencing the molten metal oxidation. The penetrated molten metal into the mould surface is oxidized, too. At the high melting temperature and in the presence of gaseous products, the silicates were formed in the contact zone between metal and sand mould mixture. The objective of these tests was to find out to what extent the composition of the mould mixture affects the formation process, shape, type and composition of the silicates. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Steel; Casting; Moulds
1. Introduction Processes of mutual influence between the molten metal and the mould material are intrinsic in complex casting processes. Many casting properties and their surface or dimensional accuracy, and other properties, were determined by processes from contact of surfaces in liquid metal–sand mould. But these processes may also bring a number of casting ) Corresponding author. Tel.: q381-11-3691722; fax: q38111-3691583.
defects or failures Žscabs, gas, holes, cracks, and so on., and therefore, they affect the structure andror casting properties. The kind and the quality of mould mixture are, of course, of major importance in surface contact processes, i.e., the intensity or appearance of particular reaction. The kind and quality of used mixture will determine the behavior at the contact surface between molten metal and sand mould. An important role in developing the interaction processes, taking place between sand mould mixture and the liquid metal, is taken by the mixture addi-
00167-577Xr00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 0 0 . 0 0 1 1 1 - 7
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
236
Table 1 Chemical composition of casting steel DIN G-X 120Mn12
Table 3 The shape and grain roundness of silica sand
Element
C
Mn
Si
Cr
P
S
Al
The shape
%
1.28
10.08
0.38
1.56
0.028
0.018
0.054
Angular Semi- SemiRounded Wellangular rounded rounded
Percentage Ž%. 10
tives. Thus, chemical and mineral compositions, kind of binder, and additives, will cause certain changes, especially at high temperatures, and will also affect the mould mixture and the reactions at the contact zone with liquid metal. The great influence on surface defect formation also involves the kind of gases, which are present in the contact zone. The magnitude of adhesion at casting surface depends on silicate properties and their structure. The silicates are formed as a result of interaction between the mould material and the liquid steel. According to some literature data w1,2x, the most promising investigations are those for preventing the occurrence of some failures in steel castings. One of those is the investigation of oxidation process at the liquid metal–sand contact. These processes affect the possibility of complete oxidation of the penetrated metal resulting in weakening of the bonds between the mould and the metal. These data from the literature were used as the starting point in this work.
2. Experimental Necessary data were obtained experimentally by casting the cylinders, 30 = 300 mm, from steel of the known thermophysical characteristics w3x and relatively small measured variations in temperature of casting Ž1578–16108C. and temperature of crystallization Ž1509–15198C.. Chemical composition of used steel, determined after casting and found to correspond to the steel DIN G-X 120Mn 12, is given in Table 1.
5
30
30
25
The mould mixture is made from: 1. Silica sand Žquartz. with the chemical composition as given in Table 2. The granulometric composition of silica sand is determined by using a sieve system with apertures from 1.00 to 0.16 mm, according to DIN 1171, from 100-g probe. The mean grain size was 0.30 mm and grain roundness is given in Table 3. 2. The binder was water-glass Žmodule 2.8; density 1.55 grcm3 . 3. Sodium sulphate ŽNa 2 SO4 . 4. The active additive — AlKŽSO4 . 2 ; MgO.
3. Results and discussion The used steel is taken from an ordinary Foundry production program. The pouring temperature was varied within a range 1570–16108C, but the initial temperature of the mould and its outer surface was 208C. During the cooling period, the additive component from a mould mixture is decomposed. Such thermal decomposition is followed by the emission of gaseous products and water steam. These generated gases influence the oxidation process of penetrated metal into the sand mould, and the forming of silicate in the contact zone liquid steel–sand mould. Under the circumstances, the binary system with Na 2 O–SiO 2 is transformed into the Na 2 O–SiO 2 – M xO y system, both with a greater viscosity and surface tension.
Table 2 Chemical composition of used KS-03 silica sand Type of sand
Content Žwt.%.
Loss of ignition
SiO 2
Al 2 O 3
Fe 2 O 3
Na 2 O
TiO 2
MnO
CaO
KS-03
97–98
2–1
0.3–0.2
0.1
0.3–0.2
0.1
trace
0.48
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
Additives, included in reactions in contact zone liquid steel–sand mold at 1450–15508C, have the following values of partial molar values for surface tension: SiO 2 Ž400 mNrm., Al 2 O 3 Ž720 mNrm., CaO Ž520 mNrm., FeO Ž590 mNrm. and MnO Ž590 mNrm. w4x. By visual monitoring, it is evident that reaction between the liquid steel and mould mixture have occurred forming the dark layer ŽFig. 1, zone 1.. In order to analyze the process on the metal– mould contact surface, the following methods were used: polarizing microscopy Žwith reflected and transmitted-light., X-ray diffraction, and electron microprobe. Samples for analyzing the metal–mould contact surface process were taken after casting, i.e., after the reaction between the mould and the molten metal, the analysis being carried out by layers determined on the grounds of colour ŽFig. 1.. The prepared samples were investigated by using a polarized-light microscope model AJenapol-UB. The samples were prepared using a standard procedure for the specified method. Mineral identifications and comparison of the obtained values with these from the literature data w3x is done. The samples’ investigation by reflected-light microscopy were also used for analysis by electron microprobe, model AJeol-
Fig. 1. Mould segment.
237
Fig. 2. Metal–mould contact zone Žtransmitted-light, X Nic., in air..
JCXA-733B with WDS and EDS and EDX analytical system. The X-ray diffraction data were obtained on a Philips PW-1710 automated diffractometer, using a Cu-tube, with a diffracted beam curved graphite monochromator, and Xe-filled proportional counter. From the first contact zone Žsee Fig. 2., it can be seen, by transmitted-light, that quartz grains are of cataclastic texture after they are infiltrated by the melt. All changes in quartz grains are the consequence of thermal action, i.e., from the melted metal heat. At the same time, the interaction between the quartz grains with the mould mixture active component and with the penetrated cast metal strands have occurred. The quartz grains, intensively cracked due to thermal stresses, are firmly bonded with a newly formed Areactive q meltB visible crystal as a black zone on Fig. 2. According to the optical characteristics, it can be seen that the melt, after solidification is finished, became mainly amorphous, because the glassy phase is present with weakly visible crystal skeletons. The liquid steel, penetrated into the mould mixture pores, is in contact with silica and other mixture grains. Therefore, such liquid steel is immediately undergoing the rapid solidification, and oxidation is partially taking place at the solid state but is always surrounded by the generated gases. It should be noted that in X-ray diffraction testing, frequently, there are problems accomplished with the identification of small quantity of mineral phases, since some phases were present at the sensitivity limit, or even below the sensitivity limit. In
238
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
Fig. 3. Mineralogical identification of newly-formed minerals of the metal–mould contact surface Žreflected-light, II Nic., in air..
these investigations, a great number of small amounts of mineral phases are registered on X-ray diffractograms, but only main diffraction peaks were analyzed. The intensive heating of contact zone is due to the contact between the liquid steel and the sand mould, until the solidification is finished. This accumulation of heat promotes the reactions of formed oxides with other mould components. In this process, the new minerals of silica type are formed: fayalite —
2FeO.SiO 2 , pyroxene — NaFeSiO6 , leucite — KAlSiO6 , plagioclase — NaAlSi 3 O 8 and glass, as can be seen from Fig. 3. These low temperature melting silicates were created in reactions of the basic oxide ions Mn2q and Fe 2q with a complex SiO 2 ions. The last oxide originated from moulding mixture components. For a better understanding, particularly in the contact zone, of the genesis of new materials during pouring, crystallization and cooling of the casting,
Fig. 4. X-ray diffractogram.
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
the X-ray is used as a comparative and helpful method. X-ray diffractogram in Fig. 4 shows the
239
greatest amount of low temperature quartz phase with a small amount of frozen crystobalite phase. It
Fig. 5. SEM and EM analyses.
240
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
can be stated that cristobalite is formed during the structural transformation at high temperature and partly from a binder agent Žwater-glass.. At such temperature, the quartz transformation caused the volume changes and cracks appearing in the contact zone. Volume changes and crack formation are responsible for obtaining the less compact grains in comparison with the initial grains, i.e., grains prior to thermal influence. Besides the mentioned mineral phases, small quantities of fayalite and woostite were observed by X-ray diffraction. The fayalite formation could be explained in two ways: Ø by reaction of infiltrated iron with primary quartz grains, Ø by reaction of iron with silica from the binder Žwater-glass.. A few, very low intensity reflections indicate the presence of only a small amount of woostite. The identification of woostite becomes difficult, particularly from the overlapping of its reflections with those for cristobalite. For correct interpretation of some reactions which were carried out, the use of electron microprobe analysis became necessary, and these results are shown in Fig. 5. Fig. 5c, e and g confirms that liquid steel penetrated into the sand mould mixture, and the presence of iron, manganese and chrome is established. Iron and manganese participated in the reaction with silica and formed the so-called reaction melt, while chromium, which came out from steel, created the individual spinels Žsee white zones in Fig. 5a.. Fig. 5b, c and e clearly shows an overlapping of the white zones, and thus, conform their mutual reaction. As for alkalis Žsee Fig. 5f., potassium is mainly bonded with reactive melt, while sodium Žsee Fig. 5d., mainly left the system. Sodium appears at quartz grains boundaries, i.e., it is bonded in the other cracks and capillary channels. The white zones were inhomogeneous, as shown by X-ray diffraction diagrams, and this can be explained by partial crystallization of silicates and ox-
ides, and inhomogeneities in chemical compositions of melt. The analogous results are obtained for another combination of mixture components and steel melt. 4. Conclusion The events appearing at the metal–sand mould contact surface are influencing intensive physical change, i.e., structure transformation in quartz Ž a b ., resulting in the formation of great number of cracks on its grain boundaries Žzones I and II.. The experimental results indicate that after contact of the metal Žliquid steel. with mould Žsand mould with active component additive., interaction processes of heterogeneous character take place. The chemical changes are reflected in intensive reaction between infiltrated strands with both quartz and the active component, and also, the glassy phase is formed Žzone I.. The penetrating components into the sand mould are iron, manganese and chromium. Iron and manganese enter into the melt, while chromium forms the spinels along the quartz grain boundaries. From the components which are present in the mould as ingredients, silicon and partially potassium has the greatest reaction importance, while sodium leaves the system. The melt composition is a complex one and contains silicon, iron, manganese and potassium. The great deal of solidified steel presents the glassy phase with an appearance of dendrites of: fayalite, woostite, spinel and a number of less important minerals.
l
References w1x A.N. Tsibrik, Fiziko-khimicheskie protsessy v kontaktnoi zone metall-forma, Naukova dumka, Kiev,1977, pp. 7–31. w2x Yu.P. Vasin, A.Y. Rasulov, Okisliteli novye protivprigarnye materialy, Chelyabinsk,1969, pp. 6–51. w3x Chemical and Physical Data and Measures, Rad, Belgrade, 1987. w4x P. Ramdohr, The Ore Minerals and Their Intergrowths, Pergamon, 1980, p. 1120.
Materials Letters 45 Ž2000. 235–240 www.elsevier.comrlocatermatlet
A contribution to study of processes on the steel cast–sand mould contact surface during casting Z. Janjusevic ˇ ´ a,) , Z. Gulisija ˇ a, S. Radosavljevic´ a, Z. Acimovic ´ ´b a
Institute for Technology of Nuclear and Other Mineral Raw Materials, Franchet d’Esperey St 86, 11000 Belgrade, YugoslaÕia b Faculty of Technology and Metallurgy, KarnegieÕa St 4, 11000 Belgrade, YugoslaÕia Received 23 August 1999; received in revised form 3 April 2000; accepted 7 April 2000
Abstract The testings involved in this paper were part of a comprehensive research project conducted to find out what complex processes were taking place at metal–mould contact surface. These investigations are of particular importance for metal casting from relatively high melting temperature, such as that of steel Žapproximately 16008C.. Steel castings, in regard to their high manufactured temperature and other specifications in pouring, need a mould mixture of such good quality. The mould mixture, used for casting steel class DIN G-X 120 Mn 12, was based on the silica sand, and with water-glass as a binder and AlKŽSO4 . 2 as an active component. This active component is, at pouring temperature of liquid steel, decomposed in the mould by thermal influence during pouring, crystallization and cooling the casting. In decomposition process of the active component, the gaseous products appear and the water-stream is generated from chemically bonded water. These processes are influencing the molten metal oxidation. The penetrated molten metal into the mould surface is oxidized, too. At the high melting temperature and in the presence of gaseous products, the silicates were formed in the contact zone between metal and sand mould mixture. The objective of these tests was to find out to what extent the composition of the mould mixture affects the formation process, shape, type and composition of the silicates. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Steel; Casting; Moulds
1. Introduction Processes of mutual influence between the molten metal and the mould material are intrinsic in complex casting processes. Many casting properties and their surface or dimensional accuracy, and other properties, were determined by processes from contact of surfaces in liquid metal–sand mould. But these processes may also bring a number of casting ) Corresponding author. Tel.: q381-11-3691722; fax: q38111-3691583.
defects or failures Žscabs, gas, holes, cracks, and so on., and therefore, they affect the structure andror casting properties. The kind and the quality of mould mixture are, of course, of major importance in surface contact processes, i.e., the intensity or appearance of particular reaction. The kind and quality of used mixture will determine the behavior at the contact surface between molten metal and sand mould. An important role in developing the interaction processes, taking place between sand mould mixture and the liquid metal, is taken by the mixture addi-
00167-577Xr00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 0 0 . 0 0 1 1 1 - 7
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
236
Table 1 Chemical composition of casting steel DIN G-X 120Mn12
Table 3 The shape and grain roundness of silica sand
Element
C
Mn
Si
Cr
P
S
Al
The shape
%
1.28
10.08
0.38
1.56
0.028
0.018
0.054
Angular Semi- SemiRounded Wellangular rounded rounded
Percentage Ž%. 10
tives. Thus, chemical and mineral compositions, kind of binder, and additives, will cause certain changes, especially at high temperatures, and will also affect the mould mixture and the reactions at the contact zone with liquid metal. The great influence on surface defect formation also involves the kind of gases, which are present in the contact zone. The magnitude of adhesion at casting surface depends on silicate properties and their structure. The silicates are formed as a result of interaction between the mould material and the liquid steel. According to some literature data w1,2x, the most promising investigations are those for preventing the occurrence of some failures in steel castings. One of those is the investigation of oxidation process at the liquid metal–sand contact. These processes affect the possibility of complete oxidation of the penetrated metal resulting in weakening of the bonds between the mould and the metal. These data from the literature were used as the starting point in this work.
2. Experimental Necessary data were obtained experimentally by casting the cylinders, 30 = 300 mm, from steel of the known thermophysical characteristics w3x and relatively small measured variations in temperature of casting Ž1578–16108C. and temperature of crystallization Ž1509–15198C.. Chemical composition of used steel, determined after casting and found to correspond to the steel DIN G-X 120Mn 12, is given in Table 1.
5
30
30
25
The mould mixture is made from: 1. Silica sand Žquartz. with the chemical composition as given in Table 2. The granulometric composition of silica sand is determined by using a sieve system with apertures from 1.00 to 0.16 mm, according to DIN 1171, from 100-g probe. The mean grain size was 0.30 mm and grain roundness is given in Table 3. 2. The binder was water-glass Žmodule 2.8; density 1.55 grcm3 . 3. Sodium sulphate ŽNa 2 SO4 . 4. The active additive — AlKŽSO4 . 2 ; MgO.
3. Results and discussion The used steel is taken from an ordinary Foundry production program. The pouring temperature was varied within a range 1570–16108C, but the initial temperature of the mould and its outer surface was 208C. During the cooling period, the additive component from a mould mixture is decomposed. Such thermal decomposition is followed by the emission of gaseous products and water steam. These generated gases influence the oxidation process of penetrated metal into the sand mould, and the forming of silicate in the contact zone liquid steel–sand mould. Under the circumstances, the binary system with Na 2 O–SiO 2 is transformed into the Na 2 O–SiO 2 – M xO y system, both with a greater viscosity and surface tension.
Table 2 Chemical composition of used KS-03 silica sand Type of sand
Content Žwt.%.
Loss of ignition
SiO 2
Al 2 O 3
Fe 2 O 3
Na 2 O
TiO 2
MnO
CaO
KS-03
97–98
2–1
0.3–0.2
0.1
0.3–0.2
0.1
trace
0.48
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
Additives, included in reactions in contact zone liquid steel–sand mold at 1450–15508C, have the following values of partial molar values for surface tension: SiO 2 Ž400 mNrm., Al 2 O 3 Ž720 mNrm., CaO Ž520 mNrm., FeO Ž590 mNrm. and MnO Ž590 mNrm. w4x. By visual monitoring, it is evident that reaction between the liquid steel and mould mixture have occurred forming the dark layer ŽFig. 1, zone 1.. In order to analyze the process on the metal– mould contact surface, the following methods were used: polarizing microscopy Žwith reflected and transmitted-light., X-ray diffraction, and electron microprobe. Samples for analyzing the metal–mould contact surface process were taken after casting, i.e., after the reaction between the mould and the molten metal, the analysis being carried out by layers determined on the grounds of colour ŽFig. 1.. The prepared samples were investigated by using a polarized-light microscope model AJenapol-UB. The samples were prepared using a standard procedure for the specified method. Mineral identifications and comparison of the obtained values with these from the literature data w3x is done. The samples’ investigation by reflected-light microscopy were also used for analysis by electron microprobe, model AJeol-
Fig. 1. Mould segment.
237
Fig. 2. Metal–mould contact zone Žtransmitted-light, X Nic., in air..
JCXA-733B with WDS and EDS and EDX analytical system. The X-ray diffraction data were obtained on a Philips PW-1710 automated diffractometer, using a Cu-tube, with a diffracted beam curved graphite monochromator, and Xe-filled proportional counter. From the first contact zone Žsee Fig. 2., it can be seen, by transmitted-light, that quartz grains are of cataclastic texture after they are infiltrated by the melt. All changes in quartz grains are the consequence of thermal action, i.e., from the melted metal heat. At the same time, the interaction between the quartz grains with the mould mixture active component and with the penetrated cast metal strands have occurred. The quartz grains, intensively cracked due to thermal stresses, are firmly bonded with a newly formed Areactive q meltB visible crystal as a black zone on Fig. 2. According to the optical characteristics, it can be seen that the melt, after solidification is finished, became mainly amorphous, because the glassy phase is present with weakly visible crystal skeletons. The liquid steel, penetrated into the mould mixture pores, is in contact with silica and other mixture grains. Therefore, such liquid steel is immediately undergoing the rapid solidification, and oxidation is partially taking place at the solid state but is always surrounded by the generated gases. It should be noted that in X-ray diffraction testing, frequently, there are problems accomplished with the identification of small quantity of mineral phases, since some phases were present at the sensitivity limit, or even below the sensitivity limit. In
238
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
Fig. 3. Mineralogical identification of newly-formed minerals of the metal–mould contact surface Žreflected-light, II Nic., in air..
these investigations, a great number of small amounts of mineral phases are registered on X-ray diffractograms, but only main diffraction peaks were analyzed. The intensive heating of contact zone is due to the contact between the liquid steel and the sand mould, until the solidification is finished. This accumulation of heat promotes the reactions of formed oxides with other mould components. In this process, the new minerals of silica type are formed: fayalite —
2FeO.SiO 2 , pyroxene — NaFeSiO6 , leucite — KAlSiO6 , plagioclase — NaAlSi 3 O 8 and glass, as can be seen from Fig. 3. These low temperature melting silicates were created in reactions of the basic oxide ions Mn2q and Fe 2q with a complex SiO 2 ions. The last oxide originated from moulding mixture components. For a better understanding, particularly in the contact zone, of the genesis of new materials during pouring, crystallization and cooling of the casting,
Fig. 4. X-ray diffractogram.
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
the X-ray is used as a comparative and helpful method. X-ray diffractogram in Fig. 4 shows the
239
greatest amount of low temperature quartz phase with a small amount of frozen crystobalite phase. It
Fig. 5. SEM and EM analyses.
240
Z. JanjuseÕic ˇ ´ et al.r Materials Letters 45 (2000) 235–240
can be stated that cristobalite is formed during the structural transformation at high temperature and partly from a binder agent Žwater-glass.. At such temperature, the quartz transformation caused the volume changes and cracks appearing in the contact zone. Volume changes and crack formation are responsible for obtaining the less compact grains in comparison with the initial grains, i.e., grains prior to thermal influence. Besides the mentioned mineral phases, small quantities of fayalite and woostite were observed by X-ray diffraction. The fayalite formation could be explained in two ways: Ø by reaction of infiltrated iron with primary quartz grains, Ø by reaction of iron with silica from the binder Žwater-glass.. A few, very low intensity reflections indicate the presence of only a small amount of woostite. The identification of woostite becomes difficult, particularly from the overlapping of its reflections with those for cristobalite. For correct interpretation of some reactions which were carried out, the use of electron microprobe analysis became necessary, and these results are shown in Fig. 5. Fig. 5c, e and g confirms that liquid steel penetrated into the sand mould mixture, and the presence of iron, manganese and chrome is established. Iron and manganese participated in the reaction with silica and formed the so-called reaction melt, while chromium, which came out from steel, created the individual spinels Žsee white zones in Fig. 5a.. Fig. 5b, c and e clearly shows an overlapping of the white zones, and thus, conform their mutual reaction. As for alkalis Žsee Fig. 5f., potassium is mainly bonded with reactive melt, while sodium Žsee Fig. 5d., mainly left the system. Sodium appears at quartz grains boundaries, i.e., it is bonded in the other cracks and capillary channels. The white zones were inhomogeneous, as shown by X-ray diffraction diagrams, and this can be explained by partial crystallization of silicates and ox-
ides, and inhomogeneities in chemical compositions of melt. The analogous results are obtained for another combination of mixture components and steel melt. 4. Conclusion The events appearing at the metal–sand mould contact surface are influencing intensive physical change, i.e., structure transformation in quartz Ž a b ., resulting in the formation of great number of cracks on its grain boundaries Žzones I and II.. The experimental results indicate that after contact of the metal Žliquid steel. with mould Žsand mould with active component additive., interaction processes of heterogeneous character take place. The chemical changes are reflected in intensive reaction between infiltrated strands with both quartz and the active component, and also, the glassy phase is formed Žzone I.. The penetrating components into the sand mould are iron, manganese and chromium. Iron and manganese enter into the melt, while chromium forms the spinels along the quartz grain boundaries. From the components which are present in the mould as ingredients, silicon and partially potassium has the greatest reaction importance, while sodium leaves the system. The melt composition is a complex one and contains silicon, iron, manganese and potassium. The great deal of solidified steel presents the glassy phase with an appearance of dendrites of: fayalite, woostite, spinel and a number of less important minerals.
l
References w1x A.N. Tsibrik, Fiziko-khimicheskie protsessy v kontaktnoi zone metall-forma, Naukova dumka, Kiev,1977, pp. 7–31. w2x Yu.P. Vasin, A.Y. Rasulov, Okisliteli novye protivprigarnye materialy, Chelyabinsk,1969, pp. 6–51. w3x Chemical and Physical Data and Measures, Rad, Belgrade, 1987. w4x P. Ramdohr, The Ore Minerals and Their Intergrowths, Pergamon, 1980, p. 1120.