CA2021212A1 - Raw material moulds and process for the manufacture of raw material moulds - Google Patents
Raw material moulds and process for the manufacture of raw material mouldsInfo
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- CA2021212A1 CA2021212A1 CA 2021212 CA2021212A CA2021212A1 CA 2021212 A1 CA2021212 A1 CA 2021212A1 CA 2021212 CA2021212 CA 2021212 CA 2021212 A CA2021212 A CA 2021212A CA 2021212 A1 CA2021212 A1 CA 2021212A1
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Abstract
ABSTRACT
A process for the manufacture of raw material moulds, particularly for use in the production of silicone or silicone alloys in an electro cupola furnace, wherein quartz sand, a non-caking carbon carrier, preferably petrol coke, and a pitch containing binder are admixed, the resulting starting mixture is compressed to briquette blanks, and the briquette blanks are processed to the raw material moulds through a solidifying heat treatment. The pitch containing binder is a binder mixture of pitch and caking coal which has a temperature of 100 to 200°C. The quartz sand and a non-caking carbon carrier are admixed with the binder mixture at a mixing temperature which is in the same temperature range as the binder mixture. The starting mixture is compressed to briquette blanks starting at the mixing temperature. The briquette blanks are subjected to a heat treatment which has an end temperature of over 450°C. Subject of the invention are also raw material moulds manufactured by that process. The raw material moulds are characterized by their long term properties such as a constant stability even after outside storage.
A process for the manufacture of raw material moulds, particularly for use in the production of silicone or silicone alloys in an electro cupola furnace, wherein quartz sand, a non-caking carbon carrier, preferably petrol coke, and a pitch containing binder are admixed, the resulting starting mixture is compressed to briquette blanks, and the briquette blanks are processed to the raw material moulds through a solidifying heat treatment. The pitch containing binder is a binder mixture of pitch and caking coal which has a temperature of 100 to 200°C. The quartz sand and a non-caking carbon carrier are admixed with the binder mixture at a mixing temperature which is in the same temperature range as the binder mixture. The starting mixture is compressed to briquette blanks starting at the mixing temperature. The briquette blanks are subjected to a heat treatment which has an end temperature of over 450°C. Subject of the invention are also raw material moulds manufactured by that process. The raw material moulds are characterized by their long term properties such as a constant stability even after outside storage.
Description
2~212~2 RAW MATERIAL MOUIJDS AND PROCESS FOR THE MANUFACTURE
OF RAW MATERIAL MOULDS
The invention relates to a process for the manufacture of raw material moulds, particularly for the manufacture of silicone or silicone alloys in an electro cupola furnace, wherein quartz sand, a non-caking carbon carrier, preferably petrol coke, and a pitch containing binder are mlxed to ~orm a starting mixture, the starting mixture is compressed to briquette blanks, and the briquette blanks are processed to raw material mouldæ through a solidifying heat treatment. For the manufacture of such raw material moulds, quartz sand of a grain size range between .05 and .2 mm is generally used, and preferably quartz sand of narrower grain slze bands vi~hin that range. It is understood that iron or iron oxide of small particle size may be admixed with the starting mixture of the raw material moulds for the production of ferro silicone. Iron or iron oxide may also be added to the heating ch~mber of the electro cupola, preferably in the form of pellets or individual pieces. The heating chamber includes the raw material moulds and quartz. The invention further relates to raw materlal moulds manufactured by this process.
Raw material moulds for the above identified application must conform to certain physical and chemical requirements. For the production of silicone it is a chemical requirement known from British Patent No. G~ 20 84 122, that silicone carbide is formed first in the raw material moulds, du~ing their journey through an upper part of the electro cupola, in accordance with the equation SiO2 ~ 3 C , SiC ~ 2 CO
To achieve this, the total carbon content of the raw material moulds must be appropriately selected. The carbon content is generally selected to be higher than stoichiometrically required (British Patent No. GB 21 50 128).
- It is a physical requirement that the raw material blanks do not break apart during their journey through the lower part of the electro cupola, and especially during the reduction of silicone to silicone carbide, so that the silicone carbide may further react according to the equation SiO2 ~ SiC = 3 Si ~ 2 C0 It will be readily apparent to a skilled person that further reactions ta~e place in the electro cupola. For example, at the high temperatures present in the furnace and in accordance with the equation SiO2 ~ C = SiO + CO
highly volatile silicone monoxide is produced and is partly lost, which reduces the yield of the silicone production and interferes with the heat balance o~ the process.
In a prior art process disclosed in German Published Application No.
DE 37 24 541, of which the present invention is an improvement, raw material moulds are produced which are made of a mixture of quartz sand, a pitch containing binder and a fine grained carbon carrier, but are free of caking coal and are formed in a binder aided briquette forming process. The heat treatment is carried out in a rotary kiln, a lower part of which is filled sufficiently high with quartz sand to provide that the heat treatment is carried out in a quart~ sand submersion bed. Thia process has proven to be advantageous. Particularly, the raw material moulds manufactured using such 2S a process substantially withstand al] stresses durlng their journey through the electro cupola so that it is guaranteed that the above mentioned chemical processes can take place in an especially controlled way. However, with respect to the long term properties oE the raw material moulds before their use in an electro cupola, raw material moulds manufactured in accordance with the prior art process may be much improved. The mechanical stability of such raw material moulds decreases with time during storage, and in soma cases decreases so far as to become unacceptable. This may be explained by air diffusing into the raw material moulds and, especially during outside storage, water penetrating into the raw material moulds, which may lead to a reduction of the binding forces of the raw material 2~12~ ~
mould bonding structure. This is not the case for raw Material moulds designed for the sa~e application, but manufactured using a high temperature briquette forming process as described in German Published Application No.
DE 30 09 ~08, wherein raw material moulds are compressed directly from a starting mixture which has a temperature of 350 to ~50 C without subjecting them ~o a solidifying heat treatment. However, it is a disadvantage of such a high temperature briquette forming process that it is costly.
The present invention provides a process for the manufacture of raw material moulds, especially for the production of silicone or silicone alloys in an electro cupola furnace, which process leads to raw material moulds which not only fulfill all physical and chemical requirements during their journey through the electro cupola furnace, but are also characterized by excellent long term properties and substantially retain their stability during transpor~ and outside storage.
This is achieved in a process in accordance with the invention, wherein a pitch co~taining binder, which is made of a binder mixture of pitch and caking coal and has a temperature between 100 and 200 C, is mixed with quartz sand and a non-caking carbon carrier at a mixing temperature within the same temperature range as the binder, the resulting starting mixture is compressed to raw material blanks starting at the mixing temperature, and the blanks are subjected to a solidi~ying heat treatment which has an end temperature of over 450 C for production of the raw material moulds. In a process in accordance with the invention, the briquette forming process which is used for the production o~ the moulds is a binder aided briquette forming process such as the process generally used in the manufacture of mineral coal briquettes. Thereiore, the technology of known binder aided briquette forming processes may be employed despite the high quartz sand content of the moulds in the present invention. Generally, commonly known briquette presses and pressures of 1 to 2 t/cm2 may be employed.
It is an unexpected result that, when the above mentioned binder aided briquette forming process is used and the above mentioned parameters are employed, the resulting raw material moulds comply with all the PAT 158~8-1 2~212 above-mentioned requirements even with respect to their long term properties. This is especially apparent, when a binder mixture ls used, which is a pitch/coal alloy. A pitch/coal alloy in accordance with the invention is given, if the pitch and the ca~lng coal ~re, so to speak, dissolved in each other so that an integration of the two components into a new binder alloy has taken place. This may be readily achieved, especially when coal of sufficiently fine grained is used. In raw material moulds manufactured by a process in accordance with the in~ention, the pitch/coal alloy is s~rprisingly unaffected by air and humidity di~fusing into the raw material moulds. Several variants of the raw material mould manu~acturi~g process in accordance with the present invention are within the scope of the invention, Especially good results are achieved if the non-caking carbon carrier, the quartz sand and the binder mixture have the same temperature during their admixture and if the admixture is carried out at a preferred temperature of about 160 C. In a preferred embodiment, the starting mixture contains 20 to 40% per weight of quartz sand, the binder Mixture and, for the remainder, petrol coke and activators. A number of activators adapted to be used in the present process are readily apparent to a person skilled in the art.
In contrast to the above described prior art process taught in German Published Applicatlon No. DE 37 24 541, wherein the solidifying heat treatment must be carried out in a rotary kiln, in accordance with the present invention, the heat treatment may also be effected in a different manner, for example, on a moving grate which passes through an appropriate oven or an appropriate heat chamber and is loaded with a single layer or multiple layers of raw material moulds. However, in a preferred embodiment of the process in accordance with the invention, the blanks are subjected to the solidifying heat treatment in a rotary kiln. A very careful heat treatment of the blanks and a high final rigidity of the moulds may be achieved if raw material blanks, which have a higher specific weight than a shooting weight of the quartz sand, are produced by selecting an appropriate mixing ratio of the components in the starting mixture and an appropriate - degree of compression of the starting mixture during the forming of the raw materlal ~.oulds, and are fed to a heated rotary kiln for the solidifying heat treatment, which kiln is filled with quartz sand to such a height that . 2 the heat treatment of the blanks i~ e~f~cted ln a quartz sand submersion bed. The quartz sand preferably has a t~mperatur~ of about 500 to 530 C, at least towards the exit end of the rotary kiln. In order to prevent the blanks from contacting each other in the kiln and to prevent their abrasion, the kiln is preferably filled with a volume of quartz sand which is larger than twice the volume of the voids within a loose filling of ~he kiln with the blanks. For the remainder oE the process in accordance with the invention, recourse to the technology disclosed in German Published Application No. DE 37 24 541 may be had. Accordingly, the raw material blanks may be formed in a pellet forming apparatus, which yields substantially spherical pellets, or in a briquette forming press. The use of the latter is preferred, since the specific weight of the briquette blanks may be controlled through an adjustment of the briquetting force of the press. The raw material blanks are fed into the kiln through an entry end thereof together with a volume of quartz sand required for retaining the volume of the submersion bed substantially constant. Both the produced moulds and the heated quartz sand leave the kiln at an exit and thereof.
The durativn of the heat treatment of the blanks and thus, the length of time the blanks remain in the kiln, is selected to provide a sufficient solidification of the blanks. The raw material moulds are preferably removed from the rotary kiln together with the least amount of quartz sand possible. However, the quartz sand may also exit the kiln at substantially the same speed as the raw material moulds in which case the quartz sand is preferably partially recycled into the kiln in such a way that the sand particles are recycled on average three times. Since only part of the quartz sand filling of the kiln is recycled in such a case, the amount of newly added, cool quartz sand may be adjusted such that the temperature oE
the quartz submersion bed is about 20Q C at the entry end of the kiln, which is advantageous for a gentle heat treatment of the blanks. It is an advantage of the heat treatment in a rotary kiln, that volatile components which evaporate from the blanks during the heat treatment may be combus~ed in the kiln above the quartz sand bed. The resulting combustion heat may be used to retain the kiln at tha required temperature and to make the heat treatment substantially independent of additional heat sources. Thus, the one or more burners which are generally provided at the entry end of a ~)2~ 2~
rotary kiln may be required for the start of the heat treatm~nt and for special situations only.
To optimize the process in accordance with the invention, it is preferred to employ a binder mixture which, with resp~ct to the s~arting mixture from whieh the moulds are pressed, contains at least 7~ per weight of pitch in the form of crude oll pitch or coal pitch, especially electrode pitch, and at least 12~ per weight of flne grained caking coal. The blndçr mixture preferably contains 7 to 12~ per weight of pit~h and 12 to 14~ per weight of fine grained caking coal. Preferably, quartz sand with a 8rain size of .05 to .2 mm and petrol coke with a grain size of less than 2 mm with at least 60~ below .5 mm, is employed.
The raw material moulds produced by the process in accordance with the invention are characterized by their long term properties and their behavior in the electro cupola furnace. Without departing from the s~ope of the invention, fine, particulate minerals may be admixed with the starting mixture. As a result, an activation of .he raw material moulds may be achieved which is effective at temperatures above 1500 C. The raw material moulds manufactured by a process in accordance with the invention may also be employed as silicone or carbon carriers during the manufacture of c~st iron in a cupola furnace.
The invention will be further described below by way of example only and with reference to a preferred embodiment of the invention. A graph, which is shown in Figure 1, forms part of the example. Figure 1 shows the pressure resistance of the raw material moulds plotted over time.
1) In order to manufacture raw material moulds for the production of silicone or silicone alloys in an electro cupola furnace, in a flrst example, 38~ per weight of quartz sand with a grain si e of .08 to .25 mm and 50~ per weight of petrol coke with a grain si~e of 2 mm were thoroughly admixed with 12~ per weight of electrode pitch at a temperature of 160 C.
The softening point of the electrode pitch as defined by Kaines was 90 C
at completion of the mixing, and the resulting starting mixture had a temperature of 145 C.
~21212 Substantially spherical blanks of about 2 cm diameter were produced from this starting mixture after cooling to 105 C using a pressure of 1.5 t/cm2, The blanks were subjected to a solidifying heat treatment in a rotary kiln as described above. l'he so manufactured raw material moulds exhibit, after outside storage, long term pressure resistance properties as illustrated by curve a in the graph of Figure 1. In the acceptable pressure resistance region, before the decrease of curve a, the moulds comply with all chemical and physical requirements in the electro cupola fur~ace.
2) In a second example, one part per weight o the electrode pitch referred to in example 1 and 1.8 parts per weight of caking coal with a grain size of up to 80~ between .l and .2 mm, are melted to a pitchlcoal alloy at a temperature of about 160 C. The first example has been repeated with 18~ of thls pitch/coal alloy replacing the electrode pitch of the first example. For the remaining steps of example 2, the steps of the first example have been repeated up to the finish of the raw material moulds.
These show, a~ter outside storage, long term pressure resistance properties as illustrated by curve b in the graph of Figure 1.
OF RAW MATERIAL MOULDS
The invention relates to a process for the manufacture of raw material moulds, particularly for the manufacture of silicone or silicone alloys in an electro cupola furnace, wherein quartz sand, a non-caking carbon carrier, preferably petrol coke, and a pitch containing binder are mlxed to ~orm a starting mixture, the starting mixture is compressed to briquette blanks, and the briquette blanks are processed to raw material mouldæ through a solidifying heat treatment. For the manufacture of such raw material moulds, quartz sand of a grain size range between .05 and .2 mm is generally used, and preferably quartz sand of narrower grain slze bands vi~hin that range. It is understood that iron or iron oxide of small particle size may be admixed with the starting mixture of the raw material moulds for the production of ferro silicone. Iron or iron oxide may also be added to the heating ch~mber of the electro cupola, preferably in the form of pellets or individual pieces. The heating chamber includes the raw material moulds and quartz. The invention further relates to raw materlal moulds manufactured by this process.
Raw material moulds for the above identified application must conform to certain physical and chemical requirements. For the production of silicone it is a chemical requirement known from British Patent No. G~ 20 84 122, that silicone carbide is formed first in the raw material moulds, du~ing their journey through an upper part of the electro cupola, in accordance with the equation SiO2 ~ 3 C , SiC ~ 2 CO
To achieve this, the total carbon content of the raw material moulds must be appropriately selected. The carbon content is generally selected to be higher than stoichiometrically required (British Patent No. GB 21 50 128).
- It is a physical requirement that the raw material blanks do not break apart during their journey through the lower part of the electro cupola, and especially during the reduction of silicone to silicone carbide, so that the silicone carbide may further react according to the equation SiO2 ~ SiC = 3 Si ~ 2 C0 It will be readily apparent to a skilled person that further reactions ta~e place in the electro cupola. For example, at the high temperatures present in the furnace and in accordance with the equation SiO2 ~ C = SiO + CO
highly volatile silicone monoxide is produced and is partly lost, which reduces the yield of the silicone production and interferes with the heat balance o~ the process.
In a prior art process disclosed in German Published Application No.
DE 37 24 541, of which the present invention is an improvement, raw material moulds are produced which are made of a mixture of quartz sand, a pitch containing binder and a fine grained carbon carrier, but are free of caking coal and are formed in a binder aided briquette forming process. The heat treatment is carried out in a rotary kiln, a lower part of which is filled sufficiently high with quartz sand to provide that the heat treatment is carried out in a quart~ sand submersion bed. Thia process has proven to be advantageous. Particularly, the raw material moulds manufactured using such 2S a process substantially withstand al] stresses durlng their journey through the electro cupola so that it is guaranteed that the above mentioned chemical processes can take place in an especially controlled way. However, with respect to the long term properties oE the raw material moulds before their use in an electro cupola, raw material moulds manufactured in accordance with the prior art process may be much improved. The mechanical stability of such raw material moulds decreases with time during storage, and in soma cases decreases so far as to become unacceptable. This may be explained by air diffusing into the raw material moulds and, especially during outside storage, water penetrating into the raw material moulds, which may lead to a reduction of the binding forces of the raw material 2~12~ ~
mould bonding structure. This is not the case for raw Material moulds designed for the sa~e application, but manufactured using a high temperature briquette forming process as described in German Published Application No.
DE 30 09 ~08, wherein raw material moulds are compressed directly from a starting mixture which has a temperature of 350 to ~50 C without subjecting them ~o a solidifying heat treatment. However, it is a disadvantage of such a high temperature briquette forming process that it is costly.
The present invention provides a process for the manufacture of raw material moulds, especially for the production of silicone or silicone alloys in an electro cupola furnace, which process leads to raw material moulds which not only fulfill all physical and chemical requirements during their journey through the electro cupola furnace, but are also characterized by excellent long term properties and substantially retain their stability during transpor~ and outside storage.
This is achieved in a process in accordance with the invention, wherein a pitch co~taining binder, which is made of a binder mixture of pitch and caking coal and has a temperature between 100 and 200 C, is mixed with quartz sand and a non-caking carbon carrier at a mixing temperature within the same temperature range as the binder, the resulting starting mixture is compressed to raw material blanks starting at the mixing temperature, and the blanks are subjected to a solidi~ying heat treatment which has an end temperature of over 450 C for production of the raw material moulds. In a process in accordance with the invention, the briquette forming process which is used for the production o~ the moulds is a binder aided briquette forming process such as the process generally used in the manufacture of mineral coal briquettes. Thereiore, the technology of known binder aided briquette forming processes may be employed despite the high quartz sand content of the moulds in the present invention. Generally, commonly known briquette presses and pressures of 1 to 2 t/cm2 may be employed.
It is an unexpected result that, when the above mentioned binder aided briquette forming process is used and the above mentioned parameters are employed, the resulting raw material moulds comply with all the PAT 158~8-1 2~212 above-mentioned requirements even with respect to their long term properties. This is especially apparent, when a binder mixture ls used, which is a pitch/coal alloy. A pitch/coal alloy in accordance with the invention is given, if the pitch and the ca~lng coal ~re, so to speak, dissolved in each other so that an integration of the two components into a new binder alloy has taken place. This may be readily achieved, especially when coal of sufficiently fine grained is used. In raw material moulds manufactured by a process in accordance with the in~ention, the pitch/coal alloy is s~rprisingly unaffected by air and humidity di~fusing into the raw material moulds. Several variants of the raw material mould manu~acturi~g process in accordance with the present invention are within the scope of the invention, Especially good results are achieved if the non-caking carbon carrier, the quartz sand and the binder mixture have the same temperature during their admixture and if the admixture is carried out at a preferred temperature of about 160 C. In a preferred embodiment, the starting mixture contains 20 to 40% per weight of quartz sand, the binder Mixture and, for the remainder, petrol coke and activators. A number of activators adapted to be used in the present process are readily apparent to a person skilled in the art.
In contrast to the above described prior art process taught in German Published Applicatlon No. DE 37 24 541, wherein the solidifying heat treatment must be carried out in a rotary kiln, in accordance with the present invention, the heat treatment may also be effected in a different manner, for example, on a moving grate which passes through an appropriate oven or an appropriate heat chamber and is loaded with a single layer or multiple layers of raw material moulds. However, in a preferred embodiment of the process in accordance with the invention, the blanks are subjected to the solidifying heat treatment in a rotary kiln. A very careful heat treatment of the blanks and a high final rigidity of the moulds may be achieved if raw material blanks, which have a higher specific weight than a shooting weight of the quartz sand, are produced by selecting an appropriate mixing ratio of the components in the starting mixture and an appropriate - degree of compression of the starting mixture during the forming of the raw materlal ~.oulds, and are fed to a heated rotary kiln for the solidifying heat treatment, which kiln is filled with quartz sand to such a height that . 2 the heat treatment of the blanks i~ e~f~cted ln a quartz sand submersion bed. The quartz sand preferably has a t~mperatur~ of about 500 to 530 C, at least towards the exit end of the rotary kiln. In order to prevent the blanks from contacting each other in the kiln and to prevent their abrasion, the kiln is preferably filled with a volume of quartz sand which is larger than twice the volume of the voids within a loose filling of ~he kiln with the blanks. For the remainder oE the process in accordance with the invention, recourse to the technology disclosed in German Published Application No. DE 37 24 541 may be had. Accordingly, the raw material blanks may be formed in a pellet forming apparatus, which yields substantially spherical pellets, or in a briquette forming press. The use of the latter is preferred, since the specific weight of the briquette blanks may be controlled through an adjustment of the briquetting force of the press. The raw material blanks are fed into the kiln through an entry end thereof together with a volume of quartz sand required for retaining the volume of the submersion bed substantially constant. Both the produced moulds and the heated quartz sand leave the kiln at an exit and thereof.
The durativn of the heat treatment of the blanks and thus, the length of time the blanks remain in the kiln, is selected to provide a sufficient solidification of the blanks. The raw material moulds are preferably removed from the rotary kiln together with the least amount of quartz sand possible. However, the quartz sand may also exit the kiln at substantially the same speed as the raw material moulds in which case the quartz sand is preferably partially recycled into the kiln in such a way that the sand particles are recycled on average three times. Since only part of the quartz sand filling of the kiln is recycled in such a case, the amount of newly added, cool quartz sand may be adjusted such that the temperature oE
the quartz submersion bed is about 20Q C at the entry end of the kiln, which is advantageous for a gentle heat treatment of the blanks. It is an advantage of the heat treatment in a rotary kiln, that volatile components which evaporate from the blanks during the heat treatment may be combus~ed in the kiln above the quartz sand bed. The resulting combustion heat may be used to retain the kiln at tha required temperature and to make the heat treatment substantially independent of additional heat sources. Thus, the one or more burners which are generally provided at the entry end of a ~)2~ 2~
rotary kiln may be required for the start of the heat treatm~nt and for special situations only.
To optimize the process in accordance with the invention, it is preferred to employ a binder mixture which, with resp~ct to the s~arting mixture from whieh the moulds are pressed, contains at least 7~ per weight of pitch in the form of crude oll pitch or coal pitch, especially electrode pitch, and at least 12~ per weight of flne grained caking coal. The blndçr mixture preferably contains 7 to 12~ per weight of pit~h and 12 to 14~ per weight of fine grained caking coal. Preferably, quartz sand with a 8rain size of .05 to .2 mm and petrol coke with a grain size of less than 2 mm with at least 60~ below .5 mm, is employed.
The raw material moulds produced by the process in accordance with the invention are characterized by their long term properties and their behavior in the electro cupola furnace. Without departing from the s~ope of the invention, fine, particulate minerals may be admixed with the starting mixture. As a result, an activation of .he raw material moulds may be achieved which is effective at temperatures above 1500 C. The raw material moulds manufactured by a process in accordance with the invention may also be employed as silicone or carbon carriers during the manufacture of c~st iron in a cupola furnace.
The invention will be further described below by way of example only and with reference to a preferred embodiment of the invention. A graph, which is shown in Figure 1, forms part of the example. Figure 1 shows the pressure resistance of the raw material moulds plotted over time.
1) In order to manufacture raw material moulds for the production of silicone or silicone alloys in an electro cupola furnace, in a flrst example, 38~ per weight of quartz sand with a grain si e of .08 to .25 mm and 50~ per weight of petrol coke with a grain si~e of 2 mm were thoroughly admixed with 12~ per weight of electrode pitch at a temperature of 160 C.
The softening point of the electrode pitch as defined by Kaines was 90 C
at completion of the mixing, and the resulting starting mixture had a temperature of 145 C.
~21212 Substantially spherical blanks of about 2 cm diameter were produced from this starting mixture after cooling to 105 C using a pressure of 1.5 t/cm2, The blanks were subjected to a solidifying heat treatment in a rotary kiln as described above. l'he so manufactured raw material moulds exhibit, after outside storage, long term pressure resistance properties as illustrated by curve a in the graph of Figure 1. In the acceptable pressure resistance region, before the decrease of curve a, the moulds comply with all chemical and physical requirements in the electro cupola fur~ace.
2) In a second example, one part per weight o the electrode pitch referred to in example 1 and 1.8 parts per weight of caking coal with a grain size of up to 80~ between .l and .2 mm, are melted to a pitchlcoal alloy at a temperature of about 160 C. The first example has been repeated with 18~ of thls pitch/coal alloy replacing the electrode pitch of the first example. For the remaining steps of example 2, the steps of the first example have been repeated up to the finish of the raw material moulds.
These show, a~ter outside storage, long term pressure resistance properties as illustrated by curve b in the graph of Figure 1.
3) In a third example, the steps of example 2 have been repeated up to the production of the blanks. However, using the same treatment time and temperature in the heat treatment, the blanks have been hardened on a moving grate. Curve c in the graph o~ Figure 1 shows the pressure resistance of the resulting raw material moulds.
A comparison of curves a, b and c s~rikingly shows the improvements in the characteristics and properties of the raw material moulds, which have been achieved through using a process in accordance with the present inventlon,
A comparison of curves a, b and c s~rikingly shows the improvements in the characteristics and properties of the raw material moulds, which have been achieved through using a process in accordance with the present inventlon,
Claims (11)
1. A process for the manufacture of raw material moulds comprising the steps of:
mixing quartz sand with a non-caking carbon carrier, and a pitch containing binder, compressing the resulting starting mixture to briquette blanks and producing said raw material moulds through a solidifying heat treatment, said pitch containing binder being a binder mixture of pitch and caking coal which has a temperature of 100 to 200°C, said quartz sand and said non-caking carbon carrier being admixed with said binder mixture at a mixing temperature which is within the same temperature range as said binder mixture temperature, said blanks being formed starting at said mixing temperature and said blanks being subjected to a solidifying heat treatment having an end temperature of over 450°C.
mixing quartz sand with a non-caking carbon carrier, and a pitch containing binder, compressing the resulting starting mixture to briquette blanks and producing said raw material moulds through a solidifying heat treatment, said pitch containing binder being a binder mixture of pitch and caking coal which has a temperature of 100 to 200°C, said quartz sand and said non-caking carbon carrier being admixed with said binder mixture at a mixing temperature which is within the same temperature range as said binder mixture temperature, said blanks being formed starting at said mixing temperature and said blanks being subjected to a solidifying heat treatment having an end temperature of over 450°C.
2. A process as defined in claim 1, wherein said binder mixture is a pitch/coal alloy.
3. A process as defined in claim 1, wherein said quartz sand, said non-caking carbon carrier and said binder mixture have the same temperature during their admixture.
4. A process as defined in claim 3, wherein said mixing temperature is about 160°C.
5. A process as defined in claim 3 or 4, wherein said blanks are subjected to said solidifying heat treatment in a rotary kiln.
6. A process as defined in claim 5, wherein a specific weight of said blanks is controlled to be higher than a shooting weight of said quartz sand, through selection of a mixing ratio of said starting mixture and a degree of compression, of said starting mixture during said compressing thereof, and said blanks are fed into a heated rotary kiln for said solidifying heat treatment, said kiln being filled with said quartz sand to such a height that said heat treatment of said blanks is effected in a quartz sand submersion bed.
7. A process as defined in claim 6, wherein said rotary kiln is filled to such an extent that a volume of said quartz sand is larger than twice a combined volume of all voids within a loose filling of said kiln with said blanks.
8. A process as defined in claim 7, wherein said binder mixture contains, in relation to said starting mixture which is used for forming said blanks, at least 7% per weight of pitch in form of one of coal pitch, crude oil pitch and electrode pitch, and at least 12% per weight of fine grained caking coal.
9. A process as defined in claim 8, wherein said starting mixture contains 20 to 40% per weight of quartz sand, said binder mixture, and for the remainder, petrol coke and activators.
10. A process as defined in claim 9, wherein said quartz sand has a grain size of .05 to .2 mm and said petrol coke has a grain size below 2 mm with at least 60% per weight below .5 mm.
11. Raw material moulds manufactured by a process as defined in any one of claims 1 to 10.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2021212 CA2021212A1 (en) | 1990-07-16 | 1990-07-16 | Raw material moulds and process for the manufacture of raw material moulds |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2021212 CA2021212A1 (en) | 1990-07-16 | 1990-07-16 | Raw material moulds and process for the manufacture of raw material moulds |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2021212A1 true CA2021212A1 (en) | 1992-01-17 |
Family
ID=4145489
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2021212 Abandoned CA2021212A1 (en) | 1990-07-16 | 1990-07-16 | Raw material moulds and process for the manufacture of raw material moulds |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2021212A1 (en) |
-
1990
- 1990-07-16 CA CA 2021212 patent/CA2021212A1/en not_active Abandoned
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| Date | Code | Title | Description |
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| FZDE | Dead |