Inorganic binder

Abstract

A composition for making cores and for metal casting processes includes a particulate refractory material, an inorganic binder including at least one alkali metal silicate, a pozzolanic additive, and a lustrous carbon former. The method includes forming a core from the composition, assembling a mold with the core, and providing molten metal.

Description

[Technical field]

[0001] The present invention relates to a composition for use as a core in a casting or molding process, a core including the composition, a mold including the core, and a method of making an article using the core. [Background technology]

[0002] In gravity casting processes, molten metal (or molten metal alloy) is poured into a preformed mold cavity that defines the outer shape of the casting, filling the mold cavity under the force of gravity. The shape of the hollow portion or internal cavity of the casting may be defined by a disposable core. The core may be bound using organic resins, powdered binders, clay minerals, or water glass (sometimes referred to as liquid inorganic binders). Currently, binding sand cores and molds with organic binders, such as organic resins, is generally not the preferred method, because the decomposition products of organic binders are often toxic, and the compositions release toxic fumes upon curing or during casting, which pose risks to foundry personnel and have other negative environmental impacts that can be costly to mitigate. A further problem with many existing core binder systems is the quality of the finished surface of the cast parts. Long casting times and the associated harsh conditions frequently result in adhesion of sand to the surface of the casting, destruction of the core itself, and ingress of metal into the core.

[0003] US Patent 4,316,744 discloses a foundry sand binder containing an aqueous solution of sodium silicate, potassium silicate or lithium silicate and containing amorphous silica, with a high proportion of silicate. The core and mold compositions disclosed in US Patent 4,316,744 are cold-setting and are hardened with carbon dioxide or a suitable acid releasing curing agent. A disadvantage of such mold compositions and in particular the method of hardening the binder system with carbon dioxide is that when the mold composition is purged with carbon dioxide, it always has a lower strength than when a procedure involving thermal hardening with a heated metal core box and heated air to purge the sand core is used. It is therefore an object of the present invention to provide a foundry mold composition that is particularly suitable for molding high strength cores in so-called heated core boxes, where the mold material can be simply hardened by purging with heated air.

[0004]

[0005] It is therefore an object of the present invention to mitigate or ameliorate the above problems. Summary of the Invention

[0006] <Configuration> According to a first aspect of the present invention there is provided a composition for making cores for use in a metal casting process. The composition may comprise a particulate refractory material. The composition may comprise an inorganic binder. The inorganic binder may comprise at least one alkali metal silicate. The composition may comprise a pozzolanic additive. The composition may comprise a lustrous carbon former.

[0007] As used herein, the term "lustrous carbon former" refers to a casting additive that forms lustrous carbon under the influence of casting conditions, typically comprising an organic compound that volatilizes at the mold-metal interface to form lustrous carbon.

[0008] The inventors of the present invention have found that cores made from the composition of the first aspect have sufficient strength to withstand the forces encountered during the casting process, have excellent de-coring properties, and avoid or minimize surface defects in the metal casting. As a further advantage, the composition of the first aspect can be used without the need for a coating to be applied to the core prior to use in a molding or casting process.

[0009] <Lastras Carbon Former> In one set of embodiments, the lustrous carbon former may be a strong lustrous carbon former. The composition may be for making cores for use in ferrous metal casting processes. In an alternative embodiment, the composition may be for making cores in high temperature non-ferrous metal casting processes such as copper casting and copper alloy casting. In this context, high temperature means about 1000° C. or higher.

[0010] The super-lustrous carbon former may comprise one or more selected from asphalt, hydrocarbon resin, polystyrene, and gilsonite. The super-lustrous carbon former may have a lustrous carbon content of at least 15%. In some embodiments, the super-lustrous carbon former may have a lustrous carbon content of at least 16%, 17%, 18%, 19%, 20%, 22%, 24%, 25%, 26%, 28%, or 30%.

[0011] The super-lustrous carbon former may comprise 0.1-1.5 wt% based on the weight of the particulate refractory material, hi some embodiments, the super-lustrous carbon former may comprise a range consisting of 0.2-1.4 wt%, 0.3-1.3 wt%, 0.4-1.2 wt%, 0.5-1.1 wt%, 0.6-1.0 wt%, 0.7-0.9 wt%, 0.8 wt%, or any combination thereof.

[0012] The inventors have found that for ferrous castings, it is advantageous if the lustrous carbon former contains 10-80 wt. % (based on the total weight of the lustrous carbon former) of a carbon-containing resin such as Gilsonite. It has been found that a high quality casting surface can be obtained when this resin is present in amounts of 0.05-0.5 wt. %, 0.1-0.4 wt. %, 0.2-0.4 wt. %, based on the weight of the granular refractory material. In particular, it has been found that the presence of this lustrous carbon former in the composition significantly improves the core removal properties after the casting process. It has been surprisingly found that this sand core can be used without coating for the casting of GJS and GJV (ferrous castings). A defect-free casting surface is obtained.

[0013] The inventors have also found that the presence of Gilsonite is advantageous in copper and copper alloy castings, resulting in cores with good cold strength and good core removal characteristics, especially when the cores are not coated prior to casting.

[0014] In a further set of embodiments, the lustrous carbon former may be a weak lustrous carbon former. The composition may be for making cores for use in a non-ferrous metal casting process. For example, the composition may be for making cores in a low temperature non-ferrous metal casting process. In this context, low temperature means below 1000°C, optionally below 900°C or below 800°C.

[0015] The weakly lustrous carbon former may include one or more of graded coal, coal dust, and seacoal. The weakly lustrous carbon former has a lustrous carbon content of less than 15%. In some embodiments, the weakly lustrous carbon former may have a lustrous carbon content of less than 14%, less than 13%, less than 12%, less than 11%, less than 10%, less than 9%, or less than 8%.

[0016] The weakly lustrous carbon former may comprise 0.1-1.5 wt% based on the weight of the particulate refractory material, hi some embodiments, the weakly lustrous carbon former may comprise a range consisting of 0.2-1.4 wt%, 0.3-1.3 wt%, 0.4-1.2 wt%, 0.5-1.1 wt%, 0.6-1.0 wt%, 0.7-0.9 wt%, 0.8 wt%, or combinations thereof.

[0017] Compositions particularly suitable for aluminum casting may contain 5-40 wt%, preferably 5-30 wt%, or 5-20 wt% of classified coal. The classified coal may have a median particle size D50 of 20 μm-500 μm, 40 μm-200 μm, or 50 μm-100 μm. Surprisingly, the trace amount of classified coal in the composition improves the casting surface quality compared to a composition without classified coal. A type of classified coal particularly suitable for the composition according to the invention is characterized by a volatile content of 30%-45%, a moisture content of 20%-30%, and a lustrous carbon content of 8-12%.

[0018] The inventors of the present invention have surprisingly found that the presence of lustrous carbon formers, and in particular small amounts of coal dust and / or natural carbon-containing resins, allows the production of cores that ensure a smooth, sand-free casting surface, especially when casting non-ferrous materials such as aluminum. The inventors have found that by using small amounts of classified coal with low concentrations of lustrous carbon, a very smooth, sand-free casting surface can be obtained, especially for aluminum castings.

[0019] Compositions in which the lustrous carbon former is selected from the group consisting of one or more of classified carbon, activated carbon, carbon black, and naturally occurring carbon-containing resins such as Gilsonite provide particularly good results in making cores.

[0020] In a further set of embodiments, two or more different lustrous carbon formers may be used. For example, the composition may include a mixture of a strong lustrous carbon former and a weak lustrous carbon former. The mixture of strong lustrous carbon former and weak lustrous carbon former may be, for example, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, or any ratio therebetween. The mixture may be configured to obtain a desired lustrous carbon content in the overall composition.

[0021] <Granular heat-resistant material> The granular refractory material may include natural refractory material, synthetic refractory material, or a combination thereof. The granular refractory material may include sand. The sand may be selected from the group consisting of silica sand, zirconium silicate sand, chromite sand, bauxite sand, olivine sand, or ceramic beads.

[0022] The sand may be of any type suitable for refractory applications, such as silica sand. In some embodiments, the granular refractory material may include any one or more conventional refractory materials, such as oxides, carbides, and nitrides of silicon, aluminum, magnesium, calcium, zirconium, and other elements. Suitable refractory materials include, but are not limited to, quartz, olivine, chromite, zircon, alumina, and the like. In some embodiments, the granular refractory material includes spherical particles, such as fly ash, and / or cenospheres. In some embodiments, the granular refractory material includes a mixture of sand and spherical particles and / or cenospheres, such as a mixture of sand and fly ash.

[0023] The granular refractory material may include virgin granular refractory material as well as recycled material.

[0024] In some embodiments, the granular refractory material has a D50 particle size of at least 20 μm, at least 50 μm, at least 100 μm, at least 250 μm, or at least 500 μm. In some embodiments, the granular refractory material has a D50 particle size of 2 mm or less, 1 mm or less, or 500 μm or less. In some embodiments, the granular refractory material has a D50 particle size of 20 μm to 2 mm, 50 μm to 2 mm, or 50 μm to 1 mm. The D50 value means that 50% of the particles have a size less than a particular diameter when analyzed by sieving. The sieving is preferably carried out using a sieving device according to DIN EN 933.

[0025] <Inorganic binder> The inorganic binder may comprise one or more of sodium silicate, potassium silicate, lithium silicate, or combinations thereof. The inorganic binder may comprise 0.5 wt% to 5 wt% by weight of the granular refractory material. The inorganic binder may comprise 1-4.5 wt%, 1.5-4 wt%, 2-3.5 wt%, or 3 wt% by weight of the granular refractory material, or a range formed from a combination thereof.

[0026] In some embodiments, the at least one alkali metal silicate comprises sodium silicate. In some embodiments, the at least one alkali metal silicate comprises potassium silicate. In one series of embodiments, the at least one alkali metal silicate comprises sodium silicate and potassium silicate.

[0027] The alkali metal silicate may be an aqueous solution. The solids content of the aqueous solution may be 30-50 wt%. In some embodiments, the solids content may be 32-48 wt%, 34-46 wt%, 35-45 wt%, 36-44 wt%, or 38-42 wt%. The solids content may be about 40 wt%.

[0028] The inorganic binder may be a thermosetting binder, which may be cured at a temperature of 50 to 250° C., for example, in a heated core box.

[0029] Commercially available binders contain a mixture of lithium and sodium silicate with a weight ratio of 2.1, solids content of 40%-45%, viscosity mPa.s (20°C) of 256, and density of 1.45-1.55 g / cm. 3 (20°C). Another commercially available water glass has, for example, a solid content of 41% to 47%, a weight ratio of 2.2 to 2.4, and a density of 1.45 to 1.55 g / cm 3 (20℃) is pure sodium silicate.

[0030] <Pozzolana additive> The pozzolanic additive may comprise 0.1 wt% to 2 wt% by weight of the granular refractory material. The pozzolanic additive may comprise 0.2-1.9 wt%, 0.3-1.8 wt%, 0.4-1.7 wt%, 0.5-1.6 wt%, 0.6-1.5 wt%, 0.7-1.4 wt%, 0.8-1.3 wt%, 0.9-1.2 wt%, 1.0-1.1 wt%, or a range consisting of a combination thereof, by weight of the granular refractory material.

[0031] The pozzolanic additive may include silica fume and / or fused silica and / or pyrogenic silica and / or microsilica. Silica fume is a very fine amorphous silica, also known as condensed silica fume, microsilica, or silica dust. In some embodiments, the pozzolanic additive includes 20-90 wt% silica fume.

[0032] The bulk density of the commercially available silica fume referred to herein is approximately 120 kg / m 3 800kg / m2 densified or compressed to 3 The specific gravity ranges from 2.1 to 2.4, and the surface area (BET) ranges from 5 to 30 m 2 / g. The D90 particle size of the silica fume may be between 0.1 μm and 1 μm. The D90 value means that 90% of the particles are equal to or smaller than a certain particle size. The typical average particle size of silica fume is preferably between 0.10 and 1.0 μm, more preferably between 0.10 and 0.5 μm, and most preferably between 0.10 and 0.30 μm. However, particle size analysis often shows the presence of numerous agglomerates with an average particle size between 10 and 100 μm. Some agglomerates are difficult to break due to the strong bonds that arise during the smelting of silicon, so that the results of conventional size measurements are often significantly different from the true particle size distribution. Modern laser particle sizers with built-in ultrasound, in combination with special dispersants, can accurately measure the above mentioned particle sizes.

[0033] A suitable fused silica contained in the additive of the composition according to the invention may be a fused silica having an average particle size preferably between 10 and 90 μm, more preferably between 20 and 70 μm, even more preferably between 30 and 50 μm. The composition may also contain a small amount of pyrogenic silica, preferably having a D50 particle size between 0.1 and 20 μm, more preferably between 0.1 and 15 μm, most preferably between 0.15 and 12 μm.

[0034] In one set of embodiments, the composition further comprises a pozzolanic filler selected from the group consisting of aluminum silicate, sintered mullite, silicon dioxide, organo-modified silicon dioxide and fly ash. All the aforementioned materials are highly reactive pozzolans. For example, aluminum silicate beads, preferably with an average particle size of 10-120 μm, more preferably 20-100 μm, and most preferably 25-80 μm, are particularly suitable. Another commercially available product is a ceramic sintered body containing up to 75% mullite. Mullite is a silicate mineral. Yet another filler is a material available as organo-modified silicon dioxide, the surface of which is modified with an epoxy silane.

[0035] <Surfactant> The inorganic binder may include a surfactant, preferably an anionic surfactant. In some embodiments, the surfactant is sodium ethylhexyl sulfate. In some embodiments, other types of surfactants, such as cationic, nonionic, or amphoteric surfactants, may be included in the inorganic binder used in the present invention. The surfactant reduces the surface tension of the liquid binder to improve the flowability of the composition. The flowability of the composition is an important characteristic that affects the molding accuracy of the mold and / or core. In general, the composition is suitable for producing casting molds and cores, but the composition is particularly suitable for producing casting cores.

[0036] Particularly suitable surfactants are, for example, anionic surfactants, and the proportion of this type in the liquid phase is preferably 0.05 to 2.0 wt%, more preferably 0.10 to 1.0 wt%, and most preferably 0.20 to 0.6 wt%.

[0037] <Other> Preferably, the composition comprises 0-0.5 wt% clay / clay minerals based on the weight of the sand, more preferably 0-0.4 wt%, most preferably 0-0.3 wt% clay / clay minerals, i.e. the composition may only contain clay as an impurity and otherwise does not contain clay minerals.

[0038] The composition may include a water repellent, such as a silicon-based organic water repellent, which may improve the resistance of the composition to humidity and improve the mechanical strength of cores made from the composition.

[0039] <Nakako> According to a second aspect of the invention there is provided a core for use in a moulding or metal casting process comprising the composition of the first aspect of the invention.

[0040] <Process> According to a third aspect of the present invention, there is provided a process for producing a metal product by metal casting. The process includes mixing compositions as described above to produce a mixture. The process includes molding and hardening the mixture to produce a core in the shape of an internal cavity of the product. The process includes combining the core with a metal casting mould such that the mould and core together define a mould cavity. The process includes delivering molten metal to the mould cavity until the mould cavity is filled. The process includes cooling and solidifying the molten metal to form the product.

[0041] The step includes mixing a composition as described above, the composition including a super-strus carbon former. The process may include delivering molten metal to the mold cavity at a temperature of at least 1000° C. until the mold cavity is filled. In some embodiments, the metal may be delivered at a temperature of at least 1050° C., 1100° C., 1150° C., 1200° C., 1250° C., 1300° C., 1350° C., 1400° C., 1450° C., or 1500° C. In a first set of embodiments, the process may be for producing ferrous metal products by ferrous metal casting. For example, the process may be for producing products from iron, such as grey iron, compacted graphite iron, ductile iron, steel, and alloys thereof. In a further set of embodiments, the process may be for producing non-ferrous metal products using non-ferrous metal casting. For example, the process may be for producing products from copper or copper alloys, such as brass and bronze.

[0042] In one set of embodiments, the process may include mixing a composition as described above, the composition including a weakly lustrous carbon former. The process may be for producing non-ferrous metal products using non-ferrous metal casting. The process may include providing the metal at a temperature of less than 1200°C. For example, the process may be for producing shaped articles from copper or copper alloys such as brass or bronze. In a further set of embodiments, the process may include providing the metal at a temperature of less than 800°C. The process may be for producing non-ferrous metal products from aluminum, zinc, tin, or other non-ferrous metals or alloys thereof.

[0043] Molding and curing the mixture may include drying the mixture. Molding and curing the mixture may include packing the mixture into a core mold. Molding and curing the mixture may be performed using a core-shooting device. Molding and curing the mixture to produce a core includes producing the core by an additive manufacturing or 3D printing process.

[0044] The method of the present invention may comprise introducing the composition into a mold and heat curing the composition at a temperature between 50°C and 250°C, preferably for a period between 30 seconds and 5 minutes. Heat curing may be performed by purging the mold composition with hot air. The heated core box technique, also referred to herein as hot box technique or heated metal core box, is particularly advantageous for preparing casting cores with the composition. Depending on the conditions and application of the core, the strength value of the core can be easily adjusted. The heated core box technique allows for a strength of 200-1500 N / cm 2The heated core box process typically involves producing cores from sand, synthetic minerals, powdered additives, and liquid binders in a core shooting machine and hardening the cores in a heated metal core box. The process allows for the production of highly complex or very complex cores, as the composition has a very high flowability and molding precision. This allows for the production of cores with relatively high edge sharpness. The advantages of this process are that the cores are easily demoldable from the mold, have high dimensional precision, fine surfaces, well-defined edges, and are easily disassembled after the casting process. The process may include producing cores from the composition in a core shooting machine and hardening the cores in a heated metal core box by purging with hot air.

[0045] The process may further include removing the product including the core from the mold. The method may include removing the core from the internal cavity by, for example, shaking, washing with water, sand blasting, shot blasting, etc. [Brief description of the drawings]

[0046] [Figure 1] FIG. 1 is a graph of the flow properties of the compositions of Table 1. [Diagram 2] FIG. 2 is a graph of the flexural strength of cores formed from the compositions of Table 1. [Diagram 3] FIG. 3 is a graph of the flow properties of the compositions of Table 2. [Figure 4] FIG. 4 is a graph of the flexural strength of cores formed from the compositions of Table 2. [Diagram 5] FIG. 5 is a graph of the flexural strength of cores formed from the compositions of Table 3. [Figure 6] FIG. 6 is a graph showing the thermogravimetric analysis of four types of Lustrous carbon formers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] <Example> <Experiment 1 - Initial composition for iron casting> A series of cores were prepared by mixing H33 type silica sand with the binders and additives listed in Table 1 below. Mixing was carried out in a Hobart mixer for 1 minute and then repeated for 2 minutes.

[0048] The flow properties of the compositions were tested using a Brookfield Powder Flow Tester to measure the flow capabilities of the compositions. A sample of each composition was then loaded into the cell of the Brookfield PFT, after which a vertical force was applied to the powder to pack it (Major Principal Consolidating Stress). A rotational force was then applied to the packed powder while maintaining the same maximum principal consolidating stress to measure the force required to initiate the flow of the powder (Unconfined Failure Strength). This process was repeated over a range of consolidation stresses, and a flow function was constructed by plotting the unconfined failure strength against the consolidation stress as shown in Figure 1 to determine the internal resistance to flow of the composition. In general, it is desirable to increase the flowability to reduce powder handling and transportation problems and to avoid molding defects. No obvious difference was observed between Examples 1-4 and Example 6. Only Example 5 showed significantly lower flowability due to the presence of carbon black in the composition.

[0049] Cross bars were produced on a Laempe laboratory machine type L1 using gas hardening processes such as CO2, cold box and hot box. The Laempe laboratory machine type L1 was developed to produce test cores with heated and unheated tooling. The sand mixture is automatically injected into the core box clamped between the side presses and can be heated at various temperatures. The release of high pressure air blows the sand in the sand storage bunker into the core box at high speed. The total elapsed shooting time was set to 1 second and the shooting pressure to 4 bar (400 kPa). All specimens were purged with heated air at 120°C for 120 seconds. The temperature of the core box was set to 140°C.

[0050] The flexural strength of the samples was measured using a Tinius Olsen H5K-T strength tester computer controlled with Q-mat software for a three-point bending test, and the results are graphed in Figure 2. The lowest strength was obtained using carbon black as the breakdown agent, ranging from 50 to 60 N / cm 2 These cores were very brittle.

[0051] [Table 1]

[0052] a Values ​​in bold are wt% relative to the weight of the particles; b The values ​​for the individual compounds listed below are wt% based on the weight of the total binder; c Values ​​for individual compounds listed below are wt% based on the weight of the total additive; 1 Sodium silicate M23NL (BASF, Monheim, Germany) 2 DSK40 (sodium 2-ethylhexyl sulfate), 0.5% (anionic surfactant, Brenntag, Enschede, The Netherlands) 3 H10 - Microsit H10 fly ash (BauMineral GmbH, Herten, Germany) 4 Graphite FP70 / 75 (IMCD Benelux BV, Rotterdam, The Netherlands) 5 Amorphous Graphite (Grafitbergbau Kaiserberg, St. Stefan ob Loeben, Austria) 6 Coke Flour M (Muco Mucher & Enstipp GmbH, Essen, Germany) 7Petrol Coke Flour (Muco Mucher & Enstipp GmbH, Essen, Germany) 8 Carbon Black (IMCD Benelux BV, Rotterdam, Netherlands) 9 Silica Fume A (COFERMIN Chemicals GmbH & Co., Essen, Germany) 10 EFA Fuller HP, fly ash (Krahn Chemie, Zaandam, Netherlands)

[0053] Casting tests were carried out on the above cores using ductile cast iron with a pouring temperature of 1355°C. After the casting process, the core residues were removed and qualitatively measured. The results are given in Table 1 above. After the casting test, the cores containing carbon black were easiest to remove. Collapsibility was slightly reduced in Examples 4 and 6. The inner surfaces of the castings were examined. It was clear that no significant differences occurred between the inner surfaces in all cases. Also, the inner surfaces in all cases were relatively rough with sand particles adhering to the inner surfaces.

[0054] <Experiment 2 - Further iron investigation> Example 6 was selected for further development and improvement. Sand mixtures based on type H33 quartz sand were mixed with binders and additives in Table 2 below. Gilsonite would be considered an additive in the context of this invention, but for ease of comparison and to simplify the testing procedure, the Gilsonite content is listed separately in Table 2. The total additive content can be calculated by adding the additive concentration and the Gilsonite concentration, since both are reported in wt% relative to the weight of the granular refractory material.

[0055] Flowability measurements were performed as in Experiment 1 above. The results are graphed in Figure 3. It was found that all compositions flowed easily, with the lower the Gilsonite content, the higher the flowability. Cores were then produced under the same conditions as in Experiment 1 above and subjected to bending strength tests. The results are graphed in Figure 4. It was shown that the bending strength of the cores decreased almost linearly with increasing Gilsonite concentration. The sample weights of all bars were between 693g and 700g. This indicates that the Gilsonite content does not have a significant effect on the compression level.

[0056] Casting tests of ductile iron were carried out at 1380°C. The castings were then cooled to room temperature before removing the core residues. The results showed that cores with small amounts of Gilsonite (disintegrant) had improved disintegration properties compared to cores without Gilsonite, as shown in Table 2 below. The disintegration properties also improved with increasing Gilsonite concentration. Removal of the core residues revealed that higher levels of Gilsonite reduced sand adhesion, and observation of the internal casting surface revealed that higher levels of Gilsonite improved surface smoothness. For Gilsonite concentrations of 0.6 wt% and above, streaks formed on the castings. The higher the concentration, the higher the sensitivity of the streaks. After sandblasting, the internal surfaces of the castings associated with cores without Gilsonite were found to have a white, shiny appearance. This was not the case when Gilsonite was present, regardless of the concentration level.

[0057] [Table 2]

[0058] a Values ​​in bold are wt% relative to the weight of the particles; b The values ​​for the individual compounds listed below are wt% based on the weight of the total binder; c Values ​​for individual compounds listed below are wt% based on the weight of the total additive; 1Sodium silicate M23NL (BASF, Monheim, Germany) 2 DSK40 (sodium 2-ethylhexyl sulfate), 0.5% (anionic surfactant, Brenntag, Enschede, The Netherlands) 4 Graphite FP70 / 75 (IMCD Benelux BV, Rotterdam, The Netherlands) 9 Silica fume A (COFERMIN Chemicals GmbH & Co., Essen, Germany) 10 EFA Fuller HP, fly ash (Krahn Chemie, Zaandam, Netherlands) 11 Natural carbon-containing resin (American Gilsonite Company, Utah, USA)

[0059] The inventors have found that lustrous carbon formers (LCFs) are particularly desirable for use in iron casting. It is believed that at higher temperatures, a higher lustrous carbon former content in the overall composition is required to achieve the desired improvement in surface quality and reduce casting defects. This improvement is achieved by using a strong LCF without significantly affecting the flowability of the composition or the strength of the cores formed therefrom. While not wishing to be bound by theory, it is believed that while a higher content of a weak LCF may theoretically provide a similar improvement in casting quality with an equivalent lustrous carbon content, the reduced flowability and core strength will result in a reduced casting quality that negates the theoretical improvement. It is believed that the lustrous carbon former content in the composition can be carefully selected to achieve optimal casting conditions without affecting workability and core strength by using a mixture of LCFs, optionally including a blend of a strong LCF and a weak LCF.

[0060] <Experiment 3 - Non-ferrous casting composition> Tests were conducted to investigate the suitability of Lustrous Carbon Former for use in non-ferrous casting processes. A series of cores were prepared using sand and the compounds in Table 3 below.

[0061] [Table 3]

[0062] a Values ​​in bold are wt% relative to the weight of the particles; b The values ​​for the individual compounds listed below are wt% based on the weight of the total binder; c Values ​​for individual compounds listed below are wt% based on the weight of the total additive; 1 Sodium silicate M23NL (BASF, Monheim, Germany) 2 DSK40 (sodium 2-ethylhexyl sulfate), 0.5% (anionic surfactant, Brenntag, Enschede, The Netherlands) 4 Graphite FP70 / 75 (IMCD Benelux BV, Rotterdam, The Netherlands) 9 Silica fume A (COFERMIN Chemicals GmbH & Co., Essen, Germany) 10 EFA Fuller HP, fly ash (Krahn Chemie, Zaandam, Netherlands) 11 Natural carbon-containing resin (American Gilsonite Company, Utah, USA)

[0063] The flow properties were tested as in experiment 1. All compositions had very similar profiles and flowed easily with no obvious differences in flow properties. A series of bars were formed using the compositions, compacted, and tested for strength as per experiment 1. The graphed results are shown in Figure 5. It was found that the presence of small amounts of tricalcium phosphate resulted in a significant reduction in flexural strength, while low concentrations of Gilsonite had little effect on strength values.

[0064] Cores made from the compositions in Table 3 were tested by trial casting in aluminum at a pouring temperature of 745°C. At high magnification, small gas defects were observed on the interior surface of the aluminum casting in Examples 15 and 16, which contained small amounts of Gilsonite. However, severe deformation occurred in the aluminum casting in Examples 15 and 16, with greater deformation observed with the higher concentrations of Gilsonite. The use of Gilsonite in aluminum casting was not considered to be beneficial.

[0065] [Table 4]

[0066] a Values ​​in bold are wt% relative to the weight of the particles; b The values ​​for the individual compounds listed below are wt% based on the weight of the total binder; c Values ​​for individual compounds listed below are wt% based on the weight of the total additive; 2 DSK40 (sodium 2-ethylhexyl sulfate), 0.5% (anionic surfactant, Brenntag, Enschede, The Netherlands) 4 Graphite FP70 / 75 (IMCD Benelux BV, Rotterdam, The Netherlands) 9 Silica fume A (COFERMIN Chemicals GmbH & Co., Essen, Germany) 12Sodium silicate aqueous solution Crystal 0230 (PQ Corporation, Eijsden, The Netherlands) 13 Sodium silicate aqueous solution ZSE874 (PQ Corporation, Eijsden, The Netherlands) 14 Kasil 1841 (PQ Corporation, Eijsden, The Netherlands) 15 Cerabeads AFS 200 (Ziegler & Co. Wunsiedel, Germany) 17 Classified coal GC-190 (James Durrance Sons Ltd, UK) 18 Classified coal GC-145 (James Durrance Sons Ltd, UK)

[0067] A series of cores for use with a permanent die in aluminum casting were prepared according to Table 4. The cores were trial cast and tested using aluminum at a pouring temperature of about 730°C. After solidification with the permanent die, the castings were stored in a preheated furnace at 500°C for 30 minutes. After solidification, core example 17 (no lustrous carbon former: classified coal) showed more sand adhesion. The use of classified coal-145 improved the surface quality compared to classified coal-190.

[0068] Without wishing to be bound by theory, it is believed that lustrous carbon formers such as Gilsonite are too tough to be effective for non-ferrous and / or low temperature casting applications.

[0069] <Experiment 4 - Study on Lastrass Carbon Former> Thermogravimetric analysis was performed on four Lustrous carbon formers: Gilsonite, Graded Coal-190, Superfine Graded Coal-240, and Coal Sand. The analyses were performed from 20 to 1000°C at a rate of 10°C / min, except for Gilsonite, which was tested at a rate of 5°C / min. As shown in Figure 6, all four Lustrous carbon formers began to lose mass at approximately 400°C, with the Gilsonite sample losing mass more rapidly than the other three Lustrous carbon formers.

[0070] Table 5 lists the Lustrous carbon formers and their typical Lustrous carbon content.

[0071] [Table 5]

[0072] While not wishing to be bound by theory, the inventors believe that the rate at which the lustrous carbon former is able to volatilize under casting conditions significantly impacts the activity of the lustrous carbon former (LCF) in reducing surface defects in the casting. At lower temperatures, such as aluminum and other non-ferrous casting processes, weak lustrous carbon formers have been found to be surprisingly effective. At higher temperatures, such as those found in ferrous casting processes, the use of strong lustrous carbon formers has been found to be surprisingly effective. As used herein, the terms "strong" and "weak" reflect both the volatility of the LCF and the overall content of lustrous carbon in the additive. Experiments with alternative carbon sources, such as graphite, have been found to be much less effective than LCF. The most effective LCF for a particular casting process is a trade-off between the strength of the LCF effect, the pouring temperature of the casting, and the desire to minimize loss of core strength with LCF addition rate.

[0073] <Experiment 6 Casting mold composition and core manufacturing> Various cores were produced under the following conditions: Sand, liquid binder and additives as shown in Table 6a below were mixed using a commercial batch mixer (Hobart) with a batch size of 20 liters. The additives and liquid binder were added in parallel with a mixing time of 2 x 1 minute.

[0074] [Table 6a]

[0075] a Values ​​in bold are wt% relative to the weight of the particles; b The values ​​for the individual compounds listed below are wt% based on the weight of the total binder; c Values ​​for individual compounds listed below are wt% based on the weight of the total additive; 2 DSK40 (sodium 2-ethylhexyl sulfate), 0.5% (anionic surfactant, Brenntag, Enschede, The Netherlands) 11 Natural carbon-containing resin (American Gilsonite Company, Utah, USA) 12 Sodium silicate aqueous solution Crystal 0230 (PQ Corporation, Eijsden, The Netherlands) 13 Sodium silicate aqueous solution ZSE874 (PQ Corporation, Eijsden, The Netherlands) 14 Kasil 1841 (PQ Corporation, Eijsden, The Netherlands) 15 Cerabead AFS 200 (Ziegler & Co. Wunsiedel, Germany) 17 Classified coal GC-190 (James Durrance Sons Ltd, UK) 19 Silicon-based organic water repellent (Wacker Chemie AG, Stuttgart, Germany) 20Fused silica 325 (Imerys Fused Minerals Greeneville Inc., Greeneville, USA) 21 Pozzolanic filler - aluminum silicate (Stauss-Perlite GmbH, Poelten, Austria) 22 QQS 26 (D50 particle size 0.26 mm) (Wolff und Muller Quarzsande GmbH, Germany); 23 F32 (D50 particle size 0.24 mm) (Quarzwerke GmbH, Frechen, Germany); 24 HB32 (D50 particle size 0.30 mm) (Quarzwerke GmbH, Frechen, Germany);

[0076] The mixture was introduced into a core shooter as shown in Table 6b below and cores were produced under the conditions as shown in the table.

[0077] Example 21 - The cores were stored for 24 hours at 20°C and 40% relative humidity and then strength tested. When measured according to experiment 1 above, the cores had a strength of about 400 N / cm 2 The alloy AlSi7Cu4Mg 0.5 The casting test pieces were cast using the same method. The pouring temperature was 760°C, and the total amount of aluminum was 39 kg for each casting test. The inner surface of the casting test piece was clean with no sand attached. No coating was applied to the core.

[0078] [Table 6b]

[0079] Example 22 - The cores were stored for 1 hour at 20°C and 50% relative humidity and then strength tested. When measured according to experiment 1 above, the cores had a strength of 350 N / cm 2The cores had a hot strength of 10 ...

[0080] Example 23 - The core was stored for 24 hours at 20°C and 50% relative humidity and then subjected to a strength test. The strength of the core measured according to experiment 1 was 500 N / cm 2 No coating was applied to the cores. Trial castings were carried out using cast iron GJS600. The pouring temperature was 1450°C and the total amount of alloy was 160 kg for each trial casting. With the cores produced as above, a smooth and sand-free surface of the test differential housing was achieved.

Claims

1. In a composition for making cores used in metal casting processes, granular refractory material, 0.5 to 5 wt% of an inorganic binder containing one or more of sodium silicate, potassium silicate, lithium silicate, or a combination thereof, 0.1 wt% to 2 wt% of a pozzolan additive containing one or more of silica fume, fused silica, calcined silica, and microsilica, 0.1 to 1.5 wt% of a lastra carbon former, comprising, wherein the above weight percentages are based on the weight of the granular refractory material, the composition.

2. For making cores used in iron-based metal casting processes, and the lastra carbon former is a strong lastra carbon former, the composition according to Claim 1.

3. The strong lastra carbon former comprises one or more of asphalt, hydrocarbon resin, polystyrene, and gilsonite, the composition according to Claim 2.

4. The strong lastra carbon former has a lastra carbon content of at least 15%, the composition according to Claim 2 or Claim 3.

5. For making cores used in non-ferrous metal casting processes, and the lastra carbon former is a weak lastra carbon former, the composition according to Claim 1.

6. The weak lastra carbon former comprises one or more of sized coal, carbon dust, and sea coal, the composition according to Claim 5.

7. The weak lastra carbon former has a lastra carbon content of less than 15%, the composition according to Claim 5 or Claim 6.

8. The granular refractory material comprises sand, the composition according to any one of Claims 1, 2, 3, 5, and 6.

9. A core formed from the composition according to any one of Claims 1, 2, 3, 5, and 6.

10. In a method for manufacturing a metal product by metal casting, (i) mixing the composition according to any one of Claims 1, 2, 3, 5, and 6 to make a mixture, (ii) molding and curing the mixture to produce a core in the shape of the internal cavity of the metal product, (iii) combining the core with a mold for metal casting so that the mold and the core together define a mold cavity. (iv) a step of supplying molten metal to the mold cavity until the mold cavity is filled; (v) a step of cooling and solidifying the molten metal to form the metal product; A method comprising the steps of:

11. The method according to claim 10 for producing an iron-based metal product by iron-based metal casting, wherein step (i) includes mixing the composition according to claim 2 or 3, and step (iv) is performed at a temperature of at least 1000°C.

12. The method according to claim 10 for producing a non-ferrous metal product by non-ferrous metal casting, wherein step (i) includes mixing the composition according to claim 5 or 6, and step (iv) is performed at a temperature of less than 1200°C.

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