TW200418599A - Method of improving the removal of investment casting shells - Google Patents

Abstract

The removal of an investment casting shell surrounding a metallic part is improved by adding a salt of alkali or alkaline earth metal to at least one of the layers of the shell.

Description

200418599 (1) Description of the invention: I: Technical field to which the invention belongs 3 Field of the invention The present invention relates generally to investment casting, and more particularly to a method for improving the removal of a mold casting shell. [Prior art] Background of the invention

Investment casting, also known as dewaxing casting, demolding casting, and precision casting, is used to make high-quality metal products that meet fairly narrow dimensional tolerances. Basically, an investment casting is made by first forming a thin-walled ceramic mold. This model is commonly known as an investment casting shell, which can be introduced by a molten metal.

The shell system is generally first constructed by making a replica or a model, which is made from a substrate to which a metal object is suitable to be melted and cast by an investment mold 15. Suitable suitable substrates for melting may include, for example, wax, polystyrene or plastic. A ceramic shell is then formed around the model. This can be done by soaking the model in a slurry containing a mixture of a liquid high melting point binder, such as colloidal silicon dioxide or ethyl silicate, plus 20 high melting point powders, such as quartz, Fused silica, hammerstone, alumina, or aluminosilicate, and then sieved the dried high melting point particles on top of the new immersion model. The most commonly used dry, high-melting-point particles include quartz, fused silica, hammer stone, alumina, and sulfite. The steps of immersing the model in a high melting point slurry and then sieving the dried high melting point 5 200418599 particles on the new immersion model can be repeated until the desired thickness of the shell is achieved. However, before the subsequent coating is applied, it is better if the coating system of the mud and the high melting point particles is dried by air each time. The shell is increased to a thickness ranging from about 1/8 to about 1/2 inch (about 0.31 cm to about 5.27 cm). After final soaking and sieving, the shell is thoroughly air-dried. The shell manufactured by this procedure is called a "marble plaster" shell because of the structure of the surface of the shell.

The shell is then heated at least to a melting point suitable for melting the substrate. At this step, the model is melted away, and the only thing left is the shell and a few remaining suitable substrates for melting. The shell is then heated to a high temperature, which is sufficient to evaporate any remaining suitable molten substrate from the shell. The shell is usually filled with molten metal before the shell is cooled from this high temperature heating. Various methods have been used to guide molten metal into the shell, including gravity, pressure, vacuum, and centrifugation. When the molten metal in the casting mold has been fully solidified and cooled, the casting is removable from the shell.

During its manufacture, investment casting molds need to withstand a large amount of mechanical stress and stress caused by drying. The ceramic case is designed to have high wet strength (high air dry strength) to prevent damage during the forming process of the case. Once the desired mold thickness is complete, the mold is dewatered and preheated to 20 to about 1800 ° F. At this temperature, the mold can be removed from the high temperature furnace and immediately filled with liquid (fused) metal. When the metal is solidified (or in a plastic state), if the mold is deformed, the size of the casting may exceed specifications. To prevent high temperature deformation of the mold, the mold system is designed to have a strong thermal strength. Once the casting is solidified and cooled, the low fire resistance is 6 to make it easy to knock out or remove the ceramic mold. Most of the dazzling model scales contain a large amount of stone dioxide. The silica is made of -amorphous (glassy) material. Liquefied lithotripsy is the most commonly called modeling material. When amorphous dioxygen is exposed to more than about 18GG. At high temperatures, trioxin will devitrify (crystallize) and form U silica. The wollastonite system has a low temperature form ("state") and a high temperature form (heart). The _state form system is close to the specific gravity of the amorphous dioxide, so that the size of the cast plate is maintained fixed, and the phase conversion The generated stress is reduced to a minimum. While cooling, the 1-state stone will change to a fine state. This phase transition will be accompanied by a volume change of about 4%, which will cause several cracks in the shell, making the mold easy to move. In addition, the Shiroishi Yuki system reduces the fire resistance of silicon dioxide contained in the casting mold of dazzle casting. Although the investment casting system is known and used for thousands of years, the investment casting market continues to grow, such as Increasing requirements for more complex and delicate structures. Because of the great demand for high quality, that is, precision casting, it is still necessary to develop a new method to produce more efficient, cost-effective, and defect-free solution casting. For example, if the strength of the shell is only maintained to the solidification point of the metal, and then when the shell cools, the strength will decrease. Therefore, through the improved knockout metal (removal of the shell), on The improvement system can be understood. The present invention is particularly satisfactory for investment casting systems that do not contain iron alloys, such as aluminum, copper, and magnesium alloys, because the melting temperature and casting temperature are not sufficient to promote white The formation of silica and the promotion of easy knockout of metal. 200418599 During the cooling of the metal part, compression occurs; compared to the ceramic shell, the metal part usually has a higher thermal expansion coefficient. When the metal part It is particularly difficult to knock out the metal part when it causes a blind hole or a small depression in the ceramic under compression. This phenomenon is especially aggravated in iron-free casting, 5 because of the high thermal expansion coefficient of such metals (> 1.8 X l (T6m / m).

The iron-free casting system made by investment casting is more fragile. Therefore, the iron-free casting system is more fragile than the aggressive shot peening and vibration cleaning methods used for steel and high-temperature alloy casting. Clean the surface with water or sandblasting. Residual ceramics on iron and steel castings are dissolved and removed using concentrated acid and alkali or molten salts. Chemical incompatibility precludes the use of aluminum and magnesium by this casting. If an adhesive system develops: when exposed to or below 1800 ° F, it has low fire resistance and is easy to knock out, the cleaning system of aluminum castings can be greatly improved. Therefore, it is desirable to provide a removal method of an investment casting housing that surrounds a metal portion.

[Summary of the Invention] Summary of the Invention The method of the present invention is called: a method of adding an alkali metal salt or an alkaline earth metal salt to at least one layer of an investment casting shell. The addition of an alkali metal salt or an alkaline earth metal 20 salt effectively improves the removal of the investment casting shell surrounding a metal part. Brief Description of the Drawings MI: Detailed description of the preferred embodiment of Embodiment 3 8 200418599 The present invention is applied to a method for improving the removal of an investment casting casing surrounding a metal part. According to the present invention, an alkali metal salt or an alkaline earth metal salt is added to at least one layer of the investment casting shell. 5 The alkali metal salt or alkaline earth metal salt that can be used in the practice of the present invention

The system includes carbonic acid # 5, sulfuric acid # 5, carbonic acid feed town, carbonic acid town, thorium sulfate, thorium carbonate and mixtures thereof. A preferred salt system for improving the alkali metal salt or alkaline earth metal salt of an investment-cast casing from a metal portion is calcium carbonate. The alkali metal salt or alkaline earth metal salt can be added to at least one layer of the investment casting shell by any conventional method known to those skilled in the art. In a preferred embodiment, the metal test salt or earth test metal salt is added to at least one layer of high melting point marl. However, in the practice of the present invention, the alkali metal salt or alkaline earth metal salt can be selectively added to at least one layer of the high melting point mud, or at least one of the high melting point mud and the high melting point mud.

The metal test salt or earth test metal salt is used at a concentration which will effectively improve the removal of the investment casting shell surrounding a metal part. The amount of the alkali metal salt or alkaline earth metal salt added to at least one layer of the shell is preferably in a range of about 1% to about 30% by weight of the shell. The amount of the alkali metal salt or alkaline earth metal salt is more preferably about 5% to about 25%, and most preferably about 8% to about 20%. The inventor of the present invention has discovered that adding the alkali metal salt or alkaline earth metal salt to at least one layer of an investment casting casing will effectively improve the removal of the investment casting casing surrounding a metal portion. 9 ^ 418599 Examples The following examples are intended to illustrate the invention and teach those skilled in the art how to make and use the invention. These illustrations are not intended to limit the invention or to limit the invention in any way. Example 1: CaC03 is mixed with high melting point mud. Use the following formula to prepare: Table 1-Mud ingredients' Concentration (ratio) ^ Colloidal silica 2 1920 g ~ ^ Deionized water 386 ¾ ^ Latrix㊣6305 polymer 2 3 4 138 g — '^ Nalcoat⑧Pl (-200 mesh) fused silica 3 1200 g ~~ Nalcoat®pi (-i2〇 mesh) fused silica 4 3600 g— ~ Nalcoat® 8815 anionic wetting agent 5 1.0 g Dow Corning⑧ Y-30 Antifoaming agent 6 " 4.0 g no impurities CaC 03 Marblemite® 7 0 g_, 288 g (6%) 7 ~ 576 g (12%), 864 g (18 %), 1200 grams (25%) of raw CaC03 40-2008 480 grams (10%), 960 grams (20%) 7 1680 grams (30%) After 72 hours of mixing, the viscosity of the slurry is No. 4 viscosity Cup

10 measurement and adjustment. The viscosity ranges from 14 to 18 seconds. A small amount of binder additives (colloidal silica + water + polymer) is used to obtain the desired rheological properties. 10 1

NalCoag (R) 1130 (8 nm, steady state sodium) (available from Ondeo Nalco) 2 Styrene butadiene emulsion at 10% based on dilute colloidal silica (available from Ondeo Nak〇) 3 Available Available from Ondeo Nalco 4 Available from Ondeo Nalco 5 70% dioctyl sulfosuccinate sodium salt (available from Ondeo Nak〇) 6 Shixiu resin latex (available from Central Michigan, USA) (D〇wC〇mingC〇rp〇rati〇n) 7 artificial marble compared to (available from imerysC〇rp〇rati〇n, Razwei, Georgia, USA) 8 8 screening grade carbon 酉 ㈣ (available From Imerys Corporat, Razville, Georgia, USA) 200418599 Once the adjustment is complete, the mud system is ready to be soaked.

The wax model was cleaned and named using Nalco® 6270 model cleaner (available from Ondeo Nalco) and then washed with water. The ribbon was immersed in each mud, and then (applied by rainfall) Nalcast® S1 and S2 5 fused silica marl (available from Ondeo Nalco) in each mud. The drying time is initially 5 hours, and when the coating is added, the drying time is increased to 3.5 hours. The final housing has two layers of Nalcast® S1 marl coating, three layers of Nalcast® S2 marl coating, plus a sealing coating (no marl). All coatings are from 73-75. F, 35% to 45% relative humidity and 10 200-300 feet per minute of air drying. After a 24-hour final drying, the shell was placed in a dryer and dried for an additional 24 hours before testing. Several kinds of shell properties were measured using a fracture coefficient (MoR) strip, which was prepared from the experimental mud. The fracture coefficient bar was fractured by a three-point bending jig on an ATS universal material testing machine (available from Butler Applied Test Systems, Inc., USA). The analog output (voltage) is input to a personal computer. The computer includes an analog-digital conversion panel and data acquisition software. The data is stored as a / load-time diagram or as a load-displacement diagram. The calculation and analysis system 20 is performed by using data acquisition software or a spreadsheet program. The following physical properties are defined by MoR samples. Fracture Load This is the maximum load that the test sample can support. The higher the load, the stronger the test sample. The load can be affected by the thickness of the shell, mud and shell composition. This property is important for predicting shell fracture and related casting disadvantages. The rupture load is measured on the test sample in a wet state (air-dried state), a heat-resistant state (constant temperature at 1800 ° F for one hour and cooled to room temperature), and a heated state (fracture at 1800 F constant temperature for one hour and breaks). 5 And records. The results are normalized and expressed as corrected fracture load (AFL). For a 2 inch test length, the AFL is simply the value of the breaking load divided by the sample width. i · Shell Thickness The thickness of the shell is affected by the mud and shell, and the process of shaping the shell. Thickness variation indicates process instability. During drying, de-soiling, preheating and casting, inconsistent shell thickness will cause stress in the shell. Severe conditions will cause the mold to fail. The mold surrounds and isolates the cooling metal. The change of thickness can affect the microstructure, shrinkage, filling rate and solidification rate of the casting. U. Modulus of Rupture (MoR) —Flat-bottom ceramic plates are prepared using a rectangular wax strip as a model. / The size of the model is 1 X 8 X 1/4 inches. The wax strip is cast using the desired shell system. After drying, the edges were removed by a belt sander. The two remaining flat pans were separated from the wax strip to obtain two test 20 samples. The sample was broken by a three-point load on an ATS universal material testing machine. The coefficient of rupture (MoR) is used to predict wax bars in wet, heat-resistant and heated states. , ...

MoR = 3PL / 2bh2 where the breaking load (lbs) 12 200418599 L = (between the supports) sample length (inches) b 2 sample width at the break point (inches) sample thickness at the break point (inches) )

This MoR value is the fracture stress. This stress is affected by the fracture load and the size of the sample 5. Since the stress is inversely proportional to the square of the shell thickness, the shell thickness is particularly important. The uneven nature of the shell surface makes its dimensions difficult to accurately measure, which results in a wide range of standard deviations. This disadvantage can be overcome by destroying and measuring a sufficient amount of test sample. iii. Bending or Deflection 10 When a load is applied to a test sample, the test sample is bent. When the sample was broken, the maximum amount of deflection was recorded. The amount of bending increases with increasing elasticity and polymer concentration. An elastic shell has the ability to resist the expansion and contraction of a wax model during the shell molding process. The amount of bending is measured for the wet condition. 15 iv · Fracture Index

The fracture index is the amount of work or energy required to fracture a shell in a wet state. The fracture index is expressed as the "toughness" of the shell, in other words, the higher the index, the stronger the material is. For example, a polypropylene bottle is "tougher" than a glass bottle and therefore has a higher fracture index. The 20 index is expressed as rupture resistance. Compared with low-index systems, high-index shell systems require more energy to destroy them. The fracture index is affected by the composition of mud and shell. The polymer additive system increases this index. Compared to hard polymers, soft polymers have a higher fracture index. This index is directly proportional to the elasticity of the shell. A shell with a variability of 13 200418599 can absorb more energy than a firm, fragile shell. The fracture index is the area under the load / displacement curve for a MoR test sample, defined by integrals. When monitoring displacement, the index is measured as (force) x (distance), or when monitoring the load time, the index is measured as (force) X (time). This load ratio is used to convert (force) X (time) to (force) X (distance). For a 2 inch test length, the test results are normalized only by the index value divided by the sample width. ν · Modulus of Elasticity (MoE)

The coefficient of elasticity, also known as Young's coefficient, MoE or elastic coefficient (elastie 10 m0dulus) ', is a proportional constant derived from the stress-strain curve. This coefficient can be measured from MoR (bending) analysis. The coefficient of elasticity is a measure of the stiffness of a material. A stiff, rigid material will exhibit a strain / stress curve with a steep slope and high MoE. A soft, elastic material will present a strain / stress curve with a gentle slope and low MoE. The 15 coefficient of elasticity is independent of the sample size. Used to compare different housing systems, this coefficient of elasticity provides an accurate method.

As shown in Table 2 below, the fire resistance decreases as the amount of non-impurity cac03 or unprocessed CaC03 in the shell increases. The best system is achieved by adding 10-20% of unprocessed CaCCb, which shows a decrease of about 30% in the refractory MoR 20 with minimal impact on the wet properties of the shell. Table 2 List of wet properties data CaC03% MoR (lbs / in2) [~ AFL (lbs) MoE (crushed / in2) No impurities BSBSis 1 0% 1 556.73 1 9 ^ 02 381 Breaking index 26.43 Bending amount (Mill) 4.77 14 6% 448.06 8.20 231 28.72 5.46 12% 406.47 7.96 228 28.11 5.03 18% 353.20 7.51 185 26.25 5.29 30% 261.82 6.26 115 23.59 5.75 Unemployed 10% 588.83 8.29 346 31.26 5.44 20% 482.67 9.00 253 31.57 5.37 30% 385.94 9.46 186 34.70 5.33 200418599 Thermal resistance data list No impurities CaC03% MoR (lbs / inch2) AFL (lbs) 0% 1016.82 15.33 6% 804.23 14.82 12% 651.27 12.59 18% 504.93 11.54 25% 397.56 9.05 Raw CaC 03% 10% 752.87 13.91 20% 738.12 15.11 30% 530.53 11.87 Example 2: CaC03 slurry added with a separate dry high-melting point (marble) coating is prepared using the following formula ... 3 Table Mud Ingredient Concentration (Proportion) 1920 g of colloidal silica, deionized water, 401 g of TX-11280 polymer, 138 g of Nalcoat⑧Pl (-200 mesh) fused silica, 1200 g of Nalcoat⑧Pl (-120 mesh), fused Silica 3600 g Nalcoat® 8815 Anionic Cushioning Agent 2.2 g Dow Corning® Y-30 Antifoaming Agent 4.0 g During the shell preparation process, another CaC03 and SiO2 plaster layers were used as follows: Gray layer, gray layer, gray layer, gray layer # # 1 # 2 # 3 # 4. # 5 15 200418599 1 S1 S1 S2 S2 'S2 2 S1 S1 CaCO Plant S2 ~~ ^ S2 3 S1 S1 CaC03 50/50 S2 + C ^ COT S2 4 S1 S1 CaC〇3 CaC03 ^ S2 CaC03 5 S1 S1 CaC03 CaC03 ~ This case test method is the same. As shown in Table 4 below, the addition of CaC03 in the marl layer reduces the shell strength, but does not include the wet strength. The best result was obtained: a CaC03 marl layer system showed a 35% decrease in fire resistance and had the least effect on thermal strength. The results of the wet property MOR, heating property MoR, and heat resistance MoR of whether the shell has a CaC03 marl coating are as follows: Table 4 List of wet properties data Formula # MoR (碎 / Inches 2) AFL (pounds) MoE (inhibits / inches 2) Bending index break (mils) 1 434.51 9.38 175 39.17 6.42 2 470.52 7.11 238 1 28.64 6.30 3 504.09 5.95 294 23.10 6.53 4 473.57 284 22.07 6.34 5 455.91 1 4.40 292 18.92 6.18 List of heating and heat resistance data Formula # Heating property MoR (lb / inch! 12 ^ Heat resistance MoR (lb / inch2) Heating property AFL (lb) Heat resistance AFL (lb) 1 1204Ji_ ^ 707.82 19.80 14.36 2 1023,11 ^ —1 ^ 12 13.14 7.40 3 619.8l __- 377.00 9.05 4.96 4 700.56 ^^-__25434 7.57 3.09 5 518.13 ^^ __13JL40 4.65 1.38 10 Example 3: CaC〇3 and dry high-dazzling point mud The mixed mud system was prepared using the following formula: Di 5 Table I Concentration (than μ! 9 Screening Grade Calcium Carbonate (ImerysCorporation from Razway, Georgia, USA) 16 200418599 Colloidal Silicon Dioxide 1920 Gram deionized water 401 g T X-11280 polymer 138 g Nalcoat⑧Pl (-200 mesh) fused silica 1200 g Nalcoat⑧P1 (-120 mesh) fused silica 3600 g Nalcoat® 8815 anionic wetting agent 2.2 g Dow Corning® Y-30 Antifoam During the shell preparation process, 4.0 g of agent was used as the plaster coating as the following mixture of CaC03 and Si02: Formula # 泥灰 层 # 1 泥灰 层 # 2 泥灰 层 # 3 泥灰 层 # 4 # 5 1 S1 S1 S2 S2 S2 2 S1 S1 S2 + 5% CaC0310 S2 + 5% CaC03 S2 + 5% CaC03 3 S1 S1 S2 + 10% CaCO3 S2 + 10% CaCO3 S2 + 10% CaCO3 4 S1 S1 S2 + 20 % CaCO3 S2 + 20% CaCO3 S2 + 20% CaCO3 5 S1 S1 S2 + 30% CaCO3 S2 + 30% CaCO3 S2 + 30% CaCO3 —The erosion test was added in order to fully express the advantages of adding CaC03. 'This advantage is reflected in the shell The physical knockout is qualitative. This new technology system 5 is just a sandblasting process that imitates the industrial use. Shell test scale

The length, width is 0.75 "to 1.5", and the thickness is 0.4 ". The test piece is placed on a fixture located on one wall of the sand blasting test box. A spring blade is attached to a 0.5 Stainless steel cover with X 0.5 "window to hold the test piece. The hood ensures that the test strips from the sample to the next sample are exposed to the same surface area and that a homogeneous blasting medium flows through the surface. The thickness of the test piece was measured before the test. The test piece is exposed to the blasting medium until the test piece is penetrated. The penetration time is measured and the erosion rate is calculated for each sample. The test is repeated on a representative number of test strips to allow precise definition of the erosion rate. As shown in Table 6 below, the addition of CaC03 and SiOAl in this marl layer reduces the strength of the refractory shell, but does not include wet strength. The best result is that 10% to 20% of CaC03 added to the marl layer system shows a 20% to 40% reduction in fire resistance and has minimal effect on thermal strength. The erosion rate data shows that a CaC03 shell containing 8% and 10% will increase the erosion rate 5 times after cooling for 24 and 48 hours. The test system for the wet properties MoR, heating properties MoR, heat resistance properties MoR and erosion of the CaC03 marl coating is as follows: Table 6 List of wet properties data

CaC03% MoR (pounds / inch 2) AFL (pounds) MoE (pounds / inch 2) Fracture Index Bending Amount (mils) 0 564.40 9.44 268 38.38 6.32 5 566.48 9.11 306 33.16 5.78 10 580.84 8.64 305 32.67 6.02 20 577.19 8.64 305 32.67 6.02 30 559.01 6.71 355 24.90 5.62 10 List of heating and heat resistance data% CaC03 Heating properties MoR (lbs / in2) Financial properties MoR (lbs / in2) Heating properties AFL (lbs) Heat resistance AFL (Lbs) 0 1326.26 932.15 19.28 16.22 5 1127.35 809.54 15.44 11.94 10 923.31 729.07 15.44 11.14 20 723.13 558.85 9.75 6.54 30 793.39 496.62 7.81 5.59 CaC03 Cooling for 2 hours (mil / second) Cooling for 24 hours (mil / second) / S) Cooling for 48 hours (mils / s) 0 4.89 4.40 4.79 2 4.51 5.13 6.38 4 4.37 10.74 9.64 6 4.46 10.71 14.71 8 4.34 14.70 25.10 10 4.23 10.58 24.28 Screening Grade Carbonate Office (available from Razwell, Georgia, USA) Imerys Corporation) 18 200418599 Although the present invention is described above with regard to preferred embodiments or illustrative embodiments, these embodiments are not To contain the entire invention or to limit the invention. Rather, the present invention is intended to include all alternatives, modified 5 types, or types equivalent to the spirit or scope defined by the scope of additional patent applications. Brief description of L scheme 3 None [Representative symbols for main elements of the scheme] None

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Claims (1)

Scope of patent application: 1. A method to improve the removal of cast-shells surrounding metal parts-where the shell counties are deposited on the intersection of high-mud mud and H-point marl -Made on top of the model, the method comprises the step of adding a 5 effective amount of metal test salt or alkaline earth metal salt to at least one layer of the shell. 2. The method of applying for item 丨 of the patent, wherein the alkali metal salt or soil-free metal salt is selected from the group consisting of carbonic acid, thiosulfan, carbonic acid, magnesium carbonate, magnesium sulfate, gill carbonate, and mixtures thereof. . 10. The method as described in item 1 of the patent application, wherein the metal test or soil test metal-free salt is carbonic acid. 4. If the method is the oldest in the scope of patent application, wherein the metal test salt or soil test metal salt is added to at least one layer of the high melting point marl. 5. As the oldest method in the scope of patent application, wherein the metal test salt or the Group 15 metal salt test is added to at least one layer of the high melting point mud. 6. The method according to the first scope of the patent application, wherein the domain inspection salt or soil inspection metal salt is added to at least one layer of the pure point mud and at least one layer of the high melting point mud. 7. The method of claim 1 in the patent application, wherein the metal test salt or soil test group 20 metal salt is added to the shell in an amount of about 1 to about 30 weight percent of the shell. At least one level. 8. The method according to item 丨 of the patent application, wherein the neometallic salt or the test metal salt is added to at least one layer of the shell in an amount of about 5 to about 25 weight percent of the shell. 20 200418599 9. The method of claim 1 in which the alkali metal salt or alkaline earth metal salt is added to at least one layer of the shell in an amount of about 8 to about 20 weight percent of the shell . 10. A method for improving the removal of an investment casting shell surrounding a metal part, wherein the shell is formed by depositing an alternating layer of a high melting point mud and a high melting point mud on a mold The method is made by adding calcium carbonate to at least one layer of the shell in an amount of about 8 to about 20 weight percent of the shell. 10 21 200418599 (1) Designated representative map: (1) The designated representative map in this case is: (). (II) Brief description of the component representative symbols of this representative map: (none) 捌 If there is a chemical formula in this case, please disclose the chemical formula that can best show the characteristics of the invention: (none)