Method for determining cast formability of magnesium alloy and determination mold

Abstract

The application provides a magnesium alloy cast forming property determination method and a determination mold shell, and solves the technical problem that an accurate determination method for the cast forming property of a magnesium alloy thin-wall casting is still in the blank of the magnesium alloy cast forming technical field, which comprises the following steps: pouring magnesium alloy liquid from a sprue into a mold shell, using the static pressure difference of the magnesium alloy liquid to make the casting fill, after the magnesium alloy liquid solidifies, measuring and calculating the height difference between the sprue and the casting in the rectangular cavity to determine the magnesium alloy cast forming property; the mold shell is provided with a sprue, a rectangular cavity and a bottom runner connecting the two, and the three form a U-shaped structure, and the rectangular cavity is connected with the atmosphere. The application can be widely applied in the magnesium alloy cast forming technical field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnesium alloy casting forming, in particular to a magnesium alloy casting forming property determination method and determination mold shell. BACKGROUND

[0002] The alloy must have good formability during casting to ensure the complete formation of the casting, therefore, formability is one of the most important indicators for measuring the casting performance of magnesium alloy. For cast magnesium alloy, the formability is usually measured by fluidity, which is an intrinsic physical property of the metal liquid. The fluidity of the liquid alloy during casting is related to many factors, including superheat, temperature gradient, latent heat, grain refinement, alloy chemical composition and solidification type. Another definition of fluidity is the inverse of viscosity, but research shows that the fluidity of the alloy has little to do with the viscosity of the liquid, but has more to do with the viscosity of the mixture of crystal suspensions and melt. The flow length of the metal liquid is determined by the early stage of solidification. Flemings et al. believe that the mechanism of fluid stop will change with the change of the solidification mode, the solidification of the metal liquid during the flow process has a smooth and dense growth front, and the center flow channel continuously becomes thinner during the flow process, when the dendrite growth front connects at a certain moment and blocks the flow path, the flow tip will stop, and the alloy stops flowing. As can be seen, the fluidity of the alloy is restricted by many factors, and cannot reflect the intrinsic formability of the alloy.

[0003] In recent years, magnesium alloy has been widely used in various fields of thin-walled castings. The rapid cooling of the thin-walled section of the casting reduces the fluidity of the metal liquid, resulting in the generation of various defects such as underfilling and shrinkage. Formability greatly affects the forming process of magnesium alloy. Therefore, how to measure the intrinsic formability of magnesium alloy is a prerequisite for obtaining high-quality thin-walled castings. At present, in the technical field of thin-walled castings, the determination method of magnesium alloy casting formability is still in the blank of the technical field of magnesium alloy casting formability. This technical problem needs to be solved urgently. SUMMARY

[0004] The purpose of the present application is to solve the above technical problems, and to provide a magnesium alloy casting formability determination method and determination mold shell, which realizes the determination of the intrinsic formability of magnesium alloy.

[0005] To this end, the present application provides a magnesium alloy casting formability determination method, which comprises:

[0006] The magnesium alloy liquid is poured from the sprue into the mold shell, the magnesium alloy liquid is poured into the rectangular cavity under the static pressure difference of the magnesium alloy liquid, and the height difference between the sprue and the casting in the rectangular cavity is measured and calculated after the magnesium alloy liquid is solidified, so as to determine the magnesium alloy casting formability; the mold shell is provided with a sprue, a rectangular cavity and a bottom gate connecting the two, which form a U-shaped structure, and the rectangular cavity is connected with the atmosphere.

[0007] Preferably, the bottom gate is communicated with the bottom of the rectangular cavity, and the height of the straight gate and the rectangular cavity is equal, and the top of the rectangular cavity is communicated with the atmosphere.

[0008] Preferably, the wax mold is provided with a straight gate wax mold, a bottom gate wax mold and a rectangular cavity wax mold, and the bottom gate wax mold is connected with the bottom of the straight gate wax mold and the rectangular cavity wax mold.

[0009] Preferably, the height of the straight gate wax mold and the rectangular cavity wax mold is equal.

[0010] Preferably, the height of the straight gate wax mold is 150-200 mm, and the diameter of the straight gate wax mold is 20-50 mm; the height of the rectangular cavity wax mold is equal to the height of the straight gate wax mold; the width of the rectangular cavity wax mold is equal to the diameter of the straight gate, and the thickness of the rectangular cavity wax mold is 0.5-2 mm; the length of the bottom gate is greater than the sum of the diameter of the straight gate and the width of the rectangular cavity wax mold, and the width of the bottom gate is greater than the diameter of the straight gate.

[0011] Preferably, the preparation method of the mold shell comprises: preparing a wax mold by injection molding process; performing multiple coating, sanding and drying operations on the wax mold with clean surface, and sintering after dewaxing to obtain the mold shell.

[0012] Preferably, the preparation method of the mold shell comprises: coating the surface layer and the back layer of the wax mold, wherein the surface layer coating is prepared by mixing corundum powder and silica sol with a powder-liquid mass ratio of 3.3-3.5:1 to ensure the smooth surface of the casting. The back layer coating is prepared by mixing corundum powder and silica sol with a powder-liquid mass ratio of 2.5-3.0:1 to bond the sanding material and ensure the strength of the mold shell. The corundum powder increases the viscosity of the coating and improves the coating hanging property to ensure the surface smoothness of the casting; the silica sol plays a role in bonding the ceramic powder and the sand.

[0013] Preferably, the preparation method of the mold shell comprises: the sanding material is corundum sand with a mesh size of 36-80.

[0014] Preferably, the preparation method of the mold shell comprises: the drying temperature is controlled at 23-35℃, and the drying relative humidity is controlled at 40-70%.

[0015] Preferably, the preparation method of the mold shell comprises: the dewaxing temperature is 160-180℃, the dewaxing pressure is 0.6-0.8 MPa, and the time is 10-30 seconds.

[0016] Preferably, the preparation method of the mold shell comprises: the sintering temperature is 850℃-1050℃, and the holding time is 2-6 hours.

[0017] Preferably, the method for preparing the mold shell comprises: coating, sanding and drying the wax mold respectively to form the first mold shell layer to the eighth mold shell layer on the surface of the wax mold from inside to outside, wherein: the first mold shell layer is a surface layer; the second mold shell layer is a surface layer slurry, and 80 mesh sand is sanded; the third mold shell layer is a back layer slurry, and 60 mesh sand is sanded; the fourth mold shell layer, the fifth mold shell layer, the sixth mold shell layer and the seventh mold shell layer are all back layer slurries, and 36 mesh sand is sanded; and the last eighth mold shell layer 48 is a surface layer coating, and sealing treatment is performed. The relative humidity of each mold shell layer is controlled at 40-70%, the drying temperature is controlled at 23-35 DEG C, and the drying time is controlled at 4-8 hours. The setting of the corundum sand mesh number in each mold shell layer mainly provides sufficient strength for the mold shell.

[0018] The application further provides a mold shell for judging the cast formability of a magnesium alloy, wherein a sprue, a runner and a rectangular cavity are arranged in the mold shell, the runner is arranged at the bottom of the sprue and the rectangular cavity, the sprue, the runner and the rectangular cavity form a U-shaped structure, the height of the sprue and the rectangular cavity is equal, and the top of the rectangular cavity is communicated with the atmosphere.

[0019] The application has the beneficial effects that: the application provides a method for judging the cast formability of a magnesium alloy and a mold shell for judging the cast formability of a magnesium alloy, magnesium alloy liquid is poured into the mold shell from the sprue, the magnesium alloy liquid is filled in the rectangular cavity by the static pressure difference of the magnesium alloy liquid, the height difference between the sprue and the castings in the rectangular cavity is measured and calculated after the magnesium alloy liquid is solidified, and the cast formability of the magnesium alloy is judged; wherein the sprue, the rectangular cavity and the runner which is communicated with the sprue and the rectangular cavity are arranged in the mold shell, the sprue, the runner and the rectangular cavity form a U-shaped structure, and the rectangular cavity is communicated with the atmosphere. The cast formability of magnesium alloys with different compositions is judged by the application, the blank of the cast formability of magnesium alloy thin-wall castings is broken, and the application has important significance for the cast formability of magnesium alloys, especially for obtaining high-quality thin-wall castings. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0021] Figure 1 The structure schematic diagram of the mold shell is shown in the figure;

[0022] Figure 2 The structure schematic diagram of the mold shell is shown in the figure; Figure 1 The structure schematic diagram of the A-A sectional view is shown in the figure;

[0023] Figure 3 The structure schematic diagram of the A-A sectional view is shown in the figure; Figure 1 ​

[0024] Figure 4 Fig. 1 is a structural diagram of a wax pattern;

[0025] Figure 5 Fig. 2 is a structural diagram of a wax pattern in Figure 4 Fig. 3 is a structural diagram of a mold shell prepared from the wax pattern;

[0026] Figure 6 Fig. 4 is a structural diagram of an enlarged view of part A shown in Figure 5

[0027] Figure 7 Fig. 5 is a structural diagram of a strip cast specimen of the present application as an example, wherein Figure 7 (a) is a structural diagram of a Mg-7Zn-2Cu-0.6Zr cast specimen; Figure 7 (b) is a structural diagram of a Mg-7Zn-3Cu-0.6Zr cast specimen;

[0028] Figure 8 Fig. 6 is a structural diagram of a spiral cast specimen as a comparative example, wherein Figure 8 (a) is a structural diagram of a Mg-7Zn-2Cu-0.6Zr cast specimen; Figure 8 (b) is a structural diagram of a Mg-7Zn-3Cu-0.6Zr cast specimen;

[0029] Figure 9 Fig. 7 is a structural diagram of a sectional view of another mold shell;

[0030] Figure 10 Fig. 8 is a structural diagram of a wax pattern to be fitted with the mold shell shown in Figure 9 Fig. 9 is a structural diagram of a mold shell prepared from the wax pattern shown in Fig. 8.

[0031] Reference signs in the drawing: 1, sprue wax pattern, 2, rectangular cavity wax pattern, 3, gate wax pattern, 4, mold shell, 5, sprue, 6, gate, 7, rectangular cavity, 8, vent hole, 9, vent hole wax column; 41, first mold shell layer; 42, second mold shell layer; 43, third mold shell layer; 44, fourth mold shell layer; 45, fifth mold shell layer; 46, sixth mold shell layer; 47, seventh mold shell layer; 48, eighth mold shell layer;

[0032] H p is the height of the sprue wax pattern 1, Ф p is the diameter of the sprue wax pattern 1; H c is the height of the rectangular cavity wax pattern 2; W c is the width of the rectangular cavity wax pattern 2, T c is the thickness of the rectangular cavity wax pattern 2; L b is the length of the gate wax pattern 3, W b is the width of the gate wax pattern 3, H b ​h1 is the height of the venting wax column 9, and h2 is the depth of the venting hole 8. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application. The methods used in the present application are conventional methods unless otherwise specified; the raw materials and devices used are conventional commercially available products unless otherwise specified.

[0034] As shown in Figures 1-3 , the present application provides a mold shell for judging the cast formability of a magnesium alloy, comprising: a mold shell 4, the mold shell 4 is provided with a straight sprue 5, a bottom sprue 6, and a rectangular cavity 7, the bottom sprue 6 is connected to the bottom of the straight sprue 5 and the rectangular cavity 7, the straight sprue 5, the bottom sprue 6, and the rectangular cavity 7 form a U-shaped structure, the height of the straight sprue 5 is equal to the height of the rectangular cavity 7, and the top of the rectangular cavity 7 is connected to the atmosphere; magnesium alloy liquid is poured into the mold shell 4 from the straight sprue 5, the magnesium alloy liquid is poured into the straight sprue 5 by using the static pressure difference of the magnesium alloy liquid, flows through the bottom sprue 6, and performs casting in the rectangular cavity 7, after the magnesium alloy liquid solidifies, the height difference between the straight sprue 5 and the casting in the rectangular cavity 7 is measured and calculated to judge the cast formability of the magnesium alloy. The smaller the difference is, the stronger the alloy formability is, and vice versa.

[0035] The mold shell 4 is preferably prepared by a wax removal method, as shown in Figure 4 , the wax mold is provided with a straight sprue wax mold 1, a bottom sprue wax mold 3, and a rectangular cavity wax mold 2, the bottom sprue wax mold 3 is connected to the bottom of the straight sprue wax mold 1 and the rectangular cavity wax mold 2, and the height of the straight sprue wax mold 1 is equal to the height of the rectangular cavity wax mold 2.

[0036] Generally, the height H p of the straight sprue wax mold 1 is 150-200 mm, the diameter Ф p of the straight sprue wax mold 1 is 20-50 mm; the height H c of the rectangular cavity wax mold 2 is equal to the height H p of the straight sprue wax mold 1; the width W c of the rectangular cavity wax mold 2 is equal to the diameter Ф p of the straight sprue wax mold 1, and the thickness T c of the rectangular cavity wax mold 2 is 0.5-2 mm; the length L b of the bottom sprue wax mold 3 is greater than the sum of the diameter Ф p of the straight sprue wax mold 1 and the width W c of the rectangular cavity wax mold 2 (i.e. L b > Ф p + W cwidth W of the under-gate wax mold 3 b greater than the diameter Φ of the straight-gate wax mold 1 p (i.e. W b > Φ p ).

[0037] The method for preparing the mold shell 4 comprises: preparing the wax mold by preferably using the injection molding process; performing multiple coating, sanding and drying operations on the wax mold with clean surface, and sintering after wax removal to obtain the mold shell 4.

[0038] Example 1

[0039] The wax mold shown in Figure 4 is prepared by using the injection molding process, and the wax mold is provided with the straight-gate wax mold 1, the under-gate wax mold 3 and the rectangular cavity wax mold 2, wherein the height H p of the straight-gate wax mold 1 is 200 mm, the diameter Φ p of the straight-gate wax mold 1 is 20 mm; the height H c of the rectangular cavity wax mold 2 is equal to the height H p of the straight-gate wax mold 1, and the value is 200 mm; the width W c of the rectangular cavity wax mold 2 is equal to the diameter Φ p of the straight-gate wax mold 1, and the value is 20 mm; the thickness T c of the rectangular cavity wax mold 2 is 1 mm; the length L b of the under-gate wax mold 3 is 50 mm, and the width W b of the under-gate wax mold 3 is 30 mm. The height H p of the straight-gate wax mold 1 is equal to the height of the straight gate 5 shown in Figure 2 .

[0040] The mold shell 4 shown in Figures 1-3 can be prepared by using the conventional wax removal method, prepared by using the conventional precision casting process, or prepared by using the following method:

[0041] as Figure 5 , Figure 6As shown, the wax pattern is subjected to slurry coating, sanding and drying operations respectively, so that the surface of the wax pattern forms the first to eighth shell layers 41 to 48 from inside to outside, wherein: the surface layer coating is prepared by mixing high-purity corundum powder with silica sol, the mesh number of the corundum powder is 325 mesh, and the mass ratio of powder to liquid is 3.3:1. The shell back layer slurry is prepared by mixing high-purity corundum powder with silica sol, the mesh number of the corundum powder is 325 mesh, and the mass ratio of powder to liquid is 2.8:1. The sanding material is corundum sand. The first shell layer 41 is the surface layer coating; the second shell layer 42 is the surface layer coating, sanding 80 mesh sand; the third shell layer 43 is the back layer slurry, sanding 60 mesh sand; the fourth shell layer 44, the fifth shell layer 45, the sixth shell layer 46, and the seventh shell layer 47 are all back layer slurries, sanding 36 mesh corundum sand; the last eighth shell layer 48 is the surface layer coating; the relative humidity of each shell layer is controlled at 70% during drying, the drying temperature is controlled at 23°C, and the drying time is controlled at 4 hours. Then, the wax is removed, the wax removal temperature is 160°C, the wax removal pressure is 0.6 MPa, and the time is 10 seconds. After the shell 4 is dewaxed, it is sintered, and the shell 4 sintering temperature is 850°C; the holding time is 4 hours.

[0042] The magnesium alloy is AM60 magnesium alloy; when the magnesium alloy liquid is poured, the actual height in the sprue 5 needs to be less than 50 mm of the height of the sprue 5, so as to form a free plane; the magnesium alloy pouring temperature is 720°C, and when the alloy is cooled to room temperature to form a casting after solidification, the shell 4 is cleaned, and the difference between the height of the sprue 5 and the height of the casting is 10 mm.

[0043] Example 2

[0044] The wax pattern as shown in Figure 4 is prepared by injection molding, and the wax pattern is provided with a sprue wax pattern 1, a gate wax pattern 3, and a rectangular cavity wax pattern 2, wherein the height H p of the sprue wax pattern 1 is 150 mm, the diameter Ф p of the sprue wax pattern 1 is 50 mm; the height H c of the rectangular cavity wax pattern 2 is equal to the height H p of the sprue wax pattern 1, and the value is 150 mm; the width W c of the rectangular cavity wax pattern 2 is equal to the diameter Ф p of the sprue wax pattern 1, and the value is 50 mm; the thickness T c of the rectangular cavity wax pattern 2 is 2 mm; the length L b of the gate wax pattern 3 is 120 mm, and the width W b of the gate wax pattern 3 is 70 mm. The height H p of the sprue wax pattern 1 is equal to the height of the sprue 5 as shown in Figure 2 .

[0045] The conventional dewaxing method can be used to prepare the wax pattern as shown in Figures 1-3The shown mold shell 4 is prepared by a conventional precision casting process, and can also be prepared by the following method:

[0046] As shown in Figure 5 , Figure 6 , the wax mold is coated with slurry, sanding and drying operation, so that the surface of the wax mold forms from the inside to the outside the first mold shell layer 41 to the eighth mold shell layer 48, wherein: the surface layer of the mold shell 4 is prepared by mixing high-purity corundum powder with silica sol, the powder size of the corundum powder is 325 mesh, and the mass ratio of powder to liquid is 3.3:1. The back layer slurry of the mold shell 4 is prepared by mixing high-purity corundum powder with silica sol, the powder size of the corundum powder is 325 mesh, and the mass ratio of powder to liquid is 2.8:1. The sanding material is corundum sand. The first mold shell layer 41 is a surface layer coating; the second mold shell layer 42 is a surface layer coating, sanding 80 mesh sand; the third mold shell layer 43 is a back layer slurry, sanding 60 mesh sand; the fourth mold shell layer 44, the fifth mold shell layer 45, the sixth mold shell layer 46, and the seventh mold shell layer 47 are back layer slurries, sanding 36 mesh corundum sand; the last eighth mold shell layer 48 is a surface layer coating; the relative humidity of each mold shell layer is controlled at 70%, the drying temperature is controlled at 23°C, and the drying time is controlled at 4 hours; then the wax is removed, the wax removal temperature is 160°C, the wax removal pressure is 0.6MPa, and the time is 10 seconds. The mold shell 4 is sintered after the wax is removed, and the sintering temperature of the mold shell 4 is 850°C; the holding time is 4 hours.

[0047] The magnesium alloy is AZ91; the actual height in the sprue 5 needs to be less than 80mm of the height of the sprue 5 to form a free plane when the magnesium alloy is poured; the pouring temperature of the magnesium alloy is 720°C, and the difference between the height of the sprue 5 and the height of the casting is 8.5mm when the alloy is cooled to room temperature to form the casting after solidification.

[0048] Example 3

[0049] The wax mold shown in Figure 4 is prepared by injection molding, and the wax mold is provided with a straight runner wax mold 1, a bottom runner wax mold 3, and a rectangular cavity wax mold 2, wherein the height H p of the straight runner wax mold 1 is 150mm, the diameter Ф p of the straight runner wax mold 1 is 20mm; the height H c of the rectangular cavity wax mold 2 is equal to the height H p of the straight runner wax mold 1, which is 150mm; the width W c of the rectangular cavity wax mold 2 is equal to the diameter Ф p of the straight runner wax mold 1, which is 20mm; the thickness T c of the rectangular cavity wax mold 2 is 1mm; the length L b of the bottom runner wax mold 3 is 60mm, and the width W b of the bottom runner wax mold 3 is 40mm. The height H p of the straight runner wax mold 1 isFigure 2 The heights of the sprues 5 are equal.

[0050] The wax pattern as shown in Figures 1-3 The mold shell 4 can be prepared by using a conventional precision casting process, or by using the following method:

[0051] The wax pattern as shown in Figure 5 , Figure 6 The wax pattern as shown in

[0052] The magnesium alloy is Mg-4Zn-1Y-0.6Zr; the actual height in the sprue 5 needs to be less than 50 mm of the height of the sprue 5 when the magnesium alloy liquid is poured, so as to form a free plane; the pouring temperature of the magnesium alloy is 750°C; after the alloy is solidified and cooled to room temperature to form the casting, the mold shell 4 is cleaned, and the difference between the height of the sprue 5 and the height of the casting is 23 mm.

[0053] Example 4

[0054] The wax pattern as shown in Figure 4 The wax pattern is provided with a sprue wax pattern 1, a gate wax pattern 3, and a rectangular cavity wax pattern 2; the height H p of the sprue wax pattern 1 is 150 mm, the diameter Ф p of the sprue wax pattern 1 is 20 mm; the height H c of the rectangular cavity wax pattern 2 is equal to the height H p of the sprue wax pattern 1, which is 150 mm; the width W c of the rectangular cavity wax pattern 2 is equal to the diameter Ф p of the sprue wax pattern 1, which is 20 mm; and the thickness T c1 mm; the length L of the bottom sprue wax mold 3 b The width W of the bottom sprue wax mold 3 is 60 mm. b The height H of the sprue wax mold 1 is 40 mm. p and Figure 2 The sprues 5 are shown to be of equal height.

[0055] Conventional dewaxing methods can be used to prepare Figures 1-3 The mold shell 4 shown is prepared using a conventional precision casting process, and can also be prepared using the following method:

[0056] like Figure 5 、 Figure 6 As shown, the wax mold is coated, sanded, and dried, forming the first shell layer 41 through the eighth shell layer 48 from the inside out. The topcoat is prepared using a mixture of high-purity corundum powder and silica sol, with a mesh size of 325 and a powder-to-liquid ratio of 3.5:1. The backing slurry for shell 4 is prepared using a mixture of high-purity corundum powder and silica sol, with a mesh size of 325 and a powder-to-liquid ratio of 2.5:1. Corundum sand is used as the sanding material. The first shell layer 41 is a topcoat; the second shell layer 42 is a topcoat slurry, sprinkled with 80-mesh sand; the third shell layer 43 is a backcoat slurry, sprinkled with 60-mesh sand; the fourth, fifth, sixth, and seventh shell layers 44, 45, 46, and 47 are backcoats, sprinkled with 36-mesh corundum sand; and finally, the eighth shell layer 48 is a topcoat. Each shell layer is dried at a relative humidity of 40%, a temperature of 35°C, and a drying time of 8 hours. Dewaxing is then performed at a temperature of 180°C, a pressure of 0.8 MPa, and a drying time of 30 seconds. After dewaxing, the shell 4 is sintered at a temperature of 1050°C and a holding time of 2 hours.

[0057] The magnesium alloy is a type of Mg–4Zn–1Ca-0.6Zr alloy. When pouring the magnesium alloy liquid, the actual height inside the sprue 5 must be 50 mm less than the height of the sprue 5 to form a free plane. The magnesium alloy pouring temperature is 750°C. After the alloy solidifies and cools to room temperature to form a casting, the mold shell 4 is cleaned and the difference between the height of the sprue 5 and the height of the casting is measured to be 18 mm.

[0058] Example 5

[0059] The technical solution of the present invention is used to determine the formability of magnesium alloys Mg-7Zn-2Cu-0.6Zr and Mg-7Zn-3Cu-0.6Zr, which have very small composition differences: using the mold shell 4 in Example 2 of the present invention, when the mold shell 4 is at room temperature and the pouring temperature is 720°C, and the height of the sprue 5 is controlled to be 80 mm, the height differences between the obtained different alloy samples and the sprue 5 are 4 mm and 17 mm, respectively, a difference of 13 mm, which can clearly reflect the effect of different compositions on formability.Figure 7 (a)、 Figure 7 (b) shown. It can be seen that the cast formability of magnesium alloy Mg-7Zn-2Cu-0.6Zr is better than that of magnesium alloy Mg-7Zn-3Cu-0.6Zr.

[0060] Comparative Example 1

[0061] Similarly, when the alloys Mg-7Zn-2Cu-0.6Zr and Mg-7Zn-3Cu-0.6Zr with very small difference in composition are measured by using the screw test sample commonly used in the prior art, the sample lengths are 401 mm and 403 mm respectively at a mold temperature of 200 ℃ and a pouring temperature of 720 ℃, and considering the measurement error, the influence of the difference in composition on the formability cannot be truly reflected, such as Figure 8 (a)、 Figure 8 (b) shown.

[0062] It can be seen from the comparison between Example 5 and Comparative Example 1 that the mold shell 4 provided with the rectangular cavity 7 is easier to determine the formability of the alloys with very small difference in composition than the mold shell 4 provided with the spiral cavity, and the height difference between the casting and the sprue can be obviously distinguished, that is, the forming capacity of the casting.

[0063] On the basis of the mold shell shown in Figure 2 , the present application further provides another form of mold shell structure, as shown in Figure 9 . A plurality of vent holes 8 are provided at the top of the rectangular cavity 7 and are connected to the atmosphere. The wax mold matched with the mold shell is based on the wax mold structure shown in Figure 4 , and a vent hole wax column 9 is connected at the top of the rectangular cavity wax mold, as shown in Figure 10 . The vent hole 8 and the vent hole wax column 9 are matched, and the depth h2 of the vent hole 8 is greater than the height h1 of the vent hole wax column 9, so that when the mold shell 4 is prepared by the wax removal method, the vent hole wax column 9 is always exposed outside the mold shell 4, and the vent hole 8 is exposed after the wax removal.

[0064] The present application provides a method for determining the cast formability of a magnesium alloy. The magnesium alloy liquid is poured into the mold shell 4 from the straight sprue 5, and the magnesium alloy liquid enters the rectangular cavity 7 through the bottom sprue 6 by using the static pressure difference of the magnesium alloy liquid, and the casting is filled in the rectangular cavity 7. After the magnesium alloy liquid solidifies, the height difference between the straight sprue 5 and the casting in the rectangular cavity 7 is measured and calculated to determine the cast formability of the magnesium alloy. The mold shell 4 is provided with the straight sprue 5, the rectangular cavity 7, and the bottom sprue 6 connecting the two, and the three constitute a U-shaped structure. The rectangular cavity 7 is connected to the atmosphere. The present application breaks the blank in the field of cast formability of magnesium alloy thin-walled castings, and has important significance for the cast formability of magnesium alloy, especially for obtaining high-quality thin-walled castings.

[0065] It should be noted that:

[0066] (1) In the present application, the magnesium alloy is one of Mg-Al-Zn system, Mg-Al-Mn system, Mg-Al-Zn-Mn system, Mg-Zn-Zr system, Mg-Zn-Ca system, Mg-Zn-Y-Zr system; in the actual operation process, preferably, the actual height in the sprue gate should be less than 50-80mm of the height of the sprue gate to form a free plane when pouring the alloy liquid;

[0067] (2) In the present application, the pouring temperature of the magnesium alloy is preferably 720-750℃, after the alloy solidifies and cools to room temperature, the difference between the height of the sprue gate and the height of the casting is measured, which can quantitatively characterize the formability of different alloys.

[0068] (3) The technical route of the present application is to prepare the sprue gate and the casting mold shell with the same height of the common cross-sprue; to pour the alloy by using the same pouring process parameters; to calculate the height difference between the sprue gate and the casting to determine the formability of the alloy.

[0069] (4) The purity of the corundum powder used for preparing the surface layer coating and the back layer slurry is preferably >99.5%, and the purity of the corundum powder used for preparing the back layer slurry is preferably >99.5%.

[0070] (5) In the preparation process of the mold shell, the powder-liquid mass ratio of the surface layer coating is preferably 3.3-3.5:1, and the mesh number of the corundum powder is preferably 300-325 mesh; the powder-liquid mass ratio of the back layer slurry is preferably 2.5-3.0:1, and the mesh number of the corundum powder is preferably 300-325 mesh; the mesh number of the sanding material is preferably 36-80 mesh; the dewaxing temperature is preferably 160-180℃, the dewaxing pressure is preferably 0.6-0.8MPa, and the time is preferably 10-30 seconds; the sintering temperature is preferably 850-1050℃, and the holding time is preferably 2-6 hours. In the actual production process, the above-mentioned powder-liquid mass ratio, mesh number of the sanding material, dewaxing process, and sintering process control range can be selected according to the actual situation.

[0071] (6) The mold shell is provided with a sprue gate 5, a rectangular cavity 7, and a bottom gate 6 connecting the two, which form a U-shaped structure, and the rectangular cavity 7 is connected with the atmosphere. Preferably, the bottom gate 6 is connected at the bottom of the sprue gate 5 and the rectangular cavity 7, and the heights of the sprue gate 5 and the rectangular cavity 7 are equal, and the top of the rectangular cavity 7 is connected with the atmosphere.

[0072] In the description of the present application, it needs to be understood that the terms "left", "right", "upper", "lower", "top", "bottom", "front", "back", "inner", "outer", "back", "intermediate" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0073] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. For example, the sprue, the rectangular cavity and the bottom gate connected with the two can form a U-shaped structure, an H-shaped structure and other structures, which can be equivalent and replaced. The present application is not only suitable for the determination of magnesium alloy casting formability, but also suitable for the determination of other alloy casting formability.

Claims

1. A method of determining cast formability of a magnesium alloy, characterized by, It comprises: The magnesium alloy liquid is poured into the mold shell from the sprue, the magnesium alloy liquid is filled in the rectangular cavity by the static pressure difference of the magnesium alloy liquid, and the height difference between the sprue and the casting in the rectangular cavity is measured and calculated after the magnesium alloy liquid is solidified to determine the magnesium alloy casting formability; the mold shell is provided with the sprue, the rectangular cavity, and a bottom gate connecting the sprue and the rectangular cavity, and the three form a U-shaped structure, and the rectangular cavity is connected with the atmosphere.

2. The method of judging cast formability of a magnesium alloy according to claim 1, characterized by The mold shell is prepared by a dewaxing method, and the wax mold is provided with a sprue wax mold, a bottom gate wax mold, and a rectangular cavity wax mold, and the bottom gate wax mold is connected to the bottom of the sprue wax mold and the rectangular cavity wax mold.

3. The method of judging the cast formability of a magnesium alloy according to claim 2, characterized by The height of the sprue wax mold is 150-200 mm, and the diameter of the sprue wax mold is 20-50 mm; the height of the rectangular cavity wax mold is equal to the height of the sprue wax mold; the width of the rectangular cavity wax mold is equal to the diameter of the sprue wax mold, and the thickness of the rectangular cavity wax mold is 0.5-2 mm; the length of the bottom gate wax mold is greater than the sum of the diameter of the sprue wax mold and the width of the rectangular cavity wax mold, and the width of the bottom gate wax mold is greater than the diameter of the sprue wax mold.

4. The method of claim 2, wherein The preparation method of the mold shell comprises the following steps: preparing the wax mold by an injection molding process; performing multiple times of slurry coating, sanding, and drying operations on the wax mold with a clean surface, sintering after dewaxing, and obtaining the mold shell.

5. The method of judging the cast formability of a magnesium alloy according to claim 4, characterized by The preparation method of the mold shell comprises the following steps: the surface layer coating is prepared by mixing corundum powder and silica sol, the mass ratio of the powder and the liquid is 3.3-3.5:1, and the mesh number of the corundum powder is 300-325; the back layer slurry is prepared by mixing corundum powder and silica sol, the mass ratio of the powder and the liquid is 2.5-3.0:1, and the mesh number of the corundum powder is 300-325.

6. The method of judging the cast formability of a magnesium alloy according to claim 4, characterized by The preparation method of the mold shell comprises the following steps: the sanding material is corundum sand, and the mesh number is 36-80.

7. The method of judging the cast formability of a magnesium alloy according to claim 4, characterized by The preparation method of the mold shell comprises the following steps: the dewaxing temperature is 160-180℃, the dewaxing pressure is 0.6-0.8MPa, and the time is 10-30 seconds.

8. The method of judging the cast formability of a magnesium alloy according to claim 4, characterized by The preparation method of the mold shell comprises the following steps: the sintering temperature is 850℃-1050℃, and the holding time is 2-6 hours.

9. The method of judging the cast formability of a magnesium alloy according to claim 5, characterized by The preparation method of the mold shell comprises the following steps: the wax mold is coated with slurry, sanding, and drying operations to form first to eighth mold shell layers on the surface of the wax mold from the inside to the outside, wherein: the first mold shell layer is the surface layer coating; the second mold shell layer is the surface layer coating, and 80 mesh sand is sanded; the third mold shell layer is the back layer slurry, and 60 mesh sand is sanded; the fourth, fifth, sixth, seventh mold shell layers are all the back layer slurry, and 36 mesh sand is sanded; the last eighth mold shell layer is the surface layer coating; the relative humidity of each mold shell layer is controlled to be 40-70% during drying, the drying temperature is controlled to be 23-35℃, and the drying time is controlled to be 4-8 hours.

10. A mold shell for judging the casting formability of a magnesium alloy, characterized in that: The mold shell is provided with a sprue, a bottom gate, and a rectangular cavity, the bottom gate is connected to the bottom of the sprue and the rectangular cavity, the three form a U-shaped structure, the height of the sprue and the rectangular cavity is equal, and the top of the rectangular cavity is connected with the atmosphere.

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