A method for controlling the interface of solid-liquid bimetal casting containing aluminum alloy

Abstract

The present invention discloses a method for controlling the interface of solid-liquid bimetallic casting containing aluminum alloy, and belongs to the process field of casting alloy. The present invention aims to solve the problem that cracks are generated along the interface direction in the existing solid-liquid bimetallic casting containing aluminum alloy. The steps of the method of the present invention are as follows: step one, control of the interface roughness of the solid metal preform; step two, integrated modeling; step three, configuration of alternating electromagnetic field and permanent magnetic rotating magnetic field, step four, integrated casting. By applying an alternating electromagnetic field and a permanent magnetic rotating magnetic field in coordination with the casting process to form an involute vortex structure at the interface of the two materials to adjust the local distribution state of the aluminum alloy molten metal in the filling process, the generation of cracks along the interface direction can be effectively avoided, and the crack incidence along the interface direction is reduced by more than 80%, and the probability of generating cracks in the direction perpendicular to the interface is not increased.

Description

Technical Field

[0001] The invention belongs to the field of alloy casting technology; specifically relates to a method for controlling a solid-liquid bimetallic casting interface containing an aluminum alloy; and a bimetallic composite casting containing an aluminum alloy. Background Art

[0002] Solid-liquid bimetal casting containing aluminum alloy refers to the process of melting aluminum alloy and pouring it on a solid preform of another metal material to form a composite casting. Before forming and connecting, the aluminum alloy is in liquid state and the other material is in solid state. This method is used to connect semi-finished parts with complex structures. The liquid metal has a high temperature and dissolves the surface of the metal matrix, forming a diffusion connection layer at the interface. It does not require high casting conditions and the process is relatively simple. It has been well applied in composite rolls, composite hammers, etc.

[0003] At present, the more mature processes are inlay casting, continuous pouring, lost foam casting and centrifugal casting. The process parameter adjustment means of these methods is mainly to control the pouring temperature of aluminum alloy. The higher the temperature, the better the metallurgical bonding effect. The higher the temperature, the easier it is to form a transition structure in the interface area of ​​the two materials. It can effectively alleviate the stress concentration caused by the difference between the two different materials in the direction perpendicular to the interface. It is an effective method to improve the interface stress state. However, as the shape of the solid preform becomes more and more complex, the process of the aluminum alloy melt filling process becomes longer and longer, and the heating difference of the aluminum alloy melt on the preform also appears. The temperature rises higher at the location where the metal liquid flows through a large amount, while the temperature of the preform in contact with the end of the metal liquid process is lower. Such a temperature difference leads to a huge solidification shear stress along the interface direction of the two different materials. When the aluminum alloy temperature is cooled to the solid-liquid two-phase region, the solidification shear stress will destroy the interface that has been connected but has not reached the maximum strength, resulting in microcracks. In severe cases, the already combined composite casting will crack along the interface direction. The interface treatment methods currently widely used are all aimed at stress concentration in the direction perpendicular to the interface, and are almost ineffective for cracks along the interface direction.

[0004] At present, the problem of cracks along the interface direction in solid-liquid bimetal casting containing aluminum alloys is mainly solved by improving the wrapping relationship between the preform and the aluminum alloy, so that as many positions as possible form a state where the aluminum alloy liquid fully encloses the solid metal material preform, and the cracks along the interface direction are compressed and welded by the solidification shrinkage of the aluminum alloy. However, this method has great limitations. For positions where the correct wrapping relationship is not formed, cracks along the interface direction cannot be avoided. The solidification shrinkage of the positions where the wrapping relationship is formed will also aggravate the tendency of cracks in the perpendicular interface direction. Moreover, too many designed wrapping positions will increase the difficulty of preparing the gradient structure at the bimetallic interface, making the process itself more difficult, thereby offsetting the advantages of simple and fast solid-liquid bimetal casting. Summary of the invention

[0005] The present invention aims to solve the problem of cracks generated along the interface direction in solid-liquid bimetallic casting containing aluminum alloy. The present invention proposes a method for regulating the interface of solid-liquid bimetallic casting of aluminum alloy, which forms an involute vortex structure at the interface of the two materials by applying an alternating electromagnetic field and a permanent magnetic rotating magnetic field in the pouring process to adjust the local distribution state of the aluminum alloy molten metal during the filling process, and alleviate the solidification shear stress generated by the heating difference of the solid preform by the aluminum alloy molten metal. At the same time, through the interaction of the two magnetic fields, the aluminum alloy molten metal flows according to the involute law when solidifying to the solid-liquid two-phase region, and finally converges to form an involute base circle. This can make the solidification shear stress along the interface direction offset each other around the base circle with the base circle as the symmetry center, and can effectively avoid the generation of cracks along the interface direction. The method of the present invention achieves the purpose of reducing the incidence of cracks along the interface direction.

[0006] In order to solve the problem of cracks generated along the interface direction in the solid-liquid bimetal casting containing aluminum alloy, the present invention proposes a method for controlling the interface of the solid-liquid bimetal casting containing aluminum alloy, which is achieved by the following steps:

[0007] Step 1: Treat the surface of the solid metal preform to make the surface roughness Ra value reach 6.3 to 12.5 microns and expose a fresh metal surface;

[0008] Step 2: encapsulating the solid metal preform processed in step 1, and then performing integrated molding to form a cavity for accommodating the aluminum alloy melt;

[0009] Step 3: Calculate the power P and frequency f of the alternating electromagnetic field generator 交变 and the rotating permanent magnet speed n that generates the permanent magnetic rotating magnetic field 旋转 , configure the alternating electromagnetic field and permanent magnet rotating magnetic field equipment according to the calculation results, and then set them at 5cm to 20cm away from the interface of the solid metal preform, the alternating electromagnetic field coil is placed parallel to the surface of the solid metal preform, the rotating axis of the rotating permanent magnet is along the normal direction of the surface of the solid metal preform, the magnetic induction intensity is controlled at 1T to 3T, and the distance between the rotating axis of the rotating permanent magnet and the symmetry axis of the alternating electromagnetic field coil is 15cm to 20cm;

[0010] Step 4: After the aluminum alloy is melted, the alternating electromagnetic field and permanent magnetic rotating magnetic field equipment are turned on, and the casting is completed using an integrated casting method.

[0011] It is further defined that the solid metal preform material in step one is titanium alloy, aluminum alloy or cast steel, for example: TA15 titanium alloy, 2195 aluminum alloy, ZG45 cast steel, etc.

[0012] It is further defined that in step one, polishing treatment is used to achieve surface treatment of the solid metal preform.

[0013] It is further defined that the polishing treatment is mechanical polishing, or chemical polishing, or a combination of chemical polishing and mechanical polishing; the mechanical polishing is shot blasting, sand blasting or sandpaper polishing.

[0014] Further defined, the operation process of integrated modeling in step 2 is:

[0015] S1: Making a pattern: Making a low-temperature pattern according to the shape of the part to be filled with the molten aluminum alloy in the composite casting, and combining the solid metal preform and the low-temperature pattern into a combined pattern;

[0016] S2: placing the combined mold on a low-temperature molding platform for molding. The molding material is polyurethane resin sand. A pouring port is left near the low-temperature mold. After the sand mold hardens, the mold is gradually heated up in a negative pressure environment so that the low-temperature mold in the mold flows out along the pouring port, while the solid metal preform remains in the mold to form a composite mold.

[0017] Further defined, in step 3, the power of the alternating electromagnetic field generator is calculated according to formula I:

[0018] P = 6.05*G / t(Ⅰ),

[0019] Among them, P (unit: kW) is the power of the alternating electromagnetic field generator, G (unit: Kg) is the mass of the aluminum alloy melt within the range of the alternating electromagnetic field, and t (unit: min) is the time required for the aluminum alloy melt to solidify to the solidus temperature.

[0020] Further defined, in step 3, the frequency of the alternating electromagnetic field generator is calculated according to formula II:

[0021]

[0022] Among them, f 交变 (Unit: Hz) is the power of the alternating electromagnetic field generator, P is the power of the alternating electromagnetic field generator, m (unit: m) is the thermal modulus at the interface of the composite casting, t (unit: min) is the time required for the aluminum alloy melt to solidify to the solidus temperature, ρ (unit: Ω·m) is the average resistivity of the aluminum alloy, γ (unit: kg / m 3 ) is the density of aluminum alloy, and δ (unit: m) is the thickness of the interface layer between the solid metal preform and the aluminum alloy.

[0023] Further defined, in step 3, the speed of the permanent magnet rotating magnetic field is calculated according to formula III:

[0024]

[0025] Among them, n旋转 (Unit: r / min) is the speed of the rotating permanent magnet that generates the permanent magnetic rotating magnetic field, G (unit: Kg) is the mass of the aluminum alloy melt within the range of the alternating electromagnetic field, m (unit: m) is the thermal modulus at the interface of the composite casting, and f 交变 (Unit: Hz) is the frequency of the alternating electromagnetic field.

[0026] It is further defined that in step four, the aluminum alloy is melted at 680°C to 755°C.

[0027] The present invention also provides an aluminum alloy bimetallic composite casting prepared by the above method.

[0028] The present invention has the following beneficial effects:

[0029] The solid-liquid bimetallic casting interface control method containing aluminum alloy of the present invention can effectively alleviate the solidification shear stress generated by the heating difference of the aluminum alloy metal liquid on the solid preform. By applying an alternating electromagnetic field and a permanent magnetic rotating magnetic field in the pouring process, when the aluminum alloy metal liquid solidifies to the temperature of the solid-liquid two-phase region, the liquid metal flows according to the involute law and converges to form an involute base circle shape, and the solidification shear stress along the interface direction can offset each other around the base circle with the center of the base circle as the symmetry center, which can effectively avoid the generation of cracks along the interface direction, reduce the crack incidence along the interface direction by more than 80%, and do not increase the probability of cracks in the direction perpendicular to the interface.

[0030] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the attached drawings are only provided for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of configuring an alternating electromagnetic field and a permanent magnetic rotating magnetic field around a casting mold of the present invention, 1—alternating electromagnetic field generator, 2—alternating electromagnetic field coil, 3—motor, 4—connecting rod, 5—permanent magnet, 6—pouring gate, 7—solid metal preform, 8—mold cavity, 9—casting mold. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0033] Embodiment 1: 3 kg of aluminum alloy in this embodiment has the following composition by mass percentage: 3% Li content, 1% Cu content, 5% Mg content, 0.2% Ti content, 0.8% Er content, and the balance is Al; the solid metal preform material is TA15 titanium alloy; the aluminum alloy solid-liquid bimetallic casting interface control method in this embodiment is achieved by the following steps:

[0034] Step 1, solid metal preform interface roughness control: the surface of the TA15 titanium alloy solid metal preform is shot peened for 50 seconds, sand blasted for 60 seconds, polished with 600# sandpaper, and then the surface residue is removed with 0.2MPa compressed nitrogen and then chemically polished to make the surface roughness Ra value reach 6.3 microns and expose a fresh metal surface;

[0035] Step 2: Integrated modeling: The surface of the TA15 titanium alloy solid metal preform is encapsulated with a plastic film for integrated modeling.

[0036] First, a pattern is made: a low-temperature pattern is made according to the shape of the part to be filled with the molten aluminum alloy in the composite casting, and the TA15 titanium alloy solid metal preform and the low-temperature pattern are combined into a combined pattern;

[0037] The combined mold is then placed on a low-temperature molding platform for molding. The molding material is polyurethane resin sand, and a pouring port is left near the low-temperature mold. After the sand mold hardens, the mold is gradually heated to 60°C in a negative pressure environment of 800Pa, so that the low-temperature mold in the mold softens and flows out along the pouring port, while the solid metal preform remains in the mold to form a composite mold.

[0038] Step 3: Configure the alternating electromagnetic field and the permanent magnet rotating magnetic field: Calculate the alternating electromagnetic field generator power (P) and the alternating electromagnetic field frequency (f 交变 ) and the speed of the rotating permanent magnet that generates the permanent magnetic rotating magnetic field (n 旋转 ).

[0039] The empirical formula for the power of the alternating electromagnetic field generator is as follows: P = 6.05*G / t (kW), which is calculated to be 6.05kW;

[0040] The empirical formula for the frequency of the alternating electromagnetic field is as follows: (Hz), calculated to be 1177Hz;

[0041] The empirical formula for the speed of the permanent magnet rotating magnetic field is as follows: (r / min), calculated to be 1050r / min.

[0042] According to the calculation results, the alternating electromagnetic field and permanent magnetic rotating magnetic field equipment were configured, and then the alternating electromagnetic field coil and the rotating magnetic permanent magnet were set 5 cm away from the interface of the TA15 titanium alloy solid metal preform. The alternating electromagnetic field coil was placed parallel to the surface of the solid metal preform, and the rotating permanent magnet's rotation axis was along the normal direction of the solid metal preform surface, and the magnetic induction intensity was 3 T. The distance between the rotating permanent magnet's rotation axis and the symmetry axis of the alternating electromagnetic field coil was 15 cm.

[0043] Step 4: integrated casting: After the aluminum alloy is melted to 755°C, the alternating electromagnetic field and permanent magnetic rotating magnetic field equipment are turned on, and an integrated casting method is used for casting to form an aluminum alloy / TA15 titanium alloy bimetallic composite casting.

[0044] The solid-liquid bimetallic casting interface control method containing aluminum alloy in this embodiment can effectively alleviate the solidification shear stress caused by the heating difference of the aluminum alloy liquid on the TA15 titanium alloy solid preform, effectively avoid the generation of cracks along the interface direction, reduce the occurrence rate of cracks along the interface direction by 80%, and does not increase the probability of generating cracks in the direction perpendicular to the interface.

[0045] Embodiment 2: 5kg of aluminum alloy in this embodiment has the following composition by mass percentage: 1% Li, 3% Cu, 3% Mg, 0.2% Ti, 0.2% Mn, and the balance Al; the solid metal preform material is ZG45 cast steel; the aluminum alloy solid-liquid bimetallic casting interface control method in this embodiment is achieved by the following steps:

[0046] Step 1, solid metal preform interface roughness control: the surface of the ZG45 cast steel solid metal preform is shot peened for 50 seconds, sand blasted for 60 seconds, and polished with 600# sandpaper, and then the surface residue is removed with 0.2MPa compressed nitrogen, so that the surface roughness Ra value reaches 12.5 microns, and a fresh metal surface is exposed;

[0047] Step 2: Integrated modeling: The surface of the ZG45 cast steel solid metal preform is encapsulated with a plastic film for integrated modeling.

[0048] First, make a pattern: make a low-temperature pattern according to the shape of the part to be filled with molten aluminum alloy in the composite casting, and combine the ZG45 cast steel solid metal preform and the low-temperature pattern into a combined pattern;

[0049] The combined mold is then placed on a low-temperature molding platform for molding. The molding material is polyurethane resin sand, and a pouring port is left near the low-temperature mold. After the sand mold hardens, the mold is gradually heated to 60°C in a negative pressure environment of 800Pa, so that the low-temperature mold in the mold softens and flows out along the pouring port, while the solid metal preform remains in the mold to form a composite mold.

[0050] Step 3: Configure the alternating electromagnetic field and the permanent magnet rotating magnetic field: Calculate the alternating electromagnetic field generator power (P) and the alternating electromagnetic field frequency (f 交变 ) and the speed of the rotating permanent magnet that generates the permanent magnetic rotating magnetic field (n 旋转 ).

[0051] The empirical formula for the power of the alternating electromagnetic field generator is as follows: P = 6.05*G / t (kW), which is calculated to be 9.45kW;

[0052] The empirical formula for the frequency of the alternating electromagnetic field is as follows: (Hz), calculated to be 2525Hz;

[0053] The empirical formula for the speed of the permanent magnet rotating magnetic field is as follows: (r / min), calculated to be 2564r / min.

[0054] According to the calculation results, the alternating electromagnetic field and permanent magnetic rotating magnetic field equipment are configured, and then the alternating electromagnetic field coil and the rotating magnetic permanent magnet are configured 20 cm away from the interface of the ZG45 cast steel solid metal preform. The alternating electromagnetic field coil is placed parallel to the surface of the solid metal preform, and the rotating permanent magnet's rotation axis is along the normal direction of the solid metal preform surface, and the magnetic induction intensity is 1 T. The distance between the rotating permanent magnet's rotation axis and the symmetry axis of the alternating electromagnetic field coil is 20 cm.

[0055] Step 4: integrated casting: After melting the aluminum alloy to 700°C, start the alternating electromagnetic field and permanent magnetic rotating magnetic field equipment, and use an integrated casting method to cast to form an aluminum alloy / ZG45 cast steel bimetallic composite casting.

[0056] The solid-liquid bimetallic casting interface control method containing aluminum alloy in this embodiment can effectively alleviate the solidification shear stress caused by the heating difference of the aluminum alloy liquid on the ZG45 cast steel solid preform, effectively avoid the generation of cracks along the interface direction, reduce the incidence of cracks along the interface direction by 85%, and do not increase the probability of generating cracks in the direction perpendicular to the interface.

[0057] Embodiment 3: This embodiment is different from Embodiment 1 in that:

[0058] 3 kg of aluminum alloy, the composition by mass percentage is as follows: Si content is 5.8%, Li content is 1%, Cu content is 0.2%, Mg content is 3%, Ti content is 0.2%, and the balance is Al;

[0059] The solid metal preform material is 2195 aluminum alloy; the power of the alternating electromagnetic field generator is 5.85kW, the frequency of the alternating electromagnetic field is 3411Hz, and the speed of the permanent magnetic rotating magnetic field is 1788r / min;

[0060] In step 4, after the aluminum alloy is melted to 680° C., the alternating electromagnetic field and permanent magnetic rotating magnetic field equipment are turned on. The other steps and parameters are the same as those in Example 1.

[0061] The solid-liquid bimetallic casting interface control method containing aluminum alloy in this embodiment can effectively alleviate the solidification shear stress caused by the heating difference of the aluminum alloy liquid on the 2195 aluminum alloy solid preform, effectively avoid the generation of cracks along the interface direction, reduce the incidence of cracks along the interface direction by 87%, and do not increase the probability of generating cracks in the direction perpendicular to the interface.

Claims

1. A method for controlling the solid-liquid bimetallic casting interface of an aluminum alloy, characterized in that: The method comprises the following steps: Step 1: Treat the surface of the solid metal preform to make the surface roughness Ra value reach 6.3 to 12.5 microns and expose a fresh metal surface; Step 2: encapsulating the solid metal preform processed in step 1, and then performing integrated molding to form a cavity for accommodating the aluminum alloy melt; Step 3: Calculate the power P and frequency f of the alternating electromagnetic field generator 交变 and the rotating permanent magnet speed n that generates the permanent magnetic rotating magnetic field 旋转 , configure the alternating electromagnetic field and permanent magnet rotating magnetic field equipment according to the calculation results, and then set them at 5cm to 20cm away from the interface of the solid metal preform, the alternating electromagnetic field coil is placed parallel to the surface of the solid metal preform, the rotating axis of the rotating permanent magnet is along the normal direction of the surface of the solid metal preform, the magnetic induction intensity is controlled at 1T to 3T, and the distance between the rotating axis of the rotating permanent magnet and the symmetry axis of the alternating electromagnetic field coil is 15cm to 20cm; Step 4: After the aluminum alloy is melted, the alternating electromagnetic field and permanent magnetic rotating magnetic field equipment are turned on, and the casting is performed using an integrated casting method, and the casting is completed; The operation process of integrated modeling in step 2 is as follows: S1: Making a pattern: Making a low-temperature pattern according to the shape of the part to be filled with the molten aluminum alloy in the composite casting, and combining the solid metal preform and the low-temperature pattern into a combined pattern; S2: placing the combined mold on a low-temperature molding platform for molding, using polyurethane resin sand as the molding material, leaving a pouring port near the low-temperature mold, and gradually heating the mold in a negative pressure environment after the sand mold hardens, so that the low-temperature mold in the mold flows out along the pouring port, while the solid metal preform remains in the mold to form a composite mold; In step 3, the power of the alternating electromagnetic field generator is calculated according to formula Ⅰ: P=6.05*G / t (Ⅰ), Wherein, P is the power of the alternating electromagnetic field generator, G is the mass of the aluminum alloy melt within the action range of the alternating electromagnetic field, and t is the time required for the aluminum alloy melt to solidify to the solidus temperature; In step 3, calculate the frequency of the alternating electromagnetic field generator according to formula II: Wherein, P is the power of the alternating electromagnetic field generator, m is the thermal modulus at the interface of the composite casting, t is the time required for the aluminum alloy melt to solidify to the solidus temperature, ρ is the average resistivity of the aluminum alloy, γ is the density of the aluminum alloy, and δ is the thickness of the interface layer between the solid metal preform and the aluminum alloy; In step 3, the speed of the permanent magnet rotating magnetic field is calculated according to formula III: Among them, n 旋转 The rotating speed of the permanent magnet that generates the permanent magnetic rotating magnetic field, G is the mass of the aluminum alloy melt within the action range of the alternating electromagnetic field, m is the thermal modulus at the interface of the composite casting, and f is 交变 is the frequency of the alternating electromagnetic field.

2. The method according to claim 1, characterized in that: In step 1, the solid metal preform material is titanium alloy, aluminum alloy or cast steel.

3. The method according to claim 1, characterized in that: In step 1, polishing is used to achieve surface treatment of the solid metal preform.

4. The method according to claim 3, characterized in that The polishing treatment is mechanical polishing, or chemical polishing, or a combination of chemical polishing and mechanical polishing; the mechanical polishing is shot blasting, sand blasting or sandpaper polishing.

5. The method according to claim 1, characterized in that In step 4, the aluminum alloy is melted at 680°C to 755°C.

6. An aluminum alloy bimetallic composite casting prepared by the method according to any one of claims 1 to 5.

Images