Method for refining second phase of as-cast AgCuNiRE alloy and AgCuNiRE alloy

Abstract

The invention provides a method for refining a second phase of an as-cast AgCuNiRE alloy and the AgCuNiRE alloy, and belongs to the technical field of metal material forming. The method for refining the second phase of the as-cast AgCuNiRE alloy, provided by the invention, comprises the following steps: carrying out first forging on an as-cast AgCuNiRE alloy blank to obtain a cube blank; carrying out multidirectional forging on the cube blank; the multi-directional forging is that second forging is carried out in the height direction, the transverse direction and the longitudinal direction of the cube blank, and the second forging comprises drawing-out and upsetting-out. According to the method, second-phase particles are subjected to multi-direction shearing and pulling in the processes of medium-temperature multi-direction forging and drawing-out and upsetting in different directions, so that the second-phase particles are crushed, the second-phase particles in the alloy are fully refined and dispersed in a matrix, casting defects are eliminated, the microstructure of the alloy is improved, and the yield of the alloy is improved. And the consistency and the stability of the alloy are improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal material forming, and in particular to a method for refining a second phase of a cast AgCuNiRE alloy and the AgCuNiRE alloy. Background Art

[0002] The commutator is the core component of a small DC motor. During operation, the commutator needs to withstand sliding friction under load conditions, which places high demands on the working layer of the commutator. Silver has excellent conductivity and corrosion resistance and is the most common commutator coating material. However, the hardness and melting point of silver are low, making it difficult to meet the use requirements of the commutator. How to improve the hardness and wear resistance of silver alloys is a research hotspot for silver alloys.

[0003] AgCuNiRE alloy, by adding rare earth elements into the alloy, makes it exist in the alloy in the form of solid solution, oxide and intermetallic compound, which has the quadruple effect of "purification", "refinement", "strengthening" and "alloying" on the alloy. It can refine the grains of silver-based electrical contact materials, strengthen the matrix, increase the recrystallization temperature and heat resistance, enhance the arc extinguishing ability, anti-welding ability and friction resistance. Therefore, it has become the main coating material for micromotor commutator pole pieces.

[0004] However, the AgCuNiRE alloy prepared by conventional smelting, extrusion and rolling methods still has the following problems: the second phase particles in the alloy are unevenly distributed, the wear resistance is unstable, and the consistency of the material service life is affected; the particle size in the alloy is uneven, and there are a small number of large particles. When rolled into foil strips, it is easy to break the coating, resulting in material scrapping; after rolling into foil strips, the alloy contains a large amount of Cu (Ni) rich fiber phase, and the material is easy to discolor and oxidize, affecting the life of the alloy. The key to the above problems is the uneven structure in the alloy, the presence of large non-deformable particles and large flaky Cu-rich phases. Therefore, choosing a more effective processing method to crush and refine the second phase particles is important for improving the application effect of AgCuNiRE alloy in commutator pole pieces. Summary of the invention

[0005] The object of the present invention is to provide a method for refining the second phase of a cast AgCuNiRE alloy and an AgCuNiRE alloy. The method provided by the present invention can fully refine the second phase of the cast AgCuNiRE alloy, improve the life consistency and stability of the alloy, and at the same time help to improve the tensile strength and hardness of the alloy.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for refining the second phase of a cast AgCuNiRE alloy, comprising:

[0008] The as-cast AgCuNiRE alloy billet is subjected to a first forging to obtain a cubic billet;

[0009] The cube billet is subjected to multi-directional forging; the multi-directional forging comprises: performing second forging in the three directions of height, transverse direction and longitudinal direction of the cube billet respectively, the second forging comprising drawing and upsetting; the initial forging temperature of the multi-directional forging is 450-500°C, and the final forging temperature is 290-310°C.

[0010] Preferably, the amount of deformation by drawing and upsetting in the second forging in each direction is independently 40 to 60%.

[0011] Preferably, the multi-directional forging is performed twice or more.

[0012] Preferably, the as-cast AgCuNiRE alloy billet is homogenized before the first forging.

[0013] Preferably, the homogenization treatment is performed at a temperature of 700 to 800° C. and for a time of 4 to 6 hours.

[0014] Preferably, after the multi-directional forging is completed, the obtained forging is subjected to vacuum annealing treatment.

[0015] Preferably, the vacuum annealing treatment is performed at a temperature of 550-650° C. and for a time of 0.5-1.5 h.

[0016] Preferably, the composition of the cast AgCuNiRE alloy is 4-6% Cu, 0.5-1% Ni, 0.1-0.3% RE, and the balance Ag in percentage by mass.

[0017] The present invention also provides an AgCuNiRE alloy obtained by processing using the method described in the above technical solution.

[0018] Preferably, the average diameter of the second phase particles in the AgCuNiRE alloy is no more than 1.5 μm, and the area fraction is greater than 12.5%.

[0019] The present invention provides a method for refining the second phase of a cast AgCuNiRE alloy, comprising: performing a first forging on a cast AgCuNiRE alloy billet to obtain a cubic billet; performing multi-directional forging on the cubic billet; the multi-directional forging is: performing a second forging in the three directions of the height, transverse direction and longitudinal direction of the cubic billet, respectively, the second forging including drawing and upsetting; the initial forging temperature of the multi-directional forging is 450-500°C, and the final forging temperature is 290-310°C. The present invention uses medium-temperature multi-directional forging to subject the second phase particles to multi-directional shearing and pulling during the drawing and upsetting in different directions, so that the second phase particles are broken, the second phase particles in the alloy are fully refined, and are dispersed in the matrix, thereby eliminating casting defects, improving the microstructure of the alloy, and improving the consistency and stability of the alloy. The results of the embodiment show that after being treated by the method provided by the present invention, the second phase in the AgCuNiRE alloy is evenly distributed, the average particle diameter is 1.5 μm, the area fraction is 13.5%, the tensile strength is 272 MPa, and the hardness is 75 HV0.2. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the process of multi-directional forging in an embodiment of the present invention;

[0021] Figure 2 This is the microstructure morphology of the as-cast AgCuNiRE alloy billet prepared in Example 1;

[0022] Figure 3 This is the AgCuNiRE alloy microstructure morphology obtained after treatment in Example 1;

[0023] Figure 4 This is the microstructure morphology of the AgCuNiRE alloy obtained after comparative example treatment. DETAILED DESCRIPTION

[0024] All raw materials of the present invention have no particular limitation on their sources and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0025] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses high purity or conventional purity in the field of silver alloys.

[0026] The present invention provides a method for refining the second phase of a cast AgCuNiRE alloy, comprising:

[0027] The as-cast AgCuNiRE alloy billet is subjected to a first forging to obtain a cubic billet;

[0028] The cube billet is subjected to multi-directional forging; the multi-directional forging comprises: performing second forging in the three directions of height, transverse direction and longitudinal direction of the cube billet respectively, the second forging comprising drawing and upsetting; the initial forging temperature of the multi-directional forging is 450-500°C, and the final forging temperature is 290-310°C.

[0029] In the present invention, the composition of the cast AgCuNiRE alloy is preferably Cu 4-6%, Ni 0.5-1%, RE 0.1-0.3%, and the balance Ag in terms of mass percentage. The present invention limits the composition and dosage of the alloy within the above range, which is beneficial to improving the comprehensive performance of the alloy and meeting the requirements of the commutator coating material. As an embodiment of the present invention, the composition of the cast AgCuNiRE alloy can be Cu 4.2-5.8%, Ni 0.6-0.9%, RE 0.12-0.26%, and the balance Ag; it can also be Cu 4.5-5.5%, Ni 0.7-0.8%, RE 0.15-0.22%, and the balance Ag.

[0030] In the present invention, the RE is preferably one or more of Ce, La, Y, and Gd, and more preferably a combination of multiple elements. In an embodiment of the present invention, the RE is Ce or Gd or a combination of Ce and Gd. Multiple rare earth elements have a composite effect, which is beneficial to the refinement and dispersion of the second phase particles and improves the tensile properties and hardness of the alloy.

[0031] The present invention performs a first forging on a cast AgCuNiRE alloy billet to obtain a cubic billet.

[0032] In the present invention, the as-cast AgCuNiRE alloy billet is preferably a cylindrical ingot. The diameter to height ratio of the cylindrical ingot is preferably 1:(2.5-2.8). The size of the cylindrical ingot is within the above range, which is conducive to forging the ingot into a cubic billet.

[0033] In the present invention, the as-cast AgCuNiRE alloy billet is preferably prepared by vacuum melting and casting. The present invention has no particular requirements on the specific parameters of the vacuum melting and casting, as long as the as-cast AgCuNiRE alloy billet can be obtained. As an embodiment of the present invention, the vacuum melting and casting can be vacuumized to 10 -1 Pa, fill with argon to 0.04-0.05MPa, raise the smelting temperature to 1200℃, melt Ag, Cu and Ni first, then add RE wrapped with Ag skin through the secondary feeding bin, stir evenly, pour into a graphite mold with a diameter of φ100mm, then cool and demold to obtain a cast AgCuNiRE alloy billet.

[0034] After cooling and demolding, the present invention preferably removes the surface defects and shrinkage cavities of the ingot to obtain a cast AgCuNiRE alloy billet. The present invention has no particular limitation on the specific method for removing the surface defects and shrinkage cavities of the ingot, as long as the defects and shrinkage cavities on the surface of the ingot can be removed. In an embodiment of the present invention, a lathe is used to remove the surface defects of the ingot, and a band saw is used to remove the shrinkage cavities.

[0035] In the present invention, the cast AgCuNiRE alloy is preferably subjected to homogenization treatment before the first forging. The temperature of the homogenization treatment is preferably 700-800°C, more preferably 730-780°C; the holding time is preferably 4-6h, more preferably 4.5-5.5h; the homogenization treatment is preferably carried out in a vacuum environment, and the vacuum degree of the vacuum environment is preferably less than 10 -1 Pa. As an embodiment of the present invention, the homogenization treatment can be performed in a vacuum treatment furnace. The present invention reduces or eliminates segregation in the alloy through homogenization treatment, improves the uneven state of the alloy crystal structure, and is beneficial to the forging process of the alloy.

[0036] The present invention has no particular limitation on the first forging method, as long as the alloy ingot can be forged into a cube. As an embodiment of the present invention, the first forging can be medium temperature forging; the temperature of the medium temperature forging can be 450-500°C.

[0037] After the cubic billet is obtained, multi-directional forging is performed on the cubic billet.

[0038] In the present invention, the multi-directional forging is to perform second forging in the three directions of height, transverse direction and longitudinal direction of the cube billet respectively, and the second forging includes drawing and upsetting.

[0039] In the present invention, the initial forging temperature of the multi-directional forging is 450-500°C, preferably 460-490°C. The present invention has no special requirements on the heating method of the ingot, as long as the ingot can be heated to the initial forging temperature. As an embodiment of the present invention, the ingot can be placed in a muffle furnace, covered with charcoal, and heated to 500°C.

[0040] In the present invention, the final forging temperature of the multi-directional forging is 290-310° C., preferably 295-305° C. The present invention limits the temperature of the multi-directional forging to the above range, which is conducive to breaking the second phase particles in the alloy and fully refining and dispersing the second particles in multi-directional shearing and pulling.

[0041] In the present invention, the second forging is preferably first drawing and then upsetting. After the second forging in one direction is completed, the second forging in the next direction is performed, and there is no order for the forging in each direction.

[0042] In the present invention, the deformation of the elongation and upsetting in the second forging in each direction is preferably independently 40-60%, and more preferably 45-55%. In an embodiment of the present invention, the deformation of the elongation and upsetting in the second forging in each direction is the same, which is 45%, 48%, 50% or 55%. The deformation directly affects the shear force of the alloy structure during the forging process. The greater the deformation, the greater the shear force, which is more conducive to the refinement of the second particles. However, excessive deformation will cause irreversible structural deformation of the alloy ingot, which is not conducive to the multi-directional forging.

[0043] In the present invention, the number of multi-directional forging is preferably more than two times. The more times the multi-directional forging is performed, the finer and more uniform the second phase particles of the alloy are. In an embodiment of the present invention, the number of multi-directional forging is 2 times.

[0044] In the present invention, after the multi-directional forging is completed, the obtained forging is preferably subjected to vacuum annealing; the temperature of the vacuum annealing is preferably 550-650°C, more preferably 580-620°C; the time of the vacuum annealing is preferably 0.5-1.5h, more preferably 0.8-1.2h. The present invention can eliminate the residual stress in the forging through vacuum annealing, which is conducive to optimizing the microstructure of the alloy.

[0045] In the present invention, when it is needed as a cladding material for a commutator paddle, the present invention preferably draws the forging obtained by the multi-directional forging to obtain an alloy plate, and then performs a vacuum annealing treatment.

[0046] The present invention has no special requirements on the specific operation of forging drawing, as long as the forging can be drawn into a plate.

[0047] The present invention uses medium-temperature multi-directional forging to subject second-phase particles to multi-directional shearing and pulling during the process of elongation and upsetting in different directions, so that the second-phase particles are broken, the second-phase particles in the alloy are fully refined, and the second-phase particles are dispersed in the matrix, thereby eliminating casting defects, improving the microstructure of the alloy, and improving the consistency and stability of the alloy.

[0048] In an embodiment of the present invention, the process of multi-directional forging is as follows: Figure 1 As shown in the figure, after the ingot is forged into a cube, the three directions of X, Y and Z are marked, and the X and Y directions are forged to extend the ingot along the Z direction, keeping the XY cross section as a square. After the deformation reaches 40-60%, it is upset to a cube along the Z axis direction; the same method is used to lengthen and upset along the Y and X axis directions respectively, thus completing a multi-directional forging.

[0049] The present invention also provides an AgCuNiRE alloy obtained by processing using the method described in the above technical solution.

[0050] In the invention, the average diameter of the second phase particles in the AgCuNiRE alloy is preferably not greater than 1.5 μm, and the area fraction is preferably greater than 12.5%. The smaller the average diameter of the second particles in the AgCuNiRE alloy and the larger the area fraction, the more conducive it is to the dispersion of the second phase particles, thereby improving the uniformity and stability of the alloy.

[0051] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] A method for refining the second phase of a cast AgCuNiRE alloy, comprising the following specific steps:

[0054] The composition of the alloy is: Cu 4wt%, 800g; Ni 0.5wt%, 100g; Ce 0.2wt%, 40g; Ag 95.3wt%, 19060g;

[0055] Vacuum induction melting ingot: Add Ag, Cu and Ni into vacuum induction melting furnace and evacuate to 10 -1 Pa, fill with argon to 0.045MPa; raise the smelting temperature to 1200℃, melt Ag, Cu and Ni first, then add RE wrapped with Ag skin through the secondary feeding bin, stir evenly, pour into a graphite mold with a diameter of Ф100mm to obtain an alloy ingot.

[0056] Ingot defect removal: The surface defects of the ingot are removed by lathe, and the shrinkage holes are cut off by band saw to obtain the as-cast AgCuNiRE alloy billet with clean surface and no defects.

[0057] Homogenization treatment: The as-cast AgCuNiRE alloy billet is placed in a vacuum heat treatment furnace for heating, and the vacuum degree is less than 10 -1 Pa, heating temperature is 750℃, keeping temperature for 4h, cooling with the furnace.

[0058] Forging: Place the ingot in a muffle furnace, cover it with charcoal, heat it to 500℃, and keep it warm for 2 hours. First, upset the round ingot and forge it into a cube by free forging. Then mark the three directions of X, Y, and Z, forge the X and Y directions, extend it along the Z axis, and ensure that the cross section (XY plane) is a square with an elongation of 50%. Then upset it to a cube along the Z axis. Use the same process to stretch and upset it along the Y and X axis directions in turn to complete a multi-directional forging. Use the same process to perform multi-directional forging twice. After the multi-directional forging is completed, stretch it along any direction and forge it into a plate with a width of 100mm and a thickness of 20mm.

[0059] Vacuum annealing: The above plate was vacuum annealed at 600°C for 1 h to obtain AgCuNiRE alloy.

[0060] The microstructure of the alloy ingot and the final AgCuNiRE alloy was observed using a scanning electron microscope. Figure 2 , Figure 3 As shown. Figure 2 , Figure 3 It can be seen that the second phase particles (dark colored parts) in the cast AgCuNiRE alloy are of different sizes and unevenly distributed; after refinement treatment, the second phase particles are significantly refined and evenly distributed.

[0061] Example 2

[0062] A method for refining the second phase of a cast AgCuNiRE alloy, comprising the following specific steps:

[0063] The composition of the alloy is: Cu 4wt%, 800g; Ni 0.5wt%, 100g; Ce 0.15wt%, 30g; Gd 0.15wt%, 30g; Ag 95.2wt%, 19040g;

[0064] Vacuum induction melting ingot: Add Ag, Cu and Ni into vacuum induction melting furnace and evacuate to 10 -1 Pa, fill with argon to 0.045MPa; raise the smelting temperature to 1200℃, melt Ag, Cu and Ni first, then add RE wrapped with Ag skin through the secondary feeding bin, stir evenly, pour into a graphite mold with a diameter of Ф100mm to obtain an alloy ingot.

[0065] Ingot defect removal: The surface defects of the ingot are removed by lathe, and the shrinkage holes are cut off by band saw to obtain the as-cast AgCuNiRE alloy billet with clean surface and no defects.

[0066] Homogenization treatment: The as-cast AgCuNiRE alloy billet is placed in a vacuum heat treatment furnace for heating, and the vacuum degree is less than 10 -1Pa, heating temperature is 750℃, keeping temperature for 4h, cooling with the furnace.

[0067] Forging: Place the ingot in a muffle furnace, cover it with charcoal, heat it to 500℃, and keep it warm for 2 hours. First, upset the round ingot and forge it into a cube by free forging. Then mark the three directions of X, Y, and Z, forge the X and Y directions, extend it along the Z axis, and ensure that the cross section (XY plane) is a square with an elongation of 50%. Then upset it to a cube along the Z axis. Use the same process to stretch and upset it along the Y and X axis directions in turn to complete a multi-directional forging. Use the same process to perform multi-directional forging twice. After the multi-directional forging is completed, stretch it along any direction and forge it into a plate with a width of 100mm and a thickness of 20mm.

[0068] Vacuum annealing: The above plate was vacuum annealed at 600°C for 1 h to obtain AgCuNiRE alloy.

[0069] Example 3

[0070] The raw materials and preparation method are the same as those in Example 1, except that the multi-directional forging is performed once.

[0071] Example 4

[0072] The preparation method is the same as that of Example 1, except that the addition amount of Ce is 0.1%, 20 g, and the addition amount of Ag is 19080 g.

[0073] Example 5

[0074] The preparation method is the same as that of Example 1, except that Ce is replaced by Gd, the added amount is 0.3%, 60 g, and Ag is 19040 g.

[0075] Comparative Example

[0076] The raw materials and preparation method are the same as those in Example 1, except that the conventional rolling process is used instead of multi-directional forging: the 100 mm round ingot obtained by casting is directly forged into a plate with a width of 100 mm and a thickness of 20 mm, and the plate is vacuum annealed at 600 ° C for 1 h to obtain an AgCuNiRE alloy with a microstructure morphology as shown in FIG. Figure 4 shown.

[0077] Test Case

[0078] The diameter and area fraction of the second phase particles in the alloys after the test examples and comparative examples were tested, as well as the tensile strength (GB / T 28487-2012) and hardness (GB / T 7997-2014) of the alloys. The second phase diameter and the second phase area fraction were statistically analyzed using Image Pro Plus software. The results are shown in Table 1.

[0079] Table 1 Second phase data and alloy performance test record

[0080] Second phase diameter / μm Second phase area fraction % Tensile strength / MPa Hardness / HV0.2 Example 1 1.5 13.5 270 70 Example 2 1.5 13.5 272 75 Example 3 2 12.5 255 67 Example 4 1.5 10.5 258 68 Example 5 1.5 13.2 267 73 Comparative Example 1 2.5 12.5 250 65

[0081] It can be seen from Table 1 that, compared with the traditional rolling process, the refinement method of the present invention can more effectively refine the second phase particles in the cast AgCuNiRE alloy; the refinement of the second phase particles is beneficial to improving the tensile strength and hardness of the alloy. By comparing Example 2 and Example 5, it can be seen that two different rare earth elements can more effectively improve the tensile strength and hardness of the alloy than one rare earth element.

[0082] It can be seen from the above embodiments and comparative examples that the method for refining the second phase particles in the cast AgCuNiRE alloy provided by the present invention can fully refine and disperse the second phase particles, thereby ensuring the consistency and stability of the alloy; and the refinement of the second phase particles is also beneficial to improving the tensile strength and hardness of the alloy, which can better meet the application requirements of the commutator pole pieces.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for refining the second phase of a cast AgCuNiRE alloy, comprising: The as-cast AgCuNiRE alloy billet is subjected to a first forging to obtain a cubic billet; Performing multi-directional forging on the cubic blank; The multi-directional forging is: performing second forging in the three directions of height, transverse direction and longitudinal direction of the cube blank respectively, the second forging includes drawing and upsetting; the initial forging temperature of the multi-directional forging is 450-500°C, and the final forging temperature is 290-310°C.

2. The method according to claim 1, characterized in that The amount of deformation by drawing and upsetting in the second forging in each direction is independently 40 to 60%.

3. The method according to claim 1, characterized in that The multi-directional forging is performed twice or more.

4. The method according to claim 1, characterized in that The as-cast AgCuNiRE alloy billet is homogenized before the first forging.

5. The method according to claim 4, characterized in that The temperature of the homogenization treatment is 700-800° C. and the time is 4-6 hours.

6. The method according to claim 1, characterized in that After the multi-directional forging is completed, the obtained forging is subjected to vacuum annealing treatment.

7. The method according to claim 6, characterized in that The temperature of the vacuum annealing treatment is 550-650° C., and the time is 0.5-1.5 h.

8. The method according to any one of claims 1 to 7, characterized in that: The components of the cast AgCuNiRE alloy are 4-6% Cu, 0.5-1% Ni, 0.1-0.3% RE and the balance Ag in terms of mass percentage.

9. AgCuNiRE alloy obtained by the method according to any one of claims 1 to 8.

10. The AgCuNiRE alloy according to claim 9, characterized in that: The average diameter of the second phase particles in the AgCuNiRE alloy is no more than 1.5 μm, and the area fraction is greater than 12.5%.

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