A method for preparing a copper-nickel-tin alloy ingot

Abstract

The present invention relates to a method for preparing a copper-nickel-tin alloy ingot, comprising the following steps: (1) preparation of raw materials and tooling molds; (2) vacuum melting; (3) casting. The vacuum melting adopted in the present invention can avoid the absorption of Ni element and ensure accurate composition; the present invention also utilizes the heat conduction of the casting mold and the previously solidified copper water, and through sequential solidification, the subsequently poured copper water can be rapidly solidified, thereby reducing segregation and also facilitating the continuous floating of the slag contained in the copper water; the surface quality of the copper-nickel-tin alloy ingot prepared by the present invention is good, and subsequent processing can be carried out after slight cleaning, with fewer risers and reduced costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of copper-nickel-tin alloys, and particularly relates to a method for preparing a copper-nickel-tin alloy ingot. Background Art

[0002] Copper-nickel-tin (CuNiSn) alloy is a new type of high-strength and wear-resistant elastic copper alloy material, whose properties are comparable to those of beryllium bronze, and it is non-toxic compared with beryllium bronze alloy; copper-nickel-tin alloy has advantages such as high thermal stability and high-temperature strength, and can serve stably for a long time in medium and high-temperature environments. Therefore, in recent years, copper-nickel-tin alloy has been widely used in automotive gears, connecting rod bushings, heavy-duty axle bushings, and marine propellers, etc.

[0003] The strengthening mechanism of copper-nickel-tin alloy is as follows: solute Sn element dissolves in the α-copper matrix, and segregation occurs in the stacking fault region, which can hinder the movement on the slip plane and the expansion of dislocation movement. Therefore, it is crucial whether the Sn element can be evenly distributed inside the alloy matrix. However, during the preparation process by traditional melting and casting methods, due to the high content of tin element in copper-nickel-tin alloy, serious dendritic segregation and macrosegregation of tin element are prone to occur during the melting and casting process.

[0004] The existing methods for preparing CuNiSn alloy ingots include: vacuum melting method, powder metallurgy method, mechanical alloying method, rapid solidification method, etc. Among them, although the vacuum melting method can suppress the back segregation of Sn to a certain extent during the melting process, during the pouring of molten copper into the ingot mold and the cooling process, due to the slow cooling rate, segregation will also occur; although the powder metallurgy method and the mechanical alloying method can accurately control the alloy composition and solve the segregation of tin element, due to high costs and production efficiency limitations, they cannot be applied in industrial mass production at present; although the rapid solidification method can omit the homogenization heat treatment process, there are also deficiencies, such as high costs, easy generation of pores, which will lead to a decline in material properties, etc.

[0005] In addition, there is a literature that adds a fourth component, such as Si, to inhibit the generation of discontinuous precipitation, but the newly added element combines with Ni to form new phases, such as Ni 31 Si 12 phase and Ni3Si phase, and this will reduce the properties such as the strength of the alloy.

[0006] Aiming at the problems of element segregation, high cost, and low production efficiency existing in the existing melting and casting technology of copper-nickel-tin alloy, the inventor of the present invention provides a lifting casting process, which aims to solve segregation, improve production efficiency, reduce casting risers, and lower costs. Summary of the Invention

[0007] In view of the above deficiencies of the existing technology, the present invention provides a method for preparing a copper-nickel-tin alloy ingot, and the specific technical solutions are as follows:

[0008] The first object of the present invention is to provide a method for preparing a copper-nickel-tin alloy ingot, comprising the following steps:

[0009] (1) Preparation of raw materials and tooling molds: The raw materials are proportioned according to the following weight percentages of elements: 6.0 - 6.2 wt% Ni, 6.0 - 6.2 wt% Sn, 0.2 - 0.3 wt% Zr, 0.15 - 1 wt% phosphor copper, and the balance copper; after cleaning and drying the inner wall of the casting mold, spray a mold release agent on the casting mold and bake it.

[0010] (2) Vacuum melting: The raw materials are melted in a vacuum induction furnace at a vacuum of -0.1 MPa and a temperature of 1320 - 1380 °C. After electromagnetic stirring and melting to clarify, the molten copper is introduced into the tundish in the vacuum casting chamber after skimming the slag. Charcoal is placed at the bottom of the tundish.

[0011] (3) Casting: After breaking the vacuum in the casting chamber of the vacuum induction furnace, transfer the tundish to the tilting device. After standing until the temperature of the molten copper drops to 1150 - 1250 °C, perform casting; use the tilting device to control the pouring of the molten copper into the casting mold. After the molten copper flows in and fills the bottom of the casting mold, then use the lifting device to make the casting mold descend uniformly at a speed of 30 - 35 mm / s; at this time, control the overflow speed of the molten copper so that the molten copper in the tilting device is continuously poured into the casting mold to achieve solidification while pouring; after complete solidification, perform demolding.

[0012] Further, the raw materials are electrolytic copper plates, nickel metal blocks, tin metal blocks, zirconium metal blocks, and phosphor copper alloys.

[0013] The raw materials need to be cleaned and dried before melting. Among the various elements in the raw materials, the Zr element plays a role in refining the grain structure and improving the processing performance of the material; it has the characteristic of combining with oxygen elements and can achieve the purpose of deoxidation during the melting and casting process.

[0014] Further, the baking temperature of the casting mold is ≥350 °C, and the baking temperature of the ladle flame is ≥750 °C.

[0015] The ladle flame is used to bake the water vapor inside the clean ladle; it can also prevent the molten copper from sticking to the surface of the ladle.

[0016] Further, the thickness of the sprayed mold release agent is 1 - 3 mm.

[0017] Further, the mold release agent is a zircon powder mold release agent.

[0018] Further, when the raw materials are subjected to vacuum melting, nickel metal blocks are placed at the bottom of the crucible, covered with electrolytic copper plates, evacuated to -0.1 MPa, and melted by power supply. After the electrolytic copper plates and nickel metal blocks are melted, tin metal blocks, zirconium metal blocks and phosphor copper alloy are added, and the temperature is continuously raised to 1320 - 1380 °C, and electromagnetic stirring is applied until the melting is complete.

[0019] During vacuum melting, copper and nickel elements that are not easily oxidized and volatilized are added first; then tin elements with low melting point and easy volatilization and zirconium elements that are easily oxidized are added. Adding them after copper and nickel are melted also reduces the heating time and improves the quality of the copper-nickel-tin alloy ingot.

[0020] Further, the temperature of the power-on melting is 1320 - 1350 °C.

[0021] Further, during the process of copper water flowing through in step (3), the tundish and the pouring device are continuously subjected to flame spraying treatment.

[0022] Since the pouring process is in the atmospheric environment, flames will spurt between the tundish and the pouring cup during the flowing-through process to create an oxygen-deficient environment. In order to prevent the nickel element in the copper water from inhaling air during the flowing-through process, and at the same time prevent the copper water temperature from dropping too much and generating cold shut.

[0023] Further, the casting mold is made of pig iron, and a water pipe circuit is arranged inside the casting mold.

[0024] The casting mold is made of pig iron, which has good heat resistance and is not easily deformed, but has poor thermal conductivity. A water pipe circuit is arranged inside the casting mold, and the copper water is quickly cooled by cooling water to accelerate the solidification speed of the copper water.

[0025] The beneficial effects of the present invention are as follows:

[0026] The present invention adopts vacuum melting to avoid the inhalation of Ni element and ensure accurate composition; the present invention also utilizes the heat conduction of the casting mold and the previously solidified copper water, and through sequential solidification, the subsequently poured copper water can be quickly solidified, thereby reducing segregation and also facilitating the continuous floating of the slag contained in the copper water; the surface quality of the copper-nickel-tin alloy ingot prepared by the present invention is good, and it can be processed subsequently after slight cleaning, with few risers, reducing costs. Description of the Drawings

[0027] Figure 1 It is the metallographic electron microscope image of the embodiment of the present invention;

[0028] Figure 2 It is the metallographic electron microscope image of the comparative example of the present invention. Detailed Embodiments

[0029] The principles and features of the present invention will be described below in conjunction with examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0030] Example:

[0031] A method for preparing a copper-nickel-tin alloy ingot, comprising the following steps:

[0032] (1) Preparation of raw materials and tooling molds: Clean and dry the raw materials, namely electrolytic copper plates, nickel metal blocks, tin metal blocks, zirconium metal blocks, and phosphorus copper alloys, and proportion them according to the following weight percentages of elements: Ni 6.0%, Sn 6%, Zr 0.3%, phosphorus copper 0.5%, and the balance being copper; Clean and dry the inner wall of the casting mold, then spray and brush a zircon powder release agent with a uniform thickness on the inner wall of the casting mold, and then bake it. The baking temperature is 350 - 360°C; The flame baking temperature of the ladle is 750 - 770°C;

[0033] (2) Vacuum melting: Melt the raw materials in a vacuum induction furnace. During vacuum melting, place the nickel metal block at the bottom of the crucible and cover it with electrolytic copper plates. Evacuate to -0.1 MPa and energize for melting. After the electrolytic copper plates and nickel metal blocks are melted, add the tin metal block, zirconium metal block, and phosphorus copper alloy, continue to heat up to 1350°C, add electromagnetic stirring, and stir until melted and slag is skimmed off. Then pour the molten copper into the tundish in the vacuum casting chamber. Place charcoal at the bottom of the tundish; When the molten copper is poured into the tundish, the charcoal at the bottom will float to the surface of the molten copper. Firstly, it can isolate the contact between the outside air and the molten copper to prevent oxidation; Secondly, it can keep warm and prevent the pouring temperature of the molten copper from being too low;

[0034] (3) Casting: After breaking the vacuum in the casting chamber of the vacuum induction furnace, lift out the tundish and transfer it to the tilting device, let it stand for a period of time, and measure the temperature multiple times during this period. When the temperature of the molten copper drops to 1180°C, carry out pouring; Use the tilting device to control the pouring of the molten copper into the casting mold. After the molten copper flows in and fills the bottom of the casting mold, then use the lifting device to make the casting mold descend at a uniform speed, and the descending speed is 32 mm / s; At this time, control the overflow speed of the molten copper so that the molten copper in the tilting device continuously pours into the casting mold, and keep the distance between the molten copper at the outlet and the liquid level of the molten copper in the casting mold constant, so as to achieve solidification while pouring; After complete solidification, carry out demolding.

[0035] Among them, since the casting process is in the atmospheric environment, during the overflow process of the molten copper in step (3), the tundish and the tilting device are continuously subjected to flame spraying treatment to create an oxygen-deficient environment. In order to prevent the nickel element in the molten copper from inhaling air during overflow and also prevent the molten copper from having too large a temperature drop and generating cold shuts. The casting mold in this example is made of pig iron, and a water pipe circuit is arranged inside the casting mold to quickly cool it with cooling water and accelerate the solidification speed of the molten copper.

[0036] Comparative example:

[0037] The steps (1) and (2) of the comparative example are the same as those of the example, and will not be elaborated here. The difference is that after the molten copper in the crucible is cooled to 1150 °C, it is directly poured into the metal mold inside the casting chamber. The mold material is steel, the cavity size is φ250*360, and after the casting is completed, the mold is lifted out after 15 minutes for demolding.

[0038] Result comparison:

[0039] Samples of the ingots prepared by the process of the example and the comparative example were taken for metallographic inspection. The sampling positions were both at the center of the ingot, as shown in Figure 1 and Figure 2 As can be seen from the metallography, for the copper-nickel-tin ingot prepared by the comparative example, the dendrites are thick, and there are segregated and aggregated Sn elements distributed between some dendrites; this is because the melting point of the Sn element is relatively low. When the main part of the molten copper has cooled, the Sn element is still in a liquid state, and during the slow cooling process, it will gradually gather together and finally form a segregated Sn-rich phase; this will affect the mechanical properties and hot working properties of the copper-nickel-tin ingot. For the copper-nickel-tin ingot prepared by the example, due to the relatively fast cooling rate of the molten copper and sequential solidification, before the Sn element segregates, the overall temperature drops below the solidus line of the alloy. Therefore, there is no segregation in the final ingot blank, and the whole is dense and defect-free; moreover, the surface quality of the copper-nickel-tin ingot prepared by the example is good, and it can be processed subsequently after a little cleaning. There are few risers, which reduces costs.

[0040] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a copper-nickel-tin alloy ingot, characterized in that, The steps include: (1) Preparation of raw materials and tooling molds: The raw materials are prepared according to the weight percentage of the following elements: 6.0-6.2wt% Ni, 6.0-6.2wt% Sn, 0.2-0.3wt% Zr, 0.15-1wt% phosphor copper and the balance copper; the inner wall of the casting mold is cleaned and dried, and then the casting mold is sprayed with a release agent and baked; (2) Vacuum smelting: the raw materials are melted in a vacuum induction furnace at a vacuum of -0.1 MPa and a temperature of 1320-1380°C, and electromagnetic stirring is used to melt the raw materials. After slagging, the molten copper is introduced into a tundish in a vacuum casting chamber, and charcoal is placed at the bottom of the tundish. When the raw materials are vacuum smelted, a nickel metal block is placed at the bottom of the crucible, and an electrolytic copper plate is covered on it. The vacuum is evacuated to -0.1 MPa, and the smelting is powered on. After the electrolytic copper plate and the nickel metal block are melted, a tin metal block, a zirconium metal block and a phosphor copper alloy are added, and the temperature is continuously raised to 1320-1380°C, and electromagnetic stirring is added to melt the raw materials. (3) Casting: After the vacuum is broken in the casting chamber of the vacuum induction furnace, the tundish is transferred to the pouring device and allowed to stand until the temperature of the molten copper drops to 1150-1250°C before pouring; the molten copper is poured into the pouring mold by the pouring device, and after the molten copper flows into and fills the bottom of the pouring mold, the pouring mold is lowered at a uniform speed by the lifting device at a descending speed of 30-35 mm / s; at this time, the flow rate of the molten copper is controlled so that the molten copper in the pouring device is continuously poured into the pouring mold to achieve solidification while pouring; demolding is performed after complete solidification; during the flow of the molten copper, the tundish and the pouring device are continuously subjected to flame spraying.

2. The preparation method of the copper-nickel-tin alloy ingot according to claim 1, characterized in that, The raw materials are electrolytic copper plates, nickel metal blocks, tin metal blocks, zirconium metal blocks, and phosphor-copper alloys.

3. The preparation method of the copper-nickel-tin alloy ingot according to claim 1, wherein The baking temperature of the casting mold is ≥350°C, and the flame baking temperature of the ladle is ≥750°C.

4. The preparation method of the copper-nickel-tin alloy ingot according to claim 1, characterized in that, The release agent is a zircon powder release agent.

5. The preparation method of the copper-nickel-tin alloy ingot according to claim 1, characterized in that, The casting mold is made of cast iron, and a water pipeline is arranged inside the casting mold.

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