Copper-steel bimetal composite casting process method

Abstract

The invention discloses a copper-steel bimetal composite casting process method, which comprises the following steps: immersing a steel substrate joint surface into a plating assistant solution for pretreatment, attaching a compact plating assistant salt film on the joint surface, pouring tin liquor, and carrying out heat preservation treatment to obtain a tin-injected steel substrate; and preheating to 800-900 DEG C, and pouring a copper alloy solution to prepare the copper-steel double-metal composite material. By changing the surface treatment process of the steel substrate, the preheating temperature of the steel substrate is reduced, the production efficiency is improved, the structure grains of the steel substrate are refined, and the comprehensive performance of the copper-steel double-metal composite material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing bimetallic composite materials, and relates to a solid-liquid composite casting process method based on copper-steel bimetal. Background Art

[0002] Copper-steel bimetallic composite materials simultaneously possess the excellent tribological properties of copper alloys and the good mechanical properties and processability of steel. They are excellent friction pair materials and have played an important role in the fields of friction pairs such as plunger pumps, bimetallic guide rings, and bearings in industrial production and applications.

[0003] The metallurgical bonding between metals is the key to the preparation of bimetallic composite materials. The interface is the most important microstructure of the composite material. Factors such as the distribution of the interface structure, bonding characteristics, atomic bonding mode, and interface reaction mode are closely related to the properties of the composite material, and the quality of the interface bonding strength directly determines the comprehensive properties of the composite material.

[0004] Currently, the most mature and widely used process for preparing copper-steel bimetallic composite materials is the solid-liquid bimetal composite casting process. This process usually requires complex surface pretreatment of the steel substrate, and then preheating the steel substrate to a relatively high temperature (above 1000°C), and then pouring the copper alloy melt to form the bimetallic composite material.

[0005] Although this process method is the most mature and widely used, there are still some problems that will affect the technology promotion and material properties:

[0006] 1) The active protection process is complex, with high technical requirements and low efficiency.

[0007] The quality requirements for the active protection of the bonding surface are high. Precise control is required for the dosage of the protective layer material, the uniformity of the active agent, etc. The efficiency is low, seriously affecting the application of this technology in large-scale and mass production.

[0008] 2) The preheating temperature is too high, which is likely to cause coarse grain structure and structural deformation, affecting the material properties.

[0009] If the preheating temperature of the steel substrate is too high, it is easy to cause coarse grains in the internal structure, resulting in a decrease in mechanical properties such as the strength, toughness, and hardness of the steel, and it is more likely to have cracks and deformations when bearing loads. In addition, high-temperature preheating may also cause external structural deformation, affecting the precise dimensions of the casting, while bringing additional energy consumption, deteriorating the production environment, and increasing the risk of high-temperature operation. Summary of the Invention

[0010] The object of the present invention is to provide a copper-steel bimetallic composite casting process method. Aiming at the drawbacks of the prior art, by changing the surface treatment process of the steel matrix and reducing the preheating temperature of the steel matrix, a more optimal casting forming process for copper-steel bimetallic composite materials is designed.

[0011] To achieve the above-mentioned invention object, the present invention proposes a casting forming process for copper-steel bimetallic composite materials with tin plating on the steel matrix and low-temperature preheating, which improves the production efficiency, refines the crystal grains of the steel matrix structure, and enhances the comprehensive performance of the copper-steel bimetallic composite materials.

[0012] Specifically, the copper-steel bimetallic composite casting process method of the present invention includes the following steps:

[0013] 1) Surface pretreatment of the steel matrix

[0014] The bonding surface of the steel matrix is completely immersed in the flux solution for pretreatment, and a dense flux salt film is attached to the bonding surface of the steel matrix.

[0015] The flux solution is obtained by mixing 40 - 45 wt% saturated ZnCl2 solution, 3 - 6 wt% saturated NH4Cl solution, 1 - 2 wt% saturated CeCl3 solution, 1 - 2 wt% saturated KF solution with the balance of water.

[0016] 2) Tin plating and heat preservation of the steel matrix

[0017] The steel matrix with the flux salt film attached is preheated to 100 - 120 °C, molten tin liquid is poured, and it is kept at 500 - 600 °C for 5 - 6 h, and then air-cooled to room temperature to obtain the tin-plated steel matrix.

[0018] 3) Casting of copper-steel bimetallic composite materials

[0019] The tin-plated steel matrix is preheated to 800 - 900 °C, and copper alloy melt is poured, and then left to stand and air-cooled to room temperature to prepare the copper-steel bimetallic composite materials.

[0020] Furthermore, the process method of the present invention also includes performing alkali washing and acid washing treatments on the bonding surface of the steel matrix in sequence before the surface pretreatment of the steel matrix.

[0021] Furthermore, preferably, the bonding surface of the steel matrix is completely immersed in the flux solution heated to 60 - 80 °C, and the soaking time each time is not less than 5 min, and the operation is repeated 3 - 5 times.

[0022] Furthermore, the preheating time of the steel matrix with the flux salt film attached is preferably 3 - 5 min.

[0023] Furthermore, the preheating time of the tin-plated steel matrix is preferably 15 - 25 min.

[0024] Furthermore, the raw materials of the present invention are weighed according to the copper alloy raw material ratio, and a copper alloy melt is obtained by melting at 1150 - 1200 °C.

[0025] Even further, the raw materials of the present invention are sequentially put into a melting device according to the order of melting points from high to low to obtain a copper alloy melt.

[0026] Even further, preferably, the melting device can be a crucible melting furnace or a pit melting furnace.

[0027] The copper - steel bimetal composite casting process method provided by the present invention adopts a composite process of tin injection for heat preservation on the steel substrate and additional low - temperature preheating, and has the following technical advantages:

[0028] 1) By replacing the surface activation layer with the method of tin injection for heat preservation on the steel substrate, while protecting the interface, high - efficiency and batch processing are realized, and the processing efficiency is improved;

[0029] 2) The tin injection for heat preservation treatment also plays a role in wetting the interface and improving atomic activity, reducing the necessity of high - temperature preheating of the steel substrate;

[0030] 3) By reducing the preheating temperature of the steel substrate, the problem of coarse grains in the steel structure is prevented, and the atomic diffusion rate is prevented from being hindered due to coarse grains. By improving the steel substrate structure, refining the grains, reducing structural deformation, the comprehensive performance of the copper - steel bimetal composite material is improved;

[0031] 4) Reducing the preheating temperature of the steel substrate also reduces energy consumption, optimizes the production environment, and reduces operation risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 are the interface coloring detection results of copper - steel bimetal composite materials prepared by different process methods.

[0033] Figure 2 are the metallographic diagrams of the steel side structure of copper - steel bimetal composite materials prepared by different process methods. EMBODIMENTS

[0034] The following further describes the specific embodiments of the present invention in detail with reference to the drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, so that those skilled in the art can better understand and utilize the present invention, rather than limiting the protection scope of the present invention.

[0035] In the embodiments of the present invention, the production processes, experimental methods, or detection methods involved, unless otherwise specified, are all conventional methods in the prior art, and their names and / or abbreviations are all conventional names in the art, which are very clear and definite in the relevant application fields. Those skilled in the art can understand the conventional process steps according to the names and apply the corresponding equipment, and implement them under conventional conditions or the conditions recommended by the manufacturer.

[0036] There are no special restrictions on the sources of various instruments, equipment, raw materials, or reagents used in the embodiments of the present invention. They are all conventional products that can be obtained through regular commercial channels, and can also be prepared according to the conventional methods well-known to those skilled in the art. Example

[0037] Example 1

[0038] The steel matrix model for preparing the copper-steel bimetallic composite material is 42CrMo. The copper alloy is cast on its inner surface to prepare the bimetallic composite material, and the copper alloy material for casting is ZCuPb10Sn10 alloy.

[0039] 1) Surface cleaning of the steel matrix

[0040] First, the surface of the steel matrix is cleaned. The steel matrix is successively ultrasonically pickled with 10% NaOH solution and ultrasonically pickled with 10% HCl solution, and finally rinsed with distilled water to remove the residual acid-base solution on the steel matrix.

[0041] 2) Pretreatment of the bonding surface of the steel matrix

[0042] Prepare a flux solution, which contains 42.5 wt% saturated ZnCl2 solution, 5 wt% saturated NH4Cl solution, 1.25 wt% saturated CeCl3 solution, and 1.25 wt% saturated KF solution.

[0043] Pour the prepared flux solution into the inside of the steel matrix, heat the whole to 80 °C, let it stand for 5 min, take it out and dry it with a hot air gun. After repeating the operation 3 times, a dense flux salt film is attached to the bonding surface of the steel matrix.

[0044] 3) Tin plating treatment of the steel matrix

[0045] Preheat the flux-treated steel matrix at 100 °C for 5 min. Use pure tin with a purity of 99.99 wt% to melt it into a tin liquid, pour it into the preheated steel matrix, put it into a preheating furnace heated to 600 °C for heat preservation treatment. After heat preservation for 5 h, take out the steel matrix and let it stand and air-cool to room temperature.

[0046] 4) Melting the copper alloy melt

[0047] Prepare and melt the copper alloy according to the composition of ZCuPb10Sn10, and set the melting temperature at 1200 °C.

[0048] 5) Cast the bimetallic composite material

[0049] Put the tin-plated steel substrate into a preheating furnace at 800 °C, take it out after preheating for 20 minutes, pour the molten copper alloy solution, and air-cool it to room temperature to prepare the copper-steel bimetallic composite material.

[0050] The technical requirements of each step above in this embodiment are relatively low, and can be processed in batches to improve the processing efficiency.

[0051] Example 2

[0052] Use the same steel substrate and copper alloy materials as in Example 1, and cast and prepare the bimetallic composite material by using the traditional process method.

[0053] 1) Surface cleaning of the steel substrate

[0054] First, perform surface cleaning on the steel substrate. Ultrasonically alkali-wash the steel substrate with a 10% NaOH solution, ultrasonically acid-wash it with a 10% HCl solution, and finally rinse the residual acid and alkali solutions on the steel substrate with distilled water until clean.

[0055] 2) Pretreatment of the bonding surface of the steel substrate

[0056] Coat the activation layer material borax on the steel substrate according to the traditional process to ensure no dead corners and no leakage points.

[0057] 3) Melting the molten copper alloy

[0058] Prepare the copper alloy according to the composition of ZCuPb10Sn10, and set the melting temperature at 1200 °C.

[0059] 4) Cast the bimetallic composite material

[0060] Put the steel substrate into a preheating furnace at 1200 °C, take it out after preheating for 20 minutes, pour the molten copper alloy solution, and let it stand and air-cool to room temperature to prepare the copper-steel bimetallic composite material.

[0061] Application example

[0062] Conduct microstructure and property tests on the copper-steel bimetallic composite materials prepared under the above two processes.

[0063] 1) Colorimetric detection

[0064] Figure 1 The interfacial colorimetric detection of the bonding surfaces of the materials prepared by the traditional process (a) and the process of the present invention (b) respectively. After the colorimetric defect inspection, it is found that the interfaces of the materials prepared by both processes are well bonded and no obvious defects are found.

[0065] 2) Shear strength test

[0066] Shear strength analysis was performed on shear specimens of the composite materials prepared by the two processes. The cross sections all appeared on the copper side, proving that the interfaces of the bimetallic composite materials prepared by the two processes achieved good metallurgical bonding. The shear strength of the sample in Example 1 reached 342.05 MPa, while the shear strength of the sample in Example 2 was only 227.55 MPa. The shear strength of the process method of the present invention was improved by 6.6%. The process method of the present invention not only ensures good bonding of the interface, but also slightly improves the bonding strength.

[0067] 3) Metallographic OM observation of steel side

[0068] The OM observation of the steel side structure is shown in the following figure: Figure 2 As shown in the figure, it can be clearly seen that the grains of the steel side structure under the traditional process (a) of Example 2 are coarse, while the grains of the steel matrix structure under the process (b) of Example 1 are obviously much smaller.

[0069] In the traditional process, due to the high preheating temperature, the steel matrix structure is completely transformed into coarse austenite, and the structure is transformed into coarse pearlite and a small amount of ferrite during the subsequent cooling. The large distribution of coarse pearlite causes the steel structure to be severely hard and brittle, reducing the toughness and plasticity of the material, and the overall performance is not high. The preheating temperature of the process method of the present invention is low, the austenitization is incomplete, and the grains are difficult to grow. After the cooling process, the steel structure is transformed into fine pearlite and ferrite. The higher ferrite content makes the steel structure hardness under the new process relatively low, its toughness and plasticity are improved, and the overall performance is optimized, which can be better applied to structures that bear impact loads.

[0070] Therefore, the copper-steel bimetallic composite casting process method that uses tin injection to keep the steel matrix warm and low-temperature preheating can greatly improve the processing efficiency. On the premise of ensuring that the interface does not lose good interface bonding, it can effectively improve the problem of coarse steel matrix grains, optimize organizational properties, and reduce energy consumption. This is of great significance to the further promotion and improvement of copper-steel bimetallic composite casting technology.

[0071] The above embodiments of the present invention do not describe all the details in detail, nor limit the present invention to the above embodiments. Various changes, modifications, substitutions and variations made by ordinary technicians in this field without departing from the principles and purpose of the present invention should be included in the protection scope of the present invention.

Claims

1. A copper-steel bimetallic composite casting process method, comprising: 1) Surface pretreatment of the steel substrate The bonding surface of the steel substrate is completely immersed in the flux solution for pretreatment, and a dense flux salt film is adhered to the bonding surface of the steel substrate; The flux solution therein is obtained by mixing 40-45wt% saturated ZnCl2 solution, 3-6wt% saturated NH4Cl solution, 1-2wt% saturated CeCl3 solution, 1-2wt% saturated KF solution and the balance of water; 2) Tin injection and heat preservation of the steel substrate The steel substrate with the flux salt film adhered is preheated to 100-120°C, molten tin liquid is poured, and it is heat-preserved at 500-600°C for 5-6h, and then air-cooled to room temperature to obtain the tin-injected steel substrate; 3) Casting the copper-steel bimetallic composite material The tin-injected steel substrate is preheated to 800-900°C, copper alloy melt is poured, and it is left to stand and air-cooled to room temperature to prepare the copper-steel bimetallic composite material.

2. The copper-steel bimetal composite casting process method according to claim 1, characterized in that It also includes performing alkali washing and acid washing treatments on the bonding surface of the steel substrate before the surface pretreatment of the steel substrate.

3. The copper-steel bimetal composite casting process method according to claim 1, characterized in that The bonding surface of the steel substrate is completely immersed in the flux solution heated to 60-80°C.

4. The copper-steel bimetallic composite casting process method according to claim 1 or 3, characterized in that The operation of immersing in the flux solution is repeated 3-5 times, and the soaking time each time is not less than 5 minutes.

5. The copper-steel bimetal composite casting process method according to claim 1, characterized in that The preheating time of the steel substrate with the flux salt film adhered is 3-5 minutes.

6. The copper-steel bimetal composite casting process method according to claim 1, characterized in that The preheating time of the tin-injected steel substrate is 15-25 minutes.

7. The copper-steel bimetallic composite casting process method according to claim 1, characterized in that The copper alloy melt is obtained by melting at 1150-1200°C.

8. The copper-steel bimetal composite casting process method according to claim 7, characterized in that The raw materials are put into the melting equipment in the order of melting point from high to low for melting to obtain the copper alloy melt.

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