Stainless steel non-ferrous metal composite bar containing framework and preparation method of stainless steel non-ferrous metal composite bar

Abstract

The invention relates to a stainless steel and nonferrous metal composite bar containing a framework and a preparation method of the stainless steel and nonferrous metal composite bar. Comprising the following steps: (1) preparing raw materials; (2) establishing a stainless steel skeleton three-dimensional model; (3) according to the established model, selective laser melting (SLM) is adopted for 3D printing, and a stainless steel framework is formed; (4) melting industrial pure copper; (5) the stainless steel framework is heated to be 20-40 DEG C higher than the melting point of pure copper, the molten copper is poured into the stainless steel framework, and an initial bar is obtained; and (6) the initial bar is subjected to rotary forging after being heated and subjected to heat preservation, and the stainless steel-copper composite bar is obtained. The structure with stainless steel as a framework support and a surface protection structure is manufactured through 3D printing, on one hand, the comprehensive mechanical property of the material is enhanced, support is provided in the axial direction of a bar, the framework is hollowed out, internal copper alloy matrixes are completely communicated in the radial direction, and the conductivity of the material is guaranteed to the maximum extent; the stainless steel skin provides effective surface protection for the internal copper alloy matrix.

Description

Technical Field

[0001] The invention belongs to the field of material preparation, and in particular relates to a stainless steel nonferrous metal composite bar containing a skeleton and a preparation method thereof. Background Art

[0002] Nonferrous metals are the basic materials for the development of the national economy. Most industries such as aviation, aerospace, automobiles, machinery manufacturing, electricity, communications, construction, and home appliances are based on nonferrous metal materials. With the rapid development of modern chemical industry, agriculture, and science and technology, nonferrous metals are becoming more and more important in human development. It is not only an important strategic material and important means of production in the world, but also an important material for indispensable consumer goods in human life. The more common nonferrous metals in actual production and life are copper alloys, copper alloys, magnesium alloys, etc. Among them, copper and copper alloys are currently one of the most widely used and economical materials. Copper alloys have good electrical and thermal conductivity, medium mechanical properties and high chemical stability, but poor cutting performance. With the different types and quantities of alloying elements added, the performance of various copper alloys varies greatly.

[0003] Industrial pure copper is the most widely used type of copper alloy. Pure copper is the copper with the highest copper content. Because of its purple-red color, it is also called red copper. The main components are copper and silver, with a content of 99.5-99.95%. Pure copper has good conductivity and is widely used in the manufacture of wires, cables, brushes, etc. However, the strength and hardness of copper alloys are generally poor, and the corrosion resistance is poorer than that of stainless steel, so copper alloys are more prone to failure than stainless steel. Common failure modes of copper wires made of industrial pure copper include corrosion, fracture, and fatigue fracture. Copper wires may corrode due to environmental factors such as water quality problems and contact with chemicals. In addition, if the surface of the copper wire is not properly protected, it is also susceptible to corrosion by chemicals in the environment, resulting in degradation or damage to the wire performance. At present, the most common way to protect copper wires is to wrap an insulating rubber sheath on the surface of the wire, but the rubber sheath usually has the disadvantages of being easy to scratch and age. Once the rubber sheath is scratched, aged and cracked, the copper wire will be directly exposed to the external environment and corrode. The breakage of the copper wire may be caused by defects in the manufacturing or installation process. For example, in electric vehicles, if the setting of the wire fixing point is unreasonable, the wire is subjected to excessive stress during vibration or movement, which may cause the wire to break near the fixing point in the long run. This kind of break is usually caused by excessive alternating stress on the fixed end of the wire, resulting in fatigue fracture of the wire near the plug-in terminal of the fixed point after running for a period of time. When copper wires are at the connection or need to be fixed for a long time or even need to withstand a certain stress in the working environment, the strength of the copper wire is not enough to support long-term use, and the risk of accidents increases.

[0004] In terms of mechanical properties, the tensile strength of 316L stainless steel is usually between 485MPa and 620MPa. The yield strength is usually between 170MPa and 310MPa, and the elongation is usually between 35% and 60%, showing good plasticity. The tensile strength of industrial pure copper is generally around 200MPa, and the yield strength is generally between 100-150MPa. The elongation of industrial pure copper is generally above 30%. In comprehensive comparison, the comprehensive mechanical properties of 316L stainless steel are better than those of industrial pure copper. In terms of corrosion resistance, copper is an excellent conductive metal, so it is widely used in electronic appliances, construction and industrial industries. However, copper has relatively weak corrosion resistance and is easily oxidized and corroded in humid, acidic or alkaline environments. Stainless steel is a corrosion-resistant material that can maintain its surface brightness and no rust marks in humid, acidic, alkaline and even high temperature and high pressure environments. The corrosion resistance of stainless steel is related to its composition and surface treatment method. Because it is doped with elements such as chromium and nickel, it has strong corrosion resistance. Stainless steel is more corrosion-resistant than copper and is suitable for equipment manufacturing and construction materials in various environments. Summary of the invention

[0005] The purpose of the present invention is to provide a stainless steel nonferrous metal composite bar with an internal skeleton structure and a preparation method. The present invention combines 3D printing technology, casting technology and rotary forging technology, and forms a multiple skeleton structure of 316L stainless steel through 3D printing, which can improve the defects of insufficient hardness and strength of common nonferrous metal alloy bars. In addition, the outer layer of 316L stainless steel can protect the internal copper alloy matrix, thereby obtaining a stainless steel nonferrous metal composite bar with an internal skeleton structure.

[0006] The technical solution to achieve the purpose of the present invention is: a method for preparing a stainless steel nonferrous metal composite bar containing a skeleton, comprising the following steps:

[0007] Step (1): raw material preparation;

[0008] Step (2): Establishing a three-dimensional model of the stainless steel skeleton;

[0009] Step (3): Based on the model established in step (2), 3D printing is performed using selective laser melting (SLM) to form a stainless steel skeleton;

[0010] Step (4): melting industrial pure copper;

[0011] Step (5): heating the stainless steel skeleton to a temperature 20-40° C. higher than the melting point of pure copper, pouring the copper liquid obtained in step (4) into the stainless steel skeleton for casting to obtain an initial rod;

[0012] Step (6): The initial rod is heated and kept warm, and then rotary forged to obtain a stainless steel copper composite rod.

[0013] Furthermore, the raw materials prepared in step (1) are 316L stainless steel raw material powder and industrial pure copper, wherein the 316L stainless steel raw material powder has a composition of Cr 16.4-Ni 11.3-Mo 2.6-Mn 0.2-Si 0.74-P 0.013-Fe Bal wt%, and a powder particle size of 15 to 53 μm.

[0014] Furthermore, the three-dimensional model of the stainless steel skeleton established in step (2) is specifically as follows: the skeleton is cylindrical as a whole, including an outermost cylindrical shell, an internal three-layer honeycomb support structure, and a cylindrical structure arranged between adjacent layers of honeycomb support structures. The cylindrical structure between adjacent honeycomb support structures is hollowed out, and the density of the honeycomb support structure decreases gradually from the outside to the inside.

[0015] Furthermore, in step (2), each hexagonal support unit of the outermost honeycomb support structure has a side length of 2±0.2 mm, each hexagonal support unit of the second outermost honeycomb support structure has a side length of 5±0.5 mm, and each hexagonal support unit of the core honeycomb support structure has a side length of 10±1 mm.

[0016] Furthermore, the specific process parameters of 3D printing in step (3) are: carried out in a continuous laser mode with a power of 190 to 220 W, a scanning interval of 60 to 70 μm, a scanning speed of 1000 to 1200 mm / s, and a powder thickness of 25 to 30 μm; the scanning strategy adopts a 67° rotation between layers.

[0017] Furthermore, step (5) casting is specifically as follows: placing the printed stainless steel skeleton into a crucible, placing the skeleton and the crucible together into a pit furnace, and setting the furnace temperature to 20-40° C. above the melting point of the matrix nonferrous alloy, so that the copper melt can enter each hexagonal honeycomb support unit;

[0018] A casting pouring cup is selected, and the molten copper is poured into the casting pouring cup. The molten copper enters the stainless steel frame through the casting pouring cup for casting, and finally a stainless steel-copper composite rod containing a frame structure is obtained.

[0019] Furthermore, the rotary forging in step (6) is specifically as follows: heating the initial rod to 80±2% of the melting point of copper, keeping the temperature for 10±2 minutes, and then rotary forging, wherein the deformation amount obtained by the rotary forging is controlled at 85±2%.

[0020] A stainless steel copper composite rod containing a skeleton structure is prepared by the above method.

[0021] Furthermore, copper alloy, aluminum alloy, magnesium alloy, aluminum or magnesium is used instead of copper.

[0022] A stainless steel nonferrous metal composite bar containing a skeleton structure is prepared by the above method.

[0023] Compared with the prior art, the present invention has the following significant advantages:

[0024] (1) The present invention adopts a mature and developed 3D printing process (selective laser melting, SLM), which can directly generate parts of any shape from computer graphics data without the help of mechanical processing or any molds, breaking through the limitations of traditional production technology and greatly shortening the product development cycle. More importantly, it meets people's various imaginations of product design and can design complex or creative products more intuitively and efficiently.

[0025] (2) The present invention cleverly combines the bionic structure, uses 316L stainless steel to construct the skeleton, and combines the stainless steel shell with the internal support skeleton structure, which can better improve the strength and hardness of the non-ferrous metal rod.

[0026] (3) The processing technology is simple, the investment is small, the safety factor is high, and the production efficiency is high.

[0027] (4) The skeleton structure can be prepared using the currently widely used 3D printing processing method, and the traditional casting technology is subsequently used. The technology is very mature and there is no need to build an additional production line. Non-ferrous metal materials and skeleton materials can be flexibly replaced.

[0028] (5) After the composite rod is cast, a high-temperature rotary forging process is used for further processing, which can not only eliminate the internal defects generated in the 3D printing and casting stages, but also adjust the size of the rod according to different usage environments, greatly expanding the scope of application of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the skeleton structure of the present invention; wherein (a) is a front view of the skeleton, (b) is a schematic diagram of a cross-section of the skeleton, and (c) is a schematic diagram of 3D printing laser scanning. Each layer is rotated 67° to reduce stress concentration, and the research plane is parallel to the XY direction.

[0030] Figure 2 Schematic diagram of the selective laser melting (SLM) method used in the present invention.

[0031] Figure 3 It is a schematic diagram of the casting steps of the present invention.

[0032] Figure 4 Schematic diagram of rotary forging. DETAILED DESCRIPTION

[0033] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0034] A stainless steel nonferrous metal composite bar containing a skeleton structure and a preparation method thereof, comprising the following steps:

[0035] Step 1: Prepare raw materials. Step 2: Use modeling software to create a 316L stainless steel skeleton 3D model. Step 3: Use selective laser melting (SLM) to manufacture the 316L stainless steel skeleton. Step 4: Melt the industrial pure copper. Step 5: Heat the stainless steel skeleton to 1100°C, and then pour the molten copper directly into the 316L skeleton for casting. Step 6: Keep the obtained rod at 80% of the melting point of the matrix for 10 minutes, and then perform rotary forging after keeping warm. Finally, a stainless steel non-ferrous metal composite rod with a skeleton structure is obtained.

[0036] In step 1, the raw materials selected are: (1) 316L stainless steel raw material powder for 3D printing (Cr16.4-Ni11.3-Mo 2.6-Mn 0.2-Si 0.74-P 0.013-Fe Bal wt%), the powder particle size is controlled at 15-53 μm. Before use, vacuum drying is performed at a temperature of 100°C and a drying time of 6 hours. (2) Non-ferrous metal raw materials, such as copper alloys, magnesium alloys, aluminum alloys, etc., can be selected according to actual use requirements. This patent takes industrial pure copper as an example.

[0037] The skeleton consists of a stainless steel shell and an internal support skeleton. Each rod is wrapped by a 3D-printed stainless steel shell, and the interior consists of a three-part honeycomb support structure. The entire internal honeycomb support structure is gradient distributed. There are three layers of support structures from the outside to the inside. The outermost honeycomb support structure is the smallest, and each hexagonal support unit has a side length of 2mm. The second outermost support structure is larger, and each hexagonal support unit has a side length of 5mm. The core support unit is the largest, and each hexagonal support unit has a side length of 10mm. The finer the honeycomb support structure, the higher the strength it can provide. The outside needs to provide protection for the material, so a higher strength support is required. The internal grid is coarser, which can ensure the connectivity of the copper matrix and protect the conductivity of the material to the greatest extent.

[0038] In step three, the stainless steel skeleton model file is converted into stl format, and the height direction of the stainless steel skeleton is defined as the printing direction through the slicing software. The scanning spacing is 60-70μm, and the number of printing layers is determined according to the printing spacing and part size to obtain the slicing file. Selective laser melting (SLM) is used for manufacturing, with a scanning speed of 1000-1200mm / s, and SLM samples are produced in a continuous laser mode with a power of 190-220W. The powder thickness is 25-30μm. The scanning strategy uses a 67° rotation between layers to reduce stress concentration.

[0039] Industrial pure copper can be replaced with various non-ferrous metals and their alloy raw materials according to different application scenarios. However, it should be noted that the melting point of the matrix must be much lower than that of the skeleton material.

[0040] The printed stainless steel skeleton is placed in a crucible to prevent the molten liquid metal from splashing, and is placed in a pit furnace together with the skeleton and the crucible. The furnace temperature is set to be above the melting point of the base nonferrous alloy. For example, the melting point of industrial pure copper used in this patent is 1084.62°C, so the furnace temperature will be set to 1100°C. The purpose of heating is to ensure the fluidity of the molten copper, reduce defects such as pores generated during the casting process, and allow the molten copper to enter each hexagonal honeycomb support unit. Select a casting pouring cup of appropriate size, then pour the copper liquid into the casting pouring cup, and enter the stainless steel skeleton through the casting pouring cup for casting, and finally obtain a stainless steel nonferrous metal composite bar containing a skeleton structure.

[0041] In step 6, the non-ferrous metal matrix material is kept warm for 10 minutes at 80% of the melting point, which can better combine the matrix and the stainless steel skeleton. Then, high-temperature rotary forging is performed. On the one hand, the casting defects generated during the casting process can be further eliminated. On the other hand, the rod can be processed according to the actual use requirements, and the rod size can be adjusted to meet the specific requirements. Finally, a stainless steel non-ferrous metal composite rod with a skeleton structure is obtained.

[0042] Example 1

[0043] Step 1: Raw material preparation. The experimental raw materials used in the present invention include: (1) 316L stainless steel raw material powder for 3D printing (Cr 16.4-Ni 11.3-Mo 2.6-Mn 0.2-Si 0.74-P 0.013-Fe Bal wt%), the powder particle size is controlled at 15-53μm. Before use, vacuum drying is carried out at a temperature of 100°C and a drying time of 6h. (2) Non-ferrous metals or alloys. This patent takes industrial pure copper as an example. In actual production, it can be selected according to demand, for example, aluminum alloy, magnesium alloy, etc. can be selected.

[0044] Step 2: Create a three-dimensional model of the 316L stainless steel skeleton using modeling software. Figure 1 This is a schematic diagram of the stainless steel skeleton model of the present invention. The skeleton includes a stainless steel shell and an internal support skeleton structure. Figure 2 This is a schematic diagram of 3D printing.

[0045] Step 3: Convert the stainless steel skeleton model file to stl format, define the height direction of the stainless steel skeleton as the printing direction through the slicing software, the scanning spacing is 60-70μm, the number of printing layers is determined according to the printing spacing and part size, and the slicing file is obtained. Selective laser melting (SLM) is used for manufacturing, with a scanning speed of 1000-1200mm / s, and SLM samples are produced in a continuous laser mode with a power of 190-220W. The powder thickness is 25-30μm. The scanning strategy uses a 67° rotation between layers to reduce stress concentration. Figure 1 (c), where the study plane is parallel to the XY direction. Figure 1 (b) Stainless steel skeleton shown.

[0046] Step 4: Melt the industrial pure copper to be used.

[0047] Step 5: If Figure 3 As shown, the printed stainless steel skeleton is placed in a crucible to prevent the molten liquid metal from splashing, and is placed in a pit furnace together with the skeleton and the crucible. The furnace temperature is set to be above the melting point of the matrix nonferrous alloy. For example, the melting point of industrial pure copper used in this patent is 1084.62°C, so the furnace temperature will be set to 1100°C. The purpose of heating is to ensure the fluidity of the molten copper, reduce defects such as pores generated during the casting process, and allow the molten copper to enter each hexagonal honeycomb support unit. A casting pouring cup of appropriate size is selected, and then the copper liquid is poured into the casting pouring cup, and the casting is carried out into the stainless steel skeleton through the casting pouring cup, and finally a stainless steel nonferrous metal composite bar containing a skeleton structure is obtained.

[0048] Step 6: If Figure 4 , heat the rod obtained in step five to 80% of the melting point of the non-ferrous metal (for example, the melting point of industrial pure copper used in this patent is about 1084.62°C, and the heating temperature of this step can be set to 870°C). The purpose of heating is to make the skeleton and the matrix better bonded. After keeping warm for 10 minutes, the rotary forging process is carried out, and the deformation is controlled at 85%. Through the rotary forging process, the size control of the stainless steel non-ferrous metal rod with a skeleton structure designed in this patent is realized, and the high-temperature rotary forging process can also eliminate defects such as pores generated during the casting process to a certain extent.

Claims

1. A method for preparing a stainless steel nonferrous metal composite bar containing a skeleton, characterized in that: The steps include: Step (1): raw material preparation; Step (2): Establishing a three-dimensional model of the stainless steel skeleton; Step (3): Based on the model established in step (2), 3D printing is performed using selective laser melting (SLM) to form a stainless steel skeleton; Step (4): melting industrial pure copper; Step (5): heating the stainless steel skeleton to a temperature 20-40° C. higher than the melting point of pure copper, pouring the copper liquid obtained in step (4) into the stainless steel skeleton for casting to obtain an initial rod; Step (6): The initial rod is heated and kept warm, and then rotary forged to obtain a stainless steel copper composite rod.

2. The method according to claim 1, characterized in that The raw materials prepared in step (1) are 316L stainless steel raw material powder and industrial pure copper, wherein the 316L stainless steel raw material powder has a composition of Cr 16.4-Ni11.3-Mo 2.6-Mn 0.2-Si0.74-P 0.013-Fe Bal wt %, and a powder particle size of 15 to 53 μm.

3. The method according to claim 2, characterized in that The three-dimensional model of the stainless steel skeleton established in step (2) is specifically as follows: the skeleton is cylindrical as a whole, including an outermost cylindrical shell, an internal three-layer honeycomb support structure, and a cylindrical structure arranged between adjacent layers of honeycomb support structures. The cylindrical structure between adjacent honeycomb support structures is hollowed out, and the density of the honeycomb support structure decreases gradually from the outside to the inside.

4. The method according to claim 3, characterized in that In step (2), each hexagonal support unit of the outermost honeycomb support structure has a side length of 2±0.2 mm, each hexagonal support unit of the second outermost honeycomb support structure has a side length of 5±0.5 mm, and each hexagonal support unit of the core honeycomb support structure has a side length of 10±1 mm.

5. The method according to claim 4, characterized in that The specific process parameters of 3D printing in step (3) are: carried out in a continuous laser mode with a power of 190 to 220 W, a scanning interval of 60 to 70 μm, a scanning speed of 1000 to 1200 mm / s, and a powder thickness of 25 to 30 μm; the scanning strategy adopts a 67° rotation between layers.

6. The method according to claim 5, characterized in that Step (5) casting is specifically as follows: placing the printed stainless steel skeleton into a crucible, and placing the skeleton and the crucible into a pit furnace, and setting the furnace temperature to 20-40°C above the melting point of the matrix nonferrous alloy so that the copper melt can enter each hexagonal honeycomb support unit; A casting pouring cup is selected, and the molten copper is poured into the casting pouring cup. The molten copper enters the stainless steel frame through the casting pouring cup for casting, and finally a stainless steel-copper composite rod containing a frame structure is obtained.

7. The method according to claim 6, characterized in that Step (6) rotary forging is specifically as follows: heating the initial rod to 80±2% of the melting point of copper, keeping the temperature for 10±2 minutes, and then rotary forging. The deformation amount obtained by rotary forging is controlled at 85±2%.

8. A stainless steel copper composite bar containing a skeleton structure, characterized in that: The method is prepared by any one of claims 1 to 7.

9. The method according to claim 1, characterized in that: Copper alloy, aluminum alloy, magnesium alloy, aluminum or magnesium is used instead of copper.

10. A stainless steel nonferrous metal composite bar containing a skeleton structure, characterized in that: The method according to claim 9 is used for preparation.

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