Method for manufacturing ODS steel through electric arc additive

Abstract

The invention discloses a method for manufacturing ODS steel through electric arc additive manufacturing. The method comprises the steps that firstly, after a substrate is subjected to surface cleaning treatment, a layer of steel is deposited with an electric arc as a heat source; then coating oxide particles on the surface; an electric arc is used as a heat source for scanning with the surface of the coating and naturally cooling, so that the single-point molten pool is overlapped with the surrounding adjacent molten pools to form a continuous molten pool; and finally, carrying out stirring friction processing and hot rolling treatment. Near-net forming of the prepared part is completed through layer-by-layer accumulation in a deposition-coating-deposition-stirring machining-hot rolling machining mode, and finally the alloy material with good forming quality and fine and dispersed internal oxide particles is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of oxide dispersion strengthened alloy preparation, in particular to a method for preparing oxide dispersion strengthened steel. Background Art

[0002] ODS steel, namely oxide dispersion strengthened alloy, is widely used in high temperature structural materials, aerospace materials, automobile engine materials and other fields. The solubility of oxides in metals is low at room temperature, and it is difficult to process and produce ODS steel using traditional methods. The preparation process of dispersion strengthened materials is generally as follows: first, the dispersion strengthened alloy powder is prepared by ball milling, then densified by a suitable solidification sintering method, and finally the material of the required size and state is prepared by heat treatment and mechanical processing. The traditional mechanical alloying method has obvious disadvantages, such as a long preparation cycle, many parameters involved in the preparation process, whether it is the ball milling process or the sintering process, and it is difficult to reasonably control the parameters to obtain the optimal process route. The size and distribution of internal oxides in ODS alloys are the key to their comprehensive mechanical properties. Unevenly distributed coarse oxides are prone to stress concentration, which cannot play a role in dispersion strengthening, so that the mechanical properties of the alloy cannot be fully exerted. Therefore, refining and homogenizing oxide particles is the most effective way to improve the performance of such materials. Compared with traditional mechanical alloying, arc additive manufacturing of ODS alloys can produce parts with complex shapes and significantly reduce production cycles. Fewer parameters need to be controlled during the production process, and the optimal process parameters can be adjusted to each other. At the same time, the characteristics of rapid arc heating and cooling can achieve microstructure refinement. However, due to the difficulty in controlling the microstructure of the alloy, the main problems that arise during arc additive manufacturing include local oxide aggregation, large oxide size, and easy formation of cracks and pores on the surface.

[0003] Friction stir processing is a material modification and composite material processing method evolved from friction stir welding. Its principle is to utilize the drastic plastic deformation and plastic metal flow of the material in the processing area caused by the stirring head to distribute and disperse the alloy powder particles added by mechanical or metallurgical means in the matrix, thereby achieving densification, homogenization and refinement of the microstructure, thereby improving the performance of the material. Summary of the invention

[0004] Based on the problems existing in the above-mentioned prior art, the present invention provides a method for manufacturing ODS steel by electric arc additive manufacturing, aiming to use electric arc as a heat source and combine it with a stir friction processing method to prepare an alloy material with fine and dispersed oxide particles, and can simplify the process flow, reduce production costs, improve production efficiency, and stabilize product performance.

[0005] The present invention solves the technical problem by adopting the following technical solution:

[0006] A method for manufacturing ODS steel by arc additive manufacturing, characterized in that it comprises the following steps:

[0007] Step 1: First, the surface of the substrate is cleaned to obtain a clean substrate;

[0008] Step 2: Use low carbon steel welding wire or martensitic steel welding wire to deposit a single layer on the substrate by line-by-line scanning with arc as heat source, as shown in the schematic diagram. Figure 1 As shown (taking low carbon steel welding wire as an example);

[0009] Step 3: Add nano-scale oxide powder (Y2O3) to a volatile organic solvent and mix well to obtain a slurry; apply the slurry on the surface of the sample with a single layer of deposition and dry it to form an oxide coating on the surface of the sample with a single layer of deposition, with a coating thickness of ≤1 mm, as shown in the schematic diagram. Figure 2 As shown;

[0010] Step 4: Apply the arc heat source to the surface of the sample oxide coating again, and use the low-carbon steel welding wire or martensitic steel welding wire to perform single-layer deposition on the sample surface in a line-by-line scanning manner. Single molten pools and adjacent scanning tracks overlap and overlap to form a continuous molten pool, so that the entire oxide coating is gradually melted, and mixed evenly with the low-carbon steel or martensitic steel in the molten pool under the action of the protective gas, and then naturally cooled to form an oxide dispersion-strengthened steel layer. The schematic diagram is shown in FIG. Figure 3 As shown;

[0011] Step 5: Use a friction stir processing method to perform solid-phase mechanical stirring on the sample surface to remove the pore defects on the surface and make the surface oxide distribution more fine and dispersed, as shown in the schematic diagram. Figure 4 As shown;

[0012] Step 6: Use hot rolling to heat-deform the entire sample, so that its grain size is greatly reduced, the distribution of the precipitated oxide phase is more uniform and dispersed, and its comprehensive mechanical properties are improved. The schematic diagram is shown in Figure 5 As shown;

[0013] Step 7: Repeat steps 3 to 6 to stack layer by layer until the ODS steel of the desired shape is obtained on the surface of the substrate, thereby completing the additive manufacturing of the ODS steel.

[0014] Furthermore, in step 2 and step 4, the specific processing parameters of the arc deposition are as follows: the parameters of the arc heat source used are: welding current of 280-320A, welding voltage of 30-34V, and welding speed of 250-350mm / s. When the arc heat source is applied to the sample, pure argon gas is used to protect the welding molten pool, and the gas flow rate is 5-10L / min. The overlap rate of a single molten pool is 70%-80%, and the overlap rate between adjacent scanning tracks is 40%-60%.

[0015] Furthermore, in step 5, the stir friction processing method is: fix the sample on the workbench of the stir friction machine, use coated cemented carbide to process it into a stirring head, the stir friction processing speed of the stirring head in the oxide dispersion strengthened steel layer is 40-60mm / min, the rotation speed of the stirring head is 750-950rmp, and a complete round of stir friction processing is performed on the entire processing area, and the overlap between adjacent stirring processing passes is 40% to 50%.

[0016] Furthermore, in step 6, the hot rolling processing method is: the sample is kept at 1000-1100°C for 30 minutes and then placed on a rolling mill workbench, and coated cemented carbide is used to process it into a roller. The roller is rolled 4-6 times with a small deformation on the entire sample surface, and the pressure of each rolling pass is 4%-5%, the roller speed is 3.5m / s, and the roller speed is 3.5m / s.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] Compared with traditional forming technology, the arc additive manufacturing technology used in the present invention can greatly shorten the preparation cycle of ODS steel, and can prepare complex parts by stacking layers in combination with a small amount of machining. Moreover, due to the characteristics of rapid heating and rapid cooling of the arc heat source, the grain size of the prepared pattern is small and the mechanical properties are excellent. In the process of additive, auxiliary stirring friction can effectively improve the surface quality of additive parts, eliminate surface pores, cracks, etc., and the subsequent rolling treatment can effectively improve the aggregation of surface oxides, making their distribution more diffuse, and the dispersion strengthening effect is more significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the present invention using an electric arc as a heat source to deposit a layer of low carbon steel on a substrate;

[0020] Figure 2 A schematic diagram of applying an oxide coating on deposited low carbon steel according to the present invention;

[0021] Figure 3 It is a schematic diagram of the present invention using an electric arc as a heat source to act on the sample oxide coating to deposit the next layer;

[0022] Figure 4 A schematic diagram of the friction stir processing of a sample surface according to the present invention;

[0023] Figure 5 It is a schematic diagram of hot rolling processing of a sample according to the present invention;

[0024] Figure 6This is a metallographic image of the ODS steel prepared in Example 1 of the present invention, wherein (a) and (b) correspond to different magnifications.

[0025] Figure 7 This is a diagram showing the internal oxide distribution of the ODS steel prepared in Example 1 of the present invention, wherein (a) and (b) correspond to different magnifications. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with specific implementation methods. This implementation method is implemented on the premise of the technical solution of the present invention, but the protection scope of the present invention is not limited to the following implementation methods.

[0027] Example 1

[0028] In this embodiment, Q345 low carbon steel is used as the substrate material, and arc additive manufacturing of ODS steel is carried out according to the following steps:

[0029] Step 1: First, a low-carbon steel plate (with a size of 100 mm×150 mm and a thickness of 8 mm) is subjected to surface cleaning treatment to remove surface pollutants and oxides to obtain a clean substrate.

[0030] Step 2: Use CHT71Ni low-carbon steel as the filler wire with a wire diameter of 2 mm. Use a welding machine to scan the sample line by line with an arc as a heat source, deposit, and wait for the deposited layer to cool naturally to form a low-carbon steel deposited layer with a thickness of 2.1 mm on the substrate.

[0031] The process parameters of the arc heat source are: welding current 280A, welding voltage 30V, welding speed 250mm / s. In the process of arc acting on the sample, pure argon (99.99% Ar) is used to protect the molten pool, and the gas flow rate is 8L / min. The overlap rate of a single molten pool is 80%, and the overlap rate between adjacent scanning tracks is 60%.

[0032] Step 3: Add nano-scale Y2O3 powder with a particle size of 20 to 50 nm into ethanol, mix evenly, and obtain a coating slurry; apply the coating slurry on the surface of the sample with a single layer of deposition, and dry it in a drying oven at low temperature to form an oxide coating with a thickness of 0.5 mm on the surface of the sample with a single layer of deposition.

[0033] Step 4: Use the same welding wire as in step 2, and apply the arc heat source to the surface of the sample oxide coating again. The arc is scanned and deposited line by line on the surface of the sample. Single molten pools and adjacent scanning tracks overlap and overlap to form a continuous molten pool, so that the entire oxide coating is gradually melted and mixed evenly with the low-carbon steel in the molten pool under the action of the protective gas to form an oxide dispersion strengthened steel layer. The specific parameters are:

[0034] The welding current is 280A, the welding voltage is 30V, and the welding speed is 250mm / s. In the process of arcing the oxide coating, pure argon (99.99% Ar) is used to protect the molten pool, and the gas flow rate is 8L / min. The overlap rate of a single molten pool is 80%, and the overlap rate between adjacent scanning tracks is 60%, and then the sample is allowed to cool naturally.

[0035] Step 5: Use the friction stir processing method to perform solid-phase mechanical stirring on the sample surface. The basic steps are: fix the sample on the workbench of the friction stir processing equipment, use a stirring head with a standard thread to perform friction stir processing, the stirring head used is made of coated cemented carbide, and the stirring needle length is 2.5mm. During the friction stir processing, the inclination angle of the stirring head is 2.5°, the rotation speed of the stirring head is 750rpm, the friction stir processing speed is 80mm / min, the downward pressure is 0.1mm, the overlap rate of adjacent stirring processing passes is 40%, and a complete round of friction stir processing is performed on the entire processing area.

[0036] Step 6: Use hot rolling to perform heat deformation treatment on the entire sample, that is, obtain the finished oxide dispersion strengthened steel product. The basic steps are: place the sample on the rolling mill workbench after keeping it at 1000°C for 30 minutes, use coated cemented carbide to process it into a roller, and perform 5 small deformation rolling on the entire sample surface with the roller. The pressure of each rolling pass is 4%, the roller speed is 3.5m / s, and the roller speed is 3.5m / s.

[0037] According to the test, the thickness of the oxide dispersion strengthened steel layer obtained in this embodiment is 2.4 mm, spherical second phase oxides exist in the matrix, and the oxide particles are fine and dispersed.

[0038] Example 2

[0039] In this embodiment, Q345 low carbon steel is used as the substrate material, and arc additive manufacturing of ODS steel is carried out according to the following steps:

[0040] Step 1: First, a low-carbon steel plate (with a size of 100 mm×150 mm and a thickness of 8 mm) is subjected to surface cleaning treatment to remove surface pollutants and oxides to obtain a clean substrate.

[0041] Step 2: Use CHT71Ni low-carbon steel as the filler wire with a wire diameter of 2 mm. Use a welding machine to scan the sample line by line with an arc as a heat source, deposit, and wait for the deposited layer to cool naturally to form a low-carbon steel deposited layer with a thickness of 2.3 mm on the substrate.

[0042] The process parameters of the arc heat source are: welding current 300A, welding voltage 32V, welding speed 250mm / s. In the process of arc acting on the sample, pure argon (99.99% Ar) is used to protect the molten pool, and the gas flow rate is 10L / min. The overlap rate of a single molten pool is 80%, and the overlap rate between adjacent scanning tracks is 60%.

[0043] Step 3: Add nano-scale Y2O3 powder with a particle size of 20 to 50 nm into ethanol, mix evenly, and obtain a coating slurry; apply the coating slurry on the surface of the sample with a single layer of deposition, and dry it in a drying oven at low temperature to form an oxide coating with a thickness of 0.5 mm on the surface of the sample with a single layer of deposition.

[0044] Step 4: Use the same welding wire as in step 2, and apply the arc heat source to the surface of the sample oxide coating again. The arc is scanned and deposited line by line on the surface of the sample. Single molten pools and adjacent scanning tracks overlap and overlap to form a continuous molten pool, so that the entire oxide coating is gradually melted and mixed evenly with the low-carbon steel in the molten pool under the action of the protective gas to form an oxide dispersion strengthened steel layer. The specific parameters are:

[0045] The welding current is 300A, the welding voltage is 32V, and the welding speed is 250mm / s. In the process of arcing the oxide coating, pure argon (99.99% Ar) is used to protect the molten pool, and the gas flow rate is 8L / min. The overlap rate of a single molten pool is 80%, and the overlap rate between adjacent scanning tracks is 60%, and then the sample is allowed to cool naturally.

[0046] Step 5: Use the friction stir processing method to perform solid-phase mechanical stirring on the sample surface. The basic steps are: fix the sample on the workbench of the friction stir processing equipment, use a stirring head with a standard thread to perform friction stir processing, the stirring head used is made of coated cemented carbide, and the stirring needle length is 2.5mm. During the friction stir processing, the inclination angle of the stirring head is 2.5°, the rotation speed of the stirring head is 950rpm, the friction stir processing speed is 100mm / min, the downward pressure is 0.3mm, the overlap rate of adjacent stirring processing passes is 40%, and a complete round of friction stir processing is performed on the entire processing area.

[0047] Step 6: Use hot rolling to perform heat deformation treatment on the entire sample to obtain the finished oxide dispersion strengthened steel product. The basic steps are: place the sample on a rolling mill workbench after keeping it at 1000°C for 30 minutes, use coated cemented carbide to process it into a roller, and perform 5 small deformation rolling on the entire sample surface with each rolling pass. The pressure is 5%, the roller speed is 3.5m / s, and the roller speed is 3.5m / s.

[0048] According to the test, the thickness of the oxide dispersion strengthened steel layer obtained in this embodiment is 2.6 mm, spherical second phase oxides exist in the matrix, and the oxide particles are fine and dispersed.

Claims

1. A method for manufacturing ODS steel by arc additive manufacturing, characterized in that: The following steps are included Step 1: First, the surface of the substrate is cleaned; Step 2: using a low carbon steel welding wire or a martensitic steel welding wire to perform single layer deposition on the substrate by using an arc as a heat source and a line-by-line scanning method; Step 3, adding nanometer-scale Y2O3 powder to a volatile organic solvent, mixing evenly, and obtaining a coating slurry; applying the coating slurry on the surface of the sample that has been deposited in a single layer, and drying the surface of the sample that has been deposited in a single layer, so that an oxide coating is formed on the surface of the sample that has been deposited in a single layer, and the coating thickness is ≤1 mm; Step 4, applying the arc heat source to the surface of the sample oxide coating again, and using the low-carbon steel welding wire or the martensitic steel welding wire again to perform single-layer deposition on the sample surface in a line-by-line scanning manner, with single molten pools and adjacent scanning tracks overlapping each other to form a continuous molten pool, so that the entire oxide coating is gradually melted, and is evenly mixed with the low-carbon steel or martensitic steel in the molten pool under the action of the protective gas to form an oxide dispersion-strengthened steel layer; Step 5, using a stir friction processing method to perform solid phase mechanical stirring on the sample surface; Step 6: Using a hot rolling method to perform thermal deformation treatment on the entire sample; Step 7: Repeat steps 3 to 6 to stack layer by layer until the ODS steel of the desired shape is obtained on the surface of the substrate, thereby completing the additive manufacturing of the ODS steel.

2. The method for manufacturing ODS steel by arc additive manufacturing according to claim 1, characterized in that: In step 2 and step 4, the parameters of the arc heat source used are: welding current 280-320A, welding voltage 30-34V, welding speed 250-350mm / s.

3. The method for manufacturing ODS steel by arc additive manufacturing according to claim 1, characterized in that: In step 2 and step 4, when the arc heat source is applied to the sample, pure argon gas is used to protect the welding pool, and the gas flow rate is 5 to 10 L / min.

4. The method for manufacturing ODS steel by arc additive manufacturing according to claim 1, characterized in that: In step 2 and step 4, the overlapping rate of a single molten pool is 70% to 80%, and the overlapping rate between adjacent scanning tracks is 40% to 60%.

5. The method for manufacturing ODS steel by arc additive manufacturing according to claim 1, characterized in that: In step 5, the stir friction processing method is: fix the sample on the workbench of the stir friction machine, use coated cemented carbide to process it into a stirring head, the stirring friction processing speed of the stirring head in the oxide dispersion strengthened steel layer is 40-60mm / min, and a complete round of stir friction processing is performed on the entire processing area, and the overlap between adjacent stirring processing passes is 40% to 50%.

6. The method for manufacturing ODS steel by arc additive manufacturing according to claim 1, characterized in that: In step 6, the hot rolling processing method is: the sample is kept at 1000-1100° C. for 30 minutes and then placed on a rolling mill workbench, and a coated cemented carbide is used to process the roller, and the roller is rolled with a small deformation amount 4-6 times on the entire sample surface.

7. The method for manufacturing ODS steel by arc additive manufacturing according to claim 1, characterized in that: The substrate is a low-carbon steel plate or a steel plate with a composition similar to that of ODS steel.

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