A powder blowing agent for powder injection metallurgy and its preparation method and application

Abstract

The invention discloses a powder blowing agent for powder spraying metallurgy and a preparation method and application thereof, belonging to the technical field of alloy smelting. The powder blowing agent contains the following elements in mass percentage: Fe: 50.0-85.0%, Cr: 0-30.0%, Ni: 0-30.0%, W: 0-5.0%, RE: 0.2-10.0%, Ti: 0.1-8.0%, Si: 0-10.0%, O: 0.1-10.0%; and the mass proportion of RE, Si, O, and Ti elements meets (RE+Si+O) / Ti is (2:1)-(50:1); the RE and O elements exist in the powder blowing agent in the form of solid solution; the RE is a rare earth. The powder blowing agent is produced by mechanical alloying, and the particle size range suitable for powder spraying metallurgy is selected by screening. The powder blowing agent can introduce solid solution oxygen into smelting steel to improve the comprehensive performance of the material.

Description

Technical Field

[0001] The invention belongs to the technical field of steel smelting, and in particular relates to a powder blowing agent used for powder spraying metallurgy in the production process of oxide dispersion strengthened alloy, and a preparation method and application thereof. Background Art

[0002] Oxide dispersion strengthening (ODS) can significantly improve the strength, high temperature resistance and service life of metal and alloy materials, and is a technical direction that has developed very rapidly in the past decade. The main feature of its microstructure is that nano-oxides (1 nm~100 nm) are evenly dispersed in the metal and alloy matrix, which pins defects such as dislocations and grain boundaries and improves material performance. The smaller the size of the nano-oxides and the higher the number density, the more obvious the improvement in material performance.

[0003] The difficulty in preparing oxide dispersion strengthened alloys lies in how to evenly disperse nano-oxides in the metal and alloy matrix. The traditional process is to mechanically alloy metal element powder or alloy powder with nano-oxide (commonly used Y2O3) in a high-energy ball mill, and then form ODS steel by hot isostatic pressing or hot extrusion; however, this process is small in scale, expensive, and has poor repeatability, and cannot meet the needs of large-scale, low-cost industrial production. If ODS alloys can be prepared on a large scale by smelting, it is expected to promote the widespread engineering application of such materials. In the published patent literature, a variety of preparation schemes have been proposed, but they all have their own limitations. For example, patent CN201711113150.3 uses vacuum induction / magnetic stirring process to make steel, and adds rare earth element Y in the mold to combine [O] in the molten steel to form ODS steel with dispersed rare earth oxides; however, this process requires strict control of the deoxidation depth and the Y powder content in the mold, and before pouring the molten steel, it is necessary to ensure that the Y powder in the mold is not oxidized. The preparation process is complicated, and the nano oxide particles are obtained only through the molten steel casting process, and there is still the problem of uneven oxide distribution. Patent CN201710805636.7 adds supersaturated oxide dispersion strengthened steel alloy powder to the molten steel, and uses the characteristics of the powder and the molten steel having similar densities to achieve uniform mixing, eliminating the phenomenon of oxides floating, aggregating and growing in the molten steel due to density differences; however, the stirring time increases with the increase in the scale of ODS steel preparation, and it is easy to have problems of uneven oxide distribution and excessively large size, which leads to reduced material toughness. Patent CN201911387729.8 uses supersaturated oxide-dispersed alloy powder to induce rapid nucleation, and combines it with short-process thin-strip continuous casting technology to prepare nano-oxide dispersion-strengthened steel. Rapid solidification avoids the uneven distribution and coarseness of oxides caused by long-term stirring of alloy powder, but the thickness of the ingot is limited, and it is difficult to directly produce large-size profiles such as medium and thick plates; at the same time, the main idea of ​​this technology is to maintain the stability of the oxide state, avoid coarsening and aggregation growth, and achieve dispersed distribution, but the oxide size cannot be further reduced and its number density cannot be increased during the process. The oxide size in the final material prepared is close to the oxide size in the raw material. Therefore, a large amount of nano-scale oxide raw materials must be used, which increases the production cost and has not yet met the needs of large-scale, low-cost industrial production of ODS alloys.

[0004] In summary, although the preparation technology of ODS alloys has made certain progress, there are still many challenges and limitations. The difficulty of the relevant technology is that if oxides are introduced into the alloy melt, the oxides will float up and aggregate and grow in the alloy melt due to the obvious density difference between the oxides and the alloy melt, resulting in uneven distribution of oxides and excessively large sizes; short-process thin-strip continuous casting technology avoids the problem of oxide agglomeration and growth in molten steel through rapid cooling, but the thickness of the thin-strip continuous casting ingot is limited, and it is difficult to produce large-sized profiles such as medium and thick plates. How to further reduce the oxide size, increase the number density, and realize large-scale low-cost industrial production while maintaining the dispersed distribution of oxides is still a key issue that needs to be urgently solved in the current field of ODS alloy preparation. Summary of the invention

[0005] The present invention aims to solve the deficiencies in the prior art. Through innovative composition and process design, a powder blowing agent containing supersaturated oxygen and rare earth (RE) solid solution components is developed. The powder blowing agent is sprayed into the molten steel through powder spraying metallurgy technology, which can not only effectively reduce the free oxygen content in the molten steel, but also utilize the reaction of solid solution oxygen and solid solution rare earth elements to precipitate nano oxides in the solid phase. This method cleverly avoids the difficulty of oxide control during the preparation process. Through careful composition design and process parameter optimization, the present invention enables rare earth oxides to be solid-dissolved into the alloy matrix in the form of RE and O atoms during the mechanical alloying process. In the subsequent hot forming process, these atoms will combine with other atoms such as O and Si to form nanoclusters, and finally precipitate into nano oxides. The key conditions for the precipitation of nano oxides in the alloy include supersaturated solid solution oxygen (concentration range of 300~1000ppm), high concentration of vacancies and solid solution rare earth elements. Different from the prior art method of maintaining the oxide stable or adding rare earth element Y in the casting mold to combine with [O] in the molten steel, the present invention adopts a dynamic process of solid solution-reprecipitation, which can generate nano-oxides with smaller size and higher number density. This innovative method completely solves the problem of oxide dispersion in the alloy smelting preparation process, thereby realizing large-scale, low-cost industrial production.

[0006] Furthermore, the powder blowing agent and its preparation method and application proposed in the present invention have changed the idea of ​​deoxidation in traditional powder spraying metallurgy. Traditional powder spraying metallurgy is a technology that uses compressed argon, nitrogen and other gases to spray metallurgical reactants (calcium-silicon, calcium oxide, magnesium, carbon and other powders) into molten steel during the steelmaking process. It can make the refining reactions such as dephosphorization, desulfurization and deoxidation of molten steel proceed quickly and fully, accelerate the floating removal speed of inclusions, effectively improve the quality of molten steel, shorten the smelting time, improve productivity, reduce energy consumption, and improve the quality of steel. Traditional powder spraying metallurgy mainly achieves the effects of dephosphorization, desulfurization and deoxidation by spraying composite oxides such as calcium oxide and reducing agents such as magnesium, aluminum and carbon into molten steel. For example, in patent CN202210678030.2, the phosphorus content in semi-steel is significantly reduced by spraying calcium ferrite powder (CaO and FeO) and limestone powder. Patent CN201110147607.9 reduces the sulfur content in steel from 50-80ppm to below 12ppm by spraying CaO-SiO2-MgO-CaF2 desulfurization powder. Patent CN201910077604.9 reduces the free oxygen content in steel by spraying graphite carbon powder. The composition design of the powder blowing agent is the key to controlling the content of oxygen and trace elements in the alloy, and is the core technology in powder spraying metallurgy.

[0007] The present invention can simultaneously obtain high solid solution oxygen content and rare earth elements in the ingot by applying the powder blowing agent to steel powder metallurgy, and form rare earth oxide nanoparticles in the subsequent thermomechanical treatment. Specifically, the generation of coarse oxides is avoided by nano-precipitation phase, and the effect of rare earth nano-oxides on improving high temperature performance is effectively utilized, and the oxygen in the alloy is converted from a harmful element to a beneficial element that plays a positive role. On the one hand, the number of coarse oxides in the high oxygen content alloy is greatly reduced to the same as the number of coarse oxides in the ultra-low oxygen content alloy, and on the other hand, a large number of rare earth oxides with a size less than 50nm are additionally generated, which have an additional pinning effect on dislocations, phase interfaces and grain boundaries, and the diffusion rate of elements is reduced by the dispersed distribution of nano rare earth oxides on fast diffusion channels such as dislocations and grain boundaries, thereby improving the high temperature strength, creep life and oxidation resistance of steel.

[0008] The following is the technical solution of the present invention:

[0009] The invention provides a powder blowing agent for powder injection metallurgy. The powder blowing agent comprises the following elements in percentage by mass: Fe: 50.0-85.0%, Cr: 0-30.0%, Ni: 0-30.0%, W: 0-5.0%, RE: 0.2-10.0%, Ti: 0.1-8.0%, Si: 0-10.0%, O: 0.1-10.0%; and the mass proportion of RE, Si, O and Ti elements meets (RE+Si+O) / Ti is (2:1)-(50:1); the RE and O elements exist in the powder blowing agent in a solid solution form; and the RE is a rare earth.

[0010] The above-mentioned powder blowing agent designed specifically for powder spraying metallurgy process has a precise composition ratio that enables rare earth element RE and oxygen O to be evenly distributed in the powder blowing agent in the form of solid solution, which is crucial to improving metallurgical efficiency and product quality. When the ratio of (RE+Si+O) / Ti is too high, that is, more than 50:1, too much oxide residue may be generated in the powder blowing agent. After these residues are added to the molten steel, they will cause the oxide particles to coarsen and affect the performance of the steel. On the contrary, if the ratio is too low, that is, less than 2:1, after adding this powder blowing agent to the molten steel, excessive titanium-containing carbides or intermetallic compounds are easily formed in the steel, and these compounds will also have an adverse effect on the performance of the steel.

[0011] The rare earth element RE is one of yttrium (Y), lanthanum (La), cerium (Ce), gadolinium (Gd), erbium (Er), neodymium (Nd), praseodymium (Pr), terbium (Tb), samarium (Sm), dysprosium (Dy) or scandium (Sc), or a combination of multiple elements thereof.

[0012] The present invention also provides a method for preparing the aforementioned blowing agent for powder injection metallurgy, comprising the following steps: placing raw material powder into a mechanical alloying sealed tank, and performing mechanical alloying under the protection of an inert atmosphere; grading and screening the mechanically alloyed powder, selecting powder with a particle size of 1 to 500 μm, and obtaining the aforementioned blowing agent;

[0013] The raw material powder comprises the following raw materials in percentage by mass: Fe: 50.0-85.0%, Cr: 0-30.0%, Ni: 0-30.0%, W: 0-5.0%, RE: 0.1-10.0%, Ti: 0.1-8.0%, Si: 0-10.0%, rare earth oxide: 0.1-10.0%, SiO2: 0-10.0%; the mass proportion of RE, Si, O and Ti elements is controlled by the relative addition amounts of RE, Ti and Si single substance powders and rare earth oxide and SiO2 powders, so that (RE+Si+O) / Ti is (2:1)-(50:1).

[0014] Furthermore, the raw material powder is prepared by one of the following three methods:

[0015] (1) Physically mixed by various raw materials according to mass percentage;

[0016] (2) A portion of the elemental powder is made into an atomized alloy powder, and the remaining elemental powder, the atomized alloy powder, the rare earth oxide, and the SiO2 powder are mixed;

[0017] (3) All the single-element powders are made into atomized alloy powders, and then the atomized alloy powders are mixed with rare earth oxides and SiO2 powders;

[0018] The atomized alloy powder is obtained by melting at least two elemental powders into an alloy and then performing an atomization powder making process to obtain the atomized alloy powder.

[0019] Preferably, the method for preparing the blowing powder comprises the following steps:

[0020] S11: using a smelting process, melting at least two of the raw materials of Fe, Cr, Ni, W, RE, Ti, and Si into an alloy according to the following composition ratio, and obtaining an atomized alloy powder through an atomization powder making process; the composition ratio is: Fe 50.0-85.0%, Cr 0-30.0%, Ni 0-30.0%, W 0-5.0%, RE 0.1-10.0%, Ti 0.1-8.0%, Si 0-10.0%;

[0021] S12: mixing the atomized alloy powder obtained in step S11 with rare earth oxide and SiO2 powder, and controlling the mass ratio of RE, Si, O and Ti elements by the relative addition amounts of the atomized alloy powder, rare earth oxide and SiO2 powder, so that (RE+Si+O) / Ti is (2:1) to (50:1);

[0022] S13: placing the raw material powder mixed in step S12 into a mechanical alloying sealed tank, and performing mechanical alloying under the protection of an inert atmosphere; performing classification and screening on the mechanically alloyed powder, and selecting powder with a particle size of 1 to 500 μm to obtain the blowing powder agent.

[0023] Furthermore, during the mechanical alloying process, alloy or ceramic balls are used as the medium, the ball-to-material mass ratio is (5:1) to (50:1), and the mechanical alloying time is 1 to 50 hours.

[0024] Furthermore, the inert atmosphere is argon.

[0025] The powder blowing agent of the present invention is applied to the production process of oxide dispersion strengthened steel through powder injection metallurgy technology. The specific application fields of oxide dispersion strengthened steel are wide, including but not limited to the manufacture of high-strength and tough steel plates for automobiles, high-performance component steels for aircraft engines and gas turbines, high-alloy steel plates used in high-temperature environments, nuclear reactor cladding tube steel plates, and non-magnetic high-strength steel plates for ships.

[0026] The present invention also provides a method for preparing oxide dispersion strengthened steel, comprising the following steps: adding the aforementioned powder blowing agent into the molten steel being smelted through a powder spraying metallurgy process, and performing subsequent thermomechanical treatment on the molten steel after the powder spraying metallurgy;

[0027] The dosage of the blowing agent is 5-50 kg / ton of steel; the powder spraying metallurgical process is specifically: using an inert carrier gas to spray the blowing agent into the molten steel at a high speed, and the blowing agent spraying speed is 5-50 kg / min.

[0028] During the powder injection metallurgy process, the inert carrier gas is separated into many small bubbles when it is injected into the molten steel at high speed, thereby accelerating the movement of the molten steel and allowing the powder blowing agent to react with the molten steel rapidly, thereby promoting efficient dispersion of trace alloying elements and significantly increasing the vacancy concentration in the solidified structure of the strengthened steel after thermomechanical treatment.

[0029] Furthermore, the inert carrier gas is argon or nitrogen.

[0030] Furthermore, the blowing pressure of the inert carrier gas is 0.3-0.8 MPa.

[0031] Furthermore, the thermomechanical treatment includes continuous casting and steel rolling.

[0032] If supersaturated dissolved oxygen and solid-solution RE, Si and other elements are introduced into the alloy through powder spraying metallurgy, it is possible to solve the problem that supersaturated O and supersaturated RE elements are difficult to add into the alloy melt, meet the necessary conditions for the formation of nano-oxides, and achieve the dispersed distribution of nano-oxides.

[0033] At the same time, RE elements are usually added to the alloy melt in the form of rare earth pure metal or rare earth intermediate alloy. Since the chemical properties of RE elements are very active, they easily react with oxygen, sulfur, nitrogen, etc. Therefore, the loss of rare earth elements in the high-temperature smelting process is relatively large, mainly including: (1) rare earth elements react with the atmosphere and cause losses; (2) during vacuum induction melting, rare earth elements react with the crucible and cause losses; (3) during electroslag remelting, rare earth elements react with oxide slag and cause losses, which leads to large fluctuations in the rare earth content in the alloy, and ultimately causes unstable performance of the alloy. Controlling the content of rare earth elements in the alloy is a technically difficult task.

[0034] It is extremely difficult to simultaneously obtain stable oxygen content and RE element content in alloy melts. In the existing technologies and public documents, no efficient preparation technology has been found to achieve the coexistence of supersaturated solid solution oxygen, high concentration vacancies and high concentration solid solution RE, Si and other elements. Compared with the existing technology, the present invention has the following beneficial effects:

[0035] 1. The powder blowing agent for powder metallurgy provided by the present invention adopts a technical concept different from the traditional powder metallurgy which reduces the oxygen content to avoid the generation of impurities such as oxides, designs a high oxygen content alloy system, supersaturates the rare earth elements and oxygen in the powder blowing agent, and can simultaneously increase the solid solution rare earth and solid solution oxygen in the steel when applied in actual powder metallurgy, and form rare earth oxides in the subsequent solidification and processing process, producing a dispersion strengthening effect, and converting the oxygen in the steel from a harmful element to a beneficial element that plays a positive role. Rare earth oxides pin dislocations and grain boundaries and reduce the diffusion rate of atoms along fast diffusion channels such as grain boundaries and phase interfaces, thereby significantly improving the high temperature strength, creep life and oxidation resistance of the steel.

[0036] 2. Compared with the traditional powder blowing agent, the powder blowing agent for powder spraying metallurgy provided by the present invention can increase the upper limit of the use temperature of the prepared steel by 50-100°C (usable temperature under the same strength) and the creep life under the same temperature and stress by 5-10 times when the main components of the steel are the same and the same smelting and casting or continuous casting process is adopted, and has excellent corrosion resistance. It has significant application economic value for improving the service temperature and service life of the steel and improving the economic benefits of the entire service cycle of the material.

[0037] 3. The powder blowing agent for powder metallurgy provided by the present invention is based on the solid phase chemical reaction between raw materials such as RE, Si and rare earth oxides, SiO2, etc. during the mechanical alloying process, and creatively realizes the simultaneous supersaturated solid solution of rare earth elements and oxygen elements in the alloy powder. By increasing the solid solution content of RE and O elements in the steel at the same time, the problem that the rare earth content in traditional rare earth-containing steel is difficult to accurately control and oxygen and rare earth cannot coexist is avoided. The solid solution rare earth and oxygen are introduced into the molten steel by uniformly dispersing the powder blowing agent in the steel, and a high number density of nanoscale rare earth oxides is formed in the steel by solid phase precipitation. Since the nano oxides in the final alloy are dynamically generated by the solid phase reaction of solid solution RE and O, the generated oxides do not need to experience a high temperature molten steel environment. Compared with the prior art, the nano oxides are smaller in size and higher in number density. At the same time, unlike the prior art that must use nano-scale oxide raw powder, this technology can use micron-scale oxides as raw powder, which effectively reduces costs.

[0038] 4. Compared with the traditional powder blowing agent, the steel prepared by using the powder blowing agent for powder spraying metallurgy provided by the present invention has better mechanical properties and organizational stability at high temperature, and has excellent corrosion resistance in oxidizing atmosphere and high-temperature steam environment, and can meet the performance requirements of special application environments such as high-strength and tough steel plates for automobiles, steel for aircraft engines and gas turbine components, high-temperature alloys, nuclear reactor cladding tubes, and non-magnetic high-strength steel for ships. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a transmission electron micrograph showing the dispersed distribution of nano-oxides in the prepared T92 material according to Example 1 of the present invention;

[0040] Figure 2 This is an optical microscopic picture of the powder blowing agent used for powder metallurgy in Example 2 of the present invention;

[0041] Figure 3 This is a transmission electron micrograph of the microstructure of oxide dispersion strengthened 316L austenitic stainless steel prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0042] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in combination with the embodiments and drawings. The embodiments are only part of the embodiments of the present invention, not all of them. In the following description, the specific features, structures, or characteristics of one or more embodiments can be combined in any suitable form, and other embodiments obtained by combining without creative work are all within the scope of protection of the present invention.

[0043] Unless otherwise specified, the ratios of the components in the following embodiments of the present invention are all weight ratios.

[0044] Example 1

[0045] This embodiment is a powder blowing agent suitable for the production of continuous casting high-strength martensitic steel, and the composition is shown in Table 1.

[0046]

[0047] Preparation process of blowing powder:

[0048] S1. Weigh and uniformly mix Fe, Cr, W, Ti, Y, Si element powders meeting the composition requirements, Y2O3 rare earth oxide and SiO2 powders;

[0049] S2. The mixed powder is mechanically alloyed under the protection of an argon inert atmosphere, the ball-to-material mass ratio is 15:1, and the mechanical alloying time is 25 hours;

[0050] S3. The powder after mechanical alloying is graded and screened, and powder with a diameter range of 50-150µm is selected to obtain a blowing powder.

[0051] The powder blowing agent obtained in S3 is used in the production of high-strength martensitic steel. The powder blowing agent is used for ladle powder spraying metallurgy, and the amount of the powder blowing agent is 10-15kg / ton of steel. The powder blowing agent is sprayed into the molten steel at a high speed using argon gas, and the spraying speed of the powder blowing agent is 15kg / min. The spraying pressure of the argon gas is 0.4MPa. After the powder spraying metallurgy, continuous casting is performed to obtain solidified high-strength martensitic steel.

[0052] The high-strength martensitic steel obtained above can be used to prepare radiation-resistant and high-temperature resistant cladding tube materials for nuclear reactors to increase the service temperature and creep performance, and improve its service life and safety.

[0053] More specifically, the powder blowing agent is used in the production of heat-resistant steel T92, and the amount of the powder blowing agent is 15kg / ton of steel. The performance comparison of the produced material is shown in Table 2, which is significantly improved compared with the traditional T92. The transmission electron micrograph of the dispersion distribution of nano-oxides in the T92 material prepared by the powder blowing agent of the present invention is shown in Figure 2. Figure 1 In the oxide dispersion-strengthened T92 material prepared by the blowing powder agent of this embodiment, transmission electron microscopy analysis and small-angle neutron scattering analysis show that the size of the nano-oxide is 3-5 nm, and the number density is 1.8×10 24 m -3 In comparison, the size of nano-oxides in 9Cr oxide dispersion strengthened steel (CLAM-ODS) prepared by CN107541666A is 5-10 nm, and the number density is 2×10 23 m -3 The nano-oxide size in 9Cr oxide dispersion strengthened steel (CLAM-ODS) prepared by CN111014602A is 6.0±1.5nm, and the number density is 1.3×10 24 m -3 Compared with the technology provided in patent CN107541666A, the nano-oxide size in the material prepared by this technology is reduced by half, and the number density is increased by one order of magnitude. Compared with CN111014602A, the present invention does not require rapid condensation of the ingot, and the nano-oxide size and number density are equally good, which is more suitable for large-scale industrial continuous casting production.

[0054] The high temperature tensile mechanical property test method of GB / T228.2-2015 and the creep property test method of GB / T 2039-2012 were adopted to take rod-shaped samples for testing, and the high temperature tensile and creep property comparison tests were conducted on the traditional T92 and the material prepared by adding the blowing powder agent of the present invention (ODS-T92), and the performance comparison is shown in Table 2. The traditional T92 is a commercial steel produced by Shanxi Taigang Stainless Steel Co., Ltd. purchased on the market.

[0055]

[0056] Example 2

[0057] This embodiment is a powder blowing agent suitable for the production of continuous casting twinning induced plasticity (TWIP) automobile steel plates, and the composition is shown in Table 3.

[0058]

[0059] Preparation process of blowing powder:

[0060] S1. Weigh and uniformly mix Fe, Ti, Y, Si metal element powders meeting the composition requirements, Y2O3 rare earth oxide and SiO2 powders.

[0061] S2. The mixed powder is mechanically alloyed under the protection of an argon inert atmosphere, the ball-to-material mass ratio is 20:1, and the mechanical alloying time is 25 hours;

[0062] S3. The powder after mechanical alloying is graded and screened, and the powder with a diameter range of 100~300µm is selected to obtain the blowing powder. The final powder microscopic morphology optical micrograph is as follows Figure 2 shown.

[0063] The powder blowing agent obtained in S3 is used in the production of high-strength and tough TWIP automobile steel plates. The powder blowing agent is used for ladle powder metallurgy, and the amount of the powder blowing agent is 10-15kg / ton of steel. The powder blowing agent is sprayed into the molten steel at a high speed using argon gas, and the spraying speed of the powder blowing agent is 10kg / min. The blowing pressure of argon gas is 0.35MPa. After powder metallurgy, continuous casting treatment is carried out to obtain solidified oxide dispersion strengthened steel, which is used to prepare TWIP automobile steel to improve its yield strength and improve its service safety.

[0064] More specifically, the powder blowing agent is used in the production of HC450 / 950TW (0.2C-MnCrSi) TWIP steel sheets. The amount of powder blowing agent is 10 kg / ton of steel. The performance comparison of the produced sheets is shown in Table 4, which is significantly improved compared with the traditional HC450 / 950TW.

[0065] The room temperature tensile mechanical property test method of GB / T 228.1-2021 was adopted to take rod-shaped samples, and the room temperature tensile properties of the traditional HC450 / 950TW and the ODS-950TW prepared by the powder blowing agent were tested. The performance comparison is shown in Table 4. The traditional HC450 / 950TW is a commercial alloy purchased from Shanghai Baosteel on the market.

[0066]

[0067] Example 3

[0068] This embodiment is a powder blowing agent suitable for the production of austenitic stainless steel (such as 316L), and the composition is shown in Table 5.

[0069]

[0070] Preparation process of blowing powder:

[0071] S1. Using a vacuum melting process, Fe, Cr, and Ni raw materials are melted into FeCrNi alloy according to the composition ratio (Fe:Cr:Ni = 65:14.8:12.8), and FeCrNi alloy powder is obtained by atomization powder making;

[0072] S2, mixing FeCrNi alloy powder meeting the composition requirements with Ti, Er, Er2O3 and SiO2 powders;

[0073] S3, the mixed powder is mechanically alloyed under the protection of argon inert atmosphere, the ball-to-material mass ratio is 15:1, and the mechanical alloying time is 15 hours;

[0074] S4. The powder after mechanical alloying is graded and screened, and powder with a diameter range of 50~250µm is selected to obtain a blowing powder.

[0075] The above-mentioned powder blowing agent was used for 316L austenitic stainless steel ladle powder spraying metallurgy, the amount of powder blowing agent was 20 kg / ton steel, and the powder blowing agent was sprayed into the molten steel at a high speed using argon gas, and the spraying speed of the powder blowing agent was 20 kg / min. The spraying pressure of argon gas was 0.5 MPa. After powder spraying metallurgy, continuous casting was carried out to obtain solidified oxide dispersion strengthened 316L austenitic stainless steel, and the transmission electron micrograph of its microstructure is shown in the following figure: Figure 3 As shown in Table 6, under the premise that other process conditions remain unchanged, the performance of the stainless steel finally obtained is significantly improved compared with the traditional 316L.

[0076] The room temperature tensile test and 650°C high temperature tensile test were conducted on the conventional 316L and the steel produced by the powder blowing agent (ODS-316L), and the performance comparison is shown in Table 6. The conventional 316L is the commercially available Shanxi Taigang 316L stainless steel plate.

[0077]

[0078] It should be noted that in other embodiments of the present invention, other different schemes obtained by making specific selections within the scope of the steps, components, ratios, and process parameters recorded in the present invention can all achieve the technical effects recorded in the present invention, so the present invention will no longer list them one by one.

[0079] The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention and do not deviate from the concept of the present invention, they belong to the protection scope of the present invention.

Claims

1. A powder blowing agent for powder metallurgy, characterized in that: The blowing powder contains the following elements in percentage by mass: Fe: 50.0~85.0%, Cr: 0~30.0%, Ni: 0~30.0%, W: 0~5.0%, RE: 0.2~10.0%, Ti: 0.1~8.0%, Si: 0~10.0%, O: 0.1~10.0%; and the mass ratio of RE, Si, O and Ti elements conforms to (RE+Si+O) / Ti is (2:1)~(50:1); the RE and O elements exist in the blowing agent in the form of solid solution; the RE is a rare earth; RE and O in the blowing agent are solid-dissolved into the alloy matrix in the form of atoms.

2. The blowing powder according to claim 1, characterized in that: The RE element is one of yttrium, lanthanum, cerium, gadolinium, erbium, neodymium, praseodymium, terbium, samarium, dysprosium or scandium, or a combination of multiple elements thereof.

3. A method for preparing a powder blowing agent for powder injection metallurgy according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: placing the raw material powder into a mechanical alloying sealed tank and performing mechanical alloying under the protection of an inert atmosphere; grading and screening the mechanically alloyed powder to select powder with a particle size of 1 to 500 μm to obtain the blowing powder agent; The raw material powder contains the following raw materials in percentage by mass: Fe: 50.0-85.0%, Cr: 0-30.0%, Ni: 0-30.0%, W: 0-5.0%, RE: 0.1-10.0%, Ti: 0.1-8.0%, Si: 0-10.0%, rare earth oxide: 0.1-10.0%, SiO2: 0-10.0%; the mass proportion of RE, Si, O and Ti elements is controlled by the relative addition amounts of RE, Ti and Si single substance powders and rare earth oxide and SiO2 powders, so that (RE+Si+O) / Ti is (2:1)-(50:1).

4. The preparation method according to claim 3, characterized in that: The raw material powder is prepared by one of the following three methods: (1) Physically mixed by various raw materials according to mass percentage; (2) A portion of the elemental powder is made into an atomized alloy powder, and the remaining elemental powder, the atomized alloy powder, the rare earth oxide, and the SiO2 powder are mixed; (3) All the single-element powders are made into atomized alloy powders, and then the atomized alloy powders are mixed with rare earth oxides and SiO2 powders; The atomized alloy powder is obtained by melting at least two elemental powders into an alloy and then performing an atomization powder making process to obtain the atomized alloy powder.

5. The preparation method according to claim 4, characterized in that: The preparation method of the blowing powder comprises the following steps: S11: using a smelting process, melting at least two of the raw materials of Fe, Cr, Ni, W, RE, Ti, and Si into an alloy according to the following composition ratio, and obtaining an atomized alloy powder through an atomization powder making process; the composition ratio is: Fe: 50.0-85.0%, Cr: 0-30.0%, Ni: 0-30.0%, W: 0-5.0%, RE: 0.1-10.0%, Ti: 0.1-8.0%, Si: 0-10.0%; S12: mixing the atomized alloy powder obtained in step S11 with rare earth oxide and SiO2 powder, and controlling the mass ratio of RE, Si, O and Ti elements by the relative addition amounts of the atomized alloy powder, rare earth oxide and SiO2 powder, so that (RE+Si+O) / Ti is (2:1) to (50:1); S13: placing the raw material powder mixed in step S12 into a mechanical alloying sealed tank, and performing mechanical alloying under the protection of an inert atmosphere; performing classification and screening on the mechanically alloyed powder, and selecting powder with a particle size of 1 to 500 μm to obtain the blowing powder agent.

6. The preparation method according to any one of claims 3 to 5, characterized in that During the mechanical alloying process, alloy or ceramic balls are used as the medium, the ball-to-material mass ratio is (5:1) to (50:1), and the mechanical alloying time is 1 to 50 hours.

7. A method for preparing oxide dispersion strengthened steel, characterized in that: The method comprises the following steps: adding the powder blowing agent for powder injection metallurgy according to any one of claims 1 to 2 into the molten steel being smelted through a powder injection metallurgy process, and performing subsequent thermomechanical treatment on the molten steel after the powder injection metallurgy; The dosage of the blowing agent is 5-50 kg / ton of steel; the powder spraying metallurgical process is specifically: using an inert carrier gas to spray the blowing agent into the molten steel at a high speed, and the blowing agent spraying speed is 5-50 kg / min.

8. The preparation method according to claim 7, characterized in that: The inert carrier gas is argon or nitrogen.

9. The preparation method according to claim 7, characterized in that: The injection pressure of the inert carrier gas is 0.3-0.8 MPa.

10. The preparation method according to claim 7, characterized in that: The thermomechanical treatment includes continuous casting and rolling.

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