A heat treatment process for additively manufactured RAFM steel

Abstract

The present invention discloses a heat treatment process for additively manufactured RAFM steel, and relates to the technical field of manufacturing processes for low-activated ferrite / martensitic steel components in nuclear fusion reactors. A heat treatment process for additively manufactured RAFM steel comprises the following steps: (1) additively manufacturing RAFM steel; (2) subjecting the RAFM steel to normalizing heat treatment, the normalizing temperature being 900-1060°C, the holding time being 30-60min, and air cooling to room temperature after holding; (3) subjecting the RAFM steel treated in step (2) to tempering heat treatment, the tempering temperature being 600-800°C, the heating rate being 5-15°C / min, the holding time being 60-120min, and air cooling to room temperature after holding. The present invention refines the grains through a rapid melting and cooling process of laser selective melting, and improves the comprehensive mechanical properties of the RAFM steel through heat treatment.

Description

Technical Field

[0001] The invention relates to the technical field of manufacturing processes for low-activated ferrite / martensitic steel components in nuclear fusion reactors, and in particular to a heat treatment process for additively manufactured RAFM steel. Background Art

[0002] Low-activation ferrite / martensitic steel (RAFM steel) has become the most promising candidate structural material in the International Thermonuclear Experimental Reactor (ITER) and future thermonuclear demonstration fusion reactors due to its high thermal conductivity, low thermal expansion coefficient, irradiation activation and excellent comprehensive mechanical properties. The first wall (FW), as a component directly facing the plasma, bears long-term aging effects such as neutron irradiation, high thermal and mechanical loads, tritium breeder corrosion, etc. The RAFM steel structural material used in the first wall should meet quite severe environmental requirements.

[0003] The design of FW structure is limited by complex geometric shapes, and its processing and manufacturing are very challenging. Traditional manufacturing methods mainly include bending, milling, hot isostatic pressing (HIP), fusion welding, machining and heat treatment, with long manufacturing cycles and low processing accuracy. Additive manufacturing (AM) technology has attracted widespread attention from scholars due to its advantages in manufacturing complex three-dimensional structures. Compared with traditional processes, selective laser melting (SLM) based on powder bed fusion has the advantages of high material utilization, short production cycle, high molding accuracy, good surface quality and excellent mechanical properties.

[0004] The specimens formed by SLM are affected by heat accumulation and have large thermal stress inside after forming. Overall, the material has high strength and high brittleness, so heat treatment is required to regulate the microstructure and mechanical properties. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a heat treatment process for additively manufactured RAFM steel. The present invention refines the grains through a laser selective melting and rapid melting cooling process, and improves the comprehensive mechanical properties of RAFM steel through normalizing and tempering heat treatment.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides a heat treatment process for additively manufactured RAFM steel, comprising the following steps:

[0008] (1) Additive manufacturing of RAFM steel;

[0009] (2) The RAFM steel is subjected to normalizing heat treatment at a normalizing temperature of 900-1060°C for a holding time of 30-60 min, and then air-cooled to room temperature;

[0010] (3) The RAFM steel treated in step (2) is subjected to a tempering heat treatment at a tempering temperature of 600-800°C, a heating rate of 5-15°C / min, a holding time of 60-120min, and air cooling to room temperature after holding.

[0011] Preferably, the method for preparing RAFM steel in step (1) comprises the following steps:

[0012] S1: The RAFM steel raw materials are melted, refined and degassed in a vacuum induction furnace, and the molten alloy is placed in a gas atomization nozzle system, where an inert gas flow is used to atomize the alloy liquid into small droplets, which are then rapidly solidified to form RAFM steel powder;

[0013] S2: The RAFM steel powder is placed in an oven for drying and then subjected to SLM powder bed fusion molding to produce RAFM steel.

[0014] Preferably, in S1, the rate of the inert gas flow is 1000-1500 Nm 3 / h.

[0015] Preferably, the RAFM steel raw material comprises the following components in percentage by mass:

[0016] C: 0.08-0.15%; Cr: 8.0-9.6%; Mn: 0.3-0.8%; W: 1.0-2.5%; V: 0.1-0.5%; Ta: 0.05-0.2%; the rest are Fe and impurity elements.

[0017] Preferably, the impurity elements include: Al, Si, Ni, Cu, P, S, Co, Nb, Mo, Ag, Sn, As, Sb, B, O, and N; wherein, Al≤0.02%, Si, Ni, Cu≤0.01%, P, S, Co, Nb, Mo≤0.005%, Ag, Sn, As, Sb, B≤0.001, O≤0.028%, and N≤0.003%.

[0018] Preferably, in S1, the powder particle size range of the RAFM steel raw material is 15-53 μm, the particle size distribution is D10=20.0 μm, D50=33.1 μm, D90=54.2 μm, the average particle size is 33.1 μm, the Hall flow rate is less than 15 s / 50g, and the bulk density is less than 4 g / cm 3 , sphericity is greater than 90%.

[0019] Preferably, in S2, the drying temperature of the RAFM steel powder is 100-120° C., and the holding time is 2-5 h.

[0020] Preferably, in S2, the parameters of the melt molding are: laser power 160-320 W, laser scanning speed 600-1200 mm / s, scanning spacing 70-90 μm, layer thickness 25-50 μm, preheating temperature 80-120 °C, oxygen content in the molding chamber is less than 100 ppm, argon purity is 99.999%, cooling time is 50-100 s, the scanning path is set to long straight line bidirectional scanning, and the interlayer deflection angle is 90°.

[0021] Preferably, the normalizing temperature in step (2) is 940-1050°C, specifically 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1020°C, or 1050°C.

[0022] Preferably, the tempering temperature in step (3) is 650-740°C, specifically 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, or 740°C.

[0023] Preferably, the heating rate during the tempering heat treatment in step (3) is any one of or both of 5°C / min, 6°C / min, 8°C / min, 10°C / min, 12°C / min, and 15°C / min.

[0024] In the present invention, if the heating rate is too fast, the RAFM steel will be heated unevenly; if the heating rate is too slow, the heat treatment efficiency is low and the time is too long. Moreover, too long a heating time will coarsen the grains and affect the performance of the RAFM steel. Therefore, the present invention is beneficial to improving the comprehensive performance of the RAFM steel by controlling the heating rate during tempering within the above range.

[0025] Preferably, the tempering and holding time in step (3) is 60-90 min, specifically 60 min, 70 min, 80 min, or 90 min.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention obtains fine-grained high-performance RAFM steel by combining SLM technology with a heat treatment process, and obtains fine martensitic structure by utilizing the rapid melting and cooling characteristics of laser. The process of laser selective melting is 3D modeling → slicing → scanning path planning → printing. By controlling the laser scanning path, nearly two-dimensional planes are superimposed to form a three-dimensional structure. No mold is required and the cost is low, the cycle is short, and the precision is high. It has unique advantages in the preparation of complex and precise metal structural parts. Subsequently, the structure is homogenized through a heat treatment process to obtain higher ductility, thereby solving the problem of loose pores and defects formed during the casting process of large metal components. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a microstructure diagram of the RAFM steel of the present invention which has not been heat treated.

[0029] Figure 2 3 is a microstructure diagram of the RAFM steel after heat treatment in Example 1 of the present invention.

[0030] Figure 3 1 is a microstructure diagram of the RAFM steel after heat treatment in Comparative Example 1 of the present invention.

[0031] Figure 4 3 is a microstructure diagram of the RAFM steel after heat treatment in Comparative Example 2 of the present invention.

[0032] Figure 5 It is a comparison chart of room temperature tensile properties of RAFM steels of Examples 1-3 of the present invention and the control group.

[0033] Figure 6 It is a comparison chart of room temperature impact properties and microhardness of RAFM steels of Examples 1-3 of the present invention and the control group.

[0034] Figure 7 It is a comparison chart of the tensile properties of RAFM steels of Examples 4-10 of the present invention and the control group. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the protection scope and implementation methods of the present invention are not limited thereto.

[0036] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0037] Example 1

[0038] This embodiment discloses a heat treatment process for additively manufactured RAFM steel, comprising the following steps:

[0039] (1) Additive Manufacturing RAFM Steel:

[0040] S1: The RAFM steel raw materials are melted, refined and degassed in a vacuum induction melting furnace, and the molten alloy is placed in a gas atomization nozzle system, where a high-speed inert gas flow is used to atomize the alloy liquid into small droplets, which are then rapidly solidified to form RAFM steel powder;

[0041] RAFM steel raw materials include the following components in mass percentage:

[0042] C: 0.10%; Cr: 8.61%; Mn: 0.63%; W: 1.5%; V: 0.3%; Ta: 0.11%; the rest are Fe and impurity elements;

[0043] Among them, impurity elements include: Al≤0.02%, Si, Ni, Cu≤0.01%, P, S, Co, Nb, Mo≤0.005%, Ag, Sn, As, Sb, B≤0.001, O≤0.028%, N≤0.003%.

[0044] The powder particle size range of RAFM steel raw materials is 15-53μm, the particle size distribution is D10=20.0μm, D50=33.1μm, D90=54.2μm, the average particle size is 33.1μm, the Hall flow rate is 12.5s / 50g, and the bulk density is 3.8 g / cm 3 , the sphericity is 95%.

[0045] S2: The RAFM steel powder is placed in a drying oven for drying at a temperature of 100°C for 5 hours, and then melt-formed by SLM powder bed to obtain RAFM steel;

[0046] The parameters of melt molding are as follows: laser power 160 W, laser scanning speed 600 mm / s, scanning spacing 90 μm, layer thickness 30 μm, preheating temperature 80 °C, oxygen content in the molding chamber less than 100 ppm, argon purity 99.999%, cooling time 50 s, scanning path setting as long straight line bidirectional scanning, and interlayer deflection angle 90°.

[0047] (2) The RAFM steel was subjected to normalizing heat treatment at a temperature of 900 °C for 30 min and then air-cooled to room temperature.

[0048] (3) The RAFM steel treated in step (2) is subjected to tempering heat treatment at a tempering temperature of 600°C, a heating rate of 5°C / min, a holding time of 60 min, and then air-cooled to room temperature.

[0049] The size of the additively manufactured RAFM steel in this embodiment is 150×60×16 mm, and the printing thickness is 20 mm.

[0050] Example 2

[0051] This embodiment discloses a heat treatment process for additively manufactured RAFM steel, comprising the following steps:

[0052] (1) Additive Manufacturing RAFM Steel:

[0053] S1: The RAFM steel raw materials are melted, refined and degassed in a vacuum induction melting furnace, and the molten alloy is placed in a gas atomization nozzle system, where a high-speed inert gas flow is used to atomize the alloy liquid into small droplets, which are then rapidly solidified to form RAFM steel powder;

[0054] RAFM steel raw materials include the following components in mass percentage:

[0055] C: 0.10%; Cr: 8.61%; Mn: 0.63%; W: 1.5%; V: 0.3%; Ta: 0.11%; the rest are Fe and impurity elements;

[0056] Among them, impurity elements include: Al≤0.02%, Si, Ni, Cu≤0.01%, P, S, Co, Nb, Mo≤0.005%, Ag, Sn, As, Sb, B≤0.001, O≤0.028%, N≤0.003%.

[0057] The powder particle size range of RAFM steel raw material is 15-53μm, the particle size distribution is D10=20.0μm, D50=33.1μm, D90=54.2μm, the average particle size is 33.1μm, the Hall flow rate is 12.5 s / 50g, and the bulk density is 3.8 g / cm 3 , the sphericity is 95%.

[0058] S2: The RAFM steel powder is placed in a drying oven for drying at a temperature of 100°C for a holding time of 2 hours, and then melt-formed by SLM powder bed to obtain RAFM steel;

[0059] The parameters of melt molding are as follows: laser power 320 W, laser scanning speed 1200 mm / s, scanning spacing 120 μm, layer thickness 50 μm, preheating temperature 100 °C, oxygen content in the molding chamber less than 100 ppm, argon purity 99.999%, cooling time 100 s, scanning path set to long straight bidirectional scanning, and interlayer deflection angle 90°.

[0060] (2) The RAFM steel was subjected to normalizing heat treatment at a normalizing temperature of 1060°C for a holding time of 60 min, and then air-cooled to room temperature.

[0061] (3) The RAFM steel treated in step (2) is subjected to tempering heat treatment at a tempering temperature of 800°C, a heating rate of 15°C / min, a holding time of 120 min, and then air-cooled to room temperature.

[0062] The size of the additively manufactured RAFM steel in this embodiment is 150×60×16 mm, and the printing thickness is 20 mm.

[0063] Example 3

[0064] This embodiment discloses a heat treatment process for additively manufactured RAFM steel, comprising the following steps:

[0065] (1) Additive Manufacturing RAFM Steel:

[0066] S1: The RAFM steel raw materials are melted, refined and degassed in a vacuum induction melting furnace, and the molten alloy is placed in a gas atomization nozzle system, where a high-speed inert gas flow is used to atomize the alloy liquid into small droplets, which are then rapidly solidified to form RAFM steel powder;

[0067] RAFM steel raw materials include the following components in mass percentage:

[0068] C: 0.10%; Cr: 8.61%; Mn: 0.63%; W: 1.5%; V: 0.3%; Ta: 0.11%; the rest are Fe and impurity elements;

[0069] Among them, impurity elements include: Al≤0.02%, Si, Ni, Cu≤0.01%, P, S, Co, Nb, Mo≤0.005%, Ag, Sn, As, Sb, B≤0.001, O≤0.028%, N≤0.003%.

[0070] The powder particle size range of RAFM steel raw material is 53 μm, the particle size distribution is D10=20.0 μm, D50=33.1 μm, D90=54.2 μm, the average particle size is 33.1 μm, the Hall flow rate is 12.5 s / 50g, and the bulk density is 3.8 g / cm 3 , the sphericity is 95%.

[0071] S2: The RAFM steel powder is placed in a drying oven for drying at a temperature of 120°C for 4 hours, and then melt-formed by SLM powder bed to obtain RAFM steel;

[0072] The parameters of melt molding are as follows: laser power 240 W, laser scanning speed 600 mm / s, scanning spacing 70 μm, layer thickness 25 μm, preheating temperature 120 °C, oxygen content in the molding chamber less than 100 ppm, argon purity 99.999%, cooling time 80 s, scanning path setting as long straight bidirectional scanning, and interlayer deflection angle 90°.

[0073] (2) The RAFM steel was subjected to normalizing heat treatment at a normalizing temperature of 940 °C for a holding time of 55 min and then air-cooled to room temperature.

[0074] (3) The RAFM steel treated in step (2) is subjected to tempering heat treatment at a tempering temperature of 650°C, a heating rate of 10°C / min, a holding time of 70 min, and then air-cooled to room temperature.

[0075] The size of the additively manufactured RAFM steel in this embodiment is 150×60×16 mm, and the printing thickness is 20 mm.

[0076] Example 4

[0077] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 940° C. and the holding time is 45 min; the tempering temperature in step (3) is 740° C. and the holding time is 90 min, and the rest is the same as in Example 1.

[0078] Example 5

[0079] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 980° C. and the holding time is 45 min; the tempering temperature in step (3) is 740° C. and the holding time is 90 min, and the rest is the same as in Example 1.

[0080] Example 6

[0081] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 1020° C. and the holding time is 45 min; the tempering temperature in step (3) is 740° C. and the holding time is 90 min, and the rest is the same as in Example 1.

[0082] Example 7

[0083] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 1050° C. and the holding time is 45 min; the tempering temperature in step (3) is 740° C. and the holding time is 90 min, and the rest is the same as in Example 1.

[0084] Example 8

[0085] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 980° C. and the holding time is 45 min; the tempering temperature in step (3) is 650° C. and the holding time is 90 min, and the rest is the same as in Example 1.

[0086] Example 9

[0087] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 980° C. and the holding time is 45 min; the tempering temperature in step (3) is 700° C. and the holding time is 90 min, and the rest is the same as in Example 1.

[0088] Example 10

[0089] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 980° C. and the holding time is 45 min; the tempering temperature in step (3) is 780° C. and the holding time is 90 min, and the rest is the same as in Example 1.

[0090] Comparative Example 1

[0091] A heat treatment process for additively manufactured RAFM steel, which is different from Example 1 in that only hot isostatic pressing (HIP) heat treatment is performed on the RAFM steel, and the process parameters are: pressure of 120 MPa, heating temperature of 920°C, holding time of 120 min, furnace cooling, and heating rate of 10°C / min.

[0092] Comparative Example 2

[0093] A heat treatment process for additively manufactured RAFM steel, which is different from Example 1 in that after the RAFM steel is subjected to the tempering heat treatment in step (3), a hot isostatic pressing heat treatment is further added, and the heat treatment process parameters are: pressure of 120 MPa, heating temperature of 920°C, holding time of 120 min, furnace cooling, and heating rate of 10°C / min.

[0094] Comparative Example 3

[0095] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 800° C., and the rest is the same as that in Example 1.

[0096] Comparative Example 4

[0097] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the normalizing temperature in step (2) is 1100° C., and the rest is the same as that in Example 1.

[0098] Comparative Example 5

[0099] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the heating rate during the tempering heat treatment in step (3) is 2°C / min, and the rest is the same as that in Example 1.

[0100] Comparative Example 6

[0101] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the heating rate during the tempering heat treatment in step (3) is 20°C / min, and the rest is the same as that in Example 1.

[0102] Comparative Example 7

[0103] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the tempering temperature in step (3) is 500° C., and the rest is the same as that in Example 1.

[0104] Comparative Example 8

[0105] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the tempering temperature in step (3) is 850° C., and the rest is the same as in Example 1.

[0106] Comparative Example 9

[0107] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the tempering holding time in step (3) is 50 minutes, and the rest is the same as that in Example 1.

[0108] Comparative Example 10

[0109] A heat treatment process for additively manufactured RAFM steel, which is different from that in Example 1 in that the tempering holding time in step (3) is 180 min, and the rest is the same as that in Example 1.

[0110] Control group

[0111] RAFM steel without any heat treatment.

[0112] Performance Testing

[0113] 1. Tensile strength: Tensile strength is the maximum bearing capacity of metal under quasi-static tensile conditions. It is the critical value of the transition from uniform plastic deformation to local concentrated plastic deformation of metal. b express.

[0114] 2. Yield strength: Yield strength is the yield limit of metal materials when yielding occurs. For RAFM steel without obvious yield phenomenon, the stress value that produces 0.2% residual deformation is specified as its yield strength, and σ s express.

[0115] 3. Elongation: Elongation is the ratio of the elongation after the original gauge length breaks of the metal material during quasi-static stretching to the initial gauge length, expressed as δ.

[0116] 4. Static toughness: Static toughness is used to reflect the material's ability to resist fracture during stress, which can be expressed as 0.5*(σ b +σ s )*δ to approximate.

[0117] The above indicators are obtained by tensile test, and the tensile test of metal materials is carried out in accordance with the GB / T228.1-2021 test standard.

[0118] 5. Impact energy: Impact energy is an indicator to measure the toughness of materials. It is the ability of materials to absorb plastic deformation work and fracture work under impact load. k The Charpy impact test is carried out in accordance with the GB / T229-2007 test standard.

[0119] 6. Vickers hardness: It is used to describe the ability of a material to resist a hard object from pressing into its surface. It is expressed as HV. The Vickers hardness test is carried out in accordance with the GB / T4340.1-2009 test standard.

[0120] The above test results are shown in Table 1.

[0121] Table 1

[0122]

[0123] According to Table 1, after normalizing and tempering heat treatment, the tensile strength and yield strength of RAFM steel decrease. This is because after heat treatment, dislocations are absorbed and the dislocation strengthening mechanism is weakened, so the strength decreases. During the heat treatment process, fine grains grow and the strength decreases. However, the elongation of RAFM steel increases after heat treatment. In addition, the present invention can make RAFM steel have higher plasticity and toughness by controlling the temperature and holding time during normalizing heat treatment and tempering heat treatment, thereby greatly improving the comprehensive performance of RAFM steel.

[0124] According to Examples 1-10, the present invention refines the grains through the rapid melting and cooling process of laser selective melting, and effectively improves the plasticity and toughness of RAFM steel through normalizing and tempering heat treatment. Moreover, according to the calculation of static toughness, the normalizing and tempering heat treatment process has a significant effect on improving the comprehensive mechanical properties of the material.

[0125] according to Figure 1-4 It can be seen that the fine-grained high-performance RAFM steel provided by the present invention regulates the internal microstructure through the heat treatment process. The microstructure before heat treatment is chessboard-shaped, with coarse columnar crystals and fine equiaxed crystals arranged in an orderly manner, and the growth of the grains has <101> The preferred orientation of the steel direction makes the structure anisotropic. After heat treatment, the grain orientation becomes more uniform. With the recrystallization process, the grains are refined, the alloy elements gather, and carbides are continuously precipitated. According to the strength theory, the refinement of grains and the precipitation of carbides have a significant effect on the mechanical properties of RAFM steel.

[0126] According to Examples 4-10 in Table 1, when the tempering temperature is kept constant at 740 °C and the normalizing temperature changes from 940 °C to 980 °C to 1020 °C to 1050 °C, the static toughness is 8500.17 MPa∙%, 9839.51 MPa∙%, 9740.70 MPa∙%, and 9338.80 MPa∙%, respectively. When the normalizing temperature is kept constant at 980 °C and the tempering temperature changes from 650 °C to 700 °C to 740 °C to 780 °C, the static toughness is 8349.12 MPa∙%, 9446.80 MPa∙%, 9839.51 MPa∙%, and 9764.44 MPa∙%, respectively. This is significantly improved compared to the static toughness (3345.73 MPa∙%) of the unheat-treated RAFM steel sample.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A heat treatment process for additively manufactured RAFM steel, characterized in that: The following steps are involved: (1) Additive manufacturing of RAFM steel; (2) The RAFM steel is subjected to normalizing heat treatment at a normalizing temperature of 900-940°C for a holding time of 30-60 min, and then air-cooled to room temperature; (3) subjecting the RAFM steel treated in step (2) to a tempering heat treatment at a tempering temperature of 600-730°C, a heating rate of 5-15°C / min, a holding time of 60-80min, and air cooling to room temperature after holding; The method for preparing RAFM steel in step (1) comprises the following steps: S1: The RAFM steel raw materials are melted, refined and degassed in a vacuum induction furnace, and the molten alloy is placed in a gas atomization nozzle system, where an inert gas flow is used to atomize the alloy liquid into small droplets, which are then rapidly solidified to form RAFM steel powder; S2: The RAFM steel powder is placed in an oven for drying, and then melt-formed by SLM powder bed to produce RAFM steel; The RAFM steel raw material includes the following components in mass percentage: C: 0.08-0.15%; Cr: 8.0-9.6%; Mn: 0.3-0.8%; W: 1.0-2.5%; V: 0.1-0.5%; Ta: 0.05-0.2%; the rest are Fe and impurity elements; The impurity elements include: Al, Si, Ni, Cu, P, S, Co, Nb, Mo, Ag, Sn, As, Sb, B, O, and N; among which B≤0.001% and N≤0.003%.

2. The heat treatment process for additively manufactured RAFM steel according to claim 1, characterized in that: Al≤0.02%, Si, Ni, Cu≤0.01%, P, S, Co, Nb, Mo≤0.005%, Ag, Sn, As, Sb≤0.001%, O≤0.028%.

3. The heat treatment process for additively manufactured RAFM steel according to claim 1, characterized in that: In S1, the powder particle size range of the RAFM steel raw material is 15-53 μm, the particle size distribution is D10=20.0 μm, D50=33.1 μm, D90=54.2 μm, the average particle size is 33.1 μm, the Hall flow rate is less than 15 s / 50g, and the bulk density is less than 4 g / cm 3 , sphericity is greater than 90%.

4. The heat treatment process for additively manufactured RAFM steel according to claim 1, characterized in that: In S2, the drying temperature of the RAFM steel powder is 100-120° C., and the holding time is 2-5 hours.

5. The heat treatment process for additively manufactured RAFM steel according to claim 1, characterized in that: In S2, the parameters of the melt molding are: laser power 160-320 W, laser scanning speed 600-1200 mm / s, scanning spacing 70-90 μm, layer thickness 25-50 μm, preheating temperature 80-120 °C, oxygen content in the molding chamber less than 100 ppm, argon purity of 99.999%, cooling time 50-100 s, scanning path set to long straight line bidirectional scanning, interlayer deflection angle 90°.

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