A high-strength and tough maraging steel wire suitable for arc additive manufacturing, its preparation method and application

Abstract

The present invention discloses a high-strength and tough maraging steel wire for arc additive manufacturing, its preparation method and application, belonging to the technical field of materials for arc additive manufacturing. The maraging steel alloy comprises the following components in mass percentage: C: ≤0.02%, Si: ≤0.5%, Mn: ≤1%, Ni: 16.0 - 20.0%, Co: 10.0 - 12.0%, Mo: 3.0 - 6.0%, Ti: 0.5 - 1.8%, Al: 0.05 - 0.20%, P: ≤0.003%, S: ≤0.003%, H: ≤5 ppm, N: ≤0.002%, O: ≤0.003%, and the balance is Fe. Using the high-strength and tough maraging steel wire of the present invention, the bulk component prepared by the arc additive manufacturing process has a stacking tensile strength ≥1500 MPa and an elongation of more than 10%.

Description

Technical Field

[0001] The present invention relates to a high-strength and tough maraging steel wire for arc additive manufacturing, a preparation method and an application thereof, and belongs to the technical field of materials for arc additive manufacturing. Background Art

[0002] Maraging steel is a kind of ultra-low carbon, high alloy and ultra-high strength steel. Due to its high strength, excellent load-bearing capacity, welding processability and other advantages, it is widely used in the fields of aviation, aerospace, shipbuilding, ordnance, rail, vehicle and mold. With the development of large-scale and functional-structure integration of construction machinery equipment, the structures of maraging steel parts are becoming more complex and diversified. However, traditional processing technologies such as casting, forging and welding are difficult to meet the manufacturing requirements of large and complex maraging steel parts. In recent years, the development of arc additive manufacturing technology has provided new processes and methods for manufacturing large and complex maraging steel parts. The arc additive manufacturing technology of maraging steel uses an arc as the heat source and maraging steel wire as the filler metal, and accumulates layer by layer and pass by pass according to the preset additive path to realize the near-net forming of large and complex parts. Compared with traditional processing technologies, the arc additive manufacturing technology of maraging steel has high material utilization rate, short single-piece trial production cycle and high yield rate; compared with laser and electron beam powder-based additive manufacturing technologies, the arc additive manufacturing technology has high material utilization rate, high forming efficiency, high density, large size of additive parts and low cost, and can realize the overall rapid forming of large and medium-complex maraging steel parts. Therefore, the arc additive manufacturing technology of maraging steel has been applied in the fields of aviation and aerospace, marine engineering machinery, ordnance equipment and mold manufacturing. However, the arc additive manufacturing technology of maraging steel still has the following problems at present: First, there is a lack of maraging steel wire suitable for arc additive manufacturing. At present, commercial ultra-high strength steel welding wires are mainly used as substitutes, but the strength is relatively low; second, there is element segregation in the microstructure of arc additive manufacturing of maraging steel, resulting in unstable mechanical properties; finally, maraging steel requires solution + aging combined heat treatment to achieve the strengthening effect, but for large maraging steel parts, there is a high risk of cracking during the solution quenching stage. The above problems seriously restrict the application and popularization of the arc additive manufacturing technology of maraging steel.

[0003] Therefore, developing maraging steel wire suitable for arc additive manufacturing has important engineering application value. Summary of the Invention

[0004] The present invention provides a high-strength and tough maraging steel wire for arc additive manufacturing. The tensile strength of maraging steel parts prepared by using this wire reaches more than 1500 MPa, and the elongation rate remains above 10%.

[0005] Meanwhile, the present invention provides a method for preparing a high-strength and tough maraging steel wire suitable for arc additive manufacturing. The composition system and process of the maraging steel wire designed in the present invention fully consider the multi-thermal cycle characteristics of the arc additive manufacturing process, and reasonably utilize the heat treatment effect of the post-deposited layer on the deposited substrate, which is prone to induce reverse transformation of austenite and precipitation of intermetallic compounds such as Ni3(Ti,Mo) and Ni(Ti,Al) in the substrate, improve the microstructure of the additive component, and synergistically enhance the strength and plasticity of the additive component.

[0006] Meanwhile, the present invention provides an application of a high-strength and tough maraging steel wire suitable for arc additive manufacturing.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A high-strength and tough maraging steel wire suitable for arc additive manufacturing, the maraging steel wire comprises the following components by mass percentage: C: ≤0.02%, Si: ≤0.5%, Mn: ≤1.0%, Ni: 16.0 - 20.0%, Co: 10.0 - 12.0%, Mo: 3.0 - 6.0%, Ti: 0.5 - 1.8%, Al: 0.05 - 0.20%, P: ≤0.003%, S: ≤0.003%, H: ≤5 ppm, N: ≤0.002%, O: ≤0.003%, and the balance is Fe.

[0009] C: The C element is an interstitial solid solution strengthening element, which can significantly improve the strength of alloy steel. However, in the wire alloy system of the present invention, it is a maraging steel. For maraging steel, the C element will cause the precipitation of large-sized TiC during the arc additive manufacturing process, significantly reducing the plasticity and toughness, and the C element will also make the arc additive manufacturing processability worse. Therefore, in the present invention, the content of the C element is controlled below 0.02%.

[0010] Si: The Si element has good deoxidation ability during the arc additive manufacturing process. However, the oxide formed by deoxidation with the Si element has a high melting point and small size, and it is difficult for the Si oxide to float up due to the relatively fast solidification rate during the arc additive manufacturing process, which is likely to cause slag inclusions and reduce the strength and elongation. Therefore, in the present invention, the content of the Si element is controlled below 0.5%.

[0011] Mn: Mn also has good deoxidation ability in the arc additive manufacturing process; Mn is considered an impurity element in traditional maraging steel and is strictly controlled; however, from the Fe-Mn phase diagram, since its alloy can form lath martensite in a wide cooling rate range, the presence of Mn also contributes to alloy strengthening; in addition, Mn as an austenite-forming element can partially replace Ni and Co, although doing so will reduce the toughness of the alloy. Therefore, the Mn content in the present invention is controlled to be less than 1%.

[0012] Mo: Mo element has a good substitution solid solution strengthening effect, and can inhibit the temper brittleness and overheating tendency caused by thermal cycles during the arc material addition process. For the maraging steel wire alloy system in the present invention, Mo can be dissolved into the matrix to change the lattice constant of the matrix, reduce the mismatch between the precipitated phase and the matrix, promote the uniform dispersion and precipitation of the precipitated phase, and inhibit the coarsening of Ni3 (Ti, Mo) and Ni (Ti, Al) precipitation phases. The alloying element that contributes to both strength and toughness in maraging steel is Mo, which is mainly due to the fact that the Mo-rich phase precipitated at the beginning of aging contributes to the strength of the steel while also ensuring the toughness of the steel; at the same time, Mo also prevents the strengthening phase from precipitating in a grid-like manner along the original austenite grain boundary, which also improves the fracture toughness of the steel; it is worth noting that too high Mo content will produce Mo-rich intermetallic compounds, which are not easy to dissolve even during high-temperature solution treatment, which will leave residual austenite in the organization and cause a decrease in toughness. Therefore, the Mo element content of the present invention is controlled at 3.0-6.0%.

[0013] Ni: Ni can inhibit the decomposition of screw dislocations in maraging steel to ensure the occurrence of cross-slip, thereby improving the plastic toughness of the steel; Ni is also an austenite-forming element. Its presence expands the austenite phase region, making it easier for the steel to obtain single-phase austenite when heated, so as to obtain lath martensite with good plasticity when cooled; but at the same time, nickel will reduce the Ms temperature and improve the stability of supercooled austenite, which is not conducive to the formation of full martensitic structure; nickel will also form precipitation phases with strengthening elements, which will lead to a decrease in the nickel content in the matrix, so in order to ensure the toughness of the alloy, the nickel content should not be too low. Ni can form precipitation phases such as Ni3 (Ti, Mo) and Ni (Ti, Al), producing a significant precipitation strengthening effect. Therefore, the Ni content in the present invention is controlled at 16.0-20.0%.

[0014] Co: Co element is dissolved in the Fe-Ni matrix of maraging steel, and promotes the precipitation of Mo intermetallic compounds (such as Ni3Mo, Fe2Mo, etc.) through the corresponding synergistic effect; in addition, Co can also increase the Ms temperature, ensuring that the alloy obtains a full martensitic structure after solid solution quenching. Therefore, the content of Co element in the present invention is controlled at 10.0-12.0%.

[0015] Ti: The Ti element has a solution strengthening effect and can precipitate in the form of Ni3Ti or NiTi, producing a significant precipitation strengthening effect. It is the main strengthening element of maraging steel. The solute distribution coefficient of the Ti element is less than 1, and it is prone to segregation between dendrites that solidify later during the solidification process of maraging steel by arc additive manufacturing. The Ti element is a ferrite-forming element and can reduce the mechanical stability of austenite (the ease of transformation of austenite to martensite under external forces). Therefore, in the present invention, by increasing the content of the Ti element, on the one hand, it can promote the precipitation of Ni-Ti intermetallic compounds in the deposited metal during the multi-thermal cycle process of maraging steel by arc additive manufacturing, producing a strengthening effect; on the other hand, it increases the segregation content of titanium element between dendrites during the arc additive manufacturing process, reduces the mechanical stability of the inverse austenite formed in the inter-dendritic region during the multi-thermal cycle process of arc additive manufacturing, and is prone to deformation-induced martensite transformation under external loads, producing a transformation-induced plasticity effect. While increasing the strength, it can ensure a high elongation rate. However, too high a Ti content will reduce the fracture toughness of maraging steel. Therefore, the Ti element content in the present invention is controlled at 0.5 - 1.8%.

[0016] Al: The Al element can precipitate in the form of NiAl or Ni3Al, producing a precipitation strengthening effect. At the same time, the Al element can deoxidize and reduce inclusions. However, when the Al content is too high, a large amount of oxide inclusions will be formed, reducing the strength and toughness, and when the Al content is too high, it will reduce the processability of maraging steel by arc additive manufacturing and increase the crack sensitivity. Therefore, the Al element content in the present invention is controlled at 0.05 - 0.20%.

[0017] Impurity elements such as H, O, N, P, and S: The H element will increase the hydrogen embrittlement sensitivity; the O element will form oxide inclusions, seriously affecting the strength and toughness; the N element will react with Ti in the steel to form TiN, reducing the toughness; P and S will reduce the toughness. Therefore, during the alloy composition design and melting process of maraging steel, the content of the above impurity elements needs to be strictly controlled. In the present invention, the H element content is controlled below 0.0005%, the O element content is controlled below 0.003%, the N element content is controlled below 0.002%, and the P and S element contents are both controlled below 0.003%.

[0018] A preparation method of a maraging steel wire suitable for arc additive manufacturing, and the maraging steel wire includes the following preparation steps:

[0019] (1) Vacuum melting: Use a vacuum melting furnace to conduct primary melting on the maraging steel alloy and cast an initially melted ingot.

[0020] (2) Electrode preparation: Forge the initially melted ingot to prepare an electrode sample.

[0021] (3) Electro-slag remelting: The electrode sample is subjected to secondary melting by the electro-slag remelting method to cast the final ingot.

[0022] (4) Hot forging: The secondary melted ingot is hot forged to prepare a bar.

[0023] (5) Hot rolling: The bar is hot rolled to prepare a wire rod.

[0024] (6) Annealing treatment: The wire rod is annealed.

[0025] (7) Drawing into wire: The annealed wire rod is drawn into wire.

[0026] (8) Cleaning and coiling: The drawn wire is cleaned, dried and coiled.

[0027] Since the drawability of maraging steel wire, the processability of arc additive manufacturing, and the mechanical properties of additive manufactured parts are very sensitive to impurities such as H, O, N, P, S, etc., it is necessary to strictly control the content of impurity elements in the wire raw materials. The present invention uses a double melting method of vacuum melting and electro-slag remelting to purify the melting of the maraging steel wire alloy ingot.

[0028] Preferably, in step (1), the vacuum degree of vacuum melting is 0 - 20 Pa, the heating temperature of the primary melted ingot is 1000 - 1200 °C, and the holding time is 6 - 8 h.

[0029] Preferably, in step (2) for electrode preparation, the primary melted ingot is held at 1000 - 1200 °C for 2 - 4 h, forged, and the final forging temperature is not lower than 850 °C. Since the ultra-high strength steel has poor plastic deformation ability, in order to avoid surface cracks and oxide scale inclusions during deformation, a relatively high initial forging and final forging temperature is adopted before electrode forging.

[0030] Preferably, in step (3) for electro-slag remelting, the electro-slag speed is 1.5 - 2.0 kg / min, the voltage is 25 - 40 V, and the current is 1.8 - 3.0 kA.

[0031] Since the ultra-high strength steel has poor plastic deformation ability, in order to avoid surface cracks and oxide scale inclusions during deformation, preferably, in step (4) for hot forging, the heating temperature of the secondary melted ingot is 1100 - 1200 °C, the holding time is 2 - 4 h, then forged, the final forging temperature is not lower than 950 °C, and then air cooled.

[0032] To avoid surface and internal cracks in the wire rod caused by too low rolling temperature, reduce the finished product rate of wire drawing and the quality of the wire, a relatively high rolling temperature and a relatively long heat preservation time are adopted during rolling. Preferably, in step (5), the forged bar is heat-preserved at 1100 - 1200 °C for 1 - 3 h and then hot continuous rolled through multiple passes to form a wire rod.

[0033] To reduce the hardness of the wire rod and improve the plastic deformation ability, preferably, in step (6), the wire rod is heat-preserved at 1100 - 1200 °C for 1 - 2 h and then air-cooled.

[0034] To reduce the hardness of the wire rod and improve the plastic deformation ability, preferably, in step (7), online annealing is carried out during wire drawing, the annealing temperature is 1000 - 1150 °C, and the annealing time is about 1 h.

[0035] Since pickling used to remove the oxide scale on the surface of the wire rod will cause hydrogen embrittlement in ultra-high strength steel, affect the wire drawing forming ability and the finished product rate, preferably, in step (7), mechanical oxide scale removal is carried out on the wire rod before wire drawing, followed by water washing, air drying, then film treatment, drying at 80 - 100 °C, and then wire drawing.

[0036] To avoid hydrogen embrittlement fracture, preferably, in step (8), alkali washing and water washing are carried out in sequence.

[0037] Application of a high-strength and tough maraging steel wire rod suitable for arc additive manufacturing in maraging steel components.

[0038] Maraging steel components include large and complex maraging steel components, and large and complex maraging steel components include ground-level rocket engine casings, main structures of tank armored vehicles, and aircraft wing hinges.

[0039] In the large and complex maraging steel components in the present invention, generally, those reaching the meter level are considered large, 1 m and above.

[0040] A maraging steel component is prepared from the high-strength and tough maraging steel wire rod obtained by the preparation method of the present invention. The preparation method is as follows: the current is 150 - 250 A, the voltage is 15 - 35 V, the wire feeding speed is 0.3 - 10 m / min, the additive manufacturing speed is 10 - 20 cm / min, and the interlayer temperature is 160 °C - 190 °C.

[0041] The tensile strength of the maraging steel component reaches above 1500 MPa, and the elongation rate remains above 10%.

[0042] The present invention relates to a high-strength and tough maraging steel wire suitable for arc additive manufacturing. Preferably, the maraging steel components are additively manufactured according to the following process parameters: current 150 - 250 A, voltage 15 - 35 V, wire feeding speed 0.3 - 10 m / min, additive manufacturing speed 10 - 20 cm / min, and interlayer temperature 160°C - 190°C.

[0043] Compared with the prior art, the advantages of the present invention are as follows:

[0044] (1) The composition design of the maraging steel wire prepared by the present invention is scientific and reasonable, reducing the content of Mo element and increasing the content of Ti element. On the one hand, the increase in Ti element content can promote the precipitation of intermetallic compounds Ni3(Ti,Mo) and Ni(Ti,Al) during the multi-thermal cycle of arc additive manufacturing of maraging steel, resulting in precipitation strengthening. On the other hand, it can increase the segregation content of Ti element between the post-solidified dendrites during the arc additive manufacturing process, reducing the mechanical stability of the reverse-transformed austenite formed in the dendritic region during the multi-thermal cycle of additive manufacturing. Under the action of external load, it is easy to undergo deformation-induced martensitic transformation, generating transformation-induced plasticity effect. While improving the strength, it can ensure a high elongation rate.

[0045] (2) The additive state tensile strength of the arc additive manufacturing deposit of the maraging steel wire prepared by the present invention can reach above 1500 MPa, and at the same time, the elongation rate can be maintained above 10%.

[0046] (3) In the prior art, the preparation of welding wires is usually vacuum melting, electroslag remelting, forging, hot rolling, and wire drawing; this is the usual preparation method for cylindrical metal materials, such as welding wires, steel bars, nails, etc. However, the post-treatment of each link is very important, especially for metal materials with relatively high strength. High-strength materials are prone to cracking, and it is necessary to heat each link to the austenite phase field temperature for homogenization and softening treatment. Therefore, whether it is after melting, forging, or rolling, softening treatment is required. Especially for the key wire drawing process, stress relief treatment during the process is needed because the drawing deformation of high-strength steel materials will generate internal stress, leading to wire failure.

[0047] (4) Existing high-strength steels are generally forgings, which are difficult to manufacture for large and complex structural parts. However, the present invention is used for additive manufacturing, which can realize the overall additive manufacturing of large and complex metal components, and can achieve a strength of 1500 MPa without post-heat treatment.

[0048] (5) What the present invention patent proposes is the composition design and manufacturing of wire materials. Compared with existing metal powders, the powder preparation process is relatively simple. In the preparation process of wire materials, especially in the rolling and wire drawing processes, the cracking and wire forming rate of high-strength materials need to be considered. The wire materials obtained by the present invention do not crack, and the wire forming rate > 99%.

[0049] (6) The strength of the wire material designed in the present invention is very high. Therefore, in the wire material preparation process, an austenite phase field temperature homogenization annealing treatment step is added to each link. In particular, stress relief annealing treatment is carried out during the wire drawing process to ensure the wire forming rate and the wire coiling performance.

[0050] (7) The wire material composition designed in the present invention has considered the characteristics of layer-by-layer and pass-by-pass stacking during the arc additive manufacturing process. The subsequent deposited metal has a heat treatment effect on the already deposited metal, resulting in the reverse transformation of austenite in the dendritic intergranular regions where Ni, Mo, and Ti three elements segregate, and the precipitation of intermetallic compounds such as Ni3(Ti, Mo) and Ni(Ti, Al) in the dendritic trunk regions. Therefore, the subsequent additive manufacturing process corresponds to the wire material composition design. For traditional such materials to reach this strength level, high-temperature solution treatment + medium-temperature aging treatment are required. However, by using the wire material of this article and the corresponding arc additive manufacturing process, a strength of 1500 MPa and an elongation of 10% can be achieved without heat treatment.

[0051] The present invention discloses a high-strength and tough maraging steel wire material suitable for arc additive manufacturing, belonging to the fields of materials for arc additive manufacturing, metallurgy, and additive manufacturing technologies. The maraging steel wire material composition system designed in the present invention fully considers the multi-thermal cycle characteristics of the arc additive manufacturing process, and reasonably utilizes the heat treatment effect of the subsequent deposited layer on the already deposited substrate, which is easy to induce reverse transformation of austenite and precipitation of intermetallic compounds such as Ni3(Ti, Mo) and Ni(Ti, Al) in the substrate, improving the microstructure of the additive manufactured component and synergistically enhancing the strength and plasticity of the additive manufactured component. By using the high-strength and tough maraging steel wire material of the present invention, the tensile strength of the bulk component prepared by the arc additive manufacturing process is ≥1500 MPa, and the elongation is more than 10%. Description of the Drawings

[0052] Figure 1 is the flowchart for the preparation of maraging steel wire material;

[0053] Figure 2 is the tensile property curve of maraging steel parts manufactured by arc additive manufacturing;

[0054] Figure 3 is the typical microstructure of maraging steel parts manufactured by arc additive manufacturing;

[0055] Figure 4 is the element distribution map of maraging steel parts manufactured by arc additive manufacturing. Detailed Embodiments

[0056] The present invention will be further described in detail below with reference to the drawings and specific embodiments. The following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0057] Example 1

[0058] A high-strength and tough maraging steel wire suitable for arc additive manufacturing. The maraging steel alloy comprises the following components by mass percentage: C: 0.02%, Si: 0.5%, Mn: 1%, Ni: 18.0%, Co: 11.0%, Mo: 4.0%, Ti: 1.0%, Al: 0.10%, P: 0.003%, S: 0.003%, H: 5 ppm, N: 0.002%, O: 0.003%, and the balance is Fe.

[0059] A preparation method of a maraging steel wire suitable for arc additive manufacturing, comprising the following steps:

[0060] (1) Vacuum melting: The maraging steel alloy is initially melted by a vacuum melting furnace with a vacuum degree of 14 Pa to obtain an initially melted ingot. The heating temperature of the initially melted ingot is 1100°C, and the holding time is 7 h.

[0061] (2) Electrode preparation: The initially melted ingot is held at 1100°C for 3 h, then forged to prepare an electrode sample. The final forging temperature is 850°C, and then it is air-cooled.

[0062] (3) Electro-slag remelting: The electrode sample is secondarily melted by electro-slag remelting with an electro-slag speed of 1.8 kg / min, a voltage of 30 V, and a current of 2.5 kA to obtain a final ingot.

[0063] (4) Hot forging: The secondarily melted ingot is heated to 1150°C with a holding time of 3 h, and then forged to prepare a bar. The final forging temperature is 950°C.

[0064] (5) Hot rolling: The bar is held at 1100°C for 2 h and hot continuous rolled through multiple passes to be rolled into a wire rod with a diameter of Φ6.5.

[0065] (6) Annealing treatment: The wire rod is held at 1150°C for 1 h and then air-cooled.

[0066] (7) Drawing into wire: The oxidized skin of the softened wire rod is mechanically removed, and after being washed with water and dried, it is subjected to film treatment, dried at 80°C, and then drawn. The drawing diameter changes as Φ6.2 → Φ5.2 → Φ4.8 → Φ4.4 → in-line annealing (annealing temperature is 1000°C, annealing time is 1 h) + alkali washing → Φ3.8 → Φ3.4 → Φ2.0 → Φ1.6 → Φ1.2.

[0067] (8) Cleaning and winding: The drawn wire is alkali-washed, water-washed, dried, and wound on a reel.

[0068] Application of a high-strength and tough maraging steel wire suitable for arc additive manufacturing in maraging steel components.

[0069] The maraging steel components include large and complex maraging steel components, and the large and complex maraging steel components include ground-level rocket engine casings, main structures of tank armored vehicles, and aircraft wing hinges.

[0070] A maraging steel component is prepared from the high-strength and tough maraging steel wire obtained by the preparation method described in this embodiment. The preparation method is as follows: the current is 200 A, the voltage is 25 V, the wire feeding speed is 5 m / min, the additive manufacturing speed is 15 cm / min, and the interlayer temperature is 180 °C.

[0071] The preparation process of the maraging steel wire is as Figure 1 shown.

[0072] The prepared maraging steel wire is used for an arc additive manufacturing forming experiment with a MOTAMAN MH6 arc welding robot, a DX100 robot control cabinet, a Fronius MagicWave 3000 welding power source, a plasma control cabinet, and a plasma additive manufacturing gun body. The substrate is made of low-alloy steel with a thickness of 12 mm. The current is 200 A, the voltage is 25 V, the wire feeding speed is 5 m / min, the additive manufacturing speed is 15 cm / min, and the interlayer temperature is 180 °C. Tensile specimens are taken along the running length direction of the welding torch. The specimens are standard tensile specimens for tensile property testing. The mechanical properties are as Figure 2 shown. As Figure 2 shown, the tensile strength of the additive manufacturing deposit in the as-deposited state of the maraging steel wire prepared in this embodiment reaches more than 1500 MPa, and the elongation rate remains above 10%.

[0073] Figure 3 is the microstructure of the maraging steel component prepared by arc additive manufacturing. Among them, Figure 3 (a) and Figure 3 (b) are respectively the longitudinal section and cross-section metallographic solidification structure diagrams of the component. It can be clearly seen from the figure that the solidification structure of this kind of component is composed of cellular dendrites and columnar dendrites. Figure 3 (c) is the SEM diagram of the component. In the figure, the rough surface presenting white areas is the cellular / columnar martensite region, and the smooth surface presenting black areas is the inter-dendritic austenite. Figure 3(d) is the EBSD phase diagram of the component, further confirming that the cellular / columnar dendritic region is martensite (blue region) and the interdendritic region is austenite (red region). The above microstructure information indicates that during the arc additive manufacturing of maraging steel, the molten pool metal solidifies according to the cellular / dendritic mode, resulting in the segregation of Ni, Mo, and Ti elements in the interdendrites during the later solidification (the partition coefficients of these solute elements are all less than 1, and the solubility of solute elements in the liquid phase is high). The microstructure produced by this solidification mode is particularly conducive to the segregation of solute elements at specific positions (interdendrites), resulting in different properties in these regions from those of the dendritic trunks. Under the conditions of high heat input and multiple thermal cycles in arc additive manufacturing, the reverse transformation of austenite occurs, producing a plasticizing and toughening effect.

[0074] Figure 4 For the element point scanning and area scanning, it can be clearly seen the segregation of Ni, Mo, and Ti elements. According to the point scanning, the content of Ti element in the interdendrites is further quantified as 0.37% and in the dendritic trunks is 1.25%.

[0075] Example 2

[0076] A high-strength and tough maraging steel wire suitable for arc additive manufacturing, the maraging steel alloy includes the following components in mass percentage: C: 0.01%, Si: 0.4%, Mn: 0.5%, Ni: 16.0%, Co: 10.0%, Mo: 3.0%, Ti: 0.5%, Al: 0.05%, P: 0.002%, S: 0.003%, H: 4 ppm, N: 0.001%, O: 0.001%, and the balance is Fe.

[0077] A preparation method of a maraging steel wire suitable for arc additive manufacturing, including the following steps:

[0078] (1) Vacuum melting: Use a vacuum melting furnace to conduct primary melting on the maraging steel alloy, with a vacuum degree of 0.5 Pa, cast to obtain an initially melted ingot, the heating temperature of the initially melted ingot is 1000 °C, and the holding time is 6 h.

[0079] (2) Electrode preparation: Keep the initially melted ingot at 1000 °C for 2 h, conduct forging to prepare an electrode sample, the final forging temperature is 880 °C, and then air cool.

[0080] (3) Electro-slag remelting: Use the electro-slag remelting method to conduct secondary melting on the electrode sample, with an electro-slag speed of 1.5 kg / min, a voltage of 25 V, and a current of 1.8 kA, and cast to obtain the final ingot.

[0081] (4) High-temperature forging: Heat the secondary melted ingot to 1100 °C, with a holding time of 2 h, and then conduct forging to prepare a bar, with a final forging temperature of 990 °C.

[0082] (5) Hot rolling: Keep the bar at 1200 °C for 1 h, and then perform multi-pass hot continuous rolling to roll it into a wire rod with a diameter of Φ6.0.

[0083] (6) Annealing treatment: Keep the wire rod at 1100 °C for 2 h, and then air-cool it.

[0084] (7) Drawing and wire making: Mechanically remove the oxide scale from the softened wire rod, perform pickling, water washing, and drying, then perform film treatment, dry at 100 °C, and then perform drawing. The drawing diameter changes as Φ5.8 → Φ5.0 → Φ4.6 → Φ4.2 → in-line annealing (annealing temperature is 1150 °C, annealing time is 1 h) + alkali washing → Φ3.6 → Φ3.2 → Φ1.8 → Φ1.4 → Φ1.0.

[0085] (8) Cleaning and winding: Perform alkali washing, water washing, drying, and winding on the drawn wire.

[0086] An application of a high-strength and tough maraging steel wire rod suitable for arc additive manufacturing in maraging steel components.

[0087] The maraging steel components include large and complex maraging steel components, and the large and complex maraging steel components include ground-level rocket engine casings, main structures of tank armored vehicles, and aircraft wing hinges.

[0088] A maraging steel component is prepared from the high-strength and tough maraging steel wire rod obtained by the preparation method of this embodiment. The preparation method is as follows: current is 150 A, voltage is 15 V, wire feeding speed is 0.3 m / min, additive manufacturing speed is 10 cm / min, and interlayer temperature is 160 °C.

[0089] The additive-state tensile strength of the additive manufacturing deposit of the maraging steel wire rod prepared in this embodiment reaches 1580 MPa, and the elongation is 12% at the same time.

[0090] Example 3

[0091] A high-strength and tough maraging steel wire rod suitable for arc additive manufacturing, and the maraging steel alloy includes the following components in mass percentage: C: 0.015%, Si: 0.3%, Mn: 0.6%, Ni: 20.0%, Co: 12.0%, Mo: 6.0%, Ti: 1.8%, Al: 0.20%, P: 0.003%, S: 0.001%, H: 3 ppm, N: 0.002%, O: 0.002%, and the balance is Fe.

[0092] A preparation method of a maraging steel wire rod suitable for arc additive manufacturing includes the following steps:

[0093] (1) Vacuum melting: The maraging steel alloy is initially melted using a vacuum melting furnace with a vacuum degree of 20 Pa, and an initially melted ingot is cast. The heating temperature of the initially melted ingot is 1200 °C, and the holding time is 8 h.

[0094] (2) Electrode preparation: The initially melted ingot is held at 1200 °C for 4 h, and then forged to prepare an electrode sample. The final forging temperature is 860 °C, and then it is air-cooled.

[0095] (3) Electro-slag remelting: The electrode sample is secondarily melted using the electro-slag remelting method. The electro-slag speed is 2.0 kg / min, the voltage is 40 V, and the current is 3.0 kA, and a final ingot is cast.

[0096] (4) Hot forging: The secondarily melted ingot is heated to 1200 °C, and the holding time is 4 h, and then forged to prepare a bar. The final forging temperature is 970 °C.

[0097] (5) Hot rolling: The bar is held at 1150 °C for 3 h and hot continuous rolled through multiple passes to be rolled into a wire rod with a diameter of Φ6.2.

[0098] (6) Annealing treatment: The wire rod is held at 1200 °C for 2 h, and then air-cooled.

[0099] (7) Drawing into wire: The oxidized skin of the softened wire rod is mechanically removed, and after being washed with water and dried, it is subjected to film treatment, dried at 90 °C, and then drawn. The drawing diameter change is Φ6.0 → Φ4.8 → Φ4.4 → Φ4.0 → in-line annealing (annealing temperature is 1150 °C, annealing time is 1 h) + alkali washing → Φ3.4 → Φ3.0 → Φ1.6 → Φ1.2 → Φ0.8.

[0100] (8) Cleaning and winding: The drawn wire is alkali-washed, water-washed, dried, and wound on a reel.

[0101] An application of a high-strength and tough maraging steel wire for arc additive manufacturing in maraging steel components.

[0102] The maraging steel components include large and complex maraging steel components, and the large and complex maraging steel components include ground-level rocket engine casings, main structures of tank armored vehicles, and aircraft wing hinges.

[0103] A maraging steel component is prepared from the high-strength and tough maraging steel wire obtained by the preparation method described in this embodiment. The preparation method is: current 250 A, voltage 35 V, wire feeding speed 10 m / min, additive manufacturing speed 20 cm / min, and interlayer temperature 190 °C.

[0104] The as-built tensile strength of the arc additive manufacturing deposit of the maraging steel wire prepared in this example reaches 1625 MPa, and the elongation is 11% at the same time.

[0105] Example 4

[0106] A high-strength and tough maraging steel wire suitable for arc additive manufacturing, the maraging steel alloy includes the following components by mass percentage: C: 0.02%, Si: 0.2%, Mn: 0.9%, Ni: 17.0%, Co: 10.5%, Mo: 5.0%, Ti: 1.6%, Al: 0.09%, P: 0.001%, S: 0.001%, H: 3 ppm, N: 0.002%, O: 0.003%, and the balance is Fe.

[0107] A preparation method of a maraging steel wire suitable for arc additive manufacturing, comprising the following steps:

[0108] (1) Vacuum melting: The maraging steel alloy is initially melted using a vacuum melting furnace, the vacuum degree is 10 Pa, and an initially melted ingot is cast. The heating temperature of the initially melted ingot is 1050 °C, and the holding time is 8 h.

[0109] (2) Electrode preparation: The initially melted ingot is held at 1150 °C for 3 h, forged to prepare an electrode sample, the final forging temperature is 850 °C, and then air-cooled.

[0110] (3) Electroslag remelting: The electrode sample is secondarily melted by the electroslag remelting method, the electroslag speed is 1.6 kg / min, the voltage is 30 V, the current is 2.5 kA, and a final ingot is cast.

[0111] (4) High-temperature forging: The secondarily melted ingot is heated to 1180 °C, the holding time is 3 h, and then forged to prepare a bar, and the final forging temperature is 960 °C.

[0112] (5) High-temperature rolling: The bar is held at 1100 °C for 1 h, and hot continuous rolling is carried out through multiple passes to roll it into a wire rod with a diameter of Φ6.4.

[0113] (6) Annealing treatment: The wire rod is held at 1200 °C for 1.5 h and then air-cooled.

[0114] (7) Drawing and wire making: The oxidized skin of the softened wire rod is mechanically removed, after washing with water and drying, film treatment is carried out, and after drying at 85 °C, drawing is carried out. The drawing diameter change is Φ6.1 → Φ4.9 → Φ4.5 → Φ4.1 → in-line annealing (annealing temperature is 1100 °C, annealing time is 1 h) + alkali washing → Φ3.5 → Φ3.1 → Φ1.7 → Φ1.3 → Φ0.9.

[0115] (8) Cleaning and winding: The drawn wire is alkali-washed, water-washed, dried, and wound on a reel.

[0116] Application of a high-strength and tough maraging steel wire suitable for arc additive manufacturing in maraging steel components

[0117] The maraging steel components include large and complex maraging steel components, and the large and complex maraging steel components include ground-level rocket engine casings, main structures of tank armored vehicles, and aircraft wing hinges

[0118] A maraging steel component is prepared from the high-strength and tough maraging steel wire obtained by the preparation method of this embodiment. The preparation method is as follows: current 180A, voltage 30V, wire feeding speed 2m / min, additive manufacturing speed 18cm / min, interlayer temperature 170°C

[0119] The tensile strength of the additive manufacturing deposit in the as-deposited state of the maraging steel wire prepared in this embodiment reaches 1532MPa, and the elongation is 12%

[0120] Comparative Example 1

[0121] The difference between this comparative example and Example 1 is only that: the interlayer temperature is not controlled, and the interlayer temperature in this comparative example is 140°C, that is, the continuous additive manufacturing strategy, resulting in a pure martensite structure in the internal organization of the final additive manufacturing component, and no precipitation strengthening phase is generated. Under this condition, the tensile strength of the additive manufacturing component is 1000MPa, and the elongation is 8%, which is consistent with the forging level

[0122] In Example 1, when the interlayer temperature is controlled at 180°C, during the additive manufacturing process, reverse austenite transformation and precipitation of intermetallic compounds occur in the deposited metal, resulting in a tensile strength of 1500MPa for the final additive manufacturing component, and the elongation still remains above 10%

[0123] In this embodiment, during the additive manufacturing process, the wire first melts into a liquid state, then solidifies into high-temperature austenite, and then when it cools to the martensite transformation temperature (Ms), the austenite-to-martensite transformation occurs. The Ms of the wire system designed in the present invention is 220 - 230°C. If the interlayer temperature is too high, the martensite transformation does not occur, resulting in low strength. If the interlayer temperature is too low, the reverse austenite transformation is insufficient, resulting in a low elongation

[0124] It should be understood that, in order to streamline the present disclosure and assist in understanding one or more of the various inventive aspects, in the foregoing description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the claims, the inventive aspects lie in less than all the features of the previously disclosed embodiments. Thus, the claims following the detailed description hereby expressly incorporate the detailed description, where each claim itself serves as a separate embodiment of the present invention.

[0125] Although the present invention has been described in terms of a limited number of embodiments, those skilled in the art in this technical field will appreciate that other embodiments can be envisioned within the scope of the invention as thus described. In addition, it should be noted that the language used in this specification has been principally selected for readability and instructional purposes and not for the purpose of explaining or limiting the subject matter of the present invention. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure of the present invention is illustrative, not restrictive, and the scope of the present invention is defined by the appended claims.

[0126] The foregoing are only the preferred embodiments of the present invention, and it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A maraging steel component, characterized in that: The high-strength and tough maraging steel wire is prepared by a preparation method of a high-strength and tough maraging steel wire suitable for arc additive manufacturing, wherein the preparation method is as follows: current 150-250A, voltage 15-35V, wire feeding speed 0.3-10m / min, additive speed 10-20cm / min, interlayer temperature 160°C-190°C; The tensile strength of maraging steel parts reaches more than 1500MPa, and the elongation remains above 10%; The method for preparing a high-strength and tough maraging steel wire suitable for arc additive manufacturing comprises the following preparation steps: S01, vacuum melting: the maraging steel alloy is initially melted in a vacuum melting furnace to obtain a primary melt ingot, the heating temperature of the primary melt ingot is 1000-1200°C, and the holding time is 6-8h; The maraging steel alloy includes the following components in mass percentage: C: ≤0.02%, Si: ≤0.5%, Mn: 0.5-1%, Ni: 16.0~20.0%, Co: 10.0~12.0%, Mo: 3.0~6.0%, Ti: 0.5~1.8%, Al: 0.05~0.20%, P: ≤0.003%, S: ≤0.003%, H: ≤5ppm, N: ≤0.002%, O: ≤0.003%, Fe is the balance; S02, electrode preparation: forging the initial melt ingot, before forging, the initial melt ingot is kept at 1000~1200℃ for 2~4h, and then forged, the final forging temperature is not less than 850℃, and the electrode sample is prepared; S03, electroslag remelting: the electrode sample is subjected to secondary smelting by electroslag remelting, the electroslag remelting speed is 1.5-2.0 kg / min, the voltage is 25-40 V, the current is 1.8-3.0 kA, and the final ingot is cast; S04, high temperature forging: the final ingot is subjected to high temperature forging. Before forging, the final ingot is heated to a temperature of 1100-1200°C for 2-4 hours of holding time, and then forged. The final forging temperature is not less than 950°C to prepare a bar; S05, high temperature rolling: the bar is kept at 1100~1200℃ for 1~3h, and then rolled into wire rod through multiple hot rolling passes; S06, annealing treatment: annealing the wire rod; the annealing process is: keeping at 1100~1200℃ for 1~2h, and then air cooling; S07, wire drawing: drawing the wire rod after annealing, and online annealing is performed during the drawing process, and the annealing temperature is 1000~1150℃; S08, cleaning and winding: cleaning, drying and winding the wire after drawing; Maraging steel parts include large complex maraging steel parts, such large complex maraging steel parts include ground-level rocket engine casings, tank armored vehicle main structures, and aircraft wing hinges; The arc additive manufacturing process is characterized by layer-by-layer deposition. The later deposited metal has a heat treatment effect on the deposited metal, resulting in austenite reversal transformation in the interdendritic region where the three elements Ni, Mo, and Ti are segregated, and the precipitation of Ni3(Ti,Mo) and Ni(Ti,Al) intermetallic compounds in the dendrite trunk region.

2. A maraging steel component according to claim 1, characterized in that: In S01, the vacuum degree of vacuum smelting is 0~20Pa.

3. The maraging steel component according to claim 1, characterized in that: In S07, the wire rod is mechanically descaled before drawing, and then treated with a film after washing and drying, and then drawn after drying at 80-100°C.

4. The maraging steel component according to claim 1, characterized in that: In S08, the cleaning is performed by sequentially performing alkaline cleaning and water cleaning.

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