Novel medium carbon steel for additive manufacturing and powder manufacturing process and additive manufacturing forming method thereof

Abstract

The invention relates to the technical field of medium carbon steel and additive manufacturing, and provides novel medium carbon steel for additive manufacturing, a powder manufacturing process of the novel medium carbon steel and an additive manufacturing forming method.The novel medium carbon steel for additive manufacturing is prepared from C, Mn, Si, Cr, P, S, V, Ni, Ti, Cu, Al and Fe; the invention further discloses a powder preparation process of the novel medium carbon steel. The powder preparation process comprises the steps of S1, blank preparation, S2, remelting refining and S3, atomization powder preparation. Components of the novel medium carbon steel suitable for additive manufacturing are provided, metal powder suitable for additive manufacturing can be prepared, a product obtained after additive manufacturing is good in structural strength and has a compact structure and a uniform and fine metallographic structure, the problem that cracks and cracks are prone to occurring in a traditional 3D printing process is solved, and the product quality is improved. The problems that a traditional forging process is not high in strength and not beneficial to lightweight design of products are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of medium carbon steel and additive manufacturing, and in particular to a novel medium carbon steel for additive manufacturing, a powder making process thereof, and an additive manufacturing forming method. Background Art

[0002] Additive manufacturing technology, referred to as 3D printing technology, has become one of the most popular disruptive technologies in the manufacturing industry because it can efficiently and quickly manufacture complex structures that cannot be made by traditional processes, combine topology optimization simulation and lattice layout to obtain new design space, and meet indicators such as lightweight and ultra-high performance. Among them, selective laser melting (SLM) is one of the most widely used metal additive manufacturing technologies. It uses a precisely focused laser spot to quickly melt the pre-laid layers of metal powder to prepare complex precision parts. It has been widely used in mechanical equipment manufacturing, aerospace, medical, biotechnology and other fields. The materials involved are the preparation of stainless steel, titanium alloy, high-temperature alloy, aluminum alloy and other parts.

[0003] SLM technology uses high-energy laser beams to process metal parts with precise structures. Its process operations mainly include the following points: (1) Use CAD software to build a three-dimensional model, use slicing software to perform slicing discrete processing, and then import the model into a molding device such as a 3D printer; (2) After the slice information is imported into the computer, the 3D printing software performs relevant processing, adopting a layer-by-layer import processing method, and then the laser irradiates the pre-spread metal powder. After processing into a layer of parts, the slice thickness is increased, the powder is spread on the forming cylinder, and laser melting and sintering are performed at each level in turn; (3) After processing, the parts are removed from the substrate and subjected to performance enhancement treatment or surface treatment such as heat treatment.

[0004] Based on the advanced production technology in the SLM molding process, SLM technology has the following advantages: (1) Products or parts do not require mold development, and can be directly 3D printed using 3D models, which reduces R&D or manufacturing cycles, reduces inventory, and activates funds; (2) There is almost no restriction on the shape of the product. Parts with complex structures such as cavities, lattices, and special shapes can be made, especially parts that cannot be made by traditional processes; (3) Reducing the number of parts can reduce assembly time, improve material utilization, and save direct costs.

[0005] Internal combustion engines are an important field of equipment manufacturing. For example, the piston is a reciprocating part in the cylinder block of an internal combustion engine. The main function of the piston is to withstand the combustion pressure in the cylinder and transmit this force to the crankshaft through the piston pin and the connecting rod. In addition, the piston, the cylinder head, and the cylinder wall together form a combustion chamber. In order to better reduce the temperature of the piston, people have invented a eutectic aluminum-silicon alloy diesel engine piston with an inner cooling oil cavity, that is, by spraying oil into the inner cooling oil cavity to cool the piston head and the ring groove. Limited by the strength of aluminum alloy materials, it cannot meet the high temperature and high explosion pressure requirements of high-power, high-strength diesel engines. Therefore, internal combustion engine practitioners began to study the use of new materials to replace aluminum alloys to meet the increasing requirements of diesel engine strengthening. Companies have successively developed cast iron pistons, articulated pistons, and integral forged steel structure pistons. However, the strength of forged products is not high, which is not conducive to product lightweight design.

[0006] The application and research of 3D printing in the field of internal combustion engines has just started, and parts printed by existing 3D printing processes are prone to cracks and splitting. Summary of the invention

[0007] In order to overcome the defects of the prior art pointed out above, the present invention provides a new type of medium carbon steel for additive manufacturing, a powder making process and an additive manufacturing forming method thereof, provides a composition of a new type of medium carbon steel suitable for additive manufacturing, and can produce metal powder suitable for additive manufacturing. The product after additive manufacturing has good structural strength, a dense structure and a uniform and fine metallographic structure, avoiding the problem of cracks and cracks that are prone to occur in traditional 3D printing processes, and solving the problem that the traditional forging process has low strength and is not conducive to lightweight design of products.

[0008] In order to solve the above technical problems, the technical solution of the present invention is: A new medium carbon steel for additive manufacturing, wherein the new medium carbon steel comprises the following ingredients: C, Mn, Si, Cr, P, S, V, Ni, Ti, Cu, Al and Fe; The weight percentages of the ingredients of the novel medium carbon steel are C: 0.34%-0.42%, Mn: 1.2%-1.6%, Si: 0.15%-0.8%, Cr: 0.05%-0.3%, P: ≤0.035%, S: 0.02%-0.075%, V: 0.08%-0.2%, Ni: ≤0.4%, Ti: 0.01%-0.04%, Cu: ≤0.3%, Al: 0.01%-0.07%, and the rest is Fe.

[0009] According to some embodiments of the present invention, the ingredients of the new medium carbon steel also include: Mo, Co, Pb, Sn, Nb, W, As, Zr, Bi, Ca, Zn, N, O, wherein the weight percentages of Mo, Co, Pb, Sn, Nb, W, As, Zr, Bi, Ca, Zn, N, and O are Mo: ≤0.08%, Co: 0.005% to 0.6%, Pb: ≤0.02%, Sn: ≤0.03%, Nb: ≤0.02%, W: ≤0.07%, As: ≤0.008%, Zr: ≤0.0004%, Bi: ≤0.02%, Ca: ≤0.003%, Zn: ≤0.02%, N: 0.01% to 0.05%, and O: ≤0.03%; The new medium carbon steel is in the form of powder, cast or forged; The powder particle size of the powder is 10um to 200um.

[0010] A novel medium carbon steel powder making process, the powder making process comprising: S1 billet preparation, S2 remelting and refining, and S3 atomization powder making; Among them, the S1 blank preparation includes the following steps: S11: placing raw materials according to the composition and proportion of the new medium carbon steel into a vacuum induction furnace for smelting; S12: Casting the molten metal smelted in step S11 under vacuum conditions to obtain a blank; S13: placing the blank obtained in step S12 in a heating furnace and heating it at a temperature of 1000° C. to 1300° C., and then rolling the blank to compact the inside of the blank; S14: cutting and surface treating the blank of step S13 to obtain a blank that is easy to be smelted in a crucible; Among them, S2 remelting refining includes the following steps: S21: placing the blank obtained in step S14 into a melting crucible, then evacuating the vacuum atomization induction melting chamber, and then performing a replacement operation with an inert gas or nitrogen of a certain purity; S22: heating the melting crucible at a certain heating rate, the heating temperature being a certain temperature above the melting point of the blank, so that the blank is remelted into molten metal, and keeping the temperature for a period of time; S23: During the heating process of step S22, the melting crucible is tilted and electromagnetic stirring is performed to mix the components of the molten metal uniformly; Among them, S3 atomization powder making includes the following steps: S31: after the molten metal in step S23 reaches the outlet temperature, tilting the smelting crucible so that the molten metal in the smelting crucible flows into the tundish and is introduced into the atomizer nozzle through the guide pipe; S32: A certain gas pressure is applied at the atomizer nozzle, and the molten metal is atomized and sprayed out under the action of the gas pressure, and condensed to form metal powder.

[0011] According to some embodiments of the present invention, the powder making burn-off rate of the composition of the new medium carbon steel billet is determined during the powder making process, and the change in the powder making burn-off rate of the new medium carbon steel billet composition is (P1-P2) / P2%. According to the change in the powder making burn-off rate, the increase in the new medium carbon steel ingredient composition in the S1 billet preparation step is (P1-P2) / P2%, wherein: P1 is the weight percentage of the billet ingredient composition, and P2 is the weight percentage of the metal powder ingredient composition.

[0012] According to some embodiments of the present invention, furnace cleaning is further included between billet preparation and remelting and before billet preparation, and the furnace cleaning includes the following steps: S101: cleaning the residual raw materials in the vacuum induction furnace until there is no residual raw materials visible to the naked eye; S102: using a vacuum device to adsorb the inner wall, corners and bends of the vacuum induction furnace for a period of time; S103: adding a single substance powder of a new medium carbon steel ingredient component of 5% to 10% of the full furnace weight of the vacuum induction furnace or a mixed powder composed of the ingredient components into the vacuum induction furnace, and covering or rotating the inner cavity of the vacuum induction furnace to mix evenly; S104: repeating steps S101 and 102 to clean the inner cavity of the vacuum induction furnace again.

[0013] According to some embodiments of the present invention, the heating rate for heating the melting crucible in step S22 includes an early heating rate, a middle heating rate and a late heating rate; The heating rate in the early stage is controlled at 50°C / min to 70°C / min, and the melting crucible is heated; The mid-term heating rate is controlled at 40°C / min to 60°C / min, and the melting crucible is heated; The heating rate is controlled at 20°C / min to 40°C / min in the later stage, and the melting crucible is heated to 1550°C to 1650°C.

[0014] According to some embodiments of the present invention, the powder making process further comprises: S4 powder screening, S5 classification and S6 anaerobic packaging; Among them, S4 powder screening includes the following steps: S41: After the metal powder obtained in step S32 is cooled, the metal powder is vibrated and sieved by a screen under the protection of an inert gas or nitrogen, and powder A with a particle size of ≤53 μm and powder B with a particle size of >53 μm are sieved out; Among them, S5 classification includes the following steps: S51: The powder A with a particle size of ≤53 μm sieved in step S41 is sieved again by a gas sieving machine to remove the powder with a particle size of <15 μm and retain the metal powder with a target particle size of 15 μm to 53 μm; S52: performing an index test on the metal powder of the target particle size screened out in step S51, and verifying the test index of each batch; Among them, S6 oxygen-free packaging includes the following steps: S61: Under a vacuum environment, oxygen-free packaging is performed on the metal powder with the target particle size in step S52.

[0015] A novel additive manufacturing method for medium carbon steel, the additive manufacturing method using metal powder manufactured by the powder making process of the novel medium carbon steel, the additive manufacturing method comprising the following steps: S201: placing the metal powder produced by the new medium carbon steel powder making process in a drying oven for drying; S202: Inert gas or nitrogen of a certain purity is injected into the printing chamber of additive manufacturing to reduce the oxygen content and control the oxygen content to be below 200 ppm; S203: heating the additively manufactured substrate to a temperature of 40° C. to 210° C.; S204: Melting the metal powder in step S201 by heat source to perform additive manufacturing to obtain a component; Wherein, the heat source includes a laser or an electron beam, and the control parameters of the heat source include: power of 40W to 2500W, scanning speed of 500mm / s to 3500mm / s, scanning spacing of 0.1mm to 0.8mm, layer thickness of 25um to 115um, and diameter of the heat source of 40um to 310um; S205: After the parts obtained in step S204 are cooled, they are taken out.

[0016] According to some embodiments of the present invention, in step S201, when the metal powder manufactured by the new medium carbon steel powder making process has a storage time of no more than 10 days, the drying temperature of the drying oven is 70° C. to 120° C., and the drying time is 4 h to 6 h; When the storage time of the metal powder produced by the new medium carbon steel powder making process is greater than 10 days, the drying temperature of the drying oven is 70° C. to 120° C., and the drying time is 15 h to 24 h.

[0017] According to some embodiments of the present invention, in the additive manufacturing forming process of the new medium carbon steel, the additive manufacturing burnout rate in the metal powder melting additive manufacturing process is determined, and the change in the additive manufacturing burnout rate is (P2-P3) / P3%. According to the change in the additive manufacturing burnout rate, the increase in the metal powder in step S201 is (P2-P3) / P3%, wherein P2 is the weight percentage of the metal powder ingredient, and P3 is the weight percentage of the additive manufacturing forming component ingredient.

[0018] After adopting the above technical solution, the beneficial effects of the present invention are: According to the novel medium carbon steel for additive manufacturing according to the embodiment of the present invention, the ingredients of the novel medium carbon steel are: C, Mn, Si, Cr, P, S, V, Ni, Ti, Cu, Al and Fe, and also include Mo, Co, Pb, Sn, Nb, W, As, Zr, Bi, Ca, Zn, N, O. Compared with the traditional medium carbon steel ingredients, the present invention uniquely adds elements such as Ti, Al, Co, N, and elements such as Zr with a lower content, thereby reducing the cost of using rare metals. At the same time, the added N can further improve the precipitation strengthening effect. Al and Zr are both strong deoxidizing elements in steel. At the same time, by controlling the weight percentage of each element in the ingredients, it can be used in various forms of metal additive manufacturing processes. The obtained product is not easy to cause cracking, macro cracks and micro cracks when viewed under a metallographic microscope or an electron microscope. By adopting a new type of medium carbon steel powder making process, the powder making process includes billet preparation, remelting refining and atomization powder making. In the billet preparation process, the obtained billet is placed in a heating furnace for heating, and the billet is rolled to compact the inside of the billet and crush the coarse austenite grains. Then, it is re-smelted in a vacuum atomization induction melting chamber, and electromagnetic stirring is performed to mix the molten metal components uniformly. Then, the molten metal is atomized and sprayed through an atomizer nozzle by an inert gas, and condensed to form metal powder. The medium carbon steel powder obtained by the above powder making process has the advantages of high target particle size yield, low oxygen and other impurity content in the powder, and high appearance sphericity, thereby solving the current domestic powder making technology limitations, the difficulty in preparing fine particle size powder, low powder yield, high oxygen and other impurity content, etc. By determining the powder burning loss rate of the new medium carbon steel billet composition during the powder making process, and increasing the amount of the new medium carbon steel ingredient in the S1 billet preparation step according to the change in the powder burning loss rate, a specific compensation coefficient is provided to ensure that the chemical composition ratio of the obtained powder is the set ratio value of the new medium carbon steel, thereby ensuring the performance of subsequent additive manufacturing products; Between billet preparation and remelting and before billet preparation, there is also a furnace cleaning process, which fully cleans the residual raw materials in the furnace body and fully covers and mixes the inside of the furnace body with single substance powder of the new medium carbon steel ingredients or mixed powder composed of the ingredients, to ensure that there are no other impurities in the furnace body and ensure that the composition of the product after smelting meets the proportion of the new medium carbon steel ingredients; The heating rate of the melting crucible includes the early heating rate, the middle heating rate and the late heating rate. By controlling the heating rates at different stages, the influence of the heating rate on the structure and performance of the material can be reduced, thereby ensuring the effect and quality of remelting and refining. The powder making process also includes powder screening, grading and oxygen-free packaging. Powder screening can screen out the powder particle size suitable for additive manufacturing, and grading can screen out the required target particle size powder from the screened powder particle size, thereby ensuring that the parts made by additive manufacturing have fine and uniform structure, high density, no cracks, and good performance; By adopting a new type of additive manufacturing method for medium-carbon steel, the heat source parameters and the temperature of the substrate are controlled during the additive manufacturing process. According to the metallographic structure and crack conditions, the optimal parameter settings during the additive manufacturing process are determined, which can avoid the problem of cracking of printed parts. At the same time, the parts produced can have stronger tensile properties and mechanical strength properties than those produced by traditional forging processes. Under the same performance requirements, the parts produced by additive manufacturing are lighter in weight, which is conducive to lightweight design of products. Through the additive manufacturing forming process of the new medium carbon steel, the additive manufacturing burnout rate of the metal powder melting additive manufacturing process is determined, and the increase in the amount of metal powder in the additive manufacturing forming step is increased according to the change in the additive manufacturing burnout rate, which provides a specific compensation coefficient for additive manufacturing, ensuring that the chemical composition ratio of the manufactured parts is the set ratio value of the new medium carbon steel, thereby ensuring the performance of the additive manufacturing products.

[0019] In summary, the present invention provides a new type of medium carbon steel for additive manufacturing, a powder making process and an additive manufacturing forming method thereof, provides a composition of a new type of medium carbon steel suitable for additive manufacturing, and can produce metal powder suitable for additive manufacturing. The product after additive manufacturing has good structural strength, a dense structure and a uniform and fine metallographic structure, avoiding the problem of cracks and cracks that are prone to occur in traditional 3D printing processes, and solving the problem that the traditional forging process has low strength and is not conducive to lightweight design of products. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without creative work. In addition, in the drawings, the components or parts are not necessarily drawn according to the actual scale.

[0021] Figure 1 This is the process flow chart of the new medium carbon steel milling process; Figure 2 This is a flow chart for furnace cleaning; Figure 3 The flowchart of the additive manufacturing method for the new medium carbon steel; Figure 4 Schematic diagram of material thermodynamic evaluation of new medium carbon steel; Figure 5 The laser scanning shows cracks when the parameters of the ingredients are not set for medium carbon steel; Figure 6 This is the billet remelting diagram; Figure 7 The morphology of metal powder produced by the powder making process of new medium carbon steel; Figure 8 The particle size distribution diagram of metal powder produced by the powder making process of new medium carbon steel; Fig. 9 A schematic diagram of a crack-free component manufactured by setting parameters according to the additive manufacturing molding method; Fig.10 Schematic diagram of cracks caused by being out of the parameter setting range; Fig.11 This is a test diagram of the tensile properties of additively manufactured parts; Fig.12 Martensitic microstructure diagram of additively manufactured parts; Fig.13 This is the ferrite and pearlite microstructure diagram of the traditional forged product; Fig.14 EBSD test image of material analysis of the new medium carbon steel printed by additive manufacturing of the present invention; Fig.15 This is the EBSD test image for material analysis of carbon steel in traditional process. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0024] At the same time, the meaning of "and / or" or "and / or" appearing in the full text includes three options. Taking "A and / or B" as an example, it includes option A, or option B, or a option in which both A and B are satisfied.

[0025] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] A new medium carbon steel for additive manufacturing according to an embodiment of the present invention, wherein the ingredients of the new medium carbon steel are: C, Mn, Si, Cr, P, S, V, Ni, Ti, Cu, Al and Fe; The weight percentage of the ingredients of the novel medium carbon steel is C: 0.34% to 0.42%, Mn: 1.2% to 1.6%, Si: 0.15% to 0.8%, Cr: 0.05% to 0.3%, P: ≤0.035%, S: 0.02% to 0.075%, V: 0.08% to 0.2%, Ni: ≤0.4%, Ti: 0.01% to 0.04%, Cu: ≤0.3%, Al: 0.01% to 0.07%, and the rest is Fe; The ingredients of the new medium carbon steel also include: Mo, Co, Pb, Sn, Nb, W, As, Zr, Bi, Ca, Zn, N, O, wherein the weight percentages of Mo, Co, Pb, Sn, Nb, W, As, Zr, Bi, Ca, Zn, N, and O are Mo: ≤0.08%, Co: 0.005%-0.6%, Pb: ≤0.02%, Sn: ≤0.03%, Nb: ≤0.02%, W: ≤0.07%, As: ≤0.008%, Zr: ≤0.0004%, Bi: ≤0.02%, Ca: ≤0.003%, Zn: ≤0.02%, N: 0.01%-0.05%, and O: ≤0.03%.

[0027] In the new medium carbon steel, the influence of each element on the performance of the new medium carbon steel is different. The required strength and toughness can be obtained by adjusting the composition. The following is an analysis of the influence of several main elements on the performance of the new medium carbon steel: (1) Carbon: Carbon is the most important element affecting the strength and toughness of medium carbon steel. As the carbon content increases, the volume fraction of pearlite increases accordingly, resulting in a linear increase in strength and hardness, but a decrease in plasticity and toughness. Therefore, in order to improve the plasticity and toughness of medium carbon steel, the method of reducing the carbon content is often used to control it.

[0028] (2) Manganese: Part of the manganese in the steel dissolves with iron to form a solid solution, and part of it combines with iron and carbon to form cementite, thereby increasing the strength of austenite and ferrite in the steel. At the same time, manganese can also delay the transformation from ferrite to pearlite, reduce the bainite phase transition temperature, achieve the effect of fine grain strengthening, and improve plasticity.

[0029] (3) Chromium: It can form insoluble carbides in steel, which can effectively prevent grain growth under short-term heating conditions. Like carbon and manganese, increasing the chromium content will reduce the volume fraction of ferrite. Increasing the manganese and chromium content will also reduce the pearlite lamella spacing. For ferrite-pearlite medium carbon steel with a pearlite volume fraction of more than 50%, the size of the pearlite lamella spacing has a significant strengthening effect on the medium carbon steel.

[0030] (4) Silicon: It can play a good role in desulfurization and deoxidation. The Si element can improve strength and hardness, increase yield point, and more importantly, increase elasticity. However, too much will affect elongation and reduce impact toughness.

[0031] (5) Sulfur: Sulfur combines with manganese in steel to form manganese sulfide, which provides nucleation sites for precipitates, thereby promoting the precipitation of ferrite and improving toughness.

[0032] (6) Vanadium: Vanadium is added to promote the precipitation strengthening effect. On the ferrite in ferrite and pearlite, interphase precipitation of V (C, N) can be formed, thereby increasing the yield strength and tensile strength.

[0033] (7) Nitrogen: Nitrogen can further enhance the precipitation strengthening effect.

[0034] (8) Titanium: It can refine the grain structure of medium carbon steel, make the internal structure of medium carbon steel dense, refine the grain force, and thus improve the strength and toughness of steel; titanium can eliminate or reduce the intergranular corrosion of steel, and can reduce aging sensitivity and cold brittleness. It can improve the "micro welding" performance by utilizing the environment where the temperature of SLM laser welding changes sharply. In addition, Ti can react with S to reduce the hot brittleness of sulfur, and titanium steel is prone to aging hardening. However, the titanium content cannot be too high. The hardness of quenched titanium steel decreases with the increase of Ti content. Because TiC is very stable, it cannot be dissolved into the solid solution even when heated to 1300°C, which reduces the carbon concentration in the alloy solid solution. Impact toughness and forgeability will also be affected.

[0035] (9) Aluminum: Aluminum is a commonly used deoxidizer in steel. Adding a small amount of aluminum to steel can refine the grains and improve impact toughness. Al and Zr are both strong deoxidizing elements in steel. Using Al can replace the precious metal Zr to reduce costs; it can refine the grain structure of steel, inhibit the aging of low-carbon steel, improve the toughness of steel at low temperatures, and improve the oxidation resistance of steel, improve the wear resistance and fatigue strength of steel, etc., and can improve the yield point, strength, and hardness; but the aluminum content is not the higher the better. If too much aluminum is used during deoxidation, it will promote the graphitization tendency of steel. When the aluminum content is high, its high-temperature strength and toughness are lower.

[0036] (10) Cobalt: Cobalt has the advantage of increasing the yield point, hardness and strength. Since the upper part of the piston is the combustion chamber, the temperature reaches 2000~3000℃. In addition, the connecting rod and crankshaft are moving parts. Adding Co element can improve the high temperature strength and wear resistance, refine the grains, and reduce the overheating tendency of steel. Adding Co to high-speed steel can improve its durability and the thermal strength (hot hardness) of steel. It increases the alloying strength of high-speed steel and promotes the formation of tempered carbides. However, the Co content cannot be too high. When the Co content is too high, it is difficult to forge because hard and brittle metal compounds are easily precipitated. In addition, there is a high tendency to decarburization.

[0037] Therefore, according to the embodiment of the present invention, compared with the traditional medium carbon steel composition, the present invention uniquely adds elements such as Ti, Al, Co, N, and elements such as Zr with a lower content, thereby reducing the cost of using rare metals. At the same time, the added N can further improve the precipitation strengthening effect. Al and Zr are both used as strong deoxidizing elements in steel. At the same time, by controlling the weight percentage of each element in the ingredient composition, it can be used for various forms of metal additive manufacturing processes. The obtained products are not prone to cracking, macro cracks and micro cracks when viewed under a metallographic microscope or an electron microscope.

[0038] The present invention designs the relevant components by using thermodynamic software and calculates the weight percentage range of chemical components that do not crack or have low crack sensitivity and their ingredients, such as Figure 4 , use the new medium carbon steel to set the ingredients and proportions to cast the relevant "button ingots", and then use the laser single-channel scanning mirror to quickly confirm and observe whether there are macro and micro cracks, such as Figure 5 , Figure 5 A and B are cracks after cracking. Afterwards, for the new medium carbon steel with cracks, adjust the weight percentage range of the chemical composition and its ingredients to determine the weight percentage of the chemical composition and its ingredients without cracking. If there are no macro cracks and micro cracks in the previous step, place the button ingot in a vacuum heat treatment furnace, or an argon furnace or a nitrogen furnace, heat it to 800℃~1200℃, keep it warm for 3h, take it out and check whether there are macro or micro cracks under a metallographic microscope or an electron microscope. The purpose of this step is to determine that the thermal cycle of the additive manufacturing and heat treatment process will not cause cracks, including macro cracks and micro cracks.

[0039] In some embodiments of the present invention, the new medium carbon steel is in the form of powder, cast or forged; Among them, the powder particle size in powder state is 10um~200um, and the powder particle size used for additive manufacturing process is 15um~64um. The additive manufacturing process includes but is not limited to selective laser melting, laser cladding surface modification technology, laser powder layer melting, electron beam melting and direct laser deposition.

[0040] like Figure 1 As shown, a new type of medium carbon steel powder making process, the powder making process includes billet preparation, remelting and atomization powder making; The blank preparation comprises the following steps: S11: placing raw materials according to the composition and proportion of the new medium carbon steel into a vacuum induction furnace for smelting; Determine the powder burning loss rate of the composition of the new medium carbon steel billet during the powder making process. The change in the powder burning loss rate of the new medium carbon steel billet composition is (P1-P2) / P2%. According to the change in the powder burning loss rate, the increase in the new medium carbon steel ingredient composition in the S1 billet preparation step is (P1-P2) / P2%, where: P1 is the weight percentage of the billet ingredient composition, and P2 is the weight percentage of the metal powder ingredient composition; Since the burnout rate of each component needs to be considered, the weight percentage of the ingredients of the metal powder is taken as the target proportion, and the increase in the proportion of the raw material components is (P1-P2) / P2%. The embodiment of the present invention is aimed at the burnout rate of the two elements Mn and S. In the actual experimental process, the two elements Mn and S are easy to burn out, as shown in the following table: Ingredients increase amount table for flour making process Ingredients Weight percentage of blank ingredients P1 (%) Weight percentage of metal powder ingredients P2 (%) Powder burning loss rate (P1-P2) / P2% Mn 1.47 1.43 2.8 S 0.026 0.024 8.33 By determining the powder burning loss rate of the new medium carbon steel billet composition during the powder making process, and increasing the amount of the new medium carbon steel ingredient in the S1 billet preparation step according to the change in the powder burning loss rate, a specific compensation coefficient is provided to ensure that the chemical composition ratio of the obtained powder is the set ratio value of the new medium carbon steel, thereby ensuring the performance of subsequent additive manufacturing products; S12: Casting the molten metal after smelting in step S11 under vacuum conditions to obtain a blank, which may be a cylindrical bar with a diameter ranging from 50 mm to 110 mm; S13: placing the billet obtained in step S12 in a heating furnace for heating. The heating furnace is a continuous step-beam heating furnace. The heating temperature is controlled at 1000° C. to 1300° C., and specifically, the heating temperature can be between 1120° C. and 1250° C. After that, the billet is rolled to compact the inside of the billet and crush the coarse austenite grains. When rolling the billet, a continuously changing hole-type rolling roller is used to eliminate the defects such as looseness and shrinkage cavities inside the cast billet through compaction, and crush the coarse austenite grains. S14: cutting and surface treating the blank in step S13, wherein the surface treatment includes removing oil stains and oxide layers from the surface, so as to obtain a blank that is easy to be smelted in a crucible, and the length of the blank after cutting is less than 800 mm.

[0041] Among them, remelting refining includes the following steps: S21: Place the blank obtained in step S14 into a melting crucible, then evacuate the vacuum atomization induction melting chamber to a vacuum pressure of ≤6.67*10 -2 Pa, then, a displacement operation is performed with an inert gas or nitrogen of a certain purity, the displacement operation number is 1 to 3 times, the inert gas can be argon, and the gas purity is controlled at ≥99.999%, wherein the melting crucible can be a graphite crucible, an alumina crucible or a zirconia crucible, and the present invention uses an alumina crucible; S22: Heat the melting crucible at a certain heating rate, and heat the temperature to a certain temperature above the melting point of the blank, so that the blank is melted into molten metal again, and keep the temperature for a period of time, such as Figure 6 As shown; Wherein, the heating rate of heating the melting crucible in step S22 includes an early heating rate, a middle heating rate and a late heating rate; The heating rate in the early stage is controlled at 50°C / min to 70°C / min, and the melting crucible is heated to 500°C to 600°C. The mid-term heating rate is controlled at 40℃ / min~60℃ / min, and the melting crucible is heated to 1000℃-1100℃; In the later stage, the heating rate is controlled at 20℃ / min~40℃ / min, the melting crucible is heated and the temperature is heated to 1550℃~1650℃, and the holding time is 10-15 minutes. By controlling the heating rate at different stages, the influence of the heating rate on the structure and performance of the material is reduced, thereby ensuring the effect and quality of remelting and refining; S23: During the heating process of step S22, the melting crucible is tilted and electromagnetic stirring is performed to mix the components of the molten metal evenly.

[0042] Wherein, atomization powder making comprises the following steps: S31: After the molten metal in step S23 reaches the outlet temperature, the smelting crucible is tilted to allow the molten metal in the smelting crucible to flow into the tundish, the insulation temperature of the tundish is between 1350°C and 1500°C, and the molten metal is introduced into the atomizer nozzle through the guide pipe, and atomized and powdered by the atomizer nozzle; S32: A certain gas pressure is applied to the atomizer nozzle, and the metal liquid is atomized and sprayed out under the action of the gas pressure, and condensed to form metal powder, such as Figure 7 As shown; In step S32, the gas used at the atomizer nozzle is an inert gas or nitrogen. The inert gas used in the embodiment of the present invention is argon. The gas pressure at the atomizer nozzle is 3.0 MPa to 4.5 MPa. The shape of the atomizer nozzle is conical, and the outlet diameter is 3.0 mm to 5.0 mm. In summary, by adopting a new type of medium carbon steel powder making process, the powder making process includes billet preparation, remelting refining and atomization powder making. During the billet preparation process, the obtained billet is placed in a heating furnace for heating, and the billet is rolled to compact the inside of the billet and break the coarse austenite grains. After that, it is re-melted in a vacuum atomization induction melting chamber, and electromagnetic stirring is performed to mix the molten metal components evenly. After that, the molten metal is atomized and sprayed out through an atomizer nozzle by an inert gas, and condensed to form metal powder. The medium carbon steel powder obtained by the above-mentioned powder making process has the advantages of high target particle size yield, low oxygen and other impurity contents in the powder, and high appearance sphericity, thereby solving the current domestic powder making technology limitations, the difficulties in preparing fine particle size powder, low powder yield, and high oxygen and other impurity contents. Problems such as.

[0043] like Figure 2 As shown, in some embodiments of the present invention, furnace cleaning is also included between billet preparation and remelting and before billet preparation, and the furnace cleaning includes the following steps: S101: cleaning the residual raw materials in the vacuum induction furnace until there is no residual raw materials visible to the naked eye; S102: Use vacuum equipment to adsorb the inner wall, corners and bends of the vacuum induction furnace for a period of time, specifically 5-10 minutes; S103: adding a single substance powder of a new medium carbon steel batching component of 5% to 10% of the full weight of the vacuum induction furnace body or a mixed powder composed of the batching components into the vacuum induction furnace, and covering or rotating the inner cavity of the vacuum induction furnace body to mix evenly; S104: repeating steps S101 and 102 to clean the inner cavity of the vacuum induction furnace again; The residual raw materials in the furnace body are fully cleaned through the furnace body cleaning process, and the inside of the furnace body is fully covered and mixed with the single powder of the new medium carbon steel ingredients or the mixed powder composed of the ingredients to ensure that there are no other impurities in the furnace body and that the composition of the product after smelting meets the proportion of the new medium carbon steel ingredients.

[0044] As shown in 1, in an embodiment of the present invention, the powder making process further includes powder screening, grading and anaerobic packaging; Wherein, powder screening comprises the following steps: S41: After the metal powder obtained in step S32 is cooled, the specific cooling temperature may be less than 80° C., the metal powder is vibrated and sieved through a screen under the protection of an inert gas or nitrogen, and powder A with a particle size of ≤53 μm and powder B with a particle size of >53 μm are sieved; The classification includes the following steps: S51: The powder A with a particle size of ≤53 μm sieved in step S41 is sieved again by a gas sieving machine, the powder with a particle size of <15 μm is removed, and the target particle size metal powder with a particle size of 15 μm to 53 μm is retained. The powder particle size suitable for additive manufacturing can be screened out by powder screening, and the required target particle size powder can be screened out from the screened powder particle size by classification, so as to ensure that the parts manufactured by additive manufacturing have fine and uniform structure, high density, no cracks, and good performance; S52: Performing index tests on the metal powder of target particle size screened out in step S51, and verifying the test indexes of each batch. The test indexes include particle size and distribution law, fluidity, tap density, loose density, sphericity, etc. Figure 8 As shown; Among them, oxygen-free packaging includes the following steps: S61: Under a vacuum environment, oxygen-free packaging is performed on the metal powder with the target particle size in step S52.

[0045] In summary, by adopting the powder making process, the powder making process includes blank preparation, remelting refining and atomization powder making, as well as powder screening, grading and oxygen-free packaging. The prepared metal powder has been tested by indicators, and the powder yield is ≥41%, the sphericity is ≥90%, the particle size distribution is D10=16.2um, D50: 33.6um, fluidity: 17.55s / 50g, loose density: 4.2g / cm3, and tap density: 5.46g / cm3. In addition, the chemical composition of the metal powder is uniform, the particle size distribution is relatively uniform, and the oxygen content is low. After experimental testing, the actual measured value is 0.016%, which meets the requirements of laser selective 3D printing technology. The printed parts have high density, no macro cracking and micro cracks, and excellent performance.

[0046] like Figure 3 As shown, a new type of medium carbon steel additive manufacturing forming method, the additive manufacturing forming method uses a metal powder manufactured by a powder making process of the new type of medium carbon steel, the key influencing factors of the additive manufacturing processing of the new type of medium carbon steel are heat source parameters and substrate temperature range, the additive manufacturing forming method includes but is not limited to selective laser melting, laser cladding surface modification technology, laser powder bed melting, electron beam melting and direct laser deposition, the energy density range of the additive manufacturing processing is 20 to 800 J / mm 3 , the energy density is defined as:

[0047] Where Ed is the energy density [J / mm 3 ], P is the power of the heat source [W], v is the scanning speed [mm / s], and h is the laser scanning spacing [mm].

[0048] The additive manufacturing method includes the following steps: S201: placing the metal powder produced by the new medium carbon steel powder making process in a drying oven for drying; Wherein, in step S201, when the metal powder produced by the new medium carbon steel powder making process is stored for no more than 10 days, the drying temperature of the drying oven is 70°C to 120°C, and the drying time is 4h to 6h; When the metal powder produced by the new medium carbon steel powder making process is stored for more than 10 days, the drying temperature of the drying oven is 70℃~120℃, and the drying time is 15h~24h; S202: Inert gas or nitrogen of a certain purity is injected into the printing chamber of additive manufacturing to reduce the oxygen content and control the oxygen content to be below 200 ppm. In the embodiment of the present invention, an inert gas is used, specifically, argon gas among the inert gases is used, and the purity of the argon gas is ≥99.999%; S203: heating the additively manufactured substrate to a temperature of 40° C. to 210° C.; S204: Melting the metal powder in step S201 by heat source to perform additive manufacturing to obtain a component; The heat source includes a laser or an electron beam, and the control parameters of the heat source include: power of 40W to 2500W, scanning speed of 500mm / s to 3500mm / s, scanning spacing of 0.1mm to 0.8mm, layer thickness of 25um to 115um, and diameter of the heat source of 40um to 310um; S205: After the parts obtained in step S204 are cooled, they are taken out.

[0049] By adopting the additive manufacturing forming method of the new medium carbon steel, the heat source parameters and the temperature of the substrate are controlled during the additive manufacturing process. According to the metallographic structure and crack conditions, the optimal parameter settings in the additive manufacturing process are determined, which can avoid the problem of cracking of the printed parts. At the same time, the obtained parts can have stronger tensile properties and mechanical strength properties than the traditional forging process. Under the same performance requirements, the parts made by additive manufacturing are lighter, which is conducive to the lightweight design of the product.

[0050] In addition, in the embodiment of the present invention, in step S204, for the additive manufacturing of the component body, the heat source control parameters are: power 250W-320W, scanning speed 900mm / s-1400mm / s, scanning spacing 0.05mm-0.25mm, layer thickness 30um-50um; and substrate heating temperature 150℃-200℃; For additive manufacturing of component surfaces, the control parameters of the heat source are: power 100W~320W, scanning speed 100mm / s~1400mm / s, scanning spacing 0.05mm~0.25mm, layer thickness 30um~50um; and substrate heating temperature 150℃~200℃; For component support additive manufacturing, the control parameters of the heat source are: power 150W ~ 320W, scanning speed 900mm / s ~ 1400mm / s, scanning spacing 0.05mm ~ 0.25mm, layer thickness 30um ~ 100um; and substrate heating temperature is 150℃ ~ 200℃, where component support refers to the part that supports the suspended part of the component during the additive manufacturing process; Parts printed with the above parameters will not have cracks.

[0051] In the additive manufacturing process of the new medium carbon steel, the additive manufacturing burnout rate in the metal powder melting additive manufacturing process is determined, the change in the additive manufacturing burnout rate is (P2-P3) / P3%, and the increase in the metal powder in step S201 is (P2-P3) / P3% according to the change in the additive manufacturing burnout rate, wherein P2 is the weight percentage of the metal powder ingredient, and P3 is the weight percentage of the additive manufacturing molding component ingredient; In the process of metal powder melting additive manufacturing, the burnout rate of each component needs to be considered. The weight percentage of the ingredients of the additive manufacturing parts is taken as the target ratio. The increase in metal powder is (P2-P3) / P3%. The embodiment of the present invention targets the burnout rates of the two elements Mn and S, as shown in the following table: Table of metal powder additions for additive manufacturing Ingredients Weight percentage of metal powder ingredients P2 (%) Weight percentage of ingredients in additively manufactured parts P3 (%) Additive manufacturing burnout rate (P2-P3) / P3 (%) Mn 1.43 1.39 2.88 S 0.024 0.022 9.09 Through the additive manufacturing forming process of the new medium carbon steel, the additive manufacturing burnout rate of the metal powder melting additive manufacturing process is determined, and the increase in the amount of metal powder in the additive manufacturing forming step is increased according to the change in the additive manufacturing burnout rate, which provides a specific compensation coefficient for additive manufacturing, ensuring that the chemical composition ratio of the manufactured parts is the set ratio value of the new medium carbon steel, thereby ensuring the performance of the additive manufacturing products.

[0052] In addition, the tensile properties of the parts obtained after the additive manufacturing process are tested. The new medium carbon steel powder prepared in the embodiment of the present invention and the parts prepared by the process parameters of the additive manufacturing molding method of the present invention have a tensile strength of more than 1200MPa. Fig.11 As shown in the figure, the tensile strength of the product forged by the traditional forging process is less than 900 MPa. Therefore, the tensile strength performance of the parts produced by the process parameters of the additive manufacturing forming method of the present invention is greater than that of the products forged by the traditional forging process. The reason is that the structure of the parts produced after the additive manufacturing process is martensite, such as Fig.12 As shown, the structure is fine and uniform with high density. The structure of traditional forged products is ferrite and pearlite, such as Fig.13 As shown, the structure is coarse. In addition, there are inclusions such as MnS in the traditional forging process. Fig.13 The dark strip-shaped morphology in the middle, although the influence of inclusions such as MnS has been reduced after forging, it still exists to a large extent. Additive manufacturing has dispersed and dispersed the inclusions as much as possible, greatly reducing the content and no longer having a negative impact on the strength. Therefore, its mechanical strength is naturally high; From the EBSD test results of the material analysis of the new medium carbon steel printed by additive manufacturing of the present invention and the medium carbon steel printed by the traditional process, as shown in FIG. Fig.14 and Fig.15As shown, the new medium carbon steel printed by additive manufacturing of the present invention has a fine, uniform structure and high density, which further explains why the parts made by the process method of the present invention have high strength.

[0053] In summary, the present invention provides a new type of medium carbon steel for additive manufacturing, a powder making process and an additive manufacturing forming method thereof, provides a composition of a new type of medium carbon steel suitable for additive manufacturing, and can produce metal powder suitable for additive manufacturing. The product after additive manufacturing has good structural strength, a dense structure and a uniform and fine metallographic structure, which solves the problem of cracks and cracking that are prone to occur in traditional processes.

[0054] It should be understood that the purpose of these embodiments is only to illustrate the present invention and is not intended to limit the protection scope of the present invention. In addition, it should also be understood that after reading the technical content of the present invention, those skilled in the art can make various changes, modifications and / or variations to the present invention, and all of these equivalent forms also fall within the protection scope defined by the appended claims of this application.

Claims

1. A new medium carbon steel for additive manufacturing, characterized by: The new medium carbon steel comprises the following ingredients: C, Mn, Si, Cr, P, S, V, Ni, Ti, Cu, Al and Fe; The weight percentages of the ingredients of the novel medium carbon steel are C: 0.34%-0.42%, Mn: 1.2%-1.6%, Si: 0.15%-0.8%, Cr: 0.05%-0.3%, P: ≤0.035%, S: 0.02%-0.075%, V: 0.08%-0.2%, Ni: ≤0.4%, Ti: 0.01%-0.04%, Cu: ≤0.3%, Al: 0.01%-0.07%, and the rest is Fe.

2. The novel medium carbon steel for additive manufacturing according to claim 1, characterized in that: The ingredients of the novel medium carbon steel also include: Mo, Co, Pb, Sn, Nb, W, As, Zr, Bi, Ca, Zn, N, O, wherein the weight percentages of Mo, Co, Pb, Sn, Nb, W, As, Zr, Bi, Ca, Zn, N, O are Mo: ≤0.08%, Co: 0.005%-0.6%, Pb: ≤0.02%, Sn: ≤0.03%, Nb: ≤0.02%, W: ≤0.07%, As: ≤0.008%, Zr: ≤0.0004%, Bi: ≤0.02%, Ca: ≤0.003%, Zn: ≤0.02%, N: 0.01%-0.05%, O: ≤0.03%; The new medium carbon steel is in the form of powder, cast or forged; The powder particle size of the powder is 10um to 200um.

3. A new type of medium carbon steel powder making process, characterized by: The milling process comprises: S1 billet preparation, S2 remelting and refining, and S3 atomization powder making; Among them, S1 blank preparation includes the following steps: S11: placing raw materials according to the composition and proportion of the new medium carbon steel into a vacuum induction furnace for smelting; S12: Casting the molten metal smelted in step S11 under vacuum conditions to obtain a blank; S13: placing the blank obtained in step S12 in a heating furnace and heating it at a temperature of 1000° C. to 1300° C., and then rolling the blank to compact the inside of the blank; S14: cutting and surface treating the blank of step S13 to obtain a blank that is easy to be smelted in a crucible; Among them, S2 remelting refining includes the following steps: S21: placing the blank obtained in step S14 into a melting crucible, then evacuating the vacuum atomization induction melting chamber, and then performing a replacement operation with an inert gas or nitrogen of a certain purity; S22: heating the melting crucible at a certain heating rate, the heating temperature being a certain temperature above the melting point of the blank, so that the blank is remelted into molten metal, and keeping the temperature for a period of time; S23: During the heating process of step S22, the melting crucible is tilted and electromagnetic stirring is performed to mix the components of the molten metal uniformly; Among them, S3 atomization powder making includes the following steps: S31: after the molten metal in step S23 reaches the outlet temperature, tilting the smelting crucible so that the molten metal in the smelting crucible flows into the tundish and is introduced into the atomizer nozzle through the guide pipe; S32: A certain gas pressure is applied at the atomizer nozzle, and the molten metal is atomized and sprayed out under the action of the gas pressure, and condensed to form metal powder.

4. The novel medium carbon steel powder making process as claimed in claim 3, characterized in that: During the powder making process, the powder making burn-off rate of the composition of the new medium carbon steel billet is determined. The change in the powder making burn-off rate of the new medium carbon steel billet composition is (P1-P2) / P2%. According to the change in the powder making burn-off rate, the increase in the new medium carbon steel ingredient composition in the S1 billet preparation step is (P1-P2) / P2%, wherein: P1 is the weight percentage of the billet ingredient composition, and P2 is the weight percentage of the metal powder ingredient composition.

5. The novel medium carbon steel powder making process according to claim 3, characterized in that: Between billet preparation and remelting refining and before billet preparation, furnace cleaning is also included, and the furnace cleaning includes the following steps: S101: cleaning the residual raw materials in the vacuum induction furnace until there is no residual raw materials visible to the naked eye; S102: using a vacuum device to adsorb the inner wall, corners and bends of the vacuum induction furnace for a period of time; S103: adding a single substance powder of a new medium carbon steel ingredient component of 5% to 10% of the full furnace weight of the vacuum induction furnace or a mixed powder composed of the ingredient components into the vacuum induction furnace, and covering or rotating the inner cavity of the vacuum induction furnace to mix evenly; S104: repeating steps S101 and 102 to clean the inner cavity of the vacuum induction furnace again.

6. The novel medium carbon steel powder making process according to claim 3, characterized in that: In step S22, the heating rate of heating the melting crucible includes an early heating rate, a middle heating rate and a late heating rate; The heating rate in the early stage is controlled at 50°C / min to 70°C / min, and the melting crucible is heated; The mid-term heating rate is controlled at 40°C / min to 60°C / min, and the melting crucible is heated; The heating rate is controlled at 20°C / min to 40°C / min in the later stage, and the melting crucible is heated to 1550°C to 1650°C.

7. The novel medium carbon steel powder making process according to claim 3, characterized in that: The powder making process also includes: S4 powder screening, S5 classification and S6 anaerobic packaging; Among them, S4 powder screening includes the following steps: S41: After the metal powder obtained in step S32 is cooled, the metal powder is vibrated and sieved by a screen under the protection of an inert gas or nitrogen, and powder A with a particle size of ≤53 μm and powder B with a particle size of >53 μm are sieved out; Among them, S5 classification includes the following steps: S51: The powder A with a particle size of ≤53 μm sieved in step S41 is sieved again by a gas sieving machine to remove the powder with a particle size of <15 μm and retain the metal powder with a target particle size of 15 μm to 53 μm; S52: performing an index test on the metal powder of the target particle size screened out in step S51, and verifying the test index of each batch; Among them, S6 oxygen-free packaging includes the following steps: S61: Under a vacuum environment, oxygen-free packaging is performed on the metal powder with the target particle size in step S52.

8. A novel additive manufacturing method for medium carbon steel, characterized in that: The additive manufacturing method uses the metal powder manufactured by the powder making process of the new medium carbon steel according to any one of claims 3 to 7, and the additive manufacturing method comprises the following steps: S201: placing the metal powder produced by the new medium carbon steel powder making process in a drying oven for drying; S202: Inert gas or nitrogen of a certain purity is injected into the printing chamber of additive manufacturing to reduce the oxygen content and control the oxygen content to be below 200 ppm; S203: heating the additively manufactured substrate to a temperature of 40° C. to 210° C.; S204: Melting the metal powder in step S201 by heat source to perform additive manufacturing to obtain a component; Wherein, the heat source includes a laser or an electron beam, and the control parameters of the heat source include: power of 40W to 2500W, scanning speed of 500mm / s to 3500mm / s, scanning spacing of 0.1mm to 0.8mm, layer thickness of 25um to 115um, and diameter of the heat source of 40um to 310um; S205: After the parts obtained in step S204 are cooled, they are taken out.

9. The novel additive manufacturing method for medium carbon steel according to claim 8, characterized in that: In step S201, when the metal powder produced by the new medium carbon steel powder making process is stored for no more than 10 days, the drying temperature of the drying oven is 70° C. to 120° C., and the drying time is 4 h to 6 h; When the storage time of the metal powder produced by the new medium carbon steel powder making process is greater than 10 days, the drying temperature of the drying oven is 70° C. to 120° C., and the drying time is 15 h to 24 h.

10. The novel additive manufacturing method for medium carbon steel according to claim 8, characterized in that: In the additive manufacturing process of the new medium carbon steel, the additive manufacturing burnout rate in the metal powder melting additive manufacturing process is determined, and the change in the additive manufacturing burnout rate is (P2-P3) / P3%. According to the change in the additive manufacturing burnout rate, the increase in the metal powder in step S201 is (P2-P3) / P3%, wherein P2 is the weight percentage of the metal powder ingredient, and P3 is the weight percentage of the additive manufacturing molding component ingredient.

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