Carbon steel powder for powder sintering type additive manufacturing

Abstract

The present invention relates to: carbon steel powder for powder sintering type additive manufacturing, the carbon steel powder comprising: 0.01 to 0.1 wt% of carbon (C); 0.01 to 0.5 wt% of silicon (Si); 0.03 to 1.0 wt% of manganese (Mn); 0.1 wt% or less of nickel (Ni); 0.1 wt% or less of chromium (Cr); 0.1 wt% or less of molybdenum (Mo); 0.04 wt% or less of oxygen (O); and the remainder of iron (Fe); and a method for powder sintering additive manufacturing the carbon steel powder by using a laser having an energy density in the range of 50 to 250 J / mm3.

Description

Carbon steel powder for powder sintering additive manufacturing

[0001] The present invention relates to carbon steel powder for additive manufacturing using a powder sintering method.

[0002] When unexpected breakdowns or defects occur at sea, ships use spare parts to cope. On average, there are approximately 5,000 types of these spare parts, which ships load onto the vessel for operation. However, the reality is that roughly 70% of these spare parts are never used during a ship's entire operating period. Meanwhile, if spare parts are insufficient, it becomes impossible to respond when they are needed during operation, resulting in greater losses in time and cost for procuring them.

[0003] Parts for ship maintenance (e.g., bolts, nuts, washers, gaskets, etc.) are primarily carbon steel components manufactured by forging and processing steel semi-finished products in the form of large plates or round bars at high temperatures (approximately 1000 degrees). In particular, high-strength parts are manufactured by adding a large amount of carbon to the semi-finished products to ensure strength, and then securing elongation through quenching and tempering heat treatments after forging. These spare parts for ships have the disadvantage of causing cost issues due to significant loss of raw materials during the processing stage, and taking a long time to supply because they must undergo forging and heat treatment.

[0004] The powder sintering additive manufacturing process (or interchangeably referred to as the powder bed fusion (PBF) process) is a type of 3D printing in which a three-dimensional article is manufactured by selectively irradiating a laser after metal powder is applied to a powder bed. Since the powder is fused into the desired shape by the thermal energy of the laser, the near net shape (NNS) of the part can be manufactured immediately.

[0005] If spare parts can be manufactured in-house on ships in operation using powder sintering additive manufacturing, there are advantages such as reduced raw material loss during processing, shortened parts supply times, the elimination of unnecessary inventory, and the ability to procure discontinued parts. However, since currently commercialized powder materials for powder sintering additive manufacturing are expensive—namely nickel, aluminum, cobalt-based alloys, and stainless steel—the excessive costs make it industrially impractical.

[0006] Korean Registered Patent No. 10-1893172 provides a metal powder for a 3D metal printer that is composed of C 0.33~0.43%, Si 0.18~0.28%, Mn 0.33~0.43%, Cr 7~9%, Mo 0.001~1.5%, W 10~13%, and the remainder being Fe in weight percent, and has excellent wear resistance, corrosion resistance, heat resistance, and hardness compared to conventional metal powders. However, the metal powder contains high amounts of expensive chromium and tungsten, and the functional and non-functional parts are manufactured with different components when manufacturing a shear die.

[0007] The present invention aims to provide carbon steel powder for additive manufacturing using a powder sintering method for manufacturing spare parts usable in ships.

[0008] One aspect of the present invention relates to a carbon steel powder for powder sintering additive manufacturing comprising 0.01 to 0.1 wt% carbon (C), 0.01 to 0.5 wt% silicon (Si), 0.03 to 1.0 wt% manganese (Mn), 0.1 wt% or less nickel (Ni), 0.1 wt% or less chromium (Cr), 0.1 wt% or less molybdenum (Mo), 0.04 wt% or less oxygen (O), and the remainder being iron (Fe). The particle size of the carbon steel powder is 10 to 60 μm. The fluidity of the carbon steel powder is 10 to 18 sec / 50 g.

[0009] Another aspect of the present invention is an energy density of 50 to 250 J / mm3 The present invention relates to a method for manufacturing carbon steel powder by powder sintering additive manufacturing using a laser of a range according to the present invention.

[0010] Another aspect of the present invention relates to a part obtained by the powder sintering additive manufacturing method described above. The part has a tensile strength of 410 MPa or more and an elongation of 18% or more, or a tensile strength of 800 MPa or more and an elongation of 12% or more.

[0011] According to the present invention, parts can be manufactured immediately when needed on a vessel in operation and applied to repairs for breakdowns and defects, thereby enabling rapid MRO (maintenance, repair, and operation).

[0012] Figure 1 is an SEM image of carbon steel powder prepared according to Example 6.

[0013] Figure 2 is an OM image of the microstructure of a specimen fabricated by additive manufacturing using a powder sintering method according to Example 4.

[0014] In this specification, % used for the content of a component element means weight %.

[0015] The present invention relates to a carbon steel powder for powder sintering additive manufacturing comprising 0.01 to 0.1 weight% carbon (C), 0.01 to 0.5 weight% silicon (Si), 0.03 to 1.0 weight% manganese (Mn), 0.1 weight% or less nickel (Ni), 0.1 weight% or less chromium (Cr), 0.1 weight% or less molybdenum (Mo), 0.04 weight% or less oxygen (O), and the remainder being iron (Fe), wherein the carbon steel powder has a particle size of 10 to 60 μm and a flowability of 10 to 18 sec / 50 g.

[0016] (1) Carbon steel powder according to the present invention

[0017] The carbon steel powder for powder sintering additive manufacturing according to the present invention comprises 0.01 to 0.1 wt% carbon (C), 0.01 to 0.5 wt% silicon (Si), 0.03 to 1.0 wt% manganese (Mn), 0.1 wt% or less nickel (Ni), 0.1 wt% or less chromium (Cr), 0.1 wt% or less molybdenum (Mo), 0.04 wt% or less oxygen (O), and the remainder being iron (Fe). The carbon steel powder has a particle size of 10 to 60 μm and a fluidity of 10 to 18 sec / 50 g.

[0018] In the carbon steel powder according to the present invention, the carbon (C) content is in the range of 0.01 to 0.1 weight%. Carbon (C) is an important element for securing the strength and hardness of carbon steel and is an element that determines the mechanical properties of carbon steel powder. If the carbon content is less than 0.01 weight%, a problem arises in that the strength of the part manufactured by powder sintering additive manufacturing is low, and if the carbon content exceeds 0.1 weight%, although the strength is high, the brittleness increases, and a phenomenon of breaking may occur upon external impact.

[0019] In the carbon steel powder according to the present invention, the silicon (Si) content is 0.01 to 0.5 weight%. Silicon (Si) is an essential alloying element of carbon steel and can contribute to improving the strength of carbon steel. In addition, it can help control the oxygen content of the carbon steel powder by acting as a deoxidizer. If the silicon (Si) content is excessively low, it is difficult to control the oxygen content, and if the silicon (Si) content exceeds the range, the brittleness of the steel increases.

[0020] In the carbon steel powder according to the present invention, the manganese (Mn) content is 0.03 to 1.0 weight%. Manganese (Mn) combines with sulfur (S) in the carbon steel to prevent brittleness by inhibiting the formation of FeS, which causes brittleness, and performs a deoxidizing action similar to silicon. In the carbon steel powder according to the present invention, if the manganese (Mn) content is less than 0.03 weight%, it is difficult to control the oxygen content, and if the manganese (Mn) content exceeds 1.0 weight%, toughness and corrosion resistance are reduced.

[0021] In the carbon steel powder according to the present invention, the nickel (Ni) content is 0.1 weight% or less. Since nickel (Ni) is a heavy metal and a rare metal and an expensive element, having a content of 0.1 weight% or less is advantageous in terms of environmental pollution and overall production costs.

[0022] In the carbon steel powder according to the present invention, the chromium (Cr) content is 0.1 weight% or less. Since the carbon steel powder according to the present invention has a very low content of chromium, which is a heavy metal and expensive, it is advantageous in terms of environmental pollution and overall production costs.

[0023] In the carbon steel powder according to the present invention, the molybdenum (Mo) content is 0.1 weight% or less. Molybdenum (Mo) can play a role in improving the strength of the carbon steel powder, but since it is an element that is excessively expensive, it loses price competitiveness as the content increases.

[0024] In the carbon steel powder according to the present invention, the oxygen (O) content is 0.04 weight% or less. If the oxygen (O) content is excessive, the brittleness may increase due to oxide formation during the additive manufacturing process, and porosity may be formed inside the part, which is the product of powder sintering additive manufacturing, causing a decrease in quality; therefore, the oxygen (O) content must be controlled to 0.04 weight% or less.

[0025] The carbon steel powder according to the present invention can be produced by gas atomization and, for example, as can be seen in the SEM image of Fig. 1, is produced as spherical particles.

[0026] The particle size of the carbon steel powder according to the present invention is 10 to 60 μm. In carbon steel powder for powder sintering additive manufacturing, the particle size affects the mechanical strength, internal porosity, and density of the final product obtained. When the particle size is within the above range, parts having mechanical properties required as spare parts for ships during powder sintering additive manufacturing can be obtained.

[0027] The carbon steel powder according to the present invention has a fluidity of 10 to 18 sec / 50 g. Fluidity refers to the degree to which the powder flows freely. Since the carbon steel powder according to the present invention must be uniformly applied to a powder bed for powder sintering additive manufacturing, it is important to ensure good fluidity. If the fluidity falls outside the above range, it causes poor melting, increased porosity, and deterioration of surface quality and mechanical properties during powder sintering additive manufacturing.

[0028] (2) Powder sintering additive manufacturing using carbon steel powder according to the present invention

[0029] The carbon steel powder according to the present invention described above is used in powder sintering additive manufacturing (i.e., powder bed fusion (PBF) method). In the powder sintering additive manufacturing process of the present invention, the carbon steel powder according to the present invention described above is applied to a powder bed, and a laser is irradiated to rapidly melt and solidify the powder to manufacture a part.

[0030] In the powder sintering additive manufacturing process of the present invention, the energy density of the laser is 50 to 250 J / mm 3 The range is 50 J / mm². The laser energy density is 50 J / mm². 3If it is less than that, the powder does not melt sufficiently, leading to increased porosity, and it is difficult to secure elongation due to the rapid cooling rate. The laser energy density is 250 J / mm² 3 In the case of excess, internal pores may be overgenerated due to the keyhole phenomenon caused by overmelting, and metal fumes and spatter that degrade the quality of the product part are generated, thereby reducing the efficiency of metal powder reuse.

[0031] (3) Characteristics of a part made of carbon steel powder according to the present invention

[0032] According to the present invention, a part manufactured by a powder sintering additive manufacturing method using carbon steel powder exhibits excellent mechanical strength and elongation.

[0033] The mechanical strength of a part manufactured according to the present invention can be determined by tensile strength and elongation. As a part to be used in a ship, the product manufactured according to the present invention must have a tensile strength of 800 MPa or more and an elongation of 12% or more, or a tensile strength of 410 MPa or more and an elongation of 18% or more. In carbon steel parts, tensile strength and elongation are properties that are difficult to achieve simultaneously. As parts required in a ship during operation, there exist series of parts requiring greater strength (e.g., high-strength bolts, etc.) and series of parts requiring greater elongation (e.g., general bolts, washers, etc.). The parts requiring greater strength are sufficient for ship parts if they have a tensile strength of 800 MPa or more and an elongation of 12% or more, and the parts requiring greater elongation are sufficient if they have a tensile strength of 410 MPa or more and an elongation of 18% or more.

[0034] According to the present invention, a part manufactured by a powder sintering additive manufacturing method using carbon steel powder has a microstructure that differs from that of a product manufactured by a conventional manufacturing method, as rapid melting and solidification of the powder by a laser are repeated during the manufacturing process. Specifically, because only localized areas are melted using a laser as a heat source, the cooling rate is very fast, and the grain size is very small compared to the grain size of a part manufactured by conventional casting. This can be confirmed in the optical microscope (OM) image of FIG. 2. Therefore, when manufacturing by powder sintering additive manufacturing using carbon steel powder according to the present invention, a part having high strength and excellent elongation can be obtained.

[0035]

[0036] Examples

[0037] Examples 1 to 6

[0038] According to Examples 1 to 6, spherical carbon steel powders were prepared by the gas atomization method with the elemental compositions listed in Table 1 below. The carbon steel powder prepared according to Example 6 is disclosed in FIG. 1. The particle size of the carbon steel powder was measured using a laser particle size analyzer. The flowability of the carbon steel powder was measured according to ASTM B213 using a powder flow-Hall flow meter as the time it takes for 50 g of powder to flow through a 2.5 mm diameter nozzle. The measured particle size and flowability are disclosed in Table 1.

[0039] Next, 40 kg of carbon steel powder prepared according to each example was used in a 3D printer for powder sintering additive manufacturing, and laser irradiated at the energy density listed in Table 1 to produce four specimens in the shape of round bars for each example. Among the mechanical properties, tensile strength and elongation were measured according to the test examples described below and disclosed in Table 2.

[0040] Comparative Examples 1 to 3

[0041] Four specimens each of Comparative Examples 1 to 3 were prepared according to the composition listed in Table 1 in the same manner as the manufacturing method of the examples described above. The energy density, which is the corresponding process condition, is also listed in Table 1 below. Among the mechanical properties, tensile strength and elongation were measured according to the test examples described later and disclosed in Table 2.

[0042] Comparative Examples 4 and 5

[0043] Comparative Examples 4 and 5 selected SS400 and Bolt 8.8, respectively, which are used as existing spare parts for ships. The content of the components of SS400 (Comparative Example 4) was disclosed by referring to KS D 3503, and that of Bolt 8.8 (Comparative Example 5) was disclosed by referring to KS B 0233.

[0044] Chemical composition (weight%) Particle size (㎛) Flowability (sec / 50g) Energy density (J / mm²) 3 )CSiMnNiCrMo Example 10.020.010.030.050.020.0520~5212.9108 Example 20.010.010.030.060.020.0520~5212.9217 Example 30.080.360.790.040.020.0117~5112.3188 Example 40.080.360.800.040.020.0117~5112.3217 Example 50.050.370.820.040.020.0117~5012.7188 Example 60.060.380.840.040.020.0117~5012.7217 Comparative Example 10.120.250.910.010.010.0015~5313.6108 Comparative Example 20.020.340.600.020.040.0116~5012.8270 Comparative Example 30.030.260.590.040.030.0116~5012.8260 Comparative Example 4 (SS400) ≤ 0.25 ≤ 0.45 ≤ 1.4 Comparative Example 5 (Bolt 8.8) 0.25~0.55

[0045] Test example

[0046] The tensile strength and elongation of the component specimens manufactured according to each example and comparative example were measured, and the lamination results were determined and disclosed in Table 2 below. For Comparative Examples 4 and 5, the known tensile strength and elongation of the existing components SS400 and Bolt 8.8 were disclosed.

[0047] Specifically, the tensile strength and elongation of the specimens were measured according to ASTM E8 standards.

[0048] Round bar-shaped specimens were manufactured by powder sintering lamination of each specimen, and the lamination results were evaluated based on the presence or absence of spatter during the manufacturing process and whether mechanical properties were satisfied. If a large amount of spatter occurred or the mechanical property criteria were not met, it was judged as defective (x). Conversely, if the mechanical property criteria were met and almost no spatter occurred, the lamination result was judged as good (o).

[0049] Tensile Strength (MPa) Elongation (%) Lamination Results Example 18 19.316° Example 2 69 6.325° Example 3 98 0.515° Example 4 92 7.014° Example 5 929.013° Example 6 929.516° Comparative Example 1 105.75° Comparative Example 2 82.54° Comparative Example 3 83.65° Comparative Example 4 (SS400) ≥ 410 ≥ 18 - Comparative Example 5 (Bolt 8.8) ≥ 800 ≥ 12 -

[0050] As described above, the particle size and flowability of the carbon steel powders prepared according to Examples 1 to 6 fall within the range of particle size and flowability defined in the present invention. Furthermore, in the case of Examples 1 to 6, the mechanical properties of the obtained specimens also satisfy the values ​​required by the present invention, and since almost no spatter occurs during the powder sintering lamination process, the powder sintering lamination results are good. Comparative Example 1 has an excessively high carbon content, so although the strength is high, it is difficult to secure elongation. Comparative Examples 2 and 3 have excessively low elongation, and the lamination results were judged to be poor due to the large amount of spatter generated during the process.

[0051] Comparative Examples 4 and 5 are parts manufactured by a conventional known casting method. They were used as control groups to compare whether a part manufactured by additive manufacturing with carbon steel powder for powder sintering additive manufacturing according to the present invention exhibits tensile strength and elongation comparable to a part manufactured by a conventional casting method.

[0052] The tensile strength, yield strength, and elongation of Examples 1 and 2 and Comparative Examples 4 and 5 are disclosed in Table 3. For Comparative Examples 4 and 5, the tensile strength, yield strength, and elongation values ​​are those presented in the KS standard.

[0053] Classification Tensile Strength (MPa) Yield Strength (MPa) Elongation (%) Specimen of Example 1 8 19.38 19.316 Specimen of Example 2 6 96.36 96.325 Specimen of Comparative Example 4 (SS400) ≥ 4 10 ≥ 275 ≥ 18 Specimen of Comparative Example 5 (Bolt 8.8) ≥ 8 00 ≥ 640 ≥ 12

[0054] The specimen of Example 1 was compared with the existing spare part, Bolt 8.8 (Comparative Example 5), and the specimen of Example 2 was compared with the existing spare part, SS400 (Comparative Example 4). As can be seen in Table 3 above, it was confirmed that the specimen according to the embodiment of the present invention had significantly superior tensile strength, yield strength, and elongation compared to the existing spare part.

Claims

Carbon steel powder for powder sintering additive manufacturing, comprising 0.01 to 0.1 wt% carbon (C), 0.01 to 0.5 wt% silicon (Si), 0.03 to 1.0 wt% manganese (Mn), 0.1 wt% or less nickel (Ni), 0.1 wt% or less chromium (Cr), 0.1 wt% or less molybdenum (Mo), 0.04 wt% or less oxygen (O), and the remainder being iron (Fe).

2. In Paragraph 1, Carbon steel powder for powder sintering additive manufacturing, with a particle size of 10 to 60 μm.

3. In Paragraph 1, Carbon steel powder for powder sintering additive manufacturing, having a fluidity of 10 to 18 sec / 50g.

4. Energy density 50 to 250 J / mm 3 A method for manufacturing carbon steel powder according to any one of claims 1 to 3 by powder sintering additive manufacturing using a laser of a range.

5. A part obtained by the powder sintering additive manufacturing method according to claim 4.

6. In Paragraph 5, The above part is a part having a tensile strength of 410 MPa or more and an elongation of 18% or more, or a tensile strength of 800 MPa or more and an elongation of 12% or more.

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