KR102562188B1 - Alloy material for metal additive manufacturing, and mold manufactured using the same, a method for manufacturing and repairing metal parts using the sam - Google Patents

Abstract

The present invention relates to an alloy material used as a toner for additive manufacturing, wherein the alloy material is, by weight, C 0.25-0.6%, Cr 6.5-11.0%, Si 0.2-6.0%, Mn 0.2-2.5%, Mo 0 It relates to an alloy material for metal additive manufacturing containing ~4.5% and the balance of Fe and unavoidable impurities, and a method for manufacturing and repairing molds or metal parts manufactured using the same.

Description

Alloy material for metal additive manufacturing and method for manufacturing and repairing molds or metal parts manufactured using the same

The present invention relates to an alloy material for metal additive manufacturing and a method for manufacturing and repairing a mold or metal part manufactured using the same.

Recently, interest in additive manufacturing technology is increasing all over the world. Additive manufacturing technology is one of the innovative technologies that can innovatively change the existing manufacturing method, and it is a technology that can produce three-dimensional objects using various materials. Compared to the traditional manufacturing method by cutting, this technology can improve manufacturing cost, time, product performance, etc. depending on the applied field, so additive manufacturing technology is being applied to the manufacturing and production of products in various fields.

Depending on the lamination method, additive manufacturing technologies include Material Extrusion (ME), Material Jetting (MJ), Binder Jetting (BJ), Sheet Lamination (SHL), and Liquid Tank. It is classified into seven types: Vat Photo Polymerization (VPP), Powder Bed Fusion (PBF), and Direct Energy Deposition (DED).

Among them, the powder bed melting (PBF) method and the energy controlled welding (DED) method are mainly applied to the additive manufacturing of metals.

In the case of the powder bed melting method, it is suitable for additive manufacturing of metal products with complex shapes where undercut occurs during additive manufacturing in the vertical direction. It is widely applied to manufacturing cooling channels of molds.

In contrast, the energy controlled welding method is disadvantageous compared to the powder bed melting method when manufacturing metal products with complex shapes where undercut occurs, but the size of the powder used is relatively large, the stacking speed is fast, and the high output This technology is suitable for manufacturing and repairing molds and high-hardness metal parts.

Metal additive manufacturing technology is expensive compared to commercial metal forging materials used in additive manufacturing, and takes a long time to manufacture compared to conventional mechanical manufacturing technology, so it is used in aviation, space, medical, power generation, and automobile industries. Research on various commercialization technologies is being actively conducted continuously in a way that is applied to high value-added industries such as In contrast, for industries with relatively low added value, such as root industries, their economic feasibility is low compared to conventional technologies, which limits their scope of application.

On the other hand, as a similar prior literature for this, Korean Patent Publication No. 10-2019-0082220 is presented.

Republic of Korea Patent Publication No. 10-2019-0082220 (2019.07.09)

The present invention provides an alloy material for metal additive manufacturing having high tensile strength and elongation during metal additive manufacturing, excellent bonding strength to a mold base material, and high hardness only through additive manufacturing without an additional heat treatment process, and a shear mold manufactured therefrom. intended to provide

However, the above purpose is exemplary, and the technical spirit of the present invention is not limited thereto.

One aspect of the present invention for achieving the above object is an alloy material used as a toner for metal additive manufacturing, wherein the alloy material is, by weight, C 0.25-0.6%, Cr 6.5-11.0%, Si 0.2-6.0% , Mn 0.2 ~ 2.5%, Mo 0 ~ 4.5%, and the balance of Fe and unavoidable impurities It relates to an alloy material for metal additive manufacturing.

In the above aspect, the alloy material may include 0.25 to 0.6% C, 8.0 to 11.0% Cr, 2.0 to 6.0% Si, 0.2 to 0.6% Mn, and the balance of Fe and unavoidable impurities, by weight%. More preferably, in weight percent, C 0.3 to 0.5%, Cr 8.0 to 10.0%, Si 2.0 to 4.0%, Mn 0.3 to 0.5%, and the balance Fe and unavoidable impurities may be included.

Alternatively, in the above aspect, the alloy material is 0.25 to 0.6% by weight, C 0.25 to 0.6%, Cr 6.5 to 8.5%, Si 0.2 to 0.6%, Mn 0.5 to 2.5%, Mo 1.6 to 4.5% and the balance of Fe and It may contain unavoidable impurities, more preferably in weight percent, C 0.3 to 0.5%, Cr 6.5 to 8.0%, Si 0.2 to 0.6%, Mn 0.8 to 2.0%, Mo 2.0 to 3.0%, and the balance of Fe and unavoidable impurities. May contain impurities.

In the above aspect, the alloy material is P 0.01 ~ 0.05%, Ni 0.05 ~ 1.0%, Mo 0.01 ~ 0.05%, Ti 0.001 ~ 0.005%, V 0.01 ~ 0.05%, Nb 0.004 ~ 0.01%, W 0.02 ~ 0.05 %, Co 0.01 ~ 0.05%, Zr 0.004 ~ 0.01%, and B 0.002 ~ 0.005% may further include any one or two or more selected from the group consisting of.

In the above aspect, the alloy material may be spherical or wire.

In addition, another aspect of the present invention is a method for manufacturing the above-mentioned alloy material for metal additive manufacturing, (a) manufacturing an ingot by casting by mixing metal materials, which are compositional components constituting metal powder, in a specified weight ratio; And (b) pulverizing the ingot through a gas atomization method.

In addition, another aspect of the present invention relates to a mold manufactured by metal additive manufacturing of the aforementioned alloy material for metal additive manufacturing, and the mold may have a functional part made of the alloy material for metal additive manufacturing.

In addition, another aspect of the present invention relates to a method for manufacturing a mold including forming a functional part by metal additive manufacturing of the above-described alloy material for metal additive manufacturing on the body part of the mold, which is a non-functional part.

In another aspect, the metal additive manufacturing may be performed under conditions of a laser power of 300 to 500 W and a powder supply rate of 3 to 7 g/min.

In addition, another aspect of the present invention relates to a method for manufacturing and repairing metal parts, which manufactures or repairs metal parts by metal additive manufacturing of the aforementioned alloy material for metal additive manufacturing.

The material obtained by metal additive manufacturing of the alloy material for metal additive manufacturing according to the present invention has high tensile strength and elongation, and has excellent bonding strength to the mold base material. In addition, compared to commercial forged mold steel materials, high hardness of 58 to 61 HRC can be achieved only through the additive manufacturing process without an additional heat treatment process.

In addition, it was impossible to manufacture molds by dividing functional parts and non-functional parts in the conventional mold manufacturing technology by mechanical processing, but using metal additive manufacturing technology, it is possible to laminate functional parts on a base material, so that non-functional parts and non-functional parts It is possible to manufacture or repair molds or metal parts by dividing functional parts.

1 is a scanning electron microscope (FE_SEM) and optical microscope measurement image of an AM_A material (non-heat treated) manufactured by metal additive manufacturing.
2 is an FE_SEM and an optical microscope measurement image of an AM_A material (heat treatment) manufactured by metal additive manufacturing.
3 is an FE_SEM and an optical microscope measurement image of an AM_B material (non-heat treated) manufactured by metal additive manufacturing.
4 is an FE_SEM and optical microscope measurement image of AM_B material (heat treatment) manufactured by metal additive manufacturing.
5 is an FE_SEM and optical microscope measurement image of an AM_G material (non-heat treated) manufactured by metal additive manufacturing.
6 is an FE_SEM and optical microscope measurement image of D2 material.
7 is a FE_SEM and an optical microscope measurement image of the forged material _C material.
8 is a microscope measurement image of a pressed surface and a shear surface for each shear steel of AM_A material, AM_B material, and AM_G material.
9 is a detailed dimension related to the shear angle given to each section of the shear mold used for the life evaluation of the inclined plane shear condition.
10 shows a shear steel for evaluating the shear life of an inclined plane.
11 shows the shear life evaluation results for each material and condition and the wear and tear state of the blade of the shear steel.
12 shows the amount of wear and damage of the shear steel made of AM_A material and forged material_C after 100,000 shearing operations.

Hereinafter, an alloy material for metal additive manufacturing and a method for manufacturing and repairing a mold or metal part manufactured using the alloy material according to the present invention will be described in detail. The drawings introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Therefore, the present invention may be embodied in other forms without being limited to the drawings presented below, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, unless there is another definition in the technical terms and scientific terms used, they have meanings commonly understood by those of ordinary skill in the art to which this invention belongs, and the gist of the present invention is described in the following description and accompanying drawings. Descriptions of well-known functions and configurations that may be unnecessarily obscure are omitted.

In the conventional mold manufacturing technology by mechanical processing, it was impossible to manufacture molds by dividing functional and non-functional parts, but using metal additive manufacturing technology, it is possible to laminate functional parts on a base material, so that non-functional parts and functional parts can be manufactured by additive manufacturing. It is possible to manufacture or repair molds or metal parts by distinguishing them.

In addition, during metal additive manufacturing, different mechanical properties can be imparted to each laminated layer by changing additive manufacturing process conditions. The additive manufacturing process is defined as a process in which both variable energy (δw) and variable mass ((δm) change. Among the process conditions, laser power and laser beam size are process variables related to variable energy, and powder supply amount and feed speed are process conditions related to variable mass. It may be possible to manufacture parts having different mechanical properties by varying process conditions.

To this end, it is important to select appropriate variable energy and variable mass, and the change in variable energy and variable mass, which are additive manufacturing process conditions, means that the melting and cooling temperatures of the additively manufactured part change, and the specific alloy component carbon (C ), chromium (Cr), manganese (Mn), etc. are properly mixed and applied to the lamination process, the mechanical properties of the laminated specimens and the distribution of carbides according to the change in variable energy and variable mass, which are additive manufacturing process conditions It is possible to manufacture differently, and it is possible to manufacture high-hardness materials only by additive manufacturing without a heat treatment process, or to manufacture parts with various mechanical properties in one part. In addition, it may be difficult to satisfy desired mechanical properties when variable energy or variable mass is not appropriate. That is, when a specific alloy material is used in the lamination process, the effect of manufacturing parts and heat treatment process can be performed at the same time. Compared to conventional metal parts and mold manufacturing technologies, it is possible to achieve effects such as reduction of manufacturing costs and improvement of manufacturing processes. In addition, compared to the conventional method of manufacturing forged materials, materials manufactured by metal additive manufacturing are made in a process of repeating melting and cooling in a local area, so the size and distribution of carbides and mechanical properties are different due to these process characteristics.

First, an alloy material for metal additive manufacturing capable of achieving excellent mechanical properties under appropriate variable energy conditions will be described.

One aspect of the present invention relates to an alloy material used as a toner for metal additive manufacturing, and more particularly, to an alloy material for direct energy deposition (DED) metal additive manufacturing. 0.25 to 0.6%, Cr 6.5 to 11.0%, Si 0.2 to 6.0%, Mn 0.2 to 2.5%, Mo 0 to 4.5%, and the balance of Fe and unavoidable impurities.

A material obtained by metal additive manufacturing of an alloy material satisfying the above composition has high tensile strength and elongation, and has excellent bonding strength to the mold base material. In addition, compared to commercial forged mold steel materials, high hardness of 58 to 65 HRC can be achieved only through the additive manufacturing process without an additional heat treatment process.

Such an alloy material may have a spherical or wire-like shape, and when the alloy material is spherical, it may have a particle size of 30 to 150 μm, and when it is wire-shaped, it may have a diameter of 10 to 50 μm. It is not limited.

More specifically, the alloy material for metal additive manufacturing can be largely divided into two compositions depending on whether or not Mo is contained.

The alloy material according to the first aspect of the present invention may include 0.25 to 0.6% C, 8.0 to 11.0% Cr, 2.0 to 6.0% Si, 0.2 to 0.6% Mn, and the balance of Fe and unavoidable impurities by weight%, , More preferably, the alloy material may include 0.3 to 0.5% C, 8.0 to 10.0% Cr, 2.0 to 4.0% Si, 0.3 to 0.5% Mn, and the balance of Fe and unavoidable impurities by weight%.

Hereinafter, the alloy composition of the alloy material according to the first aspect of the present invention will be described in detail.

Carbon (C) is an element that changes properties of steel such as strength and hardness of steel depending on its content, and is preferably contained in an amount of 0.25 to 0.6% by weight, more preferably 0.3 to 0.5% by weight. On the other hand, if the C content is less than 0.25% by weight, the hardness of the laminated material is lowered and durability is deteriorated, and if it exceeds 0.6% by weight, carbides may be precipitated from the metal powder, which is not good.

Chromium (Cr) is a metal with excellent corrosion resistance and mechanical properties, and is preferably contained in an amount of 8.0 to 11.0% by weight, more preferably 8.5 to 10.0% by weight. On the other hand, if the Cr content is less than 8.0% by weight, corrosion may occur in the laminated material, and if it exceeds 11.0% by weight, Cr is precipitated and may be harmful to the human body, which is not good.

Silicon (Si) is an element that grows it on the surface of other metals because it has little chemical reaction, and is preferably contained in 2.0 to 6.0% by weight, more preferably 2.0 to 4.0% by weight. On the other hand, if the Si content is less than 2.0% by weight, the expected effect is insignificant, and if it exceeds 6.0% by weight, the effect obtained is small compared to the input content.

Manganese (Mn) is a hard and necessary element to increase corrosion resistance and mechanical properties in metal alloys, and is preferably contained in an amount of 0.2 to 0.6% by weight, more preferably 0.3 to 0.5% by weight. On the other hand, if the Mn content is less than 0.2% by weight, the effect of improving corrosion resistance and mechanical properties is insignificant, and if it exceeds 0.6% by weight, Mn may be precipitated and mechanical properties may be deteriorated.

In addition, the alloy material according to the second aspect of the present invention, by weight, contains C 0.25 to 0.6%, Cr 6.5 to 8.5%, Si 0.2 to 0.6%, Mn 0.5 to 2.5%, Mo 1.6 to 4.5%, and the balance of Fe. and unavoidable impurities, and more preferably, the alloy material is 0.3 to 0.5% by weight, C 0.3 to 0.5%, Cr 6.5 to 8.0%, Si 0.2 to 0.6%, Mn 0.8 to 2.0%, Mo 2.0 to 3.0% and The balance of Fe and unavoidable impurities may be included.

Hereinafter, the alloy composition of the alloy material according to the second aspect of the present invention will be described in detail.

Carbon (C) is an element that changes properties of steel such as strength and hardness of steel depending on its content, and is preferably contained in an amount of 0.25 to 0.6% by weight, more preferably 0.3 to 0.5% by weight. On the other hand, if the C content is less than 0.25% by weight, the hardness of the laminated material is lowered and durability is deteriorated, and if it exceeds 0.6% by weight, carbides may be precipitated from the metal powder, which is not good.

Chromium (Cr) is a metal with excellent corrosion resistance and mechanical properties, and is preferably contained in an amount of 6.5 to 8.5% by weight, more preferably 6.5 to 8.0% by weight. On the other hand, if the Cr content is less than 6.5% by weight, corrosion may occur in the laminated material, and if it exceeds 8.5% by weight, Cr is precipitated and may be harmful to the human body, which is not good.

Since silicon (Si) has almost no chemical reaction, it is preferably contained in an amount of 0.2 to 0.6% by weight as an element for growing it on the surface of other metals. On the other hand, if the Si content is less than 0.2% by weight, the expected effect is insignificant, and if it exceeds 0.6% by weight, the effect obtained is small compared to the input content.

Manganese (Mn) is a hard and necessary element to increase corrosion resistance and mechanical properties in metal alloys, and is preferably contained in an amount of 0.5 to 2.5% by weight, more preferably 0.8 to 2.0% by weight. On the other hand, if the Mn content is less than 0.5% by weight, the effect of improving corrosion resistance and mechanical properties is insignificant, and if it exceeds 2.5% by weight, Mn may be precipitated and mechanical properties may be deteriorated.

Molybdenum (Mo) is a metal with excellent mechanical properties in a wide temperature range, and is preferably contained in an amount of 1.6 to 4.5% by weight, more preferably 2.0 to 3.0% by weight. On the other hand, if the Mo content is less than 1.6% by weight, the expected effect is insignificant, and if it exceeds 4.5% by weight, the effect obtained is small compared to the input content.

In the alloy material according to the first aspect and the second aspect, in addition to the above composition, the rest may be composed of Fe and other unavoidable impurities, and in addition to this, in order to improve the function of the metal product, the alloy material has P 0.01 to 0.05 %, Ni 0.05~1.0%, Mo 0.01~0.05%, Ti 0.001~0.005%, V 0.01~0.05%, Nb 0.004~0.01%, W 0.02~0.05%, Co 0.01~0.05%, Zr 0.004~0.01% and B may further include any one or two or more selected from the group consisting of 0.002 to 0.005%.

Phosphorus (P) is a highly pyrophoric element that ignites itself in air. If the content of P is less than 0.01% by weight, the ignition power is insignificant and has a small effect on the melting of metal powder. If the content exceeds 0.05% by weight, the ignition power is It is strong, so it ignites all other metals and makes the metal powder too soft and liquid, making it difficult to laminate during printing.

Nickel (Ni) is an element that can be forged and welded, has excellent malleability and ductility, and is less oxidized than iron, and is used for catalysts or plating of iron. If the content of Ni is less than 0.05% by weight, the effect on Ni input is insignificant, and if it exceeds 1.0% by weight, the effect obtained is small compared to the amount included.

Molybdenum (Mo) is mechanically very strong over a wide temperature range, is insoluble in normal acids, and is not eroded by concentrated nitric acid. Molybdenum steel alloyed with iron is used for cutting tools. If the content of Mo is less than 0.01% by weight, the effect obtained is insignificant, and if the content exceeds 0.05% by weight, the effect obtained compared to the content is reduced.

Titanium (Ti) has high strength, malleability, and ductility, and since an oxide film is formed on the surface, titanium (Ti) is an element that is not easily corroded by acid or seawater. Doing so will cost you more than you get.

Vanadium (V) is used as high-speed tool steel and high-strength structural steel by alloying with steel or iron. When the amount of vanadium (V) is generally less than 1% by weight, the steel has a fine surface structure and reacts with carbon to form carbides. If the content of V is less than 0.01% by weight, the effect of the V content is insignificant, and if it is contained in excess of 0.05% by weight, the cost effect is small.

Niobium (Nb) is not corroded by oxygen or strong acid, and is an element added to increase heat resistance of stainless alloys. If the content of Nb is less than 0.004% by weight, the effect on the Nb content is insignificant, and if it exceeds 0.01% by weight, the effect is small compared to the amount included.

Tungsten (W) is used for high-speed steel, permanent magnet steel, heat and corrosion resistant alloys, and tungsten carbide is used for tools. As a high price, if less than 0.02% by weight of W is contained, the effect of W content is insignificant, and if it exceeds 0.05% by weight, the effect obtained is small compared to the amount contained.

Cobalt (Co) is a shiny metal similar to iron and is ferromagnetic. It does not melt well even when heated, and rusts on the surface even when left in the air, but does not corrode easily, and has excellent oxidation resistance, abrasion resistance, and mechanical properties. If it is less than 0.01% by weight, the effect obtained by adding Co is small, and if it is more than 0.05% by weight, the effect obtained is small compared to the amount included.

Zirconium (Zr) has high corrosion resistance in high temperature water. As an element that has the property of igniting even in air, if it is less than 0.004% by weight, it is ignited in air and does not react, and if it is more than 0.01% by weight, the effect obtained is small compared to the amount contained and the cost is high economically.

Boron (B) is less reactive, but forms a compound with oxygen or nitrogen, so it is used as a degassing agent during metal smelting. , If it exceeds 0.005% by weight, the effect obtained is small compared to the amount added.

In addition, another aspect of the present invention is a method for manufacturing the above-mentioned alloy material for metal additive manufacturing, (a) manufacturing an ingot by casting by mixing metal materials, which are compositional components constituting metal powder, in a specified weight ratio; and (b) pulverizing the ingot through gas atomization.

The step (a) is a step of mixing metal materials in a weight ratio and then manufacturing an ingot by casting. For ease of handling, the ingot can be manufactured to have a weight of 1 to 100 kg. In addition, it is possible to directly powder the liquid metal produced by the casting without manufacturing an ingot, but it is more preferable to manufacture an ingot and then powder it because of convenience in handling and easy storage of raw materials.

The step (b) is a step of pulverizing the ingot through a gas atomization method, and the gas atomization method uses a vacuum induction inert gas atomization process (VIGA) and a low-temperature crucible. Vacuum induction inert gas atomization process with cold crucible (VIGA-CC), electrode induction gas atomization process (EIGA), plasma gas atomization process (PGA) etc.

More specifically, in the step (b), the ingot is melted, supplied to a molten metal nozzle, and compressed gas is injected into the flow of the molten metal flowing down from the molten metal nozzle to disperse the flow of the molten metal to produce an alloy material. can The gas used at this time may be air, nitrogen, helium or argon, and the manufactured alloy material may have a size of 30 to 150 μm. Thereafter, it may be selected and used to have a size suitable for use in metal additive manufacturing. At this time, the sorting method can be sorted using weight, magnetism, etc., and it is also possible to simply sort using a mesh having an appropriate size or to sort using a sieve.

In addition, another aspect of the present invention relates to a mold manufactured by metal additive manufacturing of the aforementioned alloy material for metal additive manufacturing. In detail, the mold may have a functional part made of the alloy material for metal additive manufacturing.

Hereinafter, a shear mold will be described as an example of the mold, but the mold according to the present invention is not limited to the shear mold.

The shearing mold refers to a mold for forming thin sheet metal using a press, and generally refers to a method of processing a metal by placing a material (thin sheet metal) on a die and then shearing it with a punch. Dies and punches used at this time are referred to as shearing molds, and since the precision of metal being processed depends on the precision of the die and punch, the precision and durability of the shearing mold are very important.

In the case of the existing shear mold, when printed using a 3D printer, the hardness and heat resistance are poor, and a post-heat treatment process is required to achieve higher hardness and durability, which requires a lot of cost and time, which increases the unit price of the shear mold. is a major cause of

On the other hand, when using the above-mentioned alloy material for metal additive manufacturing, high hardness and durability can be secured without an additional heat treatment process, wear resistance, corrosion resistance and heat resistance are excellent, life expectancy is long, and the amount of burr generation is low. Specifically, it is possible to provide a shear mold having a hardness of 58 to 65 HRC by the additive manufacturing process.

More specifically, the shearing mold according to an example of the present invention may have a shearing blade, which is a functional part, made of the alloy material for metal additive manufacturing. The shearing mold is composed of a body part and a shearing blade part laminated to the body part. The body part may be a non-functional part in a semi-finished product state. Specifically, for example, gray cast iron (FC25, FC30) and nodular graphite cast iron (FCD55), which are casting materials, are used. Alternatively, materials such as carbon steel (S45C) for mechanical structures may be used.

The manufacturing method of such a mold may include forming a functional part by metal additive manufacturing of the above-described alloy material for metal additive manufacturing on the body part of the mold, which is a non-functional part.

In detail, the above-mentioned alloy material for metal additive processing is used as a toner of a 3D metal printer of a direct energy deposition (DED) method, and the alloy material is sprayed using a nozzle and simultaneously irradiated with a laser to reflect A molten alloy material may be laminated on the main body.

In addition, in terms of manufacturing a mold having a higher hardness, the metal additive manufacturing may be performed under conditions of a laser power of 300 to 500 W and a powder supply rate of 3 to 7 g/min, more preferably 350 to 500 W. It can be performed under conditions of a laser power of 450 W and a powder feed rate of 5 to 6 g/min. Through this, it is possible to manufacture a mold having a hardness of 58 to 65 HRC.

In this case, the diameter of the laser beam may be 0.5 to 1.0 mm, the stacking height per layer may be 0.1 to 0.5 mm, the stacking width pitch per layer may be 0.1 to 1 mm, and the stacking speed may be 0.5 to 1.5 m/min.

In addition, another aspect of the present invention relates to a method for manufacturing or repairing a metal part by performing metal additive manufacturing of an alloy material for metal additive manufacturing, and manufacturing or repairing a metal part under the above-mentioned additive manufacturing conditions. Metal parts can be repaired.

Hereinafter, an alloy material for metal additive manufacturing according to the present invention and a method for manufacturing and repairing a mold or metal part manufactured using the alloy material according to the present invention will be described in more detail through examples. However, the following examples are only one reference for explaining the present invention in detail, but the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is merely to effectively describe specific embodiments and is not intended to limit the present invention. In addition, the unit of additives not specifically described in the specification may be % by weight.

[Example]

Alloy materials (wt%) for additive manufacturing were prepared according to the compositions shown in Table 1 below.

material name C Cr Mn Si Mo W V Fe AM_A 0.34 9.30 0.38 2.40 - - - balance AM_B 0.35 7.00 1.10 0.30 2.20 - - balance AM_C 0.34 10.20 0.28 3.00 - - - balance AM_D 0.35 5.50 0.35 2.20 - - - balance AM_E 0.34 8.70 1.30 1.45 - - - balance AM_F 0.36 11.45 0.43 0.30 - - - balance AM_G 0.78 4.00 0.30 0.30 5.00 6.00 2.00 balance

[Evaluation of physical properties]

Specimens were prepared by the additive manufacturing process using the above alloy materials for metal additive manufacturing, and then each physical property was evaluated according to the following method.

1) microstructure

In order to analyze the metallographic characteristics of forged and laminated materials, the metal structure state of each material was observed using a scanning electron microscope (FE_SEM) and an optical microscope.

1 and 2 show the respective microstructures of the materials to which the non-heat treatment conditions of the AM_A material and the quenching and tempering heat treatment processes at 1030 ° C and 150 ° C were applied. In the case of the AM_A material manufactured by the lamination process to which the heat treatment process was not applied, no sedimentation phase was observed in the base structure as a result of scanning electron microscope observation. However, in the case of the AM_A material to which the quenching and tempering heat treatment process was applied, it was found that some precipitated phases were finely precipitated in the matrix structure due to the quenching effect.

3 and 4 show the microstructures of the materials to which the non-heat treatment conditions of the AM_B material and the quenching and tempering heat treatment processes at 1030 ° C and 150 ° C were applied. In the case of AM_B material manufactured by the lamination process without the heat treatment process, as a result of scanning electron microscope (FE_SEM) observation, precipitated phases were observed along the grain boundaries in the base structure, and in the case of the AM_B material to which the quenching and tempering heat treatment process was applied, the matrix It was found that the precipitated phases in the structure were reduced by the application of the heat treatment process. This is considered to be a material-specific characteristic of the two materials according to the application of the heat treatment process.

5 shows scanning electron microscope observation results after additive manufacturing (non-heat treatment) of the AM_G material. As a result of the analysis, it was found that precipitated phases were precipitated along the grain boundary similarly to the AM_B material in the base structure, and compared to the AM_B material, it was analyzed that the precipitated phases were finely and uniformly precipitated. In addition, as a result of analyzing the microstructure of forged materials and materials manufactured by additive manufacturing, in the case of forged materials, precipitated phases are precipitated in irregular shapes and sizes in the matrix structure according to the application of the heat treatment process, in contrast to materials manufactured by additive manufacturing. In the base structure, precipitation phases were observed in a specific pattern along the grain boundaries. This is expected to be caused by the difference in the manufacturing process of the forged material and the laminated material applied to the experiment, and it is judged that these organizational characteristics along with the mechanical properties of the material can affect the life of the material under the conditions of use.

On the other hand, in FIGS. 6 and 7, D2 material, which is most widely used in the production of shear steel, which is a functional part of a shear mold, among commercial alloy tool steel forging materials, has excellent mechanical properties and durability compared to conventional alloy tool steel materials, and has no notch impact test Matrix HSS-based forging material with 5 times higher value than D2 material_C material (C 0.7 wt%, Cr 5.0 wt%, Mn 0.5 wt%, Si 0.2 wt%, Mo 2.3 wt%, V 0.5 wt% and remaining Fe ) is shown for the metallographic structure after heat treatment. As a result of scanning electron micrograph analysis, in the case of forged materials, it was analyzed that precipitated phases were irregularly precipitated in the base structure after the heat treatment process was applied. In addition, in the case of forged material_C, it was found that the precipitated phases were smaller and finely distributed compared to the material D2.

2) Tensile strength (MPa) and elongation (%)

Tensile strength and elongation measurements were performed using a Universal Testing Machine Instron 5988 (Instron, Norwod, MA, US). The tensile specimen was manufactured to have a total length of 72 mm, an effective square cross-section of 4 × 4 mm, an effective length of 25 mm, and a length of the parallel part of 32 mm, and the test was conducted at a speed of 1 mm/min. After testing 5 times for each specimen, the average value of the remaining three values was recorded except for the minimum and maximum values.

material name Tensile strength (MPa) Elongation (%) AM_A 1,820 8.44 AM_B 1,744 7.98 AM_C 1,795 8.15 AM_D not measurable not measurable AM_E 1,763 8.05 AM_F 1,729 7.76 AM_G not measurable not measurable

Referring to Table 2, in the case of AM_A material, tensile strength of 1,820 MPa and elongation of 8.44% were measured and showed the best mechanical properties. On the other hand, in the case of AM_D and AM_G materials, cracks occurred during additive manufacturing, making it impossible to produce tensile specimens larger than a certain size, and it was not possible to evaluate additional mechanical properties other than hardness values after additive manufacturing.

3) Joint strength (MPa)

In general, after selecting the low-cost S45C material, which is commonly applied to non-functional parts when manufacturing molds, as a base material, joint strength specimens were prepared using the method of additive manufacturing of heterogeneous materials, and the joint strength of each material was evaluated. After testing 5 times for each specimen, the average value of the remaining three values was recorded except for the minimum and maximum values.

material name Joint strength (MPa) Elongation (%) 1 time Episode 2 3rd time average 1 time Episode 2 3rd time average S45C+AM_A 646 647 648 647 9.70 9.89 9.65 9.75 S45C+AM_B 635 506 584 575 9.52 9.40 9.48 9.47 S45C+AM_C 641 645 638 641 9.54 9.67 9.82 9.68 S45C+AM_D not measurable not measurable S45C+AM_G not measurable not measurable

Referring to Table 3, when the S45C material was used as a base material and the laminated material was bonded in a heterojunction method, the bonding strength was evaluated at a level of 575 to 647 MPa. In general, the tensile strength of S45C material that is not heat treated is 569 MPa, and the tensile strength of S45C material to which tempering heat treatment is applied is 690 MPa. In the case of the S45C base material applied to the experiment, a separate heat treatment process was not applied, but it is judged to be the result of some heat treatment process applied to the interface in the process of manufacturing a bonded specimen using the additive manufacturing process. In addition, it was found that both types of laminated materials could secure a bonding strength of 80% or more of the base material standard.

On the other hand, in the case of AM_D and AM_G materials, cracks occurred during additive manufacturing, so it was not possible to manufacture bonded specimens larger than a certain size.

4) Hardness test

a) Evaluation of hardness according to additive manufacturing conditions

As shown in Table 5 below, additive manufacturing was performed by varying the laser power and powder supply speed to evaluate the Rockwell hardness. The diameter of the laser beam may be 0.8 mm, the stacking height per layer is 0.25 mm, and the stacking width pitch per layer is 0.5 mm. mm, and the lamination speed was 0.85 m/min.

material name Additive manufacturing conditions Hardness
(HRC) Laser power (W) Powder feed rate (g/min) AM_A 250 7.3 46.9 300 6.5 49.8 350 5.5 59.3 400 4.8 54.8 450 4.4 55.0 AM_B 250 7.3 53.3 300 7.0 51.1 350 6.5 55.8 400 6.5 55.7 450 5.0 60.2 500 4.6 54.4 AM_G 250 7.3 56.3 300 6.3 62.0 350 5.5 61.7 400 4.8 55.3 450 4.4 59.6

As a result of analyzing the change in hardness of the output according to the change in laser output during additive manufacturing, changes were observed in the hardness value of the output according to the change in laser output and powder supply during additive manufacturing for all three types of materials tested. In the case of powdered AM_G material, it showed the best hardness under the condition of laser output of 300 W and powder supply speed of 6.3 g/min, but due to cracks during additive manufacturing, a certain area width (4 mm) × length (4 mm) × length (100 mm) or more of additive manufacturing was not possible.

b) Evaluation of hardness according to heat treatment

After selecting the S45C material as the base material, specimens were manufactured by the method of additive manufacturing of different materials, and the Rockwell hardness of each material was evaluated by selecting non-heat treatment conditions, low-temperature tempering conditions after quenching, and high-temperature tempering conditions.

At this time, AM_A material was subjected to metal additive manufacturing under the conditions of a laser power of 350W and a powder supply speed of 5.5 g/min, and for the material AM_B under the conditions of a laser power of 450W and a powder supply speed of 5.0 g/min, and the diameter of the laser beam may be 0.8 mm, the lamination height per layer is 0.25 mm, the lamination width pitch per layer is 0.5 mm, and the lamination speed is 0.85 m/min.

Specimen manufacturing conditions Hardness
(HRC) material name Q (℃) T (℃) Forged Material_C heat treatment 59.8 S45C+AM_A - - 59.3 1030 150 60.3 180 58.0 200 58.0 400 57.0 450 56.9 500 57.1 520 57.8 550 50.1 S45C+AM_B - - 60.2 1030 150 60.0 180 58.0 200 57.0 400 55.0 450 54.9 500 55.2 550 57.1 570 53.6 - Q: quenching temperature
- T: tempering temperature

As a result of the hardness test analysis, the specimen using S45C material as a base material and laminated material AM_A and AM_B materials bonded by heterojunction method has more than 58 HRC by additive manufacturing process without additional heat treatment process compared to commercial forged mold steel material. It was confirmed that high hardness can be achieved.

5) Shear test

a) Planar shear condition life evaluation:

A shear mold for life evaluation under plane shear conditions was manufactured through an additive manufacturing process using the above alloy materials for metal additive manufacturing. At this time, AM_A material is under the conditions of 350W laser power and 5.5 g/min powder supply rate, AM_B to AM_F materials under 450W laser power and 5.0 g/min powder supply speed conditions, and AM_G material is under 300W laser power and Metal additive manufacturing was performed under the conditions of a powder supply rate of 6.3 g/min, the diameter of the laser beam may be 0.8 mm, the stacking height per layer is 0.25 mm, the stacking width pitch per layer is 0.5 mm, and the stacking speed is 0.85 m/min. has been carried out

In the case of a mold for life evaluation under flat shear conditions, since continuous shearing is performed, the shear angle was applied to the blade part at 1/2 of the material thickness when manufacturing the shear steel. In addition, to minimize the shaking and positional tolerance of the shearing steel due to the shearing operation, guide posts are applied to four corners of the mold, and uniform pressure is applied to the pad part of the upper mold for fixing the material during shearing operation. To apply, a gas spring was applied.

Planar shear conditions The mold life evaluation was performed on three types of laminated materials, and the durability life was 100,000 strokes while satisfying the condition that the burr generation of the plate due to wear and damage during the shearing operation satisfies within 5% of the material thickness without damage to the shear steel. After selecting as the target life span, the test was conducted. To do this, more than 300,000 repeated shearing operations must be performed, and the boron steel (22MnB5) material (yield strength 1,100 MPa, tensile strength 1,598 MPa, elongation 8.91%) applied to hot stamping is heated to 900℃ or higher and then cooled. It is possible to secure the tensile strength of 1.5 GPa only through the process. Therefore, for the convenience of the shear test, Docol 1500M cold plate (C 0.23 wt%, Si 0.4 wt%, Mn 1.3 wt%, P 0.02 wt%, S 0.01 wt%, Al 0.015 wt%, Nb+Ti 1.0 wt%, Cr+Mo 1.0 wt%, Cu 0.2 wt%, B 0.01 wt%, and the balance of Fe) were used together to perform a shear test, and the initial 20 times and The press was stopped every 10,000 strokes after 1000 strokes, 3000 strokes, and 5000 strokes, where life evaluation was performed, and the material manufactured using a separate heating furnace and cooling press was subjected to a shear test 5 times to perform the test. In the case of boron steel (22MnB5) material, considering the hot stamping mass production conditions, the material was heated in a heating furnace at 950 ° C for 5 minutes and then cooled in a 5 ° C cold press for 1 minute to prepare and use the specimen.

For the life evaluation shearing operation, a 140 Ton mechanical press was used, the width of the material applied during the shearing operation was 50 mm, and the pitch was 15 at the initial 20 strokes and the specific number of shears where boron steel (22MnB5) material was applied for shear life evaluation. ㎜ was applied, and in the remaining sections where Docol 1500M material is applied, 4 ㎜, which is the minimum size without scrap deformation of the material during shearing, was applied. In addition, the shear rate was applied at 40 strokes per minute (SPM), which is twice as fast as the actual mass production condition. Temperature changes during work were measured using a camera. As a result of the measurement, the temperature deviation was at the level of 15-35 ° C, and it was judged that the degradation problem would not occur because the temperature deviation was not large.

Analyzing the damage principle of the shearing steel during shearing, micro-chipping occurs at the weak part of the shearing steel blade at the beginning, and this micro-chipping generates burrs in the product in repeated shearing, and the generated burr Friction, abrasion, and abrasion occur on the shear steel, and it is judged that shear and impact loads are repeatedly applied to the shear steel, leading to breakage of the shear steel. As the number of repetitions of the work increases, such wear and tear continuously increases, and accordingly, the amount of burr generated in the product also increases. In the continuous shearing operation, directly evaluating the existence of damage and life of the shearing steel is difficult due to safety issues and technical problems regarding the evaluation method in reality because it is impossible to realize the same conditions when disassembling and reassembling the shearing steel. Therefore, in this study, considering the fact that the amount of burr generation is regulated within 5-10% of the material thickness in the shearing process in the case of general body parts, a method of evaluating the amount of burr generation of the sheared product at a specific number of shears Life and damage evaluation was conducted.

After the initial 20 shearing operations, the pressed and sheared surfaces of each sheared steel of the three materials were measured using a stereo microscope, and these are shown in FIG. 8. As a result of the analysis, no burrs were observed, the pressed surface was 0.02-0.04 mm, and the shear surface was 0.20-0.22 mm, which was similarly measured for all three types of sheared steel materials. 1,000 strokes, 3,000 strokes, 5,000 strokes, and then, based on the burr generation amount of the sheared scrap every 10,000 strokes, the life span of the sheared steel was evaluated with the goal of 100,000 strokes.

The evaluation results are briefly shown in Table 6 below, and the AM_A material was found to be the best when comprehensively considering the state of steel wear and tear.

delivery day material Burr (㎛) lifetime (only) degree of damage AM_A 33.11 10 clear AM_B 22.92 5.2 Severe wear and cracking AM_C 39.48 10 clear AM_D 42.15 10 breakage occurs AM_E 52.30 10 severe wear and tear AM_F 32.84 6.5 severe wear and tear AM_G 50.00 10 breakage occurs

As a result of the evaluation, the AM_A material completed the life evaluation of 100,000 times, and it was confirmed that the test was completed without damage as a result of checking the presence or absence of damage after disassembling the shear steel.

On the other hand, in the case of the AM_B material during the 100,000-cycle shear life evaluation, the 100,000-cycle life evaluation was not completed, and the amount of burr generation repeatedly did not meet the allowable value of the material thickness at 3.5-5.2 million cycles, and the shear steel check result was unacceptable. It was confirmed that a crack of one size occurred in the shear steel blade.

In the case of AM_C material, the life evaluation was completed 100,000 times, and as a result of checking the presence or absence of damage after disassembling the shear steel, the test was completed without damage, but the amount of burr generation was slightly higher than that of AM_A material.

In the case of AM_D material, 100,000 times life evaluation was completed, but it was confirmed that some visually observable damage occurred on the upper surface of the shear steel.

In the case of AM_E material, 100,000 cycles of life evaluation was completed, but the shear steel blade was severely worn, and the amount of burr generation did not meet the allowable value of the material thickness.

Even in the case of the AM_F material, the life evaluation of 100,000 cycles was not completed, and the amount of burr generation repeatedly at 4.5 to 6.5 thousand cycles did not satisfy the allowable value of the material thickness, and the shear steel blade was severely worn.

In the case of AM_G material, the amount of burr generation satisfies the tolerance until the end of the 100,000-time life evaluation, but as a result of checking the wear and damage state of the shear steel after the 100,000-time life evaluation, some visually observable damage occurred on the upper surface of the shear steel. that has been confirmed Wear characteristics by shearing were observed to be the best among the three materials.

b) Evaluation of life in inclined shear conditions:

Planar shear condition life evaluation In the case of shear mold, it is advantageous to compare materials relative to each other, but there is a limit to distinguish superiority or inferiority by material for selecting materials that are advantageous for the actual mass production environment. In addition, there is a limit in terms of time and cost to continuously perform more than 100,000 shear tests until the shear steel for each material is broken. Therefore, in consideration of these problems, an additional life evaluation for each material was performed by applying the slope shear condition to apply the noise factor and harsh environment in the mass production environment.

For materials and conditions to be applied, Matrix HSS type forged material_C was used to compare the relative life evaluation of shear steel, laminated material and forged material manufactured by applying and not applying heat treatment process for AM_A and AM_B materials manufactured by additive manufacturing. Including, shear steels under 5 conditions were manufactured and additional life evaluation was conducted. On the other hand, in the case of AM_G material, which was applied to life evaluation under plane shear conditions, it was excluded from this experiment because it was impossible to manufacture inclined plane shear steel due to crack generation during additive manufacturing.

Compared to flat shear condition mold, the shear mold manufacturing concept for life evaluation under inclined plane shear condition gave a specific shape to the product to be sheared, gave an inclined section of 50° and 55°, and did not reflect the shear angle. . In addition, in order to carry out the shear test until the shearing steel is damaged, it was manufactured to induce early breakage of the steel during shearing work by applying a method of dividing steep slopes and gentle slopes by shape and section. In order to give a shape to the product to be sheared and to evaluate the shearing life at the same time, the mold was manufactured with the concept of a gradual forming mold in which forming and shearing processes can be performed simultaneously in one mold. 9 shows detailed dimensions related to the shear angle assignment for each section. 10 shows a shear steel for evaluating the shear life of an inclined surface.

The life evaluation under the inclined plane shear condition was conducted under the condition that the amount of burr generation of the scrap during the shearing operation satisfies within 10% of the material thickness with the goal of 100,000 shearing operations, the same as the life evaluation under the flat shear condition. In addition, the material applied to the shear was also subjected to a shear test using a mixture of boron steel (22MnB5) material and Docol 1500M material from SSAB, Sweden. Afterwards, the life evaluation was conducted by stopping the press every 10,000 strokes and checking the amount of burrs on the scrap.

The life span of each sheared steel was evaluated under the condition that the material is automatically supplied from the coil to the mold and the shearing operation is continuously performed after molding. A shear test was performed at a speed of 40 times per minute using a mechanical 160 Ton press in consideration of the fact that molding and shearing were performed simultaneously using two coils at the same time.

11 shows the shear life evaluation results for each material and condition, as well as the wear and tear of the blade of the shear steel. 12 shows the amount of wear and damage of the shear steel made of the AM_A material non-heat treatment condition and the shear steel made of the Matrix HSS-based forged material_C after 100,000 shearing operations. As a result of analyzing the amount of wear and damage, forged material_C was found to be superior in wear characteristics, and material AM_A was found to be superior in damage characteristics.

As a result of the evaluation, in the case of the two types of laminated materials, when the heat treatment process was applied, there was no effect of improving lifespan during shearing compared to the non-heat treatment condition, and the shearing steel life of the AM_A material non-heat treatment condition and the forged material_C heat treatment condition was evaluated to be the best. .

Although the present invention has been described through specific details and limited examples as described above, this is only provided to help a more general understanding of the present invention, the present invention is not limited to the above examples, and the present invention belongs Various modifications and variations from these descriptions are possible to those skilled in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and it will be said that not only the claims to be described later, but also all modifications equivalent or equivalent to these claims belong to the scope of the present invention. .

Claims (13)

In the alloy material used as a toner for metal additive manufacturing, which contains 0.25 to 0.6% C, 8.0 to 11.0% Cr, 2.0 to 6.0% Si, 0.2 to 0.6% Mn, and the balance of Fe and unavoidable impurities in weight percent,
When the alloy material is bonded to the S45C material by metal additive processing, the bonding strength to the S45C material is 80% or more of the tensile strength of S45C,
Alloy for metal additive manufacturing, characterized in that the amount of burr generation satisfies within 5% of the material thickness in the flat shear condition life evaluation of the mold manufactured by metal additive manufacturing of the alloy material, and there is no damage after 100,000 shear life evaluation Material.
delete According to claim 1,
The alloy material is an alloy material for metal additive manufacturing, including 0.3 to 0.5% by weight, C 0.3 to 0.5%, Cr 8.0 to 10.0%, Si 2.0 to 4.0%, Mn 0.3 to 0.5%, and the balance of Fe and unavoidable impurities.
delete delete According to claim 1,
The alloy material is P 0.01~0.05%, Ni 0.05~1.0%, Mo 0.01~0.05%, Ti 0.001~0.005%, V 0.01~0.05%, Nb 0.004~0.01%, W 0.02~0.05%, Co 0.01~0.05% %, Zr 0.004 ~ 0.01% and B 0.002 ~ 0.005% further comprising any one or two or more selected from the group consisting of, an alloy material for metal additive manufacturing.
According to claim 1,
The alloy material is a spherical or wire-shaped alloy material for metal additive manufacturing.
A method for manufacturing the alloy material for metal additive manufacturing of claim 1,
(a) preparing an ingot by casting by mixing metal materials, which are components of metal powder, in a specified weight ratio; and
(b) pulverizing the ingot through gas atomization;
Method for producing an alloy material for metal additive manufacturing comprising a.
A mold manufactured by metal additive manufacturing of the alloy material for metal additive manufacturing of claim 1.
According to claim 9,
The mold is a mold in which the functional part is made of the alloy material for metal additive manufacturing.
Forming a functional part by metal additive manufacturing of the alloy material for metal additive manufacturing of claim 1 on the main body of the mold, which is a non-functional part;
The method of manufacturing a mold in which the metal additive manufacturing is performed under conditions of a laser power of 300 to 500 W and a powder supply rate of 3 to 7 g/min.
delete Manufacturing or repairing metal parts by metal additive manufacturing of the alloy material for metal additive manufacturing of claim 1,
The metal additive manufacturing method of manufacturing and repairing metal parts performed under conditions of a laser power of 300 to 500 W and a powder supply rate of 3 to 7 g/min.