JP7737017B2 - Metal wire for fusion-deposition additive manufacturing using metal 3D printers, additive manufacturing products, and manufacturing methods for additive manufacturing products - Google Patents

Description

The present invention relates to metal wire for additive manufacturing using metal 3D printers, additive manufactured products, and methods for manufacturing additive manufactured products, which maintain the high hardness and corrosion resistance required for additive manufactured products while ensuring material uniformity and wear resistance and suppressing quench cracks.

In recent years, metal 3D printers have been expected to be a revolutionary production technology, and various techniques have been proposed. The main technical methods proposed are those using metal powder and those using metal wire.

When using metal powder, for example, a manufacturing method has been disclosed in which SUS630 powder is irradiated with an electron beam, melted and solidified, and then layered in three dimensions (Patent Document 1). However, when using metal powder, the material is expensive, and the high porosity reduces the reliability of the parts. Furthermore, if the parts are simply layered, problems arise such as sensitization and material non-uniformity, necessitating a heat treatment process such as sintering. Dimensional variations also occur during sintering. Furthermore, when a binder is used, not only are debinding and sintering processes required, but sintering also causes large volume changes, which can easily lead to errors in the dimensional accuracy of the parts.

On the other hand, when using metal wire, for example, a method has been disclosed in which metal wire weld beads are stacked to form three-dimensional parts (Patent Document 2). Also, a manufacturing method has been disclosed in which stainless steel metal wire is welded and stacked using two deposition devices to reduce thermal deformation, stress, and internal cracks caused by high heat during deposition (Patent Document 3).

As such, it is difficult to obtain durable, reliable parts using conventional 3D additive manufacturing techniques that can suppress all of the following: dimensional fluctuations in parts, thermal deformation, internal cracking, voids, material uniformity, and metal structure stability. Patent Document 4 discloses a manufacturing method for 3D printers that use metal wire welding and layering to create 3D shapes. The method uses stainless steel metal wire, which has excellent heat resistance (thermal deformation resistance), material and metal structure uniformity, internal cracking resistance, and internal void resistance, and is adjusted in composition to always produce a low-C, low-N martensitic structure by controlling the transformation temperature of the metal structure.

Japanese Patent Application Laid-Open No. 2017-186653 Japanese Patent Application Laid-Open No. 2003-266174 Japanese Patent Application Laid-Open No. 2018-87379 Japanese Patent Application Laid-Open No. 2020-147785

There is a demand for additively manufactured products that are three-dimensionally produced by welding and laminating metal wires and that have high hardness, wear resistance, and corrosion resistance. One possible method is to use wire made of martensitic stainless steel as the welding material for additive manufacturing.
Conventionally, medium-high carbon martensitic stainless steels (SUS440A, SUS440C, etc.) have had the problem that when a large amount of retained austenite is generated, the hardness and wear resistance decrease.
When martensitic stainless steel wire is used to form an additively manufactured product through 3D welding and lamination, the hardness of the additively manufactured product can be uneven depending on the part, resulting in insufficient material uniformity. The additively manufactured product can also have insufficient wear resistance. Furthermore, cracks can occur in the manufactured product after additive manufacturing. It is believed that a temperature difference occurs between the top and bottom of the additively manufactured product after additive manufacturing and cooling, causing cracks due to thermal stress, which will be referred to as "quench cracks" hereinafter.
In order to solve the above-mentioned problems, an object of the present invention is to provide a martensitic stainless steel wire having excellent wear resistance by producing a shaped product at an appropriate temperature in continuous lamination, as well as a reliable part and a method for producing the same at low cost.

The present invention aims to provide metal wire for additive manufacturing using metal 3D printers, additive manufacturing products, and a method for manufacturing additive manufacturing products, which maintain the high hardness and corrosion resistance required for additive manufacturing products, while ensuring material uniformity and wear resistance and suppressing cracking.

That is, the gist of the present invention is as follows.
[1] In mass%,
It has a chemical composition including C: more than 0.35% to 1.2% or less, Si: 3.0% or less, Mn: 3.0% or less, P: 0.1% or less, S: 0.4% or less, Ni: 2.0% or less, Cr: 10 to 17%, Mo: 3.0% or less, Al: 2.0% or less, N: 0.15% or less, O: 0.015% or less, Ti: 0.03 to 0.2%, Nb: 0.03 to 0.5%, V: 0.03 to 0.5%, W: 0.03 to 0.5%, with the balance being Fe and unavoidable impurities;
A metal wire for deposition additive manufacturing using a metal 3D printer, characterized in that the carbonitride index D value defined by the following formula (1) is 100 or more.
Carbonitride index D=(500-400C-30Mn-15Ni-12Cr-8Mo)+(800Ti+700Nb+600V+500W)... (1)
In formula (1), the element symbol represents the content (mass %) of the element in the metal wire.
[2] Part of the Fe is replaced with, in mass%,
a group containing one or more of Cu: 5.0% or less, Co: 5.0% or less, and B: 1.0% or less;
a group containing one or more of Sn: 0.5% or less, Sb: 0.5% or less, Au: 0.5% or less, and In: 0.5% or less;
a group containing one or more of Mg: 0.02% or less, Ca: 0.02% or less, Hf: 0.02% or less, and REM: 0.02% or less;
The metal wire for deposition additive manufacturing using a metal 3D printer according to [1], characterized in that it contains an element included in one or more of the following groups: Ta: 2.0% or less, Zr: 2.0% or less, Pb: 0.4% or less, and Ag: 0.4% or less.

[2A] The metal wire for deposition additive manufacturing using a metal 3D printer according to [1], characterized in that it further contains, in mass%, one or more of Cu: 5.0% or less, Co: 5.0% or less, and B: 1.0% or less in place of a portion of the Fe.
[2B] The metal wire for deposition additive manufacturing using a metal 3D printer according to [1] or [2A], characterized in that it further contains, in mass%, one or more of Sn: 0.5% or less, Sb: 0.5% or less, Au: 0.5% or less, and In: 0.5% or less in place of a portion of the Fe.
[2C] The metal wire for deposition additive manufacturing using a metal 3D printer according to any one of [1], [2A] and [2B], characterized in that it further contains, in mass%, one or more of Mg: 0.02% or less, Ca: 0.02% or less, Hf: 0.02% or less, and REM: 0.02% or less in place of a portion of the Fe.
[2D] The metal wire for deposition additive manufacturing using a metal 3D printer according to any one of [1], [2A], [2B], and [2C], characterized in that it further contains, in mass%, one or more of Ta: 2.0% or less, Zr: 2.0% or less, Pb: 0.4% or less, and Ag: 0.4% or less in place of a portion of the Fe.

[3] A metal wire for deposition additive manufacturing using a metal 3D printer according to any one of [1] to [2D], characterized in that the metal wire is used as a welding material to be deposited by MIG arc welding, and when cooled at an average cooling rate of 1°C/s to 10°C/s from the end of welding to 500°C, the amount of retained austenite is 5% to 50%.
[4] An additive manufacturing product characterized in that a plurality of layers having the component composition according to any one of [1] to [2D] are formed by deposition additive manufacturing, and the amount of retained austenite is 5% to 50%.
[5] The method for manufacturing an additive manufacturing product according to claim 4, characterized in that the metal wire for additive manufacturing by a metal 3D printer according to any one of [1] to [2D] is used as a welding material for additive manufacturing by MIG arc welding, and then the metal wire is cooled from the end of welding to 500°C at an average cooling rate of 1°C/s to 10°C/s.

The present invention provides metal wire for additive manufacturing using metal 3D printers, additive manufacturing products, and methods for manufacturing additive manufacturing products, which maintain the high hardness and corrosion resistance required for additive manufacturing products while ensuring material uniformity and wear resistance and suppressing cracking.

The requirements of the present invention are explained below. Note that (%) in the following explanation refers to mass (%) unless otherwise specified.

The present invention relates to an additively manufactured product that maintains the required high hardness and corrosion resistance, while ensuring material uniformity and wear resistance and suppressing quench cracks. Here, the required high hardness means that the additively manufactured product has an Hv of 700 or more. The material uniformity means that the difference between the maximum and minimum Hv values is 80 or less when the Hv values are measured at at least five points on the additively manufactured product.
The additive manufacturing product can be produced by using the metal wire for additive manufacturing using the metal 3D printer of the present invention as a welding material and performing additive manufacturing using MIG arc welding with the metal 3D printer to produce a three-dimensional product.

The additively manufactured product can achieve the quality targeted by the present invention by containing the specified components specified below and having a retained austenite content of 5% to 50% in the steel.

First, the essential component composition of the metal wire and layered manufacturing product of the present invention will be described.
C is contained in an amount of more than 0.35% in order to ensure the necessary hardness and the necessary amount of retained austenite. It is preferably 0.40% or more. On the other hand, if C exceeds 1.2%, it becomes difficult to ensure the uniformity of the material and to suppress cracking. It is preferably 0.80% or less.

Si is effective for deoxidation during welding, but adding too much can cause a deterioration in material uniformity and promote the precipitation of intermetallic compounds during additive manufacturing, which can lead to cracking. Therefore, it is limited to 3.0% or less. Preferably, it is 0.05% or more and 2.0% or less. Si does not necessarily need to be included.

Mn is effective for deoxidation during welding, but adding too much stabilizes the austenite structure, making it difficult to harden and preventing material uniformity. Therefore, it is limited to 3.0% or less. Preferably, it is 0.05% or more and 2.0% or less. Mn does not have to be included.

P is limited to 0.1% or less to ensure material uniformity. Preferably, it is 0.05% or less. The lower the P content, the better, and there is no lower limit.

To ensure material uniformity, the upper limit of S is set at 0.4%. Preferably, it is 0.0004 to 0.10%.

Ni may be added as needed to improve the toughness and corrosion resistance of the matrix, but if it exceeds 2.0%, austenite will form and stable material uniformity will not be achieved, so the upper limit is set at 2.0%. The preferred range is 0.1 to 1.0%.

Cr is added in an amount of 10% or more to ensure material uniformity and corrosion resistance (durability). However, adding more than 17% can actually result in uneven material and metal structure. For this reason, the upper limit is set at 17%. Preferably, it is between 10.5% and 16.5%.

Mo is added to improve the corrosion resistance of the matrix, but adding more than 3.0% can cause the material and metal structure to become non-uniform. Therefore, the upper limit is set to 3.0%. Preferably, it is 0.1 to 2.0%. Mo does not need to be added.

Al is effective for deoxidation during welding, but adding too much prevents the stable formation of martensite structure and reduces material uniformity. Therefore, the upper limit is set at 2.0%. Preferably, it is 0.001 to 1.2%. It is not necessary to add Al.

N is limited to 0.15% or less to ensure material uniformity. If N exceeds 0.15%, it promotes the precipitation of carbonitride precipitates, resulting in variations in hardness and metal structure. Preferably, N is 0.05% or less. More preferably, N is 0.03% or less. The lower the N content, the better, and there is no lower limit.

O is contained at 0.015% or less to ensure adequate fluidity during welding. Adding more than 0.015% reduces material uniformity, so the upper limit is set at 0.015%. The preferred range is 0.001 to 0.01%.

Ti: 0.03-0.2%, Nb: 0.03-0.5%, V: 0.03-0.5%, W: 0.03-0.5%
The inclusion of Ti, Nb, V, and W makes it possible to utilize the hard carbides of these elements to improve wear resistance. Therefore, the content of each of Ti, Nb, V, and W is set to 0.03% or more. On the other hand, if the content of any of these elements is too high, the material uniformity decreases, so the content of Ti is set to 0.2% or less, and the content of Nb, V, and W is set to 0.5% or less.

Equation (1) above is the carbonitride index D, which indicates the degree of influence that the content of elements in steel has on carbonitride formation. The part enclosed in parentheses on the left side of the right side of equation (1) represents the Ms point, i.e., the temperature at which austenite begins to transform to martensite when cooled from a high temperature. Furthermore, the part enclosed in parentheses on the right side of equation (1) represents the empirical effect of each element on the carbonitride index D, based on data on the carbide formation energy associated with the inclusion of each element. By setting the carbonitride index D calculated using equation (1) to 100 or greater, the amount of retained austenite in the steel of an additively manufactured product can be adjusted to be below the upper limit of the preferred range of the present invention. Preferably, the carbonitride index D is 150 or greater. If the carbonitride index D is less than 100, combined with the higher C and Cr contents, the amount of retained austenite will exceed the upper limit.

The metal wire and additive manufacturing product of the present invention consist of the remainder Fe and impurities. Furthermore, it is preferable that the following components be selectively contained in place of a portion of the Fe.

Cu, Co, and B may be added as needed to improve the toughness of the matrix. However, if the Cu or Co content exceeds 5.0% each, or if the B content exceeds 1.0%, the material uniformity will deteriorate. Therefore, the upper limits for Cu and Co are set to 5.0%, and for B to 1.0%. Preferably, Cu is 4.0% or less, Co is 4.0% or less, and B is 0.3% or less.

Sn, Sb, Au, and In may be added as needed to improve the corrosion resistance of the matrix. However, adding more than 0.5% of each element will degrade material uniformity. Therefore, the upper limit is set at 0.5%. Preferably, it should be 0.4% or less.

Mg, Ca, Hf, and REM are effective for deoxidation during welding and may be added as needed. However, excessive addition of these elements can degrade material uniformity. Therefore, each element should be limited to 0.02% or less. Preferably, it should be 0.01% or less.

Ta and Zr may be added as needed to form fine precipitates in the matrix, improving heat resistance (thermal deformation resistance). Pb and Ag may also be added as needed to improve machinability after 3D printing. However, if the Ta and Zr contents exceed 2.0% each, or if the Pb and Ag contents exceed 0.4% each, material uniformity will deteriorate. Therefore, the upper limits for Ta and Zr are set at 2.0%, and for Pb and Ag at 0.4%. Preferably, Ta and Zr are 1.0% or less, and Pb and Ag are 0.3% or less.

The metal wire of the present invention has a chemical composition that includes Fe and impurities in addition to the elements described above. That is, the metal wire of the present invention is a stainless steel metal wire.
Typical unavoidable impurities include Ge, Na, Be, F, Ga, etc., and these elements are usually mixed in the steel manufacturing process as unavoidable impurities in amounts of 0.01% or less.
Furthermore, although typical optional added elements are specified in [2] above, elements not described in this specification may also be contained within a range that does not impair the effects of the present invention.

Next, we will explain the amount of retained austenite in the steel of the additively manufactured product. The additively manufactured product of the present invention contains the specified components as defined above, and the amount of retained austenite in the steel is specified to be 5% to 50%. Because retained austenite is soft and tough, the generation of 5% or more retained austenite has the effect of relieving stress against quench cracking in the hard martensite phase. However, because retained austenite has lower strength than martensite, if the amount of retained austenite exceeds 50%, the hardness and wear resistance of the additively manufactured product will decrease. Furthermore, the amount of retained austenite in the steel is preferably 15% to 40%.

In other words, the additively manufactured product of the present invention is formed by layer deposition of multiple layers having the component composition of the present invention, and is characterized by having a retained austenite content of 5% to 50%.

The method for manufacturing an AM product of the present invention is characterized by using a metal wire for AM using a metal 3D printer, having the composition of the present invention, as a welding material, to perform AM by MIG arc welding, followed by cooling at an average cooling rate of 1°C/s to 10°C/s from the end of welding to 500°C. By using metal wire having the composition of the present invention and adjusting the average cooling rate from the end of welding after AM to 500°C, within the range of 1°C/s to 10°C/s, the amount of retained austenite can be adjusted to 5% to 50%. The slower the cooling rate after AM, the more likely it is to reduce the amount of retained austenite. Therefore, when using metal wire with a predetermined composition within the composition range of the present invention and cooling at an average cooling rate within the range of 1°C/s to 10°C/s, if the amount of retained austenite is too low, the average cooling rate can be increased, and if the amount of retained austenite is too high, the average cooling rate can be decreased, resulting in the amount of retained austenite falling within the range of the present invention. The average cooling rate is set between 1°C/s and 10°C/s because slow cooling (gradual cooling) below 1°C/s causes the austenite phase after molding to change to ferrite, reducing hardness, and above 10°C/s causes thermal stress due to the temperature difference in the molded product and tensile stress due to martensitic transformation, resulting in quench cracks.

The fact that the metal wire for additive manufacturing using a metal 3D printer of the present invention can achieve the above-mentioned suitable amount of retained austenite when used as a welding material for additive manufacturing using a metal 3D printer and then MIG arc welding to achieve the desired amount of retained austenite can be confirmed by the fact that when the metal wire is used as a welding material for additive manufacturing using a metal 3D printer, the amount of retained austenite is 5% to 50% when the metal wire is MIG arc welded and cooled at an average cooling rate of 1°C/s to 10°C/s from the end of welding to the Cr carbide precipitation temperature range of 500°C. When cooled at a predetermined average cooling rate within the range of 1°C/s to 10°C/s, if the amount of retained austenite is too low, the average cooling rate is increased, and if the amount of retained austenite is too high, the average cooling rate is decreased. As a result, if the amount of retained austenite falls within the range of the present invention, the present invention is met; if not, the present invention is not met.

The metal wire of the present invention is used for additive manufacturing using a metal 3D printer. In other words, it refers to a metal wire used as a material when a metal 3D printer is used to build up weld beads of metal wire to form three-dimensional parts.

The present invention as described above provides metal wire for additive manufacturing using metal 3D printers, additive manufacturing products, and methods for manufacturing additive manufacturing products, which maintain the high hardness and corrosion resistance required for additive manufacturing products while ensuring material uniformity and wear resistance and suppressing quench cracks.

Example 1
Steels having the chemical compositions shown in Tables 1 to 3 were melted in a 45 kg vacuum melting furnace and processed into steel bars having a diameter of 11 mm by hot forging and hot extrusion. These were then repeatedly drawn and annealed to produce metal wires having a diameter of 1.2 mm. In Tables 2 and 3 and Tables 5 and 6 described below, values outside the ranges of the present invention are underlined.

The prototype metal wire was then repeatedly welded in a spiral pattern using a robotic MIG arc welder. Three-dimensional modeling was performed by stacking the wires in a stacking direction perpendicular to the welding direction, producing a hollow rectangular prism. Arc welding conditions included a shielding gas of Ar + 3% oxygen, a welding current of 200 A, an arc voltage of 30 V, and a welding speed of 200 cm/min. After the welded additive manufacturing process, the wire was cooled at an average cooling rate of 2.8 °C/s from the end of welding to 500 °C. The amount of retained austenite was evaluated. If the amount of retained austenite was outside the range of 5% to 50%, the average cooling rate was increased if the amount of retained austenite was too low, or decreased if the amount of retained austenite was too high, within the range of 1 °C/s to 10 °C/s from the end of welding to 500 °C. As a result, the amount of retained austenite was adjusted to fall within the range of the present invention. Some comparative examples could not be adjusted to fall within the range of the present invention.
The average cooling rate was measured by an infrared thermograph (thermal imaging camera) as the cooling time from the temperature of the molded article after welding to the Cr carbide precipitation temperature range of 500°C.

The manufactured square pillars were then inspected for hardness, material uniformity, wear resistance, and the presence of quench cracks. The inspection results are shown in Tables 4 and 5.

The amount of retained austenite was measured by preparing a test piece of φ5 mm×20 mm from a square pillar by electrical discharge machining and measuring it with a saturation magnetization measuring device.
The central hardness was measured using a Vickers hardness tester by embedding a cross section cut out from a square pillar perpendicular to the lamination direction in resin and polishing it, and measuring the HV hardness (load 10 kg) at the central part in the lamination direction.
To measure material uniformity, a cross section perpendicular to the stacking direction cut from a square pillar was embedded in resin and polished, and the HV hardness (load 1 kg) was measured at five points: the bottom surface of the additive manufacturing product, 1/4, 1/2, 3/4 height, and the top surface. The difference between the maximum and minimum HV values at the five points was taken as the hardness variation ΔHV. If ΔHV was 40 or less, it was marked as ◎, if it was more than 40 but less than 80, it was marked as ○, and if it was more than 80, it was marked as ×.

The wear resistance was evaluated using a pin-on-disk friction and wear tester by cutting a φ5mm x 10mm test piece (pin) from a square pillar. The disk used as the opposing wear material was emery paper (#800) with hard SiC particles bonded to it. The abrasive grain hardness corresponds to approximately 3200HV. The test piece was fixed to a sample holder, and the surface of the test piece was pressed against the rotating opposing wear material with a test load of 20N, at a sliding speed of 0.66m/s and for 30 seconds. The volume of material lost due to wear was calculated from the difference in sample thickness before and after the test, and this was taken as the wear loss V (mm ³ ). The specific wear rate C (mm ² /N) was then calculated using the following formula (2), and was marked as ◯ if it was 5.0×10 ^-8 mm ² /N or less, or × if it was greater than 5.0×10 ^-8 mm ² /N.
Specific wear amount C = wear loss amount V / (test load W × friction distance L) ... (2)

To evaluate cracking, the outer and inner surfaces of the additively manufactured product were visually inspected, with a mark of "O" indicating no cracks and a mark of "X" indicating cracks.

In additive manufacturing products using the metal wire of the present invention, the amount of retained austenite was within the preferred range of the present invention, ensuring material uniformity and wear resistance while maintaining the required high hardness, and suppressing quench cracking.

On the other hand, it is clear that the comparative steels a to ak do not satisfy the ranges specified in the present invention and do not satisfy the required properties.
In the comparative steels a, n, and aj, the carbonitride index D value is below the lower limit and the amount of retained austenite exceeds the upper limit, so that the hardness is reduced and the material uniformity and wear resistance are poor.
Comparative steel r has a low Cr content, so it is difficult to harden (prone to uneven hardening), and the uniformity of hardness is poor.

Comparative steels c, o, and s had low C contents, which reduced the base material hardness and inferior wear resistance. Comparative steel s also had lower amounts of Ti, Nb, V, and W, which are hard carbide-forming elements effective for improving wear resistance, which was another factor contributing to the deterioration. Furthermore, the amounts of retained austenite in these comparative steels c, o, and s were low, which resulted in little stress relaxation due to the retained austenite, and quench cracking occurred.
The comparative steels i, ai, aj and ak had reduced wear resistance because the contents of Ti, Nb, V and W, which are hard carbide-forming elements effective for wear resistance, were outside the lower limits.

Comparative steels c, f, and s had almost no untransformed austenite, resulting in quench cracking. It is believed that this quench cracking was caused by the large strain that accompanies volume expansion during martensitic transformation.

Example 2
Additive manufacturing products were produced using Steel B of the present invention shown in Table 1 of Example 1, with the average cooling rate from the end of welding to 500°C set to five conditions shown in Table 6 below, and the other conditions being the same as those of Example 1. The amount of retained austenite for each was evaluated and shown in Table 6. As is clear from Table 6, a relationship can be seen in which the amount of retained austenite decreases as the cooling rate slows.

Claims (5)

In mass%,
It has a chemical composition including C: more than 0.35% to 1.2% or less, Si: 3.0% or less, Mn: 3.0% or less, P: 0.1% or less, S: 0.4% or less, Ni: 2.0% or less, Cr: 10 to 17%, Mo: 3.0% or less, Al: 2.0% or less, N: 0.15% or less, O: 0.015% or less, Ti: 0.03 to 0.2%, Nb: 0.03 to 0.5%, V: 0.03 to 0.5%, W: 0.03 to 0.5%, with the balance being Fe and unavoidable impurities;
A metal wire for deposition additive manufacturing using a metal 3D printer, characterized in that the carbonitride index D value defined by the following formula (1) is 100 or more.
Carbonitride index D=(500-400C-30Mn-15Ni-12Cr-8Mo)+(800Ti+700Nb+600V+500W)... (1)
In formula (1), the element symbol represents the content (mass %) of the element in the metal wire. In place of a part of the Fe, further in mass %,
a group containing one or more of Cu: 5.0% or less, Co: 5.0% or less, and B: 1.0% or less;
a group containing one or more of Sn: 0.5% or less, Sb: 0.5% or less, Au: 0.5% or less, and In: 0.5% or less;
a group containing one or more of Mg: 0.02% or less, Ca: 0.02% or less, Hf: 0.02% or less, and REM: 0.02% or less;
The metal wire for deposition additive manufacturing using a metal 3D printer according to claim 1, characterized in that it contains one or more elements from a group containing one or more of Ta: 2.0% or less, Zr: 2.0% or less, Pb: 0.4% or less, and Ag: 0.4% or less. The metal wire for additive manufacturing using a metal 3D printer according to claim 1 or 2, characterized in that when the metal wire is used as a welding material for MIG arc welding and cooled at an average cooling rate of 1°C/s to 10°C/s from the end of welding to 500°C, the amount of retained austenite is 5% to 50%. An additively manufactured product formed by deposition additive manufacturing of multiple layers having the component composition described in claim 1 or 2, characterized in that the amount of retained austenite is 5% to 50%. The method for manufacturing an additive manufacturing product according to claim 4, characterized in that the metal wire for additive manufacturing by a metal 3D printer according to claim 1 or 2 is used as a welding material to perform additive manufacturing by MIG arc welding, and then cooling is performed from the end of welding to 500°C at an average cooling rate of 1°C/s to 10°C/s.