Method for manufacturing a stacked structure and stacked structure

Abstract

Method for manufacturing a laminated structure. For a powder material including a first powder containing a precipitation-hardening stainless steel and a second powder containing titanium carbide, a laser beam is oscillated and irradiated to melt and solidify the powder, and at least one hardened build-up layer is laminated on a substrate. The process of laminating the build-up layer is a process that satisfies 20 ≤ A ≤ 35, 1.1 ≤ B ≤ 1.3, and 40 mass% ≤ R2 ≤ 65 mass%. Here, A is the laser linear energy index, B is the powder supply speed index, and R2 is the ratio of the second powder contained in the powder material.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a laminated object and a laminated object. Background Art

[0002] Generally, in the manufacture of parts that require abrasion resistance, a method is adopted in which a material excellent in abrasion resistance (high hardness) is built up on the surface by welding or thermal spraying, or the entire part is formed from a powder material that satisfies the required characteristics by powder sintering (die forming + HIP, etc.) or additive manufacturing. In addition, a method is also adopted in which after forming a powder sintered body, it is joined to the surface of a part by diffusion bonding, brazing, or the like.

[0003] For parts that require such abrasion resistance, for example, materials containing metal, ceramic, or cermet can be used. When performing surfacing, forming, or laminated modeling of these materials, the problems are, in addition to ensuring the bonding strength with the base material and the density of the surfacing layer, especially to avoid cracks during processing. In addition, for the high life of the target parts, it is desired to form a surfacing layer with as high a hardness as possible and a large thickness (in the order of several mm). However, as the hardness and thickness increase, cracks are likely to occur during processing. Therefore, a method is required that can form the above-mentioned surfacing layer with high economy without being restricted by the size of the processed part.

[0004] For example, Patent Document 1 describes a technique in which a surfacing layer is formed by tungsten inert gas (TIG) welding using a filler material containing a ceramic reinforcing material in a high-hardness Ni-based alloy.

[0005] In addition, Patent Document 2 describes a technique in which, in the surfacing of an Fe-based welding wire in submerged arc welding (SAW) or gas metal arc welding (GMAW), a powder containing a boron carbide phase is added to the Fe-based substrate to form a relatively hard covering layer. In the examples of Patent Document 2, a structure of a surfacing layer with a Rockwell C hardness of HRc60 or more is shown, and it rises to around HRc70 depending on the alloy type.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-171644

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-501630 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] However, in the case of Patent Document 1, in addition to the improvement in weldability, although the hardness of the deposited layer formed also increases, a hardness of only about HRc50 can be obtained near the surface of the deposited layer. In addition, a filler material with high particularity is required.

[0012] In the case of Patent Document 2, in SAW, it is generally necessary to lay a flux layer on the side to be welded and perform welding in this state. The scale of the equipment is large and it is not suitable for surfacing of medium and small parts. In addition, the construction process is also complicated. In the examples of GMAW, based on the evaluation of the number of cracks in the welded test specimens produced, it is considered difficult to avoid the generation of welding cracks by the same method and form a deposited layer with a hardness of HRc60 or more.

[0013] For surface hardening alloys generally sold on the market (for example, tungsten carbide alloys of Kennametal-Stellite (Stellite is a registered trademark), and some products of nickel-based hard surface alloys of Wall Colmonoy (Colmonoy is a registered trademark)), there are products with a hardness range of HRc60 or more (~about HRc64). However, these materials have high particularity and it is mostly difficult to set appropriate welding conditions. In addition, in high-velocity oxy-fuel spraying (HVOF) using tungsten-based hard alloy powders, although a layer with a hardness of about HRc70 can be obtained for some materials, the hardened layer formed during HVOF is thin (less than 1 mm), and there are problems of low density and low adhesion to the substrate compared with welding.

[0014] Therefore, an object of the present invention is to provide a method for manufacturing a laminated object and a laminated object, which have high hardness, can form a deposited layer with a thickness of several millimeters in one pass without generating welding cracks, and can perform stable surfacing with high economy without being restricted by size.

[0015] Means for Solving the Problem

[0016] The present invention is composed of the following.

[0017] (1) A method for manufacturing a laminated object, which is a method of irradiating a powder material including a first powder containing precipitation-hardening stainless steel and a second powder containing titanium carbide with a laser beam while swinging the laser beam to melt and solidify the powder material, and laminating at least one layer of deposited layer on a substrate, wherein

[0018] the process of laminating the deposited layer is a process that satisfies the following conditional expressions [1], [2], and [3].

[0019] 20 ≤ A ≤ 35... Conditional expression [1]

[0020] 1.1 ≤ B ≤ 1.3... Conditional expression [2]

[0021] 40 mass% ≤ R2 ≤ 65 mass%... Conditional expression [3]

[0022] A = P × α / β [kJ / cm]: Laser line energy index

[0023] B = Q × α / β [g / cm]: Powder supply rate index

[0024] P [W]: Line energy from the laser beam

[0025] Q [g / min]: Supply rate of the powder material

[0026] α = W / V1

[0027] β = V2 × t

[0028] W [cm]: Scanning width of the beam spot due to the oscillatory motion

[0029] V1 [cm / min]: Scanning speed of the laser beam due to the oscillatory motion

[0030] V2 [cm / min]: Forward speed in the welding direction

[0031] t [sec]: Time for one cycle of oscillation

[0032] R2 [mass%]: Ratio of the second powder contained in the powder material

[0033] (2) A laminated structure is a laminated structure in which at least one surfacing layer containing a precipitation hardening type stainless steel alloy and titanium carbide is formed on a substrate. Among them,

[0034] The thickness of each surfacing layer is 3 mm or more and 5 mm or less, and the Rockwell C hardness of the surfacing layer is HRc60 or more and HRc65 or less.

[0035] The occupied area ratio R1 of the titanium carbide region in the microstructural observation image of the surfacing layer is 50 area% or more and 65 area% or less.

[0036] Advantages of the Invention

[0037] According to the present invention, without generating welding cracks, a surfacing layer with a high hardness and a thickness of several millimeters can be formed in one pass. In addition, stable surfacing can be carried out with high economy without size limitations. Brief Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of a laser powder surfacing apparatus for performing surfacing.

[0039] Figure 2 It is an enlarged cross-sectional view of the main part of a welding head in a welding state where the welding head is moved along the welding direction.

[0040] Figure 3 It is a schematic cross-sectional view of a laminated structure in which a single-layer surfacing layer is formed from a powder material on a base material.

[0041] Figure 4 It is an explanatory diagram schematically showing a state in which a surfacing layer is formed by melting and solidifying a powder material on a base material while causing a welding head to perform a swinging motion.

[0042] Figure 5 It shows Figure 4 an explanatory diagram of the operating conditions of the swing shown.

[0043] Figure 6 It is a graph showing the relationship between the content ratio of the second powder in each test example and the Rockwell C hardness of the surfacing layer.

[0044] Figure 7 It is an explanatory diagram showing the microstructure observation image (upper part) and the binary image (lower part) of the surfacing layer in Test Examples 2-1 to 3.

[0045] Figure 8 It is an explanatory diagram showing the microstructure observation image (upper part) and the binary image (lower part) of the surfacing layer in Test Examples 2-4 to 6.

[0046] Figure 9 It is a graph showing the relationship between the content ratio of the second powder in the powder material in Test Examples 2-1 to 6 and the occupied area ratio R1 of the TiC region included in the surfacing layer.

[0047] Figure 10 It is a graph showing the relationship between the occupied area ratio of the TiC region included in the surfacing layer in Test Examples 2-1 to 6 and the Rockwell C hardness. Detailed implementation mode

[0048] Hereinafter, with reference to the accompanying drawings, the embodiments of the present invention will be described in detail.

[0049] The method for manufacturing the laminated structure of the present invention is a method of supplying a powder material obtained by mixing a first powder containing stainless steel powder and a second powder containing titanium carbide (TiC: titanium carbide) to a base material, and irradiating a laser beam with a swing to laminate at least one hardened surfacing layer formed by melting and solidifying the powder material on the base material.

[0050] When laminating the hardened surfacing layer, as will be described in detail later, welding cracks can be prevented from occurring, and a surfacing layer with a thickness of mm level per pass can be formed with high hardness and stability. Here, one pass means one scanning path of the laser beam.

[0051] In the following description, an example of melting a powder material used for forming a hardfacing layer by laser metal deposition (LMD) is described, but the manufacturing method of this layered object is not limited thereto. For example, the laser additive manufacturing (LAM) method, direct metal laser sintering (DMLS), etc. can also be applied to the present invention. Especially in the case of laser metal deposition, since a welding robot can be used to weld the workpiece, it has the advantage of being able to improve the shape freedom of the layered object compared to the case of machining the workpiece in a working chamber.

[0052] [Laser Metal Deposition Device]

[0053] Figure 1 is a schematic structural diagram of a laser metal deposition device 100 for performing hardfacing.

[0054] The laser metal deposition device (hereinafter referred to as the LMD device.) 100 includes a welding robot 11, a laser light source unit 13, a powder material supply unit 15, and a control unit 17.

[0055] The welding robot 11 is an articulated robot provided with a swing drive unit 19 and a welding head 21 on the front end shaft. The position and posture of the welding head 21 can be arbitrarily and three-dimensionally set within the freedom range of the robotic arm. In addition, the swing drive unit 19 swings the welding head 21 in a direction crossing the welding line.

[0056] The laser light source unit 13 supplies a laser beam to the welding head 21 through an optical fiber 23. The powder material supply unit 15 supplies a powder material 39 (refer to the following Figure 2 ) for forming a hardfacing layer described later to the welding head 21 through a powder supply pipe 25. The control unit 17 includes a laser output adjustment unit 27 for adjusting the laser output power of the laser light source unit 13, and a powder material supply adjustment unit 29 for adjusting the supply amount of the powder material 39 from the powder material supply unit 15 to the welding head 21, and drives and controls each part of the LMD device 100 in an integrated manner.

[0057] The drive control performed by the control unit 17 is executed by a computer according to a program. In other words, the control unit 17 is a computer device having: a processor such as a CPU; a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory); and a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). In this case, the functions of the respective parts can be realized by the processor executing a prescribed program stored in the memory or the storage device.

[0058] Figure 2 It is an enlarged partial cross-sectional view of the main part of the welding head 21 in a state where the welding head 21 is moved along the welding direction TD while welding.

[0059] The welding head 21 is a head for laser welding using CO2 laser, YAG laser, fiber laser, disk laser, etc., and the type of laser is appropriately selected according to the laminated molded object to be produced, etc.

[0060] At the front end of the welding head 21, a laser irradiation port 31, a powder material supply port 33, and a shielding gas supply port 35 are provided.

[0061] The laser irradiation port 31 is opened at the center of the front end of the welding head 21, and the laser beam LB emitted from the laser irradiation port 31 is irradiated onto the base material 37. The laser beam LB is oscillated in the laser light source unit 13 and guided to the welding head 21 through the optical fiber 23. The linear energy of the laser beam LB acting on the welding part can be arbitrarily controlled by adjusting the intensity of the laser beam LB by the laser output adjustment unit 27.

[0062] The powder material supply port 33 is opened concentrically on the radially outer side of the laser irradiation port 31 at the front end of the welding head 21, and the powder material 39 supplied by the powder material supply unit 15 is jetted from the powder material supply port 33 onto the base material 37. The supply amount of the powder material 39 to the base material 37 can be arbitrarily controlled by the powder material supply unit 15.

[0063] In addition, the powder material supply unit 15 jets the powder material 39 together with a carrier gas from an unillustrated carrier gas supply unit from the powder material supply port 33. The powder material 39 jetted toward the base material 37 is melted by the converging laser beam LB on the surface of the base material 37 and then cooled and solidified to form a build-up layer 41.

[0064] The shielding gas supply port 35 is opened concentrically outside the powder material supply port 33 at the front end of the welding head 21, and the shielding gas G is supplied toward the base material 37. The shielding gas G suppresses oxidation of the build-up layer 41 and its periphery.

[0065] The structure of the above-described laser powder surfacing apparatus 100 is an example and is not limited thereto.

[0066] [Powder material]

[0067] The powder material supply unit 15 mechanically mixes a first powder containing a precipitation hardening type stainless steel alloy, such as SUS630 or SUS631, or a precipitation hardening type Fe alloy, such as maraging steel, and a second powder containing titanium carbide (hereinafter referred to as TiC) to prepare a powder material 39 for forming a surfacing layer. Here, the term "mechanically mix" means that different types of powder bodies are stirred and mixed with each other without any special processing.

[0068] In addition, the mixing of the first powder and the second powder can be carried out in the powder material supply unit 15, or can be carried out at a position different from the powder material supply unit 15, such as a mixer (not shown) provided in the supply path up to the welding head 21.

[0069] The powder material 39 is generally prepared by mechanically mixing commercially available powders and does not require complicated pretreatment like special powder materials for surfacing. In the manufacturing method of this laminated object, since commercially available powder materials are directly used as the first powder and the second powder, the economy is excellent.

[0070] The powder material 39 used here contains the second powder (TiC) in the range of 40% by mass or more and 65% by mass or less based on the total amount of the powder material 39. The lower limit of the content of the second powder is preferably 45% by mass or more, more preferably 50% by mass or more, and the upper limit is 65% by mass or less, preferably 63% by mass or less, more preferably 60% by mass or less. (In addition, a range set by arbitrarily combining any of the above-mentioned lower limit values and any of the upper limit values can also be said to be a preferred range.)

[0071] [Base material]

[0072] The base material 37 is in a flat plate shape, but is not limited thereto, and can also be a plate, block, or tubular body having a curved surface, and an appropriate shape is adopted according to the shape of the laminated object to be manufactured. In addition to steel materials such as stainless steel, the material of the base material 37 can also be a cobalt-based or nickel-based alloy, and various materials can be adopted according to the specifications of the product.

[0073] [Formation of surfacing layer (laminated object)]

[0074] Figure 1 The shown LMD apparatus 100 swings the welding head 21 by the swing drive unit 19 while moving the welding head 21 in the welding direction TD (Figure 2 ) Move upward while performing laser powder surfacing welding. Thereby, a surfacing layer 41 formed by melting and solidifying the powder material 39 is laminated on the base material 37 with a specified thickness.

[0075] Figure 3 It is a schematic cross-sectional view of a laminated object 43 in which a single-layer surfacing layer 41 is formed from the powder material 39 on the base material 37.

[0076] The laminated object 43 is formed by melting and solidifying a surfacing material containing precipitation-hardening stainless steel and TiC and laminating it on the base material 37, and has the base material 37 and a surfacing layer 41 composed of the surfacing material. More specifically, an intermediate layer 42 formed by mutual melting of a part of the base material 37 and a part of the surfacing layer 41 is formed between the base material 37 and the surfacing layer 41.

[0077] Although details will be described later, the thickness T1 of the surfacing layer 41 formed by a single welding (a layer formed by 1 pass) is 3 mm or more, preferably 3.5 mm or more and 5 mm or less, preferably 4.5 mm or less. In addition, the Rockwell C hardness of the surfacing layer 41 is 60 or more and 65 or less in HRc. Moreover, the occupancy area ratio R1 of the TiC region in the microstructural observation image of the surfacing layer 41 is 50 area% or more and 65 area% or less.

[0078] By making the content ratio of TiC in the powder material 39 reach 40 mass% or more as described above, the surface hardness of the surfacing layer 41 can surely reach 60 or more in Rockwell C hardness.

[0079] In the laminated object 43, the surfacing layer 41 with a thickness of 3 mm or more and 5 mm or less per layer (1 pass) can be laminated in multiple layers. Accordingly, even when the surfacing layer 41 of the target shape cannot be formed in one pass, a thick object can be formed by repeatedly forming the surfacing layer 41 in multiple passes. Therefore, a shape with a high degree of design freedom can be performed.

[0080] The above-mentioned Rockwell C hardness is an index corresponding to the content of the second powder (TiC) in the powder material 39 used when forming the surfacing layer 41. The lower limit value of the above-mentioned Rockwell C hardness corresponds to the lower limit value of the second powder content when the content of the second powder in the powder material 39 is small and the hardness increase effect obtained by adding the second powder is small. When the Rockwell C hardness is in the range of HRc60 to HRc65 of the target hardness, compared with the case where the content of the second powder is lower than the lower limit value, in addition to a significant increase in the hardness of the surfacing layer 41, welding cracks during surfacing can be avoided. In addition, when the Rockwell C hardness exceeds HRc65 as the upper limit value, welding cracks are likely to occur during surfacing.

[0081] In other words, by making the ratio (also known as the content ratio) R2 of TiC contained in the powder material 39 fall within the above range, it is possible to achieve an appropriate hardness (Rockwell C hardness HRc60 - HRc65) in the surfacing layer 41 that is difficult to develop welding cracks.

[0082] Moreover, if the occupied area ratio R1 of the TiC region in the microstructural observation image of the surfacing layer 41 is less than 50 area%, the TiC content is low, and thus it is difficult to achieve the above target hardness. When the occupied area ratio R1 is 50 area% or more and 65 area% or less, no welding cracks will occur in the surfacing layer 41, and the target hardness can be stably achieved. Additionally, when the occupied area ratio R1 exceeds 65 area%, the TiC content becomes excessive, and welding cracks are likely to occur.

[0083] <Oscillatory motion>

[0084] Next, while appropriately referring to Figure 1 , Figure 2 , an explanation will be given for the oscillatory motion during the formation of the surfacing layer 41.

[0085] Figure 4 is an explanatory diagram schematically showing a state in which the powder material 39 is melted and solidified on the base material 37 while the welding head 21 is undergoing an oscillatory motion.

[0086] To form the surfacing layer 41 from the powder material 39 on the surface of the base material 37, the oscillatory motion of the welding head 21 is repeated to scan the laser beam LB emitted from the welding head 21. Specifically, the welding head 21 is swung by the swing drive unit 19 to scan the laser beam LB irradiated on the base material 37 with a specified width as shown in Figure 4 . The specified width mentioned here is the scanning width W of the beam spot S during the oscillatory motion.

[0087] Together with the oscillatory motion, the robotic arm of the welding robot 11 is driven to move the welding head 21 forward in the welding direction TD. Through the scanning of this laser beam LB and the movement of the welding head 21 in the welding direction TD, a weld bead formed by melting and solidifying the powder material 39 is widely formed on the surface of the base material 37. Then, the next weld bead adjacent to the already formed weld bead is formed in such a way that a part of the scanning width W overlaps with the existing weld bead. By repeating this operation, the surfacing layer 41 composed of multiple rows of weld beads is laminated without gaps on the surface of the base material 37.

[0088] Figure 5 is an explanatory diagram showing Figure 4 the operating conditions of the oscillation shown.

[0089] Operations for the stacked surfacing layer 41 include an operation of oscillating the laser beam LB with a scan width W and an operation of advancing the welding head 21 in the welding direction TD. Here, let the scan speed of the welding head 21 in the oscillation direction (scan direction) be V1, and the advancing speed (welding speed) in the welding direction TD be V2, and the time required for each cycle of the oscillating motion be t.

[0090] In the process of the stacked surfacing layer 41, the following conditional expressions [1], [2], and [3] are satisfied.

[0091] 20 ≤ A ≤ 35... Conditional expression [1]

[0092] 1.1 ≤ B ≤ 1.3... Conditional expression [2]

[0093] 40 mass% ≤ R2 ≤ 65 mass%... Conditional expression [3]

[0094] Here, the parameters in the conditional expressions [1], [2], and [3] are as follows.

[0095] A = P × α / β [kJ / cm]: Laser line energy index

[0096] B = Q × α / β [g / cm]: Powder supply speed index

[0097] P [W]: Linear energy from the laser beam

[0098] Q [g / min]: Supply speed of the powder material

[0099] α = W / V1

[0100] β = V2 × t

[0101] W [cm]: Scan width of the beam spot brought by the oscillating motion

[0102] V1 [cm / min]: Scan speed of the laser beam brought by the oscillating motion

[0103] V2 [cm / min]: Advancing speed in the welding direction

[0104] t [sec]: Time for one cycle of oscillation

[0105] R2 [mass%]: Ratio of the second powder contained in the powder material

[0106] Conditional expression [1] represents an appropriate range of the laser line energy index A, which represents the linear energy of the laser beam LB irradiated on the powder material 39 on the base material 37. The laser line energy index A means the laser line energy per unit welding line during oscillating welding, and 20 ≤ A ≤ 35, preferably 20 ≤ A ≤ 30.

[0107] When the laser line energy index A is less than 20, the following problems occur: insufficient laser line energy causes incomplete melting of the powder material, occurrence of an unmelted result, or cracks during surfacing. In addition, when 20 ≤ A ≤ 35 (where B also satisfies conditional expression [2]), both of the following first and second conditions are satisfied.

[0108] · First condition: The Rockwell C hardness of the aforementioned surfacing layer 41 is 60 or more and 65 or less HRc.

[0109] · Second condition: The thickness Ta of the surfacing layer 41 formed in one pass is 3 mm or more and 5 mm or less.

[0110] Moreover, when the laser line energy index A exceeds 35, due to excessive laser line energy, the penetration of the base material 37 is large, and it is difficult for the hardness of the surfacing layer 41 under the first condition to reach 60 or more HRc.

[0111] Conditional expression [2] represents the appropriate range of the powder supply index B representing the supply speed of the powder material 39 supplied to the base material 37. The powder supply index B means the powder supply weight per unit welding line during oscillating welding, and is 1.1 ≤ B ≤ 1.3, preferably 1.15 ≤ B ≤ 1.25.

[0112] When the powder supply index B is less than 1.1, it is difficult to form a surfacing layer 41 of 3 mm or more due to insufficient powder supply. Therefore, if the addition amount of TiC powder with a small specific gravity is increased in order to increase the thickness (volume) of the surfacing layer 41, as a result, the content of TiC in the surfacing layer 41 becomes excessive and welding cracks are likely to occur. In addition, when 1.1 ≤ B ≤ 1.3 (where A also satisfies conditional expression [1]), the aforementioned first and second conditions are stably satisfied. Moreover, if the powder supply index B exceeds 1.3, residual unmelted powder is likely to occur due to excessive supply of the powder material. If the proportion of stainless steel powder with a large specific gravity is increased in order to avoid residual molten powder and perform surfacing of a specified thickness, as a result, the content of TiC in the surfacing layer 41 becomes small and it is difficult to achieve the target hardness.

[0113] Conditional expression [3] represents the appropriate range of the ratio R2 of the second powder contained in the powder material 39. The content ratio R2 of the second powder is the mass ratio of the second powder to the total mass of the first powder and the second powder, and is 40 mass% ≤ R2 ≤ 65 mass%.

[0114] When the content ratio R2 of the second powder is less than 40% by mass, the content of TiC in the surfacing layer 41 is small, and it is difficult for the hardness of the surfacing layer 41 to reach 60 HRC or more. In addition, when 40% by mass ≤ R2 ≤ 65%, compared with the case where it is less than 40% by mass as described above, the hardness increases significantly, and welding cracks during surfacing can be avoided. Moreover, when the content ratio R2 exceeds 65% by mass, the content of TiC in the surfacing layer 41 becomes excessive, and welding cracks are likely to occur during surfacing.

[0115] <Oscillating irradiation of laser beam>

[0116] Next, the effect of the oscillating irradiation of the laser beam will be described.

[0117] Generally, because the laser beam has high directivity and energy density, when the laser beam is irradiated onto the base material, the area of the minute irradiation point is intensively heated. Therefore, depending on the conditions, a keyhole is formed on the base material, and the heating is limited to the vicinity of the irradiation point.

[0118] Therefore, when the laser beam LB is made to advance in the welding direction, by oscillating at a scanning speed faster than the advancing speed, the heating area is expanded corresponding to the scanning range, and the base material within the scanning range is heated evenly. The "oscillation" mentioned here is, for example, in butt arc welding, a method of swinging the welding torch in a direction crossing the welding line to evenly melt both base materials, thereby improving the weldability. In this configuration, it is applied to the scanning of the laser beam LB.

[0119] When welding is performed by applying oscillation to the laser beam LB, the time when the beam spot irradiates near the welded part on the base material 37 is longer than the case where the laser beam LB is usually moved along the welding line (without oscillation) for welding. In other words, by applying oscillation, the linear energy near the welded part can be increased, and the heating of the base material 37 can be promoted. Therefore, when the laser beam LB is irradiated over a wide range of the base material to which the powder material 39 is supplied, the temperature difference between the surfacing layer 41 formed by melting and solidifying the powder material 39 based on the linear energy from the laser beam LB and the surface of the base material 37 heated by the laser beam LB becomes smaller, and cracks in the surfacing layer 41 due to shrinkage strain after cooling can be suppressed.

[0120] In addition, since the oscillation of the laser beam LB increases the linear energy near the welding part, the supply amount of the powder material 39 is increased during welding, enabling surfacing with a large thickness per pass. In this case, the surface of the base material 37 is thickly covered with the powder material 39, and the linear energy from the laser beam LB is consumed by the melting of this powder material 39. Therefore, excessive heating of the base material 37 by the laser beam LB can be avoided, and the penetration amount is suppressed. As a result, it is possible to easily form a surfacing layer 41 with a thickness of about 1 layer mm. For a thickness of about 3 mm to 5 mm, multi-layer surfacing that requires multiple passes is not necessary. Therefore, compared with the case of repeated surfacing, the possibility of crack occurrence can be reduced. In addition, effects such as reducing dimensional limitations, cutting construction costs, and shortening the delivery cycle can also be achieved.

[0121] As described above, by simultaneously applying the oscillation plane to the laser beam LB and increasing the powder supply amount, it is possible to suppress excessive penetration of the base material 37 while achieving surfacing with a large thickness without cracking. Generally, in laser powder surfacing, the input energy brought by the laser beam LB is used for the melting of the supplied powder material and the direct heating of the base material. If within the ranges of the aforementioned conditional expressions [1] to [3], most of the linear energy from the laser beam LB will be used for the melting of the powder material 39, and excessive heating of the base material 37 can be suppressed. In addition, since the base material 37 is also heated by the thermal energy possessed by the molten powder material 39 itself, from this point of view, the occurrence of cracks can also be reduced. In other words, the aforementioned conditional expressions [1] to [3] appropriately adjust the balance of the following three functions: the function of suppressing excessive penetration of the base material 37; the function of preventing crack occurrence; the function of making the thickness of the surfacing layer 41 reach the order of several mm.

[0122] For example, in a state where the supply amount of the powder material is small, when oscillation is applied to the laser beam, the laser beam directly irradiates the base material, and almost all of the input energy is spent on heating the base material 37. As a result, the penetration amount of the base material 37 becomes large, and the surfacing layer 41 is diluted and the hardness is reduced. In this case, although cracks in the surfacing layer 41 can be avoided, the surfacing layer 41 is thin and surfacing of the order of several mm cannot be achieved.

[0123] Furthermore, the process of forming the surfacing layer 41 by the oscillation of the above laser beam LB is not limited to Figure 1 the process of swinging the welding head 21 while moving it with the robotic arm of the welding robot 11 as shown. For example, the laser beam LB can also be in a front-back beam mode, and the tasks can be divided into the melting of the powder material 39 and surfacing, and the heating of the base material 37 for construction. In addition, as a heating device for heating the base material 37, a heating device that heats by burner heating, high-frequency induction heating, etc. can also be used in combination. In this case, the scanning range of the oscillation can be reduced, and the forward speed in the welding direction TD can be increased, thereby shortening the cycle time.

[0124] Example

[0125] By Figure 1 The laser powder surfacing device 100 shown in the figure performs surfacing on the substrate 37 of steel (SS400). The size of the substrate 37 is 50 mm in length × 50 mm in width × 20 mm in thickness. The first powder uses SUS316L and SUS630 powders, and the second powder uses TiC powder to form a single layer of surfacing layer on the entire surface of the substrate 37. The various conditions and results of the surfacing formation of each test piece are shown in Table 1.

[0126]

Table 1

[0127]

[0128] In Test Examples 1-1 to 4, the first powder of the powder material is SUS316L, the second powder is TiC, and the laser linear energy index A is a constant value of 21.9 [kJ / cm]. Under this condition, the powder supply index B and the content of the second powder (TiC) in the powder material are changed.

[0129] In Test Examples 2-1 to 6, the first powder of the powder material is the precipitation hardening type stainless steel alloy SUS630, the second powder is TiC, and the laser linear energy index A is a constant value of 21.4 [kJ / cm]. Under this condition, the powder supply index B and the content of the second powder (TiC) in the powder material are changed.

[0130] For each test example, the presence or absence of welding cracks in the surfacing layer is confirmed by penetrant inspection (PT). In the case of no welding cracks, it is evaluated as "〇", and in the case of having welding cracks, it is evaluated as "×".

[0131] In addition, the Rockwell C hardness of the surfacing layer is measured using a Rockwell hardness testing device (using scale C) for the surface layer of the machined surface obtained by face cutting the surfacing layer formed on the substrate until a depth of 3 mm. Five points on the surface layer of the machined surface are used as the measurement points, and the average value of the measurement values of each measurement point is used as the representative value of the Rockwell C hardness of the surfacing layer. Table 2 shows the hardness measurement results of five points of the test pieces in each test example.

[0132]

Table 2

[0133] Hardness measurement results of each test piece in Table 2

[0134]

[0135] Figure 6 It is a graph showing the relationship between the content ratio R2 of the second powder (TiC) in each test example and the Rockwell C hardness of the surfacing layer.

[0136] When SUS316L was used as the first powder in Test Examples 1-1 to 1-4, when the content ratio of the second powder (TiC) was increased to about 60% by mass, although the surface hardness was 60 HRC or more, welding cracks occurred (Test Example 1-4).

[0137] On the other hand, when SUS630 was used as the first powder in Test Examples 2-1 to 2-6, since the content ratio of the second powder (TiC) was about 40 to 50% by mass, the surface hardness was 60 HRC or more (Test Examples 2-3 and 2-4). In addition, when the content ratio of the second powder (TiC) was increased to more than about 70 wt%, welding cracks occurred (Test Examples 2-5 and 2-6).

[0138] From the above, by using SUS630 as the first powder and making the content ratio R2 of the second powder (TiC) 40% by mass or more and 65% by mass or less, a surfacing layer with a surface hardness of 60 HRC or more and 65 HRC or less and a thickness of several millimeters per pass (3 mm in this test example) can be formed without welding cracks. Also, if the thickness of the surfacing layer per pass exceeds 5 mm, empirically, the surface hardness will not reach the above range, or a situation such as welding cracks can be foreseen. Therefore, it can be speculated that the surface hardness can be within the above range and no welding cracks will occur as long as the thickness of the surfacing layer per pass is up to 5 mm.

[0139] Next, for the surfacing layer formed under the conditions of Test Examples 2-1 to 2-6, a scanning electron microscope was used to observe the microstructure on the surface at a depth of 3 mm. Then, through image analysis, the ratio (occupancy rate) of the black part (TiC region) in the obtained SEM image was obtained.

[0140] The steps from microstructure observation to image analysis are as follows.

[0141] (1) Mirror polishing of the surface

[0142] (2) SEM observation (magnification ×50)

[0143] (3) Identification of the black part (TiC region) after binarization of the SEM image

[0144] (4) Calculation of the occupancy area ratio R1 of the black part (TiC region)

[0145] Figure 7 It is an explanatory diagram showing the microstructure observation image (upper part) and the binarized image (lower part) of the surfacing layer in Test Examples 2-1 to 2-3. Figure 8It is an explanatory diagram showing the microstructure observation image (upper part) and the binary image (lower part) of the surfacing layer in Test Examples 2-4 to 2-6. In addition, in Table 3, the occupied area ratio of the TiC region, the content ratio R2 of the second powder (TiC), and the Rockwell C hardness value are shown together. Here, for the setting of the binary threshold, an appropriate method can be adopted. For example, the threshold closest to the edge of the TiC region in the SEM image can be adjusted and set in each observation field, etc.

[0146]

Table 3

[0147] Table 3 Calculation results of the occupied area ratio of the titanium carbide (TiC) region

[0148]

[0149] From these results, it can be seen that when the occupied area ratio R1 of the black part (TiC region) in the binary image is 50 area% or more and 65 area% or less (Test Examples 2-3, 2-4), the surface hardness is HRc60 or more and 65 or less.

[0150] Figure 9 It is a diagram showing the relationship between the content ratio R2 of the second powder (TiC) in the powder materials of Test Examples 2-1 to 2-6 and the occupied area ratio R1 of the TiC region contained in the surfacing layer.

[0151] It can be seen that the occupied area ratio R1 of the TiC region increases proportionally with the increase in the addition amount of the second powder (TiC).

[0152] Figure 10 It is a diagram showing the relationship between the occupied area ratio R1 of the TiC region contained in the surfacing layer of Test Examples 2-1 to 6 and the Rockwell C hardness.

[0153] The distribution of the Rockwell C hardness is the same as the relationship between the addition amount of the second powder (TiC) shown in Figure 6 Test Examples 2-3 and 2-4 are included in the range of approximately HRc60 or more and HRc65 or less with respect to the occupied area ratio R1 of the TiC region.

[0154] In addition, regarding the upper limit of the laser line energy index A shown in Table 1, although the materials are different, through cobalt-based alloy (Kennametal No. 1) and tungsten carbide ( The laser hardfacing of the mixed powder of the company's tungsten carbide powder product name: 4670) was confirmed. As a result, if the value of the laser linear energy index A of the swing welding condition is higher than 35 [kJ / cm], the penetration depth into the base material reaches more than 2 mm, the dilution rate of the surfacing layer becomes high, and the hardness is greatly reduced. From this, it is speculated that even when it is a mixed powder of precipitation hardening stainless steel and TiC, it is desirable that the laser linear energy index A is 35 [kJ / cm] or less.

[0155] In the results of the judgment column shown in Table 1, when there is no welding crack, the Rockwell C hardness is 60 or more and 65 or less of HRc, and the occupied area ratio R1 of the TiC region is 50 area% or more and 65 area% or less, it is evaluated as "○", and otherwise it is evaluated as "×". The thickness of each pass of the surfacing layer is 3 mm or more and 5 mm or less.

[0156] Based on the above, as in Test Examples 2-3 and 2-4, by setting conditions that satisfy the foregoing conditional expressions [1] to [3], it is possible to stably obtain a high-quality laminated object that does not have welding cracks, can obtain a hardness with high wear resistance (Rockwell C hardness is 60 or more and 65 or less of HRc), and moreover, the surfacing thickness of each pass is 3 mm or more and 5 mm or less.

[0157] The present invention is not limited to the above-described embodiments. Combinations of the components of the embodiments, or changes and applications made by those skilled in the art based on the description in the specification and well-known techniques, are all intended contents of the present invention and are included within the scope of protection claimed.

[0158] As described above, the present specification discloses the following matters.

[0159] (1) A method for manufacturing a laminated object, which is a method of swing-irradiating a powder material including a first powder containing precipitation hardening stainless steel and a second powder containing titanium carbide with a laser beam to melt and solidify it, and laminating at least one surfacing layer on a base material, wherein

[0160] The step of laminating the surfacing layer is a step that satisfies the following conditional expressions [1], [2], and [3].

[0161] 20 ≤ A ≤ 35... Conditional expression [1]

[0162] 1.1 ≤ B ≤ 1.3... Conditional expression [2]

[0163] 40 mass% ≤ R2 ≤ 65 mass%... Conditional expression [3]

[0164] A = P × α / β [kJ / cm]: Laser linear energy index

[0165] B = Q × α / β [g / cm]: Powder supply rate index

[0166] P [W]: Linear energy from the laser beam

[0167] Q [g / min]: Supply rate of the powder material

[0168] α = W / V1

[0169] β = V2 × t

[0170] W [cm]: Scanning width of the beam spot due to the oscillatory motion

[0171] V1 [cm / min]: Scanning speed of the laser beam due to the oscillatory motion

[0172] V2 [cm / min]: Forward speed in the welding direction

[0173] t [sec]: Time for one cycle of oscillation

[0174] R2 [% by mass]: Ratio of the second powder contained in the powder material

[0175] According to this method for manufacturing a laminated object, by oscillating the laser beam, the linear energy near the welded part of the base material is increased, which can promote the heating of the base material. Therefore, the temperature difference between the surfacing layer formed by melting and solidifying the powder material due to the linear energy from the laser beam and the surface of the base material heated by the laser beam becomes smaller, and the welding cracks in the surfacing layer caused by shrinkage strain after cooling can be suppressed.

[0176] In addition, since the oscillating laser beam increases the linear energy near the welded part, increasing the supply amount of the powder material during welding enables surfacing with a large thickness in one pass.

[0177] Moreover, in a state where the penetration (formation range of an intermediate layer having an intermediate hardness between the base material and the surfacing layer) is small, a surfacing layer with a thickness of several millimeters per layer can be formed. As a result, it is not necessary to perform multi-layer surfacing to ensure the surfacing layer thickness as in the past, and the possibility of welding cracks occurring during processing can be reduced. In addition, the effects of reducing dimensional limitations, cutting construction costs, and shortening the delivery cycle can also be achieved.

[0178] In addition, since a powder material mixed with generally commercially available powders such as precipitation hardening stainless steel and titanium carbide is used, there is no need to use a surfacing powder material that requires complex pretreatment, and it is excellent in economy and can form a high-quality surfacing layer.

[0179] (2) According to the method for manufacturing a laminated object described in (1), wherein the surfacing layer is laminated multiple times.

[0180] According to the manufacturing method of this laminated object, it can be shaped into any target shape, and the degree of design freedom is improved.

[0181] (3) A laminated object is a laminated object in which at least one surfacing layer containing a precipitation-hardening stainless steel alloy and titanium carbide is formed on a base material, wherein

[0182] the thickness of each layer of the surfacing layer is 3 mm or more and 5 mm or less, and the Rockwell C hardness of the surfacing layer is HRc60 or more and HRc65 or less,

[0183] the occupation area ratio R1 of the titanium carbide region in the microstructure observation image of the surfacing layer is 50 area% or more and 65 area% or less.

[0184] According to this laminated object, because of its high hardness and high-quality properties without welding cracks, the application range of products can be expanded.

[0185] (4) The laminated object according to (3), wherein the precipitation-hardening stainless steel alloy is SUS630 alloy.

[0186] According to this laminated object, compared with the case of using, for example, austenitic stainless steel alloy, it can be a structure with higher strength and excellent corrosion resistance.

[0187] (5) The laminated object according to claim 3 or 4, wherein a plurality of the surfacing layers are laminated on the base material.

[0188] According to this laminated object, any shape can be made into a high-quality property with high hardness and no welding cracks.

[0189] In addition, this application is based on a Japanese patent application (Japanese Patent Application No. 2020-43356) filed on March 12, 2020, the content of which is incorporated herein by reference.

[0190] Symbol description

[0191] 11 Welding robot

[0192] 13 Laser light source unit

[0193] 15 Powder material supply unit

[0194] 17 Control unit

[0195] 19 Swing drive unit

[0196] 21 Welding head

[0197] 23 Optical fiber

[0198] 25 Powder supply pipe

[0199] 27 Laser output adjustment unit

[0200] 29 Powder material supply adjustment unit

[0201] 31 Laser irradiation port

[0202] 33 Powder material supply port

[0203] 35 Shielding gas supply port

[0204] 37 Base material

[0205] 39 Powder material

[0206] 41 Surfacing layer

[0207] 42 Intermediate layer

[0208] 43 Stacked formed object

[0209] 100 Laser powder surfacing device

Claims

1. A method for manufacturing a laminated object, which is a method of oscillating and irradiating a powder material including a first powder containing precipitation-hardening stainless steel and a second powder containing titanium carbide with a laser beam to melt and solidify the powder material, and laminating at least one surfacing layer on a substrate, wherein, The step of laminating the surfacing layer is a step that satisfies the following conditional expressions [1], [2], and [3], 20 ≤ A ≤ 35... Conditional expression [1] 1.1 ≤ B ≤ 1.3... Conditional expression [2] 40 mass% ≤ R2 ≤ 65 mass%... Conditional expression [3] A = P × α / β: Laser line energy index, unit is kJ / cm B = Q × α / β: Powder supply speed index, unit is g / cm P: Line energy from the laser beam, unit is W Q: Supply speed of the powder material, unit is g / min α = W / V1 β = V2 × t W: Scanning width of the beam spot brought by the oscillating motion, unit is cm V1: Scanning speed of the laser beam brought by the oscillating motion, unit is cm / min V2: Forward speed in the welding direction, unit is cm / min t: Time for one cycle of oscillation, unit is sec R2: Ratio of the second powder contained in the powder material, unit is mass%.

2. The manufacturing method of the stacked object according to claim 1, wherein, The surfacing layer is laminated multiple times.

3. A laminated object, which is a laminated object obtained by the method for manufacturing a laminated object according to claim 1 or 2, and forms at least one surfacing layer containing precipitation-hardening stainless steel alloy and titanium carbide on a substrate, wherein, The thickness of each layer of the surfacing layer is 3 mm or more and 5 mm or less, and the Rockwell C hardness of the surfacing layer is HRc60 or more and HRc65 or less, The occupied area ratio R1 of the titanium carbide region in the microstructure observation image of the surfacing layer is 50 area% or more and 65 area% or less.

4. The stacked object according to claim 3, wherein, The precipitation-hardening stainless steel alloy is SUS630 alloy.

5. The stacked molded object according to claim 3 or 4, wherein Multiple layers of the surfacing layer are laminated on the substrate.

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