WO2008072303A1 - Friction welding, process for producing centrifugal gas turbine, and process for producing turbo charger - Google Patents

Abstract

A method in which a precipitation-hardened Ni-base alloy cast and either a precipitation-hardened Ni-base alloy forging or a precipitation-hardened Fe-base alloy forging are subjected to friction welding while applying pressures in two stages, i.e., a pressure (P1) and a higher pressure (P2). The method can attain a high weld strength and attain a reduction in upset distance fluctuation. The two materials to be welded are subjected to a solution heat treatment and an aging treatment so as to result in a 0.2% proof strength at a temperature in the range of room temperature to 650°C of 700 MPa or higher. Thereafter, friction welding is conducted while regulating the pressure (P2) during the welding to 500 MPa or higher. Thus, a weld strength of 1,700 MPa or higher in terms of notched room-temperature tensile strength is obtained.

Description

 Specification

 Friction welding method, centrifugal gas turbine manufacturing method, and turbocharger manufacturing method

 Technical field

 The present invention relates to a method of friction welding a precipitation-strengthened Ni-base alloy deposit and a precipitation-strengthened Ni-base alloy forged material or a precipitation-strengthened Fe-based alloy forged material. The present invention also relates to a method of manufacturing a centrifugal gas turbine in which a turbine wheel and a shaft are formed of these materials, or a turbocharger in which an exhaust side impeller and a shaft are formed of these materials.

 Background art

 [0002] Precipitation-strengthened Ni-based alloys are used for the exhaust side impellers of turbochargers, which are high-speed rotating bodies, and the turbine bin wheels of centrifugal gas turbines. On the other hand, chrome molybdenum steel tempered material, precipitation-strengthened Ni-base alloy forging or precipitation-strengthened Fe-base alloy forging, is used for the shaft that is joined to the exhaust wheel or turbine wheel. The exhaust side impeller or turbine wheel and the shaft are generally joined by friction welding.

 [0003] In friction welding, two materials are rotated relative to each other with the same axis and pressed to generate frictional heat near the contact surface, that is, the joint surface, and this heat generation softens the material. This is a method of joining in a substantially solid state. In general, the joining pressure is divided into two stages. First, the material is heated at a low pressure P1 to form a softened layer, and then the softened layer is discharged at a higher pressure P2 while joining. Regarding the rotation stop method, after issuing a rotation stop command during pressure P1, move to P2, completely issue a method to issue a rotation stop command at the same time as the transition command to pressure P2, and complete the command after the transition command to pressure P2. A method of issuing a rotation stop command after the pressure reaches P2 is known (for example, see Patent Document 1).

[0004] In recent years, instead of the precipitation-strengthened Ni-base alloy alloy713C shown in Patent Document 1, the material of the turbocharger exhaust side impeller or centrifugal gas turbine turbine wheel has been changed to Patent Document 2 with higher strength. Precipitation-strengthened Ni-based alloys such as those shown are now being used. The material of the shaft is also made of chromium molybdenum steel as disclosed in Patent Document 1. Higher strength precipitation-strengthened Ni-based alloy forgings as shown in AMS5662 have come to be used. AMS5662 is one of AEROSPACE MATERIAL SPECIFICATIONS issued by SAE International and corresponds to Inconel 718, a registered trademark of Special Metals Corporation.

 [0005] Precipitation-strengthened alloys are composed of γ 'phase, phase, γ' in the austenite phase (γ phase) of Ni or Fe.

 It is an alloy with increased high-temperature strength by precipitating intermetallic compounds such as' phase and δ phase.

 [0006] Precipitation strengthened forging alloys other than Inconel 718 include, for example, Superalloys A Technical Guide second Edition (Attached to MJ Donacnie and bJ Donacme, ASM International al 2002) p4-5, Table 1.1 There are A-286, Nimonic80A, etc. which are listed as Precipitation-hardening alloys.

 [0007] Patent Document 1: Japanese Patent Publication No. 58-19393

 Patent Document 2: USP3, 720, 509

 Disclosure of the invention

 Problems to be solved by the invention

[0008] Patent Document 1 describes a method of friction welding a precipitation-strengthened Ni-base alloy alloy713C forged material and a chromium molybdenum steel tempered material. There is a large difference in high-temperature strength between the two materials, so the precipitation-strengthened Ni-based alloy forging material is hardly deformed when bonded by friction welding, and the soft layer formed in the P1 process and the P2 process More than 90% of the burrs discharged in the process are S-chromium-molybdenum steel. Patent Document 1 discloses a method for improving the strength of the joint interface by preventing the carbides in the chromium-molybdenum steel from aligning with the joint interface at this time.

 [0009] Another problem arises when the shaft material becomes a precipitation-strengthening Ni-base alloy forging or a precipitation-strengthening Fe-base alloy forging with higher strength. An example of precipitation-strengthened Ni-based alloy forging will be explained.

 [0010] With regard to the carbide alignment problem, the chromium molybdenum steel SCM435 has a weight percentage of 0.

. 33-0 38%, SCM440 is a weight _^0/0 C: to 0.38 to 0 to 43%, precipitation strengthened Ni-based alloy forging AMS5662 is Flip wt%:.. 0 08% or less Because it contains only about 1/10 carbon of chrome-molybdenum steel! / ヽ, it shouldn't be a big problem! In the case of chromium molybdenum steel, the tempered material is friction welded, whereas in the case of precipitation strengthened Ni-based alloy forgings, the solution heat treatment state (generally hardened) In which the pressure does not exceed 277 with Brinell), and then an aging treatment is employed. Therefore, after aging, even if the material has a room temperature 0.2% yield strength of lOOOMPa or more, the room temperature 0.2% resistance during pressure welding in the solution heat treatment state is 350 to 650 MPa, which is a chrome molybdenum steel tempered material. The room temperature yield stress of SCM440 is lower than 835 MPa or more. This means that when friction welding is performed under the condition of pressure P2 of 500 MPa, in the conventional chrome molybdenum steel tempered material, most of the low-temperature part other than the soft solder layer is in the elastic region, whereas the solution heat treatment state, for example, This means that precipitation-strengthened Ni-base alloy forgings with 0.2% resistance to 450MPa at room temperature enter the plastic region even at low temperatures.

 [0012] In the case of precipitation-strengthened Ni-based alloy forgings, the strength at high temperatures (> 500 ° C) is higher than that of tempered chromium-molybdenum steel even in the solution heat treatment state. For the discharge of the layer, P2 higher than the conditions used rather than chrome-molybdenum steel tempering material is necessary. However, for precipitation-strengthened Ni-base superalloy forgings in the solution heat treatment state, increasing P2 not only increases the amount of plastic deformation but also causes the shaft to buckle during pressure welding. With a lot of danger.

 [0013] Since the quality of friction welding is difficult to perform non-destructive inspection of joints, the margin of deviation (U), that is, the length of the foreside before welding + the length of the forged material before pressure welding (the product after pressure welding) Total length). Ideally, the allowance (U) should be the total length reduction due to the soft layer discharge, but if the low temperature part other than the soft layer is also in the plastic zone, the amount of plastic deformation in the low temperature part Is also added to the approaching margin (U). In general, materials have almost no variation in deformation behavior in the elastic region, but the deformation behavior (stress-strain relationship) in the plastic region varies greatly between materials. In particular, the dispersion between materials is large in the solution heat treatment state before the final heat treatment. Variation in the margin of allowance (U) due to variations in strength between materials is a major problem in terms of quality assurance of friction welding parts of high-speed rotating bodies such as turbochargers and centrifugal gas turbines.

[0014] Also, from the viewpoint of bonding strength, in the case of forging a forging material such as a Ni- or Fe-based alloy that has higher high-temperature strength than a chrome-molybdenum steel tempered material, A higher pressure stress is required than when joining. However, as mentioned above, it dissolves at room temperature. Since the strength of Ni-base alloy forging in the heat treatment state is lower than that of chrome molybdenum steel tempered material, chromium-molybden steel can be used to reduce the variation in the margin (U) and eliminate the risk of buckling. It is necessary to join at or below the pressure welding condition of the tempered material. For this reason, there is a problem that sufficient joint strength cannot be obtained.

[0015] An object of the present invention is to provide a high-V at a stable margin in a method of friction welding a precipitation-strengthened Ni-base alloy deposit and a precipitation-strengthened Ni-base alloy forging or a precipitation-strengthening Fe-base alloy forging. It is intended to provide a friction welding method that can obtain joint strength and is extremely effective in improving the quality of the friction welding portion of a high-speed rotating body such as a turbo charger or a centrifugal gas turbine.

Means for solving the problem

 [0016] The present invention relates to a friction welding method of a precipitation strengthened Ni-based alloy forged material and a precipitation strengthened Ni-based alloy forged material or a precipitation strengthened Fe-based alloy forged material. Physically, it is characterized by a solution heat treatment and an aging treatment to increase the strength, and then applying friction welding by applying a two-stage joining pressure.

 [0017] In addition, the present invention provides a relative relationship between one material made of precipitation-strengthened Ni-based alloy forging and the other material made of precipitation-strengthened Ni-based alloy forging or precipitation-strengthened Fe-based alloy forging. The friction pressure welding method in which friction pressure welding is performed by applying pressure P1 while rotating to generate frictional heat on the contact surface, and then joining with the higher pressure P2 being applied. In this range, the 0.2% resistance is increased to 700 MPa or more so that the force can be joined, and the pressure P2 is set to at least 500 MPa.

 [0018] In addition, the present invention provides a relative relationship between one material made of precipitation-strengthened Ni-based alloy forging and the other material made of precipitation-strengthened Ni-based alloy forging or precipitation-strengthened Fe-based alloy forging. In the friction welding method in which pressure P1 is applied while rotating and frictional heat is generated on the contact surface, and then joining is performed by applying a higher pressure P2, the elastic limit stress of the two materials is the pressure. It is characterized in that heat treatment is performed so as to be higher than P2, the force is bonded, and the pressure P2 is at least 500 MPa.

[0019] The present invention relates to a turbine wheel that also serves as a precipitation-strengthened Ni-based alloy material and a shaft that comprises a precipitation-strengthened Ni-based alloy forged material or a precipitation-strengthened Fe-based alloy forged material by friction welding. From the room temperature of the precipitation-strengthened Ni-base alloy deposit and the precipitation-strengthened Ni-base alloy forging or precipitation-strengthened Fe-base alloy forging 650 The 0.2% resistance in the range of ° C is set to at least 700MPa, and friction friction welding is performed, and in the friction welding process, pressure P1 is applied while the turbine wheel and the shaft are rotated relative to each other to contact the surface. Then, frictional heat is generated, and then bonding is performed under a pressure of at least 500 MPa higher than the pressure P1.

[0020] The present invention relates to an exhaust side impeller made of a precipitation-strengthened Ni-base alloy and a shaft made of a precipitation-strengthened Ni-base alloy forging or a precipitation-strengthened Fe-base alloy forging by a friction welding method. In the method for manufacturing a turbocharger including a joining step, the temperature of the precipitation strengthened Ni-based alloy metal and the precipitation-strengthened Ni-based alloy forging or precipitation-strengthened Fe-based alloy forging is 650 ° C. Friction welding is performed after setting the 0.2% resistance in the range of at least 700 MPa, and pressure P1 is applied while relatively rotating the exhaust-side impeller and the shaft in the friction welding process. Then, friction heat is generated, and then joining is carried out under a pressure of at least 500 MPa higher than the pressure P1.

 The invention's effect

 [0021] According to the present invention, in friction welding of a precipitation strengthened Ni-based alloy forged material and a precipitation strengthened Ni-based alloy forged material or a precipitation-strengthened Fe-based alloy forged material, a stable joint and a high joint are obtained. High joint strength with a strength, for example, room temperature notch tensile strength of 1700 MPa or more can be obtained. As a result, the reliability of high-speed rotating bodies such as turbochargers and centrifugal gas turbines can be greatly improved.

 Brief Description of Drawings

 [0022] FIG. 1 is a diagram showing the relationship between stress and strain of a precipitation strengthened alloy forging.

 FIG. 2 is a schematic diagram showing the shape of a notch specimen for evaluating the strength of a joint.

 [Fig. 3] A diagram showing the relationship between notch tensile strength and offset.

 [Fig.4] Macro photo of the cross section of the joint.

 FIG. 5 is a schematic diagram showing a shape of a centrifugal gas turbine before pressure contact between a turbine wheel and a shaft.

[Fig.6] Shows the shape of a centrifugal gas turbine after pressure contact between the turbine wheel and shaft Schematic diagram.

 FIG. 7 is a schematic view showing a shape before pressure contact between a turbine wheel and a shaft in a centrifugal gas turbine, wherein the shaft is processed into a stepped shape.

 Explanation of symbols

[0023] 1 ... Turbine wheel, 2 ... shaft.

 BEST MODE FOR CARRYING OUT THE INVENTION

 [0024] In order to stabilize the shift margin (U), the precipitation-strengthened Ni-base alloy forged material or the precipitation-strengthened Fe-based alloy forged material side is also formed in as many portions as possible except for the soft soot layer generating portion. The maximum pressure stress must be within the elastic stress range. In order to obtain high joint strength, a large pressure stress is required. In order to solve these problems, it is effective to use two materials to be joined in friction welding with strength ranging from room temperature to 650 ° C, specifically 0.2% resistance to 700 MPa or more. It is. It is also effective to set the pressure P2 to 500 MPa or more. In order to increase the 0.2% resistance in the range from room temperature to 650 ° C to 700 MPa or more, it is desirable to perform solution heat treatment and aging treatment.

 [0025] By adjusting the strengths of both materials in this way, even at the maximum pressure contact pressure greater than 500MPa, both of the two materials are at least in most areas except the soft layer, that is, during pressure contact. The portion where the temperature is in the range from room temperature to 500 ° C. can be within the elastic stress range. As a result, even when the maximum pressure stress is increased in order to increase the joint strength, high-quality friction welding with little variation in the margin (U) is possible, and the shaft material is seated during pressure welding. The risk of bending is avoided.

 [0026] In applications for high-speed rotating bodies that require high strength, a deposit made of precipitation-strengthened Ni-base alloy and a forging material made of precipitation-strengthened Ni-base alloy or precipitation-strengthened Fe-base alloy In the case of friction welding, it is desirable that the room temperature notch bow I tensile strength of notch tensile specimens taken from the joint and notched in the joint is 1700 MPa or more. By making the joint room temperature notch tensile strength high in this way, the number of start / stop operations as a product increases, and even when a high load is applied to the joint, it can withstand. In order to obtain room temperature notch tensile strength of 1700 MPa or more, it is desirable that the allowance (U) is 14 mm or more.

[0027] In addition, in order to obtain a joint with high joint strength with small variation in the margin (U), 2 It is desirable to adjust the strength of each material so that the discharge angle of the soft layer generated from the material with the larger amount of soft layer is greater than 90 °.

[0028] As in the friction welding method according to the present invention, when a high P2 pressure is required and the P2 pressure may exceed the elastic limit stress of one of the materials, a marginal margin is generated during the friction welding.

Collect digital data of (U) and stress (P), graph the relationship between them, prepare this stress (P) shift margin (U) diagram in advance, and close to the reference stress (P) It is more effective to perform quality control than the U (U) diagram. Since the stress (P) -shift margin (U) diagram corresponds to the stress-strain diagram in the tensile test or compression test, the plastic deformation behavior of the material can be seen from the stress (P) shift margin (U) diagram.

[0029] The friction welding method of the present invention requires a high-strength material to cope with high-speed rotation at high temperatures, and is a turbine wheel that also serves as a precipitation-strengthened Ni-based alloy material for centrifugal gas turbines. Therefore, it is suitable as a method for joining shafts that also become precipitation-strengthened Ni or Fe-based alloy forging materials.

 [0030] Further, similarly, the friction welding method of the present invention includes an exhaust side impeller made of a precipitation-strengthened Ni-based alloy in a high-speed turbo charger and a shaft made of a precipitation-strengthened Ni or Fe-based alloy forging. It is also suitable as a method of joining the two.

 [0031] In the centrifugal gas turbine to which the friction welding method of the present invention is applied, the turbine wheel made of precipitation-strengthened Ni-based alloy material has a Ni content of 50% or more by weight%, C: 0.05-0.3%, B: 0.01 ~ 0.05%, Hf: 0.5 ~ 3.0%, Co: 8 ~ 18%, Ta: 3 ~ 8.5%, Cr: l .5 ~ 16%, Mo: 0 ~ l%, W: 5 ~ 15% , Ti: 0 ~ l.5%, A1: 4.5 ~ 5.8%, Nb: 0 ~ 2%, Re: 0 ~ 6%, V: 0 ~ 1%, Zr: 0 ~ 0.01%, Pt or platinum group element 1 type or a combination of 2 or more types: 0 to 2%, Y or a combination of 1 or 2 types of rare earth elements: 0 to 2%, a combination of 1 type or 2 types of Mg or alkaline earth metals : 0 to 0.5%, combination of one or more of Fe, Ga and Ge: preferably a composition of 0 to 5% or less.

[0032] When higher strength is required and material cost is also important, the turbine wheel made of precipitation-strengthened Ni-based alloy material is 50% Ni or more by weight, C: 0.1 to 0.3%, B: 0.016-0.05%, Hf: l. 3-3.0%, Co: 10.2-18%, Ta: 3-5%, Cr: 1. 5 ~ 16%, Mo: 0 ~ l%, W: 9 ~ 15%, Ti: 0 ~ l%, Al: 5 ~ 5.8%, Nb: 0 ~ 2%, V: 0 ~ 1%, Zr: 0 ~ 0.01%, Pt or one or more combinations of platinum group elements: 0 to 2%, Y or one or more combinations of rare earth elements: 0 to 2%, Mg or alkaline earth metal 1 type or a combination of 2 or more types: 0 to 0.1%, Fe, Ga, Ge 1 type or a combination of 2 or more types: It is preferable that the composition is 0 to 5% or less.

[0033] In addition, in order to cope with a centrifugal gas turbine in which the turbine inlet temperature is further improved for the purpose of improving thermal efficiency, when a higher high-temperature strength is required than the above, a precipitation-strengthened Ni-based alloy container is also available. The turbine wheel is made of Ni by weight of 50% or more, C: 0.1 to 0.3%, B: 0.016 to 0.05%, Hf: l.3 to 3.0%, Co: 10.2 to 18%, Ta: 2.8 ~ 4.7%, Cr: l.5 ~ 16%, Mo: 0 ~ l%, W: 9 ~ 15%, Ti: 0 ~ l%, Al: 5 ~ 5.8%, Nb: 0 ~ 2%, Re : It is preferable that the yarn is composed of 0.2 to 6%, V: 0.15% or less, and Zr: 0.03 to 0.08%.

 [0034] In the present invention, a turbine wheel that also serves as a precipitation-strengthened Ni-based alloy freight and a shaft that also serves as a precipitation-strengthened Ni- or Fe-based alloy forging material are each heat-treated, so that the room temperature force is within a range of 650 ° C. The process of adjusting the 0.2% proof stress to 700 MPa or more, and the friction that applies the maximum pressure stress greater than 500 MPa by increasing the pressure by generating friction heat while rotating the turbine wheel and shaft relatively. Enables the process of joining by the pressure welding method and the manufacturing method of the centrifugal gas turbine with the process power of heat treatment in the range of 600 ° C to 800 ° C for 2 to 8 hours after joining. Residual stress can be removed and strain can be removed by heat treatment in the range of 600 to 800 ° C, which also serves as an aging treatment for the heat-affected zone after joining.

[0035] Further, when the cutting amount of the shaft due to the mechanical cage is large, such as a stepped shaft, the friction welding surface of the shaft, the radial machining allowance and the axial machining allowance are set, and the Brinell hardness is 277. The shaft and the turbine wheel are processed in a state that does not exceed that of the solution heat treatment, and then the 0.2% proof stress in the range from room temperature to 650 ° C is adjusted to 700 MPa or more by heat treatment. After bonding, it is effective to heat-treat for 2 to 8 hours in the range of 600 ° C force and 800 ° C, and then check the final shape. The AMS5662 standard stipulates that the Brinell hardness of the solution material should not exceed 277. [0036] According to the present invention, it has become possible to bond a material having higher strength than the conventional one with high reliability. As a result, it is possible to apply high-strength materials to turbochargers and centrifugal gas turbines, and it is expected to save resources and improve CO and NOx emissions by improving efficiency.

 2

 wear. In addition, stabilization of the margin (u) leads to savings in the axial machining allowance of the material, which has the effect of reducing material costs and reducing rare metal element consumption.

 Example 1

 [0037] Precipitation-strengthened Ni-based alloy porcelain in weight%: 0.14%, B: 0.015%, Hf: 1.54%, Co: 9.99%, Ta: 3.03% , Cr: 8.33%, Mo: 0.71%, W: 9.98%, Ti: l. 0 1%, Al: 5.59%, the balance of Ni-based alloy consisting of Ni and inevitable impurities 47mm A round bar of φ X 100 mmL was prepared. The heat treatment was solution heat treatment with 1200 ° CZ2hZAr gas cooling in vacuum after fabrication, followed by two-stage aging treatment (1080 ° CZ4hZAr gas cooling in vacuum + 871 ° CZ20hZAr gas cooling in vacuum).

 [0038] On the other hand, as a precipitation strengthening type Ni-based alloy forging material, a solution based on the AMS5662 standard, a heat treatment material, and after heating at 720 ° C for 8 hours, cooling to 625 ° C in 2 hours, further 625 An aging material prepared by aging treatment at 8 ° C. for 8 hours was prepared. These materials were processed into 47mm φ X 15 OmmL round bars. In order to investigate the effect of material strength variations on the margin of allowance (U), all AMS5662 standard materials were in separate lots.

 [0039] Table 1 shows the pressure welding conditions, and Tables 2 and 3 show the tensile properties and joining results of the materials.

 [0040] [Table 1]

 table 1

Condition Prior art Present invention

C: 0.14%, B: 0.015%, Hf: 1.54% _¾ Go: 9.99%, Ta: 3.03%, precipitation-strengthened alloy gun Cr: 8.33%, Mo: 0.71 <½ material,

 W: 9.98%, Ti: 1.01%, A, 59%, balance is Ni

 Precipitation strengthened alloy forging AMS5662 standard material Precipitation strengthened alloy forging elastic limit Pa 242-490 902- 1000 Precipitation strengthened alloy forging 0.2 ¾ MPa resistance 378 to 628 1 138-1187 Primary stress P1 (MPa) 150

Secondary stress P2 (MPa) 500 600

S9 Z £ / 900Zd / 13d 0 V £ 0 £ Z recommended 00Z OAV Table 2

[ε 挲] β-Rin] S9 Z £ / 900Zd / 13d ZY £ 0 £ Z recommended OOZ OAV main

 Clothing

[0043] As the precipitation strengthening type alloy forging material, those shown in Table 2 using lots A to C having an elastic limit at room temperature of 242 to 490 MPa and a 0.2% proof stress S378 to 628 MPa are the conventional technologies. On the other hand, the present invention is shown in Table 3 using lots D to F prepared by applying an aging heat treatment to this and adjusting the elastic limit to 902 to 1000 MPa and 0.2% strength to 1138 to 1187 MPa.

 FIG. 1 is a stress strain diagram at room temperature of the AMS5662 material used for this pressure welding.

 In actual pressure welding, the deformation is compression, but the elastic limit and 0.2% resistance are almost the same on both the tension and compression sides, so it can be considered in the stress-strain diagram on the tension side.

 [0045] As is apparent from Table 2, in the prior art, the margin (U) was 11.8 to 13.3 mm and had a variation force. In the present invention, the maximum joint as shown in Table 3 Even though the secondary stress P2, which is the stress, was increased from the conventional 500 MPa to 600 MPa, the shift margin (U) was 14.7 to 14.8 mm, and the variation was greatly reduced.

 [0046] Hereinafter, the reason why the variation in the shift margin (U) can be reduced in the present invention will be described. From Fig. 1, in the conventional technology, the plastic strain when applying 500 MPa as the secondary stress P2 is 0.02% for the material (C), but about 0.8% for the material (B). It can be seen that material (A) is even larger. These plastic strains are added to the amount of deformation obtained by discharging the softened layer, which is an essential shift margin in friction welding, and this is the variation of the shift margin (U). This means that the margin (U), which is an index for quality control, is substantially governed by variations in strength between material lots, which is a major problem in quality control of friction welding. The

 On the other hand, in the case of the present invention, as shown in FIG. 1, the materials (D), (E), and (F) are elastic regions in the range up to about 900 MPa. Therefore, even when the secondary stress P2 is increased to 600 MPa, the deformation in the low temperature region other than the softened layer is basically released after unloading. ) Is not added. Therefore, in the method of the present invention, the variation in the margin of allowance (U) is greatly reduced.

[0048] Further, in order to evaluate the strength of the joint, a notch specimen having the shape shown in FIG. 2 was taken from the radial center of the joint. Fig. 2 (a) is an overall view of the notched specimen, and Fig. 2 (b) is a detailed view of part A. In order to evaluate the joint strength, it is important to align the center of the notch with the joint interface, and the tip of the notch was made to coincide with the joint interface. Prior to specimen collection, materials (A) to (C ) Was heated at 720 ° C for 8 hours, then cooled to 625 ° C in 2 hours, and then heated at 625 ° C for 8 hours. For the materials (D) to (F), the above heat treatment was simplified, heated at 720 ° C for 2 hours, cooled to 625 ° C in 1 hour, and further heated at 625 ° C for 2 hours. The reason for simplifying the heat treatment is that materials (D) to (F) are already subjected to aging treatment before pressure welding! This is because it is only necessary to reprecipitate the precipitate phase in a part, that is, a slight heat-affected zone near the bonding interface. The effect of simplified heat treatment was confirmed by measuring the hardness near the interface. Immediately after welding, the partial force softened from 220 to 280 in picker hardness. By simplified heat treatment, it is 420 to 500 in Vickers hardness, which is equivalent to the part that is affected by frictional heat during welding. It was recovered to.

 [0049] Note that the notched specimen having the shape shown in FIG. 2 was used because the strength after the aging treatment is higher than that of precipitation strengthened Ni-based alloy porcelain in the AMS5662 material. This is because, if a piece is used, it breaks at the smooth part on the precipitation-strengthened Ni-base alloy porcelain side, and an accurate comparison of joint strength cannot be made.

 [0050] Tables 2 and 3 show the evaluation results of the notch tensile strength. For the evaluation, a general screw type tensile tester was used, and the temperature was set to room temperature. Notch tensile strength is the load at break divided by the cross-sectional area of the notch. From this result, in the conventional technology, the notch tensile strength of the joint was 1679 MPa at the maximum, but in the case of the present invention, it was at least 1769 MPa, and the variation was greatly reduced. Recognize.

 [0051] FIG. 3 shows the relationship between the margin (U) and the notch tensile strength of the joining test piece according to the prior art and the present invention. It can be seen that the product of the present invention has an excellent joint strength with little variation in the shift margin (U). In addition, it can be seen from Fig. 3 that the greater the margin (U), the higher the notch tensile strength, that is, the joint strength. However, in the conventional technology, the secondary stress P2 has already exceeded the room temperature elastic limit on the precipitation-strengthened Ni-base alloy forging material side, so the secondary stress is further increased and the offset margin (U) is increased. It is difficult to increase the bonding strength.

[0052] Fig. 4 shows a cross-sectional macro photograph of the joint portion of the conventional technique and the present invention, (a) is the present invention, and (b) is the prior art. The softening layer discharge angle indicated by 0 in the figure is the angle between the outer diameter before bonding and the discharged soft soot phase, and is on the precipitation strengthened Ni-base alloy forging side. Depends on material strength. The joint specimen of the present invention has almost no change in outer diameter except at the discharge part. This means that most of the parts other than the softened layer were within the elastic deformation range at the time of pressure welding, and it is a typical joint shape of a pressure welded product with little variation in the margin (U). on the other hand

The outer diameter change of the joining test piece according to the prior art is observed even at a portion other than the discharge portion. This means that plastic deformation also occurred in the parts other than the softened layer, and the variation in the margin (U) is large! /, Which is a typical joint shape of the welded product.

[0053] In addition, as shown in Patent Document 1, when the forged material side is tempered material of SCM435, in order to increase the bonding strength, it is pressed with a secondary stress P2 exceeding 500 MPa. (B) The joint shape is the same as that of the prior art, and the shift margin is not stable. This is because the room temperature yield stress of the tempered SCM435 tempered material is 835 MPa or higher as a standard value, which is higher than the precipitation strengthened Ni-based alloy forging material used in the conventional technology, but a sudden drop in strength is observed at about 500 ° C or higher. This is because plastic deformation also occurs in the heat-affected zone due to frictional heat, and the difference in strength for each material lot affects the variation in the margin (U). Therefore, in order to obtain a high-quality friction welded product with high joint strength and stable margin, a 0.2% proof stress in the range of 650 ° C at room temperature is 700 MPa by heat treating the forging material. It is preferable to prepare so that it becomes the above.

 [0054] Next, the precipitation-strengthened Ni-based alloy porridge is higher in strength at a higher temperature than in the case of Example 1, in weight percent C: 0.13 to 0.23%, B: 0.013 to 0.00. 023%, Hf: l. 4 to 2.2%, Co: 10 to ll%, Ta: 3.5 to 5%, Cr: 6 to 8%, Mo: 0.1 to 1%, W: 11 to 12. 5%, Nb: 0.5 to 1%, Re: l. 2 to 1.5%, A1: 5 to 5.5%, Zr: 0.005 to 0.0015%, Residual force Ni A Ni-based superalloy composed of inevitable impurities was used, and friction welding was performed according to the method of the present invention.

[0055] The material on the porcelain side is a 47 mm φ X lOOmmL round bar, as in Example 1. (1080 ° CZ4hZAr gas cooling in vacuum + 87 lCZ20hZAr gas cooling in vacuum).

[0056] The precipitation-strengthened Ni-based alloy forging is the same as in Example 1 and is heated to 720 ° C for 8 hours on a solution heat-treated material based on the AMS5662 standard, and then cooled to 625 ° C in 2 hours. Furthermore, it is an aging material that has been heat-treated at 25 ° C for 8 hours, and the shape is 47mm φ X 150mmL round A stick. The pressure contact conditions were the same as in Example 1, with a primary stress P1 of 150 MPa and a secondary stress P2 of 6 OOMPa.

 [0057] Table 4 shows the results of pressure welding and the evaluation results of notch bow I tension strength by the same method as in Example 1.

[0058] [Table 4]

72ce02 ,. Table 4

After heating for an hour, it was cooled to 625 ° C in 1 hour and further heated at 625 ° C for 2 hours. From the results shown in Table 4, it is evident that even in this combination of materials, the same high joint strength as in Example 1 can be obtained.

[0060] Further, as shown in FIG. 3, the larger the margin (U), the higher the notch tensile strength, that is, the joint strength. However, in the case of the combination of materials shown in Table 2 and Table 3, the room-temperature inertia limit stress on the steel side is 686 MPa, so the secondary stress P2 is made higher than 600 MPa, and more than that, the offset margin (U) is increased. It's difficult to make it bigger. On the other hand, the combination of materials shown in Table 4 has a room temperature elastic limit stress of 800MPa on the skeleton side, and it is possible to improve the joint strength by further increasing the secondary stress P2.

 Example 2

[0061] Based on the test results of Example 1, a centrifugal turbine wheel having an axial length of about 120 mm, a blade part diameter of about 225 mm, and a pressure contact part diameter of 50 mm and a diameter of 50 mm φ X length by the friction welding method of the present invention. A 700mm shaft was joined. Turbine wheel, C by weight _{^{0/0:. 0 14%}} , B:. 0 015%, Hf:. L 54%, Co: 9. 99%, Ta: 3. 03%, Cr: 8. 33% , Mo: 0.71%, W: 9.98%, Ti: l. 01%, A1: 5.59%, the balance being a Ni-based superalloy made of Ni and inevitable impurities. This alloy was subjected to solution heat treatment with 1200 ° CZ2hZAr gas cooling in vacuum, followed by two-stage aging treatment (1080 ° CZ4hZAr gas cooling in vacuum + 871 ° CZ20hZAr gas cooling in vacuum) after fabrication. The shaft was an aged material obtained by heating a solution heat treatment material based on the AMS5662 standard at 720 ° C for 8 hours, cooling to 625 ° C in 2 hours, and then heating at 625 ° C for 8 hours. The pressure welding conditions were a primary stress P1 of 150 MPa and a secondary stress P2 of 600 MPa.

[0062] As a result, despite the fact that the length of the precipitation-strengthened Ni-based alloy forging shaft side was significantly increased from 150mm to 700mm of the joint test piece, the shift margin (U) was the joint test. It was 14.6 mm, almost the same as the piece. When joining in the plastic zone, the length X plastic strain is added to the shift margin (U) as the amount of plastic deformation, and changes in the material length affect the shift margin (U). However, in the present invention, most of the portions other than the soft heel layer are in the elastic region, and therefore, the change in the material length hardly affects the amount of deviation (U). This is extremely effective in terms of setting conditions and quality control. [0063] After pressure welding, after heating at 720 ° C for 2 hours, cooling to 625 ° C in 1 hour, and further heat treatment at 625 ° C for 2 hours, a notched specimen was prepared in the same manner as described above. The samples were collected and the bonding strength was evaluated. The notch tensile strength was 1770 MPa, which was equivalent to the joint specimen. From this result, the friction welding method of the present invention is also effective in the shape of the actual machine, and is a turbine wheel made of precipitation-strengthened Ni-based alloy and a shaft made of precipitation-strengthened Ni or Fe-based alloy forging. It was found that this method is suitable as a method of joining the two.

 FIG. 5 shows a shape of the centrifugal wheel 1 before the press contact of the turbine wheel 1 and the shaft 2 of the centrifugal gas turbine. The turbine wheel is manufactured by forging. The above heat treatment is performed before pressure welding, and then the pressure receiving surface and the joint surface are processed. The shaft is a forged material, and after the heat treatment described above, the outer diameter processing, pressure receiving surface and joint surface processing are performed. After pressure welding, after heating at 720 ° C for 2 hours, cooling to 625 ° C in 1 hour, heat treatment at 625 ° C for 2 hours, and then processing the shaft side into the shape shown in Fig. 6 . However, as can be seen from Fig. 1, there is a large difference in the 0.2% proof stress between the AMS 5662 standard solution solution and aging material, and accordingly, the room temperature hardness of the aging material is higher. Significantly higher than solution material. Therefore, the shaft side is processed into the shape shown in Fig. 7 at the solution heat treatment stage, then heated at 720 ° C for 8 hours, then cooled to 625 ° C in 2 hours, and further heated at 625 ° C for 8 hours. Treated. The stepped portion of this shaft was used as the pressure-receiving surface on the shaft side, and the primary stress P1 was 150 MPa and the secondary stress P2 was 600 MPa. After that, after heating at 720 ° C for 2 hours, cooling to 625 ° C in 1 hour, and further heat treatment at 625 ° C for 2 hours, the processing after the heat treatment was an outer diameter processing of about 2 mm in diameter and Only full length adjustment was used. As a result, the amount of cutting from the shape of FIG. 5 on the conventional shaft side to the shape of FIG. 6 can be carried out in a solution state where the material is easy to work! ヽ (low hardness!) This has made it possible to significantly reduce costs by prolonging the replacement cycle of consumables for machining and shortening the cutting time.

 Industrial applicability

[0065] According to the present invention, a high-strength material can be applied to a turbocharger and a centrifugal gas turbine, and an effect of improving efficiency is expected.

Claims

The scope of the claims  [1] Relatively rotate one material that is also a precipitation-strengthened Ni-base alloy forging and the other material that is also a precipitation-strengthened Ni-based alloy forging or a precipitation-strengthening Fe-based alloy forging. In the friction welding method in which frictional pressure is generated by applying pressure to generate frictional heat on the contact surface, and the pressure is further increased, the two materials are subjected to solution heat treatment and aging treatment to increase the mechanical strength and then friction. A friction welding method characterized by performing pressure welding.  [2] Relatively rotate one material that is also a precipitation-strengthened Ni-base alloy forging and the other material that is also a precipitation-strengthened Ni-based alloy forging or a precipitation-strengthening Fe-based alloy forging. In the friction welding method in which pressure P1 is applied to generate frictional heat on the contact surface, and then a higher pressure P2 is applied to join the two materials, the temperature ranges from room temperature to 650 ° C of 0.2. % Friction welding method characterized by increasing the resistance to 700MPa or more and joining force, and at that time, pressure P2 is at least 500MPa.  [3] Solution heat treatment and aging treatment were applied to the two above materials to achieve a room temperature force of 650 ° C.  3. The friction welding method according to claim 2, wherein the friction welding is performed after increasing 2% resistance to 700 MPa or more.  [4] The friction welding method according to claim 2, wherein a shift margin when the pressure P2 is applied is at least 14 mm.  [5] Relatively rotate one material that is also a precipitation-strengthened Ni-base alloy forging and the other material that is also a precipitation-strengthened Ni-based alloy forging or a precipitation-strengthening Fe-based alloy forging. However, in the friction welding method in which pressure P1 is applied to generate frictional heat on the contact surface and then higher pressure P2 is applied to join, the elastic limit stress of the two materials is higher than the pressure P2. A friction welding method, characterized in that heat bonding is performed so that force bonding is performed, and a pressure of at least 500 MPa is applied as the pressure P2.  [6] The friction welding method according to [5], wherein a shift margin when the pressure P2 is applied is at least 14 mm.  [7] The friction welding method according to claim 1, wherein after the friction welding is completed, an aging treatment is performed so that the time of exposure to 600 ° C or more does not exceed 8 hours. [8] Precipitation-strengthened Ni-based alloy forged turbine wheel and precipitation-strengthened Ni-based alloy forging The precipitation-strengthened Ni-based alloy and the precipitation-strengthened die are manufactured by a centrifugal gas turbine manufacturing method including a step of joining a shaft made of a material or precipitation-strengthened Fe-base alloy forging material by friction welding. Ni-based alloy forgings or precipitation-strengthened Fe-based alloy forgings have 0.2% resistance in the range from room temperature to 650 ° C at least 700 MPa, and friction welding is also performed. The pressure P1 is applied while the shaft is relatively rotated to generate frictional heat on the contact surface, and then joining is performed with a pressure at least 500 MPa higher than the pressure P1. A method for manufacturing a centrifugal gas turbine.  [9] The turbine wheel and the shaft are subjected to a solution heat treatment and an aging treatment so that the 0.2% resistance in a range from room temperature to 650 ° C. is at least 700 MPa, and then the friction welding is performed. The method for manufacturing a centrifugal gas turbine according to claim 8.  [10] The method for producing a centrifugal gas turbine according to [8], wherein after the friction welding is completed, an aging treatment is performed so that the time of exposure to 600 ° C or higher does not exceed 8 hours.  [11] The shaft is a stepped shaft, and the shaft is subjected to a cutting process in which the shaft is processed into a stepped shape in the state of the solution heat treatment, and after the friction welding, the shaft is again exposed to 600 ° C. 10. The method for producing a centrifugal gas turbine according to claim 9, wherein the aging treatment is performed and the final shape is finished after the aging treatment does not exceed 8 hours. [12] C in a weight _{^{0/0: 0.05~0.3%, B}} : 0.01~0.05%, Hf: 0.5~3.0%, Co: 8~18%, Ta: 3~8.5%, Cr: l.5~16 %, Mo: 0 ~ l%, W: 5 ~ 15%, Ti: 0 ~ l.5%, Al: 4.5 ~ 5.8%, Nb: 0 ~ 2%, Re: 0 ~ 6%, V: 0 ~ l%, Zr: 0 to 0.01%, one or more combinations of Pt or platinum group elements: 0 to 2%, one or more combinations of Y or rare earth elements: 0 to 2%, Combination of one or more of Mg or alkaline earth metal: 0 to 0.5%, combination of one or more of Fe, Ga, Ge: 0 to 5% or less, with the balance being 50% or more 9. The centrifugal gas according to claim 8, wherein the turbine wheel made of precipitation-strengthened Ni-based alloy forged NU and the shaft made of precipitation-strengthened Ni-based alloy forging or precipitation-strengthened Fe-based alloy forging are joined. A method for manufacturing a turbine. [13] C in a weight _{^{0/0: 0.1~0.3%, B}} : 0.016~0.05%, Hf: l.3~3.0%, Co: 10.2 ~18%, Ta: 3~5%, Cr: l.5 ~ 16%, Mo: 0 ~ l%, W: 9 ~ 15%, Ti: 0 ~ l%, Al: 5 to 5.8%, Nb: 0 to 2%, V: 0 to 1%, Zr: 0 to 0.01%, Pt or one or more combinations of platinum group elements: 0 to 2 %, Y or a combination of one or more of rare earth elements: 0 to 2%, Mg or a combination of one or more of alkaline earth metals: 0 to 0.1%, Fe, A combination of one or more of Ga and Ge: 0-5% or less, balance of 50% or more NU-precipitation strengthened Ni-based alloy 9. The method for producing a centrifugal gas turbine according to claim 8, wherein the shaft made of a forged material or a precipitation strengthened Fe-based alloy forged material is joined. [14] C in a weight _{^{0/0:. 0. 1~0 3}} %, B:. 0. 016~0 05%, Hf:.. L 3~3 0%, Co: 10. 2 ~18%, Ta: 2.8 to 4.7%, Cr: l. 5 to 16%, Mo: 0 to l%, W: 9 to 15%, Ti: 0 to 1%, Al: 5 to 5.8%, Nb: 0 to 2%, Re: 0.2 to 6%, V: 0.15% or less, Zr: 0.03 to 0.08%, balance 50% or more of NU 9. The method of manufacturing a centrifugal gas turbine according to claim 8, wherein the turbine wheel that also serves as a porcelain joint and the shaft made of precipitation strengthened Ni-base alloy forged material or precipitation strengthened Fe-based alloy forged material are joined.  [15] Includes a step of joining the exhaust side impeller made of precipitation-strengthened Ni-base alloy and a shaft made of precipitation-strengthened Ni-base alloy forging or precipitation-strengthened Fe-base alloy forging by friction welding. The turbocharger is manufactured in a range from room temperature to 650 ° C of the precipitation-strengthened Ni-base alloy deposit and the precipitation-strengthened Ni-base alloy forging or precipitation-strengthened Fe-base alloy forging. 0.2% resistance is at least 700MPa and friction welding is also performed, and in the friction welding process, pressure P1 is applied while relatively rotating the exhaust side impeller and the shaft, and frictional heat is applied to the contact surface. And then joining is carried out under a pressure of at least 500 MPa higher than the pressure P1.  [16] The exhaust side impeller and the shaft are subjected to a solution heat treatment and an aging treatment so that a 0.2% resistance against a room temperature force of 650 ° C is at least 700 MPa, and then the friction welding is performed. The method for producing a turbocharger according to claim 15.  17. The method for producing a turbocharger according to claim 16, wherein after the friction welding is completed, an aging treatment is performed so that the time of exposure to 600 ° C or higher does not exceed 8 hours. [18] The shaft is a stepped shaft, and the shaft is subjected to a cutting process in which the shaft is processed into a stepped shape after being subjected to the solution heat treatment. After the friction welding, the shaft is again exposed to 600 ° C. 17. The method for producing a turbocharger according to claim 16, wherein after the aging treatment is performed for not more than 8 hours, the final shape is finished after the aging treatment. C in a weight _{^{0/0: 0.05~0.3%, B}} : 0.01~0.05%, Hf: 0.5~3.0%, Co: 8~18%, Ta: 3~8.5%, Cr: l.5~16%, Mo : 0 ~ l%, W: 5 ~ 15%, Ti: 0 ~ l.5%, Al: 4.5 ~ 5.8%, Nb: 0 ~ 2%, Re: 0 ~ 6%, V: 0 ~ l%, Zr: 0 to 0.01%, Pt or one or more combinations of platinum group elements: 0 to 2%, Y or one or more combinations of rare earth elements: 0 to 2%, Mg or alkali A combination of one or more earth metals: 0 to 0.5%, a combination of one or more of Fe, Ga, and Ge: 0 to 5% or less, with a balance of 50% or more. 16. The turbocharger according to claim 15, wherein the exhaust-side impeller also serving as a type Ni-based alloy material is joined to the shaft made of precipitation-strengthened Ni-base alloy forging or precipitation-strengthened Fe-based alloy forging. Production method.