A welding method for cobalt-based high-temperature alloy

Abstract

The present invention provides a welding method for a cobalt-based high-temperature alloy. The welding method provided by the present invention comprises the following steps: a) treating a solid solution-strengthened cobalt-based high-temperature alloy ingot to obtain an alloy in a specific state; the treatment is a forging treatment or a stress relief annealing treatment after forging, and the obtained alloy in a specific state is a forged alloy or a stress relief alloy; the chemical composition of the solid solution-strengthened cobalt-based high-temperature alloy ingot is specifically as shown below; the grain size of the alloy in a specific state is 5 to 8 levels; b) welding is performed using the alloy in a specific state to obtain a weldment; c) solution treatment is performed on the weldment to obtain a product. The welding method of the present invention can effectively reduce crack defects in welds and heat-affected zones and improve the mechanical properties of welded joints, thereby obtaining stable, reliable welded joints without crack defects.

Description

Technical Field

[0001] The invention relates to the field of welding, and in particular to a welding method for a cobalt-based high-temperature alloy. Background Art

[0002] As a typical solid solution strengthened cobalt-based high temperature alloy, GH188 alloy mainly adopts W element for solid solution strengthening, and adds a small amount of C to form dispersed M6C carbides for strengthening. Excellent oxidation resistance is obtained through high Cr and a small amount of La. GH188 alloy has excellent high temperature thermal strength and high temperature oxidation resistance, and is widely used in the manufacture of parts such as aircraft engine combustion chambers, guide blades and aerospace engine thrust chambers.

[0003] Fusion welding (including argon arc welding, laser welding, and electron beam welding) is an indispensable process for manufacturing parts with this type of material. However, since a large amount of carbides often precipitate at the grain boundaries of the alloy, under the combined effects of stress and thermal cycles during welding, the densely distributed carbides at the grain boundaries dissolve and form liquid cracks. As a result, the alloy often forms macro or micro crack defects near the heat-affected zone and fusion line in engineering applications, which ultimately leads to problems such as out-of-tolerance and scrap. Summary of the invention

[0004] In view of this, the present invention provides a welding method for a cobalt-based high-temperature alloy, which can effectively reduce crack defects in the weld and the heat-affected zone and improve the mechanical properties of the weld joint, thereby obtaining a stable, reliable and crack-free weld joint.

[0005] The present invention provides a welding method for a cobalt-based high-temperature alloy, comprising the following steps:

[0006] a) treating a solid solution strengthened cobalt-based high temperature alloy ingot to obtain an alloy in a specific state;

[0007] The treatment is a forging treatment or a stress relief annealing treatment after forging, and the alloy in a specific state obtained is a forged alloy or a stress relief alloy;

[0008] The chemical composition of the solid solution strengthened cobalt-based high temperature alloy ingot includes:

[0009]

[0010]

[0011] The grain size of the alloy in the specific state is 5 to 8;

[0012] b) welding the alloy in the specific state to obtain a welded part;

[0013] c) performing a solid solution treatment on the weldment to obtain a product.

[0014] Preferably, in step a):

[0015] The forging conditions are: the starting forging temperature is ≥ 1050°C, and the final forging temperature is ≥ 950°C;

[0016] The stress relief annealing treatment is performed at a temperature of ≤1120°C.

[0017] Preferably, in step a):

[0018] The forging conditions are as follows: before forging, the ingot is heated to 1200±10°C and kept at this temperature for 10-15h, and then forging is started; the starting forging temperature is 1050-1200°C, and the final forging temperature is 950-1100°C;

[0019] The stress relief annealing treatment conditions are: heating to 1050-1120° C. at a rate of 5-15° C. / min and keeping the temperature for 2-6 hours, and then cooling to 100-300° C. at a rate of 2-10° C. / min.

[0020] Preferably, in step b), the welding is electron beam welding.

[0021] Preferably, the electron beam welding conditions are: acceleration voltage 60-150 kV, beam current 15-70 mA, welding speed 8-20 mm / s, scanning amplitude 0.5-2.0 mm.

[0022] Preferably, in step c), the conditions of the solution treatment are: temperature 1180±10° C., holding time 1 to 4 hours, followed by air cooling.

[0023] Preferably, the air cooling is rapid air cooling, and the cooling rate is 50 to 150° C. / min.

[0024] Preferably, in step a), the phase composition of the alloy in the specific state is: primary M6C, secondary M6C, lanthanum-rich compounds and austenite matrix γ phase; carbides at the grain boundaries are discontinuous and / or form chain grain boundaries.

[0025] The welding method provided by the present invention first performs a forging treatment or a stress relief annealing treatment after forging on a solid solution-strengthened cobalt-based high-temperature alloy ingot of a specific composition, thereby obtaining a forged alloy or a stress relief alloy, and uses the alloy in the specific state as a welding material for welding (i.e., welding is performed in a forged state or a stress relief state), adopts electron beam welding and controls certain conditions, and then performs a solid solution treatment after welding to obtain a product. The above process is conducive to reducing or avoiding the formation of cracks in the weld and the heat-affected zone, thereby solving the problem of over-tolerance and scrap caused by welding defects in the parts manufacturing process, greatly reducing the cost of parts manufacturing, and having important economic value; moreover, the welded joint obtained by the method of the present invention has excellent mechanical properties, which provides a good foundation for engineering applications. Therefore, the welding method of the present invention can effectively reduce the crack defects in the weld and the heat-affected zone and improve the mechanical properties of the welded joint, and obtain a stable, reliable welded joint without crack defects, which has important engineering applications and economic value.

[0026] The test results show that the weld and heat-affected zone of the welded parts obtained by the method of the present invention have no macroscopic and microscopic cracks, the room temperature tensile strength of the welded joint reaches more than 900MPa, the elongation after fracture reaches more than 40%, and the sustained fracture time under 927℃ / 83MPa conditions is more than 40 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 The microstructure morphology of the forged alloy rod obtained in step a) of Example 1;

[0029] Figure 2 This is the appearance morphology of the welded part obtained after welding in step b) of Example 1;

[0030] Figure 3 This is a metallographic inspection image of the welding product obtained in step c) of Example 1;

[0031] Figure 4 This is the metallographic detection image of the welding product obtained in step c) of Comparative Example 1. DETAILED DESCRIPTION

[0032] The present invention provides a welding method, comprising the following steps:

[0033] a) treating a solid solution strengthened cobalt-based high temperature alloy ingot to obtain an alloy in a specific state;

[0034] The treatment is a forging treatment or a stress relief annealing treatment after forging, and the alloy in a specific state obtained is a forged alloy or a stress relief alloy;

[0035] The chemical composition of the solid solution strengthened cobalt-based high temperature alloy ingot includes:

[0036]

[0037] The grain size of the alloy in the specific state is 5 to 8;

[0038] b) welding the alloy in the specific state to obtain a welded part;

[0039] c) performing a solid solution treatment on the weldment to obtain a product.

[0040] The welding method provided by the present invention first performs forging treatment or stress relief annealing treatment after forging on a solid solution-strengthened cobalt-based high-temperature alloy ingot of a specific composition, thereby obtaining a forged alloy or a stress-relieved alloy, and uses the alloy in the specific state as a welding material for welding (i.e., welding is performed in a forged state or a stress-relieved state), adopts electron beam welding and controls certain conditions, and then performs solid solution treatment after welding, thereby obtaining a product. The above process is conducive to reducing or avoiding the formation of cracks in the weld and the heat-affected zone, thereby solving the problem of over-tolerance and scrap caused by welding defects in the process of parts manufacturing, greatly reducing the cost of parts manufacturing, and having important economic value; moreover, the welded joint obtained by the method of the present invention has excellent mechanical properties, providing a good foundation for engineering applications.

[0041] Regarding step a) :

[0042] a) treating a solid solution strengthened cobalt-based high temperature alloy ingot to obtain an alloy in a specific state.

[0043] In the present invention, the chemical composition of the solid solution strengthened cobalt-based high temperature alloy ingot includes:

[0044]

[0045] Among them, the mass percentage of C can be specifically 0.06%, 0.07%, 0.08%, 0.09%, 0.10%. The mass percentage of Cr can be specifically 20%, 21%, 22%, 23%, 24%. The mass percentage of Ni can be specifically 20%, 21%, 22%, 23%, 24%. The mass percentage of W can be specifically 13%, 14%, 15%, 16%. The mass percentage of Si can be specifically 0.2%, 0.3%, 0.4%, 0.5%. The mass percentage of Fe can be specifically 1.54%. The mass percentage of Mn can be specifically 0.95%. The mass percentage of La can be specifically 0.03%, 0.04%, 0.05%, 0.06%, 0.07%.

[0046] In some embodiments of the present invention, the chemical composition of the solid solution strengthened cobalt-based high-temperature alloy ingot is: C0.06%, Cr 22.4%, Ni 23.1%, W 14.5%, Si 0.32%, Fe 1.54%, Mn 0.95%, B≤0.015%, La 0.07%, P≤0.02%, S≤0.015%, Ag≤0.001%, Bi≤0.0001%, Pb≤0.001%, Cu≤0.07%, Co and other inevitable impurity remainders. In some other embodiments of the present invention, the chemical composition of the solid solution strengthened cobalt-based high-temperature alloy ingot is: C 0.1%, Cr 24%, Ni 22%, W 16%, Si 0.5%, Fe2.0%, Mn0.9%, B≤0.015%, La 0.03%, P≤0.02%, S≤0.015%, Ag≤0.001%, Bi≤0.0001%, Pb≤0.001%, Cu≤0.07%, Co and other inevitable impurity remainders. In some other embodiments of the present invention, the chemical composition of the solid solution strengthened cobalt-based high-temperature alloy ingot is: C 0.08%, Cr 20.2%, Ni 20%, W 13%, Si0.2%, Fe 1.0%, Mn 0.8%, B≤0.015%, La 0.05%, P≤0.02%, S≤0.015%, Ag≤0.001%, Bi≤0.0001%, Pb≤0.001%, Cu≤0.07%, Co and other inevitable impurity remainders.

[0047] In the present invention, there is no special restriction on the preparation method of the solid solution strengthened cobalt-based high temperature alloy ingot, and it can be prepared according to the conventional preparation process of alloy ingots in the field, such as vacuum induction smelting, electroslag remelting and casting of the raw materials to obtain the alloy ingot.

[0048] In the present invention, the alloy used is the solid solution strengthened cobalt-based high temperature alloy of the above composition. For alloy materials, the effect of adding multiple elements to aluminum alloy materials cannot be equivalent to the cumulative effect of each element added to the aluminum alloy material. In the proportion control and proportion matching control of the elements, it not only involves the interaction and mutual restriction between the elements, but also the mutual influence and mutual restriction in the proportion matching. Therefore, alloy materials are a kind of material with relatively complex components and proportions, and are not a simple action relationship of 1+1=2 or 2-1=1 for general materials. Furthermore, for alloys of different series, or even alloys of different grades in the same series, there is no certain regularity in the influence of process conditions on material properties. The present invention provides a welding process that can effectively reduce crack defects in welds and heat-affected zones and improve the mechanical properties of welded joints for the solid solution strengthened cobalt-based high temperature alloy of the above composition. Moreover, in the prior art, there are many metal or alloy materials with inherent crack resistance, but good inherent crack resistance does not necessarily reduce cracks in the weld and heat-affected zone after being used as welding materials, because stress and thermal cycles will be generated during the welding process, which can easily lead to cracks in the weld and heat-affected zone. The present invention uses the alloy of the above composition as a welding material, and performs certain pre-welding treatment and welding treatment, which effectively reduces crack defects in the weld and heat-affected zone and improves the mechanical properties of the welded joint.

[0049] In the present invention, the solid solution strengthened cobalt-based high temperature alloy ingot is first treated to obtain a specific state alloy. In the present invention, the treatment is a forging treatment or a stress relief annealing treatment after forging, so as to obtain a forged alloy or a stress relief alloy, that is, the obtained specific state alloy is a forged alloy or a stress relief alloy.

[0050] In the present invention, the conditions of the forging treatment are preferably: the start forging temperature is ≥1050°C, and the final forging temperature is ≥950°C. More preferably, the conditions of the forging treatment are: the ingot is heated to 1200±10°C and kept warm for 10-15h before forging, and then the forging is started; the start forging temperature is 1050-1200°C, and the final forging temperature is 950-1100°C. Among them, the heating temperature before forging can be specifically 1190°C, 1195°C, 1200°C, 1205°C, 1210°C; the holding time before forging can be specifically 10h, 11h, 12h, 13h, 14h, 15h; the forging is homogenized and annealed by the above-mentioned pre-forging heating treatment. The start forging temperature may specifically be 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, 1200°C; the final forging temperature may specifically be 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C. In the present invention, the solid solution strengthened cobalt-based high temperature alloy ingot is forged into a rod or forging by the forging process, and then the forged rod or forging is processed into a welded part for subsequent welding process. In the present invention, the diameter of the rod is preferably 50 to 200 mm, specifically 50 mm, 90 mm, 150 mm, 180 mm, 200 mm.

[0051] In the present invention, the stress relief annealing treatment after forging refers to first performing a forging treatment and then performing a stress relief annealing treatment, wherein the forging treatment is the forging treatment described above and will not be repeated here. The conditions for the stress relief annealing treatment are preferably: temperature ≤ 1120°C. More preferably, the conditions for the stress relief annealing treatment are: heating to 1050-1120°C at a rate of 5-15°C / min and keeping warm for 2-6h, and then cooling to 100-300°C at a rate of 2-10°C / min. Among them, the heating rate can be specifically 5℃ / min, 10℃ / min, 15℃ / min; the holding temperature can be specifically 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, 1110℃, 1120℃; the holding time can be specifically 2h, 3h, 4h, 5h, 6h; the cooling rate can be specifically 2℃ / min, 5℃ / min, 8℃ / min, 10℃ / min. In the present invention, the solid solution strengthened cobalt-based high temperature alloy ingot is forged into a rod or forging by the above-mentioned stress relief annealing treatment after forging, and then the forged rod or forging is processed into a welded part for subsequent welding process.

[0052] In the present invention, the grain size of the alloy in a specific state obtained after forging or stress relief annealing after forging is 5 to 8, specifically 5, 6, 7, and 8; the use of ingots with the above grain size is conducive to reducing cracks in the welding process. If the grain size is too low, cracks are easily caused during welding. In the present invention, the phase composition of the alloy in a specific state obtained after forging or stress relief annealing after forging is: primary M6C, secondary M6C, lanthanum-rich compounds, and austenite matrix γ phase; carbides at the grain boundaries are discontinuous and / or form chain grain boundaries. Carbides are evenly distributed in the crystal without obvious bands.

[0053] In step a) of the present invention, the solid solution strengthened cobalt-based high temperature alloy ingot is first subjected to a specific forging treatment or a stress relief annealing treatment after forging, so as to obtain a forged alloy or a stress relief alloy. After extensive research and development and experimental verification by the applicant, welding with the alloy in this specific state (i.e. welding in the forged state or stress relief state) is beneficial to reducing or avoiding crack defects in the weld and the heat affected zone; if welding is performed in other states (for example, the alloy is subjected to a solid solution treatment and welding is performed with the solid solution alloy as the welding material), micro cracks will be generated in the weld and the heat affected zone after welding.

[0054] Regarding step b) :

[0055] b) using the alloy in the specific state to perform welding to obtain a welded part.

[0056] In the present invention, the alloy in the specific state is first processed into a workpiece to be welded in a desired shape, and then welding is performed. In some embodiments of the present invention, the alloy in the specific state obtained in step a) is first processed into a butt test ring, and then the test ring is used as a welding material for welding. More specifically, in step a), a forged bar is obtained by forging, and the forged bar is first processed into a butt test ring, and then welding is performed.

[0057] In the present invention, the welding is fusion welding, more preferably electron beam welding in fusion welding. In the present invention, the conditions of the electron beam welding are preferably: acceleration voltage 60-150kV, beam current 15-70mA, welding speed 8-20mm / s, scanning amplitude 0.5-2.0mm. Among them, the acceleration voltage can be specifically 60kV, 70kV, 80kV, 90kV, 100kV, 110kV, 120kV, 130kV. The beam current can be specifically 15mA, 20mA, 25mA, 30mA, 35mA, 40mA, 45mA, 50mA, 55mA, 60mA, 65mA, 70mA. The welding speed can be 8mm / s, 9mm / s, 10mm / s, 11mm / s, 12mm / s, 13mm / s, 14mm / s, 15mm / s, 16mm / s, 17mm / s, 18mm / s, 19mm / s, 20mm / s. The scanning amplitude can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm. After the above welding, a welded part is obtained. The present invention uses the alloy of the above specific composition as the welding material, which is more suitable for the above electron beam welding process, which is conducive to reducing or avoiding crack defects in the weld and the heat affected zone.

[0058] Regarding step c) :

[0059] c) performing a solid solution treatment on the weldment to obtain a product.

[0060] In the present invention, the conditions of the solution treatment are preferably: temperature 1180±10°C, holding time 1-4h, followed by air cooling. The air cooling is preferably rapid air cooling, with an air cooling rate of 50-150°C / min.

[0061] The solution temperature may be 1170°C, 1171°C, 1172°C, 1173°C, 1174°C, 1175°C, 1176°C, 1177°C, 1178°C, 1179°C, 1180°C, 1180°C, 1182°C, 1183°C, 1184°C, 1185°C, 1186°C, 1187°C, 1188°C, 1189°C, 1190°C. The holding time may be 1h, 2h, 3h, 4h. The air cooling rate may be 50°C / min, 60°C / min, 70°C / min, 80°C / min, 90°C / min, 100°C / min, 110°C / min, 120°C / min, 130°C / min, 140°C / min, 150°C / min.

[0062] After the above-mentioned solid solution treatment, the present invention obtains a welding product, and the welding product can be post-processed to obtain a part of a required size.

[0063] The welding method provided by the present invention first performs forging treatment or stress relief annealing treatment after forging on a solid solution-strengthened cobalt-based high-temperature alloy ingot of a specific composition, thereby obtaining a forged alloy or a stress-relieved alloy, and uses the alloy in the specific state as a welding material for welding (i.e., welding is performed in a forged state or a stress-relieved state), adopts electron beam welding and controls certain conditions, and then performs solid solution treatment after welding, thereby obtaining a product. The above process is conducive to reducing or avoiding the formation of cracks in the weld and the heat-affected zone, thereby solving the problem of over-tolerance and scrap caused by welding defects in the process of parts manufacturing, greatly reducing the cost of parts manufacturing, and having important economic value; moreover, the welded joint obtained by the method of the present invention has excellent mechanical properties, providing a good foundation for engineering applications.

[0064] The test results show that the weld and heat-affected zone of the welded parts obtained by the method of the present invention have no macroscopic and microscopic cracks, the room temperature tensile strength of the welded joint reaches more than 900MPa, the elongation after fracture reaches more than 40%, and the sustained fracture time under 927℃ / 83MPa conditions is more than 40 hours.

[0065] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0066] Example 1

[0067] 1. Welding process:

[0068] a) Forging the solid solution strengthened cobalt-based high temperature alloy ingot to obtain a forged alloy bar (diameter 90 mm). The forging conditions are as follows: heating the ingot to 1200°C for 12 hours before forging, and then starting forging; the starting forging temperature is 1050°C and the final forging temperature is 950°C.

[0069] The chemical composition of the solid solution strengthened cobalt-based high temperature alloy ingot is: C 0.06%, Cr 22.4%, Ni 23.1%, W14.5%, Si 0.32%, Fe 1.54%, Mn 0.95%, B≤0.015%, La 0.07%, P≤0.02%, S≤0.015%, Ag≤0.001%, Bi≤0.0001%, Pb≤0.001%, Cu≤0.07%, Co and other inevitable impurity residues. The grain size of the solid solution strengthened cobalt-based high temperature alloy ingot after forging is level 5.

[0070] b) The forged alloy rod is processed into two test rings (wall thickness 8 mm), and then the two test rings are welded together using an electron beam welding process to obtain a welded part.

[0071] The electron beam welding conditions are as follows: acceleration voltage 150 kV, beam current 20 mA, welding speed 10 mm / s, and scanning amplitude 0.6 mm.

[0072] c) The obtained welded part is subjected to solution treatment under the following conditions: temperature 1180°C, holding time 1h, followed by rapid air cooling (air cooling rate 50°C / min). After the above treatment, a welded product is obtained.

[0073] 2. Characterization and testing:

[0074] (1) Appearance:

[0075] The microstructure of the forged alloy rod obtained in step a) is as follows: Figure 1 Step b) The appearance of the welded part after welding is as shown in Figure 2 shown.

[0076] (2) Metallographic testing:

[0077] The welded product obtained in step c) is subjected to metallographic examination, and the results are as follows: Figure 3 As shown, it can be seen that there are no macro and micro crack defects in the weld and heat affected zone.

[0078] (3) Mechanical properties test:

[0079] The base material and the welded joint product obtained in step c) were respectively subjected to room temperature tensile property tests, and the results are shown in Table 1. The base material and the welded joint product obtained in step c) were respectively subjected to high temperature tests at 927°C and 83MPa, and the time for which the sample remained unbroken (i.e., the time required for the sample to break, referred to as the sustained breaking time) and the section shrinkage rate were recorded, and the results are shown in Table 1.

[0080] Table 1: Product performance

[0081]

[0082] Note: Yield strength Rp0.2 refers to the elongation strength when the specified non-proportional elongation is 0.2%. Elongation after fracture A refers to the ratio of the residual elongation of the gauge length after fracture to the original gauge length. Sectional shrinkage Z refers to the ratio of the maximum reduction in the cross-sectional area of ​​the specimen after fracture to the original cross-sectional area.

[0083] From the test results in Table 1, it can be seen that the room temperature tensile strength of the welded joint product reaches 910MPa, the yield strength Rp0.2 reaches 399MPa, and the elongation at break reaches more than 45%, showing excellent room temperature mechanical properties. At the same time, the sustained fracture time under 927℃ / 83MPa conditions is more than 40 hours, showing excellent high temperature mechanical properties. It can be seen that the room temperature and high temperature mechanical properties of the welded joint product can reach the same level as the parent material.

[0084] Example 2

[0085] 1. Welding process:

[0086] a) Forging the solid solution strengthened cobalt-based high temperature alloy ingot to obtain a forged alloy bar (diameter 90 mm). The forging conditions are as follows: heating the ingot to 1190°C for 15 hours before forging, and then starting forging; the starting forging temperature is 1200°C and the final forging temperature is 1100°C.

[0087] The chemical composition of the solid solution strengthened cobalt-based high temperature alloy ingot is: C 0.1%, Cr 24%, Ni22%, W 16%, Si 0.5%, Fe 2.0%, Mn 0.9%, B≤0.015%, La 0.03%, P≤0.02%, S≤0.015%, Ag≤0.001%, Bi≤0.0001%, Pb≤0.001%, Cu≤0.07%, Co and other inevitable impurity residues. The grain size of the solid solution strengthened cobalt-based high temperature alloy ingot after forging is 8 levels.

[0088] b) The forged alloy rod is processed into two test rings (wall thickness 8 mm), and then the two test rings are welded together using an electron beam welding process to obtain a welded part.

[0089] The electron beam welding conditions are as follows: acceleration voltage 60 kV, beam current 70 mA, welding speed 20 mm / s, and scanning amplitude 2.0 mm.

[0090] c) The obtained welded parts are subjected to solution treatment under the following conditions: temperature 1170°C, holding time 4h, followed by rapid air cooling (air cooling rate 150°C / min). After the above treatment, a welded product is obtained.

[0091] 2. Characterization and testing:

[0092] (1) Metallographic testing:

[0093] The metallographic examination of the welded product obtained in step c) shows that there are no macroscopic and microscopic crack defects in the weld and the heat-affected zone.

[0094] (2) Mechanical properties test:

[0095] The various performance tests were performed according to the test methods in Example 1, and the results are shown in Table 2.

[0096] Table 2: Product performance

[0097]

[0098] From the test results in Table 2, it can be seen that the room temperature tensile strength of the welded joint product reaches 925Pa, the yield strength Rp0.2 reaches 405MPa, and the elongation after fracture reaches more than 44%, showing excellent room temperature mechanical properties. At the same time, the sustained fracture time under 927℃ / 83MPa conditions is more than 46 hours, showing excellent high temperature mechanical properties. It can be seen that the room temperature and high temperature mechanical properties of the welded joint product can reach the same level as the parent material.

[0099] Example 3

[0100] 1. Welding process:

[0101] a) Forging a solid solution strengthened cobalt-based high temperature alloy ingot to obtain a forged alloy bar (diameter 90 mm). The forging conditions are as follows: heating the ingot to 1210°C for 10 hours before forging, and then starting forging; the starting forging temperature is 1100°C and the final forging temperature is 1000°C.

[0102] The chemical composition of the solid solution strengthened cobalt-based high temperature alloy ingot is: C 0.08%, Cr 20.2%, Ni 20%, W13%, Si 0.2%, Fe 1.0%, Mn 0.8%, B≤0.015%, La0.05%, P≤0.02%, S≤0.015%, Ag≤0.001%, Bi≤0.0001%, Pb≤0.001%, Cu≤0.07%, Co and other inevitable impurity residues. The grain size of the solid solution strengthened cobalt-based high temperature alloy ingot after forging is grade 6.

[0103] b) The forged alloy rod is processed into two test rings (wall thickness 8 mm), and then the two test rings are welded together using an electron beam welding process to obtain a welded part.

[0104] The electron beam welding conditions are as follows: acceleration voltage 120 kV, beam current 40 mA, welding speed 15 mm / s, and scanning amplitude 1.0 mm.

[0105] c) The obtained welded parts are subjected to solution treatment under the following conditions: temperature 1190°C, holding time 2h, followed by rapid air cooling (air cooling rate 100°C / min). After the above treatment, a welded product is obtained.

[0106] 2. Characterization and testing:

[0107] (1) Metallographic testing:

[0108] The metallographic examination of the welded product obtained in step c) shows that there are no macroscopic and microscopic crack defects in the weld and the heat-affected zone.

[0109] (2) Mechanical properties test:

[0110] Various performance tests were performed according to the test methods in Example 1, and the results are shown in Table 3.

[0111] Table 3: Product performance

[0112]

[0113] From the test results in Table 3, it can be seen that the room temperature tensile strength of the welded joint product reaches 915Pa, the yield strength Rp0.2 reaches 401MPa, and the elongation at break reaches more than 46%, showing excellent room temperature mechanical properties. At the same time, the sustained fracture time under 927℃ / 83MPa conditions is more than 46 hours, showing excellent high temperature mechanical properties. It can be seen that the room temperature and high temperature mechanical properties of the welded joint product can reach the same level as the parent material.

[0114] Comparative Example 1

[0115] 1. Welding process:

[0116] Welding is carried out in the solid solution state, as follows:

[0117] The method is implemented in accordance with Example 1, except that in step a), after the rod is forged, a solid solution treatment is performed at a temperature of 1180° C. for 1 hour to obtain a solid solution alloy. Steps b) to c) are the same as in Example 1.

[0118] 2. Characterization and testing:

[0119] (1) Metallographic testing:

[0120] The welded product obtained in step c) is subjected to metallographic examination, and the results are as follows: Figure 4 As shown, it can be seen that there are a large number of crack defects in the weld and heat affected zone.

[0121] (2) Mechanical properties test:

[0122] The various performance tests were performed according to the test methods in Example 1, and the results are shown in Table 4.

[0123] Table 4: Product performance

[0124]

[0125] It can be seen from the test results in Table 4 that the room temperature performance and high temperature endurance performance of the welded joint product are both poor, which is quite different from the parent material. The test results of (1)-(2) above prove that if welding is performed in a solid solution state, a large number of crack defects will be generated in the weld and the heat affected zone, and the mechanical properties of the welded joint are poor. However, the present invention welds in a specific forging or stress relief annealing state, which can effectively avoid the generation of a large number of crack defects in the weld and the heat affected zone and ensure excellent mechanical properties.

[0126] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A welding method for a cobalt-based high-temperature alloy, characterized in that: The following steps are involved: a) treating a solid solution strengthened cobalt-based high temperature alloy ingot to obtain an alloy in a specific state; The treatment is a stress relief annealing treatment after forging, and the alloy in the specific state obtained is a stress relief alloy; The chemical composition of the solid solution strengthened cobalt-based high temperature alloy ingot includes: C 0.06%~0.10%； Cr 20%~24%； Ni 20%~24%; W 13%~16%； Si 0.2%~0.5%; Fe ≤2.0%; Mn ≤1.0%; B ≤0.015%； La 0.03%~0.07%; P ≤0.02%； S ≤0.015%； Ag ≤0.001%; Bi ≤0.0001%; Pb ≤0.001%; Cu ≤0.07%; The balance of Co and other unavoidable impurities; The forging conditions are as follows: before forging, the ingot is heated to 1200±10°C and kept warm for 10-15h, and then forging begins; the starting forging temperature is 1050-1200°C, and the final forging temperature is 950-1100°C; The stress relief annealing treatment conditions are: heating to 1050-1120°C at a rate of 5-15°C / min and keeping the temperature for 2-6 hours, and then cooling to 100-300°C at a rate of 2-10°C / min; The grain size of the alloy in the specific state is 5 to 8; b) welding the alloy in the specific state to obtain a welded part; c) performing a solid solution treatment on the welded part to obtain a product; The conditions of the solution treatment are: temperature 1180±10° C., holding time 1-4 hours, followed by air cooling.

2. The welding method according to claim 1, characterized in that: In step b), the welding is electron beam welding.

3. The welding method according to claim 2, characterized in that: The electron beam welding conditions are: acceleration voltage 60-150 kV, beam current 15-70 mA, welding speed 8-20 mm / s, scanning amplitude 0.5-2.0 mm.

4. The welding method according to claim 1, characterized in that: The air cooling is rapid air cooling, and the cooling rate is 50-150°C / min.

5. The welding method according to claim 1, characterized in that: In step a), the phase composition of the alloy in the specific state is: primary M6C, secondary M6C, lanthanum-rich compounds and austenite matrix γ phase; carbides at the grain boundaries are discontinuous and / or form chain grain boundaries.

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