A method for preventing and treating hot cracking of a complex thin-wall structure of a 800 DEG C nickel-based superalloy

Abstract

The present application relates to a kind of prevention and control method of 800 DEG C nickel-based superalloy complex thin-walled structural member repair welding hot crack, belong to the field of welding repair technology, solve the problems of low qualified rate, repair welding hot crack tendency, poor high-temperature mechanical properties of welding point after repair welding in prior art of 800 DEG C nickel-based superalloy complex thin-walled structural member.A kind of prevention and control method of 800 DEG C nickel-based superalloy complex thin-walled structural member repair welding hot crack, preheating welding area to 300~600 DEG C before welding;Welding material is same as base material;Welding process is tungsten electrode argon arc welding, welding current is ≤70A, and welding wire diameter is ≤3mm.The high-temperature alloy complex thin-walled structural member manufacturing qualified rate is improved, and the high-temperature strength of structural member is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding repair, in particular to a method for preventing and treating hot cracking of 800 DEG C nickel-based superalloy complex thin-walled structural parts. BACKGROUND

[0002] High-temperature alloy structural parts, such as a casing, a pre-rotation nozzle, a guider support, etc., are key hot end components of an aero-engine, and their performance directly affects the thrust, efficiency, durability and safety of the engine, and is one of the key factors to improve the overall performance of the engine. Due to the design requirements of the overall and lightweight of the new generation of aero-engines, the current structural parts tend to adopt integrated design, the size of the casting is large, the internal cavity is super complex, and the wall thickness is thin, which is prone to produce metallurgical defects during casting, and often needs to be repaired by repair welding. However, since the maximum service temperature requirement of the new generation of aero-engines for the structural parts is more than 800 DEG C, in order to ensure the high-temperature strength of the structural parts, the alloy often contains a high content of Al, Ti, Nb, Mo and other elements, and the repair welding needs to be performed by using the base welding wire or the welding wire with a high content of Al, Ti, Nb, Mo and other elements, and the hot cracking tendency is large. At the same time, due to the complex structure of the casting and the large thickness difference, stress concentration is easily generated during welding, which aggravates the generation of hot cracking.

[0003] At present, although there are many studies on the repair welding of 800 DEG C nickel-based high-temperature alloy, these studies all use dissimilar welding wires with good welding performance and poor mechanical properties for repair welding, and the hot cracking tendency of the welding points is small but the high-temperature strength is low, which cannot meet the needs of the actual service environment. SUMMARY

[0004] In view of the above analysis, the embodiments of the present application aim to provide a method for preventing and treating hot cracking of 800 DEG C nickel-based high-temperature alloy complex thin-walled structural parts, to solve at least one of the problems of low qualification rate, large repair welding hot cracking tendency, poor high-temperature mechanical properties of the welding points after repair welding, etc. of the existing 800 DEG C nickel-based high-temperature alloy complex thin-walled structural parts.

[0005] The embodiments of the present application provide a method for preventing and treating hot cracking of 800 DEG C nickel-based high-temperature alloy complex thin-walled structural parts, the welding area is preheated in two stages before welding, and the preheating temperature is 300-600 DEG C; the welding material is the same as the base material; the welding process is tungsten inert gas welding, the welding current is ≤70 A, and the welding wire diameter is ≤3 mm.

[0006] Preferably, the welding process is performed in a vacuum welding box.

[0007] Notably, the wall thickness of the welding area of the thin-walled structural part is ≤3 mm and / or the welding area is located at the inner cavity position of the structural part.

[0008] Further, the two-stage preheating method of the welding area is:

[0009] S1, preheat the whole structure at 150-250℃ for 10-40min, then immediately put into the vacuum welding chamber to vacuumize and fill argon;

[0010] S2, locally preheat the welding area: preheat the welding points so that the preheating temperature of the welding points reaches 300-600℃.

[0011] Specifically, in S1, the vacuum welding chamber is first vacuumized to <8Pa, and then filled with argon to -0.01MPa to +0.05MPa.

[0012] Preferably, in S1, the preheating of the structure is carried out in an oven or a heat treatment furnace; in S2, the preheating of the welding points is carried out by an induction heater or a hot torch.

[0013] Further, in S2, when the hot torch is used for preheating, the power of the hot torch is 1000W-2000W, and the welding area is preheated from both sides, the procedure of which is: after heating the front side for 30-90s, the back side of the welding area is heated for 30-90s, and the process is repeated for 3-5 times, and finally the heating on the front side is ended; when the induction heater is used for preheating, the induction coil is placed on the welding area, and the heating time is 30-120s, wherein the power of the induction heater is 10kW-20kW.

[0014] Preferably, before welding, the welding wire and the tungsten electrode are pre-treated, the welding wire is repeatedly wiped with acetone or alcohol until the surface is free of visible contaminants and has a uniform metallic luster; the end of the tungsten electrode is ground into a flat-bottomed cone, and the length of the tungsten electrode is 3cm-20cm.

[0015] It should be noted that the single repair welding time is less than 3 minutes; before each repair welding, the casting is cooled to below 200℃.

[0016] Further, the welding area is the hole, and the repair welding sequence is from the periphery to the center.

[0017] Compared with the prior art, the present application can at least achieve one of the following beneficial effects:

[0018] 1. The present application uses welding materials with the same material quality as the base material, which can ensure the high-temperature strength of the structure, reduce the thermal stress generated by preheating before welding, thereby reducing the residual stress after welding, effectively reducing the tendency of thermal cracking, and effectively reducing the generation of welding thermal cracks and improving the qualification rate of high-temperature alloy castings.

[0019] 2, the present application adopts two-stage preheating, the whole structure and the double preheating mechanism of the welding area by optimizing the preheating procedure before welding;Before the local preheating of the welding area, the whole structure is preheated, which can effectively slow down the heat dissipation speed of the welding area, ensure the continuity of the welding process temperature, on the other hand, can reduce the temperature gradient between the welding area and the structure body, further reduce the risk of stress concentration;

[0020] The local preheating of the welding area can effectively reduce the temperature difference between the arc and the base material during welding, thereby reducing the thermal stress generated, and further reducing the residual stress after welding, effectively reducing the tendency of thermal cracking;

[0021] By strictly controlling the temperature of the whole structure preheating, the preheating effect is guaranteed while reducing the influence on the working environment in the vacuum welding chamber.

[0022] 3, the present application further optimizes the operation procedure and the repair welding sequence, controls the single repair welding time, prevents local overheating and tungsten melting loss of high density inclusions;Adopting the repair welding sequence of outside first and then center, effectively preventing stress concentration in the welding area, reducing the tendency of thermal cracking, especially for the repair welding of the perforated area, the effect is remarkable.

[0023] 4, the welding process and welding sequence of the present application have strong universality, which can adapt to the welding requirements of nickel-based high-temperature alloy with 800 DEG C in thin-walled area, uneven wall thickness area and complex inner cavity area, avoiding the complexity of formulating different processes and procedures due to regional differences or wall thickness changes, thereby significantly improving the efficiency of repair welding.

[0024] In the present application, the above technical solutions can be combined with each other to realize more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained by the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are for the purpose of illustrating preferred embodiments of the present application and are not to be construed as limiting the present application, wherein the same reference numerals in the drawings denote the same elements.

[0026] Fig. 1(a) is a schematic diagram of the long slit-shaped perforation welding sequence of the present application;

[0027] Fig. 1(b) is a schematic diagram of the near-circular perforation welding sequence of the present application;

[0028] Figure 2 Fig. 1(b) is a schematic diagram of the near-circular perforation welding sequence of the present application;

[0029] Figure 3 Picture of the real object after welding of the perforation for Example 2 of the present application;

[0030] Figure 4 Picture of the real object after welding of the perforation for Example 3 of the present application;

[0031] Figure 5 Picture of the real object after welding of the perforation for Example 4 of the present application;

[0032] Figure 6 Picture of the real object after welding of the perforation for Comparative Example 1 of the present application;

[0033] Figure 7 Picture of the X-ray after welding of the perforation for Comparative Example 2 of the present application;

[0034] Figure 8 Picture of the real object after welding of the perforation for Comparative Example 3 of the present application;

[0035] Figure 9 Picture of the preheating of the torch for the present application;

[0036] Figure 10 Picture of the preheating of the induction for the present application. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present application will be described in detail below with reference to the drawings, which form a part of this application, and together with the description, are used to illustrate the principles of the present application, but not to limit the scope thereof.

[0038] High-temperature alloy is prone to produce hot cracks and strain age cracks during welding, and the hot cracks include solidification cracks, liquation cracks, etc. Compared with the prevention of strain age cracks by post-weld heat treatment, the prevention of hot cracks is more focused on the control of metallurgical factors and welding process.

[0039] 800℃-resistant nickel-based high-temperature alloy has a high tendency of hot cracks during welding due to the high content of Al, Ti, Nb, Mo and other elements. In particular, the strengthening mechanism of the precipitation-strengthened high-temperature alloy depends on the formation of precipitated phases (such as γ' phase) in the alloy. Due to the influence of welding thermal cycle, the elements (such as Al and Ti) near the precipitated phase are prone to segregation. Based on the above reasons, if the base material body welding wire is used, the high Al and Ti content of the welding wire will further increase the hot crack sensitivity. Therefore, in the prior art, when repairing the nickel-based high-temperature alloy, a dissimilar welding wire with good welding performance and poor mechanical properties is generally used for repair welding. Although it can reduce the hot crack tendency of the welding point, the high-temperature strength is low and cannot meet the needs of the actual service environment. With the increasing requirement of high-temperature strength of structural parts, using the base material body welding wire is the best choice, and how to control the generation of hot cracks becomes the key.

[0040] In one specific embodiment of the present application, a method for preventing and treating hot cracking of a complex thin-walled structure of a 800℃-resistant nickel-based superalloy is disclosed, wherein the welding area is preheated in two stages before welding, and the preheating temperature is 300-600℃; the welding material is the same as the base material; and the welding process is tungsten inert gas welding, with a welding current of ≤70A and a welding wire diameter of ≤3mm.

[0041] Specifically, the welding area is a region with a radius of 10-20mm and the welding wire diameter is determined according to the welding current range.

[0042] Preheating the welding area before welding can reduce the temperature difference between the arc and the base material during welding, thereby reducing the thermal stress, and further reducing the residual stress after welding, effectively reducing the tendency of hot cracking; and controlling the appropriate welding current and welding wire diameter can reduce the heat input.

[0043] Preferably, the preheating temperature of the welding area before welding is 300℃, 350℃, 400℃, 450℃, 500℃, 530℃, 550℃, or 600℃. The welding current is 50A, 55A, 60A, 65A, or 70A.

[0044] Preferably, the welding process is carried out in a vacuum welding box, which effectively isolates the surrounding air, protects the welding area from oxidation, better controls the arc and molten pool, reduces welding defects, and ensures sufficient argon protection and good weld accessibility.

[0045] Further, the wall thickness of the welding area of the thin-walled structure is ≤3mm and / or the welding area is located in the internal cavity of the structure. On the one hand, the structure is large in size, contains super-complex cavities, and has a thin wall, and is prone to metallurgical defects during casting, and needs to be repaired by welding; on the other hand, the wall thickness and location of the welding area limit the release path of the welding deformation, causing stress concentration in the welding area, and further causing welding stress, making it difficult to weld.

[0046] It should be noted that the two-stage preheating method of the welding area is as follows:

[0047] S1, preheat the entire structure at 150-250℃ for 10-40min, and then immediately put it into a vacuum welding box for vacuumizing and argon filling;

[0048] S2, locally preheat the welding area: preheat the welding area to a preheating temperature of 300-600℃.

[0049] Preheating the welding area can reduce the temperature difference between the arc and the base material during welding, and the higher the preheating temperature, the more conducive to reducing thermal stress. However, if the preheating temperature is too high, it will cause excessive heat input in the welding area, which may cause overheating of the material or a decrease in the performance of the heat-affected zone.

[0050] Before local preheating of the welding area, the whole structure is preheated, which can effectively slow down the heat dissipation rate of the welding area. If the heat dissipation rate of the welding area is too fast, the pre-welding temperature of the welding area will not be enough, which will affect the continuity of the temperature during the welding process and increase the risk of welding stress and cracks. On the other hand, it can reduce the temperature gradient between the welding area and the structure body, further reducing the risk of stress concentration.

[0051] The whole structure preheating temperature needs to be strictly controlled. If the preheating temperature is too low, it cannot effectively slow down the heat dissipation rate. If the preheating temperature is too high, the working environment in the vacuum welding box will be poor, and the energy consumption will be too high.

[0052] Preferably, the whole structure preheating temperature in S1 is 150℃, 180℃, 200℃, 220℃, or 250℃.

[0053] Preferably, in S1, the vacuum welding box is first evacuated to <8Pa, and then filled with argon to -0.01MPa~+0.05MPa.

[0054] Exemplarily, in S1, the structure preheating is carried out in an oven or a heat treatment furnace; in S2, as shown in Figure 9 、 Figure 10 The welding area preheating mode is an induction heater or a hot air gun.

[0055] Specifically, in S2, when the hot air gun is used for preheating, the hot air gun power is 1000W~2000W, and double-sided preheating is carried out on the welding area. The procedure of the double-sided preheating is as follows: after heating the front surface for 30~90s, the back surface of the welding area is heated for 30~90s, and the process is repeated for 3~5 times, and finally the heating on the front surface is ended. The higher temperature on the front surface is beneficial to the control of the smaller temperature difference between the electric arc and the welding area during the front surface welding process.

[0056] In S2, when the induction heater is used for preheating, the induction coil is placed on the welding area, and the heating time is 30~120s, wherein the induction heater power is 10kW~20kW.

[0057] Preferably, before welding, the welding wire and the tungsten electrode are pre-welded. The welding wire is repeatedly wiped with acetone or alcohol until the surface is free of visible contaminants and has a uniform metallic luster. The end of the tungsten electrode is ground into a flat-bottomed cone, and the length of the tungsten electrode is 3cm-20cm.

[0058] Specifically, the single repair welding time is less than 3 minutes; before each repair welding, the casting is cooled to below 200℃.

[0059] Further, the welding area is a through-hole. When the welding area is a through-hole, more welding time and more welding times are required, and the heat input of the welding process is more difficult to control.

[0060] It should be noted that when the through-hole is welded, the repair welding sequence is peripheral first and then central.

[0061] Exemplarily, as shown in FIG. 1(a), when the through-hole is in the shape of a long slit, the repair welding sequence is to repair from both ends of the length direction of the through-hole to the middle.

[0062] Exemplarily, as shown in FIG. 1(b), when the through-hole is in the shape of a near circle, the repair welding sequence is to repair along the outer circumferential direction of the through-hole to the center.

[0063] The repair welding sequence of peripheral first and then central can prevent stress concentration at the welding points of the through-hole. The peripheral welding first allows the weld to have free shrinkage space, reduces the concentration of heat input, thereby reducing the welding stress; otherwise, stress concentration will occur because the weld of the subsequent welding will be constrained by the first welding area, resulting in stress concentration and potential crack risk.

[0064] In summary, the present application uses welding materials with the same material quality as the base material, which can ensure the high temperature strength of the structural member, and through preheating before welding, the temperature difference during welding is reduced to reduce the thermal stress generated, thereby reducing the residual stress after welding, effectively reducing the tendency of thermal cracking; control the appropriate welding current and wire diameter, reduce the heat input, effectively reduce the generation of welding thermal cracks, and improve the qualified rate of high-temperature alloy castings.

[0065] The prevention and control method of the present application for repairing welding thermal cracks of 800℃ nickel-based high-temperature alloy complex thin-walled structural members will be described below in conjunction with specific examples.

[0066] Example 1

[0067] The present embodiment provides a prevention and control method for repairing welding thermal cracks of 800℃ nickel-based high-temperature alloy complex thin-walled structural members.

[0068] The thin-walled structural member is a machine case with a material of K439B.

[0069] The welding material is a K439B body wire.

[0070] The pre-welding treatment and repair welding process includes the following steps:

[0071] S1, preheat the structural member at 200℃ for 15min, and then immediately put it into a vacuum welding box to vacuum and fill argon;

[0072] S2, the welding area is heated for 60s by using a 1500W hot air gun to heat the front surface of the welding area for 60s, and the reciprocating alternation is 5 times, and the actual temperature of the front surface of the welding area is 340℃;

[0073] S3, tungsten argon arc welding is performed, the welding current is 60A, and the welding wire diameter is Φ2mm; during welding, the single repair welding time is less than 3 minutes, before each repair welding, the cast is cooled to below 200℃, and the repair welding sequence of each welding point is from the periphery to the center.

[0074] As shown in Figure 2 , the welding point does not crack after welding, and the fluorescence and X-ray show no defects; the 800℃ high temperature yield strength of the welding point reaches 770MPa, which is more than 85% of the 800℃ high temperature yield strength of the body material, and meets the service requirements.

[0075] Example 2

[0076] The embodiment provides a method for preventing and treating repair welding hot cracks of an 800℃ nickel-based high-temperature alloy complex thin-wall structural part.

[0077] The thin-wall structural part is a machine case with K439B material.

[0078] The welding material is a K439B body welding wire.

[0079] The pre-welding treatment and repair welding process comprises the following steps:

[0080] S1, preheat the structural part at 200℃ for 15min, and then immediately put it into a vacuum welding box to extract vacuum and fill argon;

[0081] S2, the welding area is heated for 90s by using a 15kW induction heater, and the actual temperature of the front surface of the welding area is about 530℃;

[0082] S3, tungsten argon arc welding is performed, the welding current is 60A, and the welding wire diameter is Φ2mm; during welding, the single repair welding time is less than 3 minutes, before each repair welding, the cast is cooled to below 200℃, and the repair welding sequence of each welding point is from the periphery to the center.

[0083] As shown in Figure 3 , the welding point does not crack after welding, and the fluorescence and X-ray show no defects.

[0084] Example 3

[0085] The embodiment provides a method for preventing and treating repair welding hot cracks of an 800℃ nickel-based high-temperature alloy complex thin-wall structural part.

[0086] The thin-wall structural part is a machine case with K439B material.

[0087] The welding material is a K439B body welding wire.

[0088] The pre-welding treatment and repair welding process comprises the following steps:

[0089] S1, preheating the structural part at 150℃ for 35 min, and then immediately placing it into a vacuum welding chamber to be vacuumized and filled with argon;

[0090] S2, heating the welding area using an induction heater with a power of 15 kW for 50 s, and the actual temperature of the front surface of the welding area is about 350℃;

[0091] S3, performing tungsten inert gas welding, the welding current is 65 A, and the diameter of the welding wire is Φ3 mm; during welding, the single repair welding time is less than 3 min, before each repair welding, the cast is cooled to below 200℃, and the repair welding sequence of each welding point is from the periphery to the center.

[0092] As shown in Figure 4 , the welding points after welding do not crack, and the fluorescence and X-ray show no defects.

[0093] Example 4

[0094] The embodiment provides a method for preventing and treating repair welding hot cracks of a complex thin-wall structural part of a 800℃-resistant nickel-based high-temperature alloy.

[0095] The thin-wall structural part is a machine case made of K439B.

[0096] The welding material is a K439B body welding wire.

[0097] The pre-welding treatment and repair welding process comprises the following steps:

[0098] S1, preheating the structural part at 250℃ for 15 min, and then immediately placing it into a vacuum welding chamber to be vacuumized and filled with argon;

[0099] S2, heating the welding area using an induction heater with a power of 15 kW for 60 s, and the actual temperature of the front surface of the welding area is about 400℃;

[0100] S3, performing tungsten inert gas welding, the welding current is 60 A, and the diameter of the welding wire is Φ2 mm; during welding, the single repair welding time is less than 3 min, before each repair welding, the cast is cooled to below 200℃, and the repair welding sequence of each welding point is from the periphery to the center.

[0101] As shown in Figure 5 , the welding points after welding do not crack, and the fluorescence and X-ray show no defects.

[0102] Comparative Example 1

[0103] The embodiment provides a method for preventing and treating repair welding hot cracks of a complex thin-wall structural part of a 800℃-resistant nickel-based high-temperature alloy.

[0104] The material of the structural member and the welding material are the same as those in Example 1, and the preheating before welding and the welding process are basically the same as those in Example 1, except that the welding current is larger, being 100 A.

[0105] As shown in FIG. 6, the welding point cracks after welding, and the repair welding fails. Figure 6

[0106] Comparative Example 2

[0107] The embodiment provides a method for preventing and treating repair welding hot cracks of a complex thin-walled structural member of a nickel-based high-temperature alloy resistant to 800 DEG C.

[0108] The material of the structural member and the welding material are the same as those in Example 1, and the preheating before welding and the welding process are basically the same as those in Example 1, except that the single repair welding time is more than 6 minutes.

[0109] As shown in FIG. 7, the X-ray after welding shows that the welding point has cracks and contains high-density inclusions, and the repair welding fails. Figure 7

[0110] Comparative Example 3

[0111] The embodiment provides a method for preventing and treating repair welding hot cracks of a complex thin-walled structural member of a nickel-based high-temperature alloy resistant to 800 DEG C.

[0112] The material of the structural member and the welding material are the same as those in Example 1, and the preheating before welding and the welding process are basically the same as those in Example 1, except that the repair welding sequence of each welding point is not according to the principle of first periphery and then center.

[0113] As shown in FIG. 8, the welding point cracks after welding, and the repair welding fails. Figure 8

[0114] Comparative Example 4

[0115] The embodiment provides a method for preventing and treating repair welding hot cracks of a complex thin-walled structural member of a nickel-based high-temperature alloy resistant to 800 DEG C.

[0116] The thin-walled structural member is a machine case with a material of K439B.

[0117] The welding material is an IN625 welding wire.

[0118] The pre-welding treatment and the repair welding process steps are the same as those in Example 1.

[0119] The 800 DEG C high-temperature yield strength of the welding point is only about 420 MPa, which is difficult to meet the service requirement of 800 DEG C, while the 800 DEG C high-temperature yield strength of the welding point in Example 1 is 770 MPa, which is more than 85% of the 800 DEG C high-temperature yield strength of the bulk material, and meets the service requirement.

[0120] Comparative Example 5

[0121] ​​​The embodiment provides a prevention method of hot cracking of repair welding of a complex thin-wall structure piece of a nickel-based high-temperature alloy resistant to 800 DEG C.

[0122] The material of the structure piece and the welding material are the same as those in embodiment 1, and the preheating before welding and the welding process are basically the same as those in embodiment 1, and the difference lies in that the preheating temperature at the welding point is 200 DEG C.

[0123] The welding point cracks after welding, and the repair welding fails.

[0124] Comparative example 6

[0125] The embodiment provides a prevention method of hot cracking of repair welding of a complex thin-wall structure piece of a nickel-based high-temperature alloy resistant to 800 DEG C.

[0126] The material of the structure piece and the welding material are the same as those in embodiment 1, and the preheating before welding and the welding process are basically the same as those in embodiment 1, and the difference lies in that the overall preheating temperature of the structure piece is 120 DEG C.

[0127] The welding point cracks after welding, and the repair welding fails.

[0128] Comparative example 7

[0129] The embodiment provides a prevention method of hot cracking of repair welding of a complex thin-wall structure piece of a nickel-based high-temperature alloy resistant to 800 DEG C.

[0130] The material of the structure piece and the welding material are the same as those in embodiment 1, and the preheating before welding and the welding process are basically the same as those in embodiment 1, and the difference lies in that the diameter of the welding wire selected during welding is 4 mm.

[0131] In the range of welding current <= 70 A, because the diameter of the welding wire is too large, the welding wire cannot completely penetrate, that is, the welding wire cannot be fully melted to complete the repair welding of the welding point.

[0132] Embodiments 1 and 2 adopt the body welding wire to repair and repair the thin-wall structure piece by means of the through hole, strictly control the preheating temperature twice and the welding process conditions and the sequence, guarantee that the welding point does not crack after welding, and the fluorescence, X-ray has no defect display, and the 800 DEG C high temperature yield strength at the welding point meets the service requirement. As can be known from comparative example 1 and embodiment 1, the welding current during welding exceeds the range designed in the application, which leads to the cracking of the welding point and the failure of the repair welding; as can be known from comparative example 2 and embodiment 1, the single welding time during welding is too long, which leads to the increase of the heat input, the cracking of the welding point and the failure of the repair welding; as can be known from comparative example 3, comparative example 5, comparative example 6 and embodiment 1, the welding sequence and the preheating condition do not meet the requirements of the application, which leads to the cracking of the welding point and the failure of the repair welding; as can be known from comparative example 4 and embodiment 1, the welding material is different from the base material, although the crack risk can be reduced, but the 800 DEG C high temperature yield strength at the welding point is difficult to meet the service requirement; in comparative example 7, the diameter of the welding wire is too large, and in the welding current range designed in the application, the repair welding operation cannot be completed.

[0133] In summary, the application adopts the same welding material as the base material, can ensure the high temperature strength of the structural member, and reduces the thermal stress by preheating before welding to reduce the temperature difference during welding, and further reduces the residual stress after welding, effectively reduces the tendency of thermal cracking; control the appropriate welding current and wire diameter, reduce the heat input, effectively reduce the generation of welding thermal cracks, and improve the qualified rate of high temperature alloy castings.

[0134] The above is only a preferred embodiment of the application, but the protection scope of the application is not limited to this. Any changes or replacements that can be easily thought of by those skilled in the art within the technical range disclosed by the application should be covered within the protection scope of the application.

Claims

1. A method for preventing and treating hot cracking of repair welding of a complex thin-walled structural member of a nickel-based superalloy resistant to 800℃, characterized in that, The welding area is preheated in two stages before welding, to 300-600℃; the welding material is the same as the base material; the welding process is tungsten electrode argon arc welding, welding current ≤70A, welding wire diameter ≤3mm; The two-stage preheating method of the welding area is: S1, preheating the whole structure at 150-250℃ for 10-40min, then immediately put into a vacuum welding chamber to vacuumize and fill argon; S2, local preheating of the welding area: preheat the welding area, so that the preheating temperature of the welding area reaches 300-600℃; The welding area is a region with a weld as the center and a radius of 10-20mm; The single repair welding time is less than 3min; before each repair welding, the cast is cooled to below 200℃; When the welding area is a through hole, the repair welding sequence is peripheral first and then central, wherein: When the through hole is in the shape of a long slit, the repair welding sequence is from both ends of the length direction of the through hole to the middle; When the through hole is in the shape of a near circle, the repair welding sequence is from the outer periphery of the through hole to the center.

2. The control method according to claim 1, characterized by, The welding process is carried out in a vacuum welding chamber.

3. The control method according to claim 1, characterized by, The wall thickness of the welding area of the thin-walled structure is ≤3mm and / or the welding area is located in the inner cavity of the structure.

4. The control method according to claim 1, characterized by, In S1, the vacuum welding chamber is first vacuumized to <8Pa, and then filled with argon to -0.01MPa to +0.05MPa.

5. The control method according to claim 1, characterized by, In S1, the structure preheating is carried out in an oven or a heat treatment furnace; in S2, the welding area preheating method is an induction heater or a hot air gun.

6. The control method according to claim 1, characterized by, In S2, when the hot air gun is used for preheating, the hot air gun power is 1000W-2000W, double-sided preheating is carried out on the welding area, the double-sided preheating program is: after heating the front surface for 30-90s, heating the back surface of the welding area for 30-90s, repeating 3-5 times, and finally ending the heating on the front surface; when the induction heater is used for preheating, the induction coil is placed on the welding area, the heating time is 30-120s, and the induction heater power is 10kW-20kW.

7. The control method according to claim 2, characterized by, Before welding, the welding wire and the tungsten electrode are pre-treated, the welding wire is repeatedly wiped with acetone or alcohol until the surface is free of visible contaminants and has a uniform metallic luster; the end of the tungsten electrode is ground into a flat-bottomed cone, and the length of the tungsten electrode is 3cm-20cm.

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