A low temperature environment welding method for quenched and tempered steel hub disc impeller

Abstract

The present invention relates to a low temperature environment welding method for a quenched and tempered steel hub disc impeller, and relates to the technical field of quenched and tempered steel welding, which comprises the following steps: S1, a plurality of spot fixed position welds are provided on the blade, and the depth of the spot fixed position welds is 2mm-3mm; S2, the wheel cover, the wheel disc and the groove edge of the blade are first polished and brightened within 50mm on both sides, and then the oil is cleaned; S3, the welds on the blade, the wheel cover and the wheel disc are preheated, and the preheating temperature is 120℃-150℃; S4, the wheel cover and the wheel disc are correspondingly welded with the spot fixed position welds on the blade to form a spot fixed position weld, and the spot fixed position weld is at least 50mm away from the blade inlet, and the spot fixed position weld is at least 50mm away from the blade outlet; S5, the blade, the wheel cover, the wheel disc and the process impeller are assembled; S6, annealing heat treatment; S7, the process impeller is removed; S8, the wheel hub is installed; S9, the cone disk is installed; S10, the workpiece is machined and shaped as a whole. The present application has the effect of improving the welding quality of the modulated steel hub disc impeller.

Description

Technical Field

[0001] The invention relates to the technical field of quenched and tempered steel welding, in particular to a low-temperature environment welding method for a quenched and tempered steel hub disc impeller. Background Art

[0002] In the fan system, the impeller, as the core component, rotates and works to drive the entire system. In addition to the centrifugal force, the impeller is also affected by the environment and the wind system medium during operation. Under low-temperature operating conditions below -20°C, low-temperature steels such as 16MnDR, 15MnNiDR, and 09MnNiDR can generally be used as raw materials, but the tensile strength of such raw materials cannot meet the strength requirements during high-speed operation. Although the tensile strength of low-temperature high-strength steels such as 06Ni9DR or SAF2507 super duplex stainless steel meets the design requirements and has excellent low-temperature impact toughness, the steel is expensive.

[0003] At present, the hub-disc impeller in the prior art usually uses Q690 low-alloy high-strength quenched and tempered steel as raw material. Q690 is a low-alloy high-strength quenched and tempered steel, and its low-temperature resistance is mainly due to the quenching and tempering treatment of the steel plate during the manufacturing process. The hub-disc impeller has sufficient strength when running at high speed and has certain wear resistance and corrosion resistance, and the cost is controllable. The hub-disc impeller in the prior art includes blades, a wheel cover, a wheel disc, a hub and a cone disc. The wheel disc and the cone disc are both mounted on the hub. The cone disc is close to one end of the hub, and the wheel disc is close to the other end of the hub. The wheel cover is located on the side of the cone disc away from the wheel cover. The blades are evenly distributed between the wheel cover and the hub. One side of the blade is the working surface side, and the other side of the blade is the non-working surface side. The end of the blade close to the hub is the blade inlet, and the end of the blade away from the hub is the blade outlet.

[0004] Due to the poor welding performance of the tempered steel, the impact toughness of the welded joint decreases significantly in a low temperature environment, so Q690 low alloy high strength quenched and tempered steel must be preheated before welding. However, if the temperature is not properly controlled during the preheating process, it is easy to cause cracks in the quenched and tempered steel or welding deformation of the impeller, resulting in distortion of the impeller after welding, causing the impeller to have runout deviation, dynamic balance failure, and scrapping. Summary of the invention

[0005] In order to improve the welding quality of a quenched and tempered steel hub disc impeller, the present application provides a low temperature environment welding method for a quenched and tempered steel hub disc impeller.

[0006] The low temperature environment welding method of a quenched and tempered steel hub disc impeller provided in the present application adopts the following technical solution:

[0007] A low temperature environment welding method for a quenched and tempered steel hub disc impeller comprises the following steps:

[0008] S1. Several fixed spot welds are opened on the blade, and the depth of the fixed spot welds is 2mm-3mm;

[0009] S2. Polish the wheel cover, wheel disc and blade within 50mm on both sides of the groove edge to make it bright, and then clean the wheel cover, wheel disc and blade within 50mm on both sides of the groove edge to remove oil stains;

[0010] S3. Preheat the welds on the blades, wheel covers and wheel discs at a temperature of 120°C-150°C;

[0011] S4. The wheel cover and the wheel disc are welded to the spot-fixed welds on the blades to form spot-fixed welds. The spot-fixed welds are at least 50 mm away from the blade inlet and at least 50 mm away from the blade outlet.

[0012] S5, assembling blades, wheel covers, wheel discs and process impellers;

[0013] S6, annealing heat treatment;

[0014] S7, dismantling the process impeller;

[0015] S8, install the wheel hub;

[0016] S9, install the cone;

[0017] S10, the workpiece is machined and shaped as a whole.

[0018] Preferably, step S1 includes the following steps: if the thickness of the blade parent material is less than 4 mm, the length of the point-fixed weld is 5 mm-10 mm, and the spacing between adjacent point-fixed welds is 50 mm-100 mm; if the thickness of the blade parent material is between 4 mm and 12 mm, the length of the point-fixed weld is 10 mm-15 mm, and the spacing between adjacent point-fixed welds is 100 mm-200 mm; if the thickness of the blade parent material is more than 12 mm, the length of the point-fixed weld is 15 mm-20 mm, and the spacing between adjacent point-fixed welds is 150 mm-350 mm.

[0019] Preferably, the groove where the blade contacts the wheel cover in step S2 is an asymmetric K-type, and the groove where the blade contacts the wheel disc in step S2 is an asymmetric K-type, and the groove includes a butt weld groove and a fillet weld groove, the butt weld groove angle is 70°-75°, and the fillet weld groove angle is 50°-55°.

[0020] Preferably, in step S4, the welds on the blades, wheel covers and wheel discs are welded using welding rods containing 2% nickel.

[0021] Preferably, step S5 comprises the following steps:

[0022] S51, assembling the process impeller on the side of the wheel disc away from the wheel cover by spot welding;

[0023] S52, performing back welding on all fillet welds at the blades, wheel covers and wheel discs by means of segmented back welding to form bottom layer welds, wherein the segmented back welding is based on the fixed position welding of each point, and the odd-numbered sections are welded in sequence from the blade inlet to the blade outlet first, and after the odd-numbered sections are welded, the fixed position welding is cleaned with an angle grinder, and after cleaning and grinding, the even-numbered sections are welded in sequence from the blade inlet to the blade outlet, and the original fixed position welding positions are filled at the same time;

[0024] S53, keep warm and slowly cool to room temperature, remove the insulation cotton after slow cooling for 12 hours;

[0025] S54. Perform color flaw detection and surface visual inspection on all base welds, and polish the base welds with defects;

[0026] S55. Perform filler cover welding on the welds at the blades, wheel covers and wheel discs. The filler cover welding is based on the arc starting point at the blade inlet end. The distance between the arc starting point at the blade inlet end and the arc starting point of the previous welding is at least 20 mm. The interlayer temperature of the filler cover welding is 100°C-120°C.

[0027] S56. Remove the insulation cotton after slow cooling for 2h-3h.

[0028] Preferably, in step S52 and step S55, an air gun is used to sweep and preheat the weld, the air gun pauses at the same point for no more than 3 seconds, and the preheating length of the weld in step S52 and step S55 does not exceed 500 mm.

[0029] Preferably, the step S52 comprises the following steps:

[0030] S521. Preheat the working surface of the blade at the symmetrical position simultaneously with the weld at the wheel. When the temperature measured within 50 mm on both sides of the weld is between 120°C and 150°C, perform repeated preheating for 60 seconds. After preheating, use a welding wire with a diameter of 1.2 mm and a welding current not exceeding 260A. Immediately weld the working surface of the blade at the symmetrical position simultaneously with the bottom layer of the fillet weld at the wheel by means of segmented back-welding to form a base layer weld. After welding the blade and the wheel, wrap them with thermal insulation cotton for slow cooling.

[0031] S522, sweep preheating the non-working side of the blade at the symmetrical position and the weld at the wheel cover at the same time, and when the temperature measured within 50 mm on both sides of the weld is between 120° C. and 150° C., repeatedly sweep and heat for 60 seconds, and after preheating, use a welding wire with a diameter of 1.2 mm and a welding current not exceeding 260 A, and adopt a segmented back-welding method to immediately weld the non-working side of the blade at the symmetrical position and the bottom layer of the fillet weld at the wheel cover at the same time to form a base layer weld, and wrap the blade and the wheel cover with thermal insulation cotton for slow cooling after welding;

[0032] S523, use angle grinder to clean and grind the weld inside the groove;

[0033] S524, sweep preheat the non-working side of the blade at the symmetrical position and the weld at the wheel at the same time, and when the temperature measured within 50 mm on both sides of the weld is between 120°C and 150°C, sweep and heat repeatedly for 60 seconds, and after preheating, use a welding wire with a diameter of 1.2 mm and a welding current not exceeding 260A, and adopt a segmented back-welding method to immediately weld the non-working side of the blade at the symmetrical position and the bottom layer of the fillet weld at the wheel at the same time to form a base layer weld, and wrap the blade and the wheel with insulation cotton for slow cooling after welding;

[0034] S525. Preheat the working surface of the blade at the symmetrical position simultaneously with the weld at the wheel cover by sweeping. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, repeat the sweeping heating for 60s. After preheating, use a welding wire with a diameter of 1.2mm and a welding current not exceeding 260A. Use the segmented back-welding method to immediately weld the working surface of the blade at the symmetrical position simultaneously with the bottom layer of the fillet weld at the wheel cover to form a base layer weld. After the blade and the wheel cover are welded, wrap them with thermal insulation cotton for slow cooling.

[0035] Preferably, the step S55 comprises the following steps:

[0036] S551. Preheat the welds on the working surface of the blade and the wheel at the symmetrical position by sweeping. When the temperature measured within 50 mm on both sides of the weld is between 100℃-120℃, repeat the sweeping heating for 60s. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the working surface of the blade and the wheel at the symmetrical position. After welding the blade and the wheel, perform post-heat treatment at a post-heating temperature of 200℃-250℃, and then use thermal insulation cotton for heat preservation.

[0037] S552, perform sweep preheating on the non-working side of the blade at the symmetrical position and the weld at the wheel cover. When the temperature measured within 50 mm on both sides of the weld is between 100°C and 120°C, perform repeated sweep heating for 60 seconds. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately perform fill-cover welding on the weld at the non-working side of the blade at the symmetrical position and the wheel cover. After welding the blade and the wheel cover, perform post-heat treatment at a post-heat temperature of 200°C to 250°C, and then use insulation cotton for heat preservation;

[0038] S553, sweep and preheat the welds on the non-working side of the blade at the symmetrical position and the wheel disc. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, sweep and heat repeatedly for 60s. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the non-working side of the blade at the symmetrical position and the wheel disc. After welding the blade and the wheel disc, perform post-heat treatment at a post-heating temperature of 200℃-250℃, and then use insulation cotton for heat preservation;

[0039] S554. Preheat the welds on the symmetrical working surface of the blade and the wheel cover by sweeping. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, repeat the sweeping heating for 60s. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the symmetrical working surface of the blade and the wheel cover. After welding the blade and the wheel cover, perform post-heat treatment at a post-heat temperature of 200℃-250℃, and then use thermal insulation cotton for insulation.

[0040] Preferably, step S8 comprises the following steps:

[0041] S81, use neutral flame to heat and slowly bake the wheel disc plane and the outer end surface of the wheel cover.

[0042] S82. Use a jack to level the wheel disc plane and the outer cylindrical end surface of the wheel cover;

[0043] S83, machining the inner hole of the wheel disc and the mating surface of the wheel hub;

[0044] S84. Preheat the weld on the wheel hub at a temperature of 100-150°C. After the wheel hub is preheated, weld the wheel hub with a welding rod containing 2% nickel. The welding current should not exceed 180A. After welding, wrap the wheel hub with a heat-insulating cotton strip to slow down cooling.

[0045] Preferably, the step S9 comprises the following steps:

[0046] S91, level the wheel disc once,

[0047] S92. Preheat the weld on the cone disk to a temperature of 100-150°C. After preheating, weld the cone disk with a welding rod containing 2% nickel. The welding current should not exceed 180A. After welding, wrap the cone disk with a heat-insulating cotton strip to slow down cooling.

[0048] S93, performing secondary leveling on the wheel disc;

[0049] S94, a 5mm diameter stress relief hole is opened on the surface of the cone;

[0050] S95, vibration stress relief;

[0051] S96. Completely repair the stress relief hole with welding.

[0052] In summary, the present application includes at least one of the following beneficial technical effects:

[0053] 1. By sequentially performing base welding, heat preservation and slow cooling, filling and capping welding, and post-heat preservation, the coarse grains caused by continuous heat input at the welding point are reduced, thereby reducing the phenomenon of impeller welding deformation caused by continuous heat input, and extending the martensitic phase transformation point temperature, effectively controlling the probability of cracks, and reducing the deformation of the workpiece, thereby achieving the effect of improving the welding quality of the modulated steel hub disc impeller;

[0054] 2. By increasing the groove angle and adding several fixed welds, the dwell time in the high temperature zone during a single welding is reduced, and the coarse grains caused by continuous heat input at the welding point are reduced, thereby reducing the phenomenon of impeller welding deformation caused by continuous heat input, and improving the welding quality of the modulated steel hub disc impeller;

[0055] 3. Preheat, weld and slowly cool the blades at symmetrical positions at the same time to reduce asymmetric deformation of the impeller, improve the welding quality of the modulated steel hub disc impeller, and ensure the dynamic balancing accuracy of the subsequent impeller;

[0056] 4. During the welding process, welding materials containing 2% nickel are used to refine the metal grains of the weld, improve the impact toughness of the weld, and achieve the effect of improving the welding quality of the modulated steel hub disc impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a cross-sectional view showing the positional relationship between the blade and the spot-fixed welding in the embodiment of the present application.

[0058] Figure 2 It is a cross-sectional view of a hub-disc impeller in the prior art.

[0059] Figure 3 It is a schematic diagram showing the positional relationship between the working surface side of the blade and the non-working surface side of the blade in the prior art.

[0060] Figure 4 It is a cross-sectional view showing the assembly position relationship between the wheel disc and the process impeller in the embodiment of the present application.

[0061] Figure 5 It is a schematic diagram showing the position relationship between the blades and the wheel disc in the embodiment of the present application.

[0062] Figure 6 It is a schematic diagram showing the positional relationship between the blades and the wheel cover in the embodiment of the present application.

[0063] Figure 7 It is a schematic diagram showing the positional relationship between the butt weld and the wheel cover in the embodiment of the present application.

[0064] Figure 8 It is a cross-sectional view showing the positional relationship between the blades and the disc in Example 1 of the present application.

[0065] Fig. 9 It is a cross-sectional view showing the positional relationship between the blades and the wheel cover in Example 1 of the present application.

[0066] Fig.10 It is a cross-sectional view showing the positional relationship between the butt weld and the wheel cover in Example 1 of the present application.

[0067] Fig.11 It is a cross-sectional view showing the positional relationship between the blades and the disc in Example 2 of the present application.

[0068] Fig.12 It is a cross-sectional view showing the positional relationship between the blades and the wheel cover in Example 2 of the present application.

[0069] Fig.13 It is a cross-sectional view showing the positional relationship between the butt weld and the wheel cover in Example 2 of the present application.

[0070] Explanation of the accompanying reference numerals: 1. wheel cover; 2. blade; 21. non-working surface side of blade; 22. working surface side of blade; 23. blade inlet; 24. blade outlet; 3. wheel disc; 4. wheel hub; 5. cone disc; 6. spot fixed position welding; 71. butt weld groove; 72. fillet weld groove; 81. butt weld; 82. fillet weld; 9. process impeller. DETAILED DESCRIPTION

[0071] The following is combined with Figure 1-13 This application is described in further detail.

[0072] Example 1, Example 1 of the present application discloses a low temperature environment welding method for a quenched and tempered steel hub disc impeller. Figures 1 to 10 , including the following steps:

[0073] S1. Several spot-fixed welds are opened on the blades. The spot-fixed welds are smooth and full, and the depth of the spot-fixed welds is 2mm. If the thickness of the blade base material is less than 4mm, the length of the spot-fixed weld is 5mm, and the spacing between adjacent spot-fixed welds is 50mm; if the thickness of the blade base material is between 4mm-12mm, the length of the spot-fixed weld is 10mm, and the spacing between adjacent spot-fixed welds is 100mm; if the thickness of the blade base material is more than 12mm, the length of the spot-fixed weld is 15mm, and the spacing between adjacent spot-fixed welds is 150mm.

[0074] S2, using mechanical method to machine grooves on wheel cover, wheel disc and blades to keep the grooves consistent. Polish the groove edges of wheel cover, wheel disc and blades within 50mm on both sides, and then clean the oil stains within 50mm on both sides of the groove edges of wheel cover, wheel disc and blades to achieve the effect of rust removal on the groove. The groove where the blade contacts the wheel cover is an asymmetric K-type, and the groove where the blade contacts the wheel disc in step S2 is an asymmetric K-type. The groove includes butt weld groove and fillet weld groove, and the groove angle of the butt weld is increased from the conventional 60° to 70°, and the groove angle of the fillet weld is increased from the conventional 45° to 50°. The method of increasing the groove angle is adopted to reduce the residence time in the high temperature zone during a single welding, reduce the situation of coarse grains caused by continuous heat input at the welding point, thereby reducing the phenomenon of impeller welding deformation caused by continuous heat input, and improving the welding quality of the modulated steel hub disc impeller.

[0075] S3. Preheat the welds on the blades, wheel covers and wheel discs at a preheating temperature of 120°C.

[0076] S4. Weld the wheel cover and wheel disc to the spot-fixed welds on the blades to form spot-fixed welds. The welds on the blades, wheel cover and wheel discs are welded with E7015-G type welding rods containing 2% nickel to improve the toughness of the welds. The spot-fixed welds are at least 50mm away from the blade inlet and at least 50mm away from the blade outlet.

[0077] S5, assembling the blades, wheel cover, wheel disc and process impeller, step S5 includes the following steps.

[0078] S51, assemble the process impeller on the side of the wheel disc away from the wheel cover by spot welding.

[0079] S52, forming a base layer weld at all the corner welds between the blade and the wheel cover, and forming a base layer weld at all the corner welds between the blade and the wheel disc. Step S52 includes the following steps.

[0080] S521. The working surface of the blade is welded to the wheel disc for the first time. Use an air gun to sweep and preheat the working surface of the blade at the symmetrical position and the weld at the wheel disc at the same time. The air gun should not stop at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld welded after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld bead is between 120℃-150℃, use an air gun to sweep and heat repeatedly for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, the working surface of the blade at the symmetrical position is immediately welded to the bottom layer of the fillet weld at the wheel disc. In the process of welding the working surface of the blade and the bottom layer of the fillet weld at the wheel disc, the fixed position welding of each point between the working surface of the blade and the wheel disc is used as the segmentation reference. Use E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A to weld the odd-numbered sections between the working surface of the blade and the wheel disc in sequence from the blade inlet to the blade outlet. After the odd-numbered sections between the working surface of the blade and the wheel disc are welded, use an angle grinder to grind the spot-fixed welds between the working surface of the blade and the wheel disc. After the spot-fixed welds between the working surface of the blade and the wheel disc are ground, weld the even-numbered sections between the working surface of the blade and the wheel disc from the blade inlet to the blade outlet, and fill the original spot-fixed welds between the working surface of the blade and the wheel disc. When the bottom layer of the fillet welds at the working surface of the blade and the wheel disc are all welded, a base layer weld is formed between the working surface of the blade and the wheel disc, thereby reducing the hardened structure formed by instantaneous heating due to the spot-fixed welds. When the first welding of the working surface of the blade and the wheel disc is completed, wrap the working surface of the blade and the wheel disc with thermal insulation cotton to slow down the cooling.

[0081] S522. Perform the first welding between the non-working side of the blade and the wheel cover. Use an air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel cover at the same time. The air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, use an air gun to repeatedly sweep and heat for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, immediately weld the non-working side of the blade at the symmetrical position to the bottom layer of the fillet weld at the wheel cover at the same time. During the welding process of the bottom layer of the fillet weld between the non-working side of the blade and the wheel cover, the fixed position welds at each point between the non-working side of the blade and the wheel cover are used as the segmentation reference. The E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A are used to weld the odd-numbered sections between the non-working side of the blade and the wheel cover in sequence from the blade inlet to the blade outlet. After the odd-numbered sections between the non-working side of the blade and the wheel cover are welded, the fixed position welds between the non-working side of the blade and the wheel cover are cleaned with an angle grinder. After the fixed position welds between the non-working side of the blade and the wheel cover are cleaned, the even-numbered sections between the non-working side of the blade and the wheel cover are welded in sequence from the blade inlet to the blade outlet, and the original fixed position welds between the non-working side of the blade and the wheel cover are filled. When the bottom layer of the fillet weld between the non-working side of the blade and the wheel cover is completely welded, the bottom layer weld between the non-working side of the blade and the wheel cover is formed, thereby reducing the hardened structure formed by the instantaneous heating of the fixed position welds. After the non-working side of the blade and the wheel cover are welded once, the non-working side of the blade and the wheel cover are wrapped with thermal insulation cotton to slow down the cooling.

[0082] S523. Angle grinders are used to clean and grind the weld inside the groove. Carbon arc gouging is prohibited for root cleaning.

[0083] S524. Perform the first welding between the non-working side of the blade and the wheel. Use an air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel. The air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, use an air gun to repeatedly sweep and heat for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, immediately weld the non-working side of the blade at the symmetrical position to the bottom layer of the fillet weld at the wheel. During the welding process of the bottom layer of the fillet weld between the non-working side of the blade and the disc, the fixed-position welds at each point between the non-working side of the blade and the disc are used as the segmentation reference. The E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A are used to weld the odd-numbered segments between the non-working side of the blade and the disc in sequence from the blade inlet to the blade outlet. After the odd-numbered segments between the non-working side of the blade and the disc are welded, the fixed-position welds between the non-working side of the blade and the disc are cleaned with an angle grinder. After the fixed-position welds between the non-working side of the blade and the disc are cleaned, the even-numbered segments between the non-working side of the blade and the disc are welded in sequence from the blade inlet to the blade outlet, and the original fixed-position welds between the non-working side of the blade and the disc are filled. When the bottom layer of the fillet welds between the non-working side of the blade and the disc are all welded, the bottom layer weld between the non-working side of the blade and the disc is formed, thereby reducing the hardened structure formed by the instantaneous heating of the fixed-position welds. After the first welding between the non-working side of the blade and the disc is completed, the non-working side of the blade and the disc are wrapped with thermal insulation cotton to slow down the cooling.

[0084] S525. The first welding is performed on the working surface of the blade and the wheel cover. Use an air gun to sweep and preheat the working surface of the blade at the symmetrical position and the weld at the wheel cover at the same time. The air gun should not stop at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld welded after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, use an air gun to repeatedly sweep and heat for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, the working surface of the blade at the symmetrical position is immediately welded to the bottom layer of the fillet weld at the wheel cover. In the process of welding the working surface of the blade and the bottom layer of the fillet weld at the wheel cover, the fixed position welding of each point between the working surface of the blade and the wheel cover is used as the segmentation reference. The E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A are used to weld the odd-numbered sections between the working surface of the blade and the wheel cover from the blade inlet to the blade outlet. After the odd-numbered sections between the working surface of the blade and the wheel cover are welded, use an angle grinder to grind the spot-fixed welds between the working surface of the blade and the wheel cover. After the spot-fixed welds between the working surface of the blade and the wheel cover are ground, weld the even-numbered sections between the working surface of the blade and the wheel cover from the blade inlet to the blade outlet, and fill the original spot-fixed welds between the working surface of the blade and the wheel cover. When the bottom layer of the fillet welds at the working surface of the blade and the wheel cover are all welded, a base layer weld is formed between the working surface of the blade and the wheel cover, thereby reducing the hardened structure formed by instantaneous heating of the spot-fixed welds. When the first welding of the working surface of the blade and the wheel cover is completed, wrap the working surface of the blade and the wheel cover with insulation cotton to slow down the cooling.

[0085] S53, keep warm and slowly cool to room temperature. Remove the insulation cotton after slow cooling for 12 hours.

[0086] S54, perform color flaw detection and surface visual inspection on all base welds. If the base weld is flat or concave, it is qualified, and step S55 is performed; if the base weld has surface defects such as undercut and pores, the defective base weld is polished until the base weld is qualified, and then step S55 is performed.

[0087] S55, performing filling and cover welding on the welds at the blades, wheel covers and wheel discs. Step S55 includes the following steps.

[0088] S551. Perform a second welding between the working surface of the blade and the wheel. Use a flame air gun to sweep and preheat the working surface of the blade at the symmetrical position and the weld at the wheel. The flame air gun should not pause for more than 3 seconds at the same point, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the working surface of the blade at the symmetrical position and the weld at the wheel. During the process of filling and capping welding between the blade working surface side and the wheel disc weld, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filling and capping welding is between 100℃-120℃. After the blade working surface side and the wheel disc are welded, the blade working surface side and the wheel disc are post-heat treated at a post-heat temperature of 200℃, and then the blade working surface side and the wheel disc are insulated with thermal insulation cotton.

[0089] S552. Perform a second welding on the non-working side of the blade and the wheel cover. Use a flame air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel cover at the same time. The flame air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the weld between the non-working side of the blade at the symmetrical position and the wheel cover. During the process of welding the filler cover surface between the non-working side of the blade and the weld at the wheel cover, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filler cover welding is between 100℃-120℃. After the welding of the non-working side of the blade and the wheel cover is completed, the non-working side of the blade and the wheel cover are post-heat treated at a post-heat temperature of 200℃, and then the non-working side of the blade and the wheel cover are insulated with thermal insulation cotton.

[0090] S553, the non-working side of the blade is welded to the wheel for the second time. Use a flame air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel at the same time. The flame air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds at the non-working side of the blade at the symmetrical position and the wheel. During the process of filling and capping welding between the non-working side of the blade and the weld at the wheel disc, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filling and capping welding is between 100℃-120℃. After the non-working side of the blade and the wheel disc are welded, the non-working side of the blade and the wheel disc are post-heat treated at a post-heat temperature of 200℃, and then the non-working side of the blade and the wheel disc are insulated with thermal insulation cotton.

[0091] S554, perform a second welding on the working surface of the blade and the wheel cover. Use a flame air gun to sweep and preheat the symmetrical working surface of the blade and the weld at the wheel cover at the same time. The flame air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the working surface of the blade at the symmetrical position and the wheel cover. During the process of welding the filler cover surface between the blade working surface side and the wheel cover, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filler cover welding is between 100℃-120℃. After the welding of the blade working surface side and the wheel cover is completed, the blade working surface side and the wheel cover are post-heat treated at a post-heat temperature of 200℃, and then the blade working surface side and the wheel cover are insulated with thermal insulation cotton.

[0092] S56. Remove the insulation cotton after slow cooling for 2 hours.

[0093] S6, annealing heat treatment. The assembled blades, disks, wheel covers and process impellers are sent to an annealing furnace, the annealing heating rate of the annealing furnace is 100°C / h, the annealing temperature of the annealing furnace is 540°C, and the annealing holding time is 3h. After that, the assembled blades, disks, wheel covers and process impellers are slowly cooled to 200°C and then removed from the annealing furnace for air cooling.

[0094] S7. Remove the process impeller from the assembled blades, disc and wheel cover.

[0095] S8, installing the wheel hub. Step S8 includes the following steps.

[0096] S81, use neutral flame to heat and slowly bake the wheel disc plane and the outer end surface of the wheel cover.

[0097] S82. Use a jack to level the wheel disc plane and the outer cylindrical end surface of the wheel cover, so that the unevenness of the wheel disc plane and the outer cylindrical end surface of the wheel cover are both less than 0.001;

[0098] S83, machining the inner hole of the wheel disc and the mating surface of the wheel hub;

[0099] S84. Preheat the weld on the wheel hub to 100°C. After preheating, weld the wheel hub with an E7015-G electrode containing 2% nickel, and the welding current should not exceed 180A. After welding, wrap the wheel hub with a heat-insulating cotton strip to slow down cooling.

[0100] S9, installing the cone disc. Step S9 includes the following steps.

[0101] S91, level the wheel disc once,

[0102] S92. Preheat the weld on the cone disk to 100°C. After preheating, weld the cone disk with an E7015-G electrode containing 2% nickel, and the welding current should not exceed 180A. After welding, wrap it with a heat-insulating cotton strip to slow down cooling.

[0103] S93, performing secondary leveling on the wheel disc;

[0104] S94, a stress relief hole with a diameter of 5 mm is opened on the surface of the cone;

[0105] S95, vibrate the cone to eliminate the cone stress;

[0106] S96. Completely repair the stress relief hole with welding.

[0107] S10. The impeller is machined and shaped as a whole.

[0108] Example 2, Example 2 of the present application discloses a low temperature environment welding method for a quenched and tempered steel hub disc impeller. Figures 1 to 13 , including the following steps:

[0109] S1. Several spot-fixed welds are opened on the blades. The spot-fixed welds are smooth and full, and the depth of the spot-fixed welds is 3mm. If the thickness of the blade base material is less than 4mm, the length of the spot-fixed weld is 10mm, and the spacing between adjacent spot-fixed welds is 100mm; if the thickness of the blade base material is between 4mm-12mm, the length of the spot-fixed weld is 15mm, and the spacing between adjacent spot-fixed welds is 200mm; if the thickness of the blade base material is more than 12mm, the length of the spot-fixed weld is 20mm, and the spacing between adjacent spot-fixed welds is 350mm.

[0110] S2, using mechanical method to machine grooves on wheel cover, wheel disc and blades to keep the grooves consistent. Polish the groove edges of wheel cover, wheel disc and blades within 50mm on both sides, and then clean the oil stains within 50mm on both sides of the groove edges of wheel cover, wheel disc and blades to achieve the effect of rust removal on the groove. The groove where the blade contacts the wheel cover is an asymmetric K-type, and the groove where the blade contacts the wheel disc in step S2 is an asymmetric K-type. The groove includes butt weld groove and fillet weld groove, and the groove angle of the butt weld is increased from the conventional 60° to 75°, and the groove angle of the fillet weld is increased from the conventional 45° to 55°. By increasing the groove angle, the residence time in the high temperature zone during a single welding is reduced, and the situation of coarse grains caused by continuous heat input at the welding point is reduced, thereby reducing the phenomenon of impeller welding deformation caused by continuous heat input, and improving the welding quality of the modulated steel hub disc impeller.

[0111] S3. Preheat the welds on the blades, wheel covers and wheel discs at a preheating temperature of 150°C.

[0112] S4. Weld the wheel cover and wheel disc to the spot welds on the blades. Use E7015-G welding rods containing 2% nickel to weld the welds on the blades, wheel cover and wheel disc to improve the toughness of the welds. The spot weld should be at least 50mm away from the blade inlet and at least 50mm away from the blade outlet.

[0113] S5, assembling the blades, wheel cover, wheel disc and process impeller, step S5 includes the following steps.

[0114] S51, assemble the process impeller on the side of the wheel disc away from the wheel cover by spot welding.

[0115] S52, forming a base layer weld at all the corner welds between the blade and the wheel cover, and forming a base layer weld at all the corner welds between the blade and the wheel disc. Step S52 includes the following steps.

[0116] S521. The working surface of the blade is welded to the wheel disc for the first time. Use an air gun to sweep and preheat the working surface of the blade at the symmetrical position and the weld at the wheel disc at the same time. The air gun should not stop at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld welded after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld bead is between 120℃-150℃, use an air gun to sweep and heat repeatedly for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, the working surface of the blade at the symmetrical position is immediately welded to the bottom layer of the fillet weld at the wheel disc. In the process of welding the working surface of the blade and the bottom layer of the fillet weld at the wheel disc, the fixed position welding of each point between the working surface of the blade and the wheel disc is used as the segmentation reference. Use E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A to weld the odd-numbered sections between the working surface of the blade and the wheel disc in sequence from the blade inlet to the blade outlet. After the odd-numbered sections between the working surface of the blade and the wheel disc are welded, use an angle grinder to grind the spot-fixed welds between the working surface of the blade and the wheel disc. After the spot-fixed welds between the working surface of the blade and the wheel disc are ground, weld the even-numbered sections between the working surface of the blade and the wheel disc from the blade inlet to the blade outlet, and fill the original spot-fixed welds between the working surface of the blade and the wheel disc. When the bottom layer of the fillet welds at the working surface of the blade and the wheel disc are all welded, a base layer weld is formed between the working surface of the blade and the wheel disc, thereby reducing the hardened structure formed by instantaneous heating due to the spot-fixed welds. When the first welding of the working surface of the blade and the wheel disc is completed, wrap the working surface of the blade and the wheel disc with thermal insulation cotton to slow down the cooling.

[0117] S522. Perform the first welding between the non-working side of the blade and the wheel cover. Use an air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel cover at the same time. The air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, use an air gun to repeatedly sweep and heat for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, immediately weld the non-working side of the blade at the symmetrical position to the bottom layer of the fillet weld at the wheel cover at the same time. During the welding process of the bottom layer of the fillet weld between the non-working side of the blade and the wheel cover, the fixed position welds at each point between the non-working side of the blade and the wheel cover are used as the segmentation reference. The E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A are used to weld the odd-numbered sections between the non-working side of the blade and the wheel cover in sequence from the blade inlet to the blade outlet. After the odd-numbered sections between the non-working side of the blade and the wheel cover are welded, the fixed position welds between the non-working side of the blade and the wheel cover are cleaned with an angle grinder. After the fixed position welds between the non-working side of the blade and the wheel cover are cleaned, the even-numbered sections between the non-working side of the blade and the wheel cover are welded in sequence from the blade inlet to the blade outlet, and the original fixed position welds between the non-working side of the blade and the wheel cover are filled. When the bottom layer of the fillet weld between the non-working side of the blade and the wheel cover is completely welded, the bottom layer weld between the non-working side of the blade and the wheel cover is formed, thereby reducing the hardened structure formed by the instantaneous heating of the fixed position welds. After the non-working side of the blade and the wheel cover are welded once, the non-working side of the blade and the wheel cover are wrapped with thermal insulation cotton to slow down the cooling.

[0118] S523. Angle grinders are used to clean and grind the weld inside the groove. Carbon arc gouging is prohibited for root cleaning.

[0119] S524. Perform the first welding between the non-working side of the blade and the wheel. Use an air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel. The air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, use an air gun to repeatedly sweep and heat for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, immediately weld the non-working side of the blade at the symmetrical position to the bottom layer of the fillet weld at the wheel. During the welding process of the bottom layer of the fillet weld between the non-working side of the blade and the disc, the fixed-position welds at each point between the non-working side of the blade and the disc are used as the segmentation reference. The E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A are used to weld the odd-numbered segments between the non-working side of the blade and the disc in sequence from the blade inlet to the blade outlet. After the odd-numbered segments between the non-working side of the blade and the disc are welded, the fixed-position welds between the non-working side of the blade and the disc are cleaned with an angle grinder. After the fixed-position welds between the non-working side of the blade and the disc are cleaned, the even-numbered segments between the non-working side of the blade and the disc are welded in sequence from the blade inlet to the blade outlet, and the original fixed-position welds between the non-working side of the blade and the disc are filled. When the bottom layer of the fillet welds between the non-working side of the blade and the disc are all welded, the bottom layer weld between the non-working side of the blade and the disc is formed, thereby reducing the hardened structure formed by the instantaneous heating of the fixed-position welds. After the first welding between the non-working side of the blade and the disc is completed, the non-working side of the blade and the disc are wrapped with thermal insulation cotton to slow down the cooling.

[0120] S525. The first welding is performed on the working surface of the blade and the wheel cover. Use an air gun to sweep and preheat the working surface of the blade at the symmetrical position and the weld at the wheel cover at the same time. The air gun should not stop at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm, that is, the length of the weld welded after a single preheating should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, use an air gun to repeatedly sweep and heat for 60s to ensure that the preheating temperature is uniform. After the preheating is completed, the working surface of the blade at the symmetrical position is immediately welded to the bottom layer of the fillet weld at the wheel cover. In the process of welding the working surface of the blade and the bottom layer of the fillet weld at the wheel cover, the fixed position welding of each point between the working surface of the blade and the wheel cover is used as the segmentation reference. The E81T1-K2C welding wire with a diameter of 1.2mm and a welding current not exceeding 260A are used to weld the odd-numbered sections between the working surface of the blade and the wheel cover from the blade inlet to the blade outlet. After the odd-numbered sections between the working surface of the blade and the wheel cover are welded, use an angle grinder to grind the spot-fixed welds between the working surface of the blade and the wheel cover. After the spot-fixed welds between the working surface of the blade and the wheel cover are ground, weld the even-numbered sections between the working surface of the blade and the wheel cover from the blade inlet to the blade outlet, and fill the original spot-fixed welds between the working surface of the blade and the wheel cover. When the bottom layer of the fillet welds at the working surface of the blade and the wheel cover are all welded, a base layer weld is formed between the working surface of the blade and the wheel cover, thereby reducing the hardened structure formed by instantaneous heating of the spot-fixed welds. When the first welding of the working surface of the blade and the wheel cover is completed, wrap the working surface of the blade and the wheel cover with insulation cotton to slow down the cooling.

[0121] S53, keep warm and slowly cool to room temperature. Remove the insulation cotton after slow cooling for 12 hours.

[0122] S54, perform color flaw detection and surface visual inspection on all base welds. If the base weld is flat or concave, it is qualified, and step S55 is performed; if the base weld has surface defects such as undercut and pores, the defective base weld is polished until the base weld is qualified, and then step S55 is performed.

[0123] S55, performing filling and cover welding on the welds at the blades, wheel covers and wheel discs. Step S55 includes the following steps.

[0124] S551. Perform a second welding between the working surface of the blade and the wheel. Use a flame air gun to sweep and preheat the working surface of the blade at the symmetrical position and the weld at the wheel. The flame air gun should not pause for more than 3 seconds at the same point, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the working surface of the blade at the symmetrical position and the weld at the wheel. During the process of filling and capping welding between the blade working surface side and the wheel disc weld, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filling and capping welding is between 100℃-120℃. After the blade working surface side and the wheel disc are welded, the blade working surface side and the wheel disc are post-heat treated at a post-heat temperature of 250℃, and then the blade working surface side and the wheel disc are insulated with thermal insulation cotton.

[0125] S552. Perform a second welding on the non-working side of the blade and the wheel cover. Use a flame air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel cover at the same time. The flame air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the weld between the non-working side of the blade at the symmetrical position and the wheel cover. During the process of welding the filler cover surface between the non-working side of the blade and the weld at the wheel cover, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filler cover welding is between 100℃-120℃. After the welding of the non-working side of the blade and the wheel cover is completed, the non-working side of the blade and the wheel cover are post-heat treated at a post-heat temperature of 250℃, and then the non-working side of the blade and the wheel cover are insulated with thermal insulation cotton.

[0126] S553, the non-working side of the blade is welded to the wheel for the second time. Use a flame air gun to sweep and preheat the non-working side of the blade at the symmetrical position and the weld at the wheel at the same time. The flame air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds at the non-working side of the blade at the symmetrical position and the wheel. During the process of filling and capping welding between the non-working side of the blade and the weld at the wheel disc, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filling and capping welding is between 100℃-120℃. After the non-working side of the blade and the wheel disc are welded, the non-working side of the blade and the wheel disc are post-heat treated at a post-heat temperature of 250℃, and then the non-working side of the blade and the wheel disc are insulated with thermal insulation cotton.

[0127] S554, perform a second welding on the working surface of the blade and the wheel cover. Use a flame air gun to sweep and preheat the symmetrical working surface of the blade and the weld at the wheel cover at the same time. The flame air gun should not pause at the same point for more than 3 seconds, and the preheating length of the weld should not exceed 500mm. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, use a flame air gun to sweep and heat repeatedly for 60s. After preheating, use an E7015-G electrode with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the working surface of the blade at the symmetrical position and the wheel cover. During the process of welding the filler cover surface between the blade working surface side and the wheel cover, the arc starting point at the blade inlet end is taken as the standard, and the distance between the arc starting point at the blade inlet end and the arc starting point of the previous weld is at least 20mm. At the same time, the temperature of the weld is measured, and the temperature of 10 points is calculated at random. When the layer temperature is high, natural air cooling is performed, and when the layer temperature is insufficient, a flame air gun is used to supplement the heat, so that the interlayer temperature of the filler cover welding is between 100℃-120℃. After the welding of the blade working surface side and the wheel cover is completed, the blade working surface side and the wheel cover are post-heat treated, and the post-heat temperature is 250℃, and then the blade working surface side and the wheel cover are insulated with thermal insulation cotton.

[0128] S56. Remove the thermal insulation cotton after slow cooling for 3 hours.

[0129] S6, annealing heat treatment. The assembled blades, disks, wheel covers and process impellers are sent to an annealing furnace, the annealing heating rate of the annealing furnace is 150°C / h, the annealing temperature of the annealing furnace is 560°C, and the annealing holding time is 4h. After that, the assembled blades, disks, wheel covers and process impellers are slowly cooled to 200°C, and then removed from the annealing furnace for air cooling.

[0130] S7. Remove the process impeller from the assembled blades, disc and wheel cover.

[0131] S8, installing the wheel hub. Step S8 includes the following steps.

[0132] S81, use neutral flame to heat and slowly bake the wheel disc plane and the outer end surface of the wheel cover.

[0133] S82. Use a jack to level the wheel disc plane and the outer cylindrical end surface of the wheel cover, so that the unevenness of the wheel disc plane and the outer cylindrical end surface of the wheel cover are both less than 0.001;

[0134] S83, machining the inner hole of the wheel disc and the mating surface of the wheel hub;

[0135] S84. Preheat the weld on the wheel hub at 150°C. After preheating, weld the wheel hub with an E7015-G electrode containing 2% nickel, and the welding current shall not exceed 180A. After welding, wrap the wheel hub with a heat-insulating cotton strip to slow down cooling.

[0136] S9, installing the cone disc. Step S9 includes the following steps.

[0137] S91, level the wheel disc once,

[0138] S92. Preheat the weld on the cone disk to 150°C. After preheating, weld the cone disk with an E7015-G electrode containing 2% nickel, and the welding current should not exceed 180A. After welding, wrap it with a heat-insulating cotton strip to slow down cooling.

[0139] S93, performing secondary leveling on the wheel disc;

[0140] S94, a stress relief hole with a diameter of 5 mm is opened on the surface of the cone;

[0141] S95, vibrate the cone to eliminate the cone stress;

[0142] S96. Completely repair the stress relief hole with welding.

[0143] S10. The impeller is machined and shaped as a whole.

[0144] The implementation principle of the low-temperature environment welding method of a quenched and tempered steel hub disc impeller in the present application is: by sequentially performing base welding, heat preservation and slow cooling, filling and cover welding, and post-heating and heat preservation, the situation of coarse grains caused by continuous heat input at the welding point is reduced, thereby reducing the phenomenon of impeller welding deformation caused by continuous heat input, and extending the martensitic phase transformation point temperature, effectively controlling the probability of cracks, and reducing the deformation of the workpiece, thereby achieving the effect of improving the welding quality of the modulated steel hub disc impeller. In addition, the blades in symmetrical positions are preheated, welded, and post-heated and slowly cooled at the same time to reduce the asymmetric deformation of the impeller and ensure the dynamic balancing accuracy of the subsequent impeller. At the same time, during the welding process, a welding material containing 2% nickel is used for welding, which refines the metal grains of the weld and improves the impact toughness of the weld. Thereby achieving the effect of improving the welding quality of the modulated steel hub disc impeller.

[0145] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A low temperature environment welding method for a quenched and tempered steel hub disc impeller, characterized in that: The following steps are involved: S1. Several fixed spot welds are opened on the blade, and the depth of the fixed spot welds is 2mm-3mm; S2. Polish the wheel cover, wheel disc and blade within 50mm on both sides of the groove edge to make it bright, and then clean the wheel cover, wheel disc and blade within 50mm on both sides of the groove edge to remove oil stains; S3. Preheat the welds on the blades, wheel covers and wheel discs at a temperature of 120°C-150°C; S4. The wheel cover and the wheel disc are welded to the spot-fixed welds on the blades to form spot-fixed welds. The spot-fixed welds are at least 50 mm away from the blade inlet and at least 50 mm away from the blade outlet. S5, assembling blades, wheel covers, wheel discs and process impellers; The step S5 comprises the following steps: S51, assembling the process impeller on the side of the wheel disc away from the wheel cover by spot welding; S52, performing back welding on all fillet welds at the blades, wheel covers and wheel discs by means of segmented back welding to form bottom layer welds, wherein the segmented back welding is based on the fixed position welding of each point, and the odd-numbered sections are welded in sequence from the blade inlet to the blade outlet first, and after the odd-numbered sections are welded, the fixed position welding is cleaned with an angle grinder, and after cleaning and grinding, the even-numbered sections are welded in sequence from the blade inlet to the blade outlet, and the original fixed position welding positions are filled at the same time; S53, keep warm and slowly cool to room temperature, remove the insulation cotton after slow cooling for 12 hours; S54. Perform color flaw detection and surface visual inspection on all base welds, and polish the base welds with defects; S55. Perform filler cover welding on the welds at the blades, wheel covers and wheel discs. The filler cover welding is based on the arc starting point at the blade inlet end. The distance between the arc starting point at the blade inlet end and the arc starting point of the previous welding is at least 20 mm. The interlayer temperature of the filler cover welding is 100°C-120°C. S56, remove the insulation cotton after slow cooling for 2h-3h; S6, annealing heat treatment; S7, dismantling the process impeller; S8, install the wheel hub; S9, install the cone; S10, the workpiece is machined and shaped as a whole.

2. A low temperature environment welding method for a quenched and tempered steel hub disc impeller according to claim 1, characterized in that: The step S1 comprises the following steps: if the thickness of the blade parent material is less than 4 mm, the length of the point-fixed weld is 5 mm-10 mm, and the spacing between adjacent point-fixed welds is 50 mm-100 mm; if the thickness of the blade parent material is between 4 mm and 12 mm, the length of the point-fixed weld is 10 mm-15 mm, and the spacing between adjacent point-fixed welds is 100 mm-200 mm; if the thickness of the blade parent material is more than 12 mm, the length of the point-fixed weld is 15 mm-20 mm, and the spacing between adjacent point-fixed welds is 150 mm-350 mm.

3. The low temperature environment welding method of a quenched and tempered steel hub disc impeller according to claim 1 is characterized in that: The groove where the blade contacts the wheel cover in step S2 is an asymmetric K-type, and the groove where the blade contacts the wheel disc in step S2 is an asymmetric K-type, and the groove includes a butt weld groove and a fillet weld groove, the butt weld groove angle is 70°-75°, and the fillet weld groove angle is 50°-55°.

4. The low temperature environment welding method of a quenched and tempered steel hub disc impeller according to claim 1 is characterized in that: In step S4, the welds on the blades, wheel cover and wheel disc are welded using welding rods containing 2% nickel.

5. The low temperature environment welding method of a quenched and tempered steel hub disc impeller according to claim 1 is characterized in that: In step S52 and step S55, an air gun is used to sweep and preheat the weld, and the air gun pauses at the same point for no more than 3 seconds. In step S52 and step S55, the preheating length of the weld does not exceed 500 mm.

6. A low temperature environment welding method for a quenched and tempered steel hub disc impeller according to claim 5, characterized in that: The step S52 comprises the following steps: S521. Preheat the working surface of the blade at the symmetrical position simultaneously with the weld at the wheel. When the temperature measured within 50 mm on both sides of the weld is between 120°C and 150°C, perform repeated preheating for 60 seconds. After preheating, use a welding wire with a diameter of 1.2 mm and a welding current not exceeding 260A. Immediately weld the working surface of the blade at the symmetrical position simultaneously with the bottom layer of the fillet weld at the wheel by means of segmented back-welding to form a base layer weld. After welding the blade and the wheel, wrap them with thermal insulation cotton for slow cooling. S522, sweep preheating the non-working side of the blade at the symmetrical position and the weld at the wheel cover at the same time, and when the temperature measured within 50 mm on both sides of the weld is between 120° C. and 150° C., repeatedly sweep and heat for 60 seconds, and after preheating, use a welding wire with a diameter of 1.2 mm and a welding current not exceeding 260 A, and adopt a segmented back-welding method to immediately weld the non-working side of the blade at the symmetrical position and the bottom layer of the fillet weld at the wheel cover at the same time to form a base layer weld, and wrap the blade and the wheel cover with thermal insulation cotton for slow cooling after welding; S523, use angle grinder to clean and grind the weld inside the groove; S524, sweep preheat the non-working side of the blade at the symmetrical position and the weld at the wheel at the same time, and when the temperature measured within 50 mm on both sides of the weld is between 120°C and 150°C, sweep and heat repeatedly for 60 seconds, and after preheating, use a welding wire with a diameter of 1.2 mm and a welding current not exceeding 260A, and adopt a segmented back-welding method to immediately weld the non-working side of the blade at the symmetrical position and the bottom layer of the fillet weld at the wheel at the same time to form a base layer weld, and wrap the blade and the wheel with insulation cotton for slow cooling after welding; S525. Preheat the working surface of the blade at the symmetrical position simultaneously with the weld at the wheel cover by sweeping. When the temperature measured within 50mm on both sides of the weld is between 120℃-150℃, repeat the sweeping heating for 60s. After preheating, use a welding wire with a diameter of 1.2mm and a welding current not exceeding 260A. Use the segmented back-welding method to immediately weld the working surface of the blade at the symmetrical position simultaneously with the bottom layer of the fillet weld at the wheel cover to form a base layer weld. After the blade and the wheel cover are welded, wrap them with thermal insulation cotton for slow cooling.

7. The low temperature environment welding method of a quenched and tempered steel hub disc impeller according to claim 5, characterized in that: The step S55 comprises the following steps: S551. Preheat the welds on the working surface of the blade and the wheel at the symmetrical position by sweeping. When the temperature measured within 50 mm on both sides of the weld is between 100℃-120℃, repeat the sweeping heating for 60s. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the working surface of the blade and the wheel at the symmetrical position. After welding the blade and the wheel, perform post-heat treatment at a post-heating temperature of 200℃-250℃, and then use thermal insulation cotton for heat preservation. S552, perform sweep preheating on the non-working side of the blade at the symmetrical position and the weld at the wheel cover. When the temperature measured within 50 mm on both sides of the weld is between 100°C and 120°C, perform repeated sweep heating for 60 seconds. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately perform fill-cover welding on the weld at the non-working side of the blade at the symmetrical position and the wheel cover. After welding the blade and the wheel cover, perform post-heat treatment at a post-heat temperature of 200°C to 250°C, and then use insulation cotton for heat preservation; S553, sweep and preheat the welds on the non-working side of the blade at the symmetrical position and the wheel disc. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, sweep and heat repeatedly for 60s. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the non-working side of the blade at the symmetrical position and the wheel disc. After welding the blade and the wheel disc, perform post-heat treatment at a post-heating temperature of 200℃-250℃, and then use insulation cotton for heat preservation; S554. Preheat the welds on the symmetrical working surface of the blade and the wheel cover by sweeping. When the temperature measured within 50mm on both sides of the weld is between 100℃-120℃, repeat the sweeping heating for 60s. After preheating, use a welding rod with a diameter of 4mm and a welding current not exceeding 180A to immediately fill and cover the welds on the symmetrical working surface of the blade and the wheel cover. After welding the blade and the wheel cover, perform post-heat treatment at a post-heat temperature of 200℃-250℃, and then use thermal insulation cotton for insulation.

8. The low temperature environment welding method of a quenched and tempered steel hub disc impeller according to claim 1, characterized in that: The step S8 comprises the following steps: S81, use neutral flame to heat and slowly bake the wheel disc plane and the outer end surface of the wheel cover. S82. Use a jack to level the wheel disc plane and the outer cylindrical end surface of the wheel cover; S83, machining the inner hole of the wheel disc and the mating surface of the wheel hub; S84. Preheat the weld on the wheel hub at a temperature of 100-150°C. After the wheel hub is preheated, weld the wheel hub with a welding rod containing 2% nickel. The welding current should not exceed 180A. After welding, wrap the wheel hub with a heat-insulating cotton strip to slow down cooling.

9. The low temperature environment welding method of a quenched and tempered steel hub disc impeller according to claim 1, characterized in that: The step S9 comprises the following steps: S91, level the wheel disc once, S92. Preheat the weld on the cone disk to a temperature of 100-150°C. After preheating, weld the cone disk with a welding rod containing 2% nickel. The welding current should not exceed 180A. After welding, wrap the cone disk with a heat-insulating cotton strip to slow down cooling. S93, performing secondary leveling on the wheel disc; S94, a 5mm diameter stress relief hole is opened on the surface of the cone; S95, vibration stress relief; S96. Completely repair the stress relief hole with welding.

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