A titanium alloy closed impeller laser selective melting without internal support forming method

Abstract

The present invention discloses a titanium alloy closed impeller laser selective melting non-inner support forming method; It relates to the closed impeller manufacturing technology field, including: step one, establishing a three-dimensional model of the closed impeller; step two, setting the closed impeller forming process parameters, the number of sintering layers on the lower surface of the closed impeller is 20 layers, the laser power is 60W, the scanning speed is 1200mm / s, the scanning pattern is patternless, the laser power filled in the closed impeller is 190W, the scanning speed is 1200mm / s, and the scanning pattern is a strip with a width of 0.8mm; step three, forming the three-dimensional model in a laser selective melting device to obtain a closed impeller with a substrate and a bottom support; step four, after forming is completed, the formed product is post-processed to obtain a titanium alloy closed impeller without internal support. There is no internal support in the processing and forming process of the present invention, so the internal support removal step is omitted, the closed impeller forming success rate is improved, and the cost reduction and efficiency improvement purpose is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of closed impeller manufacturing, in particular to a titanium alloy closed impeller forming method by laser selective melting without internal support. Background Art

[0002] Integral impellers are typical complex-shaped parts, especially TC4 titanium alloy integral closed impellers. These are complex parts that combine difficult-to-machine materials and difficult-to-machine shapes. Typically, closed impellers are manufactured by machining. In recent years, with the rapid development of metal additive manufacturing technology, the manufacturing method for closed impellers has gradually shifted to additive manufacturing. Additively manufactured closed impellers exhibit good integrity and excellent mechanical properties. However, due to the large number of overhangs generated by the internal features of the closed impeller, internal supports must be added to the overhangs during selective laser melting (SLM) to ensure formability. Furthermore, the small gap between the front and rear shrouds in the closed impeller makes it difficult for conventional support removal tools to penetrate, making internal support removal extremely difficult. Furthermore, the interior of the closed impeller cannot be polished, and the rough inner wall of the impeller severely impacts the fatigue performance of titanium alloy closed impellers formed by selective laser melting. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for forming a titanium alloy closed impeller by laser selective melting without internal support, so as to solve the problems existing in the above-mentioned prior art. There is no internal support during the processing and forming process, thereby eliminating the step of removing the internal support, improving the forming success rate of the closed impeller, and achieving the purpose of reducing costs and increasing efficiency.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a method for forming a titanium alloy closed impeller by laser selective melting without internal support, comprising the following steps:

[0006] Step 1: Establish a three-dimensional model of the closed impeller;

[0007] Step 2: Set the closed impeller forming process parameters. The surface of the closed impeller with an angle of less than 30° to the horizontal plane is defined as the lower surface. The number of sintered layers on the lower surface is 20. The laser power is 60W, the scanning speed is 1200mm / s, and the scanning pattern is no pattern. The laser power of the filling component in the closed impeller is 190W, the scanning speed is 1200mm / s, the scanning pattern is stripe, and the stripe width is 0.8mm.

[0008] Step 3: forming the three-dimensional model in a laser selective melting device to obtain a closed impeller with a base plate and a bottom support;

[0009] Step 4: After forming is completed, the formed product is post-processed to obtain a titanium alloy closed impeller without internal support.

[0010] Optionally, in step 1, the angular tolerance of the three-dimensional model is 18° and the accuracy is 0.008 mm.

[0011] Optionally, before forming, the three-dimensional model created in step 1 is placed horizontally on a base plate, and machining allowances are added to the three-dimensional model of the closed impeller at positions where bottom supports are required.

[0012] Optionally, the forming conditions in step three are that the argon content is below 100 ppm, the scraper is a rubber scraper, the powder layer thickness is 0.03 mm, and the powder spreading speed is 50 mm / s.

[0013] Optionally, the height of the machining allowance is 2 mm.

[0014] Optionally, post-processing includes the steps of:

[0015] Step (1), cooling for 3-5 hours, taking out the formed parts from the laser selective melting equipment, and removing the powder inside;

[0016] Step (2), subjecting the parts taken out in step (1) to stress relief annealing treatment, with an annealing temperature of 910°, a holding time of 2 hours, and oil cooling;

[0017] Step (3), separating the stress relief annealed parts from the substrate using wire cutting;

[0018] Step (4) is to cut off the bottom support of the part after separating the substrate by machining to obtain a titanium alloy closed impeller without internal support.

[0019] Optionally, step (5) is also included, using three-dimensional scanning and micro CT to observe the external contour of the closed impeller and the inner cavity forming condition to ensure that the formed product is not damaged.

[0020] Compared with the prior art, the present invention has achieved the following technical effects:

[0021] Compared to the traditional closed impeller forming method using selective laser melting, this method changes the parameters of the lower surface during the closed impeller forming process, enabling the laser power to be 60W when printing the lower surface, which is lower than the traditional power. This reduces the warping tendency of the impeller's inner cavity top from 0.13mm to 0.04mm, achieving the effect of forming the inner cavity without the need for internal support structures. This method greatly simplifies the previously cumbersome support removal process, achieving the goal of reducing costs and increasing efficiency. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0023] The purpose of the present invention is to provide a method for forming a titanium alloy closed impeller by laser selective melting without internal support, so as to solve the problems existing in the above-mentioned prior art. There is no internal support during the processing and forming process, thereby eliminating the step of removing the internal support, improving the forming success rate of the closed impeller, and achieving the purpose of reducing costs and increasing efficiency.

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific embodiments.

[0025] The closed impeller structure is an existing technology, which usually includes a volute, an impeller, an impeller cover, a rotor shaft and a rear cover. The impeller is suspended and fixed on the rear cover by the rotor shaft. The impeller is covered with an impeller cover. The volute is a smooth inclined structure with a cylindrical structure at the center, similar to a cover. The open end at the bottom of the volute cooperates with the rear cover to accommodate the impeller and the impeller cover. A fluid channel coaxial with the impeller is provided in the center of the volute, and the front end of the impeller cover is overlapped with the rear end of the fluid channel. Usually, a bottom support needs to be added under the rear cover during forming. During the processing and forming process, the top of the impeller inner cavity tends to warp more, so it is necessary to add internal supports inside the volute and the rear cover, and then remove the internal supports after forming is completed, so the processing and forming efficiency is low.

[0026] The present invention provides a method for forming a titanium alloy closed impeller by laser selective melting without internal support, while ensuring the normal forming of the closed impeller. This method ensures that no internal support is added to the closed impeller, simplifies the post-processing process, improves the success rate of the closed impeller forming process, and achieves the purpose of reducing costs and increasing efficiency. The closed impeller formed by the present invention is a titanium alloy closed impeller. The specific forming process includes the following steps:

[0027] Step 1: Create a three-dimensional model of the closed impeller. The angle tolerance of the three-dimensional model is 18° and the accuracy is 0.008mm.

[0028] Step 2: In order to ensure the dynamic balance of the formed closed impeller, the three-dimensional model created in step 1 is placed horizontally on the substrate;

[0029] Step 3: Add a 2mm machining allowance to the location where the bottom support is required on the closed impeller 3D model, so that the bottom support structure can be easily removed by machining;

[0030] Step 4: Set the closed impeller forming process parameters, define the surface of the closed impeller with an angle of less than 30° to the horizontal plane as the lower surface, the number of sintered layers of the lower surface is 20, the laser power is 60W, the scanning speed is 1200mm / s, the scanning pattern is no pattern, the laser power filled in the closed impeller is 190W, the scanning speed is 1200mm / s, the scanning pattern is a strip, and the strip width is 0.8mm.

[0031] In step five, the three-dimensional model with the remaining material is formed in a selective laser melting device, resulting in a closed impeller with a base plate and supports. Selective laser melting equipment is conventional and well-known, so its specific structure is not described in detail in this document. The three-dimensional model forming conditions are: an argon content below 100 ppm, a rubber scraper, a powder layer thickness of 0.03 mm, and a powder spreading speed of 50 mm / s.

[0032] Step 6: After the forming is completed, cool for 3-5 hours, take out the closed impeller obtained in step 5, and remove the powder inside the closed impeller;

[0033] Step 7: Stress relief annealing treatment is performed on the closed impeller at an annealing temperature of 910°, a holding time of 2 hours, and oil cooling;

[0034] Step 8: Separate the closed impeller and the base plate by wire cutting;

[0035] Step nine, using machining to remove the bottom support structure at the bottom of the closed impeller;

[0036] Step 10: Use 3D scanning and micro CT to observe the outer contour and inner cavity forming of the closed impeller.

[0037] The present invention changes the parameters of the lower surface during the closed impeller forming process so that the laser power is lower when printing the lower surface, thereby reducing the tendency of warping at the top of the closed impeller inner cavity from 0.13mm to 0.04mm, thereby achieving the effect that the inner cavity can be formed without the need for an internal support structure.

[0038] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A titanium alloy closed impeller laser selective melting without internal support forming method, characterized in that: The steps include: Step 1: Create a three-dimensional model of the closed impeller. The angle tolerance of the three-dimensional model is 18° and the accuracy is 0.008mm. Step 2: Place the three-dimensional model created in step 1 horizontally on a substrate, and add a machining allowance of 2 mm at the position where the bottom support is required for the three-dimensional model of the closed impeller; Step 3: Set the closed impeller forming process parameters. The surface of the closed impeller with an angle of less than 30° to the horizontal plane is defined as the lower surface. The number of sintered layers on the lower surface is 20. The laser power is 60W, the scanning speed is 1200mm / s, and the scanning pattern is no pattern. The laser power for filling the closed impeller is 190W, the scanning speed is 1200mm / s, the scanning pattern is a strip, and the strip width is 0.8mm. Step 4: forming the three-dimensional model in a laser selective melting device to obtain a closed impeller with a base plate and bottom support; Step 5: After forming, the formed product is post-processed to obtain a titanium alloy closed impeller without internal support; Post-processing includes the following steps: Step (1), cooling for 3-5 hours, taking out the formed parts from the laser selective melting equipment, and removing the powder inside; Step (2), subjecting the parts taken out in step (1) to stress relief annealing treatment, with an annealing temperature of 910°, a holding time of 2 hours, and oil cooling; Step (3), separating the stress relief annealed parts from the substrate using wire cutting; Step (4) is to cut off the bottom support of the part after separating the substrate by machining to obtain a titanium alloy closed impeller without internal support.

2. The titanium alloy closed impeller laser selective melting without internal support forming method according to claim 1 is characterized in that: The forming conditions in step three are that the argon content is below 100 ppm, the scraper is a rubber scraper, the powder layer thickness is 0.03 mm, and the powder spreading speed is 50 mm / s.

3. The titanium alloy closed impeller laser selective melting without internal support forming method according to claim 1 is characterized in that: The method also includes step (5), wherein three-dimensional scanning and micro-CT are used to observe the outer contour of the closed impeller and the inner cavity forming condition to ensure that the formed product is free of damage.