SLMed GH3230 optical fiber laser non-penetrating deep penetration welding beam collecting area pit and hot crack inhibition process method

Abstract

The invention relates to an SLMed GH3230 optical fiber laser non-penetrating deep penetration welding beam collecting area pit and hot crack restraining process method, and belongs to the technical field of welding. The welding power is changed in a gradient mode in the power slow descending process of the convergence area, meanwhile, a runway type track repeated scanning strategy is combined, and the unique effects of reducing the pit depth of the convergence area and restraining cracks are achieved through the synergistic effect of the welding power and the runway type track repeated scanning strategy. By means of the process, under the same length of the collecting area, compared with linear welding, the depth of the pit in the longitudinal section of the welding seam collecting area is reduced by 62.8%, and cracks are completely restrained. Therefore, compared with an existing SLMed GH3230 laser welding arc suppression method, the process has the double beneficial effects of suppressing cracks and reducing the depth of the pit in the beam collection area at the same time, and the process bottleneck that the size of the pit in the beam collection area in SLMed GH3230 fiber laser non-penetrating deep penetration welding is too large and cracks are too many is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of welding technology, and particularly relates to a SLMed GH3230 optical fiber laser non-penetration deep penetration welding collection zone pit and hot crack suppression process method. BACKGROUND

[0002] GH3230 is a solid solution strengthening nickel-based superalloy, which is widely used in the manufacture of combustion chambers and inlet ducts of aerospace fields due to its excellent high-temperature strength, creep resistance and oxidation resistance. Selective laser melting (SLM) technology has been widely used in the additive manufacturing of hot end components of aircraft engines through the digital net shaping processing method of layer-by-layer accumulation. The use of SLM technology for 3D printing of GH3230 combustion chambers and inlet ducts of hot end critical components in the aerospace field is becoming mature. Under specific process background, it is necessary to carry out optical fiber laser welding on SLMed GH3230 components, and the form of the weld is non-penetration deep penetration welding. Compared with the rolling process, the crack tendency of SLMed GH3230 is higher, and the welding quality control is difficult. The particularity of the material and the harshness of the process pose strict challenges to the morphology of the collection zone and crack control.

[0003] In the process of SLMed GH3230 non-penetration deep penetration welding, the following two defects often occur in the "arc collection" stage of the power slow descent at the end of the weld: (1) Weld collection zone pit defect. When the laser beam appears instantaneous light-off or power drop, the liquid metal in the molten pool cools and shrinks rapidly, and the liquid-solid interface retracts, which leads to the formation of uneven depth pits in the weld collection zone. In severe cases, it can cause local holes or surface pits, affecting the service performance of the component. (2) Hot crack (Hot Crack) sensitive. The temperature gradient and stress concentration in the solid-liquid paste zone of the weld collection zone are obvious, and the hot stress is easy to produce at the solid-liquid interface. When the laser power or welding speed is improper, the weld forming is poor (the site is usually concave, which is easy to form stress concentration effect), local tensile stress and local molten pool solidification process of low melting point liquid film at the grain boundary, which leads to the initiation and expansion of hot cracks difficult to control, and the occurrence of weld micro-cracks or even macro-cracks in the collection zone, which reduces the mechanical properties and reliability of the joint.

[0004] Under certain process conditions (weld depth is deep and the length of the constriction zone is limited), the laser power is high, which leads to a larger weld bead concave in the constriction zone after welding of the component, which cannot meet the product manufacturing requirements. Moreover, the inherent process characteristics of fiber laser, such as high absorption rate, unstable molten pool and poor weld forming, further increase the difficulty of controlling the morphology and cracks in the constriction zone under this process condition. In addition, due to the metallurgical characteristics of GH3230 and the process characteristics of SLM, cracks are easily generated at the concave of the constriction zone, which requires secondary manual argon arc repair welding, reducing the production efficiency; at the same time, due to the poor energy control accuracy of argon arc process and the large heat affected zone, secondary cracking is easily generated, increasing the cost and process risk. Therefore, it is urgent to optimize the fiber laser welding process in the constriction zone, reduce the concave depth in the constriction zone, and suppress the crack defects, so as to improve the yield of laser welding of SLMed GH3230 components.

[0005] The process characteristics of the temperature field and flow field of the fiber laser welding molten pool in the constriction zone of SLMed GH3230 are not uniform, which is easy to produce obvious concave due to Marangoni convection effect, and induce micro-cracks in the solid-liquid paste zone, leading to the decrease of the service performance of the component. The existing energy input control means cannot simultaneously suppress the concave and cracks, and a new energy and track control method for the constriction zone is needed to achieve the beneficial effects of reducing the concave depth and suppressing the crack defects. The present application proposes a new process combining laser power gradient and laser welding track double coordinated control, which realizes the double suppression of weld bead concave and hot crack in the constriction zone under the premise of ensuring the process operability, and improves the laser welding quality and reliability of SLMed GH3230 high-temperature alloy components. The present application develops a new process method for suppressing the concave and hot crack in the constriction zone of fiber laser non-penetration deep penetration welding of SLMed GH3230, so as to realize the high-quality and high-efficiency laser welding manufacturing of SLMed GH3230 components. SUMMARY

[0006] The present application aims to provide a new process method for suppressing the concave and hot crack in the constriction zone of fiber laser non-penetration deep penetration welding of SLMed GH3230, which is characterized in that a power gradient change and slow-down curve is matched with a "runway type" track in the laser welding constriction zone, and the laser power in the constriction zone is turned off after multiple repeated running of the "runway type" track. The turning-off point, the number of repeated scanning and the parameters of the "runway type" track are optimized to reduce the concave depth in the weld bead constriction zone and suppress the generation of hot cracks in the constriction zone, thereby improving the welding quality of the component.

[0007] Further: the original welding path straight line segment is connected with the "runway type" track, the "runway type" track includes two half circular rings at the ends and runway straight line segments connected with the two half circular rings to form a closed runway structure, the original welding path straight line segment is connected with one of the runway straight line segments in a straight line, and is located outside the runway structure;

[0008] The runway type track is specifically designed with the following dimensions: wherein the runway straight line segment length L1 is 2-5 mm, the two semicircular ring radii R is 0.5-3 mm, and L1+2R<L, the original welding path straight line segment length is L2, L=L1+R+L2, and the laser beam collection area power-off position is located at the end point of the runway straight line segment, i.e. point A or point B.

[0009] The SLMed GH3230 fiber laser non-penetration deep penetration welding collection area pit and heat crack suppression process method is characterized in that: during welding, the "runway type" track is entered from the original welding path straight line segment and the "runway type" track is circularly welded along the "runway type" track, and the power gradient classification number n is 1-5 levels, which is denoted as P1, P2...Pn, 2≤n≤5, the power is gradually reduced, P1 is the maximum power, the welding seam power during deep penetration welding corresponding to the original welding path straight line segment is P1, the power is gradually reduced after entering the "runway type" track, the power is gradually reduced after entering the "runway type" track and including the circulation in the "runway type" track, until Pn, which is the minimum power in the classification, Pn, the power range is 200W-500W, and the starting point M of the power gradual reduction is arranged at a certain point of the original welding path straight line segment before the "runway type" track. n n n n

[0010] The "runway type" track is circularly repeated for 2-5 times.

[0011] The "runway type" track can be clockwise or counterclockwise.

[0012] Compared with the prior art, the present application has the following beneficial effects:

[0013] The synergistic effect of the laser power gradient and the runway type track of the present application can effectively utilize the laser power with gradual reduction, and the repeated scanning path is designed, the light-off point, the repeated scanning times and the runway type track parameters are optimized, the surface tension-temperature coefficient of the molten pool is controlled, the weld pit generated by the Marangoni convection is suppressed, so that the weld pit depth in the collection area is significantly reduced, the generation of the heat cracks in the collection area is suppressed, and the service performance of the component is improved. The power gradient, the track radius and the laser light-off point and other process parameters arranged in the present application are flexible and controllable, easy to realize on the existing laser welding equipment, and do not need additional devices, and have good engineering implementation feasibility. The method proposed can effectively suppress the weld pit depth and heat cracks in the collection area of the laser welding of other high-temperature alloys, stainless steels, titanium alloys and other materials in the rolled state and SLM manufactured, and has wide applicability and popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a schematic diagram of the welding method; ​​​​

[0015] Wherein, 1 is the laser beam, 2 is the welding track, 3 is the deep penetration welding bead, 4 is the converging zone linear weld, 5 is the "runway type" center unmelted base metal shape, 6 is the converging zone "runway type" track weld.

[0016] Figure 2 The schematic diagram of the runway type track is shown in the figure;

[0017] Wherein, 1 is the converging zone welding track, M is the converging zone starting point, L is the converging zone projection distance in the direction of the weld, L1 is the length of the "runway type" linear segment, R is the radius of the "runway type" semicircle, L2 is the length of the converging zone linear segment, A and B are the light points, N is the number of repeated scanning of the "runway type" track, and the total distance of the converging zone is S = L2 + 2N(L1 + πR).

[0018] Figure 3 The figure is a power gradient decreasing curve diagram of the converging zone;

[0019] The power change of the laser welding process is divided into three parts. First, the laser needs to go through the Ramping Up section to reach the required power for welding, the power is kept constant in the middle section, and the power is reduced in the converging zone until the welding is finished. Wherein, M is the converging zone starting point, P1 is the weld power when deep penetration welding, P2 and P3 are the converging zone gradient power points.

[0020] Figure 4 The figure is a comparison of the appearance of the weld end pits;

[0021] Figure 5 The figure is a crack state diagram of the weld converging zone;

[0022] Figure 6 The figure is a crack appearance diagram of the converging zone weld of the traditional control method. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with examples, but the present application is not limited to the following examples.

[0024] Example 1

[0025] In combination with Figure 1 and Figure 2To illustrate the embodiment, the embodiment is directed to the matching design of the power ramp-down parameter and the runway-type trajectory of the SLMed GH3230 under the requirements of the weld depth requirement ≮4 mm and the convergence zone length ≯8 mm. The projection distance L of the convergence zone along the welding direction is 8 mm. The runway-related parameters are designed as follows: the semicircular radius R of the "runway-type" trajectory is 1 mm, the straight line segment L1 of the "runway-type" trajectory is 2 mm, the runway straight line length L2 is 5 mm, and the number of repeated scanning N of the "runway-type" trajectory is 3. The light at point A is off. The power ramp-down parameter is two-section ramp-down (n=3), and the specific power parameters are P1 of 2000 W, P2 of 900 W, and P3 of 400 W. The corresponding distance of P1-P2 is the L2 segment of 5 mm, and the corresponding distance of P1-P2 segment is 2N(L1+πR)+L1=32.84 mm. The welding speed is 2 m / min. Before welding, the SLMed GH3230 wood surface is cleaned with acetone, and the workpiece is pressed tightly to ensure no deformation by using a tool. Argon protection is used, and the argon flow rate is 15 L / min. After welding, linear cutting is used along the center line of the "runway-type" straight line segment to obtain the weld convergence zone longitudinal section. Then, the weld longitudinal section is etched by using aqua regia (the volume ratio of concentrated hydrochloric acid HCl to concentrated nitric acid HNO3 is 3:1).

[0026] As shown in Figure 4 , the crater depth of the weld convergence zone obtained by the method of the present application is 90 μm, which is reduced by 62.8% compared with the same power parameter of linear welding (crater depth of 242 μm).

[0027] As shown in Figure 5 , Figure 6 As shown in the comparison, compared with the convergence of linear welding, the synergistic effect of the laser power gradient and the runway-type trajectory designed by the present application can completely inhibit the crack defects in the convergence zone.

[0028] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A SLMed GH3230 fiber laser non-penetration deep penetration welding constriction zone crater and heat check suppression process method, characterized in that, The power ramp-down curve with gradient change is matched with the "runway type" track in the laser beam collection area, and the power of the laser beam collection area is closed after multiple repeated operations of the "runway type" track; The original welding path straight line segment is connected with the "runway type" track, the "runway type" track includes two half circular rings at the ends and runway straight line segments connected with the two half circular rings to form a closed runway structure, the original welding path straight line segment is connected with one of the runway straight line segments in a straight line and is located outside the runway structure; During welding, the welding process begins on the straight section of the original welding path and then enters the "runway-shaped" trajectory, where welding is performed cyclically. The power descent strategy in the convergence region is as follows: the number of power gradient stages n ranges from 1 to 5, denoted as P1, P2, ... P n 2≤n≤5, the power decreases sequentially, with P1 being the maximum power. The weld power corresponding to the deep penetration welding of the straight segment of the original welding path is P1. After entering the "runway-shaped" trajectory, the power gradually decreases. After entering the "runway-shaped" trajectory, it is included in the cycle within the "runway-shaped" trajectory until P... n P n For the minimum power of the grade, P n The range is 200W-500W. The starting point M for power descent is set at a point on the straight section of the original welding path before the "racetrack-shaped" trajectory.

2. A SLMed GH3230 fiber laser non-penetration deep penetration welding constriction zone crater and heat check suppression process method according to claim 1, characterized in that, The specific design size of the "runway type" track is as follows: wherein, the length L1 of the runway straight line segment is 2-5 mm, the radius R of the two half circular rings is 0.5-3 mm, and L1+2R 3. A SLMed GH3230 fiber laser non-penetration deep penetration welding constriction zone crater and heat check suppression process method according to claim 1, characterized in that, During welding, the number of repeated scanning times N of the "runway type" track is 2-5 times.

4. A SLMed GH3230 fiber laser non-penetration deep penetration welding constriction zone crater and heat check suppression process method according to claim 1, characterized in that, The "runway type" track is clockwise or counterclockwise.

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