Niobium alloy longitudinal seam tailor-welding method

Abstract

The invention provides a niobium alloy longitudinal seam tailor-welding method which at least comprises the following steps that a male die is manufactured, a copper pipe provided with a vent hole is arranged in a groove in the outer surface of the male die, and the vent hole faces the interior of the groove; the scalloped segments to be welded are fixed to the outer surface of the male die, the adjacent scalloped segments are close to each other to form a welding seam, and the welding seam is arranged at the opening of the groove; a wide pressing plate is applied to the position, close to the weld joint, of the outer surface of the scalloped segment and fixed, so that the inner surface of the scalloped segment is tightly attached to the outer surface of the male die, and the weld joint gap meets the spot welding requirement; after ventilation is conducted in the groove through the copper pipe for a certain time, spot welding is conducted along the weld joint; after spot welding is completed, the wide pressing plates on the two sides of the welding seam are replaced with narrow pressing plates and fixed; welding equipment is used for welding the welding seams, and the adjacent scalloped segments are welded and fixed; and after welding is finished, the narrow pressing plate is removed, and the welded scalloped segment is taken down.

Description

Technical Field

[0001] The invention relates to the technical field of laser welding, in particular to a niobium alloy longitudinal seam welding method. Background Art

[0002] At present, the main nozzles of existing liquid rocket engines in China are all jacket structures. The advantage of such a design is that the manufacturing process is relatively mature, usually using vacuum brazing, argon arc welding, laser welding and other processes. However, this jacket structure nozzle has the following problems: the structure itself is relatively heavy, which is not conducive to improving the thrust-to-weight ratio of the engine; because vacuum brazing and laser welding have relatively strict requirements on the gap between the inner and outer walls of the jacket nozzle, and the larger the nozzle size, the more difficult it is to control the gap between the inner and outer walls in the front machining process, so it is difficult to manufacture a large-diameter jacket nozzle.

[0003] In view of the above problems, the single-wall nozzle has irreplaceable advantages. At present, the research and development of niobium alloy nozzles in China is limited to small-diameter niobium alloy nozzles (exit diameter is about 300nn), and the process method used is integral spinning.

[0004] Therefore, there is an urgent need to provide a forming process method suitable for large-size niobium alloy nozzles. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a niobium alloy longitudinal seam welding method for forming large-sized niobium alloy nozzles. The overall weight of the niobium alloy nozzle welded by the present invention has obvious advantages over the traditional jacket structure, which is conducive to improving the thrust-to-weight ratio of the engine.

[0006] The present invention provides a niobium alloy longitudinal seam welding method, which at least comprises the following steps: 1. Make a convex mold, and place a copper tube with vent holes in a groove on the outer surface of the convex mold, with the vent holes facing the inside of the groove; 2. Fix the melon segments to be welded on the outer surface of the male mold, so that adjacent melon segments are close to each other to form a weld, and the weld is placed at the opening of the groove; 3. Apply a wide pressing plate to the position of the outer surface of the melon slice near the weld and fix it, so that the inner surface of the melon slice is in close contact with the outer surface of the punch, and the weld gap meets the spot welding requirements; 4. After the air is replaced by ventilating the groove through the copper tube, spot welding is performed along the weld; 5. After the spot welding is completed, the wide pressing plates on both sides of the weld are replaced with narrow pressing plates and fixed; 6. Using welding equipment to weld the welds to fix the adjacent melon segments; 7. After welding, remove the narrow pressure plate and take out the welded melon slices.

[0007] Furthermore, the method of applying and fixing a wide pressure plate at a position near the weld on the outer surface of the melon slice so that the inner surface of the melon slice is in close contact with the outer surface of the punch and the weld gap meets the spot welding requirements is as follows: a plurality of screw holes are opened in the length direction of the wide pressure plate, and the spacing between the screw holes is equal; the wide pressure plate is pressed at a position near the weld on the outer surface of the melon slice, bolts are installed in each screw hole and tightened in sequence, and the melon slice is pressed by the bolts and the wide pressure plate so that the inner surface of the melon slice is in close contact with the outer surface of the punch; the assembly state of the weld is checked, and if the gap and the wall offset of the weld exceed the specified values, the installation tightness of each bolt is adjusted until the state of the weld meets the spot welding requirements.

[0008] Furthermore, in the above embodiment, a feeler gauge can be used to check the assembly state of the weld; wherein, the weld gap is not greater than 0.2 mm, and the weld wall offset is not greater than 0.2 mm; spot welding is performed after confirming that the weld gap and the wall offset meet the requirements.

[0009] Furthermore, a plurality of first positioning holes are processed on the outer surface of the punch, and second positioning holes are reserved at the process allowances at both axial ends of the melon segments; the melon segments are mounted on the outer surface of the punch, and the first positioning holes and the second positioning holes that are matched in place are fixed simultaneously by positioning pins.

[0010] Furthermore, when the wide pressure plate and the narrow pressure plate are installed on the outer surface of the melon slice, they are first limited by the positioning pins, and then the bolts are tightened in the screw holes.

[0011] Furthermore, the method for spot welding the weld is: passing argon gas into the groove through the copper tube for 3 to 5 minutes and then starting laser spot welding, spot welding at intervals of 50 mm.

[0012] Furthermore, the method of replacing the wide pressure plates on both sides of the weld with narrow pressure plates and fixing them is: first remove the wide pressure plate on one side of the weld, replace it with a narrow pressure plate, and tighten the bolts; then remove the wide pressure plate on the other side of the weld, replace it with a narrow pressure plate, and tighten the bolts; the size between adjacent narrow pressure plates is sufficient to accommodate the passage of the protective gas hood.

[0013] Furthermore, the distance between adjacent wide pressing plates is smaller than the distance between adjacent narrow pressing plates.

[0014] In any of the above embodiments, the copper tube is spaced apart from the inner wall of the groove, and the vent holes are evenly distributed along the axial direction of the copper tube; before spot welding, argon gas is passed through the inner cavity of the copper tube through a gas supply device to replace the air, and the argon gas is blown toward the inner wall of the groove through the vent holes and then rebounds to the weld.

[0015] Furthermore, the method for removing the narrow pressure plate after welding is as follows: first remove the narrow pressure plate on one side of the weld and pull out the positioning pin, and then remove the narrow pressure plate on the other side of the weld and pull out the positioning pin.

[0016] The present invention provides a niobium alloy longitudinal seam welding method, which has at least one of the following beneficial effects: 1. The invented niobium alloy longitudinal seam welding method can obtain a large-sized single-wall niobium alloy nozzle by laser welding, which greatly reduces the nozzle's own weight and increases the engine's thrust-to-weight ratio and specific impulse.

[0017] 2. The invented niobium alloy longitudinal seam welding method can manufacture single-wall nozzles of different sizes by changing the welding position and the number of welds, and has a wide range of applications.

[0018] 3. The invented niobium alloy longitudinal seam welding method uses positioning pins to position the punch and melon slices, and uses wide and narrow pressure plates alternately, so that the inner surface of the niobium alloy melon slices is fully supported by the punch and the outer surface is pressed by the pressure plate, which not only ensures the assembly accuracy between the melon slices, but also meets the laser welding requirements of the weld. At the same time, dual protective gas protection is achieved on the front and back of the weld, reducing the degree of oxidation on the front and back of the weld.

[0019] Those skilled in the art will recognize additional features and advantages upon reading the detailed description and upon viewing the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The figure is a flow chart of a method for longitudinal seam welding of niobium alloy according to an embodiment of the present invention.

[0022] Figure 2 It is a partial flow chart of the niobium alloy longitudinal seam welding method according to an embodiment of the present invention.

[0023] Figure 3 It is a schematic diagram of the assembly of the melon slices and the boss according to an embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram of the assembly of the wide pressing plate, melon segments and bosses according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are used to illustrate the principles of the present invention, and are not configured to limit the present invention. In addition, the structural components in the drawings are not necessarily drawn to scale. For example, the sizes of some structural components or areas in the drawings may be enlarged for other structural components or areas to help understand the embodiments of the present invention.

[0026] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of the embodiments of the present invention. In the description of the present invention, it should be noted that, unless otherwise specified, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0027] In addition, the terms "include", "comprise", "have" or any other variations thereof are intended to cover non-exclusive inclusion, so that a structure or component including a series of elements includes not only those elements, but also other mechanical elements that are not explicitly listed or inherent in the structure or component. In the absence of more restrictions, the elements defined by the sentence "include..." do not exclude the existence of other identical elements in the article or device including the elements.

[0028] Spatially related terms such as "below", "beneath", "under", "low", "above", "on", "high", etc. are used to facilitate description to explain the positioning of one element relative to a second element, indicating that these terms are intended to cover different orientations of the device in addition to orientations different from those shown in the figures. In addition, for example, "one element is above / below another element" can mean that the two elements are in direct contact, or that there are other elements between the two elements. In addition, terms such as "first", "second", etc. are also used to describe various elements, regions, parts, etc., and should not be regarded as limiting. Similar terms represent similar elements throughout the description.

[0029] For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by showing examples of the present invention.

[0030] See also Figure 1 The present invention provides a niobium alloy longitudinal seam welding method, which at least comprises the following steps: S10, making a convex mold, and placing a copper tube with vent holes in a groove on the outer surface of the convex mold, with the vent holes facing the inside of the groove.

[0031] S20, fixing the melon segments to be welded on the outer surface of the male mold, so that adjacent melon segments are close to each other to form a weld, and the weld is placed at the opening of the groove.

[0032] S30, applying and fixing a wide pressing plate at a position near the weld on the outer surface of the melon slice, so that the inner surface of the melon slice is in close contact with the outer surface of the punch, and the weld gap meets the spot welding requirements.

[0033] S40, after completing air replacement by ventilating the groove through the copper tube, spot welding is performed along the weld.

[0034] S50, after the spot welding is completed, the wide pressing plates on both sides of the weld are replaced with narrow pressing plates and fixed.

[0035] S60, welding the welds using welding equipment to fix the adjacent melon segments by welding.

[0036] S70. After welding is completed, remove the narrow pressure plate and take out the welded melon slices.

[0037] See also Figure 3 , Figure 4 In this embodiment, the male mold 1 is provided with a preset groove, and the copper tube 3 provided with a vent hole is installed in the groove for blowing out the shielding gas during the welding process. In order to prevent the shielding gas from blowing directly into the weld, the vent hole can be arranged toward the inside of the groove.

[0038] The present invention adopts a convex die 1 that matches the inner profile of a melon segment 4 (niobium alloy melon segment 4, hereinafter referred to as melon segment 4) to support the inner side of the melon segment 4, and adopts a wide pressing plate 5 or a narrow pressing plate that matches the outer profile of the melon segment 4 to press the outer side of the melon segment 4. After the inner and outer sides of the melon segment 4 are pressed at the same time, the back of the weld covers the opening of the groove, and the front of the weld is exposed between the adjacent wide pressing plates 5 or narrow pressing plates.

[0039] Among them, the interval between adjacent wide pressing plates 5 (two adjacent wide pressing plates installed behind the melon segments) is the first interval, and the interval between adjacent narrow pressing plates (two adjacent narrow pressing plates installed behind the melon segments) is the second interval, and the first interval is smaller than the second interval. The wide pressing plate 5 is closer to the weld, and the clamping effect is better, which is suitable for the assembly spot welding link. The narrow pressing plate is far away from the weld, and the movement space of the protective gas hood is reserved. The use of the protective gas hood during welding can reduce the degree of oxidation on the front of the weld.

[0040] Before spot welding the weld, first introduce shielding gas into the groove through the vent hole of the copper tube. The shielding gas hits the inner wall of the groove and then rebounds to the back of the weld. Before welding the melon slices, first ventilate the groove through the copper tube for a certain period of time. After the air replacement is completed, the weld is spot welded along the first interval using welding equipment. In order to facilitate the adjustment of the tightness of the fit between the melon slices, the interval size between adjacent wide pressure plates of the present application is small, which can meet the spot welding requirements but cannot meet the requirements of formal welding. Therefore, after the spot welding is completed, the wide pressure plates on both sides of the weld are replaced with narrow pressure plates and fixed, and then the welding equipment is used to perform longitudinal seam welding on the weld along the second interval so that the adjacent melon slices are completely welded and fixed.

[0041] The spot welding and welding methods described in the embodiments of the present invention are preferably laser welding, and electron beam welding can also be selected.

[0042] Continue to see Figure 3 and Figure 4 In the above embodiment, in order to accurately and quickly install the melon slice 4 in the appropriate position of the punch 1, the melon slice 4 and the punch 1 can be positioned simultaneously by the positioning pin 2, and then the assembly position of the melon slice 4 can be determined. For example, a plurality of first positioning holes can be processed on the outer surface of the punch 1, and second positioning holes can be reserved at the process allowances at both axial ends of the melon slice 4. The melon slice 4 is installed on the outer surface of the punch 1, and the first positioning holes and the second positioning holes that are matched in place are fixed at the same time by the positioning pin 2, so as to quickly complete the positioning and assembly of the melon slice 4 and the punch 1. It should be noted that in order to ensure the consistency of the clamping of each melon slice, the second positioning holes of each melon slice to be welded can be processed in the same position.

[0043] See also Figure 2 , Figure 3 and Figure 4 Further, S30 applies and fixes a wide pressing plate at a position near the weld on the outer surface of the melon slice, so that the inner surface of the melon slice is in close contact with the outer surface of the punch, and the weld gap meets the spot welding requirements. The method is: S31. A plurality of screw holes are provided in the length direction of the wide pressing plate, and the distances between the screw holes are equal.

[0044] S32, press the wide pressure plate on the outer surface of the melon slice close to the weld, install bolts in each screw hole and tighten them in sequence, and press the melon slice by the bolts and the wide pressure plate so that the inner surface of the melon slice is in close contact with the outer surface of the punch.

[0045] S33, checking the assembly state of the weld, if the gap and the wall offset of the weld exceed the specified value, adjusting the installation tightness of each bolt until the state of the weld meets the spot welding requirements.

[0046] When welding melon slices using the longitudinal seam welding method of this embodiment, the two melon slices 4 to be welded are pressed tightly using a wide pressing plate 5. Compared with a narrow pressing plate, the wide pressing plate 5 can more easily make the entire weld meet the spot welding requirements. In order to accurately adjust the unqualified part of the entire weld, multiple screw holes 6 can be opened in the length direction of the wide pressing plate 5, and bolts can be installed and tightened in the corresponding screw holes 6 to increase the tightness of the corresponding part of the weld (unqualified part). Among them, the bolt adjustment step and the weld inspection step can be performed alternately until the entire weld meets the spot welding requirements.

[0047] The narrow pressing plate also has a plurality of screw holes in its length direction. After the spot welding is completed, the wide pressing plate is replaced with the narrow pressing plate, and the bolts are installed in the corresponding screw holes and tightened so that the melon slices are completely fitted to the outer surface of the punch again.

[0048] The method for spot welding the weld in the embodiment of the present invention is: first, argon gas is passed into the groove through a copper tube for 3 to 5 minutes, and then the air is replaced by argon gas, and then laser spot welding is started, and spot welding is performed every 50 mm. It should be noted that the argon gas is always filled in the groove during spot welding and formal welding to reduce the degree of oxidation on the back of the weld.

[0049] In any of the above embodiments, the method for checking the weld is: using a feeler gauge to check the assembly state of the entire weld, wherein the weld gap is not greater than 0.2 mm, and the weld offset is not greater than 0.2 mm, and spot welding can be performed only after confirming that the weld gap and offset of the entire weld meet the requirements. The purpose of spot welding is to initially fix the two adjacent melon slices to ensure that the weld will not change when the narrow pressure plate is replaced.

[0050] See also Figure 3 and Figure 4 In the above embodiment, the process of installing the wide pressing plate 5 or the narrow pressing plate on the outer surface of the melon slice 4 is as follows: after the wide pressing plate 5 or the narrow pressing plate is pressed on the outer surface of the melon slice 4, it is first limited by the positioning pin 2, and then the bolt is screwed into the appropriate screw hole 6 according to the state of the weld. The inner wall of the melon slice 4 is completely fitted with the outer surface of the punch 1 by the pressing action of the wide pressing plate 5 or the narrow pressing plate, and under the support of the outer surface of the punch 1, the inner wall of the melon slice 4 will not be deformed by external force.

[0051] Furthermore, in order to reduce the impact of the pressure plate replacement process on the weld, do not remove all the wide pressure plates on both sides of the weld at the same time and then install the narrow pressure plates. Instead, first remove the wide pressure plate on one side of the weld, replace it with a narrow pressure plate and tighten the bolts, then remove the wide pressure plate on the other side of the weld, replace it with a narrow pressure plate and tighten the bolts. After all the pressure plates on both sides of the weld are replaced, the size between adjacent narrow pressure plates is sufficient to accommodate the passage of the protective gas hood. During welding, the protective gas hood is close to the surface of the melon slice to provide protective gas to the front of the weld to reduce the degree of oxidation on the front of the weld.

[0052] The protective gas drag hood in the embodiment of the present invention can refer to the protective gas drag hood disclosed in CN220902184U.

[0053] In any of the above embodiments, in order to allow the shielding gas to enter the back of the weld and to prevent the shielding gas from blowing directly onto the weld, the copper tube and the inner wall of the groove can be spaced apart, and the vent holes can be oriented toward the inside of the groove. At the same time, the vent holes are evenly distributed along the axial direction of the copper tube. Before spot welding and formal welding (welding the entire weld) of the weld, argon gas is first passed through the gas supply device to replace the air for 3 to 5 minutes into the inner cavity of the copper tube. The argon gas is blown toward the inner wall of the groove through the vent holes and then evenly rebounds to the weld, and then spot welding and formal welding are performed.

[0054] Furthermore, after the formal welding is completed, the method for removing the narrow pressure plate is as follows: first, loosen the bolts on the narrow pressure plate on one side of the weld to remove the narrow pressure plate, and pull out the positioning pin, then loosen the bolts on the narrow pressure plate on the other side of the weld to remove the narrow pressure plate, and pull out the positioning pin. After removing the welded niobium alloy melon slices, the melon slices to be welded can be replaced to continue longitudinal seam laser welding until all the melon slices are welded into a large-size niobium alloy nozzle.

[0055] The above embodiments can be combined with each other and have corresponding technical effects.

[0056] The niobium alloy longitudinal seam welding method of the present invention uses positioning pins to position the punch and the melon slices, and uses wide and narrow pressing plates alternately, so that the inner surface of the niobium alloy melon slices is fully supported by the punch and the outer surface is pressed by the pressing plate, which not only ensures the assembly accuracy between the melon slices, but also meets the laser welding requirements of the weld. At the same time, dual protective gas protection is achieved on the front and back of the weld, reducing the degree of oxidation on the front and back of the weld.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for longitudinal seam welding of niobium alloy, characterized in that: At least: A convex mold is made, and a copper tube with vent holes is arranged in a groove on the outer surface of the convex mold, with the vent holes facing the inside of the groove; Fix the melon segments to be welded on the outer surface of the male mold, and adjacent melon segments are close to each other to form a weld, and the weld is placed at the opening of the groove; A wide pressing plate is applied and fixed at a position near the weld on the outer surface of the melon slice, so that the inner surface of the melon slice is in close contact with the outer surface of the punch, and the weld gap meets the spot welding requirements; After the air is replaced by ventilation into the groove through the copper tube, spot welding is performed along the welding seam; After the spot welding is completed, the wide pressing plates on both sides of the weld are replaced with narrow pressing plates and fixed; Using welding equipment to weld the weld seam to fix the adjacent melon segments by welding; After welding is completed, remove the narrow pressure plate and take out the welded melon slices.

2. The method for longitudinal seam welding of niobium alloy according to claim 1, characterized in that: The method of applying and fixing a wide pressing plate at a position near the weld on the outer surface of the melon slice so that the inner surface of the melon slice is in close contact with the outer surface of the punch and the weld gap meets the spot welding requirements is: A plurality of screw holes are provided in the length direction of the wide pressing plate, and the spacing between the screw holes is equal; Press the wide pressing plate on the outer surface of the melon slice near the weld, install bolts in each screw hole and tighten them in sequence, and press the melon slice by the bolts and the wide pressing plate so that the inner surface of the melon slice is in close contact with the outer surface of the punch; Check the assembly status of the weld. If the gap and the wall offset of the weld exceed the specified value, adjust the installation tightness of each bolt until the state of the weld meets the spot welding requirements.

3. The method for longitudinal seam welding of niobium alloy according to claim 2, characterized in that: Use a feeler gauge to check the assembly state of the weld; wherein the weld gap is no greater than 0.2 mm, and the weld wall offset is no greater than 0.2 mm; Spot welding is performed after confirming that the weld gap and wall offset meet the requirements.

4. The method for longitudinal seam welding of niobium alloy according to claim 3, characterized in that: The outer surface of the punch is processed with a plurality of first positioning holes, and second positioning holes are reserved at the process margins at both ends of the melon slice in the axial direction; The melon slices are mounted on the outer surface of the male mold, and the first positioning holes and the second positioning holes that are matched in place are fixed simultaneously by positioning pins.

5. The method for longitudinal seam welding of niobium alloy according to claim 4, characterized in that: When the wide pressing plate and the narrow pressing plate are installed on the outer surface of the melon slice, they are first limited by the positioning pins, and then the bolts are tightened in the screw holes.

6. The method for longitudinal seam welding of niobium alloy according to claim 1, characterized in that: The method for spot welding the weld is: Argon gas is passed into the groove through the copper tube for 3 to 5 minutes, and then laser spot welding is started, with spot welding at intervals of 50 mm.

7. The method for longitudinal seam welding of niobium alloy according to claim 1, characterized in that: The method for replacing the wide pressing plates on both sides of the weld with narrow pressing plates and fixing them is: First, remove the wide pressure plate on one side of the weld, replace it with a narrow pressure plate, and tighten the bolts; then remove the wide pressure plate on the other side of the weld, replace it with a narrow pressure plate, and tighten the bolts; The dimensions between adjacent narrow pressing plates are sufficient to accommodate the passage of the protective gas drag hood.

8. The method for longitudinal seam welding of niobium alloy according to claim 7, characterized in that: The distance between adjacent wide pressing plates is smaller than the distance between adjacent narrow pressing plates.

9. The method for longitudinal seam welding of niobium alloy according to any one of claims 1 to 8, characterized in that: The copper tube is spaced apart from the inner wall of the groove, and the vent holes are evenly distributed along the axial direction of the copper tube; Before spot welding, argon gas is passed through the inner cavity of the copper tube through a gas supply device to replace the air. The argon gas is blown toward the inner wall of the groove through the vent hole and then rebounds to the weld.

10. The method for longitudinal seam welding of niobium alloy according to claim 9, characterized in that: The method for removing the narrow pressing plate after welding is as follows: first remove the narrow pressing plate on one side of the weld and pull out the positioning pin, and then remove the narrow pressing plate on the other side of the weld and pull out the positioning pin.

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