Regional performance regulation and control method for double-side double-pass EBW remelting of large-thickness titanium alloy

Abstract

The invention provides a large-thickness titanium alloy double-side double-pass EBW remelting area performance regulation and control method which comprises the following steps: step 1, when a butt joint of a first large-thickness titanium alloy workpiece 1 and a second large-thickness titanium alloy workpiece 2 is clamped, setting a welding assembly gap, and identifying the to-be-welded surfaces of the butt joint as a surface A and a surface B, welding of a first welding seam 4 in double-pass welding is conducted on the face A, welding of a second welding seam 5 in double-pass welding is conducted on the face B, and a remelting area 3 is determined according to the overlapping area of the first welding seam and the second welding seam; 2, a filling space is machined in the position, close to the root of the secondary weld joint, of the remelting area 3 so that materials can be conveniently added; 3, according to a welding seam fusion area, a heat affected area and a base material area, the remelting area 3 is subjected to area division and structure analysis; and carrying out mechanical property sample preparation and testing on different positions and different directions of the remelting area 3 by combining the shape of the section of the welding seam.

Description

Technical Field

[0001] The invention belongs to the field of titanium alloy vacuum electron beam welding and relates to a method for controlling the performance of double-sided double-pass EBW remelting regions of thick titanium alloys. Background Art

[0002] Vacuum electron beam welding (EBW), a high-energy-density welding method performed in a vacuum environment, offers advantages such as high welding power density, a large aspect ratio, minimal weld zone deformation, low energy consumption, and ease of control and automation. Compared to TIG welding, friction stir welding, laser welding with filler wire, and laser-arc hybrid welding, EBW offers significant advantages for tailor-welding large-format titanium alloy forgings (≥100mm) and has become the preferred method for welding large-thickness titanium alloys.

[0003] Extensive research has been conducted domestically and internationally on electron beam welding of thick titanium alloys, but the focus has primarily been on single-pass, full-penetration welding. Reports on double-sided, double-pass electron beam welding are rare. Currently, single-pass, full-penetration electron beam welding still suffers from issues such as poor surface finish quality, severe internal shrinkage defects, large component deformation, and a limited upper limit on penetration depth. Therefore, achieving single-pass, full-penetration welding of thick plates requires very high electron beam energy density, which results in significant spatter and the formation of defects such as undercut and incomplete welds. In practice, single-pass electron beam welding of thick titanium alloys is often performed with a backing plate on the back. The high penetration depth of single-pass welding leads to poor weld pool and keyhole stability, and is prone to void-like defects within the weld. Achieving single-pass, full-penetration welding of thick plates requires high heat input, resulting in increased weld width, a large difference in weld width between the upper and lower surfaces, and significant angular and lateral shrinkage deformation after welding. Furthermore, achieving single-pass, full-penetration welding of thick plates places stringent requirements on electron gun power and high equipment investment costs. In the domestic reports, most of the electron beam welding of thick titanium alloys adopts single-pass welding, and the maximum thickness of full penetration is 130 mm. Compared with single-pass welding, double-pass double-sided welding has the significant advantages of small deformation, large potential penetration depth, and the possibility of achieving near-net shape for electron beam welding of thick titanium alloys: (1) The heat input of single-pass welding is reduced and the weld width is narrowed, so the use of double-sided welding can significantly reduce angular deformation and lateral shrinkage deformation; (2) The welding process does not require the use of a pad, eliminating the need for the arrangement of the pad and subsequent processing steps, and near-net shape can be achieved through effective control of process parameters; (3) The advantage of a wider range of thickness applicability can achieve the welding of titanium alloy plates with a thickness of more than 200 mm. On this basis, the applicant further proposed double-pass double-sided asymmetric penetration welding of thick titanium alloy plates: first, the first electron beam welding is performed on the titanium alloy plate from the front with a larger welding power, the titanium alloy plate is flipped, and the second electron beam welding is performed on the titanium alloy plate from the back with a smaller welding power, and the electron beam is swung during welding. Compared with symmetrical penetration welding, asymmetrical penetration welding is beneficial to further improve the internal quality of the joint: since the second side welding penetration is small, the probability of porosity defects is smaller. At the same time, the electron beam swing measure during the second side welding can not only reduce the probability of porosity defects forming during the second side welding process, but also release and eliminate the porosity defects that may exist at the root of the first side welding weld.

[0004] Chinese patent CN201810678605.4 discloses a large-thickness titanium alloy plate asymmetric melting depth double-sided electron beam welding method. The patent is mainly to meet the demand of large titanium alloy frame class parts integration manufacturing, and proposes a large-thickness titanium alloy plate asymmetric melting depth electron beam welding method, aiming to solve the technical problems of high equipment cost, large post-weld deformation and many weld defects when single-sided electron beam welding is used, so as to realize high reliability manufacturing. The specific technical scheme is as follows: the front bevel of two titanium alloy plates with a thickness of 100-200mm is processed into a step with a depth and width of 4-5mm, the back bevel is processed into a step with a depth and width of 2-3mm, the welding position is cleaned, the gap step difference is less than 0.1mm; the first electron beam welding is performed on the titanium plate from the front bevel with a larger welding power, the melting depth is about 2 / 3 to 3 / 4 of the plate thickness; the welding part is turned over, the second electron beam welding is performed on the titanium plate from the back bevel with a smaller welding power, the second weld seam needs to produce a 8-10mm deep remelted area 3 on the root of the first weld seam, and a certain frequency of scanning welding is used during the second electron beam welding, and finally the butt welding of the 100-200mm large-thickness titanium alloy forge piece is completed. However, the control of the weld seam organization and performance of the remelted area 3 is not described.

[0005] Under most working conditions, the large-thickness titanium alloy electron beam welded joint bears dynamic load, and fatigue failure is the main form of joint failure. In this process, the non-uniformity of the microstructure and mechanical properties of the joint will have an important influence on the fatigue mechanism and fatigue failure law of the large-thickness titanium alloy electron beam welded joint. SUMMARY

[0006] The present application is directed to the problem of weak mechanical properties of the double-sided double-pass EBW remelted area 3 of large-thickness titanium alloy, and provides a method for controlling the performance of the double-sided double-pass EBW remelted area of large-thickness titanium alloy, which can solve the problem of the integration manufacturing of large titanium alloy frame, beam and other main load-bearing structural parts.

[0007] To achieve the above-mentioned purpose, the present application provides a method for controlling the performance of the double-sided double-pass EBW remelted area of large-thickness titanium alloy, which comprises: Step 1: when the first large-thickness titanium alloy workpiece 1 and the second large-thickness titanium alloy workpiece 2 are clamped at the butt joint, a welding assembly gap is set, and the butt joint welding surface is identified as A surface and B surface, the A surface is welded by the first weld 4 in the double-pass welding, the B surface is welded by the second weld 5 in the double-pass welding, and the remelted area 3 is determined according to the overlapping area of the first weld and the second weld; Step 2: a filler space is processed at the position where the remelted area 3 is close to the root of the second weld, so as to add material; Step 3: Divide the remelting area 3 into regions according to the weld fusion zone, heat-affected zone, and base material zone, and perform a microstructure analysis. Combined with the weld cross-sectional morphology, prepare and test the mechanical properties of the remelting area 3 at different positions and directions, and then fully characterize the microstructure and mechanical properties of the remelting area 3.

[0008] Specifically, step 3 includes: Step 31: Divide the remelted region 3 into a secondary fusion zone A, a primary fusion + primary heat-affected zone B, a primary heat-affected + primary fusion zone C, a secondary heat-affected zone D, a primary fusion zone E, a primary heat-affected zone F, a primary fusion zone G, and a primary heat-affected zone H. Based on the region division results, a thermal cycle curve is obtained by numerical simulation, and the Gleeble thermal simulation method is used to reproduce the thermal cycle process of each region in the overlapping region to obtain a simulated microstructure. Step 32: Based on the forging manufacturing requirements, along the forging direction (L), the perpendicular forging direction (T), and the forging thickness direction (S), according to the double-sided double-pass welding process characteristics, the metallographic structure, microhardness, tensile strength, impact toughness, and fatigue strength performance testing and analysis of the joint parts are carried out in sequence.

[0009] More specifically, step 32 includes: Step 321: The microhardness sampling method of the joint portion 10 is to first perform a microhardness test on the joint transverse direction TL to obtain a hardness distribution curve from the base material, the heat-affected zone to the fusion zone; then perform a microhardness test along the weld penetration direction TS to obtain a hardness distribution curve along the weld depth direction; Step 322: The tensile test specimen 11 and the impact test specimen 12 of the joint are firstly sampled in multiple layers in the transverse direction TL of the joint, with each layer containing the remelted area 3; then, samples are sampled along the weld penetration direction TS and in multiple layers along the weld length, with the U-shaped or V-shaped notch for impact toughness being placed in the remelted area 3; Step 323: The fatigue specimen 13 of the joint is sampled in a multi-layer manner in the transverse direction TL of the joint, with each layer being diversified. The remelting area 3 is staggered and sampled in two layers, one of which is a completely overlapping area, and the other is a secondary weld root area with the root tip placed in the sample. Step 324: Based on the weld morphology and structure, microhardness distribution, tensile strength and impact toughness test results, and fatigue strength test results, the mechanical properties of the joint and the remelted area 3 are comprehensively analyzed.

[0010] Specifically, the overlapping length of the two welds in the remelting area 3 is in the range of 10 mm to 15 mm.

[0011] Specifically, the position of the remelting zone 3 is based on the butt thickness and the maximum depth capability of the equipment for single-pass welding, as well as the principle of minimizing the proportion of the weld in the remelting zone 3 remaining in the final structure.

[0012] Specifically, the position of the remelting area 3 includes the middle position along the thickness direction or 1 / 3δ, 1 / 4δ and 1 / 5δ away from the B surface, wherein δ is the butt thickness of the thick titanium alloy butt joint.

[0013] Specifically, the added material includes pure titanium, titanium alloy or other metal materials.

[0014] Specifically, the added materials may be in the form of foil fillers 6 , plate fillers 7 , wire rod fillers 8 , hexagonal fillers 9 or other special-shaped structures processed by machinery. In summary, the present invention provides a method for controlling the performance of double-sided double-pass EBW remelting areas of large-thickness titanium alloys. According to the butt thickness of the workpieces and the maximum penetration capacity of the equipment, the selection principle of the position of the double-sided double-pass welding remelting area 3 is given; a filler space is set at the remelting area 3 position, and the characteristics, form, specifications, heat treatment state of the added material, as well as the processing method of the filler space and the physical precision matching requirements of the added material are clarified, which can achieve the control effect of homogenizing and strengthening the organization and mechanical properties of the remelting area 3. At the same time, a means of characterizing the weld organization and mechanical properties of the double-sided double-pass welding remelting area 3 is proposed to more accurately evaluate the comprehensive performance of the joint. The present invention can solve the problem of integrated manufacturing of large-scale titanium alloy frames and beam-type main load-bearing structural parts, realize the homogenization and strengthening of the organization and mechanical properties of large-thickness titanium alloy double-sided double-pass EBW joints along the thickness direction, improve the comprehensive performance of the joint, and thus improve the manufacturing quality of weapons and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the method for selecting the location of the remelting zone 3 for double-sided double-pass welding of thick titanium alloy; Figure 2 Schematic diagram of the control method for strengthening and toughening the microstructure and properties of the remelting zone 3 in double-sided double-pass welding of thick titanium alloy; Figure 3 Schematic diagram of weld microstructure characterization area based on double-sided double-pass welding remelting zone 3; Figure 4 Schematic diagram of the transverse and longitudinal microhardness test positions of the double-pass double-side weld of thick titanium alloy; Figure 5 Schematic diagram of the preparation position of tensile and impact specimens for double-sided double-pass welds of thick titanium alloy; Figure 6 Schematic diagram of the preparation position of fatigue specimens for double-sided double-pass welds of thick titanium alloy.

[0016] In the figure: 1-titanium alloy workpiece with the largest thickness, 2-titanium alloy workpiece with the second largest thickness, 3-remelting zone 3, 4-first weld, 5-second weld, 6-foil filler, 7-plate filler, 8-wire and rod filler, 9-hexagonal filler, 10-microhardness, 11-tensile specimen, 12-impact specimen, 13-fatigue specimen. DETAILED DESCRIPTION

[0017] The following is a further detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and examples. It should also be noted that, for ease of description, the drawings only show parts relevant to the present invention, not all structures. The detailed descriptions of the following examples and the accompanying drawings are intended to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention. That is, the specific embodiments described in the present invention are intended only to explain the present invention, not to limit the present invention.

[0018] Controlling the microstructure and properties of the remelting zone 3 is crucial for improving joint fatigue performance. This invention proposes a method for controlling the microstructure and properties of the remelting zone 3 during double-sided, double-pass EBW of thick titanium alloys, which is of great significance for the safe use of thick titanium alloy welded structures.

[0019] The present invention proposes a method for controlling the performance of the remelting zone of double-sided double-pass EBW for thick titanium alloys, including a method for selecting the position of the remelting zone 3 for double-sided double-pass welding, a method for controlling the strengthening and toughening of the microstructure and performance of the remelting zone 3, and a means for characterizing the microstructure and mechanical properties of the weld in the remelting zone 3.

[0020] Example 1 The present application provides a method for controlling the properties of a double-sided, double-pass EBW remelting area of ​​a thick titanium alloy, comprising: Step 1: When clamping the butt joint of the first and second titanium alloy workpieces 1 and 2, a welding assembly gap is set, and the surfaces to be welded of the butt joint are identified as surface A and surface B, and a remelting area 3 is determined based on surface A and surface B; The A side is welded with the first weld 4 in double-pass welding, and the B side is welded with the secondary weld 5 in double-pass welding. The overlapping area of ​​the first and secondary welds is the "remelting area 3", and the overlapping length of the two welds in the remelting area 3 is set to 10mm~15mm.

[0021] Furthermore, the position of the remelting area 3 refers to the specific planning of the specific position of the remelting area 3 based on the butt thickness of the product and the maximum depth capability of the single-pass welding of the equipment, as well as the principle of minimizing the proportion of the weld in the remelting area 3 retained in the final structure.

[0022] Exemplarily, the position of the remelting zone 3 includes the middle position along the thickness direction or 1 / 3δ, 1 / 4δ and 1 / 5δ away from the B surface, etc., which are only enumerated here and are not limitations of this clause.

[0023] Among them, the butt thickness of large-thickness titanium alloy butt joint is represented by δ.

[0024] Step 2: A filler space is machined in the remelting area 3 near the root of the secondary weld to facilitate the placement of material.

[0025] It should be noted that the added material and the filler space are closely matched, and the structure and mechanical properties of this position are regulated by component compensation and component dilution during the welding process, so as to achieve the effect of strengthening and toughening the performance of the remelting area 3.

[0026] Furthermore, the added material refers to the material selected through experiments based on the need to control the structure and performance of the remelting area 3. Generally, pure titanium or titanium alloys of different grades are added. If there are special requirements, other metal materials can be added. Furthermore, the added material can be in the form of foil filler 6, plate filler 7, wire rod filler 8, hexagonal filler 9, or other special-shaped structures through mechanical processing. The added material can also be a powder material, and the heat treatment state of the material is preferably consistent with that of the parent material. Furthermore, the filler space is formed by processing filler areas on both sides of the joint according to the position of the remelting area 3 and the specifications of the filling material. The processing method is not limited, mainly including mechanical processing, wire cutting, electrolysis, etc. The cross-sectional morphology of the filler area can be strips, rectangles, circles, hexagons, etc., and any shape that can be produced and matched with the added material can be used; Furthermore, the tight fit between the added material and the filler space means that the gap between the two should not exceed 0.3mm. Excessive gaps may cause defects such as shrinkage, cold shut, or air holes during welding. After clamping, the material should be fixed in place and secured with argon arc welding at both ends.

[0027] Step 3: Divide the remelting area 3 into regions according to the weld fusion zone, heat-affected zone, and base material zone, and perform a microstructure analysis. Combined with the weld cross-sectional morphology, prepare and test the mechanical properties of the remelting area 3 at different positions and directions, and then fully characterize the microstructure and mechanical properties of the remelting area 3.

[0028] It should be noted that different areas of the double-sided double-pass welding remelting zone 3 have undergone two thermal cycles, and there are obvious differences in the microstructure and mechanical properties.

[0029] Specifically, step 3 includes: Step 31: The region division and microstructure analysis divides the remelting region 3 into eight regions, namely, secondary fusion zone A, primary fusion + primary heat-affected zone B, primary heat-affected + primary fusion zone C, secondary heat-affected zone D, primary fusion zone E, primary heat-affected zone F, primary fusion zone G, and primary heat-affected zone H. Based on the region division results, a thermal cycle curve is obtained by numerical simulation, and the Gleeble thermal simulation technology is used to reproduce the thermal cycle process of each region in the overlapping region to obtain a simulated microstructure morphology. The simulated tissue morphology is used to analyze the microstructure of the overlapping area of ​​the actual weld joint.

[0030] It should be noted that the simulated organizational morphology provides a reference for studying the effects of grain orientation, microstructure and hardness gradient in the remelting zone 3 on mechanical properties.

[0031] Step 32: Based on the forging manufacturing requirements, along the forging direction (L), the perpendicular forging direction (T), and the forging thickness direction (S), according to the double-sided double-pass welding process characteristics, the metallographic structure, microhardness, tensile strength, impact toughness, and fatigue strength performance testing and analysis of the joint parts are carried out in sequence.

[0032] Specifically, step 32 includes: Step 321: The microhardness sampling method of the joint portion 10 is to first perform a microhardness test on the transverse direction (TL) of the joint to obtain a hardness distribution curve from the base material, the heat-affected zone to the fusion zone; then perform a microhardness test along the weld penetration direction (TS) to obtain a hardness distribution curve along the weld depth direction; Step 322: The tensile test specimen 11 and the impact test specimen 12 of the joint are firstly sampled in a multi-layered manner in the transverse direction (TL) of the joint, with each layer containing a remelted region 3; then, samples are sampled along the weld penetration direction (TS) and in a multi-layered manner along the weld length, with a U-shaped or V-shaped notch for impact toughness being placed in the remelted region 3; Step 323: The fatigue specimen 13 of the joint is sampled in a multi-layer manner in the transverse direction (TL) of the joint, with each layer being diversified. The remelting region 3 is staggered and sampled in two layers, one of which is a completely overlapping region and the other is a secondary weld root region (with the root tip placed in the center of the sample). Step 324: Based on the weld morphology and structure, microhardness distribution, tensile strength and impact toughness test results, and fatigue strength test results, the mechanical properties of the joint and the remelted area 3 are comprehensively analyzed.

[0033] Example 2 Please refer to Figure 1The present invention proposes a method for selecting the position of the remelting area 3 for double-pass welding of large-thickness titanium alloy on both sides, comprising forming a butt joint (the butt thickness is represented by δ) between a first large-thickness titanium alloy workpiece 1 and a second large-thickness titanium alloy workpiece 2, setting a welding assembly gap between the joints during clamp assembly, and identifying the surfaces to be welded of the butt joint as surface A and surface B, completing the welding of the first weld 4 and the second weld 5 according to given welding process parameters, and forming a remelting area 3, and setting the overlapping length of the two welds in the remelting area 3 to 10 mm to 15 mm.

[0034] Furthermore, in some examples, taking the titanium alloy bearing frame of a large aircraft as an example, the material is TC21 titanium alloy, the butt thickness is 160mm, and the bearing frame structure is generally a web + rib structure. If the maximum penetration depth of the unit vacuum electron beam welding is 130mm, and in accordance with the principle of "minimizing the proportion of the weld seam in the remelting area 3 retained in the final structure", the penetration depth of the first weld seam 4 can be planned to be controlled at 130mm, and the penetration depth of the secondary weld seam 5 can be controlled at 40mm, that is, the remelting area 3 is set at a position 1 / 4δ away from the B surface as described in the present invention, such as Figure 1 The middle remelting area 3 is shown at position 2.

[0035] Please refer to Figure 2 The present invention proposes a method for regulating the microstructure and toughening properties of the remelting zone 3 in double-sided double-pass welding of thick titanium alloy, that is, a filler space is processed in the remelting zone 3 near the root of the secondary weld to facilitate the placement of materials. The added materials are closely matched with the filler space. During the welding process, the microstructure and mechanical properties of this position are regulated by means of component compensation and component dilution, thereby achieving the effect of strengthening the properties of the remelting zone 3.

[0036] Furthermore, in some examples, based on the results of welding tests and performance tests, pure titanium material (TA1 / TA2 / TA3) or titanium alloys of different grades are added to the location of the remelting area 3. If there are special requirements, other metal materials can be added. The heat treatment state of the added material is preferably consistent with that of the base material. Furthermore, in some examples, based on the welding test and performance test results, the filler spaces such as the foil filler 6, the plate filler 7, the wire rod filler 8, and the hexagonal filler 9 are respectively processed on both sides of the joint butt joint according to the position selected in the remelting area 3 and the specifications of the filling material. If the foil is pure titanium material, a mechanical method can be used to process the filler space. Figure 2 A filler space in the shape of a foil filler 6 is shown, and pure titanium foil is placed in this filler area. The first thickest titanium alloy workpiece 1 and the second thickest titanium alloy workpiece 2 are clamped, and argon arc welding is performed on both sides of the workpiece joint to ensure the gap between the joints. After adding, argon arc welding is performed on both ends of the added material to ensure that the position of the weld point is not larger than the end face opening area of ​​the filler area.

[0037] Furthermore, in some examples, vacuum electron beam welding of the first weld 4 and the second weld 5 is completed according to established welding process parameters and process flow, and heat treatment is performed after welding to achieve the effect of stress relief or strengthening.

[0038] Please refer to Figures 3 to 6 The present invention proposes a method for characterizing the microstructure and mechanical properties of the weld in the remelting zone 3 of the double-sided double-pass welding process. Different areas of the double-sided double-pass welding remelting zone 3 have undergone two thermal cycles, and there are obvious differences in microstructure and mechanical properties. The remelting zone 3 is divided into regions according to the weld fusion zone, heat-affected zone, and base material zone, and the microstructure is analyzed. Combined with the cross-sectional morphology of the weld, mechanical properties samples are prepared and tested at different positions and directions of the remelting zone 3, thereby fully characterizing the microstructure and mechanical properties of the remelting zone 3.

[0039] Furthermore, in some examples, the regional division and microstructure analysis divides the remelting region 3 into eight regions, as shown in Figure 3: A: secondary fusion zone, B: primary fusion + primary heat-affected zone, C: primary heat-affected + primary fusion zone, D: secondary heat-affected zone, E: primary fusion zone, F: primary heat-affected zone, G: primary fusion zone, and H: primary heat-affected zone. Based on numerical simulation, a thermal cycle curve can be obtained. The Gleeble thermal simulation technique is used to reproduce the thermal cycle process of each region in the overlap zone, obtaining a simulated microstructure morphology with a larger volume that is similar to the actual weld joint overlap microstructure. Based on the size and shape of the simulated region, metallographic samples are prepared in the remelting region 3, and the actual microstructure morphology is obtained by region. This provides a reference for studying the effects of grain orientation, microstructure, and hardness gradient in the remelting region 3 on mechanical properties. Furthermore, in some instances, the key to mechanical property sample preparation and testing lies in determining the sampling method and conducting performance testing and analysis of the metallographic structure, microhardness, tensile strength, impact toughness, fatigue strength, etc. of the joint based on the forging direction (L direction, T direction, and S direction) of the forging. Furthermore, in some examples, the microhardness sampling method of the joint is to sample the microhardness of the joint along the weld penetration direction (TS) according to the following formula: Figure 4 By testing at the microhardness 10 test position shown, the hardness distribution curve along the depth direction of the weld can be obtained; by performing multi-layer microhardness testing along the transverse direction (TL), the hardness distribution curve from the base material, heat-affected zone to the fusion zone can be obtained.

[0040] Furthermore, in some examples, the sampling method for the tensile strength and impact toughness of the joint is to prepare along the weld penetration direction (TS) and take multiple preparations along the weld length direction. The sampling positions of the tensile specimen 11 and the impact specimen 12 are as follows: Figure 5As shown, the U-shaped or V-shaped notch for impact toughness is placed in the remelting area 3. Multiple layers are prepared in the transverse direction (TL) of the joint, with each layer containing the remelting area 3. After sample preparation, tensile properties testing and impact toughness testing are performed to obtain data such as tensile strength, yield strength, reduction of area, elongation, and impact toughness.

[0041] Furthermore, the sampling method for the fatigue strength test of the joint part is to prepare fatigue specimens 13 in a multi-layer and diversified manner in the transverse direction (TL) of the joint, wherein the remelting area 3 is staggered and prepared in two layers, one layer is the complete overlap area of ​​the weld, and the other layer is the root area of ​​the secondary weld (the root tip is placed in the sample); Furthermore, based on the results of weld morphology and structure, microhardness distribution, tensile strength and impact toughness tests, and fatigue strength tests, the mechanical properties of the joint and the remelted area 3 were comprehensively analyzed.

[0042] In summary, the present invention belongs to the field of vacuum electron beam welding of titanium alloys, and relates to a method for controlling the performance of double-sided double-pass EBW remelting areas of large-thickness titanium alloys, including a method for selecting the position of the remelting area 3 of large-thickness titanium alloy double-sided double-pass welding, wherein the position of the remelting area 3 refers to the specific position of the remelting area 3 that can be specifically planned based on the butt thickness of the product and the maximum depth capacity of the single-pass welding of the equipment, as well as the principle of minimizing the proportion of the weld in the remelting area 3 retained in the final structure; based on the selected position of the remelting area 3, a method for controlling the microstructure and performance strengthening and toughening of the remelting area 3 of large-thickness titanium alloy double-sided double-pass welding is proposed, a filler space is processed in the remelting area 3 to add materials, and the microstructure and mechanical properties of this position are controlled by component compensation and component dilution during the welding process, so as to achieve the effect of homogenizing and toughening the performance of the remelting area 3; at the same time, a means for characterizing the microstructure and mechanical properties of the weld in the remelting area 3 of double-sided double-pass welding is proposed, which completely characterizes the microstructure and mechanical properties of the remelting area 3, and provides a basis for the safe use of large-thickness titanium alloy welding structures.

Claims

1. A method for controlling the performance of double-sided double-pass EBW remelting areas of thick titanium alloy, characterized in that: include: Step 1: When clamping the butt joint of the first titanium alloy workpiece (1) and the second titanium alloy workpiece (2), a welding assembly gap is set, and the surfaces to be welded of the butt joint are identified as surface A and surface B, the surface A is welded with the first weld (4) in double-pass welding, and the surface B is welded with the second weld (5) in double-pass welding, and a remelting area (3) is determined based on the overlapping area of ​​the first weld and the second weld; Step 2: Processing a filler space in the remelting area (3) near the root of the secondary weld to facilitate the placement of material; Step 3: Divide the remelting area (3) into regions according to the weld fusion zone, heat-affected zone, and base material zone, and perform a microstructure analysis; prepare and test mechanical properties of the remelting area (3) at different positions and directions in combination with the weld cross-sectional morphology, and then fully characterize the microstructure and mechanical properties of the remelting area (3).

2. The method according to claim 1, characterized in that Step 3 includes: Step 31: Divide the remelting area (3) into secondary fusion zone A, primary fusion + primary heat-affected zone B, primary heat-affected + primary fusion zone C, secondary heat-affected zone D, primary fusion zone E, primary heat-affected zone F, primary fusion zone G, and primary heat-affected zone H; according to the area division results, a thermal cycle curve is obtained based on numerical simulation, and the Gleeble thermal simulation method is used to reproduce the thermal cycle process of each area in the overlapping area to obtain a simulated tissue morphology; Step 32: Based on the forging manufacturing requirements, along the forging direction (L), the perpendicular forging direction (T), and the forging thickness direction (S), according to the double-sided double-pass welding process characteristics, the metallographic structure, microhardness, tensile strength, impact toughness, and fatigue strength performance testing and analysis of the joint parts are carried out in sequence.

3. The method according to claim 2, characterized in that Step 32 includes: Step 321: The microhardness sampling method of the joint part (10) is as follows: first, a microhardness test is performed on the joint transverse direction TL to obtain a hardness distribution curve from the base material, the heat-affected zone to the fusion zone; then, a microhardness test is performed along the weld penetration direction TS to obtain a hardness distribution curve along the weld depth direction; Step 322: The method for sampling the tensile test specimen (11) and the impact test specimen (12) at the joint portion is as follows: first, the joint is sampled in multiple layers in a transverse direction TL, each layer being diversified, wherein the sample of one layer contains a remelting area (3); then, the sample is sampled along the weld penetration direction TS and diversified along the weld length direction, wherein a U-shaped or V-shaped notch for impact toughness is placed in the remelting area (3); Step 323: The fatigue specimen (13) of the joint is sampled by a multi-layer and diversified method in the transverse TL of the joint, wherein the remelting area (3) is staggered and prepared in two layers, one layer is a completely overlapping area, and the other layer is a secondary weld root area with the root tip placed in the sample; Step 324: Based on the results of the weld morphology, microhardness distribution, tensile strength and impact toughness test and fatigue strength test, the mechanical properties of the joint and the remelting area (3) are comprehensively analyzed.

4. The method according to claim 1, characterized in that The overlapping length of the two welds in the remelting area (3) ranges from 10 mm to 15 mm.

5. The method according to claim 1, characterized in that The position of the remelting area (3) is based on the butt thickness and the maximum depth capability of the equipment for single-pass welding, as well as the principle of minimizing the proportion of the weld in the remelting area (3) remaining in the final structure.

6. The method according to claim 1, characterized in that The position of the remelting area (3) includes the middle position along the thickness direction or 1 / 3δ, 1 / 4δ and 1 / 5δ away from the B surface, wherein δ is the butt joint thickness of the large-thickness titanium alloy butt joint.

7. The method according to claim 1, characterized in that The added material includes pure titanium, titanium alloy or other metal materials.

8. The method according to claim 1, characterized in that The added material may be in the form of foil filler (6), plate filler (7), wire rod filler (8), hexagonal filler (9), or other special-shaped structures through mechanical processing.

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