阅读说明：本技术 一种超大厚度大尺寸钛合金结构件真空电子束焊接方法 (Vacuum electron beam welding method for ultra-large-size titanium alloy structural part ) 是由 谈哲君 王志敏 步贤政 姚为 武俊飞 孙少波 韩博文 于 2021-06-30 设计创作，主要内容包括：本发明提供一种超大厚度大尺寸钛合金结构件真空电子束焊接方法,对超大厚度钛合金产品焊缝的上下表面对称施焊,并设计了焊接各步骤的参数范围,解决了当前高压电子束焊接设备焊接不易焊透该厚度产品的问题,巧妙解决了双面电子束焊接带来的焊缝中部钉尖缺陷无法排除的问题,保证了焊接质量和产品性能,适用于焊接厚度在80-130mm之间的超大厚度钛合金电子束焊接,在航空航天制造技术领域有着广泛应用前景。(The invention provides a vacuum electron beam welding method for an ultra-large-size titanium alloy structural part, which is used for symmetrically welding the upper surface and the lower surface of a welding seam of the ultra-large-size titanium alloy product, designing parameter ranges of all welding steps, solving the problem that the existing high-pressure electron beam welding equipment is difficult to weld through the thick product, skillfully solving the problem that the nail tip defect in the middle of the welding seam caused by double-sided electron beam welding cannot be eliminated, ensuring the welding quality and the product performance, being suitable for the ultra-large-size titanium alloy electron beam welding with the welding thickness of 80-130mm, and having wide application prospects in the technical field of aerospace manufacturing.)

1. A vacuum electron beam welding method for a large-size titanium alloy structural member with an ultra-large thickness is characterized by comprising the following steps:

(1) spot welding the cleaned and assembled parts to be welded;

(2) respectively carrying out electron beam tack welding on the upper surface and the lower surface of a welding seam to be welded, wherein the focusing current adopted in the tack welding is a negative value;

(3) performing electron beam formal welding on the lower surface of a welding seam to be welded, wherein the focusing current adopted in the formal welding is a negative value; in the formal welding, machining allowances are respectively arranged in front of and behind the welding line;

(4) carrying out electron beam modification welding on the lower surface of a welding seam to be welded, and cooling;

(5) performing electron beam formal welding on the upper surface of a welding seam to be welded, wherein the focusing current adopted in the formal welding is a positive value; in the formal welding, machining allowance is respectively arranged at the head and the tail of the welding line;

(6) and carrying out electron beam modification welding on the upper surface of the welding seam to be welded.

2. The vacuum electron beam welding method for the ultra-large-size titanium alloy structural part with the extra-large thickness as recited in claim 1, wherein in the step (2), the length of each section of welding seam of tack welding is 30-50mm, and the interval is 30-50 mm; and (5) the absolute value of the electron beam current for spot welding is smaller than the absolute value of the electron beam current for formal welding in the steps (3) and (5).

3. The vacuum electron beam welding method for the titanium alloy structural member with the overlarge thickness and the large size as recited in claim 1 or 2, wherein in the step (2), the focusing current of spot welding is-30 mA to-50 mA, the electron beam current is 30mA to 50mA, and the welding speed is 400 mm-700 mm-min^-1The scanning mode is circular.

4. The vacuum electron beam welding method for the ultra-large-thickness large-size titanium alloy structural part according to claim 1, wherein in the steps (3) and (5), the machining allowance for formally welding the head and the tail of the welding seam is 40-50 mm.

5. The vacuum electron beam welding method for the ultra-large-thickness large-size titanium alloy structural part according to claim 1, wherein in the step (3), the focusing current for formal welding of the lower surface of the welding seam to be welded is-120 mA to-170 mA, the electron beam current is 220 mA to 280mA, and the welding speed is 400 mm-min to 700 mm-min^-1The scanning mode is circular;

in the step (5), the focusing current for formal welding of the upper surface of the welding line to be welded is +5 to +20mA, the electron beam current is 220 to 280mA, and the welding speed is 400 to 700 mm.min^-1The scanning mode is linear.

6. The vacuum electron beam welding method for the titanium alloy structural member with the extra-large thickness and the large size as recited in claim 1, wherein in the step (4), the lower surface of the welding seam to be welded is decorated and weldedThe focusing current is-20 to +20mA, the electron beam current is 70 to 110mA, and the welding speed is 400 to 700 mm.min^-1The scanning mode is circular;

in the step (6), the focusing current for modifying and welding the upper surface of the welding line to be welded is +10 to +30mA, the electron beam current is 70 to 110mA, and the welding speed is 400 to 700mm & min^-1The scanning mode is linear.

7. The vacuum electron beam welding method for the titanium alloy structural part with the overlarge thickness and the large size as recited in claim 1, wherein in the step (3) and the step (5), machining allowance of 5mm to 7mm is added in the welding thickness direction of the lower surface and the upper surface of the welding seam to be welded respectively.

8. The vacuum electron beam welding method for the ultra-large-thickness large-size titanium alloy structural part according to claim 1, wherein in the step (1), tack welding is performed manually, and the tack depth is 1-2 mm;

in the step (1), the step of cleaning comprises:

performing alkaline washing on an area which takes the center of a welding seam as a starting point and extends 100-200mm to two sides vertical to the direction of the welding seam, drying, mechanically polishing the butt joint surface of a part to be welded and the surface of a base metal in the area which takes the center of the welding seam as a starting point and extends 30-70 mm to two sides vertical to the direction of the welding seam until bright white metallic luster is exposed, and wiping the surface clean by alcohol;

in the step (1), the assembly method is that the parts to be welded are rigidly fixed on the tool through a plurality of pressure plates, and the interval between the pressure plates is 150mm-200 mm.

9. The vacuum electron beam welding method for the titanium alloy structural member with the ultra-large thickness and the large size as recited in claim 1, wherein the vacuum degree of the steps (2) to (6) is less than or equal to 2 x 10^-5The reaction is carried out in an environment of Pa;

the scanning frequency of the steps (2) to (6) is 400-600 Hz.

10. The vacuum electron beam welding method for the ultra-large-size titanium alloy structural part with the extra-large thickness as recited in claim 1, wherein the vacuum electron beam welding method further comprises the steps of (7) post-welding quality detection and vacuum heat treatment.

Technical Field

The invention relates to a vacuum electron beam welding method for a large-size titanium alloy structural part with an overlarge thickness, and belongs to the technical field of titanium alloy electron beam welding.

Background

With the rapid development of the aerospace industry and manufacturing technology, the requirements of aircraft product performance on light and high-strength structures are greatly improved, and titanium alloy structural members with ultra-large thickness are gradually applied to product design. Taking a certain aircraft supporting part as an example (figure 1), the aircraft supporting part is formed by butting two casting titanium alloy solid blocks with the thickness of 100mm, the length of each block is about 1100mm, the butting width is about 400mm, the requirement on straightness deformation of a product after welding is not more than 3mm, the requirements on welding quality and first-time qualification rate are high, and the repair and shape correction after welding are difficult, so that higher requirements are provided for a welding technology. The electron beam welding is a welding method with the characteristics of high energy density, low heat input, small welding deformation, large depth-to-width ratio of welding seams, excellent welding protective atmosphere and the like, is widely applied to the field of metal welding, particularly aerospace manufacturing, and is extremely suitable for welding large-thickness titanium alloy structural members.

However, if the traditional medium-voltage electron beam welding method is adopted, the welding depth cannot reach 100mm due to limited heat input energy; if high-voltage electron beam welding is adopted, when the distance between a product and an electron beam gun is large, the theoretical welding depth is difficult to reach due to insufficient energy density; moreover, the adoption of a double-sided electron beam welding mode is easy to cause nail tip defects at the middle depth of a weld pool, and once the defects are generated, the defects are difficult to remove for titanium alloys with ultra-large thickness. Therefore, the product meeting the requirements of GJB1718A-2005 electron beam welding on the I-grade joint is difficult to obtain by adopting the traditional conventional electron beam welding process method.

Disclosure of Invention

The invention aims to overcome the defects and provides a vacuum electron beam welding method for an ultra-large-thickness titanium alloy structural part, which is used for symmetrically welding the upper surface and the lower surface of a welding seam of the ultra-large-thickness titanium alloy product, designs parameter ranges of all welding steps, solves the problem that the existing high-pressure electron beam welding equipment is difficult to weld through the thick product, skillfully solves the problem that the nail tip defect in the middle of the welding seam caused by double-sided electron beam welding cannot be eliminated, ensures the welding quality and the product performance, is suitable for the ultra-large-thickness titanium alloy electron beam welding with the welding thickness of 80-130mm, and has wide application prospects in the technical field of aerospace manufacturing.

In order to achieve the above purpose, the invention provides the following technical scheme:

a vacuum electron beam welding method for a large-size titanium alloy structural member with an ultra-large thickness comprises the following steps:

(1) spot welding the cleaned and assembled parts to be welded;

(2) respectively carrying out electron beam tack welding on the upper surface and the lower surface of a welding seam to be welded, wherein the focusing current adopted in the tack welding is a negative value;

(3) performing electron beam formal welding on the lower surface of a welding seam to be welded, wherein the focusing current adopted in the formal welding is a negative value; in the formal welding, machining allowances are respectively arranged in front of and behind the welding line;

(4) carrying out electron beam modification welding on the lower surface of a welding seam to be welded, and cooling;

(5) performing electron beam formal welding on the upper surface of a welding seam to be welded, wherein the focusing current adopted in the formal welding is a positive value; in the formal welding, machining allowance is respectively arranged at the head and the tail of the welding line;

(6) and carrying out electron beam modification welding on the upper surface of the welding seam to be welded.

Further, in the step (2), the length of each section of welding seam of spot welding is 30-50mm, and the interval is 30-50 mm; and (5) the absolute value of the electron beam current for spot welding is smaller than the absolute value of the electron beam current for formal welding in the steps (3) and (5).

Further, in the step (2), the focusing current of spot welding is-30 to-50 mA, the electron beam current is 30 to 50mA, and the welding speed is 400 to 700mm min^-1The scanning mode is circular.

Further, in the steps (3) and (5), the machining allowance for formally welding the head and the tail of the welding line is 40-50 mm.

Further, in the step (3), the focusing current for formal welding of the lower surface of the welding line to be welded is-120 to-170 mA, the electron beam current is 220 to 280mA, and the welding speed is 400 to 700mm < mi >n^-1The scanning mode is circular;

in the step (5), the focusing current for formal welding on the upper surface of the welding line to be welded is +5 to +20mA, the electron beam current is 220 to 280mA, and the welding speed is 400 to 700mm min^-1The scanning mode is linear.

Further, in the step (4), the focusing current for modifying and welding the lower surface of the welding seam to be welded is-20 to +20mA, the electron beam current is 70 to 110mA, and the welding speed is 400 to 700mm for min^-1The scanning mode is circular;

in the step (6), the focusing current for decorating and welding the upper surface of the welding line to be welded is +10 to +30mA, the electron beam current is 70 to 110mA, and the welding speed is 400 to 700mm min^-1The scanning mode is linear.

Further, in the step (3) and the step (5), machining allowance of 5 mm-7 mm is respectively added in the welding thickness direction of the lower surface and the upper surface of the welding seam to be welded.

Further, in the step (1), the tack welding mode is manual welding, and the tack depth is 1-2 mm;

in the step (1), the step of cleaning comprises:

performing alkaline washing on an area which takes the center of a welding seam as a starting point and extends 100-200mm to two sides vertical to the direction of the welding seam, drying, mechanically polishing the butt joint surface of a part to be welded and the surface of a base metal in the area which takes the center of the welding seam as a starting point and extends 30-70 mm to two sides vertical to the direction of the welding seam until bright white metallic luster is exposed, and wiping the surface clean by alcohol;

in the step (1), the assembly method is that the parts to be welded are rigidly fixed on the tool through a plurality of pressure plates, and the interval between the pressure plates is 150mm-200 mm.

Further, the vacuum degree of the steps (2) to (6) is less than or equal to 2 multiplied by 10^-5The reaction is carried out in an environment of Pa;

the scanning frequency of the steps (2) to (6) is 400-600 Hz.

And further. The vacuum electron beam welding method further comprises the step (7) of post-welding quality detection and vacuum heat treatment.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, the upper surface and the lower surface of the welding seam of the titanium alloy product with the ultra-large thickness are symmetrically welded by adopting an electron beam welding method, so that the problem that the product with the thickness is not easy to be welded through the welding of the current high-voltage electron beam welding equipment is solved, and the product meeting the requirements of GJB1718A-2005 electron beam welding on the I-grade joint is obtained;

(2) according to the vacuum electron beam welding method for the oversized-thickness large-size titanium alloy structural part, during formal welding, the upper surface and the lower surface are respectively welded in the upper focus (focusing current is a positive value) and the lower focus (focusing current is a negative value), so that the problem that the nail point defect in the middle of a welding line cannot be eliminated due to double-sided electron beam welding is solved ingeniously, and the welding quality and the product performance are ensured;

(3) according to the vacuum electron beam welding method for the oversized-thickness large-size titanium alloy structural part, through a large number of experiments, the optimal range of welding parameters of spot welding, formal welding and modification welding of the upper surface and the lower surface of a welding seam is obtained, the welding depth is increased, and a good and stable welding seam is obtained;

(4) the invention relates to a vacuum electron beam welding method for a large-size titanium alloy structural member with an ultra-large thickness, which particularly designs a focus current value of formal welding, firstly adopts a larger focus current value to weld a welding seam on one surface of the welding seam, adopts a smaller focus current value to weld a welding seam on the other surface after turning over, and ensures that the welding seam is welded thoroughly;

(5) according to the vacuum electron beam welding method for the oversized-thickness large-size titanium alloy structural part, machining allowances of 40-50mm are respectively added in the front and back of the welding line direction of the product, and machining allowances of 5 mm-7 mm are respectively added on the upper surface and the lower surface in the welding thickness direction, so that the problem of incomplete penetration caused by the incremental energy of arc striking or arc stopping is prevented;

(6) the vacuum electron beam welding method for the oversized titanium alloy structural part is suitable for the oversized titanium alloy structural part with the welding thickness of 80-130mm, and has wide application prospect in the technical field of aerospace manufacturing;

drawings

FIG. 1 is an assembly schematic diagram of a part to be welded in the vacuum electron beam welding method for a large-size titanium alloy structural member with an ultra-large thickness according to the present invention;

FIG. 2 is a schematic diagram of welding the upper surface of a weld joint in the vacuum electron beam welding method for the ultra-large-size titanium alloy structural member with the ultra-large thickness;

FIG. 3 is a schematic view of the lower surface of a butt weld in the vacuum electron beam welding method for the ultra-large-size titanium alloy structural member with the ultra-large thickness.

Detailed Description

The features and advantages of the present invention will become more apparent and appreciated from the following detailed description of the invention.

The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The schematic diagram of a typical large-size titanium alloy structural member with an ultra-large thickness is shown in fig. 1, and the large-size titanium alloy structural member is formed by butting two cast titanium alloy solid blocks with the thickness of 100mm, a welding joint is in a plane butting mode, the welding thickness reaches 100mm, the length of a single block is about 1100mm, the butting width is about 400mm, the requirement on straightness deformation of a product after welding is not more than 3mm, the requirements on welding quality and first-time qualification rate are high, and post-welding repair and shape correction are difficult, so that higher requirements are provided for a welding technology. The traditional medium-voltage and high-voltage electron beam welding process method is difficult to directly meet the requirements of the standard GJB1718A-2005 electron beam welding on the I-grade joint due to the problems of insufficient heat input, easy nail tip defect generation and the like. In order to solve the problem, the invention adopts special welding process and parameters and welding tool dimension by high-voltage electron beam welding equipment to realize high-quality welding and deformation control of the titanium alloy structural part with the ultra-large thickness and the large size.

The technical solution of the invention is as follows: a vacuum electron beam welding method for a large-size titanium alloy structural member with an ultra-large thickness is suitable for electron beam welding of the titanium alloy with the ultra-large thickness of between 80 and 130mm, and a welding joint is in a plane butt joint shape. The method comprises the following steps:

the preparation method comprises the following steps: in the product design stage, machining allowances of 40-50mm are added in the front and back directions along the welding line direction of the product respectively so as to prevent incomplete penetration caused by the progressive increase of energy of arc striking or arc extinguishing; the machining allowance of 5mm to 7mm can be respectively added on the upper surface and the lower surface in the welding thickness direction.

Step (1):

(11) and (6) cleaning before welding. Performing alkali cleaning on the area within the range of 100-200mm around the butt joint position of two parts to be welded 1 and 2 of the large-thickness large-size 4-inch titanium alloy structural member shown in the figures 1-3, removing impurities such as oil stains on the surface, and drying; the butt joint surface of the parts 1 and 2 to be welded and the surface of the base metal in the range of 50mm around the butt joint surface are polished completely by a mechanical cleaning mode, the cast oxide skin is removed until bright white metal luster is exposed, and the base metal is wiped clean by alcohol;

(12) the parts to be welded 1 and 2 are assembled. The welding tool is used for assembling parts to be welded 1 and 2, good butt joint of joints is guaranteed, gaps and step differences are not more than 0.2mm, a plurality of pressing plates 3 are used for clamping and fixing the parts 1 and 2, one pressing plate 3 is arranged at intervals of 150mm-200mm, and the products 1 and 2 are rigidly fixed on the tool through the pressing plates to play a role in maintaining the shape.

(13) And (5) manual welding. And uniformly tack-welding the periphery of the welding line of the assembled product by adopting a manual welding mode, wherein the tack-welding depth is preferably 1-2 mm.

(14) Hoisting and vacuumizing. After the point fixing is finished, the product and the tool are hoisted on an electron beam welding equipment platform, and the product and the tool are vacuumized after being fixed and clamped, so that the vacuum degree is ensured to be 2 multiplied by 10^-5Pa。

The parts 1 and 2 are electron beam welded by the following steps:

(2) respectively carrying out electron beam tack welding on the upper surface and the lower surface of a welding seam to be welded:

(21) as shown in fig. 2, teaching programming is performed on the upper surface 4 of the welding seam of the product through an electron beam NC (Numerical Control) program, so as to ensure that a teaching spot is in the center of the welding seam;

the upper surface 4 of the welding seam of the product is tack-welded through an electron beam 6, a lower focus (focusing current is a negative value) and a current parameter smaller than that of a formal welding electron beam are used in the tack-welding process, one section is uniformly tack-welded at intervals of 30-50mm, and each section is tack-welded for 30-50 mm;

(22) as shown in fig. 3, the product is turned to face the lower surface of the welding seam upwards through an NC program, and teaching programming is performed through an electron beam NC program to ensure that a teaching spot is in the center of the welding seam;

the lower surface 5 of the welding seam of the product is fixed by points, and the fixing process and the used parameters are consistent with the fixing process of the upper surface of the welding seam of the product;

(3) formal welding is carried out on the lower surface 5 of the welding seam of the product, the welding process is carried out by using a lower focus (focusing current is a negative value) and a scanning mode, arc striking is carried out from the end face of the head of the machining allowance of the welding seam of the product, the welding is continuously welded to the tail of the machining allowance to carry out arc closing and finish welding, and specific parameters are shown in table 1;

(4) performing modified welding on the lower surface 5 of the welding seam, wherein specific parameters are shown in table 1;

naturally cooling for 0.5-1.5 hours in the vacuum chamber;

(5) and (3) performing electron beam formal welding on the upper surface 4 of the welding seam of the product:

teaching programming is carried out through an electron beam NC program, and teaching light spots are ensured to be in the right center of a welding line;

formal welding is carried out on the upper surface 4 of the welding seam of the product, the welding process is carried out by using a mode of upper focus (focusing current is a positive value) and scanning, the arc is started from the head of the machining allowance of the welding seam of the product, the welding is finished by continuously welding to the tail of the machining allowance through arc closing, and specific parameters are shown in table 1;

(6) the top surface 4 of the weld was finish welded, the specific parameters are shown in table 1.

(7) And (3) post-treatment process:

(71) and (3) postweld quality detection: after welding, performing appearance quality detection on the electron beam welding seam, and determining whether the surface of the welding seam has defects such as cracks, burn-through and the like; the internal quality of the welding seam is detected by adopting a radioactive source transillumination mode, and the integral straightness of the product is measured by adopting a laser three-dimensional scanning mode.

(72) Vacuum heat treatment: and carrying out vacuum heat treatment on the product with qualified welding quality.

TABLE 1 welding parameter Table for each step

The upper surface and the lower surface of the welding seam can be determined at will and are the same in nature, and when one surface is determined to be the upper surface, the other surface is the lower surface.

The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.