阅读说明：本技术 钛合金板真空电子束焊接方法及磁悬浮超导低温固氮腔 (Titanium alloy plate vacuum electron beam welding method and magnetic suspension superconducting low-temperature nitrogen fixation cavity ) 是由 刘振飞 陈涛 王丽芳 姜北燕 马建国 李波 刘志宏 吴杰峰 于 2021-06-30 设计创作，主要内容包括：本发明公开了一种钛合金板真空电子束焊接方法及磁悬浮超导低温固氮腔,方法包括除气、定位焊接、深熔焊接和修饰焊接等步骤等步骤；磁悬浮超导低温固氮腔包括使用上述钛合金板真空电子束焊接方法焊接而成的TC4钛合金部件。本发明所述焊接方法不仅使TC4钛合金板之间焊接稳定、焊缝宽度均匀、无咬边、无下凹和飞溅少,而且具有焊缝内部气孔少、焊缝抗拉强度高于母材抗拉强度的特点；将利用该焊接方法所焊接的TC4钛合金部件,应用在磁悬浮超导低温固氮腔上时,使其具有由上述效果而带来的性能稳定、使用寿命长等优势。(The invention discloses a titanium alloy plate vacuum electron beam welding method and a magnetic suspension superconducting low-temperature nitrogen fixation cavity, wherein the method comprises the steps of degassing, positioning welding, deep melting welding, modification welding and the like; the magnetic suspension superconducting low-temperature nitrogen fixation cavity comprises a TC4 titanium alloy part welded by using the titanium alloy plate vacuum electron beam welding method. The welding method not only ensures that TC4 titanium alloy plates are welded stably, the width of a welding seam is uniform, no undercut, no concave and less splashing are caused, but also has the characteristics of less pores in the welding seam and higher tensile strength of the welding seam than that of a parent metal; when the TC4 titanium alloy component welded by the welding method is applied to a magnetic suspension superconducting low-temperature nitrogen fixation cavity, the titanium alloy component has the advantages of stable performance, long service life and the like caused by the effects.)

1. A vacuum electron beam welding method for titanium alloy plates is characterized in that: the method comprises the following steps:

(1) welding, weldingPreparing: putting two TC4 titanium alloy plates into a vacuum chamber of a welding machine after butt joint and compaction, presetting a TC4 titanium alloy plate in the vacuum chamber of the welding machine, vacuumizing the vacuum chamber of the welding machine, wherein the stable value of the vacuum degree in the vacuum chamber is lower than 1.4 multiplied by 10^-4mbar；

(2) And degassing: performing electron beam heating treatment on a preset TC4 titanium alloy plate, wherein the working distance is 400-450 mm, the accelerating voltage is 150kV, the electron beam current is 4-10 mA, the beam current focus is above the surface of a weld joint, the focused beam current is 2500-2600 mA, the welding speed is 3-6 mm/s, and performing reciprocating welding for 10-30 minutes;

(3) and positioning welding: the method comprises the following steps of firstly carrying out equidistant segmented tack welding along to-be-welded positions of two TC4 titanium alloy plates, and then carrying out continuous welding on the whole welding line, wherein the working distance is 400-450 mm, the acceleration voltage is 150kV, the electron beam current is 1-2 mA, the beam current focus is on the surface of the welding line, the focused beam current is 2400-2430 mA, the scanning frequency is 60-100 Hz, the scanning waveform is circular wave, the scanning diameter is 0.5-2 mm, and the welding speed is 5-10 mm/s;

(4) and deep melting welding: carrying out deep fusion welding on the welding seams of the two TC4 titanium alloy plates, wherein the welding speed is 5-10 mm/s, the focusing beam current is 2390-2420 mA, the electron beam current is 12-17 mA, the accelerating voltage is 150KV, the scanning frequency is 100-300 Hz, the scanning waveform is circular wave, and the scanning diameter is 0.2-0.5 mm;

(5) and modifying and welding: performing modification welding on the welding seams of the two TC4 titanium alloy plates, wherein the welding speed is 5-10 mm/s, the focusing beam current is 2430-2460 mA, the electron beam current is 3-6 mA, the accelerating voltage is 150KV, the scanning frequency is 20-50 Hz, the scanning waveform is circular wave, and the scanning diameter is 2-5 mm;

(6) the weld-formed part was cooled in a vacuum chamber for 60 minutes, after which the vacuum was released.

2. The vacuum electron beam welding method of a titanium alloy sheet according to claim 1, characterized in that: in the step (1), the joint between the two TC4 titanium alloy plates is I-shaped.

3. The vacuum electron beam welding method of a titanium alloy sheet according to claim 1, characterized in that: in the step (1), the maximum gap between the TC4 titanium alloy plates is less than 5% of the thickness of the TC4 titanium alloy plate, but the gap between the TC4 titanium alloy plates is not more than 0.2mm at most.

4. A magnetic suspension superconducting low-temperature nitrogen fixation cavity is characterized in that: comprising a TC4 titanium alloy part welded by a vacuum electron beam welding method of the titanium alloy sheet according to any one of claims 1 to 4.

Technical Field

The invention relates to a welding method, in particular to a vacuum electron beam welding method of a TC4 titanium alloy component in a magnetic suspension superconducting low-temperature nitrogen fixation cavity.

Background

The magnetic suspension superconductive low-temperature nitrogen fixation cavity is an important part for the future advance of a high-speed train to 'super-iron' with the speed of 600 kilometers per hour, and has been researched in Japan, and China is also in intensive development. In order to ensure the light weight and high low-temperature strength of the magnetic suspension superconducting low-temperature nitrogen fixation cavity, the box body and the flange need to be made of titanium alloy materials with high specific strength, and a plurality of TC4 titanium alloy plates need to be welded into the box body during manufacturing.

Because the TC4 titanium alloy material has the characteristics of hydrogen absorption, oxygen absorption and nitrogen absorption at high welding temperature, when the conventional gas shielded welding is used, strict inert gas protection needs to be carried out on a welding seam area, time and labor are consumed, sometimes the size and the shape of a welding part are restrained, 100% protection in place is difficult to realize by gas protection, and the hidden trouble of failure is buried in the welding seam.

The vacuum electron beam welding has the advantages of high energy density, large depth-to-width ratio of a welding seam and narrow heat affected zone of a welding joint, and meanwhile, the welding is carried out in vacuum, so that the electron beam welding technology is widely used in the industries of aviation, aerospace, nuclear power and the like. However, if the ordinary vacuum electron beam welding method is directly adopted during welding of the TC4 titanium alloy plate, the defects of many pores in the welding seam, poor surface forming, undercut, concavity, severe splashing and the like occur, which results in poor sealing performance and low tensile strength of the welding joint, and cracks are easily generated at the undercut of the welding seam, thus being difficult to meet the design requirements. Therefore, a welding method suitable for the TC4 titanium alloy plate is needed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a vacuum electron beam welding method for TC4 titanium alloy plates, which has the advantages of good weld forming, less pores in the weld, no crack, no undercut, no concave and higher tensile strength than that of a base material.

The second aspect provides a magnetic suspension superconducting low-temperature nitrogen fixation cavity for welding the TC4 titanium alloy component by using the titanium alloy plate vacuum electron beam welding method.

A vacuum electron beam welding method for titanium alloy plates comprises the following steps:

(1) and welding preparation: putting two TC4 titanium alloy plates into a vacuum chamber of a welding machine after butt joint and compaction, presetting a TC4 titanium alloy plate in the vacuum chamber of the welding machine, vacuumizing the vacuum chamber of the welding machine, wherein the stable value of the vacuum degree in the vacuum chamber is lower than 1.4 multiplied by 10^-4mbar；

(2) And degassing: performing electron beam heating treatment on a preset TC4 titanium alloy plate, wherein the working distance is 400-450 mm, the accelerating voltage is 150kV, the electron beam current is 4-10 mA, the beam current focus is above the surface of a weld joint, the focused beam current is 2500-2600 mA, the welding speed is 3-6 mm/s, and performing reciprocating welding for 10-30 minutes;

(3) and positioning welding: the method comprises the following steps of firstly carrying out equidistant segmented tack welding along to-be-welded positions of two TC4 titanium alloy plates, and then carrying out continuous welding on the whole welding line, wherein the working distance is 400-450 mm, the acceleration voltage is 150kV, the electron beam current is 1-2 mA, the beam current focus is on the surface of the welding line, the focused beam current is 2400-2430 mA, the scanning frequency is 60-100 Hz, the scanning waveform is circular wave, the scanning diameter is 0.5-2 mm, and the welding speed is 5-10 mm/s;

(4) and deep melting welding: carrying out deep fusion welding on the welding seams of the two TC4 titanium alloy plates, wherein the welding speed is 5-10 mm/s, the focusing beam current is 2390-2420 mA, the electron beam current is 12-17 mA, the accelerating voltage is 150KV, the scanning frequency is 100-300 Hz, the scanning waveform is circular wave, and the scanning diameter is 0.2-0.5 mm;

(5) and modifying and welding: performing modification welding on the welding seams of the two TC4 titanium alloy plates, wherein the welding speed is 5-10 mm/s, the focusing beam current is 2430-2460 mA, the electron beam current is 3-6 mA, the accelerating voltage is 150KV, the scanning frequency is 20-50 Hz, the scanning waveform is circular wave, and the scanning diameter is 2-5 mm;

(6) the weld-formed part was cooled in a vacuum chamber for 60 minutes, after which the vacuum was released.

A magnetic suspension superconducting low-temperature nitrogen fixation cavity comprises a TC4 titanium alloy part welded by the titanium alloy plate vacuum electron beam welding method.

The welding method not only ensures that TC4 titanium alloy plates are welded stably, the width of a welding seam is uniform, no undercut, no concave and less splashing are caused, but also has the characteristics of less pores in the welding seam and higher tensile strength of the welding seam than that of a parent metal; when the TC4 titanium alloy component welded by the welding method is applied to a magnetic suspension superconducting low-temperature nitrogen fixation cavity, the titanium alloy component has the advantages of stable performance, long service life and the like caused by the effects.

Other features and advantages of the welding method of the present invention will be described in detail in the detailed description that follows.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a weld front profile in an embodiment of the invention;

FIG. 2 is a cross-sectional profile of a weld in an embodiment of the invention;

FIG. 3 shows X-ray inspection results of a weld of a welded test piece in an embodiment of the present invention;

FIG. 4 is a transverse mechanical tensile test piece of a weld test piece in an embodiment of the invention;

fig. 5 is a transverse mechanical tensile test result of the weld test piece in the example of the invention.

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, and the scope of the present invention will be more clearly and clearly defined.

In the present embodiment, two TC4 titanium alloy plates (hereinafter referred to as titanium alloy plates) are vacuum electron beam welded, and the titanium alloy plates include a first titanium alloy plate 1 and a second titanium alloy plate 2 (as shown in fig. 1), and the heat treatment state is as follows: annealing, wherein the plate thickness is 6mm, the length is 300mm, and the width is 150 mm;

the welding requirements are as follows: the two titanium alloy plates are butted along the width direction of the plate, and are welded along the length direction of the plate, and the weld penetration is required to be more than 6 mm.

The material to be matched is a backing plate (not shown), wherein the backing plate is a titanium alloy plate with the model number of TC4, and the heat treatment state is as follows: annealing, the plate thickness was 4mm, the length was 300mm, and the width was 4 mm.

The vacuum electron beam welding method for the titanium alloy plate provided by the embodiment comprises the following steps of:

(1) polishing the first titanium alloy plate, the second titanium alloy plate and the metal surface within the range of 40mm at the periphery by using a stainless steel wire brush to expose the metal luster, and then dipping acetone by using clean silk cloth to clean the welding line and the surface of the titanium alloy plate to be welded so as to ensure that the metal surface has no impurities such as oil stains;

(2) butting and pressing the first titanium alloy plate and the second titanium alloy plate, ensuring that the maximum gap between the first titanium alloy plate and the second titanium alloy plate is less than 5% of the thickness of the titanium alloy plate, but the maximum gap between the first titanium alloy plate and the second titanium alloy plate is not more than 0.2mm, realizing an I-shaped joint, placing a backing plate on the back of a welding seam, and pressing the backing plate and the welding seam together, wherein the maximum butting gap of the embodiment is 0.1 mm;

(3) placing the assembled first and second titanium alloy plates into a vacuum chamber of a welding machine, ensuring that the working distance is 400mm, presetting a TC4 titanium alloy plate in the vacuum chamber of the welding machine, vacuumizing, and ensuring that the vacuum degree of the vacuum chamber reaches a stable value of 1.2 multiplied by 10^-4Preparing for welding at mbar;

(4) and degassing: performing electron beam heating treatment on a preset TC4 titanium alloy plate with working distance of 400mm, accelerating voltage of 150kV, electron beam current of 6mA, beam focus above weld surface, focused beam current of 2550mA, welding speed of 4mm/s, performing reciprocating welding for 10 minutes, wherein the vacuum degree stability of the vacuum chamber is 1.1 × 10^-4mbar (for the purpose ofThen, by utilizing the characteristics of high-temperature hydrogen absorption, oxygen absorption and nitrogen absorption of the titanium alloy, the residual hydrogen, oxygen and nitrogen in the vacuum chamber are removed, so that the display value of the vacuum degree in the vacuum chamber is reduced by at least 0.1 multiplied by 10 under the stable state of the vacuum degree^-4mbar, which aims to ensure stable and continuous movement of a weld pool, reduce weld spatter, inclusions and pores, and improve the internal quality of the weld and the mechanical properties of a welding joint);

(5) and positioning welding: three sections of equidistant tack welds are firstly carried out along the length direction of the positions to be welded of the first titanium alloy plate and the second titanium alloy plate, each section is 50mm long, then the whole weld is continuously welded, the welding speed is 8mm/s, the electron beam current is 1mA, the accelerating voltage is 150KV, the beam current focus is on the surface of the weld, the focusing beam current 2410mA, the scanning frequency is 70Hz, the scanning waveform is circular wave, and the scanning diameter is 1mm (aiming at using the scanning waveform to carry out the procedures of firstly segmenting tack welds and then continuously welding the whole weld, the butt joint gap precision of parts can be reduced, the assembly difficulty is reduced, the weld positioning strength is ensured, the tack weld is improved while the weld width is not increased, the tack weld of a front molten pool is ensured not to crack in the welding process, and the welding stability is improved);

(6) and deep melting welding: performing deep fusion welding on the welding seams of the first titanium alloy plate and the second titanium alloy plate, wherein the welding speed is 10mm/s, the focused beam current is 2400mA, the electron beam current is 13mA, the acceleration voltage is 150KV, the scanning frequency is 100Hz, the scanning waveform is circular wave, and the scanning diameter is 0.3mm (negative defocusing, medium-low frequency and narrow amplitude scanning deep fusion welding is used, so that air holes in the welding seams can be effectively reduced, and meanwhile, the condition that a molten pool is seriously splashed cannot occur;

(7) and modifying and welding: performing decoration welding on the welding seams of the first titanium alloy plate and the second titanium alloy plate, wherein the welding speed is 8mm/s, the focused beam 2460mA, the electron beam 5mA, the acceleration voltage is 150KV, the scanning frequency is 25Hz, the scanning waveform is circular wave, and the scanning diameter is 4mm (wherein, the problems of seam undercut and sink can be effectively removed and beautiful fish scale marks can be obtained by scanning and decoration welding with positive defocusing, low frequency and wide amplitude, and in the process of decoration welding, the seam undercut and sink can be effectively eliminated and the beautiful fish scale marks can be obtained by adjusting the focusing current and the scanning waveform and giving proper positive defocusing amount and waveform parameters);

(8) cooling the welding formed part in a vacuum chamber for 60 minutes, and then discharging the vacuum (the high-temperature titanium alloy welding line is prevented from being prematurely exposed to air and being oxidized and failed through limited cooling in the vacuum chamber);

(9) taking out the welding formed part, and cleaning a small amount of splashing on the surface of the welding seam;

(10) and performing appearance inspection, X-ray flaw detection and tensile test.

The welding seam photos of the welding formed part are shown in fig. 2 and fig. 3, and the welding seam has no crack, undercut and recess; as shown in FIG. 4, by carrying out X-ray flaw detection on the weld joint, the quality grade of the weld joint meets the I-grade requirement of NB/T47013.2-2015; sampling the welded joint according to GB/T2651-2008, performing a transverse tensile test, breaking the welded joint on the parent metal, sequencing tensile strengths measured by the tensile piece according to numbers to be 1028MPa and 1006MPa respectively, namely the tensile strength of the parent metal, and referring to FIG. 5, wherein the tensile strength of the welded joint is higher than that of the parent metal, and the conclusion is that: and (4) passing.

The embodiment provides a magnetic suspension superconducting low-temperature nitrogen fixation cavity which comprises a TC4 titanium alloy part welded by using the titanium alloy plate vacuum electron beam welding method.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.