阅读说明：本技术 一种以co2作为环境气氛的钛合金焊接系统和焊接方法 (With CO2Titanium alloy welding system and welding method as ambient atmosphere ) 是由 程方杰 樊立民 武少杰 郑震旦 薛漫野 于 2021-07-09 设计创作，主要内容包括：本发明属于焊接技术领域,公开了一种以CO-2作为环境气氛的钛合金焊接系统和焊接方法,该焊接系统包括具有顶部窗口的环境室,环境室密封连接CO-2进气管道,带孔隔板将环境室内部空间分为上半部分和下半部分,下半部分铺洒有干冰层,上半部分设置有焊接工作台；焊接方法为焊接前利用CO-2进气管道通入CO-2置换环境室内部空气,焊接过程干冰层持续向环境室内部提供CO-2。本发明充分利用CO-2气体密度大、比热容大以及比空气氧化性弱等特点,实现在充满CO-2气体的半开放环境中进行钛合金高效熔化极电弧焊；能够简化设备并降低保护成本,提高焊接过程的安全性；并且提高焊接保护形式的空间灵活性,实现复杂结构件的空间焊缝保护。(The invention belongs to the technical field of welding and discloses a welding method using CO 2 Titanium alloy welding system and welding method as an ambient atmosphere, the welding system comprising an ambient chamber with a top window, the ambient chamber being sealingly connected with CO 2 The air inlet pipeline is provided with a partition plate with holes to divide the internal space of the environmental chamber into an upper half part and a lower half part, a dry ice layer is paved on the lower half part, and a welding workbench is arranged on the upper half part; the welding method is to utilize CO before welding 2 Introducing CO into the gas inlet pipeline 2 Replacing air inside the environmental chamber, and continuously supplying CO to the interior of the environmental chamber through a dry ice layer in the welding process 2 . The invention makes full use of CO 2 The gas has the characteristics of high density, high specific heat capacity, weak oxidizing property compared with air and the like, and the filling of CO is realized 2 Titanium alloy annealing in a semi-open atmosphereEfficient consumable electrode arc welding; the equipment can be simplified, the protection cost can be reduced, and the safety of the welding process can be improved; and the space flexibility of the welding protection form is improved, and the space weld joint protection of the complex structural member is realized.)

1. With CO₂A titanium alloy welding system as an ambient atmosphere, comprising:

an environmental chamber having a top opening;

the anti-convection cover plate shields the top opening part of the environment chamber in a closed state, and the unshielded part forms a top window of the environment chamber;

CO₂inlet line of said CO₂The air inlet pipeline is hermetically connected with the environmental chamber and is communicated with the interior of the environmental chamber and used for introducing CO into the interior of the environmental chamber₂A gas;

the environment chamber comprises a perforated partition plate, a plurality of baffle plates and a plurality of baffle plates, wherein through holes are uniformly distributed on the perforated partition plate, the perforated partition plate is arranged at the bottom of the environment chamber and divides the internal space of the environment chamber into an upper half part and a lower half part, and the upper half part and the lower half part of the environment chamber are communicated through the through holes;

a dry ice layer spread on the lower half part of the environmental chamber for continuously sublimating to provide CO₂To the upper half of the environmental chamber;

a welding bench disposed at an upper half of the environmental chamber.

2. According to claim 1One of the above-mentioned is CO₂Titanium alloy welding system as ambient atmosphere, characterized in that the ambient chamber is provided with CO₂A concentration detector.

3. A CO-based composition according to claim 1₂Titanium alloy welding system as an ambient atmosphere, characterized in that said CO₂The outlet end of the air inlet pipeline is opened downwards and is positioned 0.5m above the perforated partition plate.

4. A CO-based composition according to claim 1₂The titanium alloy welding system used as the environment atmosphere is characterized in that a plurality of supporting steel bars are arranged between the partition plate with the holes and the bottom plate of the environment chamber.

5. A CO-based composition according to claim 1₂The titanium alloy welding system used as the environment atmosphere is characterized in that a positioner is arranged on the welding workbench.

6. A CO-based composition according to claim 1₂A titanium alloy welding system as an ambient atmosphere, characterized in that a carrying crane is disposed outside the ambient chamber.

7. A titanium alloy welding method based on the titanium alloy welding system according to any one of claims 1 to 6, characterized in that the method is carried out according to the following steps:

(1) opening the anti-convection cover plate, and hoisting a welding workpiece and welding equipment into the environmental chamber;

(2) closing the convection prevention cover plate, utilizing the CO₂Introducing CO into the gas inlet pipeline₂Displacing air inside the environmental chamber until the environmental chamber interior CO₂The volume concentration of the gas is more than 90%;

(3) a welding operator enters the environmental chamber from a top window of the environmental chamber to perform welding operation; the dry ice layer continuously provides CO to the interior of the environmental chamber during welding₂(ii) a If the CO inside the environmental chamber is monitored₂The CO is increased when the gas concentration is lower than the set value₂Flow of inlet line up to the ambient room CO₂The volume concentration of the gas is greater than 90%.

8. A CO-based composition according to claim 1₂Titanium alloy welding system as ambient atmosphere, characterized in that the inside of the ambient chamber is CO in step (1) and step (2)₂After the volume concentration of the gas is more than 90%, adding the CO₂The flow rate of the air inlet pipeline is adjusted to 10-15L/min.

9. A CO-based composition according to claim 7 or 8₂Titanium alloy welding system as ambient atmosphere, characterized in that said CO is displaced during the air inside said ambient chamber₂The flow rate of the air inlet pipeline is 50-80L/min.

10. A CO-based composition according to claim 7 or 8₂Titanium alloy welding system as an ambient atmosphere, characterized in that if CO inside said ambient chamber is monitored₂The CO is increased when the gas concentration is lower than the set value₂The flow rate of the air inlet pipeline is 30-40L/min.

Technical Field

The invention belongs to the technical field of welding, and particularly relates to a welding system and a welding method suitable for titanium alloy.

Background

The titanium and the titanium alloy have stronger high-temperature activity, and begin to absorb hydrogen at 250 ℃, and begin to absorb oxygen at 400 ℃ and nitrogen at 600 ℃. When the protective measures are not appropriate during the welding process, the weld joint absorbs these harmful gases, which deteriorates the joint performance. Among them, the influence of oxygen is the most serious, which causes severe oxidation of the high temperature weld metal, so proper protection measures must be taken for the welding area above 400 ℃ to avoid contacting air.

The technology commonly adopted in the engineering at present is to enable a high-temperature welding line to be in an inert gas atmosphere, and the protection mode is divided into an integral protection mode and a local protection mode.

The integral protection mode is that the whole weldment is in a completely sealed environment box (aiming at small-size workpieces, people operate outside) or an environment chamber (aiming at large-size workpieces, people and equipment are all in the environment chamber) which is filled with argon gas integrally in the welding process for integral protection. The overall protection mode usually needs a complex exhaust and inflation system in order to keep the argon gas with higher concentration in the whole environment chamber, and the argon gas needs to be continuously introduced to keep the argon gas concentration in the environment, so that the gas consumption is high, and the cost is higher. In addition, welding operators need to enter a fully-closed inert gas environment chamber, so that once a safety accident occurs, the welding operators can be rescued only by the step of opening the cabin door, the consumed time is long, and the life of the welding operators is greatly threatened.

The local protection mode is a mode of introducing inert protective gas into the traditional welding tail cover, so that the high-temperature welding line and the base metal nearby the high-temperature welding line are continuously in the inert gas atmosphere to be protected. The tail cover only has good protection effect on a plurality of regular welding seams such as long straight welding seams, annular welding seams and the like; the tail cover is designed and manufactured according to the welding seams of different structural forms and size components. And the protection effect of the tail cover is also influenced by the fitting effect and the operation skill of the assembly, and the quality stability of the welding seam is difficult to ensure. More importantly, for the spatial welding seams which are greatly existed on the complex all-titanium alloy structural part, the protection mode of the tail cover is not applicable any more.

Disclosure of Invention

The invention aims to solve the technical problem that in the titanium alloy welding process, because the welding seam metal is slow in cooling speed and long in high-temperature retention time, the welding seam metal can be seriously oxidized by oxygen in the air to further influence the welding seam quality, and provides a method for preparing a titanium alloy welding material by using CO₂Titanium alloy welding system and welding method as environment atmosphere, fully utilizing CO₂The gas has the characteristics of high density, high specific heat capacity, weak oxidizing property compared with air and the like, and is filled with CO₂Performing efficient consumable electrode arc welding of the titanium alloy in a semi-open environment of gas; compared with an integral protection mode, the device can be simplified, the protection cost can be reduced, and the safety of the welding process can be improved; compared with a local protection mode, the space flexibility of the protection mode can be improved, and the space weld joint protection of a complex structural member is realized.

In order to solve the technical problems, the invention is realized by the following technical scheme:

according to one aspect of the present invention, there is provided a method of treating a subject with CO₂A titanium alloy welding system as an ambient atmosphere comprising:

an environmental chamber having a top opening;

the anti-convection cover plate shields the top opening part of the environment chamber in a closed state, and the unshielded part forms a top window of the environment chamber;

CO₂inlet line of said CO₂The air inlet pipeline is hermetically connected with the environmental chamber and is communicated with the interior of the environmental chamber and used for introducing CO into the interior of the environmental chamber₂A gas;

the environment chamber comprises a perforated partition plate, a plurality of baffle plates and a plurality of baffle plates, wherein through holes are uniformly distributed on the perforated partition plate, the perforated partition plate is arranged at the bottom of the environment chamber and divides the internal space of the environment chamber into an upper half part and a lower half part, and the upper half part and the lower half part of the environment chamber are communicated through the through holes;

a dry ice layer spread on the lower half part of the environmental chamber for continuously sublimating to provide CO₂To the upper half of the environmental chamber;

a welding bench disposed at an upper half of the environmental chamber.

Further, the environmental chamber is provided with CO₂A concentration detector.

Further, the CO is₂The outlet end of the air inlet pipeline is opened downwards and is positioned 0.5m above the perforated partition plate.

Furthermore, a plurality of supporting steel bars are arranged between the clapboard with holes and the bottom plate of the environment chamber.

Further, a positioner is arranged on the welding workbench.

Further, a carrying crane is arranged outside the environmental chamber.

According to another aspect of the invention, a titanium alloy welding method based on the titanium alloy welding system is provided, and the method is carried out according to the following steps:

(1) opening the anti-convection cover plate, and hoisting a welding workpiece and welding equipment into the environmental chamber;

(2) closing the convection prevention cover plate, utilizing the CO₂Introducing CO into the gas inlet pipeline₂Displacing air inside the environmental chamber until the environmental chamber interior CO₂The volume concentration of the gas is more than 90%;

(3) a welding operator enters the environmental chamber from a top window of the environmental chamber to perform welding operation; the dry ice layer continuously provides CO to the interior of the environmental chamber during welding₂(ii) a If the CO inside the environmental chamber is monitored₂The CO is increased when the gas concentration is lower than the set value₂Flow of inlet line up to the ambient room CO₂The volume concentration of the gas is greater than 90%.

Further, the inside C of the environmental chamber in the step (1) and the step (2)O₂After the volume concentration of the gas is more than 90%, adding the CO₂The flow rate of the air inlet pipeline is adjusted to 10-15L/min.

Further, displacing the CO from the atmosphere inside the environmental chamber₂The flow rate of the air inlet pipeline is 50-80L/min.

Further, if CO is monitored inside the environmental chamber₂The CO is increased when the gas concentration is lower than the set value₂The flow rate of the air inlet pipeline is 30-40L/min.

The invention has the beneficial effects that:

the invention uses CO₂Titanium alloy welding system and welding method as an ambient atmosphere, using CO₂The gas is used as protective gas of the titanium alloy high-temperature welding line and is compared with inert gases Ar and CO₂The gas has the characteristics of high density, high specific heat capacity and low cost; the method specifically comprises the following advantages:

first, simplify the welding protection equipment: by introducing multiple CO channels into the bottom of the environmental chamber₂The characteristic of gas with high density can make CO₂Slowly sinks and exhausts the air in the environmental chamber, and the whole environmental chamber is gradually filled under the semi-open condition of the top anti-convection cover plate without a complex closed pressure system required by the traditional vacuum argon filling integral protection mode.

Secondly, accelerating the cooling process of the high-temperature welding seam: CO 2₂The high specific heat capacity of the alloy can accelerate the cooling of high-temperature welding lines, and compared with the traditional inert gases Ar and CO₂The gas can play a better cooling effect on the high-temperature welding seam.

Thirdly, the cost of the protective gas is reduced: welding seams with the same length are welded, and the gas cost of the invention is lower than that of the traditional integral argon filling protection mode.

Fourthly, improving the safety factor of the welding process: when a safety accident happens, welding personnel can be quickly transferred to a safe area, and the safety of the welding personnel is guaranteed.

Drawings

FIG. 1 shows a CO-based catalyst provided by the present invention₂A schematic structural diagram of a titanium alloy welding system as an ambient atmosphere;

FIG. 2 shows CO₂And the surface SEM appearance of the titanium alloy oxidation sample under different temperature nodes in the air atmosphere; wherein (a)900 ℃ to CO₂(b)900 deg.C-air, (c)1100 deg.C-CO₂(d)1100 ℃ -air;

FIG. 3 is the CO at 900 deg.C₂Surface XRD patterns of the titanium alloy oxidation sample in two atmospheres of air;

FIG. 4 shows the maximum temperature of each pass after the high temperature weld is removed from the argon protection range of the welding gun.

In the above figures: 1-an environmental chamber; 2-CO₂An air intake duct; 3-a welding workbench; 4-a clapboard with holes; 5-supporting the steel bars; 6-dry ice layer; 7-protective clothing with respiratory system; 8, carrying the crane; 9-convection prevention cover plate; 10-CO₂A concentration detector.

Detailed Description

The welding gun protective gas still adopts argon as the molten pool protective gas, and the high-temperature welding line after the molten pool is solidified adopts CO₂To protect. The density of air in the gas possibly contacted in the welding process is 1.30g/L, and CO₂Has a density of 1.97g/L, O₂The density of (A) is 1.46g/L, and the density of Ar is 1.78 g/L; it can be seen that CO₂Is about 1.52 times the density of air. According to the invention, the CO₂The semi-open structure environmental chamber 1 with an open top is designed, and then CO is continuously introduced into the bottom of the environmental chamber 1₂By means of CO₂The density relation with air can realize CO₂Filling the entire environmental chamber 1, thereby maintaining CO inside the environmental chamber 1₂And a complex inflation and exhaust system is omitted while the concentration is increased, so that the welding of large-size parts is facilitated. In addition, under the semi-open structure of the environment chamber 1, operators can avoid the complicated processes of air supply, air exhaust, wearing protective facilities and the like when entering and leaving the working environment; once an accident happens, the welding device can be quickly separated from the environment, and the safety factor of the welding process is greatly improved.

As shown in FIG. 1, the present embodiment provides a method of using CO₂The titanium alloy welding system as an ambient atmosphere comprises an open-top ambient chamber 1, the overall dimensions of the ambient chamber 1 being designed to be 4m 3m (height 3 m). The top of the environmental chamber 1 passes throughThe hinge is connected with an anti-convection cover plate 9, and the anti-convection cover plate 9 can be opened and closed through the hinge. The open part at the top of the environment chamber 1 is shielded under the closing state of the anti-convection cover plate 9, and the unshielded part forms a top window of the environment chamber 1, so that the environment chamber 1 becomes a semi-open structure. The overall structure of the environmental chamber 1 and the anti-convection cover plate 9 should be airtight except for the top window.

The environmental chamber 1 is hermetically connected with CO₂Inlet 2, CO₂The inlet end of the gas inlet pipe 2 is connected with CO outside the environmental chamber 1₂Gas work station, CO₂The outlet end of the air inlet pipe 2 is communicated with the interior of the environmental chamber 1, and the outlet end is positioned at a height of about 0.5m above the perforated partition plate 4, and the opening direction is preferably downward. CO 2₂The inlet line 2 is used to continuously feed a relatively large flow of CO into the environment chamber 1 during the initial charging phase₂Gas to meet the larger capacity requirements of the environmental chamber 1.

The inside foraminiferous baffle 4 that is close to the bottom plate and is provided with steel of environment room 1, foraminiferous baffle 4 promptly with prevent convection current apron 9 distance and be greater than foraminiferous baffle 4 and environment room 1 bottom plate distance, foraminiferous baffle 4 evenly distributed has the through-hole. Be provided with a plurality of support reinforcement 5 between foraminiferous baffle 4 and the 1 bottom plate of environment room, support reinforcement 5 can provide certain rigidity for foraminiferous baffle 4, improves the security of structure.

The internal space of the environment chamber 1 is divided into an upper part and a lower part by the perforated partition plate 4, and the lower half part and the upper half part of the environment chamber 1 can be respectively connected with the through holes uniformly distributed on the perforated partition plate 4.

The smaller space of the lower half is used for spreading the dry ice layer 6, and the dry ice layer 6 is continuously sublimated to provide CO₂Can maintain high CO in the environmental chamber 1₂And (4) concentration. On the one hand, the CO produced by the sublimation process of the dry ice layer 6₂The uniformity is high, and the environment atmosphere cannot be greatly disturbed; on the other hand, the sublimation process of the dry ice layer 6 can absorb the environmental heat and increase the cooling speed of the welding seam.

The great space of first half is the welding operation space, mainly holds weldment work platform 3 and welding operation personnel, and weldment work platform 3 can be placed on taking hole baffle 4, and welding operation personnel wear protective clothing 7 of taking respiratory usually, and protective clothing 7 of taking respiratory provides life support for welding operation personnel.

A transfer crane 8 is disposed outside the environmental chamber 1, and the transfer crane 8 is used for transferring welding operators and equipment to assist welding operation.

CO in welding₂The concentration of the protective environment directly affects the protective effect. If during welding, CO in the environmental chamber 1₂The environment is destroyed, and welding operators continue welding under the unknowing condition, which means failure of protection and directly results in scrapping of welding products. Thus CO at any moment during the welding₂The maintenance of the concentration is a key factor of welding protection, and the CO in a welding chamber must be ensured under the disturbance of different use environments and various operations in the whole welding process₂Is not polluted by air. Therefore, CO is established in the protective tank₂The concentration detection system is an important measure for ensuring the welding protection effect, and the design of the environmental chamber 1 in the indoor windless environment and the anti-convection cover plate 9 is to maintain CO₂The gas purity is economical and efficient and CO should be used₂The concentration detector 10 monitors the concentration thereof in real time. CO 2₂The concentration detector 10 uses industrial grade split CO₂The concentration real-time detector, wherein the host installation is located environment room 1 outside for real-time observation, and the probe is installed in the height department about 0.5m apart from the top at environment room 1 inner wall. Due to CO₂Density relation with air, so that CO₂The lower space of the environmental chamber 1 can be filled preferentially, so that the environmental chamber CO can be filled only by installing a probe at the height₂And monitoring the whole concentration in real time. CO should be allowed to flow throughout the welding process₂The volume concentration is maintained above 90%, and a good protection effect on the high-temperature welding line can be realized.

Compared with the traditional integral protection mode, the titanium alloy welding system is greatly simplified, and the consumed gas CO is greatly reduced₂The cost is low, and the safety coefficient of the welding process can be improved; compared with the traditional local protection mode of the dragging cover, the welding protection problem of the welding seam of the titanium alloy complex space structure is solved.

Based on the aboveThe invention also provides a titanium alloy welding system based on the CO₂The titanium alloy welding method of the titanium alloy welding system as the environment atmosphere comprises the following steps:

(1) preparation before welding

When titanium alloy welding is carried out, a proper positioner is arranged on the welding workbench 3 according to the size and the form of a welding workpiece. The convection preventing cover plate 9 is opened by a hinge, and a material such as a welding workpiece and welding equipment is hung into the environmental chamber 1 by a carrying crane 8.

(2) Charging CO₂

Closing the convection-proof cover plate 9 and using CO₂The gas inlet pipe 2 is filled with CO at a large flow rate₂To quickly replace the air in the environmental chamber 1 with a flow rate ranging from 50L/min to 80L/min for the CO in the environmental chamber 1₂After the volume concentration of the gas is more than 90 percent, the CO can be reduced₂The air inlet flow is 10-15L/min.

(3)CO₂Maintenance of the Environment

The dry ice layer 6 continuously supplies CO to the inside of the environmental chamber 1 during the welding process₂. Sublimation of the dry ice layer 6 ensures a higher CO level in the environmental chamber 1₂Concentration, technician monitoring CO outside environmental chamber 1₂The concentration detector 10 counts when the CO is₂When the volume concentration value is 90% or less, it means that the sublimation of the dry ice layer 6 is insufficient and the CO should be increased appropriately₂The flow rate of the gas inlet pipeline 2 is up to 30-40L/min until CO₂The volume concentration value is more than 90%, and the CO can be reduced₂The flow rate of the air inlet pipeline 2 is 10-15L/min.

(4) Welding operation

After the welding operator wears the protective suit 7 with the breathing system, the welding operator enters the environmental chamber 1 through the top window to perform normal welding operation.

During the welding process, laminar argon is continuously sprayed out of the nozzle of the welding gun, so that the welding pool is directly protected by argon atmosphere. The surrounding atmosphere is high concentration CO except for the local argon shield atmosphere formed by the welding gun shield gas₂The high temperature weld solidified after welding is in CO₂Under the protection of atmosphere, the titanium alloy welding process is effectively protectedAnd (4) protecting. If safety accidents such as the life support system is damaged occur in the welding process, welding operators can timely escape from dangers through the top window.

In order to adjust the space position of a workpiece at any time in welding operation, reduce the labor intensity of welding personnel and facilitate the welding operation, the positioner is arranged, and a workbench of the positioner can rotate, tip over and lift.

Therefore, the CO is provided by the invention₂Titanium alloy welding system and welding method as an ambient atmosphere, using CO₂Replacing Ar with gas as protective gas during natural cooling of high-temperature weld metal, and utilizing CO₂The characteristic that density is big, the design has the semi-open environment room 1 of top window, has simplified whole protection equipment and has reduced the cost, and has guaranteed the convenience of personnel and work piece business turn over.

The theoretical basis of the invention is as follows: after experimental research on the titanium alloy oxidation problem through a welding oxidation test platform designed by the applicant, the titanium alloy is found to be in CO along with the temperature rise₂And the degree of oxidation is increased after cooling in an air atmosphere. However, compared with the air atmosphere, the titanium alloy is in CO₂Titanium alloy and CO having less tendency to oxidize in gas atmosphere₂The critical reaction temperature of (a) is approximately 900 ℃. Thus using CO₂The method has certain feasibility as the protective gas of the titanium alloy high-temperature welding seam. The result of the welding thermal cycle measurement of each pass of the multilayer and multi-pass welding joint of the titanium alloy pulse melting electrode shows that the highest temperature of the high-temperature welding line which is separated from the argon protection of the welding gun is lower than 900 ℃.

(1) Non-isothermal oxidation test for simulated welding

To explore CO₂As feasibility of titanium alloy high-temperature welding line protective gas, the applicant designs the titanium alloy in CO by self₂Non-isothermal oxidation in an atmosphere was tested and compared to an air atmosphere. The test achieves the following conditions: the titanium alloy sample undergoes welding thermal cycle similar to that in the actual welding process, namely, the instantaneity of the welding thermal process, and has the characteristics of high heating speed, short high-temperature retention time and high cooling speed: ② solidification stage of molten pool andthe initial cooling stage is under the protection of inert atmosphere argon, and can be rapidly transferred to CO when cooled to a certain temperature₂In the atmosphere.

Therefore, a non-isothermal oxidation test platform of the titanium alloy is built, and the non-isothermal oxidation test platform mainly comprises a non-melting Inert Gas (TIG) welding gun, an atmosphere box body and an infrared pyrometer. The size of the sample is 20 × 9mm, the surface is ground to be bright by 400-mesh abrasive paper, the TIG electric arc with the current of 120A is adopted to carry out fixed-point self-melting welding for 10s at the central position of the sample, meanwhile, an infrared pyrometer is adopted to observe the central temperature of the sample in real time, after a molten pool is solidified and cooled to a certain temperature node, a steel plate for supporting the sample is drawn out, so that the sample is rapidly transferred to an atmosphere box and is naturally cooled to the room temperature in the atmosphere box. Research on titanium alloy and CO₂Non-isothermal oxidation behavior of (2), external CO₂The gas cylinder continuously introduces CO into the atmosphere box through the bottom interface of the box body₂Gas and passing CO₂The concentration detector monitors the concentration of the carbon dioxide in real time to ensure that CO is absorbed₂The concentration is higher than 90%; when carrying out a comparative test in an air atmosphere, no gas is required to be introduced into the atmosphere box.

FIG. 2 shows CO₂SEM appearance pictures of surface oxides of titanium alloy oxidation samples with different temperature nodes in two atmospheres with air can show that the temperature nodes are increased from 900 ℃ to 1100 ℃, and the titanium alloy samples are in CO₂The surface oxide particle size of the oxidized sample in both the air atmosphere and the air atmosphere increased, i.e., the degree of oxidation increased. However, the titanium alloy oxidized sample in the air atmosphere is more obvious no matter the whole oxidation degree or the remarkable degree of the oxidation degree increasing along with the temperature rise. Note that the temperature node is 900 deg.C, CO₂The oxide particles on the surface of the titanium alloy oxidation sample under the atmosphere are extremely small in size, and the obvious oxidation condition is almost avoided; on the other hand, the surface of the oxidized sample in the space-time atmosphere at 900 ℃ showed crossed rod-like oxides having an average size of 0.12 μm, and the degree of oxidation was significant. It can be considered that 900 ℃ is titanium alloy and CO₂The critical reaction temperature node, and the titanium alloy has undergone a severe oxidation reaction with air at the critical reaction temperature node. Thus titanium alloys compare air with CO₂With less tendency to oxidiseTo, CO₂Can be used as protective gas for high-temperature welding seams with the temperature of less than 900 ℃.

To CO₂The results of the X-Ray Diffraction (XRD) analysis of the surfaces of the oxidized samples at different temperature nodes in two atmospheres and air are shown in fig. 3. Can find TiO in XRD diffraction pattern of titanium alloy oxidation sample under air atmosphere at 900 DEG C₂The diffraction peak intensity is higher than that of Ti, so that more serious surface oxidation occurs at the temperature node, and TiO is used as a main oxidation product₂(ii) a And at 900 ℃ in CO₂The XRD diffraction pattern of the titanium alloy oxidation sample in the atmosphere mainly shows the diffraction peak position of Ti simple substance, and the titanium alloy is considered not to be subjected to surface oxidation, namely the titanium alloy is not mixed with CO at 900 DEG C₂An oxidation reaction occurs.

(2) Multi-layer multi-pass weld joint weld thermal cycle curve determination

In order to determine the highest temperature of the high-temperature welding seam which is not protected by welding gun protective gas, the welding heat cycle measurement is carried out on each pass of the titanium alloy pulse melting multi-layer multi-pass welding joint. The determination process comprises the following steps: the titanium alloy thick plate with the thickness of 15mm is subjected to multilayer and multi-pass welding by adopting a pulse consumable electrode welding method, the actual welding current of each pass is about 120A, and the welding thermal cycle curve of a certain point on a welding pass is measured by adopting an infrared pyrometer. The time required for leaving the argon protection range of the welding gun after the molten pool is solidified is 2s, so that the temperature value after 2s delay of the peak temperature of each welding thermal cycle temperature curve is read and taken as the highest temperature of the high-temperature welding line under the protection of the welding gun protection gas, as shown in fig. 4. The temperature values are all less than 900 ℃, namely the highest temperature is less than 900 ℃ when the high-temperature welding line is separated from the argon protection range of the welding gun, and the temperature can be measured by CO₂The gas is effectively protected.

The comprehensive test results show that compared with the air atmosphere, the titanium alloy is in CO₂The oxidation tendency in the atmosphere is obviously reduced, and the SEM appearance analysis and surface XRD analysis results of the oxide on the surface of the sample show that the titanium alloy and CO₂The critical reaction temperature of (a) is approximately 900 ℃. And the titanium alloy pulse melting electrode multilayer multi-pass welding joint is carried out in each passThe result of the welding thermal cycle measurement shows that the highest temperature of the high-temperature welding line without the argon protection of the welding gun is lower than 900 ℃. Thus, it is considered that CO is₂Can be used as the protective gas of the titanium alloy high-temperature welding line under the atmosphere condition of the environmental chamber 1.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make various changes and modifications within the spirit and scope of the present invention without departing from the spirit and scope of the appended claims.