A method for welding titanium tubes

Abstract

A method for welding titanium tubes includes the following steps: 1) setting a bevel at the weld seam of the titanium tube to be welded; 2) cleaning and preparing titanium welding wire; 3) inserting first and second end caps into the two extended ends of the titanium tube to be welded, and supplementing shielding gas through a first air inlet pipe; 4) engaging the end caps with the arc-shaped notch at the open end of the air inlet hood onto the titanium tube to be welded, so that the first notch of the first end cap and the second notch of the second end cap correspond to the weld seam, and supplementing shielding gas through a second air inlet pipe; 5) using titanium welding wire to form a root pass at the weld seam of the titanium tube to be welded; 6) sequentially forming a first, second, and third capping layer in the annular space between the root pass and the bevel, wherein the first capping layer contacts both bevel surfaces, the bottom surface of the second capping layer contacts the first capping layer and one bevel surface, and the bottom surface of the third capping layer contacts the first capping layer and the other bevel surface. This invention can effectively ensure the welding quality of titanium tubes and guarantee the structural safety of equipment.

Description

Technical Field

[0001] This invention relates to the chemical industry, and in particular to a method for welding titanium tubes. Background Technology

[0002] Titanium is very stable at room temperature, but its ability to absorb hydrogen and oxygen increases with rising temperature. Experimental studies show that titanium generally begins to absorb hydrogen, oxygen, and nitrogen from 250℃. During welding, the higher the temperature and the longer the holding time, the worse the weld plasticity. Therefore, when welding titanium, if argon arc welding is used, ordinary welding torches are insufficient because they cannot effectively protect the weld, causing the high-temperature weld and heat-affected zone to absorb hydrogen, oxygen, and nitrogen gases. Nitrogen, oxygen, and hydrogen intrusion can all form interstitial solid solutions in the weld, reducing its plasticity and toughness. Hydrogen also significantly reduces the weld's impact toughness, causing the weld joint to become embrittled. Therefore, a large-nozzle welding torch must be used. Furthermore, adequate protection must be provided in high-temperature zones above 300℃, including the weld zone and the near-weld zone.

[0003] Good gas protection and thorough cleaning of the area to be welded can prevent cracks from forming. Currently, commonly used protective devices directly shield the weld seam with a cover, but the uneven distribution of the protective atmosphere entering the cover makes it difficult to guarantee the quality of titanium tube welding. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a titanium tube welding method that can effectively ensure the welding quality of titanium tubes and guarantee the structural safety of equipment.

[0005] The technical solution of the present invention is: a titanium tube welding method, which employs a titanium tube welding protection device and includes the following steps:

[0006] The titanium tube welding protection device includes an air inlet hood, a first end cap, and a second end cap. Both the first and second end caps are conical, and the second end cap is equipped with a first air inlet pipe. The air inlet hood is cylindrical, and its internal space is filled with a first copper wire mesh. One end of the cylindrical air inlet hood is sealed and connected to a second air inlet pipe, while the other end is open and has two arc-shaped notches. These two arc-shaped notches are evenly distributed circumferentially and are adapted to the diameter of the titanium tube being welded. The shell between the two arc-shaped notches at the open end of the cylindrical air inlet hood forms a first latch and a second latch, respectively. The first latch has a first notch, and the second latch has a second notch.

[0007] 1) Set a bevel at the weld seam of the titanium tube to be welded, and clean the 20-30mm circumferential sidewall area on both sides of the weld seam to expose the metallic luster before cleaning.

[0008] 2) Take titanium welding wire, remove the oxide layer, clean it thoroughly and set it aside for use;

[0009] 3) Insert the first end cap and the second end cap into the two extended ends of the titanium tube to be welded, respectively, and supplement the protective gas through the first air inlet pipe;

[0010] 4) The air intake hood is clamped onto the titanium tube to be welded through the arc-shaped notch at the open end, so that the first notch of the first latch and the second notch of the second latch correspond to the weld seam, and protective gas is replenished through the second air intake pipe.

[0011] 5) Take titanium welding wire and form a root pass at the weld seam of the titanium tube to be welded by self-fusion. At the same time, rotate the air intake hood around the circumference of the titanium tube to be welded.

[0012] 6) Using manual wire addition, a first cover layer, a second cover layer, and a third cover layer are sequentially formed in the annular space between the root pass and the bevel. The first cover layer is in contact with two bevel surfaces respectively. The bottom surface of the second cover layer is in contact with the first cover layer and also with one bevel surface. The bottom surface of the third cover layer is in contact with the first cover layer and also with the other bevel surface.

[0013] Furthermore, it also includes a second copper wire mesh, which is filled in the titanium tube and close to the second end cap.

[0014] Preferably, the air intake shroud is made of copper.

[0015] Furthermore, the first air intake pipe and the second air intake pipe are connected to different protective air sources.

[0016] Furthermore, in step 5), the root pass is evenly divided into five segments connected end to end along the circumference of the weld.

[0017] Preferably, the bevel angle in step 1) is 30°.

[0018] The above technical solution has the following beneficial effects:

[0019] 1. This invention designs a titanium tube welding protection device with a specific structure. By supplementing different protective gas sources, a protective atmosphere can be formed in the internal and external heat-affected zones of the titanium tube to be welded, ensuring the structural strength of the weld and improving its plasticity and toughness, thereby ensuring the welding quality.

[0020] 2. In this invention, a first cover layer, a second cover layer, and a third cover layer are sequentially welded in the weld seam of a titanium tube to be welded by manual wire addition. The first cover layer is in contact with two bevel surfaces, the bottom surface of the second cover layer is in contact with the first cover layer and with one bevel surface, and the bottom surface of the third cover layer is in contact with the first cover layer and with another bevel surface. This effectively refines the titanium grains at the weld seam, ensures a dense weld structure, improves the structural strength of the weld seam, and also effectively reduces the deformation of the weld seam, ensuring welding quality.

[0021] The applicant's tests have verified that the tensile strength of the welded material using the welding method of this invention is the same as that of the titanium tube to be welded. No cracks occurred in the weld after positive and negative bending within the specified bending angle, proving that the mechanical properties are qualified.

[0022] The following description, in conjunction with the accompanying drawings and specific embodiments, provides further details. Attached Figure Description

[0023] Figure 1 This is a welding state diagram of Example 1;

[0024] Figure 2 for Figure 1 AA section view;

[0025] Figure 3 for Figure 2 Enlarged view of point M in the middle.

[0026] In the attached diagram, 1 is the air intake hood, 2 is the first end cap, 3 is the second end cap, 4 is the first air intake pipe, 5 is the second air intake pipe, 6 is the arc-shaped notch, 7 is the first latch, 8 is the second latch, 9 is the first notch, 10 is the second notch, 11 is the first cover layer, 12 is the second cover layer, and 13 is the third cover layer. Detailed Implementation

[0027] Example 1

[0028] See Figures 1 to 3 The titanium tube welding method using a titanium tube welding protection device includes the following steps:

[0029] The titanium tube welding protection device includes an air inlet hood 1, a first end cap 2, and a second end cap 3. Both the first end cap 2 and the second end cap 3 are conical, and the second end cap 3 is provided with a first air inlet pipe 4. The air inlet hood 1 is cylindrical and specifically made of copper. The internal space of the air inlet hood 1 is filled with a first copper wire mesh. One end of the cylindrical air inlet hood is sealed and connected to a second air inlet pipe 5. Both the first and second air inlet pipes are used to connect to a protective gas source, such as an argon gas source with a purity >99.99%, and are connected to different protective gas sources, meaning the two protective gas sources are independent of each other. The other end of the cylindrical air inlet hood is open and has two arc-shaped notches 6. These two arc-shaped notches 6 are evenly distributed circumferentially and are adapted to the diameter of the docking titanium tube. The shell between the two arc-shaped notches 6 at the open end of the cylindrical air inlet hood forms a first latch 7 and a second latch 8, respectively. The first latch 7 has a first notch 9, and the second latch 8 has a second notch 10.

[0030] 1) Set a bevel at the weld joint of the titanium tube to be welded, with a bevel angle of 30°. Clean the 20-30mm circumferential sidewall area on both sides of the weld joint until the metal luster is exposed, then clean it. Specifically, first use a wire brush to clean the 20-30mm circumferential sidewall area on both sides of the weld joint until the silvery-white metallic luster is exposed, then use a white silk cloth to wipe the polished area, cleaning the oil and dust attached to the surface, ensuring that the welding and bevel areas are clean. The titanium tube has a diameter of 33mm and a wall thickness of 3mm. The chemical composition and mechanical properties of the material are shown in the table below:

[0031] margin 0.013 0.013 0.0095 0.0012 0.096 >440Mpa

[0032] 2) Take titanium welding wire, sand off the oxide layer on the surface of the titanium welding wire with sandpaper, clean it with acetone and set it aside for use. Specifically, the grade is HTA1 and the diameter is 2.4mm.

[0033] 3) Insert the first end cap and the second end cap into the two extended ends of the titanium tube to be welded, respectively, and supplement the protective gas through the first gas inlet pipe. Usually, in order to ensure that the protective gas is fully dispersed and improve the utilization efficiency of the protective gas, a second copper wire mesh is also included. The second copper wire mesh is filled in the titanium tube and close to the second end cap.

[0034] 4) The air intake hood is clamped onto the titanium tube to be welded through the arc-shaped notch at the open end, so that the first notch of the first latch and the second notch of the second latch correspond to the weld seam, and protective gas is replenished through the second air intake pipe.

[0035] 5) Take titanium welding wire and form a root pass at the weld seam of the titanium tube to be welded by self-fusion. At the same time, rotate the air intake hood around the circumference of the titanium tube to be welded to form a protective atmosphere for the high-temperature welding area. Specifically, the root pass is evenly divided into five segments connected end to end along the circumference of the weld seam.

[0036] 6) Using manual wire addition, a first cover layer 11, a second cover layer 12, and a third cover layer 13 are sequentially formed in the annular space between the root pass and the bevel. The first cover layer contacts two bevel surfaces respectively, the bottom surface of the second cover layer contacts the first cover layer and also contacts one bevel surface, and the bottom surface of the third cover layer contacts the first cover layer and also contacts the other bevel surface. The welding of the two titanium tubes is completed, the weld surface is silvery white, there is no oxide color, and the weld formation is good.

[0037] 100% non-destructive testing was performed according to standard NBT4701 <<Non-destructive Testing of Pressure Equipment>>, and the inspection result was Level II, meeting the usage requirements. Mechanical property testing showed that the tensile strength of the weld reached over 400 MPa.

Claims

1. A method for welding titanium tubes, characterized in that, The use of titanium tube welding protection device includes the following steps: The titanium tube welding protection device includes an air inlet hood (1), a first end cap (2), and a second end cap (3). Both the first end cap (2) and the second end cap (3) are conical, and the second end cap (3) is provided with a first air inlet pipe (4). The air intake hood (1) is cylindrical, and the internal space of the air intake hood (1) is filled with a first copper wire mesh. One end of the cylindrical air intake hood is sealed and connected to a second air intake pipe (5). The first air intake pipe (4) and the second air intake pipe (5) are connected to different protective air sources. The other end of the cylindrical air intake hood is open and has two arc-shaped notches (6). These two arc-shaped notches (6) are evenly distributed along the circumference and are adapted to the diameter of the docking titanium pipe. The shell between the two arc-shaped notches (6) at the open end of the cylindrical air intake hood forms a first latch (7) and a second latch (8). The first latch (7) has a first notch (9), and the second latch (8) has a second notch (10). 1) Set a bevel at the weld seam of the titanium tube to be welded, and clean the 20-30mm circumferential sidewall area on both sides of the weld seam to expose the metallic luster before cleaning. 2) Take titanium welding wire, remove the oxide layer, clean it thoroughly and set it aside for use; 3) Insert the first end cap and the second end cap into the two extended ends of the titanium tube to be welded, respectively, and supplement the protective gas through the first air inlet pipe. The tube also includes a second copper wire mesh, which is filled in the titanium tube and close to the second end cap. 4) The air intake hood is clamped onto the titanium tube to be welded through the arc-shaped notch at the open end, so that the first notch of the first latch and the second notch of the second latch correspond to the weld seam, and protective gas is replenished through the second air intake pipe. 5) Take titanium welding wire and form a root pass at the weld seam of the titanium tube to be welded by self-fusion. At the same time, rotate the air intake hood around the circumference of the titanium tube to be welded. 6) A first cover layer (11), a second cover layer (12), and a third cover layer (13) are formed sequentially in the annular space between the root pass and the bevel by manual wire addition. The first cover layer is in contact with two bevel surfaces respectively. The bottom surface of the second cover layer is in contact with the first cover layer and also with one bevel surface. The bottom surface of the third cover layer is in contact with the first cover layer and also with the other bevel surface.

2. The titanium tube welding method according to claim 1, characterized in that: The air intake shroud (1) is made of copper.

3. The titanium tube welding method according to claim 1, characterized in that: Step 5) The root pass is evenly divided into five segments along the circumference of the weld, connected end to end.

4. The titanium tube welding method according to claim 1, characterized in that: Step 1) The bevel angle is 30°.

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