Preparation method of titanium steel transition pipe joint

Abstract

The invention relates to the technical field of dissimilar metal connection, and particularly provides a titanium steel transition pipe joint preparation method which comprises the steps of material preparation, external thread forming, stepped hole forming, internal thread forming, heating treatment, cleaning and connecting, vacuum furnace heating diffusion and natural cooling. In the diffusion welding process, the titanium-steel transition section generates enough pressure stress at the diffusion temperature through threaded connection and interference fit by utilizing the thermal expansion coefficient difference of titanium and steel, external pressure is not needed, diffusion welding can be carried out by using a relatively cheap argon atmosphere furnace or vacuum furnace, and batch production can be realized. The production efficiency is high and the cost is low. The problems that in the prior art, titanium steel transition pipe joints are low in preparation strength, high in cost and complex in process are effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of dissimilar metal connection, and specifically provides a method for preparing a titanium steel transition pipe joint. Background Art

[0002] Titanium and titanium alloys are widely used in aerospace, nuclear industry, chemical industry, food, medicine and other fields because of their high specific strength, strong corrosion resistance, good strength at high and low temperatures and non-toxicity.

[0003] Because titanium and common metals easily form brittle metal compounds, direct welding cannot be used. As a result, indirect welding is often used to connect titanium pipes and dissimilar metal pipes. However, indirect welding requires a transition layer, which is costly and complex, and it is difficult to ensure welding quality during on-site construction.

[0004] Therefore, transition pipe joints between titanium and dissimilar metals are further used to achieve metal welding between titanium and titanium, and dissimilar metals and dissimilar metals, greatly reducing the difficulty of welding.

[0005] There are many scenarios for connecting titanium with dissimilar metals such as carbon steel or stainless steel. There are currently two main methods for preparing titanium and steel transition pipe joints:

[0006] One method is to use titanium steel composite plates to obtain titanium steel transition pipe joints through mechanical processing (cutting); however, the length of the joint obtained in this way is limited by the thickness of the composite plate, and the strength and sealing of the joint depend on the quality of the titanium steel composite plate used;

[0007] Another method is to use titanium tubes and steel tubes, and prepare them by friction welding, diffusion welding or brazing. However, friction welding is difficult to control the weld thickness, and brittle TiFe or TiFe 2 The production of intermetallic compounds such as titanium and steel is large, and the quality of the weld is difficult to guarantee; diffusion welding can better control the weld thickness, but the weld strength is low; brazing can avoid the production of brittle intermetallic compounds between titanium and steel, and the weld can have good sealing properties, but the weld strength is also low.

[0008] Therefore, it is of great significance to design a method for preparing titanium steel transition pipe joints with high strength, low cost and simple process. Summary of the invention

[0009] The invention provides a method for preparing a titanium steel transition pipe joint, which solves the problems of low strength, high cost and complex process in the preparation of the titanium steel transition pipe joint in the prior art.

[0010] The present invention provides a method for preparing a titanium steel transition pipe joint, comprising:

[0011] S1. Prepare a titanium tube section and a steel tube section with the same inner diameter, and the wall thickness of the steel tube section is greater than the wall thickness of the titanium tube section;

[0012] S2, opening an external thread on one end of the titanium tube segment, and along the axial direction of the titanium tube segment, both ends of the external thread have a first non-opened section;

[0013] S3, turning one end of the steel pipe section and enlarging the inner diameter to form a step hole, wherein the inner diameter of the step hole is 0.2 mm-2 mm smaller than the outer diameter of the titanium pipe section;

[0014] S4, the stepped hole is provided with an internal thread, and along the axial direction of the steel pipe section, both ends of the internal thread have a second non-opening section, and the opening length of the internal thread is equal to the opening length of the external thread;

[0015] S5, heating the steel pipe section with the internal thread to 400°C-600°C;

[0016] S6, cleaning the titanium tube section with the external thread, and screwing it into the heated steel tube section, so that the external thread and the internal thread match each other, and the first non-opening section and the second non-opening section match each other; at the same time, the end face of the titanium tube section and the step surface of the step hole abut against each other;

[0017] S7. Place the installed titanium pipe section and steel pipe section into a vacuum furnace or an inert gas atmosphere furnace, heat to 800°C-900°C and maintain for 10min-30min, with a heating rate of 5°C / min-10°C / min;

[0018] S8. After diffusion is completed, the furnace is cooled to room temperature.

[0019] According to the method for preparing a titanium-steel transition pipe joint provided by the present invention, the helix angles of the external thread and the internal thread are both 55°.

[0020] According to the method for preparing a titanium-steel transition pipe joint provided by the present invention, in S6, the titanium pipe section with external threads is cleaned, comprising:

[0021] S601. Grind the outer surface of the titanium pipe section with 1000 grit sandpaper;

[0022] S602, cleaning the titanium tube section with acetone;

[0023] S603. Dry the titanium tube section with cold air.

[0024] According to the method for preparing the titanium steel transition pipe joint provided by the present invention, in S7, the heating temperature is 850° C. and the holding time is 15 min.

[0025] The method for preparing the titanium-steel transition pipe joint provided by the present invention utilizes the difference in thermal expansion coefficients between titanium and steel during diffusion welding, and through threaded connection and interference fit, so that the titanium-steel transition section generates sufficient compressive stress at the diffusion temperature, does not require external pressure, can use a relatively cheap argon atmosphere furnace or vacuum furnace for diffusion welding, and can be mass-produced. The production efficiency is high and the cost is low. The problem of low strength, high cost and complex process of preparing the titanium-steel transition pipe joint in the prior art is effectively solved.

[0026] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the cross-sectional structure of the titanium steel transition pipe joint provided by the present invention;

[0029] Figure 2 yes Figure 1 A magnified image of point A;

[0030] Figure 3 The present invention is a flow chart of a method for preparing a titanium steel transition pipe joint.

[0031] Reference numerals:

[0032] 1. Titanium tube section; 101. External thread; 102. First non-opening section; 103. Titanium tube end face; 2. Steel tube section; 201. Internal thread; 202. Second non-opening section; 203. Step surface. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Combine the following Figures 1 to 3 The embodiments shown describe the technical solution of the present invention:

[0035] The embodiment of the present invention provides a method for preparing a titanium steel transition pipe joint, such as Figures 1 to 3 As shown, including:

[0036] S1, prepare a titanium tube section 1 and a steel tube section 2 with the same inner diameter, and the wall thickness of the steel tube section 2 is greater than the wall thickness of the titanium tube section 1;

[0037] In this step, a TC4 titanium alloy pipe section with an outer diameter of 90 mm, a wall thickness of 8 mm, and a length of 100 mm is prepared; a No. 40 steel pipe section 2 with an outer diameter of 105 mm, a wall thickness of 18 mm, and a length of 150 mm is prepared;

[0038] The titanium tube section 1 is machined with a lathe to have an inner diameter of 75 mm and an outer diameter of 89 mm, and the No. 40 steel tube section 2 is machined with an inner diameter of 75 mm and an outer diameter of 104 mm, and the end faces of the titanium tube section 1 and the steel tube section 2 are machined flat;

[0039] When the interference of the overlapped part of the titanium tube section 1 is 0.55 mm at room temperature and the diffusion temperature is 850°C, the diffusion pressure is 5Mpa-10MPa.

[0040] Ensuring that the inner diameters of the two materials are consistent helps achieve a good fit and seal. The wall thickness of the steel pipe section 2 is greater than that of the titanium pipe section 1, which can provide better mechanical strength and pressure resistance, thereby enhancing the overall stability and durability of the joint.

[0041] S2, an external thread 101 is opened at one end of the titanium tube segment 1, and along the axial direction of the titanium tube segment 1, both ends of the external thread 101 have a first non-opened section 102;

[0042] In this step, the opening length of the external thread 101 is 10mm-30mm, and the helix angle is 55°. The opening of the external thread 101 can ensure that the titanium pipe section 1 can be closely matched with the internal thread 201 of the steel pipe section 2, thereby improving the reliability of the connection. At the same time, the design of the non-opening section helps to avoid stress concentration in the threaded part and enhance the strength of the connection.

[0043] S3, turning one end of the steel pipe section 2 and enlarging the inner diameter to form a step hole, wherein the inner diameter of the step hole is 0.2 mm-2 mm smaller than the outer diameter of the titanium pipe section 1;

[0044] In this step, the diameter expansion width is 20mm-50mm, that is, the diameter of the step hole is 20mm-50mm; the design of the step hole can provide better positioning accuracy and ensure the effective connection between the titanium pipe section 1 and the steel pipe section 2. In addition, the slight difference in the inner diameter helps to form a certain compression effect during the connection, thereby improving the sealing of the joint.

[0045] S4, an internal thread 201 is opened on the stepped hole, and along the axial direction of the steel pipe section 2, both ends of the internal thread 201 have a second non-opening section 202, and the opening length of the internal thread 201 is equal to the opening length of the external thread 101;

[0046] In this step, an internal thread 201 is opened in the middle section of the inner wall of the above-mentioned step hole. The parameters of the internal thread 201 are consistent with the above-mentioned external thread 101, that is, the opening length is 10mm-30mm, and the helix angle is 55°; the length of the second non-opening section 202 is also roughly equal to the length of the above-mentioned first non-opening section 102, so as to facilitate mutual cooperation.

[0047] After cooling, the first non-opening section 102 and the second non-opening section 202 are in an interference fit state.

[0048] The opening of the internal thread 201 allows the titanium pipe section 1 to be firmly screwed into the steel pipe section 2, ensuring the stability and safety of the connection. The equal opening length helps to ensure the accuracy of the fit and avoid loose connections caused by length mismatch.

[0049] S5, heating the steel pipe section 2 with the internal thread 201 to 400° C.-600° C.;

[0050] In this step, the steel pipe section 2 is heated to 400°C-600°C using a medium frequency induction heater or a resistance furnace heater;

[0051] In this step, heating is performed to cause the steel pipe section 2 to expand in diameter and to cooperate with the titanium pipe section 1 in the subsequent connection process.

[0052] S6, clean the titanium tube section 1 with the external thread 101, and screw it into the heated steel tube section 2, so that the external thread 101 and the internal thread 201 match each other, and the first non-opening section 102 and the second non-opening section 202 match each other; at the same time, the end face 103 of the titanium tube section and the step surface 203 of the step hole abut against each other;

[0053] In this step, cleaning removes surface dirt and oxides, ensuring smooth contact surfaces and improving connection reliability. The tightening process ensures effective bonding of the two materials, improving the mechanical properties and corrosion resistance of the joint.

[0054] S7, placing the installed titanium pipe section 1 and steel pipe section 2 into a vacuum furnace or an inert gas atmosphere furnace, heating to 800°C-900°C and maintaining for 10min-30min, with a heating rate of 5°C / min-10°C / min;

[0055] In this step, the installed titanium tube section 1 and steel tube section 2 are placed in a vacuum furnace or an argon gas atmosphere furnace for heating to 800°C-900°C and maintained for 10min-30min for thermal diffusion. At this time, the external thread and the internal thread, the first non-opening section 102 and the second non-opening section 202, and the titanium tube section end face 103 and the step surface 203 are all thermally diffused.

[0056] S8. After diffusion is completed, the furnace is cooled to room temperature.

[0057] The method for preparing the titanium-steel transition pipe joint provided in the embodiment of the present invention utilizes the difference in thermal expansion coefficients between titanium and steel during diffusion welding, and uses threaded connection and interference fit to generate sufficient compressive stress in the titanium-steel transition section at the diffusion temperature. No external pressure is required, and a relatively cheap argon atmosphere furnace or vacuum furnace can be used for diffusion welding, and batch production is possible. The production efficiency is high and the cost is low. The problem of low strength, high cost and complex process in the preparation of titanium-steel transition pipe joints in the prior art is effectively solved.

[0058] According to the method for preparing a titanium-steel transition pipe joint provided by the present invention, in the above S6, the titanium pipe section 1 with the external thread 101 is cleaned, comprising:

[0059] S601, grinding the outer surface of the titanium tube section 1 with 1000-grit sandpaper;

[0060] In this step, the following beneficial effects are achieved:

[0061] Remove the surface oxide layer: Titanium easily forms an oxide layer in the air. Grinding can effectively remove these oxides and improve the cleanliness of the metal surface.

[0062] Increase the smoothness of the contact surface: Grinding can reduce the surface roughness, which is more conducive to the close fit of the welding surface and improves the welding quality.

[0063] Improve the bonding quality: Through grinding, better mechanical bite can be formed, and the bonding effect of the titanium pipe section 1 and the steel pipe section 2 at high temperature can be improved.

[0064] S602, cleaning the titanium tube section 1 with acetone;

[0065] In this step, the following beneficial effects are achieved:

[0066] Removal of oil stains and impurities: Acetone is an effective organic solvent that can dissolve and remove oil stains, fingerprints, dust and other impurities on the surface of the titanium pipe section 1 to ensure a clean surface.

[0067] Improve chemical bonding: The cleaned surface can improve the chemical reactivity of subsequent welding or bonding and promote metal diffusion between titanium and steel.

[0068] S603, dry the titanium tube section 1 with cold air.

[0069] In this step, the following beneficial effects are achieved:

[0070] Removal of residual solvents: Cold air drying can effectively remove the residues of cleaning agents such as acetone to prevent them from having adverse effects on subsequent heating and bonding processes.

[0071] Avoid the influence of moisture: Ensure that the surface of the titanium pipe section 1 is dry to avoid the influence of moisture on the metal bonding, thereby improving the strength and stability of the final bonding.

[0072] In this embodiment, acetone cleaning can be used to remove oil stains, chips, oxides, etc. generated during the processing, improve the quality and gloss of the metal surface, and prepare for subsequent coating, welding, bonding and other processes.

[0073] According to the method for preparing a titanium steel transition pipe joint provided by the present invention, in the above S7, the heating temperature is preferably 850° C. and the holding time is 15 min.

[0074] In this step, the heating temperature is set to 850°C and maintained for 15 minutes, which can achieve the following beneficial effects:

[0075] Promoted diffusion welding: 850°C is one of the best temperature ranges for diffusion welding between titanium and steel. At this temperature, the atoms of titanium and steel can diffuse to each other's interface more effectively, thus forming a strong metal bond. This bond not only improves the strength of the joint, but also improves its corrosion resistance.

[0076] Controlled phase change: When titanium is heated to 850°C, it can remain in the α phase (hexagonal close-packed lattice), while steel is in the austenite state. This phase selection helps to form a good bonding interface between the two materials and avoid brittleness and cracking problems caused by phase change.

[0077] Reduce stress concentration: Through reasonable heating and holding time, the temperature of the joint area can be evenly distributed, thereby reducing the stress concentration that may occur during the cooling process. This helps to improve the fatigue resistance and service life of the joint.

[0078] Improve welding quality: Maintaining the welding time for 15 minutes can ensure sufficient diffusion and bonding between titanium and steel. Too short a time may lead to insufficient bonding, while too long a time may lead to excessive generation of brittle intermetallic compounds and reduced weld strength.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a titanium steel transition pipe joint, characterized in that: include: S1. Prepare a titanium tube section and a steel tube section with the same inner diameter, and the wall thickness of the steel tube section is greater than the wall thickness of the titanium tube section; S2, opening an external thread on one end of the titanium tube segment, and along the axial direction of the titanium tube segment, both ends of the external thread have a first non-opened section; S3, turning one end of the steel pipe section and enlarging the inner diameter to form a step hole, wherein the inner diameter of the step hole is 0.2 mm-2 mm smaller than the outer diameter of the titanium pipe section; S4, the stepped hole is provided with an internal thread, and along the axial direction of the steel pipe section, both ends of the internal thread have a second non-opening section, and the opening length of the internal thread is equal to the opening length of the external thread; S5, heating the steel pipe section with the internal thread to 400°C-600°C; S6, cleaning the titanium pipe section with the external thread, and screwing it into the heated steel pipe section, so that the external thread and the internal thread match each other, and the first non-opening section and the second non-opening section match each other, and the end face of the titanium pipe section and the step face of the step hole abut each other; S7. Place the installed titanium pipe section and steel pipe section into a vacuum furnace or an inert gas atmosphere furnace, heat to 800°C-900°C and maintain for 10min-30min, with a heating rate of 5°C / min-10°C / min; S8. After diffusion is completed, the furnace is cooled to room temperature.

2. The method for preparing a titanium steel transition pipe joint according to claim 1, characterized in that: The helix angles of the external thread and the internal thread are both 55°.

3. The method for preparing a titanium steel transition pipe joint according to claim 1, characterized in that: In S6, the titanium pipe section with the external threads is cleaned, including: S601. Grind the outer surface of the titanium pipe section with 1000 grit sandpaper; S602, cleaning the titanium tube section with acetone; S603. Dry the titanium tube section with cold air.

4. The method for preparing a titanium steel transition pipe joint according to claim 1, characterized in that: In S7, the heating temperature is 850°C and the holding time is 15 minutes.

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