Method for preparing titanium alloy seamless pipe through thermal deformation after introduction of intermediate

Abstract

The invention discloses a method for preparing a titanium alloy seamless pipe through thermal deformation after introduction of an intermediate, and belongs to the technical field of advanced machining of titanium alloy materials. The method comprises the following steps: firstly, smelting to obtain a titanium alloy cast ingot, cogging and forging the cast ingot to obtain a titanium alloy forged rod, machining to obtain a titanium alloy pipe blank, then carrying out heat treatment on the titanium alloy pipe blank, carrying out heat deformation to obtain a titanium alloy pipe, and then sequentially carrying out annealing and surface treatment on the pipe. And the titanium alloy seamless pipe is obtained. The method provided by the invention is short in production period, is not limited by the mark, the structure type and the size of the titanium alloy, can be used for preparing titanium alloy seamless pipes with different inner hole shapes and sizes, different wall thicknesses and different lengths as required, and improves the mechanical properties of the titanium alloy seamless pipes, and the prepared titanium alloy seamless pipes are accurate in size and high in yield.

Description

Technical Field

[0001] The invention relates to the technical field of advanced processing of titanium alloy materials, and in particular to a method for preparing a titanium alloy seamless pipe by introducing an intermediate and then performing thermal deformation. Background Art

[0002] China's titanium industry has undergone a long period of development. From the mid-to-late 20th century, when traditional chemical industry (alkali, fertilizer and salt production, etc.) was the main demand, it is gradually shifting to the fields of aerospace, shipbuilding, marine engineering and high-end chemical equipment. At present, my country's titanium materials are mainly used in the fields of chemical industry, aerospace, electric power, marine engineering, shipbuilding and metallurgy, among which the output of titanium alloy pipes accounts for about 20% of titanium processing materials. Titanium alloy seamless pipes have many advantages over traditional steel pipes, stainless steel pipes, copper alloy pipes, etc., such as good corrosion resistance, especially resistance to seawater corrosion and biological corrosion; high specific strength, while ensuring structural strength and stability, it can achieve the purpose of weight reduction; a variety of alloys to meet the use requirements of various fields; good biocompatibility, can be stably present in biological tissues; good processing performance, easy welding, etc.

[0003] At present, domestic titanium alloy seamless pipes are mainly produced by extrusion, rolling, drawing, spinning and other methods to produce finished pipes of different specifications and uses. However, titanium has poor thermal conductivity. During extrusion, a large temperature difference is easily generated between the surface and the center of the billet, which aggravates the unevenness of metal flow and generates a large additional tensile stress on the surface layer, resulting in cracks on the surface of the product. In severe cases, large central extrusion compression holes may be generated on the extruded bars and pipes. At the same time, the rolling equipment of titanium alloy seamless pipes is complex, the investment is large, and the requirements for tools are relatively strict. Special equipment or special molds are required for manufacturing, and the replacement of tools is complicated. Due to the small deformation per pass, many drawing passes, long production cycle, many intermediate auxiliary processes, large alloy consumption and strict requirements for lubricants, it is difficult to produce titanium alloy seamless pipes with low plasticity and high strength by drawing process. Although titanium alloy seamless pipes are favored by various fields due to their excellent performance, their application is limited due to the difficulties in the production of titanium seamless pipes, complex processing equipment, long cycle and low yield.

[0004] Therefore, how to prepare titanium alloy seamless pipes with good comprehensive performance, short preparation cycle and low cost is one of the key issues that need to be solved. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing titanium alloy seamless pipes by introducing intermediates and then hot deforming, and preparing titanium alloy gradient functional materials by hot pressing technology. The titanium alloy seamless pipes prepared by the present invention have uniform microstructure without defects, excellent mechanical properties, high yield rate, and are not limited by size, providing technical support and theoretical guidance for the preparation and application of titanium alloy seamless pipes in my country.

[0006] In order to achieve the above purpose, the technical solution of the present invention is:

[0007] A method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming the pipe comprises the following steps:

[0008] (1) Ingot Melting

[0009] Firstly, titanium alloy raw materials are uniformly mixed and pressed into electrodes, and the electrodes are melted in a vacuum consumable arc furnace to obtain titanium alloy ingots;

[0010] (2) Billeting and forging

[0011] The smelted titanium alloy ingot is blanked and forged to obtain a titanium alloy forged rod;

[0012] (3) Preparation of tube blank

[0013] The titanium alloy forged rod is firstly drilled by mechanical processing, and then the inner surface thereof is polished to prepare a titanium alloy tube blank;

[0014] (4) Heat treatment of tube blank

[0015] Placing the titanium alloy tube blank in a heating furnace for heat treatment;

[0016] (5) Thermal deformation

[0017] The heat-treated titanium alloy tube blank is subjected to thermal deformation to obtain a titanium alloy tube. The specific implementation process is: the inner surface of the heat-treated titanium alloy tube blank is coated with glass lubricant, and then assembled with an intermediate, and then thermally deformed. After the thermal deformation is completed, the intermediate is taken out to obtain the titanium alloy tube;

[0018] (6) Annealing

[0019] Annealing the titanium alloy pipe to eliminate internal stress;

[0020] (7) Surface treatment

[0021] The titanium alloy pipe is surface treated inside and outside by mechanical processing to finally obtain a titanium alloy seamless pipe.

[0022] The method is not limited by the titanium alloy grade, tissue type and size, and can prepare titanium alloy seamless pipes with different inner hole shapes, sizes, different wall thicknesses and different lengths according to needs.

[0023] In the step (1), when the titanium alloy ingot is smelted, it is smelted three times to ensure that the composition of the ingot is uniform.

[0024] In the step (2), during the blank forging, after the ingot is taken out of the furnace, it is clamped by a manipulator for forging, and each time the hammer is lowered during the forging process, the hammer is fully hammered; the two ends of the titanium alloy forging rod are single drum-shaped and convex.

[0025] In the step (3), when preparing the titanium alloy tube blank, the titanium alloy forged rod is first drilled, the inner hole is concentric with the forged rod, and then the inner surface is polished; the inner surface of the titanium alloy tube blank is smooth, without any processing marks remaining, and its roughness Ra = 0.05μm-1.6μm.

[0026] In the step (4), the heat treatment temperature of the titanium alloy tube blank is 700°C-1000°C and the holding time is 2h-3h.

[0027] In the step (5), the length of the intermediate is 120%-150% of the length of the target titanium alloy tube, and the cross-sectional area is 90%-95% of the cross-sectional area of ​​the inner hole of the titanium alloy tube blank. The intermediate is made of a metal material with poor plasticity and high strength compared with the titanium alloy tube blank; the intermediate and the titanium alloy tube blank are at room temperature when assembled; the axial deformation of the titanium alloy tube blank is uniform, no radial deformation occurs, and the intermediate does not deform during the thermal deformation process; and it is easy to separate after the thermal deformation is completed.

[0028] In the step (6), the titanium alloy pipe is annealed at a temperature of 500°C-900°C and a holding time of 1h-2h.

[0029] In the step (7), the surface treatment process is specifically as follows: after the annealing, the titanium alloy pipe is firstly subjected to wire cutting to remove both ends, and then the inner and outer surfaces of the pipe are sequentially turned and polished, and finally, petroleum ether and alcohol are sequentially used to clean until there are no pollutants, so as to obtain a titanium alloy seamless pipe.

[0030] The titanium alloy seamless pipe has a smooth surface and no residual processing marks, and the inner and outer surface roughness of the pipe is Ra=0.05μm-1.6μm.

[0031] The thermal deformation process of the prepared titanium alloy seamless pipe fully breaks up the grains, effectively weakens the unfavorable texture in the titanium alloy seamless pipe, and improves the mechanical properties of the titanium alloy seamless pipe.

[0032] The thermal deformation process is carried out by a precision forging machine, which has high forming accuracy, high yield rate and reduced cost.

[0033] The design concept of the present invention is:

[0034] First, the titanium alloy raw materials are evenly mixed and pressed into electrodes. The electrodes are melted in a vacuum consumable arc furnace to obtain titanium alloy ingots. The melting is performed three times to ensure that the composition of the ingots is uniform; the smelted titanium alloy ingots are blanked and forged. During blanking and forging, after the ingot is taken out of the furnace, it is clamped by an operating machine for forging. The hammer must be fully hammered during forging to ensure that the two ends are single-drum convex to obtain a titanium alloy forged rod; when processing the titanium alloy tube blank, the titanium alloy forged rod is first drilled, and the inner hole is concentric with the forged rod, and then the inner surface is polished to ensure that the inner surface is smooth, no processing marks remain, and the roughness of the inner surface Ra=0 .05μm-1.6μm; placing the titanium alloy tube blank in a heating furnace for heat treatment, coating the inner surface of the titanium alloy tube blank after heat treatment and insulation with glass lubricant, then combining with the intermediate, and then performing thermal deformation, the length of the intermediate is 120%-150% of the target titanium alloy tube length, and the cross-sectional area is 90%-95% of the inner hole of the titanium alloy tube blank, after the thermal deformation, the intermediate is taken out to obtain the titanium alloy tube; annealing the titanium alloy tube to eliminate internal stress; machining is used to remove the inner and outer oxide layers of the titanium alloy tube, and finally a titanium alloy seamless tube is obtained. When preparing the titanium alloy seamless steel tube of the present invention, thermal deformation is used for preparation, which ensures the uniformity of the organization, is conducive to eliminating bad textures, and the deformation process fully breaks the grains, thereby improving the comprehensive mechanical properties of the titanium alloy seamless steel tube. The intermediate is made of a material with lower plasticity and higher strength than the titanium alloy tube blank, and is at room temperature when assembled with the titanium alloy tube blank to ensure uniform deformation of the titanium alloy tube blank during thermal deformation, and easy separation after thermal deformation due to the different deformation degrees of the titanium alloy tube blank and the intermediate.

[0035] The advantages and beneficial effects of the present invention are:

[0036] The present invention provides a method for preparing a titanium alloy seamless pipe by introducing an intermediate and then performing thermal deformation. First, a titanium alloy ingot is obtained by smelting, the ingot is blanked and forged to obtain a titanium alloy forged rod, a titanium alloy tube blank is obtained by machining, and then the titanium alloy tube blank is heat treated. After the heat treatment, a titanium alloy tube is obtained by thermal deformation, and then the tube is annealed and surface treated in sequence to obtain the titanium alloy seamless pipe.

[0037] 1. When preparing titanium alloy seamless pipes by the method provided in the present invention, it is not limited to titanium alloy grades, organizational types and size restrictions, and titanium alloy seamless pipes of any grades and organizational types can be prepared.

[0038] 2. The thermal deformation process of the titanium alloy seamless pipe prepared by the method provided by the present invention fully breaks up the grains, effectively weakens the unfavorable texture in the titanium alloy seamless pipe, improves the mechanical properties of the titanium alloy seamless pipe, has precise dimensions, high yield rate and short production cycle.

[0039] 3. The titanium alloy seamless pipe prepared by the method provided by the present invention is not limited by size and equipment. Titanium alloy seamless pipes with different inner hole shapes, different wall thicknesses and different lengths can be prepared according to demand, providing technical support and theoretical guidance for promoting the application of titanium alloy seamless pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a process flow chart of the present invention;

[0041] Figure 2 It is a titanium alloy seamless pipe prepared by extrusion;

[0042] Figure 3 The hot deformation process for preparing titanium alloy seamless pipe by hot deformation;

[0043] Figure 4 It is a titanium alloy seamless tube prepared by hot deformation. DETAILED DESCRIPTION

[0044] In the specific implementation process, the present invention first uses a vacuum consumable arc furnace to melt the electrode to obtain a titanium alloy ingot, and melts it three times to ensure that the ingot composition is uniform. The smelted titanium alloy ingot is blanked and forged, and a titanium alloy tube blank is prepared by machining. The inner surface is then polished to ensure that the inner surface is smooth and no processing marks remain. The titanium alloy tube blank is placed in a heating furnace for heat treatment, and the titanium alloy tube blank after the heat treatment and insulation is completed is thermally deformed. Finally, the inner and outer oxide layers of the titanium alloy tube are removed by machining to finally obtain a titanium alloy seamless tube. The process flow is as follows: Figure 1 shown.

[0045] Below, the present invention is further described in detail by comparative examples and embodiments.

[0046] Comparative Example

[0047] The specific process of this comparative example is to first prepare a TC4 titanium alloy tube blank by extrusion forming a TC4 titanium alloy forged rod, then perform sheath extrusion in the two-phase region of the TC4 titanium alloy, and finally obtain the tube blank by surface treatment and stress relief annealing. Figure 2 The titanium alloy tube shown is from Figure 2 It can be seen that a large number of cracks are generated on the surface of TC4 titanium alloy tube.

[0048] Example

[0049] The specific process of this embodiment is as follows: first, the TC4 titanium alloy raw materials are uniformly mixed and pressed into electrodes, and the electrodes are smelted three times in a vacuum consumable arc furnace to obtain a TC4 titanium alloy ingot. After the TC4 titanium alloy ingot is taken out of the furnace, it is clamped by an operating machine for blanking and forging. During the forging process, the hammer is fully hammered each time, and the obtained TC4 titanium alloy forged rod has single drum-shaped protrusions at both ends. The TC4 titanium alloy tube blank is prepared by machining. First, the titanium alloy forged rod is drilled, and the inner hole is concentric with the forged rod. Then, the inner surface is polished to ensure that the inner surface is smooth and no processing marks remain, and a TC4 titanium alloy tube blank with a bonding surface roughness of Ra = 1.6μm is obtained. The TC4 titanium alloy tube blank is placed in a heating furnace for heat treatment at a temperature of 960°C for a holding time of 2 hours. After the holding is completed, the inner surface of the TC4 titanium alloy tube blank is coated with glass lubricant, and then assembled with the intermediate TC11 titanium alloy at room temperature. The length of the intermediate TC11 titanium alloy is 150% of the required TC4 titanium alloy tube length, and the cross-sectional area is 90% of the inner hole of the TC4 titanium alloy tube blank. It is then placed under a precision forging machine for hot deformation such as Figure 3 As shown, during the hot deformation of the tube blank, the axial deformation is uniform and no radial deformation occurs. After the hot deformation, the intermediate TC11 titanium alloy is taken out to obtain the TC4 titanium alloy tube. The TC4 titanium alloy tube is then annealed at a temperature of 500°C and a holding time of 1h. After annealing, the TC4 titanium alloy tube is firstly wire-cut to remove both ends, and then the inner and outer surfaces are turned on a lathe to remove all oxide scales. The inner and outer surfaces are then polished to ensure that the inner and outer surfaces are smooth and no machining marks remain. The roughness of the inner and outer surfaces is Ra = 1.6μm. The tube is cleaned with petroleum ether and alcohol in turn until all surfaces are free of pollutants, as shown below. Figure 4 The TC4 titanium alloy seamless tube shown in the figure can be seen that the produced TC4 titanium alloy seamless tube has no defects such as cracks on the surface and has high forming quality.

[0050] The above is only the best example of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming, characterized in that: The following steps are involved: Step 1. Ingot melting: uniformly mix the titanium alloy raw materials and press them into electrodes, and use a vacuum consumable arc to melt the electrodes to obtain a titanium alloy ingot; Step 2. Blanking and casting: Blanking and forging the titanium alloy ingot to obtain a titanium alloy forged rod; Step 3. Prepare the tube blank: firstly drill the titanium alloy forged rod by mechanical processing, and then grind the inner surface thereof to obtain the titanium alloy tube blank; Step 4. Heat treatment of the tube blank: placing the tube blank in a heating furnace for heat treatment; Step 5. Hot deformation: hot deformation is performed on the heat-treated titanium alloy tube blank to obtain a titanium alloy tube. The specific implementation process is: the inner surface of the heat-treated titanium alloy tube blank is coated with glass lubricant, and then assembled with the intermediate, and then hot deformation is performed. After the hot deformation is completed, the intermediate is taken out to obtain the titanium alloy tube; Step 6. Annealing: Annealing the titanium alloy tube to eliminate internal stress; Step 7. Surface treatment: The inner and outer surfaces of the titanium alloy tube are treated by mechanical processing to obtain a titanium alloy seamless tube; The intermediate is made of a metal material which has poor plasticity and high strength compared with the titanium alloy tube blank.

2. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: The method is not limited by the titanium alloy grade, tissue type and size, and can prepare titanium alloy seamless pipes with different inner hole shapes, sizes, different wall thicknesses and different lengths according to needs.

3. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: In step 1, the smelting times are 3 times.

4. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: In step 2, during the blank forging, after the ingot is taken out of the furnace, it is clamped by a manipulator for forging, and each time the hammer is lowered during the forging process, it is a full hammer; The two ends of the titanium alloy forged rod are convex in a single drum shape.

5. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: In step 3, the inner hole obtained by drilling is concentric with the forged rod; The inner surface of the titanium alloy tube blank is smooth, with no residual processing marks, and its roughness Ra is 0.05 μm-1.6 μm.

6. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: In step 4, during the heat treatment process, the temperature is 700°C-1000°C and the insulation time is 2h-3h.

7. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: In step 5, the length of the intermediate is 120%-150% of the length of the target titanium alloy tube, and the cross-sectional area is 90%-95% of the cross-sectional area of ​​the inner hole of the titanium alloy tube blank; The thermal deformation process is carried out using a precision forging machine; the assembly process is carried out at room temperature; During the thermal deformation process, the tube blank is uniformly deformed in the axial direction and does not change in the radial direction, and the intermediate body does not deform.

8. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: In step 6, during the annealing process, the annealing temperature is 500° C.-900° C., and the holding time is 1 h-2 h.

9. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: In step 7, the surface treatment process is specifically as follows: after the annealing, the titanium alloy pipe is firstly wire-cut to remove both ends, and then the inner and outer surfaces of the pipe are sequentially turned and polished, and finally, petroleum ether and alcohol are sequentially cleaned until there is no contaminant.

10. The method for preparing a titanium alloy seamless pipe by introducing an intermediate and then hot deforming according to claim 1, characterized in that: The titanium alloy seamless pipe has a smooth surface and no residual processing marks, and the inner and outer surface roughness of the pipe is Ra=0.05μm-1.6μm.

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