Preparation method of high-strength TC16G titanium alloy cold-rolled pipe with wall thickness of 1.0 mm-2. 0mm

Abstract

The invention discloses a preparation method of a high-strength titanium alloy cold-rolled pipe with the wall thickness of 1.0 mm-2. 0mm. The method comprises the following steps: 1, directly rolling a TC16G titanium alloy cast ingot to obtain a bar billet; 2, carrying out cross piercing and rapid cooling on the bar blank to obtain a pipe blank; 3, rounding the pipe blank and treating the inner surface and the outer surface of the pipe blank; and fourthly, the TC16G titanium alloy cold-rolled pipe is obtained through multi-pass cold rolling. The high-strength TC16G titanium alloy cold-rolled pipe with the wall thickness of 1.0 mm-2. 0mm is successfully prepared through the procedures of direct rolling, cross piercing, rapid cooling, rounding, inner and outer surface treatment and multi-pass cold rolling of the TC16G titanium alloy cast ingot, the quality of the high-strength TC16G titanium alloy cold-rolled pipe is guaranteed, meanwhile, the preparation efficiency and the yield are improved, and the preparation process is simple, easy to implement, suitable for industrial production and suitable for industrial production. The method is suitable for the technical field of titanium alloy preparation.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material processing, and in particular relates to a method for preparing a high-strength TC16G titanium alloy cold-rolled pipe with a wall thickness of 1.0 mm to 2.0 mm. Background Art

[0002] As titanium alloys are increasingly used in various fields, the demand for high-strength titanium alloy pipe products with a tensile strength of more than 930 MPa and a yield strength of more than 850 MPa is gradually increasing, making them a high-strength alloy with a relatively urgent market demand. However, even for two-phase alloys such as TC4, the yield strength in the solid solution state is more than 760 MPa. At the same time, due to the high α-phase content of alloys such as TC4, the work hardening rate is high and the strength increases rapidly during cold working, but the rolling efficiency is low and the rolling cost is high. In particular, the processing of titanium alloy materials of similar strength with a wall thickness of less than 2 mm is very difficult and has limitations. The main production methods currently used are hot extrusion and hollowing, which have low production efficiency and high cost. Therefore, conventional methods cannot produce high-strength pipes with a wall thickness of less than 2 mm.

[0003] Therefore, there is an urgent need for a preparation method for high-strength thin-walled pipes with high processing efficiency, simple process, excellent performance, and industrial production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned existing technologies and provide a method for preparing high-strength TC16G titanium alloy cold-rolled pipes with a wall thickness of 1.0mm to 2.0mm. This method successfully realizes the preparation of TC16G titanium alloy cold-rolled pipes with a wall thickness of 1.0mm to 2.0mm by designing the process of direct rolling, oblique rolling and piercing, rapid cooling, rounding, internal and external surface treatment, and multi-pass cold rolling, and controlling the processing parameters of each process. This method not only ensures the quality of TC16G titanium alloy cold-rolled pipes, but also improves the preparation efficiency and reduces production costs, solving the problem that high-strength titanium alloy pipes with a wall thickness of less than 2mm are difficult to prepare or have complicated preparation processes.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a high-strength TC16G titanium alloy cold-rolled tube with a wall thickness of 1.0 mm to 2.0 mm, characterized in that the method comprises the following steps: Step 1: rolling the TC16G titanium alloy ingot to obtain a rod blank; The chemical composition of the TC16G titanium alloy ingot meets the chemical composition requirements of the titanium alloy in the patent application number 202211677846.X; Step 2: Obliquely pierce the rod obtained in step 1 at the phase transition point from α to β phase and rapidly cool it to obtain a tube; Step 3: rounding the tube obtained in step 2 and performing internal and external surface treatment; Step 4: The tube blank after rounding and inner and outer surface treatment in step 3 is subjected to multiple cold rolling on a cold rolling tube mill to obtain a TC16G titanium alloy cold-rolled tube; during the multiple cold rolling process, the tube blank after each cold rolling pass is annealed, straightened, and inner and outer surface polished.

[0006] The present invention sequentially performs direct rolling, oblique rolling and piercing, rapid cooling, rounding, internal and external surface treatment, and multi-pass cold rolling on a TC16G titanium alloy ingot (the chemical composition of which meets the chemical composition requirements of the titanium alloy in the claims of the patent application number 202211677846.X "A titanium alloy suitable for cold working, its preparation method, and titanium alloy component"). Compared with conventional two-phase titanium alloys such as TC4 alloy, the TC16G titanium alloy ingot of the present invention has stronger fluidity and recrystallization ability at high temperature. Therefore, the present invention directly rolls the TC16G titanium alloy ingot into a rod billet for preparing a tube billet, without the need for multiple fire processing including blanking of conventional titanium alloys, thereby achieving high efficiency and high yield rate preparation; at the same time, the present invention forms a low yield strength orthorhombic martensite by oblique rolling and piercing at the phase transformation point of the α to β phase transformation and then rapid cooling, so it is easy to deform, which brings convenience to the subsequent cold rolling of the tube billet with thick tube wall, and then generates a β phase with a β content of about 40% and an α phase with a low Al content after subsequent multiple cold rolling and annealing, which is conducive to obtaining a low yield stress after annealing in the two-phase zone during the cold rolling process, thereby significantly reducing the number of cold rolling passes, and is not easy to cause damage, further improving production efficiency and yield rate, and at the same time, the high β content ensures that the TC16G titanium alloy cold-rolled tube has high strength performance. Finally, through process design and control of processing parameters of each process, the present invention not only successfully prepares TC16G titanium alloy cold-rolled pipes with a wall thickness of 1.0mm~2.0mm, but also ensures the quality of the TC16G titanium alloy cold-rolled pipes, including high-precision dimensions, high-strength mechanical properties and high flaw detection pass rate. At the same time, it improves the production efficiency, flaw detection pass rate and yield rate of TC16G titanium alloy cold-rolled pipes, and reduces production costs.

[0007] The above-mentioned method for preparing a high-strength titanium alloy cold-rolled tube with a wall thickness of 1.0 mm to 2.0 mm is characterized in that the rolling temperature in step 1 is above the phase transition point of the TC16G titanium alloy ingot. More preferably, the rolling temperature is 1100°C ± 10°C.

[0008] More preferably, in step 2 of the present invention, the rod blank is subjected to oblique rolling and piercing at the phase transition point from α to β phase, which is usually 1100° C.±10° C.

[0009] Since the bar blank is composed of low-strength, high-plasticity martensite, even if the subsequent process is limited by the rolling mill's rolling processing penetration capacity, resulting in different degrees of structural fragmentation and recrystallization from the outside to the inside, the presence of high-plasticity martensite in the bar blank can effectively avoid discontinuous deformation during processing. Therefore, it is suitable for oblique rolling piercing + cold rolling blanking process, reducing the difficulty and cost of blank making control.

[0010] The above-mentioned method for preparing a high-strength titanium alloy cold-rolled tube with a wall thickness of 1.0 mm to 2.0 mm is characterized in that there are no special requirements for the metallographic structure of the rod blank in step 1, and the flaw detection of the rod blank meets the Class B requirements in GB / T5193-2007 "Non-flaw Detection Methods for Titanium and Titanium Alloy Products".

[0011] The aforementioned method for producing high-strength titanium alloy cold-rolled tubes with a wall thickness of 1.0 mm to 2.0 mm is characterized in that the rapid cooling method in step 2 is: water cooling is used for rods with a diameter D ≥ 80 mm, and air cooling is used for rods with a diameter D < 80 mm. Different cooling methods are used for different rod sizes to ensure rapid cooling.

[0012] The above-mentioned method for preparing a high-strength titanium alloy cold-rolled tube with a wall thickness of 1.0 mm to 2.0 mm is characterized in that the cold-rolling tube mill in step 4 is an LG-type rolling mill, the total rolling deformation of the multiple cold-rolling passes is not less than 90%, the feed rate is 3 mm to 5 mm per pass, the cumulative diameter reduction is greater than 60%, and the cumulative wall reduction is greater than 75%, and the cold-rolling is completed in 5 to 8 passes. The number of cold-rolling passes used in the present invention is at least 5 fewer than that of conventional TC4 alloys.

[0013] The above-mentioned method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0mm~2.0mm is characterized in that the annealing in step 4 is carried out in a resistance furnace at an annealing temperature of 850℃±5℃.

[0014] The above-mentioned method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0mm~2.0mm is characterized in that the TC16G titanium alloy cold-rolled pipe obtained in step 4 is subjected to dimensional appearance, mechanical properties, and flaw detection inspection, and the results are: the wall thickness of the TC16G titanium alloy cold-rolled pipe is 1.0mm~2.0mm, the outer diameter deviation is +0.10mm~-0.025mm, the inner diameter deviation is ±0.08mm, the wall thickness deviation is ±0.12mm, and the flaw detection meets the standard defects: groove depth 0.225mm±0.02mm×groove width 0.8mm×groove length 25mm±0.1mm, and the room temperature mechanical properties meet the following requirements: tensile strength Rm≥930MPa, yield strength Rp 0.2≥850MPa, elongation after fracture A≥10%. The TC16G titanium alloy cold-rolled pipe prepared by the present invention has excellent dimensions, appearance, mechanical properties, water pressure, and flaw detection test results, meeting the requirements for use in engine hydraulic pipelines.

[0015] Compared with the prior art, the present invention has the following advantages: 1. Based on the characteristics of TC16G titanium alloy with good fluidity and fast thermal deformation recovery at high temperature, the present invention directly rolls TC16G titanium alloy ingots into high-plasticity rods composed of martensite, followed by a cross-rolling and piercing process, which effectively avoids the generation of cracks that are easy to expand. In this process, there is no need to make special requirements on the core structure size of the rod and the uniformity of the structure of the cross section of the rod, which reduces the control difficulty of the preparation process and effectively improves the preparation efficiency and yield rate. 2. The present invention performs rapid cooling after the oblique rolling and piercing process, which effectively refines the tube blank structure and retains part or even all of the low stress and strain martensite structure, creating good deformation conditions for subsequent cold rolling, significantly reducing the number of cold rolling passes, and further improving production efficiency and yield rate; the refined structure obtained is also conducive to ensuring the high strength performance of TC16G titanium alloy cold-rolled tubes.

[0016] 3. The present invention ensures the smooth progress of the rolling process by controlling the main parameters such as deformation, feed amount, cumulative diameter reduction, cumulative wall reduction, etc. of multiple cold rolling passes.

[0017] 4. The preparation process of the present invention is simple and easy, suitable for industrial production, and can be extended to the processing of other titanium alloy pipes that can obtain martensitic structure, and has high practical value.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the metallographic structure diagram of the optical rod blank prepared in Example 1 of the present invention.

[0020] Figure 2 This is the metallographic structure diagram of the tube blank prepared in Example 1 of the present invention.

[0021] Figure 3 This is the microstructure of the tube blank after the fourth cold rolling and two-phase region annealing in Example 1 of the present invention.

[0022] Figure 4 This is the metallographic structure diagram of the TC16G titanium alloy cold-rolled tube prepared in Example 1 of the present invention.

[0023] Figure 5 This is the metallographic structure diagram of the optical rod blank prepared in Example 2 of the present invention.

[0024] Figure 6 This is the metallographic structure diagram of the tube blank prepared in Example 2 of the present invention.

[0025] Figure 7 This is the microstructure of the tube blank after the third cold rolling and two-phase region annealing in Example 2 of the present invention.

[0026] Figure 8 This is the metallographic structure diagram of the TC16G titanium alloy cold-rolled tube prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] Example 1 This embodiment includes the following steps: Step 1. A TC16G titanium alloy ingot with a diameter of 150 mm is kept at 1100°C ± 10°C for 190 minutes and then rolled to obtain a rod blank with a diameter of Φ71 mm, which is then machined to obtain a polished rod blank with a diameter of Φ69 mm; the chemical composition of the TC16G titanium alloy ingot meets the TC16G grade standard requirements in patent application number 202211677846.X, and is composed of the following components by mass percentage: Al 3.0wt%, V 4.2wt%, Mo 5.1wt%, Cr 0.8wt%, Fe 0.6wt%, Nb 0.7wt%, and the remainder is Ti and unavoidable impurities; The metallographic structure of the polished rod blank in step 1 is as follows Figure 1 As shown, from Figure 1 It can be seen that the original β grain boundary of the organization is discontinuous, and the flaw detection of the light bar billet meets the requirements of Class B in GB / T5193-2007 "Flaw Detection Methods for Titanium and Titanium Alloy Processing Products"; Step 2: The polished rod obtained in step 1 is subjected to oblique rolling and piercing at 1100°C ± 10°C and then air-cooled to obtain a tube with an outer diameter × wall thickness of Φ71mm × 8mm; The metallographic structure of the tube in step 2 is as follows Figure 2 As shown, from Figure 2 It can be seen that the structure is needle-shaped martensite structure; Step 3: rounding the tube obtained in step 2 and machining the inner and outer surfaces; Step 4: The tube billet after rounding and inner and outer surface machining in step 3 is cold rolled on an LG type rolling mill for 8 passes, the total rolling deformation of the 8 cold rolling passes is 95%, the feed amount is 3 mm / time for the first 5 passes and 5 mm / time for the last 3 passes, the cumulative diameter reduction is 85.5%, and the cumulative wall reduction is 87.5%, to obtain a finished TC16G titanium alloy cold-rolled tube with an outer diameter × wall thickness of Φ10 mm × 1.0 mm; during the 8 cold rolling processes, the tube billet is subjected to two-phase zone annealing after each cold rolling pass, and a box-type resistance furnace is used for annealing, the annealing temperature is 800°C ± 10°C, and the annealing time is 60 min.

[0028] Figure 3 This is the microstructure of the tube blank after the 4th cold rolling and two-phase annealing in this embodiment. Figure 3 It can be seen that the structure is a spherical equiaxed α+β transformation structure, in which the β content is about 40%, which ensures that the TC16G titanium alloy tube billet has excellent cold rolling performance after two-phase zone annealing. In this embodiment, the tube billet structure after each pass of cold rolling and two-phase zone annealing does not change much, and all have similar Figure 3 Typical organization.

[0029] Figure 4 This is the metallographic structure diagram of the TC16G titanium alloy cold-rolled tube prepared in this embodiment. Figure 4 It can be seen that with Figure 3 In comparison, after rolling with a cumulative deformation of 95%, under the action of grain crushing and recrystallization in each pass, the structure and β phase content remain unchanged, but the structure becomes more uniform and fine, and the equiaxility is good, which makes TC16G titanium alloy cold-rolled tube have good strength, plasticity and flaw detection performance.

[0030] The TC16G titanium alloy cold-rolled tube prepared in this embodiment was subjected to dimensional appearance, mechanical properties, water pressure, and flaw detection inspections. The results showed that the outer diameter deviation of the TC16G titanium alloy cold-rolled tube was +0.038 mm to -0.025 mm, the inner diameter deviation was ±0.07 mm, the wall thickness deviation was ±0.10 mm, and the flaw detection inspection met the standard defects: groove depth 0.225 mm ± 0.02 mm × groove width 0.8 mm × groove length 25 mm ± 0.1 mm. The measured values ​​of the mechanical properties at room temperature are shown in Table 1 below.

[0031] Table 1

[0032] Example 2 This embodiment includes the following steps: Step 1, the TC16G titanium alloy ingot is kept at 1100°C ± 10°C for 190 minutes and then rolled to obtain a rod with a diameter of Φ86 mm; the chemical composition of the TC16G titanium alloy ingot meets the TC16G grade standard requirements in patent application number 202211677846.X, and is composed of the following components by mass percentage: Al 3.25wt%, V 4.0wt%, Mo 4.3wt%, Cr0.75wt%, Fe 0.6wt%, Nb 0.8wt%, and the rest is Ti and unavoidable impurities; The metallographic structure of the polished rod blank in step 1 is as follows Figure 5 As shown, from Figure 5 It can be seen that the structure is coarse needle-like structure without complete original β grain boundary. The flaw detection of the bar billet meets the requirements of Class A in GB / T5193-2007 "Flaw Detection Methods for Titanium and Titanium Alloy Processing Products"; Step 2: The rod obtained in step 1 is subjected to oblique rolling and piercing at 1100°C ± 10°C and then air-cooled to obtain a tube with an outer diameter × wall thickness of Φ89mm × 8mm; The metallographic structure of the tube in step 2 is as follows Figure 6 As shown, from Figure 6 It can be seen that the structure is a fine needle-shaped martensite structure; Step 3: rounding the tube obtained in step 2 and machining the inner and outer surfaces; Step 4: The tube blank after rounding and inner and outer surface machining in step 3 is cold rolled on an LG type rolling mill for 5 passes, the total rolling deformation of the 5 cold rolling passes is 90%, the feed amount is 3 mm / time, the cumulative diameter reduction is 60.7%, and the cumulative wall reduction is 75%, to obtain a TC16G titanium alloy cold-rolled tube with a finished size of outer diameter × wall thickness of Φ35 mm × 2.0 mm; during the 5 cold rolling processes, the tube blank is subjected to two-phase zone annealing after each cold rolling pass, and the annealing adopts a box-type resistance furnace, the annealing temperature is 800°C ± 10°C, and the annealing time is 60 min.

[0033] Figure 7 This is the microstructure of the tube blank after the third cold rolling and two-phase annealing in this embodiment. Figure 7 It can be seen that the structure is a spherical equiaxed α+β transformation structure, in which the β content is about 40%, which ensures that the TC16G titanium alloy tube billet has excellent cold rolling performance after two-phase zone annealing. In this embodiment, the tube billet structure after each pass of cold rolling and two-phase zone annealing does not change much, and all have similar Figure 7 Typical organization.

[0034] Figure 8 This is the metallographic structure diagram of the TC16G titanium alloy cold-rolled tube prepared in this embodiment. Figure 8It can be seen that after multiple passes of rolling and recrystallization annealing, the α structure and β structure are fully globalized, fine and uniform.

[0035] The TC16G titanium alloy cold-rolled tube prepared in this embodiment was subjected to dimensional appearance, mechanical properties, water pressure, and flaw detection inspections. The results showed that the outer diameter deviation of the TC16G titanium alloy cold-rolled tube was +0.08~-0.020 mm, the inner diameter deviation was ±0.05 mm, the wall thickness deviation was ±0.12 mm, and the flaw detection inspection met the standard defects: groove depth 0.225 mm ± 0.02 mm × groove width 0.8 mm × groove length 25 mm ± 0.1 mm. The measured values ​​of the mechanical properties at room temperature are shown in Table 2 below.

[0036] Table 2

[0037] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a high-strength TC16G titanium alloy cold-rolled tube with a wall thickness of 1.0 mm to 2.0 mm, characterized in that: The method comprises the following steps: Step 1: rolling the TC16G titanium alloy ingot to obtain a rod blank; The chemical composition of the TC16G titanium alloy ingot meets the chemical composition requirements of the titanium alloy in the patent application number 202211677846.X; Step 2: Obliquely pierce the rod obtained in step 1 at the phase transition point from α to β phase and rapidly cool it to obtain a tube; Step 3: rounding the tube obtained in step 2 and performing internal and external surface treatment; Step 4: The tube blank after rounding and inner and outer surface treatment in step 3 is subjected to multiple cold rolling on a cold rolling tube mill to obtain a TC16G titanium alloy cold-rolled tube; during the multiple cold rolling process, the tube blank after each cold rolling pass is annealed, straightened, and inner and outer surface polished.

2. The method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0 mm to 2.0 mm according to claim 1, characterized in that: The rolling temperature in step 1 is above the phase transition point of the TC16G titanium alloy ingot.

3. The method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0 mm to 2.0 mm according to claim 1, characterized in that: There are no special requirements for the metallographic structure of the bar blank described in step 1, and the flaw detection of the bar blank meets the requirements of Class B in GB / T5193-2007 "Flaw Detection Methods for Titanium and Titanium Alloy Workpieces".

4. The method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0 mm to 2.0 mm according to claim 1, characterized in that: The rapid cooling method in step 2 is: water cooling is used when the diameter of the billet is greater than or equal to 80 mm, and air cooling is used when the diameter of the billet is less than 80 mm.

5. The method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0 mm to 2.0 mm according to claim 1, characterized in that: The cold rolling mill for pipes in step 4 is an LG type rolling mill, the total rolling deformation of the multiple cold rolling passes is not less than 90%, the feed amount is 3 mm / time to 5 mm / time, the cumulative diameter reduction is more than 60%, the cumulative wall reduction is more than 75%, and it is completed in 5 to 8 cold rolling passes.

6. The method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0 mm to 2.0 mm according to claim 1, characterized in that: The annealing in step 4 is performed in a resistance furnace at a temperature of 850°C ± 5°C.

7. The method for preparing a high-strength titanium alloy cold-rolled pipe with a wall thickness of 1.0 mm to 2.0 mm according to claim 1, characterized in that: The TC16G titanium alloy cold-rolled tube obtained in step 4 was subjected to dimensional appearance, mechanical properties, and flaw detection inspections. The results showed that the wall thickness of the TC16G titanium alloy cold-rolled tube was 1.0 mm to 2.0 mm, the outer diameter deviation was +0.10 mm to -0.025 mm, the inner diameter deviation was ±0.08 mm, and the wall thickness deviation was ±0.12 mm. The flaw detection met the standard defects: groove depth 0.225 mm ± 0.02 mm × groove width 0.8 mm × groove length 25 mm ± 0.1 mm. The room temperature mechanical properties met the following requirements: tensile strength Rm ≥ 930 MPa, yield strength Rp 0.2 ≥850MPa, elongation after fracture A≥10%.

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