A method for preparing a fine-grained titanium alloy coil

Abstract

The present invention discloses a method for preparing a fine-grained titanium alloy disc, comprising the following steps: S1, using a titanium alloy ingot as a raw material, performing a first heating and forging process to obtain a first semi-finished billet; S2, performing a second heating process on the billet, performing a first rolling process, wherein the elongation coefficient of each pass does not exceed 1.3, and obtaining a second semi-finished billet; S3, performing a third heating process on the billet, performing a second rolling process, and a rolling speed of 2.1-11 m / s to obtain a titanium alloy disc; S4, annealing the titanium alloy disc, and removing the surface oxide layer and defects to obtain a titanium alloy disc with a diameter of 7.5 to 17.5 mm. The method for preparing a fine-grained titanium alloy disc of the present invention realizes quasi-transverse temperature rolling of the titanium alloy disc by controlling the heating temperature of the billet, the rolling speed, and the elongation coefficient of each pass, thereby preventing overheating of the core and ensuring good surface quality of the titanium alloy disc. The present invention can greatly improve the yield rate and production efficiency of the titanium alloy disc; and produce a titanium alloy disc with a fine grain size.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy coil manufacturing, and specifically refers to a method for preparing fine-grained titanium alloy coils. Background Art

[0002] Due to its high specific strength, excellent corrosion resistance, high temperature resistance, good biocompatibility and other advantages, titanium alloy is widely used in the fields of aerospace, medical, 3C, automotive, chemical equipment, etc. There are problems in the processing of titanium alloy materials, such as high deformation resistance, poor process plasticity, and narrow hot forming temperature range. The current technical situation of titanium alloy coils: First, a three-high mill can be used to produce small coil weight titanium alloy coils, with a single weight not exceeding 50 Kg. Second, a continuous rolling production line in a steel mill can produce large coil rolls of 1 ton level. However, the rolling speed of the continuous rolling line in the steel mill is relatively high, and the central part of the titanium alloy is severely overheated during the rolling process, the tissue uniformity is very poor, and the surface quality of the coil is also poor, which cannot meet the market demand.

[0003] In the prior art, the application number CN202311655927.4 discloses a method for manufacturing low-cost and large single-weight titanium and titanium alloy coils, including forging a titanium ingot into a metal round bar with a diameter of 95 - 135 mm by a hydraulic press or a block machine, then processing the obtained metal round bar into a metal round bar with a diameter of 90 - 130 mm on a lathe, and grinding the surface cracks and defects, and then feeding the obtained metal round bar into a heating furnace for uniform heating and rolling to 850 - 1020 °C and holding the temperature. Through continuous production, the process includes precision forging round billets, or advanced technical processes such as forging by rolling (reaching the target round billet size at one time).

[0004] Its defects are that after forging the titanium ingot, it needs to be machined on a lathe to an appropriate specification before subsequent processing, resulting in serious material waste, and the machining efficiency is low. Secondly, it uses a high-speed continuous rolling mill to perform high-speed rolling on the titanium alloy raw material. Due to its high rolling speed, the central part of the titanium alloy is severely overheated during the rolling process, the core temperature will exceed the phase change point, the tissue uniformity is very poor, and the surface quality of the coil is also poor, which cannot meet the market demand.

[0005] In view of the above, it is necessary to propose a method for preparing fine-grained titanium alloy coils to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to solve the above technical problems and provide a method for preparing fine-grained titanium alloy coils.

[0007] In order to achieve the above purpose, the present invention adopts the following technical scheme: A method for preparing fine-grained titanium alloy coils, including the following steps:

[0008] S1. Take a titanium alloy ingot as the raw material, conduct the first heating on the raw material, perform hot forging on the raw material, forge it into a square billet with a size of 160 - 200 mm, and obtain the first semi-finished billet after segmentation and surface treatment;

[0009] S2. Conduct the second heating on the first semi-finished billet, and perform the first rolling for 9 - 13 passes. The elongation coefficient of each pass does not exceed 1.3, and the total deformation is 68% - 80%. Obtain a titanium alloy bar billet, and obtain the second semi-finished billet after sawing and peeling the bar billet;

[0010] S3. Conduct the third heating on the second semi-finished billet, and perform the second rolling for 18 - 26 passes. The second rolling speed is 2.1 - 11 m / s. The coiled wire is collected into a coil by a wire coil collector, and a titanium alloy coiled wire with a diameter of Φ8 - 18 mm is obtained after cooling;

[0011] S4. Anneal the titanium alloy coiled wire in step S3, and remove the surface oxide layer and defects to obtain a titanium alloy coiled wire with a diameter of Φ7.5 - 17.5 mm;

[0012] In each of the above rolling steps, control the temperature difference between the core and the surface of the billet to be no more than 100 °C.

[0013] Furthermore, the first heating includes a preheating stage and a heating stage. The preheating temperature is 750 - 850 °C, and the holding time is 90 - 150 min. The temperature in the heating stage is 1050 - 1150 °C, and the holding time is 400 - 550 min.

[0014] Furthermore, in step S1, two upsetting and drawing operations are completed during the hot forging of the titanium alloy ingot. The forging ratio during upsetting is 1.55 - 1.65, and the total deformation is 75% - 90%; the surface treatment in step S1 includes mechanical grinding and sawing operations.

[0015] Furthermore, the second heating temperature is 850 - 950 °C, and the holding time is 120 - 180 min.

[0016] Furthermore, in step S2, the first rolling speed is 1.0 - 2.0 m / s. After the first rolling, a titanium alloy bar billet with a diameter of 102 mm is obtained. The bar billet is sawed and peeled by a centerless lathe to obtain a second semi-finished billet with a diameter of 100 mm.

[0017] Furthermore, the pass sequence of the first rolling mill adopts: flat - vertical - flat - vertical... oval - round pass sequence. When rolling in the flat - vertical - flat - vertical pass sequence, a 90° billet turning operation is performed when entering the next pass after each pass of rolling is completed.

[0018] Furthermore, the third heating temperature is 800-950° C., the holding time is 60-10 min, and the second rolling speed is 2.5-11 m / s.

[0019] Furthermore, the equipment used in the second rolling is a continuous rolling line, which includes 16 two-roller horizontal and vertical alternating high-rigidity short-stress line rolling mills, 2 cantilever pre-finishing rolling mills, and 8 heavy-duty Morgan-type top-cross 45° finishing rolling mills;

[0020] The first six two-roller horizontal and vertical alternating high-rigidity short-stress line rolling mills roll Φ50mm billets at a speed of ≤1.5m / s;

[0021] 8 finishing mills are used for rolling, and the finishing speed of the finishing mills is 2.5 to 11 m / s.

[0022] Furthermore, the elongation coefficient of each processing pass of the two-roll horizontal and vertical alternating high-rigidity short-stress line rolling mill and the cantilever pre-finishing rolling mill group does not exceed 1.3; the elongation coefficient of the finishing pass of the finishing rolling mill group does not exceed 1.25; the hole system of the continuous rolling line adopts an elliptical-circular hole system; the ovality of the rolled coil is ≤0.5mm.

[0023] Furthermore, the annealing temperature in S4 is 650-800° C., and the holding time is 60-90 min.

[0024] Compared with existing technologies, the present invention has the following advantages: The method for producing fine-grained titanium alloy coils achieves quasi-transverse temperature rolling of the titanium alloy coils by controlling the billet heating temperature, rolling speed, and elongation coefficient of each pass, preventing overheating of the core. Simultaneously, the spacing between the stands of the continuous rolling line and the cooling water supply to the rolls during rolling are rationally controlled to prevent excessive temperature drop on the titanium alloy surface, ensuring good surface quality of the titanium alloy coils. The present invention can significantly improve the yield rate and production efficiency of titanium alloy coils, producing large single-weight titanium alloy coils with fine grain size and uniform microstructure at the head and tail of the coils. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the first rolling process in a method for preparing a fine-grained titanium alloy disk according to the present invention; DETAILED DESCRIPTION

[0026] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0027] A method for preparing a fine-grained titanium alloy disk comprises the following steps:

[0028] Step 1: Use a titanium alloy ingot as the raw material, conduct the first heating on the raw material, and perform hot forging on the raw material. The first heating includes a preheating and a heating stage. The preheating temperature is 750 - 850°C, with a heat preservation time of 90 - 150 minutes. The temperature in the heating stage is 1050 - 1150°C, and the heat preservation time is 400 - 550 minutes. Forge it into a square billet with a side length of 160 - 200 mm. After the square billet is segmented and surface-treated, a first semi-finished billet is obtained;

[0029] In this step, two upsetting and drawing operations are completed during the hot forging of the titanium alloy ingot. The tonnage of the quick forging machine used for forging the titanium alloy square billet is ≥3150 tons. When upsetting, the forging ratio is 1.55 - 1.65, and the total deformation amount is 75% - 90%. The surface treatment includes mechanical grinding and sawing operations.

[0030] Step 2: Conduct the second heating on the first semi-finished billet. The second heating temperature is 850 - 950°C, and the heat preservation time is 120 - 180 minutes. Then, perform the first rolling with 9 - 13 passes on a three-high reversing mill. The first rolling speed is 1.0 - 2.0 m / s, and the elongation coefficient of each pass does not exceed 1.3 to prevent overheating of the core caused by excessive deformation per pass. The main method to solve the very poor tissue uniformity is to control the elongation coefficient of each pass and control the temperature difference between the surface and the core of the billet. The temperature difference between the core and the surface should be controlled within 50 degrees. If the core temperature is 100°C higher than the surface, the α-phase in the core tissue will significantly decrease, and the cross-sectional tissue will show obvious non-uniformity. The total deformation amount is 68% - 80%. A titanium alloy bar billet is obtained. After sawing and skinning the bar billet, a second semi-finished billet is obtained; After the first rolling, a titanium alloy bar billet with a diameter of 102 mm is obtained. After sawing and skinning on a centerless lathe, a second semi-finished billet with a diameter of 100 mm is obtained.

[0031] As Figure 1 shown, it is a pass diagram of a three-high mill. The pass of the first rolling uses the pass system of flat - vertical - flat - vertical... oval - round. When rolling in the flat - vertical - flat - vertical pass system, a 90° billet turning operation is performed when each pass of rolling is completed before entering the next pass of rolling. Perform the first rolling with 9 - 13 passes on a three-high reversing mill. As Figure 1 shown in ① - ⑫ in the figure, in the figure, ② is rolled at an intermediate position in the transverse direction relative to ①. As Figure 1 shown by the dotted arrow in ② in the figure, it is the relative contraction direction. The thickness of ② is basically the same as that of ①, but it significantly contracts in the width direction. Similarly, ③ is rolled towards the middle in the thickness direction relative to ② while the width remains the same. And so on. After multiple passes of rolling in the flat - vertical - flat - vertical... oval - round pass system, a bar billet is formed.

[0032] In this embodiment, the three-roll rolling mill rolls the blank to Φ100mm. The turning of the blank during the rolling process can be achieved through the turning guide guard, and the front and rear feeding is achieved through the roller table, so that automatic operation can be realized.

[0033] Step 3: Perform the third heating on the second semi-finished blank. The third heating temperature is 800 - 950°C, the heat preservation time is 60 - 10 min, and the second rolling speed is 2.5 - 11 m / s. And perform the second rolling for 18 - 26 passes. Specifically, the equipment used for the second rolling is a continuous rolling line, which consists of 16 two-high reversing short stress path rolling mills with alternating horizontal and vertical stands, 2 cantilever pre-finishing mill units, and 8 heavy-duty Morgan-type top-cross 45° finishing mill units. The second semi-finished blank is rolled into a Φ50mm billet by the first 6 short stress path rolling mills at a speed of ≤1.5 m / s. After the tail of the billet exits the rolling mill, it enters the 7th - 16th short stress path rolling mills for rolling after being cut off the head by the No. 1 flying shear, and then enters the 2 pre-finishing mill units for rolling; finally, it enters the 8 heavy-duty Morgan-type top-cross 45° finishing mill units for rolling; the coiled wire is collected into a coil by the wire coiler, and after cooling, a titanium alloy coiled wire with a diameter of Φ8 - 18mm is obtained; the speed of the K1 stand of the finishing mill is 2.5 - 11 m / s. During continuous rolling, the elongation coefficient of each pass of the first 18 stands does not exceed 1.3. The pass sequence of the continuous rolling line adopts an oval-round pass sequence. The ovality of the coiled wire rolled is ≤0.5mm. The pass sequence of the continuous rolling line adopts an oval-round pass sequence. The elongation coefficient of the finishing pass does not exceed 1.25 to prevent overheating of the core. According to different finished product specifications, the finishing mill can skip stands for rolling.

[0034] Step 4: Perform finished product annealing on the titanium alloy coiled wire with a diameter of Φ8 - 18mm in a pit-type or car-type annealing furnace. The annealing temperature is 650 - 800°C, the heat preservation time is 60 - 90 min, and then the surface oxide layer and defects are removed by the peeling method using a centerless lathe, and a titanium alloy coiled wire with a diameter of Φ7.5 - 17.5mm is obtained.

[0035] Example 1:

[0036] The TC4 titanium alloy coiled wire prepared by the method of the present invention has a tensile strength ≥930 MPa, a yield strength ≥800 MPa, an elongation rate ≥15%, an average grain size ≤10 μm, and an α-phase ratio ≥88%.

[0037] Example 2:

[0038] The TA4 titanium alloy flat bar prepared by the method of the present invention has a tensile strength ≥600 MPa, a yield strength ≥500 MPa, an elongation rate ≥20%, an average grain size ≤15 μm, and an α-phase ratio ≥88%.

[0039] The present invention utilizes a process of forging, 550 three-roll rolling, and hot continuous rolling to produce large single-weight, fine-grained titanium alloy discs. By controlling the billet heating temperature, rolling speed, and elongation coefficient of each pass, the present invention achieves quasi-transverse temperature rolling of the titanium alloy discs to prevent overheating of the core. Simultaneously, the spacing between the various stands of the continuous rolling line and the cooling water of the rolls during rolling are rationally controlled to prevent excessive temperature drop on the titanium alloy surface, thereby ensuring good surface quality of the titanium alloy discs. The present invention can significantly improve the yield rate and production efficiency of titanium alloy discs, producing large single-weight titanium alloy discs with fine grain size and uniform microstructure at the disc head and tail.

[0040] The present invention is also applicable to the preparation of α titanium alloy, α+β titanium alloy and β titanium alloy disks.

[0041] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a fine-grained titanium alloy disk, characterized in that: The following steps are involved: S1, using a titanium alloy ingot as a raw material, performing a first heating on the raw material, and hot forging the raw material into a 160-200 mm square billet, and then segmenting and surface treating the square billet to obtain a first semi-finished billet; In step S1, the titanium alloy ingot undergoes two upsetting operations during hot forging, with a forging ratio of 1.55 to 1.65 during upsetting and a total deformation of 75% to 90%. The surface treatment in step S1 includes mechanical grinding and sawing operations. S2, subjecting the first semi-finished product billet to a second heating and performing a first rolling process of 9-13 passes, wherein the elongation coefficient of each pass does not exceed 1.3 and the total deformation is 68% to 80%, to obtain a titanium alloy billet, which is then sawed and peeled to obtain a second semi-finished product billet; The first rolling speed is 1.0-2.0 m / s. After the first rolling, a titanium alloy billet with a diameter of 102 mm is obtained. The billet is sawed and peeled on a centerless lathe to obtain a second semi-finished billet with a diameter of 100 mm. The first rolling mill adopts a pass system of flat-vertical-flat-vertical...elliptical-circular. When rolling in the flat-vertical-flat-vertical pass system, a 90° billet turning operation is performed before the next rolling pass after each rolling pass is completed. S3, the second semi-finished product billet is subjected to a third heating and a second rolling for 18-26 passes, the coil is collected into a coil by a wire coiler, and after cooling, a titanium alloy coil with a diameter of 8 to 18 mm is obtained; The equipment used in the second rolling is a continuous rolling line, which includes 16 two-roller horizontal and vertical alternating high-rigidity short-stress line rolling mills, 2 cantilever pre-finishing rolling mills, and 8 heavy-duty Morgan-type top-cross 45° finishing rolling mills; The first six two-roller horizontal and vertical alternating high-rigidity short-stress line rolling mills roll Φ50mm billets at a speed of ≤1.5m / s; 8 finishing mills are used for rolling, and the finishing speed of the finishing mill is 2.5-11m / s; The elongation coefficient of each processing pass of the two-roll horizontal and vertical alternating high-rigidity short-stress line rolling mill and the cantilever pre-finishing rolling mill group shall not exceed 1.3; the elongation coefficient of the finishing pass of the finishing mill group shall not exceed 1.25; the pass system of the continuous rolling line adopts an elliptical-circular pass system; the ovality of the rolled coil shall be ≤0.5mm; The third heating temperature is 800-950°C; S4, annealing the titanium alloy disc obtained in step S3 and removing the surface oxide layer and defects to obtain a titanium alloy disc with a diameter of 7.5 to 17.5 mm; In each of the above rolling steps, the temperature difference of the core surface of the billet is controlled to be no more than 100°C.

2. The method for preparing a fine-grained titanium alloy disk according to claim 1, characterized in that: The first heating includes preheating and heating stages, the preheating temperature is 750-850° C., and the insulation time is 90-150 minutes. The heating stage temperature is 1050-1150° C., and the insulation time is 400-550 minutes.

3. The method for preparing a fine-grained titanium alloy disk according to claim 1, characterized in that: The second heating temperature is 850-950° C., and the holding time is 120-180 minutes.

4. The method for preparing a fine-grained titanium alloy disk according to claim 1, characterized in that: The annealing temperature in S4 is 650-800° C., and the holding time is 60-90 minutes.

Images