A method for preparing industrial pure titanium rod blank for ultra-long fine-grained oblique rolling and piercing

Abstract

The present invention discloses a method for preparing an ultra-long fine-grained industrial pure titanium bar for oblique rolling and piercing, the method comprising: first, subjecting an industrial pure titanium ingot to one-time blanking forging at 1000°C to 1050°C to obtain a rolled forging billet; second, grinding the rolled forging billet to obtain a ground billet; third, grinding the ground billet in (T β -15℃)~(T β The finished rolled bar is then rolled in one heat at a temperature of 45°C (-45°C). Fourthly, the bar is peeled and sawn to obtain the industrially pure titanium bar for cross-rolling and piercing. This invention utilizes a process of "single-heat slab-forming in the β-phase region followed by high-deformation rolling in one heat on a large-tonnage rolling mill," avoiding the problem of grain growth during multi-heat forging and heating. This combined "high-deformation in a single direction combined with alternating deformation methods" achieves efficient grain breakage, ensuring the formation of a fine-grained structure in the product. This also reduces the number of forging and grinding cycles, significantly shortening the process, increasing the length of the finished bar, and lowering production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy material processing, and in particular relates to a method for preparing an industrial pure titanium rod blank for ultra-long fine-grain oblique rolling and piercing. Background Art

[0002] Industrially pure titanium (TA1, TA2, TA3) seamless tubes possess excellent corrosion resistance and are widely used in civilian industries such as petroleum refining, chemical processing, and seawater desalination. However, their high cost is a limiting factor in their application. The use of oblique rolling and piercing to produce tube billets eliminates the need for mechanical prefabrication of the inner bore, reducing material loss and improving yield. However, this method results in relatively small deformation and limited grain refinement. Therefore, grain refinement is necessary during the bar preparation stage to improve the plasticity and deformation coordination of the billet and mitigate cracking during the cold rolling process. The conventional process for preparing fine-grained bar billets involves 1-2 rounds of open forging followed by 1-2 rounds of intermediate forging followed by 1-2 rounds of forming forging. This conventional process involves at least three rounds of forging and at least two rounds of grinding, with bar lengths generally not exceeding 5000 mm. This leads to long manufacturing cycles, high processing costs, and significant grinding and cutting losses. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a method for preparing ultra-long, fine-grained, industrial-pure titanium bar billets for cross-rolling and piercing. This method adopts the process of "single-fire cogging in the β-phase region followed by single-fire, high-deformation rolling on a large-tonnage rolling mill," which avoids the problem of grain growth during multi-fire forging and heating. Combined with "large deformation in a single direction followed by alternating multiple deformation modes," this method achieves efficient grain breakage, ensuring the formation of fine-grained structure in the final industrial-pure titanium bar billet for cross-rolling and piercing. This method also reduces the number of forging fires and polishing cycles, significantly shortens the process flow, increases the length of the final bar billet, and reduces the cost of preparing the industrial-pure titanium bar billet for cross-rolling and piercing.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing an industrial pure titanium bar billet for ultra-long fine grain oblique rolling and piercing, characterized in that the method comprises the following steps

[0005] Step 1: Using a press to perform a first-fire forging of an industrial pure titanium ingot at an initial forging temperature of 1000° C. to 1050° C., and then air-cooling to obtain a rolled forging blank; the rolled forging blank has a square cross-section with a side length of 220 mm to 280 mm and a length of not less than 800 mm;

[0006] Step 2: Grinding the rolled forging blank obtained in step 1 with a grinding wheel machine to remove surface cracks and folding defects to obtain a ground blank;

[0007] Step 3: Use a rolling mill above 450°C to grind the blank obtained in step 2 at a temperature of (Tβ -15℃)~(T β -45℃) for one heat rolling, where T β is the β phase transition temperature of industrial pure titanium, in °C. The deformation of one rolling heat is 80% to 90%. After air cooling to room temperature, the finished rolled bar is obtained. The cross-sectional diameter of the finished rolled bar is 90 mm to 120 mm, the length is not less than 6000 mm, and the grain size is not less than Grade 6 in GB / T6394-2017 "Method for Determination of Average Grain Size of Metals";

[0008] Step 4: Use a centerless lathe and a sawing machine to peel and saw the finished rolled bar blank obtained in step 3 to obtain an industrial pure titanium bar blank for oblique rolling and piercing; the length of the industrial pure titanium bar blank for oblique rolling and piercing is 1000mm~1200mm.

[0009] The present invention first performs blank forging under the condition of the β single phase region with an initial forging temperature of 1000°C to 1050°C. By utilizing the characteristics of low deformation resistance and good deformation coordination of industrial pure titanium under the high temperature condition of the β single phase region, only one blank forging is required to obtain a rolled forging blank, without the need for a large-tonnage press and with less likelihood of surface cracks, which is beneficial to reducing processing costs and grinding losses. Then, the present invention uses a large-tonnage rolling mill of 450 or more at a temperature of (T β -15℃)~(T β -45 ℃) under the condition of the ground billet is rolled once. This single-fire large deformation forming method is compared with the multi-fire small deformation forming method, which reduces the heating link and eliminates the grain growth problem caused by repeated heating. The grain crushing efficiency is higher and the grain refinement effect is better, which effectively guarantees the formation of fine-grained structure. At the same time, the square, diamond, elliptical and circular alternating deformation methods are adopted in the single-fire rolling process to further increase the deformation while realizing the alternation of difficult and easy deformation zones, thereby improving the structural uniformity of the product industrial pure titanium bar billet for oblique rolling and piercing, and the use of large-tonnage rolling mills improves the axial processing accuracy of the bar billet, reduces surface defects, and increases the length of the product industrial pure titanium bar billet for oblique rolling and piercing, thereby significantly improving the yield rate and production efficiency.

[0010] The above-mentioned method for preparing an ultra-long fine-grained industrial pure titanium rod for oblique rolling and piercing is characterized in that the cross-sectional diameter of the industrial pure titanium ingot in step 1 is 620 mm to 980 mm.

[0011] The aforementioned method for preparing an ultra-long, fine-grained, industrially pure titanium bar for cross-rolling and piercing is characterized in that, during the first-fire forging process described in step 1, the industrially pure titanium ingot is first subjected to riveting and upsetting, with the riveting and upsetting reduction being 100 mm to 150 mm. This riveting and upsetting process avoids folding and cracking at the corners of the industrially pure titanium ingot caused by temperature drops, thereby ensuring the quality of the rolled forging billet.

[0012] The aforementioned method for preparing an ultra-long, fine-grained, industrially pure titanium bar for cross-rolling and piercing is characterized in that, during the first heat of the open forging process in step 1, the hot material is returned to the furnace for temperature replenishment. This method of returning the hot material to the furnace for temperature replenishment avoids cracking of the forging due to excessively low surface temperature during the open forging process.

[0013] The aforementioned method for preparing an ultra-long, fine-grained, industrially pure titanium bar for piercing by cross-rolling is characterized in that, during the first-pass forging process in step 1, the forging blank is chamfered before the end of forging, with the chamfering reduction being 30 mm to 50 mm. This chamfering process eliminates the problem of cracking at corners that can easily occur during the subsequent first-pass rolling process, thereby ensuring product quality.

[0014] The aforementioned method for preparing an ultra-long, fine-grained, industrially pure titanium bar for cross-rolling and piercing is characterized in that the blanking method employed in the first-fire forging process in step 1 is hot chopping. Hot chopping eliminates the sawing step, shortens the process flow, and reduces production costs.

[0015] The aforementioned method for preparing an ultra-long, fine-grained, industrially pure titanium bar for cross-rolling and piercing is characterized in that the dimensional deviation of the finished rolled bar in step 3 does not exceed 1 mm. By strictly limiting the dimensional deviation of the finished rolled bar, subsequent peeling losses are significantly reduced, thereby improving the product yield.

[0016] The aforementioned method for preparing an ultra-long, fine-grained, industrially pure titanium bar for cross-rolling and piercing is characterized by straightening the finished rolled bar in step 3 until the curvature does not exceed 2 mm / m. By limiting the curvature, subsequent peeling losses are further reduced, thereby improving the product yield.

[0017] The aforementioned method for preparing an ultra-long, fine-grained, industrially pure titanium bar for cross-rolling and piercing is characterized in that the peeling amount on a single side in step 4 is 2 mm to 2.5 mm. Compared to conventional precision forging and open-die forging processes, this method significantly reduces the peeling amount, significantly improving the product yield.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention adopts the process of "single-fire blanking in the β phase region + single-fire large deformation rolling and forming on a large-tonnage rolling mill", which avoids the problem of grain growth during multi-fire forging and heating. Through "large deformation in one direction + alternating multiple deformation modes", efficient grain crushing is achieved, ensuring the formation of fine-grained structure in the product industrial pure titanium bar billet for oblique rolling and piercing. At the same time, the number of forging fires and grinding times is reduced, the process flow is significantly shortened, the length of the product bar billet is increased, and the preparation cost of industrial pure titanium bar billet for oblique rolling and piercing is reduced.

[0020] 2. The present invention adopts a large-tonnage rolling mill for forming, which improves the uniformity of the structure of the industrial pure titanium bar billet for oblique rolling and piercing, greatly increases the length of the bar billet, reduces the loss of the bar head removal, and has high axial rolling accuracy and small machining allowance, further improving production efficiency and yield rate.

[0021] 3. The cross-sectional diameter of the industrial pure titanium rod blank for oblique rolling and piercing prepared by the present invention is 90 mm to 120 mm, the length is not less than 6000 mm, and the grain size is not less than grade 6 in GB / T6394-2017 "Method for Determination of Average Grain Size of Metals", which meets the actual use requirements.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the microstructure diagram of the industrial TA2 bar blank for cross-rolling and piercing prepared in Example 1 of the present invention.

[0024] Figure 2 This is the microstructure diagram of the industrial TA2 bar blank for cross-rolling and piercing prepared in Comparative Example 1 of the present invention.

[0025] Figure 3 This is the microstructure diagram of the industrial TA1 bar blank for cross-rolling and piercing prepared in Example 2 of the present invention.

[0026] Figure 4 This is the microstructure diagram of the industrial TA2 bar blank for cross-rolling and piercing prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0027] Example 1

[0028] This embodiment includes the following steps

[0029] Step 1: Using a 2500T press, an industrial TA2 ingot with a cross-sectional diameter of 980mm is subjected to single-fire open forging at an initial forging temperature of 1050°C. In this process, the industrial TA2 ingot is first subjected to riveting and upsetting, with a riveting and upsetting reduction of 100mm to 150mm. Before the end of forging, the forging blank is chamfered, with a chamfering reduction of 30mm to 50mm. The blanking method adopted is hot chopping, and during the single-fire open forging process, the hot material is returned to the furnace for heating, and a rolled forging blank is obtained after air cooling. The rolled forging blank has a square cross-section, a side length of 220mm, and a length of 900mm.

[0030] Step 2: Grinding the rolled forging blank obtained in step 1 with a grinding wheel machine to remove surface cracks and folding defects to obtain a ground blank;

[0031] Step 3: Use 650 rolling mill to grind the blank obtained in step 2 at a temperature of (T β -45℃) for one heat rolling, where T β is the β phase transition temperature of TA2 pure titanium, in °C. The deformation of one rolling heat is 87%, and the deformation mode is alternating square, diamond, elliptical, and circular deformation. After air cooling to room temperature, the product is straightened until the curvature is 2 mm / m to obtain a finished rolled bar billet. The cross-sectional diameter of the finished rolled bar billet is 90 (+0.5, -0) mm and the length is 6800 mm.

[0032] Step 4: Use a centerless lathe and a sawing machine to peel and remove the oxide scale and saw the finished rolled bar blank obtained in step 3 to obtain an industrial TA2 bar blank for oblique rolling and piercing; the diameter of the industrial TA2 bar blank for oblique rolling and piercing is 88 mm and the length is 1000 mm~1200 mm.

[0033] Figure 1 The microstructure of the industrial TA2 bar blank for cross-rolling and piercing prepared in this embodiment is shown in FIG. Figure 1 It can be seen that the grain size rating of the industrial TA2 bar blank for oblique rolling and piercing prepared in this embodiment meets the 8.0 grade requirement of GB / T6394-2017 Metal Average Grain Size Determination Method.

[0034] Comparative Example 1

[0035] This comparative example includes the following steps

[0036] Step 1: Using a 2500T press, an industrial TA2 ingot with a cross-sectional diameter of 980mm is subjected to single-fire open forging at an initial forging temperature of 1050°C. During the process, the industrial TA2 ingot is first subjected to riveting and upsetting, with a riveting and upsetting reduction of 100mm to 150mm. Before the end of forging, the forging blank is chamfered, with a chamfering reduction of 30mm to 50mm. The blanking method adopted is hot chopping, and during the single-fire open forging process, the hot material is returned to the furnace for heating, and a rolled forging blank is obtained after air cooling. The rolled forging blank has a square cross-section, a side length of 250mm, and a length of 900mm.

[0037] Step 2: Grinding the rolled forging blank obtained in step 1 with a grinding wheel machine to remove surface cracks and folding defects to obtain a primary ground blank;

[0038] Step 3: Use a 2500T press to grind the blank obtained in step 2 at a temperature of (T β -35℃) for one round of drawing and rounding to obtain a blank bar with a diameter of 160mm;

[0039] Step 4: Grinding the blank bar obtained in step 3 to obtain a secondary ground blank;

[0040] Step 5: Use the secondary grinding blank obtained in step 4 of the SX-16 precision forging machine to forge at the initial forging temperature (T β -55℃) to obtain a precision forging billet with a cross-sectional diameter of 90 mm and a length of 5000 mm;

[0041] Step 6: Use a centerless lathe and a sawing machine to peel and remove the oxide scale and saw the fine forging bar blank obtained in step 5 to obtain an industrial TA2 bar blank for oblique rolling and piercing; the diameter of the industrial TA2 bar blank for oblique rolling and piercing is 86 mm and the length is 1000 mm~1200 mm.

[0042] Figure 2 The microstructure of the industrial TA2 bar blank for cross-rolling and piercing prepared in this comparative example is shown in FIG. Figure 2 It can be seen that the grain size rating of the industrial TA2 bar blank for oblique rolling and piercing prepared in this comparative example meets the 4.5 requirement of GB / T6394-2017 Metal Average Grain Size Determination Method.

[0043] Will Figure 1 and Figure 2 By comparison, it can be seen that compared with Comparative Example 1, the grain size of the industrial TA2 bar blank for cross-rolling and piercing prepared in Example 1 is higher, indicating that the present invention adopts the process of "single-fire blanking in the β phase region + single-fire large deformation rolling and forming by a large-tonnage rolling mill", which avoids the problem of grain growth during multi-fire forging heating, realizes efficient grain crushing, and improves the grain size of the industrial TA2 bar blank for cross-rolling and piercing.

[0044] Example 2

[0045] This embodiment includes the following steps

[0046] Step 1: Using a 1600T press, an industrial TA1 ingot with a cross-sectional diameter of 620mm is subjected to a first-fire open forging at an initial forging temperature of 1000°C. In this process, the industrial TA1 ingot is first subjected to riveting and upsetting, and the riveting and upsetting reduction is 100mm~150mm. Before the end of forging, the forging blank is chamfered, and the chamfering reduction is 30mm~50mm. The blanking method adopted is hot chopping blanking, and during the first-fire open forging process, the hot material is returned to the furnace for heating, and a rolled forging blank is obtained after air cooling; the cross-section of the rolled forging blank is square, with a side length of 280mm and a length of 1200mm;

[0047] Step 2: Grinding the rolled forging blank obtained in step 1 with a grinding wheel machine to remove surface cracks and folding defects to obtain a ground blank;

[0048] Step 3: Use 650 rolling mill to grind the blank obtained in step 2 at a temperature of (T β -15℃) for one heat rolling, where T β is the β phase transition temperature of TA1 pure titanium, in °C; the deformation amount of one rolling heat is 90%, and the deformation mode is alternating square, diamond, elliptical, and circular deformation. After air cooling to room temperature, the product is straightened until the curvature is 2 mm / m to obtain a finished rolled bar billet; the cross-sectional diameter of the finished rolled bar billet is 100 (+0.5, -0) mm, and the length is 8200 mm;

[0049] Step 4: Use a centerless lathe and a sawing machine to peel and remove the oxide scale and saw the finished rolled bar blank obtained in step 3 to obtain an industrial TA1 bar blank for oblique rolling and piercing; the diameter of the industrial TA1 bar blank for oblique rolling and piercing is 95 mm and the length is 1000 mm~1200 mm.

[0050] Figure 3 This is the microstructure of the industrial TA1 bar blank for cross-rolling and piercing prepared in this embodiment. Figure 3 It can be seen that the grain size rating of the industrial TA1 bar blank for oblique rolling and piercing prepared in this embodiment meets the grade 6.5 requirement of GB / T6394-2017 Metal Average Grain Size Determination Method.

[0051] Example 3

[0052] This embodiment includes the following steps

[0053] Step 1: Using a 1600T press, an industrial TA2 ingot with a cross-sectional diameter of 790mm is subjected to single-fire open forging at an initial forging temperature of 1000°C. In this process, the industrial TA2 ingot is first subjected to riveting and upsetting, and the riveting and upsetting reduction is 100mm-150mm. Before the end of forging, the forging blank is chamfered, and the chamfering reduction is 30mm-50mm. The blanking method adopted is hot chopping blanking, and during the single-fire open forging process, the hot material is returned to the furnace for heating, and a rolled forging blank is obtained after air cooling. The cross-section of the rolled forging blank is square, with a side length of 240mm and a length of 1500mm.

[0054] Step 2: Grinding the rolled forging blank obtained in step 1 with a grinding wheel machine to remove surface cracks and folding defects to obtain a ground blank;

[0055] Step 3: Use 650 rolling mill to grind the blank obtained in step 2 at a temperature of (T β -25℃) for one heat rolling, where T βis the β phase transition temperature of TA2 pure titanium, in °C; the deformation amount of one rolling heat is 80%, and the deformation mode is alternating square, diamond, elliptical, and circular deformation. After air cooling to room temperature, the curvature is straightened until the curvature is 2 mm / m, and a finished rolled bar is obtained; the cross-sectional diameter of the finished rolled bar is 120 (+0.5, -0) mm, and the length is 11000 mm;

[0056] Step 4: Use a centerless lathe and a sawing machine to peel and remove the oxide scale and saw the finished rolled bar blank obtained in step 3 to obtain an industrial TA2 bar blank for oblique rolling and piercing; the diameter of the industrial TA2 bar blank for oblique rolling and piercing is 115 mm and the length is 1000 mm~1200 mm.

[0057] Figure 4 The microstructure of the industrial TA2 bar blank for cross-rolling and piercing prepared in this embodiment is shown in FIG. Figure 4 It can be seen that the grain size rating of the industrial TA2 bar blank for oblique rolling and piercing prepared in this embodiment meets the 7.0 requirement of GB / T6394-2017 Metal Average Grain Size Determination Method.

[0058] 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 an ultra-long fine-grained industrial pure titanium bar for cross-rolling and piercing, characterized in that: The method comprises the following steps Step 1: Using a press to perform single-fire forging of an industrial pure titanium ingot at an initial forging temperature of 1000° C. to 1050° C., and air-cooling to obtain a rolled forging blank; the cross-sectional diameter of the industrial pure titanium ingot is 620 mm to 980 mm; the cross-sectional area of ​​the rolled forging blank is square, with a side length of 220 mm to 280 mm and a length of not less than 800 mm; Step 2: Grinding the rolled forging blank obtained in step 1 with a grinding wheel machine to remove surface cracks and folding defects to obtain a ground blank; Step 3: Use a rolling mill above 450°C to grind the blank obtained in step 2 at a temperature of (T β -15℃)~(T β -45℃) for one heat rolling, where T β is the β phase transition temperature of industrial pure titanium, in °C. The deformation of one rolling heat is 80% to 90%. After air cooling to room temperature, a finished rolled bar is obtained. The cross-sectional diameter of the finished rolled bar is 90 mm to 120 mm, the length is not less than 6000 mm, and the grain size is not less than Grade 6 in GB / T6394-2017 "Method for Determination of Average Grain Size of Metals"; Step 4: Use a centerless lathe and a sawing machine to peel and saw the finished rolled bar blank obtained in step 3 to obtain an industrial pure titanium bar blank for oblique rolling and piercing; the length of the industrial pure titanium bar blank for oblique rolling and piercing is 1000mm~1200mm.

2. The method for preparing an ultra-long fine-grained industrial pure titanium bar for cross-rolling and piercing according to claim 1, characterized in that: During the first fire forging process described in step 1, the industrial pure titanium ingot is first subjected to riveting and upsetting, and the riveting and upsetting reduction is 100 mm to 150 mm.

3. The method for preparing an ultra-long fine-grained industrial pure titanium bar for oblique rolling and piercing according to claim 1, characterized in that: In the first fire forging process described in step 1, the hot material is returned to the furnace for heating.

4. The method for preparing an ultra-long fine-grained industrial pure titanium bar for cross-rolling and piercing according to claim 1, characterized in that: During the first round of blank forging in step 1, the blank is chamfered before the end of forging, and the reduction amount of the chamfer is 30 mm to 50 mm.

5. The method for preparing an ultra-long fine-grained industrial pure titanium bar for oblique rolling and piercing according to claim 1, characterized in that: The blanking method used in the first fire forging described in step 1 is hot chopping blanking.

6. The method for preparing an ultra-long fine-grained industrial pure titanium bar for cross-rolling and piercing according to claim 1, characterized in that: The dimensional deviation of the finished rolled bar in step 3 does not exceed 1 mm.

7. The method for preparing an ultra-long fine-grained industrial pure titanium bar for cross-rolling and piercing according to claim 1, characterized in that: The finished rolled bar described in step 3 is straightened until the curvature does not exceed 2 mm / m.

8. The method for preparing an ultra-long fine-grained industrial pure titanium bar for cross-rolling and piercing according to claim 1, characterized in that: The peeling amount on one side described in step 4 is 2mm~2.5mm.

Images