Method for improving component uniformity of titanium alloy cast ingot

Abstract

The invention discloses a method for improving the component uniformity of a titanium alloy cast ingot, and belongs to the technical field of titanium alloy machining. The cast ingot is prepared through three times of smelting, the titanium alloy cast ingot is obtained by controlling mixing and smelting processes and welding the head and the tail of the cast ingot, the arc stabilizing current is changed into alternating current from direct current, the arc stabilizing current and the period are gradually increased, and the obtained cast ingot is uniform in head, middle and tail components and free of defects such as shrinkage cavities and looseness.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy processing, and in particular relates to a production method of titanium alloy ingots. Background Art

[0002] Titanium alloy is lightweight, has high specific strength, and is corrosion resistant. It is widely used in aerospace, nuclear power, petrochemical and other fields. In particular, high-end fields have higher requirements for product performance stability, and the uniformity of alloy composition is the basis for ensuring stable product performance. Due to the positive and negative segregation of alloy and impurity elements, the composition difference between the head and tail of the ingot is large. For example, Al and O tend to gather at the arc starting end of the ingot, and Fe and V tend to gather at the riser end of the ingot. High-end fields such as aviation have extremely high requirements for the uniformity of ingot composition. In order to reduce the extreme difference in the elements at the head and tail of the ingot, the amount of sawing at the head and tail is large, which reduces the ingot rate and increases the cost of use. Summary of the invention

[0003] The purpose of the present invention is to provide a method for improving the uniformity of the composition of titanium alloy ingots, which is to effectively improve the uniformity of the ingots, reduce the amount of head and tail resection, and improve the yield rate and ingot quality by controlling the extreme difference in the composition of the head and tail of the titanium alloy ingots.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for improving the composition uniformity of a titanium alloy ingot comprises the following steps:

[0006] Step 1: Mix the raw materials of titanium alloy according to the proportion of titanium alloy;

[0007] Step 2: After the raw materials are fully mixed, the electrode block is pressed and welded. The welding is carried out by vacuum electron beam welding. Six weldings are carried out on the surface along the axial direction of the electrode to form six evenly distributed welds to obtain a consumable electrode.

[0008] Step 3: Weld the primary consumable electrode with the auxiliary electrode of the same brand, and after the vacuum leakage rate of the smelting chamber reaches below 1.5Pa / min, start the first smelting to obtain a primary ingot; wherein, the ratio of the smelting current (kA) to the diameter (mm) of the primary consumable electrode is between 0.03 and 0.04kA / mm; direct current is used for arc stabilization, and the arc stabilization current is between 15 and 20A;

[0009] Step 4: flatten the head and tail of the primary ingot and then cut it in the middle, and perform annular vacuum electron beam welding on the head and tail of the ingot to obtain a secondary consumable electrode;

[0010] Step 5: Weld the secondary consumable electrode with the auxiliary electrode of the same brand, and after the vacuum leakage rate of the smelting chamber reaches below 1.5Pa / min, perform the second smelting to obtain the secondary ingot; wherein, the ratio of the smelting current (kA) to the secondary consumable diameter (mm) is between 0.035 and 0.045kA / mm; the arc is stabilized by using an alternating current, the arc stabilizing current is between 18 and 23A, and the alternating current cycle is 10 to 30S;

[0011] Step 6: Flatten the secondary ingot and cut it in the middle, and perform vacuum electron beam welding on the head and tail of the ingot to obtain a tertiary consumable electrode;

[0012] Step seven: weld the tertiary consumable electrode with the auxiliary electrode of the same brand, and after the vacuum leakage rate of the smelting chamber reaches below 1.5Pa / min, carry out the third smelting, and then perform hot capping to obtain the tertiary ingot; wherein, the ratio of smelting current (kA) to the diameter (mm) of the tertiary consumable electrode is between 0.037 and 0.05kA / mm; the arc is stabilized by AC current, the arc stabilization current is between 20 and 25A, and the AC cycle is 30 to 60S; the ratio of hot capping time (min) to smelting current (kA) is not less than 10min / kA.

[0013] Step 8: Flatten the heads of the three ingots and polish the surfaces to obtain the titanium alloy ingots.

[0014] Furthermore, in step 1, the titanium alloy is a titanium alloy such as TA18 or TA16. The Al content of the TA18 titanium alloy is 2.5-3.5%, and the V content is 2-3%. The Al content of the TA16 titanium alloy is 1.5-2.5%, and the Zr content is 2-3%. Raw materials such as sponge titanium and master alloy are mixed according to the standard proportion of titanium alloy.

[0015] Furthermore, in step one, the mixing is performed using a mixer, which first rotates forward and backward alternately with its rotation axis parallel to the ground for more than 50 times, and then rotates forward and backward alternately with its rotation axis perpendicular to the ground for more than 50 times.

[0016] Furthermore, in step 2, the vacuum leakage rate during welding is ≤1.5Pa / min, and the vacuum degree is ≤2.0Pa.

[0017] Furthermore, in step 2, the diameter of the primary consumable electrode is between 300 and 450 mm.

[0018] Furthermore, in step three, the diameter ratio of the primary consumable electrode to the auxiliary electrode of the same brand is 1.2 to 1.5:1.

[0019] Furthermore, in step three, the diameter of the primary ingot is between 400 and 560 mm.

[0020] Furthermore, in step 4, the ingot is cut in the middle after the head and tail are flattened by 10 to 20 mm.

[0021] Furthermore, in step 4, the vacuum leakage rate during welding is ≤1.5Pa / min, and the vacuum degree is ≤2.0Pa.

[0022] Furthermore, in step 4, the diameter of the secondary consumable electrode is between 400 and 560 mm.

[0023] Furthermore, in step five, the diameter ratio of the secondary consumable electrode to the auxiliary electrode of the same brand is 1.4-1.8:1.

[0024] Furthermore, in step five, the diameter of the secondary ingot is between 490 and 660 mm.

[0025] Furthermore, in step six, the secondary ingot is cut 10 to 20 mm after being flattened.

[0026] Furthermore, in step six, the vacuum leakage rate during welding is ≤1.5Pa / min, and the vacuum degree is ≤2.0Pa.

[0027] Furthermore, in step six, the diameter of the tertiary consumable electrode is between 490 and 660 mm.

[0028] Furthermore, in step seven, the diameter ratio of the tertiary consumable electrode to the auxiliary electrode of the same brand is 1.6-2.0:1.

[0029] Furthermore, in step seven, the diameters of the three ingots are between 580 and 750 mm.

[0030] Furthermore, in step eight, the three ingots are flattened by 10 to 15 mm.

[0031] Furthermore, it also includes: performing flaw detection on the titanium alloy ingot, taking one cross-section at the head, middle and tail respectively; taking 9 points on each section for component analysis, and the extreme difference of the main element of the head, middle and tail alloy is not higher than 0.3%, and the extreme difference of Fe and O is not higher than 0.03%.

[0032] Beneficial effects of the present invention:

[0033] The ingot of the present invention is prepared by three smelting processes, and the titanium alloy ingot is obtained by controlling the mixing, smelting process and welding of the head and tail of the ingot. The arc stabilizing current is changed from direct current to alternating current, and the arc stabilizing current and cycle are gradually increased. The components of the head, middle and tail of the obtained ingot are uniform, the extreme difference of the main element is not higher than 0.3%, and the extreme difference of Fe and O is not higher than 0.03%. The surface quality of the ingot is good, there is no loose defect, the peeling amount is less than 5mm, there is no shrinkage cavity after the head of the ingot is flattened for 15mm, and the yield rate is high. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0035] Example 1

[0036] The production of TA16 titanium alloy ingots with a specification of Φ600mm includes the following steps:

[0037] Step 1: Mix the raw materials such as sponge titanium, sponge zirconium, aluminum beans, ferrotitanium, titanium dioxide, etc. according to the standard proportion of the alloy and put them into the mixer. The mixer first rotates forward and backward 100 times with the rotating axis parallel to the ground, and then rotates forward and backward 100 times with the rotating axis perpendicular to the ground.

[0038] Step 2: After the raw materials are fully mixed, the electrode block is pressed and welded. The welding is carried out by vacuum electron beam welding. Six weldings are carried out on the surface along the axial direction of the electrode to form six evenly distributed welds. The diameter of the welded electrode is 330mm, which is used as a consumable electrode. The vacuum leakage rate during welding is 1.5Pa / min and the vacuum degree is 2.0Pa.

[0039] Step 3: Weld the primary consumable electrode with the auxiliary electrode of the same brand (diameter 260mm). After the vacuum leakage rate of the melting chamber reaches 1.5Pa / min, start the first melting. The melting current is 13kA, and the arc is stabilized by direct current, and the arc stabilization current is 18A. Obtain a primary ingot with a diameter of 420mm.

[0040] Step 4: Flatten the head and tail of the primary ingot by 20mm and then cut it in the middle. Perform annular vacuum electron beam welding on the head and tail of the ingot to obtain a secondary consumable electrode with a diameter of 420mm, the same as the primary ingot. The vacuum leakage rate during welding is 1.5Pa / min and the vacuum degree is 2.0Pa.

[0041] Step 5: Weld the secondary consumable electrode with the auxiliary electrode of the same brand (diameter 280mm). After the vacuum leakage rate of the melting chamber reaches 1.5Pa / min, carry out the second melting. The melting current is 19kA. The arc is stabilized by AC current, the arc stabilization current is between 20A, and the AC cycle is 30S. Thus, a secondary ingot with a diameter of 510mm is obtained.

[0042] Step 6: Flatten the secondary ingot and cut it 20mm in the middle, and perform vacuum electron beam welding on the head and tail of the ingot to obtain a tertiary consumable electrode with a diameter of 510mm, the same as the secondary ingot. The vacuum leakage rate during welding is 1.5Pa / min, and the vacuum degree is 2.0Pa.

[0043] Step 7: Weld the tertiary consumable electrode with the auxiliary electrode of the same brand (diameter 310mm). After the vacuum leakage rate of the smelting chamber reaches 1.5Pa / min, carry out the third smelting. The smelting current is 25kA. The arc is stabilized by AC current, the arc stabilization current is 23A, and the AC cycle is 60S. The hot capping time is 250min. Thus, a TA16 tertiary ingot with a diameter of 600mm is obtained.

[0044] Step 8: Flatten the head of the above three ingots by 15mm, polish the surface and then inspect them, take one cross section from the head, middle and tail. Take 9 points on each section for component analysis, the extreme difference of the main elements of the alloy at the head, middle and tail is 0.28%, and the extreme difference of Fe and O is 0.025%.

[0045] Example 2

[0046] The production of TA18 titanium alloy ingots with a specification of Φ680mm includes the following steps:

[0047] Step 1: Mix the raw materials such as sponge titanium, ferrotitanium alloy, aluminum vanadium alloy, titanium dioxide according to the standard proportion of the alloy and put them into the mixer. The mixer first rotates 80 times in a forward and reverse direction with the rotating axis parallel to the ground, and then rotates 80 times in a forward and reverse direction with the rotating axis perpendicular to the ground.

[0048] Step 2: After the raw materials are fully mixed, the electrode block is pressed and welded. The welding is carried out by vacuum electron beam welding. Six weldings are carried out on the surface along the axial direction of the electrode to form six evenly distributed welds. The diameter of the welded electrode is 400mm, which is used as a consumable electrode. The vacuum leakage rate during welding is 1.3Pa / min and the vacuum degree is 1.8Pa.

[0049] Step 3: Weld the consumable electrode with the auxiliary electrode of the same brand (300mm in diameter). After the vacuum leakage rate of the melting chamber reaches 1.3Pa / min, start the first melting. The melting current is 15kA, and the arc is stabilized by direct current, and the arc stabilization current is 19A. Obtain a primary ingot with a diameter of 490mm.

[0050] Step 4: Flatten the head and tail of the primary ingot by 20mm and then cut it in the middle. Perform annular vacuum electron beam welding on the head and tail of the ingot to obtain a secondary consumable electrode with a diameter of 490mm, the same as the primary ingot. The vacuum leakage rate during welding is 1.3Pa / min and the vacuum degree is 1.8Pa.

[0051] Step 5: Weld the secondary consumable electrode with the same brand auxiliary electrode (diameter 330mm). After the vacuum leakage rate of the smelting chamber reaches 1.3Pa / min, carry out the second smelting. The smelting current is 19kA. The arc is stabilized by AC current, the arc stabilization current is 22A, and the AC cycle is 10S. Thus, a secondary ingot with a diameter of 580mm is obtained.

[0052] Step 6: Flatten the secondary ingot by 20mm and then cut it in the middle. Perform vacuum electron beam welding on the head and tail of the ingot to obtain a tertiary consumable electrode with the same diameter as the secondary ingot, 580mm. The vacuum leakage rate during welding is 1.3Pa / min and the vacuum degree is 1.8Pa.

[0053] Step 7: Weld the tertiary consumable electrode with the auxiliary electrode of the same brand (diameter 350mm). After the vacuum leakage rate of the smelting chamber reaches 1.3Pa / min, carry out the third smelting. The smelting current is 23kA. The arc is stabilized by AC current, the arc stabilization current is 24A, and the AC cycle is 30S. The hot capping time is 240min. Thus, a TA18 tertiary ingot with a diameter of 680mm is obtained.

[0054] Step 8: Flatten the head of the above three ingots by 15mm, polish the surface and then inspect them, take one cross section from the head, middle and tail. Take 9 points on each section for component analysis, the extreme difference of the main elements of the alloy at the head, middle and tail is 0.25%, and the extreme difference of Fe and O is 0.023%.

Claims

1. A method for improving the composition uniformity of titanium alloy ingots, characterized in that: The steps include: Step 1: Mix the raw materials of titanium alloy according to the proportion of titanium alloy; Step 2: After the raw materials are fully mixed, the electrode block is pressed and welded. The welding is carried out by vacuum electron beam welding. Six weldings are carried out on the surface along the axial direction of the electrode to form six evenly distributed welds to obtain a consumable electrode. Step 3: Weld the primary consumable electrode with the auxiliary electrode of the same brand, and after the vacuum leakage rate of the smelting chamber reaches below 1.5Pa / min, start the first smelting to obtain a primary ingot; wherein, the ratio of the smelting current (kA) to the diameter (mm) of the primary consumable electrode is between 0.03 and 0.04kA / mm; direct current is used for arc stabilization, and the arc stabilization current is between 15 and 20A; Step 4: flatten the head and tail of the primary ingot and then cut it in the middle, and perform annular vacuum electron beam welding on the head and tail of the ingot to obtain a secondary consumable electrode; Step 5: Weld the secondary consumable electrode with the auxiliary electrode of the same brand, and after the vacuum leakage rate of the smelting chamber reaches below 1.5Pa / min, perform the second smelting to obtain the secondary ingot; wherein, the ratio of the smelting current (kA) to the secondary consumable diameter (mm) is between 0.035 and 0.045kA / mm; the arc is stabilized by using an alternating current, the arc stabilizing current is between 18 and 23A, and the alternating current cycle is 10 to 30S; Step 6: Flatten the secondary ingot and cut it in the middle, and perform vacuum electron beam welding on the head and tail of the ingot to obtain a tertiary consumable electrode; Step seven: weld the tertiary consumable electrode with the auxiliary electrode of the same brand, and after the vacuum leakage rate of the smelting chamber reaches below 1.5Pa / min, carry out the third smelting, and then perform hot capping to obtain the tertiary ingot; wherein, the ratio of smelting current (kA) to the diameter (mm) of the tertiary consumable electrode is between 0.037 and 0.05kA / mm; the arc is stabilized by AC current, the arc stabilization current is between 20 and 25A, and the AC cycle is 30 to 60S; the ratio of hot capping time (min) to smelting current (kA) is not less than 10min / kA. Step 8: Flatten the heads of the three ingots and polish the surfaces to obtain the titanium alloy ingots.

2. The method according to claim 1, characterized in that: In step one, the titanium alloy is TA18 or TA16 titanium alloy; the mixing is performed using a mixer, which first rotates the mixer forward and backward alternately with its axis parallel to the ground for more than 50 times, and then rotates the mixer forward and backward alternately with its axis perpendicular to the ground for more than 50 times.

3. The method according to claim 1, characterized in that In step 2, the vacuum leakage rate during welding is ≤1.5Pa / min, and the vacuum degree is ≤2.0Pa; the diameter of the primary consumable electrode is between 300 and 450mm.

4. The method according to claim 1, characterized in that: In step 3, the diameter ratio of the primary consumable electrode to the auxiliary electrode of the same grade is 1.2-1.5:1; the diameter of the primary ingot is between 400 and 560 mm.

5. The method according to claim 1, characterized in that In step 4, the primary ingot is flattened by 10 to 20 mm at the head and tail and then cut in the middle; during welding, the vacuum leakage rate is ≤1.5Pa / min, and the vacuum degree is ≤2.0Pa; the diameter of the secondary consumable electrode is between 400 and 560mm.

6. The method according to claim 1, characterized in that In step 5, the diameter ratio of the secondary consumable electrode to the auxiliary electrode of the same grade is 1.4-1.8:1; the diameter of the secondary ingot is between 490 and 660 mm.

7. The method according to claim 1, characterized in that In step six, the secondary ingot is cut 10 to 20 mm after the flat head; the vacuum leakage rate during welding is ≤1.5Pa / min, and the vacuum degree is ≤2.0Pa; the diameter of the tertiary consumable electrode is between 490 and 660mm.

8. The method according to claim 1, characterized in that: In step seven, the diameter ratio of the tertiary consumable electrode to the auxiliary electrode of the same grade is 1.6-2.0:1; the diameter of the tertiary ingot is between 580 and 750 mm.

9. The method according to claim 1, characterized in that: In step eight, the three ingots are flattened by 10 to 15 mm.

10. The method according to claim 1, characterized in that Also includes: The titanium alloy ingot is inspected, and one cross-section is taken from the head, the middle and the tail respectively; 9 points are taken from each section for component analysis, and the extreme difference of the main element of the head, the middle and the tail is not higher than 0.3%, and the extreme difference of Fe and O is not higher than 0.03%.