Method for preparing TA16 titanium alloy cast ingot through global medium energy density input

Abstract

The invention discloses a method for preparing a TA16 titanium alloy cast ingot through global medium energy density input, which comprises the following steps: mixing and pressing sponge titanium, sponge zirconium and intermediate alloy into electrode blocks, and welding a plurality of electrode blocks to obtain a consumable electrode; the consumable electrode and the vacuum consumable smelting auxiliary electrode are welded, and a welding electrode is obtained; the method comprises the following steps: smelting a welding electrode for the first time, then keeping vacuumizing, then filling argon for cooling, and carrying out scaling and head flattening treatment on an obtained cast ingot to obtain a primary cast ingot; and the primary cast ingot is subjected to turning-around welding and then subjected to secondary smelting, and the TA16 titanium alloy cast ingot is obtained after the surface of a secondary smelting cast ingot obtained after secondary smelting is turned. According to the method, the energy density and the melting speed are matched through the measures of controlling global medium energy density input in the VAR melting process and the like, the TA16 titanium alloy cast ingot is prepared through the two-time VAR melting process, and the obtained TA16 titanium alloy cast ingot is uniform in component, high in yield and free of the defects of shrinkage cavities, looseness and the like.

Description

Technical Field

[0001] The present invention relates to the field of alloy and smelting technology, and more specifically, to a method for preparing TA16 titanium alloy ingots by inputting global medium energy density. Background Art

[0002] TA16 (Ti-2Al-2.5Zr) is a near-α titanium alloy developed in the 1960s. Due to its low stress corrosion sensitivity, excellent long-term corrosion resistance, good plasticity, and easy pipe processing, it is often used in reactor exchanger steam generator piping systems, and the pipe strength can reach about 500MPa.

[0003] At present, the industry mainly uses the vacuum consumable melting method (VAR method) to produce nuclear TA16 titanium alloy ingots, which is generally melted three times. There are problems such as long process and low efficiency. As the number of melting times increases, the uniformity of the ingot composition deteriorates. The energy density of the VAR melting process is one of the most critical factors affecting the quality of the ingot. Therefore, in order to meet the requirements of high-homogeneity TA16 titanium alloy ingots in the nuclear power field, it is necessary to further optimize the VAR melting process, especially the energy density of the melting process. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing TA16 titanium alloy ingots with global medium energy density input.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing a TA16 titanium alloy ingot by global medium energy density input comprises the following steps:

[0007] (1) pressing a mixture of titanium sponge, zirconium sponge and master alloy into an electrode block, and welding a plurality of electrode blocks to obtain a consumable electrode;

[0008] (2) welding the consumable electrode and the vacuum consumable melting auxiliary electrode to obtain a welding electrode;

[0009] (3) subjecting the welding electrode to a first melting, wherein the first melting includes an arc starting stage, a stabilization stage, and a shrinkage feeding stage. After the first melting, the electrode is kept vacuumed, and then cooled by argon filling. The obtained ingot is peeled and flattened to obtain a primary ingot.

[0010] (4) The first ingot is subjected to a reverse welding and then subjected to a second smelting, wherein the second smelting includes a secondary arc starting stage, a secondary stabilization stage, and a secondary shrinkage compensation stage. The surface of the second smelted ingot obtained after the second smelting is polished to obtain the TA16 titanium alloy ingot.

[0011] Optionally, in step (1), the titanium sponge is 0A grade small-grain titanium sponge with a particle size of 1 to 20 mm; and the zirconium sponge is nuclear grade zirconium sponge with a particle size of 1 to 20 mm.

[0012] Optionally, the intermediate alloy includes titanium-iron alloy (particle size 1-10 mm), high-purity titanium dioxide (TiO2, purity ≥99.9%, particle size 20-50 nm), high-purity aluminum particles (purity ≥99%), etc.

[0013] Optionally, in step (1), the mixing time is ≥ 30 s.

[0014] Optionally, in step (2), the gap between the consumable electrode and the crucible wall is 30 to 50 mm; after welding is completed, the weld is inspected by breaking the air, and after the weld is qualified, the vacuum is re-drawn to ≤1Pa, and the leak detection rate is ≤0.8Pa / min.

[0015] Optionally, in step (3), the control time of the primary arc starting stage is ≤25min, the melting current of the primary arc starting stage is 10kA~16kA, the current increases linearly to the melting current, and enters a primary stable stage after the edge of the molten pool reaches the crucible wall; the energy density of the primary stable stage is 2800kJ / mm~3600kJ / mm, and the ratio of melting speed (kg / min) to electrode diameter (mm) is 0.015~0.030:1; the shrinkage time of the primary shrinkage stage is ≥30min, and the melting current is linearly reduced to 2kA~4kA.

[0016] Optionally, in step (3), after the first smelting is completed, the vacuum is continued for ≥1h after the power is turned off, and then argon is filled with ≥800Pa for cooling, and the cooling time is ≥6h.

[0017] Optionally, in step (4), a second smelting is performed after the vacuum degree of the U-turn welding is ≤0.5Pa and the leakage rate is ≤0.5Pa / min.

[0018] Optionally, in step (4), the control time of the secondary arc starting stage is ≤25min, the melting current of the secondary arc starting stage is 12kA~24kA, and the current increases linearly to the melting current; the energy density of the stable stage is 3600kJ / mm~5000kJ / mm, and the ratio of melting speed (kg / min) to electrode diameter (mm) is 0.020~0.035:1; the shrinkage weight of the secondary shrinkage stage satisfies 8%M~15%M, M is the ingot weight, the shrinkage time is ≥120min, and the melting current is linearly reduced to 3kA~6kA.

[0019] Optionally, in step (4), after the surface of the secondary smelting ingot obtained after the second smelting is polished, the ingot is subjected to ultrasonic flaw detection using a 2 MHz high-frequency probe, the parts that do not meet the head and tail flaw detection are cut off, and ≥8 points are taken at the head, middle and tail of the side of the ingot for component detection. The extreme difference of alloy elements in the ingot is ≤0.2%, and the extreme difference of Fe and O elements is ≤0.02%.

[0020] The invention also discloses a TA16 titanium alloy VAR ingot prepared by the above method.

[0021] Implementing the embodiments of the present invention will have the following beneficial effects:

[0022] The present invention provides a method for preparing TA16 titanium alloy ingots by inputting a global medium energy density. By optimizing the VAR smelting process, controlling the global medium energy density input in the VAR smelting process and other measures, the TA16 titanium alloy ingots are prepared by two VAR smelting processes for consumable electrodes and crucibles of different specifications by matching the energy density and the melting rate. The obtained TA16 ingots have uniform composition, high yield, and are free of metallurgical defects such as shrinkage cavities and porosity, thereby achieving the purpose of improving the molten pool state and increasing the uniformity of ingot element distribution. A nuclear TA16 titanium alloy ingot with a shallow shrinkage cavity depth and high homogeneity is developed. After subsequent processing, the produced rods, pipes and other products can be used in high-end equipment fields such as nuclear power, aerospace, and marine equipment. The technology can be applied in industry, which greatly improves the competitiveness of the products, has high added value, and has considerable economic benefits and technical display. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0024] The present invention discloses a method for preparing a TA16 titanium alloy ingot by inputting a global medium energy density, comprising the following steps:

[0025] (1) A mixture of titanium sponge, zirconium sponge and master alloy is pressed into an electrode block, and a plurality of electrode blocks are welded to obtain a consumable electrode.

[0026] In a specific embodiment, in step (1), the titanium sponge is a 0A grade small-grain titanium sponge with a particle size of 1 to 20 mm; the zirconium sponge is a nuclear grade zirconium sponge with a particle size of 1 to 20 mm; the intermediate alloy includes titanium-iron alloy (TiFe32, particle size ≤10 mm), high-purity titanium dioxide (TiO2, purity ≥99.9%, particle size 20 to 50 nm), high-purity aluminum particles (purity ≥99%), etc.

[0027] In a specific embodiment, the mixing time is ≥30s.

[0028] (2) The consumable electrode is welded with the vacuum consumable melting auxiliary electrode to obtain a welding electrode.

[0029] In a specific embodiment, in step (2), the gap between the consumable electrode and the crucible wall is 30 to 50 mm; after welding is completed, the weld is inspected by breaking the air, and after the weld is qualified, the vacuum is re-drawn ≤1Pa, and the leak detection rate is ≤0.8Pa / min.

[0030] (3) The welding electrode is melted for the first time, and the first melting includes an arc starting stage, a stabilization stage, and a shrinkage feeding stage. After the first melting, the vacuum is maintained, and then argon is filled for cooling. The obtained ingot is peeled and flattened to obtain a primary ingot.

[0031] In a specific embodiment, in step (3), the control time of the primary arc starting stage is ≤25min, the melting current of the primary arc starting stage is 10kA-16kA, the current increases linearly to the melting current, and the primary stable stage is entered after the edge of the molten pool reaches the crucible wall; the energy density of the primary stable stage is 2800kJ / mm-3600kJ / mm, and the ratio of melting speed (kg / min) to electrode diameter (mm) is 0.015-0.030:1; the feeding time of the primary feeding stage is ≥30min, and the melting current is linearly reduced to 2kA-4kA

[0032] In a specific embodiment, in step (3), after the first smelting is completed, the vacuum is continued for ≥1h after the power is turned off, and then argon is filled with ≥800Pa for cooling, and the cooling time is ≥6h.

[0033] (4) After the first ingot is turned around and welded, it is melted for the second time. The second melting includes a second arc starting stage, a second stabilization stage, and a second shrinkage feeding stage. The surface of the second melted ingot obtained after the second melting is polished to obtain a TA16 titanium alloy ingot.

[0034] In a specific embodiment, in step (4), the second melting is performed after the vacuum degree of the U-turn welding is ≤0.5Pa and the leakage rate is ≤0.5Pa / min.

[0035] In a specific embodiment, in step (4), the control time of the secondary arc starting stage is ≤25min, the melting current in the secondary arc starting stage is 12kA~24kA, and the current increases linearly to the melting current; the energy density in the stable stage is 3600kJ / mm~5000kJ / mm, and the ratio of melting speed (kg / min) to electrode diameter (mm) is 0.020~0.035:1; the feeding weight in the secondary feeding stage satisfies 8%M~15%M, M is the ingot weight, the feeding time is ≥120min, and the melting current is linearly reduced to 3kA~6kA.

[0036] In a specific embodiment, in step (4), the surface of the secondary smelting ingot obtained after the second smelting is polished, and then the ingot is ultrasonically inspected using a 2 MHz high-frequency probe, and the parts that do not meet the head and tail inspection are cut off. ≥8 points are taken at the head, middle and tail of the side of the ingot for component detection, and the extreme difference of alloy elements in the ingot is ≤0.2%, and the extreme difference of Fe and O elements is ≤0.02%.

[0037] The present invention also discloses a TA16 titanium alloy VAR ingot prepared by the method of any embodiment of the present invention.

[0038] The following are specific embodiments

[0039] Example 1

[0040] The production specification is φ500mm / 1t grade nuclear small size TA16 titanium alloy ingot, including the following steps:

[0041] Step 1: Weigh and mix 0A grade small-grain titanium sponge (particle size 2-10mm), nuclear grade zirconium sponge (particle size 2-10mm), aluminum particles, titanium dioxide, and titanium-iron alloy according to the proportion of ingredients (mixing time 45s), press electrode blocks, and weld multiple electrode blocks to obtain consumable electrodes.

[0042] Step 2: Weld the consumable electrode in step 1 with the vacuum consumable melting auxiliary electrode. Use the same brand of auxiliary electrodes as much as possible, and control the gap between the consumable electrode and the crucible wall to about 40mm. After welding, break the air to check the weld. After the weld is qualified, re-evacuate the vacuum to ≤0.8Pa, and the leak rate is ≤0.8Pa / min.

[0043] Step 3: After the leakage rate of step 2 is qualified, the first smelting is carried out. The smelting process is divided into arc starting, stabilization, and shrinkage stages. The arc starting stage is controlled for 20 minutes. The smelting current in the arc starting stage is 14kA. The current increases linearly to the smelting current. After the edge of the molten pool reaches the crucible wall, it enters the stable smelting stage; the energy density in the stable smelting stage is 3360kJ / mm, and the smelting speed (kg / min) and the electrode diameter (mm) are 0.017; the shrinkage time in the shrinkage stage is 45 minutes, and the smelting current is linearly reduced to 3kA.

[0044] Step 4: After the power is turned off for the first smelting in step 3, continue to maintain the vacuum for 1 hour, then fill with argon 1000Pa for cooling, and the cooling time is 6.5 hours; after the ingot is taken out of the furnace, it is peeled 2mm according to the surface condition of the ingot to ensure that the surface impurities and oxidation parts are removed cleanly; the riser end (shrinkage feeding end) of the ingot is flattened.

[0045] Step 5: Turn around and weld the primary ingot obtained in step 4, that is, weld the arc-starting end of the primary ingot to the auxiliary electrode, and then carry out the second smelting after the vacuum degree is ≤0.5Pa and the leakage rate is ≤0.5Pa / min. The control time of the arc-starting stage of the secondary smelting is 25min, the smelting current in the arc-starting stage is 16kA, and the current increases linearly to the smelting current; the energy density in the stable smelting stage is 4032kJ / mm, and the ratio of the smelting speed (kg / min) to the electrode diameter (mm) is 0.024; in the shrinkage stage, the shrinkage weight is 120±20kg, the shrinkage time is 130min, and the smelting current is linearly reduced to 4.5kA

[0046] Step 6: After the surface of the secondary smelting ingot obtained in step 5 is polished, a 2MHz high-frequency probe is used to perform ultrasonic flaw detection on the ingot. After the parts that do not meet the head and tail flaw detection are cut off, 8 points are taken at the head, middle and tail of the side of the ingot for composition detection. The extreme difference of Al element is 0.16%, the extreme difference of Zr element is 0.18%, the extreme difference of Fe is 0.013%, and the extreme difference of O is 0.015%.

[0047] The present invention adopts two VAR smelting processes and global medium energy density input to prepare TA16 titanium alloy ingots, the smelting process is short, and the obtained φ500mm / 1t grade nuclear small-size TA16 titanium alloy ingots have uniform high composition and no metallurgical defects.

[0048] Example 2

[0049] The production specification is φ660mm / 2t grade TA16 titanium alloy ingot for welding materials, including the following steps:

[0050] Step 1: Weigh and mix 0A grade small-grain titanium sponge (particle size 1-20 mm), nuclear grade zirconium sponge (particle size 1-20 mm), aluminum particles, titanium dioxide, and titanium-iron alloy according to the proportion of ingredients (mixing time 30 seconds), press electrode blocks, and weld multiple electrode blocks to obtain consumable electrodes.

[0051] Step 2: Weld the consumable electrode in step 1 with the vacuum consumable melting auxiliary electrode. Use the same brand of auxiliary electrodes as much as possible, and control the gap between the consumable electrode and the crucible wall to about 40mm. After welding, break the air to check the weld. After the weld is qualified, re-evacuate the vacuum to ≤0.8Pa, and the leak rate is ≤0.8Pa / min.

[0052] Step 3: After the leakage rate of step 2 is qualified, the first smelting is carried out. The smelting process is divided into arc starting, stabilization, and shrinkage stages. The arc starting stage is controlled for 25 minutes. The smelting current in the arc starting stage is 16kA. The current increases linearly to the smelting current. After the edge of the molten pool reaches the crucible wall, it enters the stable smelting stage; the energy density in the stable smelting stage is 3377kJ / mm, and the smelting speed (kg / min) and the electrode diameter (mm) are 0.019; the shrinkage time in the shrinkage stage is 50 minutes, and the smelting current is linearly reduced to 4kA.

[0053] Step 4: After the power is turned off for the first smelting in step 3, continue to maintain the vacuum for 1 hour, then fill with argon 1000Pa for cooling, and the cooling time is 8 hours; after the ingot is taken out of the furnace, peel 3mm according to the surface condition of the ingot to ensure that the surface impurities and oxidation parts are cleanly peeled off; flatten the riser end (shrinkage feeding end) of the ingot.

[0054] Step 5: The primary ingot obtained in step 4 is turned around for welding, that is, the arc-starting end of the primary ingot is welded to the auxiliary electrode, and the vacuum degree is ≤0.5Pa and the leakage rate is ≤0.5Pa / min, and then the second smelting is carried out. The arc-starting stage of the secondary smelting is controlled for 25min, the smelting current in the arc-starting stage is 24kA, and the current increases linearly to the smelting current; the energy density in the stable smelting stage is 4320kJ / mm, and the ratio of the smelting speed (kg / min) to the electrode diameter (mm) is 0.021; in the feeding stage, the feeding weight is 200±40kg, the feeding time is 150min, and the smelting current is linearly reduced to 6kA.

[0055] Step 6: After the surface of the secondary smelting ingot obtained in step 5 is polished, a 2MHz high-frequency probe is used to perform ultrasonic flaw detection on the ingot. After the parts that do not meet the head and tail flaw detection are cut off, 8 points are taken at the head, middle and tail of the side of the ingot for composition detection. The extreme difference of Al element is 0.14%, the extreme difference of Zr element is 0.13%, the extreme difference of Fe is 0.012%, and the extreme difference of O is 0.010%.

[0056] The present invention adopts two VAR smelting processes and global medium energy density input to prepare TA16 titanium alloy ingots, the smelting process is short, and the obtained φ600mm / 2t grade TA16 titanium alloy ingots for welding materials have uniform high composition and no metallurgical defects.

[0057] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing TA16 titanium alloy ingots with global medium energy density input, characterized in that: The following steps are involved: (1) pressing a mixture of titanium sponge, zirconium sponge and master alloy into an electrode block, and welding a plurality of electrode blocks to obtain a consumable electrode; (2) welding the consumable electrode and the vacuum consumable melting auxiliary electrode to obtain a welding electrode; (3) subjecting the welding electrode to a first melting, wherein the first melting includes an arc starting stage, a stabilization stage, and a shrinkage feeding stage. After the first melting, the electrode is kept vacuumed, and then cooled by argon filling. The obtained ingot is peeled and flattened to obtain a primary ingot. (4) The first ingot is subjected to a reverse welding and then subjected to a second smelting, wherein the second smelting includes a secondary arc starting stage, a secondary stabilization stage, and a secondary shrinkage compensation stage. The surface of the second smelted ingot obtained after the second smelting is polished to obtain the TA16 titanium alloy ingot.

2. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (1), the titanium sponge is a 0A grade small-grain titanium sponge with a particle size of 1 to 20 mm; and the zirconium sponge is a nuclear grade zirconium sponge with a particle size of 1 to 20 mm.

3. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (1), the mixing time is ≥ 30 s.

4. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (2), the gap between the consumable electrode and the crucible wall is 30 to 50 mm; after welding is completed, the weld is inspected by breaking the air, and after the weld is qualified, the vacuum is re-drawn ≤1Pa, and the leak detection rate is ≤0.8Pa / min.

5. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (3), the control time of the primary arc starting stage is ≤25min, the melting current of the primary arc starting stage is 10kA-16kA, the current increases linearly to the melting current, and enters a primary stable stage after the edge of the molten pool reaches the crucible wall; the energy density of the primary stable stage is 2800kJ / mm-3600kJ / mm, and the ratio of melting speed (kg / min) to electrode diameter (mm) is 0.015-0.030:1; the feeding time of the primary feeding stage is ≥30min, and the melting current is linearly reduced to 2kA-4kA.

6. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (3), after the first smelting is completed, the vacuum is continued for ≥1h after the power is turned off, and then argon is filled with ≥800Pa for cooling, and the cooling time is ≥6h.

7. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (4), the second melting is carried out after the vacuum degree of the U-turn welding is ≤0.5Pa and the leakage rate is ≤0.5Pa / min.

8. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (4), the control time of the secondary arc starting stage is ≤25min, the melting current of the secondary arc starting stage is 12kA-24kA, and the current increases linearly to the melting current; the energy density of the stable stage is 3600kJ / mm-5000kJ / mm, and the ratio of melting speed (kg / min) to electrode diameter (mm) is 0.020-0.035:1; the feeding weight of the secondary feeding stage satisfies 8%M-15%M, M is the ingot weight, the feeding time is ≥120min, and the melting current is linearly reduced to 3kA-6kA.

9. The method for preparing TA16 titanium alloy ingot by global medium energy density input according to claim 1, characterized in that: In step (4), the surface of the secondary smelting ingot obtained after the second smelting is polished, and then the ingot is ultrasonically inspected using a 2 MHz high-frequency probe, and the parts that do not meet the head and tail inspection are cut off. ≥8 points are taken at the head, middle and tail of the side of the ingot for component detection. The extreme difference of alloy elements in the ingot is ≤0.2%, and the extreme difference of Fe and O elements is ≤0.02%.

10. A TA16 titanium alloy VAR ingot prepared by the method according to any one of claims 1 to 9.