阅读说明：本技术 钛合金铸锭及其制备方法 (Titanium alloy ingot and preparation method thereof ) 是由 肖祥澳 李超 樊凯 潘艺夫 陈领 于 2021-08-18 设计创作，主要内容包括：本发明涉及一种钛合金铸锭及其制备方法,包括步骤：以含有易偏析元素的钛合金非成品锭作为自耗电极,采用真空自耗电弧熔炼进行成品熔炼,所述成品熔炼包括依次进行的稳定熔炼阶段和补缩阶段；所述补缩阶段的熔炼电流逐级降低,且各级的熔炼电流降低速率依次为(0.02～0.5)KA/min→(0.02～0.2)KA/min→(0.2～2)KA/min→(0.02～0.2)KA/min。本发明在常规补缩工艺的基础上,大幅降低补缩阶段前期的电流降低速率,并控制各级的电流降低速率,如此实现缓慢抬升熔池、降低熔池深度,在降低缩孔深度的同时,减轻冒口区心部元素偏析倾向,从而改善冒口区成分偏析和β斑的问题。(The invention relates to a titanium alloy ingot and a preparation method thereof, comprising the following steps: taking a titanium alloy non-finished product ingot containing easily segregated elements as a consumable electrode, and smelting a finished product by adopting vacuum consumable arc smelting, wherein the smelting of the finished product comprises a stable smelting stage and a feeding stage which are sequentially carried out; the smelting current in the feeding stage is gradually reduced, and the reduction rate of the smelting current in each stage is sequentially (0.02-0.5) KA/min → (0.02-0.2) KA/min → (0.2-2) KA/min → (0.02-0.2) KA/min. On the basis of the conventional feeding process, the current reduction rate at the early stage of the feeding stage is greatly reduced, and the current reduction rates of all stages are controlled, so that the molten pool is slowly lifted, the depth of the molten pool is reduced, the segregation tendency of the core element of the riser area is reduced while the depth of a shrinkage cavity is reduced, and the problems of component segregation and beta spot of the riser area are solved.)

1. A preparation method of a titanium alloy ingot is characterized by comprising the following steps:

taking a titanium alloy non-finished product ingot containing easily segregated elements as a consumable electrode, and smelting a finished product by adopting vacuum consumable arc smelting, wherein the smelting of the finished product comprises a stable smelting stage and a feeding stage which are sequentially carried out; the smelting current in the feeding stage is gradually reduced, and the reduction rate of the smelting current in each stage is sequentially (0.02-0.5) KA/min → (0.02-0.2) KA/min → (0.2-2) KA/min → (0.02-0.2) KA/min.

2. The preparation method of claim 1, wherein the smelting current in the stable smelting stage is 7KA to 25KA, the smelting voltage is 24V to 36V, the arc stabilizing current is AC 1A to 20A, and the stirring period is 1s to 20 s.

3. The method according to claim 2, wherein the feeding stage process is performed at KA/V/min:

(6～10)/(25～28)/(15～60)→(5～8)/(25～27)/(25～60)→(4～6)/(24～27)/(1～20)→(2.5～4)/(23～26)/(30～120)。

4. the preparation method according to any one of claims 1 to 3, wherein the arc stabilizing current in the feeding stage is AC 1A to 15A, and the arc stabilizing period is 1s to 20 s; in the feeding stage, the arc stabilizing current is gradually reduced along with the gradual reduction of the smelting current.

5. The preparation method according to claim 4, wherein in the feeding stage, the arc stabilizing current process corresponding to each stage of melting current is (6-14) A → (5-10) A → (4-8) A → (2-6) A.

6. The method of any one of claims 1 to 3, further comprising a step of preparing the non-finished ingot of titanium alloy by:

preparing raw materials required for preparing a titanium alloy ingot into an electrode block, and performing vacuum consumable arc melting for at least 1 time by taking the electrode block as a consumable electrode to obtain the titanium or titanium alloy non-finished product ingot.

7. The method according to claim 6, wherein in the step of preparing the non-finished titanium alloy ingot, the vacuum consumable arc melting has a melting current of 11KA to 25KA, a melting voltage of 29V to 36V, an arc stabilizing current of 6A to 18A, a vacuum degree of 10.0Pa or less, and a cooling time after melting is not less than 4 hours.

8. The preparation method according to any one of claims 1 to 3, wherein the diameter specification of the consumable electrode is phi 420mm to phi 820mm, the diameter specification of the prepared titanium alloy ingot casting product is phi 500mm to phi 900mm, and the total weight is 2000Kg to 12000 Kg; and starting to enter the feeding stage when the weight of the remaining unfused consumable electrode after the finished product is smelted is 60-600 Kg.

9. The production method according to any one of claims 1 to 3, wherein the titanium alloy unfinished ingot containing an easily segregatable element contains Cu.5 wt.% or Fe.1.0 wt.% or Cr.2.0 wt.% or Mo.5.0 wt.% or Nb.8.0 wt.% or Cu + Fe.0.7 wt.% or Cr + Fe.2.0 wt.% or Cr + Cu.1.5 wt.% or Mo + Nb.7 wt.%.

10. A titanium alloy ingot produced by the production method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of titanium alloy, in particular to a titanium alloy ingot and a preparation method thereof.

Background

When the titanium alloy is smelted in a vacuum consumable electrode (VAR) way, a titanium alloy ingot is gradually and upwards solidified from the bottom of the ingot in sequence, and the equilibrium distribution coefficient K of each alloy element in the titanium alloy₀The difference of the degrees of segregation makes some alloy elements of the titanium alloy ingot regularly distributed at each part of the whole ingot to generate segregation effect. Equilibrium distribution coefficient K₀Elements more than 1 can be enriched at the bottom and the edge of the ingot, and the process is called positive segregation; equilibrium distribution coefficient K₀The element less than 1 can be enriched in the head part and the core part of the ingot, and is called negative segregation. K₀The further away from 1, the greater the tendency to segregate; meanwhile, the higher the content of the segregation-prone alloy elements in the titanium alloy is, the greater the segregation degree is. Common segregation-prone elements include Cu, Fe, Cr, Mo, Nb, and the degree of segregation K₀0.27, 0.3, 0.56, 1.83 and 1.58 respectively, wherein Cu, Fe and Cr are negative segregation elements, and Mo and Nb are positive segregation elements.

And in the final stage of the titanium alloy VAR smelting, the shrinkage cavity and the loosening depth of the head of the cast ingot are reduced by adopting a step-by-step current reduction mode, the current reduction rate is gradually reduced, and the feeding time generally accounts for 1/4-1/3 of the total smelting time. For the easily segregated alloy, the riser area is the final solidification part of the ingot, and the electric arc heats the central molten pool of the head of the ingot for a long time in the feeding process, so that sufficient thermodynamic and kinetic conditions are provided for the diffusion and segregation of the segregation elements, and the phenomena of segregation of negative segregation elements and depletion of positive segregation elements in the center of the riser area are aggravated. When the core component of the dead head area is segregated to a certain degree, irregular beta spots are formed.

The conventional feeding method usually reduces current rapidly in the early stage of feeding to realize rapid reduction of heat input and lifting of shrinkage cavity, but cannot solve the problem of component segregation of a riser region of an ingot, and the component segregation of the head of the conventional feeding method cannot be completely eliminated after the shrinkage cavity is sawn, so that the structural performance of the head of a bar in subsequent bar forging is deteriorated and beta spots are caused. In order to avoid the quality influence of the composition segregation of the riser area of the ingot on the forged bar, the minimum sawing amount is usually determined, and the riser is additionally sawed, so that the cutting amount of the head of the ingot is large, and the yield loss is increased.

Disclosure of Invention

Accordingly, there is a need for a titanium alloy ingot and a method for producing the same, which can improve the problems of center component segregation and β -spots in the riser region of an easily segregating titanium alloy ingot.

A preparation method of a titanium alloy ingot comprises the following steps:

taking a titanium alloy non-finished product ingot containing easily segregated elements as a consumable electrode, and smelting a finished product by adopting vacuum consumable arc smelting, wherein the smelting of the finished product comprises a stable smelting stage and a feeding stage which are sequentially carried out; the smelting current in the feeding stage is gradually reduced, and the reduction rate of the smelting current in each stage is sequentially (0.02-0.5) KA/min → (0.02-0.2) KA/min → (0.2-2) KA/min → (0.02-0.2) KA/min.

In some embodiments, the smelting current in the stable smelting stage is 7 KA-25 KA, the smelting voltage is 24V-36V, the arc stabilizing current is AC 1A-20A, and the stirring period is 1 s-20 s.

In some of these embodiments, the process KA/V/min of the feeding stage is:

(6～10)/(25～28)/(15～60)→(5～8)/(25～27)/(25～60)→(4～6)/(24～27)/(1～20)→(2.5～4)/(23～26)/(30～120)。

in some embodiments, the arc stabilizing current in the feeding stage is AC 1A-15A, and the arc stabilizing period is 1 s-20 s; in the feeding stage, the arc stabilizing current is gradually reduced along with the gradual reduction of the smelting current.

In some embodiments, in the feeding stage, the arc stabilizing current process corresponding to the smelting current at each stage is (6-14) A → (5-10) A → (4-8) A → (2-6) A.

In some of these embodiments, the method of making further comprises the step of making the titanium alloy unfinished ingot:

preparing raw materials required for preparing a titanium alloy ingot into an electrode block, and performing vacuum consumable arc melting for at least 1 time by taking the electrode block as a consumable electrode to obtain the titanium or titanium alloy non-finished product ingot.

In some embodiments, in the step of preparing the titanium alloy non-finished product ingot, the melting current of the vacuum consumable arc melting is 11KA to 25KA, the melting voltage is 29V to 36V, the arc stabilizing current is 6A to 18A, the vacuum degree is below 10.0Pa, and the cooling time after melting is not less than 4 hours.

In some embodiments, the diameter specification of the consumable electrode is phi 420 mm-phi 820mm, the diameter specification of the prepared titanium alloy ingot casting finished product is phi 500 mm-phi 900mm, and the total weight is 2000 Kg-12000 Kg; and starting to enter the feeding stage when the weight of the remaining unfused consumable electrode after the finished product is smelted is 60-600 Kg.

In some embodiments, the titanium alloy unfinished ingot containing the easily segregated element contains Cu more than or equal to 0.5 wt% or Fe more than or equal to 1.0 wt% or Cr more than or equal to 2.0 wt% or Mo more than or equal to 5.0 wt% or Nb more than or equal to 8.0 wt% or Cu + Fe more than or equal to 0.7 wt% or Cr + Fe more than or equal to 2.0 wt% or Cr + Cu more than or equal to 1.5 wt% or Mo + Nb more than or equal to 7.0 wt%.

A titanium alloy ingot is prepared by the preparation method.

According to the invention, on the basis of a conventional feeding process, the current reduction rate at the early stage of the feeding stage is greatly reduced, and the current reduction rates of all stages are controlled to be (0.02-0.5) KA/min → (0.02-0.2) KA/min → (0.2-2) KA/min → (0.02-0.2) KA/min in sequence, so that the molten pool is slowly lifted, the depth of the molten pool is reduced, the segregation tendency of elements in the center of a riser is reduced while the depth of a shrinkage cavity is reduced, the problems of component segregation and beta spot in the riser area are improved, and the feeding effect is improved.

Drawings

FIG. 1 is a schematic diagram showing a longitudinal section of a feeder head area of examples 1 to 4 of the present invention and comparative examples 1 to 4;

FIG. 2 is a graph showing the results of measuring the composition of a sample taken from a longitudinal section of a riser area of TC17 having a size of 680mm in example 1 of the present invention;

FIG. 3 is a photograph of macrostructures of a longitudinal section of a riser area TC17 having a diameter of 680mm in example 1 of the present invention after heat treatment at 25 ℃ below the transformation point;

FIG. 4 is a graph showing the results of measuring the composition of a sample taken from a longitudinal section of a riser area of TB6 having a diameter of 680mm in example 2 of the present invention;

FIG. 5 is a graph showing the results of measuring the composition of a sample taken from a longitudinal section of a riser area of a TC32 ingot with a diameter of 780mm according to example 3 of the present invention;

FIG. 6 is a graph showing the results of measuring the composition of a sample taken from a longitudinal section of a riser area of TC32 ingot of phi 880mm gauge according to example 4 of the present invention;

FIG. 7 is a photograph of a macrostructure of a longitudinal section of a feeder region TC17 having a diameter of 680mm in comparative example 1 of the present invention after heat treatment at 25 ℃ or less than the transformation point.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

An embodiment of the present invention provides a method for producing a titanium alloy ingot, including the steps of:

taking a titanium alloy non-finished product ingot containing easily segregated elements as a consumable electrode, and smelting a finished product by adopting vacuum consumable arc smelting, wherein the smelting of the finished product comprises a stable smelting stage and a feeding stage which are sequentially carried out; the smelting current in the feeding stage is gradually reduced, and the reduction rate of the smelting current in each stage is sequentially (0.02-0.5) KA/min → (0.02-0.2) KA/min → (0.2-2) KA/min → (0.02-0.2) KA/min.

Wherein, the unit KA/min is kiloampere per minute, and means the value of current reduction per minute.

Wherein the segregation-prone element comprises at least one of Cu, Fe, Cr, Mo and Nb.

The technical personnel of the invention find through a great deal of research that the rapid current reduction in the early stage of the feeding stage is one of the keys of causing the composition segregation and the serious beta spot of the easily segregated alloy dead head area. Further, within a certain range of the current reduction rate, the segregation degree has positive correlation with the magnitude of the current reduction rate. Therefore, on the basis of a conventional feeding process, the current reduction rate in the early stage of the feeding stage is greatly reduced, and the current reduction rates of all stages are controlled to be (0.02-0.5) KA/min → (0.02-0.2) KA/min → (0.2-2) KA/min → (0.02-0.2) KA/min in sequence, so that the molten pool is slowly lifted, the depth of the molten pool is reduced, the tendency of element segregation in the top opening area is reduced while the depth of a shrinkage cavity is reduced, the problems of component segregation and beta spot in the top opening area are solved, and the feeding effect is improved.

In addition, due to the reduction of the depth of the shrinkage cavity, the yield loss caused by extra sawing can be reduced, and the yield can be improved.

By controlling the current reduction rate in the early stage of the feeding stage to be greatly reduced and controlling the current reduction rate in each stage to be in the range, the consumable electrode can be enabled to store a complete residual plate after the feeding stage, so that the phenomenon that the residual plate falls off due to coring in the last stage of smelting and the riser depth is increased is avoided, in addition, an oxide layer exists in a welding nodule welded by the auxiliary electrode, and the phenomenon that the welding nodule is melted into a molten pool to cause local oxygen-enriched segregation can be avoided by keeping the complete residual.

In some embodiments, the smelting current in the stable smelting stage is 7 KA-25 KA, the smelting voltage is 24V-36V, the arc stabilizing current is AC (alternating current arc stabilizing) 1A-20A, and the stirring period is 1 s-20 s.

Further, the smelting current in the first stable smelting stage is 13 KA-17 KA, the smelting voltage is 32V-33V, and the arc stabilizing current is AC (alternating current arc stabilizing) 10A-15A.

Furthermore, the smelting current in the second stable smelting stage is 19KA to 25KA, the smelting voltage is 33V to 35V, and the arc stabilizing current is AC (alternating current arc stabilizing) 12A to 18A.

Further, the process KA/V/min at the feeding stage is as follows:

(6～10)/(25～28)/(15～60)→(5～8)/(25～27)/(25～60)→(4～6)/(24～27)/(1～20)→(2.5～4)/(23～26)/(30～120)。

in one specific example, the process at the feeding stage is KA/V/min: 7.5/26.5/45 → 6/26/45 → 5/25/2 → 2.5/24/70. Here is represented by: within 45min, the smelting current and the smelting voltage are linearly changed to 7.5KA and 26.5V respectively; then, in 45min, the smelting current and the smelting voltage are respectively changed into 6KA and 26V in a linear mode, namely the smelting current in 45min is reduced by 1.5KA in a linear mode, the smelting voltage is reduced by 0.5V in a linear mode, and the current reduction rate is 0.03 KA/min; then, within 2min, the smelting current and the smelting voltage are respectively changed into 5KA and 25V in a linear mode; then, the melting current and the melting voltage are changed into 2.5KA and 24V respectively in a linear way within 70 min. The labels of this class have the same meaning.

In some embodiments, the arc stabilizing current in the feeding stage is AC 1A-15A, and the arc stabilizing period is 1-20 s; in the feeding stage, the arc stabilizing current is gradually reduced along with the gradual reduction of the smelting current.

Further, in the feeding stage, the arc stabilizing current process corresponding to the melting current at each stage is (6-14) A → (5-10) A → (4-8) A → (2-6) A.

Furthermore, in the feeding stage, the arc stabilizing current process corresponding to the smelting current at each stage is (10-12) A → (8-10) A → (6-8) A → (4-6) A.

In some embodiments, the method for preparing a titanium alloy ingot further comprises the step of preparing a titanium alloy unfinished ingot:

preparing raw materials required for preparing the titanium alloy ingot into an electrode block, and performing vacuum consumable arc melting for at least 1 time by taking the electrode block as a consumable electrode to obtain a titanium alloy non-finished product ingot.

Further, the preparation steps of the titanium alloy non-finished ingot comprise: preparing materials and mixing materials according to raw materials required for preparing a titanium alloy ingot, and then pressing into an electrode block; generally, a plurality of electrode blocks obtained by pressing are required to be stacked and welded into a long welding electrode, the welding electrode is subjected to vacuum consumable arc melting for at least 1 time, and the consumable electrode in the S1 is obtained by flat head after being cooled and discharged from a furnace. Wherein, the welding step can be carried out by adopting a vacuum plasma welding mode.

Further, in the step of preparing the titanium alloy non-finished product ingot, the smelting current of vacuum consumable arc smelting is 11 KA-25 KA, the smelting voltage is 29V-36V, the arc stabilizing current is 6A-18A, the vacuum degree is below 10.0Pa, and the cooling time after smelting is not less than 4 hours. The arc stabilizing current can be alternating current or direct current, or AC/DC.

Specifically, the preparation steps of the titanium alloy non-finished ingot comprise the following specific steps S1-S3.

S1: preparing raw materials required by preparing a titanium alloy ingot, mixing the raw materials, pressing the raw materials into an electrode block, loading the electrode block into the center of a crucible with a corresponding specification, placing the electrode block into a vacuum consumable arc furnace, installing an auxiliary electrode on a pneumatic chuck of an electrode rod, sealing the furnace, and vacuumizing.

S2: when the pre-vacuum is below 5.0Pa and the leakage rate is below 1.0Pa/min, butt welding the auxiliary electrode and the consumable electrode in a vacuum electric arc furnace, cooling for no less than 45min after welding, opening the furnace to clean weld beading, sealing the furnace again and evacuating.

S3: when the pre-vacuum reaches below 1.33Pa and the leak rate is below 0.6Pa/min, carrying out vacuum consumable arc melting on the welded electrode for 2 times, carrying out first and second vacuum consumable arc melting, controlling the vacuum degree below 10.0Pa, the melting current at 11-25 KA, the melting voltage at 29-36V and the arc stabilizing current at 6-18A in the two melting processes, and cooling for not less than 4 hours after melting to obtain a titanium alloy non-finished product ingot.

In some embodiments, the diameter specification of the consumable electrode is phi 420 mm-phi 820mm, the diameter specification of the prepared titanium alloy ingot casting finished product is phi 500 mm-phi 900mm, and the total weight is 2000 Kg-12000 Kg; and starting to enter a feeding stage when the weight (namely the reserved weight) of the remaining unfused consumable electrode in finished product smelting is 60 Kg-600 Kg. Further, the reserve weight at the beginning of the feeding phase varies with the magnitude of the smelting current at the end of the stable smelting phase, and in particular increases with the increase of the smelting current at the end of the stable smelting phase.

Further, the specification of the crucible in the step of smelting the finished product is phi 500-phi 900 mm.

In some embodiments, the titanium alloy unfinished ingot containing the easily segregated element contains Cu ≥ 0.5 wt%, Fe ≥ 1.0 wt%, Cr ≥ 2.0 wt%, Mo ≥ 5.0 wt%, Nb ≥ 8.0 wt%, Cu + Fe ≥ 0.7 wt%, Cr + Fe ≥ 2.0 wt%, Cr + Cu ≥ 1.5 wt%, or Mo + Nb ≥ 7.0 wt%.

In some specific examples, the titanium alloy ingots produced are TC17, TB6, TC32 titanium alloys.

In order to make the objects, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The following described examples are only preferred embodiments of the present invention, which can be used to describe the present invention and should not be construed as limiting the scope of the present invention. It should be understood that any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Example 1:

1) a preparation process of TC17 (nominal component Ti-5Al-2Sn-2Zr-4Mo-4Cr) titanium alloy ingot with phi 680mm specification comprises the following steps:

the selected raw materials are uniformly mixed according to elements and proportion required by TC17 alloy, then pressed into TC17 electrode blocks with the size of phi 420 multiplied by 200mm on an oil press, the pressed electrode blocks are combined into electrodes with the size of phi 420 multiplied by 4800mm, and then the electrodes are welded into the consumable electrode for smelting in a plasma welding box under the protection of argon. Melting a welding electrode for 2 times by adopting vacuum consumable arc, controlling the vacuum degree below 10.0Pa in the first and second vacuum consumable arc melting, wherein the stable melting current of the first melting is 13KA, the melting voltage is 32V, and the stable arc current is 10A; and the secondary smelting stable smelting current is 21KA, the smelting voltage is 35V, the arc stabilizing current is 12A, the cooling time after smelting is not less than 4 hours, and the TC17 titanium alloy non-finished ingot with the phi 580mm specification is obtained.

Taking a flat-headed TC17 titanium alloy non-finished ingot with the specification of phi 580mm as a consumable electrode, smelting a finished product in a vacuum consumable arc furnace, wherein the specification of a crucible is phi 680mm, the smelting current is 13KA, the smelting voltage is 29V, the arc stabilizing current is AC 12A, the stirring period is 10s, and when the consumable electrode is remained with 350Kg, feeding is started by gradually reducing the current, and the reduction rate of the smelting current is about (unit, KA/min): 0.12 → 0.03 → 0.5 → 0.04. The specific process for reducing the current step by step is (KA/V/min):

7.5/26.5/45 → 6/26/45 → 5/25/2 → 2.5/24/70, the arc stabilizing current for each stage is (A): 10 → 8 → 6 → 4. Then tripping and cooling to obtain a titanium alloy finished product ingot.

2) Performance detection

The head of the TC17 titanium alloy ingot with the diameter of 680mm prepared by the process is subjected to ultrasonic flaw detection, and a flaw signal is found only at a position 45mm away from the end face of the head.

And sawing a riser at a position 100mm away from the end face of the head of the ingot of the TC17 titanium alloy with the specification of phi 680mm prepared by the process, longitudinally cutting the riser along the central axis, and sampling and analyzing the chemical component distribution of main elements and the beta spot inspection of the longitudinal section of the riser area.

FIG. 1 is a schematic diagram of a longitudinal section sampling of an ingot riser, and the positions of 1-15 sampling points are shown on the schematic diagram, wherein R is the radius of the ingot. FIG. 2 is a graph showing the results of component detection of a longitudinal section of a feeder head region of a TC17 ingot having a diameter of 680mm, wherein the fluctuation of the elemental composition of the main elements Al, Sn, Zr, Mo and Cr is 0.13, 0.08, 0.12, 0.13 and 0.15 in wt.%.

As can be seen from FIG. 2, the obtained TC17 titanium alloy ingot had good compositional uniformity in the head region, and had a variation in the macro-composition of the main element within 2000 ppm. Wherein, the abscissa is the position of the sampling point label shown in fig. 1, and the ordinate is the mass percentage content of the element in unit%; the same applies below.

FIG. 3 is a photograph of a macrostructure of a titanium alloy cast ingot riser area of TC17 with the specification of phi 680mm, which is prepared by the process, longitudinally cut along a central axis, and then subjected to heat treatment at a temperature of below 25 ℃ of a phase transition point, and the result shows that: no beta spot generated by micro-component segregation is found on the longitudinal hypoid structure of the dead head area.

Example 2:

1) a preparation process of a phi 680mm specification TB6 (nominal component Ti-10V-2Fe-3Al) titanium alloy ingot comprises the following steps:

the selected raw materials are uniformly mixed according to the elements and the proportion required by the TB6 alloy, then the raw materials are pressed into a TB6 electrode block with the size of phi 420 multiplied by 200mm on an oil press, the pressed electrode blocks are combined into an electrode with the size of phi 420 multiplied by 4800mm, and then the electrode is welded into a consumable electrode for smelting in a plasma welding box under the protection of argon. Melting a welding electrode for 2 times by adopting vacuum consumable arc, controlling the vacuum degree below 10.0Pa in the first and second vacuum consumable arc melting, wherein the stable melting current of the first melting is 13KA, the melting voltage is 32V, and the stable arc current is 10A; and the secondary smelting has stable smelting current of 19KA, smelting voltage of 34V, arc stabilizing current of 12A and cooling time not less than 4 hours after smelting to obtain phi 580mm specification TB6 titanium alloy ingot.

Taking a flat-headed TB6 titanium alloy ingot with the specification of phi 580mm as a consumable electrode, smelting a finished product in a vacuum consumable arc furnace, wherein the specification of a crucible is phi 680mm, the smelting current is 12KA, the smelting voltage is 29V, the arc stabilizing current is AC 12A, the stirring period is 10s, and when the consumable electrode is left for 260Kg, feeding is started by adopting step-by-step current reduction, and the current reduction rate is about (KA/min) in sequence: 0.09 → 0.02 → 0.5 → 0.04. The specific process for reducing the current step by step is (KA/V/min):

7/26.5/35 → 6/26/45 → 5/25/2 → 2.5/24/70, the arc stabilizing current corresponding to each stage is (A): 10 → 8 → 6 → 4, then tripping and cooling to obtain the finished titanium alloy ingot.

2) Performance detection

Ultrasonic flaw detection is carried out on the head of the TB6 ingot with the diameter of 680mm prepared by the process, and a defect signal is only found at a position 35mm away from the end face of the head.

And sawing a riser at a position 100mm away from the end face of the head of the ingot from the TB6 ingot with the specification of phi 680mm prepared by the process, longitudinally cutting the riser along the central axis, and sampling and analyzing the chemical component distribution of main elements and checking beta spots of the longitudinal section of the riser area. The longitudinal section sampling schematic diagram of the cast ingot riser is shown in figure 1.

FIG. 4 is a graph showing the results of component detection of a longitudinal section of a feeder head region of a TB6 ingot having a diameter of 680mm, wherein the fluctuations of the elemental compositions of Al, V and Fe, which are major elements, are 0.13, 0.17 and 0.16, respectively, in wt.%.

As can be seen from FIG. 4, the obtained TB6 alloy ingot has good composition uniformity in the riser region, and the macroscopic composition deviation of the main element is within 2000 ppm.

The riser area of the TB6 ingot with the phi 680mm specification prepared in the above way is longitudinally cut along the central axis, and then the macrostructure is observed after heat treatment at 25 ℃ below the phase transformation point, and no beta spot generated by microcosmic component segregation is found on the longitudinally cut macrostructure of the riser area.

Example 3:

1) a preparation process of TC32 (nominal component Ti-5Al-3Mo-3Cr-1Zr-0.15Si) titanium alloy ingot with the specification of phi 780mm comprises the following steps:

according to the elements and the proportion required by the TC32 alloy, the selected raw materials are uniformly mixed and then pressed into a TC32 electrode block with the size of phi 480 multiplied by 200mm on an oil press, the pressed electrode blocks are combined into an electrode with the size of phi 480 multiplied by 4800mm, and then the electrode is welded into a consumable electrode for smelting in a plasma welding box under the protection of argon. Melting a welding electrode for 2 times by adopting vacuum consumable arc, controlling the vacuum degree below 10.0Pa in the first and second vacuum consumable arc melting, wherein the stable melting current of the first melting is 15KA, the melting voltage is 33V, and the stable arc current is 10A; and the secondary smelting has stable smelting current of 25KA, smelting voltage of 35V, arc stabilizing current of 15A and cooling time not less than 4 hours after smelting to obtain TC32 titanium alloy ingots with phi 680mm specification.

Taking a flat-headed TC32 titanium alloy ingot with the specification of phi 680mm as a consumable electrode, smelting a finished product in a vacuum consumable arc furnace, wherein the specification of a crucible is phi 780mm, the smelting current is 19KA, the smelting voltage is 33V, the arc stabilizing current is AC 16A, the stirring period is 12s, and when the consumable electrode is left for 500Kg, feeding is started by adopting step-by-step current reduction, and the current reduction rate is about (KA/min) in sequence: 0.33 → 0.04 → 0.5 → 0.04. The specific process for reducing the current step by step is (KA/V/min):

8.5/27/35 → 6.5/26.5/45 → 5.5/26/2 → 3/24.5/60, the arc stabilizing current of each stage is (A): 12 → 10 → 8 → 6, then tripping and cooling to obtain the finished titanium alloy ingot.

2) Performance detection

The head of the TC32 cast ingot with the diameter of 780mm prepared by the process is subjected to ultrasonic flaw detection, and a defect signal is only found at a position 40mm away from the end face of the head.

And sawing a riser at a position 100mm away from the end face of the head of the cast ingot, and longitudinally cutting the cast ingot with the TC32 with the specification of phi 780mm, wherein the cast ingot is prepared by the process, and sampling and analyzing the chemical component distribution of main elements and the beta spot inspection are carried out on the longitudinal section of the riser area. The longitudinal section sampling schematic diagram of the cast ingot riser is shown in figure 1.

FIG. 5 is a graph showing the results of component detection of a longitudinal section of a feeder head region of a TC32 ingot with a phi 780mm standard, wherein the fluctuation of the elemental composition of Al, Mo, Cr, Zr and Si is 0.13, 0.15, 0.16, 0.12 and 0.016 in wt.%.

As can be seen from FIG. 5, the obtained TC32 alloy ingot had good compositional uniformity in the riser region, and had a major element macro-compositional deviation within 2000 ppm.

The riser area of TC32 ingot with the phi 780mm specification prepared in the above way is longitudinally cut along the central axis, and then the macrostructure is observed after heat treatment at 25 ℃ below the phase transformation point, and no beta spot generated by microcosmic component segregation is found on the longitudinally cut macrostructure of the riser area.

Example 4:

1) a preparation process of TC32 (nominal component Ti-5Al-3Mo-3Cr-1Zr-0.15Si) titanium alloy ingot with a phi 880mm specification comprises the following steps:

according to the elements and the proportion required by the TC32 alloy, the selected raw materials are uniformly mixed and then pressed into a TC32 electrode block with the size of phi 580 multiplied by 200mm on an oil press, the pressed electrode blocks are combined into an electrode with the size of phi 580 multiplied by 4800mm, and then the electrode is welded into a consumable electrode for smelting in a plasma welding box under the protection of argon. Melting a welding electrode for 2 times by adopting vacuum consumable arc, controlling the vacuum degree below 10.0Pa in the first and second vacuum consumable arc melting, wherein the stable melting current of the first melting is 17KA, the melting voltage is 33V, and the stable arc current is 12A; and the secondary smelting has stable smelting current of 25KA, smelting voltage of 35V and arc stabilizing current of 18A, and cooling time after smelting is not less than 5 hours, so as to obtain TC32 titanium alloy ingots with phi 780mm specification.

Taking a flat-headed TC32 titanium alloy ingot with the specification of phi 780mm as a consumable electrode, smelting a finished product in a vacuum consumable arc furnace, wherein the specification of a crucible is phi 880mm, the smelting current is 22KA, the smelting voltage is 34V, the arc stabilizing current is AC 18A, the stirring period is 15s, and when the consumable electrode is left for 600Kg, feeding is started by adopting step-by-step current reduction, and the current reduction rate is about (KA/min) in sequence: 0.4 → 0.06 → 0.75 → 0.04. The specific process for reducing the current step by step is (KA/V/min):

10/28.5/30 → 7.5/26.5/45 → 6/25/2 → 3/24.5/75, the arc stabilizing current for each stage is (A): 12 → 10 → 8 → 6, then tripping and cooling to obtain the finished titanium alloy ingot.

2) Performance detection

Ultrasonic flaw detection is carried out on the head of the TC32 cast ingot with the diameter of phi 880mm prepared by the feeding process, and a defect signal is only found at a position 45mm away from the end face of the head.

And sawing a riser at a position 100mm away from the end face of the head of the cast ingot, and longitudinally cutting the cast ingot with the TC32 of the phi 880mm specification prepared by the feeding process along the central axis, and sampling and analyzing the chemical component distribution of main elements and the beta spot inspection of the longitudinal section of the riser area. The longitudinal section sampling schematic diagram of the cast ingot riser is shown in figure 1.

FIG. 6 is a graph showing the results of component measurement of a longitudinal section of a feeder head region of a TC32 ingot with a phi 880mm specification, wherein the component fluctuations of the main elements Al, Mo, Cr, Zr and Si are 0.15, 0.17, 0.12 and 0.015 in wt.%.

As can be seen from FIG. 6, the obtained TC32 alloy ingot had good compositional uniformity in the riser region, and had a major element macro-compositional deviation within 2000 ppm.

The riser area of TC32 cast ingot with phi 880mm specification prepared by the steps is longitudinally cut along the central axis, heat treatment is carried out at 25 ℃ below the phase transformation point, and then the macrostructure is observed, and no beta spot generated by microconstituent segregation is found on the longitudinally cut macrostructure of the riser area.

Comparative example 1:

comparative example 1 is essentially the same as example 1, except that: the reduction rate of the smelting current in the feeding stage of finished product smelting is about (KA/min) in sequence: 1 → 0.5 → 0.05 → 0.03. Specifically, the other steps are the same, except that: and (3) smelting a finished product in a vacuum consumable electric arc furnace until the consumable electrode is melted to the residual 180Kg, and feeding by reducing current step by step, wherein the process of reducing the current is (KA/V/min): 8/28/5 → 7/27/2 → 5/26/40 → 2.5/25/90, then tripping and cooling to obtain the finished ingot of titanium alloy.

After obtaining a finished titanium alloy ingot, when flaw detection is carried out on the side surface of the ingot, a shrinkage cavity signal is found to exist at a position 80mm away from the end surface of the head of the ingot.

And sawing a riser at a position 100mm away from the end face of the head of the ingot, longitudinally cutting along the central axis, and sampling and analyzing the chemical component distribution of main elements and detecting beta spots of the longitudinal section of the riser area.

Wherein, the distribution result of the chemical components of the main elements shows that: the compositional fluctuations of Al, Sn, Zr, Mo and Cr elements were 0.26, 0.10, 0.22, 0.34 and 0.42, respectively, and it was found that the distribution uniformity of the main elements in comparative example 1 was lower than that in example 1. The results of the beta plaque examination are shown in FIG. 7, which is a macroscopic structure of the feeder region after heat treatment at 25 ℃ below the transformation point in the longitudinal section. The results show that: a clear white and bright beta-spot area exists in the center of a part 100mm away from the end face of the head.

Comparative example 2:

comparative example 2 is substantially the same as example 2 except that: the current reduction rate in the feeding stage of the finished product smelting is about (KA/min) in turn: 0.8 → 0.5 → 0.04 → 0.03. Specifically, the other steps are the same, except that: and (3) smelting a finished product in a vacuum consumable electric arc furnace until the consumable electrode remains 250Kg, and feeding by reducing current step by step, wherein the process of reducing current is (KA/V/min): 8/28/5 → 7/27/2 → 5/25/50 → 2.5/25/82, then tripping and cooling to obtain the finished ingot of titanium alloy.

After obtaining a finished titanium alloy ingot, when flaw detection is carried out on the side surface of the ingot, a shrinkage cavity signal is found to exist at a position 75mm away from the end surface of the head of the ingot.

And sawing a riser at a position 100mm away from the end face of the head of the ingot, longitudinally cutting along the central axis, and sampling and analyzing the chemical component distribution of main elements and detecting beta spots of the longitudinal section of the riser area.

Wherein, the distribution result of the chemical components of the main elements shows that: the compositional fluctuations of Al, V and Fe elements were 0.22, 0.29 and 0.46, respectively, and it was found that the distribution uniformity of the main elements in comparative example 2 was lower than that in example 2. The longitudinal section of the riser area is subjected to heat treatment at a temperature of 25 ℃ below the phase transformation point, and a white and bright beta-spot area exists in a heart macrostructure 100mm away from the end face of the head.

Comparative example 3:

comparative example 3 is substantially the same as example 3 except that: the reduction rate of the smelting current in the feeding stage of finished product smelting is about (KA/min) in sequence: 1.5 → 0.5 → 0.04 → 0.03. Specifically, the other steps are the same, except that: and (3) smelting a finished product in a vacuum consumable electric arc furnace until the consumable electrode remains 250Kg, and feeding by reducing current step by step, wherein the process of reducing current is (KA/V/min): 9/29/6 → 7.5/27/3 → 5.5/26/50 → 3/25/80, and then tripped and cooled to obtain the finished ingot of titanium alloy.

After obtaining a finished titanium alloy ingot, when flaw detection is carried out on the side surface of the ingot, a shrinkage cavity signal is found to exist at a position 65mm away from the end surface of the head of the ingot.

And sawing a riser at a position 100mm away from the end face of the head of the ingot, longitudinally cutting along the central axis, and sampling and analyzing the chemical component distribution of main elements and detecting beta spots of the longitudinal section of the riser area.

Wherein, the distribution result of the chemical components of the main elements shows that: the compositional fluctuations of Al, Mo, Cr, and Zr elements were 0.24, 0.25, 0.39, and 0.19, respectively, and it was found that the distribution uniformity of the main elements in comparative example 3 was lower than that in example 3. The longitudinal section of the riser area is subjected to heat treatment at a temperature of 25 ℃ below the phase transformation point, and a white and bright beta-spot area exists in a heart macrostructure 100mm away from the end face of the head.

Comparative example 4:

comparative example 4 is essentially the same as example 4, except that: the reduction rate of the smelting current in the feeding stage of finished product smelting is about (KA/min) in sequence: 2 → 0.8 → 0.04 → 0.03. Specifically, the other steps are the same, except that: when finished products are smelted in a vacuum consumable electric arc furnace until the consumable electrode reaches 300Kg, feeding is started by reducing current step by step, and the process of reducing current is (KA/V/min): 10/30/6 → 7.5/27/3 → 5.5/26/55 → 3.5/25/75, and then tripping and cooling to obtain a finished ingot of titanium alloy.

After obtaining a titanium alloy finished product ingot, when flaw detection is carried out on the side surface of the ingot, a shrinkage cavity signal is found to exist at a position 85mm away from the end surface of the head of the ingot.

And sawing a riser at a position 100mm away from the end face of the head of the ingot, longitudinally cutting along the central axis, and sampling and analyzing the chemical component distribution of main elements and detecting beta spots of the longitudinal section of the riser area.

Wherein, the distribution result of the chemical components of the main elements shows that: the compositional fluctuations of Al, Mo, Cr, and Zr elements were 0.29, 0.31, 0.44, and 0.18, respectively, and it can be seen that the distribution uniformity of the main elements in comparative example 4 was lower than that in example 4. The longitudinal section of the riser area is subjected to heat treatment at a temperature of 25 ℃ below the phase transformation point, and a white and bright beta-spot area exists in a heart macrostructure 100mm away from the end face of the head.

According to comparative examples 1-4, in the finished product smelting of titanium alloy, for easily segregated alloy with higher content of segregated elements, the riser area is the final solidification part of the cast ingot, feeding is carried out by adopting the step-by-step current reduction mode, and the reduction rate of the smelting current in the early stage is higher, so that the phenomena of segregation element segregation and depletion of positive segregation elements in the center of the riser area are aggravated. When the core component of the dead head area is segregated to a certain degree, irregular beta spots are formed. As ingot diameter increases, both the size and the tendency to form beta plaques increase.

In embodiments 1 to 4 of the invention, by optimizing the step-by-step current reduction process, the current reduction rate in the early stage of the feeding stage is greatly reduced, and the current reduction rates of the respective stages are controlled to be (0.02 to 0.5) KA/min → (0.02 to 0.2) KA/min → (0.2 to 2) KA/min → (0.02 to 0.2) KA/min in sequence, so that the problems of component segregation and β spots in a feeder head area are solved, and the feeding effect is improved.

In addition, the invention greatly reduces the depth of the shrinkage cavity, greatly reduces the cutting amount of the head of the cast ingot compared with the comparative example, and further improves the yield. For example, comparative example 4 has a shrinkage cavity signal at a position 85mm away from the end face of the head of the ingot, so that the head of the ingot is cut off in a large amount. Whereas example 4 found a defect signal only at 45mm from the head end face, i.e. the shrinkage cavity depth was greatly reduced.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims, and the description and the drawings can be used for explaining the contents of the claims.