A method for preparing a high-molybdenum equivalent titanium alloy ingot

Abstract

The application discloses a preparation method of high-molybdenum equivalent titanium alloy ingot, and the preparation method is suitable for preparing titanium alloy ingots with a diameter of greater than or equal to 600 mm and comprises the following steps: step S1, various raw materials with a predetermined proportion are weighed respectively, and the various raw materials are sieved to obtain various coarse-particle-diameter raw materials that do not pass through the sieve holes and various fine-particle-diameter raw materials that pass through the sieve holes; step S2, the various fine-particle-diameter raw materials are uniformly mixed for the first time, and nine electrode rods are prepared after the uniform mixing; step S3, the various coarse-particle-diameter raw materials are uniformly mixed for the second time, the uniformly mixed coarse-particle-diameter raw materials are poured into the die cavity of a hydraulic press, the electrode rods are uniformly distributed in the die cavity of the hydraulic press and are inserted into the coarse-particle-diameter raw materials, and then an electrode block is prepared by using the hydraulic press; and step S4, each electrode block is sequentially subjected to assembly welding and smelting processing to obtain a finished titanium alloy ingot; and the application improves the uniformity of raw material distribution and effectively solves the problem that high-molybdenum equivalent titanium alloy ingots are prone to segregation during smelting.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy, and particularly relates to a preparation method of high-molybdenum-equivalent titanium alloy ingot. BACKGROUND

[0002] According to the method of classifying titanium alloys according to the size of molybdenum equivalent, high-molybdenum-equivalent titanium alloys are mainly represented by beta titanium alloys and TC21, TC18, TC12 and other “alpha+beta” two-phase titanium alloys containing Mo, V and Cr. Due to the multiple types and high contents of alloying elements, the alloys have strong solid solution strengthening and second phase dispersion strengthening effects, and thus have excellent high-temperature creep performance, endurance performance and damage tolerance performance, which can greatly prolong the service life and service cycle of aero-engine structural parts. Under the environment of continuously pursuing weight reduction of aircraft in the aviation industry, the outstanding advantages of the above-mentioned titanium materials in terms of light weight, high strength and high temperature resistance will make them have great potential in related fields.

[0003] High contents of high-melting-point elements and beta-stabilizing elements such as Cr, Fe and V which are prone to segregation are the main characteristics of high-molybdenum-equivalent titanium alloy materials in terms of element composition. At present, such alloys are generally produced by VAR melting. During melting, the intermediate alloy and titanium sponge are uniformly mixed and pressed into electrode blocks, and the electrode blocks are welded and then melted into ingots for use. Due to the characteristics of the processing technology, the particle size of the intermediate alloy containing Mo and Nb is generally below 1 mm at present. Such intermediate alloy is prone to the following problems during melting:

[0004] 1. During raw material mixing and pressing, local accumulation layers are formed by dropping into the lower part along the gaps of the raw materials;

[0005] 2. The small-particle intermediate alloy containing Mo and Nb (particle size not greater than 1 mm) has a high melting point, and the local accumulation layers cannot be homogenized by melting, resulting in local accumulation and macroscopic segregation of the material, thereby causing scrap. The electrode preparation method of mixing and pressing after mixing cannot avoid the above problems. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of high-molybdenum-equivalent titanium alloy ingot to solve the problem of ingot segregation caused by adding small-particle intermediate alloy, i.e. the fine-particle raw materials are prone to falling into the bottom of the electrode to form local accumulation during raw material mixing and electrode block pressing, and the local accumulation is prone to incomplete melting during subsequent melting, thereby causing macroscopic segregation.

[0007] The present application adopts the following technical scheme: a preparation method of high-molybdenum-equivalent titanium alloy ingot, the preparation method is suitable for preparing titanium alloy ingots with a diameter of not less than 600 mm, and comprises the following steps:

[0008] Step S1: Weigh various raw materials in a predetermined ratio respectively, and screen various raw materials using a sieve with a screen hole diameter of 3 mm to obtain various coarse particle size raw materials that do not pass through the screen holes and various fine particle size raw materials that pass through the screen holes;

[0009] Step S2: Mix various fine particle size raw materials for the first time. After mixing, pour them into a semi - continuous electrode extruder to prepare 9 electrode rods;

[0010] Step S3: Mix various coarse particle size raw materials for the second time. After mixing, pour them into the mold cavity of a hydraulic press. Distribute the 9 electrode rods evenly in the mold cavity of the hydraulic press and insert them into the coarse particle size raw materials, and then press them using the hydraulic press to obtain an electrode block;

[0011] Step S4: Repeat steps S1 - S3 to obtain a predetermined number of electrode blocks, and successively perform group welding and melting on each electrode block to obtain a finished titanium alloy ingot.

[0012] Further, when inserting each electrode rod, insert the electrode rod vertically.

[0013] Further, when distributing each electrode rod, the arrangement method of the electrode rods is as follows:

[0014] Place 1 electrode rod at the center position of the mold cavity of the hydraulic press,

[0015] Take 4 electrode rods and arrange them in a circular pattern around the center position of the mold cavity of the hydraulic press with the center position as the axis, such that the connection lines of the 4 electrode rods form a square,

[0016] Take 4 electrode rods and arrange them respectively at the center positions of each side of the square so that the 9 electrode rods are arranged in a "rice" shape.

[0017] Further, the mixing time for the first mixing in step S2 is 60 - 90 s.

[0018] Further, the diameter of the electrode rod is Φ20 - 50 mm.

[0019] Further, the mixing time for the second mixing in step S3 is 120 - 180 s.

[0020] Further, the melting in step S4 includes first melting, second melting, and third melting;

[0021] The conditions for the first melting are: melting current is 6 - 9 kA, melting voltage is 31 - 33 V, arc - stabilizing current is 8 - 10 A, and AC stirring time is 15 s;

[0022] The conditions for the second melting are: melting current is 13 - 18 kA, melting voltage is 31 - 33 V, arc - stabilizing current is 9 - 12 A, and AC stirring time is 15 s;

[0023] The third melting condition is: the melting current is 17-22kA, the melting voltage is 31-33V, the arc stabilizing current is 10-14A, and the AC stirring time is 15-30s.

[0024] The beneficial effects of the present application are:

[0025] The present application is based on the combination of semi-continuous extrusion method and traditional mixing process, and the raw materials are screened according to the predetermined ratio. First, the fine particle size raw materials are mixed, and a semi-continuous electrode extruder is used to prepare an electrode rod with a diameter of Φ20-50mm in a cylindrical shape. Then, the coarse particle size raw materials are mixed and poured into the mold cavity of a hydraulic machine. The electrode rod is uniformly inserted into the mold cavity of the hydraulic machine to prepare the electrode. Finally, the finished product is obtained through assembly welding and melting processing.

[0026] The present application can significantly improve the electrode density and distribution uniformity, and is suitable for the production of large size homogeneous ingots. The fine particle size raw materials are densified through the electrode extrusion process, effectively avoiding the problem of sinking and agglomeration of the fine particle size raw materials when they are dispersedly distributed. At the same time, the mixing method is combined to make the electrode rod obtained by extrusion uniformly arranged inside the electrode block, improving the raw material distribution uniformity and effectively solving the problem of easy segregation of high-molybdenum equivalent titanium alloy ingot during the melting process, thereby improving the composition uniformity.

[0027] The present application uses a semi-continuous extruder to extrude a small size electrode rod, avoiding the dropping and accumulation of fine particle size raw materials during the pressing process. The electrode rod is inserted into the coarse particle size raw materials to form a distribution pattern of the coarse particle size raw materials evenly wrapping the electrode rod. During the melting process, the peripheral area of the electrode rod is preferentially melted, and the latent heat released by the preferentially melted coarse particle size raw materials melts the wrapped electrode rod, thereby making the melting of the coarse particle size raw materials and the fine particle size raw materials tend to be synchronized, and the metal convection and solute diffusion are more sufficient, and the alloy element distribution is uniformized, thereby fundamentally solving the problem of easy segregation of high-molybdenum equivalent ingot. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a plan view of the electrode rod arrangement of the present application.

[0029] Figure 2 It is a side view of the electrode rod of the present application.

[0030] Among them, 1, electrode rod; 2, peripheral area. DETAILED DESCRIPTION

[0031] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0032] The present application discloses a preparation method of a high-molybdenum equivalent titanium alloy ingot, which is suitable for preparing titanium alloy ingots with a diameter of ≥Φ600 and consists of the following steps:

[0033] Step S1: Weigh various raw materials with a particle size range of 0.83 - 25.4 mm in a predetermined ratio, and screen the various raw materials using a sieve mesh with a sieve hole diameter of 3 mm to obtain various coarse particle size raw materials that do not pass through the sieve holes and various fine particle size raw materials that pass through the sieve holes. The raw materials at least include titanium sponge and aluminum molybdenum.

[0034] Step S2: First, mix the various fine particle size raw materials, and after mixing, pour them into a semi - continuous electrode extrusion machine to prepare 9 electrode rods 1. Each electrode rod 1 is a columnar structure; the length of the electrode rod 1 is equal to the height of the die cavity of the hydraulic press.

[0035] Step S3: Second, mix the various coarse particle size raw materials, and after mixing, pour them into the die cavity of the hydraulic press. Distribute the electrode rods 1 evenly in the die cavity of the hydraulic press and insert them into the coarse particle size raw materials. Then, use the hydraulic press to press to obtain an electrode block. When inserting each electrode rod 1, insert the electrode rod 1 vertically. Furthermore, the height of the prepared electrode block is equal to the length of the electrode rod 1.

[0036] Uniformly lay the mixture of various coarse particle size raw materials in the die cavity of the hydraulic press, insert the electrode rods 1 into the mixture of various coarse particle size raw materials in sequence and arrange them in an array. The electrode rods 1 in adjacent rows are staggered, that is, the electrode rods 1 in adjacent rows are arranged in a staggered manner, and their arrangement method is as Figure 1 and Figure 2 shown. When distributing each electrode rod 1, the arrangement method of the electrode rod 1 is: place 1 electrode rod 1 at the center position of the die cavity of the hydraulic press, take 4 electrode rods 1 and arrange them in a circular pattern around the center position of the die cavity of the hydraulic press, so that the connection lines of the 4 electrode rods 1 form a square. Take 4 electrode rods 1 and arrange them at the center position of each side of the square respectively, so that the 9 electrode rods 1 are arranged in a "cross" shape.

[0037] During the melting process, the outer peripheral area 2 of the electrode rod 1 melts first. The latent heat of crystallization released by the preferentially melted coarse particle size raw materials causes the wrapped electrode rod to melt. Furthermore, the melting of the coarse particle size raw materials and the fine particle size raw materials tends to be synchronized, metal convection and solute diffusion are more sufficient, and the distribution of alloy elements reaches homogenization, thus fundamentally solving the problem that high - molybdenum - equivalent ingots are prone to segregation.

[0038] Step S4: Repeat steps S1 - S3 to obtain a predetermined number of electrode blocks, and successively perform group welding and melting on each electrode block to obtain a finished titanium alloy ingot.

[0039] During preparation, when weighing various raw materials in a predetermined ratio in step S1, it can be weighed according to the amount used for a single electrode block, and 9 electrode rods are prepared in step S2. Figure 1For the arrangement mode of the 9 electrode rods 1, the connecting line of the 8 electrode rods 1 located at the edge forms a square, and 1 electrode rod 1 is inserted into the center position of the square, 9 electrode rods 1 are inserted into the coarse-grained raw material to prepare an electrode block, and then the steps S1-S3 are repeated to prepare a predetermined number of electrode blocks, and then each electrode block is sequentially subjected to group welding and smelting processing in step S4 to obtain a finished titanium alloy ingot.

[0040] In step S2, the mixing time of the first mixing is 60-90s, and the diameter of the electrode rod 1 is Φ20-50mm. The diameter of the electrode rod 1 can be adaptively adjusted according to the die cavity area of the hydraulic machine. In step S3, the mixing time of the second mixing is 120-180s. The distance between the electrode rods 1 can be calculated by the formula: (D1-3D2-60) / 3, wherein D1 is the diagonal length of the die cavity of the hydraulic machine, and D2 is the diameter of the electrode rod.

[0041] In step S4, the smelting includes first smelting, second smelting and third smelting. The first smelting conditions are: smelting current is 6-9kA, smelting voltage is 31-33V, arc current is 8-10A, and AC stirring time is 15s. The second smelting conditions are: smelting current is 13-18kA, smelting voltage is 31-33V, arc current is 9-12A, and AC stirring time is 15s. The third smelting conditions are: smelting current is 17-22kA, smelting voltage is 31-33V, arc current is 10-14A, and AC stirring time is 15-30s.

[0042] For the problem of segregation, in recent years, there have been reports that sponge titanium is mixed with Mo-containing alloy by grinding (Patent No. CN200710188547.9). However, the average mixing time of the single electrode block is as long as 1-5h, and the production efficiency is low. At the same time, some methods try to improve the alloy preparation means, gradually introducing powder metallurgy into the preparation of intermediate alloy, that is, first using powder metallurgy to prepare intermediate alloy rods (Patent No. CN113322388A), and then crushing into flaky intermediate alloy with appropriate particle size (Patent No. CN10527843A). However, the powder metallurgy method has high cost and long process. More importantly, the flaky intermediate alloy is light in quality, and has weak binding capacity with the base alloy during pressing, and is also easy to fall into the molten pool during smelting, thereby forming local segregation. Therefore, the problem of segregation has not been well solved.

[0043] Example 1

[0044] This embodiment takes TB9 alloy as an example to illustrate the preparation method of the present application in detail.

[0045] Step S1: take 79.9 kg of titanium sponge with a particle size of 0.83-25.4 mm, 6.405 kg of aluminum-molybdenum 60 alloy with a particle size of 0-0.5 mm, 1.671 kg of titanium-molybdenum 32 alloy with a particle size of 0-5 mm, 10.5 kg of aluminum-vanadium 85 alloy with a particle size of 1-6 mm, 4.407 kg of zirconium sponge with a particle size of 3-15 mm, 6.545 kg of metallic chromium with a particle size of 1-3 mm, and 0.5712 kg of titanium-iron 32 alloy with a particle size of 3-6 mm, and screen the various raw materials using a screen with a mesh size of 3 mm to obtain coarse particle size raw materials and fine particle size raw materials.

[0046] Step S2: take the various fine particle size raw materials for the first time mixing, the mixing time is 70 s, and pour into a semi-continuous electrode extruder to obtain 9 electrode rods 1 with a diameter of Φ35 mm and a length of 275 mm.

[0047] Step S3: take the various coarse particle size raw materials for the second time mixing, the mixing time is 180 s, pour into the cavity of a 3500T hydraulic machine, uniformly distribute the electrode rods 1 in the cavity of the hydraulic machine and insert the coarse particle size raw materials, the interval of the electrode rods 1 is 131 mm, and then press using the hydraulic machine to obtain electrode blocks with a specification of Φ560*275 mm; repeat the above steps for 14 times to obtain 14 electrode blocks.

[0048] Step S4: weld, melt and process the electrode blocks according to 1*14 groups to obtain finished titanium alloy ingots, wherein the melting includes first time melting, second time melting and third time melting, the conditions of the first time melting are that the melting current is 9 kA, the melting voltage is 31-33 V, the stable arc current is 10 A, and the alternating current stirring time is 15 s; the conditions of the second time melting are that the melting current is 18 kA, the melting voltage is 31-33 V, the stable arc current is 12 A, and the alternating current stirring time is 15 s; the conditions of the third time melting are that the melting current is 22 kA, the melting voltage is 31-33 V, the stable arc current is 14 A, and the alternating current stirring time is 15 s.

[0049] After lathe flat head and skinning of the product prepared in the embodiment, take the chip-like samples from the head and upper, middle upper, middle, middle lower and lower of the ingot respectively for composition analysis, and the composition analysis results are shown in Table 1:

[0050] Table 1: Main element composition of the prepared TB9 alloy

[0051]

[0052] Example 2

[0053] This embodiment takes TC12 alloy as an example to illustrate the preparation method of the application in detail. The preparation method of this embodiment is the same as that of Example 1, except that:

[0054] In step S1, 91.8 kg of titanium sponge with a particle size of 0.83-25.4 mm, 2.573 kg of zirconium sponge with a particle size of 3-15 mm, 3.132 kg of titanium-tin 80 alloy with a particle size of 0-5 mm, 6.331 kg of aluminum-molybdenum 60 alloy with a particle size of 0-0.5 mm, 1.872 kg of aluminum-niobium 60 alloy with a particle size of 0-1.2 mm, 4.699 kg of chromium flake with a particle size of 1-3 mm, and 2.366 kg of aluminum bean with a particle size of 3-18 mm are weighed, and a sieve with a mesh size of 3 mm is selected;

[0055] In step S2, the mixing time of the first mixing is 90 s; the prepared electrode stick 1 has a diameter of Φ20 mm and a length of 275 mm;

[0056] In step S3, the mixing time of the second mixing is 150 s; the interval of each electrode stick 1 is 123 mm, and the prepared electrode block has a specification of Φ490×275 mm.

[0057] In step S4, the difference of the smelting conditions is that the smelting current is 7 kA and the arc stabilizing current is 8 A in the first smelting, the smelting current is 15 kA and the arc stabilizing current is 9 A in the second smelting, and the smelting current is 19 kA and the arc stabilizing current is 12 A in the third smelting.

[0058] After the lathe flat head and skinning of the product prepared in the embodiment are performed, the scrap-like samples are taken from the head and upper, middle upper, middle, middle lower, and lower of the ingot, respectively, for component analysis, and the component analysis results are shown in Table 2:

[0059] Table 2 Component of TC12 alloy prepared

[0060]

[0061] Example 3

[0062] The preparation method of the embodiment is described in detail taking TC18 alloy as an example, and the preparation method of the embodiment is the same as that of Example 1, except that:

[0063] In step S1, 96.5 kg of titanium sponge with a particle size of 0.83-25.4 mm, 1.204 kg of chromium flake with a particle size of 1-6 mm, 9.808 kg of aluminum-molybdenum 60 alloy with a particle size of 0-0.5 mm, 3.682 kg of aluminum-vanadium 85 alloy with a particle size of 1-6 mm, and 1.666 kg of aluminum bean with a particle size of 3-18 mm are weighed, and a sieve with a mesh size of 3 mm is selected;

[0064] In step S2, the mixing time of the first mixing is 60 s; the prepared electrode stick 1 has a diameter of Φ50 mm and a length of 275 mm;

[0065] The mixing time of the second mixing in step S3 is 120 s; the interval of each electrode rod 1 is 143 mm, and the electrode block with a size of Φ640x275 mm is prepared.

[0066] In step S4, the melting conditions are different: the melting current is 6 kA and the arc current is 8 A in the first melting, the melting current is 13 kA and the arc current is 10 A in the second melting, and the melting current is 17 kA, the arc current is 10 A and the AC stirring time is 30 s in the third melting.

[0067] After lathe flat head and skinning of the product prepared in the embodiment, the scrap-like samples are taken from the head and upper, middle upper, middle, middle lower and lower of the ingot respectively for composition analysis, and the composition analysis results are shown in Table 3:

[0068] Table 3: Main element composition of the prepared TC18 alloy

[0069]

[0070] In embodiments 1-3, the main element difference of the obtained ingot is not greater than 0.15 wt.%, and the composition uniformity is good, which indicates that the method is practical and feasible, and can be used for preparing homogenized high-molybdenum equivalent titanium alloy ingot.

[0071] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a high-molybdenum equivalent titanium alloy ingot, characterized in that, The described preparation method is applicable to the preparation of titanium alloy ingots with a diameter ≥ Ф600mm, and consists of the following steps: Step S1: Weigh various raw materials according to a predetermined ratio, and screen various raw materials using a sieve mesh with a sieve pore diameter of 3mm to obtain various types of coarse particle size raw materials that do not pass through the sieve pores and various types of fine particle size raw materials that pass through the sieve pores; Step S2: First mix various types of fine particle size raw materials, and after mixing, pour them into a semi - continuous electrode extrusion machine to prepare 9 electrode rods (1); Step S3: Second mix various types of coarse particle size raw materials, and after mixing, pour them into the mold cavity of a hydraulic press. Arrange the 9 electrode rods (1) evenly in the mold cavity of the hydraulic press and insert them into the coarse particle size raw materials, and then use the hydraulic press to press to obtain an electrode block; Step S4: Repeat Steps S1 - S3 to obtain a predetermined number of electrode blocks, and successively perform group welding and melting on each electrode block to obtain a finished titanium alloy ingot.

2. The method for preparing a high-molybdenum equivalent titanium alloy ingot according to claim 1, characterized in that, When inserting each electrode rod (1), insert the electrode rod (1) vertically.

3. The method for preparing a high-molybdenum equivalent titanium alloy ingot according to claim 1, characterized in that, When arranging each electrode rod (1), the arrangement method of the electrode rods (1) is as follows: Place 1 electrode rod (1) at the center position of the mold cavity of the hydraulic press, Take 4 electrode rods (1) and arrange them in a circular arrangement around the center position of the mold cavity of the hydraulic press so that the connection lines of the 4 electrode rods (1) form a square, Take 4 electrode rods (1) and arrange them at the center position of each side of the square so that the 9 electrode rods (1) are arranged in a "rice" shape.

4. A method for preparing a high-molybdenum equivalent titanium alloy ingot according to claim 2 or 3, characterized in that, The mixing time for the first mixing in Step S2 is 60 - 90s.

5. The method for preparing a high-molybdenum equivalent titanium alloy ingot according to claim 4, characterized in that, The diameter of the electrode rod (1) is Φ20 - 50mm.

6. The method for preparing a high-molybdenum equivalent titanium alloy ingot according to claim 5, characterized in that, The mixing time for the second mixing in Step S3 is 120 - 180s.

7. The method for preparing a high-molybdenum equivalent titanium alloy ingot according to claim 6, characterized in that, The melting in Step S4 includes first melting, second melting, and third melting; The conditions for the first melting are: melting current is 6 - 9kA, melting voltage is 31 - 33V, arc - stabilizing current is 8 - 10A, and AC stirring time is 15s; The conditions for the second melting are: melting current is 13 - 18kA, melting voltage is 31 - 33V, arc - stabilizing current is 9 - 12A, and AC stirring time is 15s; The conditions for the third melting are: melting current is 17 - 22kA, melting voltage is 31 - 33V, arc - stabilizing current is 10 - 14A, and AC stirring time is 15 - 30s.

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