CN110724852A - WSTi1400 ultrahigh-strength titanium alloy and preparation method thereof - Google Patents
WSTi1400 ultrahigh-strength titanium alloy and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of titanium alloy processing, and relates to a WSTi1400 ultrahigh-strength titanium alloy which comprises the following elements in percentage by weight: cr: 5.0% -9.0%, Mo: 4.0% -8.0%, V: 3.0% -7.0%, Al: 2.0% -6.0%, Nb: 0.0 to 4.0 percent of Fe, less than or equal to 2.00 percent of Fe, less than or equal to 0.30 percent of O, and the balance of Ti and inevitable impurities, wherein the sum of the weight percentages of the components is 100 percent. The titanium alloy prepared by the method has high transverse and longitudinal uniformity, breaks through the chemical composition uniformity control technology of industrial ton-grade large-size cast ingots, reduces the burning loss of aluminum elements in the smelting process, avoids the metallurgical defects of non-melting blocks formed by high-melting-point molybdenum, vanadium and niobium elements and the like, and obtains the titanium alloy with the strength of more than 1400MPa and the fracture toughness of more than 55 MPa.m0.5The titanium alloy rod of (1).
Description
Technical Field
The invention belongs to the technical field of titanium alloy processing, and particularly relates to a WSTi1400 ultrahigh-strength titanium alloy and a preparation method thereof.
Background
With the development of aerospace technology, the development of domestic high-performance aviation equipment urgently needs an ultrahigh-strength and high-toughness titanium alloy suitable for large-size aviation structural parts, wherein the strength requirement of the titanium alloy is more than 1400MPa, and the fracture toughness is more than 55 MPa.m0.5. At present, no titanium alloy meeting the requirements exists at home and abroad, and the high-strength titanium alloy for aviation structural parts which is already in service and is produced in large scale comprises Ti55531, Ti5553, TC18 and TB6, the design strength of the titanium alloy is not more than 1300MPa, and the fracture toughness of the titanium alloy is about 40 MPa.m0.5。
WSTi1400 is an ultrahigh-strength near-beta titanium alloy with 1400MPa level, nominal components are Ti-7Cr-6Mo-5V-4Al-1Nb-0.5Fe, slow eutectoid elements Cr, Mo and Fe are improved on the basis of Ti55531 and Ti5553, the strength and toughness of the material are facilitated, a beta eutectic element Nb of Ti is introduced, and the room-temperature plasticity, hot workability and welding performance of the material are improved. In addition, the alloy has small content of impurity elements in gaps, improves the damage tolerance performance of the material, and can meet the design requirement of long service life of structural parts.
In order to obtain comprehensive matching of strength, toughness and fatigue performance, a large amount of molybdenum, chromium, vanadium, aluminum, iron and niobium are added into the WSTi1400 alloy, and because the alloy contains a large amount of slow eutectoid elements and insoluble elements, the problems of easy element segregation, rich niobium non-melting blocks and other metallurgical defects are solved, and meanwhile, due to the addition of a large amount of beta stable elements, the alloy has low phase change point, large deformation resistance and difficult control of deformation uniformity in the forging process. Therefore, the composition uniformity control technology and the bar structure uniformity control technology are the technical difficulties and key technologies for preparing the alloy.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the WSTi1400 ultrahigh-strength titanium alloy and the preparation method thereof, which solve the problem of controlling the uniformity of the components of easily segregated elements such as molybdenum, chromium and iron and high melting point elements such as molybdenum, vanadium and niobium in the WSTi1400 alloy.
In order to achieve the purpose, the invention provides the following technical scheme:
in one aspect, the invention provides a WSTi1400 ultrahigh-strength titanium alloy, which consists of the following elements in percentage by weight: cr: 5.6% -7.5%, Mo: 4.8% -6.5%, V: 4.6-5.3%, Al: 3.8% -4.5%, Nb: 0.8 to 1.3 percent of Fe, less than or equal to 0.8 percent of O, less than or equal to 0.30 percent of O, the balance of Ti and inevitable impurities, the total amount of impurity elements is less than or equal to 0.30 percent, and the sum of the weight percentages of the components is 100 percent.
Furthermore, the elements Cr, Mo, V, Al, Nb and Fe are derived from binary and multi-element master alloys.
Furthermore, the multi-element intermediate alloy is made of AlMoVCr quaternary alloy, Nb is added in the form of Nb47Ti, Mo is added in the form of AlMo alloy, and V is added in the form of AlV alloy, so that the segregation risk of high-melting-point alloy such as Mo, Cr and Nb is reduced.
Furthermore, the Ti adopts 0.83-12.7 mm of granular titanium sponge.
On the other hand, the invention also provides a preparation method of the WSTi1400 ultrahigh-strength titanium alloy, which comprises the following steps:
step 1), preparing an electrode:
the materials are prepared according to the following weight percentages: cr: 5.6% -7.5%, Mo: 4.8% -6.5%, V: 4.6-5.3%, Al: 3.8% -4.5%, Nb: 0.8 to 1.3 percent of Fe, less than or equal to 0.8 percent of O, less than or equal to 0.30 percent of O, the balance of Ti and inevitable impurities, the total amount of impurity elements is less than or equal to 0.30 percent, and the sum of the weight percentages of the components is 100 percent; carrying out single-block electrode mixing on the mixture, and pressing into an electrode block;
step 2), welding a consumable electrode:
clamping the electrode block obtained in the step 1) by using a clamp, and welding the electrode block into a consumable electrode by using a non-tungsten argon protection plasma box;
step 3), carrying out three times of vacuum melting on the consumable electrode obtained in the step 2) by adopting a vacuum consumable electric arc furnace to obtain a WSTi1400 titanium alloy ingot;
step 4), heating the WSTi1400 titanium alloy ingot obtained in the step 3) to 930-1200 ℃ above a phase transition point for 3-5 times of upsetting-drawing forging, keeping the temperature for 120-720 min, then discharging, carrying out two upsetting-drawing, controlling the forging ratio at 1.60-1.80, dividing a hammer to carry out uniform-speed reduction, fully crushing a coarse cast-state tissue, and heating to T below the phase transition pointβCarrying out 2-5 times of fire drawing at the temperature of (20-60) DEG C, carrying out one-heading one-drawing, adopting a deformation mode of flat square and diagonal drawing, controlling the forging ratio to be 1.60-1.80, carrying out air cooling after forging, and breaking and spheroidizing the high-strength Wei's structure to obtain uniform fuzzy crystals, thus obtaining the high-strength titanium alloy large-size bar with uniform structure.
Further, the electrode block in the step 1) is pressed into a square electrode by a large hydraulic press.
Further, the welding current of the electrode block in the step 2) is 220-400A, and the welding voltage is 30-45V.
Further, the first melting parameters of the three times of vacuum melting in the step 3) are as follows: the specification of the crucible is phi 160-560 mm, the vacuum degree before melting is less than or equal to 2.0Pa, the gas leakage rate is less than or equal to 1.0Pa/min, the melting voltage is 30-40V, the melting current is 15-24 kA, the arc stabilizing current is 3.0-14.0A, and the cooling time is 6-10 h.
Further, the parameters of the third vacuum melting and the second melting in the step 3) are as follows: the crucible specification is phi 220-phi 640mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.8Pa/min, the melting voltage is 34-40V, the melting current is 16-28 kA, the arc stabilizing current is 5.0-16.0A, and the cooling time is 6-12 h.
Further, the third vacuum melting parameters in the step 3) are as follows: the crucible specification is phi 280-phi 720mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.5Pa/min, the melting voltage is 34-40V, the melting current is 18-28 kA, the arc stabilizing current is 8.0-18.0A, and the cooling time is 6-12 h.
Further, in the step 4), the hammer is pressed down at a constant speed, the forging is subjected to air cooling or water cooling after the coarse as-cast structure is fully crushed, and the size of the obtained crystal grains is not more than 5 mm.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
according to the WSTi1400 ultrahigh-strength titanium alloy, the granular AlMoVCr quaternary alloy, the Nb47Ti, the AlMo, the AlV and other binary intermediate alloys and the 0.83-12.7 mm small-grain sponge titanium are adopted, and the introduction of the Nb element enables the difference between the alpha elastic modulus and the beta elastic modulus in the WSTi1400 alloy to be small, the modulus matching degree to be high, and the toughness and plasticity level of the alloy to be improved; by introducing the AlMoVCr quaternary alloy, the problem of difficult compatibility of two elements of Mo and Cr on one intermediate alloy is solved, the problem of uniformity of distribution is effectively solved by material screening and granularity control of the intermediate alloy, the longitudinal components of the cast ingot obtained by the method can be effectively controlled within 3000ppm, beta spots of the bar are detected at 25 ℃ below a phase transition point, and metallurgical defects are not found.
According to the preparation method of the WSTi1400 ultrahigh-strength titanium alloy, a single electrode is adopted for mixing materials before electrode pressing, and the materials are fully and uniformly mixed; the electrode completes the whole electrode welding process in the non-tungsten electrode vacuum plasma welding box, thereby avoiding the pollution of tungsten or other impurities and the oxidation of the electrode; carrying out three times of smelting by adopting a vacuum consumable electrode arc furnace, and strictly controlling parameters such as vacuum degree, gas leakage rate and the like in the smelting process, so that the transverse uniformity and the longitudinal uniformity of the components of the whole ingot are improved, and the impurity content is reduced; in the preparation process of the bar, a plurality of times of high-temperature forging is adopted above a phase transformation point, the as-cast structure is fully refined, equiaxial and uniform beta grains are obtained, a plurality of modes such as diagonal drawing and flat square are adopted below the phase transformation point, the forging ratio is strictly controlled, and the high-strength and high-toughness WSTi1400 titanium alloy large-size bar with the diameter of 300-500 mm, uniform structure and good performance batch stability is prepared. The preparation method successfully breaks through the chemical component uniformity control technology of industrial large-scale ingots of 1 ton grade, 3 ton grade and 5 ton grade, controls the burning loss of aluminum element in the smelting process, avoids the metallurgical defects of non-melting blocks of high-melting-point niobium element and the like, effectively solves the problems of component segregation, content control of impurities and interstitial elements, batch stability and the like, and is suitable for industrial production of WSTi1400 titanium alloy ingots with the specification of phi 280-phi 720 mm.
Drawings
FIG. 1 is a schematic view showing a longitudinal 5-point sampling of a titanium alloy ingot obtained by the method of the present invention;
FIG. 2 is a schematic view showing transverse 9-point sampling of a titanium alloy ingot obtained by the method of the present invention;
FIG. 3 is a chemical composition diagram of 5 points in the longitudinal direction of an ingot obtained in example 4 of the present invention;
FIG. 4(a), FIG. 4(b), FIG. 4(c), FIG. 4(d), FIG. 4(e), FIG. 4(f) are transverse 9-point chemical composition diagrams of an ingot obtained in example 4 of the present invention;
FIG. 5(a) is a view showing a forged state of macrostructure of a bar obtained in example 4 of the present invention;
FIG. 5(b) is a view showing a forged state of the edge structure of the bar obtained in example 4 of the present invention;
FIG. 5(c) is a high-power structure forged state of R/2 bar obtained in example 4 of the present invention;
FIG. 5(d) is a high-power forged bar material obtained in example 4 of the present invention;
FIG. 6 is a graph showing the tendency of the phase transformation driving forces (energy difference) of the alpha and beta phases of Ti 555-based alloy to vary with the components of Cr, Fe and Nb;
FIG. 7 is a bar graph of elastic modulus mismatch between the phases of M28, Ti5553, TC18 titanium alloy alpha and beta.
Wherein, I, ingot casting, II, longitudinal 5 sampling points, III, cross section 9 sampling points.
Detailed Description
The invention effectively solves the problem of integral forging of 2-5 tons of forging stock by fully utilizing the advantages of alloy design and forging process, introduces Nb element in the aspect of composition to achieve the strengthening effect, does not change the phase transformation point of the alloy, fully considers the influence of Al element on the phase transformation point during design, controls Al at a higher level, can balance the reduction of the phase transformation point caused by the increase of Cr and Fe content, ensures that the phase transformation point of the alloy is between 810 and 820 ℃, provides temperature guarantee for the preparation of large-scale forging stock, effectively controls the deformation resistance and ensures the forgeability of the large-scale forging stock. In addition, the improvement of Cr and Fe accelerates the grain refinement capability of the alloy to a certain extent, the beta grain size of the WSTi1400 alloy large forging stock can be controlled to be 200um, and the traditional TC18, Ti5553 and Ti1023 beta grain sizes are usually 300 um-400 um. In the aspect of forging process, comprehensive deformation and recrystallization temperature are reasonably designed through high-low high circulation, the structure uniformity and the performance stability of the phi 300-phi 500mm bar are ensured, and for the final phi 400 bar with single weight more than 2 tons, the heat treatment can reach 1400MPa, the elongation is 7 percent, and the KIC is 67 MPa.m0.5。
The invention is described in further detail below with reference to the following figures and examples:
example 1:
the invention provides a WSTi1400 ultrahigh-strength titanium alloy which comprises the following elements in percentage by weight: cr: 5.6% -7.5%, Mo: 4.8% -6.5%, V: 4.6-5.3%, Al: 3.8% -4.5%, Nb: 0.8 to 1.3 percent of Fe, less than or equal to 0.8 percent of O, less than or equal to 0.30 percent of O, the balance of Ti and inevitable impurities, the total amount of impurity elements is not more than 0.20 percent, and the sum of the weight percentages of the components is 100 percent.
Further, Cr, Mo, V, Al, Nb and Fe elements are derived from binary and multi-element intermediate alloys, the multi-element intermediate alloys are AlMoVCr quaternary alloys, Nb is added in a form of Nb47Ti, Mo is added in a form of AlMo alloys, V is added in a form of AlV alloys, and Ti is sponge titanium particles of 0.83-12.7 mm.
The preparation method of the WSTi1400 ultrahigh-strength titanium alloy specifically comprises the following steps:
step 1), preparing an electrode:
the weight percentages of the elements are as follows: cr: 5.6% -7.5%, Mo: 4.8% -6.5%, V: 4.6-5.3%, Al: 3.8% -4.5%, Nb: 0.8 to 1.3 percent of Fe, less than or equal to 0.8 percent of O, less than or equal to 0.30 percent of O, the balance of Ti and inevitable impurities, the total content of impurity elements is less than or equal to 0.20 percent, the sum of the weight percentages of the components is 100 percent, the alloy proportion is calculated, the granular AlMoVCr quaternary alloy, the Nb47Ti binary alloy, the AlMo binary alloy and the AlV binary alloy are respectively weighed, and the granular AlMoVCr quaternary alloy, the Nb47Ti binary alloy, the AlMo binary alloy and the sponge titanium with the granularity of 0.83 to 12.7mm are subjected to single-block electrode mixing, and are pressed into an electrode.
Step 2), welding a consumable electrode:
clamping the electrode block obtained in the step 1) by using a clamp, and welding the electrode block into a square electrode, namely a consumable electrode, by using a non-tungsten argon protection plasma box, wherein the welding current of the electrode is 220-400A, and the welding voltage is 30-45V; wherein, the welding spot is required to be silver gray or light yellow, thereby preventing the welding spot from being oxidized and preventing metallurgical defects such as high-density inclusion and the like.
And 3), carrying out three times of vacuum melting on the consumable electrode obtained in the step 2) by adopting a vacuum consumable electrode arc furnace:
smelting for the first time: placing the consumable electrode obtained in the step 2) in a crucible with the specification of phi 160-phi 560mm, wherein the vacuum degree before melting is less than or equal to 2.0Pa, the gas leakage rate is less than or equal to 1.0Pa/min, the melting voltage is 30-40V, the melting current is 15-24 kA, the arc stabilizing current is 3.0-14.0A, and the cooling time is 6-10 h;
smelting for the second time: inverting and re-melting the ingot subjected to primary melting and chamfering, wherein the specification of a crucible is phi 220-phi 640mm, the vacuum degree before melting is less than or equal to 1.8Pa, the air leakage rate is less than or equal to 0.8Pa/min, the melting voltage is 34-40V, the melting current is 16-28 kA, the arc stabilizing current is alternating current 5.0-16.0A, the cooling time is 6-12 h, and chamfering treatment is carried out on the ingot on a lathe after the melting is finished;
and (3) smelting for the third time: and (3) inverting and re-melting the ingot subjected to secondary melting and chamfering, wherein the specification of a crucible is phi 280-phi 720mm, the vacuum degree before melting is less than or equal to 1.8Pa, the air leakage rate is less than or equal to 0.5Pa/min, the melting voltage is 34-40V, the melting current is 18-28 kA, the arc stabilizing current is 8.0-18.0A, and the cooling time is 6-12 h, so that the WSTi1400 titanium alloy ingot is obtained.
Step 4), preparing large-size bars:
forging above the phase transformation point: cogging at 1170 ℃, fully crushing the as-cast structure, forging at high temperature of 1100 ℃, 1040 ℃, 1000 ℃, 950 ℃ and the like respectively, keeping the temperature for 120-720 min, discharging, performing two-upsetting and two-drawing, air cooling after forging, controlling the forging ratio to be 1.60-1.80, pressing at constant speed by a hammer, fully crushing the coarse as-cast structure, and obtaining 2-3 mm isometric beta grains.
Forging with the following transformation points: heating below the phase transition point to TβAnd (3) discharging the material after the temperature is kept at (20-60) DEG C for 120-720 min, performing primary upsetting-drawing for 2-5 times by using deformation modes such as flat square and diagonal drawing, controlling the forging ratio to be 1.60-1.80, and performing air cooling after forging to break and spheroidize the microstructure of the Wei-Gong body to obtain uniform fuzzy crystals in a low-power manner.
The method adopts the intermediate alloy and the sponge titanium with small particles of 0.83-12.7 mm, strictly controls the oxygen content and the content of other impurity elements in the raw materials, adopts a single electrode for mixing materials before the electrode is pressed, and fully and uniformly mixes the materials; the electrode completes the whole electrode welding process in the non-tungsten electrode vacuum plasma welding box, thereby avoiding the pollution of tungsten or other impurities and the oxidation of the electrode; the vacuum consumable electrode arc furnace is adopted for carrying out three times of smelting, parameters such as vacuum degree, gas leakage rate and the like are strictly controlled in the smelting process, so that the transverse uniformity and the longitudinal uniformity of the components of the whole ingot are improved, and the impurity content is reduced. The method successfully breaks through the chemical component uniformity control technology of industrial large-scale ingots of 1 ton, 3 ton and 5 ton, reduces the burning loss of aluminum elements in the smelting process, and avoids the metallurgical defects of non-melting blocks formed by high-melting-point molybdenum, vanadium and niobium elements and the like. Effectively solves the problems of component segregation, content control of impurities and interstitial elements, batch stability and the like, and is suitable for industrial production of WSTi1400 titanium alloy ingots with the specification of phi 280-phi 720 mm.
Through reasonable setting of deformation modes and deformation temperatures above and below the phase change point, the large-size titanium alloy bar with excellent tissue uniformity is obtained.
Example 2:
the invention also provides a preparation method of the WSTi1400 ultrahigh-strength titanium alloy, which comprises the following steps:
step 1), the weight percentages of the elements are as follows: cr5.8%, Mo5.5%, V5.0%, Al4.0%, Nb1.0%, Fe0.5%, O less than or equal to 0.30%, and the balance Ti and inevitable impurities, wherein the total amount of impurity elements is not more than 0.20%, the sum of the weight percentages of the components is 100%, respectively weighing AlMoVCr quaternary alloy, Nb47Ti, AlMo, AlV and small-particle sponge titanium with the particle size of 0.83-12.7 mm to carry out single-block electrode mixing, pouring the mixed raw materials into a die cavity of a large-scale hydraulic press and pressing into a compact electrode block, wherein the pressing force is 20MPa, and the pressure maintaining time is 4 s;
step 2), clamping an electrode block by using a clamp, welding the pressed electrode block into a consumable electrode by using a non-tungsten argon protection plasma box, wherein the welding current is 200A, the welding voltage is 35V, and the welding spot is required to be silver gray or light yellow, so that metallurgical defects such as welding spot oxidation, high-density inclusion and the like are prevented;
and 3), carrying out three times of vacuum melting on the consumable electrode obtained in the step 2 by adopting a vacuum consumable electrode electric arc furnace to obtain an ingot type cast ingot with the diameter of 560mm, wherein the specific melting parameters are as follows:
step 4), forging above the transformation point: cogging at 1170 ℃, fully crushing the as-cast structure, forging at high temperature of 1100 ℃, 1000 ℃ and the like respectively, keeping the temperature for 120-540 min, discharging, performing two-upsetting and two-drawing, controlling the forging ratio to be 1.60-1.80, pressing at constant speed by a hammer, fully crushing the coarse as-cast structure, and obtaining isometric beta grains of 2-3 mm;
forging with the following transformation points: heating below a phase transition point to a T beta-30 ℃ diagonal drawing one-heading one-drawing, T beta-35 ℃ flat square drawing one-heading one-drawing, T beta-40 ℃ flat square drawing one-heading one-drawing, heating and insulating for 120-540 min, controlling the forging ratio between 1.60-1.80, carrying out 3-time upsetting-drawing, T beta-40 ℃ direct drawing, T beta-45 ℃ chamfered edge and T beta-45 ℃ round falling, and carrying out air cooling after forging to obtain a phi 400mm specification bar.
Example 3:
the invention also provides a preparation method of the WSTi1400 ultrahigh-strength titanium alloy, which comprises the following steps:
step 1), the weight percentages of the elements are as follows: cr6.5%, Mo5.0%, V5.0%, Al 4.2%, Nb1.0%, Fe0.2%, O less than or equal to 0.30%, and the balance Ti and inevitable impurities, wherein the total amount of impurity elements is not more than 0.20%, the sum of the weight percentages of the components is 100%, respectively weighing AlMoVCr quaternary alloy, Nb47Ti, AlMo, AlV and small-particle sponge titanium with the particle size of 0.83-12.7 mm to carry out single-block electrode mixing, pouring the mixed raw materials into a die cavity of a large-scale hydraulic press and pressing into a compact electrode block, wherein the pressing force is 20MPa, and the pressure maintaining time is 4 s;
step 2), clamping the electrode block obtained in the step 1) by using a clamp, welding the pressed electrode block into a consumable electrode by using a non-tungsten argon protection plasma box, wherein the welding current is 200A, the welding voltage is 35V, and the welding spot is required to be silver gray or light yellow, so that metallurgical defects such as welding spot oxidation, high-density inclusion and the like are prevented;
and 3), carrying out three times of vacuum melting on the consumable electrode obtained in the step 2) by adopting a vacuum consumable electrode electric arc furnace to obtain an ingot type cast ingot with the diameter of 640mm, wherein the specific melting parameters are as follows:
step 4), forging above the transformation point: cogging at 1170 ℃, fully crushing the as-cast structure, forging at high temperature of 1100 ℃, 1000 ℃, 950 ℃ and the like respectively, keeping the temperature for 300-540 min, discharging, performing two-upsetting and two-drawing, controlling the forging ratio to be 1.60-1.80, pressing at constant speed by a hammer, fully crushing the coarse as-cast structure, and performing air cooling/water cooling after forging to obtain 2-3 mm equiaxial beta grains.
Forging with the following transformation points: heating below a phase transition point to a tip beta-30 ℃ diagonal drawing-first heading-first drawing, a tip beta-35 ℃ flat square drawing-first heading-first drawing, a tip beta-40 ℃ flat square drawing-first heading-first drawing, controlling the forging ratio to be 1.60-1.80, heating and insulating time to be 300-540 min for carrying out 3-time heading drawing, a tip beta-40 ℃ direct drawing, a tip beta-45 ℃ chamfer and a tip beta-45 ℃ round falling, and air cooling after forging to obtain a phi 300 specification bar.
Example 4:
the invention also provides a preparation method of the WSTi1400 ultrahigh-strength titanium alloy, which comprises the following steps:
step 1), the weight percentages of the elements are as follows: cr6.5%, Mo5.6%, V5.0%, Al4.2%, Nb1.0%, Fe0.2%, and the balance of Ti and inevitable impurities, wherein the total amount of impurity elements is not more than 0.20%, the sum of the weight percentages of the components is 100%, respectively weighing AlMoVCr quaternary alloy, Nb47Ti, AlMo, AlV and small-particle sponge titanium with the particle size of 0.83-12.7 mm to carry out single-block electrode mixing, pouring the mixed raw materials into a die cavity of a large hydraulic press and pressing into a compact electrode block, wherein the pressing force is 20MPa, and the pressure maintaining time is 4 s;
step 2), clamping the electrode block obtained in the step 1) by using a clamp, welding the pressed electrode block into a consumable electrode by using a non-tungsten argon protection plasma box, wherein the welding current is 200A, the welding voltage is 35V, and the welding spot is required to be silver gray or light yellow, so that metallurgical defects such as welding spot oxidation, high-density inclusion and the like are prevented;
and 3), carrying out three times of vacuum melting on the consumable electrode obtained in the step 2) by adopting a vacuum consumable electrode electric arc furnace to obtain an ingot type cast ingot with phi of 720mm, wherein the specific melting parameters are as follows:
and 4, forging above the phase transformation point: cogging at 1170 ℃, fully crushing the as-cast structure, forging at high temperature of 1100 ℃, 1040 ℃, 1000 ℃, 950 ℃ and the like respectively, keeping the temperature for 420-720 min, discharging, performing two-upsetting and two-drawing, controlling the forging ratio to be 1.60-1.80, pressing at constant speed by a hammer, fully crushing the coarse as-cast structure, and performing air cooling/water cooling after forging to obtain 2-3 mm equiaxial beta grains.
Forging with the following transformation points: heating below a phase transition point to a T beta-30 ℃ diagonal heading one-heading at T beta-40 ℃, controlling the forging ratio to be 1.60-1.80, carrying out 3-fire heading, carrying out T beta-40 ℃ direct-heading, T beta-45 ℃ chamfered edge and T beta-45 ℃ round falling.
According to the illustration in fig. 1 and 2, sampling and chemical composition detection are carried out on the longitudinal head, upper, middle, lower and tail 5 points and the cross section 9 points of the WSTi1400 alloy large-scale ingot with the specifications of phi 540mm, phi 640mm and phi 720mm prepared in the embodiment, wherein the longitudinal head, upper, middle, lower and tail 5 points and the cross section 9 points are respectively phi 540mm, phi 640mm and phi 720mm, and data show that the element components of each part of the ingot are uniformly distributed and the stability among batches is good; the chemical composition analysis results of the phi 720mm specification WSTi1400 titanium alloy ingot obtained in the example 4 are respectively shown in fig. 3 and fig. 4(a) to 4(f) (the ordinate is the weight percentage of elements), wherein the chemical composition of the longitudinal 5 points is listed in table 1, the fig. 4(a) to 4(f) respectively show the content distribution of different sampling points of each element, fig. 5(a) is a forged low magnification microstructure photograph of the bar obtained in the example 4 of the present invention, fig. 5(b) to 5(d) are forged high magnification microstructure photographs of the bar obtained in the example 4 of the present invention, and table 2 is the performance results of the phi 400 specification titanium alloy bar obtained in the example 4 of the present invention.
TABLE 1 vertical 5-point chemical composition of WSTi1400 titanium alloy ingot with phi 720mm specification
TABLE 2 Phi 400mm specification bar material room temperature mechanical properties
According to the test results, the WSTi1400 titanium alloy industrial-grade large ingot produced by the smelting process technology has uniform components and good batch stability, and is suitable for industrial production.
In conclusion, the invention is a technical scheme generated on the basis of researching the influence of Nb, Cr and Fe contents on the phase change driving force and modulus matching of the high-strength high-toughness titanium alloy, and research results show that:
the Nb element is used for replacing elements such as Cr, Fe and the like with the same mass fraction, the driving force of beta-alpha phase transformation can be increased, see fig. 6, and fig. 6 is a graph showing the variation trend of the driving force (energy difference, see fig. 6 ordinate) of the alpha and beta phase transformation of the Ti 555-based alloy along with the components of Cr, Fe and Nb (see fig. 6 abscissa), so that the volume fraction and the dispersion degree of the alpha of the strengthening phase in the alloy are increased, the strength of the alloy is improved, and the strength of the material is improved from 1200MPa to 1400 MPa.
The elastic modulus calculation shows that compared with other high-strength high-toughness titanium alloys such as Ti5553 and TC18, the introduction of Nb element causes small difference of alpha and beta elastic modulus in WSTi1400 alloy, as shown in FIG. 7, FIG. 7 is a bar graph of elastic modulus mismatch between alpha and beta phases of several typical high-strength high-toughness titanium alloys, wherein (a) is the modulus of a body, (b) is the shear modulus, (c) is the Young modulus, the abscissa represents three alloys, and the ordinate represents the elastic modulus Delta E between alpha and beta phases as 100 (E)α-Eβ)/Eβ(ii) a As can be seen from FIG. 7, the modulus matching degree is high, so that the toughness and plasticity level of the alloy is improved, and the alloy integrates the two characteristics, is mainly designed to be ultrahigh in strength and has high damage tolerance.
Therefore, the problems of toughness, forgeability and metallurgical segregation are comprehensively considered in the alloy design stage, the problem of structural uniformity is guaranteed through reasonable process design in the forging stage, and meanwhile, the problem of material requirement of large-size aviation forgings is solved by obtaining the ultra-strong and high-toughness titanium alloy forging stock through the guarantee.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention.
It is to be understood that the present invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. The WSTi1400 ultrahigh-strength titanium alloy is characterized by comprising the following elements in percentage by weight: cr: 5.6% -7.5%, Mo: 4.8% -6.5%, V: 4.6-5.3%, Al: 3.8% -4.5%, Nb: 0.8 to 1.3 percent of Fe, less than or equal to 0.8 percent of O, less than or equal to 0.30 percent of O, the balance of Ti and inevitable impurities, the total amount of impurity elements is less than or equal to 0.30 percent, and the sum of the weight percentages of the components is 100 percent.
2. The WSTi1400 ultra-high strength titanium alloy of claim 1, wherein the Cr, Mo, V, Al, Nb, Fe elements are derived from binary and multi-element master alloys.
3. The WSTi1400 ultrahigh-strength titanium alloy according to claim 2, wherein the multi-element intermediate alloy is an AlMoVCr quaternary alloy, Nb is added in the form of Nb47Ti, Mo is added in the form of AlMo alloy, V is added in the form of AlV alloy, and Ti is titanium sponge particles of 0.83-12.7 mm.
4. The preparation method of the WSTi1400 ultrahigh-strength titanium alloy is characterized by comprising the following steps of:
step 1), preparing an electrode:
the materials are prepared according to the following weight percentages: cr: 5.6% -7.5%, Mo: 4.8% -6.5%, V: 4.6-5.3%, Al: 3.8% -4.5%, Nb: 0.8 to 1.3 percent of Fe, less than or equal to 0.8 percent of O, less than or equal to 0.30 percent of O, the balance of Ti and inevitable impurities, the total amount of impurity elements is less than or equal to 0.30 percent, and the sum of the weight percentages of the components is 100 percent; carrying out single-block electrode mixing on the mixture, and pressing into an electrode block;
step 2), welding a consumable electrode:
clamping the electrode block obtained in the step 1) by using a clamp, and welding the electrode block into a consumable electrode by using a non-tungsten argon protection plasma box;
step 3), carrying out three times of vacuum melting on the consumable electrode obtained in the step 2) by adopting a vacuum consumable electric arc furnace to obtain a WSTi1400 titanium alloy ingot;
step 4), heating the WSTi1400 titanium alloy ingot obtained in the step 3) to 930-1200 ℃ above a phase transition point for 3-5 times of upsetting-drawing forging, keeping the temperature for 120-720 min, then discharging, carrying out two upsetting-drawing, controlling the forging ratio at 1.60-1.80, dividing a hammer to carry out uniform-speed reduction, fully crushing a coarse cast-state tissue, and heating to T below the phase transition pointβCarrying out 2-5 times of fire drawing at the temperature of (20-60) DEG C, carrying out one-heading one-drawing, adopting a deformation mode of flat square and diagonal drawing, controlling the forging ratio to be 1.60-1.80, carrying out air cooling after forging, and breaking and spheroidizing the high-strength Wei's structure to obtain uniform fuzzy crystals, thus obtaining the high-strength titanium alloy large-size bar with uniform structure.
5. The method for preparing the WSTi1400 ultrahigh-strength titanium alloy according to claim 4, wherein the electrode block of the step 1) is pressed into a square electrode by a large hydraulic press.
6. The method for preparing the WSTi1400 ultrahigh-strength titanium alloy according to claim 4, wherein the welding current of the electrode block in the step 2) is 220-400A, and the welding voltage is 30-45V.
7. The method for preparing the WSTi1400 ultrahigh-strength titanium alloy according to claim 4, wherein the parameters of the first melting of the three times of vacuum melting in the step 3) are as follows: the specification of the crucible is phi 160-560 mm, the vacuum degree before melting is less than or equal to 2.0Pa, the gas leakage rate is less than or equal to 1.0Pa/min, the melting voltage is 30-40V, the melting current is 15-24 kA, the arc stabilizing current is 3.0-14.0A, and the cooling time is 6-10 h.
8. The method for preparing the WSTi1400 ultrahigh-strength titanium alloy according to claim 4, wherein the parameters of the third vacuum melting and the second melting in the step 3) are as follows: the crucible specification is phi 220-phi 640mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.8Pa/min, the melting voltage is 34-40V, the melting current is 16-28 kA, the arc stabilizing current is 5.0-16.0A, and the cooling time is 6-12 h.
9. The method for preparing the WSTi1400 ultrahigh-strength titanium alloy according to claim 4, wherein the third vacuum melting parameter in the step 3) is as follows: the crucible specification is phi 280-phi 720mm, the vacuum degree before melting is less than or equal to 1.8Pa, the gas leakage rate is less than or equal to 0.5Pa/min, the melting voltage is 34-40V, the melting current is 18-28 kA, the arc stabilizing current is 8.0-18.0A, and the cooling time is 6-12 h.
10. The method for preparing the WSTi1400 ultrahigh-strength titanium alloy according to claim 4, wherein in the step 4), the forging is subjected to air cooling or water cooling after a hammer is pressed at a constant speed and a coarse as-cast structure is fully crushed, and the obtained grain size is not more than 5 mm.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111304493A (en) * | 2020-04-21 | 2020-06-19 | 重庆金世利航空材料有限公司 | Superstrong high-plasticity titanium alloy and preparation method thereof |
| CN114381632A (en) * | 2020-10-20 | 2022-04-22 | 重庆理工大学 | Novel titanium alloy and preparation method thereof |
| CN114457259A (en) * | 2022-01-23 | 2022-05-10 | 西部超导材料科技股份有限公司 | Fine-grain TC4 titanium alloy bar and preparation method thereof |
| CN115852284A (en) * | 2022-11-11 | 2023-03-28 | 西部超导材料科技股份有限公司 | Heat treatment process for TB18 ultrahigh-strength and high-toughness titanium alloy |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111304493A (en) * | 2020-04-21 | 2020-06-19 | 重庆金世利航空材料有限公司 | Superstrong high-plasticity titanium alloy and preparation method thereof |
| CN111304493B (en) * | 2020-04-21 | 2022-03-15 | 重庆金世利航空材料有限公司 | Superstrong high-plasticity titanium alloy and preparation method thereof |
| CN114381632A (en) * | 2020-10-20 | 2022-04-22 | 重庆理工大学 | Novel titanium alloy and preparation method thereof |
| CN114457259A (en) * | 2022-01-23 | 2022-05-10 | 西部超导材料科技股份有限公司 | Fine-grain TC4 titanium alloy bar and preparation method thereof |
| CN115852284A (en) * | 2022-11-11 | 2023-03-28 | 西部超导材料科技股份有限公司 | Heat treatment process for TB18 ultrahigh-strength and high-toughness titanium alloy |
| CN115852284B (en) * | 2022-11-11 | 2024-02-02 | 西部超导材料科技股份有限公司 | TB18 ultra-high strength and toughness titanium alloy heat treatment process |
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