Preparation method of TC8-1 titanium alloy bar with high toughness and structure uniformity

Abstract

The invention relates to a preparation method of a TC8-1 titanium alloy bar with high toughness and structure uniformity, belongs to the technical field of titanium alloy bar preparation, and solves the problems that a bar prepared by an existing method is poor in structure uniformity, pseudo coarse grains cannot be eliminated, and the transverse and longitudinal performance dispersity of the bar is large. Comprising the following steps: weighing pure metal and / or alloy according to the nominal composition proportion of the TC8-1 titanium alloy, mixing, pressing into an electrode, welding into an electrode group, completing three times of vacuum consumable electric arc melting to obtain a titanium alloy cast ingot, and testing the specification size and Tbeta of the titanium alloy cast ingot; forging the titanium alloy cast ingot, detecting the height-diameter ratio of a forging stock, and determining whether to distribute the forging stock according to the height-diameter ratio of the forging stock; heating the forging stock near T beta, preserving heat, quickly transferring the forging stock to a water tank, and performing water cooling to room temperature; and the forging stock is forged, the height-diameter ratio of the forging stock is detected, whether the forging stock is divided or not is determined according to the height-diameter ratio of the forging stock, and the titanium alloy bar is obtained. The bar prepared through the method is good in structure and performance uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium alloy bar preparation, and particularly relates to a TC8-1 titanium alloy bar preparation method with high toughness and uniform structure. BACKGROUND

[0002] TC8-1 titanium alloy is a high-performance martensitic two-phase titanium alloy, belonging to Ti-Al-Mo-Sn-Zr-Si alloy, and the nominal composition is Ti-6.3Al-1Sn-1Zr-3.3Mo-0.18Si. The TC8-1 titanium alloy has high strength, good plasticity and toughness at room temperature and high temperature, and the long-term use temperature of the TC8-1 titanium alloy can reach 500 DEG C, and the TC8-1 titanium alloy has good thermal stability, hot working process and damage tolerance performance. The TC8-1 titanium alloy is widely used in PD-14, AI-322 and BK2500M compressor multi-stage disc and integral blade disc at abroad, and is also widely used in aero-engine disc forgings at home, and the weight of the forgings is less than 35 kg, belonging to small and medium-sized disc forgings.

[0003] The TC8-1 titanium alloy bar as a semi-finished product of disc forgings has high toughness and uniform structure, which plays a crucial role in the metallurgical quality of the disc forgings. The existing titanium alloy bar preparation pursues large-scale billets, and the process of single large length significantly improves the efficiency and yield, but is not conducive to the uniform refinement of the structure, and is not matched with the high quality control requirement of the small-sized TC8-1 titanium alloy forgings, so it is urgent to research a TC8-1 titanium alloy bar preparation method with high uniformity of the structure, which meets the production demand of large-scale industrial ingots without reducing the production efficiency, yield and affecting the batch consistency. SUMMARY

[0004] In view of the above analysis, the present application aims to provide a TC8-1 titanium alloy bar preparation method with high toughness and uniform structure, to solve the problems of poor uniformity of the TC8-1 titanium alloy bar prepared by the existing TC8-1 titanium alloy bar preparation method, the inability to eliminate pseudo coarse grains and the large dispersion of the bar transverse and longitudinal performance.

[0005] The purpose of the present application is mainly realized by the following technical solutions:

[0006] The present application provides a TC8-1 titanium alloy bar preparation method with high toughness and uniform structure, comprising the following steps:

[0007] S1: a certain amount of pure metal and / or alloy is weighed according to the nominal composition of the TC8-1 titanium alloy, the raw materials are mixed and pressed into electrodes, the electrodes are welded into an electrode group, and a titanium alloy ingot is obtained after three vacuum consumable arc melting, and the size of the titanium alloy ingot and the beta phase transition point temperature T β are tested.

[0008] S2: forging the titanium alloy ingot obtained in step S1, detecting the height-diameter ratio of the forged blank during the forging process, and determining whether to split the forged blank according to the height-diameter ratio of the forged blank;

[0009] S3: heating the forged blank obtained in step S2 at T β -15℃ to T β +15℃, rapidly transferring the forged blank to a water tank after the heat preservation, and water cooling the forged blank to room temperature;

[0010] S4: forging the forged blank obtained in step S3, detecting the height-diameter ratio of the forged blank during the forging process, and determining whether to split the forged blank according to the height-diameter ratio of the forged blank, to obtain a titanium alloy bar.

[0011] Further, step S2 comprises:

[0012] S21: heating and deforming the titanium alloy ingot obtained in step S1 at T β +(50-200℃), measuring the height-diameter ratio of the forged blank after each heating and deforming process, determining whether to split the forged blank according to the height-diameter ratio of the forged blank, performing 3-4 heating and deforming processes in total, and performing 1-2 upsetting and drawing deforming processes in each heating and deforming process, to obtain a single first forged blank or multiple first forged blanks;

[0013] S22: heating and deforming the single first forged blank or the multiple first forged blanks at T β -(15-30℃), performing 1-2 heating and deforming processes, performing 1-2 upsetting and drawing deforming processes in each heating and deforming process, to obtain a single second forged blank or multiple second forged blanks.

[0014] Further, step S4 comprises:

[0015] S41: heating and deforming the single third forged blank or the multiple third forged blanks obtained in step S3 at T β -(30-50℃), measuring the height-diameter ratio of the forged blank after each heating and deforming process, determining whether to split the forged blank according to the height-diameter ratio of the forged blank, performing 2-4 heating and deforming processes in total, and performing 1-2 upsetting and drawing deforming processes in each heating and deforming process, to obtain a single fourth forged blank or multiple fourth forged blanks;

[0016] S42: heating and deforming the single fourth forged blank or the multiple fourth forged blanks at T β -(40-70℃), performing 2-4 heating and deforming processes, and performing 1 upsetting and drawing deforming process or 1 drawing deforming process in each heating and deforming process, to obtain a titanium alloy bar.

[0017] Further, in step S3, the heat preservation time is calculated according to 0.3-0.5 min / mm, where mm refers to the diameter of the forged blank;

[0018] The time for rapidly transferring the forged blank to the water tank is ≤120 s.

[0019] Further, in step S21, the height-diameter ratio of the forging blank after each heating is measured, and whether to perform the material division is determined according to the height-diameter ratio of the forging blank, including: measuring the height-diameter ratio of the corresponding forging blank after each heating, if the height-diameter ratio of the forging blank after the heating is ≤3.5, the material division is not performed, and the next heating is continued;

[0020] If the height-diameter ratio of the forging blank after the heating is >3.5, the material division is performed to obtain multiple blank materials, and then each blank material is subjected to the next heating.

[0021] Further, the height-diameter ratio of each blank material is 1.5-2.0.

[0022] Further, in steps S21 and S22, the upsetting deformation is 30-50%, and the elongation deformation is 40-70%.

[0023] Further, in step S41, the height-diameter ratio of the forging blank after each heating is measured, and whether to perform the material division is determined according to the height-diameter ratio of the forging blank, including: measuring the height-diameter ratio of the corresponding forging blank after each heating, if the height-diameter ratio of the forging blank after the heating is ≤3.5, the material division is not performed, and the next heating is continued;

[0024] If the height-diameter ratio of the forging blank after the heating is >3.5, the material division is performed to obtain multiple blank materials, and then each blank material is subjected to the next heating.

[0025] The height-diameter ratio of each blank material is 1.5-2.5.

[0026] Further, in step S41, the upsetting deformation is 30-60%, and the elongation deformation is 40-80%;

[0027] In step S42, the upsetting deformation is 30-50%, and the elongation deformation is 25-50%.

[0028] Further, in step S42, the continuous elongation deformation of 1 heating is performed in 2-4 heatings, and the cumulative elongation deformation is not more than 70%.

[0029] Compared with the prior art, the present application can at least achieve one of the following beneficial effects:

[0030] 1. The preparation method of the TC8-1 titanium alloy rod of the present application, after the first stage of forging is completed, the subsequent elongation deformation is performed in the two-phase zone (close to the phase transition point, at T β -15℃ to T β+15 ℃ internal heating and insulation followed by rapid water cooling) can reduce the deformation of the α phase layer, promote the recrystallization and refinement of the original β grains in the β phase region, and refine the as-cast structure of the titanium alloy ingot through billeting in the single-phase region (β phase region) and deformation in the two-phase region (α phase and β phase). This fundamentally solves the problem of the inability to eliminate pseudo-coarse grains when the subsequent bars are used to prepare titanium alloy disc forgings.

[0031] 2. The present invention divides the forging blanks with a relatively large height-to-diameter ratio during the forging process, strictly controls the deformation and temperature during the forging process, promotes the equiaxed α phase, and improves the consistency of the transverse and longitudinal properties of the material; compared with the single large-length process in the prior art, the cumulative unidirectional drawing deformation is reduced from more than 90% to less than 70%, solving the problems of the current titanium alloy bar preparation that the pursuit of large-size billets and single large-length high-yield processes is not conducive to uniform refinement of the structure, and the bar has large dispersion in transverse and longitudinal properties.

[0032] 3. The titanium alloy bars prepared by the method of the present invention have high uniformity in structure and performance, and can be directly cut and die-forged subsequently, meeting the high-quality production requirements of TC8-1 titanium alloy miniaturized forgings (less than 35 kg) without reducing the yield rate and affecting the consistency of the batch.

[0033] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0035] Figure 1 This is the macrostructure of the 180 mm TC8-1 titanium alloy bar of Example 1;

[0036] Figure 2 The microstructure of the Ø180 mm TC8-1 titanium alloy bar of Example 1;

[0037] Figure 3 This is the macrostructure of the Ø260mm TC8-1 titanium alloy bar of Example 2;

[0038] Figure 4 The microstructure of the Ø260 mm TC8-1 titanium alloy bar of Example 2;

[0039] Figure 5Macrostructure of the tail of a Ф180 mm TC8-1 titanium alloy bar for Comparative Example 1;

[0040] Figure 6 Microstructure of a Ф180 mm TC8-1 titanium alloy bar for Comparative Example 2.

[0041] Reference signs:

[0042] 1-pseudo coarse grain. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present application will be described in detail below with reference to the drawings, which form a part of this application, and together with the embodiments of the present application illustrate the principles of the present application, but not limit the scope of the present application.

[0044] The present application provides a preparation method of a TC8-1 titanium alloy bar with high toughness and uniform microstructure, comprising the following steps:

[0045] S1: a certain amount of pure metals and / or alloys is weighed according to the nominal composition of TC8-1 titanium alloy, the raw materials are mixed and pressed into electrodes, the electrodes are welded into an electrode group, and a titanium alloy ingot is obtained after three vacuum consumable arc melting, and the size of the titanium alloy ingot and the beta phase transition point temperature T β are tested.

[0046] The nominal composition of the TC8-1 titanium alloy is Ti-6.3Al-1Sn-1Zr-3.3Mo-0.18Si.

[0047] S2: the titanium alloy ingot obtained in step S1 is forged, and the height-diameter ratio of the forged blank is detected during the forging process, and it is determined whether the forged blank is divided according to the height-diameter ratio of the forged blank.

[0048] S21: the titanium alloy ingot obtained in step S1 is heated and deformed at T β +(50-200℃) (i.e. the beta phase transition point temperature T β above 50-200℃), the height-diameter ratio of the forged blank is measured after each heating and deforming, and it is determined whether the forged blank is divided according to the height-diameter ratio of the forged blank, a total of 3-4 heating and deforming is performed, each heating and deforming is 1-2 upsetting and drawing deformations, and a single first forged blank or multiple first forged blanks are obtained.

[0049] S22: the single first forged blank or the multiple first forged blanks are heated and deformed at T β -(15-30℃) (i.e. the beta phase transition point temperature T β below 15-30℃), 1-2 heating and deforming is performed, each heating and deforming is 1-2 upsetting and drawing deformations, and a single second forged blank or multiple second forged blanks are obtained.

[0050] Specifically, in step S21, the titanium alloy ingot obtained in step S1 is cast in a T β +(50~200℃)(i.e. β phase transition point temperature T β The titanium alloy ingot is heated and deformed at 50-200°C above, at which time the titanium alloy ingot is mainly in the single-phase region (β phase region), and the β phase has good plasticity, which is convenient for blanking operation; the aspect ratio of the corresponding forging blank is measured after each fire, and whether the forging blank after the fire treatment is to be divided according to the aspect ratio of the forging blank is determined, if the aspect ratio of the forging blank after the fire treatment is ≤3.5, no division is performed, and the next fire treatment is continued; if the aspect ratio of the forging blank after the fire treatment is >3.5, division is performed, and after division, the aspect ratio of each billet separated from the forging blank is ensured to be between 1.5 and 2.0, and then each billet is subjected to the next fire treatment together; the aspect ratio measurement and fire treatment of the forging blank are cyclically performed, and a total of 3-4 fire treatments are performed, each fire is 1-2 times of upsetting deformation, the upsetting deformation is 30-50%, and the drawing deformation is 40-70%, and finally the first forging blank is obtained.

[0051] It should be noted that in step S21, the aspect ratio of the corresponding forging blank is measured after each firing. If the material is never split, the first forging blank is a single bar blank; if the material is split at least once, the first forging blank is a bar blank set consisting of multiple bars, rather than a single bar blank. In this step, the present invention selectively reduces the forging specifications of the forging blank according to the aspect ratio of the forging blank, which can improve the deformation uniformity of the forging heating machine, improve the water cooling effect of the subsequent heat treatment, and improve the structural uniformity and α of the forging blank. p (Equiaxed primary α phase) refinement effect.

[0052] Specifically, in step S22, a single first forging blank or multiple first forging blanks are placed in T β -(15~30℃)(i.e. β phase transition point temperature T β The steel is heated and deformed at 15-30℃ for 1-2 fires, with 1-2 upsetting deformations per fire. The upsetting deformation is 30-50%, and the elongation deformation is 40-70%, to obtain a single second forging blank or multiple second forging blanks. It should be noted that when the temperature drops to T β -(15~30℃)(i.e. β phase transition point temperature T β After the temperature drops below 15-30°C, the single first forging billet or multiple first forging billets enter the two-phase region where α phase and β phase coexist. Forging in the temperature range of the two-phase region (near the phase transformation point) can reduce the deformation of the α phase sheet layer, promote the recrystallization and refinement of the original β grains in the β phase region, and refine the cast structure of the titanium alloy ingot through billet opening in the single-phase region (β phase region) and deformation in the two-phase region (α phase and β phase).

[0053] S3: The forging blank obtained in step S2 is placed on a T β -15℃ to Tβ Heat at +15℃, keep warm, then quickly transfer to a water tank and cool to room temperature;

[0054] Place a single second forging billet or multiple second forging billets on T β -15℃ to T β Heat within +15℃, keep warm and then quickly transfer to a water tank. The holding time is calculated according to 0.3-0.5min / mm, where mm refers to the diameter of the forging blank. The time of quick transfer to the water tank is ≤120s. Cool with water to room temperature to obtain a single third forging blank or multiple third forging blanks.

[0055] It should be noted that, in actual production, titanium alloy bars are mostly prepared using a process furnace with a furnace temperature uniformity of ±10°C, which means that the actual heating temperature of the second forging blank may fluctuate by 10°C around the set temperature; TC8-1 titanium alloy kept at a higher temperature above the β phase transformation point will cause abnormal grain growth; therefore, the present invention comprehensively considers that the heating temperature of the second forging blank is controlled near the β phase transformation point: it can retain the grains with disordered orientation under this condition on the basis of refining the α lamellae (the orientation of the grains is relatively disordered, which helps to improve the isotropy of the material and reduce the performance difference caused by anisotropy), laying the foundation for the nucleation and spheroidization of the α phase (i.e., the formation of disordered, equiaxed and fine α phases) in the subsequent deformation process, and can also retain the fine and uniform β grains formed by the blank forging in step S2, avoiding the forging blank repeatedly entering a higher temperature curve above the phase transformation point, causing pseudo-coarse grains to be continuously inherited to the disc forging. At the same time, if the heating temperature of the second forging blank is higher than the β phase transformation point but controlled at T β Below +15℃, the driving force for grain growth is insufficient. Within this temperature range, the α-lamellae can still be refined and the grain size is uniformly oriented and dispersed, which helps to improve the comprehensive performance of titanium alloy bars.

[0056] S4: Forging the forging blank obtained in step S3, detecting the aspect ratio of the forging blank during the forging process, and determining whether to divide the forging blank according to the aspect ratio of the forging blank to obtain titanium alloy bars.

[0057] S41: The single third forging blank or the plurality of third forging blanks obtained in step S3 are placed on a T β -(30~50℃)(i.e. β phase transition point temperature T β and performing heating deformation at 30-50° C., measuring the aspect ratio of the forging blank after each fire, and determining whether to divide the forging blank according to the aspect ratio of the forging blank. A total of 2-4 fires are performed, with 1-2 upsetting and drawing deformations in each fire, with an upsetting deformation amount of 30-60% and a drawing deformation amount of 40-80%, to obtain a single fourth forging blank or multiple fourth forging blanks.

[0058] S42: Place the single fourth forging blank or multiple fourth forging blanks on T β- (40-70°C) (i.e. below the β transus temperature Tβ) β The titanium alloy bar is obtained by heating deformation at 40-70°C, and 2-4 heating times, each time being 1 upsetting and drawing deformation or 1 elongation deformation.

[0059] Specifically, in step S41, the single third forging blank or the multiple third forging blanks obtained in step S3 are heated at T β - (30-50°C) (i.e. below the β transus temperature Tβ) β The titanium alloy bar is obtained by heating deformation at 40-70°C, and 2-4 heating times, each time being 1 upsetting and drawing deformation or 1 elongation deformation.

[0060] Specifically, in step S42, the single fourth forging blank or the multiple fourth forging blanks are heated at T β The titanium alloy bar is obtained by heating deformation at 40-70°C, and 2-4 heating times, each time being 1 upsetting and drawing deformation or 1 elongation deformation.

[0061] It should be noted that the forging of the single third forging blank or the multiple third forging blanks after heat treatment in step S3 in step S4 is upsetting and drawing deformation and reforming in the two-phase region, which can effectively refine the α phase and β phase. By controlling the deformation and temperature in the forging process, the equiaxialization of the α phase can be promoted, and the consistency of the transverse and longitudinal performance of the material can be improved. Compared with the prior art single large length process, the cumulative unidirectional elongation deformation is reduced from more than 90% to less than 70%.

[0062] The method for preparing TC8-1 titanium alloy bars of the present invention, after the first stage of forging in step S2 is completed, forging in a two-phase region (near the phase transformation point) temperature range in step S3 can reduce the deformation of the α phase sheet layer, promote the recrystallization and refinement of the original β grains in the β phase region, refine the as-cast structure of the titanium alloy ingot by blanking in the single-phase region (β phase region) and deforming in the two-phase region (α phase and β phase), and fundamentally solve the problem of pseudo coarse grains that cannot be eliminated when the bars are subsequently used to prepare titanium alloy disc forgings. By dividing the forging billets with a large height-to-diameter ratio during the forging process, the deformation amount and temperature during the forging process are strictly controlled, the equiaxed α phase is promoted, and the consistency of the transverse and longitudinal properties of the material is improved. Compared with the existing single-length long process, the cumulative unidirectional drawing deformation is reduced from more than 90% to less than 70%, solving the problems that the current titanium alloy bar preparation process that pursues large-size billets and single-length long high yield rate is not conducive to uniform microstructure refinement and the bar has large dispersion in transverse and longitudinal properties. The titanium alloy rods prepared by the method of the present invention have high uniformity in structure and performance, and can be directly cut and die-forged subsequently, meeting the high-quality production requirements of TC8-1 titanium alloy miniaturized forgings (below 35 kg) without reducing the yield rate and affecting the batch consistency.

[0063] Example 1

[0064] This embodiment provides a method for preparing a TC8-1 titanium alloy bar with high toughness and structural uniformity, comprising the following steps:

[0065] S1: A certain amount of pure metal and / or alloy is weighed according to the nominal composition ratio of TC8-1 titanium alloy, the raw materials are mixed and pressed into electrodes, which are welded into an electrode group. After three vacuum consumable arc melting processes, a titanium alloy ingot is obtained;

[0066] Among them, the nominal composition ratio of TC8-1 titanium alloy is Ti-6.3Al-1Sn-1Zr-3.3Mo-0.18Si, the test titanium alloy ingot size is Ф590×1200mm, and the β phase transition point temperature T β It is 1000℃.

[0067] S2: Forging the titanium alloy ingot obtained in step S1, detecting the aspect ratio of the forging blank during the forging process, and determining whether to separate the forging blank according to the aspect ratio of the forging blank;

[0068] S21: The titanium alloy ingot obtained in step S1 is heated to 1150°C (i.e., the β phase transition point temperature T βS1: heating deformation at 50°C above, after finishing one heating (the heating is one upsetting and one elongation, upsetting deformation is 30%, elongation deformation is 65%), the height-diameter ratio of the corresponding forging blank is 5.3, which is greater than 3.5, three equal parts are carried out, the three equal parts are Φ420mm×750mm, the height-diameter ratio of each blank after the three equal parts is 1.8;

[0069] Then, continue to forge each blank at 1150°C for 2 heating, according to the size of each blank, the deformation mode is selected to be two upsets and two elongations or one upset and one elongation, upsetting deformation is 40-50%, elongation deformation is 40-50%, three first forging blanks are obtained;

[0070] The specifications of the three first forging blanks are all Φ400mm×780mm

[0071] S22: heating deformation of the three first forging blanks at 980°C (i.e. β phase transition point temperature T β below 20°C, one heating is finished, the heating is two upsets and two elongations, upsetting deformation is 40-50%, elongation deformation is 40-50%, three second forging blanks are obtained;

[0072] The specifications of the three second forging blanks are all Φ400mm×760mm

[0073] S3: heating the three second forging blanks at 1000°C (i.e. T β ) for 200min (calculated according to 0.3-0.5min / mm) and then quickly transferred to a water tank, the transfer time is 90s, water cooling to room temperature, three third forging blanks are obtained;

[0074] The specifications of the three third forging blanks are all Φ400mm×760mm

[0075] S4: forging the three third forging blanks in step S3, titanium alloy bars are obtained:

[0076] S41: heating the three third forging blanks obtained in step S3 at 960°C (i.e. β phase transition point temperature T β below 40°C, after finishing one heating (the heating is one upset and one elongation, upsetting deformation is 45%, elongation deformation is 75%), the height-diameter ratio of the three third forging blanks is 3.8, 3.9, 3.8 respectively, which are all greater than 3.5, so two equal parts are carried out, the height-diameter ratio of each blank after the two equal parts is about 1.9, the specifications after the two equal parts are Φ320mm×600mm;

[0077] Then, continue to forge each blank at 950°C (i.e. β phase transition point temperature T βThe six fourth forging blanks are heated at 930 ℃ (i.e. the β phase transformation point temperature T

[0078] The specification of the six fourth forging blanks is: Φ300mm×740mm

[0079] S42: The six fourth forging blanks are heated at 930 ℃ (i.e. the β phase transformation point temperature T β The six fourth forging blanks are heated at 930 ℃ (i.e. the β phase transformation point temperature T

[0080] The TC8-1 titanium alloy bar of Φ180mm prepared in the embodiment is taken, and one of the bars is taken for macrostructure and microstructure tests, and the macrostructure and microstructure are shown in Figs. 1 and 2, respectively. Figure 1 and Figure 2 According to the rating of GJB 2218A-2018, the macrostructure ratings of the head, middle and tail are grade 1, and the microstructure ratings of different positions are all grade 3, the microstructure uniformity is high, and the difference is small.

[0081] The impact performance of the TC8-1 titanium alloy bar of Φ180mm prepared in the embodiment is excellent, and the room temperature impact mechanical properties and transverse and longitudinal mechanical properties of several bars are measured, and it can be seen from Table 1 that the room temperature impact mechanical properties thereof are much higher than those of the comparative example under the same heat treatment system (920-950℃ / 1-4h, AC+570-600℃×1h, AC), as shown in Table 1 (two bars are taken to test the KU2 of the head and tail); the transverse and longitudinal tensile mechanical properties have no obvious difference, as shown in Table 2 (two bars are taken to test).

[0082] Embodiment 2

[0083] The embodiment provides a preparation method of a TC8-1 titanium alloy bar with high toughness and uniform microstructure, comprising the following steps:

[0084] S1: A certain amount of pure metal and / or alloy is weighed according to the nominal composition of TC8-1 titanium alloy, the raw materials are mixed and pressed into electrodes, the electrodes are welded into an electrode group, and a titanium alloy ingot is obtained after three vacuum consumable arc melting;

[0085] The nominal composition of the TC8-1 titanium alloy is Ti-6.3Al-1Sn-1Zr-3.3Mo-0.18Si, the size of the titanium alloy ingot is Φ590×1180mm, and the β phase transformation point temperature T β is 1005℃.

[0086] S2: Forging the titanium alloy ingot obtained in step S1, detecting the aspect ratio of the forging blank during the forging process, and determining whether to separate the forging blank according to the aspect ratio of the forging blank;

[0087] S21: The titanium alloy ingot obtained in step S1 is heated to 1160°C (i.e., the β phase transition point temperature T β Above 155℃) heating deformation, after completing one fire (this fire is one upsetting and one drawing, the upsetting deformation is 40%, the drawing deformation is 60%), the height-to-diameter ratio of the corresponding forging billet is measured to be 5.1, which is greater than 3.5, and the material is divided into three equal parts. The specifications of the three equal parts are: Φ420mm×720mm. After dividing, the height-to-diameter ratio of each billet is 1.7;

[0088] Then, each billet is forged twice at 1160°C. According to the size of each billet, the deformation mode is selected as two upsetting and two drawing or one upsetting and one drawing, with the upsetting deformation amount of 40-50% and the drawing deformation amount of 40-50% to obtain three first forging billets.

[0089] The specifications of the three first forging blanks are: Φ420mm×720mm

[0090] S22: The three first forging blanks are heated to 990°C (i.e., the β phase transformation point temperature T β The steel is heated and deformed at 15°C, and the first fire is two upsetting and two drawing, the upsetting deformation is 40-50%, and the drawing deformation is 40-50%, to obtain three second forging blanks;

[0091] The specifications of the three second forging blanks are: Φ420mm×700mm

[0092] S3: Heat the three second forging blanks at 1010℃ (i.e. T β After heating at 5°C (above 5°C), keeping the temperature for 200 minutes (calculated at 0.3-0.5 minutes / mm), quickly transferring to a water tank for 120 seconds, and cooling to room temperature with water to obtain three third forging blanks;

[0093] The specifications of the three third forging blanks are: Φ420mm×700mm

[0094] S4: Forging the three third forging blanks in step S3 to obtain titanium alloy bars:

[0095] S41: The three third forging blanks obtained in step S3 are respectively heated at 965°C (i.e., the β phase transformation point temperature T βAfter completing one fire (one upsetting and one drawing, upsetting deformation amount 45%, drawing deformation amount 75%), the height-to-diameter ratios of the three third forging billets were measured, which were 1.75, 1.75, and 1.70, respectively, all less than 3.5. No material was divided, and each billet was continued to be heated at 965℃ (i.e., the β phase transition point temperature T β The forging process is carried out for three times at a temperature of 40°C. After each forging, the height-to-diameter ratio of the corresponding forging blank is tested and all are less than 3.5, so no material separation is performed. In the three forgings, each forging process is two upsetting and two drawing or one upsetting and one drawing, with an upsetting deformation of 40-50% and a drawing deformation of 40-60%, to obtain three fourth forging blanks.

[0096] The specifications of the three fourth forging blanks are: Φ350mm×1020mm

[0097] S42: The three fourth forging blanks are heated to 940°C (i.e., the β phase transformation point temperature T β The steel bars were heated and deformed at 65°C (180°F) for one fire, with a drawing deformation of 60% to obtain three 260mm Ø titanium alloy bars.

[0098] Three TC8-1 titanium alloy bars with a diameter of 260 mm were prepared in this embodiment. One of them was tested for macrostructure and microstructure. The macrostructure and microstructure were shown in Figure 2. Figure 3 and Figure 4 According to the GJB 2218A-2018 rating, the macroscopic structure of the head, middle and tail is rated as level 1, and the microscopic structure at different positions is rated as level 3, with high tissue uniformity and small extreme difference.

[0099] The three TC8-1 titanium alloy bars with a diameter of 260 mm prepared in this embodiment have excellent impact properties. Several of them are randomly selected to measure the room temperature impact mechanical properties and transverse and longitudinal mechanical properties. It can be seen from Table 1 that under the same heat treatment system (920-950°C / 1-4h, AC+570-600°C×1h, AC), the room temperature impact mechanical properties are much higher than those of the comparative example, see Table 1 (randomly select two to test the head and tail KU2), and there is no obvious difference in the transverse and longitudinal tensile mechanical properties, see Table 2 (randomly select two for testing).

[0100] Comparative Example 1

[0101] This comparative example intends to prepare TC8-1 titanium alloy bars with the same specifications as those in Example 1. The preparation method is similar to that in Example 1, except that: in step S3, the three second forging blanks are heated at 1030°C (i.e., T β +30℃), keep warm for 200min (calculated according to 0.3-0.5min / mm), then quickly transfer to a water tank for 90s, and cool to room temperature with water to obtain three third forging blanks.

[0102] The six TC8-1 titanium alloy bars with a diameter of 180 mm prepared in this comparative example were taken to observe the macrostructure of the tail. Figure 5 As shown in the figure, it can be seen that there are pseudo coarse grains, which will be inherited into subsequent parts and are difficult to eliminate.

[0103] The six TC8-1 titanium alloy bars with a diameter of 180 mm prepared in this comparative example have excellent impact properties. Several of them were randomly selected to measure the room temperature impact mechanical properties and transverse and longitudinal mechanical properties. It can be seen from Table 1 that under the same heat treatment system (920-950°C / 1-4h, AC+570-600°C×1h, AC), the room temperature impact mechanical properties are lower than those of Example 1, see Table 1 (randomly select two to test KU2 at the head and tail); due to the presence of pseudo-coarse grains, the elongation and cross-sectional reduction rate of the pseudo-coarse grains in the lateral position of the rod head are significantly reduced, resulting in a decrease in the tensile plasticity of the rod, see Table 2 for details (randomly select two for testing).

[0104] Comparative Example 2

[0105] This comparative example intends to prepare TC8-1 titanium alloy bars with the same specifications as in Example 1. The preparation method is similar to that in Example 1, except that the material is not divided in step S21, and the material is divided into two equal parts in step S41. The specific steps are as follows:

[0106] S1: A certain amount of pure metal and / or alloy is weighed according to the nominal composition ratio of TC8-1 titanium alloy, the raw materials are mixed and pressed into electrodes, which are welded into an electrode group. After three vacuum consumable arc melting processes, a titanium alloy ingot is obtained;

[0107] Among them, the nominal composition ratio of TC8-1 titanium alloy is Ti-6.3Al-1Sn-1Zr-3.3Mo-0.18Si, the test titanium alloy ingot size is Ф590×1200mm, and the β phase transition point temperature T β is 1000℃.

[0108] S2: Forging the titanium alloy ingot obtained in step S1, detecting the aspect ratio of the forging blank during the forging process, and determining whether to separate the forging blank according to the aspect ratio of the forging blank;

[0109] S21: The titanium alloy ingot obtained in step S1 is heated to 1150°C (i.e., the β phase transition point temperature T β Above 50℃) heating deformation, after completing one fire (the fire is one upsetting and one drawing, the upsetting deformation is 30%, the drawing deformation is 65%), the height-to-diameter ratio of the corresponding forging blank is measured to be 5.3, which is greater than 3.5, and no material separation is performed;

[0110] Then continue to forge the forging blank at 1150℃ for two times. According to the size of the forging blank, the deformation mode is selected as one upsetting and one drawing, the upsetting deformation is 40%, and the drawing deformation is 50%; thus, a single first forging blank is obtained;

[0111] The specifications of the single first forging billet are: Φ420mm×2200mm

[0112] S22: The first forging blank is heated to 980°C (i.e., the β phase transformation temperature T β The steel is heated and deformed at 20°C or below, and the first fire is a second upsetting and a second drawing, the upsetting deformation is 40-50%, and the drawing deformation is 40-50%, to obtain a single second forging blank;

[0113] The specifications of a single second forging blank are: Φ420mm×2200mm

[0114] S3: Heat the second forging blank at 1000℃ (T β ) and heat for 200 min (calculated according to 0.3-0.5 min / mm), then quickly transfer to a water tank for 90 s, and water-cool to room temperature to obtain a single third forging blank;

[0115] The specifications of a single third forging blank are: Φ420mm×2200mm

[0116] S4: Forging the single third forging blank in step S3 to obtain a titanium alloy bar:

[0117] S41: The single third forging blank obtained in step S3 is heated to 960°C (i.e., the β phase transformation point temperature T β After one fire (one upsetting and one pulling, upsetting deformation of 45%, pulling deformation of 75%), the height-to-diameter ratio is measured to be 4.9, which is greater than 3.5, and the material is divided into two equal parts. After the material is divided, the specification of each blank is Φ400mm×980mm, and the height-to-diameter ratio is about 2.5;

[0118] Then, each blank is heated to 950℃ (i.e., the β phase transition point temperature T β 50℃ or below) forging for three times, the deformation mode is two upsetting and two drawing or one upsetting and one drawing, the upsetting deformation is 30-60%, and the drawing deformation is 40-60%, to obtain two fourth forging blanks;

[0119] The specifications of the two fourth forging blanks are: Φ320mm×1700mm

[0120] S42: The two fourth forging blanks are heated to 930°C (i.e., the β phase transformation point temperature T β The steel bars were heated and deformed at 70°C for 3 times, with each time being a drawing deformation and a cumulative drawing deformation of 135%, to obtain two 180mm Ø titanium alloy bars.

[0121] Two Ф180mm titanium alloy bars were prepared in the comparative example, the microstructure of one of the bars is shown in Figure 6 The spheroidization of the medium axis alpha phase in the longitudinal microstructure of the bar is poor, and the elongated structure and poor uniformity of the microstructure and properties.

[0122] The impact properties of the two Ф180mm TC8-1 titanium alloy bars prepared in the comparative example are excellent, and the room temperature impact mechanical properties and the transverse and longitudinal mechanical properties of several bars are measured, as shown in Table 1, under the same heat treatment system (920-950℃ / 1-4h, AC+570-600℃×1h, AC), the room temperature impact mechanical properties are lower than those of Example 1, see Table 1 (one bar is randomly selected to test the KU2 of the head and tail); the difference of the room temperature elongation after fracture of the bar in the transverse and longitudinal directions is large, and the difference of the room temperature shrinkage after fracture is large, see Table 2 (one bar is randomly selected for testing).

[0123] Table 1 Room temperature impact mechanical properties of the bars prepared in the examples and the comparative examples

[0124] Serial number Room temperature impact mechanics performance KU2, J Example 1 (Ø180mm) 59.3、51.8、53.9、56.7 Example 2 (Ø260mm) 51.1、53.3、54.3、50.0 Comparative Example 1 (Ø180mm) 45.2、43.1、43.5、40.9 Comparative Example 2 (Ø180mm) 40.2、39.8

[0125] Table 2 Transverse and longitudinal mechanical properties of the bars in the examples and the comparative examples

[0126]

[0127]

[0128] The room temperature impact mechanical properties KU2 of the Ф180mm TC8-1 titanium alloy bar prepared in the present application are ≥50J (for example, 51.8-59.3J), and the room temperature impact mechanical properties KU2 of the Ф260mm TC8-1 titanium alloy bar prepared in the present application are ≥50J (for example, 50-54.3J);

[0129] The TC8-1 titanium alloy bar with a diameter of 180 mm prepared by the present invention has a tensile strength of ≥1011 MPa (e.g., 1011-1031 MPa) at room temperature, a specified non-proportional elongation strength Rp0.2 ≥905 MPa (e.g., 907-926 MPa), an elongation after fracture ≥15% (e.g., 15.2-18.0%), and a cross-sectional reduction rate ≥47% (e.g., 47.1-54.2%); the absolute value of the difference in tensile strength between the transverse and longitudinal directions (head) of the TC8-1 titanium alloy bar with a diameter of 180 mm is ≤7 MPa (e.g., 3-7 MPa), and the absolute value of the difference in tensile strength between the transverse and longitudinal directions (tail) is ≤12 MPa (e.g., 1-12 MPa). The absolute value of the difference in non-proportional elongation strength between the transverse and longitudinal directions (head) is Rp0.2 ≤ 9 MPa (e.g., 4-9 MPa), and the absolute value of the difference in non-proportional elongation strength between the transverse and longitudinal directions (tail) is Rp0.2 ≤ 12 MPa (e.g., 1-12 MPa); the absolute value of the difference in elongation between the transverse and longitudinal directions (head) is ≤ 0.8% (e.g., 0.8-1.1%), and the absolute value of the difference in elongation between the transverse and longitudinal directions (tail) is ≤ 1.8% (e.g., 1.8-2.8%); the absolute value of the difference in cross-sectional shrinkage between the transverse and longitudinal directions (head) is ≤ 4.5% (e.g., 4.2-5%), and the absolute value of the difference in cross-sectional shrinkage between the transverse and longitudinal directions (tail) is ≤ 0.1% (e.g., 0.1-6%);

[0130] At 500°C, the tensile strength of TC8-1 titanium alloy bar with a diameter of 180 mm at room temperature is ≥680 MPa (such as 682-706 MPa), the non-proportional elongation strength Rp0.2 is ≥525 MPa (such as 527-550 MPa), the elongation after fracture is ≥19.5% (such as 19.6-22.8%), and the cross-sectional reduction rate is ≥69.5% (such as 69.8-75.4%); the absolute value of the difference in tensile strength between the transverse and longitudinal directions (head) of TC8-1 titanium alloy bar with a diameter of 180 mm is ≤22 MPa (such as 1-22 MPa), and the absolute value of the difference in tensile strength between the transverse and longitudinal directions (tail) of TC8-1 titanium alloy bar with a diameter of 180 mm is ≤6 MPa (such as 1-6MPa); the absolute value of the difference in non-proportional elongation strength between the transverse and longitudinal directions (head) is Rp0.2≤15MPa (e.g. 2-14MPa), and the absolute value of the difference in non-proportional elongation strength between the transverse and longitudinal directions (tail) is Rp0.2≤15MPa (e.g. 1-13MPa); the absolute value of the difference in elongation after fracture between the transverse and longitudinal directions (head) is ≤3.5% (e.g. 1.3-3.2%), and the absolute value of the difference in elongation after fracture between the transverse and longitudinal directions (tail) is ≤1.5% (e.g. 0.3-1.1%); the absolute value of the difference in cross-sectional shrinkage between the transverse and longitudinal directions (head) is ≤5.5% (e.g. 3.4-5.3%), and the absolute value of the difference in cross-sectional shrinkage between the transverse and longitudinal directions (tail) is ≤2.5% (e.g. 1.1-2.1%).

[0131] The Ф260 mm TC8-1 titanium alloy bar prepared by the method has a tensile strength at room temperature of ≥1015 MPa (such as 1017-1034 MPa), a specified non-proportional elongation strength Rp0.2 of ≥905 MPa (such as 906-925 MPa), an elongation after fracture of ≥15% (such as 15.5-17.8%), and a reduction of area of ≥42% (such as 42.8-57.5%); the Ф180 mm TC8-1 titanium alloy bar has an absolute value of a difference in tensile strength in the transverse direction and the longitudinal direction (head) of ≤11 MPa (such as 3-11 MPa), an absolute value of a difference in tensile strength in the transverse direction and the longitudinal direction (tail) of ≤13 MPa (such as 2-13 MPa); an absolute value of a difference in specified non-proportional elongation strength Rp0.2 in the transverse direction and the longitudinal direction (head) is ≤7 MPa (such as 3-7 MPa), and an absolute value of a difference in specified non-proportional elongation strength Rp0.2 in the transverse direction and the longitudinal direction (tail) is ≤20 MPa (such as 5-19 MPa); an absolute value of a difference in elongation after fracture in the transverse direction and the longitudinal direction (head) is ≤2.5% (such as 0-2.3%), and an absolute value of a difference in elongation after fracture in the transverse direction and the longitudinal direction (tail) is ≤1.8% (such as 0.5-1.8%); an absolute value of a difference in reduction of area in the transverse direction and the longitudinal direction (head) is ≤13% (such as 7-12.8%), and an absolute value of a difference in reduction of area in the transverse direction and the longitudinal direction (tail) is ≤6.5% (such as 1.5-6.3%);

[0132] The Ф260 mm TC8-1 titanium alloy bar prepared by the method has a tensile strength at room temperature of ≥690 MPa (such as 692-708 MPa), a specified non-proportional elongation strength Rp0.2 of ≥525 MPa (such as 529-547 MPa), an elongation after fracture of ≥21.5% (such as 21.5-23.6%), and a reduction of area of ≥68% (such as 68-75.5%); the Ф180 mm TC8-1 titanium alloy bar has an absolute value of a difference in tensile strength in the transverse direction and the longitudinal direction (head) of ≤16 MPa (such as 5-16 MPa), and an absolute value of a difference in tensile strength in the transverse direction and the longitudinal direction (tail) of ≤10 MPa (such as 2-9 MPa); an absolute value of a difference in specified non-proportional elongation strength Rp0.2 in the transverse direction and the longitudinal direction (head) is ≤7 MPa (such as 3-7 MPa), and an absolute value of a difference in specified non-proportional elongation strength Rp0.2 in the transverse direction and the longitudinal direction (tail) is ≤18 MPa (such as 4-18 MPa); an absolute value of a difference in elongation after fracture in the transverse direction and the longitudinal direction (head) is ≤2% (such as 0.8-2%), and an absolute value of a difference in elongation after fracture in the transverse direction and the longitudinal direction (tail) is ≤0.6% (such as 0.1-0.6%); an absolute value of a difference in reduction of area in the transverse direction and the longitudinal direction (head) is ≤6% (such as 2.5-6%), and an absolute value of a difference in reduction of area in the transverse direction and the longitudinal direction (tail) is ≤6% (such as 0.5-5.7%).

[0133] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing TC8-1 titanium alloy bars with high toughness and structural uniformity, characterized in that: The following steps are involved: S1: According to the nominal composition ratio of TC8-1 titanium alloy, a certain amount of pure metal and / or alloy is weighed, the raw materials are mixed and pressed into electrodes, which are welded into an electrode group. After three vacuum consumable arc melting processes, a titanium alloy ingot is obtained. The size and β phase transition temperature T of the titanium alloy ingot are tested. β ; S2: Forging the titanium alloy ingot obtained in step S1, detecting the aspect ratio of the forging blank during the forging process, and determining whether to separate the forging blank according to the aspect ratio of the forging blank; S3: The forging blank obtained in step S2 is placed on a T β -15℃ to T β Heat at +15℃, keep warm, then quickly transfer to a water tank and cool to room temperature; S4: Forging the forging blank obtained in step S3, detecting the aspect ratio of the forging blank during the forging process, and determining whether to divide the forging blank according to the aspect ratio of the forging blank to obtain titanium alloy bars.

2. The preparation method according to claim 1, characterized in that Step S2 includes: S21: The titanium alloy ingot obtained in step S1 is cast on a T β + (50-200℃) heating deformation, measuring the height-to-diameter ratio of the forging billet after each fire, and determining whether to split the forging billet according to the height-to-diameter ratio, a total of 3-4 fires are performed, each fire having 1-2 times of upsetting deformation, to obtain a single first forging billet or multiple first forging billets; S22: Place the single first forging billet or multiple first forging billets on T β - (15-30°C) heating deformation, 1-2 fires, 1-2 upsetting deformations per fire, to obtain a single second forging blank or multiple second forging blanks.

3. The preparation method according to claim 1, characterized in that Step S4 includes: S41: The single third forging blank or the plurality of third forging blanks obtained in step S3 are placed on a T β - (30-50℃) heating deformation, measuring the height-to-diameter ratio of the forging billet after each fire, and determining whether to split the forging billet according to the height-to-diameter ratio, a total of 2-4 fires are performed, with 1-2 upsetting deformations per fire to obtain a single fourth forging billet or multiple fourth forging billets; S42: Place the single fourth forging blank or multiple fourth forging blanks on T β - (40 ~ 70 ℃) heating deformation, 2 to 4 fire times, each fire time is 1 upsetting deformation or 1 drawing deformation, to obtain titanium alloy rods.

4. The preparation method according to claim 1, characterized in that In step S3, the holding time is calculated as 0.3 to 0.5 min / mm, where mm refers to the diameter of the forging blank; The time for rapid transfer to the sink is ≤120s.

5. The preparation method according to claim 2, characterized in that In step S21, measuring the aspect ratio of the forging billet after each firing, and determining whether to perform material separation according to the aspect ratio of the forging billet includes: measuring the aspect ratio of the corresponding forging billet after each firing, and if the aspect ratio of the forging billet after the firing is ≤3.5, not performing material separation and continuing to the next firing; If the height-to-diameter ratio of the forging billet after the fire treatment is greater than 3.5, the material is divided into multiple billets, and then each billet is subjected to the next fire treatment together.

6. The preparation method according to claim 5, characterized in that The height-to-diameter ratio of each blank is 1.5-2.

0.

7. The preparation method according to claim 6, characterized in that In the steps S21 and S22, the upsetting deformation is 30-50%, and the drawing deformation is 40-70%.

8. The preparation method according to claim 3, characterized in that In step S41, measuring the aspect ratio of the forging billet after each firing, and determining whether to perform material separation according to the aspect ratio of the forging billet includes: measuring the aspect ratio of the corresponding forging billet after each firing, and if the aspect ratio of the forging billet after the firing is ≤3.5, not performing material separation and continuing to the next firing; If the height-to-diameter ratio of the forging billet after the fire treatment is greater than 3.5, the billet is divided into multiple billets, and each billet is then processed together for the next fire treatment; The height-to-diameter ratio of each blank is 1.5 to 2.

5.

9. The preparation method according to claim 8, characterized in that In step S41, the upsetting deformation is 30-60%, and the stretching deformation is 40-80%; In step S42, the upsetting deformation is 30-50%, and the drawing deformation is 25-50%.

10. The preparation method according to claim 9, characterized in that In step S42, if there is a continuous drawing deformation at one of the fires 2 to 4, the cumulative drawing deformation does not exceed 70%.

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