WO2008004906A1 - Procédé de fabrication d'un blanc en feuille à partir d'un alliage de titane - Google Patents

Procédé de fabrication d'un blanc en feuille à partir d'un alliage de titane Download PDF

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Publication number
WO2008004906A1
WO2008004906A1 PCT/RU2007/000123 RU2007000123W WO2008004906A1 WO 2008004906 A1 WO2008004906 A1 WO 2008004906A1 RU 2007000123 W RU2007000123 W RU 2007000123W WO 2008004906 A1 WO2008004906 A1 WO 2008004906A1
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Prior art keywords
rolling
temperature
deformation
carried out
billet
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PCT/RU2007/000123
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English (en)
Russian (ru)
Inventor
Vladimir Vasilievich Astanin
Oskar Akramovich Kaibyshev
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Institut Problem Sverkhplastichnosti Metallov Ran
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Application filed by Institut Problem Sverkhplastichnosti Metallov Ran filed Critical Institut Problem Sverkhplastichnosti Metallov Ran
Priority to EP07747854A priority Critical patent/EP2048260A4/fr
Priority to US11/912,649 priority patent/US20080302451A1/en
Publication of WO2008004906A1 publication Critical patent/WO2008004906A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals

Definitions

  • the invention relates to the field of metal forming, and more particularly to sheet rolling, and relates to a method for manufacturing a semi-finished sheet of titanium alloy with a submicrocrystalline structure suitable for low-temperature superplastic deformation.
  • the invention can be used in the manufacture of thin-sheet, including foil, semi-finished product from low-plastic biphasic titanium alloy.
  • the quality of the semi-finished sheet is determined by the characteristics interconnected by means of modes and methods of rolling: surface condition, accuracy of geometric dimensions and shape, mechanical properties due to structure, incl. grain size, semi-finished product, as well as anisotropy or isotropy of mechanical properties, due to the type of metallographic texture formed during rolling.
  • the thickness variation of the sheet semi-finished product can be transverse and longitudinal, respectively, along and across the direction of rolling. Violation of the form, as a rule, is expressed in the occurrence of waviness, warpage of the sheet prefabricated. Any change in the rolling conditions and characteristics of the rolled material is reflected in the final thickness and shape of the semi-finished sheet. In this case, the main factor affecting the formation and change of final dimensions in thickness is the rolling force. It is assumed that the elastic deformation of the working stand is directly proportional to the rolling force [1].
  • Hot rolled strips are usually semi-finished products for subsequent cold rolling.
  • Cold rolling of hot rolled pickled strips is carried out using intermediate annealing [1].
  • a particularly large number of intermediate anneals are required by slightly ductile two-phase titanium alloys.
  • the cold-rolled semi-finished product is characterized by the presence of a pronounced metallographic texture, leading to anisotropy of its properties.
  • Anisotropy of the properties of the semi-finished sheet in most cases is undesirable. An exception may be attributed, perhaps, to electrical steel. If the sheet semi-finished product is subsequently subjected to deformation to obtain a product, such as a shell, then the anisotropy of its properties is not only undesirable, but even unacceptable.
  • the solution to the problem is the use of warm rolling, in which the disadvantages inherent in both hot and cold rolling are not so clearly manifested.
  • CMK submicrocrystalline
  • HK nanocrystalline
  • CMK and HK sheet semi-finished product The presence of a structure in a CMK and HK sheet semi-finished product is very relevant, since it further ensures the manufacture of a complex-shaped product by superplastic molding or in a superplastic molding process combined with diffusion welding (SPF / DS) using the effect of low-temperature superplasticity. Lowering the temperature of molding and / or diffusion welding can increase the durability of the tooling used in these processes and make them generally more economical. There is an opportunity to get a better connection of sheet titanium semi-finished products by reducing the saturation with gases of the surfaces to be joined.
  • the preform has a coarse-grained lamellar or partially recrystallized globular-lamellar structure.
  • An electric resistance furnace KS-300 is used to heat the workpieces.
  • the superplasticity regime requires strict compliance with such deformation parameters as the deformation temperature, strain rate, and grain size in the workpiece under isothermal conditions in the deformation zone.
  • the pretreatment of the preform to a structure with a submicron grain size is carried out by methods other than rolling by pressure treatment, since it is believed that it is not possible to carry out intensive and uniform plastic deformation of the material over the cross section of the preform to obtain a homogeneous submicrocrystalline structure in the sheet prefabricated.
  • multilateral deformation which includes a set of operations of upsetting and drawing with the change of deformation axes.
  • the objective of the invention is to improve the quality of a semi-finished sheet of titanium alloy, intended for further low-temperature superplastic deformation by stabilizing grain size, achieving a more complete isotropy of properties, and also by reducing the thickness variation of the semi-finished product, improving the quality of its surface, while reducing the economic cost of the technological cycle receiving a sheet semi-finished product.
  • Another objective of the invention is to expand the technological capabilities of the method by producing particularly thin-sheet semi-finished products, including foil with predetermined geometric dimensions, surface cleanliness and grain size.
  • An additional object of the invention is to reduce the possible transverse thickness difference of the sheet semi-finished product and increase the degree of flatness.
  • Another additional objective of the invention is to further reduce the cost of implementing the technological cycle of obtaining a sheet of semi-finished product, including the stage of preparation of the structure in the original workpiece.
  • the tasks are solved in the case when the method of manufacturing a semi-finished sheet of titanium alloy suitable for low-temperature superplastic deformation, including rolling a workpiece with a prepared structure at a temperature below the polymorphic transformation temperature in isothermal or quasi-isothermal conditions provided by heating the rolls, differs from the known that rolling is carried out in a low-temperature superplastic mode deformation, in this case, predominantly, in the first pass, the deformation is carried out with the degree ⁇ > ⁇ m j n , where ⁇ m j n is the minimum degree at which the structural state of the alloy is formed in the selected temperature-speed rolling mode, which is necessary to ensure the cooperative grain-boundary slippage (KZGP), in addition, after each subsequent rolling pass, immediately upon exiting the deformation zone, the workpiece is cooled to fix the structural state obtained during deformation, except for t On the other hand, during furnace heating of the billet for the next rolling pass, the heating time is limited in order to avoid disturbing the structural state of the alloy obtained in the previous rolling pass
  • - rolling is carried out at a temperature selected in the temperature range from T PP -450 to T PP -350 ° C; - rolling is carried out with a strain rate selected in the speed range from 10 "3 to 10 '1 s '1 ;
  • the workpiece is heated by contact with the work rolls;
  • - for rolling use a workpiece with a prepared globular structure, with a grain size of less than 1 micron;
  • - for rolling use a workpiece with a prepared lamellar structure, with a grain size in the cross section of less than 1 ⁇ m;
  • - preparation of the structure in the billet for rolling is carried out by pre-rolling the initial billet with a grain size of at least one cross section, not more than 10 microns, until a degree of deformation of at least 80% is reached, while rolling starts at a temperature selected in the temperature range from T pp - 300 ° C to T pp - 200 ° C, and finish at a temperature not lower than the temperature of the main rolling with the strain rate selected in the range from 10 2 to 10 ° c " ⁇ ;
  • - preparation of the structure in the billet for rolling is carried out by preliminary rolling of the initial billet with a grain size of 10 to 80 ⁇ m, carried out in two stages, and at the first stage, the initial billet is rolled to a degree of deformation of not more than 60%, while rolling starts at a temperature , selected in the temperature range of T pp - 200 ° c to T pp - 5O 0 c and finished at a temperature not lower than the temperature of the primary rolling at a strain rate is selected in the range of from 10 "2 to 10" is rolled on the second stage for otovku under isothermal or quasi-isothermal conditions at a temperature and strain rate with the main rolling to achieve the degree of strain 20-30%.
  • - rolling is carried out using a rolling mill having two workers and at least four backup rolls;
  • the method is not only designed to produce a semi-finished sheet suitable for low-temperature superplastic deformation, but also the rolling itself is carried out in the low-temperature superplasticity mode.
  • efforts aimed at preparing the structure in the billet for rolling are spent more strictly for their intended purpose.
  • the technical essence of the rolling method it is more important to change, compared with the known solution, the technical essence of the rolling method.
  • the main mechanism of alloy deformation under conditions of superplasticity is grain boundary slippage (CGP).
  • CGP grain boundary slippage
  • Involvement in the process of deformation of the entire or most of the volume of pre-fabricated ZGP takes on a cooperative character - KZGP [6, 7].
  • KZGP grain boundary slippage
  • the grains do not stretch and remain equiaxed or in other words globular.
  • the formation of both a metallographic and crystallographic texture occurs to a much lesser extent.
  • the texture if the texture took place in the initial billet, then during deformation under conditions of superplasticity, due to KZGP, the texture is scattered.
  • KZGP during rolling provides an isotropy of the properties of the semi-finished sheet in any arbitrary direction on the sheet plane.
  • KZGP When a deforming force is applied, KZGP does not begin to develop immediately.
  • a shear band is formed, combining a large number of consecutively conjugated grain boundaries. This process occurs according to the principle of self-organization and is associated with an increase in angles in triple joints (straightening of boundaries).
  • an intensive increase in the flow stress is observed, which entails an increase in the deformation force (Fig. 7, 8).
  • the flow stress is established at a stationary level or gradually decreases.
  • the specific value of the degree of deformation required to establish the process depends on the grain size in the deformable workpiece, the smaller the grain size, the smaller the degree of deformation required to form the necessary structural state.
  • the stage of stable flow corresponds to the superplasticity regime, when KZGP acts as the main mechanism of deformation.
  • KZGP acts as the main mechanism of deformation.
  • the presence of formed shear bands, that is, KZGP, is judged, as noted above, by the flow stress - strain diagram (hereinafter simplified stress - strain), which is removed for the simplest and most obvious case of sample loading - uniaxial tension (continuous line in Fig. 7 ) It should be noted that with small degrees of deformation (10-15%), the values of relative strains during tension and during rolling (compression) are close, and the comparison is valid.
  • shear bands mainly in the first pass, so that in subsequent passes, when the workpiece section again falls into the deformation zone, already have formed shear bands, and as a result, if possible, in all subsequent passes to stabilize the plastic characteristics of the rolled material and the force rolling.
  • a workpiece with a prepared, globular CMK or HK structure is subjected to rolling, already after 5-7% deformation, the structural state necessary for the implementation of KZGP is achieved. If a workpiece with a prepared, lamellar structure with a plate size in the cross section of less than 1 ⁇ m is subjected to rolling, the degree value can be larger than in the previous case and amount to 10-15%.
  • FIG. Figure 8 shows a diagram taken for a continuous and fractional process of loading a sample with partial (at 100 ° C) cooling during removal of the load, which shows the convergence of both graphs.
  • warm rolling provides semi-finished sheet products with high accuracy and surface finish due to the almost complete elimination of the formation of a gas-saturated layer and scale.
  • the reduction in rolling forces characteristic of superplasticity, and the elimination of the further processing of the sheet prefabricated product to remove the gas-saturated layer, as well as the absence of the need for vacuum result in a significant reduction in the economic costs of implementing the technological cycle of producing high-quality sheet prefabricated products, despite the need to heat the rolls.
  • each particular deformation temperature carried out in the superplasticity mode corresponds to its specific grain size.
  • this is a grain size of less than 1 ⁇ m. This implies the need for special preparation of the structure in the procurement, since industrial steel today does not meet the specified requirements.
  • the invention is concretized and supplemented. Experimentally verified optimal temperature and speed strain intervals under conditions of low-temperature superplasticity are presented, which are suitable for most titanium alloys.
  • the technique which is that when rolling to achieve a compression ratio of 30-60%, after every three to five longitudinal passes, turn the workpiece through 90 ° and conduct a transverse passage, and the rest of the deformation typed during rolling in one direction, allows you to increase the degree of flatness of the card. After 60% reduction, platelet disturbance is not significant.
  • the difference from the known method [5] is that there a similar technique is used only to ensure anisotropy of the properties of the card in the corresponding directions on its plane.
  • the workpiece In the manufacture of prefabricated sheets with a thickness of not more than 1 mm, the workpiece is heated directly by contact with the work rolls. This process can be considered quasi-isothermal. Due to the small thickness of the sheet and the slow rolling speed in the deformation zone rather quickly, already at the initial stage of rolling, the required temperature is established. A workpiece of a greater thickness warms up slowly, or may not have time to warm up to a predetermined temperature during rolling, therefore, such a workpiece is heated in a furnace immediately before rolling. In this case, as a rule, use a continuous furnace. To implement low-temperature superplasticity and KZGP during rolling use a workpiece with a prepared structure.
  • the structure should be a homogeneous structure with equiaxed (globular) grains, with a size of less than 1 micron.
  • the structure may be such in the initial procurement, that is, prepared in advance by known methods [4, 5]. In this case, in order for the KZGP to "work)), it is enough to form shear bands between the grains, which corresponds, as was noted, approximately 5-10% of the deformation.
  • the structure can be prepared in such a way as to transform into the necessary structure during rolling, mainly in the first pass.
  • This requirement “meets the lamellar structure with elongated grains, with a cross-sectional size of from 0.9 to 1.5 microns.
  • the low rolling temperature and the slow deformation rate during rolling provide the dynamic recrystallization process with the division of the plates and the formation of very small, about 0.2 ⁇ m, equiaxed grains. Isothermal conditions ensure the uniformity of the course of this process and its smooth transition into the process of formation of shear bands. In this case, approximately 10-15% deformation is required.
  • KZGP develops, that is, in the absence of dynamic recrystallization, the grains retain their shape and size.
  • Such a lamellar structure can be obtained by preliminary rolling the initial billet.
  • the billet is subjected to preliminary rolling, which is started at a temperature that is lower than the polymorphic transformation temperature by 200 to 300 0 C, and injected at a temperature not lower than the temperature of the main rolling with a strain rate selected in velocities ranging from 10 "2 to 10 ° sec" 1.
  • the strain rate selected in this interval contributes to the active process of dynamic recrystallization.
  • the degree of deformation exceeds the degree, of the order of 70%, necessary for the development of dynamic recrystallization. The latter means that in the process of deformation, the grains acquire an equiaxed shape, and then they lose it again, that is, are elongated.
  • the preform acquires a lamellar structure, with a cross-sectional size of the plates from 0.9 to 1.5 ⁇ m. If the grain size in the original billet exceeds 10 ⁇ m, the billet is subjected to preliminary rolling in two stages. Moreover, at the first stage, the initial billet is rolled to a degree of deformation of not more than 60%, while rolling starts in the temperature range from T pp -300 0 C to T pp -200 ° C and is completed at a temperature not lower than the rolling temperature with a strain rate selected in the range from 10'2 to 10 s "1.
  • the workpiece is rolled under isothermal conditions at a temperature and with a strain rate of the main rolling until a strain of 20-30% is reached.
  • a feature of such a two-stage rolling is that the degree of deformation at at the first stage, the degree of deformation should be less than that leading to the formation of equiaxed (globular) grains in the workpiece as a result of dynamic recrystallization. Deformation with a degree of less than 60% only leads to elongation and thinning of the plates. If the grains become equiaxed and are large enough, then Subsequently, significant deformation will be needed to give them a plate shape.To prevent the development of the process of dynamic recrystallization, thin plates can be obtained.
  • heating for the first pass of the main rolling may be accompanied by static recrystallization, which contributes to some leveling of the structure and globularization of the grains.
  • the structure is completely leveled, and the grains acquire equiaxed shape already during the main rolling process.
  • the highest dimensional accuracy of a semi-finished sheet product can be achieved if rolling is carried out using a rolling mill having two workers and at least four backup rolls, for example a six-roll mill (Fig. L).
  • the cooling of the backup rolls in direct contact with the work rolls allows, firstly, to increase the rigidity of the roll system. Secondly, the uneven cooling of the backup rolls directly in contact with the work rolls allows you to create a slight gradient along the length of the barrel of the work roll, sufficient to reduce the transverse thickness variation of the sheet. The most optimal is the cooling of the backup rolls by cooling the respective bearing units.
  • the cooling intensity of the bearing units in this case depends on the required value of the roll barrel
  • an adjustable electric resistance heater integrated in the roll, which allows you to set the optimum temperature of the roll depending on the grade of alloy and grain size in the workpiece for rolling.
  • FIG. 1 is a diagram of a method
  • Fig.Z is the microstructure and electron diffraction pattern of the sheet semi-finished product obtained after rolling the initial billet with a structure prepared by methods other than rolling;
  • Figure 4 - the microstructure of the initial billet prepared by rolling in one stage, x500;
  • Figure 5 the microstructure of the initial billet prepared by rolling in two stages, x500;
  • 6 is a microstructure of a sheet of semi-finished product obtained after rolling the initial billet with the structure prepared by rolling;
  • FIG. 7 stress-strain diagrams for a continuous and fractional process with intermediate annealing without load for 1 min;
  • Fig. 8 is a stress-strain diagram for a continuous and fractional process with partial (at 100 ° C) cooling during unloading; Fig.9 - the calculated deflection of the backup roll under the action of the experimentally obtained rolling force.
  • the maximum difference in the deflection of the middle part and the edge of the barrel is 0.054 mm.
  • KTP 18x10 "6 and a wolf diameter of 150 mm, it is compensated by a temperature difference of 40 ° C.
  • FIG. 1 shows: 1 - rolled billet; 2 - work rolls with built-in heaters (the latter are not shown in the figure); 3 - backup rolls (number - four); 4 - feedthrough preheating furnace. Examples of specific performance of the method:
  • Examples are given on methods for manufacturing a prefabricated sheet 0.3 mm thick and a 0.05 mm thick foil from titanium alloys BT-6 and BT-22.
  • Two-phase titanium alloys BT22 and BT6 were processed.
  • the temperature of the polymorphic transformation and the chemical composition of the alloys in mass. % are given in table 1. Examples are given for the manufacture of strips with a thickness of 0.1; 0.5 and 0.7 mm. Table 1
  • Example 1 It is necessary to obtain by rolling a sheet of two-phase titanium alloy BT6 0.5 mm thick.
  • the initial billet with a thickness of 14 mm and a size of 6O x 100 mm, with a grain size of 0.4 ⁇ m (Fig. 2) was obtained by multiaxial precipitation with decreasing temperature to 600 0 C [5].
  • the rolling temperature was chosen 56O 0 C, which is 43O 0 C lower than the temperature of the polymorphic transformation.
  • the linear speed of rotation of the rolls 1 mm / s, which corresponded to the strain rate in the center 5xlO "3 s " 1 .
  • the initial billet was rolled on a six-roll mill LIS-6/200, with heated work rolls with a diameter of 65 mm (Fig. 1).
  • the heating temperature of the work rolls is 560 0 C.
  • the rolls were heated from the inside by built-in resistance electric heaters.
  • the heating of the backup rolls occurs as a result of contact with the work rolls and reaches 120-180 ° C in the middle of the roll barrel.
  • the cooling of the backup rolls is carried out by pumping liquid lubricant through the bearing units.
  • the cooling rate is selected so that the temperature difference between the middle and the edge of the barrel of the backup rolls is 40 ⁇ 5 ° C, which provides compensation for the deflection of the rolls and obtain a uniform sheet thickness.
  • the temperature of the backup rolls is controlled by a thermal imager.
  • a feed-through furnace was installed at the mill inlet (Fig. 1), the heating temperature in which was 560 0 C.
  • the degree of deformation in the first pass was 15%. As we approach the final thickness, the degree of deformation per passage decreases. Total number of passes 32.
  • the preform was cooled in air to a temperature of 400 to 45O 0 C. Before each subsequent pass, the preform was placed in a continuous furnace. The heating time was determined from the calculation of 1 min per 1 mm of thickness, which is sufficient only for heating the workpiece and does not imply holding the workpiece at a temperature. After reaching a strip thickness of 5 mm, the length of the workpiece becomes greater than the length of the continuous furnace.
  • the workpiece is fed to the rolls.
  • the rest of the workpiece is heated by a continuous furnace as the strip enters the deformation zone.
  • the long billet cannot be heated entirely, since at a low rolling speed this will lead to exposure at the rolling temperature.
  • the length of the heated zone of the kiln was 300 mm. This technique provides heating, but limits the residence time of the billet at rolling temperature, which allows you to maintain the structural state of the material between passes, which is necessary for the implementation of the main mechanism of superplasticity.
  • the furnace temperature was set equal to 400 to 450 ° C, and the final heating was carried out directly from the work rolls when the strip entered the contact zone.
  • the resulting sheets were thoroughly examined. Deviations of the sheet thickness from the specified 0.5 mm did not exceed 0.02 mm.
  • the surface was covered with a dense thin oxide film of a dark blue color with no signs of scale.
  • the methods of microstructural analysis and microhardness measurements showed the absence of gas saturation of the surface layer at a depth of more than 1 ⁇ m.
  • the intensity of the texture maxima, characterizing the degree of anisotropy did not exceed two units of pole density.
  • the temperature of the feed-through furnace at the inlet of the mill was 550 ° C.
  • the linear speed of the rolls was 1 mm / s, which, at 10% compression during the passage, ensured a deformation rate in the center of 6x10 "3 s " 1 . This corresponds to the conditions of low temperature superplasticity for a given alloy.
  • the use of a feed-through furnace eliminates the undercoating of the workpiece at such a low feed rate.
  • the workpiece was cooled in air.
  • the resulting stripes were coated with a dense dark blue oxide film. Microstructural analysis and microhardness measurements showed the absence of gas saturation of the surface layer, at least at a depth whiter than 1 ⁇ m.
  • Deviations of the sheet thickness from the specified 0.7 mm did not exceed 0.01 mm.
  • Example 3 Similar to example 1 except that the rolling temperature was chosen equal to 600 0 C, and the deformation per pass at the initial stage was 20%. At the same roll rotation speed (1 mm / s), the deformation rate in the center was 1, IxIO -2 C "1. This also corresponds to the conditions of low-temperature superplasticity for an alloy with a given grain size at a given temperature. As a result, the number of passes is reduced to 23 while maintaining the geometric parameters of the resulting sheet. In this case the grain size of the original workpiece is preserved. This technique has achieved a significant increase in process productivity.
  • Example 4 Similar to example 1 except that at the initial stage of rolling, after every 3 passes, the workpiece was rotated 90 ° and a transverse pass was made. This technique was performed until a reduction ratio of 60% was achieved, while the workpiece width became equal to the roll barrel length (200 mm). To achieve the necessary combination of the degree of compression and the width of the workpiece, the dimensions of the original workpiece, in contrast to example 1, were selected 16 x 60 x 80 mm, This method has achieved the following goals:
  • Example 5 Similar to example 1, but aimed at obtaining sheets with a thickness of less than 0.5 mm.
  • the strip When the strip reaches the specified value, it is fed to the hot rolls without preliminary heating, or the temperature of the input device is set to not more than Vi T rolling.
  • This technique limits as much as possible the residence time of the workpiece at the rolling temperature, which helps to maintain the state of superplasticity of the material between the passes and increases the accuracy of the final rolling in thickness.
  • Example 6 As the initial billet taken industrial bar BT22 alloy with a diameter of 60 mm with a plate structure with an average plate size of 80 x 6 microns.
  • the billet is heated to a temperature of 850 ° C, which is 30 ° C lower than the temperature of polymorphic transformation, and 300 0 C higher than the temperature of the main rolling.
  • the workpiece is rolled on a DUO 300 mill, on cold rolls, at a speed of 200 mm / s. With a compression ratio of 20% per pass, this corresponds to a strain rate of 1.2 s "1.
  • the rolling is carried out in several passes to a thickness of 10 mm, which is 83% reduction. After the first three passes, the workpiece is turned and one transverse pass is performed.
  • the workpiece temperature decreases in each pass by 10-15 ° C up to 700 ° C.
  • the degree of compression per pass is reduced, which leads to a gradual decrease in the deformation rate in the center to values below 10 s "1 .
  • the scale is cleaned from the preform and the gas-saturated layer of 0.12 mm on each side is removed.
  • a lamellar structure is formed with thin grains elongated in the rolling direction, the average size of which in the transverse direction is 1.3 ⁇ m (Fig. 4).
  • the final rolling was carried out analogously to example 2. But in the first pass, an increased pressing force of the rolling stand was required.
  • the lamellar structure is gradually transformed into a globular submicrocrystalline and the process goes into a low-temperature superplasticity mode.
  • the structure of the obtained sheet is less uniform than in the case of a submicrocrystalline preform, but also submicrocrystalline. With a grain size of 0.4-0.5 microns and an elongation coefficient in the longitudinal section of the strip 1.4. The crystallographic texture is poorly expressed.
  • Example 7 As the initial billet, a BT22 alloy billet with a size of 100x60x60 mm and an average grain size of 50 ⁇ m was taken. The workpiece is heated to a temperature of 820 0 C. The workpiece is rolled on a DUO 300 mill, on cold rolls, at a speed of 100 mm / s. With a compression ratio of 20% per pass, this corresponds to a strain rate of 0.7 s "1. The rolling is carried out in two stages, with several passes at each. The first stage is rolling to a thickness of 27 mm, which is 55% compression. In the preliminary process rolling temperature of the workpiece decreases at each pass by 10-15 0 C up to 65O 0 C.
  • Patent RU 2058418 IPC C22F 1/18, 1996.
  • Patent RU 2224047 IPC C22F 1/18, 2004.

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Abstract

L'invention concerne un procédé de fabrication d'un blanc en feuille à partir d'un alliage de titane possédant une structure micro-cristalline, qui est adapté à la déformation superplastique à basse température. L'invention peut s'utiliser de la manière la plus efficace lors de la fabrication d'un blanc en feuille mince (y compris le feuil) à partir d'un alliage de titane biphasé à faible plasticité. Le procédé comprend le laminage du blanc à structure préalablement préparée à une température inférieure à celle de la transformation polymorphe dans des conditions isothermiques ou quasi-isothermiques assurées par le réchauffement des cylindres de laminage. Le laminage est effectué dans le mode de déformation superplastique à basse température. Au stade du premier passage notamment, la déformation est effectuée avec un degré εmin, qui correspond au degré minimal auquel on effectue, dans un mode de laminage à vitesse et température sélectionnées, un état structurel de l'alliage qui est nécessaire pour assurer glissement coordonné à la limite des grains lors de la déformation. Après chaque tour de laminage successif, directement à la sortie du foyer de déformation, le blanc est refroidi pour fixer l'état structurel obtenu lors de la déformation. Pendant le réchauffement au four avant un tour de laminage successif, on limite le temps de réchauffement pour éviter toute perturbation de l'état structurel de l'alliage, obtenue au tour de laminage précédent. On parvient à améliorer ainsi la qualité du blanc en feuille à partir d'un alliage en titane destiné à une déformation superplastique ultérieure à basse température.
PCT/RU2007/000123 2006-07-06 2007-03-14 Procédé de fabrication d'un blanc en feuille à partir d'un alliage de titane WO2008004906A1 (fr)

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Application Number Priority Date Filing Date Title
EP07747854A EP2048260A4 (fr) 2006-07-06 2007-03-14 Procédé de fabrication d'un blanc en feuille à partir d'un alliage de titane
US11/912,649 US20080302451A1 (en) 2006-07-06 2007-03-14 Method of Manufacturing Semi-Finished Sheet Products From Titanium Alloy

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CN112916644A (zh) * 2021-01-18 2021-06-08 中国航发北京航空材料研究院 一种包套叠轧制备TiAl合金板材的方法
CN113231469A (zh) * 2021-05-10 2021-08-10 贵州大学 一种锌基复合材料用铝合金材料包套热轧的方法
CN114561533A (zh) * 2022-04-08 2022-05-31 攀钢集团研究院有限公司 一种纯钛薄板表面晶花的加工方法

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CN114309116B (zh) * 2021-11-18 2023-10-24 洛阳双瑞精铸钛业有限公司 一种宽幅超薄钛箔带材的制备方法

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CN102921731A (zh) * 2012-11-13 2013-02-13 西部钛业有限责任公司 一种钛合金薄板的温轧加工方法
CN112916644A (zh) * 2021-01-18 2021-06-08 中国航发北京航空材料研究院 一种包套叠轧制备TiAl合金板材的方法
CN113231469A (zh) * 2021-05-10 2021-08-10 贵州大学 一种锌基复合材料用铝合金材料包套热轧的方法
CN113231469B (zh) * 2021-05-10 2023-04-18 贵州大学 一种锌基复合材料用铝合金材料包套热轧的方法
CN114561533A (zh) * 2022-04-08 2022-05-31 攀钢集团研究院有限公司 一种纯钛薄板表面晶花的加工方法
CN114561533B (zh) * 2022-04-08 2024-03-12 攀钢集团研究院有限公司 一种纯钛薄板表面晶花的加工方法

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