RU2192328C2 - Method for making expanded ring blanks of high-alloy nickel alloys - Google Patents

Abstract

FIELD: plastic metal working, namely manufacture of expanded ring blanks. SUBSTANCE: method comprises steps of subjecting initial blanks-washers before heating them to deep overageing; applying heat insulation coating upon them; heating for expanding at (950-1000)C during 1-2 hours. The whole process of deformation of blank-washers is divided by two-three transitions. Overageing, heat insulation and heating for expanding are performed before each transition. Temperature rise before beginning reaging is realized gradually by three stages. At first transition deformation is realized by (20-30)%, at second transition - by (30-40)%, at third transition - by 40% and more. Sizing of expanded blanks and their expanding are realized for overaged blanks. Method provides enhanced quality of ring blanks of high-alloy nickel alloys with quantity of γ′-phase exceeding 25% due to elimination of blank cracking. EFFECT: high-quality expanded ring blanks with uniform fine grain structure. 6 cl, 4 dwg

Description

 The invention relates to the processing of metals by pressure, in particular to methods for manufacturing ring blanks for parts of gas turbine engines, and can find application in industries where various ring-shaped products are made from aging nickel alloys, in particular from alloys with a γ′-phase amount of more than 25 %

 A known method of manufacturing annular blanks from hot-rolled profiles of aging nickel alloys, comprising the manufacture of welded rings of rectangular cross section, their warm rolling under conditions close to isothermal, provided by controlling the heat generation by dosing the degree and speed of deformation, to obtain simple or curly sections with a degree strain of at least 10% after two-stage heating in the temperature range of a heterogeneous state, hot or cold calibration and subsequent heat treatment, the modes of which are determined by the rolling parameters [1]. The main advantage of hot calibration is the possibility of a greater degree of deformation in one transition (up to 1-5%) than in the case of cold calibration (up to 1-2%). The main advantage of cold calibration is to obtain the highest accuracy of ring blanks in diameter.

 The disadvantage of this method is the impossibility of its use for aging nickel alloys with a γ′-phase amount of more than 25% due to the low initial ductility and the limited possibility of their deformation during one heating, as well as due to their unsuitability for welding.

 A known method of manufacturing rolled annular blanks from aging nickel alloys, including the manufacture of the original rings of rectangular cross section, welded or seamless, a warm two-junction rolling under conditions close to isothermal provided by controlling the deformation heat by metering the degree and speed of deformation, to obtain simple or shaped sections with a degree of deformation of at least 20% after two-stage heating in the temperature range of a heterogeneous state and the subsequent calibration and heat treatment, and the first rolling transition is carried out with a degree of deformation of 20-30%, and during the second, after additional heating under the same conditions as before the first transition, they are rolled to obtain the parameters of the cross section and diameter of the finished products [2] (prototype )

 The disadvantage of this method is the impossibility of its use for aging alloys with a γ′-phase amount of more than 25% due to the impossibility of bringing such alloys into a heat-stable overheated state in a heterogeneous temperature range by combining stepwise heating and cooling in order to select phases with heating under rolling, resulting in cracking.

 Alloys with a γ′-phase amount of more than 25% are not used for the manufacture of products using welding, therefore, welded billets for rolling cannot be made from them. The manufacture of seamless blanks for rolling is also fraught with great difficulties, especially at the stage of flashing and overclocking: a large number of cracks are formed, including large (this depends primarily on the mass of the workpieces and on the ratio of the height and diameter of the bar of measured length and size of the final ring product). As a rule, in especially unfavorable cases of the ratios of the specified parameters of the initial billet and the final product after upsetting, instead of flashing and distillation, drilling of the required hole and, if necessary, turning around the outer diameter are used. However, for rings weighing less than 30-40 kg (this also depends on the ratio of the parameters of the initial billet and the final product), sludge, flashing and acceleration are used (sometimes with a small groove in the inner diameter to remove small cracks). These operations are more preferable to drilling and turning when they are used, so less metal goes into the charge: when drilling 100% of the metal from the zone forming the hole, it goes into the charge in the form of chips, and only 15-30% when flashing volume of the specified zone in the form of an otter.

The situation with cracking is further aggravated by the fact that, as a rule, the difficultly obtained initial billets for rolling from the indicated alloys with massive sections are already at the stage of heating them after being put into the furnace with temperatures above ~ 1050 ^o С, they are prone to cracking as a result of "thermal shock "along the inner surface of the initial billets (since it is on their inner surface that the maximum thermal stresses are accumulated during the heating stage [3]). Cracks in this case have a pronounced intergranular nature [4]. In addition, during the transfer of heated preforms from such alloys with the possibility of separating a large amount of the γ′-phase from the furnace to the mill, additional decomposition occurs due to a partial decrease in temperature before rolling, with the release of fine particles that sharply reduce ductility and increase the possibility of crack formation.

Calibration of these rolled blanks by diameter is carried out after heating at high temperatures (1100-1140 ^o C) and, like rolling, is accompanied by intense cracking, therefore, it is made in several transitions up to 0.5-1.5%.

The technical result of the invention:
providing the possibility of 3-transitional deformation without cracks (with an increase in its permissible degree from transition to transition) of the initial blanks from aging nickel alloys with the amount of γ′-phase exceeding 25%;
- prevention of cracking due to "thermal shock" and due to a decrease in ductility due to additional decay during the transfer of workpieces from the furnace to the mill;
- ensuring the preservation of the temperature of the onset of deformation close to the temperature of heating under rolling;
- preventing crack formation during calibration, expanding the allowable range of deformation during it, using, if necessary, more accurate calibration in the cold state;
- the formation of a homogeneous fine-grained structure and, as a consequence, a high and stable level of mechanical properties.

The specified technical result is achieved by the fact that the initial preforms are converted into an overdone state in the furnace for heat treatment before heating for rolling by heating for 0.5-2.0 hours and a temperature 10-30 ^° C higher than the temperature of dissolution of the γ′-phase of this alloy, slow cooling with a furnace at a speed of 0.5-1.0 deg / min to a temperature of 1000-950 ^o C and holding at this temperature for 3-10 hours, followed by cooling in air, and heating under rolling is carried out in a heating furnace at 950-1000 ^o C for 1-2 hours. Specified heat treatment Before heating under rolling, it allows you to form a sawtooth (toothed) structure of the grain boundaries in the blanks before rolling, which completely prevents their tendency to crack during subsequent deformation and repeated heating. Heating blanks for rolling at temperatures of 950-1000 ^o C is optimal. When heated above 1000 ^o C, the alloy becomes less overdeveloped, and therefore less thermo-stable, which negatively affects deformability. Heating of blanks for rolling below 950 ^o With cause a significant drop in the level of initial ductility and increased resistance to deformation, which makes it difficult to implement the process of rolling.

The choice of heating temperature for rolling in the range of 1000-950 ^o With is accompanied by the following considerations:
- the lower the temperature selected within the specified interval, the less the likelihood of cracking during rolling and the finer and more homogeneous the structure in the finished product after complete heat treatment, however, the load on the mill is greatest (due to higher deformation resistance), and the plasticity is somewhat goes down;
- the higher the temperature selected within the specified interval, the lower the load on the mill and the higher the initial ductility; however, the structure formed in the finished product after rolling, calibration, and complete heat treatment becomes somewhat coarser and less uniform than when lower temperatures of this range are used.

Prevention of cracking from the effects of "thermal shock" during sudden heating to temperatures above ~ 1050 ^o C is ensured by the fact that the temperature reaches 10-30 ^o C higher than the temperature of complete dissolution of the γ′-phase of the alloy used before transferring it to overdone in three stages: the first is heating to 700 ± 50 ^o C, ~ 1 h, the second is further heating to 950 ± 50 ^o C, ~ 1 h and the third to a temperature 10-30 ^o C above the temperature of complete dissolution γ ′ - phases of the alloy used.

The prevention of cracking due to a decrease in ductility from additional decomposition and due to a decrease in ductility as a result of cooling by 40-70 ^° C is ensured by the fact that after overcooking, heat-insulating coating is applied to the original rings after overcooking before rolling, for example, asbotkan is glued. This coating significantly reduces (minimizes) the heat loss of billets heated for rolling during transportation from the furnace to the mill.

The prevention of cracking due to a decrease in ductility from additional decomposition and due to a decrease in ductility as a result of stirring by 40-70 ^° C is ensured by the fact that heat-insulating coatings (e.g. asbotkan) are applied to the original rings after overcooking before rolling. This coating significantly reduces (minimizes) the heat loss of billets heated for rolling during transportation from the furnace to the mill.

 The deformation capabilities of workpieces made of aging nickel alloys with a γ′-phase amount of more than 25% are significantly increased due to the separation of the rolling process into 3 transitions (depending on the cross-sectional size and final diameter), and the allowable power interval of each of them (when switching from one to to another) gradually increases due to the manifestation of a more pronounced serration of the grain boundaries, as well as due to the alignment of the sizes of the grains themselves, the average value of which from the transition to the transition gradually decreases, and the alignment of the sizes upnyayuschihsya due to overaging particles γ'-phase.

 Taking into account the indicated change in the deformability of the workpieces, the entire rolling process, for example, rings of large diameter, is divided into three transitions, the first of which is carried out at a degree of 20-30%, the second at 30-40%, and the third at 40% or more. It should be borne in mind that if the diameter of the final product is small and deformation of only 20-30% is necessary to obtain it, then rolling out, of course, is carried out in just one transition. In three transitions, rings of large diameter with a large total deformation (over ≈ 60%) are rolled out. In intermediate situations, the rolling is carried out in two transitions. For example, at an initial thickness of the blank section for a ring of 100 mm after rolling by ~ 30%, it becomes equal to 70 mm, and after rolling in the second transition by 30-40% (from 70 mm), it will be 49-42 mm (t. e. the total deformation in this case will be equal to 51-58%, and not 60-70%, as it seems at first glance). Thus, with a total deformation of up to 20-30%, the rolling is carried out in one transition, up to 50-60% in two transitions, in all other cases in three transitions.

 The increase in the deformation capabilities of the rolled blanks from transition to transition is also ensured by the fact that overcooking and applying a heat-insulating coating is performed before each heating for each rolling transition.

In order to reduce decomposition (and, as a consequence, embrittlement) during the calibration process due to intensive cooling from contact with a massive calibration tool, the calibration itself is carried out not after high-temperature heating at 1100-1140 ^o С (as is done in the majority of cases) , as well as rolling, after overcooking, due to the use of the same step heat treatment as before rolling, and in the same way as when rolling, a heat-insulating coating is used. That is, before calibration, the rolled rings are transferred to an overdone state by heating for 0.5-1.0 hours at a temperature of 10-30 ^o C above the temperature of complete dissolution of the γ′-phase of the alloy used (for alloy EP 742ID ~ at 1140 -1160 ^o ), slow cooling with a furnace at a speed of 0.5-1.0 deg / min to a temperature of 1000-950 ^o C and holding at this temperature for 3-10 hours, followed by cooling in air, and heating under calibration is carried out at 950-1000 ^o C for 1-2 hours. The heating under calibration in a predetermined range 950-1000 ^o C preferably sps Men about 1000 ^o C (e.g., 990 ± 10 ^o C), because Calibration deformation is small (<5%) compared to rolling (for which a single strain is ≥20%), the heat effect of deformation is practically absent, the heat transfer to the tool is very large (due to touching it along the entire contour, and not in a separate running contour zone, as during rolling) - all this causes cooling rings to be more accelerated per unit time during calibration than rolling. This is the reason why it is necessary to maintain a higher heating temperature for calibration in a given optimal range of 950-1000 ^o C. As a result of the above heat treatment of insulation and heating for calibration, the deformation capabilities during hot calibration are significantly increased compared with calibration after heating at 1100-1110 ^o С up to 4-5%. If necessary, calibration can be performed in the cold state up to 1-2%. To do this, the workpieces after stepwise heat treatment (overcooking) need to be cooled rapidly in water (and heat insulation and heating should not be used for calibration), as a result of which the release of finely dispersed γ′-phase particles that reduce ductility is completely suppressed. After calibration, the final heat treatment is performed according to the technical specifications for the finished product.

 Re-curing is carried out by slow cooling from temperatures slightly higher than the dissolution temperature of the γ′-phase of the alloy used, to temperatures that provide a rather large proportion of the release of large particles of this γ′-phase (~ up to 50-80% of the maximum possible amount in the alloy used). As a result of this, an aging alloy gains an increased level of ductility in the temperature range of the heterogeneous state compared to various other states and most importantly, it becomes significantly less prone to decomposition under conditions that change during rolling and calibration of temperatures than in the case of deformation without using overcooking.

 A distinctive feature of the overdone state: particles of the γ′-phase are large, uniform in size and evenly distributed in the volume of grains and grain boundaries; the distances between the particles are relatively large (significantly tens of times greater than, for example, after standard aging); the deformation capabilities of an aging alloy in this state at low temperatures (in the temperature range of a heterogeneous state) are highest in comparison with any other states. Slow cooling from high temperatures of aging alloys with a large potentially possible amount of the γ′-phase (for example, over 25%) provides the optimal alternation of particles of the γ′-phase and carbides at the grain boundaries. The indicated alternation of particles is accompanied by the formation of a sawtooth (toothed) structure of grain boundaries, which is a very effective means of suppressing the tendency of aging alloys to crack formation in the temperature range of deformation [5] (which occurs in them mainly along the grain boundaries).

 Thus, the indicated technical result of the invention leads to the realization of the possibility of defect-free rolling and calibration of ring blanks from highly alloyed aging nickel-based alloys (for example, from EP 742 alloy), which in the recent past were considered suitable only for deformation by pressing or extrusion [6].

In cases where the cross sections of the initial blanks for rolling are relatively small, paragraph 2 of the claims can be used only before the first transition of rolling. And before the second and third transitions of rolling (for any cross-sections of the largest size), claim 2 of the claims can be used partially (heating does not start from a temperature of 700 ± 50 ^o C, but immediately from a temperature of 900 ± 50 ^o C) or are not used at all. The admissibility of all this is being verified experimentally.

A comparative analysis of the claimed solution shows that the new method differs from the known one in that the initial preforms are subjected to special heat treatment before rolling by slow cooling with a furnace from the temperature range of a homogeneous state to temperatures of 1000-950 ^o C and holding at these temperatures. Moreover, in order to prevent the manifestation of thermal shock (mainly - before the first transition of rolling), the temperature is reached at a homogeneous state smoothly, in three stages. To reduce heat loss during the transfer of workpieces from the furnace to the mill, a heat-insulating coating is applied to them (at the initial moment of rolling, most of it, as a rule, crumbles). The whole process of deformation during rolling is divided into three transitions, the initial reserve of plasticity in each of which, when moving from one to another, gradually increases. Re-conditioning and thermal insulation are carried out before each rolling transition. Heating under rolling is carried out in the temperature range 975 ± 25 ^o C for 1-2 hours

Hot calibration is also performed in an overdone state after heating at 990 ± 10 ^o C for 1-2 hours. The permissible degree of deformation in this case is 1-5%. In the case when high accuracy of the inner diameter is required or additional straightening is necessary after hot calibration, a cold calibration is performed (up to 1-2%), before which the workpieces are sharply cooled in water after overcooking.

 As can be seen from the description of the invention, the workpieces undergo special heat treatment before rolling. In this regard, the heating for rolling becomes different: the temperature level and the heating time for rolling and calibration in the proposed method are significantly lower and less than in the prototype method and represents only one temperature step. Moreover, special heat treatment can significantly expand the permissible range of hot calibration from 0.5-1.5% to 1-5%. And in the case when, after special heat treatment, there is a sharp cooling in water, it becomes possible to calibrate in the cold state by 1-2%. It follows from the foregoing that the proposed method with respect to the prototype method has significant distinguishing features.

 A technical solution is known [2] (prototype), in which ring billets of heat-resistant nickel alloys are subjected to warm two-junction rolling under conditions close to isothermal, with degrees of deformation of at least 20%, after two-stage heating in the heterogeneous state temperature range, with the first rolling transition blanks are carried out with a degree of deformation of 20-30%, and the second, after repeated two-stage heating, to the final dimensions of the products.

 However, this method of rolling ring blanks is implemented only for alloys with a moderate amount of γ′-phase (up to approximately 25%), because in this case, due to the relative simplicity of the heterogenization mode, it can be combined with heating under rolling. It is practically not applicable to alloys with a γ′-phase content of over 25% because of the need for more complete overcooking and because of the difficulties in implementing a long two-stage heat treatment mode that provides overcooking in furnaces used for heating under rolling. Therefore, billets from alloys with a large amount of γ′-phase are subjected to a long two-stage heat treatment before rolling in special thermal furnaces, which are not part of the ring rolling complex of equipment, and they are heated for rolling in a heating furnace located near the mill, which only provides access to the temperature of the last stage preceding the heat treatment, at which an overdone condition is recorded in the workpieces. At the same time, due to the very limited initial ductility of aging nickel alloys with a γ′-phase amount of over 25%, the whole rolling process is divided into 13 transitions (depending on the cross-sectional area of the workpieces), the deformation capabilities within each of which gradually increase due to the formation of a structure with jagged grain boundaries and with a combination of particle sizes of the γ′-phase with grain sizes of solid solution close to optimal.

If in the prototype method two-stage heating with intermediate slow cooling and subsequent exposure at a second stage temperature is used to isolate large particles of the γ′-phase due to overcooking (which ultimately leads to an increase in ductility at warm deformation temperatures), then in the new method along with The goal of isolating large particles of the γ′-phase is the goal of forming sawtooth (toothed) grain boundaries and increasing the thermal stability of the alloy through a more complete than in the prototype, overcooking cooling by cooling to the same or lower temperatures (by ~ 50 ^o C) and holding them. In addition, if in the prototype method the rolling process is divided into two transitions with the aim of increasing the plasticity reserve of the workpiece metal, which has not yet been fully used at the first transition, for the second rolling transition by grinding the grains of the solid solution due to recrystallization as a result of heating of the first stage with the second two-stage heating and overcooking during slow cooling and at the second stage of it, then in the new method, the rolling process is divided into three transitions in order to restore the the reserve of plasticity of the metal of the workpieces at each completed transition with a simultaneous increase in its value from transition to transition due to the combined effect of recrystallization and overcooking during two-stage heating. However, if in the prototype method the cooling of billets during transportation from the furnace to the mill is used as a positive effect for adding the alloy (in order to bring it to a more stable state), then in the new method this cooling, on the contrary, is minimized by applying a heat-insulating coating (the greatest stabilization is achieved by cooling in a furnace to lower temperatures). And finally, if in the prototype method, calibration is performed after heating at 1120 ± 20 ^o C to a degree not exceeding 0.5-1.5% (which, nevertheless, is accompanied by intense cracking), then in the new method, hot calibration can carried out after heating at 990 ± 10 ^o C (after special heat treatment) to a degree of 1-5%, and if after special heat treatment to cool the workpieces in water, it becomes possible to calibrate them at room temperature by 1-2%. If necessary, the main part of the calibration can be carried out in hot form, and adjusting the dimensions to more accurate values can be carried out in cold form. These differences indicate the novelty of the proposed solution.

 The invention is illustrated by photographs of the General view of the workpieces, as well as macro - and microstructure. Figure 1 shows a General view of the workpiece, rolled by the prototype method (a), the macrostructure and cracks in the cross section (b) and the microstructure in the crack formation zone (c). Figure 2 presents the annular blank after the first transition rolling according to new technology: a - view from the inside, b - view from the outside. Figure 3 presents the workpiece (a) and its cross section (b) after the second transition rolling, calibration and heat treatment. In FIG. 4 presents the comparative characteristics of the microstructure (x100 and x500) of the annular blanks of alloy EP742 ID manufactured by the prototype method, (a) and the new technology (b).

The proposed method was tested in the manufacture of ring billets from EP 742ID alloy (the amount of γ′-phase is ≈35% [6], the temperature of complete dissolution of the γ′-phase is ≈1130 ^o С [7]). Testing was carried out in parallel according to two options: the prototype method and the new method. Both initial washers (one for each option) weighing ~ 50 kg with an inner diameter of 170 ⁺² mm, a section thickness of 80 ⁺² mm, and a section height of 96 ^{+ 2 mm} were made by upsetting, turning along the outer diameter, and drilling holes with a diameter of 170 mm.

 According to the prototype method, the first rolling transition was carried out to a degree of ~ 30%. On the outer, inner and end surfaces of the washer cooled after rolling, cracks were found to a depth of ~ 15 mm from the inside and to ~ 10 mm from the outside and from the ends. The washer was machined ~ 20 mm from the inside and ~ 15 m from the outside and from the ends. Repeated heating and rolled out the second transition (also by 30%). Many deep cracks formed on all surfaces, and from the inside, deeper (up to half the thickness of the section) than outside. In the corner zones, the cracks are most open (see figure 1).

According to new technology, the puck was subjected to heat treatment for the first time without using claim 2 of the claims (it was heated immediately at 1140 ^{° C.} ). Then it was pasted over with asbot cloth and dried. Then they heated for 1.5 hours at 960-980 ^o C and rolled out by 30%. In the cooled washer on the inner surface, relatively deep cracks (up to ~ 10 mm — see FIG. 2a) that were wide open as a result of rolling were found to have remaining defects without defects (see FIG. 2b). The puck was hollowed out by 15 mm from the inside, heated to a temperature of 1140 ^° C (in accordance with claim 2) with a smooth exit, cooled with a furnace in accordance with paragraph 1 of the claims, glued with asbot cloth, dried, heated for 1.5 hours at 960-980 ^o C and rolled out by 40%. The obtained annular blank had perfectly smooth inner, outer and end surfaces (see figure 3). It was then calibrated in the hot state to bring the diameter to the exact value by calibration in the cold state, in accordance with paragraph 6 of the claims.

 The study of the microstructure of both blanks showed that the grain boundaries in the blank made by the prototype method were smooth, thickened in some areas due to the separation of continuous layers of the γ′-phase (see figa, x500), and in the blank, manufactured by the new technology, they are serrated, thin, and the γ′-phase is large, (0.8-1.0 microns), evenly distributed in the metal volume (it is clearly visible even with an increase of x500 - see fig. 4b). The mechanical properties and parameters of the micro- and macrostructures of the heat-treated billet obtained by the new technology fully meet the requirements of TU for finished products.

 So, on the example of the alloy EP 742ID, it is shown that the manufacture by rolling of defect-free ring blanks from aging nickel alloys with an amount of γ′-phase over 25% is possible using the present invention. Various other technology options that do not contain slow heating and subsequent overcooking due to slow cooling to obtain serrated grain boundaries and a large, evenly distributed γ′-phase are also invariably accompanied by multiple cracking, as well as the prototype method (such results are not shown in the description of the invention )

Using the proposed method for the manufacture of ring billets from aging nickel alloys with a γ′-phase amount of more than 25% will allow:
- to ensure the manufacture of economical blanks for various GTE ring parts from expensive and scarce high-alloy alloys (such as EP 742, EP 741, etc., which until now are not used in the form of rolling rings);
- to ensure the formation of grain boundaries in deformable workpieces of the toothed structure, causing increased deformability and complete prevention of crack formation;
- to reduce the metal consumption of billets for ring-shaped parts of gas turbine engines due to the transfer to the ring rolling blanks made by stamping, forging, undercut, etc.

 - to ensure a uniform fine-grained structure in the final products and, as a result, a high and stable level of mechanical properties.

Sources of information
1. RF patent 2013175.

 2. RF patent 2069595.

 3. Shustovich V.M. Strength analysis of ring parts of metallurgical equipment. M.: Mechanical Engineering, 1976, p.134.

 4. Heat resistant alloys for gas turbines. Translation from English. M.: Metallurgy, 1981, p. 367.

 5. Hessinger G.Kh. Powder metallurgy of heat-resistant alloys. Translation from English. Chelyabinsk: Metallurgy, 1988, p.118-119, 177.

 6. Maslenkova EA, S.B. Maslenkov, etc. The structure and properties of the heat-resistant alloy KhN62BMKTYU (EP 742) -MiTOM, 1992, 11, p.20-24.

 7. Maslenkov S.B., Kabanov I.V. et al. Influence of temperature and strain rate on the ductility of KhN62BMKTYu alloy. - MITOM, 1991, 10, p.21-23.

Claims (6)

1. A method of manufacturing a rolled ring billets from high-alloyed nickel alloys, including obtaining the initial rings of rectangular cross section by draft, piercing and stripping or draft, drilling and turning dimensional billets from rods of large diameter, heating and warm rolling on a ring rolling mill with a degree of deformation at each transition exceeding 20% under conditions close to isothermal, with the provision of regulation of deformation heat generation by dosing the degree and rate of deformation after heating in int the temperature range of the heterogeneous state until rectangular or curly sections are obtained, heating, diameter calibration in the heated state and final heat treatment in the form of quenching with different cooling rates and one or two-stage aging, characterized in that the initial rings are obtained from aging nickel alloys with γ ′ -phase in excess of 25%, for the transfer of which into an overdone state before heating the source rings for warm rolling, they are heat treated in the form of heating for 0.5 - 2.0 hours with support a temperature higher than 10 - 30 ^o With the temperature of the complete dissolution of the γ′-phase of the alloy used, slow cooling with the furnace at a speed of 0.5 - 1.0 deg / min to a temperature of 1000 - 950 ^o With and holding at this temperature for 3 - 10 hours, followed by cooling in air, and heating under rolling is carried out at 950 - 1000 ^o C for 1 - 2 hours 2. The method according to p. 1, characterized in that before heat treatment for overcooking, the initial rings are heated to a temperature that is 10-30 ^° C higher than the temperature of complete dissolution of the γ′-phase of the alloy used, in three stages: in the first, heating to a temperature 700 ± 50 ^o С for one hour, in the second - to a temperature of 950 ± 50 ^o С for one hour, in the third - to a temperature that exceeds by 10 - 30 ^o С the temperature of complete dissolution of the γ′-phase.  3. The method according to p. 1 or 2, characterized in that a heat-insulating coating is applied to the original rings before heating them under warm rolling.  4. The method according to any one of paragraphs. 1-3, characterized in that the warm rolling on the ring rolling mill is carried out in three transitions, in the first - with a degree of deformation of 20 - 30%, in the second - with a degree of deformation of 30 - 40%, in the third - 40% or more.  5. The method according to any one of paragraphs. 1-4, characterized in that the heat treatment for parsing the rings and applying heat-insulating coatings to them is carried out before heating for each transition of warm rolling.  6. The method according to any one of paragraphs. 1-5, characterized in that before heating the rolled annular blanks for calibration, they are heat treated for overcooking according to the heat treatment modes for overcooking the rings before warm rolling, and the heated rolled blanks for calibration are heated according to the heating modes of the rings for warm rolling.

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