RU2301845C1 - Method of production of items from high-temperature wrought nickel alloy - Google Patents

Abstract

FIELD: production of items from high-doped high-temperature wrought nickel alloys for disks of gas-turbine engines.

SUBSTANCE: proposed method includes vacuum induction melting for obtaining ingot for deformation. At least one cycle of pre-extrusion is performed which is followed by recrystallization annealing. Extrusion of blank is performed in die by repeated forcing of blank from cylindrical to taper part of die at temperature below T_c.d.γ' by 55-95C. Die is heated to temperature not below T_c.d.γ' -250C and not above the blank heating temperature. Rate of deformation

, where T_c.d.γ' is temperature of complete dissolving of γ' phase. During each subsequent stage of forcing-out the blank, direction of forcing out is reversed as compared with previous stage. Prior to final deformation, blank is subjected to intermediate annealing. Items made from high-temperature nickel alloy have homogeneous structure in complex stampings and stable level of properties ensuring reduction of extrusion force and final deformation.

EFFECT: enhanced efficiency; increased factor of utilization of metal.

7 cl, 1 dwg, 3 tbl, 6 ex

Description

The invention relates to the field of metallurgy, and in particular to the production of products from highly alloyed heat-resistant wrought nickel alloys, in particular GTD disks.

Known methods for producing disks of nickel heat-resistant alloys, in which a deformation is used an ingot of vacuum induction smelting followed by vacuum arc remelting (VI + VDP). To develop a technological process, the percentage of the γ'-phase content in the alloy, the temperature of its complete dissolution (Тпγγ), the temperature of nonequilibrium solidus, and the temperature of solidus (Ts) are determined. In order to obtain a preform with uniform recrystallized grain, which has increased ductility, the ingot is homogenized, repeatedly deformed using intermediate annealing and heating, and its transverse dimensions are reduced by pressing or rotational forging. Next, repeated deformation is carried out to increase the diameter of the workpiece (EP patent No. 0248757, US patent No. 5120373, 5693159).

The disadvantages of the methods are the need for large and energy-intensive equipment for the smelting of large diameter ingots and their deformation. In addition, rods from high-temperature-resistant alloys can only be obtained by pressing with high deformation forces, which requires the use of powerful specialized equipment - horizontal hydraulic presses. At the same time, the CMM is reduced due to large departing during the pressing operation (press balance and output end).

A known method of manufacturing disks of highly alloyed heat-resistant nickel alloys, including:

- vacuum induction smelting;

- obtaining a cast billet for deformation by directional crystallization in a ceramic form of constant cross section with a temperature gradient at the solidification front of 20-200 ° C / cm;

- homogenizing annealing in the temperature range Tprγ'-10 ° C ÷ Tsol with subsequent cooling to 900-1000 ° C at a rate of ≤55 ° C / h;

- preliminary deformation by sediment in isothermal conditions for 2 or more times in the temperature range Tprγ'-80 ° C ÷ Tprγ '+ 10 ° C, with a total degree of deformation of more than 55% and intermediate annealing in the same temperature range;

- the final deformation in isothermal conditions in the temperature range Tprγ '- 20-100 ° C;

- heat treatment, consisting of preliminary annealing in the temperature range 900-1100 ° C, processing on a solid solution with regulated cooling and aging in the temperature range 650-1050 ° C (RF patent 2215059).

The disadvantage of this method is the limited total degree of deformation during upsetting of the ingot, which does not allow to obtain a homogeneous structure in complex-shaped large-sized stampings (with a large difference in the degrees of deformation over the stamping cross section) before heat treatment.

The closest analogue, taken as a prototype, is a method for producing a product from heat-resistant nickel alloy.

The method includes:

- vacuum induction smelting;

- obtaining an ingot for deformation with a diameter of 320 mm by vacuum arc remelting;

- homogenizing annealing at a temperature of 20-30 ° C above the complete dissolution of the γ'-phase (Tprγ ') for 4-8 hours, with cooling with a furnace to the temperature of maximum coagulation of the γ'-phase, then in air;

- pressing the ingot in a container with a degree of 65-75% per bar at a temperature below Tprγ 'at 40-60 ° C;

- cutting the bar into measuring blanks;

- prepress in a closed container with a degree of 35-50% at a temperature below Tprγ 'at 60-80 ° C;

- the final deformation by combining precipitation and stamping at a temperature below Tprγ 'by 40-60 ° C with a degree of 75-85%;

- heat treatment, consisting of preliminary annealing at a temperature below Tprγ 'of 100-130 ° C, treatment for a solid solution at a temperature of Tprγ' ± 10 ° C with regulated cooling and subsequent aging (AS USSR 1637360).

The prototype method has the following disadvantages:

- the application of the method of smelting a large ingot (VDP) does not provide sufficient uniformity in the structure and chemical composition of the alloy, which is the reason for the instability of properties in stampings;

- low metal utilization due to the large shrinkage shell in the ingots, large waste during the pressing operation (press balance and output end);

- the untreated macrostructure of the initial billet (press product) requires large degrees of deformation at the final stamping stage, which is not always possible, especially in complex forgings;

- great pressing efforts and the use of powerful specialized equipment - horizontal hydraulic presses.

The technical task of the invention is the creation of a method for producing products from heat-resistant nickel alloy with a uniform structure in complex forgings (with a large difference in the degrees of deformation over the stamping cross section) and a stable level of properties, which provides a reduction in pressing forces and final deformation, the possibility of using universal equipment, and an increase in the utilization rate metal.

, где Тпрγ′ - температура полного растворения γ′-фазы, причем на каждом последующем этапе выдавливания заготовки направление выдавливания меняют на противоположное относительно предыдущего этапа, а перед окончательной деформацией заготовку подвергают промежуточному отжигу.To achieve this goal, a method for producing a product from heat-resistant nickel alloy is proposed, which includes vacuum induction smelting, obtaining an ingot for deformation, homogenizing annealing of the ingot, pressing and pre-pressing the workpiece, final deformation and heat treatment, characterized in that at least one is carried out before pressing preliminary pre-pressing followed by recrystallization annealing, pressing the workpiece is carried out in a stamp consisting of a cylindrical and conical parts, Uteem multiple extrusion billet at a temperature below 55-95 ° C Tprγ 'of the cylindrical portion of the taper die heated to a temperature not lower Tprγ' - 250 ° C and not higher than the heating temperature of the preform, at a strain rate

where Tprγ ′ is the temperature of complete dissolution of the γ′-phase, and at each subsequent stage of extrusion of the workpiece, the direction of extrusion is reversed relative to the previous stage, and before the final deformation, the workpiece is subjected to intermediate annealing.

An ingot for deformation is obtained in the form of a measured cast billet, mainly by methods of directed crystallization, by vacuum-arc remelting, by investment casting.

в штампе, нагретом до температуры не ниже Тпрγ′ - 250°С и не выше температуры нагрева заготовки.Prepressing the workpiece before pressing is carried out in one or several transitions at a temperature Tprγ ′ - 95 ° С≤Т≤Тпрγ ′ + 10 ° С with a single degree of deformation of 20-40% and a speed

in a stamp heated to a temperature not lower than Тпрγ ′ - 250 ° С and not higher than the heating temperature of the workpiece.

Recrystallization annealing of the preform is carried out at a temperature of Tprγ′-20 ° C≤T≤Tprγ ′ + 30 ° C for 3-6 hours, cooling is carried out to a temperature of 200-250 ° C below Tprγ ′ at a speed of 15-30 ° C / hour .

The intermediate annealing of the preform is carried out at a temperature of 50 ÷ 95 ° C below Tprγ ′ with a holding time of at least 6 hours and cooling at a speed of 20-60 ° C / h to a temperature of 200-250 ° C below Tprγ ′ followed by cooling of the preform in air.

и степенью деформации не более 85% в штампах, нагретых до температуры не ниже Тпрγ′ - 200°С и не выше температуры нагрева заготовки.The final deformation is carried out at a temperature of 55-95 ° C below Tprγ ′ with a speed

and a degree of deformation of not more than 85% in dies heated to a temperature not lower than Tprγ ′ - 200 ° C and not higher than the heating temperature of the workpiece.

After the first stage of extrusion of the workpiece with a volume equal to or less than the volume of the conical part of the stamp, the workpiece is pressed in the cylindrical part of the stamp with a degree of pressing up to 45%.

и степенью деформации до 45%, и подпрессовки заготовки в цилиндрической части штампа обеспечивают формирование в заготовке зерна величиной менее 10 мкм в процессе контролируемой динамической рекристаллизации. Получение подобной структуры позволяет реализовать эффект сверхпластичности при окончательной штамповке, снизить усилия деформации, повысить стойкость штампового инструмента и обеспечить формирование однородной мелкозернистой структуры в сложнопрофильных штамповках. Прессование заготовки по предложенному способу позволяет избежать потерь на пресс-остаток и выходной конец, снизить удельные усилия прессования в 3-5 раз (до 200-300 МПа) по сравнению со способом-прототипом и проводить деформацию на универсальных гидравлических прессах малой мощности без использования специального оборудования.Compression of a workpiece by repeated extrusion of a workpiece at a temperature of 55-95 ° C below Tprγ ′ into the conical part of the die, heated to a temperature not lower than Tprγ ′ - 250 ° C and not higher than the heating temperature of the workpiece, with a strain rate

and a degree of deformation of up to 45%, and pre-pressing the workpiece in the cylindrical part of the stamp ensures the formation of grain in the workpiece with a size of less than 10 microns in the process of controlled dynamic recrystallization. Obtaining such a structure allows you to realize the effect of superplasticity in the final stamping, to reduce the deformation forces, to increase the resistance of the stamping tool and to ensure the formation of a homogeneous fine-grained structure in complex forgings. Pressing the workpiece according to the proposed method allows to avoid losses on the press residue and the output end, to reduce the specific pressing forces by 3-5 times (up to 200-300 MPa) in comparison with the prototype method and to deform on universal hydraulic presses of low power without using special equipment.

Obtaining a measured cast billet can significantly reduce dendritic segregation compared to a large ingot for several billets, which allows to increase the level and uniformity of product properties, reduce the complexity of the manufacturing process of cast billet and metal loss due to:

- improving the surface quality of the cast billet, which reduces the machining allowance;

- reduce or eliminate the formation of a shrink shell and a good structure and surface of the bottom of the ingot.

в штампе, нагретом до температуры не ниже Тпрγ' - 250°С и не выше температуры нагрева заготовок, позволяет получить однородную деформацию по всему объему заготовки и при последующем отжиге обеспечить равномерную рекристаллизацию.Prepressing the cast billet at a temperature Tprγ'-95 ° C≤T≤Tprγ '+ 10 ° C with a single degree of deformation of 20-40% and speed

in a stamp heated to a temperature not lower than Tprγ '- 250 ° C and not higher than the heating temperature of the workpieces, it is possible to obtain uniform deformation over the entire volume of the workpiece and, upon subsequent annealing, to ensure uniform recrystallization.

Recrystallization annealing of the preform at a temperature of Tprγ'-20 ° C≤T≤Tprγ '+ 30 ° C for 3-6 hours allows you to get a homogeneous matte macrostructure in the preforms with a micrograin size of 100-250 microns.

If technological operations of preliminary prepressing of the cast billet and subsequent recrystallization annealing of the billet are excluded, the untreated macrostructure is preserved in the press rod, which requires large degrees of deformation at the final stamping stage, which is not always possible. In complex forgings made from such blanks, an inhomogeneous macrostructure is formed. Stampings with such a structure have unstable mechanical properties over the volume of the workpiece.

Cooling to a temperature of Tprγ '- 200-250 ° C at a speed of 15-30 ° C / hour allows for maximum coagulation of the γ'-phase, which allows to increase the technological plasticity of the material and reduce the pressing and settling forces.

The technological scheme of the proposed method of pressing is illustrated by the drawing, where 1 is the conical part of the stamp, 2 is the cylindrical part of the stamp, 3 and 4 are the opposite end surfaces of the workpiece.

Examples of implementation

Under experimental conditions, disks made of heat-resistant nickel alloys EK 151 and EP 975 with a diameter of 210 mm were obtained. Examples of obtaining disks by the proposed method and the prototype method are presented in table 1.

Example 1

Ingots of alloy for EK 151 disks containing 48% of the γ'-phase with a temperature of its complete dissolution of 1165 ° C were smelted in a vacuum induction furnace. Billets for deformation of ⌀ 103 × 50 mm and a weight of 25 kg were obtained by directional crystallization.

Homogenizing annealing was carried out at a temperature of 1200 ° C; the ingot was cooled at a rate of 30 ° C / h.

в закрытом контейнере, нагретом до температуры 1000°С.Prepressing was carried out at a heating temperature of the workpiece 1150 ° C with a degree of deformation of 30% and speed

in a closed container heated to a temperature of 1000 ° C.

Recrystallization annealing was carried out at a temperature of 1180 ° C for 4 hours, cooling to a temperature of 950 ° C at a rate of 20 ° C / hour.

в штампе, нагретом до температуры 915°С.Pressing was carried out by extruding a workpiece in a stamp in two stages according to the scheme shown in the drawing, where 1a is the first stage of pressing, 1c is pressing with a change in the position of the workpiece by 180 °, at a heating temperature of the workpiece 1110 ° C. The total degree of deformation of 64% with a specific pressing force of 250 MPa and speed

in a stamp heated to a temperature of 915 ° C.

Intermediate annealing was carried out at a temperature of 1110 ° C for 7 hours, cooling to a temperature of 950 ° C at a rate of 40 ° C / hour.

в штампе, нагретом до температуры 965°С.The final deformation of the disk blank was carried out at a temperature of 1110 ° C with a degree of deformation of 5 in the hub and 60% in the stamping sheet and the strain rate

in a stamp heated to a temperature of 965 ° C.

As a result, stamping with a uniform matte macrostructure and a micrograin size of 8-10 microns was obtained.

After hardening heat treatment, a homogeneous microstructure with a micro grain size of 80-100 microns was obtained.

Example 2 is performed analogously to example 1 according to the modes shown in table 1. Workpieces for deformation were obtained by vacuum-arc remelting.

Example 3

Alloy for EP 975 disks containing 58% of the γ'-phase with a temperature of its complete dissolution of 1198 ° C.

EP 975 alloy ingots were smelted in a vacuum induction furnace. Billets for deformation of ⌀ 103 × 250 mm and a weight of 25 kg were obtained by directional crystallization.

Homogenizing annealing was carried out at a temperature of 1215 ° C; the ingot was cooled at a rate of 30 ° C / h.

в штампе, нагретом до температуры 1000°С.Prepressing was carried out at a heating temperature of the workpiece 1150 ° C with a degree of deformation of 30% and speed

in a stamp heated to a temperature of 1000 ° C.

Recrystallization annealing was carried out at a temperature of 1210 ° C for 4 hours, cooling to a temperature of 950 ° C at a rate of 20 ° C / hour.

в штампе, нагретом до температуры 1000°С.The second preliminary prepressing was also carried out at a heating temperature of the workpiece 1150 ° C with a degree of deformation of 30% and speed

in a stamp heated to a temperature of 1000 ° C.

Recrystallization annealing was carried out at a temperature of 1210 ° C for 4 hours, cooling to a temperature of 950 ° C at a rate of 20 ° C / hour.

The pressing was carried out by extruding the workpiece in a stamp in two stages according to the scheme shown in the drawing (a, b, c), where 1b is the intermediate pre-pressing after the first stage of pressing at a heating temperature of the workpiece of 1130 ° C.

Intermediate annealing was carried out at a temperature of 1120 ° C for 7 hours, cooling to a temperature of 950 ° C at a rate of 40 ° C / hour.

в штампе, нагретом до температуры 980°С.The final deformation of the disk blank was carried out at a temperature of 1130 ° C with a degree of deformation of 5 in the hub and 60% in the stamping sheet and the strain rate

in a stamp heated to a temperature of 980 ° C.

After hardening heat treatment, a homogeneous microstructure with a micro grain size of 80-90 microns was obtained.

Example 4

Alloy for EP 975 disks containing 58% of the γ'-phase with a temperature of its complete dissolution of 1198 ° C.

EP 975 alloy ingots were smelted in a vacuum induction furnace. Workpieces for deformation of ⌀ 103 × 250 mm and a weight of 15 kg were obtained by investment casting.

Homogenizing annealing, pre-pressing and recrystallization annealing are performed analogously to example 3 according to the modes shown in table 1.

в штампе, нагретом до температуры 948°С.Pressing was carried out by extruding the workpiece in the stamp at the 1st stage of extrusion, settling the workpiece in the cylindrical part of the stamp and extruding the workpiece at the 2nd stage according to the scheme shown in the drawing (a, c, b), at a heating temperature of the workpiece 1113 ° C with a total degree of deformation of 74% and speed

in a stamp heated to a temperature of 948 ° C.

The intermediate annealing and final deformation of the disk blank were carried out analogously to example 3 according to the modes shown in table 1.

Example 5 (prototype method).

Alloy for EK 151 disks containing 48% of the γ'-phase with a temperature of its complete dissolution of 1165 ° С.

Alloy EC 151 was smelted in a vacuum induction furnace. Ingots ⌀ 320 mm and weighing 2000 kg were obtained by vacuum arc remelting.

Homogenizing annealing of the ingots was carried out at a temperature of 1200 ° C; the ingot was cooled at a rate of 30 ° C / h.

The ingot was pressed onto a bar at a temperature of 1110 ° С with a degree of deformation of 70% in a die heated to a temperature of 400 ° С.

The bar was cut into measured billets weighing 25 kg.

The pressing was carried out at a temperature of 1000 ° C with a degree of deformation of 40% in a closed container, heated to a temperature of 400 ° C.

The final stamping was carried out at a temperature of 1110 ° C with a degree of deformation of 5% in the hub and 80% in the blade web in the die, heated to a temperature of 400 ° C.

Example 6 (prototype method).

Alloy for EP 975 disks containing 58% of the γ'-phase with a temperature of its complete dissolution of 1198 ° C.

Alloy EP 975 was smelted in a vacuum induction furnace. Ingots ⌀ 320 mm and weighing 2000 kg were obtained by vacuum arc remelting.

Homogenizing annealing of the ingots was carried out at a temperature of 1220 ° C; the ingot was cooled at a rate of 30 ° C / h.

The ingot was pressed onto a bar at a temperature of 1150 ° С with a degree of deformation of 70% in a die heated to a temperature of 400 ° С.

The bar was cut into measured billets weighing 25 kg.

The pressing was carried out at a temperature of 1145 ° C with a degree of deformation of 40% in a closed container heated to a temperature of 400 ° C.

The final stamping was carried out at a temperature of 1150 ° C with a degree of deformation of 5% in the hub and 80% in the blade web in the die, heated to a temperature of 400 ° C.

Analysis of table 2 shows that in the stamping of complex discs made of heat-resistant nickel alloys EK 151 and EP 975, obtained by the proposed method, a homogeneous structure and stable mechanical properties are formed.

Stamping disks obtained by the prototype method have a significant heterogeneity of the structure and mechanical properties in terms of the volume of the workpiece. The size of the micrograin in the zone of intense deformation (disk blade) is 2-2.5 times larger than in the zone of difficult deformation (hub). At the same time, the level of strength characteristics differs by more than 15-20% depending on the cutting zone of the samples.

As can be seen from table 3, pressing according to the proposed method by the method of multiple extrusion allows 3-5 times to reduce the specific pressing forces in comparison with the prototype method. The reduction in pressure during the proposed method allows the use of universal equipment for pressing and stamping - a vertical hydraulic press with a force of 630 tf. Pressing according to the prototype method is possible only when using more powerful equipment - a horizontal hydraulic press with a force of 10,000 tf.

Pressing by the proposed method allows to increase the utilization of metal by more than 2 times compared with pressing by the prototype method.

Heating stamps during pressing and final deformation by the proposed method will reduce the specific efforts by 1.5-2 times. Obtaining stampings with high CMM will not only reduce the consumption of materials, but also reduce the complexity of machining by reducing the allowance.

Obtaining stampings with a homogeneous structure and stable mechanical properties will improve the reliability of critical products made from stampings of heat-resistant nickel alloys.

table 2 The structure and mechanical properties after heat treatment of the disks obtained by the proposed method and the prototype method No. p / p Alloy Canvas Hub Tensile strength σ _in , MPa Elongation δ,% Relative narrowing ψ,% Grain size, microns Tensile strength σ _in , MPa Elongation δ,% Relative narrowing ψ,% Grain size, microns The proposed method one EC 151 1510 15.8 16,0 80-100 1510 15.0 16,0 90-100 2 EC 151 1520 16,0 17.0 70-80 1500 16.5 17.0 80-90 3 EP 975 1550 20,0 18.0 80-90 1530 18.0 18.0 90-100 four EP 975 1530 17.5 19.0 70-90 1550 16.5 19.0 80-90 Prototype 5 EC 151 1510 16,0 17.0 80-90 1390 13.5 15.0 250-280 6 EP 975 1530 17.0. 17.0 80-100 1400 13.0 17.0 200-250

Table 3 Technological characteristics of obtaining disks by the proposed method and the prototype method. No. p / p Alloy Ingot weight, kg Pressing Final stamping The pressing force, MPa CMM for pressing Pressing equipment Punching Force, MPa Stamping equipment Stamping CMM The proposed method one EC 151 25 200 0.95 Vertical hydraulic pressurization 630 tf. 210 Vertical hydraulic press with a force of 630 tf. 0.7 2 250 0.95 280 0.7 3 EP 975 25 250 0.95 300 0.7 four fifteen 350 0.90 320 0.65 Prototype 5 EC 151 2000 1000 0.45 Horizontal hydraulic press with a force of 10,000 t.p. 450 0.45 6 EP 975 2000 1100 0.4 500 0.4

Claims (7)

1. A method of obtaining a product from a heat-resistant nickel alloy, including vacuum induction smelting, obtaining an ingot for deformation, homogenizing annealing of the ingot, pressing and pre-pressing the workpiece, final deformation and heat treatment, characterized in that at least one pre-pressing is performed before pressing subsequent recrystallization annealing, pressing the workpiece is carried out in a stamp, consisting of a cylindrical and conical parts, by repeatedly extruding the workpieces and at a temperature of 55-95 ° C below Tprγ ′ from the cylindrical to the conical part of the stamp, heated to a temperature not lower than Tprγ ′ - 250 ° C and not higher than the heating temperature of the workpiece, with a strain rate

where Tprγ ′ is the temperature of complete dissolution of the γ′-phase, and at each subsequent stage of extrusion of the workpiece, the direction of extrusion is reversed relative to the previous stage, and before the final deformation, the workpiece is subjected to intermediate annealing. 2. The method according to claim 1, characterized in that the ingot is obtained in the form of a measured cast billet, mainly by directional crystallization, by vacuum-arc remelting, by investment casting. 3. The method according to claim 1, characterized in that the pre-pressing of the preform before pressing is carried out in one or more transitions at a temperature Tprγ′-95 ° ≤T≤Tprγ ′ + 10 ° C with a single degree of deformation of 20-40% and a speed

in a stamp heated to a temperature not lower than Тпрγ ′ - 250 ° С and not higher than the heating temperature of the workpiece. 4. The method according to claim 1, characterized in that the recrystallization annealing of the preform is carried out at a temperature of Tprγ′-20 ° C ≤ T Т Tprγ ′ + 30 ° C for 3-6 hours, cooling is carried out to a temperature of 200-250 ° C below the temperature Tprγ ′ at a rate of 15-30 ° C / h. 5. The method according to claim 1, characterized in that the intermediate annealing of the preform is carried out at a temperature of 50-95 ° C below Tprγ ′ with a holding time of at least 6 hours and cooling at a speed of 20-60 ° C / h to a temperature of 200-250 ° C below Tprγ ′ followed by cooling the workpiece in air. 6. The method according to claim 1, characterized in that the final deformation is carried out at a temperature of 55-95 ° C below Tprγ ′ with a speed

and a degree of deformation of not more than 85% in dies heated to a temperature not lower than Tprγ ′ - 200 ° C and not higher than the heating temperature of the workpiece. 7. The method according to claim 1, characterized in that after the first stage of extrusion of the workpiece with a volume equal to or less than the volume of the conical part of the stamp, prepress is carried out in the cylindrical part of the stamp with a degree of deformation of up to 45%.