RU2127160C1 - Method of making hollow tubular blank for producing seamless tubes from pseudo-alpha and (alpha+beta)-titanium alloys - Google Patents

Abstract

FIELD: tube production. SUBSTANCE: method comprises steps of forging ingot to rod at several transitions and at temperature of α-range in transitions from first until last but one and at temperature of (α+β)-range in last transition; cutting rod by lengths of multiple value, drilling axial hole in it, extruding intermediate billet at normalized ratio of temperature and elongation values, cutting received blank by lengths of multiple value, boring axial opening, turning lateral surface and finally extruding billet at normalized ratio of temperature and elongation values. Temperature and elongation values at intermediate and final extrusion processes are calculated according to claimed formulae. EFFECT: finely dispersed uniform microstructure along thickness of tube wall. 1 cl

Description

 The invention relates to pipe production and can be used in the manufacture of seamless pipes from pseudo-α and (α + β) -titanium alloys.

 A known method of manufacturing a hollow tube billet for the production of seamless pipes from titanium alloys, including from pseudo-α and (α + β) -titanium alloys, including forging an ingot into a bar in several transitions at a temperature above the temperature of the polymorphic transformation, forming a checker (billlets) ) by cutting to a multiple size, turning the side surface and drilling an axial hole, heating to a temperature above the polymorphic transformation temperature and pressing (Technological instruction TI-03-019-T-93 "Production of pressed pipes 3150 are on the press (Mn 30.891) "- Verkhnya Salda, VSMPO-, 1993, p 3)..

 The known method coincides with the claimed method according to the following essential features: forging an ingot into a bar in several transitions at temperatures of the β region at transitions from the first to the penultimate, forming billlets by pressing by cutting to a multiple size, turning the side surface and making an axial hole, heating the billlets and pressing.

 The disadvantages of this method are the instability of the microstructure along the cross section of the wall of the pipe billet, the appearance of β grains due to deformation overheating, which during subsequent cold rolling of the pipe leads to uneven deformation and destruction of the metal, as well as high laboriousness in the manufacture of billets, in particular for drilling operations.

 A known method of manufacturing a hollow tubular billet from a pseudo-α-titanium alloy Ti-3Al-2.5V, including forging an ingot into a bar in several transitions at temperatures of the β-region at the first transition and (α + β) - the region at the remaining transitions with at least 18 (degree of deformation 94.5%), design of billlets for pressing by turning the side surface of the bar, cutting to a multiple size and drilling an axial hole, heating billlets to a temperature below the polymorphic transformation temperature and pressing a hollow tube billet with a hood from 5 to 10 ( Ti-3Al-2.5 V. Common Name: Tubing Alloy, ASTM Grade 9 UNS Number: R 56320/1994, p. 282) - prototype.

 This method allows to obtain a finely dispersed uniform microstructure along the wall thickness.

 This method coincides with the known method according to the following essential features: forging an ingot into a bar in several transitions at temperatures of the β-region at the first transition and (α + β) - region at the last transition, processing the bill for pressing by turning the side surface of the bar, cutting it by a multiple size and the execution of the axial hole, heating billlets to a temperature below the temperature of polymorphic transformation and pressing.

 The disadvantages of this method are the low yield of metal due to the large loss of metal when drilling an axial hole, amounting to 25% of the mass of billlets, and the high complexity when drilling an axial hole.

 The problem to which the claimed invention is directed, is to increase profitability by increasing the yield of metal in the manufacture of a hollow pipe billet and reducing the complexity of obtaining an axial hole in the billet.

 The technical result achieved by the implementation of the claimed invention is to reduce metal losses during the execution of the axial hole, as well as reducing the complexity when forging the bar and obtaining an axial hole.

где T_пп - температура полиморфного превращения сплава, ^oC;

сопротивление деформации с учетом скорости деформации и температуры деформации, среднее по очагу деформации, МПа;
c - удельная теплоемкость сплава, КДж/кг•К;
ρ - плотность материала сплава, кг/м³;

вытяжка при промежуточном прессовании, причем вытяжку ограничивают меньшим из двух значений, рассчитанных по формулам

где Δt₁ - приращение температуры в процессе прессования, ^oC;
[F] - допустимая нагрузка на прессе, кН;
A_з1 - площадь сечения заготовки при промежуточном прессовании, мм²,
после чего выполнение осевого отверстия при формировании биллетса под окончательное прессование осуществляют расточкой полученного при промежуточном прессовании осевого отверстия, а окончательное прессование ведут при температуре:

где

сопротивление деформации с учетом скорости деформации и температуры деформации, среднее по очагу деформации, МПа;
μ₂ - вытяжка при окончательном прессовании;
с вытяжкой, ограниченной меньшим из двух значений, рассчитанных по формулам:

где Δt₂ - приращение температуры в процессе окончательного прессования, ^oC;
A_з2 - площадь сечения заготовки при окончательном прессовании, мм².The specified technical result is achieved by the fact that in the known method of manufacturing a hollow tube billet for the production of seamless pipes from pseudo-α and (α + β) -titanium alloys, including forging the ingot into a bar in several transitions at temperatures of the β-region at the first transition and ( α + β) - areas at the last transition, forming billlets for pressing by turning the side surface of the bar, cutting it to a multiple size and making an axial hole, heating billlets to a temperature below the polymorphic transformation temperature and press According to the invention, the forging of the tube billet is forged at transitions from the second to the last but one at temperatures of the β-region, and at the last transition, forging is performed with a degree of deformation of 20–40%, after which an intermediate bill is additionally formed by cutting to a multiple size and flashing or drilling axial bore, which is subjected to additional intermediate pressing at a temperature determined by the formula:

where T _PP - the temperature of the polymorphic transformation of the alloy, ^o C;

deformation resistance taking into account the strain rate and deformation temperature, average over the deformation zone, MPa;
c is the specific heat of the alloy, KJ / kg • K;
ρ is the density of the alloy material, kg / m ³ ;

hood with intermediate pressing, and hood is limited to the smaller of the two values calculated by the formulas

where Δt ₁ is the temperature increment during the pressing process, ^o C;
[F] - permissible load on the press, kN;
A _C1 - the cross-sectional area of the workpiece during intermediate pressing, mm ² ,
after which the execution of the axial hole in the formation of billlets for the final pressing is carried out by the bore obtained from the intermediate pressing of the axial hole, and the final pressing is carried out at a temperature:

Where

deformation resistance taking into account the strain rate and deformation temperature, average over the deformation zone, MPa;
μ ₂ - exhaust during final pressing;
with a hood limited to the smaller of the two values calculated by the formulas:

where Δt ₂ is the temperature increment in the process of final pressing, ^o C;
A _C2 - the cross-sectional area of the workpiece during the final pressing, mm ² .

 Distinctive features of the claimed method from the closest to it are the altered temperature regime of the forging of the ingot into the bar at transitions from the second to the last but one inclusive, namely, forging at temperatures of the β-region, a significantly lower degree of deformation at the last transition of forging of the ingot in (α + β) - areas: 20 - 40%, formation of intermediate billlets by cutting to a multiple size and drilling or flashing of an axial hole, pressing intermediate billlets with a regulated temperature ratio, determine according to formula (1), and hoods defined by formulas (2) and (3), the form of execution of the axial hole of the billlet for final pressing: boring of the hole obtained by intermediate pressing, regulating the ratio of temperature and hood of the final pressing, determined by the formulas ( 4), (5) and (6).

 The essence of the claimed method is as follows.

 Forging the ingot into the bar at temperatures of the β-region to the penultimate transition allows to increase the reduction, forging speed and thereby reduce the complexity and costs of forging while ensuring a uniform β-structure over the cross section. Forging at the last transition in the (α + β) - region with a degree of deformation of 20 - 40% destroys the high-angle boundaries of β-grains, grinds the structure and forms an (α + β) - structure.

 Due to the fact that the turning of the bar is carried out on a larger diameter, with the same minimum amount of removal, metal loss by chips and the complexity of manufacturing the bar are reduced.

 Due to the fact that the axial hole is drilled in a rod of a larger diameter, metal losses and laboriousness during drilling are several times reduced.

 The hole in billlets can be obtained by firmware.

 Due to the fact that the intermediate pressing is carried out at a temperature lower than the polymorphic transformation temperature, with a regulated hood, which ensures that the metal does not overheat and deform in the (α + β) region, grain refinement and the (α + β) structure necessary for final pressing.

 Due to the fact that the formation of billlets for final pressing is carried out by cutting the intermediate billlet into parts, by boring the axial hole and turning with a minimum metal removal, with the exception of the drilling operation of each billlets, the costs of machining billlets are reduced.

 Due to the fact that the final pressing is carried out at a temperature lower than the polymorphic transformation temperature with a regulated hood, it is possible to obtain a tube billet with a given microstructure with reduced metal losses and laboriousness in the operations of forging a rod, drilling an axial hole and turning, which helps to solve the problem - increase profitability at the production of pipe billets while maintaining the requirements for accuracy, macro- and microstructure.

 The number of transitions during the forging of the ingot into the bar in the β-region, the modes of intermediate heat treatments, the total drawing of the intermediate and final pressing of the workpiece, and the strain rate are the know-how of production.

 The method is as follows.

Полученный промежуточный биллетс ⌀ 275 к ⌀ 61 • 690 мм подвергают промежуточному прессованию при 870^oC, затем разрезают на части длиной 260 мм и растачивают отверстие на ⌀ 61 мм. По допустимому усилию прессования определяют значение вытяжки при прессовании на готовый размер по формуле (6), μ $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ = 6,5. По допустимой температуре деформационного нагрева определяют вытяжку μ $\genfrac{}{}{0ex}{}{\text{1}}{\text{2}}$ по формуле (5) и принимают с учетом распрессовки μ₂ = 3,76. Температуру T₂ нагрева под окончательное прессование определяют по формуле (4):

Полученный биллетс под прессование ⌀ 133 • ⌀ 61 • 260 мм нагревают до температуры T₂ и прессуют трубную заготовку на готовый размер ⌀ 86 • ⌀ 59 мм.An ingot of ⌀ 540 mm from a Ti-3Al-2.5V alloy with T _pp = 935 ^° C is forged into a bar of ⌀ 287 mm in several transitions, the last transition being carried out in the (α + β) region with a strain of 30%. The resulting bar is machined by ⌀ 275 mm, cut into slots 690 mm long, an axial hole ⌀ 61 mm is drilled in each krat. The allowable pressing force determines the hood μ $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ by the formula (3), μ $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ = 6.9. The allowable temperature of the deformation heating determines the hood μ $\genfrac{}{}{0ex}{}{\text{1}}{\text{1}}$ by the formula (2), μ $\genfrac{}{}{0ex}{}{\text{1}}{\text{1}}$ = 5.13. Taking into account the error in determining the temperature of the polymorphic transformation and the accuracy of measuring the temperature of the metal, μ ₁ = 5.27 is taken into account taking into account extrusion. The heating temperature T ₁ is determined by the formula (1):

The obtained intermediate billet ⌀ 275 to ⌀ 61 • 690 mm is subjected to intermediate pressing at 870 ^° C, then cut into pieces 260 mm long and a hole is drilled into на 61 mm. By the permissible pressing force, the value of the hood is determined when pressing to the finished size according to the formula (6), μ $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ = 6.5. The allowable temperature of the deformation heating determines the hood μ $\genfrac{}{}{0ex}{}{\text{1}}{\text{2}}$ by the formula (5) and take into account the extrusion μ ₂ = 3,76. The temperature T ₂ heating under the final pressing is determined by the formula (4):

The resulting billet for pressing ⌀ 133 • ⌀ 61 • 260 mm is heated to a temperature of T ₂ and the tube billet is pressed to a finished size of ⌀ 86 • ⌀ 59 mm.

 According to the claimed method, metal loss during turning of a bar of ⌀ 287 mm by ⌀ 275 mm is 8.2%, when drilling a hole of ⌀ 61 mm - 4.5; and when boring the holes of the intermediate billlets, another 2.7%, while the complexity of drilling decreases by 4 to 10 times, depending on the hood during the first pressing, which generally reduces metal loss compared with the prototype from 33.7% to 15, 4% and increases the profitability of production.

 According to the existing technology, the forging of the bar is carried out up to ⌀ 145 mm, grind to a size of ⌀ 133 mm, a hole ⌀ 61 mm is drilled, while the metal loss during turning of the bar is 16%, while drilling the hole is 17.7%.

 As follows from the foregoing, the achievement of the technical result is the reduction of metal losses and laboriousness is provided only with the inextricable and interconnected implementation of all the essential features of the claimed method.

In addition to the specified technical result achieved, the claimed method also has additional advantages:
- the bore provides a higher surface quality of bills when pressing a tube billet,
- the head equipment of the metallurgical cycle is unloaded - forging presses.

Claims (1)

A method of manufacturing a hollow tube billet for the production of seamless pipes from pseudo-α and (α + β) -titanium alloys, comprising forging an ingot into a bar in several transitions at temperatures of the β-region at the first transition and the (α + β) -region at the last transition making billet for pressing by turning the side surface of the bar, cutting it to a multiple size and making an axial hole, heating the billet to a temperature below the polymorphic transformation temperature and pressing the tube billet, characterized in that the ingot is forged into a bar at the transitions from the second to the last but one, they are carried out at temperatures of the β-region, and at the last transition, forging is performed with a degree of deformation of 20–40%, after which an intermediate bill is additionally formed by cutting to a multiple size and piercing or drilling an axial hole, which is subjected to additional intermediate pressing at a temperature determined by the formula:

where T _PP - the temperature of the polymorphic transformation of the alloy, ^o With;

deformation resistance taking into account the strain rate and deformation temperature, average over the deformation zone, MPa;
s - specific heat of the alloy, KJ / kg • K;
ρ is the density of the alloy material, kg / m ³ ;
μ - hood during intermediate pressing,
moreover, the hood is limited to the smaller of the two values calculated by the formulas:

where Δt ₁ is the temperature increment during the pressing process, ^o С;
[F] - permissible load on the press, kN;
A _C1 - the cross-sectional area of the workpiece during intermediate pressing, mm ² ,
after which the execution of the axial hole in the formation of billlets for the final pressing is carried out by the bore obtained from the intermediate pressing of the axial hole, and the final pressing is carried out at a temperature:

Where

deformation resistance taking into account the strain rate and deformation temperature, average over the deformation zone, MPa;
μ ₂ - exhaust during final pressing,
with a hood limited to the smaller of the two values calculated by the formulas

where Δt ₂ is the temperature increment in the process of final pressing, ^o C;
A _C2 - the cross-sectional area of the workpiece during the final pressing, mm ² .