RU2175994C2 - Method of making bars and strips from commercial titanium - Google Patents

Abstract

FIELD: metallurgy; making bars and strips from commercial titanium at specified α-structure. SUBSTANCE: method consists in heating blank deformed preliminarily in β-zone at temperature which is below polymorphic transition point by 40 to 180 C; heating is effected at rate of 8 to 10 C/min; then, blank is subjected to deformation in α-area during several stages at degree of deformation per stage of 20 to 30% and at total degree of deformation stipulated by required size of grain in finished article, after which article is subjected to annealing at temperature of 600 to 800 C, after-annealing cooling and cold deformation at degree of 1 to 1.5%; total degree of deformation in α-area is found from the following relationship:ε= 323.12d^-0,405, where D is required diameter of grain in finished article, mcm. EFFECT: specification of required and adequate degree of deformation in α-area depending on required size of micrograin in finished article. 3 dwg, 2 ex

Description

 The invention relates to the field of metallurgy, in particular to methods for processing titanium alloys, and can be used to obtain bars and strips of technical titanium by hot rolling with recrystallized α-structure from a workpiece having a β-structure.

A known method of producing rods and strips of industrial titanium from a billet having a β-structure containing hot deformation at an α-region temperature with a degree of deformation of 30-40% and subsequent annealing at a temperature of 600-800 ^o C (Titanium alloys. Metallography of titanium alloys. - M .: Metallurgy, 1980, S. 275) - prototype.

 The disadvantage of this method is that in cases where the customer has specified the size of the micrograin in the finished bar or strip, it is very difficult to choose the required degree of deformation to obtain it. In practice, they usually do the following: they set an overestimated degree of deformation in order to obtain micrograins known to be smaller in size than the customer requires, although it is known that the deformation of a workpiece made of technical titanium at temperatures of the α region is much higher in energy consumption than at temperatures β -regions due to the higher resistance to deformation of the material at temperatures of the α-region. To obtain a microstructure with a grain size of less than 100 μm, the degree of deformation of 30–40% at α-region temperatures is clearly insufficient.

The claimed method coincides with this method according to the following essential features: heating the preform, pre-deformed in the β-region, deformation of the preform in the α-region, annealing, annealing temperature range of 600-680 ^o C.

 The problem to which the claimed invention is directed is to obtain a finished product (rods and strips) from technical titanium with a regulated grain size with minimal energy consumption.

 The technical result achieved by the implementation of the invention is to specify the necessary and sufficient degree of deformation in the α-region, depending on the required size of the micrograin in the finished product.

The specified technical result is achieved by the fact that in the method of producing rods and strips of technical titanium with a regulated α-structure, containing pre-deformed in the β-region of the workpiece, deformation in the α-region and annealing at a temperature of 600-680 ^o C, the workpiece is heated to a temperature of 40-180 ^o C to lower than the polymorphic transformation temperature at 8-10 ^o C / min, the deformation carried out in several steps with a degree at the stage of 20-30% and a total degree regulated desired grain size in the finished ed Lee and determined from the relationship: ε = 323,12 d ^-0,405% (1) where d - desired grain size in the final product, m and after annealing is carried out and the subsequent cold deformation with a degree of 1-1.5%.

где: S₁ - площадь поперечного сечения готового изделия, мм²,
ε - рассчитанная степень деформации, деленная на 100.The method is implemented as follows. According to the grain size specified in the order, by means of formula (1) or the graph shown in FIG. 1, determine the necessary and sufficient total degree of deformation. Based on the calculated degree of deformation and a given value of the diameter of the rod or the cross-sectional area of the strip, the cross-sectional area of the initial billet (S ₀ ) deformed in the β-region is determined by the formula:

where: S ₁ - the cross-sectional area of the finished product, mm ² ,
ε is the calculated degree of deformation divided by 100.

The workpiece with the calculated cross-sectional dimensions is heated to a temperature of T _PP - (40 - 180) ^o C. Heating in the indicated temperature range provides optimal ductility of technical titanium under conditions of rational performance of the deformation process and prevents the possibility of overheating to temperatures close to T _PP , due to for permissible measurement error. Heating is carried out at a rate of 8 - 10 ^o C / min, which due to the low thermal conductivity of industrial titanium provides a uniform distribution of temperature fields throughout the volume of the heated workpiece.

 Under the conditions of long rolling, deformation is carried out in several stages, the so-called passes, with a degree of deformation of 20 - 30% per pass. The set values of the degree of deformation provide a sufficiently high productivity of the process without deformation heating and uncontrolled growth of α-grain. The deformed billet is subjected to annealing, during which its natural warpage (curvature) occurs, to eliminate which subsequent dressing is performed in the cold one with a degree of deformation of 1-1.5%. The specified range of degrees of deformation provides an effective elimination of arising distortions without residual stresses in the finished product.

 The invention is illustrated by graphic materials, where in FIG. 1 shows a graph of the degree of deformation versus the required grain size, determined by the formula (1), in FIG. 2 shows the microstructure of a bar ⌀ 10 mm of the alloy W1-0 obtained according to example 1, in FIG. 3 - microstructure of the rod ⌀ 85 mm alloy W1-0 obtained in example 2.

 The invention was tested during the rolling of bars of the W1-0 alloy at a longitudinal rolling mill 450 and radial-shear rolling mills GSP 10.

 Example 1

d = 19,06 мм
Выбрали исходную заготовку диаметром 19,5 мм, прокатанную на стане 450 из заготовки диаметром 130 мм при температуре 1000^oC ( β-область). Нагрели в электрической печи сопротивления со скоростью 10^oC/мин до температуры 750^oC (Т_пп - 160^oC). Прокатали на стане РСП 10 до 10 мм за 4 прохода с разовыми обжатиями со степенью деформации 24 - 29% по маршруту
⌀ 19,5 - ⌀ 17,0 - ⌀ 14,5 - ⌀ 12,2 - ⌀ 10,1 мм.By order, it was required to obtain bars ⌀ 10 mm of W1-0 alloy (T _pp = 910 ^o C) with a microstructure determined by a grain size of not more than 40 microns. According to the formula (1) or according to the schedule (Fig. 1), the necessary degree of deformation was determined:
ε = 323.12 • 40 ^-0.405 = 72.5 (%)
Calculated the diameter of the initial billet:

d = 19.06 mm
We chose the initial billet with a diameter of 19.5 mm, rolled on a mill 450 from a billet with a diameter of 130 mm at a temperature of 1000 ^o C (β-region). Heated in an electric resistance furnace at a speed of 10 ^o C / min to a temperature of 750 ^o C (T _PP - 160 ^o C). Laminated at the RSP mill 10 to 10 mm in 4 passes with single compressions with a degree of deformation of 24 - 29% along the route
⌀ 19.5 - ⌀ 17.0 - ⌀ 14.5 - ⌀ 12.2 - ⌀ 10.1 mm.

Then the rods were annealed at a temperature of 600 ^o C and subjected to cold straightening with a degree of deformation of 1%. The microstructure (x 100) of the bar is shown in FIG. 2. Customer requirements are satisfied.

 Example 2

d = 126 мм
Исходную заготовку диаметром 126 мм, откованную при температуре 1050^oC ( β - область), нагрели в электрической печи сопротивления до температуры 870^oC (Т_пп - 40^oC) со скоростью 9^oC/мин и прокатали на стане 450 за 3 прохода с разовыми обжатиями со степенью деформации 23% на диаметр 85,5 мм. Затем прутки подвергли отжигу при 650^oC и холодной правке со степенью деформации 1,16%. Микроструктура (х 100) прутка представлена на фиг. 3. Требования заказчика удовлетворены.By order, it was required to obtain bars ⌀ 85 mm of W1-0 alloy (T _pp = 910 ^o C) with a microstructure determined by a grain size of not more than 80 microns. According to the formula (1) or the graph (Fig. 1), the necessary degree of deformation was determined
ε = 323.12 • 80 ^-0.405 = 54.8 (%)
Calculated the diameter of the original workpiece

d = 126 mm
An initial billet with a diameter of 126 mm, forged at a temperature of 1050 ^o C (β - region), was heated in an electric resistance furnace to a temperature of 870 ^o C (T _pp - 40 ^o C) at a speed of 9 ^o C / min and rolled on a 450 mill for 3 a passage with single crimps with a degree of deformation of 23% by a diameter of 85.5 mm. Then the rods were annealed at 650 ^o C and cold straightened with a degree of deformation of 1.16%. The microstructure (x 100) of the bar is shown in FIG. 3. Customer requirements are satisfied.

Claims (1)

A method for producing rods and strips from technical titanium with a regulated α-structure, comprising heating a preform deformed in the β-region of the workpiece, deformation in the α-region and annealing at a temperature of 600-680 ^° C, characterized in that the workpiece is heated to a temperature of 40 -180 ^o C lower than the polymorphic transformation temperature at a speed of 8-10 ^o C / min, the deformation carried out in several steps with a degree at the stage of 20-30% and a total degree regulated desired grain size in the finished product, and determined from the relation ^{Ia: ε = 323,12 d -0,405 (%} ), where d - desired grain size in the final product, m and after annealing is carried out and the subsequent cold deformation with a degree of 1-1.5%.

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