JPH0454527B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] Lightweight and high-strength titanium alloys, especially Ti-6Al-4V and Ti-6Al-6V-2Sn, are used as structural materials for aircraft.
α+β type titanium alloys, represented by , are often used. In addition, in order to effectively utilize the space inside an aircraft, in addition to the usual titanium alloy rods and tubes with circular cross sections, the use of tubes with non-circular cross sections such as squares, rectangles, and rhombuses is gradually increasing. are doing. The present invention relates to a method of manufacturing such a non-circular cross-section tube made of α+β titanium alloy. [Prior art] Manufacturing of pipe materials with non-circular cross sections made of metal is as follows:
Generally, materials with good workability are formed by cold drawing, and materials with poor workability are formed into a tube with a desired cross-section by hot extrusion. [Problems to be solved by the invention] However, α+β type titanium alloys usually have
It has poor workability and cannot be processed by cold drawing, and it is difficult to obtain thin products with uniform wall thickness by processing by hot extrusion. [Means for Solving the Problems] The present inventors utilize the superplasticity phenomenon in α+β type titanium alloys to propose a method for relatively easily manufacturing a non-circular cross-section tube of uniform wall thickness of said alloys. It is. That is, the present invention provides a blank tube assembly in which end plates are sealed at both ends of a blank tube with a circular cross section made of α+β type titanium alloy, and an inner tube is airtightly inserted into one of the end plates. is inserted into a non-circular mold having a hollow part with a predetermined non-circular cross section, and the raw tube assembly and the non-circular mold are heated to 800 to 900°C in a heating device in a vacuum furnace, and at the same time, high pressure is applied through the internal feed pipe. A non-circular cross section of an α+β type titanium alloy characterized by introducing an inert gas of a group zero element into the raw tube and deforming the raw tube at a strain rate of 10 ^-2 sec ^-1 to ^{10 -5} sec ^-1 . Pipe manufacturing method and the method of inserting the above-mentioned raw pipe assembly into a non-circular mold having a hollow portion of a predetermined non-circular cross section, and providing end plates at both ends of the non-circular mold, so that the parts other than the ends of the raw pipe assembly are In addition to sealing the inside of the non-circular shape, an external conduit is airtightly inserted into one end plate of the non-circular conduit, and a low-pressure Group Zero element inert gas is passed through the external conduit to the outside of the blank tube assembly and the non-circular shape. Introduced between the inside of the circle,
While heating the tube to 800 to 900℃ using a heating device, a high-pressure group zero element inert gas is introduced through the internal pipe to strain the tube at a strain rate of 10 ^-2 sec ^-1 to ^{10 -5} sec ^-1. This is a method for manufacturing a non-circular cross-section tube of α+β type titanium alloy, which is characterized by deforming the tube. The present invention will be explained in detail below. α+ such as Ti−6Al−4V and Ti−6Al−6V−2Sn
The maximum elongation of β-type titanium alloys increases significantly within the range defined by specific temperatures and strain rates;
It is known that it exhibits a so-called superplastic phenomenon that facilitates processing. In the present invention, the superplastic region means a maximum elongation of 300%.
This is the region defined by the temperature and strain rate in which the above conditions can be obtained. As an example, the superplastic region for Ti-6Al-4V titanium alloy will be explained. Figure 6 is a diagram showing the relationship between strain rate, maximum elongation, and temperature when deforming the titanium alloy, where the horizontal axis is the strain rate (Sec ^-1 ), the vertical axis is the maximum elongation (%), and the numbers attached to the curve. indicates temperature (°C). In the same figure, the temperature between 800℃ and 900℃
The region defined by the strain rate of 10 ^-2 Sec. ^-1 to 10 ^-5 Sec. ^-1 is the region where the maximum elongation of 300% can be obtained, so the region is the region defined by the present invention for Ti-6Al-4V. This is the superplastic region. The first method of the present invention is carried out by the following procedure. As shown in FIG. 1, a blank tube 1 is sealed with end plates 2 and 3, and an internal pipe 4 is airtightly inserted into the end plate 3 to produce a blank tube assembly 5. Next, as shown in FIG. 2, the blank tube assembly 5 is inserted into a non-circular mold 6, and heated together with the blank tube assembly 5 and the non-circular mold 6 in a heating device 8 in a vacuum furnace 7. A high-pressure inert gas is introduced into the raw pipe 1 of the raw pipe assembly 5 through the internal pipe 4 to remove the raw pipe 1.
The heating temperature and the strain rate of the deformation are set to values that maintain the raw pipe 1 within the superplastic region specific to the material of the raw pipe 1. Here, the inert gas refers to a gas of a group zero element such as argon. Further, the pressure of the inert gas is set to a value determined for a predetermined strain rate by equation (iii) derived from the following generally known equations (i) and (ii). P=(r ₂ ² .r ₁ ² )σ/r ₂ ² (1+r ₁ ² /r ₂ ² ) ……(i) σ=K・ε〓 ^m ……(ii) P=(r ₂ ² −r ₁ ² /r ₂ ² (1+r ₁ ² /r ₂ ² )K・ε〓 ^m ……
(iii) However, P: Pressure σ: Stress r ₁ : Inner diameter r ₂ : Outer diameter ε: Strain rate K: Constant m: Constant Here, K and m are numerical values that depend on the individual material and temperature. Determine it in advance by experiment. The second method of the present invention is carried out by the following procedure. After inserting the raw pipe assembly 5 shown in FIG. After sealing the mold 6 and closely inserting the external pipe 11 into the end plate 10, a low-pressure inert gas is passed through the external pipe 11 between the outside of the raw pipe assembly 5 and the inside of the non-circular mold 6. introduced,
While preventing oxidation of the outer surface of the raw pipe 1, the raw pipe 1 is heated in the heating device 8, and at the same time, high-pressure inert gas is introduced into the raw pipe 1 of the raw pipe assembly 5 through the internal feed pipe 4 to heat the raw pipe 1. The temperature, strain rate, inert gas, and pressure of the high-pressure inert gas introduced into the blank tube 1 during the deformation are selected in the same manner as in the first method of the present invention. The pressure of the low-pressure inert gas introduced between the outside of the raw pipe assembly 5 and the inside of the non-circular mold 6 is such that the amount of inert gas supplied is necessary to prevent oxidation of the outer surface of the raw pipe 1. be the value given. [Example] Examples of the present invention are shown below. Example 1 A pipe with a rectangular cross section as shown in Table 3 was obtained by the first method of the present invention using the raw pipe shown in Table 1 under the conditions shown in Table 2 and using a non-circular cross-sectional shape shown in FIG. Ta.

[Table] As a comparative example, the blank tubes shown in Table 1 were molded in the atmosphere under the conditions shown in Table 2. Gas pressure was applied by inert gas. The outer surface was severely oxidized, and cracks occurred during deformation due to insufficient deformability of the oxidized part, resulting in
It was impossible to mold the product into the shape shown in the table. Further, as another comparative example, the raw tubes shown in Table 1 were molded in a vacuum furnace under the conditions shown in Table 2. Pressure was applied by introducing nitrogen gas inside the tube. Ti nitride was formed on the inner surface of the tube, and cracks occurred during deformation due to insufficient deformability of the nitrided portion, making it impossible to form the product into the product shape shown in Table 3. This shows that the use of an inert gas containing a Group Zero element is an essential condition.

【table】

[Table] Example 2 Using the raw pipes shown in Table 4 under the conditions shown in Table 5 and using the non-circular cross-sectional shapes shown in FIG. Obtained.

【table】

【table】

[Table] Using the raw pipe shown in Table 1, using the non-circular shape shown in Fig. 4 under the conditions shown in Table 2, and using the method of the first invention of the present application, the third
Tests for forming the rectangular cross-section tubes shown in the table were conducted at temperatures of 750-950°C. The results of the molding test were
Shown in the table. Note that the molding temperatures of 750°C and 950°C are comparative examples.

〔Effect of the invention〕

As explained above, the method of the present invention makes it possible to manufacture a non-circular cross-section tube with high dimensional accuracy, which was previously impossible, and its effects are extremely large.

[Brief explanation of drawings]

Fig. 1 is a blank pipe assembly, Fig. 2 is an explanatory diagram of the first method of the present invention, Fig. 3 is an explanatory diagram of the second method of the present invention, and Figs. 4 and 5 are non-circular pipes. Fig. 6 is a diagram showing the relationship between strain rate, maximum elongation, and temperature in a Ti-6Al-4V titanium alloy, and the values appended to the curves in the figure indicate the temperature. 1...Main pipe, 2...End plate, 3...End plate, 4...
Internal pipe, 5...Main pipe assembly, 6...Non-circular type, 7...
...Vacuum furnace, 8...Heating device, 9...End plate, 10...
...End plate, 11...External pipe.

Claims (1)

[Scope of Claims] 1. A blank tube assembly made of a blank tube made of α+β type titanium alloy and having a circular cross section, with end plates sealed at both ends, and an inner tube airtightly inserted into one of the end plates. The solid body is inserted into a non-circular shape having a hollow part with a predetermined non-circular cross section, and the raw tube assembly and the non-circular shape are heated to 800~800℃ in a heating device in a vacuum furnace.
At the same time as heating to 900℃, high pressure inert gas of group zero element is introduced into the tube through the internal pipe to deform the tube at a strain rate of 10 ^-2 sec ^-1 to ^{10 -5} sec ^-1 . A method for manufacturing a non-circular cross-section tube made of α+β type titanium alloy, characterized by the following. 2. A blank pipe assembly consisting of end plates sealed at both ends of a blank pipe with a circular cross section made of α+β type titanium alloy, and an internal pipe inserted airtightly into one of the end plates, is placed in a predetermined non-contact position. It is inserted into a non-circular shape having a hollow part with a circular cross section, and end plates are provided at both ends of the non-circular shape, and the parts other than the ends of the blank pipe assembly are sealed inside the non-circular shape. An external pipe is airtightly inserted into one end plate, and a low-pressure group zero inert gas is introduced between the outside of the raw pipe assembly and the inside of the non-circular shape through the external pipe, and a heating device is used. 800
At the same time as heating to ~900℃, high-pressure group zero element inert gas is introduced into the tube through the internal pipe to deform the tube at a strain rate of 10 ^-2 sec ^-1 to ^{10 -5} sec ^-1 . A method for manufacturing a non-circular cross-section tube of α+β type titanium alloy.