Method for producing pipe from technically pure titanium with radial texture

FIELD: metallurgy.

SUBSTANCE: workpieces are made in the form of rings; deformed so that thicknesses of their walls are reduced and their diameter is increased, and then, their ends are butt welded till a pipe is obtained. Deformation of rings with wall thickness reduction is performed by rolling on a ring-rolling mill or by forging on a mandrel using forging equipment. Radial texture is preserved throughout the pipe length.

EFFECT: producing a pipe from technically pure titanium with radial texture.

3 cl, 6 dwg, 2 ex

 

The proposed method relates to the field of metallurgy, and in particular to methods of creating textured status of materials having a hexagonal close-Packed crystal lattice, in the main, such as alpha-titanium.

Basically, in the tubes from titanium and zirconium alloys are trying to get the radial texture of the metal, due to their better resistance against the development of cracks.

Further explanation of the circumstances connected with textured state, will use the notion of parameters Cairns (J.J. Kearns On the relationship among 'f' texture factors for the principal planes of zirconium, hafnium and titanium alloys. Journal of Nuclear Materials. 2001. V.299. No. 2. P.171-174).

The prior art method for the production of pipes made of materials able hexagonal close-Packed lattice, then the GPU-grid (U.S. patent US 4765174. Texture enhancement of metallic tubing material having a hexagonal close-packed crystal structure / Cook Charles S, Sabol, George P. the Applicant Westinghouse Electric Corporation [US]. IPC B21B 21/00, B21C 37/06, B21C 37/30. Publ. 1988-08-23. Priority 1987-02-20).

A method is proposed to use the operation of reducing the diameter of the pipe with a simultaneous decrease in wall thickness. This leads to the achievement of the deformation in the radial direction (εr<0) and the same compression deformation in the tangential direction (εφ<0) in the presence of tensile strain along the length of the workpiece. The presence of compressive deformation the radial direction leads to the formation of radial texture and increasing the value of Cairns f rfrom 0.33 characteristic retexturising state, to 0.5.

In the description of the patent, however, noted that the best option is the formation of a schema deformation in the radial direction (εr<0) and tensile strain in the tangential direction (εφ>0). This is achieved through the operation of increasing the pipe diameter with decreasing wall thickness. The presence of such schemes strain state can give a more acute radial texture in the workpiece and to increase the parameter Cairns responsible for the radial component.

In particular, by using the described intake can increase the parameter Cairns in the radial direction frto a value of 0.66. This achievement is made due to the fact that the implemented scheme deformed state, in which there is only one strain compression (when two tensile deformations), which is directed along the radius of the workpiece.

In particular, these studies found that the compression with logarithmic degree of deformation of the wall, εr=-εφ=- 0.1 parameter Cairns frincreases in the value of 0.12.

The closest to the essential features of the claimed object (the prototype) is a method for the production of titanium tubes (U.S. Patent No. 5332454. Titanium or titanium based alloy corrosion resistant tubing fom welded stock / Meredith Steven E., Benjamin James F. the Applicant Sandvik Special Metals [US]. IPC C22F 1/18. Publ. 1994-07-26. Priority from 1992-01-28).

The method involves receiving pipes of commercially pure titanium with a radial texture and includes obtaining hollow workpieces, their deformation and welding. Including the method includes flat rolling stepsaway (sheet) blanks, folding it into the pipe, the sealed edges of the longitudinal welding. The essence of this technical solution is that when the flat rolling a deformed state, in which the thickness of the sheet creates a deformation ratio, and the length of the workpiece - deformation strain. The width of the workpiece deformation is absent due to the presence of schema plane deformation. For metals with HCP lattice texture is created in the direction of creating a strain compression. Because during rolling deformation were directed by the thickness of the blank, after coagulation tubes these deformations turned into a radial, which led to the creation of radially oriented texture.

The disadvantage of the prototype is the inability to save textured condition along the circumference of the pipe due to the presence of a longitudinal welding seam, in which the radial texture is not formed.

In addition, the longitudinal seam is poorly resists the action of tangential stresses PR is the use of pipes under the action of high pressure, and this is the purpose of the pipes.

The proposed method of producing pipes of commercially pure titanium with a radial texture includes obtaining hollow workpieces, their deformation and welding. It differs in that the gain of the workpiece in the form of rings, the ring is deformed to reduce the thickness of their walls and increase in diameter and weld ends butt weld with getting a pipe.

Deformation rings with decreasing wall thickness is performed by rolling on the ring rolling mill.

In another embodiment, the deformation of rings with decreasing wall thickness exercise forging mandrel for forging equipment.

The essence of the proposed technical solution is the following. During rolling of rings is achieved by deformation of the extension in the tangential direction (εφ>0), the compression deformation in the radial direction (εφ<0), and deformation elongation in a high-rise direction is missing (εz=0). Thus, in this scheme, the strain state are one warp elongation and one shorter. When this radial texture is formed along the axis of shortening, i.e. in the radial direction.

The weld seam is not along the longitudinal direction and along the transverse direction, is not dangerous from the standpoint of destruction from the action of tangential stresses. In addition, in this case n is t violations prior texture along the circumference of the pipe, since the welding seam is not directed along the pipe, and is made in the transverse direction.

Figure 1 shows the profile of the original piece. Figure 2 shows the scheme of ring rolling. Figure 3 shows in the form of an elementary volume of a cube with schema directions of deformation. Figure 4 shows a ring of enlarged diameter. Figure 5 shows the diagram of the welding rings of enlarged diameter. Figure 6 shows the scheme of forging rings.

The method is as follows. At the first stage hollow billet 1 (figure 1) is made in the form of rings using well-known methods of processing metals by pressure, for example, a method of pressing and subsequent cutting to length. In the second stage of preparation in the form of rings is subjected to deformation with decreasing wall thickness of the rings and receiving of rings increased diameter. Reducing the wall thickness of the rings, and receive rings of enlarged diameter, carried out by rolling on the ring rolling mill. Figure 2 shows that the workpiece 1 is deformed two rolls, the outer roller 2 is located on the outer surface of the hollow billet 1, and the inner roller 3 is located inside the cavity of the ring. Joint compression rolls, the wall thickness of the workpiece decreases, and the diameter of the workpiece increases. Figure 3 shows in the form of a cube elementary volume 4 metal billet in the process. Compression of the billet proishodit the direction of the radius, therefore, the deformation εr<0 and are deformations of compression. Billet size in the tangential (Cordova) direction increases, therefore, the deformation εφ>0 and deformations are lengthening. Figure 4 shows a ring of enlarged diameter 5, which has a wall thickness reduced relative to the original size. At the third stage (figure 5) ring of enlarged diameter butt weld (weld areas designated as 6), resulting in the pipe 7.

A variant of this method is the replacement of admission rolling rings for the reception of forging rings. Figure 6 shows that the die or the press plate 8 acts on the outer diameter of the hollow billet 1, and the inner diameter of the workpiece based on the fixed mandrel 9. As a result of such exposure, the wall thickness is locally reduced and the diameter of the workpiece increases. After removal of firing pin 8 of the workpiece 1 is turned at a given angle, and the compression process is repeated, achieving a uniform deformation along the circumference of the workpiece.

Example 1. At the first stage receives the procurement of commercially pure titanium in the form of rings. For this purpose a hollow workpiece outer diameter of 60 mm and an inner diameter of 50 mm is cut to length and get a ring with a wall thickness of 5 mm At the second stage of preparation in the form of rings is subjected to deformation at Calabro atom mill with reduction of wall thickness up to 4.5 mm Thus the outer diameter of the ring is increased to 65.6 mm, and the inner to 56.6 mm, the Degree of deformation of the wall is εr=-εφ=-0,1. Thus, the degree of deformation, which, as was shown above, the parameter Cairns frincreases in the value of 0.12, i.e. acuity is increased radial texture. In the third phase of the received ring of enlarged diameter weld ends butt weld with getting a pipe.

Example 2. At the first stage receives the procurement of commercially pure titanium in the form of rings. For this purpose a hollow workpiece outer diameter of 60 mm and an inner diameter of 50 mm is cut to length and get a ring with a wall thickness of 5 mm At the second stage of preparation in the form of rings is subjected to deformation in the ring rolling mill with reduction of wall thickness up to 4 mm While the outer diameter of the ring is increased to 72.8 mm, and the inner to 64.8 mm, the Degree of deformation of the wall is εr=-εφ=-0,2. There was twice higher degree of deformation, which, as was shown above, the parameter Cairns frincreases in the value of 0.24, i.e. acuity is increased radial texture. In the third phase of the received ring of enlarged diameter weld ends butt weld with getting a pipe.

It should be noted that the textured condition in the method prototype for a length of the first circumference of the pipe was broken due to the presence of a longitudinal welding seam, in the proposed method, this is not the case, since the longitudinal welding seam is missing.

The technical result consists in achieving and maintaining textured condition along the circumference of the pipe.

1. The way to get the pipe out of commercially pure titanium with a radial texture, including the production of hollow workpieces, their deformation and welding, characterized in that the gain of the workpiece in the form of rings, the ring is deformed to reduce the thickness of their walls and increase in diameter and weld ends butt weld with getting a pipe.

2. The method according to claim 1, characterized in that the deformation of rings with decreasing wall thickness is performed by rolling on the ring rolling mill.

3. The method according to claim 1, characterized in that the deformation of rings with decreasing wall thickness exercise forging mandrel for forging equipment.



 

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