JP2002302748A - Method for manufacturing titanium or titanium alloy rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a titanium or a titanium alloy rod is surely obtained in a high yield without causing partial cutting and breakage. SOLUTION: The method for manufacturing the titanium or titanium alloy rod comprises the following steps: a rolling step S2 where titanium or titanium alloy stock b1 is worked into a wire rod b2 of prescribe cross-sectional size; an annealing step S5 where the wire rod b3 after pickling S3 and finish rolling S4 is annealed; a surface flaw removal step S6 where the surface flaw of the wire rod b3 is removed by cutting; and a cutting step S7 where the wire rod b4 after the cutting off of the surface flaw is formed into a straight bar product. The annealing step S5 is carried out under the condition that the wire rod b3 is heated and held to and at 800-830 deg.C in vacuum or in an inert-gas atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rod made of titanium or a titanium alloy used for molding, for example, an engine valve.

[0002]

2. Description of the Related Art The above-mentioned titanium alloy rod has been used in FIG.
It is manufactured through manufacturing steps S1 to S8 as shown in FIG. That is, the material obtained by melting S1 a predetermined component of titanium alloy in a vacuum or the like is subjected to wire rolling S2,
It is a coiled wire having a diameter of about 12 mm. After the wire is pickled S3 to remove oxides on the surface, finish rolling S4 is performed.
By applying a coil-shaped wire b1 having a diameter of about 6 mm
Is obtained.

Then, as shown in FIG. 4A, the coiled wire rod b1 is annealed in a vacuum to soften it by annealing S5. Further, after passing through a plurality of grooved rollers arranged in a nested manner to form a linear wire b1, surface flaw removal (so-called shaving processing) S6 for removing surface flaws of the wire b1 is performed. The surface flaw removal step S6 is performed as shown in FIG.
This is performed by the shaving device 40 shown in (B) and (C). As shown in FIGS. 4 (B) and 4 (C), the device 40 has an outer cylinder 42 rotatably supported via a bearing 43 at a tip end of a cylindrical holder 41 and is directly connected to a motor M. A plurality of (four) blocks 46 to 49 supported by the inside of the outer cylinder 42 while being rotated by the pulley 44 and the belt 45, and a rough cutting tool K1 mounted near the center of each of the blocks 46 to 49 and on the inlet side. To K4 and finish cutting tools k1 to k4 attached to the outlet side.

[0004] From the left side of FIG.
The wire rod b1 immediately after the correction is removed by a rotating coarse cutting tool K1 to K3 or the like, and its surface is cut and removed with a thickness of about several hundred μm, and then the cut surface is smoothed by a finishing cutting tool k1 to k4 or the like. It is sent to the right side in FIG. Such wire rod b
As shown in FIG. 4 (A), after being cut S7 into a linear bar having a predetermined length, the bar 2 is further subjected to surface polishing S8 to obtain a titanium alloy bar product. . However, in the annealing step S5, the wire b1 formed into a coil shape is softened and a small bend occurs partially.
As shown in FIG. 4 (D), in the shaving device 40 in the surface flaw removing step S6, an uneven cutting state in which the peripheral surface (surface) of the wire rod b1 is cut unevenly may occur. For this reason, there has been a problem that the yield of titanium or titanium alloy bars is reduced.

[0005]

In order to prevent the above-mentioned uneven cutting, it is possible to correct and eliminate small bending caused by annealing by increasing the straightening force on the wire b1 at the time of straightening performed immediately before the surface flaw removing step. It is. However, there is a problem in that if the straightening force is increased, the wire b1 is broken, and the surface flaw removing step S6 itself stops. An object of the present invention is to solve the problems in the conventional technology described above, and to provide a manufacturing method for manufacturing a titanium or titanium alloy bar material reliably and with high yield without causing partial cutting or breakage. (Purpose).

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to optimize the annealing temperature or to adjust the annealing temperature so as not to cause breakage in the straightening process immediately before removing the surface flaw. In addition to this, the idea is to perform an annealing step after removing the surface flaws. That is, the first method for producing a titanium or titanium alloy rod according to the present invention includes a rolling step of using a titanium or titanium alloy material as a wire having a predetermined cross-sectional dimension, and an annealing step of annealing the wire.
Thereafter, a surface flaw removing step of cutting and removing surface flaws of the wire rod and a cutting step of using the wire rod as a rod are included, and the annealing step is performed at 800 ° C. in a vacuum or in an inert atmosphere. Performed under the condition of heating and holding at 830 ° C.
It is characterized by the following.

Further, a second method for producing a rod made of titanium or a titanium alloy according to the present invention comprises a rolling step of using a titanium or titanium alloy material as a wire having a predetermined cross-sectional dimension, and cutting a surface flaw of the wire. A surface flaw removing step of removing, a subsequent annealing step of annealing the wire, and a cutting step of using the wire as a rod, wherein the annealing step is performed at 800 ° C. in a vacuum or in an inert gas atmosphere. ~ 830 ° C
And heating and holding conditions. still,
The heating temperature in each annealing step is 820 ± 10 ° C.
(810-830 ° C.).

That is, the present invention has been found to prevent the occurrence of a specific embrittlement phenomenon when titanium or a titanium alloy is heated in a temperature range of less than 800 ° C. (about 500 ° C. to 740 ° C.). , In order to optimize the annealing temperature. For this reason, as in the first manufacturing method, it is possible to prevent breakage at the time of straightening after the annealing step and increase the straightening force. As a result, uneven cutting at the time of removing surface flaws can be reduced. Also, a second manufacturing method (Claim 2)
As described above, before the annealing step, the surface flaw removing step of cutting the surface including the hard oxide film and the surface flaw in the wire is performed, so that the wire does not have a small bend, so that the wire can be corrected with a high straightening force. Thereby, partial cutting of the wire can be prevented during surface cutting. In addition, in the subsequent annealing step, since a hard oxide film is not formed on the surface including the surface layer, even if the wire is slightly bent, the straightening force at the time of straightening afterwards can be increased and breakage can be prevented. As a result, both partial cutting and breakage can be prevented beforehand, so that a titanium or titanium alloy bar product can be manufactured with high yield.

Particularly, the heating temperature in the annealing step is set to 820.
By setting the temperature within the range of ± 10 ° C., the above-mentioned embrittlement phenomenon can be avoided more surely, so that it is possible to manufacture a titanium or titanium alloy bar with a high yield without breaking during straightening. . The heating temperature in the annealing step is 8
If the temperature is lower than 00 ° C., the embrittlement phenomenon is caused. If the temperature exceeds 830 ° C., the embrittlement phenomenon is saturated and the heat energy is lost. In order to prevent these, the temperature is set in the range of 800 to 830 ° C.

[0010] Further, the surface flaw removing step may include the step of preheating the (coiled) wire to at least 50 ° C or more.
The present invention also includes a method of producing a rod made of titanium or a titanium alloy (claim 3), which is to correct the rod (in a linear shape) and then remove the surface flaw of the wire by cutting. According to this, in any of the first and second manufacturing methods, the deformation resistance of the titanium or titanium alloy wire is reduced by preheating, the wire is less likely to break during straightening, and the straightness (straightness) due to straightening is reduced. Degree) is improved. For this reason, uneven cutting at the time of surface flaw removal can be prevented. Therefore, the yield in the manufacturing process of the titanium or titanium alloy bar can be improved. The preheating temperature is desirably 7
5 ° C. or more, more preferably 100 ° C., and 100 ° C.
It is more desirable to make the above.

[0011] In addition, there is provided a method for producing a titanium or titanium alloy bar comprising a finish rolling step of further reducing the diameter of the wire after the pressing between the rolling step and the annealing step. Included in the present invention. According to this, since the surface flaw removal and annealing steps can be performed in a more accurate state, it is possible to manufacture a titanium or titanium alloy bar in a stable state with good dimensional accuracy and yield.

[0012]

Preferred embodiments of the present invention will be described below with reference to the drawings. The row indicated by the solid arrow on the left side in FIG. 1A is a flowchart showing the first method for producing a titanium or titanium alloy bar according to the present invention. As shown in FIG. 1 (A), after a titanium alloy having a predetermined alloy composition is melted S1 in a vacuum or the like, the resulting material is obtained.
(Ingot) b1 is hot rolled S2. Rolling process S2
As shown in FIG. 1 (B), the material b1 is passed through a pair of rollers 1 and 1 having a concave groove 2 on its peripheral surface to reduce the diameter, thereby forming a coil-shaped wire having a predetermined sectional dimension b2
And

Next, the wire b2 is pickled S3 to remove oxides on its surface, and then subjected to finish rolling S4. In the finish rolling step S4, for example, as shown in FIG. 1 (C), a step of passing between three pairs of symmetric rollers 4 having a concave groove 6 on the peripheral surface may be mentioned. As a result, a coil-shaped wire b3 having a circular cross section and a diameter reduced to about 6 mm is obtained. Further, as shown in FIG. 1A, the wire b3 is subjected to an annealing step S5, and thereafter, a surface flaw removing step S6 for removing surface flaws immediately after preheating and straightening. In the annealing step S5, after the wire b3 wound in a coil shape is charged into a heat treatment furnace (not shown), the wire b3 is heated to 800 ° C. to 830 ° C. in a vacuum or an inert gas atmosphere for a predetermined time (5 to 10 hours). This is done by holding the crossing.

FIGS. 2A and 2B are graphs showing the results of an investigation conducted on the effect of annealing temperature in an experiment conducted to find out the proper annealing conditions for titanium or a titanium alloy. That is, Ti-6wt% Al-2wt% Sn-2wt% Mo
-4wt% Zr alloy composition, said rolling S2, pickling S
3. Finished rolling S4 and surface skin cutting, and a hard oxide film (TiO ₂ ) formed on the surface at the time of rolling S2, etc.
A test piece was collected from a sample of the wire rod b3 from which was removed.
After heating and holding these test pieces in vacuum at 100 ° C. to 830 ° C. for 6 hours, a tensile test (JIS: No. 4) was performed, and the tensile strength and the drawing ratio (cross-sectional reduction ratio) were measured.
The graph shown in FIG. 2 (A) was obtained. According to this, when the heating temperature exceeded 500 ° C., there was a tendency that the drawing ratio rapidly decreased. However, in the temperature range above 800 ° C,
It has been found that softening causes a recovery to a so-called high toughness state in which the tensile strength decreases and the draw ratio increases.

In another experiment, the effect of the hard oxide film (TiO ₂ ) formed on the surface on the toughness of the wire b3 was investigated. That is, a test piece was obtained from a sample of the wire b3 having the same alloy composition as above, performing the rolling S2, the pickling S3, and the finish rolling S4, and forming a hard oxide film (TiO ₂ ) on the surface. . The test piece has the same diameter as the wire b3. After heating and holding these test pieces in a vacuum at 100 ° C. to 830 ° C. for 6 hours, the same tensile test as above was performed to measure the tensile strength and the draw ratio, and the graph shown in FIG. 2 (B) was obtained. Was. According to the graph of FIG. 2B, in the temperature range of 500 to 700 ° C., as in the graph of FIG.
In, there is a tendency that the draw ratio is improving. In particular, at 820 to 830 ° C., the drawing ratio was restored to 10% or more. These results indicate that the hard oxide film (Ti
Even if O ₂ ) is a wire b3 formed on the surface, 800
It is suggested that annealing at a temperature of not less than ℃ can reduce breakage in subsequent straightening.

Further, as compared with the graph of FIG.
In both graphs, both the tensile strength and the reduction ratio were lowered because, in the latter case, a sample was taken from a wire b3 having a hard oxide film (TiO ₂ ) formed on the surface by high-temperature heating during rolling S2. Because he did. 80 after that
Although the drawing ratio tends to recover by annealing at 0 ° C. or more, the drawing ratio is lower than that of the sample used in the graph of FIG. 2A from which the oxide film has been removed in advance, that is, a slightly brittle property (low toughness). Was confirmed. From the above results,
In the annealing step S5, in order to prevent breakage in the subsequent straightening, the wire b3 is set at 800 ° C. or higher, more preferably at 8 ° C.
The fact that it is preferable to perform the reaction in a temperature range of 20 ± 10 ° C. has been proved.

The wire b3 softened by the above annealing S5
On the other hand, as shown in FIG. 1A, desirably, after performing a straightening process in a preheated state, surface flaw removal (surface flaw removal) S6 is performed. That is, as shown in FIG. 3 (A), the surface flaw removing step S6 rewinds the wire b3 after the finish rolling S4 wound in a coil shape around the support 12 of the left turntable 11, and places the wire b3 in the heater 13. After preheating to 50 ° C. or higher by passing through, the central straightening device 10 and the left shaving device 20 are passed.

It is desirable that the wire b3 be preheated by the heater 13 and then straightened for the following reason. Ti
Each of the rolling S2, the pickling S3, and the finish rolling S4 is performed on the material b1 having an alloy composition of -6 wt% Al-2 wt% Sn-2 wt% Mo-4 wt% Zr to obtain a plurality of wire rods b.
3 was obtained. The test piece cut out from the wire b3 was set to 0
Each of the tensile tests was individually performed while individually maintaining the temperature at 25 ° C., 25 ° C., 50 ° C., 75 ° C., and 100 ° C., and the elongation rate and the reduction ratio (cross-sectional reduction rate) were measured at each of the above temperatures.
The graph shown in (B) was obtained. According to this, at 50 ° C. or higher, the elongation exceeds 10% and the draw ratio becomes 48% or more. In particular, at 100 ° C., the elongation is about 19% and 50%.
The aperture ratio was above.

From the above results, by preheating the wire b3 to 50 ° C. or more (50 to 100 ° C. or more) with the heater 13, the deformation resistance is reduced and the toughness is increased, so It can be understood that breakage in can be prevented. As shown in FIG. 3 (A), the preheated wire b3 passes between the grooved rollers r1 to r5 nested on the vertical platform 14 of the straightening device 10 in a loosely meandering manner, and then on the horizontal platform 16. Gently meandering between the grooved rollers R1 to R5 mounted in a nested manner. As a result, the wire b3 is straightened into a straight wire b3 with no curl without breakage.

As shown in FIG. 3A, when the corrected wire rod b3 passes through the shaving device 20, an oxide film (T
The hard surface layer having iO ₂ ) is cut off (after step S6). Shaving device 20 used for removing such surface flaws
As shown in FIGS. 3 (C) and 3 (D), a cylindrical holder 22 mounted on a base 21, an outer cylinder 26 rotatably supported at its tip via a bearing 24, and And four blocks 28 to 34 symmetrically supported in front of a flange 27 protruding inside the outer cylinder 26.
The outer cylinder 26 is rotated via a belt 25 wound around a pulley 23 rotated by a motor M. Each of the blocks 28 to 34 includes rough cutting tools K1 to K4 mounted near the center and on the inlet side, and finish cutting tools k1 to k4 mounted on the outlet side.

From the left side of FIG.
The wire rod b3 immediately after the correction is cut and removed by a rotating coarse cutting tool K1 to K4 with a thickness of about several hundred μm, and the cut surface is smoothed by a finishing cutting tool k1 to k4. It is sent to the right side of FIG. 3C as a titanium alloy wire b4. As a result, the bar b3 becomes a bar b4 having a predetermined diameter and no flaws or oxide films on the surface. Then, as shown in FIG. 1 (A), the wire b4 having been subjected to the above-described surface flaw removal S6 is straightened and cut into a linear bar of a predetermined length S7, and the surface thereof is, for example, Surface polishing S by a method such as shot peening
8 is done. Thus, a bar material made of titanium or a titanium alloy is obtained. By upsetting and forging one end of the bar material along the axial direction, a titanium product such as an engine valve can be obtained.

In the present invention, after the finish rolling S4 in FIG. 1 (A), a bar made of titanium or a titanium alloy can be obtained by the second manufacturing method indicated by the one-dot chain line in FIG. That is, as shown in FIG. 1 (A), surface flaws are obtained after preheating and straightening at a temperature of 50 ° C. or more to the wire b3 obtained through the melting S1, the rolling S2, the pickling S3, and the finish rolling S4. This is a method of performing a surface flaw removing step S6 to be removed and an annealing step S5 for heating and maintaining the temperature at 800 to 830 ° C. thereafter. The surface flaw removal step S6 is the same as that shown in FIG.
As shown in (A), the wire b3 after the finish rolling S4 is rewound, preheated to 50 ° C. or higher by passing through the heater 13, and passed through the straightening device 10 to form a straight wire b.
After that, the wire is passed through the shaving device 20 shown in FIGS. 3C and 3D to form a wire b4. Thereafter, it is straightened and cut S7 in the same manner as described above to become a bar b4, and the surface is polished S8 to obtain a bar product made of titanium or a titanium alloy.

In the second manufacturing method according to the present invention as described above, the hard oxide film (TiO ₂ ) generated on the surface of the material b1 at the time of rolling S2 is removed in the surface flaw removing step S6, and the small wire b3 is removed. Since there is no bending, straightening can be performed with a high straightening force, and uneven cutting during surface cutting can be prevented.
Moreover, in the subsequent annealing step S5, no oxide film is formed on the surface, so that even if a small bend occurs in the wire rod b4, it is possible to prevent breakage during the subsequent straightening process. As a result, since the straightening force in the surface flaw removing step S6 and the cutting step S7 can be increased, the linearity (straightness) of the wire can be improved and breakage can be reliably prevented. Therefore, it is possible to reliably and accurately manufacture a bar made of titanium or a titanium alloy without causing breakage or uneven cutting.

The manufacturing method of the present invention is not limited to the embodiment described above. For example, the bars (wires) to be subjected to each of the manufacturing methods of the present invention are not limited to circular cross-sections, but also have regular polygons such as square cross-sections, hexagons, and octagons, and modified polygons including rectangles. Or oval, angled, or channel shaped sections. In addition, a wire having a small cross section having these cross sections is also included. Further, the titanium alloy of the rod (wire) to be subjected to the method of the present invention includes the Ti-6 wt% Al-2 wt% Sn-2 wt%.
Not limited to Mo-4wt% Zr, pure titanium, Ti-8wt% A
α-type Ti alloy such as l-1wt% V-1wt% Mo, Ti-
Α + β-type Ti alloys such as 6 wt% Al-4 wt% V and β-type Ti alloys such as Ti-13 wt% V-11 wt% Cr-3 wt% Al also include alloys capable of forming an oxide film on the surface. .

Further, the rolling S2, pickling S3, annealing S
5, and the respective steps of preheating, straightening, and surface flaw removal S6 can be performed by a continuous line without winding and rewinding the titanium alloy wires b2, b3, and b4 into a coil shape. And the above finish rolling S4, cutting S
7, or a continuous line including at least one of the steps of surface polishing S8. When the continuous treatment is performed by the first manufacturing method, the preheating in the next step (S6) can be omitted by utilizing the residual heat of annealing S5. Further, the surface flaw removal S6 is not limited to the shaving apparatus 20, and a fixed or rotary cutter capable of cutting a surface layer including the surface flaw of the wire b3 may be used.

[0026]

According to the method of the present invention for producing a rod made of titanium or titanium alloy, the steel is annealed in a temperature range of 800 ° C. or more after rolling, so that the embrittlement phenomenon (high tensile strength and low drawing) Rate) can be avoided. For this reason, in the first manufacturing method (claim 1), it is possible to reduce breakage during correction and removal of surface flaws after the annealing step. Further, in the second manufacturing method (Claim 2), since the hard oxide film on the surface of the wire is removed by the surface flaw removing step performed before the annealing step, it can be corrected with a high straightening force without small bending, so that partial cutting can be performed. Since an oxide film is not formed in the subsequent annealing step, even if a small bend occurs in the wire, it is difficult for the wire to break during a subsequent straightening process. As a result, the straightening force before and after the annealing step can be enhanced, breakage can be prevented, and a rod having high linearity (straightness) can be obtained.

Further, according to the manufacturing method of the third aspect, since the titanium alloy wire is reduced in deformation resistance and improved in toughness by the preheating before the straightening, the breakage during the straightening and removal of the surface flaw immediately after the straightening are performed. Uneven cutting at the time can be prevented. As a result, the yield in the process of manufacturing a titanium or titanium alloy bar can be improved. In addition, according to the manufacturing method of claim 4, since the surface flaw removal and the annealing step can be performed in a more accurate state, the titanium or titanium alloy rod can be stably maintained with good dimensional accuracy and yield. Can be manufactured.

[Brief description of the drawings]

FIG. 1A is a flowchart showing first and second manufacturing methods according to the present invention, FIG. 1B is a schematic view showing a rolling step, and FIG. 1C is a schematic view showing a finish rolling step.

FIGS. 2A and 2B are graphs each showing a relationship between an annealing temperature, a tensile strength, and the like.

3A is a schematic diagram showing a surface flaw removing step in the method of the present invention, FIG. 3B is a graph showing a relationship between a preheating temperature and an elongation percentage, etc., and FIG. 3C is a dashed line in FIG. FIG. 4D is an enlarged cross-sectional view of a portion C, and FIG. 4D is a cross-sectional view taken along a line DD in FIG.

FIG. 4A is a flowchart showing a conventional manufacturing method,
(B) and (D) are schematic diagrams showing the surface flaw removal process, and (C) is
Sectional drawing by the viewing angle along CC line | wire in (B).

[Explanation of symbols]

S2: rolling step S4: finishing rolling step S5: annealing step S6: preheating / correction / surface flaw removal step (surface flaw removal step) S7: cutting step b1 ……… materials b2 to b4… wires

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22F 1/00 C22F 1/00 630K 651 651B 683 683 686 686 686A 691 691B

Claims (4)

[Claims] A step of rolling a titanium or titanium alloy material into a wire having a predetermined cross-sectional dimension; an annealing step of annealing the wire; and a surface flaw removing step of cutting and removing surface flaws of the wire thereafter. And a cutting step of using the wire as a rod, wherein the annealing step is performed in a vacuum or an inert gas atmosphere under conditions of heating and holding at 800 ° C. to 830 ° C. Or a method of manufacturing a titanium alloy bar. 2. A rolling step of using a titanium or titanium alloy material as a wire having a predetermined cross-sectional dimension, a surface flaw removing step of cutting and removing surface flaws of the wire, and a subsequent annealing step of annealing the wire. And a cutting step of using the wire as a rod, wherein the annealing step is performed in a vacuum or an inert gas atmosphere under conditions of heating and holding at 800 ° C. to 830 ° C. Or a method of manufacturing a titanium alloy bar. 3. The step of removing surface flaws includes correcting the wire in a state where the wire is preheated to at least 50 ° C. or higher, and subsequently cutting and removing surface flaws of the wire. Item 3. The method for producing a titanium or titanium alloy bar according to item 1 or 2. 4. The method according to claim 1, further comprising, between the rolling step and the annealing step, a finishing rolling step of further reducing the diameter of the wire after the rolling. A method for producing titanium or titanium alloy bars.