JP5644103B2 - Method for producing titanium alloy bar - Google Patents

Description

  The present invention relates to a method for manufacturing a bar made of titanium alloy used for manufacturing various products by performing machining or the like.

  Titanium alloys are light in weight, high in strength, and excellent in corrosion resistance. For example, they have been widely used as materials for forming artificial aggregates and various machine parts. In order to manufacture these various products, titanium alloys are first processed into, for example, a rod material having a diameter of about 8 to 60 mm and a length of about 3 to 6 m by subjecting a billet of titanium alloy to rolling and subsequent correction and surface processing. Then, the obtained titanium alloy bar is subjected to machining or the like to form a final titanium alloy product. FIG. 3 is a flowchart showing a conventional manufacturing method of this titanium alloy bar.

That is, as shown in FIG. 3, the billet W ₁ of a titanium alloy having a predetermined component and material, this cut s2 then subjected to rolling s1, a predetermined cross-sectional dimension and a predetermined length of the bar, the bar After the structure is adjusted by annealing s3, the bend of the bar is corrected by press correction s4, and then the surface flaw removal s5 is performed by cutting and removing the surface flaw of the bar with a shaving device or the like, and then cold correction s6 by finally straightening the bending of the bar, subjected to surface polishing s7 by centerless grinder or the like, is that to obtain the bar product W ₂ is a titanium alloy bar as a target.

However, when the bar product W ₂ obtained in the above process is machined into a titanium alloy product, defective products such as local deformation of the thin-walled portion of the processed product or bending deformation of the entire product may occur. In addition, the above-described deformation during precision machining causes problems such as the machining itself becoming impossible. It is seen to be due to residual stress of the bar products W _2, the presence of and try to measure the actual residual stress of the bar product W ₂ large axial residual stress (e.g. more than 480 MPa) was confirmed.

  The occurrence of the residual stress is considered to be mainly caused by the cold correction s6 immediately before the surface polishing s7 during the process shown in FIG. -291029 (Patent Document 1), such as a straightening method of a titanium alloy straight bar that heats and holds a titanium alloy bar at a high temperature, or a cold straightening s6 that is a source of residual stress. Instead, it is also possible to adopt a rod and wire continuous straightening device that warms the rod and wire by applying current and heating while applying tension to the rod and wire as disclosed in JP-A-8-300044 (Patent Document 2). It is done.

However, the method disclosed in Patent Document 1 is to insert a small number of rods into a container and hold it at a high temperature for a long time (for example, 40 minutes or more), and this heating is performed in a separate process from correction. because it takes a lot of time until obtaining the bar product W _2, and has a problem that the productivity is poor. Further, Patent Document 2 discloses that the invention is preferably applied to a continuous thin wire that is continuously fed, but in the case of a rod having a larger diameter than this, a tension-adding roll. In the case of a bar that is much shorter than a continuous wire, there is insufficient heating / tension applied part at the tip and tail end of the bar, so Incorrect correction occurs, and both ends need to be largely cut away, resulting in poor yield.

JP-A-10-291029 JP-A-8-300044

  The present invention has been made in view of the above points, and can produce a titanium alloy bar whose residual stress is suppressed to a small amount with high productivity and high yield. The purpose is to provide.

  In order to achieve the above object, the method for producing a titanium alloy bar according to claim 1 comprises annealing a bar obtained by rolling a billet of titanium alloy to a predetermined cross-sectional dimension and cutting it to a predetermined length. A first annealing step, a correction step for correcting the bending of the bar material after the annealing, a surface wrinkle removal step for cutting and removing the surface wrinkles of the bar material after the correction, and the bar material after the surface wrinkle removal A second annealing step for annealing, a warm correction step for correcting the bending of the bar after the annealing in a state in which the bar is heated to a temperature of 600 ° C. or more and a β transformation point or less, and after the correction And a surface polishing step of polishing the surface of the bar to obtain a bar product.

  As titanium alloys used in the present invention, Ti-3Al-2.5V, Ti-3Al-2.5V-S-REM, Ti-3Al-3.5Sn-0.8Mo-1.4V-0.1Si, Ti-3Al-5Sn-1Mo-0.25Si, Ti-4.5Al-3V-2Mo-2Fe, Ti-5Al-2.5Fe, Ti-5Al-2Sn-2Zr-4Mo-4Cr, Ti-6Al-4V, Α + β type titanium alloys such as Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo, Ti-6Al-2Fe-0.1Si, and Ti-22V-4Al, Ti-3Al-8V-6Cr-4Zr -4Mo, Ti-13V-11Cr-3Al, Ti-11.5Mo-6Zr-4.5Sn, Ti-10V-2Fe-3Al, Ti-15V-3Cr-3Sn- 3Al, Ti-15Mo-5Zr, Ti-15Mo-5Zr-3Al, Ti-15Mo-2.7Nb-3Al-0.2Si, Ti-9.5V-2.5Mo-3Al, Ti-20V-4Al-1Sn, Examples thereof include β-type titanium alloys such as Ti-16V-4Sn-3Al-3Nb, Ti-6.8Mo-4.5Fe-1.5Al, Ti-6Al-4V-10Cr-1.3C.

  In the present invention, the heating temperature of the bar in the warming process is set to 600 ° C. or more in detail about the relationship between the heating temperature during the warming process and the residual stress of the bar product after the surface polishing process. This is based on the knowledge obtained as a result of experiments and investigations, and the residual stress is suppressed to a small value (see the section of Examples for specific numerical examples) by setting the temperature to 600 ° C. or higher. . The reason why the heating temperature is not higher than the β transformation point is that if the temperature exceeds the β transformation point, crystal grains become coarse and impact value and fatigue strength decrease, which is avoided.

  According to the first aspect of the present invention, the straightening process of the bar immediately before the surface polishing process is performed by warming straightening the bar in a state where the bar is heated to a predetermined temperature within the temperature range. By using the process, it is possible to obtain a titanium alloy bar whose residual stress is suppressed to a small amount at the same time as removing the strain of the bar. This makes it possible to produce a bar made of titanium alloy with good performance and high yield.

  In this invention, the heating of the bar in the warming process can be performed by energization heating or induction heating. However, as in the invention of claim 2, the heating of the bar in the warming process is conducted by energization. A structure that is performed by heating is particularly preferable because temperature control is easy and even a bent bar can be heated to a uniform temperature.

  In the present invention, the roll correction in the warm correction process can be performed by two-roll correction or multi-roll correction. However, as in the invention of claim 3, the roll correction in the warm correction process is performed by two-roll correction. A configuration that is performed by a machine is particularly preferable because small bending of the bar does not occur.

  Moreover, in this invention, although the straightening process of the bar after the first annealing process may be performed by cold press correction or the like as in the conventional manufacturing method, as in the invention according to claim 4, If the bar straightening process after the first annealing step is composed of a warm straightening process in which a bar heated to a temperature of 500 ° C. or higher and a β transformation point or lower is composed of a roll straightening process, the straightening of the bar is corrected. At the same time, the deviation in the diameter of the bar material generated during rolling, which is the previous process, is reduced in the repair direction by this warm correction (refer to the section of Examples for specific numerical examples), which is particularly preferable.

  As described above, according to the present invention, a titanium alloy bar whose residual stress is suppressed to a small amount can be manufactured with high productivity and high yield.

  Further, in addition to the above effect, according to the invention of claim 2, the heating temperature of the bar during warm correction can be easily controlled, and even a bent bar can be heated to a uniform temperature. A homogeneous titanium alloy bar without excessive residual stress can be obtained.

  Further, in addition to the above effect, according to the invention of claim 3, since a small bend does not occur during warm correction, a titanium alloy rod having excellent straightness without increasing the polishing allowance for surface polishing. A material can be obtained.

  Further, in addition to the above effect, according to the invention of claim 4, the uneven diameter difference of the bar material generated during rolling is reduced in the repair direction by this warm correction, and the surface flaw removing step which is a subsequent step Since the fluctuation amount of the cutting resistance at the time is reduced, the processing speed at the time of removing surface defects can be increased to improve the productivity.

It is a flowchart of the manufacturing method of the bar made from a titanium alloy which shows an example of embodiment of this invention. It is the schematic of the equipment used for warm correction process S7 in FIG. It is a flowchart which shows the manufacturing method of the conventional titanium alloy rod.

Hereinafter, an embodiment of the present invention will be described with reference to an example shown in FIGS. FIG. 1 is a flowchart of a method for producing a titanium alloy bar according to the present invention. A billet W ₁ obtained by melting, ingot-making, and forging a titanium alloy having a predetermined component is provided with a heating furnace, a rough rolling mill row, and finish rolling. After rolling S1 with a rolling machine having a machine row, cutting S2 such as hot saw cutting is performed, and a straight rod-like bar (round 24 mm, length 4 m, for example) having a predetermined cross-sectional dimension and length (for example, round 4 mm) Bar).

  Next, after performing the structure adjustment by applying annealing S3 which is the first annealing step to the bar using an annealing furnace, correction S4 for correcting the bending of the bar after the annealing is performed. This correction is to correct the bending to pass the bar through the apparatus for the surface flaw removal step S5, which is a subsequent process, and the correction method is cold (normal temperature) performed by a press straightener. In addition to press correction, warm roll correction in which the rod is heated to a predetermined temperature and then corrected by a two-roll correction machine or a multi-roll correction machine is used. Among these, warm roll straightening is superior to cold press straightening in that the straightening takes a short time and productivity is high, and in warm roll straightening, the heating temperature of the bar is 500 ° C. or more and the β transformation point or less. This temperature is particularly preferable because the rolls of the bar can be easily straightened and the deviation in the diameter of the bar is improved (reduced). The reason why the heating temperature is not higher than the β transformation point is that if the temperature exceeds the β transformation point, the crystal grains become coarse and the impact value and fatigue strength decrease, which is avoided. And as the apparatus for this warm roll correction | amendment, the warm correction equipment 1 (however, the heating temperature lower limit is different) for warm correction process S7 mentioned later can be used conveniently.

  Next, for the bar material after the straightening step S4, after removing the surface wrinkles S5 by a peeling device in order to remove the rolling wrinkles on the bar surface, In order to remove the generated residual stress, annealing S6 which is a second annealing step is performed using an annealing furnace.

Then, as a final correction to ensure the straightness required by straightening the bends remaining bars as bar product W _2, performs warm straightening S7. In this warm straightening step S7, the bar is straightened after heating the bar to a temperature not lower than 600 ° C. and not higher than the β transformation point. The reason for limiting the heating temperature range is as described above.

The heating of the bar in this warm correction step S7 can be performed by energization heating or induction heating. However, the energization heating is preferable because temperature control is easy and even a bent bar can be heated uniformly. Further, the roll correction can be performed by a two-roll correction machine or a multi-roll correction machine, but the two-roll correction is less likely to bend, and the following surface polishing step S8 can be smoothly performed and the bar product W having excellent straightness. ₂ is preferable.

Figure 2 is an illustration schematically a warm straightening equipment 1 for warm straightening step S7 in the above, 2 is a resistance heating apparatus, the end of the bar B ₁ after the annealing step S6 is corrected target The energizing clamps 2a and 2a to be gripped are connected to a power source 2b, and 3 is a two-roll straightening machine. The bar B ₁ after the annealing step S6 is supplied from the feed part 4 to the current heating apparatus 2 part by part by a transfer means (not shown) so as to have a predetermined temperature not less than 600 ° C. and not more than the β transformation point. After being heated and energized over time, it is transported onto the transport path 5, passed between the upper roll (concave roll) 3 a and the lower roll (convex roll) 3 b of the two-roll straightening machine 3, and warmed and then transported. After passing over the path 6, it is transferred to the bar collecting part 7 as a corrected bar B ₂ and is in a collected state.

For bar B ₂ after S7 above warm straightening step, subjected to a surface polishing S8 by centerless grinder, by removing the mill scale portion of the bar surface, the manufacturing method of this titanium alloy rod material the final product small bar product W ₂ residual stress is is that obtained.

  Next, specific examples of the method for producing a titanium alloy bar according to the present invention will be described in more detail together with comparative examples.

[Example 1]
A round bar-like bar with a diameter of 24 mm and a length of 4 m is obtained by subjecting a billet W ₁ made of Ti-6Al-4V to a square bar-like billet W ₁ having a cross section of 116 mm × 116 mm and a length of 4 m to rolling S1 and subsequent cutting S2. After this bar material was subjected to annealing S3 at 740 ° C. for 1.5 hours in an annealing furnace, cold press straightening (indicated as cold PK in Table 1) by a press straightening machine as the straightening step S4 After removing surface flaw removal S5 with a cutting allowance of 1.5 mm using a peeling device, annealing is performed at 650 ° C. for 1 hour in an annealing furnace, and the warm straightening equipment is applied to the obtained bar B ₁ with 1, subjected to warm straightening S7 in heating temperature 800 ° C., subjected to cash 0.5mm surface polishing S8 in scraping the centerless grinder against bar B ₂ after the correction, the diameter 22 mm, length 4m It was obtained of the bar products W _2.

For this bar product W _2, the residual stress in and from the bar surface of 1.1mm inner position at the position of 1m from one end of the bar, under X-ray diffraction measurement conditions and analysis conditions below The measurement results are shown in Table 1. Note This measurement is the average of the measured values of the three samples of the bar products W _2, those obtained in the same manner the residual stress measurements for other examples and comparative examples below.
Measurement conditions Measurement method: Parallel tilt method Measurement mode: ψ0 constant method Peak angle (degrees): 142.0
Stress constant (MPa / degree): -258.09
Collimator (mm): 1.0 (diameter)
Voltage (kV): 40
Current (mA): 30
Target: CuKα
ψ angle (degree): 0, 3, 6, 9, 12, 15, 18, 21, 24
Analysis conditions Peak search method: Peak top method Background points: High 5, Low 5
Number of smoothing points: 25

[Example 2 and Comparative Example 1]
Other subjected to warm straightening S7 at the heating temperature shown in Table 1, to obtain a bar product W ₂ in the same manner as in Example 1, with respect to the bar product W _2, the same measuring method as in Example 1 Table 1 shows the measurement results obtained by measuring the residual stress.

[Comparative Examples 2 and 3]
As the warm straightening step S7, cold press straightening was performed using a press straightening machine instead of warm straightening (Comparative Examples 2 and 3), and in Comparative Example 3, the annealing step S6 was omitted. and give the bar product W ₂ in the same manner, with respect to the bar product W _2, showing a measurement result of measuring the residual stress by the same measuring method as in example 1 in Table 1. In Comparative Example 3, the annealing step S6 is omitted as described above, and cold press straightening is performed after the surface flaw removing step S5. Therefore, all the steps of Comparative Example 3 are the steps shown in FIG. This is an example of a conventional method for producing a titanium alloy bar.

[Examples 3 to 6 and Comparative Examples 4 and 5]
As the correction step S4, the warm correction equipment 1 is used instead of the cold press correction to perform the warm correction at the heating temperature shown in Table 1, and the warm correction S7 is performed at the heating temperature shown in Table 1. Otherwise, the bar product W ₂ was obtained in the same manner as in Example 1, and the measurement results of measuring the residual stress of this bar product W ₂ by the same measurement method as in Example 1 are shown in Table 1.

  As shown in Table 1, the residual stress is reduced by setting the heating temperature of the bar in the warm correction step S7 to 600 ° C. or more, and the superiority of the present invention is clear.

[Examples 7 to 10]
Next, in order to investigate the influence of the heating temperature of the bar in the straightening step S4 on the deviation of the diameter of the bar, the same rolling S1, cutting S2, and annealing S3 as in Example 1 are performed on the same billet as in Example 1. When the cold press straightening by the cold press straightening device is performed as the straightening step S4 on the bar material having a diameter of 24 mm obtained through the respective steps, and the different 3 shown in Table 2 using the warm straightening equipment 1 Table 2 shows the results of measuring the difference in diameter between the bars before and after each correction when warm correction was performed at various heating temperatures.

  The deviation in diameter was calculated as the difference between the maximum and minimum values of the diameter of the bar (24 mm in diameter) measured by a micrometer at a position 1 m from one end of the bar. Table 2 shows the average deviation diameter obtained by measuring five samples of the bar for each condition.

  As shown in Table 2, by setting the heating temperature of the bar in the straightening step S4 to 500 ° C. or higher, the deviation in the diameter of the bar after the straightening step S4 is reduced in the repair direction compared to before the straightening. Yes.

  The present invention is not limited to the embodiments and examples described above. For example, the bar material type, the heating temperature in each step, the device used, and the like may be other than those described above.

S1 ... rolling step, S2 ... cutting step, S3 ... annealing step, S4 ... straightening step, S5 ... surface flaws removing step, S6 ... annealing step, S7 ... warm straightening step, S8 ... surface polishing process, W 1 _... billet, W ₂ ... Bar product, B ₁ ... Bar material, B ₂ ... Bar material, 1 ... Warm straightening equipment, 2 ... Current heating device, 3 ... 2 roll straightening machine.

Claims (4)

A first annealing step of annealing a bar obtained by rolling a billet of a titanium alloy into a predetermined cross-sectional dimension and cutting it to a predetermined length;
A straightening process to correct the bending of the bar after annealing,
A surface wrinkle removing step of cutting and removing the surface wrinkles of the bar after the correction;
A second annealing step for annealing the bar material after removal of the surface flaws;
A warm straightening step of correcting the roll of the bar after the annealing in a state where the bar is heated to a temperature of 600 ° C. or higher and a β transformation point or lower;
The surface polishing step of polishing the surface of the bar after correction to make a bar product,
A method for producing a titanium alloy bar material, comprising:   The method for manufacturing a titanium alloy bar according to claim 1, wherein the heating of the bar in the warming process is performed by energization heating.   The method for producing a titanium alloy bar according to claim 1 or 2, wherein the roll straightening in the warm straightening step is performed by a two-roll straightening machine.   The rod straightening step after the first annealing step comprises a warm straightening step of roll straightening a rod heated to a temperature not lower than 500 ° C and not higher than a β transformation point. The manufacturing method of the bar made from a titanium alloy of any one of these.

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