JP4987640B2 - Titanium alloy bar wire for machine parts or decorative parts suitable for manufacturing cold-worked parts and method for manufacturing the same - Google Patents

Description

  The present invention is a titanium alloy rod for machine parts or decorative parts, which is excellent in cold workability, manufactured by cold forging or shear cutting mainly for screws such as bolts and nuts, automobile parts, ornaments, etc. The present invention relates to a wire product and a manufacturing method thereof.

  In recent years, titanium products have come to be used in screws such as bolts and nuts, automobile parts, and decorative parts such as watches, cameras, and glasses. These are mainly used for applications utilizing the excellent corrosion resistance of titanium, harmlessness to human bodies and living bodies, and light weight. Among these, when particularly high strength is not required and low manufacturing cost and high cold workability are important, pure titanium is used. For example, JIS H4650 (2001) “bar of titanium and titanium alloy” 1 materials (TB270H (hot finish), TB270C (cold finish)), or 2 materials (TB340H (hot finish), TB340C (cold finish)) are often used. In order to further reduce the cost, header processing is adopted as a method of cold forging the bolt head to manufacture the bolt. This is a method for producing bolts efficiently by continuously forging the bolt heads in the cold using a material that has been cut to a predetermined length in advance. Conventionally, when using a titanium material with strength equal to or greater than two kinds of materials for this header processing, an adiabatic shear deformation band is generated in the processed part, and cracks are often generated along it, resulting in an extreme yield loss. There was a problem of bringing. In addition, when the titanium material excluding the β alloy has strength equal to or greater than the two kinds of materials, it often has material anisotropy in the C cross section, and as a result, cracks occur along the direction of inferior workability during header processing. Is easy to extend and cannot be formed into bolts. For these reasons, it was found that a titanium material that exhibits a strength equal to or higher than the two kinds of materials, except for some β alloys, is not suitable for bolt manufacturing by header processing. Therefore, when low manufacturing cost is important, cracks do not occur even when header processing is performed, and one type material having a small material anisotropy in the C cross section has been used in a limited manner.

  Therefore, there is a high need for a material having higher strength that can be manufactured at a low cost with processability similar to that of a single material. In addition, when using one type of material for this manufacturing process, burrs and burrs are generated on the cut surface in the shear cutting process for adjusting the length of the wire processing coil to the length of the header processing material immediately before header processing. There is a problem that the vicinity of the cut portion is deformed. This is because the strength of the first kind material is low and the ductility is high, so that the shearing process applied by the shear does not cause an immediate break, but involves a small amount of plastic deformation.

  Moreover, in order to suppress the occurrence of burrs, burrs and the like when cutting a shear with one kind of material, light drawing with a surface reduction rate of about 5 to 15% is often performed. This is because the ductility is lowered slightly by strengthening the cold work and the cutting performance is improved. However, there are still no burrs and burrs, and they are not necessarily fundamental measures.

On the other hand, in order to improve header workability, it may be effective to improve cold workability by adding Cu to titanium. Patent Literature 1, Patent Literature 2, and the like have been disclosed as titanium alloys to which Cu has been added so far. The former is to refine the structure uniformly by heating to the two-phase temperature range of the Ti—Cu alloy to reduce the macro pattern, and there is no description about improvement of cold workability including header processing. The latter is intended to increase the strength by actively precipitating Ti ₂ Cu, etc., and to utilize antibacterial properties, but there is no limit on the amount of O that governs the strength of the alloy, and header processing is not possible. Intensity regions are also included. Actually, in the examples in Patent Document 2, only an alloy having a maximum tensile strength of 750 MPa or more is illustrated, and it is clear that the alloy does not show an alloy that pursues header workability requiring high cold workability. It is.

JP 2004-2953 A Japanese Patent Laid-Open No. 11-80867

  Provided is a titanium alloy bar wire for machine parts or decorative parts, which is more excellent in cold workability such as header processing and shear cutting than JIS 1 and 2 type pure titanium, and a method for producing the same.

  The present invention is made on the background of the above circumstances, has a header processing equivalent to or better than JIS Class 1 pure titanium, has a cold workability such as shear cutting ability, and has a strength equivalent to or higher than two kinds of materials. An object of the present invention is to provide an optimum titanium alloy bar wire as a cold-worked part and a method for producing the same.

In order to solve the above problems, the present invention is based on the following means.
(1) 0.3% to 1.8% Cu by mass, 0.18% or less O, 0.30% or less Fe, the balance Ti and less than 0.3% impurity elements, Titanium alloy for mechanical parts or decorative parts having excellent shear cutting property and cold forgeability, comprising 1000 nm of Ti ₂ Cu and unavoidable precipitated phase in a volume fraction of 0.05 to 3.5% Bar wire.
(2) In the manufacture of the titanium alloy bar wire according to (1), the final annealing is performed in a temperature range of 480 to 750 ° C., and for mechanical parts having excellent shear cutting ability and cold forgeability Or the manufacturing method of the titanium alloy bar wire for decoration parts.
(3) Furthermore, after the final annealing, cold drawing with a surface reduction rate of 15% or less is performed. For mechanical parts having excellent shear cutting ability and cold forgeability according to (2), Manufacturing method of titanium alloy bar wire for decorative parts.
(4) A method for producing a titanium product, characterized by performing shear cutting using the titanium alloy rod described in (1) and then performing header processing.

  It is possible to provide a titanium alloy bar wire for machine parts or decorative parts and a method for producing the same, which is more excellent in cold workability such as header processing and shear cutting than JIS 1 and 2 type pure titanium.

In order to solve the above-mentioned problems, the present inventors have investigated in detail the influence of component elements on the cold workability of titanium. As a result, a certain amount of Cu was added to titanium, and Ti ₂ Cu and inevitable precipitation phase ( Hereinafter, it is possible to improve the workability in the header processing and shear cutting process as compared with JIS Class 1 pure titanium by finely precipitating the precipitation phase such as Ti ₂ Cu) and adjusting the amount of O appropriately. I found it possible.

  The present invention has been made based on this finding. The reason why various additive elements shown in the present invention described in the above (1) (hereinafter, abbreviated as the present invention (1)) are selected and the reason why the addition amount range is limited are shown below.

Cu is solid-dissolved in the titanium α phase up to 1.5% by mass. It is known that Cu in a solid solution has an effect of enhancing the high temperature strength by strengthening the solid solution and strengthening without impairing the occurrence of twin deformation, and the effect is disclosed in Japanese Patent Application Laid-Open No. 2005-298970 and the like. ing. This publication is characterized by finding and utilizing the effect of improving the cold workability and increasing the high-temperature strength by solute Cu. On the other hand, when an appropriate amount of precipitated phase such as Ti ₂ Cu is generated in the α phase in the Ti—Cu alloy, the strength is increased by precipitation strengthening and the α phase grain growth is suppressed by the pinning effect on the α grain boundary. There is an effect. When the inventors control the amount of precipitation phase such as Ti ₂ Cu, the amount of strengthening is such that it does not cause the generation of adiabatic shear deformation zone during header processing, and solid solution Cu improves cold workability. And found a new contribution to improving header processability. In addition, the formation of a proper amount of fine Ti ₂ Cu and other precipitated phases refines the α grains and provides moderate precipitation strengthening, and the strength is adjusted so as not to generate burrs and burrs during shear cutting. It was also clear.

At this time, if the major axis of the precipitation phase such as Ti ₂ Cu is an ultrafine size of less than 10 nm, it does not contribute to precipitation strengthening. It does not contribute to the refinement of the particle size, and none of them is useful for improving shear cutting performance. Therefore, the volume fraction of the precipitated phase such as Ti ₂ Cu having a major axis of 10 to 1000 nm needs to be a predetermined amount. It is more preferable to suppress the amount of precipitated phase such as Ti ₂ Cu outside the major axis range.

Further, if the volume fraction of the precipitated phase such as Ti ₂ Cu having a major axis of 10 to 1000 nm is less than 0.05%, the precipitation strengthening ability is not sufficient, and burrs and burrs are generated by shear cutting. On the other hand, if the volume fraction of the precipitated phase such as Ti ₂ Cu exceeds 3.5%, the precipitation strengthening ability becomes too high, and adiabatic shear deformation band is generated at the time of header processing, which makes it impossible to process. Therefore, the precipitation phase of Ti ₂ Cu or the like having a major axis of 10 to 1000 nm needs to be precipitated by 0.05 to 3.5% by volume fraction. Furthermore, in applications where high header workability and precise shear cutting properties are required, such as precision parts, the precipitated phase of Ti ₂ Cu having a major axis of 10 to 1000 nm has a volume fraction of 0.50 to 3. It is desirable that 0% is deposited.

The upper limit of the Cu addition amount is set to 1.8%. If the Cu content exceeds this limit, the Ti ₂ Cu phase is generated with a volume fraction exceeding 3.5%, so that the precipitation strengthening amount becomes too large. In addition, it causes adiabatic shear deformation in header processing, and at the same time, the precipitated particles become larger than 1000 nm and the pinning effect on the grain boundary is reduced, the α grains are coarsened, and the burr and burrs at the time of shear cutting increase. is there. Moreover, the minimum addition amount of Cu that can uniformly precipitate the precipitation phase such as Ti ₂ Cu in the alloy and uniformly bring about the pinning effect to the α grain boundary to refine the α particle size is 0.3%. Therefore, it is necessary to add 0.3% or more of Cu.

  Since O has an action of solid solution in the α phase and strengthening of the solid solution, if added excessively, adiabatic shear deformation band is generated during header processing. The α phase of pure titanium and light alloy titanium has high plastic deformability due to competition between slip deformation and twin deformation, but if O content exceeds 0.18%, twin deformation is suppressed and it is the minimum for header processing. Since the required cold workability is impaired, the upper limit of the O amount is set to 0.18%. At this time, if precise header workability is required, it is desirable that the upper limit of the O amount be 0.13%.

Fe is a β-stabilizing element and expresses a β-phase from room temperature to a high temperature range. If the Fe content is 0.30% or less, β phase generation is slight, but if added over this, the amount of β phase increases, and Cu that tends to concentrate in the β phase concentrates in the β phase. To do. Thus, since the precipitated phase such as Ti ₂ Cu concentrates and precipitates in the β phase enriched with Cu, the precipitated phase is easily coarsened, and a uniform distribution state cannot be obtained. As a result, a region in which the pinning effect on the α grain boundary cannot be exhibited locally occurs, and the α grain becomes coarse in that portion, and shear cutting performance is deteriorated. Therefore, the Fe content needs to be 0.30% or less.

  The invention described in (2) above (hereinafter abbreviated as the present invention (2)) particularly relates to a method of manufacturing a bar wire used for screws such as bolts and nuts. That is, the present invention (2) is a method for producing a bar wire having a titanium alloy component according to the present invention (1), which is manufactured through a process such as surface treatment such as melting, hot rolling, and peeling. It is the manufacturing method of the titanium alloy bar wire excellent in shear cutting property and cold forgeability of this invention (1) characterized by performing in the temperature range of 480-750 degreeC.

This is a condition aimed at obtaining an appropriate amount of a fine precipitated phase mainly composed of Ti ₂ Cu in order to ensure workability in the shear cutting and header processing steps.

That is, 480 to 750 ° C. is a temperature range in which a precipitated phase such as Ti ₂ Cu is a fine size having a major axis of about 10 to 1000 nm and is easily precipitated uniformly with a volume fraction of 0.05 to 3.5%. By annealing in this temperature range, the cold workability of the bar wire can be improved.

The temperature Tp (° C.) at which Ti ₂ Cu precipitation occurs depends on the amount of Cu, and can be approximately expressed by the following Ti ₂ Cu precipitation curve equation from the Ti—Cu equilibrium diagram.
Tp (° C.) = 730 [% Cu] ^0.126
Here, [% Cu] is the mass% of Cu.

  Therefore, the final annealing temperature is preferably in the range of 480 to 750 ° C. and lower than Tp.

If the final annealing temperature is less than 480 ° C., the annealing time required to obtain a precipitation amount sufficient to exert the effect of the precipitation phase such as Ti ₂ Cu is long, which is not suitable for industrial production. On the other hand, if the final annealing temperature exceeds 750 ° C., excessive coarsening of the precipitated phase such as Ti ₂ Cu occurs within a short time, and the size of the precipitated phase such as Ti ₂ Cu is optimal for industrial production. It becomes impossible to control.

  The optimum annealing time varies depending on the temperature within the range of 480 to 750 ° C., but is preferably about 30 minutes to 16 hours. The lower the temperature within this temperature range, the longer the optimum annealing time.

  The invention according to claim 3 (hereinafter abbreviated as the present invention (3)) further comprises the present invention (1) characterized in that after the final annealing, cold drawing with a surface reduction rate of 15% or less is further performed. It is a manufacturing method. By performing cold drawing with a surface reduction rate of 15% or less, moderate work hardening occurs in the entire length of the rod and wire, and the homogeneity of cold workability such as cold forgeability and shear cutting ability is improved. Therefore, when emphasizing quality stabilization over the entire length of the wire product, it is preferable to perform cold drawing with a surface reduction rate of 15% or less. However, if cold drawing exceeding a surface reduction rate of 15% is performed, the work hardening becomes too large, and there is no problem in practice at the time of header processing, but a wrinkled pattern may be induced. Therefore, the cold wire drawing is performed at a surface reduction rate of 15% or less.

<Example 1>
A titanium material having the composition shown in Table 1 was melted by a vacuum arc melting method, this was hot-forged into a billet, heated to 860 ° C., and then hot-rolled to a wire having a diameter of 13 mm.

  After stripping and pickling the hot-rolled wire to remove the oxide scale, the wire was made into a wire having a diameter of 10 mm by cold drawing, and then subjected to vacuum annealing at 680 ° C. for 5 hours as a final heat treatment. gave.

  Test Nos. 4, 5 and 6 were coated with a lubricant after the final heat treatment and lightly drawn at a surface area reduction ratio of 14.8, 12.0 and 10.0%, respectively. About 2 m of the end portion was not lightly drawn but left as the final heat treatment, and added to the test material as test numbers 51, 52 and 53, respectively. On the other hand, in the test numbers 1 to 3 and 7 to 20, after the final heat treatment, after applying the lubricant, the wire was lightly drawn at an area reduction rate of 8.5 to 13.5% and used as a test material.

These test materials were subjected to shear cutting and header processing to evaluate workability. In the shear cutting test, the cut height is measured after cutting with a shear cutting machine with a clearance of 0.1 mm. In the header processing test, a hemispherical head with a diameter of 15 mm is used at the end of the test piece by the header processing machine. Was subjected to cold forming, and the presence or absence of cracking by visual inspection was evaluated. Furthermore, a tensile test piece was collected from the sample after annealing, and the tensile characteristics were also examined. In addition, a specimen for metallographic observation was collected, the longitudinal section was etched with a 2% aqueous hydrofluoric acid solution, a scanning electron microscope (FE-SEM) equipped with an electrolysis electron gun with an energy dispersive X-ray analyzer. ) Was used to observe the precipitation phase of Ti ₂ Cu and the like, and the volume fraction of the precipitation phase having a major axis of 10 to 1000 nm was examined within the observation cross section. That is, observation was performed at a magnification of 3000 times to 100,000 times in accordance with the size of the precipitated phase, and the precipitated phase occupying a region where the Cu concentration was uniformly high was recognized as a precipitated phase such as Ti ₂ Cu. Then, the area occupancy was measured, and this value was directly used as the volume fraction of the precipitated phase such as Ti ₂ Cu. As will be described later, most of the precipitated phases having a major axis of 10 to 1000 nm are confirmed to be Ti ₂ Cu, and these precipitated phases have a substantially isotropic shape, and anisotropy is not recognized in the distribution state. This is because.

In addition, although the FE-SEM observation cannot accurately measure the Cu concentration of the deposited phase of less than 1 μm exposed on the surface, it can be confirmed semi-quantitatively that the atomic ratio of Ti: Cu is approximately 2: 1, or the mother It can be confirmed that Cu is contained in a higher concentration than the phase. Here, the precipitated phase in which the higher concentration of Cu is detected than the parent phase is regarded as Ti ₂ Cu and inevitable precipitated phase. The reason is that, as a result of conducting observation, analysis, and electron diffraction by a transmission electron microscope equipped with an energy dispersive X-ray analyzer using a thin film sample, the samples of test numbers 4 to 20 and 51 to 53 were obtained. This is because 48 of the 50 precipitated phases within the range of 1000 nm were identified as Ti ₂ Cu. The remaining two were β phases having a Cu concentration relatively closer to the parent phase than Ti ₂ Cu.

  The main chemical components, room temperature tensile test results, precipitation phase fraction, shear cutting ability, and header workability of each specimen were evaluated. Here, in the shear cutting property test, the test piece was evaluated for the height of burrs in the cut surface after shear cutting, and the height was less than 0.05 mm as a pass, and the height was 0.05 mm or more. When it was less than 0.1 mm, a triangle mark was given, and a cross mark of more than 0.1 mm. Furthermore, in the header workability test, the head part after header processing was visually observed, and a circle was marked when no crack was observed, and an x was marked when crack was observed. These evaluation results are shown together in Table 1.

In Table 1, Test No. 1 is JIS type 2 pure titanium, and Test No. 2 is an example of an alloy to which about 1 to 2% of Al is added. Both test numbers 1 and 2 were cracked by header processing and could not be processed into bolts. This is due to the generation of adiabatic shear deformation band due to material anisotropy in the former, and to the cold workability degradation due to the suppression of twin deformation in the latter. In these materials, the formation of precipitated phases such as Ti ₂ Cu is not observed.

In contrast, test numbers 4, 5, 6, 8, 9, 11, 12, 13, 14, 16, 17 which are examples of the present invention (1) manufactured by the method described in the present invention (2). , 18, 19 and 20 showed strength levels corresponding to JIS class 2, and all showed high total elongation. No cracks could be visually confirmed during header processing, and the workability was good. At the same time, even with shear cutting, burrs and burrs with a height exceeding 0.05 mm do not occur on the cut surface, it has good cutting properties, and it is reproducible in tests conducted multiple times for each test number. A good cut surface shape was obtained, and the quality was stable. In addition, all of these contain a precipitation phase such as Ti ₂ Cu having a major axis of 10 to 1000 nm in a volume fraction of 0.05 to 3.5%, and it is clear that the amount of precipitation is in an appropriate range. .

On the other hand, in Test Nos. 3 and 10, burrs exceeding 0.1 mm were generated at the time of shear cutting, and cutting performance was insufficient. Among these, in test number 3, the amount of Cu added is below the lower limit of 0.3% of the present invention, and the amount of precipitated phases such as Ti ₂ Cu produced is also less than 0.05%. In this material, a precipitation phase sufficient to suppress grain growth during annealing could not be obtained, and thus partially coarsened, resulting in uneven deformation during cutting, resulting in burrs. On the other hand, in Test No. 10, coarse precipitate phases such as coarse Ti ₂ Cu exceeding 1000 nm were generated in part. This is because the content of Fe, which is a β-stabilizing element, was added in excess of 0.30% which is the upper limit of the present invention, so the amount of β-phase increased, and Cu was concentrated and concentrated there. Precipitated phases are formed, and these cannot suppress grain growth, so that burrs are generated locally.

In Test Nos. 7 and 15, cracks occurred during header processing, and sufficient workability was not obtained. The reason for this is that in Test No. 7, since the Cu addition amount exceeded 1.8% which is the upper limit of the present invention, the precipitated phase of Ti ₂ Cu and the like exceeded 3.5% in volume fraction. This is because a large amount precipitated and the cold ductility was impaired. In Test No. 15, since the oxygen content was added exceeding 0.18% which is the upper limit of the present invention, twin deformation was suppressed, and cold workability required for header workability was not obtained. It is.

  In the materials of test numbers 14, 18, and 20 according to the present invention, a wrinkle-like surface pattern of 0.05 mm or less occurred during header processing. This is a surface defect that does not cause a problem in practice and is generally acceptable. However, in applications that require precision machining, it is desirable that such a surface pattern does not occur. This is because these materials have a relatively high O content of 0.15 to 0.16%, and twin deformation is slightly less likely to occur than those with a lower O content. Therefore, depending on the application, it is desirable to set the upper limit of O amount to 0.13%.

As described above, a titanium alloy bar wire having an element content defined in the present invention and a volume fraction of a precipitated phase such as Ti ₂ Cu having a major axis of 10 to 1000 nm is excellent in shear workability and cold forgeability. However, if the amount of alloying elements specified in the present invention and the volume fraction of the precipitated phase such as Ti ₂ Cu are deviated, both cold workability and strength are obtained. I can't be satisfied.

  Test Nos. 51 to 53 were not drawn lightly after vacuum annealing, but both shear cutting performance and header workability were good results. However, in the shear cutting performance test conducted several times for each test piece number, 0.01 to 0.04 mm height burrs and burrs appeared on the cut surface, and the sizes thereof showed variations. On the other hand, test Nos. 4 to 6 with 10% light wire drawing have the same chemical components as test pieces Nos. 51 to 53, but burrs and burrs appearing on the cut surface are 0.03 mm or less in height. There was little variation and quality stability was high.

<Example 2>
Using a hot rolled wire with a diameter of 13 mm, which is an intermediate product when producing materials of test numbers 6, 11, and 18 in Table 1, stripping and pickling to remove the oxide scale, followed by cold drawing A wire with a diameter of 10 mm was used. Then, after vacuum annealing under the conditions shown in Tables 2 to 4, after applying a lubricant, light drawing was performed at a surface reduction rate of 10%. This wire was subjected to shear cutting and header processing to evaluate workability. In particular, in the shear cutting ability test, the height of the burrs was scrutinized. Further, a tensile test piece was collected from the sample after annealing, and the tensile characteristics were examined. The metal structure observation test piece was etched with a 2% aqueous hydrofluoric acid solution and used in the method described in Example 1 using FE-SEM. A precipitated phase such as Ti ₂ Cu having a major axis of 10 to 1000 nm was observed, and the volume fraction was measured. These evaluation results are also shown in Tables 2 to 4.

Tables 2, 3, and 4 show the results of the wire materials having the compositions shown in Test No. 6, Test No. 11, and Test No. 18, respectively. It can be seen that both have high ductility, and there is no practical problem with shear cutting performance and header workability. In particular, test numbers 22, 23, 24, 27, 28, 29, 30, 32, 33, and 34, in which the final annealing was performed in the temperature range of 500 to 730 ° C., were not good because the burrs in shear cutting could not be visually confirmed. Showed good cutting properties. On the other hand, test numbers 21, 25, 26, 31, and 35 all had high ductility and header workability. However, test numbers 21, 26, and 31 had a thin wrinkle pattern that had no practical problems during header processing. In the test numbers 25 and 35, burrs having a height of less than 0.05 mm that were not problematic in practice occurred. This is because in the test numbers 21, 26, and 31 where the annealing temperature is less than 500 ° C., the strength slightly increases due to the formation of a precipitated phase such as Ti ₂ Cu. On the other hand, in the test numbers 25 and 35 where the annealing temperature exceeds 730 ° C., a part of the precipitated phase such as Ti ₂ Cu is re-dissolved to reduce the amount of precipitated phase, and partly the grain size becomes coarse This is because the grain boundary pinning effect is slightly reduced. These results show that when a level that does not cause a practical problem in header workability and shear cutting performance is required, an annealing temperature of 480 to 750 ° C. is suitable. In parts that require high header workability and precise shear cutability at the same time, by performing annealing at 500 to 730 ° C. It is clear that it is more preferable to disperse the precipitated phase such as Ti ₂ Cu uniformly and finely.

<Example 3>
Using a hot rolled wire with a diameter of 13 mm, which is an intermediate product when producing the materials of test numbers 5, 6, and 13 in Table 1, stripping and pickling to remove the oxide scale, and then cold drawing A wire with a diameter of 10 mm was used. It was subjected to furnace-cooled vacuum annealing at 650 ° C. for 4 hours, and after applying a lubricant, it was drawn at a surface reduction ratio shown in Tables 5-7. This wire was subjected to shear cutting and header processing to evaluate workability. In particular, in the shear cutting property test, the height of the burrs was examined. Further, a tensile test piece was collected from the sample after annealing, and the tensile characteristics were examined. The metal structure observation test piece was etched with a 2% aqueous hydrofluoric acid solution and used in the method described in Example 1 using FE-SEM. A precipitated phase such as Ti ₂ Cu having a major axis of 10 to 1000 nm was observed, and the volume fraction was measured. These evaluation results are also shown in Tables 5 to 7.

  Tables 5, 6, and 7 show the results of the wire materials having the compositions shown in Test No. 5, Test No. 6, and Test No. 13, respectively. It can be seen that both have high ductility, and there is no practical problem with shear cutting performance and header workability. In particular, the testability of test numbers 36, 37, 38, 41, 42, 43, 45, 46, and 47, in which the final wire drawing was performed at a surface reduction rate of 15% or less, both had extremely good header workability and shear cutting performance. It was. On the other hand, all of test numbers 39, 40, 44, and 48 had high ductility and header workability, but a thin wrinkle pattern having a level of no practical problem was generated after header processing. This is because the wire drawing area reduction ratio exceeds 15%, and the strength slightly increases and the ductility slightly decreases due to cold working. These results are at a level that is practically acceptable, but for parts that require both high header workability and precise shear cutting ability, the cold drawing of the final product is reduced by 15% or less. It is clear that it is more preferable to appropriately manage the work hardening amount by carrying out at a rate.

  The titanium alloy bar wire of the present invention is suitable for parts subjected to cold forging, including screw parts such as bolts and nuts in applications that require corrosion resistance and cold workability such as header processing and shearing. , Especially can be utilized.

Claims (4)

It consists of 0.3 to 1.8% Cu, 0.18% or less O, 0.30% or less Fe, the balance Ti and unavoidable impurity elements, and a major axis of 10 to 1000 nm of Ti ₂ Cu and unavoidable. A titanium alloy bar wire for a machine part or a decorative part having excellent shear cutting ability and cold forgeability, characterized by containing a precipitating phase in a volume fraction of 0.05 to 3.5%.   In the manufacture of the titanium alloy bar wire according to claim 1, the final annealing is performed in a temperature range of 480 to 750 ° C, and for mechanical parts or decorative parts having excellent shear cutting ability and cold forgeability. Manufacturing method of titanium alloy bar wire.   Further, after the final annealing, cold drawing with a surface reduction rate of 15% or less is performed. Titanium for machine parts or decorative parts having excellent shear cutting ability and cold forgeability according to claim 2 Manufacturing method of alloy bar wire.   A method for producing a titanium product, wherein the titanium alloy bar wire according to claim 1 is subjected to shear cutting and then header processing.