TW201414856A - Titanium sheet - Google Patents

Abstract

A titanium sheet with its thickness below 0.2 mm is disclosed, whose main body contains Fe below 0.1 mass% and O (oxygen) below 0.1 mass%; it satisfies the sheet thickness (mm)/particle diameter (mm) >=3 and the particle diameter >=2.5 <mu>m; and its surface contains a cured layer; the depth from the surface of the region of the aforementioned cured layer is above 200 nm and below 2 <mu>m. A titanium sheet is endowed with the excellent processability and high surface hardness, for example, capable of being properly used in various applications particularly an acoustic member (a speaker vibration plate, etc.).

Description

Titanium sheet Field of invention

The present invention relates to a titanium thin plate, and more particularly to a high-strength titanium thin plate having excellent workability and high surface hardness, and which is excellent in workability even in a speaker diaphragm or the like. The present application claims priority based on Japanese Patent Application No. 2012-179861, filed on Jan.

Background of the invention

Titanium materials are used in chemical factories, construction, and many other industrial materials, as well as materials for consumer products such as camera bodies, clocks, sporting goods, etc., because of their high specific strength and excellent corrosion resistance. use. A thin plate having a thickness of 0.2 mm or less, such as a foil, is used for an acoustic member (a speaker diaphragm, etc.) and an anti-corrosion film. Sheets and the like are used for their characteristics.

In general, metallic materials have a tendency to be required to have high strength, and are also required to be processable. Titanium materials are no exception, not only processability, but also require high strength. However, since the workability is generally lowered when the strength is increased, it has been conventionally attempted to optimize the balance between strength and workability by controlling the amount of oxygen, the amount of iron, the crystal grain size, and the like in the titanium material.

For example, Patent Document 1 discloses a titanium plate which is suppressed by setting the O (oxygen) content in the titanium material to a predetermined value while increasing the Fe content (Fe: 0.1 to 0.6 mass%). When the ductility of the titanium plate is lowered, the strength is increased, and the average particle diameter is 10 μm or less to improve the formability.

Patent Document 2 discloses a Ti plate material having excellent moldability, and the Ti plate material has an Fe content of 300 ppm or more and a [Fe+O+N+H] amount of 1500 ppm or less, and also limits nitrogen in addition to iron amount and oxygen amount. Quantity and amount of hydrogen.

Further, Patent Document 3 discloses a method for producing a pure titanium plate by setting the amount of iron, the amount of oxygen, and further the nickel and chromium gauges to a predetermined range, and setting the average particle diameter to 20 to 80 μm so that even if purity is used. When the low-cost raw materials are low, the formability can be maintained.

However, any of the techniques described in the above-mentioned patent documents is a technique in which a widely used titanium material having a plate thickness of 0.3 to 1 mm is used.

On the other hand, a thin plate and a foil having a plate thickness of 0.2 mm or less used in a diaphragm of a speaker or the like are thinner than a widely used material and have poor workability. Therefore, even if the techniques described in the above Patent Documents 1 to 3 are applied, there is a problem that processing defects occur.

In the case of the workability of the titanium thin plate having a plate thickness of 0.2 mm or less, Patent Document 4 discloses a method for producing a titanium foil excellent in moldability. When this technique is used, the 25 μm-thick titanium foil can be controlled by rolling under predetermined rolling conditions and the crystal grain size is controlled to be 14 to 14 in terms of ASTM No., thereby ensuring a good Allison value ( Erichsen value).

However, a titanium foil having a thickness of 0.2 mm or less is required to have good shape retention after molding. In general, it is possible to ensure good shape retention by increasing the strength of the material, and on the other hand, there is a problem that good workability cannot be obtained. Further, although the portion subjected to the major processing is subjected to work hardening to obtain strength, good shape retainability can be obtained, but the shape retainability is deteriorated in the portion where the work rate is low.

For example, Patent Document 5 discloses a technique in which a layer containing a carbide and/or a nitride containing titanium is formed as an inner surface layer by glow annealing or vacuum annealing, followed by electrolytic pickling. This technique prevents the titanium base material from adhering to the mold by preventing the soft titanium base material from coming into contact with the mold, and forming the titanium surface with an oxide layer excellent in lubricity at the time of pressurization. When this technique is used, it is possible to prevent the carbide and/or nitride of titanium from coming into contact with the mold and preventing the mold from being worn.

However, the titanium foil having a thickness of 0.2 mm or less is less severely processed as disclosed in Patent Document 5. For example, the processing of a vibrating plate or the like of a speaker is usually formed into a dome shape by applying an internal pressure, and the contact with the mold during processing is less than the molding using a normal thin plate press, and the surface lubricity of the material itself is not Too much a problem. Therefore, even if the technique described in Patent Document 5 is applied, the workability improving effect cannot be exhibited by the lubricating effect of the oxide. Moreover, since the technique is carried out by electrolytic pickling, and the technique is applied to a titanium foil of 0.2 mm or less, the yield drop is not negligible. Not only that, but also the uneven thickness of the board, which makes it impossible to ship as a product.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent No. 4605514

Patent Document 2: Japanese Patent Laid-Open Publication No. 63-103043

Patent Document 3: Japanese Patent No. 3228134

Patent Document 4: Japanese Patent No. 2616181

Patent Document 5: Japanese Patent Laid-Open Publication No. 2009-97060

Summary of invention

The present invention has been made in view of such circumstances, and an object thereof is to provide a titanium thin plate having a titanium plate having a thickness of 0.2 mm or less, which is excellent in shape retainability and workability.

In order to solve the problem, the inventors of the present invention have focused on the surface hardness of the titanium foil, and in consideration of the fact that the surface is hard and the internal phase is softer than the surface, the shape retainability and the workability can be coherent, and the titanium thin plate can be used for the purpose. The method of improving the workability and surface hardness is discussed.

As an effective means for improving the workability of the titanium thin plate, first, it is considered to reduce elements such as iron and oxygen. These elements are elements which are inevitably brought into the manufacture, and are also described in Patent Documents 1 to 3 disclosed above, and must be limited to a predetermined amount or less.

Secondly, it is considered that the crystal grains are coarsened. By coarsening, it is possible to easily produce twin crystal deformation which is important for the workability of the titanium material, and it is possible to improve workability. Because the crystal grain size is the final finishing annealing step Since it is controlled, it can be easily controlled by changing annealing conditions.

Therefore, a tensile test was performed using a titanium thin plate having a plate thickness of 0.2 mm or less to investigate the elongation. As a result, even if the thickness of the sheet is 0.2 mm or less, as in the conventional knowledge, the crystal grains are made fine, and the elongation is lowered. However, when the titanium thin plate having a plate thickness of 0.2 mm or less is clearly understood, the crystal grains may be excessively coarsened and the elongation may be lowered. Moreover, whether or not this phenomenon occurs depends on the ratio of the thickness of the sheet to the particle diameter, and it is clearly understood that the thickness/particle diameter of the sheet is <3. Further, in the case of a thin plate having a thickness of about 0.3 to 1 mm, since the particle diameter is approximately in the range of 10 to 60 μm, the phenomenon in which the elongation due to coarsening of crystal grains is lowered does not occur.

As a result of the investigation, the crystal grain size is coarsened in the range of the plate thickness/particle diameter ≧3 in accordance with the thickness of the product sheet, and the workability of the titanium thin plate having a plate thickness of 0.2 mm or less can be maximized.

In the course of further investigation, many cracks occurred during press working. When investigating the cause, it is clear that the amount of carbon and the amount of nitrogen in the vicinity of the material surface are higher in the portion where the crack occurs. Usually, when a sheet having a thickness of 0.2 mm or less is produced, after cold rolling, it is softened to impart formability. Processability glow annealing (BA = Bright Annealing). However, if the cleaning line before annealing is insufficient in oil removal, a large amount of rolling oil remains on the surface of the material, so that the amount of carbon intrusion in the vicinity of the surface of the material increases. When the nitrogen gas remaining in the annealing furnace is replaced with a nitrogen gas, if the substitution is insufficient, a large amount of nitrogen remains, which causes a large amount of nitrogen to enter.

The invaded carbon and nitrogen form TiC and TiN, and the surface hardness is increased because of the solid solution strengthening, even if the thickness is 0.2 mm or less. The shape of the titanium sheet is also improved in shape retention. However, when the intrusion is too deep, the elongation of the material is remarkably lowered. In order to coexist the above characteristics (that is, the increase in surface hardness and the decrease in elongation inhibition), it is necessary to set the penetration depth of carbon, nitrogen, and oxygen to be in the range of 200 nm to 2 μm from the surface. That is, the region of the hardened layer formed by the intrusion of carbon, nitrogen, and oxygen must be in the range of 200 nm to 2 μm from the surface.

The present invention has been made based on the knowledge of the above-described studies and has a high-strength titanium thin plate having excellent workability described below.

That is, a titanium thin plate having a thickness of 0.2 mm or less; a main body having Fe of 0.1 mass% or less and an O (oxygen) of 0.1 mass% or less; which satisfies the plate thickness (mm) / particle diameter (mm) ≧ 3 and having a particle diameter of μ2.5 μm; and having a hardened layer on the surface, and the region of the hardened layer has a depth from the surface of 200 nm or more and 2 μm or less.

The titanium thin plate of the present invention can ensure stable processability by performing finish annealing (glow annealing) at 500 ° C or higher and 850 ° C or lower by BAF (batch heat treatment) or continuous annealing after cold rolling. It is better.

The term "titanium sheet" as used herein refers to a sheet or foil having a pure titanium for industrial use specified in JISH 4600 and having a sheet thickness of 0.2 mm or less.

The above-mentioned "particle diameter" means the average particle diameter obtained by the quadrature method defined by JISH0501. It is also emphasized that it is described as "average particle size".

In addition, the term "hardened layer" refers to oxygen and nitrogen formed by carbon and nitrogen, oxygen, and nitrogen and oxygen contained in a gas atmosphere of an annealing furnace, which are derived from the surface of the rolling oil remaining on the surface during annealing. , a concentrated layer of carbon.

The titanium thin plate of the present invention has a thickness of 0.2 mm or less and a titanium thin plate which is excellent in workability and high surface hardness, and is suitable for use in various types including acoustic members (speaker vibrating plates, etc.). Titanium sheet (foil) for the purpose of use.

Fig. 1 is a graph showing the relationship between crystal grain size and elongation in a tensile test of a titanium thin plate.

Fig. 2 is a graph showing the relationship between stress and strain in a tensile test of a titanium thin plate (foil) having a thickness of 25 μm.

Fig. 3 is a graph showing the relationship between the sheet thickness/particle diameter and the elongation in the tensile test of the titanium sheet.

Fig. 4 is a view showing the relationship between the thickness of the hardened layer of the titanium thin plate and the surface hardness.

Fig. 5 is a graph showing the relationship between the thickness of the hardened layer and the elongation of the titanium thin plate having a thickness of 100 μm and a sheet thickness/particle diameter of ≧3.

Form for implementing the invention

The titanium thin plate of the present invention is a titanium thin plate having a thickness of 0.2 mm or less as described above, and the main body has Fe of 0.1 mass% or less and O (oxygen) of 0.1 mass% or less; and the sheet thickness (mm)/particle diameter is satisfied. (mm) ≧3 and a particle diameter of μ2.5 μm; and having a hardened layer on the surface, and the region of the hardened layer has a depth from the surface of 200 nm or more and 2 μm or less.

In the present invention, a titanium thin plate having a plate thickness of 0.2 mm or less is used as The object is to provide a high-strength titanium thin plate which is excellent in workability, such as a speaker diaphragm or the like.

In the titanium thin plate of the present invention, the Fe of the predetermined main body is 0.1 mass% or less for the following reasons. That is, Fe is an element which stabilizes the β phase, and when the β phase exists, the growth of the crystal grain during annealing is hindered by the β phase. Since the content is more remarkable when the content is more than 0.1 mass%, the content of Fe is set to 0.1 mass% or less. The lower limit is not particularly limited. However, since industrially, the incorporation of Fe is unavoidable and contains 0.01 mass% or more. Therefore, the preferred lower limit is made 0.01 yen%.

Further, the O (oxygen) of the main body is set to be 0.1 mass% or less in order to suppress the decrease in workability. Although the titanium thin plate is increased in strength by the addition of O, the workability is lowered, and the tendency becomes remarkable when the content is more than 0.1 mass%. Therefore, the content of O is set to be 0.1 mass% or less. The lower limit is not particularly limited, and since O is similar to Fe, it is unavoidable in industrial production, and therefore the preferred lower limit is made 0.01 yen%.

Moreover, the term "main body" means the inside of the hardened layer formed on the surface of the titanium thin plate. In the present invention, the Fe concentration in the main body is 0.1 mass% or less, and the O concentration is 0.1 mass% or less.

In the titanium thin plate of the present invention, it is necessary to satisfy the particle diameter ≧2.5 μm because, as shown in Fig. 1, when the particle diameter is less than 2.5 μm, the elongation is drastically lowered and the workability is lowered.

Fig. 1 is a graph showing the relationship between crystal grain size and elongation in a tensile test of a titanium thin plate. As shown in the figure, when the crystal grain size is less than 2.5 μm, even if there is no non-recrystallized grain, the elongation is large because of excessively high strength. The amplitude is low.

In the titanium thin plate of the present invention, it is necessary to satisfy the plate thickness (mm) / particle diameter (mm) ≧ 3 (hereinafter, "plate thickness (mm) / particle diameter (mm)" is also described only as "plate thickness / grain" The path is based on the following reasons.

Fig. 2 is a graph showing the relationship between stress and strain in a tensile test of a titanium thin plate (foil) having a thickness of 25 μm. In the same figure, "particle diameter: 5.3 μm" and "particle diameter: 12.3 μm" are measurement results for test pieces each having an average particle diameter of 5.3 μm and 12.3 μm.

As shown in Fig. 2, after any of the test pieces was uniformly elongated, local deformation was started and fracture was reached. The amount of local deformation is small, and the amount of uniform deformation is an index of the workability of the uniform elongation system, and the low system indicates that the workability is low.

In the deformation of the polycrystalline material, when one crystal grain is deformed, the deformation of the crystal grains around it is moderated. However, in the case where the number of crystal grains in the thickness direction of the sheet is small, the contribution of one crystal grain to the deformation becomes large, and since the deformation is performed by the specific crystal grain, the local deformation system starts early. Figure 2 shows this state.

Therefore, the upper limit of the average crystal grain size range in which workability can be improved by coarse granulation is determined by the ratio of the number of crystal grains present in the thickness direction of the sheet, that is, the sheet thickness/particle diameter.

Fig. 3 is a graph showing the relationship between the sheet thickness/particle diameter and the elongation in the tensile test of the titanium sheet. As shown in Fig. 3, from either of the plate thicknesses of 25 μm to 150 μm, the elongation was significantly lowered near the plate thickness/particle diameter = 3, and it was found that the plate thickness (mm) / particle diameter (mm) must be satisfied. ≧ 3.

Further, in the titanium thin plate of the present invention, a region having a depth of 200 nm or more and 2 μm or less is required to have a hardened layer. In other words, it is necessary to have a hardened layer having a thickness of 200 nm to 2 μm in the vicinity of the surface.

The hardened layer is a concentrated layer of oxygen, nitrogen, and carbon formed by carbon and nitrogen, oxygen derived from the rolling oil remaining on the surface during annealing, and nitrogen and oxygen contained in the gas atmosphere of the annealing furnace. It contains a region of 0.5 mass% or more of oxygen, a region containing 0.5 mass% or more of nitrogen, a region containing 0.5 mass% or more of carbon, or a region containing 0.5 mass% or more of oxygen, nitrogen, and carbon. Further, the thickness of the hardened layer can be measured using a GDS (Glow Discharge Luminescence Analyzer).

Fig. 4 is a view showing the relationship between the thickness of the hardened layer of the titanium thin plate and the surface hardness. As shown in Fig. 4, the thicker the hardened layer, the higher the surface hardness becomes. When the thickness of the hardened layer is thinner than 200 nm, it is the same as the hardness of the material measured in the cross section of the material (shown in Fig. 4), and hardness increase cannot be observed. Further, when the surface hardness is insufficiently increased, the shape retention property is poor. Therefore, the thickness of the hardened layer is set to 200 nm or more.

Fig. 5 is a graph showing the relationship between the thickness of the hardened layer and the elongation of the titanium thin plate having a thickness of 100 μm and a sheet thickness/particle diameter of ≧3. As shown in Fig. 5, even if the thickness of the hardened layer is too thick even if the thickness of the hardened layer is ≧3, the elongation is low and the workability is lowered. Therefore, the thickness of the hardened layer is set to be 2000 nm (2 μm) or less.

The titanium thin plate of the present invention is preferably subjected to finishing annealing at 500 ° C or higher and 850 ° C or lower by BAF or continuous annealing after cold rolling to ensure stable workability.

When the annealing temperature is low, the recrystallized grains remain and the workability is low. Since the recrystallization temperature of the titanium thin plate of the present invention is 500 ° C, the finish annealing is performed at 500 ° C or higher. Moreover, in order to provide an equiaxed structure in which the balance of excellent strength and ductility (elongation) is easily obtained, it is set to 850 ° C or less. Although the operation can be performed in accordance with the purpose of the annealing treatment in the usual operation, the workability can be stably ensured by performing the finish annealing under the above-described preferable temperature conditions.

The thickness of the hardened layer can be changed, for example, by the washing step which is usually performed after cold rolling, and the residual nitrogen and oxygen amount of the bright annealing furnace are changed to have a target thickness.

[Examples]

The following tests were carried out in order to secure the effects of the present invention.

First, a cold-rolled sheet having a thickness of 25 μm to 150 μm was produced by cold rolling and intermediate annealing for one type of pure titanium (thickness: 0.5 mm) prescribed in JISH4600. Next, finishing annealing was performed by changing the conditions in the Ar environment (dew point ≦ -40 ° C) to change the crystal grain size. Moreover, any of oxygen, nitrogen, and carbon is concentrated on the surface of the plate by the rolling oil remaining on the surface of the plate or the atmosphere of the annealing furnace to form a hardened layer. The thickness (depth) of the hardened layer is adjusted by changing the residual amount of the rolling oil and the amount of nitrogen and oxygen in the environment during the annealing.

Each of the cold-rolled sheets (each test piece) subjected to the finishing annealing was processed into a test piece having a parallel portion width of 6.25 mm and a parallel portion length of 50 mm, and then subjected to a tensile test. Further, the thickness of the plate, the crystal grain size, the surface hardness, and the thickness of the hardened layer were measured for each test piece. Will be used in each test piece used in the examples. The measurement results of the Fe concentration (main body mass%) and the O concentration (main body mass%) are collectively shown in Table 1.

The tensile test was set to 0.5%/min in the direction parallel to the rolling direction (L direction), and the strain rate was set to 0.2% yield strength, and then set to 20%/min until the break and at room temperature. get on.

The crystal grain size is obtained by performing square approximation using an integration method for a region of 40,000 μm ² or more on the surface of the sample.

The surface hardness was measured by using a Vickers hardness tester, and the Vickers indenter was pressed into the surface of the sample at a load of 0.245 N (25 gf) and evaluated at an average value of 10 points.

The thickness of the hardened layer is analyzed by using the GDS in the region of 4 mm in diameter on the surface of the sample, and the depth direction of oxygen, nitrogen, carbon, titanium, and iron is analyzed by an Ar ion sputter, and is set to be among oxygen, nitrogen, and carbon. The concentration of either of them or the total concentration of these is 0.5 mass% or more. In the case of quantification, each of the measured values is carried out as follows. Zinc oxide (containing 19.8 mass% of oxygen) is used for the oxygen system, and Worthite iron-based stainless steel (containing 0.3 mass% of nitrogen) is used for the nitrogen system. The titanium alloy (containing 0.12 mass% carbon) was used for the correction, and the depth direction analysis of each element was performed by corresponding to the measurement site (depth) of pure titanium (JIS type 1).

In Table 1, since the characteristic values of the titanium materials vary depending on the thickness of the sheet and the contents of Fe and O (main body concentration), the respective ones are compared under substantially the same conditions. Moreover, even if the plate thickness and the content of Fe and O are the same, since it is influenced by the particle diameter, it is carried out in consideration of the particle diameter. Further, the shape retainability is evaluated by the fact that the shape is deformed due to the deformation of the portion having a small amount of processing, and can be evaluated by the magnitude of the 0.2% proof stress of the respective plate pressures.

In Comparative Example 1 and Comparative Example 4, any of the unrecrystallized grains remained. The elongation is significantly lower.

In any of Comparative Examples 2, 3, 5, 6, 11, 12, 16, and 17 (sheet thickness/particle diameter) <3, the elongation was remarkably low. In particular, Comparative Example 17 has a lower elongation than Comparative Examples 18 to 23 of the present invention.

In any of Comparative Example 7 and Comparative Example 13, when the crystal grain size was too fine (less than 2.5 μm), the elongation was low.

The thickness of the hardened layer of Comparative Examples 8, 10, and 12 was lower than that of the thickness (200 nm or more and 2 μm or less) specified in the present invention. In particular, since the thickness/particle diameter of the comparative example 12 was less than 3 and the hardened layer was also thick, the elongation was lower than that of the inventive examples 11 to 17. Since Comparative Example 16 had a plate thickness/particle diameter of less than 3 and a hardened layer was also thick, the elongation was lower than that of Inventive Examples 18 to 23.

The thicknesses of the hardened layers of Comparative Examples 9, 14, and 15 were thin (less than 200 nm), the 0.2% proof stress was low, and the shape retention was poor. In particular, in Comparative Example 14, the yield strength was remarkably low as compared with Example 22 of the present invention having substantially the same particle diameter. Comparative Example 15 showed that the yield strength was remarkably lower than that of Inventive Example 23, in which the particle diameter was substantially the same.

When summarized in the same plate thickness, as below.

"About 25μm material"

Since Comparative Example 1 was not recrystallized, the elongation was low.

The thicknesses/particle diameters of the sheets of Comparative Examples 2 and 3 were less than 3, and the elongation, yield strength, and tensile strength were lower than those of Examples 1 to 5 of the present invention.

"About 50μm material"

Since Comparative Example 4 was not recrystallized, the elongation was low.

The thicknesses/particle diameters of the sheets of Comparative Examples 5 and 6 were less than 3, and the elongation, yield strength, and tensile strength were lower than those of Examples 6 to 10 of the present invention.

"About 100μm"

Comparative Example 7 was excessively finely granulated, resulting in a low elongation.

Although Comparative Example 8 satisfied the sheet thickness/particle diameter ≧3, the hardened layer was thick and the elongation was low.

In Comparative Example 9, the hardened layer was thin, and the yield strength was remarkably low as compared with Example 17 of the present invention having substantially the same particle diameter.

In Comparative Example 10, the hardened layer was thick, and the elongation was lower than in Examples 11 to 17 of the present invention.

In Comparative Example 11, the thickness/particle diameter of the base plate was less than 3, and the elongation was lower than that of Examples 11 to 17 of the present invention.

Since Comparative Example 12 had a plate thickness/particle diameter of less than 3 and a hardened layer was also thick, the elongation was lower than that of Examples 11 to 17 of the present invention.

"About 150μm"

Comparative Example 13 was excessively finely granulated, resulting in a low elongation.

In Comparative Example 14, the hardened layer was thin, and the yield strength was remarkably low as compared with Example 22 of the present invention having substantially the same particle diameter.

In Comparative Example 15, the hardened layer was thin, and the yield strength was remarkably low as compared with Example 23 of the present invention having substantially the same particle diameter.

Since Comparative Example 16 had a plate thickness/particle diameter of less than 3 and a hardened layer was also thick, the elongation was lower than that of Inventive Examples 18 to 23.

Comparative Example 17 had a plate thickness/particle diameter of less than 3, and the elongation was lower than that of Examples 18 to 23 of the present invention.

On the other hand, any of Examples 1 to 23 of the present invention satisfies the conditions specified in the present invention, and exhibits high elongation and surface hardness.

Industrial availability

The titanium thin plate of the present invention has excellent workability and high surface hardness, and can be used as a wide range of applications such as consumer lighting products such as speaker diaphragms and industrial materials.

Claims (2)

A titanium thin plate having a thickness of 0.2 mm or less; a main body having Fe of 0.1 mass% or less and an O (oxygen) of 0.1 mass% or less; which satisfies a plate thickness (mm) / a particle diameter (mm) ≧ 3 and a particle The diameter ≧ is 2.5 μm; and has a hardened layer on the surface, and the region of the hardened layer has a depth from the surface of 200 nm or more and 2 μm or less. The titanium sheet of claim 1 which, after cold rolling, is subjected to finishing annealing by BAF or continuous annealing at a temperature of 500 ° C or more and 850 ° C or less.