JPH093573A - Pure titanium for building materials, pure titanium plate and method for producing the same - Google Patents

Abstract

(57) [Summary] [Object] To provide a pure titanium for building materials which is inexpensive and has good moldability, a pure titanium plate for building materials having a glossy suppressed light ray reflection and a slight surface texture, and a manufacturing method thereof. [Constitution] The following pure titanium for building materials, a pure titanium plate for building materials and a manufacturing method thereof. In terms of weight ratio, the contents of Fe, Ni and Cr satisfy the following formulas (1), (2) and (3) (unit: ppm), oxygen (O) is 900 ppm or less, and the balance is Ti.
Pure titanium for building materials consisting of unavoidable impurities. 100 ≦ Fe ≦ 600 Formula (1) 100 ≦ Ni + Cr ≦ 700 Formula (2) Fe + Ni + Cr ≦ 1000 For building materials having the same chemical composition as Formula (3) and having an average crystal grain size of 70 μm or less after cold rolling and annealing. Pure titanium plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pure titanium for building materials such as roofing materials and outer wall materials, a pure titanium plate and a method for producing the same, and in particular, it is possible to use an inexpensive titanium raw material and has excellent workability. TECHNICAL FIELD The present invention relates to pure titanium for use, a pure titanium plate for building materials which has a low light reflection and a suppressed surface gloss, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Titanium is used for various purposes because it is lightweight and extremely excellent in corrosion resistance. Recently, in addition to interior building materials, their use as exterior building materials such as roofing materials and outer wall materials is also increasing. In particular, since titanium has excellent corrosion resistance to seawater, it has been increasingly applied to buildings in coastal areas with the development of waterfronts.

As the titanium for building materials, moldability and workability are required, so that soft industrial pure titanium is mainly used. There are 1 to 3 types of industrial pure titanium (hereinafter referred to as pure titanium) defined in JIS H4600, which are classified by the Fe and O content rates. Among them, one kind with a small amount of Fe and O is often used for building materials, and the chemical composition is H ≦ 0.013 by weight%.
%, O ≦ 0.15%, N ≦ 0.05%, Fe ≦ 0.20
%, Balance Ti.

When pure titanium is used as a building material, it is often used unpainted to take advantage of its beautiful surface. When titanium is used unpainted, a calm surface texture or color tone is preferred for interior use. Further, for exterior use, a titanium plate having a surface texture in which light reflection is suppressed is required in consideration of giving a calm atmosphere to a structure and not hindering the operation of an aircraft.

Sheets of pure titanium are generally manufactured in the following steps. First, a high-purity sponge-like metal titanium, which is a raw material, is pressed to form a columnar electrode. Using this electrode as a consumable electrode, arc melting is performed under vacuum to produce an ingot. Next, the ingot is subjected to slab rolling to produce a slab for hot rolling. After hot rolling and cold rolling a titanium slab that has been surface-treated such as removal of surface defects,
It is softened by annealing to give formability and workability. As this annealing treatment, there are a vacuum annealing method of heating under vacuum and a continuous annealing method of heating a band-shaped titanium plate in a continuous furnace in the atmosphere.

In the case of the continuous annealing method, after the annealing, a pickling treatment is performed using an acid such as nitric hydrofluoric acid in order to remove the scale generated on the surface of the titanium plate. By this pickling treatment, a glossy titanium thin plate with good surface quality is finished.

In order to expand the use of pure titanium as a building material, the most strongly demanded is to reduce the price of pure titanium. Although it is suitable for building materials, it is not widely used due to its high price.

Therefore, regarding pure titanium for building materials,
In order to further expand the application, at least the following (a) and (b), and in order to use as an exterior material, it is necessary to simultaneously solve the problem of (c).

(A) The price (manufacturing cost) is low.

(B) Good workability and moldability.

(C) The surface gloss is suppressed.

The titanium raw material has a great influence on the production cost of titanium. The high-purity titanium sponge currently used is expensive because it requires a large amount of electric power for its purification. Therefore, it is difficult to reduce the manufacturing cost of titanium for building materials by the method using high-purity sponge titanium. Although it is effective to reduce cost by using inexpensive sponge titanium with low purity and low purity, N
There is a problem that impurities such as i and Cr are mixed. There is also a method of using inexpensive titanium scrap instead of high-purity titanium sponge, but inevitable mixing of Fe and O is unavoidable. Further, since stainless steel may be mixed in the scrap, the content of impurities such as Ni and Cr may increase. Fe, O mixed, Fe
Is more than 600 ppm and O is more than 900 ppm, the hardness of pure titanium becomes high and bending workability becomes poor. Also, N
Since i and Cr also increase the hardness of pure titanium, they impair the formability and workability of pure titanium. With regard to the use of such inexpensive raw materials, these problems have not been solved,
The reality is that it has not yet been industrialized.

Usually, when a pure titanium thin plate is formed and processed, wavy defects called peco are likely to occur. When this surface defect occurs, the appearance is significantly impaired when it is used as a roofing material or an outer wall material, and the characteristics such as the beauty of the surface peculiar to titanium are lost. As a measure for improving the formability of a pure titanium plate and preventing such defects, Japanese Patent Publication No.
No. 10329 discloses that a pure titanium thin plate for forming having an average crystal grain size of 5 to 28 μm is manufactured by cold rolling and continuous annealing, and deformation beyond an elastic limit is not given between annealing and forming. Discloses a pure titanium thin plate used for forming.

Further, as a method for pickling treatment for removing the scale of the titanium plate after the annealing treatment and obtaining a titanium plate having a beautiful surface without pit defects, Japanese Patent Publication No. Sho 60-
The following method is disclosed in Japanese Patent No. 25506. In this method, the titanium plate is immersed in or sprayed with a hydrofluoric acid aqueous solution containing 2 g / l or more of hydrofluoric acid or a mixed aqueous solution of hydrofluoric acid and sulfuric acid containing 2 g / l or more of hydrofluoric acid. It is a method of pickling treatment. It is said that a product with a beautiful surface can be obtained as compared with the conventional pickling treatment with nitric hydrofluoric acid.

[0015]

As described above, in order to use titanium as a building material, in addition to the characteristics of the current pure titanium, (a) it is inexpensive, (b) formability and workability. It is necessary to simultaneously solve the two problems of good (hereinafter referred to as moldability), and in order to use as an exterior material, (c) the surface property of which reflection of light rays is suppressed Three issues must be resolved.

The methods of Japanese Patent Publication No. 6-10329 and Japanese Patent Publication No. 60-25506 cannot solve (a) and (b) or (a) to (c) at the same time.

The present invention has been made in order to solve the above problems, and is inexpensive, has a good moldability, is pure titanium for building materials, and has a surface with a low gloss and a low light reflection. It is an object of the present invention to provide a pure titanium plate for building materials having properties and a method for manufacturing them.

[0018]

In order to solve the above-mentioned problems, the inventors of the present invention have studied the use of titanium scrap and low-purity sponge titanium as an inexpensive titanium raw material. Fe contained in
It was found that if the amounts of O, Ni, and Cr are limited to an appropriate range, the formability will not be impaired. Furthermore, an appropriate amount of F
A pure titanium plate containing e, Ni, and Cr is subjected to a pickling treatment that is controlled under predetermined conditions to reduce the surface gloss, and is suitable for building materials with a calm surface texture and color tone. We found that a titanium plate was obtained. The present invention has been completed based on these results, and has the following gist.

In weight ratio, the contents of Fe, Ni and Cr are expressed by the following formulas (1), (2) and (3) (unit: p
pm), oxygen (O) is 900 ppm or less, and the balance is pure titanium for building materials consisting of Ti and inevitable impurities, 100 ≦ Fe ≦ 600 Formula (1) 100 ≦ Ni + Cr ≦ 700 Formula (2) Fe + Ni + Cr ≦ 1000 A pure titanium plate for building materials having the same chemical composition as that of the formula (3) and having an average crystal grain size after cold rolling and annealing of 70 μm or less, pure titanium scrap and / or titanium sponge is melted as a main raw material. A method for producing pure titanium for building materials, the following formula (4),
(5) (unit:% by weight) and a method for producing a pure titanium plate for building materials, which is subjected to pickling treatment with a nitric hydrofluoric acid aqueous solution satisfying (6) 2 ≦ HF ≦ 7 Formula (4) 4 ≦ HNO ₃ ≦ 20 Formula (5) 1 ≦ HNO ₃ / HF ≦ 5 Formula (6)

[0020]

[Function] As a raw material for producing pure titanium, the present inventors have
Even when titanium scrap or sponge titanium of low purity is used, if the content ratios of Fe, Ni, and Cr are appropriate, the formability of pure titanium is not impaired.
Furthermore, it has been found that when Fe, Ni, and Cr are contained in appropriate amounts, it is advantageous for the production of pure titanium for building materials whose surface gloss is suppressed. This made it possible to use titanium scrap or sponge titanium of low purity as a raw material for producing pure titanium.

In the present invention, pure titanium such as O, Fe, Ni,
The Cr content, the average crystal grain size of the pure titanium plate, and the pickling conditions after annealing were defined as described above. The basis is as follows.

From the viewpoint of the formability of the pure titanium plate, the contents of the above four elements must be within the following ranges. Fe and O
Has an Fe content of 600 ppm and an O content of 90
When it exceeds 0 ppm, the hardness of pure titanium becomes high,
Bendability (formability) deteriorates. Therefore, the upper limits of Fe and O are set to 600 ppm and 900 ppm, respectively.

Further, Ni and Cr are F with respect to pure titanium.
It has a hardening ability of about 1/2 of e, the sum of Ni and Cr contents (Ni + Cr) exceeds 700 ppm, and the sum of Fe, Ni and Cr contents (Fe + Ni + Cr) is 100 ppm.
If it exceeds 0 ppm, the hardness of pure titanium becomes high and the formability such as bending workability becomes poor. Therefore, Ni + Cr is 700ppm or less, Fe + Ni + Cr is 1000ppm
Below.

From the viewpoint of the surface gloss of the pure titanium plate, F
It is better to contain e, Ni, and Cr in appropriate amounts. These elements tend to segregate at the crystal grain boundaries of pure titanium. The segregated portion is preferentially corroded during pickling after cold rolling and annealing of the titanium material, so that irregularities are formed on the pure titanium surface. As a result, the surface of pure titanium is
The gloss is suppressed and it is difficult to reflect light rays. On the other hand, if the content of these elements is too low, the crystal grain boundaries are less likely to be corroded during pickling, so that no unevenness enough to suppress gloss is formed on the surface. Therefore, the product after pickling has a smooth surface and high gloss, and gives a glittering impression. Therefore, the three elements of Fe, Ni and Cr are
It needs to be contained to some extent, and Fe 100 ppm or more and Ni + Cr 100 ppm or more are required to obtain a product whose surface gloss is suppressed by pickling. F
When the content of e, Ni, and Cr is within the range between this lower limit and the upper limit defined from the viewpoint of the above-mentioned formability,
It is possible to obtain a pure titanium plate having a low surface gloss and good moldability, which is the object of the present invention.

Since it is desirable that the O content in pure titanium be low, the lower limit is not specified, but since it is unavoidable to mix from the raw materials, it is practically about 200 ppm.

In addition to the above Fe, Ni, and Cr contents, the crystal grain size of the pure titanium plate affects the surface gloss of the pure titanium plate. When the average crystal grain size obtained by the JIS H0501 quadrature is 70 μm or more, the effect of suppressing the surface gloss is small. This is because when the respective crystal grains are too large, the irregularities of the crystal grain boundaries are less likely to be reflected in the suppression of surface gloss. Therefore, the crystal grain size of pure titanium is 7
It is desirable that the thickness be 0 μm or less. The lower limit of the average crystal grain size is not specified. In actual production, the lower limit is about 5 μm.

With respect to the surface gloss of the pure titanium plate, it is desirable to select appropriate pickling conditions in addition to the contents of the above three elements and the average crystal grain size. An aqueous solution of hydrofluoric acid is used as a pickling solution for the pure titanium plate after annealing. When the concentration of hydrofluoric acid (HF) is less than 2% by weight (hereinafter, the concentration of the pickling solution is indicated by weight), the scale of pure titanium surface generated by annealing cannot be sufficiently removed. On the other hand, if the concentration of HF exceeds 7%, the reaction during pickling is vigorous and unevenness called acid burning occurs on the surface of the pure titanium plate. In addition, acid (H
If the concentration of (NO ₃ ) is less than 4%, the pickling reaction product adheres to and remains on the pure titanium surface after pickling, and the surface becomes dirty and becomes uneven blackish. . HNO ₃
If the concentration exceeds 20%, the glossiness of the surface becomes too high, so that a pure titanium plate with suppressed surface gloss cannot be obtained. H
The reason why the glossiness becomes high when the concentration of NO ₃ is too high is because nitric acid works to suppress the pickling reaction of titanium.
This is because preferential corrosion of the crystal grain boundaries does not occur easily and irregularities are not easily formed at the crystal grain boundaries.

As for the pickling solution, it is desirable to select appropriate conditions for the concentration ratio of both HF and HNO ₃ as well as the concentration ratio of both, HNO ₃ / HF. When HNO ₃ / HF is less than 1, the surface of the pure titanium plate after pickling becomes dirty and becomes a blackish color with unevenness. When HNO ₃ / HF exceeds 5,
Since the surface gloss of the pure titanium plate becomes too high, a pure titanium plate with suppressed surface gloss cannot be obtained.

Therefore, as the pickling solution used in the present invention, the concentration of HF is 2% or more and 7% or less, the concentration of HNO ₃ is 4% or more and 20% or less, and the concentration ratio of both is HNO ₃ / HF.
A nitric hydrofluoric acid aqueous solution having a ratio of 1 or more and 5 or less is suitable.

The pure titanium of the present invention has a F content within the above range.
e, Ni and Cr are allowed to be contained. Therefore, an inexpensive raw material such as titanium scrap or sponge titanium having a low purity can be used as a titanium raw material for producing pure titanium. These raw materials may be used alone or in combination. Further, in these raw materials, when the contents of Fe, Ni, Cr, etc. are too high, it is preferable to adjust the components by blending sponge titanium having high purity. The content of Fe, Ni, Cr, etc. as impurities contained in titanium raw materials such as titanium scrap or sponge titanium having low purity has a wide fluctuation range. Therefore, when using these raw materials, the content rate of the impurity element should be investigated in advance,
It is necessary to determine the raw material composition so that it falls within the chemical composition range of pure titanium of the present invention.

[0031]

【Example】

(Example 1) In Example 1, the effect of the O, Fe, Ni and Cr contents on the formability and surface gloss of the pure titanium plate was investigated.

Table 1 shows the chemical composition of 20 pure titanium-titanium ingots used for preparing the test materials. Specimen material N
o. 1 to 13 are pure titanium of the present invention, and the test material No. 14 ~
20 is pure titanium as a comparative material.

[0033]

[Table 1]

As the titanium raw material for melting the titanium ingot, the test material No. 1-10 and No. For 14 to 20, high-purity sponge titanium (JIS H2151
-1 type) was used. Specimen No. For 11 to 13, fine chip-like titanium scrap (O: 0.045
%, Fe: 0.025%, Ni: 0.007%, Cr:
0.0067%, all in weight%) was used. In addition,
Pure F as a raw material for adjusting the Fe, Ni and Cr contents
e, pure Ni and pure Cr were used. The ingot was melted by using a plasma arc furnace and melting a raw material in a predetermined mixing ratio in an argon atmosphere. The ingot has a thickness of 20 mm, a width of 60 mm, a length of 150 mm, and a weight of 800 g.

The obtained ingot was heated to 950 ° C., forged to a thickness of 10 mm, further heated to 850 ° C. and hot-rolled to a thickness of 5 mm. The rolled material was machined to a thickness of 4 mm in order to remove surface scale. After that, thickness 4mm to 0.8m
Cold rolled to m.

From the material after rolling, width 20 mm, length 15
A test piece of 0 mm was cut out. The test piece was annealed by holding it at a temperature of 700 ° C. for 5 minutes in the atmosphere. A 30 ° C. nitric hydrofluoric acid aqueous solution (HF: 3%, HNO ₃ : 10%, HNO ₃ / HF:
The sample was subjected to pickling treatment under the condition of being immersed in 3.3) for 2 minutes, and the scale on the surface of the test piece generated during annealing was removed. The average crystal grain size of each test piece was about 10 to 80 μm.

The evaluation of the test piece is performed by the Vickers hardness of the moldability and the surface gloss of JIS Z8741 60.
Depends on the degree of gloss by the specular gloss method. The hardness was measured on the longitudinal section of the test piece, and the gloss was measured on the rolled surface.

Table 1 also shows the results of these investigations.
When the Vickers hardness exceeds 170, the hardness is too high and the moldability deteriorates. Therefore, the moldability was determined to be poor (x).
Further, when the glossiness exceeds 30, the surface quality is not suppressed, and in that case, the surface gloss is determined to be poor (x). The reason why the glossiness of 30 or less is good (◯) is that this range is a specular glossiness that provides a central luster of medium gloss under the measurement conditions of 60-degree specular gloss in accordance with JISZ8741. Match.

As is clear from Table 1, the test material No. 1 to
The pure titanium plate of No. 13 of the present invention has good moldability and suppressed surface gloss, and has characteristics suitable for a building material, which is the object of the present invention. On the other hand, the test material No. 14 ~
It was confirmed that the 20 pure titanium plates for comparison had a poor formability or surface gloss because the chemical composition range was outside the range of the present invention. Further, the test material No. using titanium scrap as the titanium raw material. For 11 to 13, since the chemical composition is within the scope of the present invention, moldability,
Good surface gloss. From this result, it was confirmed that even if a raw material other than high-purity sponge titanium was used as the titanium raw material, the characteristics of the pure titanium plate were not affected as long as the chemical composition was within the range of the present invention.

Example 2 The effect of crystal grain size on the surface gloss of a pure titanium plate was investigated. As the test material, the test material No. used in Example 1 was used. A cold rolled material having the same chemical composition as in No. 6 was used. From cold rolled material, length 20mm, width 20mm
Cut out the test piece of 550 ℃ to 50 ℃
Each test piece was annealed under the condition of holding each temperature up to 850 ° C. for 5 minutes to prepare test pieces having different average crystal grain sizes. Furthermore, the annealed test piece was subjected to pickling treatment under the same conditions as in Example 1. The average crystal grain size of the obtained test piece was measured in a longitudinal section parallel to the rolling direction according to the quadrature method of JIS H0501, and the specular gloss of the surface was measured by the same method as in Example 1. Table 2 shows the survey results.

[0041]

[Table 2]

It can be seen that the pure titanium plates of the present invention (Test Nos. 1 to 6) having an average crystal grain size of 70 μm or less have a surface glossiness of 30 or less, and have a surface texture with suppressed gloss. . On the other hand, when the average crystal grain size exceeds 70 μm (Test No. 7), the surface glossiness exceeds 30, and it can be said that the glossiness is too high. From this result, it was confirmed that the average crystal grain size of the pure titanium plate is preferably 70 μm or less.

Example 3 The effect of pickling conditions on glossiness was investigated. As the test material, the test material No. used in Example 1 was used. A cold rolled material having the same chemical composition as in No. 6 was used. The cold-rolled material is annealed under the conditions of 700 ° C. and a holding time of 5 minutes.
A test piece of 0 mm and a width of 50 mm was cut out. This test piece was pickled with a nitric hydrofluoric acid aqueous solution under each condition shown in Table 3. The temperature of the pickling solution was 30 ° C. and the holding time was 2 minutes. With respect to the test piece after pickling, the effect of pickling including descaling property was investigated by observing the surface, and the surface glossiness was measured by the same method as in Example 1. Table 3 shows the results of these investigations.

[0044]

[Table 3]

Test No. of the present invention example Regarding Nos. 1 to 11, since the pickling condition is within the range of the present invention, the surface of the test piece is clean without any residual scale or stain. Further, the glossiness is 30 or less, and the surface texture is suitable for building materials in which the gloss is suppressed. On the other hand, the test No. of the comparative example. Regarding Nos. 12 to 25, since the pickling conditions are out of the range of the present invention, many of the scales and stains are observed on the surface of the test piece. Furthermore, the glossiness is 3
Most of them exceed 0. As described above, in the case of the comparative example, none of them satisfied all the conditions that the scale remained, there was no stain, and the glossiness was 30 or less.

From these results, it was confirmed that the conditions of the present invention are suitable as pickling conditions.

[0047]

EFFECT OF THE INVENTION Pure titanium for building materials of the present invention contains O, Fe,
Since it is allowed to contain a predetermined amount of Ni and Cr, inexpensive titanium scrap or sponge titanium having a low purity can be used as a raw material for producing pure titanium. Therefore, it is possible to obtain pure titanium which has a formability for a building material and is inexpensive. Further, pure titanium contains appropriate amounts of Fe, Ni, and Cr, and in addition to the average crystal grain size of the pure titanium plate being within a predetermined range, appropriate conditions for pickling after annealing are determined. Therefore, it is possible to obtain a pure titanium plate for a building material, which has a surface texture with a suppressed surface gloss and a slight reflection of a light ray, and which is suitable for an exterior. in this way,
According to the pure titanium for building materials, the pure titanium plate and the method for producing the same of the present invention, it is possible to obtain an inexpensive pure titanium and a pure titanium plate suitable for building materials. It has an excellent effect.

Claims (4)

[Claims] 1. The content ratio of Fe, Ni and Cr in terms of weight ratio is represented by the following formulas (1), (2) and (3) (unit: pp
m) and oxygen (O) is 900 ppm or less,
Pure titanium for building materials, characterized in that the balance comprises Ti and inevitable impurities. 100 ≦ Fe ≦ 600 Formula (1) 100 ≦ Ni + Cr ≦ 700 Formula (2) Fe + Ni + Cr ≦ 1000 Formula (3) 2. A pure titanium plate for building material, which has the chemical composition of claim 1 and has an average crystal grain size of 70 μm or less after cold rolling and annealing. 3. The method for producing pure titanium for building materials according to claim 1, wherein pure titanium scrap and / or titanium sponge is melted as a main raw material. 4. The pure titanium plate according to claim 2 is pickled with an aqueous solution of nitric hydrofluoric acid satisfying the following formulas (4), (5) (unit:% by weight) and (6). A method for producing a pure titanium plate for building materials, which comprises: 2 ≦ HF ≦ 7 Formula (4) 4 ≦ HNO ₃ ≦ 20 Formula (5) 1 ≦ HNO ₃ / HF ≦ 5 Formula (6)