JP2002242359A - Pure titanium material for building material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pure titanium material for a building material suitable for the building material such as a roofing plate, an exterior wall material or the like. SOLUTION: For the pure titanium material having more than 0.1% to 20% of the residual ratio of an oxidizing film (scale) of the surface after the descale, after the pure titanium material is annealed in the atmosphere, when an acid pickling treatment is applied to make descale, the residual ratio of the scale of the surface becomes more than 0.1% to 20% to enable the pure titanium material to manufacture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pure titanium material for a building material used as a building material such as a roof plate material and an outer wall material.

[0002]

2. Description of the Related Art Titanium has features such as light weight, excellent corrosion resistance, and a small coefficient of thermal expansion. Taking advantage of these features, titanium is widely used in roofing materials and the like. In particular, in a beach area where salt contained in seawater is scattered, a problem of corrosion occurs with a conventional stainless steel roofing material, and thus a titanium roofing material is increasingly used. In addition, titanium has been frequently used as an exterior material of a high-rise building, and its use as a building material has been increasing.

[0003] As a titanium material for building materials, JIS H4
1 to 3 types of pure titanium plates for industrial use specified in 600,
Among them, one kind of soft titanium plate is mainly used. Such titanium materials for building materials (hereinafter, referred to as “pure titanium materials for building materials” or simply “pure titanium materials”) include, for example, 100 to 600 ppm of Fe,
A pure titanium sheet for building which is suitable for exteriors whose surface gloss is suppressed by containing 100 to 700 ppm of Ni and Cr and making the total content of Fe, Ni and Cr 1000 ppm or less is known (Japanese Patent No. 3052787). No.).

[0004] When pure titanium is used for an exterior such as a roof, there is no particular problem because the corrosion resistance is good, but the oxide film on the surface gradually grows and discolors during long-term use. The problem has come out. When the oxide film on the surface of the pure titanium material grows and the thickness increases, coloring due to interference color occurs partially or entirely depending on the thickness of the film, and the metal color at the beginning of construction is lost, so building The appearance of the object is significantly impaired.

[0005] The above-mentioned discoloration is problematic in that it occurs violently in the poorly drained area of the outer surface of the building, and the discoloration progresses mainly in a portion where rainwater flows. The mechanism by which this discoloration occurs is not completely understood, but if water remains on the surface of the pure titanium material, sulfur oxides and the like in the atmosphere dissolve in this water to produce a thin acid,
It is considered that the discoloration proceeds by dissolving a trace amount of titanium from the pure titanium material by the chemical reaction with the acid.

[0006] In order to suppress the time-dependent discoloration of titanium and titanium alloy used for building exterior materials and the like, for example, Japanese Patent Application Laid-Open No. 8-283985 discloses an oxide film formed on the surface of titanium or a titanium alloy material. Ni, C on the surface layer
u, Cr, Au, Ag, at least one of platinum group elements,
Alternatively, a technique has been proposed in which plating is performed with a thickness of 0.1 μm or less made of an alloy containing them as a main component.
According to this method, discoloration of the surface of the titanium or titanium alloy material can be suppressed. However, an increase in manufacturing cost due to plating is inevitable.

In Japanese Patent Application Laid-Open No. 2000-1729, an oxide film having a thickness of 10 nm (100 angstroms) is present on a substrate surface, the C content in the surface oxide film is 30 atomic% or less, and A titanium or titanium alloy material excellent in discoloration resistance and having a C content of 30 atomic% or less in a base layer under an oxide film has been proposed. In this titanium or titanium alloy material, the oxide film N
Since C, which is a barrier to Ox, SOx, and the like and degrades the corrosion resistance of the base titanium material, is suppressed to a predetermined amount or less, discoloration is considered to be difficult. However, the measurement of the thickness of the oxide film and the amount of C in the oxide film must be performed by Auger electron spectroscopy, which takes a lot of time and troubles in assuring the quality of the entire product. In addition, it is not always a sufficient solution to the above-mentioned problem that partial discoloration occurs at a portion where rainwater or the like flows on the outer surface of a building.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and is pure titanium for building materials which is hardly discolored even when used for a long time as a building material such as a roof plate material and an outer wall material. The task is to provide materials.

[0009]

In order to solve the above-mentioned problems, the present inventors have made various studies. As a result, in the manufacturing process of the pure titanium material, after being formed to a predetermined thickness by cold rolling, it is formed on the surface during an annealing process (annealing process in the atmosphere) for imparting formability and workability. It has been found that the water repellency of the surface of the pure titanium material greatly differs depending on the presence or absence of the scale (oxide film), which significantly affects the discoloration that occurs in the poorly drained area in the outer surface of the building.

[0010] Pure titanium materials (for example, plate materials) for building materials are generally subjected to slab-rolling of ingots obtained by arc-melting sponge-like titanium metal under vacuum, and further hot-rolling and cold-rolling. It is manufactured by performing an annealing treatment after the thickness is increased. As methods of the annealing treatment, there are an atmosphere annealing method in which annealing is performed in an argon atmosphere and an air annealing method in which annealing is performed in the air.In the case of the air annealing method, the scale formed on the surface of the pure titanium material after annealing is used. In order to remove them, they are immersed in a molten salt and pickled. During the immersion in the molten salt and the pickling treatment, if the scale (oxide film) on the surface of the pure titanium material is not completely removed but is partially left, the water repellency of the surface of the pure titanium material is improved, It is possible to suppress discoloration occurring mainly in a part where the drainage of the outer surface of the building is poorly drained or where rainwater flows.

The present invention has been made based on such knowledge, and the gist lies in the following pure titanium material for building materials.

[0012] A pure titanium material for building materials having an oxide film formed by annealing treatment remaining on a surface thereof, wherein the residual ratio of the oxide film is 0.1% or more and 20% or less.

The term "residual rate of oxide film" as used herein means an oxide film formed by an annealing treatment in the air after a predetermined thickness is obtained by cold rolling (hereinafter referred to as "scale" according to a common name). ), That is, the ratio of the scale remaining on the surface of the pure titanium material without being separated from the base material by descaling by pickling after annealing. This "residual rate" is obtained by observing the surface of the pure titanium material with a microscope at a magnification of about 100 times, and pressing 20 straight lines orthogonal to each other at equal intervals in the vertical and horizontal directions in the observation visual field (these are referred to as "remaining rates"). The total number of intersections of the straight lines is 400),
The ratio of the number of intersections where a scale exists to the total number of intersections (400 points) is expressed as a percentage.

In a pure titanium material for building materials whose surface scale residual ratio falls within the above range (0.1% or more and 20% or less), the contact angle with water (pure water) on the surface is 80 degrees. That is all. Therefore, the pure titanium material for building materials described above can be defined as a “pure titanium material having a contact angle of 80 ° or more with water on the surface”. In addition, the said "contact angle" refers to the point P where the outer edge of the water droplet 2 contacts the pure titanium material surface 1 in FIG. 1 schematically showing the shape of the water droplet when the water droplet is dropped on the surface of the pure titanium material. An angle θ formed between a tangent L (that is, a tangent at a point P of a curve S representing the contour of the water droplet 2) and the pure titanium material surface 1. The drop of water is 1 ml (milliliter).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a pure titanium material for building materials of the present invention will be described in detail.

The pure titanium material for building material of the present invention is a pure titanium material having a scale remaining rate of 0.1% or more and 20% or less on the surface after descaling. Usually, it is a plate material, that is, a pure titanium plate.

The residual ratio of the scale is 0.1% or more and 20% or more.
It is necessary to: The residual ratio of the scale is 0.
When the content is less than 1%, the water repellency of the surface of the pure titanium material is deteriorated, and water tends to remain on the surface of the pure titanium material. As described above, sulfur oxides in the atmosphere dissolve in this water. It is thought that a thin acid is generated, and a chemical reaction between the acid and titanium occurs to promote discoloration. On the other hand, when the residual ratio exceeds 20%, the surface of the pure titanium material becomes black as a whole, and the appearance is impaired.

When the residual ratio of the scale is within the above range, the contact angle with water on the surface of the pure titanium material becomes 80 degrees or more. Therefore, the contact angle with water on the surface is 80
If it is not less than the degree, the water repellency of the surface of the pure titanium material is improved, and it is possible to suppress the discoloration that occurs at the center of the outer surface of the building where rainwater or the like flows as described above.

The pure titanium material for building materials according to the present invention, when the pure titanium material is annealed in the air and then subjected to pickling and descaling, the residual ratio of scale on the surface is 0.1% to 20%. It can be manufactured by the following.
The “pure titanium material” refers to a pure titanium material having a predetermined thickness or shape, which can be subjected to an annealing process for imparting formability and workability. For example,
It refers to a pure titanium plate obtained by subjecting an ingot obtained by arc melting to slab rolling, and further hot rolling and cold rolling to a predetermined thickness.

As described above, pure titanium materials for building materials are:
Usually, ingot obtained by arc-melting sponge-like metallic titanium is subjected to bulk rolling, further hot-rolled and cold-rolled to a predetermined thickness, and then subjected to an annealing treatment. As a method of the annealing treatment, there are an atmosphere annealing method in which annealing is performed in an argon atmosphere, and an atmospheric annealing method in which annealing is performed in the air, but the scale generated during annealing partially remains on the surface. In producing the titanium material, an atmospheric annealing method is employed. This is because it is difficult to partially form the scale on the surface of the pure titanium material as described above only by atmosphere annealing. The reason for performing the annealing treatment is to control the crystal grain size and adjust the mechanical properties to impart moldability and workability.

After the annealing, the scale formed on the surface of the pure titanium material is removed by pickling, but at this time, not all the scale formed on the surface of the pure titanium material is removed. Part. In other words, when descaling, the protrusions on the surface of the material are descalated preferentially, and the descaling is relatively delayed in the recesses. Therefore, an appropriate stage before the entire surface is completely descaled (the residual ratio of scale) At the stage when the ratio becomes 0.1% or more and 20% or less). The “appropriate stage” can be easily grasped by previously obtaining the relationship between the conditions of the pickling treatment (for example, the temperature of the pickling solution, the immersion time, etc.) and the residual ratio of the scale. In the pickling treatment, a commonly used aqueous solution of nitric hydrofluoric acid may be used.

In performing the above pickling treatment, usually, after the annealing treatment, the pure titanium material is first immersed in a molten salt and then in a pickling tank. The immersion treatment in the molten salt prior to the pickling treatment is performed because the removal of the scale by the pickling treatment is performed by dissolving the base material and dropping the scale on the base material surface. The reason is that the scale on the surface of the base material is partially broken by immersion, so that the pickling liquid can easily reach the surface of the base material.

As described above, the pure titanium material for building materials of the present invention can be easily prepared by slightly changing the conditions of the pickling treatment and leaving a part of the scale formed on the surface of the pure titanium material by the annealing treatment. It can be manufactured at low cost.

[0024]

EXAMPLE A plate material of one kind of pure titanium (thickness: 0.5 mm, as-rolled state) specified in JIS H4600 was used as a raw material, and heated at 800 ° C. for 5 minutes in the air to scale the surface. Generated. Then, the molten salt (NaO
H, was immersed in a mixed salt) of NaNO ₃ and NaCl, nitric-hydrofluoric acid aqueous solution under the conditions shown in Table 1 _(HNO 3: 10 wt%, HF: 3 wt%) performed pickling treatment with the surface scale Was changed. The scale survival rate is
As described above, the surface of the pure titanium plate after the pickling treatment is
Microscopic observation was performed under a magnification of 0, and the ratio was obtained from the ratio of the number of intersections having a scale to the total number of intersections. In addition, in order to improve the accuracy, the scale residual ratio shown in Table 1 is 10% for each of the pure titanium sheet materials that have been descaled under the respective conditions.
Observed in a visual field (total number of intersections: 4000 points), it is the residual rate calculated by the following formula.

Scale remaining rate = (number of intersection points where scale exists / 4000) × 100

[0026]

[Table 1] A test piece for exposure (width 70 mm x length 100 mm) was collected from each of the pure titanium plate materials thus obtained, and exposed for about 2 years in a beach area. The degree of discoloration was investigated by measuring the color difference (δE) with a meter.

The contact angle with water on the surface of the plate was measured. The contact angle was measured on the surface of each pure titanium plate by 1
ml of distilled water was dropped, and the above-mentioned contact angle θ was measured by a contact angle measuring device.

Scale residual ratio, contact angle and color difference (δ
Table 1 also shows the measurement results of E). When the color difference (δE) before and after exposure was 2 or more, there was a color difference. When it was less than 2, it was evaluated that there was no color difference.
Indicated with a mark or a circle.

From the results shown in Table 1, it is found that No. 1 having a scale residual ratio within the range specified in the present invention. 2-No. In the case of the pure titanium plate material of No. 7, the contact angle was 80 degrees or more, and it could be evaluated that there was no color difference, and it was found that discoloration was suppressed. Further, when the residual ratio of the scale was reduced or increased from about 7%, the color difference tended to increase. Note that N
o. The pure titanium plate material of No. 1 had a high residual ratio of scale and had a blackish surface, so that it was judged to be of no commercial value and the exposure test was not performed.

[0030]

The pure titanium material for building materials of the present invention is hardly discolored even when used for a long period of time, and is suitable as a building material such as a roof plate material and an outer wall material. The pure titanium material can be easily and inexpensively manufactured by leaving a predetermined amount of scale on the surface during descaling after the annealing treatment.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a contact angle with water on a surface of a pure titanium material, and is a diagram schematically showing a shape of a water droplet when a water droplet is dropped on the surface.

[Explanation of symbols]

 1: Pure titanium material surface 2: Water drop θ: Contact angle

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2E001 DH00 FA04 FA16 GA12 GA43 HB08 HF00 KA01 MA01 2E108 CC01 GG00 2E110 AA26 AB02 AB04 BB01 EA09 GA08W GB05W 2E162 CB11 EA00

Claims (1)

[Claims] 1. A pure titanium material for building materials in which an oxide film generated by an annealing treatment remains on the surface, wherein the residual ratio of the oxide film is 0.1% or more and 20% or less. Pure titanium material.