JP3303534B2 - Industrial pure titanium and its production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to industrial pure titanium and a method for producing the same.

[0002]

2. Description of the Related Art Titanium has excellent corrosion resistance and is often used in severe corrosive environments such as marine environments and structural materials for chemical plants. Above all, industrial pure titanium has the highest workability and is most commonly used. However, due to the high manufacturing cost of titanium materials, despite their excellent corrosion resistance, their use is currently restricted compared to other competitive materials such as stainless steel.

Conventionally, various studies have been made to reduce the production cost of titanium materials. However, attention has been paid to a technique of utilizing scrap, which can significantly reduce the cost of reducing or refining titanium ore, which has a high specific gravity in the cost. I have.

[0004]

It is advantageous to use inexpensive low-quality scrap as much as possible in order to reduce costs, but using low-quality scrap increases the amount of impurity elements. In particular, when the Fe concentration is increased, in the case of industrial pure titanium, there arises a problem that corrosion resistance in a non-oxidizing environment such as sulfuric acid or hydrochloric acid is impaired.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. Even if the Fe concentration is increased to some extent due to the use of low-quality scrap, pure titanium for industrial use which has excellent corrosion resistance in a non-oxidizing environment and It is an object of the present invention to provide a manufacturing method thereof.

[0006]

Means for Solving the Problems The object of the present invention is to control the amount of scrap used to reduce the Fe content to 0.1% by mass%.
% And 0.19 % or less, add hot working, and then
In transformation start temperature from α phase to β phase (hereinafter, referred to as T [alpha.) Was annealed below, are solved by a manufacturing method of industrial pure titanium of the crystal grain size and 30μm or less. Further, the problem is solved by industrially pure titanium which is a hot-worked material having the above-mentioned Fe content and whose crystal grain size is controlled to 30 μm or less. These industrial grades of titanium exhibit better corrosion resistance in non-oxidizing environments. As the hot working, hot working such as forging and hot rolling can be applied as in the examples described later. In the present invention,
"Add hot working and then anneal below Tα"
Is to perform annealing after hot working as in the examples described later.
That is.

[0007]

The details will be described in Examples, but the relationship between the corrosion rate, the annealing temperature, and the crystal grain size in a non-oxidizing environment was studied by using several types of pure titanium having different Fe contents.

FIG. 1 shows that the Fe content is 0.10 mass % and 0.1% by mass .
The relationship between the corrosion rate of pure titanium at 15 mass % (shown as 0.10 wt% and 0.15 wt% in the figure) and the annealing temperature is shown. It can be seen that the lower the annealing temperature of any pure titanium, the lower the corrosion rate and the higher the corrosion resistance. In particular, at an annealing temperature lower than the transformation start temperature Tα from the α phase to the β phase, a corrosion rate of 30 mm / year or less is obtained, and an excellent content equivalent to that of ordinary industrial pure titanium having an Fe content of about 0.05 mass %. It shows excellent corrosion resistance.

Although the lower limit of the Fe content is not always clear, the result of 0.10 mass% shown in FIG.
In order to adjust the content to less than 0.1 mass%, the lower limit of the Fe content is set to 0.1 in consideration of the fact that the utilization of low-quality scrap is less than 50% and the effect of cost reduction is reduced.
mass%. When the Fe content exceeds 0.3 mass%, a corrosion rate of 30 mm / year or less was not obtained even when annealing was performed at a temperature of Tα or less .

From the results of FIG. 1, the annealing temperature is limited to the transformation start temperature Tα from α phase to β phase or lower.

FIG. 2 shows the relationship between the corrosion rate of pure titanium having an Fe content of 0.10 mass% and the crystal grain size. 3 grain size
When the thickness is 0 μm or less, the corrosion rate is 10 mm / year or less, and it can be seen that extremely excellent corrosion resistance is exhibited. Note that Fe
When the content exceeds 0.3 mass%, the crystal grain size becomes 30 μm.
Even below, a corrosion rate of 30 mm / year or less could not be obtained. Therefore , in order to obtain extremely excellent corrosion resistance, it is necessary to set the Fe content to 0.1% or more and 0.19 % or less by mass% and the crystal grain size to 30 μm or less as in the examples described later. desirable.

[0012]

EXAMPLES Six types of industrial pure titanium having Fe contents as shown in Table 1 were melted and ingots were heated at 1050 ° C.
Slabbing forging to 200mm thick slabs and without the heating, the 100mm thickness in rough rolling subsequent 850 ° C. heating, then 85
A hot-rolled sheet having a thickness of 10 mm was prepared by finish rolling at 0 ° C. After holding the hot-rolled sheet at various temperatures for 1 hour and performing air-cooled annealing, the thickness is 5 mm, the width is 20 mm, and the length is 40 mm.
Sample was taken, and the surface was polished by wet polishing of # 400.
A corrosion test was performed. Corrosion tests were conducted in 24% boiling sulfuric acid at 24%.
The test was performed in a non-oxidizing environment immersed for a long time. The corrosion rate was determined from the weight change before and after the test, and the corrosion resistance was evaluated.
As described above, in the case of ordinary industrial pure titanium having an Fe content of about 0.05 mass %, a corrosion rate of 30 mm / year or less is always obtained regardless of the production conditions.
/ Year corrosion rate was used as an evaluation reference value of corrosion resistance.

The results are shown in Table 1. Sample N in this table
o. In Nos. 1 to 4, when the annealing temperature is equal to or lower than the transformation start temperature Tα from α phase to β phase, a corrosion rate of 30 mm / year can be obtained, and excellent corrosion resistance is exhibited. Table 1 also shows the results of the measurement of the crystal grain size after annealing. Sample No. 1 having an Fe content within the range of the present invention is also shown. In Nos. 1 to 3 , a corrosion rate of 10 mm / year was obtained when the crystal grain size was 30 μm, and extremely excellent corrosion resistance was exhibited. Specifically, Sun
Pull No. Annealing temperature of 550 ° C. 2 in 5
50 ° C. and 600 ° C .; 3, 600 ° C sump
Excellent corrosion resistance with a corrosion rate of 10 mm / year or less
Is shown. On the other hand, Sample No. having an Fe content outside the range of the present invention. 5 is 30 m under any conditions
Although a corrosion rate of less than m / year is obtained and excellent corrosion resistance is shown, low-quality scrap can hardly be used to control such a low Fe content, and cost reduction cannot be achieved. From the above, scrap can be used and extremely excellent resistance
Conditions for obtaining corrosion (corrosion rate 10 mm / year) are Fe
Content is 0.10 to 0.19%, annealing temperature is Tα or less,
And the crystal grain size is 30 μm or less. Remarks in Table 1
In the column, the case where the corrosion rate is 30 mm / year or less is referred to as “the present invention.
Example), but the corrosion rate is 10 mm / year or less.
The reason for this is that a sample having a crystal grain size of 30 μm or less as described above.
Limited to pull. Further, Sample No. having an Fe content outside the range of the present invention. 6 is 30 m under any conditions
A corrosion rate of m / year or less cannot be obtained, and the corrosion resistance is poor.

[0014]

[Table 1]

Although the cause of the above phenomenon is not always clear, it is considered as follows. That is, when the annealing temperature is set to Tα or lower, the formation of the second phase having a high Fe content and poor corrosion resistance is suppressed, so that the corrosion resistance is improved. Further, when the crystal grain size is set to a fine structure of 30 μm or less, the total area of the crystal grain boundaries increases, the Fe concentration per unit area at the grain boundaries decreases, and the formation of the second phase having poor corrosion resistance is suppressed. Corrosion resistance is improved. Fe content 0.3 ma
If the content exceeds ss %, these effects are not sufficiently exerted. If the content is less than 0.1 mass %, a second phase having a high concentration of Fe and having poor corrosion resistance is not formed so that it is not necessary to use these effects. .

The low-quality scrap utilization rate is lower than that of the sample No. having an Fe content of 0.15 mass %. 60 for 2
%Met. Therefore, by adjusting the Fe content within the range of the present invention, a significant cost reduction can be achieved.

[0017]

Industrial Applicability Since the present invention is constructed as described above, even if the Fe concentration is increased to some extent due to the use of low-quality scrap, pure titanium for industrial use which has excellent corrosion resistance in a non-oxidizing environment and its titanium. A manufacturing method can be provided.

[Brief description of the drawings]

FIG. 1 Fe content of 0.10 mass % and 0.15 mass %
FIG. 4 is a graph showing the relationship between the corrosion rate of industrial pure titanium and the annealing temperature.

FIG. 2 is a graph showing the relationship between the corrosion rate and the crystal grain size of pure titanium for industrial use having an Fe content of 0.10 mass %.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-252747 (JP, A) JP-A-5-70913 (JP, A) JP-A-63-270449 (JP, A) Japan Standards Association, "JIS Handbook Non-Ferrous", 1st edition, 1st printing, Japan Standards Association, April 20, 1990 (58) Fields investigated (Int. Cl. ⁷ , DB name) C22F 1/00-3 / 02 C22C 1/00-49/14

Claims (2)

(57) [Claims] 1. The Fe content is 0.1% or more by mass% .
Was adjusted to 19% or less, hot working was added, followed by annealing below the transformation starting temperature to β-phase from the α phase, 30.mu. grain size
m or less . 2. The Fe content is 0.1% or more in mass% .
It is a hot-worked material of 19 % or less and has a crystal grain size of 30μ.
m or less.