JP3398555B2 - Titanium sheet for forming and its manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium thin plate for forming, which is excellent in scratch resistance for preventing the occurrence of surface flaws due to seizure with a tool during secondary working, and a method for producing the same. is there. The main uses of titanium thin plates for forming are plates for heat exchangers that require press formability,
There are welded titanium pipes. In particular, in a welded titanium pipe that is roll-formed and TIG-welded at the abutting part, a lubricant cannot be used during roll-forming in order to maintain the soundness of the welded part, so the titanium thin plate itself, which is the raw material, has scratch resistance. Sex is required.

[0002]

2. Description of the Related Art Various treatments are performed to modify the surface of titanium. First, regarding the nitriding treatment, an example of ion nitriding is described in "Titanium processing technology" (edited by Titanium Association of Japan, published by Nikkan Kogyo Shimbun, Ltd., 1992, p. 180). Ion nitriding is described as having good wear resistance at a treatment temperature of 850 ° C. or higher, which is relatively high, although ion nitriding can be performed more efficiently than ordinary gas nitriding. As an example, in Japanese Patent Laid-Open No. 10883/1989, after forming a titanium alloy plate into a key shape, about 85
It is said that a titanium key with excellent wear resistance can be obtained by nitriding at 0 ° C. For example, in ammonia gas,
After treatment for 16 hours, a TiN layer having a thickness of 12 μm and a diffusion layer having a thickness of 50 μm (the nitrogen-rich layer is estimated to be 62 μm) are obtained. As described above, the conventional nitriding treatment is performed for the purpose of imparting long-term wear resistance to the finished product in the shape of the final product. However, when it is applied to a titanium thin plate that is premised on a forming process, there is a drawback that the surface is cracked during bending, for example.

Further, Japanese Patent Laid-Open No. 63-111161 proposes a wire drawing method in which a titanium alloy wire is oxidized in a temperature range of 450 to 750 ° C. and then lubricated to prevent seizure. This method of oxidation treatment has a disadvantage that when applied to a titanium thin plate, the colored portion needs to be removed after the molding process, because uneven coloring such as blue color occurs.

Further, in Japanese Patent Laid-Open No. 3-294471, an oxide film having a specific thickness is formed on the surface of a titanium plate and then annealed in a non-oxidizing atmosphere to form a surface hardened layer. A method for producing a titanium plate having excellent seizure properties and having a uniform metallic luster is disclosed. This method has a drawback that the manufacturing cost is high because the oxide film is formed by an anodic oxidation method in order to obtain an oxide film having a uniform specific thickness.

Further, in Japanese Patent Laid-Open No. 1-201452, after titanium is cold-rolled with a specific rolling oil, the oil is left and annealed in a non-oxidizing atmosphere to obtain a surface hardening containing TiC as a main component. It is described that a layer is formed and the scratch resistance is improved. This method has a drawback in that the quality is difficult to stabilize because oil remains depending on the cleaning ability of the cleaning liquid.

[0006]

In the present state of the art, the present invention has the characteristics that there is no deterioration of the material, there is no uneven coloring such as blue, and the quality is cheap and the quality is easy to stabilize.
A titanium thin plate for forming, which has a film excellent in seizure resistance with a tool, and a manufacturing method thereof.

[0007]

In order to solve the above-mentioned problems, the present invention has a nitrogen-enriched layer on the surface and has a thickness of 0.5 μm or more and 5 μm or less. Titanium sheet, preferably its thickness is 1.5
The gist is a titanium thin plate for forming, which is characterized in that it is not less than μm and not more than 5 μm.

Further, the titanium is heated in a nitriding atmosphere at a heating temperature of 550 ° C. or higher and 700 ° C. or lower. A gist of the method for producing a titanium thin plate for forming is characterized in that the as-manufactured titanium is heated in a nitriding atmosphere at a heating temperature of 600 ° C. or higher and 700 ° C. or lower.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION First, a surface having a nitrogen-enriched layer,
The thickness of 0.5 μm or more and 5 μm or less means that if the thickness is less than 0.5 μm, it cannot be said that the seizure property with the tool is sufficiently improved, and that the thickness exceeds 5 μm. Then, since it is colored in a light gold color, a problem of color unevenness is likely to occur.

On the other hand, generally, when the thickness of the nitrogen-rich layer is large, the material deteriorates. The present inventors have found that the thickness of the nitride-enriched layer is
If the thickness is 1.5% or less (3% or less on both sides),
It was confirmed that there was almost no effect on the tensile properties.
It was also confirmed by a hydraulic bulge test that the moldability did not deteriorate. From this result, there is no material deterioration up to 6 μm of nitrogen-enriched layer with respect to the thinnest plate thickness of 0.4 mm used for forming titanium thin plate, but as described above, there is a coloring problem, so 5 μm or less I am trying.

Further preferably, the thickness is 1.5
The thickness of 1.5 μm or more and 5 μm or less means that the thickness is 1.5
This is because from μm or more, for example, sufficient seizure resistance is exhibited against roll forming of a welded titanium pipe.

Since the surface of the nitrogen-rich layer on the surface is relatively thin, it is manufactured by RSV of Germany, ANALYMAT.
It was determined from the results of mainly measuring the amounts of N and Ti in the depth direction with a −2504 type glow discharge emission spectrophotometer. Table 1 shows the measurement conditions of the analyzer.

[0013]

[Table 1]

The method used in Nippon Steel Techno Research Co., Ltd. was used to calculate the relationship between composition (amount of N and Ti) and depth from the relationship between emission intensity and sputtering time. The outline of this method is that TiN is used as a reference sample for obtaining the composition from the emission intensity, and the density for obtaining the depth from the amount of sputtering is obtained from N for TiN and Ti for metallic titanium. An example of the obtained results is shown in FIG. From the intersection of the N curve of this figure and the N level of the base metal,
The thickness of the nitrogen-enriched layer is about 2.2μ as shown by the arrow.
It can be read as m. Actually, the diameter is 4 when sputtering.
It is expected that this value will be smaller than this value due to the variation in depth within mm, but for convenience, this value was used as the thickness of the nitrogen-enriched layer.

The method for producing a titanium thin plate for forming according to the present invention is premised on a batch type annealing furnace which is industrially used for annealing a titanium coil and which can be evacuated. The reason why titanium is heated in the nitriding atmosphere at a heating temperature of 550 ° C. or higher and 700 ° C. or lower is that the nitrogen-rich layer can be formed at low cost by heating in the nitriding atmosphere. Further, if the temperature is lower than 550 ° C., the nitriding reaction is slow and it takes a long time. This is because the deterioration of the material becomes a problem. Here, the nitriding atmosphere is, for example, a nitrogen atmosphere having a purity of 99.999% or more. Ammonia gas may cause embrittlement due to hydrogen absorption and deterioration of formability due to it, and ion nitriding cannot form an electric field almost uniformly on the entire coil-shaped surface.
Not suitable for the present invention.

Further, preferably, the as-cold-rolled titanium is heated in a nitriding atmosphere at a heating temperature of 600.degree.
The reason why heating is performed at a temperature of 0 ° C. or lower is that annealing can be performed simultaneously with nitriding. The preferred heating temperature is 60
The reason why the temperature is 0 ° C. or higher is that the recrystallization and grain growth necessary for workability are sufficiently generated. It should be noted that, when the as-cold-rolled titanium was nitrided at a relatively low temperature, it was recognized that the titanium was more likely to be nitrided as compared with the nitrided product after annealing.

Since the present invention uses nitriding in a nitriding atmosphere, if titanium is thoroughly washed and the impure gas of the nitrogen gas introduced in the furnace is controlled, it can be produced with extremely stable quality.

[0018]

Example No. of Table 2 1-4 and No. Regarding 11 to 13, cold rolled product coils (annealed) of two types of pure titanium having a plate thickness of 0.5 mm were prepared. Moreover, No. Regarding Nos. 5, 6 and 14, a cold rolled coil (unannealed) of pure titanium type 2 having a plate thickness of 0.5 mm was prepared. These coils were vacuumed using a batch type vacuum annealing furnace, and then nitrided in a nitriding atmosphere under various heating temperatures and heating time conditions shown in Table 2. Next, slit these coils into hoops,
Welded pipes were manufactured and the seizure resistance was evaluated by the presence or absence of roll flaws. The deterioration of the material was evaluated by the adhesion bendability, and the presence or absence of coloring was evaluated by visual observation. The above results are also shown in Table 2.

The method of forming the pipe was a method of making the squeeze roll to have a large and constant reduction to a level where seizure flaws are generated in a hoop which is a product annealed in an ordinary Ar atmosphere. The one in which the burn-in defect was eliminated was evaluated as ◯, the one in which the burn-in defect was reduced was evaluated as Δ, and the one in which the burn-in defect was generated was evaluated as x. For close contact bending, those with no cracks are marked with ○, and cracks with No. 14 was designated as x. Moreover, No. 12 and 13 were also marked with x. As for coloring, those with no coloring were marked with ◯, those with an extremely thin gold color were marked with Δ, and those colored with gold were marked with x.

For example, No. 1 of the present invention example. In No. 1, a titanium product coil was heated in a nitrogen atmosphere at 550 ° C. for 5 hours, and the surface layer thereof had a 0.5 μm nitrogen-rich layer. In the pipe making, seizure flaws were reduced, there was no cracking in tight bending, and there was no coloring. As a result of the above, it was determined that the coil was superior to the conventional product coil, and the overall evaluation was evaluated as ◯ (good).

No. Nos. 5, 6 and 14 are the results of the test using the as-cold rolled coil (unannealed). No.
No. 5 has good adhesion bending by heating at 600 ° C., but N
o. No. 14 had poor adhesion bending due to insufficient recrystallization and grain growth by heating at 550 ° C. Furthermore, N
o. No. 5 was nitrided after annealing. Compared with No. 3, the nitrogen-enriched layer has the same thickness in a short time.

As a result of the above, 0.5 μm or more on the surface,
In the case of having a nitrogen-enriched layer of 0 μm or less, and preferably having a nitrogen-enriched layer of 1.5 μm or more and 5.0 μm or less on the surface, titanium that is comprehensively superior to the problems of the present invention is obtained. It can be a thin plate.

Further, such a titanium thin plate has a heating temperature of 550 ° C. or higher and 700 ° C. in a nitriding atmosphere of titanium.
It is obtained by heating at the following temperature, and preferably, as cold-rolled titanium is also heated at a heating temperature of 600 ° C. or higher and 700 ° C. or lower in a nitriding atmosphere, which also serves as an annealing step. be able to.

[0024]

[Table 2]

[0025]

EFFECTS OF THE INVENTION According to the present invention, there is provided a titanium thin plate for forming, which is free from problems such as material deterioration and coloring, has stable quality, and exhibits excellent seizure resistance during secondary processing such as roll forming. it can.

[Brief description of drawings]

FIG. The figure which shows the nitrogen concentration of 6 and depth.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Kosei 3434 Shimada, Hikari City, Yamaguchi Prefecture Shin Nippon Steel Co., Ltd. Hikari Steel Works (56) Reference JP-A-2-25559 (JP, A) ( 58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 8/24

Claims (2)

(57) [Claims] 1. A titanium thin plate for forming, which has a nitrogen-enriched layer on its surface and has a thickness of 0.5 μm or more and 5 μm or less. 2. The method for producing a titanium thin plate for forming according to claim 1, wherein the titanium is heated in a nitriding atmosphere at a heating temperature of 550 ° C. or higher and 700 ° C. or lower.