JPS6360269A - Heat-treatment of metallic titanium - Google Patents

Abstract

PURPOSE:To produce metallic Ti having fine surface luster and superior mechanical properties by heat treating metallic Ti under specified conditions in a high purity nitrogen atmosphere having a specified dew point. CONSTITUTION:Metallic Ti formed into a sheet or a wire rod by cold working is held at about 600-800 deg.C for <=5min in a gaseous N2 atmosphere having <=-30 deg.C dew point and <=700ppm concn. of O2 in a bright annealing furnace for steel. The metallic Ti is then cooled to <=300 deg.C in the same N2 atmosphere so as to prevent the tarnish of the surface during cooling. Since the existing equipment and the inexpensive treating gas are utilized, metallic Ti having superior characteristics is produced at a low cost.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to heat treatment of titanium metal.

[Prior art] Cold-worked titanium metal is usually heat treated at 600 to 800°C, but since titanium metal is a highly active metal, at high temperatures of 300°C or higher, it is susceptible to oxides, nitrides, and hydrogen. Therefore, heat treatment of titanium metal has traditionally been carried out in a high vacuum or in an argon gas atmosphere, but it requires special equipment and is difficult to handle in a high vacuum or argon gas atmosphere. This may result in increased costs.

Alternatively, when using existing equipment such as a bright annealing furnace for steel, a long and complicated process is required to change the atmosphere inside the furnace to argon gas, and a cheaper and simpler heat treatment method is desired. Ta.

[Problems to be Solved by the Invention] The object of the present invention is to heat-treat titanium metal in an atmosphere of high-purity nitrogen to produce titanium metal that has a glossy surface and excellent mechanical properties. The purpose of this is to inexpensively and easily produce superior titanium metal using existing equipment such as bright annealing furnaces for steel.

[Means for solving problems] The present invention uses titanium metal at a dew point of -30°C or lower.

600 to 800 in a nitrogen atmosphere with less than 700 ppm of oxygen
This is a heat treatment method for titanium metal, which is characterized in that the titanium metal is kept in a furnace at a temperature of 5 minutes or less for a required time of 5 minutes or less, and then cooled to 300°C or less in the atmosphere.

[Function, Examples] The present inventors performed a heat treatment on the metal titanium thin plates shown in Table 1 by holding them in various nitrogen atmospheres at 800°C for 5 minutes, and then cooling them to 300°C in the same atmosphere. The thickness and gloss of the oxide film on the surface of thin metal titanium plates were investigated.

FIG. 1 is a diagram showing the relationship between the surface film thickness of metallic titanium and the nitrogen atmosphere gas composition after heat treatment. In FIG. 1, 1 shows the case where the dew point of the nitrogen atmosphere gas is 112°C, 2 shows the case where the dew point is 120°C, 3 shows the dew point of 130°C, and 4 shows the case where the dew point is 158°C. In addition, chain MA-A in the figure indicates the thickness of the oxide film on the surface of metallic titanium.
, D, S (Glow discharge emission spectrometry: manufactured by RFV, Germany)
The figure shows the case of 500 people. The present inventors have found that when the thickness of the oxide film on the surface of metallic titanium is less than 500 mm, the surface of metallic titanium is not colored and excellent metallic luster is maintained. That is, in the range where the oxide film thickness is below A-A in FIG. 1, metallic luster is always maintained.

In order to reduce the thickness of the oxide film on the surface of metallic titanium to 500 Å or less, as shown in Fig. 1, for example, in nitrogen gas with a dew point of 120°C, the oxygen concentration should be reduced to about 350 ppm or less (point B in the figure).
For nitrogen gas with a dew point of 130°C, it is approximately 700 ppm or less (point C in the diagram), and when the dew point is 158°C, it is approximately 800 ppm.
The oxygen concentration can be managed as follows.

Next, the present invention will be specifically explained.

In the present invention, metallic titanium refers to a titanium material that is heat treated after cold working, such as a thin plate or wire, and is desired to have excellent material quality and beautiful surface properties after heat treatment. In the present invention, nitrogen gas with a dew point of 130° C. or less and an oxygen concentration of 700 ppm or less is used, but the conditions for this nitrogen gas are within a range that can be easily managed with existing equipment, such as a bright annealing furnace for steel, and As mentioned above, this is the range in which titanium metal with excellent metallic luster can be obtained. Heat treatment is 600-800℃
However, if the temperature is below 600°C, the toughness after heat treatment will be insufficient, and in the case of thin plates or wires, heating at 800°C for more than 5 minutes will not improve the quality of the material. do not have.

Although Fig. 1 shows an example of heating at 800°C for 5 minutes, if the heating temperature is lower than this or the heating time is shorter than this, the thickness of the oxide film on the surface of titanium metal will be It is clear that it is even thinner than 3 in Figure 1 and provides excellent metallic luster. In the present invention, the titanium metal after heating is 300
The sample is cooled in the same nitrogen atmosphere to a temperature below 0.degree. C., in order to prevent discoloration during cooling.

Table 2 shows a comparison of the heat treatment conditions and the properties of titanium metal after heat treatment of the same thin plates of titanium metal as in Table 1, A when heat treated by the method of the present invention, and B when heat treated in a conventional argon gas atmosphere. It is. As shown in Table 2 A, titanium metal heat-treated by the method of the present invention has standard mechanical properties, and its surface has a silvery white and excellent metallic luster. It has the same properties as heat-treated material B.

Table 2 * GLO5S 肚T [MI1SE, GM-3M, Murakami Color Co., Ltd.].

[Effects of the Invention] According to the present invention, it is possible to heat-treat titanium metal inexpensively and easily without using expensive argon gas or a high-vacuum annealing furnace, and to produce excellent titanium metal that is comparable to conventional products. became possible. In addition, the dew point of nitrogen gas and oxygen 1 of the present invention
The degree of heat treatment of titanium metal is within the range that can be sufficiently controlled using existing equipment such as steel, so it is now possible to easily heat treat titanium metal with existing equipment without installing special equipment. The effect is great.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the dew point of a nitrogen atmosphere, the oxygen concentration, and the oxide film thickness on the surface of metal titanium after heat treatment. 1: Dew point -12℃, 2: Dew point -20℃, 3: Dew point -30
℃, 4: Dew point -58℃.

Claims (1)

[Claims] Metal titanium, dew point: -30℃ or less, oxygen: 700pp
A method for heat treatment of titanium metal, characterized by holding it in a furnace at 600 to 800°C for a time of 5 minutes or less in a nitrogen atmosphere of 300°C or less, and then cooling it in the atmosphere to 300°C or less.