JPS6367549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a rolled titanium alloy material with a good structure, particularly a method for producing a rolled material of α+β type titanium alloy having a uniform and fine crystal structure and excellent mechanical properties. Regarding. Titanium alloy has specific strength (ratio of strength to weight)
Because of its large strength, it is suitable for applications that require high reliability, such as aircraft and space development equipment that require lightweight and high strength, and high temperature, high load,
It is used in applications that require durability under harsh conditions such as corrosion. However, for these applications, simply having high strength and high corrosion resistance is not enough, especially when supplied in the form of wire or rod, during the manufacturing stage into the final product as a bolt or structural component. Appropriate ductility is essential as it always goes through a forming process. In order to improve this ductility, it is essential to have a uniform and fine structure. By the way, titanium alloy material is one of the difficult-to-process materials.
There are few reports regarding its manufacturing method. For example, a rolled material is disclosed in JP-A-51-77385, but a rolled material has not been put to practical use, nor has there been any report thereof. By the way, the production of the above-mentioned forged material is carried out after β forging.
Continuously perform processing of 10% or more in the α+β region, then heat to the β region, and then process α at a cooling rate of 20℃/min or more.
This is done by cooling to the +β region or α region, thereby making the structure finer. The present inventors have conducted intensive research on hot rolling of titanium alloys in order to provide a method for producing a rolled titanium alloy material with high strength and high ductility. As a result, according to the findings of the present inventors, when high-speed rolling of titanium alloy is carried out using equipment for high-speed rolling of steel, it is possible to prevent the temperature rise due to processing heat of the titanium alloy as much as possible to maintain a good structure. I came to the conclusion that it was necessary to do so. In particular, the final finish rolling process of wire rod rolling is designed to be very compact, and therefore a very large amount of processing is performed in a short period of time. Therefore, in the case of titanium alloys, the temperature rises abnormally during this finish rolling process, causing structural defects. In order to prevent heat generation, cooling may first be considered, but since the heat is generated during processing, water cooling immediately after rolling did not seem to make much sense from a conventional perspective, but the present invention According to their experiments, it was found that such rapid cooling is extremely effective, that is, by quenching in this manner, a material with a good structure and extremely high toughness can be obtained. Also, when performing high-speed machining, a rapid temperature rise occurs, but when such a rapid temperature rise occurs, there is a time lag, so
As a result, the transformation point also rose, and it was found that β-transformation of the rolled material could be prevented by high-speed and high-level processing. Thus, in the present invention, α+β
When manufacturing type titanium alloy rolled material, α+β
α+β type titanium characterized by heating the mold alloy to 1050°C or less to start rolling, giving it 50% or more processing within a temperature range of 950 to 700°C in a finishing rolling mill group, and rapidly cooling immediately after rolling. This is a method for manufacturing rolled alloy material. According to the present invention, the rolled material is heated to 1,050°C or lower, because if the temperature exceeds 1,050°C, gas absorption in the surface layer becomes significant, reducing workability and causing cracks. In the latter half of rolling, that is, in the finish rolling mill group in a series of continuous rolling, the temperature is 950 to 700℃.
Hot rolling is carried out in the temperature range of
If the temperature exceeds 950°C, the β phase increases and becomes an acicular structure even after water cooling, which is undesirable. On the other hand, if the temperature exceeds 700°C, the workability becomes extremely poor and cracks occur. In addition, in the present invention, in the latter half of rolling,
More than 50% of processing is added by rolling in the range of 950 to 700℃, which is due to high-speed processing (finish rolling speed is generally 1 M/S or more) that performs advanced processing in the finishing rolling mill group. According to
This is because the temperature rise becomes rapid, and therefore the transformation point shifts to the high temperature side, that is, transformation does not occur even at temperatures exceeding the transformation point, and processing in the β region can be avoided. That is, when manufacturing plates and bars using a multi-stand continuous rolling mill, the temperature of the rolled material due to processing heat during rolling increases more than that of steel, especially since titanium alloy has a high specific strength. In particular, in the production of bars, a series of groove rolling mills are lined up, for example, about 25 stands, and the temperature rise is particularly significant at the final stage, that is, the last finishing mill group consisting of one third of the stands. Therefore, it is sufficient to control the temperature rise at this final stage. The β-transformation caused by such temperature rise can be effectively prevented by rolling at high speed or by rapidly cooling immediately after rolling. Therefore, according to the present invention, processing with a total reduction of 50% or more is carried out in a temperature range of 950 to 700°C by a group of finishing mills. Thus, the actual rolling
It will be carried out in the α+β region of 950 to 700℃,
Combined with rapid cooling immediately after rolling, it is possible to effectively refine the structure. Typical α+β type titanium alloys to which the present invention is applied are Ti-6Al-4V and Ti-4Al-4Mn, and other examples include Ti-7Al-4Mo and Ti-
3Al−2.5V, Ti−4Al−3Mo−1V, Ti−2Fe−
Examples include 2Cr-2Mo. However, it will be understood that the invention is not limited thereto. The invention will now be further explained in connection with examples. Example 1 ton of ingot was produced by vacuum arc melting of Ti-6Al-4V alloy, and after blooming and rolling, peeling was performed to remove surface defects, and then as shown in Table 1. , round bars with diameters of 23 mm and 130 mm were produced and rolled into round bars with a diameter of 9 mm using a continuous hole rolling mill. Table 1 summarizes the rolling conditions and mechanical properties of the obtained bars. In the table, symbols A to G are examples according to the present invention, and symbols H and I are comparative examples. As can be seen from the results in Table 1, by water cooling after rolling, a significant increase in strength and improvement in ductility were observed, and the resulting microstructures were all good. In the comparative example, due to the temperature increase due to high-speed rolling, the temperature in the center of the rolled material exceeded the transformation point.
Therefore, it is thought that processing was performed in the β region, resulting in poor structure. 【table】

Claims (1)

[Claims] 1. When manufacturing α+β type titanium alloy rolled material using a continuous rolling mill, the α+β type alloy is heated to 1050°C or less to start rolling, and the finish rolling mill group produces 950°C.
Gives more than 50% processing within the temperature range of ~700℃,
α+β characterized by rapid cooling immediately after rolling
Method for producing type titanium alloy rolled material.