JPS5825421A - Manufacture of titanium alloy rolling material having satisfactory texture - Google Patents

Abstract

PURPOSE:To manufacture a titanium alloy which has a satisfactory texture and is excellent in mechanical property, by hot-rolling a rolling material obtained from an (alpha)+(beta) type titanium alloy ingot, in an (alpha)+(beta) area, giving it sufficient internal distortion, and after that, executing are equi-axes crystal forming treatment. CONSTITUTION:A rolling material is obtained by cogging an ingot of an (alpha)+ (beta) type titanum alloy such as Ti-6Al-4V, etc. Subsequently, this material is hot-rolled by giving >=50% draft in an (alpha)+(beta) area, and accumulation of internal distortion is increased, so that recrystallization in the following equi-axed crystal forming treatment is simplified. Subsequently, the obtained hot rolling material is hot-rolled, and after that, immediately, it is slowly cooled to about 700 deg.C at a speed of about 150 deg.C/hr by means of furnace cooling and is subjected to the equi-axed crystal forming treatment, and after that, is is cooled in the atmosphere to room temperature, by which it is possible to obtain a rolling material of an (alpha)+(beta) type titanium alloy, which has a satisfactory crystal structure being uniform and fine, and is excellent in mechanical property.

Description

Detailed Description of the Invention The present invention provides a method for producing a rolled titanium alloy material with a good structure,
The present invention relates to a method for producing an α+β deaf prickly tough alloy rolled material having a uniform and fine crystal structure and excellent mechanical properties.

Titanium alloys have a high strength-to-weight ratio (strength to weight ratio), so they are suitable for applications that require high reliability, such as aircraft and space development equipment that require light weight and high strength. Or, it requires durability under harsh conditions such as high temperature, high load, and high rot★.
- For which applications it is not sufficient to simply have high strength and high corrosion resistance, especially when KFi is supplied in the form of II or rods, during the manufacturing process into the final product as a melt or as a structural part. Since it must go through forming processing, it is essential that it has extremely high ductility. And this ductile reform! It is essential that IK has a uniform and fine structure.

By the way, titanium alloy material is one of the difficult-to-process materials, and there are almost no reports regarding its manufacturing method. For example, forged materials are disclosed in JP-A-51-77885,
There are no examples of rolled material being put to practical use, and there are no reports of it being used in Kitakami.

Incidentally, 1. The structure of the above-mentioned forged material is that after β forging, processing of 10% or more is continuously performed in the α+β region.

Next, after heating to the β region, α + at a cooling rate of 20°C/min or more
Cooling to the β region or α region is performed from K, thereby making the structure finer.

The inventors of the present invention have conducted extensive research to provide a method for producing rolled T1 alloy material that exhibits a uniform and fine structure and has excellent mechanical properties. It was discovered that this method is extremely effective for uniform and fine graining, and the present invention was completed.

Here, the present invention involves blooming an α+β type titanium alloy ingot, and rolling the obtained rolled material in the α+β range of 60! This is a method for producing a rolled titanium alloy material with a good structure, which is characterized by hot rolling with a working degree of X or higher, and then subjecting the obtained good hot rolled material to equiaxed rolling treatment.

Here, the equiaxed heavy forming process is immediately followed by hot rolling, followed by gradual cooling, preferably by furnace cooling at 150°C/h to 00°C.
cooled at a rate of about 100 m or less, then cooled to room temperature in the air, or after hot rolling, maintained at a temperature of 800 to 950°C for a predetermined period of time, generally for 80 minutes or more, preferably for 1 hour or more,
After further K or hot rolling, it is first allowed to cool down to 700°C or less, then reheated in a furnace maintained at 860 to 950°C and kept at SOO to 950°C for a predetermined time, generally tj 80 minutes or more, preferably 1 hour or more. This is a treatment in which the formation of isowa island crystals is promoted by this treatment.According to the present invention, 60% or more of processing is achieved in the α+β region during hot rolling. It is done, but α+
Providing a working degree of 50% or more in the β region greatly reduces the accumulation of internal strain, facilitates recrystallization during slow cooling or reheating in the subsequent equiaxed superposition process 11, and facilitates equiaxed formation. It promotes the production of one grain. In the isothermal formation process, when isothermal holding is carried out, it is held at 800 to 960°C for a predetermined time, but if this isothermal holding temperature exceeds 950°C, the proportion of I in the tissue becomes too large. Organizational improvements become more rapid. On the other hand, if the temperature i is lower than 800° C., the recrystallization reaction itself will be delayed in time, making it impractical.

The equiaxed mass thus obtained is a crystal whose grain morphology is isodirectional, and ideally it consists of crystal grains that do not extend in any particular direction in any cross section.

The present invention thus relates to a method for manufacturing a rolled titanium alloy material, such as a titanium alloy plate or a titanium bar, and the shape wA is not particularly limited as long as it is manufactured by a rolling method. The titanium alloy is preferably an α+β type titanium alloy, a typical example of which is Ti-6At-4V, but other examples include TI-8Mn, TITl-
4Al-4,Ti-? Al-4Mo.

T1-8Al-2h5V, T i-4Aj1-4Aj
-4, T i -4kl-8M.

-IV, Ti-2Fe-2Cr-2Mo, Tl-5
Examples include At-175cr-L25F.

Here, the processing kFi in the present invention is defined as follows.

I 00 The attached drawings are diagrams schematically explaining the equiaxed layer forming process in the EJAK of the present invention. Figure 2 shows the case where the material is left to cool and then heated and held again at 800 to 950°C.The higher the temperature, the shorter the heating holding time. Good. Slow cooling can be carried out to 700°C, and after that, it may be left to cool in the atmosphere. Even when cooling once and then reheating, let it cool to ti700°C if necessary. It may be reheated, but if the rolling finishing temperature is lower than 800°C, it may be reheated to 800°C.
~960'CK It is necessary to perform a process of holding for a predetermined time (see FIG. 2).

The invention will now be further explained in connection with examples.

Example Tl-6At-4V alloy was vacuum arc melted to produce a 1 ton ingot, which was bloomed and then peeled to remove surface flaws, as shown in Table 1. , diameter 66■
A round bar to a square bar of 1 g G-square was produced and rolled into a round bar with a diameter of 86 pieces using a continuous hole rolling mill.

The respective rolling conditions and results are summarized in Table 1.

Note that various methods for determining tissues have been presented as standards based on past experience and achievements. For ζζ, as shown in Figure 8, the one with α+β equiaxed heavy structure is classified as first class lol! , see Figure 8 (IL)), the isoforce ratio of one grain has not progressed, that is, the state in which something similar to the processed structure remains is 4.
(see Figure 8 (d)), and as an intermediate stage, those with a low degree of residual processed structure (see Figure 8 (e))
, those with insufficient isocycle conversion (see section 8-0)) and 8th grade and 2nd grade! There were 4 classes in total, divided into 1lltK. Grades 1 to 2 are structures that can withstand practical use, and grades 8 to 4 are structures that require renumbering.

As can be seen from the results shown in Table 1, in A-G obtained by the method of the present invention, the degree of processing in the α+β region is 50% or more, and the rolled eel is cooled by slow cooling or slow reheating. By doing so, it is possible to obtain a good structure with a grade 1 or 2 structure. On the other hand, in the case where the degree of working in the α+β region is low and the steel is allowed to cool after rolling, the structure is judged to be grade 8 to 4, which indicates a poor structure.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams schematically explaining the isometric tool forming process in the present invention; FIG. a), (b)
, (e) and (d) are grade 1, grade 2, and grade 8, respectively.
Isamu/Tuzo corresponding to grade and grade 4 kumisen, 2 figure time 藺

Claims (1)

[Claims] The α+β deaf prickly tough alloy ingot is rolled, and the resulting compressed material is hot rolled with a working degree of 60% or more in the α+β region.1st, the resulting good hot rolled material is subjected to equiaxed crystal formation treatment. A method for producing a rolled titanium alloy material with a favorable structure.