JPS62149859A - Production of beta type titanium alloy wire - Google Patents

Abstract

PURPOSE:To produce a wire having good dimensional accuracy and good surface quality by subjecting a beta type titanium alloy successively to heating treatments respectively at specific temps. in the atm. and vacuum, then cooling the alloy at a specific rate and subjecting the cooled alloy to a soln. heat treatment then to cold drawing. CONSTITUTION:The beta type titanium alloy strand is heated for about 1min-1hr at 400-650 deg.C in the atm. to form an oxide film on the surface. The strand is then heated and held for about 5-60min to and at about the beta transformation point or above - beta transformation point + about 400 deg.C or below in the vacuum or inert gaseous atmosphere and thereafter the strand is cooled at a cooling rate of >=1.8 deg.C/min and is thereby subjected to the soln. heat treatment. A lubricating agent is applied on the surface of the strand consisting of the betatitanium alloy subjected to such soln. heat treatment and the strand is cold drawn. The wire after the drawing is descaled and is subjected to a soln. heat treatment or aging treatment for solutionization, etc., according to the requirements for the final product.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a β-type titanium alloy wire, and in particular to a method for producing a wire with good dimensional accuracy and surface quality. Regarding the method.

Background of the lecture Titanium and titanium alloys have excellent specific strength, corrosion resistance, and heat resistance, and are therefore used in a wide range of applications such as aerospace materials, various chemical plants, and seawater desalination equipment.

Conventionally, titanium alloys include T i -6A l -4
α-10β-type titanium alloys, such as V-alloys, have been widely used, but α+β-type alloys have poor cold workability and rely on cutting for much of the processing, resulting in low yields in the final product. It has the disadvantage of being very low. Therefore, α+
The use of β-type titanium alloys has been expanding in recent years because they have superior cold workability and high strength compared to β-type alloys.

One of the fields in which this is used is wire rods as materials for Pol 1-type materials, spring materials, etc., which take advantage of their excellent cold workability and high strength when subjected to aging treatment. In other words, the β-type titanium alloy has excellent cold workability in the β single set after solution treatment, so cold drawing is easy.
Depending on the purpose of use, high strength can be obtained by subjecting this wire to aging heat treatment after forming.

In addition, the β-type titanium alloy in this specification refers to the entire metastable β-type titanium alloy that forms a single β group even at room temperature by rapid cooling from the β region, precipitates the α phase by aging treatment, and has age hardenability. In particular, Ti-15V-3Cr-3Sn- has excellent cold workability and does not induce emulsion side.
3A1 alloy, Ti-15Mo-52r-3A1 alloy, T
i-11,5Mo-6Zr-4,5Sn alloy, 1'
Examples include alloys such as i-13V-L I Cr-3A I alloy.

In general, titanium materials such as pure titanium have excellent cold workability, and can be cold-drawn and drawn to a high degree of workability.

However, such titanium materials have the disadvantage that they easily seize with tools, and if only a normal lubricant for drawing wire is used, it may seize with drawing dies and wire drawing I can't. Moreover, even if the wire can be drawn, many large die flaws will occur on the surface of the material, resulting in a defective product.

For this reason, titanium materials generally have 40
The wire is heated at a temperature of 0 to 650° C. to form an oxide film with lubricating properties on the surface, and then a lubricant is applied to the wire for drawing.

However, in the case of β-type titanium alloy, 4. O0~650
When atmospheric heating is performed at °C, the α phase precipitates in the β phase and the material hardens, resulting in a significant decrease in cold workability and difficulty in wire drawing.

To avoid this, it is possible to form an oxide film on the surface by heating in the atmosphere at a temperature above the β-transformation point at which the α-phase does not precipitate, but most β-type titanium alloys have a β-transformation point of 7.
The temperature is 50'C or higher, and the oxide film formed by atmospheric heating in this temperature range becomes hard and brittle. Therefore, it cannot be used as a lubricating film during drawing and wire drawing. Moreover, when the titanium material is heated in the atmosphere in the β phase, it easily absorbs oxygen, and the parent phase under the oxide film also forms an oxygen-rich layer with poor workability.

Therefore, in cold drawing wire drawing of β-type titanium alloy,
It is not possible to use the same method as for pure titanium.

On the other hand, as a manufacturing technology for wire rods, there are methods that use roller dies or groove rolling instead of drawing wire drawing.
In wire drawing by these methods, the dimensional accuracy of the manufactured wire is poor, and particularly good roundness cannot be obtained, so that it cannot be used as a product as it is.

Therefore, when such a roller die or groove rolling is used, drawing wire drawing is more or less required as a subsequent process.

Because of this situation, there has conventionally been no Ti-effective method for drawing and wire-drawing β-type titanium alloys.

In view of the situation described in ``Emi-(l戊)'' 2, the present invention enables cold drawing wire drawing processing of β-type titanium alloy without causing seizure with dies, and improves dimensional accuracy and surface quality. (1) We provide a method for manufacturing wire rods with good γ.

That is, in the cold drawing process of the β+24 titanium alloy, the present invention generates an oxide film on the surface of the 1-cough alloy by heating it in the air at 400 to 650'C, and then heats it in the atmosphere in a vacuum or an inert gas atmosphere. , β-type titanium alloy wire is heated to a temperature equal to or higher than the β-transformation point, and then subjected to solution treatment by cooling at a rate of 1.8°C/min or higher, followed by cold drawing and wire drawing. This relates to a manufacturing method.

Specific details of (2) The titanium alloy material to which the present invention is directed is a β-type titanium alloy material with excellent cold workability, and is particularly effective in β-type titanium alloys in which martensite is not induced by cold working. be.

Titanium alloy products generally start with an ingot breakdown process in order to destroy the cast structure of the ingot and obtain an intermediate material suitable for subsequent processes. Ingot breakdown is performed by blooming or forging an ingot. Next, the manufactured billet is processed into a cable wire for cold wire drawing through a rolling process of hot rolling to a predetermined size and a descaling process such as pickling and peel link processing.

This cable wire is used as a raw material and subjected to cold wire drawing according to the product dimensions, and finally heat treatment such as annealing (solution treatment) or aging treatment is performed according to the use of the product.

The main process of the present invention is a process of cold drawing the hot-rolled wire that has been descaled by drawing, and the processing period in the previous process is not a requirement of the present invention. Any process can be used. In addition, there is no objection to performing roller die or groove rolling in the cold wire drawing process. When such a processing method is used, the cold wire drawing of the present invention is finally performed in order to improve dimensional accuracy.

As mentioned above, conventional cold drawing wire drawing of titanium-based materials involves heating the strands in the atmosphere at a temperature of 400 to 650°C to generate an oxide film with lubricating properties on the surface, and then This was done by applying a lubricant for wire drawing.

However, in the case of β-type titanium alloys, when heated at a temperature of 400 to 650°C, which produces an oxide film with lubricating properties, the α phase precipitates, significantly reducing the cold workability of the material. .

Therefore, in order to form a single β pair with excellent cold workability, it is necessary to heat it to a temperature exceeding the β transformation point, but the β transformation point of most target β-type titanium alloys is 750°C. When heated in the atmosphere to a temperature exceeding 750°C, the oxide film turns gray and loses its lubricating performance.

Therefore, in the case of β-type titanium alloys, the production process of an oxide film with lubricating performance and the solution treatment process are separated, and, for example, wires that have been drawn in advance by roller dies or groove rolling to strands or intermediate dimensions are is heated in the air at a temperature of 400 to 650°C for 1 minute to 1 hour to form an oxide film. Naturally, the heating time varies depending on the heating temperature, and heating is performed for a long time at a low temperature and for a short time at a high temperature. The oxide film produced here has a color ranging from brownish-purple to dull purple, and has good lubrication performance. As the heating furnace for this treatment, either a continuous furnace or a batch furnace can be used. The heating method may be an electric furnace or a heating furnace using fuel such as heavy oil or propane. Since the Nl cable partial pressure differs depending on the furnace used, the temperature and time may be adjusted in each furnace.

Next, the wire subjected to the above treatment is heated and held in vacuum or in an inert gas at a temperature equal to or higher than the β transformation point for 5 to 60 minutes to 1.8°C.
Solution treatment is performed by cooling at a rate of 2/min or more.

The reason why the solution treatment is performed in vacuum or in an inert gas is to prevent the surface oxidation performed in the previous step from proceeding any further.

Heating at a temperature higher than the β-transformation point is done in the previous step 4.
This is to dissolve the α phase precipitated by heating at 00 to 650°C into the β phase, and the upper limit temperature is preferably below the β transformation point +400°C. This is because heating at a temperature exceeding the β transformation point +400'C causes the β grains to become coarser and the ductility of the material to decrease.

The reason why the heating time was set to 5 to 60 minutes is because diffusion is not sufficient if the heating time is 5 minutes or less, and the α phase precipitated in the previous step is sufficient.
! '! This is to prevent loss of time, and the reason why we set it to 60 minutes or less is to avoid losing 60 minutes.
Addition of time exceeding 0 minutes;:! ! This is because if this is done, the β grains will become coarser and the ductility of the material will decrease.

The reason why the cooling rate was set to 1.8℃/min or more was 1.
．． This is because if the cooling rate is less than 8° C./min, precipitation of α phase may occur during cooling of the material, which may reduce cold workability.

A lubricant 1, such as a metal soap lubricant or molybdenum disulfide, which is generally used for cold drawing of titanium-based materials, is applied to the surface of the β-type titanium alloy wire that has been solution-treated in this way, and cold drawing is performed. I do.

The wire rod after wire drawing is descaled by pickling, and then subjected to solution treatment, solution aging treatment, etc., depending on the requirements of the final product.

Benefits of the invention - We have established a cold drawing wire drawing technology for β-type titanium alloys, which has been increasingly used in recent years, and have made it possible to manufacture wire rods with good dimensional accuracy and surface quality.

Real Part J1 and Comparative Example As one of the β-type titanium alloys, a hot-rolled wire rod with a diameter of 12 mmφ was manufactured from a Ti-15V-3Cr-3Sn-3A1 alloy having the ordinary components shown in Table 1. Next, the oxide film and oxygen-enriched layer of this wire were removed by peeling, and the wire was drawn with a roller die to obtain a diameter of 3.
A wire rod with a diameter of 1.5 nvnφ was produced as a prototype using a strand of wire with a diameter of 0 mmφ as a test material.

The results of trial production of this wire rod are shown in Table 2 together with comparative examples. Second
The oxide coating treatment (*1) shown in the table was carried out using a continuous heavy oil heating furnace, and the solution treatment (*2) was heated in a vacuum using a three-room type vacuum heating furnace and cooled with Ar gas. Roundness (*3) indicates the difference between the maximum and minimum diameters in a round cross section of a wire.

As shown in the results in Table 2, 1. Cold drawing wire drawing using the method of the present invention was able to draw wire from 3.0 mmφ to 1.5 mmφ, but this method deviated from the method of the present invention.

In other words, in the case of only the oxide film treatment as in the case of conventional pure titanium, or in the case of atmospheric heating at a temperature range approximately 50°C above the β transformation point (800°C), the The line will break. Also, deep die scratches occurred on the surface. On the other hand, wire drawing was performed using roller dies and groove rolling.

Although it is possible to draw wire up to 1.5 mφ, the roundness is significantly greater than that obtained by drawing and drawing, and roll flaws remain. From the above, it can be seen that the method of the present invention is highly effective in obtaining wire rods with excellent dimensional accuracy and surface quality.

Table 1 Chemical composition of sample material (wt%) Margin below

Claims (1)

[Claims] During cold drawing wire drawing of β-type titanium alloy, an oxide film is formed on the surface of the alloy by heating in the air at 400 to 650°C, and then this is heated to a temperature higher than the β transformation point in a vacuum or in an inert gas atmosphere. temperature, followed by 1.8°C/mi
A method for manufacturing a β-type titanium alloy wire, which comprises cooling at a rate of n or more and solution treatment, followed by cold drawing and wire drawing.