JPS62120469A - Manufacture of titanium alloy material excellent in strength and ductility - Google Patents

Abstract

PURPOSE:To easily manufacture a Ti alloy material excellent in mechanical properties such as strength, ductility, etc., at a low cost by applying hot working to a Ti alloy stock having a specific composition consisting of V, Cr, Sn, Al and Ti under proper conditions. CONSTITUTION:In manufacturing a Ti alloy material consisting of, by weight, 14-16% V, 2.5-3.5% Cr, 2.5-3.5% Sn, 2.5-3.5% Al, and the balance Ti with inevitable impurities and further containing, if necessary, <=0.3% O, working is started after heating a stock for hot working to 900-1,050 deg.C. Successively, above-mentioned working stock is subjected to working at >=50% draft at at least 650-900 deg.C, where at >=30% draft at 650-850 deg.C, and working is finished at 650-800 deg.C. In this way, Ti-15V-3Cr-3Sn-3Al alloy material having superior mechanical properties and uniform structure can be obtained with obviating the necessity of cold working.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a titanium alloy material having excellent mechanical properties such as strength and ductility.

[Prior Art and Problems of A] Ti-15V-3Cr-3Sn-3Δg alloy has recently been widely used as a β-type alloy having high strength and excellent cold workability. This means that the tan alloy has ri
-6AJ -4V alloy and other α-)-β type 9-n alloys have significantly superior cold workability, allowing the adoption of cold-bracing cages and saving labor in machining the culm. It is.

However, the above Ti-15V-3Cr-3Sn
-3Δg alloy material (hereinafter referred to as the present alloy material 1) has conventionally been difficult to manufacture by hot working. This is because the non-uniformity of the mechanical properties and structure of this alloy material is a bottleneck, and hot working alone is insufficient to achieve sufficient mechanical properties and uniformity of the structure. This is because it was considered difficult to enter.

Therefore, this alloy material is rarely used as hot-worked, and in the past, it was generally produced through a three-step process: hot working, solution treatment, and cold working. By adding a cold working step after the processing step, improvements in mechanical properties and uniformity of mechanical properties and structure were attempted. However, this method requires a large number of steps and is not easy to manufacture, resulting in problems with productivity and production costs.

[Means for Solving the Problems] The present invention was created through repeated research and experiments in order to solve the above-mentioned conventional problems. It is an object of the present invention to provide a method for easily manufacturing the present alloy material having excellent mechanical properties and structure similar to the steps (solution treatment step - cold working step) using only a hot working step.

In order to achieve this objective, the present invention is designed to strictly control the hot working process and processing rate of materials for hot working (slabs, billets, etc.) in order to obtain the alloy material. In other words, V: 14 to 16 wt%,
Cr: 2.5-3. swt%, 3n: 2
．． 5-3.51N%, △fJ: 2.5-3.5
When manufacturing a titanium alloy material consisting of wt%, balance Ti and unavoidable impurities, for hot IJn 1: <r +
Heat 4 to 900°C or higher and 1050°C or lower with one finger 1 (Start processing, at least 650°C or higher and 900°C or lower to achieve a processing rate of 50%).
Add processing with a processing rate of 30% or more below, and 6! IO℃ or higher
[This process is characterized by finishing the processing at a temperature of 800°C or lower.

It should be noted that the titanium alloy material used in the present invention is
．． By avoiding the content of up to 3% or less, the strength of the present alloy material can be further increased.

The present invention will be explained in detail below.

The Bhutan alloy material produced in the present invention has a V: 14
-1(iW(%, Cr: 2.5-3.5wt%,
Sn: 2.5-3, 5Wj%, AJl: 2.5-3
．． 5 wt%, balance Ti and unavoidable impurities, including 0.3% or less oxygen. Although it is possible to increase the strength of the present alloy material by adding M cords, if the strength exceeds 0.13%, cold workability (cold formability) deteriorates significantly. Immediately solution treatment (800℃X2omin
→Water cooling), if the content of oxygen is 0.3% or less, it is possible to form a close contact surface, but if it exceeds 0.3%, bending will not be possible.
Even if J3 was used at −10t, breakage was observed, making it practically unapplicable.

This component is made into rB in a vacuum arc melting furnace or the like, and the melted ingots 1 to 1 are heated in a bulk furnace or continuous furnace, and then forged or bloomed to create a material for hot working.

Heating the ingot; the temperature is preferably 1000°C or more and 1200°C or less. The reason for this is that heating below 1000°C causes the casting structure to remain until the subsequent process, resulting in a decline in mechanical properties, as well as a decline in the workability of the ingot breakers during forging or blooming. cause, 120
This is because heating to a temperature exceeding 0° C. causes a significant decrease in yield due to oxidation.

When hot working the above-mentioned material for hot working, processing is started after heating to Ui of 900° C. or more and 1050° C. or less in a batch furnace or a continuous furnace. Thus, one important point of the present invention is to control the heating temperature of wood for hot processing.

After hot working, this alloy material is subjected to solution treatment and aging treatment before use, but the structure tends to become non-uniform during aging.
This leads to uneven mechanical properties and quality deterioration of this alloy material.
This is due to the non-uniformity of flash precipitate molecular motion and is caused by the segregation of added elements.

As a countermeasure to this, conventional methods sequentially perform ■ hot working, ■ solution treatment, ■ cold working, ■ solution treatment, and ■ aging treatment.
C It is considered a final product. In other words, following the hot working process, a cold working process is added as an essential process, and the hot (cold) kneading solution treatment (7+lI L-reconsolidation process) is repeated twice1.
In particular, the added elements are homogenized to ensure a homogeneous final product.

The present invention eliminates such a complicated process and strictly controls the heating temperature of the material for hot processing to a constant value f(), thereby achieving homogenization of the added elements and uniformity of the structure. The condition is to start processing after heating the material for hot processing to a temperature of 900° C. or higher and 1050° C. or lower in the β high temperature range.

The reason why the upper limit of the heating temperature was set at 1050°C is that if the heating temperature exceeds this temperature, the grain growth of β grains will be significant, resulting in coarsening and non-uniformity of β grains in the final product, which will deteriorate the mechanical properties. This is because it causes a decrease in

In addition, the lower limit of the heating temperature was set at 900°C because if the heating temperature is lower than this, the diffusion of the added elements will not be uniform.
This is because the problem of non-uniformity of the mechanical properties and structure of the final product arises as well as a decrease in the mechanical properties.

In addition, in some cases, the present invention may be applied to a material for hot processing of 90%
Start processing after heating to a temperature of 0°C or more and 1050°C or less,
It is also possible to recrystallize the β crystal by performing processing in a recrystallization region of 900° C. or higher, thereby further improving the homogenization of the additive elements.

Next, in the present invention, after heating the material for hot working as described above, hot working is performed under the following conditions.

(1) The processing rate is at least 50% or more at 650°C or more and 900°C or less, and 30% or more at 650°C or more and 850°C or less.

(2) The finishing temperature is 650°C or more and 800°C or less.

The importance of the present invention is to apply the heating temperature in this manner and strictly control the hot heating method. , at a point (hru.

In the conventional method, hot working T culm is followed by cold working.Working strain is applied to the workpiece in the culm, and the υβ product is homogenized and refined through recrystallization behavior in the subsequent solution treatment process. Attempts were made to homogenize the additive elements and improve the mechanical quality during aging. The present invention changes this idea and controls the processing rate in the low temperature range after the hot processing condition -F.
There is a tau that produces the same effect as two cold heaters.

The processing rate in (1) was specified in order to refine the β grains and modify the mechanical properties of the final product. This is because it is necessary to control the processing rate at
Only when 30% or more of processing is applied at temperatures below 0°C, a uniform rolling deformation structure is created.
The solution-treated structure also becomes uniform and fine. As a result, the mechanical properties and uniformity of these heat-treated materials deteriorate. If the processing rate is small, non-uniform recrystallization and recovery structure will occur in the solution heat treatment after hot rolling, and as a result, aging precipitation will become non-uniform in the subsequent aging heat treatment.

The reason why the lower limit of processing temperature and finishing temperature is set at 650℃ or higher is because when the processing temperature is lower than 650℃, the processing deformation resistance increases, making processing difficult, and α crystals precipitate during processing, causing the final product to deteriorate. This is because the mechanical properties and uniformity of the structure deteriorate.

The reason for limiting the finishing temperature to 800°C or less is that if the finishing rolling temperature exceeds 800°C, the rolling deformation structure becomes a non-uniform recovery structure during the cooling process after (middle) hot rolling. This is because the mechanical properties of the solution aged material deteriorate due to the uniform recovery structure. In other words, this non-uniform recovery structure affects the uniformity of the solution-aged structure after hot rolling, resulting in a decrease in the mechanical properties and non-uniformity of these heat-treated materials. It's for a reason.

[Rei/I! ! lPA] Next, examples of the present invention will be shown.

■Table 1 shows the chemical composition (wt%) of the test month.
The diameter of the l alloy ingot is 550mjR, and after heating it to 1050°C, it is heated to 100. It was forged thickly to create a material for hot processing.

Table 1 ■ The above materials for hot processing were processed under various hot processing conditions, and the results of investigating the mechanical properties of each are shown in Table 2 below.
In the 1° hot working shown in the table, test j1 was precipitated from the above hot working wood + J, and the test piece was heated to a temperature range of 1100°C to 875°C, and then the finishing temperature 1α was 800°C. The experiment was carried out at a temperature range of 625°C to 625°C. The top plate thickness is 10 mm. Hot heating 1. The subsequent solution treatment step is 800℃ x 20m1
n → Air cooling, aging treatment regulations are 480℃ x 14 hours
r-+ air cooling (STAl), 510°C x 14 hr → air cooling (
STA2) article 2 f1. Some materials It (1 in the table)
! +, 16), after hot working, solution treatment and cold working (5 cold working in L direction) were carried out for comparison.

■The mechanical properties of the processed materials in Table 2 are as follows: plate thickness 7tta from the plate thickness center, '4' row 12.5m, G, 1, 5
Ten 0 m plate-shaped tensile test pieces were taken in the L direction for each processing condition and investigated.

Further, the β grain size in the table was determined by measuring the β grain size at L/(thickness section parallel to the rolling direction) using a line segment method for each processing condition.

In addition, the ultrasonic flaw detection noise level in Table 2 is as follows:
G V15-1.4=50%.

Iv, as is clear from Table 2, the processed yarn 1' of the present invention
PJIj in t, materials of 1 to 9 are S 1-A
1 to strength 135, 9 f/am 2 or more, elongation 5%
Above, Sr'A2 has a strength of 130Kgf/11m2 or more,
Excellent strength and ductility with an elongation of 5% or more have been obtained, and the standard difference in strength is 0.3 or less, with small variations. These mechanical properties are equivalent to the material of the conventional method No. 16 (adding cold working culm after hot working culm).

On the other hand, if one of the conditions of heating temperature, finishing temperature, processing temperature and processing rate specified by the present invention is missing b, 0!
110-15) G, mechanical properties are inferior to materials made by conventional methods. From this, the material for hot processing is 9
After heating to a temperature of 00°C or more and 1050°C or less, at least 650°C or more and 900°C or less with a processing rate of 50% or more, and then heating at a rate of 650°C or more and 850'''C or less] [Add processing with a rate of 30% or more, and It is clear that finishing the processing at a temperature of 800°C or higher is an essential condition for producing this alloy material with excellent mechanical properties as hot-processed.

Further, according to the present invention, the noise level during ultrasonic flaw detection is significantly reduced, and the ultrasonic detection 14 becomes easier.

This is because the structure is made more uniform by employing the present invention, and in this respect it is better than materials made by conventional methods.

[Effect of the invention] According to the present invention described above, Ti -15V-
Manufacturing of 3Cr-3Sn-3AN alloy material 83
By controlling the temperature and processing rate of hot working, it is possible to easily produce butane alloy materials with excellent mechanical properties equivalent to those of cold-worked materials, without performing cold working. (II is done.

Patent applicant: Nippon Kokan Co., Ltd. Same as Nippon Mining Co., Ltd.

Claims (2)

[Claims] (1) V: 14-16wt%, Cr: 2.5-3.5w
t%, Sn: 2.5-3.5wt%, Al: 2.5-3
．． In producing a titanium alloy material consisting of 5wt%, balance Ti and unavoidable impurities, 900% of the material for hot processing was used.
Start processing after heating to a temperature of 1050°C or higher, at least 650°C or higher and 900°C or lower, with a processing rate of 50% or more,
And the processing rate is 30% at 650℃ or higher and 850℃ or lower.
A method for producing a titanium alloy material with excellent strength and ductility, which comprises performing the above processing and completing the processing at a temperature of 650°C or higher and 800°C or lower. (2) The method for producing a titanium alloy material according to claim 1, wherein the titanium alloy material contains 0.3% or less of oxygen.