JPH02163334A - Titanium alloy having excellent cold workability - Google Patents

Abstract

PURPOSE:To obtain the title alloy having excellent cold workability at low cost by regulating specific wt.% of Nb, V, Al, Fe, Cr, Mn, Zr, O and the balance Ti as the components of a titanium alloy. CONSTITUTION:As the components of a titanium alloy, by weight, 10 to 40% Nb, 1 to 10% V, 2 to 8% Al, each <=1% of Fe, Cr and Mn, <=3% Zr, 0.05 to 0.3% O and the balance Ti are regulated. The alloy is used as the material for aircraft, the material for corrosion-resistant structure or the like.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to titanium alloys used as aircraft materials, corrosion-resistant structural materials, etc., and in particular to titanium alloys that have excellent plastic workability in cold 1#J1. Regarding.

(Problems to be solved by the prior art and the invention) Titanium alloys have a hexagonal α-type 0 structure due to their room temperature structure.
alloys, β-type alloys based on body-centered cubic products, and these two
It is roughly divided into three types of α + β type alloys containing phases, among which α
Type alloys have particularly excellent high-temperature and cryogenic properties, and β-type alloys are advantageously used as high-strength, high-toughness alloys near room temperature. Furthermore, α+β type alloys have intermediate properties.

Today, the amounts of these two types of titanium alloys used are still small, so methods are being used to vary the properties by changing heat treatment conditions. The most common titanium alloy is Ti-6AI-4V, which belongs to the α+β type alloy.
This accounts for approximately 75% of the titanium alloy used.

This Ti-6^1-4V alloy has a simple composition system, is easy to manufacture, has sufficient strength, and has a specific gravity almost the same as pure titanium.
Although it is a highly reliable and excellent alloy backed by a proven track record of use, it has the drawback of poor cold processing performance. Among these, the plastic workability is poor, and cold till M medium processing has an area reduction rate of 2.
The limit is approximately 0%, and cold forging in particular is practically impossible. Therefore, this kind of titanium alloy products are mainly manufactured by cutting, but the material yield is low.

This low material yield and high processing costs drive up product prices and limit applications.

On the other hand, β-type titanium alloys having the above-mentioned body-centered cubic crystal structure, such as Ti-11,5No-6Zr-4,53
nTi -+3V -11cr -3AI etc. have a high cold deformability compared to other titanium alloys, but these alloys have a hardness (HRC) of 3 even in the solution treatment state.
Therefore, when cold wire drawing or cold forging is performed, problems such as die seizure and abnormal wear occur.

(Means for Solving the Problems) Against this background, the present invention has been made to provide a titanium alloy that is lightweight, has high strength, and has excellent cold workability. , the composition of the titanium alloy is Nb:
10~40% by weight, ■: 1~10fi amount%, AI=2~
8 weight%, Fe, Cr, Nn: each 1% by weight or less,
Zr: 311% by weight or less, O: 0°05 to 0.3% by weight,
The reason is that the remainder is made of Ti.

As described above, in the present invention, Nb and V are added as alloy components, but each of these is known as a β-stable element when used alone.

However, for example, when Wb is added alone as an alloying component, the workability is improved, but if it is added in excess of a certain amount, the strength becomes low and it cannot be put to practical use. Also, Nb is 1
Since the specific gravity is considerably larger than that of Ti alloy, adding a large amount of Nb will increase the specific gravity of the Ti alloy, which will reduce its lightweight property.

On the other hand, according to experiments conducted by the present inventors, V is not as effective as Wb in terms of improving workability, but Nb has the advantage of not reducing the strength of the alloy, and is particularly effective against Ti-Nb alloys.
It was found that the addition of . Figure 2 shows this situation (the horizontal axis in the figure is V
(The vertical axis shows the degree of strength improvement.)

Therefore, the present inventors focused on adding Nb and ■ together as β-stable elements in order to improve processing performance, and further compensated for the decrease in strength due to the addition of these components by adding AI. Through various experiments, the appropriate range of addition of these components was determined, and the above invention was completed.

Therefore, the range of addition amounts of these additive components will be explained in detail next.

(1) Nb: 10 to 40% by weight As mentioned above, Nb is added to β-oxidize the Ti alloy, and its lower limit is 10% by weight.

The upper limit is 40% by weight. The reason is that the amount added is 10
If it is less than 1i%, the β conversion will be insufficient and the workability will not be improved sufficiently, and if it is more than 40tlii%, the workability will be sufficient but the strength will be too low and the specific gravity will also become large. This is because the features of the Ti alloy will be diminished.

(2) V: I~10 heavy stitching% V is the same as Nb (Ti alloy tip is β-formed, but N
When used in combination with b, it is necessary to add in a range of 1 to 10i1%. This is because if the amount of V is less than 1% by weight, the effect of V addition will not appear, and conversely, if it is added in excess of 10% by weight, the effect will be saturated.

(3) AI+2 to 81% AI, contrary to Nb and V, alpha-izes the Ti alloy, and works to increase the strength of the Ti alloy through precipitation hardening. However, if the amount added is less than 2% by weight, almost no effect will be observed, while if it is more than 8% by weight, cold workability will be impaired and corrosion resistance will also be reduced.

(4) Fs, Cr, Mn: each 1% by weight or less Fe,
Cr and Mn each have the function of β-izing the Ti alloy and increasing its strength, but if the content exceeds lfi%, the ductility decreases, the workability deteriorates, and there is a risk that the corrosion resistance will decrease. be.

(5) Zr: 3% by weight or less Including an appropriate amount of Zr increases the strength of the Ti alloy, but
If the content exceeds 3% by weight, cold workability will deteriorate.

(6) O: 0, 05 to 0.3 ball weight% 0 is an element that is highly effective in increasing strength without deteriorating corrosion resistance. The effect appears at 0.05% by weight or more, 0.314%
Although there is a tendency for the ductility to decrease slightly, the strength is significantly improved.

However, if it exceeds 0.3.33%, cold workability will be significantly reduced and it will become practically unusable.

(Example) Next, in order to clarify the features of the present invention, examples thereof will be described in detail below.

The raw materials having the compositions shown in Table 1 were plasma melted, then vacuum arc melted (melted twice), and hot forged into a round bar with a diameter of 20m.
The test piece 10 shown in FIG. 3(A) was prepared by heating (heating at 1 hour at 100° C., followed by water cooling) and cutting, and its hardness and deformability were investigated. The results are shown in Table 1 and
It is shown in the figure. The hardness was measured using the Rockwell C scale, and the source of deformation was measured using test piece 10.
This was done by compressing the material in the axial direction and examining the strain when a crack (indicated by X in FIG. 1) occurs. Here, the strain is an amount expressed as in ho/h (ho: initial height of test piece 10, h: height of compressive deformation amount 12).

From the results shown in Table 1 and FIG. 1, it can be seen that the examples of the present invention have high deformability and excellent cold workability.

The embodiments of the present invention have been described in detail above, but one embodiment of the present invention is a 5T moat implemented in IE with various changes made without departing from the spirit thereof.

(Effects of the Invention) The titanium alloy of the present invention has excellent cold workability, especially good plastic workability, and is also suitable for Nb-46,57i as a superconducting material.
Since scraps of Ti-6AI-4V and Ti-6AI-4V can be used as raw materials, it has the advantage that it can be provided at low cost. Especially Nb-46,57i as a superconducting material
Conventionally, scraps had to be thrown away because they had no use for them, but with the present invention, they can now be used as materials for titanium alloys, making it possible to use resources effectively and at the same time reducing the cost of titanium alloys. will be fulfilled.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the deformability of a titanium alloy that is an example of the present invention, and Figure 2 is a diagram showing the relationship between the amount of V added and the improvement in strength when V is added to a Ti-Nb alloy. FIG. Figure 3 (A) is a diagram showing a test piece prepared for characterizing a titanium alloy according to an embodiment of the present invention, and Figure 3 (B) shows the shape of the test piece in (A) after being compressed. FIG. 10: Test piece 12: Compression deformed product Figure ■ Addition amount C

Claims (1)

[Claims] Nb: 10-40% by weight, V: 1-10% by weight, Al:
2 to 8% by weight, Fe, Cr, Mn: 1% by weight or less each, Z
A titanium alloy with excellent cold workability, characterized in that r: 3% by weight or less, O: 0.05 to 0.3% by weight, and the balance consists of Ti.