JPH02258960A - Heat treatment for titanium alloy - Google Patents

Abstract

PURPOSE:To produce a titanium alloy capable of being formed into superior mirror-finished state by successively subjecting an alpha plus beta titanium alloy or a beta titanium alloy to beta solution treatment, rapid cooling, and ageing treatment successively under respectively specified conditions. CONSTITUTION:An alpha plus beta titanium alloy or a beta titanium alloy is formed into the desired shape, subjected to beta solution treatment at a temp. of the beta transformation temp. or above, and cooled rapidly down to room temp., so as to be formed into martensitic single phase or beta single phase. Subsequently, the above alloy is subjected to ageing treatment at a temp. of the beta transformation temp. or below and cooled slowly down to room temp., by which alpha precipitates on the martensitic phase or beta phase are finely precipitated. By this method, the titanium alloy whose surface can be uniformly polished by means of polishing treatment and formed into mirror- finished state can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for heat treating titanium alloys.

[Summary of the invention]

In the present invention, after forming an α+β type titanium alloy and a β type alloy, they are subjected to β solution treatment at a temperature above the β transformation point, and then rapidly cooled to room temperature to form a martensite single phase or β single phase, and then below the β transformation point. The molded body is aged at a temperature of 100 mL to finely precipitate α precipitates on the martensitic phase or β phase, and the molded body is then subjected to mirror finishing treatment to obtain a mirror finish.

[Conventional technology]

In general, α+β type titanium alloy compacts are a binary alloy of a hard phase and a soft phase, and because of the difference in hardness and workability between the α and β phases, they are mirror-finished. Also, a mirror state cannot be obtained. In addition, even in the compact of β-type titanium alloy, α phase is present, although the amount is small, so α phase and β
Due to the difference in hardness and workability with the phase, a mirror finish cannot be obtained even if a mirror finish is applied.

Conventionally, heat treatment methods for titanium alloy molded bodies were developed in accordance with the Japanese Patent Publication No. 58 in order to increase the strength or toughness of the molded bodies.
As shown in JP-A-48025 and JP-A-61-281860, after solution treatment is performed at a temperature below the β-transform temperature, the material is rapidly cooled, and then an aging treatment is performed at a temperature below the solution treatment temperature. In this type of treatment, the pro-eutectoid α phase remains, and there is a difference in hardness and workability between the pro-eutectoid α phase and the phase precipitated from the β phase due to aging treatment. However, a mirror state cannot be obtained.

Therefore, titanium alloy molded bodies have been used with surface treatments such as plain patterns or overcoats.

[Problem to be solved by the invention]

Titanium alloys have many advantages such as high specific strength, high temperature strength, and good corrosion resistance, so they are widely used in structural and mechanical parts. Although heat treatment is performed for functional reasons such as corrosion resistance and vibration isolation, there is no requirement for appearance and a mirror finish is not required.

However, in recent years, titanium alloys have been used for decorative items due to their characteristics of low specific gravity, good corrosion resistance, high hardness, and a luxurious feel. It was used for patterns and could not be used for mirror surfaces.

This means that titanium alloys have a hard phase and a soft phase (
Fig. 1 (A+) Therefore, in the mirror finishing process, the soft phase is selectively polished (Fig. 1 D) or the soft phase is broken or fallen off (Fig. 1 0), resulting in the finished surface This is because unevenness is formed on the surface, resulting in a blank pattern, and a mirror surface cannot be obtained.

[Means for solving the five problems] Therefore, in order to solve these problems, the present invention
After β-type titanium alloy or β-type titanium alloy is subjected to β-solution treatment at a temperature above the β-transformation point, it is rapidly cooled to room temperature and aged at a temperature below the β-transformation point, so that the entire surface becomes a martensitic phase and a β-phase. Precipitates are finely precipitated from the microstructure.

[Effect]

The α+β type titanium alloy becomes a martensitic single-phase structure by heating and holding it at a temperature equal to or higher than the β transformation point (β solution treatment) and then rapidly cooling it. - On the other hand, a β-type titanium alloy becomes a β single-phase structure by heating and holding it at a temperature equal to or higher than the β transformation point and then rapidly cooling it. Furthermore, by aging at a temperature below the β transformation point, α or ω phases are finely precipitated on the martensitic phase or β silk. The titanium alloy surface is uniformly polished by polishing to a mirror finish on a structure in which the α phase or ω phase is precipitated on a martensite substrate or in a structure in which an α phase or ω phase is precipitated on a β silk fabric. The state is obtained.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

Example-1 In this example, α+β type (Near β type) shown in Table 1 was used.
Titanium alloy was used.

Figure 2 shows the structure of titanium alloys subjected to various heat treatments.

Figure 2 shows the structure of the titanium alloy before heat treatment, α+
It shows the structure of β2 phase.

FIG. 2B shows a structure obtained by oil cooling after solution treatment at 750° C. for 0.5 h, and shows an α+β two-phase structure.

Table β transformation point 780°C Figure 2 0 shows a structure obtained by oil cooling after solution treatment at 750°C for 0.5 hours, and then air cooling after aging treatment at 500°C for 5 hours. The precipitated and pro-eutectoid α phase remains as it is.

FIG. 2 0 shows a structure obtained by oil cooling after solution treatment at 850° C. for 0.5 hours, and shows a martensitic structure.

Figure 2 (■) shows a structure obtained by oil cooling after solution treatment at 850°C for 0.5 hours, and then air cooling after aging treatment at 400°C for 0.5 hours. There is.

Figure 2 [F] shows a structure obtained by oil cooling after solution treatment at 850°C for 0.5 hours, and then air cooling after aging treatment at 400°C for 16 hours. It is precipitated.

Figure 2 0 shows a structure obtained by oil cooling after solution treatment at 850°C for 0.5 hours, and then air cooling after aging treatment at 500°C for 16 hours, in which fine α phase precipitates in the form of needles from the martensite base. are doing.

In this way, by solution-treating the titanium alloy at a temperature above the β-transformation point (780°C) and cooling it with oil, a martensitic single-phase structure with no remaining α-phase can be obtained, and the solution treatment time is More than 5 minutes were required.

From this state, by further aging treatment at a temperature below the β transformation point, a fine ω phase precipitated from the martensite at temperatures below 450°C, and a fine α phase precipitated from the martensite at temperatures above 450°C &lI! tIi is obtained. On the other hand, when solution treatment is oil-cooled at a temperature below the β transformation point, a &11 weave with α+β2 phases is formed.When further aging treatment is performed at a temperature below the β transformation point, a fine α phase precipitates from the β phase, and the pro-eutectoid α phase is It is a surviving organization. Next, the hardness of titanium alloys subjected to various heat treatments is shown in FIGS. 3 and 4.

Figure 3 shows quenching after solution treatment at 850°C for 0.5h.
FIG. 3 is a diagram showing the hardness of a titanium alloy that has been further subjected to aging treatment.

Titanium alloys that have only been subjected to solution treatment have a Pinkers hardness of H.
ν260, and 11ν350 or more at each aging treatment temperature of 2 hours, indicating that the aging treatment effect has occurred.

This is due to the precipitation of fine α phase or ω phase from the martensite ground.

Figure 4 shows quenching after solution treatment at 750°C for 0.5h.
FIG. 3 is a diagram showing the hardness of a titanium alloy that has been further subjected to aging treatment. Titanium alloys that have only been subjected to solution treatment have a Pinkers hardness of 11.
v 240, but due to aging process it becomes 400'C・5
Hv 420. It was hardened to Hv 370 in 5 hours at 500°C, and the hardening effect was obtained by precipitation of fine α phase or ω phase from the α+β phase.

Next, Table 3 shows the results of mirror finishing treatment applied to titanium alloys that had been subjected to various heat treatments.

X Mirror finishing was achieved by polishing with sandpaper, polishing with an abrasive, and further polishing with puff polishing.

Table 3 is a table showing the non-roughness and surface condition after polishing,
The surface roughness is expressed as the maximum/best average of the maximum surface roughness Rmax measured at seven locations at intervals of 2T1 m for each sample.

After solution treatment at 750°C for 0.5h, oil cooling and further 500°C
Titanium alloy subjected to aging treatment for 5 hours at ℃ has a Hv370
Although it is hardened and has little waviness and surface roughness, α
The difference in hardness between the phase and the β phase causes uneven polishing, resulting in a blank pattern.

On the other hand, solution treatment was performed at 850°C for 0.5h, cooled in oil, and further 4
Titanium alloys that have been aged at 50°C for 5 hours or at 500°C for 5 hours have high Vickers hardness, low surface roughness, and fine α or ω phase precipitates uniformly on the martensite surface, resulting in uneven polishing. A mirror-like state is obtained. In addition, titanium alloys subjected to special treatment at 400°C for 5 hours have no α phase or ω phase precipitated,
There are some unevenness due to polishing.

Based on the above, α + β type titanium alloys can be made from martensite by a heat treatment process in which solution treatment is performed at a temperature above the β transformation point, rapidly cooled to room temperature, and then aged at a temperature below the β transformation point. It has a structure in which α phase or ω phase is precipitated, and a good mirror state is achieved by mirror finishing treatment.

Example 2 In this example, a typical α+β type titanium alloy shown in Table 4 was used and various heat treatments shown in Table 5 were performed.

Figure 5 shows the structure of titanium alloys subjected to various heat treatments.

Figure 5 shows the &g weave of titanium alloy before heat treatment, α
+β2 phase &ll weave is shown.

FIG. 5B shows an m-weave that was subjected to oil cooling after solution treatment at 900° C. for 0.5 h, and shows a structure of α+β two phases.

FIG. 5 0 of Table 5 shows a structure obtained by oil cooling after solution treatment at 1050° C. for 0.5 hours, and shows a martensitic structure.

Figure 5 0 shows a structure obtained by oil cooling after solution treatment at 1050°C for 0.5 hours, and air cooling after aging treatment at 400°C for 16 hours. , shows the book.

Fig. 5 (D to ()D are each 1050℃・0.5h
After solution treatment, cooled in oil and further heated at 500℃ for 6 hours.
This is a Mi weave that has been air-cooled after aging treatment at 0°C for 16 hours and 700°C for 16 hours, and shows a state in which α phase has been finely precipitated from the martensite base.

In this way, the titanium alloy becomes a martensitic single-phase structure by solution treatment at a temperature higher than the β transformation point (995° C.) and cooling to room temperature at a rate higher than oil cooling. Furthermore, by aging treatment at a temperature below the β transformation point from this state, the ω phase is finely precipitated from the martensitic base (aging temperature: 400°C), or the α phase is finely precipitated from the martensite base (aging temperature: 400°C). (Aging treatment temperature: 400°C) & becomes a weave. In addition, when solution treatment is performed at a temperature below the β transformation point and cooled with oil, α + β two-phase M
When an i-texture is obtained and further subjected to aging treatment at a temperature below the β transformation point, a structure is obtained in which the α phase or the ω phase is finely precipitated from the β phase, and the pro-eutectoid α phase remains.

Next, Figure 6 shows the hardness of titanium alloys subjected to various heat treatments.
It is shown in FIG.

When oil-cooled after solution treatment at 1050° C. for 0.5 h, a Pinkers hardness of Hv335 is obtained, but by further aging treatment below the β transformation point, Hv is improved to 350 to 370. This is an effect due to Mlm in which α phase or ω phase is finely precipitated from martensite grains.

On the other hand, a titanium alloy oil-cooled after solution treatment at 900°C for 0.5h shows (Iv350), and even after further aging treatment at 600°C for 5h, it shows tlv345. Although the phase is finely precipitated, the amount of β phase is small and hardness is not improved.

Next, Table 6 shows the results of mirror finishing the titanium alloys that have been subjected to various heat treatments.

Table 6 * Mirror finish was achieved by polishing with sand vapor, polishing with an abrasive, and then puff polishing.

From Table 6, titanium alloys that have been solution-treated at 900°C for 0.5 hours and then oil-cooled, and titanium alloys that have been further aged at 600°C for 5 hours cannot obtain a mirror finish even if they are subjected to mirror finishing treatment. , oil cooling after solution treatment at 1050°C for 0.5h, further 500°C for 16h, 600°C for 16h,
The titanium alloy that has been subjected to various aging treatments at 700° C. for 16 hours has a good mirror finish due to the mirror finish treatment.

However, when aging treatment is performed at 400℃ for 16 hours,
The α phase or ω phase was not completely precipitated, and a mirror surface state could not be obtained.

Based on the above, α + β type titanium alloys are heat-treated by solution treatment at a temperature above the β transformation point, rapidly cooled to room temperature, and then aged at a temperature below the β transformation point. It has a structure in which α phase or ω phase is precipitated, and a good mirror state is achieved by mirror finishing treatment.

Example 3 In this example, β-type titanium alloys shown in Table 7 were used and various heat treatments shown in Table 8 were performed.

Table 7 Table 8 β trend point: 730℃ Figure 8 shows the structure of titanium alloys subjected to various heat treatments.

Figure 8 shows the structure of the titanium alloy before heat treatment, in which the β grain boundaries are elongated and elongated.

FIG. 8B shows the structure of a titanium alloy that has been oil-cooled after solution treatment at 750° C. Login, and has a β single-phase m weave with equicyclic islands.

Figure 8 0 shows the structure of a titanium alloy that was solution-treated at 750°C for 10 ml, cooled in oil, and then aged at 450°C for 40 hours. The α phase is finely precipitated from the entire surface of the β phase. .

FIG. 80 shows the structure of a titanium alloy that was oil-cooled after solution treatment at 700° C. and 10 ml, in which the α phase is mixed with the β phase.

The eighth diagram shows the structure of a titanium alloy that was solution-treated at 700°C and 10+sin, then oil-cooled, and then aged at 450°C for 40 hours, in which the α phase is finely precipitated from the β phase. The pro-eutectoid α phase remains.

In this way, the titanium alloy becomes a β-single-phase structure by solution treatment at a temperature above the β-transformation point (730°C) and cooling to room temperature at a rate faster than oil cooling. By aging at a temperature of , a structure in which fine α or ω phases are precipitated from the β phase can be obtained.

Next, FIG. 9 shows the hardness of titanium alloys subjected to various heat treatments.

According to FIG. 9, the titanium alloy was heated at 750°C and 10IIli.
The Vickers hardness of the titanium alloy obtained by oil cooling after solution treatment of n is Hv260, but a hardness of Hv300 or more is obtained by aging treatment at a temperature of 600°C or less. Furthermore, the aging treatment time is 40 hours or more for better treatment effects. This is due to the effect of forming a structure in which the α phase or ω phase, which is thinner than the β phase, precipitates.Table 9 shows the results of mirror finishing treatment performed on titanium alloys that have been subjected to various heat treatments.

*The mirror finish was achieved by polishing with sandpaper, polishing with an abrasive, and further polishing.

Table 9 shows that titanium alloys that were subjected to oil cooling after solution treatment at 750° C. for 0 m1n, and then subjected to aging treatment at 450° C. for 40 hours, were subjected to mirror finishing treatment to obtain a good mirror finish.

From the above, β-type titanium alloys are produced by solution treatment at a temperature above the β transformation point, rapid cooling to room temperature, and then aging treatment at a temperature below the β transformation point. The structure has a precipitated phase or ω phase, and a good mirror finish is achieved by mirror finishing treatment.

〔Effect of the invention〕

As explained above, according to the present invention, α+β type titanium alloy or β type titanium alloy is heat treated to uniformly and finely precipitate α phase and ω phase precipitates from a martensite single phase or β single phase state. This product can form a mirror-like structure and achieve a good mirror finish through mirror finishing treatment.It is a high-grade window that gives a mirror effect without sacrificing the high hardness and scratch resistance of titanium alloy. It is possible to provide certain decorative items.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional titanium alloy molded body before mirror finishing treatment, Figure 1 B, 0 is a cross-sectional view of a conventional titanium alloy molded body after mirror finishing treatment, and Figure 2 is a Ti9.5V
Micrograph (x 400) showing the alloy structure before heat treatment of 2.5Mo-3jj, Figure 2B is Ti-9,5V-
Solution treatment of 2,5Mo-3AI (750°C-0,5
h) Micrograph showing the alloy structure after oil cooling (x 400
), Figure 2 0 is Ti -9,5V-2,5Mo -3A
Micrograph (x 400) showing the alloy structure after solution treatment (750°C, 0.5h), oil cooling, and further aging treatment (500°C, 5h), Figure 2 0 is Ti-9,5V- 2,
A micrograph (x 400) showing the alloy structure after solution treatment (850°C, 0.5 h) of 5Mo 3N and oil cooling. Micrograph showing the alloy structure after oil cooling (850°C, 0.5h) and further aging treatment (400°C, +6h)
X400), the second diagram is Ti-9,5V-2,5Mo
-3N solution treatment (850°C, 0.5h), oil cooling, and aging treatment (450°C, 16h).
Solution treatment of 5V-2,5Mo-3H (850℃・0
．． s! showing the alloy structure after oil cooling after 5 hours) and further aging treatment (500℃ arching for 6 hours)! J Microscope Otoscope Photo 400), Figure 3 is a diagram showing the Vickers hardness of the alloy after solution treatment of Ti-9,5V 2.5Mo 3N (850°C, 0.5 h), oil cooling, and further aging treatment. , FIG. 4 shows Tt -9,
Solution treatment of 5V-2,5Mo-3AI (750℃・
Figure 52 shows the alloy structure before heat treatment of Ti-6Al-6V under a microscope (x 400); Figure 5 shows the Ti-6Al-6V alloy structure before heat treatment. -6A! 4V (D solution treatment (900℃・0.
5h) Micrograph showing the alloy structure after oil cooling (X400
), Figure 5 0 shows the solution treatment of Tt-6Al-4V (90
After oil cooling (0℃・0.5h), aging treatment (600℃・
5h) Micrograph (X 400) showing the alloy structure,
Figure 5 0 shows the solution treatment of T knee 6/'J-4V (105
A micrograph (X400) showing the alloy structure after oil quenching (0°C, 0.5h). (400℃・16h) Micrograph (X400) showing alloy & 11 weave, Figure 5 [F] shows Ti-6N-4V solution treatment (1050℃・0.5h) followed by oil cooling and further aging treatment. A micrograph (X400) showing the alloy structure after Ti-6A/-4V was solution-treated (1050°C for 0.5h), cooled in oil, and then aged (600°C). A micrograph (x 400) showing the alloyed Mi weave subjected to Ti-6A/-4V solution treatment (1050°C for 0.5h), oil cooling, and further aging treatment (600°C for 0.5h). A micrograph (x 400) showing the alloy structure at ℃・16b), Figure 6 is Tt-6A! Figure 7 shows the Pinkers hardness of the alloy that was oil-cooled after 4V solution treatment (1050°C, 0.5h) and then aged.
Figure 8 (4) shows the Pinkers hardness of the alloy which was oil-cooled after solution treatment at 6A/-4V (900°C, 0° for 5 hours) and further subjected to aging treatment.
Micrograph showing the alloy structure of 3Cr before heat treatment (X40
0), the 8th diagram is Ti-15V-3Al 3Sn-3
A micrograph (X400) showing the alloy structure after Cr solution treatment (750°C lomin) and oil cooling, Fig. 8 0 is T
i-15V -3kl -3Sn -3Cr was subjected to solution treatment (750°C arch in), oil cooling, and further aging treatment (45°C).
Micrograph (X40
0), Figure 8 0 is Ti-15V-3/V-3Sn-3C
Micrograph (X400) showing the alloy structure after oil cooling after solution treatment (7oO℃・10nin) of Ti
-15V -3AI -3Sn -3Cr solution treatment (700°C, 10ml) followed by oil cooling and further aging treatment (4
Micrograph (X
400), Figure 9 shows Ti 15V 31'J 3
It is a figure which shows the Pinkers hardness of the alloy which was oil-cooled after solution treatment (700 degreeC, 10mln) of Sn-3Cr, and was further aged. 1...Hard phase 2...Soft phase or higher Applicant Seiko Electronic Industries Co., Ltd. Agent Patent attorney Keinosuke Hayashi (A) (B) (C) 17 Prescription time (hr) Part 3 Figure 1 Effect 5 Tomo (1) Figure 4 Harugakimon (hr) Figure 6

Claims (3)

[Claims] (1) In the heat treatment method for α+β type titanium alloy or β type titanium alloy, after β solution treatment at a temperature higher than the β transformation temperature, rapid cooling to room temperature, and further aging treatment at a temperature lower than the β transformation temperature. Characteristic heat treatment method for titanium alloys. (2) A method for heat treatment of an α+β type titanium alloy or a β-type titanium alloy, including a first step in which the main structure of the α+β-type titanium alloy or the β-type titanium alloy is a martensitic phase or a β-phase, and the martensitic phase Alternatively, a method for treating a titanium alloy comprising a second step of precipitating an α phase, an ω phase, or a precipitate consisting of an α phase and an ω phase from the β phase. (3) In the method for producing a titanium alloy molded body made of an α+β type titanium alloy or a β type titanium alloy, the α+β
forming a type titanium alloy or a β-type titanium alloy into a molded body of a desired shape, subjecting the molded body to β-solution treatment at a temperature equal to or higher than the β-transformation temperature,
1. A method for producing a titanium alloy molded body, which comprises rapidly cooling to room temperature, then aging treatment at a temperature below the β transformation temperature, slow cooling to room temperature, and then polishing the molded body.