JP2010255023A - Method for manufacturing strengthened alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a strengthened alloy, by which a strengthened alloy having an enhanced tensile strength can be obtained while reducing the time required for an aging treatment. <P>SOLUTION: The method for manufacturing the strengthened alloy includes: a solution treatment step S1 where an alloy material is immersed in molten lithium held at a solution treatment temperature higher than the solution temperature of a solute metal of the alloy material; a solution treatment halting step S2 where the alloy material is immersed in molten lithium held at a cooling temperature lower than the solution treatment temperature, after the solution treatment step S1; an aging treatment step S3 where the alloy material is immersed in molten lithium held at an aging treatment temperature which is lower than the solution temperature, after the solution treatment halting step S2; and an aging halting step S4 where the alloy material is immersed in molten lithium held at an aging halting temperature lower than the aging treatment temperature, after the aging treatment step S3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a reinforced alloy.

  It has long been practiced that carbon steel and other alloys are subjected to solution treatment such as quenching and then subjected to aging treatment such as tempering to obtain desired mechanical properties.

  Among them, titanium alloys are light, high in strength, and high temperature resistance and corrosion resistance, so that their applications are rapidly expanding in recent years. The basic crystal structure of metallic titanium is a dense hexagonal crystal (α phase) at room temperature, but when heated to a temperature higher than the β transformation point (about 885 ° C for pure titanium), body-centered cubic crystals (β phase) are formed. The α phase is formed again upon cooling. Titanium alloys in which alloy elements such as aluminum (Al) and vanadium (V) are incorporated into titanium metal, various metal structures are formed by changing the component ratio, heating temperature, heating rate, and cooling rate. There are various characteristics of the titanium alloy after this.

  Among α + β type alloys in which α and β phases coexist at room temperature, the solution is heated to a temperature higher than the temperature at which the alloy element diffuses into the solute metal to form a solid solution (solution temperature). When the crystallization treatment is performed, a β phase is formed in the metal structure, and after that, when rapidly cooled, an α ′ martensite phase is formed inside the β phase. Furthermore, when the solution-treated alloy is heated at a temperature lower than the solution treatment temperature (aging treatment), a fine α-phase is formed inside the β-phase. At this time, since the composition ratio of each phase formed in the metal structure and the size of the crystal of each phase change, an alloy having different strength and elongation from that before the heat treatment is formed.

  Here, a means is known in which a solution-treated titanium alloy is heated to a predetermined temperature with a high-frequency heating device, and the temperature of the titanium alloy is maintained for a predetermined time and subjected to an aging treatment, and then air-cooled (non-native). (See Patent Documents 1 and 2). Further, there is known a means for natural cooling after immersing the solution-treated titanium alloy in molten lithium at a predetermined temperature (see Patent Document 1).

JP 2006-016691 A

Goro Morita and three others, “Strengthening of Ti-6Al-4V alloy by short-time two-step high-frequency heat treatment”, Journal of the Japan Institute of Metals, The Japan Institute of Metals, October 2002, Vol. 68, No. 10 No., p. 862-867 Goro Morita and 3 others, “Effect of short-time two-step heat treatment on fatigue strength of Ti-6Al-4V alloy”, Materials, Japan Society for Materials Science, April, 2007, Vol. 56, No. 4, p. 345-351

  However, when the aging treatment is performed by rapidly heating the titanium alloy to a predetermined temperature (for example, at 8 s) with a high-frequency heating device as in Non-Patent Document 1, the surface temperature of the titanium alloy heated by the high frequency becomes uniform. It is difficult to heat to a temperature higher than a predetermined temperature due to overshoot of the heating device. Therefore, in the non-patent document 2 published later, when performing an aging treatment with a high-frequency heating device, it has been improved to heat to a predetermined temperature over a long time (for example, at 360 s). Aging takes a long time. Moreover, although the alloy obtained by the means of nonpatent literature 1 and nonpatent literature 2 improved 0.2% proof stress and tensile strength, there was a tendency for ductility to fall with improvement in strength.

  As another means, there is a means for immersing a solution-treated titanium alloy in molten lithium as in Patent Document 1 and performing an aging treatment, followed by natural cooling. When the present inventor processed the titanium alloy using this means, the 0.2% proof stress, tensile strength and ductility of the alloy were all increased, but the 0.2% proof stress, tensile strength and ductility were further increased. It was desired to increase.

  Accordingly, an object of the present invention is to provide a method for producing a reinforced alloy capable of obtaining a reinforced alloy having a 0.2% proof stress, a tensile strength and a ductility higher while shortening the time required for aging treatment. And

  The present inventors performed the aging treatment step by immersing the alloy material after the solution treatment in molten lithium held at the aging treatment temperature, and then melting the alloy material at the aging stop temperature lower than the aging treatment temperature. By immersing in lithium and performing an aging stop step, excessive growth of the α phase having a high tensile strength is suppressed, while transformation of the highly ductile β phase formed between the α phases into the α phase is suppressed. As a result, the present invention has been completed.

  (1) A solution treatment step of immersing the alloy material in molten lithium held at a solution treatment temperature higher than the solution treatment temperature of the solute metal of the alloy material, and the solution treatment temperature after the solution treatment step. A solution stop step of immersing the alloy material in molten lithium held at a lower cooling temperature, and after the solution stop step, the alloy material is added to the molten lithium held at an aging treatment temperature lower than the solution treatment temperature. A method for producing a reinforced alloy comprising: an aging treatment step of immersing; and an aging stop step of immersing the alloy material in molten lithium held at an aging stop temperature lower than the aging treatment temperature after the aging treatment step.

  (2) The manufacturing method according to (1), wherein in the aging stop step, the alloy material is immersed in molten lithium at 350 ° C. or lower.

  (3) The manufacturing method according to (1) or (2), wherein a titanium alloy is used as the alloy material.

  According to the present invention, after the solution treatment, the alloy material is immersed in molten lithium held at the aging treatment temperature and subjected to the aging treatment step, and then the molten material held at the aging stop temperature lower than the aging treatment temperature. By carrying out the aging stop process by immersing in lithium, the excessive growth of the α phase having a large tensile strength is suppressed while the cooling time to the aging stop temperature is shortened, and the ductility formed between the α phases is high. Transformation of β phase to α phase is suppressed. Therefore, it is possible to provide a production method in which a reinforced alloy having 0.2% proof stress, tensile strength and ductility is obtained.

It is a flowchart which shows the embodiment in the manufacturing method of the reinforced alloy of this invention. It is a graph which shows the change of the surface temperature of the alloy material by the manufacturing method of the reinforced alloy of this invention. It is sectional drawing which shows the manufacturing apparatus preferably used with the manufacturing method of the reinforced alloy of this invention.

  Next, embodiments of the method for producing a strengthened alloy according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an embodiment of a method for producing a reinforced alloy according to the present invention. FIG. 2 is a graph showing changes in the surface temperature of the alloy material by the method for producing a strengthened alloy of the present invention. FIG. 3 is a cross-sectional view showing a production apparatus preferably used in the method for producing a reinforced alloy according to the present invention.

  As shown in FIG. 1, the manufacturing method of the strengthened alloy of this embodiment is equipped with solution treatment process S1, solution treatment stop process S2, aging treatment process S3, and aging stop process S4.

(Alloy material)
The alloy material 50 used in this manufacturing method has a solution temperature of the melting lithium (181 ° C.) among the materials having an α-phase tensile strength greater than the β-phase and a β-phase elongation at break larger than the α-phase. ) And lower than the boiling point of molten lithium (1342 ° C.). An example of the alloy material 50 that satisfies these requirements is a titanium alloy. More specifically, Ti-6Al-4V alloy is mentioned. When a Ti-6Al-4V alloy is used, a part of the metal structure is a dense hexagonal crystal by the solution treatment step S1 in which the surface temperature of the alloy material is rapidly heated to a solution treatment temperature higher than 850 ° C. The phase transitions from the phase to the β phase which is body-centered cubic and has a high elongation at break.

  The alloy material 50 may be formed by rolling or cutting in advance before the heat treatment. Thereby, since processing strain accumulates inside the alloy material 50, it is easy to form crystal nuclei when the alloy material 50 is heated and cooled, and the metal structure after the heat treatment can be made finer.

(Heat treatment equipment)
A heat treatment apparatus used in this manufacturing method includes, for example, a solution treatment tank 12, a solution stop tank 13, an aging heating tank 14 and an aging stop tank 15 in a heat treatment chamber 11 as shown in FIG. 1 is mentioned. This heat treatment apparatus 1 includes a moving mechanism 27, and moves the alloy material 50 sequentially to the molten lithium L <b> 1 to L <b> 4 accommodated in the solution treatment tank 12, solution treatment stop tank 13, aging heating tank 14 and aging stop tank 15. Immerse.

  Here, the heat treatment apparatus 1 may be provided with the sealable inlet chamber 30 on one side of the heat treatment chamber 11 and with the sealable outlet chamber 40 on the other side. At this time, the entrance chamber 30 is provided with a door 31 that separates the inside of the entrance chamber 30 from the outside air, and a door 32 that separates the interior of the entrance chamber 30 and the inside of the heat treatment chamber 11. On the other hand, the exit chamber 40 is provided with a door 41 that separates the interior of the exit chamber 36 from the interior of the heat treatment chamber 11 and a door 42 that separates the interior of the exit chamber 36 from the outside air. An inlet chamber 30 and an outlet chamber 36 are provided in the heat treatment chamber 11 and the inside of the heat treatment chamber 11 is filled with an inert gas (for example, argon gas) that does not react with the molten lithium L1 to L4. Since it becomes difficult to leak outside, the reaction between molten lithium and air or water vapor can be suppressed.

(S1) Solution Treatment Step The alloy material 50 is heated, and the surface temperature of the alloy material 50 is maintained at a solution treatment temperature T1 that is higher than the solution treatment temperature. Thereby, a part of the alloy component of the alloy material 50 is diffused into the solute metal to form a β-phase solid solution of the solute metal.

  As means for heating the alloy material 50, means for immersing the alloy material 50 in the molten lithium L1 heated to the solution treatment temperature T1 is used. Thereby, the overshoot of the temperature of the alloy material 50 becomes difficult to occur. For this reason, the tensile strength of the alloy material 50 by the abnormal heating to the alloy material 50, breaking elongation, and the fall of 0.2% yield strength can be suppressed. In addition, since the heat is quickly transferred to the alloy material 50 by the molten lithium having a high thermal conductivity, the alloy material 50 can be heated more quickly, and a solid solution of β phase of the solute metal can be formed in a short time. Therefore, while avoiding enlargement due to the growth of crystals contained in the metal structure, it is possible to reduce the incorporation of hydrogen and oxygen into the metal structure when the alloy material 50 is in solution, Decrease in tensile strength, breaking elongation and 0.2% proof stress due to the formation of voids can be suppressed.

  As shown in FIG. 3, a specific example of this heating means is that molten lithium L1 heated to the solution treatment temperature T1 is accommodated in the solution treatment tank 12, and is carried into the heat treatment chamber 11 from the inlet chamber 30 of the heat treatment apparatus 1. A means for immersing the alloy material 50 thus obtained in the molten lithium L1 can be mentioned. Here, in order to adjust the temperature of the molten lithium L1 accommodated in the solution treatment tank 12, for example, a heater 21 for heating the molten lithium L1 is used.

  The solution treatment temperature T1 in the solution treatment step S1 is set to a temperature higher than the solution treatment temperature of the alloy material 50. Here, the solution temperature of the alloy material 50 varies depending on the composition of the alloy material 50 and the like, but is often in the range of 700 ° C. to 1100 ° C., for example. More specifically, in the case of a Ti-6Al-4V alloy, the solution temperature is in the range of 850 ° C to 1000 ° C.

  The solution time for maintaining the surface temperature of the alloy material 50 heated in the solution treatment step S1 at the solution treatment temperature T1 depends on the temperature at which the alloy material 50 is heated, the thickness of the alloy material 50, and the use of the reinforced alloy. Although it sets suitably, it can be 10 seconds or more and 300 seconds or less, for example. In particular, by setting the solution time to 10 seconds or more, the temperature is sufficiently increased to the inside of the alloy material 50 after the solution time has elapsed, so that the β phase of the solute metal and the alloy component are brought to the inside of the alloy material 50. A solid solution can be formed. On the other hand, by setting the solution time to 300 seconds or less, the β crystal formed by heating is prevented from growing and increasing in size, and therefore, the refinement of the metal structure of the alloy material 50 can be promoted. Here, as a means for maintaining the surface temperature of the alloy material 50, for example, the temperature of the molten lithium L1 in which the alloy material 50 is immersed is adjusted by the heater 21 and maintained at the solution treatment temperature T1.

(S2) Solution Treatment Stopping Step The alloy material 50 after the solution treatment step S1 is cooled to a solution treatment stop temperature T2 lower than the solution treatment temperature (step S21 in FIG. 2). By cooling the alloy material 50 to the solution stop temperature T2, the phase change from the β phase to the α phase is suppressed, and a part of the β phase remains in the metal structure in a state where the alloy components are dissolved. At this time, by rapidly cooling the alloy material 50, an α ′ martensite phase is formed in the metal structure of the alloy material 50. Therefore, by rapidly cooling to the solution stop temperature T2, a fine structure in which the alloy element composed of the α ′ martensite phase and the residual β phase is dissolved can be formed in the alloy material 50. The solution stop temperature T2 is appropriately selected depending on the composition of the alloy material 50. For example, when a Ti-6Al-4V alloy is used as the alloy material 50, it is preferably lower than 500 ° C, more preferably lower than 300 ° C. preferable.

  As means for rapidly cooling the alloy material 50 to the solution stop temperature T2, means for immersing the alloy material 50 in molten lithium L2 adjusted to the solution stop temperature T2 is used. Thereby, since heat is quickly taken away from the alloy material 50 by the molten lithium L2 having high thermal conductivity, the alloy material 50 can be cooled more rapidly.

  A specific example of this cooling means is a means for immersing the alloy material 50 in molten lithium L2 at a cooling temperature stored in the solution stop tank 13 in the heat treatment chamber 11 of the heat treatment apparatus 1 as shown in FIG. It is done. Here, in order to adjust the temperature of the molten lithium L2 accommodated in the solution stop tank 13, for example, a heater 22 for heating the molten lithium L2 and a fan 23 for cooling the molten lithium L2 are used.

  After the alloy material 50 is cooled by immersing it in the molten lithium L2 in the solution stop tank 13, the alloy material 50 is further cooled to a temperature lower than the melting point (181 ° C.) of lithium, more specifically to room temperature (room temperature). (Step S22 in FIG. 2). Thereby, since precipitation of the α phase inside the alloy material 50 is further reduced, it is possible to suppress the decrease of the α ′ martensite phase and the residual β phase over time. The cooling means for the alloy material 50 after being taken out from the solution stop tank 13 is, for example, natural cooling that is exposed to an inert gas atmosphere inside the heat treatment chamber 11 of the heat treatment apparatus 1 as shown in FIG. Can be mentioned.

  Here, you may perform machining, such as rolling, with respect to the alloy material 50 after performing solution-solution stop process S2. As a result, many processing strains are formed in the internal structure of the alloy material 50. Therefore, when this is heated again, recrystallization of the internal structure can proceed simultaneously from these many strains, and the crystal formed when heated again can be refined.

(S3) Aging treatment step The alloy material 50 is heated to an aging treatment temperature T3. At this time, the alloy material 50 contains a solid solution in which an alloy element is dissolved in a solute metal of an α phase, an α ′ martensite phase, and a β phase. By heating such an alloy material 50 to the aging treatment temperature T3, the β phase containing the alloy element is easily decomposed into a fine α phase and a compound containing the alloy element. Therefore, with respect to the reinforced alloy obtained after aging treatment of the alloy material 50, the ratio of α-phase crystals can be increased, and the tensile strength and 0.2% proof stress of the alloy material 50 can be increased.

  Here, the aging treatment temperature T3 when performing the aging treatment step S3 is lower than the β transformation temperature (885 ° C. in the case of Ti-6Al-4V alloy) at which the solute metal transforms into the β phase, preferably 400 ° C. or more. The temperature is within the range of 650 ° C or lower. In particular, when a Ti-6Al-4V alloy is used as the alloy material 50, the surface temperature of the alloy material 50 when performing the aging treatment step S3 is more preferably maintained at 600 ° C. or lower. When the temperature of the alloy material 50 becomes higher than necessary, the α phase formed in the alloy material 50 is likely to be transformed into a β phase having a low tensile strength. This is because it drops rapidly.

  The heating of the alloy material 50 to the aging treatment temperature T3 in the aging treatment step S3 is performed in a short time. As a result, a part of the β phase of the solute metal is decomposed to produce an α phase crystal having a large tensile strength and a small particle size, while a compound of the solute metal and the alloy element is generated, and these products During this period, a highly ductile β phase remains. Therefore, about the reinforced alloy after performing aging treatment process S3, elongation at break can be raised, raising tensile strength and 0.2% yield strength. Therefore, a reinforced alloy having both hardness and robustness can be obtained.

Examples of means for heating the alloy material 50 to the aging treatment temperature T3 in a short time include a means for immersing the alloy material 50 in molten lithium heated to the aging treatment temperature T3. Thereby, heat is quickly transferred to the alloy material 50 by molten lithium (41.4 W / mK) having a higher thermal conductivity than air (2.41 × 10 ⁻² W / mK). Therefore, a large number of α-phase crystal nuclei can be precipitated in a short time from the β phase of the solute metal, and a fine structure of the α phase of the solute metal can be formed in these crystal nuclei. Therefore, the grain size of the α phase crystals contained in the strengthened alloy can be reduced, and the β phase crystals can easily enter between the α phase crystals, thereby increasing the breaking elongation. At this time, the surface temperature of the alloy material 50 becomes substantially equal to the temperature of the molten lithium in about 1 to 2 seconds after the alloy material 50 is immersed in the molten lithium.

  A specific example of this heating means is a means for immersing the alloy material 50 in an aging heating tank 14 containing molten lithium heated to an aging treatment temperature T3 in the heat treatment chamber 11 of the heat treatment apparatus 1 shown in FIG. . In order to adjust the temperature of the molten lithium inside the aging heating tank 14, for example, a heater 24 for heating liquid lithium is used.

  In the aging treatment step S3, the aging treatment time for immersing the alloy material 50 in the molten lithium L3 heated to the aging treatment temperature T3 is appropriately selected depending on the thickness and shape of the alloy material 50, for example, 30 seconds or more and 30 minutes or less. It is preferable to make it. In particular, by setting the aging treatment time to 30 seconds or more, the alloy material 50 is easily heated to the aging treatment temperature T3, so that the tensile strength and 0.2% proof stress of the alloy material 50 can be further increased. On the other hand, when the aging treatment time is set to 30 minutes or less, the α phase of the solute metal grows more than necessary in the alloy material 50 and is difficult to increase in size, thereby suppressing the decrease in breaking elongation due to the decrease in the β phase of the solute metal. can do.

(S4) Aging stop step The alloy material 50 after the aging treatment step S3 is cooled in a short time until the surface temperature reaches the aging stop temperature T4 (step S41 in FIG. 2). Thus, further growth of the α-phase crystals of the solute metal formed by the aging treatment step S3 is suppressed at least on the surface of the alloy material 50, and the β phase remaining in the alloy material 50 is changed to the α phase. The transformation of is suppressed. In addition, the formation of excess α phase makes it difficult for the alloy metal to become supersaturated in the solute metal, and it is difficult to produce a compound of the alloy metal. Therefore, the average particle diameter of the α phase of the strengthened alloy after the aging stop can be reduced, and the fine metal structure composed of the α phase crystals and the residual β phase is maintained, and the fracture elongation of the obtained strengthened alloy is increased. be able to. Thus, it has not been known in the past that the 0.2% proof stress, tensile strength, and ductility of the reinforced alloy are increased by cooling after performing the aging treatment step S3.

As means for cooling the alloy material 50 in a short time, means for immersing the alloy material 50 in molten lithium L4 adjusted to the aging stop temperature T4 is used. As a result, heat is rapidly taken away from the alloy material 50 by molten lithium (41.4 W / mK) having a higher thermal conductivity than air (2.41 × 10 ⁻² W / mK). Therefore, the alloy material 50 can be rapidly cooled. Here, the aging stop temperature T4 is appropriately set from a temperature range higher than the melting point (181 ° C.) of lithium and lower than the aging treatment temperature T3. For example, it is 350 ° C. or lower, more preferably 300 ° C. or lower. Thus, the growth of the α phase of the solute element can be suppressed. The aging stop temperature T4 may be the same temperature as the solution stop temperature T2 in the solution stop step S2.

  Specific examples of the cooling means include means for immersing the alloy material 50 in the aging stop tank 15 containing molten lithium L4 in the heat treatment chamber 11 of the heat treatment apparatus 1 as shown in FIG. Here, in order to adjust the temperature of the molten lithium L4 accommodated in the aging stop tank 15, for example, a heater 25 for heating the molten lithium L4 and a fan 26 for cooling the molten lithium L4 are used. At this time, the surface temperature of the alloy material 50 immersed in the molten lithium is cooled to the aging stop temperature T4 in about 1 to 2 seconds.

  In the aging stop step S4, the time for immersing the alloy material 50 in the molten lithium L4 adjusted to the aging stop temperature T4 is appropriately selected depending on the thickness and shape of the alloy material 50, and is preferably set to, for example, 10 seconds or more. . In particular, by setting the immersion time to 10 seconds or longer, the growth of α-phase crystals inside the alloy material 50 can be suppressed, so that the tensile strength and 0.2% yield strength of the alloy material 50 can be further increased.

After the alloy material 50 is immersed in molten lithium L4 in the aging stop tank 15 and cooled, the alloy material 50 is further cooled to a temperature lower than the melting point of lithium (181 ° C.), more specifically to room temperature (room temperature) ( Step S42 in FIG. In addition, as a cooling means of the alloy material 50 taken out from the aging stop tank 15, natural cooling which exposes to the atmosphere of inert gas inside the heat processing chamber 11 of the heat processing apparatus 1 as shown, for example in FIG. 3 is mentioned.
The strengthened alloy obtained through the aging stop step S4 removes lithium adhering to the surface using a cleaning means (not shown). Thereby, the heat_generation | fever etc. by contact with lithium, air, and water can be reduced. Examples of the means for cleaning the reinforced alloy include a means for ultrasonic cleaning by immersing in a large amount of water.

As mentioned above, although one embodiment of the manufacturing method of the reinforced alloy of this invention was demonstrated, this invention is not restrict | limited to the embodiment mentioned above.
For example, the heat treatment apparatus 1 is not limited to this mode. For example, the solution stop tank 13 and the aging stop tank 15 may be formed of the same molten lithium tank, and the solution treatment tank 12 and the aging heating tank 14 May be composed of the same molten lithium bath. Thereby, since the number of the molten lithium tanks used for manufacture of a reinforced alloy is reduced, the quantity of the molten lithium used for the heat processing apparatus 1 can be reduced, simplifying the heat processing apparatus 1. FIG. However, when the solution treatment tank 12 and the aging heating tank 14 are composed of the same molten lithium tank, the output of the heater 21 (24) is adjusted as appropriate, and when used as the solution treatment tank 12, molten lithium. Is set to the solution treatment temperature T1, and when used as the aging heating tank 14, the temperature of the molten lithium is set to the aging treatment temperature T3.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

[Example 1]
A Ti-6Al-4V alloy (β transformation temperature: 885 ° C.) was used as the alloy material. A thermocouple was attached to the surface of the alloy material in order to measure the surface temperature.

  In order to heat and cool the alloy material, a heat treatment apparatus having a sealed heat treatment chamber filled with argon gas was used. Among these, an inlet chamber that can be sealed by a door is provided on one side of the heat treatment chamber, and an outlet chamber that can be sealed by a door is provided on the other side. And in the inside of the heat treatment chamber, a solution treatment tank, a solution stop tank, an aging heating tank and an aging stop tank each containing molten lithium were provided.

  Among these, the temperature of the molten lithium accommodated in the solution treatment tank is adjusted to 980 ° C. which is a solution treatment temperature using a heater, and the alloy material carried into the heat treatment chamber from the inlet chamber of the heat treatment apparatus is subjected to the solution treatment. It was immersed in the molten lithium of the tank. Thereafter, the temperature of the molten lithium in which the alloy material was immersed was maintained for a solution time of 60 seconds.

  Next, the alloy material was transferred to a solution stop tank, and the alloy material was rapidly cooled. When immersing the alloy material in the solution stop tank, the temperature of the molten lithium contained in the solution stop tank is a solution stop temperature using a heater that heats the molten lithium and a fan that cools the molten lithium. The temperature was adjusted to 200 ° C. After being immersed in molten lithium in a solution stop tank, the alloy material was further exposed to an inert gas atmosphere in a heat treatment chamber and cooled to room temperature.

  Next, the alloy material was immersed in an aging heating tank. Here, when the alloy material was immersed in an aging heating tank, the temperature of the molten lithium accommodated in the aging heating tank was adjusted to 550 ° C., which is an aging treatment temperature, using a heater. After immersing the alloy material in the aging heating tank, the temperature of the molten lithium in which the alloy material was immersed was maintained for 10 minutes, and the surface temperature of the alloy material was maintained at the aging temperature. .

  Next, the alloy material was transferred to an aging stop tank, and the alloy material was rapidly cooled. When the alloy material is immersed in the aging stop tank, the temperature of the molten lithium accommodated in the aging stop tank is 200 ° C., which is an aging stop temperature using a heater that heats the molten lithium and a fan that cools the molten lithium. Adjusted. At this time, the surface temperature of the alloy material decreased to the aging treatment temperature 2 seconds after being immersed in molten lithium. After being immersed in molten lithium in an aging stop tank, the alloy material was further exposed to an inert gas atmosphere in a heat treatment chamber and cooled to room temperature.

  The reinforced alloy obtained by aging the alloy material was subjected to ultrasonic cleaning in a large amount of water to remove lithium adhering to the surface, and then subjected to a tensile test according to JIS Z 2241. 2% yield strength, tensile strength and elongation at break were measured.

[Comparative Example 1]
Compared to Example 1, the alloy material was cooled in the aging stop step S4 without being immersed in the molten lithium in the aging stop tank. That is, the alloy material taken out from the aging tank as in Example 1 was exposed to an inert gas atmosphere in the heat treatment chamber without being immersed in the aging stop tank, and cooled to room temperature. At this time, the surface temperature of the alloy material fell below 200 ° C., the same as the aging stop temperature, one hour after the alloy material was pulled out of the molten lithium. The rest is the same as in the first embodiment.

[Comparative Example 2]
Compared to Example 1, the aging treatment time in the aging treatment step S3 was lengthened, and the alloy material was cooled in the aging suspension step S4 without being immersed in the molten lithium in the aging suspension tank. That is, the alloy material taken out from the solution treatment tank and cooled to room temperature in the same manner as in Example 1 was heated to 550 ° C., which is an aging treatment temperature, using a heater without being immersed in the aging heating tank. At this time, the alloy material was heated to the aging temperature for about 2 seconds. After the surface temperature of the alloy material reached the aging treatment temperature, the surface temperature of the alloy material was maintained at the aging treatment temperature for 2 hours.

  Next, the heating of the alloy material by the heater was stopped, and the alloy material was exposed to an inert gas atmosphere in the heat treatment chamber and cooled to room temperature. At this time, the surface temperature of the alloy material fell below 200 ° C., the same as the aging stop temperature, one hour after the alloy material was pulled out of the molten lithium. The rest is the same as in the first embodiment.

  JIS Z for Example 1, Comparative Example 1 and Comparative Example 2 with respect to the alloy material before the solution treatment step S1 (before the test) and the strengthened alloy after the aging stop step S4 (after the test) The measured values of the mechanical strength by the tensile test according to 2241 are shown in the following [Table 1].

From the results of the examples and comparative examples, for example, the following can be understood.
Compared with Comparative Examples 1 and 2 in which the alloy material was not immersed in molten lithium at the aging stop temperature, Example 1 in which the alloy material was immersed in molten lithium at the aging stop temperature shortened the cooling time to the aging stop temperature. It can be seen that the 0.2% proof stress, tensile strength and elongation at break of the aging strengthened alloy are all increased.

DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 11 Heat processing chamber 12 Solution treatment tank 13 Solution stop tank 14 Aging heating tank 15 Aging stop tank 21, 22, 24, 25 Heater 23, 26 Fan 30 Inlet chamber 40 Outlet chamber 31, 32, 41, 42 Door 27 Moving mechanism 50 Alloy material L1-L4 Molten lithium

Claims (3)

A solution treatment step of immersing the alloy material in molten lithium held at a solution treatment temperature higher than the solution treatment temperature of the solute metal of the alloy material;
After the solution treatment step, a solution stop step of immersing the alloy material in molten lithium held at a cooling temperature lower than the solution treatment temperature;
After the solution stopping step, an aging treatment step of immersing the alloy material in molten lithium held at an aging treatment temperature lower than the solution treatment temperature;
An aging stop step of immersing the alloy material in molten lithium held at an aging stop temperature lower than the aging treatment temperature after the aging treatment step.   The manufacturing method according to claim 1, wherein in the aging stop step, the alloy material is immersed in molten lithium at 350 ° C. or lower.   The manufacturing method according to claim 1, wherein a titanium alloy is used as the alloy material.

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