Heat treatment method for secondary solid solution and aging of Ti60 forge piece

Abstract

The invention belongs to the field of heat treatment of metal materials, and particularly relates to a secondary solid solution and aging heat treatment method for a Ti60 forge piece. The method comprises the following steps: 1, carrying out solid solution on a formed Ti60 forge piece: heating the Ti60 forge piece to 15-25 DEG C below the beta transformation temperature, carrying out heat preservation for 1-3 hours, and carrying out oil cooling; secondly, the Ti60 forge piece obtained in the first step is heated to 25-35 DEG C below the beta transformation temperature, heat preservation is conducted for 1-3 h, furnace cooling is conducted to about 900-920 DEG C, heat preservation is conducted for 1 h, and then the Ti60 forge piece is discharged out of the furnace and subjected to oil cooling; and 3, aging is conducted on the forge piece obtained after two times of solid solution, specifically, the forge piece obtained after solid solution is heated to 700 DEG C, heat preservation is conducted for 8 h, and the forge piece is discharged out of the furnace and air-cooled.

Description

Technical Field

[0001] The invention belongs to the field of heat treatment of metal materials, and specifically relates to a heat treatment method of Ti60 forgings by secondary solid solution + aging. Background Art

[0002] Ti60 alloy is a Ti-Al-Sn-Zr-Mo titanium alloy, to which a small amount of Si, C, Nb, and Ta elements are added. It is a near-α-type high-temperature titanium alloy designed for use in environments below 600°C. Its aluminum equivalent is 8.8, and its primary α-phase content is greatly affected by the solid solution temperature, and the content and morphology of the primary α-phase have an important influence on the performance of forgings. Some data show that if the solid solution temperature increases by 20°C, the volume fraction of the primary α-phase will decrease by 20%, and its thermal stability and plasticity will decrease significantly; as the volume fraction of the primary α-phase increases, the creep resistance decreases monotonically. In actual production, it is difficult to accurately control the content of the primary α-phase through the traditional one-time solid solution + aging heat treatment method, and the plasticity is often unqualified due to too little primary α-phase content. Summary of the invention

[0003] The present invention provides a double solution + aging heat treatment method, and makes clear provisions on the double solution temperatures, solution duration, solution cooling method, aging temperature and duration, etc., which can effectively improve the content and morphology of the primary α phase and ultimately achieve the effect of improving the plasticity of Ti60 forgings.

[0004] A Ti60 forging secondary solid solution + aging heat treatment method, characterized by comprising the following steps:

[0005] Step 1: Solvent-treat the formed Ti60 forging:

[0006] Heat the Ti60 forging to 15℃~25℃ below the β transformation temperature, keep warm for 1~3h, and cool with oil;

[0007] Step 2: Perform secondary solid solution treatment on the forgings after step 1:

[0008] Heat the Ti60 forging again to 25-35°C below the β transformation temperature, keep it warm for 1-3 hours, furnace cool it to about 900°C-920°C, keep it warm for 1 hour, and then take it out of the furnace and oil cool it.

[0009] Step 3: Aging of the forgings after step 2:

[0010] Aging of forgings after two solid solution treatments: heat the forgings after solid solution treatment to 700°C, keep warm for 8 hours, and air cool them out of the furnace.

[0011] Furthermore, the specific primary solution temperature of Ti60 forgings is related to the phase transformation point. When the phase transformation point temperature is high, the primary solution temperature needs to be reduced to 20°C to 25°C below the β transformation temperature. When the phase transformation point temperature is low, the primary solution temperature needs to be reduced to 15°C to 20°C below the β transformation temperature to balance the error caused by the phase transformation point test.

[0012] Furthermore, the oil temperature during the primary solution and secondary solution oil cooling needs to be controlled at 20-50° C., and the oil cooling transfer time needs to be controlled within 60 seconds to ensure a better solution effect.

[0013] Furthermore, the solution time of step one is 1 to 3 hours, and the thicker the thickness, the longer the insulation time.

[0014] Furthermore, the secondary solution temperature needs to be lower than the primary solution temperature so as not to eliminate the influence of the primary solution.

[0015] Furthermore, the less the equiaxed α phase content of the forging after the primary solid solution, the lower the secondary solid solution temperature is selected.

[0016] Furthermore, the cooling method of step 2 is to cool the product to 900°C to 920°C in a furnace, keep the temperature for 1 hour and then cool the product in oil.

[0017] Beneficial effects of the present invention: Ti60 forgings processed by the present invention not only have a microstructure that meets the requirements, but also obtain strength and toughness indicators that meet the requirements. The method of the present invention can effectively control the primary α phase content, thereby controlling the comprehensive mechanical properties of Ti60 forgings. The process is simple and stable, the operation is convenient, and it is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a high-magnification organizational diagram of the embodiment before rework.

[0019] Figure 2 This is a high-magnification microstructure diagram after heat treatment repair provided by the present invention. DETAILED DESCRIPTION

[0020] The present invention provides a Ti60 forging secondary solid solution + aging heat treatment method, which has the following advantages:

[0021] In the first step, the formed Ti60 forging is subjected to a solid solution treatment.

[0022] Heat the Ti60 forging to 15℃~25℃ below the β transformation temperature, keep it warm for 1~3h, and cool it with oil. During heating, the α phase dissolves and transforms to the β phase. During cooling, due to the use of oil cooling, the oil temperature is controlled at 20~50℃, and the oil cooling transfer time is ≤60s to ensure that the solid solution cooling rate exceeds 50℃ / min. The size of the primary α phase becomes smaller and the content decreases. The alloy structure undergoes a transformation from the β phase to the α' martensite. The precipitated α' phase is fine, and the strength of the alloy is high, but the plasticity is reduced, resulting in unqualified conditions.

[0023] The second step is to perform secondary solid solution on the forgings after step one:

[0024] The Ti60 forgings are heated again to 25-35℃ below the β transformation temperature, kept at this temperature for 1-3h, furnace cooled to about 900℃-920℃, kept at this temperature for 1h, and then removed from the furnace for oil cooling. Since the first half was furnace cooled, the cooling rate was basically reduced to 3℃ / min-5℃ / min. At this time, part of the β phase will undergo β→α phase transformation in the range of 900-920℃. At this time, keep it in this range for 1h, so that part of the α' phase is transformed into the α phase. Then continue to choose oil cooling. The starting temperature of martensite transformation is generally around 900℃, and oil cooling can continue to ensure the strength of the forgings.

[0025] The third step is to age the forgings after step 2:

[0026] Aging of forgings after two solid solution treatments: Heat the forgings after solid solution treatment to 700℃, keep them at this temperature for 8h, and air cool them after they are taken out of the furnace. During the aging process, the remaining α' phase continues to transform into the α phase. In this process, phase transformation processes such as the decomposition of the solid solution, the formation and growth of the precipitated phase α and silicide occur, which continuously improves the strength of the forgings. However, it should be noted that the aging time should not be too long, otherwise it will cause the precipitated phase to grow and reduce the plasticity and toughness of the alloy.

[0027] In summary, the present invention specifies the heat treatment process parameters of double solution + aging of Ti60 forgings by comprehensively considering the influence of parameters such as the double solution temperature, solution time, solution cooling method, aging temperature and time on the microstructure and performance of the forgings. The Ti60 forgings can obtain qualified microstructures through parameter control, and the unqualified plasticity of the forgings can be effectively improved to obtain excellent comprehensive mechanical properties. The process is simple and stable, the operation is convenient, and it is suitable for industrial production.

[0028] Example

[0029] In this embodiment, a ring forging with an outer dimension of Ф753×Ф658×141 is used, and the plasticity of the forging is unqualified after a single solution + aging heat treatment system; the specific data is shown in Table 1:

[0030] Table 1

[0031]

[0032] At this time, the primary α phase in the forging is only 8% to 10%. Figure 1 ; 15% to 35% do not meet the standard requirements; re-heat treatment of forgings: primary solution treatment: Tβ-22℃×2h, oil cooling; secondary solution treatment: Tβ-35℃×2h, furnace cooling to 920℃×1h, oil cooling; aging: 700℃×8h, air cooling, the data after repair are shown in Table 2.

[0033] Table 2

[0034]

[0035] After re-heat treatment, the strength of the forgings decreased slightly, but the elongation and cross-sectional shrinkage increased significantly, and the α phase content increased to about 18-20%. Figure 2 , effectively improving the plasticity of forgings and ensuring comprehensive performance.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A Ti60 forging secondary solid solution + aging heat treatment method, characterized in that: The following steps are involved: Step 1: Solvent-treat the formed Ti60 forging: Heat the Ti60 forging to 15℃~25℃ below the β transformation temperature, keep warm for 1~3h, and cool with oil; Step 2: Perform secondary solid solution treatment on the forgings after step 1: Heat the Ti60 forging again to 25-35°C below the β transformation temperature, keep it warm for 1-3 hours, cool it in the furnace to 900-920°C, keep it warm for 1 hour, and then take it out of the furnace and oil cool it; Step 3: Aging of the forgings after step 2: Aging of forgings after two solid solution treatments: heat the forgings after solid solution treatment to 700°C, keep warm for 8 hours, and air cool them out of the furnace.

2. The method according to claim 1, characterized in that The specific primary solution temperature of Ti60 forgings is related to the phase transformation point. When the phase transformation point temperature is high, the primary solution temperature needs to be reduced to 20℃~25℃ below the β transformation temperature. When the phase transformation point temperature is low, the primary solution temperature needs to be reduced to 15℃~20℃ below the β transformation temperature to balance the error caused by the phase transformation point test.

3. The method according to claim 1, characterized in that The oil temperature during the primary solution and secondary solution oil cooling needs to be controlled at 20-50° C., and the oil cooling transfer time needs to be controlled within 60 seconds to ensure a better solution effect.

4. The method according to claim 1, characterized in that: The solution time of step one is 1 to 3 hours, and the thicker the thickness, the longer the insulation time.

5. The method according to claim 1, characterized in that The secondary solution temperature needs to be lower than the primary solution temperature so as not to eliminate the impact of the primary solution.

6. The method according to claim 5, characterized in that The less the equiaxed α phase content of the forging after the primary solid solution, the lower the secondary solid solution temperature should be.

7. The method according to claim 1, characterized in that The cooling method of step 2 is to cool the furnace to 900℃~920℃, keep it warm for 1h and then take it out of the furnace and oil cool it.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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