A heat treatment method of secondary solid solution + aging of Ti60 forgings

Abstract

The application belongs to the field of metal material heat treatment, and particularly relates to a heat treatment method of secondary solid solution + aging of Ti60 forgings. The method comprises the following steps: step one, solid solution of the formed Ti60 forgings: heating the Ti60 forgings to 15-25 DEG C below the beta transformation temperature, keeping warm for 1-3 hours, and oil cooling; step two, heating the Ti60 forgings completed in step one to 25-35 DEG C below the beta transformation temperature, keeping warm for 1-3 hours, furnace cooling to 900-920 DEG C, keeping warm for 1 hour, and then discharging and oil cooling; and step three, aging of the forgings after twice solid solution: heating the solid-solutioned forgings to 700 DEG C, keeping warm for 8 hours, discharging, and air cooling.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metal material heat treatment, and particularly relates to a heat treatment method of secondary solid solution + aging of Ti60 forgings. BACKGROUND

[0002] Ti60 alloy is a Ti-Al-Sn-Zr-Mo titanium alloy, wherein a small amount of Si, C, Nb and Ta elements are added, and is a near-alpha type high-temperature titanium alloy designed for use in an environment below 600 DEG C. The aluminum equivalent of the alloy is 8.8, and the content of primary alpha phase is greatly affected by the solid solution temperature. The content and form of the primary alpha phase have an important influence on the performance of the forgings. According to data, when the solid solution temperature is increased by 20 DEG C, the volume fraction of the primary alpha phase is reduced by 20%, and the thermal stability and plasticity are greatly reduced. With the increase of the volume fraction of the primary alpha phase, the creep resistance monotonously decreases. In actual production, it is difficult to accurately control the content of the primary alpha phase by the traditional heat treatment method of one-time solid solution + aging, and the plasticity is often unqualified due to too little content of the primary alpha phase. SUMMARY

[0003] The application provides a heat treatment method of two-time solid solution + aging, and clearly regulates the two-time solid solution temperature, solid solution time, solid solution cooling mode, aging temperature and time, so that the content and form of the primary alpha phase can be effectively improved, and the plasticity of the Ti60 forging is finally improved.

[0004] A heat treatment method of secondary solid solution + aging of Ti60 forgings, characterized in that the method comprises the following steps:

[0005] Step one: one-time solid solution of the formed Ti60 forging:

[0006] The Ti60 forging is heated to 15 DEG C to 25 DEG C below the beta transformation temperature, is kept for 1 to 3 hours, and is oil-cooled.

[0007] Step two: secondary solid solution of the forging completed in step one:

[0008] The Ti60 forging is heated to 25 to 35 DEG C below the beta transformation temperature again, is kept for 1 to 3 hours, is furnace-cooled to about 900 DEG C to 920 DEG C, is kept for 1 hour, and is then taken out of the furnace and oil-cooled.

[0009] Step three: aging of the forging completed in step two:

[0010] The forging after the two-time solid solution is aged: the forging after the solid solution is heated to 700 DEG C, is kept for 8 hours, is taken out of the furnace, and is air-cooled.

[0011] Further, the specific primary solid solution temperature of the Ti60 forge piece is related to the phase transition point, when the phase transition point temperature is high, the primary solid solution temperature needs to be reduced to 20-25 DEG C below the beta transition temperature, when the phase transition point temperature is low, the primary solid solution temperature needs to be reduced to 15-20 DEG C below the beta transition temperature, so as to balance the error caused by the phase transition point test.

[0012] Further, the oil temperature of the primary solid solution and the secondary solid solution oil cooling needs to be controlled at 20-50 DEG C, and the oil cooling transfer time needs to be controlled within 60s, so as to ensure better solid solution effect.

[0013] Further, the solid solution time of step one is 1-3h, and the thicker the thickness, the longer the holding time.

[0014] Further, the secondary solid solution temperature needs to be lower than the primary solid solution temperature, so as to not eliminate the influence caused by the primary solid solution.

[0015] Further, the less the equiaxed alpha phase content of the forge piece after the primary solid solution, the lower the selected secondary solid solution temperature.

[0016] Further, the cooling mode of step two is furnace cooling to 900-920 DEG C, holding for 1h and then furnace oil cooling.

[0017] The Ti60 forge piece treated by the method has not only the required microstructure, but also the required strength index and toughness index. The method can effectively control the primary alpha phase content, thereby controlling the comprehensive mechanical properties of the Ti60 forge piece, and the process is simple, stable and convenient to operate, and is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The high magnification microstructure diagram before the repair of the embodiment.

[0019] Figure 2 The high magnification microstructure diagram after the repair of the embodiment using the heat treatment provided by the application. DETAILED DESCRIPTION

[0020] The Ti60 forge piece secondary solid solution + aging heat treatment method provided by the application has the following advantages:

[0021] First, the formed Ti60 forge piece is subjected to primary solid solution.

[0022] Ti60 forging is heated to 15-25℃ below the beta transition temperature, and is kept for 1-3h, and is oil cooled. During heating, the alpha phase is dissolved to beta phase, and during cooling, by controlling the oil temperature to 20-50℃, and oil cooling transfer time ≤60s, the primary alpha phase size is reduced, and the content is reduced, the alloy microstructure is changed from beta phase to alpha' martensite, the precipitated alpha' phase is fine, the strength of the alloy is high, but the plasticity is reduced, and unqualified conditions occur.

[0023] In the second step, the forging after the first step is subjected to secondary solid solution:

[0024] The Ti60 forging is heated again to 25-35℃ below the beta transition temperature, and is kept for 1-3h, and is furnace cooled to about 900-920℃, and is kept for 1h, and then is taken out of the furnace and is oil cooled. Since the first half is cooled in the furnace, the cooling rate is reduced to 3-5℃ / min, at this time, part of the beta phase will be transformed from beta to alpha phase at 900-920℃, and at this time, the alpha' phase is transformed into alpha phase by keeping for 1h in the range. Then continue to choose oil cooling, and the martensite transformation starts at about 900℃, and oil cooling can continue to ensure the strength of the forging.

[0025] In the third step, the forging after the second step is subjected to aging:

[0026] The forging after the two solid solutions is subjected to aging: the solid solution forging is heated to 700℃, and is kept for 8h, and is taken out of the furnace and is air cooled, and during the aging process, the remaining alpha' phase continues to transform into alpha phase. In this process, the decomposition of the solid solution, the formation and growth of the precipitated phase alpha and silicide, and other phase transformation processes occur, which continuously improve the strength of the forging, but attention should be paid to that the aging time should not be too long, otherwise the precipitated phase will grow, and the plasticity and toughness of the alloy will be reduced.

[0027] In summary, the present application considers the influence of the two solid solution temperatures, solid solution time, solid solution cooling method, aging temperature and time on the microstructure and performance of the forging, and specifies the heat treatment process parameters of the Ti60 forging two solid solutions + aging, which can make the Ti60 forging obtain qualified microstructure, and effectively improve the unqualified plasticity of the forging to obtain excellent comprehensive mechanical properties. The process is simple, stable, easy to operate, and suitable for industrial production.

[0028] Embodiment

[0029] In this embodiment, the outer size of the annular forging is Ф753*Ф658*141, and the plasticity of the forging after the first solid solution + aging heat treatment system is unqualified. The specific data is shown in Table 1:

[0030] Table 1

[0031]

[0032] At this time, the high-magnification primary α phase of the forging is only 8% to 10%, as shown in Figure 1 ; the 15% to 35% does not meet the standard requirement; the forging is re-heat treated: one solid solution: Tβ-22℃×2h, oil cooling; two solid solutions: Tβ-35℃×2h, furnace cooling to 920℃×1h, oil cooling; aging: 700℃×8h, air cooling, and the data after the repair is shown in Table 2.

[0033] Table 2

[0034]

[0035] After the re-heat treatment, the strength of the forging is slightly reduced, but the elongation and the area reduction are significantly improved, the α phase content is increased to about 18% to 20%, as shown in Figure 2 , and the plasticity of the forging is effectively improved, and the comprehensive performance is ensured.

[0036] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but the protection scope of the present application is not limited to this, any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered in the protection scope of the present application.

Claims

1. A heat treatment method of secondary solid solution + aging of a Ti60 forging, characterized by, The method comprises the following steps: Step one: once solid solution of the shaped Ti60 forge piece is carried out: The Ti60 forge piece is heated to 15-25℃ below the beta transformation temperature, kept for 1-3h, and oil cooled; Step two: twice solid solution of the forge piece after step one is carried out: The Ti60 forge piece is heated again to 25-35℃ below the beta transformation temperature, kept for 1-3h, furnace cooled to 900-920℃, kept for 1h, then taken out of the furnace and oil cooled; Step three: aging of the forge piece after step two is carried out: The forge piece after twice solid solution is aged: the forge piece after solid solution is heated to 700℃, kept for 8h, taken out of the furnace and air cooled; The specific once solid solution temperature of the Ti60 forge piece is related to the phase transition point, when the phase transition point temperature is high, the once solid solution temperature needs to be reduced to 20-25℃ below the beta transformation temperature, when the phase transition point temperature is low, the once solid solution temperature needs to be reduced to 15-20℃ below the beta transformation temperature, so as to balance the error caused by the phase transition point test; The oil temperature during the once and twice solid solution oil cooling needs to be controlled to 20-50℃, and the oil cooling transfer time needs to be controlled to be within 60s, so as to ensure good solid solution effect; The solid solution time of step one is 1-3h, the thicker the thickness, the longer the keeping time; The twice solid solution temperature needs to be lower than the once solid solution temperature, so as to not eliminate the influence caused by the once solid solution; The less the equiaxed alpha phase content of the forge piece after once solid solution, the lower the selected twice solid solution temperature; The cooling mode of step two is furnace cooling to 900-920℃, keeping for 1h, then taking out of the furnace and oil cooling.

2. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the method of claim 1.

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