Stepped TC32 titanium alloy free forging structure property control method

Abstract

The invention belongs to the field of forging hot working, and relates to a method for controlling the structure performance of a stepped TC32 titanium alloy free forge piece. The method comprises the following steps: forging: carrying out two-phase region forging by adopting a quick forging machine or a free forging hammer as required, upsetting or drawing out and shaping a bar, and carrying out one-heating-number or multi-heating-number material separation drawing out according to the size of a forge piece to obtain a final forge piece; and heat treatment, wherein quasi-beta annealing or double annealing is conducted according to the structure state requirement of the forge piece, and air cooling or air cooling is adopted as a cooling mode.

Description

Technical Field

[0001] The invention belongs to the field of forging hot processing and relates to a method for controlling the microstructure and properties of a step-type TC32 titanium alloy free forging. Background Art

[0002] TC32 titanium alloy has comprehensive high-performance characteristics such as medium-to-high strength, high plasticity, high toughness, fatigue resistance, and damage tolerance, and has process characteristics such as low cost and simple process. It has gradually become a new backbone material for aircraft structural parts. The main problems are as follows: 1. As a new backbone material, TC32 titanium alloy has insufficient experience in regulating and controlling the microstructure and properties of forgings, and further exploration is needed. 2. The forging heating temperature and time, deformation amount and other process parameters of TC32 step forgings need to be further quantified and strictly controlled. 3. The quasi-β annealing and double annealing heat treatment heating temperature and time, cooling method and other process parameters of TC32 step forgings need to be specifically quantified and strictly controlled to improve the qualification rate of forgings. Summary of the invention

[0003] The technical problem to be solved by the present invention is: to propose two-phase zone forging, rough machining and heat treatment process parameters for TC32 titanium alloy step forgings, to solve the matching problem of specific control points such as forging temperature, forging thermal insulation coefficient, forging forming method, forging deformation, forging deformation process control, rough machining equivalent thickness requirements, quasi-β annealing and double annealing heat treatment system, heat treatment cooling method and the organizational properties of forgings, so as to achieve qualified and stable delivery of forgings in batches.

[0004] Technical solution:

[0005] A method for controlling the microstructure and properties of a step-type TC32 titanium alloy free forging is provided, comprising:

[0006] Forging: Use a fast forging machine or a free forging hammer for two-phase forging as needed to upset or lengthen and shape the bar, and perform one or more fires of divided material lengthening according to the size of the forging to obtain the final forging;

[0007] Heat treatment: Quasi-β annealing or double annealing is carried out according to the requirements of the forging microstructure, and air cooling or wind cooling is adopted for cooling.

[0008] Furthermore, for forgings with complex structures, before heat treatment, the method further includes:

[0009] Rough machining: Rough machining is performed on the forgings according to the part size while ensuring the machining allowance and the standard requirements of the forgings to obtain rough-machined parts, thereby reducing the equivalent thickness of the forgings; the equivalent thickness of the forgings after rough machining must meet the requirements of 50mm to 200mm.

[0010] Furthermore, the forging temperature is selected to be below the phase change point (30-50)°C, the cold material heating insulation coefficient is calculated as 0.8min / mm, and the hot material returning to the furnace insulation coefficient is calculated as 0.5min / mm. Hot material returning to the furnace is preferred for heating between firings. Cold material heating is adopted when grinding and removal of damage are required depending on the damage of the forgings, and air cooling is adopted after forging.

[0011] Furthermore, multi-fire and multi-stage drawing includes:

[0012] The first fire uses the bar to be upset or stretched and shaped. The width and thickness of the billet obtained after shaping meet the maximum cross-sectional size of the forging. The subsequent fires are divided and stretched for one or more fires;

[0013] The maximum deformation of a single fire is ≤35%. During drawing, the feed amount of each hammer is 1 / 3 to 1 / 2 of the thickness to be pressed, and the deformation of each hammer is 10% to 15%.

[0014] Furthermore, the specific heat treatment system of quasi-β annealing is as follows:

[0015] The first stage of quasi-β annealing: the empty furnace is heated to 35℃ below the β phase transformation point, kept at this temperature for ≥10min, the forgings are loaded, and then heated to 35℃ below the β phase transformation point, kept at this temperature for 150±15min, and then heated to 15℃ above the phase transformation point in 40min~50min, with a heating coefficient of 0.35min / mm, and then air-cooled after being taken out of the furnace; the forgings are placed sideways during loading and cooling, with a spacing of ≥100mm between forgings, and the temperature is monitored by thermocouples at the maximum and minimum cross-sections of the forgings during the entire first stage of quasi-β annealing;

[0016] The second stage of quasi-β annealing: put it into the warm-charging furnace, then raise the temperature to 565℃, keep it at this temperature for 360±15min, and then air-cool it after it comes out of the furnace.

[0017] Further, the specific heat treatment system of double annealing is as follows:

[0018] Primary annealing: warm-charged furnace, heating to 875°C, heating coefficient 0.6-0.8min / mm, dispersed air cooling or air cooling;

[0019] Secondary annealing: put it in a warm furnace, raise the temperature to 550℃, keep it at this temperature for 6h, and then cool it in air or by wind.

[0020] Furthermore, when the equivalent thickness of the double annealed forging is ≥125mm, air cooling is required to improve the microstructure and performance of the forging. During air cooling, the spacing between the forgings is ≥500mm, and the distance from the fan is 800mm to 1500mm.

[0021] Furthermore, when the equivalent thickness of the double annealed forging is less than 125 mm, air cooling is used as the cooling method; and air cooling is used as the cooling method for the quasi-β annealing.

[0022] Beneficial effects: The process parameters for two-phase forging, rough machining and heat treatment of TC32 titanium alloy step forgings are proposed to solve the matching problem of specific control points such as forging temperature, forging insulation coefficient, forging forming method, forging deformation, forging deformation process control, rough machining equivalent thickness requirements, quasi-β annealing and double annealing heat treatment system, heat treatment cooling method and the microstructure and performance of forgings, so as to achieve qualified and stable delivery of forgings in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1a This is a schematic diagram of the structure of a forging in a quasi-β annealing heat treatment state according to an embodiment of the present invention.

[0024] Figure 1b This is a schematic diagram of the structure of a forging in a double annealing heat treatment state according to an embodiment of the present invention.

[0025] Figure 2 It is a schematic diagram of the forging deformation process steps of the present invention.

[0026] Figure 3 It is a rough processing diagram of the present invention.

[0027] Figure 4 This is a schematic diagram of furnace loading and cooling for the quasi-β annealing heat treatment of forgings according to the present invention.

[0028] Figure 5 This is a schematic diagram of cooling the forging after double annealing heat treatment of the present invention. DETAILED DESCRIPTION

[0029] The present invention proposes two-phase zone forging, rough machining and heat treatment process parameters for TC32 titanium alloy step forgings to solve the matching problem of various process parameters, control points and forging microstructure and performance. The specific steps are as follows.

[0030] Example 1

[0031] The present invention provides a method for controlling the microstructure and properties of a step-type TC32 titanium alloy free forging, such as Figure 3 Forgings shown, the process is as follows Figure 2 As shown, the method includes:

[0032] Step 1: Forging

[0033] Use a fast forging machine or a free forging hammer for two-phase zone forging. The forging temperature is (30-50)℃ below the phase change point. The cold material heating insulation coefficient is calculated as 0.8min / mm, and the hot material return insulation coefficient is calculated as 0.5min / mm. Hot material return heating is preferred between fires. Cold material heating is used when grinding and removal of damage are required depending on the damage of the forging. The first forging fire uses bars for upsetting or drawing and shaping. After shaping, the width and thickness dimensions meet the maximum cross-sectional dimensions of the forging. Subsequent fires are divided into multiple fires for drawing and the maximum deformation of a single forging fire is ≤35%. The feed amount of each hammer during drawing is 1 / 3-1 / 2 of the thickness to be pressed, and the deformation of each hammer is 10%-15%. After forging, air cooling is used to obtain the final forging ( Figure 1a ).

[0034] Step 2: Rough Machining

[0035] According to the part size, the forging is rough-machined on the basis of ensuring the machining allowance and the standard requirements of the forging to obtain a rough-machined part, thereby reducing the equivalent thickness of the forging.

[0036] Preferably: the equivalent thickness of the forging after rough machining should meet the requirements of 50mm to 200mm ( Figure 3 ).

[0037] Step 3: Heat Treatment

[0038] Quasi-β annealing, air cooling after annealing.

[0039] The specific heat treatment system for quasi-β annealing is as follows:

[0040] The first stage of quasi-β annealing: heat the empty furnace to 35℃ below the β phase transformation point, keep it warm for ≥10min, load the forgings, heat it to 35℃ below the β phase transformation point, keep it warm for 150±15min, and then heat it to 15℃ above the phase transformation point in 40min~50min. The heating coefficient is 0.35min / mm. After taking out of the furnace, air cool it. Figure 4 );

[0041] The second stage of quasi-β annealing: put it into the warm furnace, then heat it to 565℃, keep it warm for 360±15min, and air cool it after it comes out of the furnace. Figure 4 ).

[0042] Preferably: further, the forgings are placed sideways during charging and cooling, the forging spacing is ≥100 mm, and the temperature is monitored by thermocouples at the maximum and minimum cross-sections of the forgings during the entire first stage of quasi-β annealing.

[0043] Example 2

[0044] The present invention provides a method for controlling the microstructure and properties of a step-type TC32 titanium alloy free forging, the method comprising:

[0045] Step 1: Forging

[0046] Use a fast forging machine or a free forging hammer for two-phase zone forging. The forging temperature is (30-50)℃ below the phase change point. The cold material heating insulation coefficient is calculated as 0.8min / mm, and the hot material return insulation coefficient is calculated as 0.5min / mm. Hot material return heating is preferred between fires. Cold material heating is used when grinding and removal of damage are required depending on the damage of the forging. The first forging fire uses bars for upsetting or drawing and shaping. After shaping, the width and thickness dimensions meet the maximum cross-sectional dimensions of the forging. Subsequent fires are divided and drawn in one fire. The maximum deformation of a single forging fire is ≤35%. The feed amount of each hammer during drawing is 1 / 3-1 / 2 of the thickness to be pressed, and the deformation of each hammer is 10%-15%. After forging, air cooling is used to obtain the final forging ( Figure 1b ).

[0047] Step 2: Heat Treatment

[0048] Double annealing

[0049] The specific heat treatment system for double annealing is as follows:

[0050] Primary annealing: warm-charged furnace, heating to heating temperature 875℃, heating coefficient 0.6~0.8min / mm, dispersed air cooling or wind cooling.

[0051] Secondary annealing: put it in a warm furnace, raise the temperature to 550℃, keep it at this temperature for 6h, and then cool it in air or by wind.

[0052] Preferably: when the equivalent thickness of the double annealed forging is ≥125mm, air cooling is required to improve the microstructure and performance of the forging. When air cooling is used, the spacing between the forgings is ≥500mm and the distance from the fan is 800mm to 1500mm. For specific placement methods, see Figure 5 .

[0053] Example 3

[0054] A type of machine beam free forgings such as Figure 1a As shown, the rod material is TC32, specification The outline dimensions of the forging are: 1350×435×310. The design methods of forging, rough machining, heat treatment, etc. are as follows.

[0055] Step 1: Forging

[0056] Heating at the phase change point (30-50)℃, 4-6 forgings are performed; the deformation of each forging is distributed in 15%-35%, the feed amount of each hammer during drawing is 1 / 3-1 / 2 of the thickness to be pressed, and the deformation of each hammer is 10%-15%. The cooling method after forging is air cooling.

[0057] Step 2: Rough Machining

[0058] The forgings are rough-machined according to the part size and forging standard requirements to obtain rough-machined parts with an equivalent thickness of ~125mm.

[0059] Step 3: Heat Treatment

[0060] Quasi-β annealing is adopted, and the specific heat treatment system is as follows:

[0061] The first stage of quasi-β annealing: heat the empty furnace to 35℃ below the β phase transformation point, keep warm for ≥10min, put in the forgings, heat again to 35℃ below the β phase transformation point, keep warm for 150±15min, then heat to 13℃ above the phase transformation point in 40min, keep warm After taking it out of the oven, let it air cool;

[0062] The second stage of quasi-β annealing: put it into the warm-charging furnace, then raise the temperature to 565℃, keep it at this temperature for 360±15min, and then air-cool it after it comes out of the furnace.

[0063] After the implementation of the present invention, two-phase zone forging, rough machining and heat treatment process parameters of TC32 titanium alloy step forgings are proposed to solve the matching problem of specific control points such as forging temperature, forging thermal insulation coefficient, forging forming method, forging deformation, forging deformation process control, rough machining equivalent thickness requirements, quasi-β annealing and double annealing heat treatment system, heat treatment cooling method and the organizational properties of forgings, so as to achieve qualified and stable delivery of forgings in batches.

Claims

1. A method for controlling the microstructure and properties of step-type TC32 titanium alloy free forgings, characterized in that: include: Forging: Use a fast forging machine or a free forging hammer for two-phase forging as needed to upset or lengthen and shape the bar, and perform one or more fires of divided material lengthening according to the size of the forging to obtain the final forging; Heat treatment: Quasi-β annealing or double annealing is carried out according to the requirements of the forging microstructure, and air cooling or wind cooling is adopted for cooling.

2. The method according to claim 1, characterized in that For forgings with complex structures, before heat treatment, the method further includes: Rough machining: Rough machining is performed on the forgings according to the part size while ensuring the machining allowance and the standard requirements of the forgings to obtain rough-machined parts, thereby reducing the equivalent thickness of the forgings; the equivalent thickness of the forgings after rough machining must meet the requirements of 50mm to 200mm.

3. The method according to claim 1, characterized in that The forging temperature is selected to be below the phase change point (30-50)℃, the cold material heating insulation coefficient is calculated as 0.8min / mm, and the hot material returning to the furnace insulation coefficient is calculated as 0.5min / mm. Hot material returning to the furnace is preferred for heating between firings. Cold material heating is adopted when grinding and removal of damage are required depending on the damage of the forgings. Air cooling is adopted after forging.

4. The method according to claim 3, characterized in that Multi-fire and multi-stage pulling, including: The first fire uses the bar to be upset or stretched and shaped. The width and thickness of the billet obtained after shaping meet the maximum cross-sectional size of the forging. The subsequent fires are divided and stretched for one or more fires; The maximum deformation of a single fire is ≤35%. During drawing, the feed amount of each hammer is 1 / 3 to 1 / 2 of the thickness to be pressed, and the deformation of each hammer is 10% to 15%.

5. The method according to claim 1, characterized in that The specific heat treatment system for quasi-β annealing is as follows: The first stage of quasi-β annealing: the empty furnace is heated to 35℃ below the β phase transformation point, kept at this temperature for ≥10min, the forgings are loaded, and then heated to 35℃ below the β phase transformation point, kept at this temperature for 150±15min, and then heated to 15℃ above the phase transformation point in 40min~50min, with a heating coefficient of 0.35min / mm, and then air-cooled after being taken out of the furnace; the forgings are placed sideways during loading and cooling, with a spacing of ≥100mm between forgings, and the temperature is monitored by thermocouples at the maximum and minimum cross-sections of the forgings during the entire first stage of quasi-β annealing; The second stage of quasi-β annealing: put it into the warm-charging furnace, then raise the temperature to 565℃, keep it at this temperature for 360±15min, and then air-cool it after it comes out of the furnace.

6. The method according to claim 1, characterized in that The specific heat treatment system for double annealing is as follows: Primary annealing: warm-charged furnace, heating to 875°C, heating coefficient 0.6-0.8min / mm, dispersed air cooling or air cooling; Secondary annealing: put it in a warm furnace, raise the temperature to 550℃, keep it at this temperature for 6h, and then cool it in air or by wind.

7. The method according to claim 6, characterized in that When the equivalent thickness of double annealed forgings is ≥125mm, air cooling is required to improve the microstructure and performance of the forgings. During air cooling, the spacing between forgings is ≥500mm, and the distance from the fan is 800mm to 1500mm.

8. The method according to claim 6, characterized in that When the equivalent thickness of the double annealed forging is less than 125mm, air cooling is used for cooling; air cooling is used for quasi-β annealing.

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