Annealing method of martensite titanium alloy material

Abstract

The invention relates to the technical field of titanium alloy annealing, in particular to an annealing method of a martensite titanium alloy material. The method specifically comprises the following steps that firstly, a martensite titanium alloy material part is fed into a furnace at 800 DEG C, the temperature is increased to 940 + / -10 DEG C, and heat preservation is conducted for 1.5-3 h; 2, cooling to 680 + / -20 DEG C, and keeping the temperature for 2-4 hours; and thirdly, after heat preservation is finished, the part is cooled, and the part is obtained. Compared with the prior art, according to the technical scheme, the technological parameter range is smaller than before, technological parameters are more reasonable, operability is higher, the percent of pass is greatly increased, the percent of pass of one-time inspection is increased to 98% from 50%, and energy consumption and labor cost caused by repeated reworking are reduced.

Description

Technical Field

[0001] This application relates to the field of titanium alloy annealing technology, and in particular to an annealing method for martensitic titanium alloy materials. Background Technology

[0002] For (α+β) type titanium alloys with a nominal composition of Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si, designated TC6 in China, the parts are generally used in an annealed state, but solution aging strengthening heat treatment is also possible. Existing annealing methods include ordinary annealing, isothermal annealing, and double annealing. Relevant standards also recommend the temperature range, time, and cooling method for ordinary annealing, isothermal annealing, and double annealing. The standards specify the following parameters for ordinary annealing: heating at (800~850)℃ and holding for (1~2) hours followed by air cooling; for isothermal annealing: heating at (870~920)℃ and holding for (1~2) hours followed by furnace cooling to (550~650)℃ and holding for 2 hours followed by air cooling; for double annealing: heating at (870~920)℃ and holding for (1~2) hours followed by air cooling, then heating at (550~650)℃ and holding for (2~5) hours followed by air cooling. Regarding the performance requirements after annealing, only the tensile strength Rm≥980MPa after ordinary annealing is specified. There are no requirements for hardness and strength indicators after isothermal annealing and double annealing.

[0003] For existing TC6 material parts, when the design does not require specific hardness or strength, the M-state (annealed) material is generally directly machined into parts, while the R-state (hot-rolled) material is machined into parts after annealing. When the design requires reducing the hardness of the R-state (hot-rolled) and M-state (annealed) raw materials, the only current method is isothermal annealing. The parameters are heating at (870~920)℃ and holding for (1~2) hours, followed by furnace cooling to (550~650)℃, heating and holding for 2 hours, and then air cooling. However, this method is not yet mature, and the first-pass yield rate is only 50%.

[0004] Whether in the R (hot-rolled) or M (annealed) state, the hardness of TC6 raw material is generally 37–41 HRC. Designers select different hardness indices based on the service conditions of the TC6 material parts. When a designer requires 32–36 HRC, the annealing schemes recommended by existing standards cannot meet the technical requirements. This is because the parameters recommended by the standards have no direct correlation with the final hardness or strength values. Furthermore, there is no conversion relationship between the hardness and strength of titanium alloys in national and industry standards. This means that annealing process design cannot determine parameters based on hardness or strength values, resulting in poor production operability. Production workers can only continuously adjust parameters within the process range, performing rework operations. After multiple reworks, the hardness or strength of the parts still does not meet the design requirements, necessitating further adjustments to process parameters until the annealed hardness meets the design requirements. In short, the existing process technology requires multiple adjustments, lacks operability, has low production efficiency, and high production costs.

[0005] Therefore, finding an annealing method for martensitic titanium alloys with a smaller range of process parameters, more reasonable process parameters, better operability, and the ability to significantly improve the yield rate and reduce energy consumption and labor costs caused by multiple reworks is an urgent problem to be solved. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems in the prior art, this application provides an annealing method for martensitic titanium alloy materials, which is specifically achieved through the following technical solution.

[0007] An annealing method for martensitic titanium alloy materials includes the following steps:

[0008] Step 1: The martensitic titanium alloy parts are placed in the furnace at 800℃, heated to 940±10℃, and held for 1.5 to 3 hours. To minimize the hardness of the parts, the isothermal annealing temperature must be increased. The inventors of this application have determined through experiments that if the hardness is to be reduced to 32 to 36 HRC, the annealing temperature should be set to (940±10)℃.

[0009] Step 2: Cool to 680±20℃ and keep warm for 2~4 hours.

[0010] Step 3: After the heat preservation is completed, the parts are cooled to obtain the final product. To minimize the hardness of the parts, it is necessary to increase the isothermal temperature and extend the isothermal time after furnace cooling. Through experiments, the inventors of this application determined that if the hardness is to be reduced to 32-36 HRC, the isothermal temperature should be set to (680±20)℃ and the isothermal time should be set to (2-4)h.

[0011] Furthermore, the martensitic titanium alloy material is a martensitic (α+β) type titanium alloy material. Specifically, it is a TC6 titanium alloy with a nominal composition of Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si.

[0012] Furthermore, the method is an annealing method for TC6 titanium alloys with a hardness of 32-36 HRC.

[0013] Furthermore, the heating rate in step one is no more than 150℃ / h.

[0014] Furthermore, the cooling in step two is furnace-side cooling, and the cooling rate is no more than 100°C / h.

[0015] Furthermore, the cooling in step three is achieved through natural cooling in the air.

[0016] Compared with the prior art, the technical effects created by this application are reflected in:

[0017] (1) This application addresses TC6 titanium alloys in the R (hot-rolled) and M (annealed) states with a raw material hardness greater than 36 HRC. When the design requires a part hardness of 32–36 HRC, using the ordinary annealing method, the part is heated at (820–840) °C and held for (1–2) hours before air cooling. The resulting hardness value is higher than 36 HRC, which does not meet the design requirements. Using the double annealing method, the part is heated at (860–880) °C and held for (1–2) hours before air cooling in the first annealing process, and then heated at (580–600) °C and held for (2–3) hours before air cooling in the second annealing process. The resulting hardness value is higher than 36 HRC, which does not meet the design requirements. Using the isothermal annealing method, the part is heated at (860–880) °C and held for (1–2) hours, then furnace cooled to (610–630) °C and held for (2–3) hours before air cooling. The resulting hardness value is higher than 36 HRC, which does not meet the design requirements. Existing annealing techniques cannot meet the hardness index of 32-36 HRC. Therefore, by refining the parameters and optimizing the process design, a new annealing process for TC6 titanium alloy with a hardness index of 32-36 HRC has been invented.

[0018] (2) Existing TC6 titanium alloy annealing technology cannot effectively guide production. The first-pass yield is only 50%, and multiple reworks are required when the first pass fails. After rework, the hardness is slightly reduced to about 35-37 HRC, and the first-pass yield increases to 70%, but it still cannot meet the 32-36 HRC requirement. Multiple reworks not only increase the cost of electricity and labor, but also delay the production schedule. Through technical breakthroughs, a new TC6 titanium alloy annealing process with a hardness of 32-36 HRC was invented. This method has a first-pass yield of 98%, achieving cost reduction and efficiency improvement.

[0019] (3) Compared with the prior art, the technical solution of this application has a smaller range of process parameters, more reasonable process parameters, and stronger operability, which greatly improves the pass rate, increases the first-time pass rate from 50% to 98%, and reduces the energy consumption and labor costs caused by multiple reworks. Attached Figure Description

[0020] Figure 1 This is a flowchart of the annealing temperature change process in this application. Detailed Implementation

[0021] The technical solution of this application will be further defined below with reference to specific implementation methods, but the scope of protection is not limited to the description.

[0022] Example 1

[0023] The parts are made of martensitic (α+β) type titanium alloy material, which is TC6 titanium alloy with a nominal composition of Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si.

[0024] Step 1: Place the martensitic titanium alloy parts into the furnace at 800℃, raise the temperature to 940℃, and hold for 2 hours.

[0025] Step 2: Cool to 680℃ and keep warm for 3 hours.

[0026] Step 3: After the heat preservation is completed, the parts are cooled down, and the product is obtained.

[0027] Using the method in Example 1, the parts were processed and statistically analyzed, and the final first-pass yield was 98%, which can significantly improve the pass rate and reduce the energy consumption and labor costs caused by multiple reworks.

[0028] Example 2

[0029] The parts are made of martensitic (α+β) type titanium alloy material, which is TC6 titanium alloy with a nominal composition of Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si.

[0030] Step 1: Place the martensitic titanium alloy parts into the furnace at 800℃, raise the temperature to 950℃, and hold for 3 hours.

[0031] Step 2: Cool to 700℃ and keep warm for 4 hours.

[0032] Step 3: After the heat preservation is completed, the parts are cooled down, and the product is obtained.

[0033] Example 3

[0034] The parts are made of martensitic (α+β) type titanium alloy material, which is TC6 titanium alloy with a nominal composition of Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si.

[0035] Step 1: Place the martensitic titanium alloy parts into the furnace at 800℃, raise the temperature to 930℃, and hold for 1.5 hours.

[0036] Step 2: Cool to 660℃ and keep warm for 2 hours.

[0037] Step 3: After the heat preservation is completed, the parts are cooled down, and the product is obtained.

[0038] Finally, it should be noted that the above embodiments are merely representative examples of this application. Obviously, the technical solutions of this application are not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this application should be considered within the scope of protection of this application.

Claims

1. An annealing method for martensitic titanium alloy materials, characterized in that, Includes the following steps: Step 1: Place the martensitic titanium alloy parts into the furnace at 800℃, heat to 940±10℃, and hold for 1.5~3 hours; Step 2: Cool to 680±20℃ and hold for 2-4 hours; Step 3: After the heat preservation is completed, the parts are cooled down, and the product is obtained.

2. The annealing method for martensitic titanium alloy material according to claim 1, characterized in that, The martensitic titanium alloy material is a martensitic (α+β) type titanium alloy material.

3. The annealing method for martensitic titanium alloy materials according to claim 2, characterized in that, The martensitic (α+β) type titanium alloy material is TC6 titanium alloy.

4. The annealing method for martensitic titanium alloy material according to claim 3, characterized in that, The nominal composition of the TC6 titanium alloy is Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si.

5. The annealing method for martensitic titanium alloy material according to claim 3, characterized in that, It is an annealing method for TC6 titanium alloys with a hardness of 32-36 HRC.

6. The annealing method for martensitic titanium alloy material according to claim 1, characterized in that, The heating rate in step one shall not exceed 150℃ / h.

7. The annealing method for martensitic titanium alloy material according to claim 1, characterized in that, The cooling in step two is furnace-side cooling.

8. The annealing method for martensitic titanium alloy material according to claim 7, characterized in that, The furnace cooling process has a cooling rate of no more than 100°C / h.

9. The annealing method for martensitic titanium alloy material according to claim 1, characterized in that, The cooling in step three is achieved through natural cooling in the air.

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