Method for processing of tc16 titanium alloy bar for cold heading

Abstract

The application discloses a processing method of TC16 titanium alloy rod for cold upsetting, and is specifically implemented according to the following steps: step 1, selecting a round rod blank qualified in flaw detection; step 2, performing flat square hole type rolling on the rod blank selected in step 1 after heating, and air cooling after rolling; step 3, performing centerless turning and skin removing treatment on the rolled rod blank treated in step 2; step 4, performing air heat treatment on the rod blank treated in step 3; step 5, performing straightening treatment on the rod treated in step 4; step 6, performing grinding and polishing treatment on the rod straightened in step 5; and step 7, performing coating treatment on the rod treated in step 6, so as to obtain the TC16 titanium alloy rod for cold upsetting. The method can provide large-size TC16 rods meeting cold upsetting processing requirements.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal processing technology, and relates to a processing method for TC16 titanium alloy bars for cold heading. Background Technology

[0002] TC16 titanium alloy is an α+β high-strength two-phase titanium alloy with a nominal composition of Ti-3Al-5Mo-4.5V. Its β-phase stabilization coefficient is 0.83, exhibiting good hardenability and low sensitivity to stress concentrations caused by notches and torsion. It can also be heat-treated for strengthening. Furthermore, this alloy has low strength and good plasticity in the annealed state, making it an excellent material for cold heading of aerospace fasteners. In Russia, cold heading is commonly used to directly produce fasteners, and the performance of the cold-deformed fasteners meets the requirements without subsequent heat treatment. This process is simple and cost-effective. However, cold heading involves large deformation of the material under high strain rate loading conditions, resulting in a complex stress state. It is a technique involving many factors such as materials science, mechanics, and heat transfer. Numerous process parameters are involved in cold heading, and the factors affecting the quality of cold heading are also complex.

[0003] According to conventional processes, TC16 bars with a diameter of Φ≥8.0mm cannot pass the 1 / 4 forging ratio test requirement for cold upsetting, and therefore cannot meet the processing requirements for cold-headed fasteners. Summary of the Invention

[0004] The purpose of this invention is to provide a processing method for TC16 titanium alloy bars for cold heading, which can provide large-size TC16 bars that meet the requirements of cold heading.

[0005] The technical solution adopted in this invention is a processing method for TC16 titanium alloy bars used in cold heading, specifically implemented according to the following steps:

[0006] Step 1: Select round bar blanks that have passed the flaw detection test;

[0007] Step 2: The bar billet selected in Step 1 is heated and then rolled through a flat square die, followed by air cooling.

[0008] Step 3: The rolled billet processed in Step 2 is subjected to a centerless milling process to remove the outer skin.

[0009] Step 4: Perform atmospheric heat treatment on the billet processed in Step 3;

[0010] Step 5: Straighten the bar material after step 4.

[0011] Step 6: Grind and polish the bar after straightening in step 5.

[0012] Step 7: Coating the bar material after step 6 to obtain TC16 titanium alloy bar material for cold heading.

[0013] The invention is further characterized in that,

[0014] In step 1, the specifications of the bar billet are Φ45mm~Φ55mm.

[0015] In step 2, the heating temperature does not exceed the phase transformation temperature of the billet, and the heating time is 1 hour.

[0016] In step 2, there are 12 rolling passes, of which the first 11 passes require a pause, with a pause time of 3s to 20s.

[0017] In step 4, the atmospheric heat treatment process is as follows: the heat treatment temperature is 700℃~820℃, the holding time is 2h, and then the furnace is cooled to 550℃ and then air cooled.

[0018] In step 5, the straightening process uses either thermal tension straightening or roller thermal straightening, with a straightening temperature of 500℃~680℃.

[0019] In step 6, the total grinding amount is ≥0.4mm and the grinding amount per pass is ≤0.3mm.

[0020] In step 7, the coating material is MoS2.

[0021] The beneficial effect of the present invention is that the processing method of TC16 titanium alloy bar for cold heading can be tested by cold upsetting. When the forging ratio is 1 / 4, there are no cracks on the sample surface. The bar that passes the cold upsetting test can be used in the field of cold heading of fasteners. Attached Figure Description

[0022] Figure 1 The image shows the microstructure of a 8.0mm TC16 titanium alloy bar for cold heading obtained in Example 1 of this invention.

[0023] Figure 2 The image shows the microstructure of a 10.0mm TC16 titanium alloy bar for cold heading obtained in Example 2 of this invention.

[0024] Figure 3 This is a microstructure diagram of a 12.0mm TC16 titanium alloy bar for cold heading obtained in Example 3 of the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0026] This invention provides a method for processing TC16 titanium alloy bars for cold heading, specifically implemented according to the following steps:

[0027] Step 1: Select round bar blanks that have passed the flaw detection test;

[0028] The billet specifications are Φ45mm~Φ55mm, the microstructure is a forging microstructure above the phase transformation point, the low magnification microstructure is uniform, and the high magnification microstructure and performance are not required. The chemical composition of the billet is shown in Table 1.

[0029] Table 1. Composition of TC16 titanium alloy billet (wt.%)

[0030]

[0031] Step 2: After heating the bar billet selected in Step 1, roll it through a flat square die. The rolled surface should be smooth and free of defects such as folds and cracks. After rolling, air cool it.

[0032] The heating temperature does not exceed the phase transformation temperature of the billet (800℃~850℃), the heating time is 1 hour, and the rolling passes are 12. The first 11 passes require a stop time of 3s~20s, which is mainly related to the rolling pass. The stop times are 20s, 20s, 18s, 18s, 15s, 15s, 10s, 10s, 8s, 6s, and 3s respectively.

[0033] Step 3: The rolled billet processed in Step 2 is subjected to a centerless milling process to remove the outer skin.

[0034] Step 4: Perform atmospheric heat treatment on the billet processed in Step 3;

[0035] The specific process of atmospheric heat treatment is as follows: the heat treatment temperature is 700℃~820℃, the holding time is 2h, and then the furnace is cooled to 550℃ and then air cooled.

[0036] Step 5: Straighten the bar material after step 4.

[0037] The straightening process uses either thermal tension straightening or roller thermal straightening, with a straightening temperature of 500℃~680℃.

[0038] Step 6: Grind and polish the bar after straightening in step 5.

[0039] Among them, the total grinding amount of the grinding process is ≥0.4mm, and the grinding amount per pass is ≤0.3mm;

[0040] Step 7: The bar material treated in Step 6 is coated with MoS2 to obtain TC16 titanium alloy bar material for cold heading.

[0041] Example 1

[0042] Prepare 8.0mm TC16 titanium alloy straight bars for cold heading.

[0043] Step 1: Select round bar blanks that have passed the flaw detection test;

[0044] Among them, the specifications of the billet are Φ45mm~Φ55mm, the microstructure is a forging microstructure above the phase transformation point, the low magnification microstructure is uniform, and the high magnification microstructure and performance are not required.

[0045] Step 2: Heat the bar billet selected in Step 1 to 800℃ in a box furnace and hold for 1 hour. Then, roll it to Φ9.5mm using a two-roll reversible rolling mill with a flat square pass. Roll for a total of 12 passes, with a deformation of 10% to 30% per pass. The first 11 passes require a pause, with pause times of 20s, 20s, 18s, 18s, 15s, 15s, 10s, 10s, 8s, 6s, and 3s respectively, to ensure a final rolling temperature ≥600℃. After rolling, air cool.

[0046] Step 3: The rolled billet processed in Step 2 is subjected to a centerless machining process to remove the outer layer until it reaches Φ8.6mm.

[0047] Step 4: Perform atmospheric heat treatment on the material processed in Step 3;

[0048] The specific process of atmospheric heat treatment is as follows: the heat treatment temperature is 800℃, the holding time is 2h, and then the furnace is cooled to 550℃ and then air cooled.

[0049] Step 5: Perform roller hot straightening on the bar material processed in Step 4. The straightening temperature is 500℃, the straightening necking is ≤0.2mm, and the curvature after straightening is ≤1.0mm / m.

[0050] Step 6: Grind and polish the bar after straightening in step 5.

[0051] Among them, the grinding process is to the bar material size of Φ7.970mm~Φ7.995mm, the polishing process is to the bar material size of Φ7.970mm~Φ7.995mm, the out-of-roundness is ≤0.010mm, and the surface finish Ra≤1.2μm;

[0052] Step 7: The bar material treated in Step 6 is coated with MoS2 to obtain TC16 titanium alloy bar material for cold heading.

[0053] The performance tests of the products prepared using this embodiment are shown in Table 2, and the metallographic images of the microstructure are shown in [Table 2]. Figure 1 , Figure 1 The left image shows the metallographic microstructure of the transverse section, and the right image shows the metallographic microstructure of the longitudinal section. The obtained TC16 titanium alloy bar meets the processing requirements of cold heading fasteners.

[0054] Table 2 Performance results of TC16 bar stock Φ8.0mm

[0055]

[0056] Example 2

[0057] Cold-forged TC16 titanium alloy straight bars with a diameter of 10.0 mm were used to prepare the pallet nut.

[0058] Step 1: Select round bar blanks that have passed the flaw detection test;

[0059] Among them, the specifications of the billet are Φ45mm~Φ55mm, the microstructure is a forging microstructure above the phase transformation point, the low magnification microstructure is uniform, and the high magnification microstructure and performance are not required.

[0060] Step 2: Heat the bar billet selected in Step 1 to 830℃ in a box furnace and hold for 1 hour. Then, roll it to Φ11.5mm using a two-roll reversible rolling mill with a flat square pass. Roll for a total of 12 passes, with a deformation of 10% to 30% per pass. The first 11 passes require a pause, with pause times of 20s, 20s, 18s, 18s, 15s, 15s, 10s, 10s, 8s, 6s, and 3s respectively, to ensure a final rolling temperature ≥600℃. After rolling, air cool.

[0061] Step 3: The rolled bar billet processed in Step 2 is subjected to a centerless machining process to remove the outer layer until it reaches Φ10.6mm.

[0062] Step 4: Perform atmospheric heat treatment on the billet processed in Step 3;

[0063] The specific process of atmospheric heat treatment is as follows: the heat treatment temperature is 820℃, the holding time is 2h, and then the furnace is cooled to 550℃ and then air cooled.

[0064] Step 5: Perform hot tension straightening or roller hot straightening on the bar material processed in Step 4. The straightening temperature is 680℃, the straightening necking is ≤0.2mm, and the curvature after straightening is ≤1.0mm / m.

[0065] Step 6: Grind and polish the bar after straightening in step 5.

[0066] Among them, the grinding process is to the bar material size of Φ9.950mm~Φ9.995mm, the polishing process is to the bar material size of Φ9.950mm~Φ9.995mm, the out-of-roundness is ≤0.010mm, and the surface finish Ra≤1.2μm;

[0067] Step 7: The bar material treated in Step 6 is coated with MoS2 to obtain TC16 titanium alloy bar material for cold heading.

[0068] The performance tests of the products prepared using this embodiment are shown in Table 2, and the metallographic images of the microstructure are shown in [Table 2]. Figure 2 , Figure 2 The left image shows the metallographic microstructure of the transverse section, and the right image shows the metallographic microstructure of the longitudinal section. The obtained TC16 titanium alloy bar meets the processing requirements of cold heading fasteners.

[0069] Table 3 Performance results of TC16 bar stock Φ10.0mm

[0070]

[0071] Example 3

[0072] Prepare 12.0mm TC16 titanium alloy straight bars for cold heading.

[0073] Step 1: Select round bar blanks that have passed the flaw detection test;

[0074] Among them, the specifications of the billet are Φ45mm~Φ55mm, the microstructure is a forging microstructure above the phase transformation point, the low magnification microstructure is uniform, and the high magnification microstructure and performance are not required.

[0075] Step 2: Heat the bar billet selected in Step 1 to 850℃ in a box furnace and hold for 1 hour. Then, roll it to Φ13.5mm using a two-roll reversible rolling mill with a flat square pass. Roll for a total of 12 passes with a deformation of 10% to 30% per pass. The first 11 passes require a pause, with pause times of 20s, 20s, 18s, 18s, 15s, 15s, 10s, 10s, 8s, 6s, and 3s respectively, to ensure a final rolling temperature ≥600℃. After rolling, air cool.

[0076] Step 3: The rolled bar billet processed in Step 2 is subjected to a centerless machining process to remove the outer layer until it reaches Φ12.6mm.

[0077] Step 4: Perform atmospheric heat treatment on the billet processed in Step 3;

[0078] The specific process of atmospheric heat treatment is as follows: the heat treatment temperature is 700℃, the holding time is 2h, and then the furnace is cooled to 550℃ and then air cooled.

[0079] Step 5: Perform roller hot straightening on the bar material processed in Step 4. The straightening temperature is 580℃, the straightening necking is ≤0.2mm, and the curvature after straightening is ≤1.0mm / m.

[0080] Step 6: Grind and polish the bar after straightening in step 5.

[0081] Among them, the grinding process is to the size of the bar material being Φ11.950mm~Φ11.995mm, the polishing process is to the size of Φ11.950mm~Φ11.995mm, the out-of-roundness is ≤0.010mm, and the surface finish Ra is ≤1.2μm;

[0082] Step 7: The bar material treated in Step 6 is coated with MoS2 to obtain TC16 titanium alloy bar material for cold heading.

[0083] The performance tests of the products prepared using this embodiment are shown in Table 3, and the metallographic images of the microstructure are shown in [Table 3]. Figure 3 , Figure 3 The left image shows the metallographic microstructure of the transverse section, and the right image shows the metallographic microstructure of the longitudinal section. The obtained TC16 titanium alloy bar meets the processing requirements of cold heading fasteners.

[0084] Table 3 Performance results of TC16 bar stock Φ12.0mm

[0085]

Claims

1. A method for processing TC16 titanium alloy bars for cold heading, characterized in that, The specific steps are as follows: Step 1: Select round bar blanks that have passed the flaw detection test; Step 2: The bar billet selected in Step 1 is heated and then rolled through a flat square die, followed by air cooling. In step 2, the heating temperature does not exceed the phase transformation temperature of the billet; In step 2, there are 12 rolling passes, of which the first 11 passes require a pause, with a pause time of 3s to 20s; Step 3: The rolled billet processed in Step 2 is subjected to a centerless milling process to remove the outer skin. Step 4: Perform atmospheric heat treatment on the billet processed in Step 3; Step 5: Straighten the bar material after step 4. In step 5, the straightening process uses thermal tension straightening or roller thermal straightening, and the straightening temperature is 500℃~680℃. Step 6: Grind and polish the bar after straightening in step 5. Step 7: Coating the bar material processed in Step 6 to obtain TC16 titanium alloy bar material for cold heading. The specifications of TC16 titanium alloy bar material for cold heading are Φ8.0mm~12.0mm. When the forging ratio is 1 / 4, there are no surface cracks.

2. The processing method for TC16 titanium alloy bars for cold heading according to claim 1, characterized in that, In step 1, the specifications of the bar billet are Φ45mm~Φ55mm.

3. The processing method for TC16 titanium alloy bars for cold heading according to claim 1, characterized in that, In step 4, the atmospheric heat treatment process is as follows: the heat treatment temperature is 700℃~820℃, the holding time is 2h, and then the furnace is cooled to 550℃ and then air cooled.

4. The processing method for TC16 titanium alloy bars for cold heading according to claim 1, characterized in that, In step 6, the total grinding amount is ≥0.4mm and the grinding amount per pass is ≤0.3mm.

5. The processing method for TC16 titanium alloy bars for cold heading according to claim 1, characterized in that, In step 7, the coating material is MoS2.

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