Preparation method of a Ti-Mo-Ni-Y rare earth titanium alloy sheet

Abstract

The present invention discloses a preparation method of a Ti-Mo-Ni-Y rare earth titanium alloy plate, belonging to the technical field of titanium alloy melting. The titanium alloy in the present invention is a Ti-Mo-Ni-Y titanium alloy, and its chemical composition by mass percentage includes: Mo: 0.23-0.40%, Ni: 0.71-0.9%, Y: 0.0095-0.15%, and the balance is Ti. The preparation method is as follows: 25-40% of the uniformly mixed Ti-15Mo master alloy and sponge titanium is used as layer A, and pure Y particles and nickel chips are wrapped with pure titanium foil and arranged along the central position of the four equal parts as layer B, and a columnar ingot is pressed in the arrangement of A-B-A-B-A; the feeding speed y of the electron beam cold hearth melting furnace and the melting speed x satisfy the formula y = kx, where 0.000834 ≤ k ≤ 0.00167, and a titanium alloy slab with uniform composition is obtained by melting. Then, milling is carried out and it is directly rolled into a plate without forging. Among them, the total number of rolling passes is 12, and the total deformation amount is 97%. On the one hand, the method of the present invention can reduce the volatilization of rare earth Y element during the melting process, and the composition of the slab is more uniform; on the other hand, a titanium alloy slab with significantly refined grains can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy smelting, and particularly relates to a method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy plate. Background Art

[0002] As for traditional titanium alloys used in the chlor-alkali industry, in addition to requiring excellent corrosion resistance, their strength is still a very important indicator. With the development of industrialization, the strength level of titanium alloys is difficult to meet the increasingly demanding industrial service standards, resulting in a short service life of titanium alloys during their industrial applications and restricting the long-term application of titanium alloys. Therefore, mass-producing high-strength and high-corrosion-resistant titanium alloys is a very meaningful task.

[0003] During the actual process of electron beam cold hearth melting of titanium alloy ingots, the addition of rare earth elements can improve the crystal structure of titanium alloys, reduce the grain size, and increase the strength and hardness of titanium alloys. Rare earth elements can also form solid solutions with titanium alloys to increase the strength of titanium alloys. However, due to the easy volatility of rare earth elements, it is difficult to control the uniformity of product composition during the melting process. At the same time, due to the too high melting point of rare earth oxides, they are not suitable as raw materials for electron beam cold hearth melting. Therefore, controlling the volatilization of rare earth elements and the uniformity of ingots during the melting process is of great significance for the preparation of high-quality high-strength and high-corrosion-resistant titanium alloys. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy plate, which specifically includes the following steps:

[0005] (1) Set the composition of the required Ti-Mo-Ni-Y titanium alloy as the nominal composition for melting, and calculate and accurately weigh titanium sponge, Ti-15Mo master alloy, nickel chips, and pure Y particles.

[0006] (2) Wrap the pure Y particles and nickel chips with pure titanium foil to form an alloy packet, and then mix the Ti-15Mo master alloy and titanium sponge evenly and dry them.

[0007] (3) Divide the dried mixture of Ti-15Mo master alloy and titanium sponge into 3 equal parts and add them in 3 times. Divide the alloy packet into two equal parts and add them in two times. Specifically: first add the evenly mixed Ti-15Mo master alloy and titanium sponge, then add the alloy packet along the center position of the four equal parts to form an alloy packet layer, then add the Ti-15Mo master alloy and titanium sponge, continue to add the alloy packet along the center position of the four equal parts, and finally add the remaining Ti-15Mo master alloy and titanium sponge, and press them into columnar ingots.

[0008] (4) Uniformly arrange the ingot blocks in the feeding chamber of the electron beam cold hearth melting furnace. The feeding is a continuous process, and as time goes by, the feeding speed is directly proportional to the melting speed. Among them, the feeding speed y and the melting speed x satisfy the formula y = kx, where 0.000834 ≤ k ≤ 0.00167. A flat ingot of Ti-Mo-Ni-Y rare earth titanium alloy with uniform composition is obtained by melting.

[0009] (5) After milling the as-cast alloy ingot, it is directly rolled into plates without forging.

[0010] Preferably, in step (1) of the present invention, the raw materials are cleaned and dried. Among them, the sponge titanium is 0A grade sponge titanium with a purity higher than 99.8%.

[0011] Preferably, the drying conditions in step (2) of the present invention are: drying at 100 - 200 °C for 2 - 3 h.

[0012] Preferably, in step (3) of the present invention, the uniformly mixed Ti-15Mo master alloy and sponge titanium are added in three times. The mass percentage added for the first time is 25 - 40%, the mass percentage added for the second time is 25 - 40%, and the remaining is added for the third time.

[0013] Preferably, in step (4) of the present invention, the melting vacuum degree needs to reach 1.0×10 -3 ~1.0×10 -8 Pa, the melting speed is 600 - 800 kg / h, and the melting temperature is 1800 - 2100 °C.

[0014] Preferably, in step (5) of the present invention, the non-forging direct rolling starting rolling temperature for the first fire is 930 - 940 °C, rolling for 5 passes with a reduction rate of 75 - 85% to ensure the crushing of the large dendritic crystals in the ingot. The rolling temperature for the second fire is 840 - 850 °C, rolling for 7 passes with a reduction rate of 88 - 88%. The total rolling is 12 passes, and the total deformation is 97%.

[0015] The inventor found that the EB furnace melting process is a semi-continuous casting process, from the non-steady state to the steady state. As the melting time prolongs, the melt continuously flows into the mold, and the molten pool becomes deeper. At this time, by adjusting the speed of the feeding chamber, it can make the previous batch of sponge titanium blocks completely solidify while reducing the depth of the molten pool, avoiding the formation of defects, and obtaining high-quality and uniform products.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] (1) The present invention uses a flat ingot obtained by one-time melting in an electron beam cold hearth furnace (EB furnace), while the traditional vacuum consumable arc furnace (VAR furnace) needs to be melted 3 - 4 times. And the EB furnace melting can fully remove high- and low-density inclusions, shorten the process flow, reduce the melting cost, and can obtain large-sized flat ingots.

[0018] (2) The present invention innovatively proposes an ABABA material distribution method (A is Ti-15Mo master alloy and sponge titanium, and B is an alloy material package), which can effectively reduce the volatilization of the Y element, reduce alloy loss, and improve the uniformity of the alloy composition.

[0019] (3) The novel Ti-Mo-Ni-Y titanium alloy flat ingot prepared by the present invention significantly refines the titanium alloy grains by adding a trace amount of rare earth Y element, thereby increasing the yield strength by 7.8-14.9% and the tensile strength by 8-24.2%.

[0020] (4) The equation relationship between the feed chamber speed and the smelting speed described in the present invention can, on the one hand, avoid poor product performance caused by too slow a melting speed and too fast a feed chamber speed, and on the other hand, avoid slow production rate and high production cost caused by too fast a melting speed and the feed chamber speed failing to keep up. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the material distribution method of the present invention;

[0022] Figure 2 It is the microstructure diagram of Ti-0.32Mo-0.8Ni-0.01Y alloy;

[0023] Figure 3 It is the microstructure diagram of Ti-0.31Mo-0.82Ni-0.05Y alloy;

[0024] Figure 4 It is the microstructure diagram of Ti-0.23Mo-0.87Ni-0.1Y alloy;

[0025] Figure 5 This is the microstructure diagram of the comparative example Ti-0.3Mo-0.8Ni alloy. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0027] Example 1

[0028] A method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy plate, the specific steps are as follows (see Figure 2 ):

[0029] (1) Clean and dry 0A grade titanium sponge with a purity higher than 99.8%, Ni chips, pure Y particles and Ti-15Mo master alloy, and prepare the ingredients. The estimated melting weight is about 9800 kg.

[0030] (2) Wrap the pure Y particles with pure titanium foil to form an alloy material package. Then, mix the Ti-15Mo master alloy, nickel chips, and sponge titanium evenly and dry them. The drying time is 2 h, and the drying temperature is 200 °C.

[0031] (3) Divide the dried mixture of Ti-15Mo master alloy and sponge titanium into 3 equal parts and add them in 3 times. Divide the alloy material package into two equal parts and add them in two times. Specifically: First, add the evenly mixed Ti-15Mo master alloy and sponge titanium, then add the alloy material package along the central position of the four equal parts to form an alloy material package layer, then add the Ti-15Mo master alloy and sponge titanium, continue to add the alloy material package along the central position of the four equal parts, and finally add the remaining Ti-15Mo master alloy and sponge titanium, and press them into a 150 Kg columnar ingot.

[0032] (4) Arrange the sponge titanium blocks evenly in the charging box of the electron beam cold hearth melting furnace, melt the sponge titanium blocks. The melting speed is 600 Kg / h, the melting temperature is 1900 °C, and the size of the melted titanium alloy slab is 8100 mm in length × 1040 mm in width × 220 mm in thickness; the speed y of the feeding chamber and the melting speed x satisfy the formula y = 0.00111x.

[0033] (5) Use a milling machine to mill the oxide scale of the titanium alloy slab, and perform non-forging straight rolling on the milled slab with a size of 8000 mm in length × 1020 mm in width × 200 mm in thickness. The starting rolling temperature for the first hot rolling is 940 °C, rolling 5 passes, with a reduction ratio of 75%, ensuring the crushing of the large dendritic crystals in the ingot. The rolling temperature for the second hot rolling is 840 °C, rolling 7 passes, with a reduction ratio of 88%. The total number of rolling passes is 12, and the total deformation is 97%. The final thickness of the sheet is 6 mm.

[0034] (6) After rolling, wait for the sheet to cool to room temperature and take metallographic and mechanical property specimens from the center of the sheet.

[0035] Example 2

[0036] A preparation method of a Ti-Mo-Ni-Y rare earth titanium alloy sheet, the specific steps are as follows (see Figure 3 ):

[0037] (1) Charge the grade 0 sponge titanium with a purity higher than 99.8%, nickel chips, pure Y particles, and Ti-15Mo master alloy after cleaning and drying, and the expected melting weight is about 9800 Kg.

[0038] (2) Wrap the pure Y particles with pure titanium foil to form an alloy material package. Then, mix the Ti-15Mo master alloy, nickel chips, and sponge titanium evenly and dry them. The drying time is 3 h, and the drying temperature is 100 °C.

[0039] (3) The dried Ti-15Mo master alloy and titanium sponge mixture is divided into three equal parts and added in three times. The alloy charge packet is divided into two equal parts and added in two times. Specifically: first add the uniformly mixed Ti-15Mo master alloy and titanium sponge, then add the alloy charge packet along the central position of the four equal parts to form an alloy charge packet layer, then add the Ti-15Mo master alloy and titanium sponge, continue to add the alloy charge packet along the central position of the four equal parts, and finally add the remaining Ti-15Mo master alloy and titanium sponge, and press them into 150 Kg columnar ingots.

[0040] (4) Arrange the titanium sponge blocks evenly in the charge box of the electron beam cold hearth melting furnace, melt the titanium sponge blocks, the melting speed is 700 Kg / h, the melting temperature is 1880 °C, and the size of the melted titanium alloy slab is 8120 mm in length × 1080 mm in width × 230 mm in thickness; the speed y of the feeding chamber and the melting speed x satisfy the formula y = 0.000834x.

[0041] (5) Use a milling machine to mill the oxide scale of the titanium alloy slab, and perform non-forging straight rolling on the milled slab with a length of 8000 mm × a width of 1020 mm × a thickness of 200 mm. The starting rolling temperature of the hot rolling in one pass is 935 °C, rolling 5 passes, and the reduction rate is 80% to ensure the crushing of the large dendritic crystals in the ingot. The rolling temperature in the second pass is 845 °C, rolling 7 passes, and the reduction rate is 85%. The total number of rolling passes is 12, and the total deformation is 97%. The final thickness of the sheet is 6 mm.

[0042] (6) After rolling, wait for the sheet to cool to room temperature and take metallographic and mechanical property specimens from the center of the sheet.

[0043] Example 3

[0044] A preparation method of a Ti-Mo-Ni-Y rare earth titanium alloy sheet, the specific steps are as follows (see Figure 4 ):

[0045] (1) Charge the grade 0 titanium sponge with a purity higher than 99.8%, Ni chips, pure Y particles and Ti-15Mo master alloy after cleaning and drying, and the expected melting weight is about 9800 Kg.

[0046] (2) Wrap the pure Y particles with pure titanium foil to form an alloy charge packet, and then mix the Ti-15Mo master alloy, nickel chips and titanium sponge evenly and dry them. The drying time is 2 h, and the drying temperature is 150 °C.

[0047] (3) The dried Ti-15Mo master alloy and titanium sponge mixture is divided into three equal parts and added in three times. The alloy charge packet is divided into two equal parts and added in two times. Specifically: first add the uniformly mixed Ti-15Mo master alloy and titanium sponge, then add the alloy charge packet along the center position of the four equal parts to form an alloy charge packet layer, then add the Ti-15Mo master alloy and titanium sponge, continue to add the alloy charge packet along the center position of the four equal parts, and finally add the remaining Ti-15Mo master alloy and titanium sponge, and press them into 150 Kg columnar ingots.

[0048] (4) Arrange the titanium sponge blocks evenly in the charge box of the electron beam cold hearth melting furnace, melt the titanium sponge blocks, the melting speed is 800 Kg / h, the melting temperature is 2080 °C, and the size of the melted titanium alloy slab is 8135 mm in length × 1056 mm in width × 213 mm in thickness. The speed y of the feeding chamber and the melting speed x satisfy the formula y = 0.00167x.

[0049] (5) Use a milling machine to mill the oxide scale of the titanium alloy slab, and perform non-forging straight rolling on the milled slab with a length of 8000 mm × a width of 1020 mm × a thickness of 200 mm. The starting rolling temperature for the first hot rolling is 930 °C, rolling is carried out for 5 passes, and the reduction ratio is 85%, ensuring the fragmentation of the large dendritic crystals in the as-cast ingot. The rolling temperature for the second pass is 850 °C, rolling is carried out for 7 passes, and the reduction ratio is 80%. The total number of rolling passes is 12, and the total deformation is 97%. The final thickness of the sheet is 6 mm.

[0050] (6) After rolling, wait for the sheet to cool to room temperature and take metallographic and mechanical property specimens from the center of the sheet.

[0051] Comparative Example 1

[0052] The raw materials and steps used in this example are the same as those in Example 1, except that: no pure Y particles are added.

[0053] Comparative Example 2

[0054] The raw materials and steps used in this example are the same as those in Example 1, except that: step (3) is modified to: mix the alloy charge packet with the mixture of Ti-15Mo master alloy and titanium sponge evenly, and press them into columnar ingots.

[0055] Comparative Example 3

[0056] The raw materials and steps used in this example are the same as those in Example 1, except that: in step (4), the speed of the feeding chamber is equal to the melting speed.

[0057] Comparative Example 4

[0058] The raw materials and steps used in this example are the same as those in Example 1, except that: in step (5), the hot rolling conditions are: the starting rolling temperature is 940 °C, rolling is carried out for 12 passes, the total deformation is 97%, and the final sheet thickness is 6 mm.

[0059] The alloy sheets of Examples 1-3 and Comparative Examples 1-4 were analyzed as follows:

[0060] (1) Mechanical property analysis

[0061] Tensile tests were carried out on the alloy sheets of Examples 1-3 and Comparative Examples 1-4; 5 groups of tensile specimens were taken for each group to ensure reliable experimental results; the room temperature unidirectional tensile experiment was carried out using an American MTS E45 universal material testing machine, and the pulling speed was 1 mm / min to obtain relevant data such as mechanical properties. The test results are shown in Table 1.

[0062] Table 1 Test results of the mechanical properties of the titanium alloy sheets of Examples 1-3 and Comparative Examples 1-4

[0063]

[0064] It can be seen from the comparison between Example 1 and Comparative Example 1 that the yield strength increased by up to 14.9%, the tensile strength increased by 24.2%, and the elongation did not decrease significantly. The reason is that a trace amount of rare earth Y element was added in the present invention. The addition of Y element can effectively limit the growth of grains. As Figures 2 to 4 It can be seen that the titanium alloy of the present invention is composed of very fine basket-like α phases. After adding Y element in the present invention, the α clusters are significantly more refined. The microstructure is the finest after adding 0.1Y. While the microstructure of Comparative Alloy 1 is composed of long strip-like α phases and is relatively coarse. Due to the addition of Y element in the present invention, the microstructure of the titanium alloy is significantly refined and will exist in the form of nano-particles Y2O3 at the grain boundaries, hindering the movement of dislocations, thereby increasing the yield strength and tensile strength of the titanium alloy obtained in the present invention.

[0065] It can be seen from the comparison between Example 1 and Comparative Example 2 that the yield strength increased by up to 13.5%, the tensile strength increased by 21.6%, and the elongation increased. The reason is that when the alloy material package is mixed evenly with the mixture of Ti-15Mo master alloy and sponge titanium in Comparative Example 2, the Y particles will leak during the standing time after mixing, resulting in the enrichment of Y particles at the bottom of the columnar material block, while there are few or no Y particles in the middle and upper parts. At this time, the yield strength and tensile strength of the alloy both decreased significantly.

[0066] It can be seen from the comparison between Example 1 and Comparative Example 3 that the yield strength is increased by 3.6%, the tensile strength is increased by 15.8%, and the elongation is also increased. The reason is that in Comparative Example 3, the melting speed is equal to the feeding speed. When the first batch of materials enters the molten pool, they have not completely melted yet. At this time, the melting speed will be slower than the feeding speed, resulting in the situation that the materials of the previous batch in the molten pool have not completely melted while the next batch of materials has already reached the molten pool. Finally, the composition of the ingot obtained by melting is uneven, so the yield strength and tensile strength are reduced.

[0067] It can be seen from the comparison between Example 1 and Comparative Example 4 that the yield strength is increased by 6.1%, the tensile strength is increased by 2.7%, and the elongation is also increased. The reason is that direct single-pass rolling causes cracking at the edges of the alloy, resulting in a reduction in the yield strength and tensile strength of the alloy.

Claims

1. A method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy sheet, characterized in that, Specifically, it includes the following steps: (1) Set the composition of the required Ti-Mo-Ni-Y rare earth titanium alloy sheet to the smelting nominal composition, and calculate and accurately weigh titanium sponge, Ti-15Mo master alloy, nickel chips and pure Y grains; (2) Wrap the pure Y grains and nickel chips with pure titanium foil to form an alloy charge packet, and then mix the Ti-15Mo master alloy and titanium sponge evenly and dry them; (3) Divide the dried mixture of Ti-15Mo master alloy and titanium sponge into 3 equal parts and add them in 3 times. Divide the alloy charge packet into two equal parts and add them in 2 times. Specifically: first add the evenly mixed Ti-15Mo master alloy and titanium sponge, then add the alloy charge packet along the center position of each quarter to form an alloy charge packet layer, then add the Ti-15Mo master alloy and titanium sponge, continue to add the alloy charge packet along the center position of each quarter, and finally add the remaining Ti-15Mo master alloy and titanium sponge, and press them into columnar ingots; (4) Arrange the columnar ingots evenly in the feeding chamber of the electron beam cold hearth melting furnace. The feeding is a continuous process, and as time goes by, the feeding speed is proportional to the melting speed. Among them, the feeding speed y and the melting speed x satisfy the formula y = kx, where 0.000834 ≤ k ≤ 0.00167; melt to obtain a Ti-Mo-Ni-Y rare earth titanium alloy slab with uniform composition; (5) After milling the surface of the Ti-Mo-Ni-Y rare earth titanium alloy slab, perform non-forging straight rolling to form a sheet.

2. The method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy sheet according to claim 1, characterized in that: In step (1), the raw materials are cleaned and dried. Among them, the titanium sponge is 0A grade titanium sponge with a purity higher than 99.8%.

3. The method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy sheet according to claim 1, characterized in that: The drying conditions in step (2) are: drying at 100 - 200 °C for 2 - 3 h.

4. The method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy sheet according to claim 1, characterized in that: In step (4), the melting vacuum degree needs to reach 1.0×10 -3 ~1.0×10 -8 Pa, the melting speed is 600 - 800 kg / h, and the melting temperature is 1800 - 2100 °C.

5. The method for preparing a Ti-Mo-Ni-Y rare earth titanium alloy sheet according to claim 1, characterized in that: In step (5), the non-forging straight rolling one-fire starting rolling temperature is 930 - 940 °C, rolling 5 passes with a reduction rate of 75 - 85% to ensure crushing of the coarse dendritic crystals in the ingot. The two-fire rolling temperature is 840 - 850 °C, rolling 7 passes with a reduction rate of 80 - 88%. The total rolling is 12 passes and the total deformation is 97%.

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