A sulfur-containing free-cutting titanium alloy without adding heavy metals and a preparation method thereof

Abstract

The present invention discloses a sulfur-containing free-cutting titanium alloy without adding heavy metals and a preparation method thereof, belonging to the field of non-ferrous metal materials. The composition of the free-cutting titanium alloy material is as follows by mass percentage: S: 0.2-0.4%; O: 0.3-0.45%; B: 0.003-0.006%; C≤0.03%; N≤0.03%, and the balance is titanium and unavoidable impurities. The present invention also discloses a preparation method of the raw material titanium sponge for the free-cutting titanium alloy material and a method for preparing the free-cutting titanium alloy material. Through unique composition design and preparation process, the present invention avoids the addition of heavy metals for fixing S in the free-cutting titanium alloy, makes the titanium alloy of the present invention have better biocompatibility, makes the titanium sulfide compounds in the titanium alloy evenly distributed, improves the chip breaking property and the cutting edge lubrication condition, solves the problems of the uniformity of the distribution of element S and element B and the surface cracking of the hot-worked titanium alloy material containing element S, shortens the production cycle, reduces the cost, and significantly improves the cutting performance of the titanium alloy.

Description

Technical Field

[0001] The invention relates to the field of nonferrous metal materials, and in particular to a sulfur-containing free-cutting titanium alloy without adding heavy metals and a preparation method thereof. Background Art

[0002] Titanium and titanium alloys have been widely used in aerospace, automobile manufacturing, medical equipment and many other fields due to their low density, high strength, good corrosion resistance, excellent biocompatibility and many other advantages. However, the poor cutting performance of titanium alloys (also known as titanium materials) has severely limited its efficient processing and wide application in industrial production, as shown below:

[0003] High temperature in the cutting zone: Titanium has a low thermal conductivity, which is only one-fourth of that of iron. During the cutting process, the heat generated is difficult to discharge and accumulates on the cutting edge, causing the temperature in the cutting zone to rise sharply, which not only accelerates the wear of the tool, but also affects the surface quality and dimensional accuracy of the machined parts.

[0004] High hardness and severe work hardening: Titanium will experience significant work hardening during processing, and its surface is prone to react with gases in the air to form a "tissue hardening layer". This greatly increases the cutting force on the tool during cutting, aggravates tool wear, and even causes tool breakage, which seriously reduces the tool life and increases processing costs.

[0005] High chemical activity: Titanium has high chemical activity and will react chemically with the components in the tool during the cutting process, resulting in an increase in the friction coefficient between the tool and the titanium material and a serious phenomenon of tool sticking. A large amount of heat is concentrated on the blade, further aggravating the wear of the tool and affecting the processing accuracy and surface quality.

[0006] Low elastic modulus: Titanium has a low elastic modulus and is prone to springback during processing. This will not only cause stress on the back of the tool, aggravating tool wear, but also seriously affect the surface accuracy of the processed parts, resulting in large processing size deviations, making it difficult to meet high-precision processing requirements.

[0007] At present, in order to improve the cutting performance of titanium materials, research is mainly carried out in the following three directions:

[0008] Develop high-performance cutting tools: Research and develop high-hardness, high-toughness, and high-temperature resistant cutting tool materials, such as carbide tools and ceramic tools, to improve the wear resistance and heat resistance of the tools and adapt to the cutting of titanium materials. However, these high-performance tools are expensive and still cannot fully meet the needs of efficient and high-precision processing of titanium materials under certain complex processing conditions.

[0009] Improve cutting conditions: Ultra-low temperature machining or appropriate cooling and lubricating media are used to reduce the temperature in the cutting zone, reduce tool wear and work hardening. Ultra-low temperature machining requires special equipment and processes, with high costs; while choosing an appropriate cooling and lubricating medium can improve machining conditions to a certain extent, but the improvement effect on cutting performance is limited, and it may bring problems such as environmental pollution.

[0010] Design easy-to-cut material components and microstructures: On the one hand, by optimizing the strength-plasticity matching of titanium metal, reducing the strength-plasticity product, thereby reducing cutting resistance; on the other hand, adding precipitate-forming elements to promote the formation of a second phase that is brittle, has weak interfacial bonding, or has certain lubricating effects itself, improving the chip breaking property of titanium metal. However, there are many problems in the implementation of traditional methods. For example, adding certain elements may lead to increased costs and poor biocompatibility.

[0011] In addition, as an easy-to-cut element, adding S to titanium materials is beneficial to improving cutting performance. The principle is that S combines with Ti to form an easy-to-cut titanium sulfide compound. However, when using traditional melting methods, liquid S and Ti will stratify after the sponge titanium melts, resulting in uneven distribution of titanium sulfide compounds and affecting the improvement effect of cutting performance. Therefore, heavy metals such as rare earths that can fix S must be added to existing easy-to-cut titanium alloy compositions. And as the S content in titanium materials increases, the hot working performance of titanium materials will be greatly reduced, especially the surface is prone to cracking, which severely restricts the development and application of S-containing easy-to-cut titanium alloys.

[0012] In summary, the existing methods for improving the cutting performance of titanium materials have various limitations. Developing a sulfur-containing easy-to-cut titanium alloy that does not add heavy metals, has low costs, excellent cutting performance, and stable hot working performance, as well as its preparation method, has important practical significance. Summary of the Invention

[0013] Based on this, to overcome the deficiencies of the above-mentioned prior art, a sulfur-containing easy-to-cut titanium alloy that does not add heavy metals and its preparation method are provided, aiming to solve the problems of high costs, poor biocompatibility of existing easy-to-cut titanium alloys, uneven element distribution, and surface cracking during hot working of S-containing titanium alloys, and then apply the easy-to-cut titanium alloy to the fields of human contact equipment and food processing equipment.

[0014] To achieve the above objectives, the following technical solutions are adopted:

[0015] The present invention provides a sulfur-containing easy-to-cut titanium alloy material that does not add heavy metals. The composition of the sulfur-containing easy-to-cut titanium alloy material is calculated by mass percentage as follows: S: 0.2 - 0.4%; O: 0.3 - 0.45%; B: 0.003 - 0.006%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and unavoidable impurities.

[0016] In some embodiments, the composition of the sulfur-containing free-cutting titanium alloy material is by mass percentage: S: 0.4%; O: 0.3%; B: 0.003%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and unavoidable impurities.

[0017] In some embodiments, the composition of the sulfur-containing free-cutting titanium alloy material is by mass percentage: S: 0.2%; O: 0.4%; B: 0.006%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and unavoidable impurities.

[0018] The present invention also provides a method for preparing sponge titanium as the raw material of the sulfur-containing free-cutting titanium alloy material as described above, including the following steps:

[0019] S101. During the production process of the Kroll process, TiCl4 gas, H2S gas and BCl3 gas are simultaneously introduced into the reaction kettle.

[0020] S102. Obtain sponge titanium particles with a maximum particle diameter ≤ 6 mm through distillation and multi-stage crushing treatment.

[0021] S103. Place the sponge titanium particles flat and bake them in an oven at 500 - 550 °C for 50 - 90 minutes.

[0022] In some embodiments, the multi-stage crushing includes three-stage crushing processes of jaw crushing, cone crushing and roll crushing in sequence.

[0023] In some embodiments, in step S101, the molar ratio of Ti:S is controlled to be 99:(0.36 - 0.71), and the molar ratio of Ti:B is controlled to be 99:(0.006 - 0.012).

[0024] The present invention also provides a method for preparing the sulfur-containing free-cutting titanium alloy material as described above from the sponge titanium particles obtained by the preparation method as described above, including:

[0025] Press the sponge titanium particles into a blank; stack the blanks into a TA1 sleeve and evacuate and seal; perform hot isostatic pressing sintering under argon protection to obtain a square blank for rolling; heat the sintered square blank to 900 - 930 °C and then roll it into a free-cutting titanium alloy material coil through a hot continuous rolling mill.

[0026] In some embodiments, the step of "pressing the sponge titanium particles into a blank" includes:

[0027] Press the sponge titanium particles into a blank under a pressure of 500 - 900 MPa.

[0028] In some embodiments, in the hot isostatic pressing sintering step:

[0029] The sintering temperature is 900 - 1000 °C, the pressure is 90 - 100 MPa, and the sintering time is 3 - 5 h.

[0030] In some embodiments, the heating rate of the hot isostatic pressing sintering is 2 - 5 °C / min.

[0031] The present invention has the following beneficial technical effects:

[0032] Through unique composition design and preparation process, and by means of solid-state sintering, the present invention avoids the separation of Ti and S during the liquid melting process, also avoids the addition of heavy metals necessary for fixing S, and at the same time makes the titanium sulfide compounds in the titanium alloy evenly distributed, improving the chip breaking property and the cutting tool tip lubrication condition, and solving the problem of the uniformity of the distribution of element S and element B. By adopting the method of using an external S-free jacket, and taking advantage of the good workability of the outer surface jacket, it avoids the exposure of the poorly machinable S-containing part on the outside, solves the problem of hot working surface cracking of the titanium alloy material containing element S, shortens the production cycle, reduces the cost, and significantly improves the cutting performance of the titanium alloy.

[0033] The sulfur-containing free-cutting titanium alloy material of the present invention without adding heavy metals contains layered titanium sulfide compounds. The titanium sulfide compounds are soft and prone to interlayer slip. The evenly distributed titanium sulfide compounds play a role in improving the chip breaking property of the chips and improving the cutting tool tip lubrication condition. The composition of this titanium alloy contains boron, and boron is a grain refinement element in the titanium alloy. Fine grains are more conducive to high-temperature deformation, reducing the high-temperature flow stress and preventing deformation cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0035] Figure 1 It is a flowchart of the method for preparing the free-cutting titanium alloy material of the present invention;

[0036] Figure 2 It is a metallographic diagram of the free-cutting titanium alloy material of Embodiment 1 of the present invention;

[0037] Figure 3 It is a metallographic diagram of the free-cutting titanium alloy material of Embodiment 2 of the present invention;

[0038] Figure 4 It is a metallographic diagram of the titanium alloy material of the comparative example. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following further elaborates on the embodiments of the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0040] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments of the present invention are described in detail, those skilled in the art can easily appreciate that various modifications are feasible without substantially departing from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, parameters, etc. of the following exemplary embodiments.

[0041] Based on the above objectives, in the first aspect of the embodiments of the present invention, a sulfur-containing free-cutting titanium alloy material without adding heavy metals is proposed. The composition of the sulfur-containing free-cutting titanium alloy material is by mass percentage: S: 0.2 - 0.4%; O: 0.3 - 0.45%; B: 0.003 - 0.006%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and other unavoidable impurities in the sponge titanium, mainly including Fe, Si, Mg, H, etc. For the unavoidable impurities, it is required that the content of a single impurity ≤ 0.05%, and the sum of the contents of the unavoidable impurities ≤ 0.1%.

[0042] In the second aspect of the embodiments of the present invention, a preparation method of a sulfur-containing free-cutting titanium alloy material is proposed. Figure 1 The following shows a schematic flowchart of this method.

[0043] As Figure 1 shown, the preparation may include the following steps:

[0044] S101. During the Kroll process, synchronously introduce TiCl4 gas, H2S gas, and BCl3 gas into the reaction kettle.

[0045] S102. Obtain sponge titanium particles with a maximum particle diameter ≤ 6 mm through distillation and multi-stage crushing treatment.

[0046] S103. Place the sponge titanium particles flat and bake them in an oven at 500 - 550 °C for 50 - 90 minutes.

[0047] S104. Press the sponge titanium particles into blanks; stack the blanks into a TA1 jacket and evacuate and seal them; perform hot isostatic pressing sintering under argon protection to obtain square blanks for rolling; heat the sintered square blanks to 900 - 930 °C and then roll them into free-cutting titanium alloy material coils through a hot continuous rolling mill.

[0048] Among them, S101 - S103 are the preparation methods of the raw material titanium sponge for the sulfur - containing free - cutting titanium alloy material, which increases the oxygen content. The main effective element contents of the obtained titanium sponge are: S: 0.2 - 0.4%; O: 0.3 - 0.45%; B: 0.003 - 0.006%; S104 is the method of preparing the free - cutting titanium alloy material from the titanium sponge particles prepared by S101 - S103.

[0049] In a preferred embodiment of the present invention, the multi - stage crushing includes three crushing processes of jaw crushing, cone crushing, and roll crushing in sequence.

[0050] In a preferred embodiment of the present invention, in step S101, the molar ratio of Ti:S is controlled to be 99:(0.36 - 0.71), and the molar ratio of Ti:B is controlled to be 99:(0.006 - 0.012).

[0051] In a preferred embodiment of the present invention, the step of "pressing the titanium sponge particles into a blank" includes:

[0052] Pressing the titanium sponge particles into a blank under a pressure of 500 - 900 MPa.

[0053] In a preferred embodiment of the present invention, in the hot isostatic pressing sintering step: the sintering temperature is 900 - 1000 °C, the pressure is 90 - 100 MPa, and the sintering time is 3 - 5 h.

[0054] In a preferred embodiment of the present invention, the heating rate of the hot isostatic pressing sintering is 2 - 5 °C / min.

[0055] In a preferred embodiment of the present invention, the hot continuous rolling mill includes a rough rolling mill, an intermediate rolling mill, and a finishing rolling mill arranged in sequence, and the total deformation elongation rate ≥ 120.

[0056] In a preferred embodiment of the present invention, the wall thickness of the TA1 sheath is 10 - 15 mm, and the residual air pressure after vacuum pumping .

[0057] In a preferred embodiment of the present invention, the bulk density of the titanium sponge particles is 2.2 - 2.5 g / cm³.

[0058] In the preparation method of the present invention, there is no liquid melting process, and alloying elements are introduced in the preparation stage of titanium sponge, which solves the problem of the distribution uniformity of the main free - cutting element S and the grain growth inhibition element B, and overcomes the problem of the stratification of liquid S and Ti in the traditional melting method.

[0059] By using the method of pressing - block heating and isostatic pressing, a layer of TA1 with excellent deformation performance is coated on the surface of the square billet, which solves the problem of surface cracking during the hot processing of sulfur - containing titanium materials.

[0060] The traditional multiple melting and forging to produce billets is shortened to one-time hot isostatic pressing, thus shortening the production and processing cycle. At the same time, the hot isostatic pressing achieves net shaping, eliminating the need for ingot peeling and surface milling and grinding of billets, improving the raw material utilization rate and reducing the production cost.

[0061] Improved cutting performance: The titanium alloy of the present invention contains titanium sulfide compounds with a layered structure, and this titanium sulfide compound is soft and prone to interlayer slip. During the cutting process, the uniformly distributed titanium sulfide compounds can improve the chip breaking property of the chips, making the chips easier to break and discharge. At the same time, it can also improve the lubrication conditions at the tool tip, reduce the friction between the tool and the titanium alloy, lower the cutting force, and thus significantly improve the cutting performance of the titanium alloy.

[0062] Grain refinement and improvement of processing performance: Boron contained in the alloy is a grain refinement element. During the solidification and processing of the titanium alloy, boron can inhibit the growth of grains, enabling the titanium alloy to form a fine grain structure. The fine grains are more conducive to high-temperature deformation, reducing the high-temperature flow stress, improving the plasticity and toughness of the material, effectively preventing deformation cracking during the processing, and improving the hot processing performance of the titanium alloy.

[0063] Improved element distribution uniformity: The present invention does not have the traditional liquid melting process, but instead incorporates alloying elements S and B at the sponge titanium preparation stage. By adding H2S and BCl3 gases during the reduction process of producing sponge titanium by the Kroll process, S and B are uniformly distributed in the sponge titanium, solving the problem of the distribution uniformity of the main free-cutting element S and the grain growth inhibiting element B, and overcoming the problem of liquid S and Ti stratification in the traditional melting method.

[0064] Solution to the problem of hot working surface cracking: By using the method of pressing and heating for hot isostatic pressing, a layer of TA1 with excellent deformation performance is coated on the surface of the square billet. TA1 can effectively protect the surface of the sulfur-containing titanium material during the hot working process, alleviating the problem of hot working surface cracking caused by the increase in S content, and ensuring the quality and performance stability of the titanium alloy during the hot working process.

[0065] Reduced production cost: The traditional multiple melting and forging to produce billets is shortened to one-time hot isostatic pressing, simplifying the production process flow and shortening the production and processing cycle. At the same time, the near-net shaping technology of hot isostatic pressing eliminates the need for processes such as ingot peeling and surface milling and grinding of billets, reducing material loss, improving the raw material utilization rate, thus reducing the production cost and enhancing the market competitiveness of the product.

[0066] The present invention is further illustrated by the following examples.

[0067] Example 1

[0068] A sulfur-containing free-cutting titanium alloy without adding heavy metals, with the following mass percentages: S: 0.4%; O: 0.3%; B: 0.003%; C ≤ 0.03%; N ≤ 0.03%, the balance being titanium and unavoidable impurities. Among the unavoidable impurities, the content of a single impurity is required to be ≤ 0.05%, and the total content of unavoidable impurities is ≤ 0.1%.

[0069] The preparation method of the above sulfur-containing free-cutting titanium alloy without adding heavy metals is as follows:

[0070] Sponge titanium is produced by the Kroll process. During the reduction process, TiCl4 gas, H2S gas and BCl3 gas are mixed and added, and the proportions of each gas are determined according to Ti:S = 99:0.71 and Ti:B = 99:0.006.

[0071] The sponge titanium ingot obtained in the above step is crushed by a multi-stage crusher, and the crushed material is screened by a vibrating screen with a screen hole diameter of 6 mm. The large particles are sent back to the crusher, and the small particles enter the next step.

[0072] The sponge titanium obtained in the above step is spread on a tray with a thickness ≤ 40 cm and sent into an oven at 500 °C for baking for 60 minutes.

[0073] The sponge titanium obtained in the above step is placed in a square mold and pressed into a 175 mm cube sintered block by an 8000-ton hydraulic press, and the compacting pressure is 600 MPa.

[0074] Thirty sintered blocks of sponge titanium obtained in the above step are loaded into a rectangular box welded by 2 mm TA1 titanium plates. The inner cavity size of the box is 175 mm × 175 mm × 5250 mm, and it is welded and sealed in a vacuum welding box to obtain a sintered blank.

[0075] The sintered blank is placed in a hot isostatic pressing furnace under argon protection for sintering. The sintering temperature is 900 °C, the pressure is 90 MPa, and the sintering time is 4 h to obtain a square billet for rolling.

[0076] The square billet is heated to 900 - 930 °C and rolled by a hot continuous rolling mill to obtain a sulfur-containing free-cutting titanium alloy coil without adding heavy metals.

[0077] Example 2

[0078] A sulfur-containing free-cutting titanium alloy without adding heavy metals, with the following mass percentages: S: 0.2%; O: 0.4%; B: 0.006%; C ≤ 0.03%; N ≤ 0.03%, the balance being titanium and unavoidable impurities. Among the unavoidable impurities, the content of a single impurity is required to be ≤ 0.05%, and the total content of unavoidable impurities is ≤ 0.1%.

[0079] The preparation method of the above sulfur-containing free-cutting titanium alloy without adding heavy metals is as follows:

[0080] Use the Kroll process to produce titanium sponge. During the reduction process, TiCl4, H2S, and BCl3 are added in a mixture, and the gas ratio is determined according to Ti:S = 99:0.36 and Ti:B = 99:0.012.

[0081] Crush the titanium sponge ingot obtained in the above step with a multi-stage crusher, and screen the crushed material with a vibrating screen with a screen hole diameter of 6 mm. The large particles are sent back to the crusher, and the small particles enter the next step.

[0082] Lay the titanium sponge obtained in the above step flat on a tray with a thickness ≤ 40 cm, and send it into an oven at 550 °C for baking for 90 minutes.

[0083] Place the titanium sponge obtained in the above step in a square mold, and use an 8000-ton hydraulic press to press it into a 175-mm cube sintered block. The compaction pressure is 600 MPa.

[0084] Load 30 sintered blocks of titanium sponge obtained in the above step into a rectangular box welded by 2-mm TA1 titanium plates. The inner cavity size of the box is 175 mm × 175 mm × 5250 mm, and it is welded and sealed in a vacuum welding box to obtain a sintered blank.

[0085] Place the sintered blank in a hot isostatic pressing furnace under argon protection for sintering. The sintering temperature is 900 °C, the pressure is 90 MPa, and the sintering time is 4 h to obtain a square billet for rolling.

[0086] Heat the square billet to 900 - 930 °C, and use a hot continuous rolling mill to roll it to obtain a sulfur-containing free-cutting titanium alloy coil without adding heavy metals.

[0087] Comparative example

[0088] A titanium alloy, the composition of which is by mass percentage: O: 0.3%; B: 0.006%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and unavoidable impurities. It is required that the content of a single impurity in the unavoidable impurities ≤ 0.05%, and the sum of the contents of the unavoidable impurities ≤ 0.1%.

[0089] The preparation method of this titanium alloy is as follows:

[0090] Use a vacuum consumable electrode skull melting furnace to melt the titanium alloy. The melting temperature is 1680 °C and the time is 20 minutes. Fill the mold shell with the titanium alloy melt by means of negative pressure casting; the vacuum degree of negative pressure casting is 50 Pa, and the negative pressure is 0.1 Mpa;

[0091] The titanium alloy faucet blank undergoes solution and aging antibacterial heat treatment. The solution heat treatment is to put the furnace into the room temperature, heat up with the furnace, the heating rate is 10℃ / minute, the solution temperature is 830℃, the solution time is 5h, and it is water cooled to room temperature; the aging temperature is 450℃, and the aging time is 16h.

[0092] The following methods were used to test the performance of the embodiments and comparative examples of the present invention:

[0093] (1) Hardness test: The hardness test of the embodiment and the comparative example was carried out using a micro Vickers hardness tester. The test standard was GBT 4340.1-2009 Metallic Material Vickers Hardness Test. The load was 500 g. Each sample was tested 4 times, and the average value was selected as the final result.

[0094] (2) Cutting performance test: The test equipment is a spike® wireless cutting force test system produced by German pro-micro. The tool is a Φ10 mm 62-degree carbide end mill. The cutting fluid is mineral oil. The speed is 5000 rpm. The milling method is side milling. The tool feed speed is 800 mm / min. The cutting depth is 4 mm and the side cutting depth is 0.4 mm. Each sample is tested 3 times, and the average value is selected as the final result.

[0095] The performance test results of the embodiments and comparative examples are shown in Table 1. The hardness value 1 in Table 1 represents the hardness value of the first test. The hardness value 2 in Table 1 represents the hardness value of the second test. The hardness value 3 in Table 1 represents the hardness value of the third test. The hardness value 4 in Table 1 represents the hardness value of the fourth test. The bending moment 1 in Table 1 represents the bending moment value of the first test. The bending moment 2 in Table 1 represents the bending moment value of the second test. The bending moment 3 in Table 1 represents the bending moment value of the third test.

[0096] Table 1 Performance test results of embodiments and comparative examples

[0097]

[0098] The metallographic photographs of each embodiment and comparative example after grinding and polishing are as follows: Figures 2 - 4 As shown, compared with the comparative example, the titanium alloy material in the embodiment introduces an easy-to-cut phase that is beneficial to cutting after alloying, thereby improving the cutting performance of the titanium alloy material.

[0099] It can be seen from Examples 1-2 that the higher the sulfur content, the lower the cutting bending moment of the alloy and the better the cutting performance; the higher the oxygen content in the alloy, the higher the hardness of the alloy, but the cutting bending moment will also increase and the cutting performance will decrease; although the hardness of the comparative example is low, sulfur is not added to improve the cutting performance, and the cutting performance is poor.

[0100] The above are exemplary embodiments disclosed by the present invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments disclosed by the present invention as defined by the claims. Although the elements disclosed by the embodiments of the present invention can be described or claimed in individual form, they can also be understood as multiple unless explicitly limited to the singular.

[0101] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the embodiments disclosed by the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other variations in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present invention shall be included within the protection scope of the embodiments of the present invention.

Claims

1. A sulfur-containing free-cutting titanium alloy material without adding heavy metals, characterized in that, The composition of the sulfur-containing free-cutting titanium alloy material is as follows by mass percentage: S: 0.2 - 0.4%; O: 0.3 - 0.45%; B: 0.003 - 0.006%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and unavoidable impurities; The preparation method of the raw material titanium sponge for the sulfur-containing free-cutting titanium alloy material includes the following steps: S101. During the Kroll process, TiCl4 gas, H2S gas, and BCl3 gas are simultaneously introduced into the reaction kettle; S102. Through distillation and multi-stage crushing treatment, titanium sponge particles with a maximum particle diameter ≤ 6 mm are obtained; S103. The titanium sponge particles are laid flat and baked in an oven at 500 - 550 °C for 50 - 90 minutes; The method for preparing the sulfur-containing free-cutting titanium alloy material from the titanium sponge particles obtained by the above preparation method includes: Pressing the titanium sponge particles into a billet; stacking the billets into a TA1 sleeve and evacuating and sealing; performing hot isostatic pressing sintering under argon protection to obtain a square billet for rolling; heating the sintered square billet to 900 - 930 °C at high temperature and then rolling it into a coil of sulfur-containing free-cutting titanium alloy material by a hot continuous rolling mill.

2. The sulfur-containing free-cutting titanium alloy material according to claim 1, wherein The composition of the sulfur-containing free-cutting titanium alloy material is as follows by mass percentage: S: 0.4%; O: 0.3%; B: 0.003%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and unavoidable impurities.

3. The sulfur-containing free-cutting titanium alloy material according to claim 1, characterized in that, The composition of the sulfur-containing free-cutting titanium alloy material is as follows by mass percentage: S: 0.2%; O: 0.4%; B: 0.006%; C ≤ 0.03%; N ≤ 0.03%, and the balance is titanium and unavoidable impurities.

4. A method for preparing titanium sponge, which is a raw material of the sulfur-containing free-cutting titanium alloy material according to claim 1, characterized in that, Including the following steps: S101. During the Kroll process, TiCl4 gas, H2S gas, and BCl3 gas are simultaneously introduced into the reaction kettle; S102. Through distillation and multi-stage crushing treatment, titanium sponge particles with a maximum particle diameter ≤ 6 mm are obtained; S103. The titanium sponge particles are laid flat and baked in an oven at 500 - 550 °C for 50 - 90 minutes.

5. The method according to claim 4, wherein The multi-stage crushing includes three-stage crushing processes of jaw crushing, cone crushing, and roll crushing in sequence.

6. The method according to claim 4, wherein In step S101, the molar ratio of Ti:S is controlled to be 99:(0.36 - 0.71), and the molar ratio of Ti:B is controlled to be 99:(0.006 - 0.012).

7. A method for preparing a free-machining titanium alloy material from the titanium sponge particles obtained by the preparation method according to any one of claims 4-6, characterized in that, Including: Pressing the titanium sponge particles into a billet; stacking the billets into a TA1 sleeve and evacuating and sealing; performing hot isostatic pressing sintering under argon protection to obtain a square billet for rolling; heating the sintered square billet to 900 - 930 °C at high temperature and then rolling it into a coil of sulfur-containing free-cutting titanium alloy material by a hot continuous rolling mill.

8. The method according to claim 7, wherein The step of "pressing the titanium sponge particles into a billet" includes: Pressing the titanium sponge particles into a billet under a pressure of 500 - 900 MPa.

9. The method according to claim 7, wherein In the hot isostatic pressing sintering step: The sintering temperature is 900 - 1000 °C, the pressure is 90 - 100 MPa, and the sintering time is 3 - 5 h.

10. The method according to claim 9, wherein The heating rate of the hot isostatic pressing sintering is 2 - 5 °C / min.

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