Sulfur-fixing multi-element composite free-cutting titanium alloy and preparation method thereof

Abstract

The invention discloses a sulfur-fixing multi-element composite free-cutting titanium alloy and a preparation method thereof, and belongs to the field of non-ferrous metal materials. The sulfur-fixing multi-element composite free-cutting titanium alloy comprises a matrix component group and a sulfur-fixing component group, the matrix component group comprises Ti, S, O, Al, Fe, Sn, C and N; the sulfur fixation component group comprises Cr, Cu, Mn, Mo and V; wherein the mass percentage of the component S is 0.06-0.12%. The invention further discloses a method for preparing the sulfur-fixing multi-element composite free-cutting titanium alloy. According to the sulfur-fixing multi-element composite free-cutting titanium alloy, the stability of sulfide is improved through multi-element alloying, the titanium alloy comprises Ti-Cr-Cu-Mn-Mo-S sulfur compounds of a layered structure, and the uniformly-distributed titanium sulfur compounds have the effects of improving the chip breaking property of cuttings and improving the lubricating condition of a tool nose.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of non-ferrous materials, in particular to a sulfur-fixed multi-element composite free-cutting titanium alloy and a preparation method thereof. BACKGROUND

[0002] Multi-element alloy materials have become an indispensable basic material in the field of precision manufacturing due to their unique advantages in the field of high-performance functional materials and engineering materials. In high-end application scenarios such as digital 3C products, medical devices, aerospace, etc., the requirements for the cutting performance, surface quality and lightweight of alloy materials are increasing. Free-cutting alloy improves cutting performance by introducing specific additive phases, which is of great significance to reduce processing cost and improve product precision.

[0003] The existing free-cutting alloy cutting performance improvement mechanism mainly falls into two categories: one is to introduce low-melting-point softening phases (such as lead-tin, lead-bismuth, indium-bismuth, etc.) into the matrix, which causes the softening phase to melt or soften through frictional heating during cutting, promotes chip fracture and improves chip removal performance; the second is to add high-melting-point hardening phases (such as boron, carbon, oxides, nitrides, etc.), which form a discontinuous structure by taking advantage of the difference in flowability between the matrix and the hardening phase, achieving fracture control during cutting. However, alloy systems based on low-melting-point phases (such as 6012, 6262, etc. containing lead) have been gradually restricted due to the biological toxicity and environmental hazards of lead elements, and must be shifted to a lead-free technology path.

[0004] Titanium alloy, as a typical high-strength lightweight material, has a growing demand in the fields of biomedical, consumer electronics, etc. Sulfur (S) element has been proven to significantly improve the cutting performance of titanium alloy, the principle of which is to form titanium sulfide compounds as free-cutting phases. However, in the traditional smelting process, liquid sulfur and titanium melt are prone to phase separation, resulting in uneven distribution of compounds; and with the increase of sulfur content, the hot working performance of titanium material decreases sharply, and the risk of surface cracking increases significantly. The existing technology achieves sulfur fixation by introducing rare earth elements, but the presence of rare earth elements may cause human contact allergy or poisoning problems.

[0005] Therefore, it is of great practical significance to develop a new type of free-cutting titanium alloy with uniform distribution and fixation of sulfur elements and safety problems of rare earth elements, as well as a preparation method thereof. SUMMARY

[0006] Therefore, in view of the above technical problems, the present application provides a sulfur-fixed multi-element composite free-cutting titanium alloy and a preparation method thereof, which aims to solve the problems of uniform distribution and fixation of sulfur elements and safety problems of rare earth elements through multi-element composite design, and provides an innovative solution for the industrial application of lead-free free-cutting titanium alloy.

[0007] In order to achieve the above purpose, the following technical solutions are adopted: The application provides a sulfur-fixed multi-element composite free-cutting titanium alloy, which comprises a base component group and a sulfur-fixing component group. The base component group comprises Ti, S, O, Al, Fe, Sn, C and N. The sulfur-fixing component group comprises Cr, Cu, Mn, Mo and V. The component S is 0.06-0.12% by mass percentage.

[0008] In some embodiments, the mass fraction ratio of Cr:Cu:Mn:Mo:V:S is (15-20):(6-8):(4-6):(5-8):(6-10):1.

[0009] In some embodiments, the remaining components of the sulfur-fixed multi-element composite free-cutting titanium alloy are 0.1-0.2% of O, 2.00-3.00% of Al, 0.05-0.15% of Fe, 0.05-0.15% of Sn, ≤0.03% of C, ≤0.03% of N, and the balance is titanium and unavoidable impurities by mass percentage.

[0010] The application also provides a method for preparing the sulfur-fixed multi-element composite free-cutting titanium alloy, comprising the following steps: S101. Raw material preparation: titanium source, aluminum source, chromium source, copper source, molybdenum source, sulfur source, manganese source, aluminum source, vanadium source, iron source and tin source are pressed into electrode blocks, and the electrode blocks are welded to form consumable electrodes S102. The consumable electrodes are subjected to twice vacuum consumable smelting: First smelting: the consumable electrodes are placed into a first water-cooled copper crucible, and the vacuum degree of the first smelting is controlled to be 0.1-1.0 Pa, so that the electrolyte impurities (mainly magnesium chloride MgCl2) in the sponge titanium are effectively removed, and the formation of large-particle powder inclusions is prevented; Second smelting: the ingot after the first smelting is placed into a second water-cooled copper crucible; H2S gas is filled to adjust the vacuum degree of the second smelting to 1-2.5 Pa; after smelting, low-temperature cooling water is used for cooling, wherein the inlet water temperature of the cooling water is controlled to be ≤5 ℃, and the outlet water temperature of the cooling water is controlled to be ≤15 ℃, and the faster cooling speed can refine the liquid-analyzed free-cutting phase; S103. Ingot forming: after the ingot after the second smelting is subjected to surface peeling treatment, the ingot is opened by radial forging at a temperature interval of 1050-1100 ℃ to obtain a square billet; S104. Hot rolling: the square billet is heated to 920-940 ℃ and then hot-rolled to obtain a free-cutting disc.

[0011] In some embodiments, the diameter of the first water-cooled copper crucible is ≤340 mm; and the diameter of the second water-cooled copper crucible is ≤400 mm.

[0012] In some embodiments, the outlet water temperature of the vacuum consumable melting cooling water is lower than 15 DEG C.

[0013] In some embodiments, the melting voltage of the twice vacuum consumable melting is 28-32 V, and the melting current is 2-6 KA.

[0014] In some embodiments, the vacuum degree control method of the secondary melting is as follows: after the electrode is welded after the ingot is loaded into the furnace, vacuum is extracted to below 0.5 Pa, the vacuum pump is kept to extract air to reach a stable 0.5+ / -0.1 Pa, the gas filling valve is opened to fill H2S gas to 1.5 Pa, and the melting process is ensured to be within a range of 1-2.5 Pa by adjusting the H2S gas filling flow.

[0015] In some embodiments, the billet section size of the square billet is 140-155 mm*140-155 mm, and the square billet length is between 4.5 m and 5.8 m.

[0016] In some embodiments, in the hot rolling process of step S104, the surface of the free-cutting disc is temperature-compensated when the section diameter of the free-cutting disc is less than or equal to 17 mm and the rolling speed is greater than 10 m / s, and the surface temperature is between 900 DEG C and 930 DEG C after temperature compensation.

[0017] In some embodiments, the surface of the free-cutting disc is temperature-compensated by using a high-frequency induction heating device, and the power of the high-frequency induction heating device is 450-600 kW.

[0018] The present application has the following beneficial technical effects: The sulfurized multi-element composite free-cutting titanium alloy of the present application improves the stability of sulfides through multi-element alloying, and the titanium alloy contains a layered Ti-Cr-Cu-Mn-Mo-S sulfide compound, and the uniformly distributed titanium sulfide compound has the effects of improving the chip breaking property of the chip and improving the lubrication condition of the tool tip.

[0019] The preparation method of the sulfurized multi-element composite free-cutting titanium alloy of the present application introduces a small amount of hydrogen sulfide gas in the secondary melting process, which helps to improve the yield of S and the uniform distribution of S in the ingot. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1A flow chart of the method for preparing the sulfur-fixing multi-element composite free-cutting titanium alloy of the present application; Figure 2 A 50 times metallographic image of the sulfur-fixing multi-element composite free-cutting titanium alloy of Example 1 of the present application; Figure 3 A 500 times metallographic image of the sulfur-fixing multi-element composite free-cutting titanium alloy of Example 1 of the present application; Figure 4 An EDS spectrum of the sulfur-fixing multi-element composite free-cutting titanium alloy of Example 1 of the present application; Figure 5 A metallographic image of the titanium alloy material of the comparative example. DETAILED DESCRIPTION

[0022] In order to make the objects, technical solutions and advantages of the present application clearer, the following further describes the embodiments of the present application with reference to the specific embodiments and the accompanying drawings.

[0023] It should be understood that the embodiments of the present application shown in the example embodiments are only illustrative. Although only a few embodiments are described in detail in the present application, those skilled in the art can easily appreciate that various modifications are possible without departing from the teachings of the present subject matter. Accordingly, all such modifications should be included within the scope of the present application. Other substitutions, modifications, changes and omissions can be made to the design, operating conditions and parameters of the following example embodiments without departing from the spirit of the present application.

[0024] Based on the above purpose, in a first aspect of the embodiments of the present application, a sulfur-fixing multi-element composite free-cutting titanium alloy is provided, which comprises a base component group and a sulfur-fixing component group. The base component group comprises Ti, S, O, Al, Fe, Sn, C and N. The sulfur-fixing component group comprises Cr, Cu, Mn, Mo and V. The content of component S is 0.06-0.12% by mass.

[0025] The mass ratio of Cr:Cu:Mn:Mo:V:S is (15-20):(6-8):(4-6):(5-8):(6-10):1.

[0026] The mass percentage of each of Cr, Cu, Mn, Mo and V is a multiple of the mass percentage of S. The mass percentage of S is 0.06-0.12%.

[0027] The remaining components of the sulfur-fixed multi-element composite free-cutting titanium alloy are as follows in terms of mass percentage: O: 0.1-0.2%; Al: 2.00-3.00%; Fe: 0.05-0.15%; Sn: 0.05-0.15%; C≤0.03%; N≤0.03%, and the balance is titanium and unavoidable impurities. The content of each of the unavoidable impurities is required to be ≤0.05%, and the total content of the unavoidable impurities is ≤0.1%.

[0028] The above element ratio is to ensure that Cu can form CuTi2, Cu2S and other series of compounds with Ti and S elements in the material.

[0029] By means of the multi-element composite design (base component group + sulfur-fixing component group), the sulfur (S) is effectively fixed in the titanium alloy, the problem of liquid sulfur and titanium melt stratification in traditional smelting is avoided, the titanium sulfide compounds are uniformly distributed, and thus the cutting performance is improved; meanwhile, S as a free-cutting element forms titanium sulfide compounds, reduces the cutting resistance, and improves the chip removal performance.

[0030] By optimizing the mass ratio of the sulfur-fixing component group (Cr, Cu, Mn, Mo, V) to S, the sulfur-fixing effect is synergistically enhanced, and the stable existence of S in the alloy is ensured; meanwhile, the multi-element composite can balance the mechanical properties (such as strength and hardness) and cutting performance of the alloy, and avoid the performance imbalance caused by a single sulfur-fixing element.

[0031] In a second aspect of embodiments of the present application, a method for preparing the sulfur-fixed multi-element composite free-cutting titanium alloy as described above is provided. Figure 1 A schematic flowchart of the method is shown.

[0032] As shown in the method, the preparation can include the following steps: Figure 1 S101. Raw material preparation: titanium sources, aluminum sources, chromium sources, copper sources, molybdenum sources, sulfur sources, manganese sources, aluminum sources, vanadium sources, iron sources and tin sources are pressed into electrode blocks, and are welded to form consumable electrodes; S102. The consumable electrodes are subjected to two vacuum consumable smelting: First smelting: the consumable electrodes are placed into a first water-cooled copper crucible, and the vacuum degree of the first smelting is controlled at 0.1-1.0 Pa; Second smelting: the ingot after the first smelting is placed into a second water-cooled copper crucible; H2S gas is filled to adjust the vacuum degree of the second smelting to 1-2.5 Pa; and after smelting, low-temperature cooling water is used for cooling, wherein the inlet water temperature of the cooling water is controlled at ≤5℃, and the outlet water temperature of the cooling water is controlled at ≤15℃; S103. Ingot forming: after the ingot after the second smelting is subjected to surface peeling treatment, the ingot is opened by radial forging at a temperature range of 1050-1100℃ to obtain a square billet; ​S104. Hot rolling: the square billet is heated to 920-940℃ and then hot rolled to obtain the free-cutting disc.

[0033] The titanium source, the aluminum source, the chromium source, the copper source, the molybdenum source, the sulfur source, the manganese source, the aluminum source, the vanadium source, the iron source and the tin source comprise 0A grade titanium sponge (chemical formula: Ti, particle size ≤24.5mm), aluminum beans (chemical formula: Al, particle size ≤15mm), chromium particles (chemical formula: Cr, particle size ≤5mm) or aluminum-chromium intermediate alloy (such as Al 70 Cr, particle size ≤5mm), copper bars (chemical formula: Cu, diameter ≤2mm, length ≤15mm), titanium white powder (chemical formula: TiO2, particle size ≤58μm or 250 mesh), titanium-silicon alloy (chemical formula: Ti 50 Si, particle size ≤6mm) or aluminum-silicon alloy (such as Al 40 Si, particle size ≤6mm), titanium-molybdenum alloy (chemical formula: Ti 32 Mo, particle size ≤8mm), manganese sulfide (MnS, particle size ≤160μm or 90 mesh), aluminum-vanadium alloy (chemical formula: Al 55 V, particle size ≤8mm), titanium-iron alloy (Ti32Fe, particle size ≤6mm), titanium-tin alloy (Ti 80 Sn, particle size ≤6mm).

[0034] By twice vacuum consumable melting (especially the second melting is adjusted by H2S to adjust the vacuum degree) combined with low-temperature cooling, the S element is effectively fixed to prevent its volatilization or stratification with titanium; the radial forging breakdown and hot rolling process refines the grain and improves the uniformity of the structure and the processing performance; finally, the free-cutting disc with excellent cutting performance and good surface quality is obtained.

[0035] In a preferred embodiment of the present application, the diameter of the first water-cooled copper crucible is ≤340mm; the diameter of the second water-cooled copper crucible is ≤400mm. In a preferred embodiment of the present application, the cooling water is cooled by a low-temperature water chiller.

[0036] The crucible size and the cooling water temperature are strictly controlled to minimize the segregation during the solidification process and prevent the loss of sulfur at high temperature for a long time.

[0037] In a preferred embodiment of the present application, the melting voltage of the twice vacuum consumable melting is 28-32 V, and the melting current is 2-6 KA. This ensures that the molten pool reaches the edge to obtain a good surface ingot.

[0038] In a preferred embodiment of the present application, the outlet water temperature of the cooling water of the vacuum consumable melting is lower than 15℃.

[0039] In a preferred embodiment of the present invention, the method for controlling the vacuum degree of secondary melting is as follows: after the ingot is loaded into the furnace and the electrodes are welded, the vacuum is evacuated to below 0.5 Pa, the vacuum pump is kept at a stable 0.5 ± 0.1 Pa, the gas charging valve is opened to charge H2S gas to 1.5 Pa, and the vacuum degree of secondary melting is ensured to be between 1 and 2.5 Pa by adjusting the gas charging flow rate of H2S during the melting process.

[0040] Introducing trace amounts of hydrogen sulfide gas helps improve sulfur yield and uniform distribution in the ingot. The mass percentage of sulfur is strictly controlled between 0.06% and 0.12%, and it must form free-machining phases such as Cu₂S with Cu. The introduction of H₂S replenishes the sulfur source, prevents sulfur from volatilizing and being lost at high temperatures in the form of SO₂, and ensures that the sulfur content meets design requirements. By adjusting the vacuum level and H₂S flow rate, the distribution and size of sulfides such as Cu₂S are controlled, segregation is reduced, and free-machining properties are improved (e.g., reducing cutting resistance and improving surface quality).

[0041] In a preferred embodiment of the present invention, a secondary polished ingot is obtained by mechanically peeling off the surface of the smelted ingot. To reduce forging cracking, the secondary ingot must be blanked using a radial forging mill. The present invention employs high-temperature multi-fire secondary radial forging, which can effectively prevent surface cracking of easily cracked titanium alloys during the blanking process.

[0042] In a preferred embodiment of the present invention, the billet cross-sectional dimensions are 140~155mm × 140~155mm, and the billet length is between 4.5m and 5.8m. Optimizing the billet cross-sectional dimensions (140~155mm × 140~155mm) and length (4.5m~5.8m) facilitates subsequent radial forging and hot rolling, reduces processing passes, and improves production efficiency; at the same time, it avoids the risk of uneven temperature or cracking caused by excessively large dimensions, thereby improving the yield.

[0043] In a preferred embodiment of the present invention, during the hot rolling process in step S104, when the cross-sectional diameter of the free-cutting coil is ≤17mm and the rolling speed is greater than 10m / s, the surface of the free-cutting coil is heated by a high-frequency induction heating device with a power of 450~600kW. After heating, the surface temperature is between 900~930℃, ensuring that high-speed rolling does not cause cracking and that the core and surface microstructure are uniform. Surface induction heating is performed when the rolling speed is higher than 10m / s to prevent surface cracking and improve microstructure uniformity.

[0044] The present invention will be further illustrated by the following examples.

[0045] Table 1. Alloy composition of Examples 1-3 (mass fraction / %)

[0046] Embodiment 1 A sulfurized multi-element composite free-cutting titanium alloy belongs to the Ti-Cr-Cu-Mn-Mo-V-S system, and the phase composition is alpha phase + free-cutting beta phase + sulfide. The mass percentage of each component is shown in Table 1, the upper limit of the proportion of each sulfurized element, the balance is titanium and unavoidable impurities, the content of each single impurity in the unavoidable impurities is required to be ≤0.05%, and the sum of the contents of the unavoidable impurities is ≤0.1%. The composition obtains more sulfide content, and the application purpose is the field with particularly high requirements for cutting performance.

[0047] The preparation method of the above-mentioned sulfurized multi-element composite free-cutting titanium alloy is as follows: (1) S101. Raw material preparation: uniformly mix the raw materials, press the electrode block, and weld it into a consumable electrode, the titanium source, aluminum source, chromium source, copper source, molybdenum source, sulfur source, manganese source, aluminum source, vanadium source, iron source and tin source include 0A grade sponge titanium (chemical formula Ti, particle size ≤24.5mm), aluminum beans (chemical formula Al, particle size ≤15mm), chromium particles (chemical formula Cr, particle size ≤5mm) or aluminum-chromium intermediate alloy (such as Al70Cr, particle size ≤5mm), copper strip (chemical formula Cu, diameter ≤2mm, length ≤15mm), titanium white powder (chemical formula TiO2, particle size ≤58μm or 250 mesh), titanium-silicon alloy (chemical formula Ti 50 Si, particle size ≤6mm) or aluminum-silicon alloy (such as Al 40 Si, particle size ≤6mm), titanium-molybdenum alloy (chemical formula Ti 32 Mo, particle size ≤8mm), manganese sulfide (MnS, particle size ≤160μm or 90 mesh), aluminum-vanadium alloy (chemical formula Al 55 V, particle size ≤8mm), titanium-iron alloy (Ti 32 Fe, particle size ≤6mm), titanium-tin alloy (Ti 80 Sn, particle size ≤6mm).

[0048] (2) S102. The raw materials are subjected to two vacuum consumable smelting, and the smelting voltage of the two vacuum consumable smelting is 30±3.5V, and the smelting current is 3±0.3KA.

[0049] (3) Once smelting: the vacuum degree of the first smelting is controlled at 0.1~1.0Pa; and a smaller current, the diameter of the first water-cooled copper crucible is 340mm; (4) Secondary smelting: the ingot after primary smelting is put into a secondary water-cooled copper crucible; the diameter of the secondary water-cooled copper crucible is 400 mm. H2S gas is filled to adjust the vacuum degree of the secondary smelting to 1-2.5 Pa; after smelting, low-temperature cooling water is combined for cooling, wherein the inlet water temperature of the cooling water is controlled to be ≤5℃, and the outlet water temperature of the cooling water is controlled to be ≤15℃; the secondary smelting vacuum degree control method is as follows: after the ingot is welded with the electrode, vacuum is extracted to below 0.5 Pa, the vacuum pump is kept pumping to achieve a stable 0.5±0.1 Pa, the gas filling valve is opened to fill H2S gas to 1.5 Pa, and the smelting process is ensured to be within the range of 1-2.5 Pa by adjusting the H2S gas filling flow.

[0050] (5) S103. Ingot forming: after the ingot after secondary smelting is subjected to surface skinning treatment, it is opened by radial forging at a temperature interval of 1050℃ to obtain a square billet; the billet cross-sectional size of the square billet is 140×140 mm, and the length of the square billet is between 4.5 m and 5.8 m.

[0051] (6) S104. Hot rolling processing: the square billet is heated to 930℃ and then hot-rolled to obtain a free-cutting disc. When the cross-sectional diameter of the free-cutting disc is ≤17 mm and the rolling speed is greater than 10 m / s, the surface of the free-cutting disc is subjected to temperature compensation, the surface of the free-cutting disc is subjected to temperature compensation by using a high-frequency induction heating device, the power of the high-frequency induction heating device is 500 kW, and the surface temperature after temperature compensation is between 900-930℃.

[0052] Example 2 A sulfurized multi-element composite free-cutting titanium alloy belongs to the Ti-Cr-Cu-Mn-Mo-V-S system, and the phase composition is α phase + free-cutting β phase + sulfide. The mass percentage of each component is shown in Table 1, each sulfurized element is taken in the lower limit, the balance is titanium and unavoidable impurities, the content of each single impurity in the unavoidable impurities is required to be ≤0.05%, and the sum of the contents of the unavoidable impurities is ≤0.1%. The composition obtains a small amount of sulfide content, and is suitable for fields requiring both cutting performance and mechanical properties.

[0053] The preparation method of the above-mentioned sulfurized multi-element composite free-cutting titanium alloy is as follows: (1) S101. Raw material preparation: uniformly mix the raw materials and press the electrode block, and weld it into a consumable electrode, the titanium source, aluminum source, chromium source, copper source, molybdenum source, sulfur source, manganese source, aluminum source, vanadium source, iron source and tin source include 0A grade sponge titanium (chemical formula is Ti, particle size ≤24.5mm), aluminum beans (chemical formula is Al, particle size ≤15mm), chromium particles (chemical formula is Cr, particle size ≤5mm) or aluminum-chromium intermediate alloy (such as Al70Cr, particle size ≤5mm), copper bar (chemical formula is Cu, diameter ≤2mm, length ≤15mm), titanium white powder (chemical formula is TiO2, particle size ≤58μm or 250 mesh), titanium-silicon alloy (chemical formula is Ti 50 Si, particle size ≤6mm) or aluminum-silicon alloy (such as Al 40 Si, particle size ≤6mm), titanium-molybdenum alloy (chemical formula is Ti 32 Mo, particle size ≤8mm), manganese sulfide (MnS, particle size ≤160μm or 90 mesh), aluminum-vanadium alloy (chemical formula is Al 55 V, particle size ≤8mm), titanium-iron alloy (Ti 32 Fe, particle size ≤6mm), titanium-tin alloy (Ti 80 Sn, particle size ≤6mm).

[0054] (2) S102. The raw materials are subjected to two vacuum consumable smelting, and the smelting voltage of the two vacuum consumable smelting is 32±3V, and the smelting current is 6±0.35KA.

[0055] (3) First smelting: the vacuum degree of the first smelting is controlled at 0.1~1.0Pa; corresponding to a larger smelting current, the diameter of the first water-cooled copper crucible is 300mm; (4) Second smelting: the ingot after the first smelting is put into the second water-cooled copper crucible; the diameter of the second water-cooled copper crucible is 380mm. Adjust the vacuum degree of the second smelting to 1~2.5Pa by charging H2S gas; after smelting, combined with low-temperature cooling water for cooling, wherein the inlet water temperature of the cooling water is controlled at ≤5℃, and the outlet water temperature of the cooling water is controlled at ≤15℃; the second smelting vacuum degree control method is as follows: after the ingot is loaded and the electrode is welded, the vacuum is extracted to below 0.5Pa, the vacuum pump is kept pumping to achieve a stable 0.5±0.1Pa, the gas charging valve is opened to charge H2S gas to 1.5Pa, and the smelting process is ensured to be within the range of 1~2.5Pa by adjusting the charging flow of H2S.

[0056] (5) S103. Ingot forming: after the ingot after the second smelting is subjected to surface peeling treatment, it is opened by radial forging at a temperature interval of 1100℃ to obtain a square billet; the billet cross-sectional size of the square billet is 155mm×155mm, and the square billet length is between 4.5m~5.8m.

[0057] (6) S104. Hot rolling processing: the square billet is heated to 940℃ and then hot-rolled to obtain the free-cutting disc. When the cross-sectional diameter of the free-cutting disc is less than or equal to 17mm and the rolling speed is greater than 10m / s, the surface of the free-cutting disc is heated by a high-frequency induction heating device, the power of the high-frequency induction heating device is 600kW, and the surface temperature of the free-cutting disc is between 900-930℃ after heating.

[0058] Example 3 A sulfurized multi-element composite free-cutting titanium alloy belongs to Ti-Cr-Cu-Mn-Mo-V-S system, and the phase composition is α phase + free-cutting β phase + sulfide. The mass percentage of each component is shown in Table 1, the proportion of each sulfurized element is the intermediate value, the balance is titanium and unavoidable impurities, the content of each single impurity is less than or equal to 0.05%, and the total content of the unavoidable impurities is less than or equal to 0.1%. The composition obtains a moderate sulfide content, and the application purpose is the field with high requirements for cutting performance.

[0059] The preparation method of the above-mentioned sulfurized multi-element composite free-cutting titanium alloy is as follows: (1) S101. Raw material preparation: uniformly mix the raw materials, press the electrode block, and weld it into a consumable electrode. The titanium source, aluminum source, chromium source, copper source, molybdenum source, sulfur source, manganese source, aluminum source, vanadium source, iron source and tin source include 0A grade sponge titanium (chemical formula: Ti, particle size ≤24.5mm), aluminum beans (chemical formula: Al, particle size ≤15mm), chromium particles (chemical formula: Cr, particle size ≤5mm) or aluminum-chromium intermediate alloy (such as Al 70 Cr, particle size ≤5mm), copper bar (chemical formula: Cu, diameter ≤2mm, length ≤15mm), titanium white powder (chemical formula: TiO2, particle size ≤58μm or 250 mesh), titanium-silicon alloy (chemical formula: Ti 50 Si, particle size ≤6mm) or aluminum-silicon alloy (such as Al 40 Si, particle size ≤6mm), titanium-molybdenum alloy (chemical formula: Ti 32 Mo, particle size ≤8mm), manganese sulfide (MnS, particle size ≤160μm or 90 mesh), aluminum-vanadium alloy (chemical formula: Al 55 V, particle size ≤8mm), titanium-iron alloy (Ti 32 Fe, particle size ≤6mm), titanium-tin alloy (Ti 80 Sn, particle size ≤6mm).

[0060] (2) S102. The raw materials are subjected to two vacuum consumable melting, and the melting voltage of the two vacuum consumable melting is 30±3V, and the melting current is 5±0.4KA.

[0061] (3) First smelting: the vacuum degree of the first smelting is controlled at 0.1-1.0 Pa; the diameter of the first water-cooled copper crucible is 340 mm; (4) Second smelting: the ingot after the first smelting is put into a second water-cooled copper crucible; the diameter of the second water-cooled copper crucible is 400 mm. The vacuum degree of the second smelting is adjusted to 1-2.5 Pa by charging H2S gas; after smelting, low-temperature cooling water is used for cooling, wherein the inlet temperature of the cooling water is controlled at ≤5 ℃, and the outlet temperature of the cooling water is controlled at ≤15 ℃; the vacuum degree control method of the second smelting is as follows: after the ingot is loaded into the furnace and the electrode is welded, the vacuum is extracted to below 0.5 Pa, the vacuum pump is kept pumping to achieve a stable 0.5±0.1 Pa, the gas charging valve is opened to charge H2S gas to 1.5 Pa, and during the smelting process, the charging flow of H2S is adjusted to ensure that the vacuum degree of the second smelting is between 1-2.5 Pa.

[0062] (5) S103. Ingot forming: after the ingot after the second smelting is subjected to surface peeling treatment, it is opened up at a temperature interval of 1050 ℃ by radial forging to obtain a square billet; the billet cross-sectional size of the square billet is 150 mm×150 mm, and the length of the square billet is between 4.5 m-5.8 m.

[0063] (6) S104. Hot rolling: after the square billet is heated to 920 ℃, hot rolling is performed to obtain a free-cutting disc. When the cross-sectional diameter of the free-cutting disc is ≤17 mm and the rolling speed is greater than 10 m / s, the surface of the free-cutting disc is subjected to temperature compensation, the surface of the free-cutting disc is subjected to temperature compensation by using a high-frequency induction heating device, the power of the high-frequency induction heating device is 450 kW, and the surface temperature after the temperature compensation is between 900-930 ℃.

[0064] Comparative Example A titanium alloy, by mass percentage: Al: 6.0%, V: 4.0%, O: 0.3%; S: 0.06%; Fe: 0.12%; C≤0.03%; N≤0.03%, the balance being titanium and unavoidable impurities, the content of each single impurity being ≤0.05%, and the total content of the remaining impurities being ≤0.1%. The preparation method of the titanium alloy is as follows: (1) S101. Raw material preparation: the raw materials are uniformly mixed to press an electrode block, and then welded into a consumable electrode; the titanium source, aluminum source, iron source, and sulfur source, vanadium source, and oxygen source include 0A-grade sponge titanium (chemical formula: Ti, particle size ≤24.5 mm), aluminum beans (chemical formula: Al, particle size ≤15 mm), ferrous sulfide (FeS, particle size ≤160 μm or 90 mesh), aluminum-vanadium alloy (chemical formula: Al 55 V, particle size ≤8 mm), and titanium white (chemical formula: TiO2, particle size ≤58 μm or 250 mesh).

[0065] (2) S102. The raw material is subjected to two vacuum self-consumption smelting, and the smelting voltage of the two vacuum self-consumption smelting is 30±3V, and the smelting current is 7±0.6KA.

[0066] (3) Once smelting: the vacuum degree of once smelting is controlled at 1.0~2.0Pa; the diameter of the once water-cooled copper crucible is 450mm; (4) Twice smelting: the ingot after once smelting is put into a twice water-cooled copper crucible; the diameter of the twice water-cooled copper crucible is 650mm. The vacuum degree of twice smelting is 1~1.5Pa; after smelting, combined with circulating cooling water for cooling, wherein the inlet water temperature of the cooling water is controlled at ≤25℃, and the outlet water temperature of the cooling water is controlled at ≤40℃.

[0067] (5) S103. Ingot forming: after the ingot after twice smelting is subjected to surface skinning treatment, the billet is obtained by opening the billet at a temperature interval of 1050℃ through radial forging; the billet cross-section size of the square billet is 150mm×150mm, and the length of the square billet is between 4.5m~5.8m.

[0068] (6) S104. Hot rolling processing: the square billet is heated to 940℃ and then hot-rolled to obtain an easy-to-cut disc.

[0069] The following methods are used to test the performance of the examples and the comparative examples in the present application: (1) Hardness test: the hardness of the examples and the comparative examples is tested by using a micro Vickers hardness tester, the test standard is “GBT 4340.1-2009 Metal Materials Vickers Hardness Test”, the load is 500g, each sample is tested 4 times, and the average value is selected as the final result.

[0070] (2) Cutting performance test: the test equipment is a wireless cutting force test system equipped with spike® produced by Germany pro-micro, the cutter is Φ10mm 62-degree hard alloy end mill, the cutting fluid is mineral oil, the rotating speed is 5000r / min, the milling method is side milling, the cutter feed speed is 800mm / min, the cutting depth is 4mm, and the side cutting depth is 0.4mm. Each sample is tested 3 times, and the average value is selected as the final result.

[0071] The performance test results of the examples and the comparative examples are shown in Table 2. Hardness value 1 in Table 2 represents the hardness value of the first test. Hardness value 2 in Table 2 represents the hardness value of the second test. Hardness value 3 in Table 2 represents the hardness value of the third test. Hardness value 4 in Table 2 represents the hardness value of the fourth test. Bending moment 1 in Table 2 represents the bending moment value of the first test. Bending moment 2 in Table 2 represents the bending moment value of the second test. Bending moment 3 in Table 2 represents the bending moment value of the third test.

[0072] Table 2. Performance test results of examples and comparative examples

[0073] The metallographic photos of the polished examples 1 and comparative examples are shown in Figures 2-3 、 Figure 5 Compared with the comparative examples, the titanium alloy material in the examples introduces the easy cutting phase beneficial to cutting after alloying, and improves the cutting performance of the titanium alloy material.

[0074] Figure 4 The EDS spectrum of the sulfurized multi-element composite easy cutting titanium alloy of example 1 is shown, and the points are marked on it, and the alloy composition of each measuring point is shown in the following table 3. In table 3, the data in table 3 is the total mass fraction of Cr, Cu, Mn, Mo, V and S, and the mass fraction of Cr, Cu, Mn, Mo, V and S is obtained. The local composition of each point in table 3 shows that Cr, Cu, Mn, Mo, V and S exist in each point.

[0075] Table 3. Composition table of spectrum points of example 1 (mass fraction / %)

[0076] The above is the exemplary embodiment disclosed by the present application, but it should be noted that various changes and modifications can be made without departing from the scope of the embodiments disclosed by the present application defined by the claims. Although the elements of the embodiments disclosed by the present application can be described or claimed in individual form, they can also be understood as plural unless explicitly limited to singular.

[0077] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to suggest that the scope of the embodiments disclosed by the present application (including claims) is limited to these examples; under the idea of the embodiments of the present application, the technical features of the above embodiments or different embodiments can also be combined, and there are many other changes of different aspects of the embodiments of the present application as above. In order to be brief, they are not provided in details. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principles of the embodiments of the present application shall be included in the protection scope of the embodiments of the present application.

Claims

1. A sulfur-fixed, multi-element, composite free-machining titanium alloy, characterized in that, The base component group comprises Ti, S, O, Al, Fe, Sn, C and N; The base component group comprises Ti, S, O, Al, Fe, Sn, C and N; The sulfur-fixing component group comprises Cr, Cu, Mn, Mo and V; The component S is 0.06-0.12% by mass percentage.

2. The sulfur-inoculated, multi-element, composite free-machining titanium alloy of claim 1, wherein, The mass fraction ratio of Cr:Cu:Mn:Mo:V:S is (15-20):(6-8):(4-6):(5-8):(6-10):

1.

3. The sulfur-inoculated, multi-element, composite free-machining titanium alloy of claim 2, wherein, The remaining components of the sulfur-fixing multi-element composite free-cutting titanium alloy are as follows by mass percentage: O: 0.1-0.2%; Al: 2.00-3.00%; Fe: 0.05-0.15%; Sn: 0.05-0.15%; C≤0.03%; N≤0.03%, and the balance is titanium and unavoidable impurities. The base component group comprises Ti, S, O, Al, Fe, Sn, C and N; 4. A method of making a sulfur-inoculated, multi-element, complex free-machining titanium alloy according to any one of claims 1-3, characterized in that, S101. Raw material preparation: the titanium source, aluminum source, chromium source, copper source, molybdenum source, sulfur source, manganese source, aluminum source, vanadium source, iron source and tin source are pressed into electrode blocks, and are welded to form a consumable electrode; S102. The consumable electrode is subjected to two vacuum consumable smelting: First smelting: the consumable electrode is placed into a first water-cooled copper crucible, and the first smelting vacuum degree is controlled to be 0.1-1.0 Pa; Second smelting: the ingot after the first smelting is placed into a second water-cooled copper crucible; H2S gas is filled to adjust the second smelting vacuum degree to 1-2.5 Pa; after smelting, low-temperature cooling water is used for cooling, wherein the inlet water temperature of the cooling water is controlled to be ≤5℃, and the outlet water temperature of the cooling water is controlled to be ≤15℃; S103. Ingot forming: after the ingot after the second smelting is subjected to surface peeling treatment, the ingot is opened by radial forging at a temperature interval of 1050-1100℃ to obtain a square billet; S104. Hot rolling: the square billet is heated to 920-940℃ and then hot-rolled to obtain a free-cutting disc. The diameter of the first water-cooled copper crucible is ≤340 mm; and the diameter of the second water-cooled copper crucible is ≤400 mm.

5. The method of claim 4, wherein, The outlet water temperature of the cooling water for vacuum consumable smelting is lower than 15℃.

6. The method of claim 4, wherein, The second smelting vacuum degree control method is as follows: after the ingot is placed into the furnace and the electrode is welded, the vacuum is pumped to be lower than 0.5 Pa, the vacuum pump is used to pump the gas to be stable at 0.5±0.1 Pa, the gas filling valve is opened to fill H2S gas to 1.5 Pa, and during the smelting process, the H2S gas filling flow rate is adjusted to ensure that the second smelting vacuum degree is in the range of 1-2.5 Pa.

7. The method of claim 4, wherein, The billet cross-sectional size of the square billet is 140-155 mm×140-155 mm, and the length of the square billet is 4.5-5.8 m.

8. The method of claim 4, wherein, During the hot rolling of step S104, the surface of the free-cutting disc is supplemented with heat when the cross-sectional diameter of the free-cutting disc is ≤17 mm and the rolling speed is greater than 10 m / s, and the surface temperature after the heat supplementing is 900-930℃.

9. The method of claim 4, wherein, A high-frequency induction heating device is used to supplement the heat of the surface of the free-cutting disc, and the power of the high-frequency induction heating device is 450-600 kW.

10. The method of claim 9, wherein, ​

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