Low-cost large-size titanium alloy ingot for ocean engineering and preparation method thereof

Abstract

The application belongs to the technical field of titanium alloy, and relates to a low-cost large-size titanium alloy ingot for ocean engineering and a preparation method thereof. The ingot replaces expensive V elements or Nb elements with relatively low-priced Sn elements and Cr elements, thereby reducing the preparation cost and facilitating large-scale application in the field of ocean engineering; and by strictly controlling process parameters such as vacuum degree and air leakage rate in the three-time vacuum consumable melting process, the distribution coefficient of alloy elements is close to 1, the segregation of chemical components in the ingot is reduced, the uniformity of chemical components in the titanium alloy ingot is effectively ensured, the industrialized preparation of a Φ920mm large-size 8-ton ingot is successfully realized, and the problems such as component segregation are effectively solved. And the diameter of the rod prepared by using the finished ingot can reach more than 400mm, the annealed room temperature mechanical properties of the rod are excellent, and the performance level reaches that of TC4 and Ti80.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy, and relates to a low-cost large-specification titanium alloy ingot for marine engineering and a preparation method thereof. BACKGROUND

[0002] It is known in the art that titanium alloy has been widely applied in the field of marine engineering due to excellent specific strength, corrosion resistance, fatigue resistance and welding performance. As a structural material, titanium alloy has good matching of strength and toughness, which can ensure the safety of the structure and reduce the overall weight of the structure. At present, the high-strength titanium alloy in the field of marine engineering mainly includes Ti-6Al-4V (domestic brand TC4) alloy and Ti-6Al-3Nb-2Zr-1Mo (domestic brand TA31, also known as Ti80) alloy. Both of the two alloys have high matching of strength and toughness, and also have good plasticity and welding performance. However, the two alloys of TC4 and Ti80 have high raw material prices due to the contained V element and Nb element respectively, so that the comprehensive cost is relatively high, which is not suitable for large-scale application in the field of marine engineering.

[0003] In addition, with the development of the related manufacturing industry in the domestic field of marine engineering, the development trend of equipment such as ships, vessels and deep divers is large-scale and integration, and among them, reducing the welding seam and manufacturing load-bearing components by using large-specification integral forgings or plates will become a development trend. However, the final size of the preparation of large-specification titanium alloy forgings or plates is limited by the size of the forging blank or plate blank, and to further improve the size of the forging blank or plate blank, a larger-specification titanium alloy ingot needs to be provided. The large-specification titanium alloy ingot with uniform composition and organization is of great significance to improve the quality consistency, stability and yield of the forging blank. Therefore, the preparation of large-specification titanium alloy ingot with a diameter of more than 720 mm and uniform composition is particularly crucial for the improvement of the level of equipment related to marine engineering. However, with the increase of the diameter of the titanium alloy ingot, the difficulty of melting increases, the composition segregation is more obvious, and the composition uniformity of the ingot is difficult to be guaranteed.

[0004] Therefore, the application is proposed. SUMMARY

[0005] The application aims to overcome the shortcomings of the prior art, and provides a low-cost large-specification titanium alloy ingot for marine engineering and a preparation method thereof, which is suitable for preparing a large-specification structural material titanium alloy ingot for service in the field of marine engineering, can reduce the comprehensive preparation cost while considering the alloy strength, toughness and welding performance, and can effectively control the element segregation degree and the content of interstitial elements.

[0006] To achieve the above-mentioned purpose, the application provides the following technical scheme:

[0007] In one aspect, the present application provides a low-cost large-size titanium alloy ingot for ocean engineering, which is composed of the following elements in percentage by weight: Al: 5.0% to 7.5%, Mo: 1.0% to 3.0%, Sn: 0.5% to 1.5%, Cr: 1.0% to 3.0%, Zr: 1.0% to 3.5%, Fe: ≤0.25%, Si: ≤0.15%, C: ≤0.10%, N: ≤0.05%, O: ≤0.15%, H: ≤0.015%, and the balance of Ti and unavoidable impurities, with the total amount of impurities being not more than 0.30%.

[0008] Further, the Mo element is derived from a powdered aluminum-molybdenum alloy with a molybdenum content of 50.0% to 70.0%, the Sn element is derived from a scrap tin-titanium alloy with a tin content of 60.0% to 80.0%, the Cr element is derived from a granular aluminum-chromium alloy with a chromium content of 50.0% to 70.0%, and the Zr element is derived from a granular 1st grade zirconium sponge with a purity of greater than 99.7% and a size of 2.0mm to 8.0mm.

[0009] Further, the Al element is derived from the powdered aluminum-molybdenum alloy, the granular aluminum-chromium alloy, and a granular aluminum bean with a purity of greater than 99.8% and a size of 8.0mm to 13.0mm, the O element is derived from a titanium dioxide powder with a purity of greater than 99.0%, and the Ti element is derived from the tin-titanium alloy, the titanium dioxide, and a granular 0th grade titanium sponge with a purity of greater than 99.7% and a size of 3.0mm to 12.7mm.

[0010] In another aspect, the present application also provides a preparation method of the low-cost large-size titanium alloy ingot for ocean engineering, which specifically comprises the following steps:

[0011] S1, preparing electrodes: mixing the powdered aluminum-molybdenum alloy, the scrap tin-titanium alloy, the granular aluminum-chromium alloy, the granular aluminum bean, and the titanium dioxide powder, as well as the granular titanium sponge and the zirconium sponge into single block electrodes, and then pressing the mixture into electrode blocks using an oil press;

[0012] S2, welding the consumable electrodes: under argon protection, connecting multiple electrode blocks in S1 together by using a non-tungsten vacuum plasma welding box to obtain a primary consumable electrode;

[0013] S3, placing the primary consumable electrode in S2 into a vacuum consumable arc furnace for the first time to perform smelting, and then obtaining a primary ingot after cooling in the furnace;

[0014] S4, performing in-furnace welding on multiple primary ingots in S3 in a way of butt welding of ingot heads and ingot bottoms to obtain a secondary consumable electrode; wherein the in-furnace welding current is 3.0 to 20.0kA, and the voltage is 24 to 30V;

[0015] S5, the secondary consumable electrode in S4 is placed in a vacuum consumable arc furnace for second melting, and the secondary ingot is obtained after furnace cooling;

[0016] S6, the secondary ingot in S5 is placed in a vacuum consumable arc furnace for third melting, and the finished ingot is obtained after furnace cooling.

[0017] Further, the molybdenum content of the powdery aluminum molybdenum alloy in S1 is 50.0%-70.0%, the tin content of the scrap tin titanium alloy is 60.0%-80.0%, the chromium content of the granular aluminum chromium alloy is 50.0%-70.0%, the purity of the granular aluminum bean is greater than 99.8%, the diameter is 8.0mm-13.0mm, and the purity of the titanium dioxide powder is greater than 99.0%; the purity of the granular 1st grade sponge zirconium is greater than 99.7%, and the specification is 2.0mm-8.0mm; the purity of the granular 0th grade sponge titanium is greater than 99.7%, and the specification is 3.0mm-12.7mm.

[0018] Further, the welding current of the group welding connection in S2 is 300-500A, the welding voltage is 40-90V, and the argon pressure is greater than 80000Pa.

[0019] Further, the process parameters of the first melting in S3 are as follows: the crucible specification is Φ560-Φ640mm, the pre-melting vacuum degree is less than or equal to 1.0Pa, the air leakage rate is less than or equal to 1.0Pa / min, the melting voltage is 30-40V, the melting current is 15-30kA, the stable arc current is direct current 10-20A, and the cooling time is 6-8h.

[0020] Further, the process parameters of the second melting in S5 are as follows: the crucible specification is Φ640-Φ850mm, the pre-melting vacuum degree is less than or equal to 1.0Pa, the air leakage rate is less than or equal to 0.5Pa / min, the melting voltage is 34-40V, the melting current is 10-30kA, the stable arc current is alternating current 15-25A, and the cooling time is 6-10h.

[0021] Further, the process parameters of the third melting in S6 are as follows: the crucible specification is Φ850-Φ920mm, the pre-melting vacuum degree is less than or equal to 1.0Pa, the air leakage rate is less than or equal to 0.5Pa / min, the melting voltage is 30-40V, the melting current is 20-28kA, the stable arc current is alternating current 15-28A, and the cooling time is 6-10h.

[0022] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0023] (1) The titanium alloy ingot uses Sn and Cr elements to replace the relatively high-priced Nb and V elements, and is prepared by using a large-size ingot, so that the comprehensive cost can be reduced, and the large-scale application in the field of ocean engineering is facilitated.

[0024] (2) Select 3.0mm-12.7mm small granular 0-grade titanium sponge and 2.0mm-8.0mm small granular 1-grade zirconium sponge, which can strictly control the oxygen content and other impurity element content in raw materials; high-purity titanium dioxide powder is added to accurately control the gap element content. Through three vacuum self-consumption smelting, the vacuum degree, air leakage rate and other parameters are strictly controlled during the smelting process, and the optimized smelting process parameters are selected, so that the distribution coefficient of alloy elements is close to 1, the segregation of chemical composition in the ingot is reduced, the uniformity of the chemical composition in the titanium alloy ingot is effectively ensured, the industrialized preparation of Φ920mm large specification, 8-ton grade ingot is successfully realized, the problems such as composition segregation are effectively solved, the absolute value of the deviation of each main element composition phase is not more than 3000ppm, which can meet the requirement of composition uniformity.

[0025] (3) The rod diameter prepared by the Φ920mm large specification, 8-ton grade ingot prepared by the present application can reach more than 400mm, the annealed room temperature mechanical properties are excellent, the tensile strength R m ≥850MPa, the yield strength R p0.2 ≥750MPa, the elongation A≥12%, the fracture toughness K IC ≥100MPa·m 1 / 2 , the strength and toughness are excellent, and the performance level reaches that of TC4 and Ti80. BRIEF DESCRIPTION OF DRAWINGS

[0026] The drawings herein are incorporated into the specification and form part of the specification, which together with the specification is used to explain the principles of the present application.

[0027] Figure 1 It is a schematic diagram of longitudinal 3-point sampling of the ingot prepared in example 3 of the present application;

[0028] Figure 2 It is a schematic diagram of transverse 17-point sampling of the ingot prepared in example 3 of the present application;

[0029] Figure 3 It is a longitudinal 3-point Al, Mo, Sn, Cr, Zr element content distribution diagram of the ingot obtained in example 3 of the present application;

[0030] Fig.4(a), Fig.4(b), Fig.4(c) are Al, Mo, Sn, Cr, Zr element content distribution diagrams of different positions of the transverse 17 points of the ingot obtained in example 3 of the present application;

[0031] Figure 5 It is a comparison diagram of room temperature tensile properties of Φ400mm rod prepared by example 3 of the present application and TC4 alloy and Ti80 alloy;

[0032] Figure 6A comparison chart of the fracture toughness of the Φ400mm bar prepared by the embodiment 3 of the present application with that of TC4 alloy and Ti80 alloy. DETAILED DESCRIPTION

[0033] The exemplary embodiments will be described in detail herein below, and the embodiments described in the following exemplary embodiments do not represent all the embodiments consistent with the present application. Rather, they are merely examples of products, methods consistent with some aspects of the present application as detailed in the appended claims.

[0034] The present application provides a low-cost large-size titanium alloy ingot for ocean engineering, which is composed of the following elements in percentage by weight: Al: 5.7% to 6.2%, Mo: 1.0% to 1.5%, Sn: 1.0% to 1.5%, Cr: 1.5% to 2.0%, Zr: 1.5% to 2.0%, Fe: ≤0.25%, Si: ≤0.15%, C: ≤0.10%, N: ≤0.05%, O: ≤0.15%, H: ≤0.015%, the balance being Ti and unavoidable impurities, the total amount of impurities being not more than 0.30%, and the sum of the above components being 100%.

[0035] In addition, the present application also provides a preparation method of the low-cost large-size titanium alloy ingot for ocean engineering, which specifically comprises the following steps:

[0036] S1, preparing an electrode:

[0037] The alloy ratio is calculated according to the weight percentage of each element, and the powder-shaped aluminum molybdenum alloy with a molybdenum content of 50.0% to 70.0%, the scrap-shaped tin titanium alloy with a tin content of 60.0% to 80.0%, the granular aluminum chromium alloy with a chromium content of 50.0% to 70.0%, the granular aluminum beans with a purity greater than 99.8%, and the titanium dioxide powder with a purity greater than 99.0% are weighed, and are mixed with the small granular 1st grade sponge zirconium with a particle size of 2.0mm to 8.0mm and the small granular 0th grade sponge titanium with a particle size of 3.0mm to 12.7mm to form a single electrode block, and after being uniformly mixed, the electrode block is pressed into an electrode block using a large oil press, and the pressing pressure is greater than or equal to 25MPa, and the pressing time is greater than or equal to 5s.

[0038] S2, welding the consumable electrode:

[0039] Under the protection of argon, a plurality of single electrode blocks in S1 are connected together by a non-tungsten vacuum plasma welding box to form an octahedral electrode, i.e. a consumable electrode, the current for welding the electrode is 300 to 500A, the welding voltage is 40 to 90V, and the argon pressure is greater than 80000Pa. After welding, the welding points are checked, and the welding points are required to be light yellow or silver in color to prevent oxidation or other metallurgical defects such as welding cracks.

[0040] S3, the consumable electrode in S2 is placed in a vacuum consumable arc furnace for first smelting, and the smelting parameters are as follows: the crucible specification is Φ560-Φ640 mm, the vacuum degree before smelting is less than or equal to 1.0 Pa, the air leakage rate is less than or equal to 1.0 Pa / min, the smelting voltage is 30-40 V, the smelting current is 15-30 kA, the stable arc current is direct current 10-20 A, the cooling time is 6-8 h, and the primary ingot is obtained after furnace cooling, and the ingot is chamfered by a lathe.

[0041] S4, a plurality of the primary ingots in S3 are inductively welded in a furnace in a way that the ingot head is butt welded with the ingot bottom, and the secondary consumable electrode is obtained, the in-furnace welding current is 3.0-20.0 kA, and the voltage is 24-30 V.

[0042] S5, the secondary consumable electrode in S4 is placed in a vacuum consumable arc furnace for second smelting, and the smelting parameters are as follows: the crucible specification is Φ640-Φ850 mm, the vacuum degree before smelting is less than or equal to 1.0 Pa, the air leakage rate is less than or equal to 0.5 Pa / min, the smelting voltage is 34-40 V, the smelting current is 10-30 kA, the stable arc current is alternating current 15-25 A, the cooling time is 6-10 h, and the ingot is chamfered by a lathe after smelting.

[0043] S6, the secondary ingot in S5 is placed in a vacuum consumable arc furnace for third smelting, and the finished ingot is obtained after furnace cooling. The smelting parameters are as follows: the crucible specification is Φ850-Φ920 mm, the vacuum degree before smelting is less than or equal to 1.0 Pa, the air leakage rate is less than or equal to 0.5 Pa / min, the smelting voltage is 30-40 V, the smelting current is 20-28 kA, the stable arc current is alternating current 15-28 A, the cooling time is 6-10 h, and the finished ingot is obtained after furnace cooling.

[0044] The titanium alloy ingot for marine engineering provided by the application uses Sn and Cr elements to replace the higher-priced Nb and V elements, and is prepared in a large-size ingot type, so that the comprehensive cost can be reduced and the large-scale application in the marine field is facilitated. High-grade 0-grade small granular titanium sponge with a size of 3.0mm-12.7mm and 1-grade small granular zirconium sponge with a size of 2.0mm-8.0mm are selected, and the oxygen content and the content of other impurity elements in the raw materials are strictly controlled; high-purity titanium dioxide powder is added to accurately control the content of interstitial elements. Through three times of vacuum consumable melting, the vacuum degree, air leakage rate and other parameters in the melting process are strictly controlled, and the optimized melting process parameters are selected, so that the distribution coefficient of the alloy elements is close to 1, the segregation of the chemical components in the ingot is reduced, and the uniformity of the chemical components in the titanium alloy ingot is effectively ensured; the industrialized preparation of the Φ920mm large-size 8-ton ingot is successfully realized, the problems such as component segregation are effectively solved, the absolute value of the deviation of each main element component phase is not more than 3000ppm, and the requirement for the uniformity of the components is met. Moreover, the diameter of the rod prepared from the Φ920mm large-size 8-ton ingot prepared by the application is more than 400mm, the annealed room temperature mechanical properties are excellent, the tensile strength R m ≥850MPa, the yield strength R p0.2 ≥750MPa, the elongation A≥12%, the fracture toughness K IC ≥100MPa·m 1 / 2 , the strength and toughness are excellent, the performance level reaches that of TC4 and Ti80, and the titanium alloy ingot for large-size structural materials is suitable for preparing large-size structural materials for marine engineering.

[0045] In order for those skilled in the art to better understand the technical solutions of the application, the application will be further described in detail below with reference to the drawings and examples.

[0046] Example 1

[0047] Step 1, according to the weight percentage of each element: Al: 5.7%, Mo: 1.0%, Sn: 1.0%, Cr: 1.5%, Zr: 1.5%, O: 0.08%, the balance is Ti and inevitable impurities, the total amount of impurity elements is not more than 0.30%, and the sum of the above component weight percentages is 100%, respectively, take the powdered aluminum molybdenum alloy with a molybdenum content of 50.0% to 70.0%, the scrap tin titanium alloy with a tin content of 60.0% to 80.0%, the granular aluminum chromium alloy with a chromium content of 50.0% to 70.0%, and the granular aluminum beans with a purity greater than 99.8% and the titanium dioxide powder with a purity greater than 99.0%, and mix the small granular 1st grade zirconium sponge with a particle size of 2.0mm to 8.0mm and the 3.0mm to 12.7mm small granular 0th grade titanium sponge; then pour the mixed and uniform raw materials into the mold of a large oil press and press into a dense electrode block, the pressing force is 25MPa, and the holding time is 5s.

[0048] Step 2, under the protection of argon, a non-tungsten electrode vacuum plasma welding box is used to connect the multiple single block electrode blocks in step 1 together, the electrode welding current is 350A, the welding voltage is 45V, the argon pressure is 82000Pa, and the welded spot after welding is required to be light yellow or silver, preventing the welded spot from being oxidized or having welding cracks and other metallurgical defects.

[0049] Step 3, place the consumable electrode in step 2 in a vacuum consumable arc furnace for the first time to melt, the melting parameters are: crucible specification Φ560mm, pre-melting vacuum degree ≤1.0Pa, air leakage rate ≤1.0Pa / min, melting voltage 30-35V, melting current 15-20kA, stable arc current direct current 10-12A, cooling time 6h, after cooling with the furnace, a primary ingot is obtained, and the ingot is chamfered by a lathe.

[0050] Step 4, two primary ingots in step 3 are connected by the way of welding the ingot head and the ingot bottom in the furnace to obtain a secondary consumable electrode, the in-furnace welding current is 15.0-18.0kA, and the voltage is 24-28V.

[0051] Step 5, place the secondary consumable electrode in step 4 in a vacuum consumable arc furnace for the second time to melt, the melting parameters are: crucible specification Φ640mm, pre-melting vacuum degree ≤1.0Pa, air leakage rate ≤0.5Pa / min, melting voltage 34-38V, melting current 17-22kA, stable arc current alternating current 15-18A, cooling time 8h, and the ingot is chamfered by a lathe after melting.

[0052] Step 6, the second ingot in step 5 is placed in a vacuum consumable arc furnace for third melting, and the melting parameters are as follows: the crucible size is Φ720mm, the vacuum degree before melting is less than or equal to 1.0Pa, the air leakage rate is less than or equal to 0.5Pa / min, the melting voltage is 32-37V, the melting current is 20-23kA, the stable arc current is AC 15-18A, and the cooling time is 10h, and the finished product ingot with a size of Φ720mm is obtained after cooling with the furnace.

[0053] Example 2

[0054] Step 1, according to the weight percentage of each element: Al: 6.0%, Mo: 1.3%, Sn: 1.2%, Cr: 2.0%, Zr: 2.0%, O: 0.085%, the balance is Ti and unavoidable impurities, and the total amount of impurity elements is not more than 0.30%, the sum of the above component weight percentages is 100%, and the following components are weighed: powdered aluminum-molybdenum alloy with a molybdenum content of 50.0%-70.0%, scrap tin-titanium alloy with a tin content of 60.0%-80.0%, granular aluminum-chromium alloy with a chromium content of 50.0%-70.0%, and granular aluminum beans with a purity of greater than 99.8% and titanium dioxide powder with a purity of greater than 99.0%, and small granular 1st grade zirconium sponge with a particle size of 2.0mm-8.0mm and small granular 0th grade titanium sponge with a particle size of 3.0mm-12.7mm are mixed as a single block electrode; then the mixed raw materials are poured into the mold of a large oil press and pressed into a dense electrode block, the pressing force is 25MPa, and the holding time is 7s.

[0055] Step 2, under the protection of argon, a plurality of single block electrode blocks in step 1 are connected together by using a non-tungsten electrode vacuum plasma welding box, the electrode welding current is 400A, the welding voltage is 48V, the argon pressure is 83000Pa, and the welded spot after welding is required to be light yellow or silver, preventing oxidation or other metallurgical defects such as welding cracks.

[0056] Step 3, the single consumable electrode in step 2 is placed in a vacuum consumable arc furnace for first melting, and the melting parameters are as follows: the crucible size is Φ640mm, the vacuum degree before melting is less than or equal to 1.0Pa, the air leakage rate is less than or equal to 0.7Pa / min, the melting voltage is 32-37V, the melting current is 17-21kA, the stable arc current is DC 12-15A, and the cooling time is 6h, and the first ingot is obtained after cooling with the furnace, and the ingot is chamfered by a lathe.

[0057] Step 4, two first ingots in step 3 are inductively welded in the furnace by butt welding of the ingot head and the ingot bottom, and a second consumable electrode is obtained, the inductive welding current is 17.0-20.0kA, and the voltage is 26-30V.

[0058] Step 5, the second consumable electrode in step 4 is placed in a vacuum consumable arc furnace for second melting, the melting parameters are: the size of the crucible is Φ720mm, the vacuum degree before melting is less than or equal to 1.0Pa, the air leakage rate is less than or equal to 0.5Pa / min, the melting voltage is 36-40V, the melting current is 18-23kA, the stable arc current is AC 16-18A, the cooling time is 8h, and the ingot is chamfered on the lathe after melting.

[0059] Step 6, the second ingot in step 5 is placed in a vacuum consumable arc furnace for third melting, the melting parameters are: the size of the crucible is Φ850mm, the vacuum degree before melting is less than or equal to 1.0Pa, the air leakage rate is less than or equal to 0.5Pa / min, the melting voltage is 34-38V, the melting current is 22-25kA, the stable arc current is AC 16-18A, the cooling time is 10h, and the finished product ingot with a size of Φ850mm is obtained after cooling in the furnace.

[0060] Example 3

[0061] Step 1, according to the weight percentage of each element: Al: 6.2%, Mo: 1.5%, Sn: 1.0%, Cr: 2.0%, Zr: 2.0%, O: 0.082%, the balance is Ti and unavoidable impurities, the total amount of impurity elements is not more than 0.30%, the sum of the above component weight percentages is 100%, and the aluminum-molybdenum alloy powder with a molybdenum content of 50.0%-70.0%, the tin-titanium alloy scrap with a tin content of 60.0%-80.0%, the aluminum-chromium alloy particles with a chromium content of 50.0%-70.0%, and the granular aluminum beans with a purity greater than 99.8% and the titanium dioxide powder with a purity greater than 99.0% are weighed, and are mixed with small granular 1st grade zirconium sponge with a particle size of 2.0mm-8.0mm and small granular 0th grade titanium sponge with a particle size of 3.0mm-12.7mm to form a single block electrode; then the mixed raw materials are poured into the mold of a large oil press and pressed into a dense electrode block, the pressing force is 27MPa, and the holding time is 7s.

[0062] Step 2, under the protection of argon, a plurality of single block electrode blocks in step 1 are connected together by a non-tungsten electrode vacuum plasma welding box, the electrode welding current is 500A, the welding voltage is 50V, the argon pressure is 83000Pa, the welding spot after welding is required to be light yellow or silver, and oxidation or other metallurgical defects such as welding cracks are prevented.

[0063] Step 3, the primary consumable electrode described in step 3 is placed in a vacuum consumable arc furnace for first smelting, the smelting parameters are: the size of the crucible is Φ720mm, the vacuum degree before smelting is ≤1.0Pa, the air leakage rate is ≤0.7Pa / min, the smelting voltage is 35-40V, the smelting current is 19-23kA, the stable arc current is direct current 14-17A, the cooling time is 8h, and the primary ingot is obtained after cooling with the furnace, and the ingot is chamfered by a lathe.

[0064] Step 4, two primary ingots described in step 3 are inductively welded in the furnace in the way of butt welding of the ingot head and the ingot bottom, and the secondary consumable electrode is obtained, the inductive welding current is 17.0-20.0kA, and the voltage is 26-30V.

[0065] Step 5, the secondary consumable electrode described in step 4 is placed in a vacuum consumable arc furnace for second smelting, the smelting parameters are: the size of the crucible is Φ850mm, the vacuum degree before smelting is ≤1.0Pa, the air leakage rate is ≤0.5Pa / min, the smelting voltage is 36-40V, the smelting current is 20-25kA, the stable arc current is alternating current 18-20A, the cooling time is 8h, and the ingot is chamfered by a lathe after smelting.

[0066] Step 6, the secondary ingot described in step 5 is placed in a vacuum consumable arc furnace for third smelting, the smelting parameters are: the size of the crucible is Φ920mm, the vacuum degree before smelting is ≤1.0Pa, the air leakage rate is ≤0.5Pa / min, the smelting voltage is 35-40V, the smelting current is 24-28kA, the stable arc current is alternating current 18-20A, the cooling time is 10h, and the Φ920mm finished product ingot is obtained after cooling with the furnace.

[0067] According to Figure 1 and 2 , the Φ920mm finished product ingot of 8 tons in example 3 is sampled and chemically analyzed at 3 longitudinal points and 17 transverse points, and the results are shown in Figure 3 and 4, wherein the chemical components of the 3 longitudinal points are listed in table 1, and figure 4 shows the transverse distribution of different elements at the head, middle and tail positions of the ingot, and it can be seen that the components of each element are uniformly distributed.

[0068] Table 1 Chemical components of 3 longitudinal points of Φ920mm finished product ingot

[0069]

[0070] From the data in table 1, combined with Figure 3 -4, it can be seen that the large-size titanium alloy ingot obtained by the preparation method provided by the application has uniform components, reduces the burning loss of low-melting-point Al elements, and effectively controls the segregation behavior of Mo and Cr elements prone to segregation, and is suitable for industrial production.

[0071] Figure 5 and Figure 6 The Φ400mm rod is prepared by using the Φ920mm large-size, 8-ton ingot according to the application, and the room temperature tensile strength and fracture toughness in the annealed state are compared with those of TC4 and Ti80 alloys. It can be known through comparison that the tensile strength R m of the rod is 862MPa, the yield strength R p0.2 is 778MPa, the elongation A is 12.5%, the fracture toughness K IC is 108MPa·m 1 / 2 , the strength and toughness are well matched, and the performance level reaches that of TC4 and Ti80. Therefore, the method provided by the application is suitable for preparing large-size structural material titanium alloy ingot for service in the field of marine engineering, and has a wide application prospect.

[0072] The above description is merely a specific implementation of the application, which enables those skilled in the art to understand or implement the application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application.

[0073] It should be understood that the application is not limited to the above described and that various modifications and changes can be made without departing from the scope thereof. The scope of the application is limited only by the claims appended hereto.

Claims

1. A low-cost, large-size titanium alloy ingot for marine engineering, characterized in that, By weight percentage, it consists of the following elements Composition: Al: 5.7%~6.2%, Mo: 1.0%~1.5%, Sn: 1.0%~1.5%, Cr: 1.5%~2.0%, Zr: 1.5%~2.0%, Fe: ≤0.25%, Si: ≤0.15%, C: ≤0.10%, N: ≤0.05%, O: ≤0.15%, H: ≤0.015%, with the balance being Ti and unavoidable impurities, and the total amount of impurity elements not exceeding 0.30%. The Mo element is derived from powdered aluminum-molybdenum alloy with a molybdenum content of 50.0%~70.0%, the Sn element is derived from chipped tin-titanium alloy with a tin content of 60.0%~80.0%, the Cr element is derived from granular aluminum-chromium alloy with a chromium content of 50.0%~70.0%, and the Zr element is derived from granular grade 1 sponge zirconium with a purity greater than 99.7% and a size of 2.0mm~8.0mm. The Al element is derived from powdered aluminum-molybdenum alloy and granular aluminum-chromium alloy, as well as granular aluminum granules with a purity greater than 99.8% and a size of 8.0mm to 13.0mm; the O element is derived from titanium dioxide powder with a purity greater than 99.0%; the Ti element is derived from tin-titanium alloy and titanium dioxide, as well as granular grade 0 sponge titanium with a purity greater than 99.7% and a size of 3.0mm to 12.7mm.

2. The method for preparing low-cost, large-size titanium alloy ingots for marine engineering according to claim 1, characterized in that, Specifically, the steps include the following: S1. Electrode preparation: Powdered aluminum-molybdenum alloy, chipped tin-titanium alloy, granular aluminum-chromium alloy, granular aluminum pellets and titanium dioxide powder, as well as granular sponge titanium and sponge zirconium are mixed into single electrode blocks. After being mixed evenly, they are pressed into electrode blocks using a hydraulic press. S2, Welding consumable electrode: Under argon protection, multiple electrode blocks in S1 are welded together using a non-tungsten inert gas vacuum plasma welding box to obtain a primary consumable electrode. S3. The primary consumable electrode described in S2 is placed in a vacuum consumable arc furnace for the first melting, and after cooling with the furnace, a primary ingot is obtained. The process parameters for the first melting are: crucible size Φ560~Φ640mm, vacuum degree before melting ≤1.0Pa, leakage rate ≤1.0Pa / min, melting voltage 30~40V, melting current 15~30kA, arc stabilization current DC 10~20A, and cooling time 6~8h. S4. Multiple primary casting ingots from S3 are welded in the furnace by butt welding the riser to the ingot bottom to obtain secondary consumable electrodes; wherein the furnace welding current is 3.0~20.0kA and the voltage is 24~30V. S5. The secondary consumable electrode described in S4 is placed in a vacuum consumable arc furnace for a second melting process. After cooling in the furnace, a secondary ingot is obtained. The process parameters for the second melting process are as follows: crucible size is Φ640~Φ850mm, vacuum degree before melting is ≤1.0Pa, leakage rate is ≤0.5Pa / min, melting voltage is 34~40V, melting current is 10~30kA, arc stabilization current is AC 15~25A, and cooling time is 6~10h. S6. The secondary ingot described in S5 is placed in a vacuum self-consuming electric arc furnace for a third melting, and the finished ingot is obtained after cooling in the furnace. The process parameters for the third melting are: crucible size Φ850~Φ920mm, vacuum degree before melting ≤1.0Pa, leakage rate ≤0.5Pa / min, melting voltage 30~40V, melting current 20~28kA, arc stabilization current AC 15~28A, and cooling time 6~10h.

3. The method for preparing low-cost, large-size titanium alloy ingots for marine engineering according to claim 2, characterized in that, In S1, the molybdenum content of the powdered aluminum-molybdenum alloy is 50.0%~70.0%, the tin content of the chipped tin-titanium alloy is 60.0%~80.0%, the chromium content of the granular aluminum-chromium alloy is 50.0%~70.0%, the purity of the granular aluminum pellets is greater than 99.8%, the diameter is 8.0mm~13.0mm, and the purity of the titanium dioxide powder is greater than 99.0%; the purity of the granular grade 1 sponge zirconium is greater than 99.7%, and the size is 2.0mm~8.0mm; the purity of the granular grade 0 sponge titanium is greater than 99.7%, and the size is 3.0mm~12.7mm.

4. The method for preparing low-cost, large-size titanium alloy ingots for marine engineering according to claim 2, characterized in that, The welding current for the assembly connection in S2 is 300~500A, the welding voltage is 40~90V, and the argon pressure is greater than 80000Pa.

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