Low-cost TA4 titanium alloy strip preparation process

Abstract

The invention provides a low-cost TA4 titanium alloy strip preparation process which comprises the following steps: step 1, preparing a TA4 slab ingot by adopting an electron beam cold hearth smelting furnace die casting method, and carrying out integral machining on the upper surface and the lower surface of a cast ingot by using a large integral cutter head milling machine to obtain a slab; 2, rolling the plate blank to obtain a hot-rolled coil; thirdly, the hot coil is rolled to 3.0-3.8 mm, annealing is conducted, and oxide skin removing treatment is conducted; step 4, trimming two sides, rolling to 1.8-2.5 mm, and carrying out heat treatment; step 5, trimming two sides, rolling to 0.7-1.2 mm, and carrying out heat treatment; sixthly, finished product rolling is conducted after the two sides are trimmed, the rolling process deformation is 20-30%, the rolling target thickness is 0.4-0.5 mm, the pass deformation is smaller than or equal to 7%, the tension is 25-75 kg / mm < 2 >, and the rolling speed is 30-60 m / min; step 7, heat treatment; and 8, stretch bending and straightening. By controlling the rolling process deformation, the rolling target thickness, the pass deformation, the tension and the rolling speed, the rolling deformation nonuniformity is weakened, the plate shape is improved and optimized, rib forming is avoided, and finally stable production of the TA4 titanium alloy strip is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy strip preparation, and in particular to a low-cost TA4 titanium alloy strip preparation process. Background Art

[0002] TA4 titanium alloy has excellent corrosion resistance and specific strength, and has broad application prospects in 3C electronics, petrochemicals, medical, aerospace, shipbuilding and marine engineering. At present, TA4 titanium alloy coils are mainly prepared by VAR smelting forging slab forging and rolling, and its production process is long and costly. On the other hand, the rolling process of TA4 titanium alloy cold-rolled titanium strip is prone to abnormalities such as strip breakage and rib formation, which leads to scrapping of the coil, so it is difficult to achieve stable mass production of TA4 titanium alloy coils.

[0003] In 2020, the applicant filed a patent application CN112122382A for a process method for preparing wide-width ultra-thin cold-rolled titanium strip coils for rolling composite. Through innovation and optimization of process routes and parameters such as composition design, slab preparation, cold coil rolling, heat treatment, and flattening and correction, the slabs are prepared by EB furnace mold casting flat ingots, and the surface is processed using a large integral cutter disc. After the mother strip is cold rolled, the method of first trimming and then annealing is adopted. A low-tension rolling control method is adopted in the rolling stage of the finished product. The finished product heat treatment is carried out by long-term insulation and furnace cooling hood annealing. The rolling flattening method is selected to further improve the shape of the strip after annealing. The prepared cold-rolled titanium strip coil has a width of more than 1000 mm, a thickness of 0.1 to 0.3 mm, a straight plate shape, excellent comprehensive mechanical properties, and a high rolling composite rate with dissimilar metals. At the same time, it can significantly reduce the cost of titanium metal for composite materials. However, CN112122382A is for TA1 grade titanium alloy, and TA4 titanium alloy has higher strength, 300-500MPa higher than TA1 titanium coil. If TA4 titanium alloy strip is directly prepared by the preparation process of CN112122382A, it is easy to break the strip and rib, resulting in poor quality of the finished product. Summary of the invention

[0004] In view of this, the present invention aims to propose a low-cost TA4 titanium alloy strip preparation process to solve the problem of strip breakage and rib formation that are prone to occur during the preparation of TA4 titanium alloy strip.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A low-cost TA4 titanium alloy strip preparation process comprises the following steps:

[0007] Step 1: Prepare TA4 flat ingots by electron beam cold bed melting furnace casting method, the obtained flat ingots have a width of ≥1000 mm and a thickness of 170-220 mm, and use a large integral cutter milling machine to machine the upper and lower surfaces of the ingot to obtain slabs;

[0008] Step 2: using a Steckel mill to roll TA4 strip, the billet heating temperature is 800-950° C., and the slab is rolled through a rough rolling unit and a finishing rolling unit to obtain a titanium alloy hot-rolled coil;

[0009] Step 3: Use a six-roll mill to roll the hot coil to 3.0-3.8 mm, and use a continuous annealing, shot blasting and pickling line to anneal and remove oxide scale on the titanium coil. The heat treatment annealing temperature is 700-800°C;

[0010] Step 4: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the titanium coil to 1.8-2.5 mm, with a rolling deformation of 16-55%, and a pass deformation of ≤15%. Use a continuous annealing, shot blasting, and pickling line to heat treat the titanium coil at a heat treatment annealing temperature of 700-800°C.

[0011] Step 5: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the titanium coil to 0.7-1.2 mm, with a rolling deformation of 33-70% and a pass deformation of ≤10%. Use a bell-type annealing furnace to heat treat the titanium coil at a heat treatment annealing temperature of 600-680°C.

[0012] Step 6: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the finished product. The rolling process deformation is 20-30%, the rolling target thickness is 0.4-0.5mm, the pass deformation is ≤7%, and the tension is 25-75kg / mm 2 , rolling speed 30~60m / min;

[0013] Step 7: heat-treating the cold-rolled titanium strip coil in a protective atmosphere hood annealing furnace at a temperature of 600 to 680° C. for a holding time of 7 to 12 hours;

[0014] Step 8: Use a stretching and straightening unit to straighten the finished titanium coil, with an elongation of 0.5-1.0%.

[0015] Furthermore, in step one, when an electron beam cold hearth melting furnace (EB furnace) is used, sponge titanium, titanium dioxide and ferro-titanium alloy are selected for briquetting to prepare briquette electrodes, the smelting electron gun current is 5.0 to 15.0 A, and the smelting rate is 300 to 1200 kg / h.

[0016] Furthermore, in step one, the cutter diameter of the large integral cutter milling machine is greater than the slab width, the width is 1300-1500 mm, the single-sided milling thickness is ≥3 mm, and the thickness difference of the slab cross section after machining is ≤3 mm.

[0017] Furthermore, in step 1, the composition of the slab is controlled so that the mass percentage of impurity element Fe is ≤0.50%, the mass percentage of C is ≤0.20%, the mass percentage of N is ≤0.10%, and the mass percentage of O is ≤0.40%.

[0018] Furthermore, in step one, an anti-oxidation coating is applied on the upper and lower surfaces and sides of the slab.

[0019] Furthermore, the thickness of the anti-oxidation coating is 0.3-1.0 mm.

[0020] Furthermore, in step 2, the rough rolling thickness is 30-60 mm, the deformation rate of each pass is ≤35%, and the finishing rolling thickness is 4-6 mm, the deformation rate of each pass is ≤30%.

[0021] Furthermore, in step three, the rolling deformation is 20-50%, and the pass deformation rate is ≤15%.

[0022] Furthermore, in step 4, step 5 and step 6, when trimming the edges on both sides, the width of the trimming on one side is ≥ 5 mm.

[0023] Compared with the prior art, the low-cost TA4 titanium alloy strip preparation process described in the present invention has the following advantages:

[0024] (1) During the rolling of finished products, the rolling deformation, rolling target thickness, pass deformation, tension and rolling speed are controlled to reduce the unevenness of rolling deformation, improve and optimize the plate shape, avoid ribs, and finally achieve stable production of TA4 titanium alloy strip.

[0025] (2) The use of an EB furnace with a refining function to prepare slabs can significantly reduce defects such as inclusions and holes in the finished TA4 titanium alloy strip caused by metallurgical quality problems, and obtain strips with beautiful surface quality.

[0026] (3) Before each cold rolling process, edge trimming is used to eliminate edge cracking defects and reduce the risk of cold-rolled finished strip breakage. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be noted that the data in the following experimental examples are obtained by the inventor through a large number of experiments. Due to space limitations, only a part of them is shown in the specification, and those of ordinary skill in the art can understand and implement the present invention under these data. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these changes or modifications also fall within the scope protected by the present application.

[0028] A low-cost TA4 titanium alloy strip preparation process comprises the following steps:

[0029] Step 1: Prepare TA4 flat ingots by electron beam cold bed melting furnace casting method, the obtained flat ingots have a width of ≥1000 mm and a thickness of 170-220 mm, and use a large integral cutter milling machine to machine the upper and lower surfaces of the ingot to obtain slabs;

[0030] Specifically, in step 1, when an electron beam cold hearth melting furnace (EB furnace) is used, sponge titanium, titanium dioxide and ferro-titanium alloy are selected for briquetting to prepare briquette electrodes, the smelting electron gun current is 5.0 to 15.0 A, and the smelting rate is 300 to 1200 kg / h.

[0031] The cutter diameter of the large integrated cutter milling machine is greater than the slab width, the width is 1300-1500mm, the single-side milling thickness is ≥3mm, and the thickness difference of the slab cross section after machining is ≤3mm. Specifically in the present invention, the model of the large integrated cutter milling machine is ZGTX1.

[0032] Furthermore, after obtaining the slab, an anti-oxidation coating is applied to the upper and lower surfaces and the side surfaces of the slab. The anti-oxidation coating includes glass powder, a binder and water, and the thickness of the coating is 0.3 to 1.0 mm. Since the anti-oxidation coating is a prior art, it will not be described here. Applying the anti-oxidation coating on the surface of the slab helps to improve the surface quality of the titanium coil.

[0033] In the composition of the slab, the mass percentage of impurity element Fe is ≤0.50%, the mass percentage of C is ≤0.20%, the mass percentage of N is ≤0.10%, and the mass percentage of O is ≤0.40%. By controlling the composition of impurity elements Fe, O, C, and N, and using a long-term heat preservation and furnace cooling hood annealing method to perform finished product heat treatment in the subsequent preparation process, it is beneficial to reduce the strength of the titanium strip, improve the elongation, and make it have excellent mechanical properties.

[0034] In step 1 of the present invention, an EB furnace is used to cast a flat ingot to prepare a slab. The EB furnace has the advantages of high melting vacuum, high superheat, and good removal of high and low density inclusions. The EB furnace with a refining function is used to prepare the slab, which can significantly reduce the defects such as inclusions and holes in the finished TA4 titanium alloy strip caused by metallurgical quality problems, and obtain a strip with beautiful surface quality. In addition, the use of a single-melting EB flat ingot as a blank has fewer production processes, a high yield, and a blanking cost reduction of more than 20% compared with the traditional two or three VAR melting and multi-fire forging and grinding to manufacture the slab, which is conducive to reducing the production cost of titanium strips.

[0035] The EB furnace is combined with a large integral cutter head to process the upper and lower surfaces of the ingot. Compared with the traditional VAR smelting round ingot forging slab small cutter head processing method, the slab size is more regular, there is no thickness difference on the surface, and the cross-sectional thickness is uniform. It can significantly reduce the risk of plate shape defects such as edge waves, rib waves, and middle waves in thin strip products caused by uneven slab thickness, and reduce the risk of ribs and strip breaks in finished product rolling.

[0036] Step 2: using a Steckel mill to roll TA4 strip, the billet heating temperature is 800-950° C., and the slab is rolled through a rough rolling unit and a finishing rolling unit to obtain a titanium alloy hot-rolled coil;

[0037] Specifically, in step 2, the rough rolling thickness is 30-60 mm, the deformation rate of each pass is ≤35%, and the finishing rolling thickness is 4-6 mm, the deformation rate of each pass is ≤30%.

[0038] Step 3: Use a six-roll mill to roll the hot coil to 3.0-3.8 mm, and use a continuous annealing, shot blasting and pickling line to anneal and remove oxide scale on the titanium coil. The heat treatment annealing temperature is 700-800°C;

[0039] Specifically, in step three, the rolling deformation is 20-50%, and the pass deformation rate is ≤15%.

[0040] Step 4: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the titanium coil to 1.8-2.5 mm, with a rolling deformation of 16-55%, and a pass deformation of ≤15%. Use a continuous annealing, shot blasting, and pickling line to heat treat the titanium coil at a heat treatment annealing temperature of 700-800°C.

[0041] Step 5: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the titanium coil to 0.7-1.2 mm, with a rolling deformation of 33-70% and a pass deformation of ≤10%. Use a bell-type annealing furnace to heat treat the titanium coil at a heat treatment annealing temperature of 600-680°C.

[0042] Step 6: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the finished product. The rolling process deformation is 20-30%, the rolling target thickness is 0.4-0.5mm, the pass deformation is ≤7%, and the tension is 25-75kg / mm 2 , rolling speed 30~60m / min;

[0043] Specifically, the main reasons for the occurrence of ribs are unstable rolling and uneven rolling deformation. Slight deviation and inclination of the titanium strip during rolling cause ribs. On the other hand, the deterioration of the titanium strip plate shape and excessive tension are also the causes of ribs. In step six, in order to avoid ribs in the rolling of the finished product, a smaller finished rolling deformation, a smaller pass deformation, a small tension and a slow rolling method are adopted in the cold rolling stage of the finished product. The small finished rolling deformation is used to weaken the uneven rolling deformation, the small pass deformation is used to improve and optimize the plate shape, the slow rolling is used to avoid the deviation and inclination of the titanium strip, and the small tension rolling method is used to avoid ribs caused by excessive tension. The present invention finally achieves the stable production of TA4 titanium alloy strip by reasonably controlling the rolling deformation, the pass deformation, the tension and the rolling speed, and greatly improves the rib problem of the finished titanium alloy strip, so that the finished product has better quality.

[0044] Step 7: heat-treating the cold-rolled titanium strip coil in a protective atmosphere hood annealing furnace at a temperature of 600 to 680° C. for a holding time of 7 to 12 hours;

[0045] Step 8: Use a stretching and straightening unit to straighten the finished titanium coil, with an elongation of 0.5-1.0%.

[0046] As a preferred example of the present invention, in step 4, step 5 and step 6, when trimming the edges on both sides, the single-side trimming width is ≥5mm. The main reason for the breaking of TA4 titanium coil during rolling is edge cracking. The present invention trims the titanium coil before each cold rolling process to eliminate the risk of breaking caused by edge cracking during the cold rolling process.

[0047] The present invention discloses a low-cost TA4 titanium alloy strip preparation process, which uses a single EB smelting flat ingot to prepare TA4 slabs, shortening the slab making process, reducing the cost of TA4 strips, and improving the surface quality of titanium coils by coating the slab surface with an anti-oxidation coating and optimizing the hot rolling process. At the same time, by optimizing the composition design, the trimming treatment before the cold rolling process, and the parameter control in the finished product cold rolling stage, the technical problems of TA4 strip breaking and rib formation during rolling are solved. The prepared TA4 titanium alloy coil has excellent performance, high yield rate, and low production cost. The width reaches more than 1000mm and the thickness is 0.4-0.5mm, which has broad application prospects. The finished coils obtained by the preparation process of the present invention are sampled and inspected. The plate shape satisfies ≤5mm / m, and the yield strength (R P0.2 ) satisfies 485~655MPa, and the elongation A satisfies ≥20%.

[0048] Example 1

[0049] Step 1. Prepare TA4 flat ingots by EB furnace casting method, select sponge titanium, titanium dioxide and titanium alloy for briquetting to prepare briquette electrodes, smelting electron gun current 8.0A, smelting rate 1000kg / h. The obtained flat ingot width is 1280mm and thickness is 190mm. Use ZGTX1 integral cutter milling machine to machine the upper and lower surfaces of the ingot as a whole, the cutter diameter is greater than the slab width, the single-sided milling thickness is 5mm, the cross-sectional thickness difference of the slab after machining is 1mm, and the upper and lower surfaces and sides of the slab are coated with 0.5mm anti-oxidation coating. In the titanium slab, the mass percentages of Fe, C, N, and O impurity elements are 0.30%, 0.08%, 0.01%, and 0.35%, respectively.

[0050] Step 2: Use a furnace coil mill to roll TA4 strip, the billet heating temperature is 900°C, and the slab is rolled by a rough rolling unit and a finishing rolling unit to obtain a titanium alloy hot-rolled coil, wherein the rough rolling thickness is 30mm, and the pass deformation rate is ≤35%; the finishing rolling thickness is 4mm, and the pass deformation rate is ≤30%.

[0051] Step 3: Use a six-roll mill to roll the hot coil to 3.0 mm, with a rolling deformation of 25% and a pass deformation rate of ≤15%. Use a continuous annealing, shot blasting and pickling line to anneal and remove oxide scale on the titanium coil. The heat treatment annealing temperature is 750°C.

[0052] Step 4: perform trimming on both sides, with a single-side trimming width of 10 mm. After trimming, use a twenty-high rolling mill to roll the titanium coil to 2.0 mm, with a rolling deformation of 33.3% and a pass deformation of ≤15%. Use a continuous annealing, shot blasting and pickling line to heat treat the titanium coil, and the heat treatment annealing temperature is 800°C.

[0053] Step 5: perform trimming on both sides, with a single-side trimming width of 10 mm. After trimming, use a 20-roller mill to roll the titanium coil to 0.7 mm, with a rolling deformation of 65% and a pass deformation of ≤10%. Use a hood annealing furnace to heat treat the titanium coil at a heat treatment annealing temperature of 650°C.

[0054] Step 6: Trim the edges on both sides, with a single-side trimming width of 10 mm. After trimming, use a 20-roll mill to roll the finished product, with a pass deformation of ≤7% and a tension of 50 kg / mm 2 , rolling speed 40m / min, rolling deformation 28.5%, rolling target thickness 0.5mm.

[0055] Step 7: Use a protective atmosphere hood annealing furnace to heat treat the cold-rolled titanium strip coil at a heat treatment temperature of 650° C. and a holding time of 10 hours.

[0056] Step 8: Use a stretching and bending straightening unit to straighten the finished titanium coil, with an elongation of 1.0%.

[0057] Example 2

[0058] Step 1. Prepare TA4 flat ingots by EB furnace casting method, select sponge titanium, titanium dioxide and titanium alloy for briquetting to prepare briquette electrodes, smelting electron gun current 15.0A, smelting rate 1200kg / h. The obtained flat ingot width is 1060mm and thickness is 200mm. Use ZGTX1 integral cutter milling machine to machine the upper and lower surfaces of the ingot as a whole, the cutter diameter is greater than the slab width, the single-sided milling thickness is 3mm, the cross-sectional thickness difference of the slab after machining is 3mm, and the upper and lower surfaces and sides of the slab are coated with 0.3mm anti-oxidation coating. In the titanium slab, the mass percentages of Fe, C, N, and O impurity elements are 0.25%, 0.10%, 0.005%, and 0.38%, respectively.

[0059] Step 2: Use a furnace coil mill to roll TA4 strip, the billet heating temperature is 880°C, and the slab is rolled through a rough rolling unit and a finishing rolling unit to obtain a titanium alloy hot-rolled coil, wherein the rough rolling thickness is 40mm, and the pass deformation rate is ≤35%; the finishing rolling thickness is 4.5mm, and the pass deformation rate is ≤30%.

[0060] Step 3: Use a six-roll mill to roll the hot coil to 3.5 mm, with a rolling deformation of 22.2% and a pass deformation of ≤15%. Use a continuous annealing, shot blasting and pickling line to anneal and remove oxide scale on the titanium coil, with a heat treatment annealing temperature of 780°C.

[0061] Step 4: perform trimming on both sides, with a single-side trimming width of 8mm. After trimming, use a twenty-roll rolling mill to roll the titanium coil to 2.2mm, with a rolling deformation of 37.1% and a pass deformation of ≤15%. Use a continuous annealing, shot blasting and pickling line to heat treat the titanium coil, and the heat treatment annealing temperature is 800°C.

[0062] Step 5: perform trimming on both sides, with a single-side trimming width of 5 mm. After trimming, use a 20-high rolling mill to roll the titanium coil to 0.7 mm, with a rolling deformation of 68.1% and a pass deformation of ≤10%. Use a hood annealing furnace to heat treat the titanium coil at a heat treatment annealing temperature of 660°C.

[0063] Step 6: Trim the edges on both sides, with a single-side trimming width of 5mm. After trimming, use a 20-roll mill to roll the finished product, with a pass deformation of ≤7% and a tension of 37kg / mm 2 , rolling speed 50m / min, rolling deformation 28.5%, rolling target thickness 0.5mm.

[0064] Step 7: Use a protective atmosphere hood annealing furnace to heat treat the cold-rolled titanium strip coil at a heat treatment temperature of 650° C. and a holding time of 8 hours.

[0065] Step 8: Use a stretching and bending straightening unit to straighten the finished titanium coil with an elongation of 0.5%.

[0066] Comparative Example 1

[0067] The preparation process and production parameters of Comparative Example 1 and Example 1 are the same, and the only difference is that in Comparative Example 1, the Fe content of the titanium slab is 0.7%, and the O content is 0.5%.

[0068] Comparative Example 2

[0069] The preparation process and production parameters of Comparative Example 2 and Example 2 are the same, and the only difference is that Comparative Example 2 adopts the VAR smelting round ingot forging slab small cutter processing method, and the cross-sectional thickness difference of the obtained slab reaches 5mm. No trimming is performed before cold rolling, and the finished product rolling variable is 50%, from 1.0mm to 0.5mm.

[0070] Comparative Example 3

[0071] The preparation process and production parameters of Comparative Example 3 and Example 1 are the same, the only difference is that in step 6, the tension is 100kg / mm 2 , rolling speed 100m / min.

[0072] Comparative Example 4

[0073] The preparation process and production parameters of Comparative Example 4 and Example 1 are the same, and the only difference is that in step seven, the heat treatment temperature is 550°C.

[0074] The finished titanium coils prepared in Examples 1 to 2 and Comparative Examples 1 to 4 were sampled and tested, and the results are shown in Table 1.

[0075] Table 1

[0076]

[0077] The chemical composition in Comparative Example 1 is different from that in this application, resulting in the mechanical properties of the finished TA4 titanium alloy strip not meeting the requirements. On the other hand, due to the high content of O and Fe elements, the strip strength is high, and the strip breaks many times during the rolling process, resulting in the scrapping of the coil. In Comparative Example 2, because no trimming was performed before cold rolling, the sharp corners and burrs of the trimming caused cracks, resulting in two strip breaks. On the other hand, the thickness difference of the slab cross section reached 5mm. After rolling and annealing of the three small coils, the unevenness was about 15mm / m, with obvious ribs and double-sided waves. At the same time, the deformation of the finished product was large, and the finished product had rib defects during rolling, resulting in the scrapping of the coil. The tension and rolling speed of Comparative Example 3 are large, and the titanium strip deviates and tilts many times during the rolling process. Moreover, the tension is too large and the rolling speed is fast, resulting in serious rib phenomenon. In Comparative Example 4, because the heat treatment temperature is 550℃, the mechanical properties of the finished titanium strip do not meet the requirements of this patent. In Examples 1 to 2 using the preparation process of the present invention, no strip breakage or rib formation occurs during rolling, and the TA4 titanium alloy coil has a high yield, stable production, a straight plate shape, excellent comprehensive mechanical properties, and a low cost.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-cost TA4 titanium alloy strip preparation process, characterized in that: The steps include: Step 1: Prepare TA4 flat ingots by electron beam cold bed melting furnace casting method, the obtained flat ingots have a width of ≥1000 mm and a thickness of 170-220 mm, and use a large integral cutter milling machine to machine the upper and lower surfaces of the ingot to obtain slabs; Step 2: using a Steckel mill to roll TA4 strip, the billet heating temperature is 800-950° C., and the slab is rolled through a rough rolling unit and a finishing rolling unit to obtain a titanium alloy hot-rolled coil; Step 3: Use a six-roll mill to roll the hot coil to 3.0-3.8 mm, and use a continuous annealing, shot blasting and pickling line to anneal and remove oxide scale on the titanium coil. The heat treatment annealing temperature is 700-800°C; Step 4: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the titanium coil to 1.8-2.5 mm, with a rolling deformation of 16-55%, and a pass deformation of ≤15%. Use a continuous annealing, shot blasting, and pickling line to heat treat the titanium coil at a heat treatment annealing temperature of 700-800°C. Step 5: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the titanium coil to 0.7-1.2 mm, with a rolling deformation of 33-70% and a pass deformation of ≤10%. Use a bell-type annealing furnace to heat treat the titanium coil at a heat treatment annealing temperature of 600-680°C. Step 6: trim the edges on both sides. After trimming, use a 20-high rolling mill to roll the finished product. The rolling process deformation is 20-30%, the rolling target thickness is 0.4-0.5mm, the pass deformation is ≤7%, and the tension is 25-75kg / mm 2 , rolling speed 30~60m / min; Step 7: heat-treating the cold-rolled titanium strip coil in a protective atmosphere hood annealing furnace at a temperature of 600 to 680° C. for a holding time of 7 to 12 hours; Step 8: Use a stretching and straightening unit to straighten the finished titanium coil, with an elongation of 0.5-1.0%.

2. The low-cost TA4 titanium alloy strip preparation process according to claim 1, characterized in that: In step 1, when an electron beam cold hearth melting furnace (EB furnace) is used, sponge titanium, titanium dioxide and ferro-titanium alloy are selected for briquetting to prepare briquette electrodes, the smelting electron gun current is 5.0 to 15.0 A, and the smelting rate is 300 to 1200 kg / h.

3. The low-cost TA4 titanium alloy strip preparation process according to claim 1, characterized in that: In step 1, the cutter diameter of the large integral cutter milling machine is greater than the slab width, the width is 1300-1500 mm, the single-sided milling thickness is ≥3 mm, and the thickness difference of the slab cross section after machining is ≤3 mm.

4. The low-cost TA4 titanium alloy strip preparation process according to claim 1, characterized in that: In step 1, the composition of the slab is controlled so that the mass percentage of impurity element Fe is ≤0.50%, the mass percentage of C is ≤0.20%, the mass percentage of N is ≤0.10%, and the mass percentage of O is ≤0.40%.

5. The low-cost TA4 titanium alloy strip preparation process according to claim 1, characterized in that: In step one, an anti-oxidation coating is applied on the upper and lower surfaces and sides of the slab.

6. The low-cost TA4 titanium alloy strip preparation process according to claim 5, characterized in that: The thickness of the anti-oxidation coating is 0.3-1.0 mm.

7. The low-cost TA4 titanium alloy strip preparation process according to claim 1, characterized in that: In step 2, the rough rolling thickness is 30-60 mm, the deformation rate of each pass is ≤35%, and the finishing rolling thickness is 4-6 mm, the deformation rate of each pass is ≤30%.

8. The low-cost TA4 titanium alloy strip preparation process according to claim 1, characterized in that: In step three, the rolling deformation is 20-50%, and the pass deformation rate is ≤15%.

9. The low-cost TA4 titanium alloy strip preparation process according to claim 1, characterized in that: In step 4, step 5 and step 6, when trimming on both sides, the width of the trimming on one side shall be ≥ 5 mm.

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