Method for improving actual yield from sponge titanium to blank titanium ingot through EB furnace casting

Abstract

The invention relates to a method for improving the actual yield from sponge titanium to blank titanium ingots through EB furnace casting. The method comprises the following steps that firstly, raw materials are prepared; the method comprises the following steps of (1) processing sponge titanium, (2) processing return scraps, (3) distributing and making heads, and (4) inspecting and sawing after casting. The method not only reduces waste of sponge titanium, guarantees head quality of cast ingots, but also enables sporadic reclaimed materials to be used, and in this way, saw cutting loss caused by unqualified head components can be effectively reduced, and economic benefits are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of smelting, and particularly relates to a method for improving actual yield of sponge titanium to rough titanium ingot in EB furnace smelting and casting. BACKGROUND

[0002] In the starting stage of pure titanium EB smelting and casting, the process of preheating of an electron beam gun and establishment of a cold bed molten pool is needed. In the heating process, the atmosphere in the furnace is unstable due to water vapor and the like, and the titanium liquid flowing into the crystallizer has a high oxygen and nitrogen content, which exceeds the national standard in severe cases. As the starting process continues, the vacuum environment in the furnace gradually tends to be stable, and the smelting condition is reached. Therefore, the oxygen and nitrogen content of the cast ingot gradually decreases from the head to the rear, and reaches the target requirement. After the ingot is taken out, it is found that the length of the abnormal composition of the head of the cast ingot usually reaches 100-300 mm. Taking the crystallizer with a specification of 1260*230 mm as an example, about 130-390 kg of the cast ingot needs to be sawn, and the cast ingot is made of standard sponge titanium smelting and casting. That is to say, for every smelting and casting of a 1260*230 mm cast ingot, 130-390 kg of sponge titanium will become return material, which will cause great loss in mass production.

[0003] At the same time, the plate, edge wire and the like including the ingot head are return materials, and the quantity is scattered and the composition uniformity is difficult to guarantee. Even if they are used in titanium ingot smelting with relatively low quality requirements, they are difficult to be used in batches due to the lack of sufficient composition data in material grouping, insufficient weight, or the influence of the specification and size on the distribution of the feeding bin and the like. SUMMARY

[0004] The application is exactly to solve the above-mentioned problems and defects, and provides a method for improving actual yield of sponge titanium to rough titanium ingot in EB furnace smelting and casting.

[0005] The application adopts the following technical scheme.

[0006] The application provides a method for improving actual yield of sponge titanium to rough titanium ingot in EB furnace smelting and casting.

[0007] Step 1) preparation of raw materials;

[0008] The raw materials include sponge titanium and return materials, and the return materials are cast ingot blocks or slices sawn down in pure titanium EB furnace smelting and casting;

[0009] Step 2) treatment of return materials;

[0010] The return materials are subjected to shot blasting, pickling, water washing, drying, composition inspection and moisture testing;

[0011] Step 3) material distribution and starting;

[0012] According to the position of preheating and preheating sweep, good cloth; according to the head process to make head;

[0013] Step 4) After melting and casting, the sawing is inspected;

[0014] After the completion of melting and casting, cooling and ingot, according to the normal order, the surface is milled and the skin is scraped, then the sample is taken for composition inspection, according to the inspection, the sawing position is determined, and the head sawing is completed.

[0015] Further, in step 1) of the application, according to the actual size of the crystallizer to be used, the weight range of the planned sawing is calculated according to the sawing head amount of 100-300mm, and the final calculation of the required return material weight is about 98% of the blank material yield.

[0016] Further, in step 1) of the application, the return material needs to meet the requirements of O content ≤0.3%, N content ≤0.2%, and moisture content ≤0.05%.

[0017] Further, in step 1) of the application, the actual size of the return material meets the requirements of cloth distribution, avoids blocking during pushing, and can be placed in the appropriate position to meet the requirements of the first melting into titanium liquid into the crystallizer.

[0018] Further, in step 1) of the application, when the return material is a plurality of plates, a titanium strip must be placed between the two plates.

[0019] Further, in step 2) of the application, nitric acid and hydrofluoric acid mixed solution are used for pickling; the concentration of nitric acid is 140-160g / I, the concentration of hydrofluoric acid is 30-40g / I, the mixing ratio of nitric acid and hydrofluoric acid is 3.5-5:1, and the pickling temperature is 20-50℃.

[0020] Further, in step 2) of the application, the water washing temperature is 20-40℃.

[0021] Further, in step 2) of the application, the drying temperature is 70-90℃.

[0022] Further, in the step 3) of the present application, the head-making process comprises the following steps: the EB gun starting sequence is: 5# EB gun→4# EB gun→3# EB gun→2# EB gun→1# EB gun→6# EB gun→7# EB gun; the voltage of the 7 EB guns is 30kV, the current of the 1#, 2#, 3#, 4# EB guns is controlled at 4±1.5A in the preheating stage, the current of the 5# EB gun is controlled at 4±0.5A, and the current of the 6#, 7# EB guns is gradually increased to 3.0±0.5A according to the preheating degree; the 1#, 2#, 3#, 4#, 6#, 7# EB guns all adopt P1 pattern scanning (i.e. scanning the responsible area uniformly according to the inherent frequency, and the scanning spot energy is set to 60%-80%, but the scanning is not started, and the scanning is started again according to the liquid flow condition when the blocking point trend is found), and the 5# EB gun pattern is changed from P1→P2→P3 according to the titanium liquid amount in the cooling bed (P1 is only started in the preheating stage before the titanium material in the roughing cooling bed is completely opened, P2 is started when the raw materials in the roughing and refining areas are completely opened, P3 is started when the titanium liquid in the roughing and refining areas is full and smoothly connected with the overflow port, and the overflow channel between the refining area and the crystallizer is completely connected); as the vacuum gradually stabilizes, the return material is about to be completely opened, and the current of the 6#, 7# EB guns is gradually increased to 6.5±1A; thus, the head-making is completed, and the melting and casting stage is entered.

[0023] Further, the step 4) of the present application comprises the following requirements for sampling inspection after the ingot milling is completed: 1 sample is taken at each of 100, 150, 200, 250mm from the head of the ingot for composition inspection, and the sampling position meeting the overall requirements of the ingot is determined as the sawing position of the ingot head after the composition inspection is completed.

[0024] Compared with the existing titanium ingot melting and casting head-making technology, the present application has the following advantages:

[0025] 1) The return material is used to replace the original sponge titanium for head-making, so that the standard sponge titanium raw material can be basically used for the melting and casting of the ingot product, and the head-making process with gradually increasing current makes the vacuum environment in the furnace stable in the head-making stage, thereby ensuring the environment for subsequent melting and casting.

[0026] 2) The recycled material treated by a certain process and meeting the requirements of charging into the furnace is used to replace the standard sponge titanium for ingot head-making, and the head-making process is used, so that the composition of the head of the ingot after sawing according to the planned sawing amount meets the requirements.

[0027] 3) The present application reduces the waste of sponge titanium, ensures the quality of the head of the ingot, and enables the sporadic recycled material to be used; in this way, the sawing loss caused by the unqualified composition of the head can be effectively reduced, and the economic benefit can be improved.

[0028] The present application will be further explained in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Schematic diagram for returning material distribution position;

[0030] Figure 2 Schematic diagram for electron beam gun scanning pattern in head-making stage.

[0031] Figure 1 Reference numerals are as follows: 1-melting chamber, 2-feeding chamber, 3-cold bed rough refining zone, 4-cold bed fine refining zone, 5-crystallizer, 6-hydraulic pushing rod, 7-titanium sponge briquette, 8-returning material distribution zone. DETAILED DESCRIPTION

[0032] The following examples are only a part of the technical solutions of the present application, and are not a limitation on all the technical solutions of the present application. The examples of the present application are provided to further explain and illustrate the details of the technical solutions of the present application.

[0033] See Figure 1 , Figure 2 as shown.

[0034] Specific Example 1

[0035] According to the plan, a 1060*230mm crystallizer is used to cast EB slab T524003R.

[0036] Before melting and casting, the head cutting amount is 100-300mm according to experience, and it is determined that 112-336kg of returning material should be added. According to the collection and arrangement of the returning material on site, 5 pieces of pickling head and tail plates with a thickness of 3-8mm and a length of 2m (nominal size) are selected, and the actual measured size meets the distribution requirements, and the actual weight is 322kg.

[0037] The plates are subjected to shot blasting and pickling and pickling treatment, and the plates are separated by titanium strips. Then, water washing is performed, and drying is performed after water washing; nitric acid and hydrofluoric acid mixed solution is used during pickling, the concentration of nitric acid is 150g / I, the concentration of hydrofluoric acid is 30g / I, the ratio of nitric acid and hydrofluoric acid mixed acid is 4:1, the pickling temperature is 25℃, and the surface residual oxide is washed away. The water washing temperature is about 40℃, which further removes the surface oil stains and stains, and then the water stains are dried by a hot air blower, and the drying temperature is about 70-80℃.

[0038] After drying, sampling is performed, and gas element content testing is performed, the O content of the three groups of samples is respectively: 0.13%, 0.15%, and 0.09%, and the N content is respectively: 0.03%, 0.05%, and 0.03%, and the composition meets the use requirements; sampling is performed for moisture content testing, and the moisture content is 0.01%, and the moisture content meets the use requirements;

[0039] The distribution is completed according to the first melting and casting position of the head-making, and the preparation work before melting and casting is completed.

[0040] The head-making process was carried out, and before the return material was completely melted, the actual vacuum inside the furnace reached 0.01Pa-0.03Pa, which was stable within the suitable melting range.

[0041] After melting and casting, the ingot is cooled and removed.

[0042] The sampling and testing results are as follows:

[0043]

[0044] Based on the inspection results, the head was sawn at 200mm, and the sawn ingot was weighed to obtain the actual yield of sponge titanium to blank: 98.5%.

[0045] Specific Example 2

[0046] According to the plan, a 1260*230mm crystallizer will be used to melt and cast EB flat ingots T524162R.

[0047] Before casting, based on experience, the amount of head to be cut is 100-300mm, and it is determined that 133-399kg of return material should be added. Based on the collection and sorting of return material on site, a total of 350kg of broken edge wire is selected.

[0048] The edge wires have already undergone pickling during the initial processing. After washing with water, they are dried. The pickling process uses a mixture of nitric acid and hydrofluoric acid, with a nitric acid concentration of 150 g / L and a hydrofluoric acid concentration of 40 g / L, at a ratio of 3.5:1. The pickling temperature is approximately 25°C, removing residual oxide scale from the surface. The water washing temperature is approximately 40°C to further remove surface oil and stains. Afterward, the water stains are dried using a hot air blower at a temperature of approximately 70-80°C.

[0049] After drying, samples were taken for gaseous element content testing. The O content of the three samples was 0.08%, 0.08%, and 0.07%, respectively, and the N content was 0.01%, 0.01%, and 0.01%, respectively. The composition meets the usage requirements. Samples were also taken for moisture content testing, and the moisture content was 0.01%, which meets the usage requirements.

[0050] Complete the material placement according to the first melting and casting position of the head, and complete the pre-melting and casting preparations.

[0051] The head-making process was carried out, and before the return material was completely melted, the actual vacuum inside the furnace reached 0.01Pa-0.03Pa, which was stable within the suitable melting range.

[0052] After melting and casting, the ingot is cooled and removed.

[0053] The sampling and testing results are as follows:

[0054]

[0055] Based on the test results, the head was sawn at 150mm, and the sawn ingot was weighed to obtain the actual yield of sponge titanium to blank: 98.7%.

[0056] The above descriptions are merely some specific embodiments of the present invention (since the present invention encompasses numerical ranges, the embodiments cannot be exhaustive; the scope of protection described in the present invention includes the numerical range and other technical aspects of the present invention). Specific content or common knowledge known in the solutions is not described in detail here (including but not limited to abbreviations, acronyms, and units conventionally used in the art). It should be noted that the above embodiments do not limit the present invention in any way. For those skilled in the art, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the scope of protection of the present invention. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for improving the actual yield of sponge titanium to raw titanium ingots through EB furnace melting and casting, characterized in that, The method includes the following steps: Step 1) Raw material preparation; The raw materials include sponge titanium and recycled materials, wherein the recycled materials are ingot blocks or slices sawn off during the pure titanium EB furnace casting process. Step 2) Return material processing; The returned material is shot blasted, pickled, washed, and dried, and its composition and moisture content are tested. Step 3) Make the head out of fabric; Prepare the fabric according to the position for firing and preheating; then make the head according to the head-making process. Step 4) Inspect and saw after melting and casting; After melting, casting, cooling and unloading the ingot, the surface is milled and peeled off in the normal sequence, then samples are taken for composition testing. Based on the test results, the saw head position is determined and the head is sawn off.

2. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, In step 1), based on the actual crystallizer specifications to be used, and according to the saw head length of 100-300mm, the planned sawing weight range is calculated. Based on the experience that the blank yield is about 98%, the weight of the required return material is finally calculated.

3. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, In step 1), the returned material must meet the following requirements: O content ≤ 0.3%, N content ≤ 0.2%, and moisture content ≤ 0.05%.

4. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, In step 1), the actual size of the returned material meets the requirements of the fabric, avoids jamming during material pushing, and can be placed in a suitable position to meet the requirement of being melted into titanium liquid first and entering the crystallizer.

5. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, In step 1), when the returned material consists of multiple sheets, a titanium strip must be placed between the two sheets.

6. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace melting and casting according to claim 1, characterized in that, In step 2), a mixture of nitric acid and hydrofluoric acid is used for pickling; the concentration of nitric acid is 140-160 g / L, the concentration of hydrofluoric acid is 30-40 g / L, the ratio of nitric acid to hydrofluoric acid is 3.5-5:1, and the pickling temperature is 20-50℃.

7. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, In step 2), the water washing temperature is 20-40℃.

8. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, In step 2), drying with hot air at 70-90℃ is sufficient.

9. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, In step 3), the head-making process includes the following steps: The EB gun startup sequence is as follows: EB gun #5 → EB gun #4 → EB gun #3 → EB gun #2 → EB gun #1 → EB gun #6 → EB gun #7; the voltage of the seven EB guns is 30kV. During the preheating stage, the current of EB guns #1, #2, #3, and #4 is controlled at 4±1.5A, the current of EB gun #5 is controlled at 4±0.5A, and the current of EB guns #6 and #7 is gradually increased to 3.0±0.5A according to the preheating level; EB guns #1, #2, #3, #4, #6, and #7 all use P1 pattern scanning, while the pattern of EB gun #5 is changed from P1 to P2 to P3 according to the amount of titanium liquid in the cooling bed; as the vacuum gradually stabilizes and the return material is about to be completely melted, the current of EB guns #6 and #7 is gradually increased to 6.5±1A; at this point, the head making is completed, and the casting stage begins.

10. The method for improving the actual yield of sponge titanium to raw titanium ingots by EB furnace casting according to claim 1, characterized in that, Step 4) includes sampling and inspection after the ingot milling is completed, in accordance with the following requirements: starting from 100mm from the top of the ingot, take one sample at 100, 150, 200 and 250mm respectively for composition inspection. After the inspection is completed, the sampling position that meets the overall requirements of the ingot is determined as the sawing position of the ingot head.

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