KR102190598B1 - Method for pretreatment of titanium scrap and titanium-iron alloy ingot manufactured using pretreated titanium scrap - Google Patents

Abstract

The present invention relates to a method of pretreatment of titanium scrap and a titanium-iron alloy ingot manufactured using the pretreated titanium scrap, and more particularly, sodium pyrophosphate (Na ₄ P ₂ O ₇ , TSPP), sodium metasilicate (Na ₂ SiO ₃ ) and a mixture of any one sodium salt selected from the group consisting of a mixture thereof and an aqueous solution containing sodium hydroxide (NaOH), and a method of pretreatment of titanium scrap comprising the step of washing the titanium scrap and such It relates to a titanium-iron alloy ingot manufactured using the titanium scrap pretreated by the method.

Description

Titanium-iron alloy ingot manufactured using the pretreatment method of titanium scrap and pretreated titanium scrap {METHOD FOR PRETREATMENT OF TITANIUM SCRAP AND TITANIUM-IRON ALLOY INGOT MANUFACTURED USING PRETREATED TITANIUM SCRAP}

The present invention relates to a method of pretreatment of titanium scrap and a titanium-iron alloy ingot manufactured using the pretreated titanium scrap, and in more detail, the titanium scrap can be cleaned in an eco-friendly manner by excluding the use of acids or organic solvents. And, it relates to a method of pretreatment of titanium scrap capable of reducing oxygen, nitrogen and carbon content through this, and a titanium-iron alloy ingot manufactured using the titanium scrap pretreated by this method.

In general, domestic titanium metal is entirely dependent on imports, except for some recycling of scrap, which can be seen as essentially because there is no industrial base for manufacturing sponge titanium from titanium ore.

On the other hand, advanced countries such as the United States and Japan, where large amounts of titanium scrap are generated, have small and large specialized titanium pretreatment companies, and manufacture titanium ingots by re-melting titanium scrap. However, in the domestic titanium scrap market, the demand/supply of exports at low prices and imports at high prices is unstable, and the basis of the recycling technology industry for titanium scraps is weak.

In the future, not only the aircraft market, but also general industrial and consumer goods demand will show a steadily growing trend, and the global demand will continue to exceed production, but the titanium recycling market is relatively weak.

In recent years, due to such a request, a demand for recycling of titanium has been raised, and a technology for refining and recycling metal scrap or sponge is in the spotlight.

However, conventionally, due to the high melting point and high chemical activity of titanium, the smelting-refining-melting process consumes high technology and a lot of energy, and the manufacturing cost is high as well as the difficult processability of titanium itself. There was a problem.

In addition, in the case of high-quality titanium scrap, it is possible to produce ingots through remelting, but titanium scraps with high content of impurities (oxygen, nitrogen, carbon, etc.) mainly generated during processing of plates and wires do not have a separate refining process. It is difficult to obtain high-purity titanium.

On the other hand, in order to remove impurities from the titanium scrap having a lot of impurities, conventionally, it was washed with an acid such as nitric acid, hydrochloric acid, or hydrofluoric acid, or washed with an organic solvent such as alcohol and acetone. The use of solvents causes problems in the environment and safety.

Accordingly, an object of the present invention is to provide an eco-friendly method for pretreating titanium scrap by excluding the use of acids and organic solvents during the pretreatment process for recycling titanium scrap.

Further, another object of the present invention is to provide a titanium-iron alloy ingot in which the content of impurities such as oxygen, nitrogen and carbon is reduced by using the titanium scrap obtained through the pretreatment method.

In order to achieve the above object, the pretreatment method of titanium scrap according to an aspect of the present invention is composed of sodium pyrophosphate (Na ₄ P ₂ O ₇ , TSPP), sodium metasilicate (Na ₂ SiO ₃ ), and mixtures thereof. And washing the titanium scrap using a mixture of an aqueous solution containing any one sodium salt selected from the group and sodium hydroxide (NaOH).

In this case, the weight ratio of the sodium salt and the sodium hydroxide may be 1:2 to 1:8, more preferably 1:2 to 1:8/3.

Further, the concentration of the aqueous solution containing sodium hydroxide may be 0.1 to 3.0 M, more preferably 0.5 to 2.0 M.

In addition, the step of washing the titanium scrap may be performed through a stirring device.

On the other hand, the titanium-iron (Ti-Fe) alloy ingot according to another aspect of the present invention is manufactured using titanium scrap pretreated by the method of the present invention.

According to the pretreatment method of titanium scrap according to an embodiment of the present invention, it is possible to clean the titanium scrap in an eco-friendly way by excluding the use of acids or organic solvents. do.

Further, a titanium-iron (Ti-Fe) alloy ingot having a low impurity content may be manufactured from titanium scrap pretreated by the pretreatment method.

The following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the detailed description of the present invention, which will be described later. It is limited only to and should not be interpreted.
1 is a photograph showing a titanium scrap.
2 is a photograph showing a raw material of titanium scrap of Comparative Example 1.
3 is a photograph showing a Ti-30Fe alloy ingot manufactured using the titanium scrap raw material of Comparative Example 1.
4 is a photograph showing a Ti-30Fe alloy ingot prepared using the titanium scrap of Example 3.
5 is a photograph showing a Ti-30Fe alloy ingot manufactured using the titanium scrap of Example 4.
6 is an XRD graph of Ti-30Fe alloy ingots manufactured using the titanium scraps of Examples 3 and 4 and Comparative Example 1. FIG.
7 is a SEM (EDS) photograph of a Ti-30Fe alloy ingot prepared using the titanium scrap of Example 4 and Comparative Example 1. FIG.

Hereinafter, the present invention will be described in more detail.

The pretreatment method of titanium scrap according to an aspect of the present invention is any one sodium selected from the group consisting of sodium pyrophosphate (Na ₄ P ₂ O ₇ , TSPP), sodium metasilicate (Na ₂ SiO ₃ ), and mixtures thereof. And washing the titanium scrap by using a mixture of salt and an aqueous solution containing sodium hydroxide (NaOH).

1 is a photograph showing a titanium scrap. Since titanium metal is an expensive metal, titanium scrap, more precisely, titanium turning scrap, generated during processing of titanium metal must be recycled. At this time, titanium scrap is widely used as a raw material for alloy ingots.

In titanium, turning scraps are generated through mechanical processing such as milling, and the content of impurities such as oxygen and nitrogen in the scrap increases due to deterioration, and the content of carbon impurities rapidly increases due to contamination by cutting oil and oils. do. When an alloy ingot is manufactured using such scrap, the content of impurities such as oxygen, nitrogen and carbon increases in the ingot, which adversely affects the physical properties of the final product.

Conventionally, washing was performed using an acid such as nitric acid, hydrochloric acid, or hydrofluoric acid, or an organic solvent such as alcohol and acetone, but there was a problem in the environment and safety due to the use of an acid or an organic solvent. However, in the present invention, any one sodium salt selected from the group consisting of sodium pyrophosphate (Na ₄ P ₂ O ₇ , TSPP), sodium metasilicate (Na ₂ SiO ₃ ), and mixtures thereof, and basic sodium hydroxide are included. By using the mixed solution of the aqueous solution, it is possible to ensure safety and eco-friendly washing.

Here, the weight ratio of the sodium salt and the sodium hydroxide may be 1:2 to 1:8, preferably 1:2 to 1:8/3. When the content ratio is satisfied, the content of impurities of oxygen, nitrogen, and carbon can be most efficiently reduced.

In addition, the concentration of the aqueous sodium hydroxide solution may be 0.1 to 3.0 M, preferably 0.5 to 2.0 M.

If the concentration of the aqueous sodium hydroxide solution is less than the lower limit of the numerical range, the effect of adding sodium hydroxide is insignificant, and if it exceeds the numerical range, the effect of removing oxygen and nitrogen impurities is rather reduced, which is not preferable.

In more detail, when titanium scrap is immersed in a high-concentration sodium hydroxide aqueous solution, porous titanium dioxide is formed on the surface, which causes a slight increase in oxygen concentration. Since the contaminant is again adsorbed to the porous film, the nitrogen concentration slightly increases, so the concentration of the aqueous sodium hydroxide solution is preferably 3.0 M or less, and more preferably 2.0 M or less.

At this time, the cleaning method may be washing by simply immersing the titanium scrap in the mixed solution, and washing by immersing the titanium scrap in the mixed solution and stirring through a stirring device. At this time, when agitating using a stirring device such as a drum washing machine, a strong stirring force acts, so even if the concentration of the substance contained in the mixed solution is lowered, the effect of reducing impurities may be equal or better.

Meanwhile, a titanium-iron (Ti-Fe) alloy ingot according to another aspect of the present invention is manufactured using titanium scrap pretreated by the method of the present invention.

The titanium scrap pretreated through the above-described pretreatment method has reduced impurities such as oxygen, nitrogen, and carbon, and the titanium-iron alloy ingot of the present invention made from such scrap has a low impurity content, so that high-quality ingots can be obtained. have. In this case, the ingot may be manufactured through a vacuum arc remelting (VAR) method, an electron beam melting (EBM) method, a plasma arc melting (PAM) method, or the like.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

1. Pretreatment of titanium scrap using aqueous NaOH solution

The gas impurity concentration of the raw material of titanium scrap is shown in Table 1 below.

Gas type Oxygen nitrogen carbon Concentration (ppm) 2,478 445 17,136

Regarding the gas impurity content in Table 1, oxygen and nitrogen were measured by the method according to ASTM E1409-13, and carbon was measured by the method according to ASTM E1019-11. Referring to Table 1, it was analyzed as 2,478 ppm of oxygen, 445 ppm of nitrogen, and 17,136 ppm of carbon. In particular, since the content of carbon is high, measures to reduce this are required.

Table 2 below shows the results obtained by measuring the impurity concentrations of oxygen and nitrogen according to the concentration of the NaOH aqueous solution when NaOH aqueous solution was used as a pretreatment cleaning solution for scrap. At this time, using 200 ml of NaOH aqueous solution, 10 g of scrap was washed through three simple immersion and washing with water, and then the impurity concentration was measured.

NaOH aqueous solution concentration Oxygen (ppm) Nitrogen (ppm) No pretreatment 2,478 445 0.5 M 2,063 252 1.0 M 1,958 281 2.0 M 1,566 139 3.0 M 1,728 172

Referring to Table 2, it can be confirmed that the content of oxygen and nitrogen impurities was reduced by washing the titanium scrap using NaOH aqueous solution, and the 2.0 M NaOH aqueous solution, which had the most excellent reduction effect, was determined as the base solution, which will be described later Further experiments were carried out.

2. Pretreatment of titanium scrap using a mixture of NaOH aqueous solution and sodium salt

Table 3 shows the results of measuring the impurity concentrations of oxygen, nitrogen and carbon according to the content of sodium pyrophosphate when a mixture of 2.0 M NaOH aqueous solution and sodium pyrophosphate (TSPP) is used as a pretreatment cleaning solution for scrap. Shows. At this time, using a mixture prepared by mixing 2, 4, 6, and 8 g of sodium pyrophosphate in 200 ml of 2.0 M NaOH aqueous solution (NaOH content is 16 g), 10 g of scrap is simply deposited and washed with water 3 After washing through the process of 1, the impurity concentration was measured.

division TSPP content Oxygen (ppm) Nitrogen (ppm) Carbon (ppm) Total reduction rate Example 1 2 g 1,254 31 826 89.48% Example 2 4 g 1,161 12 371 91.80% Example 3 6 g 1,087 13 343 92.81% Example 4 8 g 1,192 17 272 92.62%

Referring to Table 3, by further adding sodium pyrophosphate to the NaOH aqueous solution, it can be confirmed that the reduction rate of oxygen, nitrogen and carbon is about 90%, and in particular, in the case of Examples 3 and 4, the efficiency is the most. It was high.

Table 4 shows the impurity concentrations of oxygen, nitrogen and carbon when a mixture of 2.0 M NaOH aqueous solution and sodium metasilicate (Na ₂ SiO ₃ ) is used as a pretreatment cleaning solution for scrap according to the content of sodium metasilicate. Shows the displayed result value. At this time, using a mixture prepared by mixing 2, 4, 6 and 8 g of sodium metasilicate in 200 ml of 2.0 M NaOH aqueous solution (NaOH content is 16 g), 10 g of scrap is simply deposited and washed with water 3 The impurity concentration was measured after washing through the above procedure.

division Na ₂ SiO ₃ content Oxygen (ppm) Nitrogen (ppm) Carbon (ppm) Total reduction rate Example 5 2 g 1,742 98 3,738 72.19% Example 6 4 g 1,484 61 2,131 81.67% Example 7 6 g 1,353 34 1,542 85.40% Example 8 8 g 1,319 35 845 89.04%

Referring to Table 4, although the effect is somewhat lower than when sodium pyrophosphate is mixed, it can be seen that the content of gas impurities is reduced even when sodium metasilicate is further added to the NaOH aqueous solution. In particular, in the case of Examples 7 and 8, the total reduction rate was measured to be 85% or more.

Table 5 below shows the results obtained by measuring the impurity concentrations of oxygen, nitrogen and carbon when a mixture of 0.5 M NaOH aqueous solution and sodium pyrophosphate (TSPP) was used as a pretreatment cleaning solution for scrap. At this time, using a mixture prepared by mixing 150 g of sodium pyrophosphate to 15 L of 0.5 M NaOH aqueous solution (NaOH content is 300 g), 1 kg of scrap is immersed in a washing solution for 9 minutes using a drum washing machine and washed with water. After washing for a total of 50 minutes through three processes, the impurity concentration was measured.

division How to wash Oxygen (ppm) Nitrogen (ppm) Carbon (ppm) Total reduction rate Example 9 Drum washing machine 1,286 9 188 92.61%

Referring to Table 5, when washing using a drum washing machine, a strong stirring force acts together, so even if the concentration of the NaOH aqueous solution is lowered to 0.5 M, the impurity reduction rate was measured to exceed 92%. The concentration of sodium pyrophosphate in the mixture was approximately 10 g/L, and Example 1, which exhibited similar sodium pyrophosphate concentration, showed a reduction rate of 89.48%. In the case of Example 1, even though the concentration of the NaOH aqueous solution was 2.0 M, it can be seen that the total reduction rate was rather increased in Example 9 than in Example 1.

3. Pretreatment of titanium scrap using organic solvent

Table 6 below shows the results obtained by measuring the impurity concentrations of oxygen, nitrogen and carbon when acetone, an organic solvent, is used as a pretreatment cleaning solution for scrap. At this time, the impurity concentration was measured after washing 20 g of scrap by a simple immersion method using 400 ml of acetone.

Washing liquid Oxygen (ppm) Nitrogen (ppm) Carbon (ppm) Total reduction rate Acetone 1,293 17 127 92.83%

Referring to Table 6, when the scrap was washed using acetone, the total reduction rate was measured to be 92.83%, and result values almost similar to those of Examples 3 and 4 of the present application were obtained. In view of the environmental pollution problem and the degree of harm to the body, it is more preferable to use the mixed solution of the present invention rather than using acetone as an organic solvent.

4. Fabrication of Ti-Fe alloy ingot using titanium scrap

Ti-30Fe ingots were prepared by vacuum arc melting method using each of titanium scraps (Comparative Example 1) not subjected to pretreatment, and titanium scraps pretreated according to Examples 3 and 4.

2 is a photograph showing a raw material of titanium scrap of Comparative Example 1, FIG. 3 is a photograph showing a Ti-30Fe alloy ingot manufactured using the raw material of titanium scrap of Comparative Example 1, and FIGS. 4 and 5 are each of Example 3 And a photograph showing a Ti-30Fe alloy ingot manufactured using the titanium scrap of Example 4.

The concentrations of impurities of oxygen, nitrogen, and carbon in the prepared Ti-30Fe alloy ingot were measured and shown in Table 7 below. At this time, with respect to the gas impurity content, oxygen and nitrogen were measured by the method according to ASTM E1409-13, and carbon was measured by the method according to ASTM E1019-11.

Ti-30Fe ingot Oxygen (ppm) Nitrogen (ppm) Carbon (ppm) Total reduction rate Scrap raw materials 2,478 445 17,136 - Ingot using Comparative Example 1 1,671 60 5,525 63.83% Ingot using Example 3 1,155 27 296 92.63% Ingot using Example 4 1,062 31 275 93.18%

Referring to Table 7 above, in the case of using the titanium scrap pretreated according to Examples 3 and 4, the total impurity reduction rate was measured to be 90% or more, and it can be confirmed that a high purity Ti-30Fe alloy ingot was obtained. .

5. XRD analysis and SEM photo analysis of Ti-Fe alloy ingot

XRD analysis was performed on the Ti-30Fe alloy ingots prepared using the titanium scraps of Examples 3 and 4 and Comparative Example 1, and is shown in FIG. 6.

6, in the ingot according to Comparative Example 1, in addition to the Ti-Fe intermetallic compound, which is the target composition, Ti-C compounds were also generated, but in the ingots according to Examples 3 and 4, Ti-C compounds due to the removal of carbon impurities. This did not occur, and an alloy ingot having a desired target composition could be produced.

On the other hand, SEM photographs and EDS (Energy dispersive spectrometry) analysis were performed on the Ti-30Fe alloy ingots prepared using the titanium scrap of Example 4 and Comparative Example 1, and shown in FIG. 7.

Referring to FIG. 7, it can be seen that the contents of oxygen and carbon were lowered in the matrix of the ingot according to Example 4, and the contents of titanium and iron, which are the main elements, were increased.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of rights of

Claims (7)

A mixture of sodium pyrophosphate (Na ₄ P ₂ O ₇ , TSPP), sodium metasilicate (Na ₂ SiO ₃ ), and an aqueous solution containing sodium hydroxide (NaOH) and any one sodium salt selected from the group consisting of mixtures thereof Including the step of washing the titanium scrap using,
The pretreatment method of titanium scrap, characterized in that the concentration of the aqueous solution containing sodium hydroxide is 0.1 to 3.0 M. The method of claim 1,
The weight ratio of the sodium salt and the sodium hydroxide is 1:2 to 1:8, characterized in that the pretreatment method of titanium scrap. The method of claim 2,
The weight ratio of the sodium salt and the sodium hydroxide is 1:2 to 1:8/3, characterized in that the pretreatment method of titanium scrap. delete The method of claim 1,
The pretreatment method of titanium scrap, characterized in that the concentration of the aqueous solution containing sodium hydroxide is 0.5 to 2.0 M. The method of claim 1,
The step of washing the titanium scrap is a pre-treatment method of titanium scrap, characterized in that made through a stirring device. Claims 1 to 3, a titanium-iron (Ti-Fe) alloy ingot manufactured using the titanium scrap pretreated by the method of any one of claims 5 and 6.

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