JPS6365608B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing LiBaF ₃ , and more particularly to a method for producing LiBaF ₃ of a desired particle size simply and inexpensively. ShoLiBaF ₃
Although there are no particular restrictions on the use of this method, it is especially useful and attracts attention in the welding field, so the following explanation will be mainly focused on the case where it is applied to the welding field. LiBaF ₃ , which is a composite of LiF and BaF ₂ , is used as a raw material for welding flux, and exhibits extremely excellent properties as a slag forming agent, shielding agent, and arc stabilizer, and has many advantages such as low inherent moisture content. Demand as a raw material for welding flux is expected to continue to grow in the future. By the way, since LiBaF ₃ does not exist in nature, it is currently being produced using wet methods such as mixing solutions of Li and Ba compounds and precipitating the product obtained by reacting in this solution (hereinafter referred to as precipitation method). It is manufactured by However, the precipitation method has a complicated manufacturing process and high manufacturing costs, and it is difficult to obtain
Since the grain size of LiBaF ₃ is extremely fine, on the order of several μm, it causes various inconveniences in the field of welding and the like.
That is, when LiBaF ₃ is used as a flux raw material for a composite wire for self-shielded arc welding, the syntron properties are very poor, making it difficult to uniformly fill the flux into the metal sheath. As a result, when welding is performed using the composite wire, welding workability deteriorates, and variations occur in the mechanical performance of the weld metal. It has also been confirmed that when LiBaF ₃ is used as a flux raw material for coated arc welding rods, drying cracks are more likely to occur on the flux coated surface. The present invention has been made in view of these circumstances, and aims to provide a method that can economically produce LiBaF ₃ with a desired particle size. For example, in the welding field, the above syntronic property etc. The purpose is to economically produce LiBaF ₃ with a particle size that can be maintained well. The method of the present invention, which achieves the above object,
The gist is that LiF and BaF ₂ are mixed to obtain a particle size of 800 μm or less, fired in an oxidizing atmosphere, and then crushed to adjust the particle size. Hereinafter, the configuration and effects of the present invention will be explained in order. The particle size of LiF and BaF ₂ , which are the raw materials for producing LiBaF ₃ , must be 800 μm or less in order to increase the reaction area between the particles during firing and allow the bonding reaction between the two to proceed quickly and sufficiently. For further improvement, it is desirable to make the particle sizes of LiF and BaF ₂ similar. Also, the mixing ratio of LiF and BaF ₂ can be set arbitrarily, but if either LiF or BaF ₂ is too large, LiBaF ₃
The residual amount of unreacted LiF or BaF ₂ is excessive compared to the amount of LiBaF 3 produced, and LiBaF ₃ occupies the fired product.
The percentage of On the other hand, it is extremely difficult to isolate LiBaF ₃ from these fired mixtures, and in practice, even a small amount of LiF or BaF ₂ mixed in does not have a big effect, so it is not always necessary to perform a separation operation. However, as mentioned above, if the ratio of LiBaF ₃ in the fired product is too low, the characteristics of LiBaF ₃ will not be exhibited, and we experimentally investigated various optimal raw material blending ratios and found that BaF ₂ /LiF (weight ratio) I learned that it is desirable to set it to 1-9. Next, the above-mentioned mixture is fired in an oxidizing atmosphere, for example, in the air, but either a continuous firing furnace such as a rotary kiln or a batch-type firing furnace may be used for firing. It goes without saying that it is desirable to use a firing furnace that can sufficiently withstand high temperatures and has a uniform temperature distribution. It goes without saying that the firing conditions should be set so that a finished sintered product with good sintering condition can be obtained; for example, the sintering temperature should be 650 to 775°C and the sintering time should be 0.5 hours or more. It is hoped that If the sintering temperature is lower than 650℃, the sintering state will be insufficient and unreacted LiF and
As BaF ₂ remains, there is a tendency for the fluidity to deteriorate after pulverization (described later). On the other hand, the sintering temperature is 775
If the temperature exceeds ℃, the mixture will become molten, and it will take a lot of time and a large crushing force to cool and solidify the molten material and then crush it, and the kiln itself will be exposed to excessively high temperatures, which will shorten the life of the equipment. This is always disadvantageous in terms of the length of the kiln and the ease of maintenance of the kiln. Furthermore, if the firing time is too short, sintering tends to be insufficient, so it is desirable to set the firing time to 0.5 hours or more. Incidentally, it is not preferable to make the firing time excessively long, as this results in wasteful consumption of energy. When using the fired product obtained above as a raw material for welding flux, etc., it is necessary to adjust the particle size to an appropriate size after crushing, and through this operation, LiBaF ₃ of the desired particle size can be obtained. I can do it. There are no particular restrictions on the crushing means and particle size adjusting means, and conventional methods may be used. When using LiBaF ₃ produced by the method of the present invention as a welding flux raw material, it is desirable to adjust the particle size composition so that it is 500 μm or less and the content of components of 74 μm or less is 90% by weight or less. . However, if the particle size is too large, it becomes difficult to uniformly fill the metal sheath with flux when used, for example, as a filling component in composite wire for self-shielded arc welding, and in coated arc welding rods, flux to the core wire becomes difficult to fill. Paintability deteriorates. On the other hand, if the particle size is too small, in the former case, the syntron properties will deteriorate, which will adversely affect welding workability and the properties of the weld metal, and in the latter case, dry cracking will easily occur in the coating layer. In addition, fine particulate LiBaF ₃ obtained by the above-mentioned wet method
It is also possible to obtain similar LiBaF ₃ by further performing operations such as calcination, pulverization, and particle size adjustment similar to those described above. However, since this method requires more steps, the operation is more complicated than the wet method, and its practical value is extremely poor from an industrial perspective. The present invention is configured as described above, and has a diameter of 800 μm.
Since LiF and BaF ₂ with the following particle sizes are mixed and fired in an oxidizing atmosphere, the bonding reaction between LiF and BaF ₂ is quickly and fully achieved, resulting in a composite product.
LiBaF ₃ can be obtained efficiently. Furthermore, LiBaF ₃ having a desired particle size can be obtained by changing the degree of pulverization and the mesh of the particle size control device when pulverizing the above-mentioned fired product and adjusting the particle size. Since the method of the present invention is a dry method, handling of the product is easy, and the process is simple, so the desired product can be obtained economically. Examples of the present invention will be described below. Example Mixture A of LiF and BaF ₂ with the mixing ratio shown in Table 1
~H (20 to 30 g) was placed in an alumina crucible, charged into an electric furnace, and fired under the conditions shown in Tables 2 and 3. The fired product was cooled and pulverized to adjust the particle size. The components of each baked product obtained were identified by X-ray diffraction. The firing conditions are shown in Table 2, and the identification results are shown in Table 3.

【table】

【table】

【table】

【table】

[Table] Tables 2 and 3 show that in H in which the particle size of LiF and BaF ₂ was excessive, a satisfactory firing state could not be obtained even if the firing conditions were set to the preferable range of 650 to 775°C. On the other hand, in the case of A to G having an appropriate particle size structure, a good sintered state was obtained by adjusting the firing conditions. Note A~H
In either case, when the firing temperature is as low as 625°C, the firing reaction does not proceed sufficiently, and unreacted LiF and
A large amount of BaF ₂ remains. On the other hand, the firing temperature is 800
If the temperature is too high, the mixture becomes molten and requires a great deal of effort to grind and adjust the particle size. In addition, in E where the amount of LiF blended is too small, a large amount of unreacted LiF remains and _the content ratio of LiBaF ₃ in the fired product decreases.
I was not able to fully draw out the strengths of the company. On the other hand, in F where the amount of BaF ₂ is too small, unreacted BaF ₂
A large amount of LiBaF 3 remained, and the proportion of LiBaF ₃ in the fired product decreased, making it impossible to take advantage of its advantages. Usage Example 1 Composite wires for self-shielded arc welding having the compositions shown in Table 4 below were manufactured using LiBaF ₃ manufactured by the method of the present invention. Using this, self-shielded arc welding was performed under the following welding conditions. The syntron properties during wire production and workability during welding were as shown in Table 4. Welding conditions test plate: Mild steel (19mm ^t × 125mm ^w × 350mm ^l ) Test method: JIS Z 3313 Welding current: 250 A (DCSP) Welding voltage: 21~22V Welding speed: 10~23cm/min Welding position: Downwards steel Sheath: 2mmφ 〃Components: C…0.04, Si…0.01, (weight%) Mn…
0.35, P...0.017, S...0.008, Fe and unavoidable impurities...remainder

【table】

[Table] All of Nos. 1 to 3 shown in Table 4 satisfy the present invention, but when applied to the welding field, none other than No. 1 are preferable for the following reasons. That is,
Since No. 1 has good firing conditions and grain size structure, both syntron properties and welding workability are good. On the other hand, in No. 2, the particle size of LiBaF ₃ is too large, so the flux filling state inside the steel sheath is uneven, making the arc unstable and welding workability poor. on the other hand
In No. 3, the particle size of LiBaF ₃ was too small, resulting in poor syntron properties and uneven flux filling, resulting in poor welding workability. In No. 4, the firing temperature was too low, so the LiBaF ₃ obtained was insufficiently fired, and the fluidity of the fired product after pulverization deteriorated, resulting in poor syntron properties and welding workability. Usage Example 2 Using LiBaF ₃ , etc. produced by the method of the present invention, a flux for coated arc welding rods having the composition shown in Table 5 below was prepared, a fixing agent was added to it, and the flux was applied to the outer periphery of the wire. A coated arc welding rod was manufactured. The coating properties and dry cracking resistance during manufacture of the welding rods were as shown in Table 5. Core wire: 4.0mm〓×400mm ^L (mild steel) Fixing agent: Sodium silicate + potassium silicate Judgment criteria Paintability: After applying flux to the core wire, if there are no defects such as "scratching" on the surface of the flux, it is judged as "good". (n=20) Dry cracking resistance: 20 welding rods coated with flux were naturally dried, and 24 hours later, visually inspected for surface cracks.If there were no cracks on any of the welding rods, it was evaluated as It was rated as "good".

[Table] All of Nos. 5 to 7 shown in Table 5 satisfy the present invention, but when applied to the welding field, none other than No. 5 are preferable for the following reasons. That is,
In No. 5, the firing conditions and particle size composition were appropriate, so both paintability and cracking resistance were good. On the other hand, in No. 6, the particle size was slightly excessive, so the paintability deteriorated. On the other hand, No. 7 had too many fine grains, so drying cracks occurred.

Claims (1)

[Claims] 1 Mix LiF and BaF ₂ with a particle size of 800 μm or less,
A method for producing LiBaF ₃ , which comprises firing in an oxidizing atmosphere and then pulverizing to adjust the particle size.