JPS6034614B2 - Electroslag remelting method - Google Patents

Description

Detailed Description of the Invention The present invention relates to an electroslag remelting method, and particularly relates to an electroslag remelting method capable of producing homogeneous aluminum and/or sulfur-containing steel or alloy with little variation in aluminum and sulfur content. be.

In steels and alloys that intentionally contain aluminum (AI) to impart material properties such as age hardening or for nitriding, and intentionally contain sulfur (S) to improve machinability, etc. For purposes such as removing non-metallic inclusions and making the coin coin structure sound (refining the crystalline structure), it may be necessary to re-dissolve the coin coin lump obtained by dissolving it in the atmosphere.

Conventionally, the redissolution method in such cases is as follows:
Two methods have been put into practical use: the electroslag remelting method (ESR method) and the vacuum arc melting method, but when comparing the two methods, the coin coins obtained by vacuum arc melting require skin care. Therefore, the yield of the ESR method is approximately 94%.
%, which is 85% worse than ESR in terms of the omission of surface care and yield of the coin coins obtained.
The supremacy of law is recognized. However, when the normal electroslag remelting method is applied to copper or alloys containing AI and S as described above, N
The oxidation and desulfurization progressed significantly, and the AI and S in the sun were removed, making it impossible to obtain steel ingots or alloy mirror ingots with the desired composition. Therefore, the following solutions have been proposed as solutions to the problems encountered in electroslag remelting of steels or alloys containing AI or S.

That is, first, measures against fluctuations in the composition of AI include: (1) supplying an inert gas such as argon to prevent AI from oxidizing; (t2) reducing oxides that are easily reduced, such as Si02, in the slag as much as possible; Scale adhering to the base material used as a glue consumable electrode may be removed with a grinder in advance, and as a countermeasure against fluctuations in S content, CaF2/mountain as described in Hakama Kaisho No. 49-62311 may be used. 20
3/Method of using Mg○ type slag, JP-A-50-53
For example, there is a method using a slag containing 2 to 4 times the amount of S contained in the pole electrode (base material) as described in Japanese Patent No. 217. However, according to various studies conducted by the present inventors, even with these solutions, variations in AI and S in the resulting remelted coin coins cannot be easily eliminated, and variations in the base material still remain. In the remelting process, a non-negligible loss of AI and S is caused, and problems arise such as a difference in the amount of AI and S between the bottom and the head of the remelted coin coin coin, It has become clear that the problems of AI fluctuations and S fluctuations in the electroslag remelting method have not been fully resolved.

In this regard, the present inventors conducted further studies in view of the above circumstances, and found that slag has superior meltability and fluidity, as well as superior ability to swell non-metallic inclusions. Calcium fluoride (CaF2), which is used unconditionally as the main component, has a great influence on the fluctuations of N and S, and the conventional CaF2-based slag is replaced with magnesium fluoride (MgF2)-based slag. They discovered that by changing the amount of Al and/or S in the steel or alloy, it is possible to effectively suppress variations in the amount of AI and/or S, and arrived at the present invention.

Therefore, an object of the present invention is to significantly suppress fluctuations in the content of N and/or S in steel or alloy during electroslag remelting, and to significantly suppress fluctuations in the content of N and/or S in the resulting remelted coin coins, especially in the bottom and head portions. The objective is to provide a method that can extremely minimize compositional fluctuations between the slag components, and for this purpose, when remelting electroslag of steel or alloy containing mountains and/or S, at least 45% of the slag composition is
The reason is that a slag containing 2% M is used.

As described above, by using the MgF2-based slag in place of the conventional Cap2-based slag according to the present invention, the loss of AI and S during the remelting process can be significantly suppressed, and the resulting remelted coin coins The variation in the amount of N and S in the slag could be significantly reduced, and a homogeneous mirror mass could be obtained.Why did the use of MgF2-based slag produce such excellent effects? The reason for this has not yet been specifically elucidated.

However, in any case, it has become possible to easily stabilize and equalize the amount of AI and S in a coin coin by simply using MgF2-based slag, which is extremely useful industrially. It is true that there is. Note that the material to be remelted in the present invention as described above is steel or alloy containing a predetermined amount of N and/or S in order to improve the material properties etc. as described above. These are prepared according to generally known conventional dissolution methods.

Such steels or alloys usually contain approximately 0.1% to several percent of AI and approximately 0.01% to approximately 0.2% of S in order to obtain predetermined performance. They are forced to do so. and such AI-containing and/or
Alternatively, S steel or alloy is used as a consumable electrode, and the electroslag is remelted in the same manner as in the past, but in the present invention, Mg
It is characterized by the use of F2-based slug.

That is, a slag with an MgF2 content (based on weight; the same applies hereinafter) of at least 45% or more, preferably 50 to 80% is used. In addition, the slag component with M of 2 has the same excellent ability to swell nonmetallic inclusions as conventional CaF2, and has high meltability and fluidity, making it suitable as the main slag component. However, the object of the present invention can be satisfactorily achieved by its presence in a predetermined amount. Further, in the present invention, the MgF2-based slag preferably contains 5 to 40% of aluminum oxide (AI203) as a slag component. This N203 is important in increasing the electrical resistivity of the slag, and its presence in a predetermined amount facilitates the remelting operation, ensuring a smooth and beautiful ingot surface. This has the effect of suppressing N in the material) from becoming an oxide, in other words, suppressing the loss of AI and improving the yield of AI. Note that when the amount of AI203 exceeds 40%, the slag melting point becomes high and it becomes difficult to melt it. Furthermore, MgF according to the present invention as described above
2-based slag contains an amount of AI (alone) not exceeding approximately 7%, depending on the amount of AI and/or S contained in the matrix.
and/or S (single element) in an amount not exceeding about 5%.

AI prevents fluctuations in the nails in the resulting re-dissolved rust mass and stabilizes it at a high level, and similarly, S also prevents fluctuations in S in the resulting re-dissolved mirror mass and stabilizes it at a high level. In addition, the slag of the present invention may contain known slag components as necessary.

For example, when a N-containing material is used as the base material, known calcium oxide (CaO) is included for desulfurization. Furthermore, magnesium oxide (M treatment) is preferably included in order to prevent oxidation of Mg in the slag. These other slag compounding components, including impurities, are used in a total amount of about 7% or less. In the present invention, it is also possible to include a certain amount of CaF2, which has been conventionally used, as a slag component, as long as it does not significantly impede the object of the present invention. In the present invention, normal melting operation conditions are applied to remelting electroslag for a predetermined base material using slag having such a composition, and generally, the electroslag is melted in air or in an inert atmosphere. Re-dissolution is performed at

The steel soul and alloy ingots obtained using this electroslag remelting method have the effect of removing nonmetallic inclusions and improving the health of the coin bullion structure, which can be obtained with the conventional electroslag remelting method. Furthermore, it goes without saying that the aircraft has achieved effects such as smoothing and beautifying the rusted skin, as well as AI and/or S
The deflection of the coins was significantly improved, and therefore they were evenly dispersed within the rust mass, making it possible to create a homogeneous coin coin with little AI fluctuations and S fluctuations between the bottom and the top.

Although some examples will be shown below to clarify the present invention more specifically, it goes without saying that the present invention is not limited in any way by the description of these examples. Note that all percentages in the examples are based on weight. Example 1 C=0.12%, Si=0.40%, Mn=1.60%
, using a steel ingot obtained by atmospheric melting containing AI = 1.00% and S = 0.120% as a consumable electrode, M bait 2 = 7
1.5%, mountain 203 = 20%, S: 3.5% and N = 5
% or slag B in which the MgF2 component of slag A was replaced with conventional CaF2, in an electroslag remelting furnace at a current density of 102 A/metre.

The S content and AI content in the obtained steel ingot were measured at the bottom (t) position, 1/3 position, 2/3 position, and head (To) position of the steel ingot.
p) position, and the results are shown in FIGS. 1 and 2.

Note that the symbols A and B in those figures correspond to the symbols of the slags used. As is clear from the results shown in FIGS. 1 and 2, when using MgF2-based slag A according to the present invention, S
The fluctuations and N fluctuations are extremely small, and the S content and AI
The content is stabilized at a high level, so the loss of S and N in the base metal is suppressed, and S and peaks are effectively introduced into the remelted steel ingot, resulting in a homogeneous steel ingot. .

On the other hand, when conventional slag B based on Cap2 is used, significant variations in the content of both S and AI are observed between the bottom parts, and the amount of S and AI that is introduced into the remelted steel ingot is found to be significant. The amount has also decreased considerably, indicating that a loss of these components has occurred. Example 2 Electroslag was prepared in the same manner as in Example 1 using a steel ingot containing C=0.12%, Si=0.4%, Mn=1.60% and N=1.00% as a consumable electrode. Re-dissolved.

The slag used was MgF2-A, which is the same as that in Example 1.
I203 series, CaF2・-N203 series,
Experiments were conducted in two cases in which the AI content was changed to 5% and 2%. The total amount of AI at the head and the AI at the bottom of the obtained remelted steel ingot. The relationship with the amount of Mg according to the present invention is shown in FIGS. 3a and 3b, respectively.
When F2-N203 series slag is used [Figure 3b], a relationship between the head AI content and the bottom AI content close to the ideal line (dashed line) is obtained, and the AI content of the steel core is stable at a high level. It is recognized that

In these figures, 0 indicates the results for the 2% mountain blended slag, and 0 indicates the results for the 5% AI blended slag. Example 3 A steel ingot containing about 0.12% S was remelted into electroslag using the same machine as in Example 1.

Then, as a result of analyzing the obtained ingot, when MgF2-based slag A according to the present invention was used, both the bottom and the top of the ingot showed an S content of about 0.115%, and the overall He acknowledged that the coins are homogeneous. On the other hand, when the conventional CaF2-based slag B is used, the S content is about 0.045% at the bottom and about 0.070% at the top, with significant S fluctuations and a low level of S content. A significantly lower and more heterogeneous coin lump was obtained.

Example 4 A! 203=20%, CaF2=20%, MgF2=5
Electroslag was remelted using the conditions of Example 1 except for using a slag containing 1.5%, S=3.5%, and N=5%.

The S content of the obtained steel soul was 0.075% at the bottom and 0 at the head.
．． 085%, and S fluctuation was small.

In addition, the AI capacity is 0.95% at the bottom and 1.05% at the head.
, with significantly less variation. Example 5
Ni/Cr/Mo/AI=77/21/3/0.21(
%) and Ni/Cr/N=65/32 no 3.04(%
), electroslag regeneration was performed using slag with the compositions N203/MgF2/AI = 20/79/1 (%) and 15/79/6 (%), respectively. Dissolution was performed.

The average N analysis value of the bottom and head of the obtained product (alloy mirror block) was 0.18% in the former case and 3.12 in the latter case.
%, and it was recognized that AI was highly stabilized in the product.

[Brief explanation of the drawings] Figures 1 and 2 are graphs showing the S variation and AI variation in the steel ingot, respectively, determined in Example 1, and Figures 3a and b are graphs, respectively, showing the S variation and AI variation in the steel ingot, determined in Example 2. 2 is a graph showing the relationship between the head AI content and the bottom AI content when CaF2-N203-based slag and MgF2-N203-based slag are used. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. Electroslag remelting characterized by using slag containing at least 45% magnesium fluoride as a slag component when electroslag remelting steel or alloy containing aluminum and/or sulfur. Law. 2. The method according to claim 1, wherein the slag further contains 5 to 40% aluminum oxide as a slag component. 3. The slag further includes aluminum as a slag component in an amount not exceeding about 7%, and the aluminum-containing steel or alloy is remelted.
or the method described in paragraph 2. 4. The method of claim 1 or 2, wherein the slag further contains sulfur as a slag component in an amount not exceeding about 5%, and the sulfur-containing steel or alloy is remelted. 5. The slag further comprises as slag components not more than about 7% aluminum and not more than about 5% sulfur, and the steel or alloy containing aluminum and sulfur is remelted. The method according to scope 1 or 2.