JPS6343452B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a metal modifier used when adding it to molten metal. It is known from DRPNr.304185 that steel is directly alloyed with B by reduction of Na or Ca borates. In addition, Metal Progress, 34 (1937) reported that cast iron was melted under a borax coating to obtain hard cast iron similar to white pig iron. and iron and steel,
41 (1955), p. 11, it is known that an appropriate amount of B can be alloyed into steel by adding B ₂ O ₃ to carbide slag and then adding Al or Fe-Ti in a 2-t Elou furnace. There is. Although there are many reports on the method of producing B-containing steel by reducing the boride added to slag, the yield of B is uncertain and it has not yet been used industrially. Industrially, B is almost always added to the ladle as ferroboron. By the way, since the solid solubility of B in Fe is small, it is known that even a small amount of addition precipitates the compound Fe ₂ B and creates crystal nuclei, which is one of the reasons for the refinement of the structure in the cast and rolled state. ing. According to other research results, trace amounts of B reduce the rate of pearlite and bainite formation in steel, thus significantly improving their hardenability, but it is known that homogenization heat treatment at high temperatures minimizes this effect. It is being (Am.Soc.Metals, Prep.No.10, [1945]
39: Steel, 118 [1946], 98.) There are various reports on the effect of B on the mechanical properties of steel, but in general, the hardness and tensile strength of C steel and Ni steel increase with the addition of B. It is known that the toughness increases significantly, the toughness decreases rapidly, and the workability is generally poor. For example, according to Iron & Steel, 16 [1944], 443, SAE
-1035 steel (C: 0.35%) The results of the test are shown in Table 1.

[Table] That is, the addition of B increases the yield point and tensile strength, but tends to decrease the elongation and reduction of area. It is also known that the addition of boron increases the chill depth and hardness of cast iron. In addition, there have been research reports on improving the grain size of aluminum alloys by adding boron, and there are also reports that high-resistance iron alloys are sometimes mixed in as impurities with aluminum and copper used in electrical conductors. It has been announced that the harm caused by this impurity can be neutralized by adding several hundredths of a percent of boron. An object of the present invention is to propose an advantageous method for producing a modifier used in modifying metals by adding B as described above. This purpose is achieved by employing the following method, in which at least one selected from orthoboric acid, metaboric acid, pyroboric acid, boric anhydride, and borax is mixed with metallic magnesium in a molar ratio of 1/3 to 2. Mainly by heating and sintering the mixture mixed within the ratio range in one of air atmosphere, air-blocking atmosphere, and inert gas atmosphere.
It is made by containing unsaturated oxides of B and Mg in an Mg-B-O based amorphous compound, and also contains Mg ₂ B ₂ O ₅ , Mg ₃ (BO ₃ ) ₂ and MgO as inevitable impurities. A method for producing a metal modifier characterized by obtaining a metal modifier. Next, the present invention will be explained in detail. The present inventor has developed a metal modifier produced by the production method of the present invention in a steel bath having a composition that should have a solidified structure consisting of a large amount of pearlite phase and a small amount of ferrite phase according to normal casting. The present invention was conceived based on the new finding that when treated with , the pearlite phase in the cast structure decreases and the ferrite phase increases, the tensile strength decreases, and the elongation and reduction of area greatly increase. It is. On the other hand, it is known that when a steel bath is treated with B according to the conventional method, the tensile strength increases as described above, but the elongation and reduction of area decrease. Therefore, it is a new phenomenon discovered by the present inventors that the modifying effect of the modifier produced by the production method of the present invention is qualitatively completely different from that of the conventional method. be. The metal modifier produced by the production method of the present invention includes orthoboric acid (H ₃ BO ₃ ), metaboric acid (HBO ₂ ), pyroboric acid (H ₂ B ₄ O ₇ ), boric anhydride (B ₂ O ₃ ), borax (Na ₂ B ₄ O ₇ ) and metallic magnesium in a predetermined molar ratio range is heated to remove a part of the B oxide. It is a modifier consisting of an Mg-B-O type compound that is reduced by Mg and mainly contains unsaturated oxides of B and Mg. In addition to Mg-BO-based amorphous compounds that have the effect of modifying metals,
Crystalline Mg ₂ B ₂ O ₅ , Mg ₃ (BO ₃ ) ² , which has no effect
Contains MgO as an inevitable impurity. In the metal modifier produced by the production method of the present invention, unlike the above-mentioned known B-containing alloy, there is no metallic B, as seen from the X-ray diffraction diagram in FIG.
Also, clear crystalline Mg ₂ B ₂ O ₅ , Mg ₃ (BO ₃ ) ₂ ,
The presence of small amounts of MgO and other impurities was observed, and observation using a polarizing microscope revealed the presence of an amorphous, ie, glassy, Mg-B-O compound. By the way, by adding a metal modifier produced by the production method of the present invention to a molten metal of iron, iron alloy, aluminum, or aluminum alloy, the structure and/or mechanical properties of the above-mentioned metals or alloys can be changed. We have found that improvements can be made as described below, but in order to explore the mechanism by which the modifier produced by the production method of the present invention can modify the aforementioned metals and alloys, we have developed the production method of the present invention. Among the various compounds inevitably present in the modifier produced by this method, Mg ₂ B ₂ O ₅ , Mg ₃ (BO ₃ ) ₂ , MgO
Whether or not the metal to be treated is modified is determined by adding each of these high-purity products individually or a mixture of two or three of them to the molten metal. After investigation, it was found that there was no change in the structure and/or mechanical properties of the metal material to be treated, and therefore, these unavoidable compounds had no modifying ability. Therefore, it has been confirmed that the Mg-B-O-based amorphous compound, which is present in the modifier produced by the production method of the present invention and cannot be isolated or synthesized independently, has the modifying effect. It is considered to have the following. however,
Although the exact principle by which this Mg-BO-based amorphous compound exerts its modifying effect is still unclear, the Mg-BO-based amorphous compound contained in the product produced by the production method of the present invention Amorphous compounds are thermally unstable, such as Mg ₂ B ₂ O _(5-x) or Mg ₃
[BO _(3-y) ] ₂ (however, a positive number of x < 5, y < 3), and when added to molten metal, it immediately reacts with the molten metal and exerts a reforming effect. The present inventor considers that this may be possible. The metal modifier produced by the production method of the present invention exhibits slower and more stable reactivity toward molten metal than known metallic magnesium, and the metal modifier exhibits a reaction that is qualitatively different from the reaction toward molten metal. For example, for iron and steel, cementite is decomposed to increase the ferrite phase, and for AC-2A aluminum alloy, the Mg-Cu eutectic is decomposed to maintain the Al-Si eutectic. let That is, the modification effect obtained by the metal modifier produced by the production method of the present invention cannot be obtained at all with the conventionally known metal modifiers. Next, the experimental results of modifying various metals and alloys using the metal modifier produced by the production method of the present invention will be explained with reference to experimental data. (1) 1300 kg of SC-46 (JIS carbon steel casting product type 3) is melted in an acid-lined low frequency induction furnace.
After this molten metal was forcibly deoxidized with aluminum in a furnace, a portion of the molten metal was cast as it was into a Y block, and the other portion was poured into a ladle while the molten metal was flowing into a Y block. After adding a modifier having the composition shown in the table and pouring the molten metal into the ladle, it was stirred lightly with a steel rod, and immediately cast into a Y block.
It was processed into a JIS-4 test piece and subjected to testing. The amount of the modifier added was 100g per 1300kg of molten metal, and the addition ratio was 0.0077%. The composition of the molten metal is C0.21%, Si0.60%, Mn0.47%,
P0.020%, S0.009%, and the test results for test pieces taken from each Y block are as shown in Table 2, and the microscopic structures are shown in Figure 2 A, B, C, and D. It is like that.

【table】

【table】

[Table] According to Table 2 and Figures 2A to 2D, the material produced by the production method of the present invention without the addition of a metal modifier has a structure of a large amount of pearlite and a small amount of ferrite. See Figures A and B],
On the other hand, the added material has a structure consisting of a small amount of pearlite and a large amount of ferrite [see Figure 2 C and D], so the former has a high tensile strength but almost no elongation and a small reduction of area. be. It was found that the latter, that is, the one with the modifier added, had a lower tensile strength but a significantly larger elongation and reduction of area.
In the conventionally known materials to which ferroboron containing metal B is added, the modification properties as produced by the modifier produced by the production method of the present invention described above have not been known at all. Furthermore, the above SC-46 has a high casting wall thickness sensitivity, so if the weight of the casting exceeds 500 kg and the wall thickness fluctuates greatly, approximately 10%
In order to prevent the occurrence of cracks in the castings, the molds were separated by waiting for natural cooling for several days. Even if the mold is broken out immediately after solidification, no cracks will occur, which has a great effect on saving casting space and shortening the production period of the product.Furthermore, by using this modifier, elongation and drawing are reduced. Since the improvement is remarkable, as-cast processing is also possible, simplifying heat treatment, and the economic effect is extremely large. (2) AC-2A (JIS aluminum alloy casting type 2 A)
400Kg was melted in a foundry crucible furnace, and after deoxidizing and degassing, part of it was put into a sand mold (vertical type - diameter approx. 30mm,
The length is about 400 mm), and the other part is about 10 mm long for drawing hot water.
Kg was sampled, and a metal modifier having the composition shown in Table 5 obtained by the production method of the present invention was poured into a separately preheated water pump, and the molten metal was poured into it, stirred with a steel rod, and immediately molded into a sand mold. The same shape as above) was cast, and each was processed into a JIS No. 4 test piece and used for testing. The amount of modifier added is 1g and 10g for 10kg of molten metal, respectively, and the addition ratio to the molten metal is
They were 0.01% and 0.1%. The test results for each sample are shown in Table 3, and the microscopic structures are shown in Figure 3 A, B, C, and D. The composition of the molten metal is Cu3.88%, Si4.50
%, Mg0.15%, Zn0.72%, Fe0.56%, Mn0.30
%, the balance is Al.

[Table] As shown in Table 3 and Figures 3A to 3D, the materials produced by the production method of the present invention without the addition of metal modifiers have a skeleton-like structure in the Al base as shown in Figure 3A and Figure 3B. The Mg-Cu eutectic and the network-like Al-Si eutectic crystallize, but the Mg-Cu eutectic disappears in all the added materials.
Only the Al-Si eutectic remains, and as a result, the tensile strength of the additive material is slightly higher than that of the non-additive material, and the elongation is also significantly higher. Diminished. As seen in the experimental data, a remarkable effect was observed in the recycling of low-grade aluminum scrap. (3) 3500 kg of FC-20 (JIS gray cast iron product type 3) was melted in a low frequency induction furnace, and part of it was directly cast into a Y block. The metal modifier shown in Table 5 was added, stirred lightly with a steel rod, and immediately cast into a Y block, each of which was processed into a JIS-4 test piece and used for testing. The amount of modifier added is 2 g and 5 g, respectively, per 10 kg of molten metal, and the addition ratio is 0.02.
%, 0.05%. The composition of the molten metal is
C3.51%, Si1.78%, Mn0.52%, P0.05%,
S is 0.04%. The results of various tests conducted on the above-mentioned additive-free materials and additive materials show that in terms of the microstructure, the additive-free materials are A.
Although some crystallization of eutectic graphite was observed in the type graphite, the eutectic graphite disappeared and only type A graphite crystallized. The mechanical properties of both materials were as shown in Table 4, and no clear changes were observed.

[Table] Next, the method for producing the metal modifier of the present invention will be explained. At least one selected from orthoboric acid, metaboric acid, pyroboric acid, boric anhydride, and borax is mixed with metallic magnesium in a molar ratio of 1/3 to 2, and the mixture is placed in an air atmosphere or in an air-blocking atmosphere. When heated in the atmosphere or in an inert gas atmosphere, the two react violently and sinter, resulting in the metal modifier of the present invention being obtained. By the way, 3 parts by weight of boron oxide and 1 part by weight of magnesium
When parts by weight are placed in a Shamotsu crucible and heated to 900-1000℃ in an electric furnace or gas furnace,
Shortly after, a violent reaction occurs and reduction occurs, and when this product is purified by treatment with hydrochloric acid, B90-95%,
Mainly composed of B with 3 to 4% Mg, with a small amount
It is known that products containing Mg ₃ B ₂ are obtained. In addition, when 2 parts by weight of boron oxide and 5 parts by weight of metal magnesium are heated in the same manner, B70% is obtained.
It is known that a product consisting mainly of Mg ₃ B ₂ with 30% Mg is obtained. The method for producing a metal modifier of the present invention is partially similar to the above-mentioned known method, but is characterized by the absence of metal state B, as shown in the X-ray diffraction diagram in FIG.
It is considered that unsaturated oxides of B and Mg are contained in the Mg-B-O glass mixture in a dissolved form, and Mg 2 B 2 O 5 and Mg ₂ B ₂ O ₅ as inevitable impurities.
Contains _Mg3 ( _BO3 ) ₂ and MgO. The reason why the mixing ratio of the boron compound and Mg is limited to a range of 1/3 to 2 in terms of molar ratio in the present invention is as follows.
If the ratio is smaller than 1/3 or larger than 2, the effect of modifying the metal will be small, so the mixing ratio should be within the range of 1/3 to 2 in terms of molar ratio. The metal modifier produced by the production method of the present invention needs to be added to the metal or alloy in a molten state, and there are various ways of adding it as follows. (a) The modifier produced by the production method of the present invention is added little by little into the flow of the metal or alloy melted in the furnace when it is poured into a ladle or mold. (b) A modifier produced by the production method of the present invention is added in advance to a ladle or mold, and then a molten metal or alloy is poured. (c) A modifier produced by the production method of the present invention is added to the molten metal received in a vibrating or rotating ladle, and the ladle is vibrated or rotated. (d) A lance pipe is inserted into the molten metal received in a ladle or mold, and the modifier produced by the production method of the present invention, which is suspended in an inert gas, is injected under pressure. (E) A thin plate of iron, aluminum, copper, or each alloy is coated with a modifier produced by the production method of the present invention to form a pipe shape or a continuous flexible pipe shape that can be freely wound. none,
It is added intermittently or continuously to the molten metal or alloy contained in a ladle, continuous casting tundish, or continuous casting mold. In the metal modifier produced by the production of the present invention,
For example, metals, alloys, or compounds thereof having deoxidizing, desulfurizing, denitrifying, and/or degassing functions can be mixed within a range that does not reduce the effects thereof. Further, it is within the technical scope of the present invention to mix other types of modifiers in a roundabout way with the modifier produced by the production method of the present invention. In addition, the present inventor has discovered that Ca, Sr,
The production method of the present invention can also be applied to a sintered product obtained by adding at least one type of Ba, boric acid, or Al or Si capable of reducing borate to borate in place of or together with Mg and heating and sintering the mixture. We are currently conducting research on the idea that it may have the same modifying properties as the modifier produced in this way.

[Brief explanation of the drawing]

Figure 1 shows the X-ray diffraction diagram of the metal modifier produced by the production method of the present invention, and A and B of Figure 2 show the X-ray diffraction diagram of the metal modifier produced by the production method of the present invention. Photomicrographs of the steel without metal modifiers, c and d are photomicrographs of the steel with this modifier added, and a and b of Figure 3 are the photomicrographs of the steel produced by the production method of the present invention without the addition of the metal modifier. Micrograph of aluminum alloy,
C and D are micrographs of an aluminum alloy to which this modifier has been added, A of Figure 4 is a micrograph of cast iron produced by the manufacturing method of the present invention without the addition of a metal modifier, B and C. is a micrograph of cast iron with this modifier added.

Claims (1)

[Claims] 1. A mixture of at least one selected from orthoboric acid, metaboric acid, pyroboric acid, boric anhydride, and borax and metallic magnesium in a molar ratio of 1/3 to 2 in an air atmosphere, air. By heating and sintering in either a cutoff atmosphere or an inert gas atmosphere, Mg--B-, which mainly contains unsaturated oxides of B and Mg, is produced.
A method for producing a metal modifier, characterized by obtaining an O-based amorphous compound.