JPH0359976B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial application field) In recent years, with the advancement of science and technology, devices that use magnetism as part of large steel structures, such as devices with a diameter of 1 km and a circumference of approximately 3
A device was developed to discover new elementary particles by accelerating and accumulating electrons and positrons in opposite directions to approximately 300 Meν in a Km collider, causing them to collide head-on, and investigating the reactions that occur at that time. Excellent magnetic properties are required of the thick steel plates used for the iron core of the magnets used. The present invention relates to a thick plate for direct current magnetization having high magnetic properties suitable for such uses, and a method for manufacturing the same. (Prior Art) Conventionally, pure iron, electromagnetic soft iron rods and electromagnetic soft iron plates specified in JISC22503 and C2504 are known as steel materials that are used under DC magnetization conditions and have excellent magnetic properties.
However, pure iron is difficult to obtain in large scale industrially, and even if it were obtained, it would not be possible to incorporate it into a large steel structure to form a structure due to strength problems. JISC2503 is 1.0
~16mmφ diameter rod, JISC2504 0.5~4.5
They are thin plates with a thickness of mm, and are used for relays and electromagnets, but are limited to small sizes. For example, the object of the present invention is 500mm thick x 4000mm wide.
In order to obtain a large magnetic solid of up to 8000 mm x 8000 mm, it would be necessary to laminate a considerable number of sheets, making it virtually impossible to manufacture in terms of production costs and manufacturing technology. Furthermore, it is difficult to have excellent magnetic properties in the thickness direction as well. On the other hand, it is not classified as magnetic.
Using JISG4051 carbon steel for machine structure S10C,
There is an example of a 250 mm diameter being hot worked and used as a magnetic material, but in this case no consideration is given to the magnetic properties, so the maximum magnetic permeability μ = B/H (H (indicates the magnetizing force (Oe) and B indicates the magnetic flux density (Gs)) is low at 1800 or less, and can only be applied to extremely limited applications. Furthermore, from the viewpoint of magnetic properties, it is important for electrical steel sheets to have little magnetic deterioration due to magnetic aging.
Therefore, for electromagnetic steel sheets with a thickness of 1 mm or less used for the iron core of rotating machines such as motors, and electromagnetic steel sheets with a thickness of 1 mm or less used for the iron core of transformers, for example, Through decarburization annealing, we have reached a carbon content that does not cause magnetic aging. However, the plate thickness 20 that the present invention targets
In the case of steel plates with a thickness of mm or more, it is impossible to decarburize them due to the thickness. (Object of the Invention) The object of the present invention has been made in view of the above points. It is an object of the present invention to provide a thick plate for magnetization and a manufacturing method with little difference in magnetic properties in the thickness direction thereof. (Structure of the Invention) In order to achieve the above object, the present invention is structured as follows. C in weight%: 0.01%
Below, Si: 0.30% or less, Mn: 0.50% or less, Cr:
0.05% or less, Mo: 0.02% or less, Cu: 0.05% or less,
Al: 0.005-0.06%, N: 0.01% or less, O: 0.003
% or less, P: 0.01% or less, S: 0.01% or less, the remainder substantially consists of iron, and the maximum magnetic permeability (μ = B /
H): A thick plate for direct current magnetization with a thickness of 20 mm or more and a magnetic property of 2000 or more. And after hot working a steel ingot or slab with the above ingredients to a predetermined size, it is subsequently annealed at 600-720℃ for 3-10 hours, or 850-720℃.
Maximum magnetic permeability (μ=B/H): 20mm thick with magnetic properties of 2000 or more, characterized by grain adjustment and/or dehydrogenation heat treatment at 980℃ for 10 minutes to 2 hours. The above method for producing a thick plate for direct current magnetization. The inventors of the present invention have repeatedly conducted various experiments in order to obtain a thick plate for direct current magnetization with good magnetic properties. It was discovered that there are two points to be solved: ensuring homogeneity of magnetic properties in the direction, and minimizing the component that increases the demagnetization rate in order to improve the magnetic properties. To ensure the first point, homogeneity of magnetic properties, a. Reduce components that cause non-metallic inclusions. (P,S,
O) B Reduce components that are likely to segregate. (P,S,
C) Eliminate void defects. (Decrease in H, etc.) D. Make crystal grains as uniform as possible in the thickness direction of the plate. It was confirmed that this is an extremely effective method. Furthermore, as for the second point, components that increase the demagnetization rate include C, Si, Mn, Cu, Cr, Mo, and N, and it was confirmed that it is effective to reduce these as much as possible, and the present invention was completed. It is. Next, the reason for limiting the ingredients of the present invention will be described. is the element with the highest demagnetization rate of magnetic properties, and reducing it as much as possible contributes to not increasing the demagnetization rate. Also, from the point of view of magnetic aging, the lower the magnetic aging, the less deterioration over time and the ability to use it permanently with good magnetic properties, so it is best not to contain it. However, reducing the content to 0% requires a significant increase in smelting costs, making it industrially unprofitable. Therefore, the acceptable range for magnetic property deterioration is limited to 0.01% or less. From the viewpoint of demagnetization rate of magnetic properties, it is preferable that Si and Mn be as small as possible, and it is best not to include them. However, when used in a large steel structure, it is necessary to ensure the minimum necessary strength in addition to magnetic properties. In this sense, Si is limited to 0.30% or less and Mn is limited to 0.50% or less as a range in which magnetic property deterioration can be tolerated. Cr, Mo, Cu, and N increase the demagnetization rate of magnetic properties, so the smaller the content, the better, and in order to reduce the degree of segregation, it is necessary to keep them as low as possible.
It is best not to contain it. However, the content is 0
%, the smelting cost increases significantly and it is not industrially profitable. Therefore, the acceptable range for magnetic property deterioration is 0.05% or less for Cr and 0.02% for Mo.
Hereinafter, Cu is 0.05% or less and N is 0.01% or less. Al is used as a deoxidizing agent and is an essential element for homogenizing the internal material when the plate thickness is thick as in the present invention.Although it is added in an amount of 0.005% or more, if it is added too much, inclusions will be formed and the properties of the steel will change. The upper limit is
Must be 0.060% or less. P, S, and O form nonmetallic inclusions in steel and segregate, which hinders the movement of domain walls.As their content increases, the coercive force increases and the magnetic properties deteriorate. The less the better, and it is best not to include it. However, reducing the content to 0% significantly increases smelting costs, making it unprofitable industrially. Therefore, the acceptable range for deterioration of magnetic properties is 0.010% or less for P and S, and 0.010% or less for O.
It was set to 0.003% or less. The maximum magnetic permeability μ is used in a device that utilizes magnetic properties, and is set to 200 or more as the minimum value necessary to exhibit sufficient magnetic properties. The plate thickness was set to 20 mm or more because the minimum plate thickness is 20 mm, which requires uniformity in the thickness direction as a thick plate for DC magnetization and measures against void defects. There is no upper limit because forming by hot forging can produce products that are thicker than the steel ingot. Next, the manufacturing method will be described. The steel solvent may be melted by either the converter melting method or the electric furnace melting method, and if necessary, it may be added through a refining process such as ladle refining or vacuum degassing to add components that increase the demagnetization rate (C, Si, Mn, Cr, Mo,
In addition to minimizing the amount of P, S, and O that inhibit the movement of the magnetic flux barrier by forming and segregating nonmetallic inclusions, the amount of P, S, and O that inhibits the movement of the magnetic flux barrier is reduced. Furthermore, since void defects due to the large plate thickness become an obstacle to increasing the magnetic flux density and impair the homogeneity of magnetic properties, it is effective to reduce H, which promotes void defects, by known low hydrogen blowing, vacuum It is preferable to reduce the amount of hydrogen by degassing or the like to reduce the size of void defects in the later steps of ingot formation and continuous casting. Next, in the hot working step, no special operation is required for heating conditions before processing, and the form of hot working may be either rolling using a rolling mill or forging using a forging machine. The above-mentioned void defects are always generated in the solidification process of steel, although they may be large or small, and the means to eliminate them must be through rolling or forging, so the role of the hot working process is important. In other words, specifically, hot working that increases the amount of work per hot working and causes deformation to reach the center of the plate thickness is effective, and in the case of rolling, the well-known high shape ratio rolling is applied. It is preferable to do so. Next, following hot working, a dehydrogenation heat treatment is performed to adjust the crystal grains and/or to adjust the thickness of the product plate, but in order to save energy, the ferrite crystal grains are charged into a heat treatment furnace without cooling after hot working. The objective is to increase the magnetic flux density by making the particles more uniform and coarser, and to thoroughly eliminate void defects by dehydrogenation. As for this heat treatment, annealing is most preferable in terms of magnetic properties, and if it is necessary to ensure a certain degree of strength, normalizing is effective although the magnetic properties are slightly degraded. Although the grain adjustment and dehydrogenation treatment described above may be performed separately, it is efficient to perform the heat treatment once in order to save energy. The present inventors organized the experimental results regarding the preferable crystal grain size in terms of magnetic properties and obtained the relationship shown in FIG. 1. According to this, in order to ensure a maximum magnetic permeability of 2000 or more, it is necessary to make the ferrite crystal grain size coarse and regular, with a grain size of about -3 to 4. The heat treatment conditions for this are 600°C to 720°C x 3 to 10 hours for annealing, and 850°C for normalizing.
Heat treatment for 10 minutes to 2 hours at 980°C is required. If the annealing temperature is less than 600°C, sufficient dehydrogenation efficiency cannot be expected. If it exceeds 720°C, the initial hydrogen solubility increases, making it difficult to reduce the load on the dehydrogenation efficiency of thick materials, which is not preferable. If the annealing time is less than 3 hours, sufficient dehydrogenation cannot be achieved, which is disadvantageous. On the other hand, if it exceeds 10 hours, the dehydrogenation effect decreases and it is not economical. If the normalization temperature is less than 850°C, the crystal grains may become mixed grains, which is not preferable. On the other hand, at a high temperature exceeding 980°C, grains become finer due to recrystallization, which is undesirable. If the normalizing time is less than 10 minutes, a sufficient normalizing effect cannot be obtained and it is difficult to obtain a uniform grain size. On the other hand, even if the treatment exceeds 2 hours, the effect of grain adjustment is small and the shape of the steel sheet deteriorates in the case of thin steel sheets, which is not preferable. When the grain adjustment and dehydrogenation treatment heating is annealing, it is slowly cooled in a furnace to at least 500°C and then allowed to cool in the atmosphere. In the case of normalizing, the material is heated to a predetermined temperature and then slowly cooled or left to cool in the atmosphere. Next, examples will be listed together with comparative examples. The molten steel refined by the converter steel manufacturing method was further subjected to ladle refining and vacuum degassing treatment to obtain steel having the chemical components shown in Table 1. After ingot-forming and soaking the steel, it was finished into a plate with a thickness of 20 to 500 mm by hot forging or hot rolling in consideration of countermeasures against void defects. Subsequently, annealing or normalization was applied, and in the case of annealing, the material was slowly cooled in a furnace to 500°C, and then allowed to cool in the atmosphere to perform grain adjustment and dehydrogenation heat treatment. Table 1 shows the ferrite grain size, maximum magnetic permeability, and tensile strength of the obtained thick steel plate.

【table】

Table Thus, Examples 1 to 7 show examples of the invention, and Examples 8 to 10 show comparative examples. Examples 1 and 2 were forged to 500 mm and 400 mm, subjected to grain adjustment and dehydrogenation by finish annealing, and have uniform, coarse grains and high magnetic property values. Example 4 has a high content of C, Si, and Mn, and is finished to a thickness of 400 mm by rolling and normalizing, and has a strength that can be used for structural purposes at the expense of some magnetic properties. Examples 3, 5, 6, and 7 are rolled-
In particular, the one manufactured by annealing, Example 3, has a lower content of C, Si, and Mn than Example 2, and has high magnetic properties even though the ferrite crystal grain size is -2. . In Example 5, the C and Si contents are slightly higher, and the magnetic properties are at a medium level. Example 6 is made of steel having the same composition as Example 4, made to a thickness of 45 mm, and is annealed to coarsen the ferrite crystal grains to ensure magnetic properties and increase strength. Example 7 is finished with a plate thickness of 20 mm and has high magnetic properties because all the components that increase the demagnetization rate are at low levels. On the other hand, in Examples 8 to 10, the rolling temperature was 250 to 200.
It is finished in mm. In the case of example 8, C,
The content of Si, P, S, Cu, Cr, Mo, and Al exceeds the upper limit, and the magnetic properties are low because the composition has a high demagnetization rate and because no heat treatment is performed. In Example 9, the chemical components are within the range of the present invention, but since no heat treatment was performed, the ferrite crystal grain size is on the fine grain side, resulting in a low magnetic property level and a large difference in property values in the thickness direction. Example 10 has low magnetic properties because C is outside the upper limit and no heat treatment was performed. Figure 2 shows JISG4051 S10C material (as rolled).
The magnetic field strength (horizontal axis) and magnetic flux density (vertical axis) were investigated for JISC2504 type 0 and the present invention material.JISC2504 shows the standard value, and the other values are actually measured values. As is clear from the figure, the material of the present invention exhibits superior values to JISC2504 in low and medium magnetic field strengths. This shows that the thick plate for DC magnetization according to the present invention can be used for a wide range of magnetic properties, even considering that the magnetic field strength generally used in practical use is low to medium strength. There is. (Effects of the Invention) As described in detail above, according to the present invention, it is possible to successfully provide a thick steel plate with uniform high electromagnetic properties by appropriately limiting the ingredients, and to utilize the magnetic properties caused by direct current magnetization. It can be applied to structures, and its manufacturing method is extremely economical as it simultaneously performs grain adjustment and dehydrogenation heat treatment without cooling after hot working and limiting the ingredients described above. It has great industrial effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the relationship between ferrite particle size number and maximum magnetic permeability, and FIG. 2 is an explanatory diagram showing the relationship between magnetic field strength and magnetic flux density.

Claims (1)

[Claims] 1% by weight: C: 0.01% or less, Si: 0.30% or less,
Mn: 0.50% or less, Cr: 0.05% or less, Mo: 0.02%
Below, Cu: 0.05% or less, Al: 0.005-0.06%,
N: 0.01% or less, O: 0.003% or less, P: 0.01% or less, S: 0.01% or less, the remainder substantially consisting of iron,
Maximum magnetic permeability (μ=B/H): Thick plate for direct current magnetization with a thickness of 20 mm or more and a magnetic property of 2000 or more. 2 C: 0.01% or less, Si: 0.30% or less,
Mn: 0.50% or less, Cr: 0.05% or less, Mo: 0.02%
Below, Cu: 0.05% or less, Al: 0.005-0.06%,
N: 0.01% or less, O: 0.003% or less, P: 0.01% or less, S: 0.01% or less, the remainder being substantially iron after hot working a steel ingot or slab to the specified dimensions. Annealing at 600-720℃ for 3-10 hours,
Or maximum magnetic permeability (μ=B/H) characterized by normalizing at 850-980℃ for 10 minutes to 2 hours:
A method for producing a thick plate for direct current magnetization with a thickness of 20 mm or more and a magnetic property of 2000 or more.