JPS6345443B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of the Invention) The present invention relates to a high magnetic permeability hot-rolled iron plate, particularly an electromagnetic iron core that is a main component of a cyclotron, or an extra-thick electromagnetic soft iron plate for magnetic shielding necessary to block the influence of a magnetic field. It is something. (Prior Art) Thin plates generally used in transformers are well known as electromagnetic soft iron plates. In the case of thin plates, in order to prevent energy loss due to eddy currents that inevitably occur when forming AC magnetic circuits, they are made thinner, that is, laminated, and are used by creating oxidized scale on the surface. ing. However, in the case of thick plates that are also used as structural members,
Since the strength of a thick plate is also utilized, it is impossible to achieve lamination by thinning the walls as described above, so unless the electrical resistance is increased, its use is limited to situations where a static magnetic field is generated. however,
Possible uses for the thick plate include electromagnetic iron cores for large cyclotrons for elementary particle experiments or small cyclotrons for medical use, and magnetic shields for large scientific measurement devices, and the development and improvement of such devices will contribute greatly to the advancement of technology. Therefore, there are high expectations for the development of excellent materials for this purpose. (Object of the Invention) The performance required of the iron plate used in the above-mentioned device is that it is important to have high magnetic permeability and to be inexpensive since it is used in large quantities. The purpose of the present invention is to provide a method for producing a hot rolled iron plate having high magnetic permeability and at low cost. Furthermore, another object of the present invention is to provide a method for manufacturing an extremely thick soft iron plate that has high magnetic permeability and is inexpensive, without any loss in mechanical properties for use as a structural member. (Summary of the Invention) The present inventors have made extensive studies to achieve the above-mentioned object, and have found that it is necessary to increase magnetic permeability and magnetic flux density in low magnetic fields for use in magnetic shielding as described above. , to obtain high magnetic permeability in thick plates, impurity elements, especially C, which forms precipitates,
We learned that it is effective to reduce the amount of N, S, and O as much as possible; to coarsen the ferrite particle size; and to appropriately use sol.Al. Focusing on these, we continued our research. However, they discovered that by combining these three materials, a material with a magnetic permeability that was unprecedentedly high could be obtained at a low cost, and the present invention was completed. That is, the influence of the C content among impurity elements is as shown in FIGS. 1a and 1b. In addition, Fig. 1 shows rolling finishing temperature of 800℃ and annealing of 850℃.
It was obtained under the conditions of 1 hour at ℃. C
As the content increases, the permeability decreases, while the coercive force
Hc increases, which is not desirable. Other elements N, S,
Similarly, magnetic permeability can be increased by reducing O as much as possible. P is not precipitated in the amount normally contained, and no adverse effects due to P are observed. The rolling conditions for coarsening the ferrite grain size include a pre-rolling heating temperature, a rolling reduction adjustment temperature, a rolling reduction rate, and a finishing temperature. First, as for rolling conditions, it is important to create conditions that allow sufficient grain growth during the next step of annealing. Therefore,
During rolling heating, 1150
Must be heated below ℃. When rolling, it is desirable that the as-rolled material has a fine-grained structure with residual rolling strain. For this purpose, low-temperature rolling is used, that is, the finishing temperature of rolling is 800℃ or less, the cumulative rolling reduction rate from 975℃ to finishing temperature is 35% or more, and then cooling is carried out at a rate of 10℃/min or more, and if the plate is particularly thick, it is water-cooled and rolled. Make sure that the processing strain is carried over to the next process of annealing. That is,
Hot rolling at a high reduction rate at low temperature is applied to the agglomerated and roughened AlN, and the rolling strain in the resulting fine grain composition is made to remain by rapid cooling. in advance
If you use steel whose composition is originally adjusted to be a single ferrite phase up to about 910°C, the coolant obtained as described above can be annealed at the high temperature side of the ferrite single phase range of 800 to 910°C. Abnormal grain growth occurs, and the ferrite grain size grows coarse. Furthermore, Al fixes N, neutralizes the negative effects of N on magnetic properties, and improves toughness. Also solid solution
Since Al improves magnetic properties, it is essential to use Al with an appropriate capacity. Figure 2 shows 0.01C−
Maximum permeability μmax and coercive force for 0.4Si steel
The effect of the amount of sol.Al on Hc is shown (as in Figure 1, the experimental conditions of finishing rolling temperature of 800℃ and annealing of 850℃ for 1 hour are adopted). It can be seen that this is effective in obtaining magnetic permeability. This is because as the amount of sol.Al increases, fine AlN, which has a crystal grain refining effect, decreases, and coarse AlN, which has a small grain refining effect, increases, resulting in an effect that promotes the coarsening of ferrite grain size and the solid solution Al itself. This is thought to be due to the superimposed effect of improving magnetic properties due to the increase in . Therefore, the present invention provides, in weight percent, C: 0.02% or less, Si: 0.50% or less, Mn: 0.50% or less, P: 0.050% or less, S: 0.015% or less, sol.Al: 0.010 to 0.80%, N: 0.006% or less, Oxygen: 0.005% or less, and if necessary, Nb: 0.015 to 0.250%, V:
A steel billet or slab with a steel composition consisting of at least one selected from the group consisting of 0.015 to 0.500% and Ti: 0.015 to 0.250%, the balance being Fe and unavoidable impurities is heated to 1150℃ or less, and the cumulative temperature at 975℃ to finishing temperature is heated to 1150℃ or less. It is characterized by hot rolling under the conditions of a rolling reduction of 35% or more and a finishing temperature of 800°C or less, then cooling at a cooling rate of 10°C/min or more, and after cooling, annealing at 800 to 910°C. Maximum magnetic permeability without processing distortion
4000 or more, magnetic flux density 1.35T or more in a magnetic field of 5Oe,
This is a method for manufacturing a hot-rolled iron plate with high magnetic permeability. Iron plates manufactured according to the invention, especially for example 6
~500mm thick plate has maximum permeability without processing distortion
4000 or more, but thick plates are usually used after bending, machining, and welding, so they are rarely used without distortion. The greatest feature of the thick plate manufactured by the present invention is that it has high magnetic permeability even after cold working, and cold working strain 3
It is possible to obtain a maximum permeability of 2000 or more within %. Although the present invention relates to a method for producing a hot-rolled material as described above, more precisely, it also includes an annealing step subsequent to hot rolling, rather than as-is hot-rolling. This is to achieve coarse growth of ferrite by the above-mentioned annealing from a coarse grained state with the processing strain introduced by hot rolling remaining. (Aspects of the Invention) Below, the reason for limiting the steel composition and each manufacturing condition specified in the present invention will be described. In order to obtain high magnetic permeability, it is desirable that C be as low as 0.03% or less, preferably 0.02% or less, otherwise it will be difficult to obtain high magnetic permeability after cold working. Adding more than 0.50% of Si deteriorates the toughness, and although increasing the amount of Si improves the magnetic permeability, the saturation magnetic flux density decreases, so the amount of Si was set to 0.50% or less.
In the applications targeted by the present invention, the required saturation magnetic flux density is constant at about 2.1 T (Tesla), and it is rather important to increase the magnetic permeability. Mn is necessary to prevent hot embrittlement due to S, but adding a large amount reduces magnetic permeability.
0.50% or less. Adding a large amount of P is undesirable as it deteriorates the toughness and forms center segregation of the CC slab, but removal of P is always accompanied by an increase in cost, so it is set at 0.050% or less. S produces MnS and reduces magnetic permeability, so
It was set to 0.020% or less, preferably 0.015% or less. When sol.Al is added in an amount of 0.010% or more, it has the effect of making solute N harmless and increasing the magnetic permeability due to the effect of solid solute Al. However, if it is added in an amount exceeding 1.00%, the flow of the molten metal during steelmaking is poor, and the problem with refractories. Since the deterioration is significant,
The content was 0.0150 to 1.0%, preferably 0.015 to 0.80%. It is desirable that the N content be as low as possible, and if it is added in excess of 0.006%, the ferrite particle size becomes difficult to coarsen, so in the present invention, the N content is set to 0.006% or less. Since oxygen forms non-metallic inclusions, it must be kept at 0.005% or less. Furthermore, in order to neutralize the adverse effects of solid solution C and N and obtain high magnetic permeability, in addition to the above basic components, if necessary,
Nb: 0.015-0.250%, V: 0.015-0.500% and
Ti: 0.015 to 0.250% of one or more types is contained for the following reasons. When Nb is added in an amount of 0.015% or more, it combines with C and N and becomes coarse when the rolling heating temperature is below 1150℃.
Since it forms Nb (C, N), it is effective in making impurity elements, especially C and N, harmless. but,
Adding more than 0.250% not only significantly increases cost but also harms magnetic properties, so it was set at 0.015 to 0.20%. V is effective in fixing C and N like Nb when added in an amount of 0.015% or more, but adding more than 0.50% causes an increase in cost, so V is added in an amount of 0.015 to 0.50%.
And so. Addition of Ti in an amount of 0.015% or more fixes C and N and renders them harmless, but if added in an amount exceeding 0.250%, the toughness deteriorates significantly.
The range shall be 0.015% to 0.250%. Next, regarding the rolling conditions, first, the pre-rolling heating temperature is set to 1150° C. or less in order to prevent C and N precipitates, such as AlN, from forming a solid solution and cause them to aggregate and coarsen. Finishing temperature below 800℃
Setting the cumulative rolling reduction ratio of 975℃ to finishing temperature at 35% or more is necessary to make the grains as fine as possible in the rolled state, while also allowing the rolling strain to remain, which tends to cause abnormal grain growth of ferrite during the next annealing process. This is to do so. In the case of thick plates, the reason for water cooling after rolling is to leave the rolling strain until the next process and make it easier for abnormal grain growth to occur due to strain annealing. In addition, by adjusting the composition as described above, the steel used in the present invention has a single phase of ferrite up to 910°C, so it can be annealed at 800 to 910°C to obtain sufficient grains under the above composition and rolling conditions. can cause growth. Grain growth is insufficient below 800°C. Thus, according to the invention, the adjustment of impurities,
Through the combination of manufacturing conditions and the addition of sol.Al, they interact to produce a material with excellent magnetic properties, especially high magnetic permeability, despite the thickness of the plate. Examples Hot-rolled materials were manufactured under the conditions shown in the table below by varying the manufacturing conditions for a series of steels A to K having the steel compositions also shown in the table. The slab was a cast slab manufactured by continuous casting. The results are also summarized in the table, and as can be seen from this, as long as it is manufactured under the above chemical composition and manufacturing conditions within the scope of the present invention, ferrite can be produced as coarse particles with a particle size number of 3 or less without processing distortion. It is possible to obtain a maximum magnetic permeability of 4000 or more in a state of 4,000 or more, and a maximum magnetic permeability of 2000 or more with a processing strain of 3% or less. Furthermore, in a state of 0% processing strain, a magnetic flux density of 1.35 T or more can be obtained with a magnetic field of 5 Oe.

【table】

【table】

[Table] (Note) *: Outside the scope of the present invention

[Brief explanation of the drawing]

Figures 1a and 1b are graphs showing the influence of C content on maximum permeability (μmax) and coercive force (Hc), respectively; and Figure 2 is
It is a graph showing the influence of sol.Al content on maximum magnetic permeability (μmax) and coercive force (Hc).

Claims (1)

[Claims] 1% by weight: C: 0.02% or less, Si: 0.50% or less, Mn: 0.50% or less, P: 0.050% or less, S: 0.015% or less, sol.Al: 0.010 to 0.80%, N: 0.006% or less, Oxygen: 0.005% or less, and if necessary, Nb: 0.015 to 0.250%, V:
A steel billet or slab with a steel composition consisting of at least one selected from the group consisting of 0.015 to 0.500% and Ti: 0.015 to 0.250%, the balance being Fe and unavoidable impurities is heated to 1150℃ or less, and the cumulative temperature at 975℃ to finishing temperature is heated to 1150℃ or less. It is characterized by hot rolling under the conditions of a rolling reduction of 35% or more and a finishing temperature of 800°C or less, then cooling at a cooling rate of 10°C/min or more, and after cooling, annealing at 800 to 910°C. Maximum magnetic permeability without processing distortion
4000 or more, magnetic flux density 1.35T or more in a magnetic field of 5Oe,
A method for manufacturing a high permeability hot rolled iron plate.