JPH04280921A - Production of steel sheet for particle accelerator by continuous annealing - Google Patents

Abstract

PURPOSE:To mass-produce a steel sheet for particle accelerator excellent in magnetic properties at a low cost. CONSTITUTION:A slab having a composition consisting of, by weight, <=0.01% C, <=0.3% Si, 0.1-1.0% Mn, <=0.3% P, <=0.02% S, <=0.01% Sol.Al, <=0.01% N, and the balance iron with inevitable impurities is heated at 950-1150 deg.C and finishing temp. is regulated to >=950 deg.C to form a hot rolled coil. This coil is cold-rolled to 0.9-2.5mm thickness. The resulting steel sheet is subjected to recrystallization annealing at 750-900 deg.C by means of continuous annealing and cooled slowly from the recrystallization temp. down to 450 deg.C at 1-20 deg.C/sec cooling rate, and the final temper rolling is done at <=0.4% reduction of area. By this method, the steel sheet for particle accelerator excellent in magnetic properties as to have >=2800 D.C. magnetic permeability at 10e can be produced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention basically relates to the production of steel plates for particle accelerators, which are used as yoke materials for circular or linear accelerators.

0002

BACKGROUND OF THE INVENTION In recent years, construction of large particle accelerators has become popular for research on elementary particles and research using synchrotron radiation. A particle accelerator requires a steel material as a yoke. Currently, some planned particle accelerators have circumferential lengths of up to 90 km, requiring tens of thousands of tons of steel plates for the yokes. The characteristics required of this yoke material are excellent DC excitation characteristics and strength for structural use. The excitation characteristic required for the yoke of a particle accelerator is a stable and high magnetic flux density from low to high magnetic fields, so a pure iron steel plate with a small amount of Si, etc. is required, but the magnetic flux density is particularly low in low magnetic fields. Desired. In addition, the plate thickness is 0 to ensure strength for structural use.
．． A thickness of 9 mm or more is used, but if it becomes too thick, it becomes difficult to punch out in the final process, so a thickness of 2.5 mm or less is often used.

Conventionally, non-oriented electrical steel sheets, which are a type of electrical steel sheets, are known to have excellent magnetic properties.
Most plate thicknesses are 0.5 mm or 0.35 mm, and 0.
．． It is not possible to manufacture sheets with a thickness of 9 mm or more due to restrictions on the electromagnetic steel sheet production line. Further, an example of improving the magnetic properties of a steel plate having a thickness of 20 mm or more as an electromagnetic thick plate is known, for example, in Japanese Patent Application Laid-Open No. 1-142028, but productivity is poor because it cannot be wound into a coil. Furthermore, cold-rolled steel sheets such as steel sheets for automobiles with a thickness of about 0.5 to 3 mm are manufactured by continuous annealing, but their magnetic properties are extremely unsatisfactory. In addition, the material used as the electromagnetic soft iron plate has a thickness of 0.6 to 4.5 mm, and its magnetic properties are JIS C
There are some excellent ones as defined in 2504. However, manufacturing requires high-temperature, long-time batch annealing, and the application is limited to small equipment, so it is not possible to mass-produce and at low cost, which is necessary for particle accelerators. Doesn't match. In this way, the thickness of 0.9 to 2
．． 5mm steel plates have not been manufactured to date.

0004

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems, the present invention specifically provides a plate having a thickness of 0.9 to 2,000, which has excellent magnetic properties with a DC magnetic permeability μ1 of 2,800 or more at 1 Oe.
．． A method for manufacturing a 5 mm steel plate for particle accelerators is provided.

[0005]

[Means for Solving the Problems] The features of the present invention for solving the above problems are as follows: C≦0.01% by weight, Si≦0
．． 3%, Mn: 0.1-1.0%, P≦0.3%, S
≦0.02%, Sol. Al≦0.01%, N≦0.0
A slab with 1% balance of iron and unavoidable impurities.
After heating at 950 to 1150°C and hot rolling to a finishing temperature of 910°C or higher to obtain a hot rolled coil, cold rolling to 0.9 to 2.5 mm, and then continuous annealing to 75 mm.
Recrystallization annealing at 0 to 900℃, from recrystallization temperature to 45
1O
The objective is to manufacture a steel plate for particle accelerators that has excellent magnetic properties with a DC magnetic permeability of 2,800 or more. below,
The details of the present invention are as follows.

[0006]

[Function] In order to obtain a high magnetic flux density, the inventors believe that 1.
) Minimize the amount of non-ferromagnetic elements and minimize the number of fine-sized precipitates that interact with domain walls and grain boundaries. 2) To increase the grain size and reduce the number of grain boundaries. 3) Changing the crystal texture to improve {100} in products
To increase the number of grains with plane orientation. 4) Minimize internal stress in the product as much as possible. The present invention was completed by confirming the necessity of the above, designing a manufacturing means, and conducting tests.

First, the reason for limiting the component composition will be described. C: If the amount of C is too large, carbides will precipitate and the magnetic properties will deteriorate, so the content should be 0.01% or less. Si: Although Si is an effective element for ensuring the strength of the steel sheet, it is limited to 0.3% or less due to the problem of addition cost. Mn: Mn is important for controlling the size of sulfide precipitation; if it is less than 0.1%, MnS will precipitate finely, inhibiting crystal grain growth and domain wall movement, and particularly deteriorating excitation characteristics in low magnetic fields. Must be avoided. Also, 1.0
If it exceeds 1.0%, there is a problem of addition cost, so it should be 1.0% or less.

P: P is an element that is very effective in increasing the strength of steel sheets, but when it exceeds 0.3%, it segregates at grain boundaries and on the steel sheet surface, suppressing grain growth. .3
% or less. S: S forms sulfides, inhibits grain growth, and at the same time suppresses domain wall movement, worsening low magnetic field characteristics.
0.2% or less. Sol. Al: Sol. Al forms nitrides that inhibit grain growth and at the same time suppress domain wall motion, resulting in poor low-field characteristics, so the content should be 0.01% or less. N: N combines with Al to form nitrides, inhibiting grain growth and at the same time suppressing domain wall motion, resulting in poor low-field characteristics, so the content should be 0.01% or less. In addition, fixed elements of N and S such as B and Cu, and Sn and Sb for texture improvement
Addition of grain boundary segregation type elements such as these does not impair the effects of the present invention.

Molten steel containing the above elements is continuously cast to form a slab, and the slab is heated at a heating temperature of 950℃.
The temperature should be in the range of ~1150°C. The reason for this is that at temperatures above 1150°C, solid solution of sulfides and nitrides occurs, producing fine precipitates during hot rolling, which suppresses grain growth. In addition, if it is less than 950°C, the finishing temperature of hot rolling described below 91
This is because it is not possible to ensure a temperature of 0°C or higher. During hot rolling, it is necessary to control the finish rolling completion temperature (finishing temperature), and the finishing temperature needs to be 910°C or higher. Because γ
A hot coil structure with a large crystal grain size can be obtained at temperatures above 910°C, and this makes it possible to obtain coarse crystal grains in the final product, and furthermore, it is possible to increase the number of grains with {100} plane orientation in the final product. Because it can be done. In addition, the winding temperature is not particularly regulated, but from the point of view of self-annealing.
00°C or higher is desirable. Hot coil thickness is 1.5-6
．． 5 mm is preferred. The reason is that a reduction ratio of 40 to 75% in the subsequent cold rolling is appropriate from the viewpoint of texture.

[0010] The hot rolled coil is pickled and cold rolled. The finished thickness after cold rolling is 0.9 to 2.5 mm, which is required for a yoke steel plate for a particle accelerator. The temperature reached in recrystallization annealing after cold rolling needs to be 750 to 900°C. Below 750℃, the crystal grain size is small, so μ1 ≧2
I can't secure 800. Temperatures exceeding 900°C must be avoided because if the material enters the γ phase at a temperature exceeding 900°C, the texture will become random and the magnetism will deteriorate due to transformation strain during cooling.

[0011] Also, the cooling rate from the maximum temperature at this time is important. Furthermore, the rolling reduction rate of the subsequent temper rolling is also important. Examples of experiments conducted regarding these cooling speeds and pressure adjustment reduction rates are reported below. Table 1 shows the components of the sample materials.

[Table 1] A slab containing this component and the rest substantially containing Fe is 110
A hot coil with a thickness of 3.5 mm was produced by heating at 0°C to a finishing temperature of 950°C, which was pickled and cold rolled to a 1.5mm thick coil.
mm thickness, and the temperature reached by continuous annealing was 800°C.
After conducting an experiment in which the cooling rate was varied during cooling from 800°C to 450°C, the pressure was adjusted to 0.38% and magnetic measurements were taken to obtain Figure 1. Further, FIG. 2 shows an example in which an experiment was conducted by varying the rolling reduction ratio of pressure regulation for materials whose cooling rates were changed. As can be seen from Figures 1 and 2, the cooling rate is 2.
μ1 ≧2 when the temperature is 0℃/second or less and the pressure regulation is 0.4% or less
This is a necessary condition to obtain 800. This cooling rate can be achieved, for example, by so-called air-water cooling using nitrogen and water spray. The cooling rate is 450℃ from the maximum temperature.
Up to 450 is important, and in our experiments, up to 450
At temperatures below °C, there is no problem with magnetism at cooling rates up to 150 °C/sec. Furthermore, at temperatures below 450°C, the magnetic properties will not be adversely affected even if a thermal history such as soaking is included at a cooling rate halfway to room temperature. The slower the cooling rate from the maximum temperature to 450°C, the better the magnetic properties, but excessive slow cooling poses a problem in productivity, so the lower limit is set at 1°C/sec. After all, the appropriate cooling rate from the maximum temperature to at least 450°C is 1~20°C/sec, and the reduction rate of skin pass rolling is 0.
．． Must be 4% or less. In addition to shape correction by skin pass rolling, it is also possible to use a leveler or the like, but the elongation rate must similarly be controlled to 0.4% or less. Next, examples will be described.

0012

[Example] (Example 1) Molten steel containing the chemical components shown in Table 2 was continuously cast into a slab, and the slab was heated to 1000°C.
Hot rolling was carried out at a finishing temperature of 950°C.
The coiling temperature was set at 650°C to form a hot coil with a thickness of 3.7 mm. Then, after cold rolling to 1.8 mm, 8
After soaking at 30℃ for 10 seconds, heat to 350℃ 3
Cool for 0 seconds (cooling rate: 16℃/second), then 60℃
The mixture was cooled to room temperature at a cooling rate of 1/sec. Pressure adjustment was carried out at a reduction rate of 0.3% to correct the shape, and the sample for magnetic property measurement was placed in a ring (
Wire cut into pieces (outer diameter 120 mm x inner diameter 80 mm), and stack 5 sheets to meet JIS C 25 DC magnetic properties.
Table 2 was obtained by measuring according to 50.

[Table 2] As shown in Table 2, sample No. 1 containing the components within the scope of the present invention. In (1) and (2), the magnetic permeability μ1 exceeded 2800. C,Mn
, P.S., Sol. Comparative sample No. 1 in which Al, N, etc. are outside the scope of the present invention. (3), (4), (5), (6), (7
) and (8) could not satisfy the magnetic permeability μ1≧2800.

(Example 2) Sample No. 2 shown in Table 2. (1)
A slab containing the chemical components of was hot-rolled under the conditions shown in Table 3, and a hot coil with a thickness of 3.2 mm was manufactured at a coiling temperature of 600°C. Next, it was cold rolled to 1.2 mm and recrystallized annealed at 800°C for 6 seconds in nitrogen.
℃ at 10℃/sec. Then 15 at 450℃
It was subjected to soaking treatment for 2 seconds and cooled to room temperature at 100° C./second. A leveler was used for shape correction, and the elongation rate was set to 0.1%. Magnetic properties were measured in the same manner as in Example 1.

[Table 3] As seen in the table, it was necessary for the slab heating temperature and finishing temperature to be within the range of the present invention to obtain the desired magnetic permeability.

(Example 3) Molten steel having the components shown in Table 4 was continuously cast, and the slab was heated at 1020°C for 20 minutes.The finishing temperature was 920°C, the coiling temperature was 630°C, and a 4.0 mm thick hot coil was formed. was manufactured. Then, cold rolled to 2.3m
The experiment shown in Table 5 was conducted to measure the magnetism.

[Table 4]

[Table 5] Recrystallization temperature is 750 to 900℃, μ1 ≧2800
(experiments of samples (1) to (4)), 450
The cooling rate to ℃ must be 20℃/second or less (sample (
5) to (8) experiments), the reduction ratio of skin pass rolling was required to be 0.4% or less (experiments of samples (9) to (11)). From these facts, it was possible to obtain excellent magnetic properties only under conditions that satisfied the scope of the present invention.

[0015]

[Effects of the Invention] As explained above, the present invention has the effect of making it possible to mass-produce steel sheets for particle accelerators with excellent magnetic properties at low cost by strictly controlling the composition, hot rolling conditions, and continuous annealing conditions. has.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between cooling rate and magnetic permeability after recrystallization annealing.

FIG. 2 is a diagram showing the relationship between the reduction ratio of temper rolling and magnetic permeability at each cooling rate after recrystallization annealing.

Claims (1)

[Claims] [Claim 1] C≦0.01% by weight, Si≦0
．． 3%, Mn: 0.1-1.0%, P≦0.3%, S
≦0.02%, Sol. Al≦0.01%, N≦0.0
A slab with 1% balance of iron and unavoidable impurities.
Heating at 950-1150℃, hot rolling, finishing temperature 9
After obtaining a hot-rolled coil at 10°C or higher, it is cold-rolled to 0.
．． 9~2.5mm, then continuous annealing to 750~
Recrystallization annealed at 900℃, then 450℃ from the recrystallization temperature
The product has a DC magnetic permeability of 2800 or more at 1 Oe, which is characterized by cooling at a cooling rate of 1 to 20°C/sec during the rolling process, and performing the final temper rolling at a reduction rate of 0.4% or less. A method for manufacturing a steel plate for particle accelerators using continuous annealing that has excellent magnetic properties.