JPS6283422A - Manufacture of electrical steel sheet excellent in punchability - Google Patents

Abstract

PURPOSE:To manufacture an electrical steel sheet combining superior punchability and magnetic properties by subjecting a steel having a specific composition containing a large amount of C to hot rolling, annealing at a specific temp., cold rolling, and then recrystallization annealing. CONSTITUTION:The steel consisting of, by weight, 0.1-1.0% C, <=3.5% Si, one or more kinds among <=2.0% N, <=1.0% Al and <=1.0% Cu and the balance Fe with inevitable impurities is hot-rolled. Subsequently, the steel is annealed at 600-800 deg.C to precipitate graphite, which is subjected to cold rolling and recrystallization annealing. Further, in the precipitation of graphite, it is preferable that soaking time is regulated according to the components in order to perfect the precipitation.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a 1tlia chain plate which has immersed magnetic properties and has extremely good punchability.

<Background technology> Generally, electromagnetic steel sheets are used as materials for various transformers, ballasts, and iron cores of various types of electric appliances, but in recent years, they have been used for improving the small edges and sieve performance of electrical appliance products, and for energy saving1. From this point of view, there is a growing demand for high-performance electrical steel sheets with even higher magnetic properties.

On the other hand, electromagnetic steel sheets undergo a punching and laminating process before being formed into the iron core of transformer FE machines and TT IIf II machines, so they not only have excellent quantity characteristics but also have good punching properties. They are also required to be prepared.

For this reason, conventionally, when making 1112 type electrical steel sheets, the surface was coated with an organic component such as acrylic resin to ensure coulometric insulation and provide external lubrication for the punching process. Measures 4 have been taken, but when assembling molded products, the edges are sometimes welded to fix the laminated iron cores, and in this case, the coating skin is removed during welding. There was a problem in that the wired components during the exchange were likely to evaporate and cause welding defects such as blowholes, which inevitably limited the coating film thickness.

For these reasons, there has been a strong desire to develop an electrical steel sheet in which the material itself has dipped punchability.

By the way, as the punching work for the 6B 'd'tl board continues, the punch bar 11 gets worn out, and the clearance between the punch and die gradually widens, resulting in an increase in the number of burrs on the punched product. For this reason, if the value of the above-mentioned "9 burrs" becomes larger than the value, it becomes necessary to perform mold polishing Ff4 (a). Therefore, in electromagnetic machines, a steel plate that can be punched out more in one die polishing is evaluated to have better punching properties.

In other words, in order to improve the punching property of the steel plate, it is necessary to include precipitates and inclusions in the steel sheet to reduce the "peelability" of the steel plate during punching, as seen in free-cutting steel. It is effective to raise the level.

However, in order to improve the magnetic properties of electrical steel sheets, it is considered necessary to reduce the supply of impurity elements in the C-temperature and to suppress precipitates and inclusions.
There has been an extremely troublesome problem in that high-grade electrical steel sheets have poor punching properties.

<Means for solving the blanking point> The present inventors have solved the problems mentioned above in 1. in the production of electric 6θ steel sheets, and have developed an electromagnetic material that has both excellent magnetic properties and good punchability. As a result of repeated research in order to provide steel sheets, the following findings were obtained: (a) It is possible to heat steel that contains a much higher amount of C than is common knowledge in conventional electrical steel sheets. When annealing under specific conditions is performed after rolling, coarse graphite is precipitated in the steel sheet matrix, and the punchability of the steel sheet is significantly improved. The amount of molten C becomes extremely low, and the coarsely precipitated graphite at t7 does not interfere with grain growth or movement of domain walls, so the substrate is coated with elements such as Si and Ag that are effective in reducing eddy current loss. If a ferrite structure is used, an electromagnetic steel sheet with magnetic properties comparable to that of a conventional ultra-low C type magnetic steel sheet can be used.

(cl) Even if the above-mentioned high C-containing steel is hot rolled 12, cold rolled and then subjected to graphite precipitation annealing, the punchability of TRI is noticeably improved; however, graphite annealing after hot rolling causes coarse graphite precipitation. When cold rolling is performed after that, the state shown in FIG. 1(a) changes from the state shown in FIG. 1(b).
), the coarse graphite 1 extends in the rolling direction and is distributed in a long and narrow manner, increasing the effective graphite area A in the punching direction (arrow direction in FIG. 1) and further improving punching performance. In Fig. 1, numeral 2 indicates an electromagnetic steel sheet, and numeral 3 indicates expanded graphite. If graphite precipitation annealing is performed again after baling and then cold rolling, an electromagnetic steel sheet with improved punchability can be obtained even if the graphite precipitation annealing time of the hot rolled sheet is short.

This invention was made based on the above findings, and contains C: 0.1 to 1.0% (hereinafter, % representing the component ratio is a weighted %), Si: 3.5% or less. and also contains one or more of the following: Ni: 2.0% or less, AJ: 1.0% or less, Cu: 1.0% or less, and the balance is Fe and unavoidable impurities. extended, then 600
After annealing at ~800°C to precipitate graphite, cold rolling is performed and then recrystallization annealing is performed? or 6
After annealing at 00 to 800°C to precipitate the bluff, cold rolling is performed.

Next, 600~b An electromagnetic steel sheet that has both excellent punchability and magnetic properties by precipitating and filtration of graphite? It has the following characteristics:

Next, the reason why the composition and treatment conditions of the steel material are numerically limited as described above in the method of the present invention will be explained.

A. Composition of material steel MI composition a) C C precipitates in the steel plate as coarse graphite by prescribed annealing, and is an Iiv component that improves the punchability of the steel plate, but if its content is less than 0.1%, coarse graphite will form. Precipitation becomes difficult and sufficient punching effect cannot be secured, while if the content exceeds 10%, hot rolling becomes difficult.
Therefore, the C content was determined to be 01 to 1.0%.

b) 5i Si is an effective component for improving the magnetic properties of electric 6!1m plates and promoting the precipitation of graphite, but if its content exceeds 3.5%, the workability of the iron will deteriorate, so Si-containing The risk of death was set at 3.5% or less. Although Si exhibits certain effects even in extremely small amounts, the content is preferably 0.1% or more. Better to secure it.

c) Nl, Al + and Cu These components are also effective elements for promoting the precipitation of graphite, and even if added in an amount < mm, they exhibit a certain effect, so one or more of them can be included. 2.
Ni over 0%, M over 1.0%, and 1.0
Even if the Cut content exceeds 2.0%, the graphite precipitation promoting effect does not significantly improve, and it is economically unfavorable.
．． The Cu content was determined to be 0% or less, and the Cu content was determined to be 1.0% or less.

B. Processing conditions a) Temperature of annealing to precipitate graphite If the temperature of graphite precipitation annealing (including cases where it also serves as recrystallization annealing) is 600°C or less, sufficient graphite precipitation will not be achieved. It is difficult to stably secure satisfactory magnetic properties, and the same problem occurs even when the annealing temperature for graphite precipitation exceeds 800°C, so the annealing temperature was set at 600 to 800°C.

In this way, in the case of steel with the above-mentioned composition, the most effective annealing temperature for graphite precipitation is 600 to 800°C, but in order to completely prevent graphite precipitation, the soaking time should be adjusted according to the composition. It is preferable to do so.

Note that normal conditions are sufficient for the hot rolling and cold rolling carried out in the method of this invention, and for recrystallization annealing not intended to precipitate graphite, either box annealing or continuous annealing may be adopted. There is no problem. However, box annealing is preferably used for graphite precipitation annealing and recrystallization annealing that also serves as graphite precipitation.

Next, the present invention will be explained using examples and comparing with comparative examples.

<Example> Example 1 First, the first
After obtaining a steel slab with the composition shown in the table, it was hot-rolled to form a 2.3M thick hot-rolled coil, which was then sequentially subjected to graphite precipitation annealing, pickling, and cold rolling. A .5cm thick cold-assembled sheet was produced.

Next, the above cold-rolled coil is recrystallized and annealed'? The magnetic properties and punchability of the electrical hH steel sheet obtained by this process were measured. Incidentally, the punching property was evaluated by the number of punching operations until the "burr" reached 50 μm.

The obtained results are shown in Table 2 together with the processing conditions.

The results shown in Table 2 also show that by adopting the method of the present invention, it is possible to stably produce an electrical steel sheet with significantly superior punchability despite having the same magnetic properties as conventional ultra-low C electrical steel sheets. ．． It is clear that it can be manufactured using

In this example, box annealing was used as recrystallization annealing, but it was also confirmed that a TAI steel plate with equivalent performance could be obtained even if continuous annealing was used instead of box annealing, which tends to impair flatness. However, in this case, it is desirable to set the annealing temperature to 700°C or higher.

In addition, the punching properties of electric 6F1 steel sheets are generally evaluated by measuring the number of punches until one burr becomes 50 μm, but this requires a large-sized test piece, and It also takes a lot of time to set up the mold, measure it, etc.

However, the present inventor found that by measuring the variation relationship between the punch stroke and punching load during one punching process as shown in Fig. 2, and comparing the results, it is possible to accurately evaluate the punchability of the electrical steel sheet. It was discovered by et al.

That is, in Fig. 2, the shear stroke (S) in the range indicated by the arrow corresponds to the part where the material breaks in shear due to its viscosity during punching. This is the important part. Therefore, the smaller the shear stroke is compared to the plate thickness, the more brittle the material is punched and the smaller the burr.
By comparing the shearing strokes, punching performance can be accurately evaluated.

Now, Figure 3 shows the shear stroke ratio (relative to plate thickness) of a steel plate produced by the method of the present invention and a steel plate produced from conventional steel (extremely low C@) with almost the same composition except for the C-containing coating. From Figure 3, the relationship between the shearing strength and the shearing strength is as follows:
It can be seen that the steel sheet produced by the method of the present invention has smaller "burrs" during punching than the conventional material θ), and has fewer central pillars in the mold, resulting in markedly improved punchability. It is obvious that it is a steel plate.

By the way, Fig. 4 is a microscopic photograph showing the electric steel sheet produced by the method shown in Test No. 1. However, extrusion with improved n-removal properties will be well covered. In addition, when the C material contained in the same bath 12 was measured in the base material at this time, it was confirmed that the value was 5 oppm or less.

Real power example 2 The same move as in real power example 1++m"2 @1-&
Hot-rolled coil (thickness 2, 3
M)? The coil was then sequentially subjected to graphite precipitation annealing, pickling and cold FE rolling to produce a cold rolled coil of 0.5 mW.

Subsequently, the W''A properties and punchability of the electric α* steel sheet obtained by recrystallization annealing (11-1), which also served as galafite precipitation annealing during bat rolling coil history, were measured.

The obtained results and processing conditions are shown in Table 3. The punching property was evaluated using the above-mentioned "shear stroke ratio".

From the results shown in Table 3, it is clear that even if graphite precipitation treatment is performed twice before and after cold-open rolling, if m, which has a component composition that satisfies the conditions specified in the present invention, is used, the magnetic properties and punching will be improved. It is clear that a Fi1m plate with excellent properties can be obtained.
I can also understand that.

<Summary Effects> As described above, according to the present invention, it is possible to stably produce an electric wire 611m1 that not only has excellent magnetic properties but also has extremely good punching properties. This will bring about useful effects for industry, such as making it possible to

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the distribution state of coarse graphite precipitated in the construction method of the present invention and the state of the coarse graphite expanded by cold rolling. Fig. 1(b) shows the state as it is precipitated by processing after hot rolling, and Fig. 1(b) shows the state after being stretched by cold rolling. Figure 2 of TOA is a graph showing the relationship between the punch stroke and cart during punching of electrical steel sheets, Figure 3 is a graph comparing the shear strength and shear stroke ratio of the invention material and conventional material, Figure 4 1 is a microscopic micrograph of a cross section of a steel plate molded according to the present invention obtained by a central example. In the drawing. 1...Coarse graphite, 2...Electromagnetic steel sheet-3
...Extended graphite. Day ro residence〉 10 taste 1 [ (%) old ρ-[7-1 to the currency-I! @

Claims (2)

[Claims] (1) Contains C: 0.1 to 1.0%, Si: 3.5% or less, and Ni: 2.0% or less, Al: 1.0% or less, Cu : 1.0% or less, and the balance is Fe and unavoidable impurities.
A method for manufacturing an electrical steel sheet having both excellent punchability and magnetic properties, characterized by precipitating graphite by annealing at 00°C, followed by cold rolling, and then recrystallization annealing. (2) Contains C: 0.1 to 1.0% and Si: 3.5% or less in weight proportion,
and. A steel containing at least one of Ni: 2.0% or less, Al: 1.0% or less, Cu: 1.0% or less, and the balance consisting of Fe and unavoidable impurities is hot rolled, and then 600-8
Excellent punchability and magnetic properties characterized by annealing at 00°C to precipitate graphite, followed by cold rolling, followed by recrystallization annealing at 600-800°C to further precipitate graphite. A method for manufacturing electrical steel sheets that combines the following.