JPH02277747A - Semiprocess nonoriented silicon steel sheet having excellent blanking properties - Google Patents

Abstract

PURPOSE:To obtain the steel sheet having improved blanking properties by regulating the compositional limiting value and controlling the recrystallization rate in the structure of the steel sheet after subjected to final finish annealing to a prescribed range. CONSTITUTION:Sheet-manufacturing is executed so that the recrystallization rate (alpha) after final finish annealing in a steel sheet of prescribed sheet thickness constituted of, by weight, <=0.005% C, <=1.0% Si, 0.1 to 0.5% Mn, <=0.2% P, <0.01% S, <=0.5% Al and the balance Fe with inevitable impurities is controlled to 50<=alpha<=80 (%). In this way, good punching properties in which the height of burrs is reduced can be obtd. and no problem is produced as for the growth of the grains at the time of stress relief annealing even if unrecrystallization structure is left, by which stable magnetic characteristics can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semi-processed non-oriented electrical steel sheet that is intended for strain relief annealing in customers.

[Conventional technology]

So-called low-grade non-oriented electrical steel sheets with a Si content of 1% or less are
Although it has a high iron loss value, it has a high magnetic flux density and is low cost, so it is used in large quantities in small motors for household electrical appliances. Such steel sheets are broadly divided into fully processed materials, which are punched by customers and then assembled into products as is, and semi-processed materials, which are subjected to strain relief annealing after punching. For semi-processed materials, the magnetic properties before strain relief annealing are not important, and it is necessary to show excellent magnetic properties after strain relief annealing. In addition, since these steel plates are punched in large quantities using a continuous punching machine, they can be stably punched into good shapes, and the wear of the molds is small.
Excellent punchability is considered to be a very important characteristic of products.

Punching performance is determined not only by factors on the steel plate side, such as the flatness and material of the steel plate, and the type and thickness of the insulating film, but also by factors on the customer side, such as the material of the mold, clearance, and the type and amount of lubricant used. acts in a complex manner. For this reason,
Improvements in punchability are still not sufficient, and there is still a high demand for steel sheets with even a slight improvement in punchability.

Conventionally, in order to improve the punchability of electrical steel sheets, for semi-processed materials, the following techniques were used: ■ A commonly known technique of adjusting hardness through skin pass rolling after finish annealing.

■Technology that performs final finish annealing at a low temperature of 700°C or less for a short time to increase hardness by reducing the recrystallized grain size. (Unexamined Japanese Patent Publication No. 60-106915) ■ A technique for increasing hardness by performing final finish annealing as recovery annealing below the recrystallization temperature. (Tokuko Showa 62
(No. 21849, Japanese Patent Publication No. 82-49321) (1) A technique of adjusting the C content to about 0.03 to 0.1 θ%, rapidly cooling after annealing, and subsequently performing temper rolling to increase hardness. (Japanese Unexamined Patent Publication No. 58-34114), studies have been conducted with emphasis on adjusting the hardness of steel plates, particularly on increasing the hardness.

[Problem to be solved by the invention]

According to the above method, the hardness of the steel sheet increases and the punching property is improved to some extent, but the level is by no means satisfactory (it is not sufficient to achieve sufficient punching with a method that uses only hardness adjustment). Therefore, the inventors of the present invention conducted extensive experiments in order to develop an electrical steel sheet with better punchability.The inventors of the present invention found that in order to obtain better punchability, it was necessary to improve the strength of the steel sheet rather than simply adjusting the hardness. It was discovered that it is necessary to optimize the structure and control the recrystallization rate from the viewpoint of structure control.

[Structure of the invention]

The present invention was made based on such knowledge, and aims to improve the punchability of semi-processed non-oriented electrical steel sheets that are subject to strain relief annealing. The punching property is improved by controlling the ratio of crystalline parts to 50% to 80%.

That is, the semi-processed non-oriented electrical steel sheet of the present invention has C
: 0.005wt% or less, Si: 1.0wt% or less, M
n: O, 1 to 0.5 wt%, P: 0.2 wt% or less, S
: less than 0.01 wt%, ^jl:o, 5 wt% or less, the remainder consists of Fc and unavoidable impurities, and its basic principle is that the recrystallization rate α after final annealing is 50≦α≦80 (%). Features.

Below, the content of the present invention will be explained in detail based on the results of experiments conducted by the present inventors for improving punched housing.

Slabs of steel A and steel B in Table GA1 were heated to 1200°C, then hot rolled at a finishing temperature of 850°C, followed by pickling,
It was cold rolled into a 0.5 m thick steel plate. Figure 1 shows the relationship between steel plate hardness and paring height when 10,000 samples were punched out of each of these steel plates whose hardness was varied by final annealing at different temperatures. As shown in the figure, in this experiment, it can be seen that for both Steels A and B, the par height does not change uniformly with hardness, but that only specific regions exhibit extremely excellent punching properties. Furthermore, the hardness level of the region with excellent punchability varies by more than 40 points depending on the steel type, and it is also much better than other types of materials with the same hardness level. It can be seen that steel plates cannot be uniquely defined by their hardness. Therefore, we again examined in detail the factors governing punchability, and found that all of these specimens exhibiting extremely excellent punchability had a partially recrystallized structure because they were annealed near the recrystallization temperature. This is because the first factor that influences punchability is the structure of the steel sheet.
The hardness of the steel plate is only a secondary factor, and in order to improve punchability, it is necessary to improve the steel plate structure in the unrecrystallized or recrystallized structure [11] This suggests that a greater effect can be obtained by partial recrystallization.

Figure 2 is a replot of the recrystallization rate α for the region with extremely excellent punchability and its vicinity from the data in Figure 1, in order to see in more detail the influence of the recrystallization rate on the punchability. be. Incidentally, the recrystallization rate was determined as an area ratio from a photograph of the cross-sectional structure.

As is clear from the figure, there is not much difference in Paris height depending on the steel type, and it depends almost exclusively on the recrystallization rate.
For both C, the Paris height is the smallest in the region where the recrystallization rate is 50% to 80%, and in other regions where the recrystallization rate is 80 to 100% or the recrystallization rate is 50 to 0%, the Paris height is sharp. It can be seen that there is an increase in The reason why the Paris height shows such a change is thought to be that when the recrystallization rate is low, the wear of the mold progresses due to hard unrecrystallized parts, and conversely, when the recrystallization rate is close to 100%. This is thought to be due to the presence of a soft recrystallized structure that causes adhesion between the steel sheet and the mold, leading to accelerated wear of the mold.

On the other hand, in the steel of the present invention having a recrystallization rate of 50% to 80%, the ratio of hard unrecrystallized parts is small, so that the adverse effect on die wear is small. Rather, it is thought that due to the presence of a suitable amount of brittle unrecrystallized parts, cracks propagate easily during punching, and the shear energy is lower than that of a completely recrystallized material, improving punchability. Regarding the problem of adhesion, since there is a mixture of recrystallized and non-recrystallized structures, it is thought that the hard non-recrystallized parts will peel off the recrystallized parts that have been baked into the mold, and the adhesion between the steel sheet and the mold will increase. is also less likely to occur.

In the present invention, based on the influence of the recrystallization rate on the punchability described above, the recrystallization rate is 50%, which significantly reduces the par height.
The range of ~80% is defined as the optimal tissue range for improving punchability.

Next, the reasons for limiting the components in the present invention will be explained.

If a large amount of CTC is contained, decarburization annealing will take a long time, and if decarburization is insufficient, magnetic properties will deteriorate due to magnetic aging, so the steel should be made of ultra-low carbon steel with a content of 0.005 wt% or less. .

SL: An increase in Si has a great effect of increasing resistivity and reducing iron loss, but if it exceeds 1vL%, it decreases the magnetic flux density in a high magnetic field and also leads to an increase in cost.
t% or less.

Mn: Mn has the effect of precipitating and coarsening S in steel as MnS and improving grain growth during strain relief annealing, so the lower limit is set to 0.1 νt%. The upper limit is set at 0.5 wt% from a cost perspective.

Although FDP is effective in improving punching properties, the upper limit is set at 0.2 wt% due to cost considerations.

SOS is an element that is essential to magnetic properties, and is limited to less than 0.01 wt% in order to control the total amount of MnS precipitation.

AN: Like Si, AII has a great effect of reducing iron loss, but if it exceeds 0.5 vL%, the magnetic flux density decreases significantly, so it is set to 0.5 vL% or less.

Note that the addition of trace elements such as Sn, Sb, and B has little effect on punching properties and is therefore not essential in the present invention, but may be added to improve magnetic properties.

〔Example〕

The three types of steel slabs shown in Table 2 were heated to 1200°C.
Hot rolling was carried out under finishing conditions of 850°C, followed by pickling and cold rolling to obtain a steel plate with a thickness of 0.5 mm.

For these steel sheets whose recrystallization rate was changed by changing the finish annealing temperature, the punchability was evaluated by the par height after -Gallo punching, and the magnetic properties after strain relief annealing were also investigated. As is clear from the results shown in Table 3, in the steel of the present invention with a recrystallization rate of 50% to 80%,
It can be seen that the par height was extremely reduced in all cases, and good punching performance was obtained. On the other hand, each invented steel
The magnetic properties after strain relief annealing are at the same level regardless of the recrystallization rate, and even if an unrecrystallized structure remains, there is no problem with grain growth during strain relief annealing, and stable magnetic properties can be obtained. All of the materials with recrystallization rates other than the range of the present invention had a high par height and good punchability was not obtained.

〔effect〕

As described above, according to the present invention, in a semi-processed non-oriented electrical steel sheet, C
There is no deterioration in product properties such as magnetic aging caused by pressure adjustment or deterioration of flatness due to pressure adjustment, and it is possible to provide a steel sheet with extremely excellent punchability economically.

Table 1 No. table 4,

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between steel sheet hardness and paris height, and Fig. 2 is a graph showing the relationship between steel plate recrystallization rate and paris height. Figure 2 Recrystallization rate (CA)

Claims (1)

[Claims] C: 0.005wt% or less, Si: 1.0wt% or less,
Mn: 0.1 to 0.5 wt%, P: 0.2 wt% or less,
It consists of S: less than 0.01 wt%, Al: 0.5 wt% or less, the remainder Fe and unavoidable impurities, and the recrystallization rate α after final annealing is 50≦α≦80 (%). A semi-processed non-oriented electrical steel sheet with excellent punchability.