DE3107942C2 - Non-oriented silicon steel sheet with uniform magnetic properties - Google Patents

Abstract

The invention relates to a non-oriented silicon steel sheet with low watt loss and uniform magnetic properties, which contains 1.5 to 3.5% Si, has a particularly low C content and a low soluble Al content, and a ratio of B to N in the range from 0.4 to 2.0 and further contains at least one rare earth element. The relationship between watt loss and Ce content is shown in FIG.

Description

The subject of the invention is a non-ventilated silicon steel sheet with uniform magnetic properties.

Among the silicon steel sheets that are soft magnetic materials, there are the following types: Grain-oriented silicon steel sheets that are recrystallized Have collecting texture, which crystallographically with the designation (UO) [001] and its (HO) -plane in the rolling plane and your [001! -orientation in the rolling direction hai, and non-ventilated silicon steels with negligible orientation. These Materials are used as Elsenkern for electrical equipment, which for certain applications can be selected based on your magnetic and mechanical properties and your manufacturing costs.

For example, grain-oriented silicon steel sheet is excellent because of its high cost magnetic properties in general for transformers and mast transformers of large capacity used. It is namely very easily magnetizable in the rolling direction, i. H. in [O0]) direction, has a very low wattage loss and very high permeability.

On the other hand, ventilated stainless steel sheet is used Usually subdivided into the following two classes: Longer-value, non-ventilated stainless steel sheet with a Sl content between almost 0 and 1.5% and high Quality, chlorine-vented silicon steel sheet with over 1.5% Sl. Since these materials have such a poor orientation that it is negligible, and yours Costs Are Low, They Are Used In Large Scale For klclndlmenslonlene electric motors, medium-sized transformers, and medium to large rotating machines used.

A key trait that is common to those who are not very young Slllzlumslahlblech is required, Is a low watt loss value, The watt loss mainly consists of the hysteresis loss and the eddy current loss. In the case of non-oriented SHizIum steel sheet, the hysteresis loss is prevented most effectively by that the crystal grain size is increased. Eddy current loss can be reduced by increasing the resistivity of the steel; H. with others Words, by adding alloying elements such as Si.

ίο A means of increasing the crystal grain size represents a high-temperature annealing that is carried out over a long period of time. However, this is disadvantageous for reasons of cost. There are also long glow tents with them usually carried out continuous annealing drive hard to get to.

The inhibition of the growth of the crystal grains is is known to be closely related to inclusions and precipitates distributed in the steel. The size of the inclusions and excretions and their dispersion stand are very important. In general, it is believed that the presence of a lot of fine inclusions and precipitates are not favorable to the growth of crystal grains. As substances that are dispersed in Phase Contained in non-oriented silicon steel sheet are, various oxides, such as AIjOj or SiÜ2, and various sulfides and nitrides such as MnS and AlN can be mentioned. As for the oxides, must these were only collected during steel production and allowed to float up as deoxidation products the. In addition, there must be oxidation during pouring ßens the molten steel can be prevented. As a result of recent advances in steelmaking, Oxide inclusions can be easily prevented. A widely used method for off Switching of the sulphides consists in a careful through conduct the desulfurization in steel production, while at the same time a sufficient amount of Mn or of a similar element is added. Then the heating temperature of the slab before hot rolling becomes so that the MpS kept the growth of the

Crystal grains are not adversely affected. Through the Sulphides do not use this method Difficulty. To keep the inclusion of nitrides low. is

it is best to keep the nitrogen content in steel production as low as possible. However, a consistent reduction in the nitrogen content in silicon steel to values below 10 ppm is very difficult. Usually the nitrogen content is around 30 ppm.

The reaction of N with Al, which is used for deoxidation, or with Al contained in silicon alloys leads to the formation of AlN. Since an Al level in the range of 0.005 to 0.15% is harmful to the door Growth of the crystal body is, was at the manuf Development of lower value non-oriented silicon steel sheet with a content of less than about 1.0 to 1.5% Sl the amount of Al for deoxidation as far as possibly reduced, preferably to values below 0.005%. Be! high-quality, non-oriented slllzl steel sheet with a grade greater than about 1.0 up to 1.5% Sl, the Al content is set to values above 0.15% and the AlN is excreted in a form which does not interfere with the growth of crystal grains, if the steel slab is heated.

In the former case, however, there are some Difficulty trowels, such as insufficient deoxidation in the Steel manufacture or the appearance of surface η defects in the steel sheet. In the latter case increase as a result

the consumption of a large amount of Al is inevitable the manufacturing costs,

As an effective method for stabilizing the deoxidation in steel production while avoiding the increase in costs caused by the use of large amounts of Al, a cheap method for the production of non-oriented Sllizlumstahlbtech with excellent watt loss values by adding Boron suggested. It has been found, however, that in the production of steel sheet with a very low C content (at most n.015%) by this process, the product does not have completely uniform magnetic properties.

A composition for a cold rolled, non-oriented silicon steel characterized by the following composition, given in% by weight: 0.5 to 4% silicon, up to 0.8% aluminum, 0.05 to 0.5% manganese, not more than 0.012% sulfur, up to not more than 0.196% carbon and an effective amount of up to 400 ppm cerium, remainder iron, is known from DE-OS 26 22 353. With this steel composition the Cergehail is used to control sulphide formation and to prevent the environmentally harmful smoke that usually occurs when the melt is desulfurized occurs. The Al content is given without a lower limit; however, a range of 0.2 to 0.5% Al is preferred.

It is an object of the invention to provide a non-oriented silicon steel sheet with uniform magnetic properties. This task is achieved by a steel with the composition according to claim 1.

The invention relates to a non-oriented silicon steel sheet with uniform magnetic properties, consisting of:

at most 0.015% carbon

1.5 to 3.5 * silicon

0.05 to 1.0 * manganese

0.005 to 0.08% acid soluble aluminum

0.001 to 0/120% of at least one rare earth element at most 0.015% sulfur

at most 0.010% oxygen

0.005% nitrogen or less

Remainder iron and unavoidable impurities,

which is characterized in that the steel additionally contains boron, in such an amount that the Ratio of boron to nitrogen ranges from 0.4 to 2.0.

In the accompanying drawing:

Fig. 1 is a graph showing the relationship between the Si content and the ratio of precipitated nitride to total nitrogen;

Fl g. Fig. 2 is a graph showing the relationship between Ce content and watt loss;

Flg. 3 is a graph showing the fluctuation of Walt's loss.

Investigations into the excretion behavior of Nitride with a very low C content (at most 0.015%) have shown that in a steel with a content of at least 1.5% SI, in particular with at least 2.0% SI, and at most 0.010% C, the amount of N which precipitates out as nitride in the hot-rolled sheet, very low is; see Flg. 1.

FIG. I shows in a graph the relationship between the ratio (in %) of the nitride precipitation to the total nitrogen content and the Si content (in%).

The chemical composition of the sample is such that the content of C is at most 0.010%, of soluble Al 0.008 to 0.050%, for N at most 0.005% and for B 0.0010 is up to 0.0050%.

■ i The insufficient nitride precipitation in the hot-rolled steel sheet is therefore probably the cause of the inequality of the watt loss values for very low carbon content. Based on this assumption, investigations were made

in which it was found that the tendency for small changes in watt loss can be eliminated and the magnetic properties made uniform when using silicon steel with a very low C content and a low content of soluble

ü Lichem Al boron is added, so that the ratio B to N is in a certain range and when a small amount of a rare earth element also coexists. The invention is explained in detail below tert.

The steel according to the invention is used, for example, in an electric furnace, Siemens-Martln-Of: n or a converter, and then, if necessary, in refined in a vacuum refining oven in order to

i:> content to be reduced to a maximum of 0.015%. Preferred is a C content of at most 0.010%, in particular at most 0.005%. Then the required amounts of Al, Si, Mn, B and the rare earth metal added.

m The Si content is controlled depending on the required amount of watt loss. However, if the Si content is over 3.5%, the cold rollability of the Steel deteriorates. Because a high quality non-oriented silicon steel sheet is obtained by the invention

js should be, the Sl content is set to the range of 1.5 concentrated to 3.5%.

Al is added to deoxidize the steel. A Soluble Al content of less than 0.005% results in insufficient deoxidation. An insufficient one

ji · Soluble Al content also causes difficulty in slab casting, leads to an increase in Splinter formation on the surface of the steel and causes chlechle results with respect to the addition of B and the rare earth element. The Al content therefore becomes

J ι to at least 0.005 * fesigeseUL Ein hüliei Al-Gehaii on the other hand, not only leads to an increase in costs, but also destroys the effects of 3 and the rare earth metal. The Al content should therefore not exceed 0.08% be. Is preferred for the soluble Al content

κ »the range from 0.015 to 0.050%.

Mn is added in an amount of at least 0.05% in order to prevent brittle fracture in hot rolling and to compensate for the resistivity of the steel due to the low Al content to

«To reduce his loss of water. On the other hand, the

The upper limit of the Mn content is set at 1.0% because the

magnetic properties of the steel due to high Mn content will deteriorate.

Since S deteriorates the magnetic properties,

bo will be its content r, us at most 0.015%, preferably not more than 0.007%.

After O also the magnetic properties Generally deteriorates and also causes useless consumption of B and rare earth metals,

bj wlid limit his salary to a maximum of 0.010%.

When the de · N content exceeds 0.005%, it causes deterioration of the inherent magnetic sounds and causes costs as a result of the increase in the required

the same B content. The upper limit for the N content is therefore set at 0.005%.

The B content of the steel is adjusted so that the weight ratio of B to N is in the range of 0.4 to 2.0, since the watt loss increases as this ratio becomes higher or lower. Since a rare earth element is contained in the steel, the preferred range of the ratio B / N is 0.6 to 1.5 from the viewpoint of reducing the watt loss.

Another important element besides the B described above is the rare earth metal. At least 0.001% of at least one rare earth metal is necessary to prevent the non-uniformity of magnetic properties in some degree in Slllzlumstahl with very low C and a low-soluble Al content is observed. If the content of the rare earth element is more than 0.02%, the amount of inclusions increases so much that deterioration of the critical properties is prevented. The content of the rare earth element is therefore set in the range of 0.001 to 0.020%.

The results of the investigations relating to the values of the watt loss in Slllzlum steels with very low C content and low soluble Al content. which contain Ce as a rare earth metal together with B, have been carried out, in Flg. 2 shown.

In addition to Ce and B, the steel samples contain 0.003 to 0.008% C. 0.005 to 0.080% soluble Al and 2.2% Sl.

In Flg. 2 means:

X no boron addition

Δ Ratio B / N below 0.4 or above 2.0 O Ratio B / N In the range from 0.4 to 2.0.

In Flg. 2 It can be seen that stainless steel with a ratio B / N in the range from 0.4 to 2.0. the also contain Ce, have a low wattage loss, In particular, silver steels with 0.001 to 0.020% Ce have a low watt loss and excellent magnetic properties. The effect of the simultaneous presence of B and Ce is remarkable for steels with a very low carbon content of at most 0.005%.

On the other hand, there is the watt loss in Slllzlum steels. which contain Ce alone or have a B / N ratio of less than 0.4 or more than 2.0, high.

A mixture of metals can be used as the rare earth metal an ordinal number between 57 and 71 can be used. Misch metal, about 50% Ce, the rest mainly Lanthanum and neodymium. Is an inexpensive one Example of such a mixture. Ce is used as the preferred catfish.

All suitable methods for pouring the steel melt into a slab or a BIiKk and for processing the ingot or the slab are possible. The steel slab is heated as usual in a furnace to a temperature in the range of 1050 to 1250 "C and rolled to a thickness in the range of about 1.5 to 3.0 mm. After removing the oxidized surface layer of the hot-rolled sheet, it becomes 2V rolled to the thickness of the end product The hot rolled sheet can be annealed or double cold rolled, in which case the annealing / wiping is carried out in two cold rolling steps, or a combination of these process steps can be used.

The cold-rolled sheet is continuously annealed and coated with an insulating film. It becomes the end product obtain.

The examples illustrate the invention.

Example I.

Steel slabs with the specified in Table I. Composition are made in the converter, refurbished in a vacuum degassing vessel and thoroughly cleaned Continuous casting produced. The resulting slabs are heated in a furnace to 1150 "C to a thickness of 2. "! mm hot-rolled, if necessary annealed at 900 ° C, descaled and then to a thickness of 0.5 mm cold rolled. The cold-rolled sheets are then annealed at 900 or 950 ° C for 60 seconds magnetic properties of Epsteln samples of each steel sheet are summarized in Table II.

Tabel I. Classification C. Si Mn solves. Al S. N B. Β / Ν Ce O sample % 0 / % % % % % % β / No. invention 0.003 2.20 0.25 0.025 0.007 0.0022 0.0020 0.91 0.004 0.003 1 invention 0.004 2.22 0.30 0.065 0.007 0.0018 0.0030 i, 67 0.008 0.0 ^ 2 2 invention 0.003 "» Ir 0.41 0.028 0.006 0.0026 0.0020 0.77 0.014 0.002 3 invention 0.003 2.25 0.66 0.018 0.007 0.0021 0.0030 1.43 0.017 0.004 4th invention 0.004 2.88 0.30 0.022 0.005 0.0026 0.0022 0.85 0.005 0.002 5 invention 0.005 2.93 0.62 0.043 0.005 0.0023 0.0031 1.35 0.009 0.002 6th invention 0.003 2.92 0.22 0.032 0.004 0.0023 0.0020 0.87 0.016 0.002 7th invention 0.004 2.83 0.18 0.044 C.004 0.0020 0.0024 1.20 0.011 0.002 8th comparison 0.004 2.30 0.26 0.031 0.007 0.0026 0.0022 0.85 0.026 0.004 9 comparison 0.004 2.16 0.20 0.022 0.006 0.0031 - - 0.009 0.003 10 comparison 0.003 2.27 0.36 0.024 0.007 0.0022 0.0022 1.00 - 0.002 11th comparison 0.021 2.19 0.33 0.021 ο, ουό 0.0033 0.0029 0.88 0.010 0.004 12th comparison 0.004 3.01 0.22 0.033 0.004 0.0024 0.0020 0.83 0.024 0.002 13th comparison 0.004 2.88 0.22 0.038 0.004 0.0026 - - 0.013 0.002 14th comparison 0.003 2.95 0.26 0.035 0.004 0.0023 0.0024 1.04 - 0.004 15th comparison 0.025 2.83 0.21 0.041 0.004 0.0026 0.0020 0.77 0.008 0.002 16

Table II Classification

Process steps after hot rolling the steel sheet

Temp, of the magnetic Final properties

glowing, _w 15/50, β 50, T

° ^c W / kg

Invention Invention Invention Invention Invention Invention Invention comparison comparison comparison comparison comparison comparison comparison

Descaling cold rolling final annealing

Descaling cold rolling final annealing

Descaling cold rolling final annealing

Descaling cold rolling final annealing

Annealing-descaling-cold-rolling-final annealing

Annealing-descaling-cold-rolling-final annealing

Annealing-descaling-cold-rolling-final annealing

Annealing-descaling-cold-rolling-final annealing

Descaling cold rolling final annealing

Unlearning cold rolling final annealing

Descaling cold rolling final annealing

Descaling cold rolling final annealing

Annealing-descaling-cold-rolling-final annealing

Annealing-descaling-cold-rolling-final annealing

Annealing-descaling-cold-rolling-final annealing

Annealing-descaling-cold-rolling-final annealing

900 3.89 , 67 900 3.95 1.66 900 3.98 1.65 900 4.05 , 66 950 3.25 , 68 950 3.19 , 67 950 3.30 , 68 950 3.31 , 68 900 4.52 , 66 900 4.66 , 67 900 4.18 , 66 900 4.42 .67 950 3.88 , 69 950 3.94 .69 950 3.55 , 69 950 3.69 , 68

Note T = Tesla example

Samples Nos. 3 and 11 of Example 1 are selected for their very low C content. There are "sarmgewalzie sheets of each sample prepared, descaled, cold rolled to a thickness of 0.5 mm and then annealed for 60 seconds at 900 ⁼ C. The average value of the watt loss and its change is measured for these sheets. FIG. 3 shows the fluctuation in the value for the watt loss for the sheets from sample no. 3 (unshatched) and 11 (hatched).

In Flg. 3 It can be seen that the steel sheet of the invention with watt loss values W 15/50 between 3.6 and 4.0 W / kg excellent in comparison to the comparison sheet Is.

The analysis values, the average values of the Wattage loss and the standard deviation of the samples are summarized in Table III.

Tabel III Analysis values. % Mn soluble Al S. N B. B / N Ce Watt loss, W / kg Default- f.
I. sample Chemical Si By deviation No. C. 0.41 0.028 0.006 0.0026 0.0020 0.77 0.014 cut 0.15 2.15 0.36 0.024 0.007 0.00; 2 0.0022 1.00 3.93 0.25 3 0.003 2.27 4.18 11th 0.003

The results of Examples 1 and 2 show that SlIIzI-umstahlbleche with little watt loss as well as little deviation can be obtained by the invention.

For this purpose 2 sheets of drawings

Claims (3)

Patent claims: 1. Slightly ventilated steel sheet with uniform magnetic properties, consisting of: at most 0.015% carbon 1.5 to 3.556 silicon 0.05 to 1.0% manganese 0.005 to 0.08% acid-soluble aluminum 0.001 to 0.020% at least of a side earth metal at most 0.015% sulfur at most 0.010% oxygen 0.005% nitrogen or less Rest of Elsen and inevitable impurities characterized in that the steel additionally contains boron in such an amount that the boron to nitrogen ratio ranges from 0.4 to 2.0. 2. Non-organic silicon steel sheet according to claim 1, but containing at most 0.010% carbon contains. 3. Nlchtorlentlertes silicon steel sheet according to claim 1 and 2, but containing at most 0.005% carbon, 0.015 to 0.050% acid-soluble aluminum and Contains 0.001 to 0.020% cerium.