PL167046B1 - Method of obtaining high-silicon steel having regular oriented grain - Google Patents

Abstract

1. The method of producing high-silicon and ni 'regular grain oriented carbon steel and thicknesses ranging from about 0.35 mm / 14 mils / up to about 0.15 mm (6 mils) or less, characterized that a hot rolling strip is being prepared made of silicon steel with a percentage by weight from about 3.0% to about 4.5% silicon and less than 0.07% carbon this hot strand is annealed, removed from it if necessary needs scale, then cold rolled to of intermediate thickness, then the material of _ intermediate thickness between pirate annealing heating temperature from about 900 ° C (1650 ° F) to BQ about 1150 ° C (2100 ° F), for a holding period from about 1 to about 30 seconds, cool from temperature annealing to a temperature of about 540 ° C / 1000 ° F / to about 650 ° C (1200 ° F) at a rate below 835 ° C / 1500 ° F / per minute then cools quickly to temperatures from about 600 ° F to about 540 ° C / 1000 ° F / at rates greater than 835 ° C / 1500 ° F / na one minute after which the material is hardened in water and also the silicon steel is cold-calcined to the final finish thickness and then decarburized silicon steel of the final thickness, the decarburized steel is coated with the substance annealing and finally the steel is aged silicon for secondary recrystallization.

Description

The invention relates to a method of making regular grain oriented high silicon low carbon steel, preferably from 0.35 mm-14 mils to about 0.15 mm-6 mils or less in thickness.

The present invention relates to a silicon steel having a Goss texture / or a roof / Miller / 110 / [001] indices. These types of silicon steels are generally referred to as grain oriented electrical steels. These steels can be divided into two basic groups: with regular grain oriented and grain oriented with high permeability. Manganese and sulfur and / or selenium are used to inhibit crystal growth in regular grain oriented electric steels. Their permeability is at 796 A / m. Aluminum nitrides, boron nitrides, or other compounds known to be used in the production of high permeability electrical steels are known to be inhibitory to grain growth by their addition or use in place of manganese sulphides and / or selenides; the permeability of such steels is above 1870 A / m. The present invention relates to cubic texture silicon steels.

The traditional method of producing regular grain oriented electrical steels has been to prepare the appropriate alloy in traditional equipment, then refresh and cast into billets or slabs. Preferably, the weight percentage of the steel is less than 0.1% carbon, about 0.025% to about 0.25% manganese, about 0.01% to 0.035% sulfur and / or selenium, about 2.5% to about 4.0 % silicon, with a target silicon content of about 3.15%, less than 50 ppm / parts per million / nitrogen and less than about 100 ppm total aluminum, with the remainder being primarily iron. Boron and / or copper can be added if necessary.

In the case of steel casting ingots, it is then either hot rolled into slabs or rolled directly from the ingots to strip. When continuous casting is used, the slabs may be pre-rolled by the method of US Patent No. 4,718,951. In the case of industrial scale production, the method of the invention can also advantageously be used for strip casting. The slabs are hot rolled at about 1400 ° C (2550 ° F) to a hot roll strip of appropriate thickness and annealed at about 1010 ° C (1850 ° F) with a soak of approximately 30 seconds. The hot strand is cooled to ambient temperature. The material is then cold rolled to an intermediate thickness and annealed

167,046 inter-operative at about 950 ° C (1740 ° F) with a 30 second hold, and then cooled, e.g., in air, to ambient temperature. After intermediate annealing, the electric steel is cold rolled to the final dimension. After reaching its final thickness, the steel is subjected to traditional decarburization annealing to recrystallize, reduce the carbon content to anti-aging levels, and form a fayalite oxide film. In general, decarburization annealing is conducted at a temperature of from about 830 ° C to about 843 ° C (1525 ° F to 1550 ° F) in a wet hydrogen atmosphere for a time sufficient to reduce the carbon content to about 0.003% or less. The steel is then coated with an annealed protective material, e.g. magnesia, and finally annealed at about 1,200 ° C (2,200 ° F) for twenty-four hours. The task of this annealing is secondary recrystallization. Reaction of the fayalite layer with the protective coating produces a forsterite or a glass-like rolling coating.

Suitable methods for producing regular grain oriented silicon steels (Goss texture) are described in U.S. Patent Nos. 4,202,711, 3,764,406, and 3,843,422.

In recent years, in order to reduce core losses in regular grain oriented products, attention has been paid to increasing the volume resistivity by increasing the silicon content in order to reduce the macro-scale eddy current losses. However, the expected improvement due to the increase in the silicon content was essentially not achieved. Until now, the typical approach to this problem has been to increase both the percentages of silicon and carbon to achieve improved magnetic performance. It was found that the simultaneous raising of the silicon and carbon content accelerates the onset of grain boundary melting during annealing of ingots / slabs at high temperatures and increases the brittleness of the steel during post-hot rolling treatment. This particularly applies to the deterioration of machining and cold rolling parameters of high-silicon and high-carbon materials. In order to obtain the permanent magnetic properties of the finished, regular grain oriented electrical steels, it is necessary for the production of the silicon steel to be decarburized to a carbon content of 0.003% or less. However, increasing the silicon content delays decarburization, which makes it difficult to produce high-silicon and high-carbon materials.

U.S. Patent No. 4,898,626 describes a very fast annealing which involves heating the electric steel at a rate of 100 ° C (180 ° F) per second to a temperature above the recrystallization temperature, nominally 675 ° C (1250 ° F). This procedure may be used at any stage of the process, at least following the first cold rolling step and prior to decarburization annealing prior to final annealing. Advantageously, this may take place after the cold rolling has been completed and prior to decarburization annealing. The very fast annealing may be performed either prior to the decarburization annealing or it may be one of the decarburization annealing steps, e.g. a heating step.

The present invention is based on the discovery that in the production of regular grain oriented electrical steels, the intermediate annealing after the first cold rolling step and its cooling cycle have a significant influence on the magnetic quality of the finished product. The following factors are also of great importance: the percentage by volume of austenite formed during annealing, products remaining after austenite decomposition and carbide inclusions formed during cooling. The rate of cooling after intermediate annealing, which does not allow the austenite to decompose after this operation, due to the separation of fine carbide particles, causes the following effects: lower permeability, less stable secondary grain growth and / or increased secondary grain dimensions. Moreover, a higher silicon content increases the activity of the carbon, increasing the temperature of the separated carbides and producing coarse grain carbides. As a result of this problem, which arise due to improper cooling after completion of the intermediate annealing, are further increased in the case of high-silicon steels. These problems have been solved by the method according to the invention.

167 046

A method of producing a grain oriented high silicon low carbon electrical steel with a thickness ranging from about 0.35 mm (14 mils) to about 0.15 mm (6 mils) or less is to prepare a hot silicon steel strip of by weight percentage of about 3.0% to about 4.5% of silicon and less than 0.07% of carbon, this hot strip is annealed, scale is removed from it if necessary, then cold rolled to an intermediate thickness and then subjecting the intermediate thickness material to an intermediate annealing at a soak temperature of from about 900 ° C (1650 ° F) to about 1150 ° C (2100 ° F) for a soak period of about 1 to about 30 seconds. Then cooling slowly from the soak temperature to from about 540 ° C (1000 ° F) to about 650 ° C (1200 ° F) at a rate below 835 ° C (1500 ° F) per minute and then cooling rapidly to a temperature of from about 600 ° F (315 ° C) to about 1000 ° F (540 ° C) at a rate above 835 ° C / 1500 ° F / minute, followed by water quench and silicon steel cold rolled to the final thickness, then the silicon steel of the final thickness is decarburized, the decarburized steel is coated with an annealing protection and finally annealed with silicon steel for secondary recrystallization.

Preferably a hot steel strip is prepared with a silicon weight content of about 3.25% - 3.75%.

Preferably, the hot strip is annealed at a temperature of about 1010 ° C (1850 ° F) for a soak time of about 30 seconds and then cooled in air to ambient temperature.

Preferably, the silicon steel is rapidly annealed above 675 ° C (1250 ° F) at a rate greater than 100 ° C / 180 ° F / per second after final thickness is given to the silicon steel but prior to decarburization.

Preferably, the material is subjected to an intermediate annealing with a soaking time of about 3 to about 8 seconds.

Preferably, the material is inter-annealed at an annealing temperature of from about 900 ° C (1650 ° F) to about 930 ° C (1700 ° F).

Preferably, the material is subjected to an intermediate annealing at a soaking temperature of about 915 ° C (1680 ° F).

Preferably, the slow cooling ends at about 595 ° C 30 ° C (1100 ° F 50 ° F).

Preferably, slow cooling is performed at a rate of from about 280 ° C (500 ° F) to about 585 ° C (1050 ° F) per minute.

Preferably, the rapid cooling rate is from about 2500 ° F to about 1945 ° C (3500 ° F) per minute.

Preferably, the material is subjected to an intermediate annealing temperature of about 915 ° C (1680 ° F) and a soaking time of from about 3 seconds to about 8 seconds and then slowly cooled at a rate of about 280 ° C (500 ° F) to about 585 ° C / 1,050 ° F / minute, this slow cooling ends at about 595 ° C 30 ° C (1100 ° F ± 50 °) and the rapid cooling is performed at a rate of about 1390 ° C / 2500 ° F / up to about 1945 ° C / 3500 ° F / minute.

Preferably, the hot strand is prepared from silicon steel containing, by weight percent, less than 0.07% carbon, about 0.025% to 0.25% manganese, about 0.01% to 0.035% sulfur and / or selenium, about 3.0% up to about 4.5% silicon, less than 100 parts per million aluminum, less than 50 parts per million nitrogen, additions of boron and / or copper, if desired, the balance being essentially iron.

Preferably, after the silicon steel has been finalized but prior to decarburization, it is very rapidly annealed to a temperature above 675 ° C (1250 ° F) at a heating rate above 100 ° C / 180 ° F / per second.

Preferably, before intermediate annealing and before cold rolling to intermediate thickness, the hot strip is annealed at a temperature of about 1010 ° C (1850 ° F) with a soaking time of about 30 seconds and cooling in air to ambient temperature, and particularly preferably the steel is subjected to a very rapid annealing. which is the heating step as part of the decarburization annealing.

167 046

Preferably also after intermediate annealing and after giving the silicon steel its final thickness, but prior to decarburization, it is also subjected to a very rapid annealing to a temperature above 675 ° C / 1250 ° F at a heating rate above 100 ° C / 180 ° F / per second, and especially preferably the steel undergoes a very rapid annealing which is the heating step involved in the decarburization annealing.

Preferably, a hot strip is prepared from silicon steel containing by weight percent less than 0.05% carbon, about 0.04% to 0.08% manganese, about 0.015% to 0.025% sulfur and / or selenium, about 3.25% to about 3.75% silicon, less than 100 parts per million aluminum, less than 50 parts per million nitrogen, additions of boron and / or copper, if desired, the balance being essentially iron.

Thus, a method of producing regular textured silicon steel with a thickness of from about 0.35 mm (14 mils) to about 0.15 mm (6 mils) or less involves preparing electrical steel with a weight percentage of less than about 0.07% carbon. , about 0.025% to 0.25% manganese, about 0.01% to 0.035% sulfur and / or selenium, about 3.0% to 4.5% silicon, less than 100 parts per million total aluminum, less than about 50 parts per million nitrogen, supplemented mainly with iron. If necessary, boron and / or copper can be added to it.

For this purpose, a starting material, hereinafter referred to as hot strip, is produced, which can be done by many methods known in the art, such as ingot casting / continuous casting and hot rolling or by strip casting. The hot strand is annealed at about 1010 ° C (1850 ° F) for about 30 seconds followed by cooling in air to ambient temperature. It has been found that the strip annealing step can be omitted especially in the production of regular grain oriented electrical steel containing an amount of silicon corresponding to the lower value within the allowable range. The electrical steel is then cold rolled to an intermediate thickness. After rolling, the steel is subjected to an intermediate anneal at about 900 ° C (1,650 ° F) to about 1,150 ° C (2,100 ° F), and preferably from about 900 ° C (1,650 ° F) to about 930 ° C (1,700 ° F). / with a soak period of from about 1 to about 30 seconds, and preferably from about 3 to about 8 seconds. After annealing, the steel is subjected to two-stage cooling. The first cooling step is a slow step ranging from the soaking temperature to a temperature of about 540 ^° C (1000 ° F) to about 650 ° C (1200 ° F), and preferably 595 ° C 30 ° C / 1100 ° F ± 50 ° F / at a rate of less than about 835 ° C / 1500 ° F / minute, and preferably at a rate of from about 280 ° C / 500 ° F / to 585 ° C / 1050 ° F / minute. The second cooling step is a high speed step above 835 ° C / 1500 ° F / minute, and preferably at a rate of 1390 ° C / 2500 ° F / up to about 1945 ° C / 3500 ° F / minute, followed by water quench at a temperature from about 600 ° F (315 ° C) to about 1000 ° F (540 ° C). After completion of the intermediate annealing, the steel is cold rolled to its final thickness, decarburized, coated with an annealing protective substance and subjected to a final annealing aimed at secondary recrystallization.

In the method preferred according to the invention, the steel is subjected to a very rapid annealing according to the above description. This annealing may be carried out at any stage of the technological process, following at least the first stage of cold rolling and before decarburization. in general, it is preferable to carry it out after the cold rolling has been completed and before the decarburization annealing. As already described above, very rapid annealing may be one of the decarburization annealing steps, e.g. a heating step.

The method of the present invention produces cubic grain oriented high-silicon steels from a charge having a chemical composition of from about 3% to about 4.5% silicon and a low carbon content of less than 0.07%. The process sequence of the inventive process is the same as in the conventional process outlined above with three exceptions. First of all, annealing of the hot roll strip can be eliminated. This is especially true for steels with a silicon content in the lower range of the above range. However, it is preferred that the hot strand annealing step is included in the process of the present invention.

167 046

Second, the present invention employs a modified intermediate annealing procedure followed by a first cold rolling step. Preferably, this procedure includes a brief heating at a temperature below that typically used in prior art technology and a two-stage temperature controlled cooling cycle. This process will be described in detail below.

Interoperative annealing and cooling in accordance with the present invention decomposes the austenite during the first, slow cooling step, followed by the precipitation of fine cementite particles in the second, rapid cooling step. A short annealing period and austenite decomposition are possible due to the existence of low-melting carbon.

Finally, the process of the invention preferably includes a very rapid annealing followed by decarburization. This process improves all magnetic properties due to the improved texture after recrystallization.

The method according to the invention is presented on the basis of an exemplary course of the technological process, in the drawing, which shows a graph showing the course of temperature as a function of time for the annealing cycle according to the invention and the course of a typical known intermediate annealing.

In the method according to the invention, the process flow for the production of regular grain oriented high silicon and low carbon steels is traditional and essentially the same as described in the prior art, with three exceptions. The first exception is the possibility of omitting the hot strand annealing if necessary. Hot strip annealing is recommended where the equipment and conditions allow it, as it reduces the brittleness of this type of electric steels and increases the susceptibility to cold rolling. Moreover, it increases the stabilization of secondary recrystallization. If done, the annealing should be at about 1010 ° C (1850 ° F) with a soak for about 30 seconds. After annealing, the steel is cooled in air to ambient temperature. The second exception is the introduction of intermediate annealing and cooling according to the invention following the first cold rolling step. Finally, a third exception is optional but recommended to perform a very fast annealing prior to decarburization.

after the first cold rolling step, the steel is subjected to an intermediate annealing process according to the invention. Reference is made to the drawing in which the graph of temperature versus time for an intermediate annealing according to the invention is shown. It also shows, in dashed lines, the course of temperature as a function of time in the case of a typical in-process annealing used so far.

The main advantage of the invention is the discovery that it is possible to control the course of the intermediate annealing and the subsequent cooling cycle, which allows the carbide to be refined. Annealing and cooling connected with it eliminate the above-described disadvantages related to the increased silicon content.

During the heating of the intermediate annealing at about 1250 ° F (675 ° C) in approximately 20 seconds after the steel is put into the furnace, recrystallization occurs, followed by normal crystal growth. The beginning of recrystallization is marked in the figure by point 0. Above about 690 ° C / 1280 ° F / the dissolution of carbides begins as indicated in point A in the figure. The process proceeds with increasing speed as the temperature increases. Above about 900 ° C / 1650 ° F / a small amount of ferrite is converted to austenite. Austenite accelerates the dissolution of carbon and limits normal crystal growth, thereby stabilizing their size. In the annealing used heretofore, annealing at a temperature of about 950 ° C (1740 ° F) was performed for at least 25 to 30 seconds. In an intermediate annealing according to the invention, the annealing time is from about 1 to about 30 seconds, and preferably from about 3 to about 8 seconds. It was found that the annealing temperature is not a critical parameter. It may be operated at a temperature of from about 900 ° C (1,650 ° F) to about 1,150 ° C (2,100 ° F). Preferably, it is conducted at a temperature of from about 900 ° C (1650 ° F) to about 930 ° C (1700 ° F) and most preferably at about 915 ° C (1680 ° F). Shorter times are recommended

167,046 and lower annealing temperatures, as this reduces the proportion of p <^^ w ^ austenite. Moreover, the austenite, existing in the form of scattered clusters within the boundaries of the primary ferrite crystals, is finer, and therefore easier to decompose into ferrite with carbon in solid solution and then separate from the solution as fine carbide particles. The effect of increasing the temperature or the soaking time is the enlargement of the austenite clusters, which are enriched in carbon very quickly compared to the original ferrite mesh. Both the growth of austenite and its carbon enrichment inhibit its decomposition during cooling. The most desirable structure leaving the pie is a recrystallized ferrite mesh containing less than 5% austenite evenly distributed throughout the material in the form of fine clusters. At the end of the annealing, the carbon will be in solid solution, ready to separate again on cooling. The basic argument for changing the temperature and soaking time during annealing is the regulation of the growth of austenite clusters. The lower temperature reduces the austenite volume fraction it produces. Shorter times reduce carbon diffusion, thereby inhibiting the increase in the size and amount of austenite. Lower temperature, reduced volume fraction and finer austenite structure facilitate its decomposition during the cooling cycle.

The cooling phase begins immediately after the soaking phase. The cooling according to the invention takes place in two stages. The first stage is from heating up to point E in the figure. This is a slow step, starting at the holding temperature and going up to about 540 ° C (1000 ° F) to about 650 ° C (1200 ° F), and preferably up to about 595 ° C 30 ° C / 1100 ° F. ± 50 ° F /. In this stage, austenite is decomposed into carbon-saturated ferrite. Under equilibrium conditions, austenite decomposes into carbon-saturated ferrite at temperatures from about 900 ° C (1,650 ° F) to about 770 ° C (1,420 ° F). However, the dynamics of the cooling process is such that the decomposition of austenite does not begin to a significant extent until the average temperature in this range is 815 ° C (1500 ° F) and continues to a temperature just below 1100 ° F (595 ° C).

The result of a defective austenite decomposition process during the first cooling stage is the formation of martensite and pearlite. The effect of the possible formation of martensite is an increase in the size of secondary crystals and deterioration of the arrangement quality / 110 / / 001 /. Its presence negatively affects the accumulation of energy in the second stage of cold rolling, as a result of which there is a deterioration and an increase in the non-uniformity of magnetic parameters of the finished electric steel products. Finally, martensite degrades the mechanical properties, especially the cold rolling performance. Perlite is less harmful but also binds undesirable carbon.

As shown above, the decomposition of austenite begins near the point marked in the figure by C and continues approximately to point E. At point D, fine particles of cementite begin to separate from the carbon-saturated ferrite. Under equilibrium, at temperatures below 690 ° C (1280 ° F), carbides begin to precipitate from the carbon-saturated ferrite solution. However, some supercooling is needed in the actual process to start the extraction. This precipitation begins to a significant extent near the temperature of 650 ° C (1200 ° F). Note that the decomposition of austenite to carbon-enriched ferrite and the precipitation of carbide from the ferrite overlap to some extent. Carbide comes in two forms: as an intercrystalline layer and as fine intragranular inclusions. The former precipitates at temperatures above about 1060 ° F (570 ° C) and the latter below about 1060 ° F (570 ° C). The cooling rate during the slow cooling step, illustrated by the line between points C and E in the figure, is less than 1500 ° F / 835 ° C / minute, and preferably from about 280 ° C / 500 ° F / to about 585 ° C / 1050 ° C. F / per minute.

The second stage of the cooling phase, rapid cooling, begins at point E in the drawing and continues to point G, within the temperature range of 600 ° F to 1000 ° F / 315 ° C to 540 ° C. At point G, the strip is quenched in water, co

167 046 completes the rapid cooling stage. The temperature of the strip after water quench is about 65 ° C (150 ° F) or less, shown in the figure as 25 ° C (75 ° F) room temperature. Preferably, the cooling rate during the second stage is from about 2500 ° F (1390 ° C) to about 3500 ° F (1945 ° C) per minute, and preferably greater than 1665 ° C (3000 ° F) per minute. Due to this cooling rate, fine carbide particles can be precipitated.

It can be seen from the above description that the condition for obtaining the desired microstructure of the material is to fully carry out the intermediate annealing and cooling phase according to the invention, and the critical factor is the precise regulation of their course. The typical heretofore process illustrated in the drawing took at least 3 minutes and ended in a water bath, not shown, with a belt speed of about 57 meters / 220 feet / minute. The intermediate annealing according to the invention takes about 2 minutes and 10 seconds, which enables a strip speed of about 80 meters / 260 feet / minute to be used. In this regard, it should be noted that the annealing phase according to the invention makes it possible to increase the efficiency of the production line. After annealing, it is neither necessary nor desirable to age the material, as it has been found to result in the formation of enlarged secondary crystals, resulting in a deterioration of the magnetic properties of the finished electrical steel products.

After intermediate annealing, the second stage of cold rolling takes place, during which the material thickness is reduced to the required final value. In this step, steel can be decarburized, coated with a protective substance before annealing, followed by a final annealing with the purpose of secondary recrystallization.

In the procedure preferred according to the invention, the electric steel is subjected to a very rapid annealing which is carried out after cold rolling but before decarburization. To this end, the material already having the appropriate thickness is heated at a rate above 180 ° F / per second to a temperature above 675 ° C (1250 ° F). Preferably, the electric steel is heated at a rate of the order of 540 ° C / 1000 ° F / per second. Moreover, it is preferable that the very fast annealing constitutes the heating step of the decarburization annealing phase.

Preferably, the chemical percentage by weight of the steel of the invention should be as follows: less than 0.05% carbon, about 0.04% to about 0.08% magnesium, about 0.015% to about 0.025% sulfur and / or selenium, about 3 , 25% to about 3.75% silicon, less than 100 parts per million aluminum, less than 50 parts per million nitrogen, boron and / or copper if desired, and the rest predominantly iron.

Very fast annealing improves the texture after recrystallization due to the formation of more primary crystals (110/001), and also helps to reduce the size of the secondary crystals. The use of very fast annealing reduces the sensitivity of the process to uneven material thickness in the intermediate and final stages, and improves and unifies the magnetic parameters of regular grain oriented silicon steels.

Example 1. Four charges were melted in the weight percentages given in Table 1. From these charges, slabs with a thickness of 200 mm (8 /) were continuously cast, pre-rolled to a thickness of 150 mm / 6 ", and reheated to 1,400 ° C (2,550 ° F) and hot rolled to a 2.1 mm (0.084) thick hot strip for further processing. The hot strand was then annealed at 1010 ° C (1850 ° F) and cold rolled to various intermediate thicknesses. The drains A and B were annealed in a typical, hitherto used method with annealing at a temperature of 950 ° C / 1740 ° C / for 25-30 seconds, and then cooled to normal ambient temperature, while the drains C and D were subjected to an intermediate annealing method according to the present invention. invention. After intermediate annealing, the materials were cold rolled to a final thickness of 0.18 mm (7 mils) and 0.28 mm (9 mils). After cold rolling, the materials were decarburized at 830 ° C (1525 ° F) under moist hydrogen, coated with MgO and finally annealed at 1200 ° C (2200 ° F). The final magnetic parameters of the materials obtained by the methods described are presented in Table 3.

167 046

Table 1

Symb. C. Me S. Si Al Cu P. N AND 0.0288 0.059 0.0198 3.41 0.0013 0.092 0.006 0.0042 B 0.0296 0.059 0.0209 3.42 0.0014 0.118 0.006 0.0038 C. 0.0265 0.058 0.0218 3.44 0.0012 0.097 0.005 0.0040 D 0.0274 0.058 0.0212 3.36 0.0012 0.085 0.006 0.0035

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167 046

From the results presented, it is clearly seen that the in-process annealing technology of the invention improves core loss and increases the stability of secondary crystal growth in regular grain oriented materials of this type.

Example II. During production trials, additional samples of triggers A and B were taken for laboratory tests. Processing on the production line was done in the same way as in the conventional method of example 1, however, after the cold rolling to intermediate thickness had been completed, material samples were taken on the line and processed in the laboratory according to the method of the present invention, where appropriate the times and temperatures of the intermediate annealing and the control of the cooling phase, as well as the more advantageous, very fast annealing after the completion of cold rolling but before decarburization. The very rapid annealing step was the heating step during the decarburization annealing in which the material was heated from room temperature to (1375 ° F) at a rate of 556 ° C / 1000 ° F / per second. Upon completion of the intermediate annealing, the material was cold rolled to a final thickness of 0.18 mm (7 mils) and decarburized at 830 ° C (1525 ° F) in a wet hydrogen atmosphere using either conventional techniques or very fast annealing while heating. After decarburization, the MgO samples were coated and subjected to a final anneal at 1200 ° C (2200 ° F). The results of this procedure are presented in Table 3.

Table 3

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The method according to the invention with very fast annealing:

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1856

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It is clearly seen from the results presented that the in-process annealing technology according to the invention improves core losses and increases the stability of secondary crystal growth in materials of this type with a regular texture. The use of the more preferred method of supplementing the intermediate annealing according to the present invention with additional very fast annealing further improves the magnetic parameters of the material.

The invention may be modified without prejudice to its essence.

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Claims (18)

Patent claims A method of producing high silicon and low carbon regular grain oriented steel with a thickness ranging from about 0.35 mm (14 mils) to about 0.15 mm (6 mils) or less, characterized by preparing a hot strip of steel silicon with a weight percentage of about 3.0% to about 4.5% silicon and less than 0.07% carbon, this hot strip is annealed, scale is removed from it, if necessary, then cold rolled to an intermediate thickness, then subjecting the intermediate thickness material to an intermediate annealing at a soak temperature of about 900 ° C (1650 ° F) to about 1150 ° C (2100 ° F) for a soak period of about 1 to about 30 seconds, cooling from the soaking temperature to a temperature of about 540 ° C (1000 ° F) to about 650 ° C / 1200 ° F at a rate of less than 1500 ° F / 835 ° C, then rapidly cooled to about 315 ° C / 600 ° F / up to about 540 ° C / 1,000 ° F / at rates above 835 ° C / 1,500 ° F / per minute after where the material is quenched in water and the silicon steel is cold calibrated to its final thickness, then the silicon steel of the final thickness is decarburized, the decarburized steel is coated with a protective substance against annealing and finally annealed with silicon steel for secondary recrystallization. 2. The method according to p. The process of claim 1, wherein the hot strip of steel is prepared with a silicon weight content of about 3.25% - 3.75% by weight. 3. The method according to p. The process of claim 1, wherein the hot strip is annealed at a temperature of about 1010 ° C (1850 ° F) for a soaking time of about 30 seconds and then cooled in air to ambient temperature. 4. The method according to p. The process of claim 1, wherein, after the silicon steel has been finalized but prior to decarburization, it is rapidly annealed to a temperature above 675 ° C (1250 ° F) at a rate above 100 ° C / 180 ° F / per second. 5. The method according to p. The method of claim 1, wherein the material is subjected to an inter-operative annealing with a holding time of about 3 to about 8 seconds. 6. The method according to p. The method of claim 1, wherein the material is inter-annealed at a soak temperature from about 900 ° C (1650 ° C) to about 930 ° C (1700 ° F). 7. The method according to p. The process of claim 6, wherein the material is subjected to an intermediate annealing at a soaking temperature of about 915 ° C (1680 ° F). 8. The method according to p. The process of claim 1, wherein the slow cooling ends at about 595 ° C 30 ° C (1100 ° F - 50 ° F). 9. The method according to p. The process of claim 1, wherein the slow cooling rate is from about 280 ° C (500 ° F) to about 585 ° C (1050 ° F) per minute. 10. The method according to p. The process of claim 1, wherein the rapid cooling rate is from about 2500 ° F to about 1945 ° C (3500 ° F) per minute. 11. The method according to p. The material of claim 1, wherein the material is subjected to an intermediate annealing temperature of about 915 ° C (1680 ° F) and a soaking time of about 3 seconds to about 8 seconds, and then slowly cooled at a rate of about 280 ° C / 500 ° C. F) to about 585 ° C (1050 ° F) per minute, with this slow cooling ending at a temperature of about 595 ° C 30 ° C (1100 ° F ± 50 ° F) and the fast cooling rate being from about 1,390 ° C (2,500 ° F) to about 1945 ° C (3,500 ° F) per minute. 12. The method according to p. The method of claim 1, wherein the hot strip is prepared from silicon steel containing, in percent by weight, less than 0.07% carbon, about 0.025% to 0.25% manganese, about 0.01% to 0.035% sulfur and / or selenium, about 3.0% to about 4.5% silicon, less than 100 parts per million aluminum, less than 50 parts per million nitrogen, additions of boron and / or copper, the balance being iron. 16 * 7046 13. The method according to p. The process of claim 1, wherein after the silicon steel has been finalized but prior to decarburization, it is very rapidly annealed to a temperature above 675 ° C (1250 ° F) at a heating rate above 100 ° C / 180 ° F / per second. 14. The method according to p. The process of claim 11, wherein prior to intermediate annealing and prior to cold rolling to intermediate thickness, the hot strand is annealed at about 1010 ° C (1850 ° F) with a holding time of about 30 seconds and air cooling to ambient temperature. 15. The method according to p. The process of claim 13, wherein the steel undergoes a very rapid annealing, which is a heating step as part of the decarburization annealing. 16. The method according to p. 14, characterized in that after annealing międzyoperacyjnym and after transmission of silicon steel the final thickness and before decarburization subjected to very quickly annealed to a temperature above 675 ° C / 1250 ° F / heating rate of greater than 1 (X) ^O C / 180 ° F / per second. 17. The method according to p. The process of claim 16, characterized in that the steel undergoes a very rapid annealing, which is a heating step as part of the decarburization annealing. 18. The method according to p. The process of claim 1, wherein the hot strip is made of silicon steel containing, in percent by weight, less than 0.05% carbon, about 0.04% to 0.08% manganese, about 0.015% to 0.025% sulfur and / or selenium, about 3.25% to about 3.75% silicon, less than 100 parts per million aluminum, less than 50 parts per million nitrogen, boron and / or copper additions, the balance being iron.