CS208383B1 - Steel for making the oriented transformer belts - Google Patents

Description

It is known that the starting steel generally contains 2.0 to 4.0% by weight of silicon, 0.02 to 0.08% by weight of carbon, 0.003 to 0.100% by weight of sulfur, selenium or tellurium, or a combination of these elements, 0.03 to 0%. 20% by weight of manganese, up to 0.05% by weight of aluminum, and the remainder being iron and impurities. The steel is cast into the ingot molds or continuously, hot rolled, cold rolled to a final thickness of 0.1 to 0.5 mm in one or two stages with annealing, decarburizing and finally annealing high temperature above 1000 ° C for reaching the final texture. The final product is required to minimize re-magnetization losses with the highest possible magnetic induction, which is used in transformer cores assembled or wound from these bands.

The particular composition of the starting steel can be modified in various ways. It is known that, in order to obtain the best magnetic properties of the finished oriented trafopass, it is recommended that the sulfur content is in the range of 0.015 to 0.030 weight percent and the manganese content is in the range of 0.05 to 0.08 weight percent, recommended between 2.5 and 4.0. Other patents recommend that in addition to the condition that the ratio of manganese to sulfur content be in the range of 2.5 to 4.0, the condition that the manganese and copper contents by weight are in relation to:

Mn + content (0.1 to 0.25 x Cu content) = 0.05 to 0.24. Still other methods recommend a certain ratio of sulfur to aluminum. The above starting steel compositions for an oriented transformer belt have some drawbacks.

First, the magnetic properties of the finished steel product of this composition often have an uneven structure, characterized by different grain size and the occurrence of areas with small and imperfectly oriented grain. Such areas of abnormal structure impair the magnetic properties achieved.

Secondly, in the treatment of steel of this composition, it is necessary to use high slab heating temperatures or long dwell times at a temperature prior to hot rolling to a strip which is further cold rolled and processed according to the conventional process described above.

The use of high temperatures entails considerable operating costs, the complex construction of atypical furnaces, and the problems of removing liquid slag arising on the slab surface in considerable quantities at temperatures above 1350 ° C.

These drawbacks are remedied by steel for the production of Goss-textured oriented transformer belts containing 2.0 to 4.0% silicon, 0.02 to 0.06% carbon, 0.02 to 0.20% manganese, 0.004 to 0.010% nitrogen, 0.003 to 0.030% of sulfur, traces of up to 0.050% of aluminum, 0.02 to 0.3% of copper and the remainder iron, in weight%, according to the invention. The principle of the invention is that the ratio of manganese to sulfur in the steel is 5 to 40.

When processing slabs of steel of this composition, heating temperatures of up to 1350 ° C are sufficient, so that the problems associated with the formation of liquid slag in the heating furnaces are eliminated, there is no need to use special heating furnaces and production costs do not exceed the acceptable level. The structure of this steel oriented transformer belt is uniform and the magnetic properties achieved are excellent.

Exemplary embodiment

In the steel aggregate, steel with a weight composition of 3.0% silicon, 0.03% carbon, 0.12% manganese, 0.012% sulfur, 0.007% nitrogen, 0.008% aluminum and 0.08% copper is produced. Steel ingots are rolled to slabs, slabs are heated to 1320 ° C and rolled to a strip thickness of 2.5 mm. The strip is annealed to a temperature of 950 ° C and after immersion it is cold rolled to a thickness of 0.7 mm. After recrystallization annealing, the strip is cold rolled to a thickness of 0.35 mm. Then the strip is dehumidified at 800 ° C in moistened hydrogen and finally high temperature annealing at 1200 ° C for 24 hours. The structure of the finished oriented strip is ronomeric, the magnetic properties are excellent, P ₁₇ = 1.39 W / kg, B ₁₀₀₀ = 1.85 T, where

P ₁₇ are specific losses at 1.7 T induction

^E j Bioo induction at a field strength of 10 to / m.

In another example, a steel containing 3.25% silicon, 0.025% carbon, 0.15% manganese, 0.005% sulfur, 0.008% nitrogen, 0.005% aluminum and 0.20% copper was produced by weight. After rolling the ingots into slabs, they are heated to a temperature of 1330 ° C and rolled to a strip of 2.3 mm thickness and an intermediate thickness of 0.75 mm. Further processing is the same as in the previous case. The observed values of specific losses P _{1> 7} = 1.35 W / kg and the induction at the field intensity 10 Az / m were B ₁₀₀₀ - 1.83 T.

In another case, the steel of the previous composition containing only manganese contained more than 0.16% by weight, with a different sulfur content of 0.008% by weight. The slabs after heating to 1340 ° C were rolled onto a strip of 2.6 mm thickness with an intermediate thickness of 0.80 mm. The strip was decarburized at 820 ° C, the other processing conditions were the same as in the previous case. The magnetic properties of this steel according to the invention were excellent: specific losses Pj ₇ = 1.40 W / kg and B ₁₀₀₀ = 1.82 T.

Claims (1)

SUBJECT OF THE INVENTION Steel for the manufacture of oriented transformer strips with Goss texture, containing by weight 2,0 to 4,0% of silicon, 0,02 to 0,006% of carbon, 0,02 to 0,20% of manganese, 0,004 to 0,010% of nitrogen, 0,003 to 0.030% sulfur, traces up to 0.050% aluminum and 0.02 to 0.3% copper, the remainder iron, characterized in that the ratio of manganese to sulfur in the steel is 5.0 to 40.