DE1931420B1 - Use of a steel that has been vacuum-treated in the liquid state as a dynamo tape - Google Patents

Description

It is known that dynamo tape with magnetic reversal losses of 2.5 to 4.0 W / kg with alternating field magnetizations of 10 kG (50 Hz) with a thickness of 0.35 to 1.0 mm made of steel with a silicon content from 1.0 to 2.0%, a starting carbon content of more than 0.015% and partly with an aluminum content from 0.10 to 0.50%. The strip or sheet is hot and cold rolled for this purpose and then decarburizing and recrystallizing either in a continuous furnace, box furnace or in annealed in a so-called 'open coil hood annealing furnace. Disadvantages of these known processes are that they are essentially caused by the alloys with silicon and / or aluminum-related low magnetic induction values at all field strengths and frequencies of the dynamo sheets or strips produced.

It is also known (cf. Sam-arin, "Physikalisch -chemische bases der Deoxydation von Stahl", 1960) to produce transformer steel with Si contents of about 3% in a vacuum furnace and to subject the intermediate annealed, rolled strip to a final anneal. The watt losses (W / kg) are reduced by this treatment compared to steel produced in a conventional induction furnace and the values of the magnetic saturation are increased. A method for producing silicon-containing steel for magnetic purposes is also known (see US Pat. No. 2,287,467). This known steel has an initial carbon content of about 0.02 to 0.06% and an Si content down to 0.05%. After an intermediate annealing and cold rolling, decarburization annealing at temperatures is carried out from about 900 ⁰ C 730.bis. Closing. borrowed is still known (see Houdremont, "Hand-, buch der Sonderstahlkunde", 1956, p. 1403) that in a steel with 0.003 to 0.02% C, about 0.04% Mn and about 0.01% Si and an increasing phosphorus content of up to about 0.25%, the values of the mechanical properties, namely elongation, tensile strength and yield point, increase. Also known from German Offenlegungsschrift 1 433 799 is a process for the production of wrought iron or fluoro iron with improved electrical properties, in which a steel containing 0.03 to 0.14% carbon, 0.008 to 0.15% phosphorus , 0.38 to 0.76% manganese, a maximum of 0.03% sulfur and a maximum of 0.02% silicon, after processing into sheet metal, consisting of hot rolling, coiling at 649 to 704 ⁰ C, subsequent cold reduction and decalcifying at ■ a temperature between 621 and 7Q4 ° C on a carbon content of less than 0.008 ^ Z _0, annealing aufwejjst at a temperature of 816-843 ⁰ C and abschließendem temper rolling the strip ^, -improved magnetic properties. Disadvantageously, in this known "method, as in the method known from German Auslegeschrift 1 261146, additional annealing and additional deformation are carried out in order to achieve core losses of about 7 and 9 W / kg at 50 Hz, respectively.

The invention is based on the object of specifying a steel which, with the same core losses like the steels alloyed with Si and / or Al, compared to these, increased magnetic induction values having. Another object of the invention is compared to the known processes for the production of Dynamo tape to specify a simplified procedure.

These objects are achieved by using a steel that has been vacuum-treated in the liquid state and consists of less than 0.015% carbon, 0.050 to 0.250% phosphorus, the remainder iron with the production-related impurities, which is hot-rolled, pickled, cold-rolled and then in a continuous furnace at a temperature of 750 to 1100 ⁰ C has been decarburized to less than 0.010% carbon for 2 to 7 minutes, as a dynamo tape with a magnetic reversal loss of 2.5 to 4.0 W / kg with an alternating field magnetization of 10 kG (50 Hz) and one alloyed with silicon Steel increased magnetic induction of at least 500 to 1000 G with alternating field strengths between 5 and 300 A / cm (50 Hz). Instead of being treated in a continuous furnace, the above-mentioned steel can expediently also be annealed to less than 0.01% carbon in a stationary furnace at 650 to 950 ° C. for 30 minutes to 24 hours.

Appropriately, it is also provided that with a phosphorus content of less than 0.050% Manganese is added in the amount of 0.50 to 1.10%. Shall the properties of the steel according to the invention can be further improved, so is a deoxidation with up to 0.80% manganese and / or up to 0.50% silicon and / or up to 0.10% aluminum is advantageously possible.

The advantages of the steel to be used according to the invention are to be seen in the fact that the magnetization or induction values can be increased in a simple manner at the same time with the mentioned magnetic reversal losses by at least 500 and up to 20,000 compared to conventional silicon-alloyed steels , whereby the performance of the electrical devices made of this material is increased without increasing the operating weight. As the performance of electrical appliances, e.g. B. the torque of electric motors is significantly influenced by the magnetic induction values at certain speeds, dynamo tapes, which have higher magnetic induction values with the same magnetic reversal losses, are to be preferred over the known silicon-alloyed tapes. In addition to very good aging resistance, the steel has a purely ferritic structure with small amounts of tertiary cementite and, without re-rolling, a tensile strength of 35 to about 50 kp / mm ² , so that increased burr formation and smearing during punching are prevented and good tool life is guaranteed.

In the following the production of the invention Steel to be used and the properties achieved are explained in more detail on the basis of exemplary embodiments.

Three different steels A, 'B and C were in the Siemens-Martin-Qfen (A, B) and induction furnace (C) melted and then treated in a vacuum system in the liquid state. The chemical The composition of the steels after the vacuum treatment is shown in Table 1.

Table 1 Steel A CVo SiVo MnVo P% ,. s Vo NVo AlVo Steel B 0.007
0.008
0.015 0.02
<0.01
<0.01 0.34
0.33
0.46 0.148
0.207
0.140 0.014
0.016
0.022 0.003
0.003
0.006 0.006
<0.003
<0.003 Steel C

After hot rolling of the steels A and B, the tape in 15% sulfuric acid was mm to the dimension of 1000 x 2 stained at about 98 ⁰ C, at a fünfge vigorous tandem mill to the dimensions of 1000 x 0.5 cold rolled mm and 980 · Trimmed 0.50 mm. Steel C was hot-rolled to dimensions 110 x 2.0 mm on a continuous medium strip mill and, after the same pickling, was cold-rolled to 110 x 0.50 mm on a two-high stand in five passes. After the decarburizing recrystallization annealing in a continuous furnace at 850 to 900 ° C and residence times between 3 and 7 minutes, the values of the re-magnetization losses F 10 given in Table 2 for 850 ° C and in Table 3 for 900 ° C, averaged from longitudinal and transverse samples, resulted _{0) 5} in W / kg with an alternating field magnetization of 10 kG.

Table 2 V
4 min. awakening
5 min. 16 min. 3.7
3.3
nb · 7 min: 3 min. 3.8
3.3
3.75 3.8
3.4
3.6 ; 3.5-
.3.2
3.3: Steel A 3.9
3.5
4.0 Steel B Steel C

Table 3

3 min. Linger
4 min. 15 min. 3.4
3.1
3.85 it
6 min. 7 min. Steel A 3.4
3.5
.4.0 3.3
3.2
3.9 3.4
3.1
n: b. 3.3
3.1
3.8 Steel B. SteelC

The residual carbon content in percent of the steels after the recrystallizing decarburization annealing in an inner atmosphere _; partially burned gas with 12% H ₂ , T ⁰ J ₀ CO, 6% CO ₂ , remainder N ₂ and a dew

point of +20 ⁰ C is shown in Table 4.

Tabel

Residual carbon content (%) after decarburization and recrystallization 850 ° C / 4 min. I 850 ° C / 7 min. I 900 ° C / 4 min. I 900 ° C / 7 min.

Steel A
Steel B
SteelC

0.002
0.003
0.0095

0.001
0.002
0.007

0.002 0.001 0.010

0.001 0.001 0.009

The obtained after decarburization and recrystallization at 850 ⁰ C in 4 minutes magnetic induction values are given as mean values of longitudinal and transverse test pieces in Table 5 below. For comparison, a steel D 0.92 ° / ₀ Si and 0.08% Al and a steel E containing 1.0% Si and 0.20% Al whose Ummägnetisierungsverluste V 10 _0j5 kg measured at 2.6 W / were specified.

In the case of an annealing treatment at 900 ^° C. for 4 minutes, the differences in the measured values can hardly be ascertained.

Table 5

B 25 B 50 BlOO B 300 Steel A 16.9
17.2
nb
16.5
16.4 18.4
18.8
nb
17.4
17.2 18.9
19.3
19.0
18.4
18.2 19.9
20.3
nb
19.4
19.2 Steel B .. Steel C Steel D Steel E.

Dynamo tapes with a core loss of 2.3 to 3.6 W / kg with alternating field magnetizations (50 Hz) of 10 kG (see Table 6).

Table 6 40 goodness tape
or
Sheet thickness Around- Magnetic inductions
(kG) at least B 50 BlOO B 300 magnetic
ization
loss 16.4 17.5 20.1 (mm) FlO B 25 16.5 17.6 20.0 Dyba 23 0.50 (W / kG) 15.3 16.6 17.7 19.8 45 Dyba26 0.50 2.3 15.5 16.8 17.8 19.7 Dyba 30 0.50 2.6 15.6 Dyba 36 0.50 3.0 15.8 3.6

A comparison of the measured values with the minimum values for magnetic induction according to the new proposal of DIN 46 400 for cold-rolled shows that the cold-rolled steel strip or steel strip subjected to final annealing in a continuous furnace sheet according to the invention, the minimum values of the magnetic induction specified in accordance with the DIN standard exceeds 200 to 2000 G.

The mechanical properties achieved in 4 minutes after decarburization and recrystallization at 850 and 900 ^° C. are shown in Table 7.

Tabel

Mechanical properties after decarburization and recrystallization

Stretch limit
a _s (kp / mm ² )

at 850 ° G / 4 min.
tensile strenght
a _B (kp / mm ² ) elongation at break
c, (%)

Stretch limit
Cs (kp / mm ² )

at 900 ° C / 4 min. tensile strength Ob (kp / mm ² )

Elongation at break

Steel A.
Steel B.
SteelC

28.8
30.9
30.8

38.9
41.1
39.0 59.5
47.5
52.5

29.3
29.8
31.2

39.7 39.8 39.5

50.5 50.5 52.5

The mechanical properties determined, in particular the tensile strength, result in the steel according to the invention with the appropriate setting of the gap a good punching behavior. Otherwise, the steels showed a purely ferritic quality after decarburization Vessels with small residues of tertiary cementite and an ASTM grain size between 5 and 8 as well a good non-metallic degree of purity.

Claims (4)

Patent claims: 1. Use of a vacuum-treated in the liquid state steel consisting of less than 0.015 _^0/0 carbon, 0.050 to 0.250% phosphorus residue iron with impurities resulting from manufacture, the hot rolled, pickled, cold rolled, and then in a continuous furnace at a temperature of 750 to HOD ⁰ C has been decarburized for 2 to 7 minutes to less than 0.010% carbon, as a dynamo tape with a core loss of 2.5 to 4.0 W / kg with an alternating field magnetization of 10 kG (50 Hz) and one compared to a conventional one with silicon Alloy steel increased magnetic induction of at least 500 to 1000 G with alternating field strengths between 5 to 300 A / cm (50Hz) 2. Use of a steel, vacuum-treated in the liquid state, of the composition according to claim 1, which is hot-rolled, pickled, cold-rolled and then stationary in a closed furnace chamber at 650 to 950 ^° C. for 30 minutes to 24 hours to less than 0.01% carbon , for the purpose of claim 1. 3. Use of a steel consisting of less than 0.05% phosphorus, 0.5 to 1.1% manganese, The remainder of iron with the production-related impurities, treated according to claim 1 or 2, for the purpose of claim 1. 4. Use eiaes steel of the composition according to claim 1 or 3, of up to 0.8% manganese and / or up to 0.5% silicon and / or up to 0.1% of Al ^to ioium, treated according to claim 1 or 2, for the purpose of claim 1.