JPH0686624B2 - High tensile strength non-oriented electrical steel sheet manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a high tensile strength non-oriented electrical steel sheet, and relates to a magnetic material having low iron loss and high strength for a high speed rotating machine and an electromagnetic switch. The present invention relates to a method for producing a suitable magnetic material having excellent wear resistance.

(Prior Art) Conventionally, the rotational speed required for rotating equipment is 100,000 rp at most.
It is about m, and laminated electromagnetic steel sheets have been used as materials for rotors. Recently, ultra-high speed rotation of 200,000 to 300,000 rpm has been required, and the centrifugal force applied to the rotor may exceed the strength of electrical steel sheets.

Therefore, a solid rotor made of cast steel having sufficient strength is usually used for the ultra-high speed rotating machine instead of the electromagnetic steel plate. However, in this case, a complicated machining process of cutting the rotor out of the cast steel block is required, so that the cost is high, and moreover, there is a problem that the eddy current loss is larger than that of the laminated type and the efficiency of the motor is significantly reduced. There is.

In addition, since the contact surface of the electromagnetic switch wears as it is used, a magnetic material having excellent wear resistance as well as magnetic characteristics is desired.

In response to such needs, non-oriented electrical steel sheets having high tensile strength have recently been studied and some proposals have been made. For example, Japanese Patent Laid-Open No. 60-238421 discloses that Si should be 3.5
~ 7.0%, Mn: 0.1 ~ 11.5%, Ni: 0.1 ~ 20.0
%, Co: 0.5-20.0%, Ti: 0.05-3.0%, W: 0.05-3.0
%, Mo: 0.05 to 3.0%, Al: 0.5 to 13.0% of a solid solution strengthening component 1.0 to 20.0% slab is used as a raw material, and after hot rolling 100 to 600 Repeated warm rolling at ℃, rolled to the final plate thickness, annealed, and the tensile strength was 50 kg / mm ²
It is a method for manufacturing the above high tensile strength non-oriented electrical steel sheet.

This requires a troublesome warm rolling because it has a high Si content that is difficult to roll, but there is a possibility that plate breakage will increase during rolling, resulting in lower productivity and lower yield. There is room for improvement.

In JP-A-61-84360, Ni: 8-20%, Mo: 0.2-5.0
%, Al: 0.1 to 2.0%, Ti: 0.1% 1.0%, Cr 1.0 to 10.0%, a high tensile soft magnetic material for a high speed rotating electric motor has been proposed. This is an extremely expensive material because it contains a large amount of Ni and Mo and Cr.

Further, JP-A-61-9520 discloses that Si: 2.5-7.0% and Ti: 0.0
5 ~ 3.0%, W: 0.05 ~ 3.0%, Mo: 0.05 ~ 3.0%, Ni: 0.1 ~ 2
0.0%, Al: 0.5-13.0% of 1 type or 2 or more types of 1.0-2
A high tensile strength non-oriented electrical steel sheet is produced by a rapid solidification method using molten steel containing 0.0%. Since this is a special process, it cannot be manufactured by ordinary manufacturing equipment for electromagnetic steel sheets, and it is considered difficult to industrially manufacture it.

(Problems to be Solved by the Invention) As described above, a proposal has been made for the production of a high tensile strength non-oriented electrical steel sheet, but it is industrially stably produced using ordinary electrical steel sheet production equipment. The reality is that it hasn't arrived yet.

Further, since the high tensile strength non-oriented electrical steel sheet is used as a material for ultra-high speed rotating electric devices and electromagnetic switches as described above, it must have high tensile strength, low iron loss and excellent magnetic flux density. is there.

The present invention has a yield strength YP ≧ 55 kg / mm ² , a tensile strength TS ≧ 60 kg / mm ² , a hardness Hμv ≧ 150, high strength, wear resistance, and magnetic flux density suitable as a material for ultra-high speed rotating machines and electromagnetic switches. It is an object of the present invention to stably manufacture a high tensile strength non-oriented electrical steel sheet having excellent magnetic properties of B50 ≧ 1.60T on an industrial scale without causing plate breakage or the like.

(Means for Solving Problems) The present inventors have conducted various experiments and studies in order to achieve the above object. That is, the present invention is C: 0.01% or less, Si: 2.0% or more 3.
5% or less, Mn: 0.1% or more and 10.0% or less, P: 0.20% or less, Al:
0.10% or more and 1.50% or less, B: 0.008% or less, and optionally 6.0% or less of Ni with the balance being iron and unavoidable impurities, hot-rolling the slab with the balance between iron and unavoidable impurities. 550 by quenching at an average cooling rate of 1000 ° C / min or more
The grain boundary P segregation concentration is 0.40% or less by winding at a temperature of ℃ or less, and then it is annealed without annealing or hot-rolled sheet annealing, cold rolling, and annealing to obtain high tensile strength and excellent magnetic properties. It is a method of manufacturing a grain-oriented electrical steel sheet.

First, the steel composition will be described.

C is a component that deteriorates magnetic properties, and if it is contained in excess of 0.01 (wt)%, iron loss increases, so the content is made 0.01% or less. Incidentally, C may be decarburized by a hot-rolled plate or a cold-rolled plate instead of being decarburized by steelmaking and put in the above range.

Si increases the specific resistance of steel, reduces eddy currents, reduces iron loss, and increases tensile strength, but the content is 2.0%.
If less than, the effect is small. Further, if it exceeds 3.5%, the steel becomes brittle and the magnetic flux density of the product is further lowered.
% Or less.

Mn not only increases the tensile strength of steel, but also increases the specific resistance and decreases the iron loss, but if it is less than 0.1%, it is less effective, and 10.0%.
, The magnetic flux density of the product will decrease, so 0.1 to 10.0
%. It is preferably more than 1.0% and 5.0%.

P is a significant element that increases tensile strength, but 0.2%
If it exceeds, embrittlement becomes severe and it becomes difficult to perform hot rolling, cold rolling, etc. on an industrial scale, so the upper limit is made 0.20%.

When a product such as an iron core is punched from a steel plate or used on the end face as it is sheared, if it is exposed to an atmosphere of 150 ° C or higher for a long time, P0.03% or more may cause apparent deterioration of elongation. It is considered that this is due to the fact that the fracture surface of the high tensile strength steel sheet relatively easily contains microcracks, and strain aging.

Therefore, if the elongation after aging becomes a problem for the application, adopt a smooth and strain-free end surface processing method.

It is effective to punch with sandpaper and remove the sheared surface layer.

If the content of P is 0.03% or less, the above problem does not occur.

Al needs to be at least 0.10% as a deoxidizer, and the inclusion of Al improves strength and decreases iron loss due to an increase in resistivity, but if it exceeds 1.50%, embrittlement becomes a problem. Therefore, 0.10 to 1.50%.

B segregates at the crystal grain boundaries, and P has the effect of suppressing embrittlement due to grain boundary segregation. However, if it exceeds 0.008%, it becomes significantly embrittled, so the upper limit is made 0.008%.

Further, Ni is contained if necessary. Ni has little adverse effect on the magnetic properties and is effective in improving the tensile strength, but if it exceeds 6.0%, the magnetic flux density is greatly reduced, so it is made 6.0% or less.

A steel slab containing the above components and the balance of iron and inevitable impurities is melted in a converter and manufactured by continuous casting or ingot-slab rolling.

The steel slab is heated in a known manner and then for example 0.5 to
Hot rolled to a plate thickness of 3.5 mm. The control of the cooling rate from the finish outlet of hot rolling to the winding is important for enhancing the cold rolling property of the steel sheet, and cooling is performed at a cooling rate of 1000 ° C. or more per minute.

Furthermore, the coiling temperature is important and the coiling temperature is below 550 ° C. Under conditions outside this range, that is, when the average cooling rate is less than 1000 ° C / min, or when coiled at a temperature higher than 550 ° C, the P segregation concentration at the crystal grain boundaries exceeds 0.4%, Since it becomes coarse, it becomes extremely brittle, and the plate often breaks during the subsequent rolling.

After hot rolling, cold rolling is performed, or if it is necessary to further improve the magnetic properties, hot rolled sheet annealing is performed at 500 to 1
It is performed at 000 ° C. for 5 seconds to 15 minutes, and then cold rolled. It is 50 that the hot-rolled sheet annealing is performed within the above temperature and time range.
This is because if the temperature is lower than 0 ° C or shorter than 5 seconds, the annealing effect that further enhances the magnetic properties does not appear. On the other hand, if the temperature exceeds 1000 ° C or 15 minutes, the crystal grains become coarse and the sheet breaks during cold rolling, It reduces the strength of the product.

After cold rolling, annealing is performed at 700 to 900 ° C for 5 seconds to 15 minutes.
The reason is that, at 700 ° C. or less than 5 seconds, a sufficient annealing effect for reducing iron loss and improving magnetic flux density does not appear, and the rolling structure remains or the flatness remains unimproved. 90
If the temperature exceeds 0 ° C or 15 minutes, the crystal grains become coarse and the strength decreases, and a high tensile strength steel sheet cannot be obtained.

In the annealing of this cold-rolled sheet, decarburization may be carried out in a decarburizing atmosphere if necessary.

(Example) Example 1 C: 0.0023%, Si: 3.2%, Mn: 1.5%, P: 0.102%, Al: 0.67
Steel slab test material A containing 5% and B: 0.0051% with the balance being iron and unavoidable impurities, and steel slab test material B containing 1.50% Ni and the rest being iron and unavoidable impurities , Hot rolled to a plate thickness of 2.0 mm, processed at an average cooling rate from hot rolling finish rolling to winding of 500 to 2000 ° C./min and a winding temperature of 400 to 600 ° C. without hot-rolled sheet annealing, or The hot-rolled sheet annealing conditions were changed within the range of (840 to 1100) ° C × (5 to 30) seconds, cold rolled to a sheet thickness of 0.5 mm, and then (650 to 925) ° C for 30 seconds. Annealing was performed, and mechanical properties, iron loss of W15 / 50 and magnetic flux density of B50 were measured.

For the magnetic measurement, 30 mm × 320 mm Epstein test pieces (rolling direction and right-angled half amount) were used. Moreover, the P segregation concentration of the crystal grain boundary of the hot rolled sheet was analyzed by an Auger analyzer.

The results are shown in Table 1.

As is clear from the results shown in Table 1, the samples A5, A7, A9, B10, B12: B14: B15 produced under the conditions of the present invention were rolled without causing sheet breakage and yield strength YP. 64-68 kg
/ mm ² , tensile strength TS is 74 ~ 76 kg / mm ^2, with high strength characteristics,
Furthermore, it has excellent iron loss W15 / 50 and magnetic flux density B50.

Example 2 C: 0.0015 to 0.004% by weight, Si: 2.8 to 3.23%, Mn: 0.04
~ 3.05%, P: 0.005-0.50%, Al: 0.50-2.00%, B: 0.00
A steel slab specimen containing 0 to 0.0100% and Ni: 0.75 to 1.80% with the balance being iron and inevitable impurities was hot-rolled to a plate thickness of 2.0 mm, from hot rolling finish rolling to winding. Cooling rate is 2000 ℃ per minute, winding temperature is 400 ℃, 800 ℃ ×
After performing hot-rolled sheet annealing for 30 seconds, cold rolling reduces the sheet thickness to 0.
The mechanical properties and magnetic properties of a steel sheet having a thickness of 5 mm and annealed at 750 ° C. for 30 seconds were measured.

Epstein test specimens with magnetic characteristics of 30 mm × 320 mm were sheared by half each from the rolling direction and the perpendicular direction to W1.
The iron loss of 5/50 and the magnetic flux density of B50 were measured.

The results are shown in Table 2.

As is clear from the results shown in Table 2, Samples 1 to 9 produced under the conditions of the present invention were rolled without causing plate breakage, yield strength YP was 61 to 71 kg / mm ² , tensile strength TS. 70 to 81
It has high strength characteristics at kg / mm ² , and also has excellent iron loss W15 / 50 and magnetic flux density B50.

(Effects of the Invention) As described above, according to the present invention, a non-oriented electrical steel sheet having high tensile strength and wear resistance and excellent magnetic properties, which is very suitable as a material for an ultra-high speed rotating machine and an electromagnetic switch. However, it is stably manufactured without causing troubles such as plate breakage.

Claims (4)

[Claims] [Claim 1] C: 0.01% or less by weight% Si: 2.0% or more and 3.5% or less Mn: 0.1% or more and 10.0% or less P: 0.20% or less Al: 0.10% or more and 1.50% or less B: 0.008% or less , A slab with the balance being iron and unavoidable impurities is hot-rolled, cooled at an average cooling rate of 1000 ° C / min or more between the hot rolling finish outlet and winding, and wound at a temperature of 550 ° C or less, A high tensile strength non-oriented electrical steel sheet, characterized in that the P segregation concentration at grain boundaries is 0.40% or less, cold rolling is performed, and annealing is performed at a temperature of 700 ° C. or more and 900 ° C. or less for 5 seconds or more and 15 minutes or less. Production method. 2. By weight%, C: 0.01% or less Si: 2.0% or more and 3.5% or less Mn: 0.1% or more and 10.0% or less P: 0.20% or less Al: 0.10% or more and 1.50% or less B: 0.008% or less , Hot-rolling a slab with the balance being iron and unavoidable impurities, cooling at an average cooling rate of 1000 ° C / min or more between the hot rolling finish outlet and winding, winding at a temperature of 550 ° C or less, and graining. The P segregation concentration of the boundary is 0.40% or less, then annealing is performed for 5 seconds or more and 15 minutes or less at a temperature of 500 ° C or more and 1000 ° C or less, and cold rolling is performed for 5 seconds or more at a temperature of 700 ° C or more and 900 ° C or less. A method for producing a high tensile strength non-oriented electrical steel sheet, which comprises performing annealing for 15 minutes or less. [Claim 3] C: 0.01% or less by weight% Si: 2.0% or more and 3.5% or less Mn: 0.1% or more and 10.0% or less P: 0.20% or less Al: 0.10% or more and 1.50% or less B: 0.008% or less Ni: 6.0 %, With the balance consisting of iron and unavoidable impurities, hot-rolled, cooled at an average cooling rate of 1000 ° C / min or more between the hot rolling finish outlet and winding, and a temperature of 550 ° C or less. Coiled, the P segregation concentration in the grain boundary is 0.40% or less, cold rolled, and annealed at a temperature of 700 ° C to 900 ° C for 5 seconds to 15 minutes. For manufacturing high-performance electrical steel sheet. 4. By weight%, C: 0.01% or less Si: 2.0% or more and 3.5% or less Mn: 0.1% or more and 10.0% or less P: 0.20% or less Al: 0.10% or more and 1.50% or less B: 0.008% or less Ni: 6.0 %, With the balance consisting of iron and unavoidable impurities, hot-rolled, cooled at an average cooling rate of 1000 ° C / min or more between the hot rolling finish outlet and winding, and a temperature of 550 ° C or less. The P segregation concentration at the grain boundary is adjusted to 0.40% or less, then annealed at a temperature of 500 ° C. or higher and 1000 ° C. or lower for 5 seconds or longer and 15 minutes or shorter, and cold rolled to 700 ° C. or higher and 900 ° C. or lower. A method for producing a high tensile strength non-oriented electrical steel sheet, which comprises performing annealing for 5 seconds or more and 15 minutes or less at a temperature.