JPH04187718A - Production of nonoriented magnetic steel sheet having high tensile strength and low iron loss - Google Patents

Abstract

PURPOSE:To produce a nonoriented magnetic steel sheet having high tensile strength and low iron loss by the use of ordinary magnetic steel sheet manufacturing equipment by forming a slab of steel, in which respective contents of C and Si+Al are limited, into a hot coil by means of hot rolling under the prescribed process conditions and then subjecting this coil to cold rolling and annealing. CONSTITUTION:A slab or continuously cast slab having a composition containing, by weight, <=0.01% C and 4-7% (Si+Al) is previously subjected to hot rolling at 10-70% reduction of area in a state of hot slab of about 1000-1200 deg.C under heating or under remaining heat resulting from direct delivery after slabbing or continuous casting. Subsequently, the slab is reheated to 950-1100 deg.C and formed into a hot coil by means of hot rolling so that the temp. of a plate at the conclusion of finish rolling is regulated to >=700 deg.C. Then, this coil is cold-rolled and annealed, by which the above steel sheet can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a non-oriented electrical steel sheet with high strength and low core loss, which is required for high-speed rotating machines and the like.

The rotor of a rotating machine is mainly made of laminated electromagnetic mesh plates. Recently, in fields such as machine tools and semiconductor processing, there has been an increasing need for high-speed rotation of rotating machines to improve productivity and processing accuracy, and along with this, there is a need for high-strength electrical steel sheets that can sufficiently withstand the centrifugal force. It is becoming.

By the way, the rotation speed of the current rotating machine is 100,000 rpm.
The tensile strength was less than 100,000 rpm, and could be handled with existing electromagnetic steel sheets, but as the speed increased and the speed exceeded 100,000 rp+m, the tensile strength increased. It is expected that there will be situations in which even high-grade non-oriented electromagnetic copper sheets, which are the most expensive among magnetic steel sheets, cannot withstand. That is, the tensile strength of the current general non-oriented electrical steel sheet is the highest, about 55 kg'/an'', and a material with a tensile strength higher than that or 60 kg'/an'' is required. Furthermore, in order to achieve high efficiency in a rotating machine, it is naturally required that the rotating machine has both strength and low iron loss.

(Prior Art) In response to such demands for higher strength, several proposals regarding high tensile strength electrical steel sheets have been made.

For example, in Japanese Patent Publication No. 58-18424, ``contains 4 to 23% by weight of nickel, 0.7 to 3.2% by weight of aluminum, and contains a total of 0.05 to 0% of one or more of titanium, zirconium, niobium, and tantalum. A high-strength soft magnetic material for electric motor rotors has been proposed, which is characterized by containing .01% by weight, the balance being iron, and a small amount of deoxidized, sulfuric acid elements, and unavoidable impurities. The iron loss is W + szs at a plate thickness of 0.5 mm.
. is approximately 15 W/kg, which is significantly worse than that of ordinary electrical steel sheets.

Furthermore, in Japanese Patent Application Laid-Open No. 61-9520, rSi: 2.5
~7.0% by weight, Ti: 0.05~3.0% by weight
, W: 0.05-3.0% by weight, Mo: 0.0
5 to 3.0% by weight, Ni: 0.1 to 20.0% by weight, and i: 0.5 to 13.0 weight%. Molten steel containing in the range of .0% by weight is continuously supplied onto a cooling body whose cooling surface renews and moves at high speed, and is cooled and solidified to make it thinner. A method for producing high tensile strength non-directional quenched ribbon has been proposed, which is characterized by warm or cold rolling at a rolling reduction rate of 90% to obtain the final thickness, followed by final annealing. Currently, this method has poor accuracy in product plate thickness and shape, and has not been put into practical use industrially.

Furthermore, in Japanese Patent Application Laid-open No. 62-256917, it is stated that "Si: 2.0% or more and less than 3.5%, C: 0.0
08% or less, P: 0.03% or more and less than 0.2%,
and Mn.

One or two types of Ni in weight%, 0.3%≦Mn
Contains +Ni<10%, with the balance consisting of Fe and unavoidable impurity elements, tensile strength TS: 65 kg'/m
o” or more, and high frequency iron loss W S/l...: 50W
/kg or less, magnetic flux density B,. : A high tensile strength non-oriented electrical steel sheet for rotating machines with excellent mechanical and magnetic properties of 1.65T or more was proposed, and this is a method of adding P, Mn+L, solid solution strengthening elements, to the conventional electrical steel sheet material. It has been added more. However, in general, when solid solution strengthening elements are added, cold rollability deteriorates and manufacturing becomes difficult with normal equipment.
No specific solution to this problem is mentioned.

As mentioned above, in order to achieve high tensile strength, in any case, the current! Contains more solid solution-strengthening elements than magnetic steel sheets, so it is better than normal! When manufacturing magnetic steel sheets using equipment, cracking during cold rolling is an unavoidable problem.

On the other hand, in order to prevent such cracks, for example,
As proposed in Publication No.-238421, 100
Warm rolling at ~600°C is required, but warm rolling at temperatures above 100°C is difficult to maintain with current cold rolling equipment.
Some kind of equipment modification is required, and the rolling oil
Because it is forced to be used at temperatures over 100°C,
There are many problems such as the lubricating performance tends to deteriorate, the plate shape deteriorates, and a uniform plate thickness cannot be obtained.

(Problems to be Solved by the Invention) The purpose of the present invention is to achieve high tensile strength, which has recently been in increasing need.
The purpose of the present invention is to make it possible to manufacture a non-oriented electrical steel sheet with low iron loss using ordinary electrical steel sheet production equipment.

Another object of the present invention is to provide a method that allows rolling at a rolling temperature range that can be easily operated in common cold rolling equipment, that is, below 80°C.

Another object of the present invention is that the tensile strength is 60 kg'/
An object of the present invention is to provide a method for manufacturing a non-oriented electrical steel sheet having an iron loss (W+5/S.) of 8 W/kg or less on rrm 2.

(Means for Solving the Problems) The present invention has the following features: 1. C: 0.01 wt% or less, Si+AI! ,
: A blooming slab or continuous casting slab containing 4 to 7 wt%,
Hot rolling is carried out at a reduction rate of 10 to 70% under heating or under residual heat from direct conveyance after blooming or continuous casting, and then reheated to a temperature of 950 to 1100°C for finishing. A non-directional electromagnetic coil with high tensile strength and low core loss characterized by hot rolling to a plate temperature of 700°C or higher at the end of rolling, followed by cold rolling, and then annealing. Steel plate manufacturing method 2, C: 0.01 t% or less, Si+Al:
3wt% or more and less than 4%, and Si+Aj! +M
n+Ni+15P: A blooming slab or continuous cast slab containing 5 to 10-t% is heated or in a hot slab state under residual heat by direct conveyance after blooming or continuous casting, at a reduction rate of 10 to 7.
0% hot rolling, then reheating to a temperature of 950 to 1100°C, hot rolling such that the plate temperature at the end of finish rolling is 700°C or higher, and then cold rolling. This is a method for manufacturing a non-directional electromagnetic control plate with high tensile strength and low core loss, which is characterized by rolling and then annealing.

(Function) In general, when considering the simultaneous achievement of high tensile strength and low core loss, the main components should be Si and Af, which have high specific resistance, as alloying elements. %), although the tensile strength increases, the cold rollability deteriorates, making cold rolling difficult with normal cold rolling equipment.

As a result of examining methods for improving this cold-rollability, the inventors found that cold-rollability can be improved by making the hot-rolled sheet structure finer.

Furthermore, as a result of intensive research into methods for refining the structure of hot-rolled sheets, we decided to perform heating → rolling called P treatment in advance before heating the slab in the hot-rolling process. It has been found that by lowering the temperature (referred to as "temperature") lower than usual and further hot rolling at FDT≧700°C, the structure of the hot-rolled sheet becomes extremely fine and the cold rollability is significantly improved.

Next, i1! of the effect of improving cold rollability by the method of the present invention! I will explain the verification experiment.

C: 0.002%, Si: 3.3%, Af: 2.
Mn: 0.25, excluding 1%. P: 0.
A slab with a thickness of 215 m containing 0.12% and the remainder substantially consisting of Fe was subjected to P treatment (heating →
After rolling) and subsequent hot rolling heating, FDT was 7.
A hot rolled sheet with a thickness of 2.3 wn was obtained by hot rolling at a temperature of 00°C or higher. After pickling this hot-rolled sheet, it is cold-rolled to zero
．． Cold-rolled plate with a thickness of 5 mm, (700-800°C) x 1
Annealing was performed for 10 minutes.

Cold rolling was possible at a cold rolling temperature of 75°C within the range of combination conditions shown in Table 1, which also includes the results of cold rolling properties. However, the hot rolled sheet treated with P treatment at a hot rolling heating temperature of 900 to 1100°C and an FDT of 650°C broke when cold rolled at 75°C;
Rolling was possible at °C. Also, even if P treatment is applied,
All hot-rolled sheets treated at a hot-rolling heating temperature of 1150°C and hot-rolled sheets without P treatment are shown in Table 2. The mechanical properties and magnetic properties of the annealed sheets under each condition that allowed cold rolling in Table 1 are shown in Table 2. shows.

For reference, Table 3 shows the properties of current non-oriented electrical steel sheets, but as is clear from the comparison with Table 2, according to the present invention,
The tensile strength is extremely high, and the core loss is within a range that allows it to be used as an electromagnetic material for rotating machines.

Table 3 also shows Nb-based high-strength cold-rolled steel sheets (CNb-based) ISLA
) is also shown for comparison, and although its tensile strength is high, its magnetic properties are extremely poor, which shows how excellent the properties shown in Table 2 according to the present invention are.

Table 3 The method of the present invention allows cold rolling of sheets with a thickness of 0.5 as an example of high-strength cold-rolled steel sheets (even in the range of Si+Af content of 4% or more, which was difficult to conventionally cold-roll). becomes easier.

Next, the reasons for limiting the numerical values of the present invention will be described.

Since C is a harmful component to iron loss, it is set to 0.01% or less. Preferably, it is 0.004% or less from the viewpoint of aging.

If Si + Al exceeds 4%, cold rolling becomes difficult, so it was included in the scope of the present invention. However, if Si + Al exceeds 7%, the method of the present invention will not be able to roll the steel sheet at 100°, which is difficult to achieve with ordinary electrical steel sheet manufacturing equipment. Since warm rolling of C or higher is required, the upper limit was set at 7%.

Both Si and AP have a large effect of increasing resistivity and are effective elements for lowering iron loss, and also have the effect of increasing tensile strength. Therefore, Si and Aff are important constituent factors of the present invention with the same effect.

In addition, other solid solution strengthening elements (Mn, P, Ni, etc.) make cold rolling difficult, but if they are added as components of the present invention with the following considerations, the cold rolling properties of such steels can be improved. The method of the present invention is also effective.

Next, even in the range of CO,01 t% or less and Si + Af in the range of 3% or more and less than 4%, Mn, P, Ni,
5%≦Si+Al+Mn+Ni+15P≦10
As with the case where Si+Aff is 4% or more, it is difficult to cold roll with normal equipment under the limit of 4% or more, so cold rolling is possible by applying the method of the present invention in such cases as well. Become.

The reason why the upper limit is set to 10% or less is that if the upper limit is exceeded, 10%
This is because warm rolling at 0″C or higher becomes necessary.

In this case, Si+Aj2 is set to 3% or more because Si
This is because even if +Aff is set to less than 3% and the strength is increased with other solid solution elements, the iron loss will be large for an IT electrical steel sheet, which does not meet the purpose of the present invention.

Although there are no particular restrictions on the amount, an appropriate amount, for example 0.005%, is added to strengthen grain boundaries and improve cold rollability.
You may add the following amount.

Furthermore, although S, O, and N as impurity elements are not particularly restricted, it is desirable that they be as small as possible from a magnetic standpoint.

The heating temperature for P treatment is not particularly important and is not regulated, but as long as the temperature allows P treatment rolling, a lower temperature is preferable.

1000-1200°C is suitable.

If a continuous cast slab or a blooming slab is obtained at a temperature of about 1000 to 1200°C that allows P treatment rolling, P treatment rolling can be performed without P treatment heating under direct hot slab delivery. good.

The rolling reduction ratio of the P treatment is as described above (If it is less than 10%, there is no effect, so the lower limit is set to 10%.The upper limit is not limited in terms of improving cold rollability, but if the rolling reduction ratio exceeds 70%, the load on the rolling mill will increase. is excessive, so the upper limit is set to 70%.

As mentioned above, the hot rolling heating temperature is limited to 950 to 1100°C. At a hot rolling heating temperature of less than 950°C, it is practically difficult to achieve an FDT of 700°C or higher due to heat dissipation until the end of hot rolling finish rolling. I can't get tissue.

In addition, in the P treatment, heating and rolling may be repeated two or more times, and in this case, the P treatment heating from the second time onwards is
It is necessary to carry out the process within the range of ~1100″C.

The annealing temperature was set to 700 to further increase the tensile strength.
~850°C is suitable. If it is too low, the rolled structure remains, which is unfavorable in terms of magnetic properties, and if it is too high, the crystal grains become large and the tensile strength decreases.

Note that when the annealing temperature is higher than 850°C, although the tensile strength decreases, the magnetic properties, particularly the iron loss, become significantly lower than that of conventional electrical steel sheets within the composition range of the present invention. In the above experimental example, -1515 (1 = 2.20
W/kg, which can be said to be another feature of the present invention.

Next, a general method for manufacturing a high tensile strength electrical steel sheet according to the present invention will be described.

The molten steel of the present invention that has been produced through the converter-degassing process is generally cast to 200% by continuous casting or ingot-making to blooming rolling.
The slab is ~300 mm thick. Next, for P treatment, it is heated in a hatch furnace or continuous furnace, rolled down by 10 to 70% in a blooming mill, hot rolling mill, etc., and then heated to 950 to 1100°C in a slab heating furnace, etc. in the hot rolling process. After that, it is hot-rolled to a FDT of 700°C or higher to form a hot coil having a thickness of, for example, 1.5 to 3.5 +a.

The hot coil is descaled by pickling, etc., and annealed at 700 to 850°C after cold rolling.

In the above process, hot-rolled sheet annealing may be performed to improve magnetic properties, but when annealing is carried out, it is preferable to carry out at 900"C or less. If the temperature exceeds 900"C, cold rollability will deteriorate significantly. It is from.

(Example) Slabs of each component shown in Table 4 were subjected to P treatment heating at 1000°C, rolled at the P treatment reduction ratio shown in Table 4, heated at the hot rolling heating temperature shown in the same table, and hot rolled. A hot coil with a thickness of 2.6 mm was used.

The results of investigating the cold rollability during cold rolling (rolling temperature near 0"C) after pickling are shown in the same table. All comparative examples without P treatment showed no cracks or cracks during cold rolling. However, when the method of the present invention was applied, Si+
AA! is 4 to 7% and Si + Al: 3% or more4
% and Si+AI! , +Mn+Ni+1
5P: Cold rolling was possible in all ranges of 5 to 10%.

(Effects of the invention) As described above, the Si + Al content, which is difficult to cold-roll with ordinary electrical steel sheet manufacturing equipment, is 4 to 7% and the Si
+ Affi: 3% or more and less than 4%, and Si +
Aj2+ Mn + Ni + 15P: 5-10
If the method of the present invention is applied to each range of %, cold rolling becomes possible, and high-alloy electromagnetic conditioning plates, such as high tensile strength electromagnetic steel sheets, which could not be produced industrially in the past, can now be produced.

Claims (1)

[Claims] 1. A blooming slab or continuous cast slab containing C: 0.01 wt% or less and Si + Al: 4 to 7 wt% is heated or heated under residual heat by direct conveyance after blooming or continuous casting. In one state,
Hot rolling is carried out at a rolling reduction of 10 to 70%, then reheated to a temperature of 950 to 1100°C, and hot rolled to a temperature of 700°C or higher at the end of finish rolling to form a hot coil. A method for producing a non-oriented electrical steel sheet with high tensile strength and low iron loss, characterized by cold rolling this and then annealing it. 2. C: 0.01wt% or less, Si+Al: 3wt% or more and less than 4%, and Si+A
1+Mn+Ni+15P: A blooming slab or continuously cast slab containing 5 to 10 wt% is heated, or in a hot slab state under residual heat from direct conveyance after blooming or continuous casting, at a reduction rate of 10 to 10.
70% hot rolling, then reheating to a temperature of 950 to 1,100°C, hot rolling such that the plate temperature at the end of finish rolling is 700°C or higher, and then cold rolling. A method for manufacturing a non-oriented electrical steel sheet with high tensile strength and low iron loss, characterized by rolling and then annealing.