JP2013052444A - Method of manufacturing steel strip or steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a steel strip or a steel sheet which permits omission of a slit process, improvement of an yield in the course from a start material to products, improvement of an yield in the course from a thin steel strip sheet to products, manufacturability by small-scale equipment, and availability for manufacturing products ranging from high-mix low-volume products to large-lot specified products, in a method which, in order to manufacture a comparatively thin and narrow steel strip or steel sheet, has been conventionally worked out through the process of rolling an ordinary hot-rolled or cold-rolled steel sheet to a prescribed thickness, and then slitting and further rolling, or slitting in advance and then rolling to a prescribed thickness.SOLUTION: The method is either a method in which a steel wire rod, or a steel wire or a steel bar composed of commercially-supplied carbon steel or ferritic stainless steel, or austenitic stainless steel is used as a start material and it is rolled to a final thickness with flat rollers in a cold temperature region, or a method in which after first the material is rolled with caliber rollers in the cold temperature region, it is rolled to the final thickness with the flat rollers in the cold temperature region, or after first it is rolled with the caliber rollers in a warm temperature region, rolled to the final thickness with the flat rollers in the cold temperature region, and a large strain is introduced from a step of the start material to a prescribed step of an intermediate material and a final material.

Description

The present invention relates to a method for producing a high strength and ductile steel strip or steel plate used for structural precision parts in automobiles, home appliances, electrical / electronic devices, and the like.

In recent years, among the electrical and electronic devices found in automobile fuel efficiency improvements, home appliances, IC lead frames, etc., among the narrow thin plates of metal materials used to make precision components, the plate width is 20- There is a need for a “narrow strip metal plate” that is sufficient if it is about 30 mm or less and has a plate thickness of 1 mm or less, preferably about 0.2 mm or less. There are various uses for the narrow strip metal plate, and examples thereof include micro motors such as watches and cameras, needles, shafts or gears, and orifice plates of fuel injection devices. The main methods of processing such narrow strip metal plates for such applications include cutting, shearing, laser processing, and press processing.

Although there are differences depending on the application and processing method as characteristics to be possessed by such a thin strip metal plate as a material, a common important matter is that it has appropriate strength and is excellent in ductility. It is that you are. On the other hand, there are various important items from the viewpoint of manufacturing a narrow strip metal plate, but basically, materials suitable for applications and processing methods are industrially reduced in terms of resource and energy savings. It is desirable to satisfy the requirements of the material user by a manufacturing method that can be lowered as much as possible so as not to raise it as much as possible.

Conventionally, a method for manufacturing a thin strip metal plate is to first select a type of metal material as a starting material, and to manufacture a strip-shaped metal material (in the case of steel) manufactured by equipment and a manufacturing method that can be mass-produced relatively inexpensively Obtain a relatively large amount of steel strip or flat steel). Next, a thin strip metal plate is manufactured from the strip-shaped metal material. In the production, the thickness and width of the ribbon metal plate are determined in consideration of the use of the product and the product specification. At this time, it is also important to consider so that the yield of the ribbon metal plate from the ribbon metal plate to the final product can be as high as possible. Moreover, the process of slitting narrowly increases the cost.

  In the case of a thin steel plate, wide and narrow names often have a width of about 500 mm as the boundary. In the present invention, the metal type is steel. Generally, a steel strip is a coiled coil, and a steel plate is a flat plate. Accordingly, the present invention also follows this.

  Cold-rolled steel sheets having a thickness of up to about 0.8 mm are manufactured by an iron manufacturer having a large-scale facility. In this case, the plate width is about 800 to 1000 mm or more, and the process is hot rolling, pickling, and cold rolling. Furthermore, in order to manufacture a strip or steel plate having a thickness of 0.8 mm or less, a width of 500 mm or less, and up to several tens of mm, conventionally, cold rolling of the cold-rolled steel sheet is further repeated in a secondary rolling manufacturer. In this way, the thickness is reduced to about 0.1 mm. If a normal cold-rolled steel sheet is used as a starting material, it is good to make a thin and wide sheet. is there.

  Repeating rolling means work hardening, and it is necessary to change the structure from a work hardening structure to an equiaxed structure by annealing during cold rolling or after cold rolling. The cold rolling process can accumulate a large amount of strain in the material, but this strain energy is scattered by annealing. It has been reported that the method of cold rolling + annealing is a method that can produce fine-grained steel. However, in order to produce fine-grained steel by cold working, it is necessary to introduce a large strain during cold working. Cold rolling + annealing does not always produce fine grains.

Many parts manufactured from narrow and thin strips or steel plates are often small and do not require wide materials. A width of 30 mm or less is often sufficient. When a narrow-width material is assumed, a cold-rolled steel sheet that requires a slit is not necessarily required. Ordinary cold-rolled steel sheet (usually, the plate width is about 800 to 1000 mm or more), a narrow steel strip by hot rolling or a cold-rolled steel strip (normally, the plate width is about 200 to 600 mm). ), Steel wire or cold rolled steel wire by hot rolling with a diameter smaller than the plate width of any of them or a length between opposite sides, or steel bar hot or cold rolled By using the starting material, it is possible to greatly omit the process. The hot-rolled steel wire described above is far less expensive than the cold-rolled steel sheet or the narrow-width material of the hot-rolled steel sheet.

Hot rolled steel wire has a diameter of 6 mmφ or more, or a length between opposite sides of 6 mm or more, and introduces a large strain by rolling from the diameter or the length between opposite sides to a thickness of 0.2 mm, for example. can do.
Moreover, if rolling is carried out to 3 mmφ by adding hole roll rolling in the middle, a large strain can be introduced at this stage. If a large strain can be introduced, the grain size can be controlled by subsequent annealing, and as a result, the mechanical properties can also be controlled. The inventor has invented a method for manufacturing a steel strip or a steel plate having a fine structure, a high strength and high ductility, a thin plate thickness and a narrow plate width by using the hot rolled steel wire or the like as a starting material. did.
The features of the present invention will be described below.

The strip steel or steel plate production method of the first invention is a method of rolling a steel wire, steel wire or bar steel made of carbon steel, ferritic stainless steel or austenitic stainless steel to produce the strip steel or steel plate, Is rolled at a rolling temperature within a range of 250 ° C. or less to produce a strip or a steel plate. Then, the following formula (1):
ln (d ₀ /t)≧2.3 (1)
d ₀ : Steel wire shape or diameter of steel wire or steel bar or length between opposite sides t: Characteristic of satisfying thickness of strip steel or steel plate after rolling.

The strip steel or steel plate manufacturing method of the second invention is a method of rolling a steel wire, steel wire or bar steel made of carbon steel, ferritic stainless steel or austenitic stainless steel to manufacture the strip steel or steel plate, The rolled material obtained by performing hole roll rolling at a rolling temperature within a range of from 250 to 250 ° C. is rolled into a plate shape by flat roll rolling. Then, the following formula (1):
ln (d ₀ /t)≧2.3 (1)
d ₀ : Steel wire shape or diameter of steel wire or steel bar or length between opposite sides t: Characteristic of satisfying thickness of strip steel or steel plate after rolling.

In the method for manufacturing a steel strip or steel plate according to the third aspect of the invention, in rolling the steel wire, steel wire or steel bar into a rolled material in the method for manufacturing the steel strip or steel plate according to the second invention, the following formula (2):
d ₁ ≦ d ₀ × 0.6 (2)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₁ : Characteristic of satisfying diameter of rolled material or length between opposite sides.

A method for producing a steel strip or steel plate according to a fourth aspect of the present invention is the method for producing a steel strip or steel plate according to 2 or 3, wherein the steel wire, steel wire or steel bar is perforated at a rolling temperature within a range from room temperature to 250 ° C. In the final pass of the perforated roll rolling, a deformed cross-section material obtained by making the cross section into an oval shape or a rectangular shape by a flat box perforated roll is rolled by the flat roll rolling. It is made into a plate shape. Then, the following formula (3):
d ₂ ≦ d ₀ 0.3 (3)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₂ : Characteristic of satisfying short side length of deformed cross-section material.

The method for manufacturing a steel strip or steel plate according to a fifth aspect of the present invention is the method for manufacturing a steel strip or steel plate according to the fourth aspect of the invention, wherein the deformed cross-section material is further rolled with a flat roll at a rolling temperature within a range from room temperature to 250 ° C. The ribbon-shaped material obtained by carrying out 1 pass or 2 passes is rolled into the plate shape by the flat roll rolling. Then, the following formula (4):
d ₃ ≦ d ₀ × 0.25 (4)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₃ : Characteristic of satisfying thickness of strip-shaped material.

The strip steel or steel plate manufacturing method according to a sixth aspect of the present invention is the strip steel or steel plate manufacturing method according to any one of 2 to 5, wherein the roll or roll is rolled at a rolling temperature within a range from the normal temperature to 250 ° C. or less. Is characterized by including one or more rollings by a combination of an oval hole roll and a subsequent square hole roll.

The strip steel or steel plate production method of the seventh invention is a method for producing a steel strip or steel plate by rolling a steel wire, steel wire or bar steel made of carbon steel, ferritic stainless steel or austenitic stainless steel. A rolled material obtained by carrying out a perforated roll rolling at a rolling temperature within a range of from above ° C to below 800 ° C is rolled into a plate shape by flat roll rolling. Then the following formula (1):
ln (d ₀ /t)≧2.3 (1)
d ₀ : Diameter of steel wire or steel wire or bar or length between opposite sides t: Characteristic in satisfying thickness of strip steel or steel plate after rolling.

In the method for manufacturing a steel strip or steel plate according to the eighth invention, in the method for manufacturing a steel strip and steel plate according to the seventh invention, when rolling the steel wire, steel wire or steel bar into a rolled material, the following formula (5):
d ₁ ′ ≦ d ₀ × 0.6 (5)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₁ ': Characteristic of satisfying diameter of rolled material or length between opposite sides.

A method for producing a steel strip or steel plate according to a ninth invention is the method for producing a steel strip or steel plate according to the seventh or eighth invention, wherein the steel wire material, steel wire or steel bar is within a range of more than 250 ° C to 800 ° C or less. In the final pass of the perforated roll rolling, the oval perforated roll or the flat box perforated roll is used to roll the irregular cross-section material having an oval or rectangular cross section by the flat roll rolling. To form a plate, and then the following formula (6):
d ₂ '≦ d ₀ × 0.3 (6)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₂ ′: Characteristic of satisfying short side length of deformed cross-section material.

The method for manufacturing a steel strip or steel plate according to a tenth aspect of the invention is the method for manufacturing a steel plate according to the ninth aspect of the invention, wherein the deformed cross-section material is further rolled with a flat roll at a rolling temperature within a range of from 250 ° C to 800 ° C. A strip-like material obtained by performing one pass or two passes is rolled into the plate shape by the flat roll rolling. Then, the following formula (7):
d ₃ ′ ≦ d ₀ × 0.25 (7)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₃ ′: Characteristic in satisfying thickness of thin strip material.

The strip steel or steel plate manufacturing method according to an eleventh aspect of the present invention is the method of manufacturing a steel strip or steel plate according to any of the seventh to tenth aspects of the present invention, wherein the hole at a rolling temperature within the range from above 250 ° C to 800 ° C is used. The die roll rolling is characterized in that rolling by a combination of an oval hole roll and a subsequent square hole roll is included one or more times.

A strip steel or steel plate manufacturing method according to a twelfth aspect of the present invention is the strip steel or steel plate manufacturing method according to any one of the first to eleventh aspects of the present invention, or a strip steel finally obtained from the steel wire rod, steel wire or bar steel or The plastic strain calculated by using the finite element method at the center of the plate width or the center of the plate thickness of the steel strip or the steel plate introduced with the plastic working in rolling on the steel plate is 2.3 or more. It has the feature in making.

The method for manufacturing a steel strip or steel plate according to a thirteenth aspect of the present invention is the method for manufacturing a steel strip or steel plate according to any of the first to twelfth aspects of the invention, during rolling with a flat roll, after rolling, or both during and after rolling. In the above, the steel strip or the steel plate is characterized by being annealed within a range of 400 ° C to 700 ° C.

  A method for manufacturing a steel strip or steel sheet having a super-fine structure, high strength, high ductility, and high shear workability at a low cost in manufacturing a steel strip or steel sheet having a thin plate thickness and a narrow plate width. Can be provided. Here, as the level of refinement and mechanical properties of the band steel or steel sheet, the average grain boundary interval is 2 μm or less, further 0.6 μm or less, the yield strength is 600 MPa or more, and The ratio between the breaking strength and the tensile strength is as excellent as 1.2 or more.

Since the steel strip or steel plate manufactured in the present invention is narrow to some extent and thin in thickness, it will be hereinafter also referred to as a steel strip steel plate.

(1) About introduction amount of strain e With respect to a starting material made of carbon steel, ferritic stainless steel, or austenitic stainless steel (these diameters or lengths between opposite sides are expressed by d ₀ ) from normal temperature When producing a strip steel sheet by rolling the sheet thickness to t by performing flat roll rolling at a rolling temperature within a range of 250 ° C. or less, the formula (1):
ln (d ₀ /t)≧2.3 (1)
By satisfying the condition, a large strain can be introduced. In the present invention, depending on the use of the steel strip, the strength and ductility may be ensured without necessarily annealing the steel strip and reducing the dislocation density inside the material. In some cases, it may be desirable to increase the ductility to an excellent level while maintaining above the value. Considering this case, it is necessary to satisfy the above formula (1).
At that time, the strain to be introduced into the material to be rolled is that the rolling temperature is in the cold temperature region (in the present invention, from room temperature to 250 ° C. or less) and in the warm temperature region (in the present invention, 250). It is effective in any case of over ℃ to 800 ℃.
Furthermore, as long as a large strain satisfying the formula (1) is introduced, the rolling method may be a perforated roll rolling or a flat roll rolling, and the amount of strain introduced per pass May be within the capacity range of a rolling mill of a production factory that is normally performed.

Next, the reason why it is necessary to satisfy the formula (1) in order to introduce the large strain into the material to be rolled will be described.
The strip steel sheet to be produced according to the present invention needs to obtain a work-hardened structure that has a substantially fine structure in a state of being rolled at the stage where the rolling is completed with a flat roll. Here, the work hardened structure uses the ferrite grain boundary interval TH as an index, and it is necessary that TH ≦ 2 μm. Desirably, TH ≦ 0.6 μm.
From the viewpoint of sufficiently increasing the dislocation density, the strain e needs to be e ≧ 2.3.
Hot rolling or hot the start material produced by forging (these diameter or an opposite side surface between the length, both the d _0, referred to herein as "the thickness of the starting material") Average ferrite grain diameter of Is generally known to be 10-20 μm.
In this starting material, when strain is introduced by rolling in both the cold temperature region and the warm temperature region, the average ferrite grain boundary interval TH (μm) of the obtained steel material is the initial grain size. and D _0, the strain introduced into the material to be rolled and e, geometrically,
TH = D ₀ exp (−e) (A)
It becomes.
Therefore, from equation (A) and e = ln (d ₀ / t),
TH = D ₀ exp (t / d ₀ ) (B)
Where t: thickness of the steel material obtained by rolling
d ₀ : The thickness of the starting material is obtained.

In the present invention, for example, as the maximum value of _{d 0} of the start _material, and d 0 = 20 mm, the average crystal grain size _{D 0,} in the case of D 0 = 20 [mu] m, the maximum value of the thickness t of the thin strip steel Assuming that t = 2 mm, the average ferrite grain boundary interval TH can be set to TH = 2 μm according to the above equation (B).
Although TH ≦ 0.6 μm is desirable, in order to realize this under the above conditions, e ≧ 3.5 may be set according to the above equation (A).

(2) Strain e to be introduced by the intermediate stage From the starting material (the d ₀ ) to the strip steel sheet (the t), the material to be rolled in the intermediate stage of the rolling process (the d ₁ and d in the present invention) ₂ or, by any) of d _3, by introducing a strain of a predetermined amount of the material being rolled, when considering the entire rolling process, the variation of the amount of strain per rolling pass is large rolling pass schedule It can be avoided. In order to set such a path schedule, the following formula (2), (3) or (4), or formula (2 ′), (3 ′) or (4 ′):
d ₁ ≦ d ₀ × 0.6 (2)
d ₂ ≦ d ₀ × 0.3 (3)
d ₃ ≦ d ₀ × 0.25 (4)
d ₁ ′ ≦ d ₀ × 0.6 (5)
d ₂ '≦ d ₀ × 0.3 (6)
d ₃ ′ ≦ d ₀ × 0.25 (7)
It is desirable to satisfy at least one of them.

(3) Selection of the cross-sectional shape of the material to be rolled in the intermediate stage <1> Select the cross-sectional shape of the rolled material in the intermediate stage as a circle or a rectangle (diameter or opposite side length d ₁ or In the case of d ₁ ^′ ) In this case, the hole shape of the final pass of the hole roll rolling can be square or round. It is also possible to purchase a desired commercial coil. There is no particular limitation.
<2> When the cross-sectional shape of the intermediate stage is an odd-shaped cross-sectional material (short side length d ₂ or d ₂ ^′ ) that is an oval or rectangular material in this case. It is desirable to prevent the occurrence of surface flaws due to the twisting of the material due to the biting failure in the step of biting into the first pass of rolling into the strip steel plate having the target size.
<3> When the cross-sectional shape of the intermediate stage is a ribbon-like material (thickness d ₃ or d ₃ ^′ )
Since the flat roll rolling of 1 pass or 2 passes is performed after <2> above, the cross-sectional shape of the material to be rolled is further closer to the size and shape of the final strip steel plate. The pass schedule of multi-pass flat roll rolling can be used flexibly. Therefore, it is desirable in the operation of the rolling process.

(4) Inclusion of an oval + square pass schedule in hole roll rolling By adopting such a pass schedule, the rolling direction can be reduced from as many directions as possible. Therefore, it is effective for introduction of plastic strain (ε) by calculation using a finite element method capable of more accurately evaluating the introduction of strain, and can make the necessary condition for crystal grain refinement superior.

(5) About the direction of biting of the material to be rolled into the hole-type roll By making the reduction direction by the oval hole-type roll and the reduction direction by the square hole-type roll or the round hole-type roll next to this perpendicular, the plastic strain ( It is effective for introducing ε).
In addition, when a material having a square cross-section is bitten into the oval hole-type roll, the material to be rolled is made to bite at an angle of 45 ° with respect to the rolling-down direction of the immediately preceding square hole-type roll. Rolling can be performed so that the opposite side surface of the quadrilateral is rolled down by the curved surface of the oval hole type. By doing this, even if the area reduction rate per pass is large, the material does not fall or twist during rolling, the cross-sectional shape is good, and the surface property can be kept good. . Furthermore, it is advantageous for introducing strain to the center of the material to be rolled, and contributes to the refinement of crystal grains.

(6) Relationship between the area reduction ratio and the roll peripheral speed ratio in the perforated roll rolling Distance between roll axis centers in the rolling line direction between the oval perforated roll and the square perforated roll or the round perforated roll (denoted by L) Between the radius of each perforated roll (represented by D _(OV) / 2, D _(SQ) / 2 or D _(RD) / 2, respectively), the relationship of the following formula (8a) or (8b) To meet
L ≦ {(D _(OV) / 2) + (D _(SQ) / 2 ₎ } × 1.5 (8a)
L ≦ {(D _(OV) / 2) + (D _(RD) /2)}×1.5 (8b)
In addition, the outer peripheral speed (represented by V _(OV) , V _(SQ), or V _(RD) , respectively _{) of} each of the hole-type rolls is the same as the oval hole-type roll and the square hole-type roll or the round hole-type roll. In order to satisfy the relationship of the following formula (9a) or (9b) between the total surface area reduction ratio of the material to be rolled by two hole rolls ₍ indicated by R _{(OV + SQ)} or R _{(OV + RD))} ,
V _(SQ) / V _(OV) = _{A.R (OV + SQ)} + B (9a)
V _(RD) / V _(OV) = _{A.R (OV + RD)} + B (9b)
Where A and B are constants,
0.017 ≦ A ≦ 0.019
0.66 ≦ B ≦ 0.68
By rolling, the material to be rolled does not twist, and the degree of fullness of the material to be rolled into the downstream perforated roll becomes appropriate, and the prevention of surface flaws and the control of the cross-sectional shape are improved.

(7) About annealing of the strip steel sheet By introducing a large strain in the rolling process from the starting material to the strip steel sheet, it is a matter of course that the yield strength is as high as 1.0 GPa or more in the state of rolling. However, the aperture RA is also maintained at 20% or more. Therefore, depending on the application, it can be used without annealing. However, when a further balance between strength and ductility is required, the annealing properties of the strip steel sheet obtained by the manufacturing method of the present invention are controlled within the range of 400 to 700 ° C. and the mechanical properties are controlled. can do.

(8) When the average ferrite grain boundary interval TH is 2 μm or less, the strength of the ribbon steel sheet structure can be improved by making the TH finer. It is desirable from the strength and ductility balance that this is 2 μm or less. More desirably, it is 0.6 μm or less. Furthermore, it is more desirable if the average ferrite crystal grain spacing TH with an orientation difference angle of 5 ° or more in the thickness direction of the thin steel plate is 0.6 μm or less.

  Examples that fall within the scope of the present invention are described. The steel strip and steel plate may be expressed as a thin steel strip.

A commercially available hot rolled steel wire coil having the chemical composition shown in Table 1 and a wire diameter d0 of _6.0 mmφ was used as a starting material. The average crystal grain size of the cross section in the C direction of this 6.0 mmφ hot-rolled steel wire was 10 μm.

  The coil of the above-mentioned 6.0 mmφ hot-rolled steel wire rod is subjected to hot-hole roll rolling by multiple passes from multiple directions within a predetermined temperature range, and the coil of steel fine wire rod by 2.8 mmφ hot-hole rolling. This was further processed into a coil of a strip steel plate having a plate thickness of 0.16 mm and a plate width of 20 mm by cold rolling of multi-pass flat rolls appropriately annealed between passes. Hereinafter, the warm hole roll rolling method and the flat roll cold rolling method will be described.

[Warm hole type roll rolling method]
As a warm hole type roll rolling apparatus, a test warm hole type roll rolling apparatus showing a schematic appearance of the side surface shown in FIG. 1 was used. In the figure, reference numeral 19 'designates a rolling base in which two perforated roll rolling mills are arranged close to each other in series (hereinafter referred to as "two-proximity rolling base" in this specification, The rolling mill on the upstream side of the line is referred to as “first rolling mill”, and the rolling mill on the downstream side is referred to as “second rolling mill”). Reference numeral 9 denotes a coil feeder for steel wire rod, and reference numeral 18 denotes a steel wire rod. It is a coil winding device.

FIG. 2 shows a pair of perforated rolls (2) of the first rolling mill (1) and a pair of perforated rolls (4) of the second rolling mill (3), which constitute the two-machine proximity rolling base (19 ′). 3 is a schematic perspective view showing the relative disposition relationship of FIG. 3, and FIG. 3 is a diagram illustrating the axial centers (j ₁ ) and ( When j ₂ ) is projected in the vertical direction, it is perpendicular to the axes j ₁ and j _{2 in} a state in which the two-machine proximity rolling base is virtually raised so that both axes overlap vertically. It is the side view seen from the surface.
Using the above-described warm hole type roll rolling apparatus, the following first to third steps of warm hole type roll rolling were performed.

<1> First, as a first step, the hole shape of the first rolling mill of the two-machine proximity rolling base is set to an appropriate oval, the hole shape of the second rolling mill is set to an appropriate square, and the wire diameter of the starting material is A 6.0 mmφ hot-rolled steel wire coil was hot-rolled and rolled into a coiled steel wire. The reduction in area of the material in the first step was 46.2%.

<2> Next, as the second step, the coil-shaped steel wire obtained in the first step, the hole shape of the first rolling mill to the appropriate oval, and the hole shape of the second rolling mill to the appropriate After recombination into a square, it was subjected to warm hole roll rolling to obtain a coiled steel wire. At that time, the cross-sectional shape of the steel wire to be caught in the oval hole type roll of the first rolling mill is a square shape, but as shown in FIG. 4, the oval shape (A) of the first rolling mill is The opposite side surface of the square shape (B) of the cross-section of the steel wire rod was bitten into the curved surface of the perforated roll. By doing so, a large plastic strain can be made uniform inside the material, which is effective for refining ferrite crystal grains. The same applies to the next third step. The reduction in area of the material in the second step was 38.0%.

<3> And, as the third step, the coiled steel wire obtained in the second step, the hole shape of the first rolling mill to an appropriate oval, and the hole shape of the second rolling mill After recombination to an appropriate round, it was warm-rolled and rolled to prepare a thin steel wire rod by coil-shaped warm-hole roll rolling with a wire diameter of 2.8 mmφ.
Also in this case, when the first rolling mill is bitten, as in the second step, as shown in FIG. 4, the steel wire rod is against the curved surface of the oval-shaped roll of the first rolling mill (A). The opposite side surface of the quadrangular shape (B) of the cross section of was taken in. In addition, the area reduction rate of the material in the third step was 35.1%. The total area reduction rate of the material from the first step to the third step is 78.2%.

Table 2 shows the shape and dimensions of the roll hole molds of the first and second rolling mills in each of the warm hole roll rolling conditions from the first process to the third process. In the table, B = long side length of oval hole type, H = maximum length of short side of oval hole type (maximum short axis length), C = length between opposite sides of square hole type, Z = round hole The diameter of the mold. The diameters (D) of the hole rolls are all 100 mm, the widths (Q) of the hole rolls are all 40 mm, and the distance between roll axis centers in the rolling line direction between the first rolling mill and the second rolling mill ( L) is all 110 mm (see FIG. 3 for D, Q, and L).

In any of the first to third steps of this warm hole roll rolling in Example 1, the material to be rolled is caught in the oval hole mold in the first rolling mill. The diameter of the material to be caught in the first rolling mill of the first step corresponds to the diameter d ₀ of the steel fine wire materials start material in the present invention.
In the first step, the material bitten into the oval hole mold of the first rolling mill has a circular cross section, d ₀ = 6.0 mm,
In the second step, the material bitten into the oval hole mold of the first rolling mill has a quadrangular cross section, C = 3.9 mm,
In the third step, the material bitten into the oval hole mold of the first rolling mill has a quadrangular cross section and C = 3.1 mm.
It is. Since the maximum minor axis length (H) of the oval hole type in each of the first to third steps is 2.5 mm, 2.0 mm, and 2.1 mm in order, the ratio value between them is as follows. It becomes.
In the first step, H / d ₀ = 2.5 / 6.0 = 0.42,
In the second step, H / C = 2.0 / 3.9 = 0.51,
In the third step, H / C = 2.1 / 3.1 = 0.68
These are all 0.70 or less. As described above, when the roll-type rolling with the ratio value of 0.70 or less is performed, a large strain is introduced into the material to be rolled with a relatively small area reduction ratio and a small number of passes, and ferrite It is effective for refining crystal grains.

Further, in any of the first to third steps, the distance (L) between the hole roll axis centers in the rolling line direction between the first rolling mill and the second rolling mill is close, and this hole roll axis center. The distance (L) is smaller than the sum (D ₁ + D ₂ ) of the roll roll radii of the first and second rolling mills (in either step, L = 110 mm, D ₁ + D ₂ = 100 + 100 = 200 mm) ), Because the formula (8a) or (8b) is satisfied, even if the area reduction ratio in each step is large, the material does not fall or twist during rolling, and the cross-sectional shape is good, and the surface The properties were also good. And it is effective for the refinement | miniaturization of a ferrite crystal grain to the center part of a steel fine wire.
Furthermore, the total area reduction ratio (R) of the material to be rolled by the two perforated rolls in each of the first to third steps is 46.2%, 38.0%, 35.1% in order, and the ratio of the outer diameter peripheral speed of the grooved rolls of the second rolling mill relative to the outer diameter peripheral speed of the grooved rolls of the first rolling mill _{(V (1)) (V} (2)),
In the first step, V ₍₂₎ / V ₍₁₎ = 1.50,
In the second step, V ₍₂₎ / V ₍₁₎ = 1.30,
In the third step, V ₍₂₎ / V ₍₁₎ = 1.28
It was.

Therefore, the relationship between the total area reduction ratio R and the outer diameter peripheral speed ratio V ₍₂₎ / V ₍₁₎ of the hole roll is expressed by the following expression corresponding to the expressions (9a) and (9b). Since it satisfy | fills, torsion did not generate | occur | produce in a to-be-rolled material, and the filling degree of the to-be-rolled material with respect to the hole shape of the hole-type roll of each 2nd rolling mill was favorable.
V ₍₂₎ / V ₍₁₎ = A · R _{(2 + 1)} + B
Where A and B are constants,
0.017 ≦ A ≦ 0.019
0.66 ≦ B ≦ 0.68

In the above, the warm hole roll rolling in Example 1 was performed at a temperature of the material to be rolled between 460 and 540 ° C. from the start to the end of rolling in any of the first to third steps. And after completion | finish of rolling, it air-cooled.
The tensile test and the microstructure of the ferrite were observed by sampling from the steel fine wire coil having a wire diameter of 2.8 mmφ obtained by the above warm hole roll rolling. As a result, the tensile strength was 710 MPa, the drawing was 75.5%, the ferrite structure was equiaxed grains, and the average grain size was 1 μm.
The test conditions and test results are summarized in Tables 3 and 4.
In the above, the diameter (d ₀ ) of the start material is d ₀ = 6.0 mm, and the diameter (d ₁ ) of the steel fine wire material obtained by perforated roll rolling is d ₁ = 2.8 mm. because there is,
_{d 1 / d 0 = 0.47 ≦} 0.6
Thus, the expression (5) is satisfied among the requirements of the present invention.

[Cold flat roll multiple pass rolling method]
Next, a thin steel plate having a thickness of 0.16 mm is prepared by cold flat roll rolling of the steel thin wire wound in the coil shape of the hot hole roll rolling finish with a wire diameter of 2.8 mmφ obtained above. did. The cold flat roll rolling method is as follows.
The steel fine wire of the above-mentioned 2.8 mmφ warm hole type roll rolling was made 0.16 mm thick × 20 mm wide in the following cold rolling steps (1) to (4).
(1) A coiled 2.8 mmφ warm-rolled steel wire was subjected to a plurality of passes by cold cross rolling to form a coil having a thickness of 1.2 mm × 10 mm.
(2) This was softened and heat-treated in a nitrogen gas atmosphere at 450 ° C. for 30 minutes, cooled in the furnace, and subjected to multiple passes of cold rolling to obtain a coil having a thickness of 0.43 mm.
(3) This was softened and heated in a nitrogen gas atmosphere at 450 ° C. for 30 minutes, cooled in the furnace hollow, and subjected to multiple passes by cold cross rolling, so that a strip steel sheet of 0.215 mm thickness × 20 mm width was obtained. A coil was used.
(4) Next, after slitting the coil side part, a coil of 0.16 mm thick strip steel plate was finished by performing a plurality of passes of cold rolling.

In the above, the diameter (d ₀ ) of the start material in the warm hole roll rolling is d ₀ = 6.0 mm, and the thickness (t) of the strip steel plate obtained in the step (4) is , T = 0.16 mm,
ln (d ₀ /t)=3.6≧2.4
Therefore, the expression (1) is satisfied among the requirements of the present invention.

A specimen for a tensile test was sampled from the obtained coil of a 0.16 mm-thick steel strip, and a tensile test piece was prepared and subjected to a tensile test. The drawing and breaking strength were calculated by ignoring the width reduction at the time of breaking and measuring only the thickness reduction.
Table 5 shows the results of the tensile test and the average ferrite grain boundary interval TH in the plate thickness direction.

  From the above test results, the strip steel plate obtained in Example 1 has a tensile strength of 0.8 GPa, a yield strength of 0.75 GPa, a breaking strength of 1.7 GPa, and a breaking strength / tensile strength. It can be seen that the steel sheet is as high as 2.1 and the drawing is as excellent as 52.8%, which is a thin steel plate having high strength and excellent ductility.

A commercial steel wire coil having a chemical composition (SUS430 series) shown in Table 6 and a wire diameter of 6.0 mmφ was used as a starting material. The average crystal grain size in the C-direction cross section of this 6.0 mmφ steel wire was 10 μm.

  The coil of the 6.0 mmφ steel wire rod is subjected to a total of 5 passes of cold roll rolling in the following first to third steps and a flat roll rolling of 1 pass in the fourth step. A strip-shaped material (coil) having a thickness of 1.1 mm and a width of 6.9 mm was prepared. Subsequently, this was formed into a coiled strip steel plate having a thickness of 0.16 mm and a width of 10.0 mm by flat roll rolling of a plurality of passes consisting of a plurality of steps in the cold.

<Cold hole type roll rolling + Cold one pass flat roll rolling>
The equipment used is the equipment used in the warm hole type roll rolling used in Example 1, but the rolling temperature condition is different from the normal temperature to the cold rolling temperature range of 200 ° C. or less, The pass-type rolls used in the first and second steps are substantially the same as those used in Example 1, and the third and fourth steps use a roll different from that in Example 1. It was done in. However, the setting conditions regarding the relationship between the surface reduction ratio (R) of the material to be rolled and the rotational peripheral speeds (V _(OV) , V _(SQ) ) of the front and rear rolls in the first and second steps are the following ( 9a) was set to satisfy the equation.
V _(SQ) / V _(OV) = _{A.R (OV + SQ)} + B (9a)
Where A and B are constants,
0.017 ≦ A ≦ 0.019
0.66 ≦ B ≦ 0.68
Both the first step and the second step were two-pass rolling by a square hole type next to the oval hole type, and the first rolling mill and the rolling direction by the second rolling machine were set at right angles.
In the third step, only the first rolling mill was used and an oval hole mold was used. In the second step and the third step, as the direction of the material to be rolled to be engaged with the oval hole mold of the first rolling mill, the opposite side surface of the quadrilateral of the cross section of the rolled material is reduced by the curved surface of the oval hole type. In addition, the rolling was performed so that the rolling direction is at an angle of 45 ° with respect to the rolling direction received by the material to be rolled in the immediately preceding pass (see FIGS. 1 to 4).
In the fourth step, only the first rolling mill is used, this is replaced with a flat roll, and cold flat roll rolling of one pass is performed to obtain a strip-shaped material having a thickness of 1.1 mm and a plate width of 6.9 mm, The coil was wound up.
The cross-sectional dimensions of the material to be rolled at the end of each of the first to fourth steps were as follows.
After the first step: a quadrangular shape with a length between opposite sides of 4.0 mm × 4.0 mm After the second step: a square shape with a length between opposite sides of 3.5 mm × 3.1 mm End of the third step After: Oval shape with short side of 2.5 mm x long side of 4.7 mm After completion of the fourth step: Thin strip material with thickness of 1.1 mm x width of 6.9 mm

In the above, the diameter (d ₀ ) of the start material is d ₀ = 6.0 mm, and the thickness (d ₃ ) of the ribbon-like material obtained in the fourth step is d ₃ = 1.1 mm. From
d ₃ / d ₀ = 0.18 ≦ 0.25
Therefore, the expression (4) is satisfied among the requirements of the present invention.

<Flat roll rolling with multiple passes in cold>
Next, using a one-stand four-high rolling mill, with a work roll having a roll diameter of 120 mm and a roll width of 270 mm, cold flat roll rolling of 1 pass per process is performed in 7 steps for a total of 7 passes, resulting in a total of 7 passes. By rolling, a coil of a strip steel plate having a plate thickness of 0.16 mm and a plate width of 10.0 mm was obtained from the coiled strip material having a plate thickness of 1.1 mm × width of 6.9 mm. The decrease in the thickness of the material to be rolled by the 7-pass cold flat roll rolling is as follows (the units are all mm).
Thickness 1.1mm → 0.7 → 0.4 → 0.3 → 0.25 → 0.2 → 0.18
→ The rolling temperature of the strip steel plate having a thickness of 0.16 mm and a width of 10.0 was less than 200 ° C. throughout the entire process from the starting material to the strip steel plate.

In the above, the diameter (d ₀ ) of the starting material in the cold roll rolling in the cold is d ₀ = 6.0 mm, and the thickness of the strip steel plate obtained by the flat roll rolling by multiple passes in the cold Since (t) is t = 0.16 mm,
ln (d ₀ /t)=3.6≧2.4
Therefore, the expression (1) is satisfied among the requirements of the present invention.

In FIG. 5, the external appearance photograph of the obtained coiled strip steel plate is shown. The surface properties of the coil are good.

Test materials for cold rolling (test materials before annealing) and the following test materials for annealing were collected from the coil material having a thickness of 0.16 mm and a width of 10.0.

Example 2 (four examples below)
As cold rolled (before annealing)
450 ° C. × 40 minutes annealed material 550 ° C. × 40 minutes anneal material 650 ° C. × 40 minutes anneal material Comparative Example 2
Annealed at 750 ° C x 40 minutes

Each test material was subjected to a tensile test and a Vickers hardness test. Moreover, the microstructure was observed by SEM. In addition, the Vickers hardness test was also performed on each material in a rolling intermediate stage having a thickness of 1.1 mm to 0.18 mm.
Table 7 shows the test results.

6A to 6E show the relationship between the annealing temperature and various mechanical properties.
When a tensile test piece with a test piece shape of 5 mm wide × gauge length 40 mm was made on a 0.16 mm material as it was cold-rolled and subjected to a tensile test, it was broken only by elastic deformation, without plastic deformation. To do. The tensile strength was 1.2 GPa, but there was no ductility.

When this material was subjected to 40 minutes at 550 ° C., the tensile strength decreased to 0.9 GPa (yield strength was 0.8 GPa). Furthermore, when the annealing temperature was 40 minutes at 650 ° C., the tensile strength decreased to 0.5 GPa. Furthermore, when the annealing temperature is 750 ° C., the tensile strength is 0.35 GPa (Comparative Example 2).
By changing the annealing temperature, the tensile strength TS can be controlled in the range of 0.5 to 1.2 GPa.
At this time, the yield strength YS is 0.4 to 1.1 GPa, and the ratio FS / TS between the breaking strength FS and the tensile strength TS exceeds 1.2, and the ductility is also excellent. .

In Example 2, the structure is elongated by annealing at 450 ° C. and 550 ° C. × 40 minutes, and the ferrite grain boundary interval TH is TH <1 μm. In contrast, in the case of annealing at 650 ° C. × 40 minutes, it is equiaxed and its TH is 1.6 μm. In the annealing of Comparative Example 2 at 750 ° C. × 40 minutes, the structure is equiaxed and the TH is as large as 6 μm.

A guillotine shear test was performed on a strip steel sheet with a thickness of 0.16 mm.
<1> As cold-rolled material, <2> 450 ° C. × 40 minutes, <3> 550 ° C. × 40 minutes, <4> 650 ° C. × 40 minutes, and <5> 750 ° C. × 40 which is Comparative Example 2. Min for each annealed material. As the guillotine shear test conditions, a test piece of 0.16 mm thickness × 10 mm width × about 1 m length was prepared and a guillotine shearing test was performed. At that time, the clearance between the fixed blade and the movable blade was almost zero.
FIG. 7 shows an appearance photograph of the sheared surface.
The overall evaluation of the shear plane is classified into good (◯), slightly good (Δ), and slightly poor (×).
<1> In the material without annealing (as cold-rolled), the shear plane ratio is uneven, and the distribution is about 25 to 70% (x), mainly about 30%.
In <2> 450 ° C. × 40 minute annealed material, the distribution is about 30% to about 80% (×).
The <3> 550 ° C. × 40 minute annealed material has a relatively stable distribution between about 70% and about 90% (Δ).
In the case of <4> 650 ° C. × 40 minute annealed material, the shear plane ratio is 95% or more, which is a good result (◯).
<5> Also in the 750 ° C. × 40 minute annealed material of Comparative Example 2, the shear plane ratio is 95% or more, which is a good result (◯).
From the above results, it is desirable to perform annealing, and it is understood that 450 to 700 ° C. is an appropriate condition.
Thus, it can be seen that the ribbon steel sheet of the present invention obtained by the manufacturing method of Example 2 has a fine ferrite grain boundary interval TH, high strength, and excellent ductility. .

As a starting material, a part of the same coil as that used in Example 2 was divided and used. That is, a coil of a commercially available hot rolled steel wire having a chemical composition (SUS430 series) shown in Table 6 and a wire diameter of 6.0 mmφ was used as a starting material. The average crystal grain size of the cross section in the C direction of this 6.0 mmφ hot-rolled steel wire was 10 μm.
Using the coil of the above-described 6.0 mmφ hot-rolled steel wire rod, the hot roll rolling and the flat roll were also used. The hot hole roll and flat roll rolling methods in Example 3 are all the same as in Example 2 except that the rolling temperature is set in the range of 400 to 600 ° C. That is, the used perforated roll rolling apparatus, the shape of the perforated roll of 5 passes from the first step to the third step, the pass schedule, the specifications of the flat roll of 1 pass in the fourth step, and the first step The rolling direction of the material to be rolled in the fourth step and the direction of biting of the material to be rolled into the perforated roll are the same as in Example 2, and further, the material to be rolled by hole roll rolling in the first and second steps. The setting condition (refer to the equation (9a)) regarding the relationship between the surface area reduction ratio and the rotational peripheral speed ratio of the front and rear rolls was also performed according to the setting condition in Example 2 (see FIGS. 1 to 4).
The cross-sectional dimensions of the material to be rolled at the end of each of the first to fourth steps were as follows.
After the end of the first step: a quadrangular shape with a length between opposite sides of 4.1 mm × 4.0 mm After the end of the second step: a square shape with a length between opposite sides of 3.4 mm × 3.3 mm End of the third step After: oval shape with a short side of 2.4 mm × long side of 4.5 mm After the completion of the fourth step: a thin plate shape with a thickness of 1.0 mm × a width of 7.2 mm Thus, a thickness of 1.0 mm × a width of 7. A 2 mm coiled ribbon material was prepared.

In the above, the diameter (d ₀ ) of the starting material is d ₀ = 6.0 mm, and the thickness (d ₃ ^′ ) of the ribbon-like material obtained in the fourth step is d ₃ = 1.0 mm. because there is,
d ₃ ^' / d ₀ = 0.17 ≦ 0.25
Therefore, the expression (4 ′) is satisfied among the requirements of the present invention.
Next, this was formed into a coiled strip steel sheet having a plate thickness of 0.18 mm and a width of 13.1 mm by cold flat roll rolling of a plurality of passes consisting of a plurality of cold processes. This multi-pass flat roll rolling was also performed under the same rolling conditions using the same apparatus as in Example 2.

In the above, the diameter (d ₀ ) of the starting material in the hot-hole roll rolling in the warm condition is d ₀ = 6.0 mm, and the thickness of the strip steel plate obtained by flat roll rolling with multiple passes in the cold Since (t) is t = 0.18 mm,
ln (d ₀ /t)=3.5≧2.3
Therefore, the expression (1) is satisfied among the requirements of the present invention.
FIG. 8 shows an appearance photograph of the obtained coil. The coil surface and edge properties are good.

  Sampling was performed from the strip steel plate of the coil material finished with the plate thickness of 0.18 mm × plate width of 13.1 mm, and the annealing test was performed in the same manner as in Example 2, and the test material before annealing (as cold-rolled Test material) and a test material annealed under the following conditions were prepared.

Example 3 (four examples below)
As cold rolled (before annealing)
450 ° C. × 40 minutes annealed material 550 ° C. × 40 minutes anneal material 650 ° C. × 40 minutes anneal material Comparative Example 3
A tensile test and a Vickers hardness test were performed for each test material at 750 ° C. × 40 minutes. Moreover, the microstructure was observed by SEM.
Table 8 shows the test results.

6A to 6E show the relationship between the annealing temperature and various mechanical properties, and FIG. 9 shows a stress-elongation curve.
When a tensile test was performed on a 0.16 mm material as cold-rolled with the same specimen shape as in Example 2 and Comparative Example 2, the tensile strength was 1.2 GPa, but the total elongation was 2 % Or less.
When this material was annealed at 450 ° C. for 40 minutes, the tensile strength decreased to 1.0 GPa. It is suggested that the internal dislocation density was lowered by annealing.
When the annealing temperature is 40 minutes at 550 ° C., the tensile strength decreases to 0.8 GPa. Total elongation exceeded 2%. Furthermore, when the annealing temperature is 40 minutes at 650 ° C., the tensile strength decreases to 0.5 GPa. Furthermore, the elongation becomes as large as 6.2%. Similar to Example 2, the tensile strength can be controlled in the range of 0.5 to 1.2 GPa by changing the annealing temperature. On the other hand, when the annealing temperature is 750 ° C., the total elongation increases to 16%, but the tensile strength becomes 0.4 GPa (Comparative Example 3).
At this time, the yield strength YS is 0.4 GPa to 0.9 GPa, and the ratio FS / TS between the breaking strength FS and the tensile strength TS exceeds 1.2, and the ductility is also excellent. .

In FIG. 10, the metal structure by SEM observation of each material is shown.
In the annealing at 450 ° C. and 550 ° C., the structure is elongated, and the ferrite grain boundary interval TH is 0.4 to 0.5 μm. On the other hand, in the case of annealing at 650 ° C. × 40 minutes, it is equiaxed and its particle size is 1.5 μm.

A guillotine shearing test was performed under the same conditions as in Example 2 for each material.
FIG. 11 shows a photograph of the appearance of the sheared surface.
If the overall evaluation of the shear surface is classified as good (○), slightly good (△), or slightly bad (×),
<1> Somewhat unsatisfactory with cold rolled material (x)
<2> Slightly good for the annealed material at 450 ° C. × 40 minutes (Δ)
<3> In the annealed material at 550 ° C. × 40 minutes, almost the entire surface is a sheared surface, which is good (◯)
<4> In the annealed material at 650 ° C. and 750 ° C. × 40 minutes, almost the entire surface is a sheared surface, which is good (◯)
<5> In the annealed material of 750 ° C. × 40 minutes, which is Comparative Example 4, good (◯)
It is.

When the above results are combined, it is desirable that annealing is performed on a thin steel plate obtained by flat roll rolling in a cold state, and 450 to 700 ° C. is an appropriate condition.
Thus, it can be seen that the ribbon steel sheet of the present invention obtained by the manufacturing method of Example 3 has a fine ferrite grain boundary interval TH, high strength, and excellent ductility. .

A part was divided from the same coil used in Examples 2 and 3 having the chemical component composition (SUS430 system) shown in Table 6, and this was used as a starting material. This is a coil of a commercially available hot-rolled steel wire with a wire diameter of 6.0 mmφ, and the average crystal grain size in the cross section in the C direction is 10 μm.
As a test apparatus, a work roll having a roll diameter of 120 mm and a roll width of 270 mm was used in a one-stand four-high rolling mill apparatus used in cold flat roll rolling in the second half of Example 2 and Example 3. The above-mentioned 6.0 mmφ starting material is subjected to flat roll rolling in a single pass of 1 pass per process in 7 steps for a total of 7 passes, resulting in a coil shape having a thickness of 0.19 mm × width of 12.4 mm A strip steel plate was obtained.
The progress of the plate thickness reduction by the seven passes is as follows (all units are mm).
Start material 6.0mmφ → 3.11 → 1.66 → 1.18 → 0.76
→ 0.50 → 0.26 → Thickness 0.19 × Width 12.4 mm

In the above, the diameter (d ₀ ) of the starting material in flat roll rolling in the cold is d ₀ = 6.0 mm, and the thickness of the strip steel plate obtained by flat roll rolling by 7 passes in the cold Since (t) is t = 0.19 mm,
ln (d ₀ /t)=3.6≧2.3
Therefore, the expression (1) is satisfied among the requirements of the present invention.
FIG. 12 shows a photograph of the appearance of the obtained coil. The surface properties of the coil are good.
Sampling was performed from the above-described coil material ribbon steel sheet having a thickness of 0.19 mm × sheet width of 12.4 mm, and an annealing test was performed in the same manner as in Example 2, and the test material before annealing (as cold-rolled Test material) and a test material annealed under the following conditions were collected.
Example 4 (four examples below)
As cold rolled (before annealing)
450 ° C. × 40 minutes annealed material 550 ° C. × 40 minutes anneal material 650 ° C. × 40 minutes anneal material Comparative Example 4
A tensile test and a Vickers hardness test were performed for each test material at 750 ° C. × 40 minutes. Moreover, the microstructure was observed by SEM. The Vickers hardness test was also performed on each material in the rolling intermediate stage having a thickness of 3.11 mm to 0.26 mm.
Table 9 shows the test results.

FIG. 13 shows a stress-strain curve.
Table 9 shows the test results.
6A to 6E show the relationship between the annealing temperature and various mechanical properties.

For a 0.19 mm material that is still cold-rolled, a tensile test piece having a width of 5 mm × gauge length of 50 mm, which is the same test piece shape as in Examples 2 and 3 and Comparative Examples 2 and 3, is prepared and pulled without annealing. When the test was conducted, the tensile strength was 1.1 GPa, but it was 2% in total.
When this material was annealed at 450 ° C. for 40 minutes, the tensile strength decreased slightly. When the annealing temperature is 550 ° C. for 40 minutes, the tensile strength decreases to 0.9 GPa (the yield point is 0.8 GPa). The total spread was about 2.4%. Furthermore, when the annealing temperature is 650 ° C. for 40 minutes, the tensile strength decreases to 0.5 GPa. Furthermore, the total elongation is as large as 3%. By changing the annealing temperature, the tensile strength can be controlled in the range of 0.5 GPa to 1.2 GPa. On the other hand, when the annealing temperature is 750 ° C., the total elongation increases to 9%, but the tensile strength becomes 0.4 GPa (Comparative Example 4).

At this time, the yield strength YS is 0.4 GPa to 1.0 GPa, and the ratio FS / TS between the breaking strength FS and the tensile strength TS is 1.6 or more, which is excellent in ductility.
In FIG. 14, the metal structure by SEM observation of each material is shown.
In the annealing at 450 ° C. and 550 ° C., the structure is elongated, and the ferrite grain boundary interval TH is 0.4 to 0.5 μm. On the other hand, in the case of annealing at 650 ° C. × 40 minutes, it is equiaxed and its TH is 1.2 μm.

A guillotine shearing test was conducted under the same conditions as in Examples 2 and 3 for each material.
FIG. 15 shows an appearance photograph of the sheared surface.
If the overall evaluation of the shear surface is classified as good (○), slightly good (△), or slightly bad (×),
<1> Somewhat unsatisfactory with cold rolled material (x)
<2> Slightly good for the annealed material at 450 ° C. × 40 minutes (Δ)
<3> In the annealed material at 550 ° C. × 40 minutes, almost the entire surface is a sheared surface, which is good (◯)
<4> Good (◯) when annealed at 650 ° C. and 750 ° C. × 40 minutes.
<5> Even in the annealed material of Comparative Example 4 at 750 ° C. × 40 minutes, the shear surface is good (◯).
Thus, it can be seen that the ribbon steel sheet of the present invention obtained by the manufacturing method of Example 4 has a fine ferrite grain boundary interval TH, high strength, and excellent ductility. .

To summarize the above results, it is desirable to anneal the strip steel sheet obtained by flat roll rolling in the cold, and by defining the annealing temperature within the range of 450 to 700 ° C., TS ≧ 0 5 GPa, YS ≧ 0.4 GPa, RA ≧ 40%, and FS ≧ 0.7 GPa can all be secured, and it is understood that a strip steel plate having ductility can be obtained.

  Manufacturing flow not previously disclosed reduces manufacturing costs, eliminates the slitting process, improves yield from starting materials to products, improves yield from thin steel strips to products, possibility of manufacturing with small-scale equipment, small amount Therefore, it can be used from a wide variety of products to production of specific varieties in large quantities.

It is a general | schematic external view of the side surface of the warm hole type | mold roll rolling apparatus used by the Example and the comparative example. Relative arrangement of a pair of hole rolls of the first rolling mill and a pair of hole rolls of the second rolling mill that constitute the two-proximity rolling base of the warm hole roll rolling apparatus used in Examples and Comparative Examples It is a schematic perspective view which shows a relationship. When the axial center of the perforated roll of the first rolling mill in FIG. 2 is projected in the vertical direction, a plane perpendicular to the axial center in a state of being virtually raised so that both axial centers overlap vertically It is the side view seen from. It is explanatory drawing of making it the opposite side surface of the cross-section of a to-be-rolled material square-shaped with respect to the curved surface of a perforated roll of an oval shape of a 1st rolling mill). It is a figure which shows the coil external appearance photograph of Example 2 and a comparative example. It is a figure which shows the relationship between the annealing temperature of Examples 2-4 and Comparative Examples 2-4 and various mechanical properties. It is a figure which shows the shear surface appearance photograph of Example 2 and Comparative Example 2. FIG. It is a figure which shows the external appearance photograph of the coil of Example 3 and the comparative example 3. FIG. 4 is a graph showing stress-elongation curves of Example 3 and Comparative Example 3. It is a figure which shows the metal structure by the SEM observation of Example 3 and Comparative Example 3. It is a figure which shows the shear surface external appearance photograph of Example 3 and Comparative Example 3. FIG. It is a figure which shows the external appearance photograph of the coil of Example 4 and the comparative example 4. FIG. 6 is a graph showing stress-strain curves of Example 4 and Comparative Example 4. It is a figure which shows the metal structure by SEM observation of Example 4 and Comparative Example 4. It is a figure which shows the shear surface appearance photograph of Example 4 and Comparative Example 4.

1 1st rolling mill in 2 rolling mills (19 ') 2 1st rolling mill roll pair 3 2nd rolling mill 4 2nd rolling mill roll pair 4' square hole B Second rolling mill
5 Rolled steel wire material 6 Rolling pass line direction 7a 7b Rolling pass line lower-side 2 machines Perforated (oval hole type) roll of the first rolling mill included in the rolling base 8, 8 'Rolled material by rolling mill 4' Direction of rolling applied to 9 Steel wire rod supply device 10 Pinch roll 11 Straightener 12 Heating device 18 Coil winder 19'2 Proximity rolling base

The strip steel or steel plate production method of the first invention is a method of rolling a steel wire, steel wire or bar steel made of carbon steel, ferritic stainless steel or austenitic stainless steel to produce the strip steel or steel plate, Is rolled at a rolling temperature within a range of 250 ° C. or less to produce a strip or a steel plate. At that time, the average ferrite grain boundary interval TH (μm) of the obtained steel material is expressed by the following formula (B):
TH = D ₀ exp (t / d ₀ ) (B)
D ₀ : Initial particle size
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides
t: Thickness of strip or steel plate after rolling
As well as
TH ≦ 0.6μm
It has the characteristics in satisfying.

The strip steel or steel plate manufacturing method of the second invention is a method of rolling a steel wire, steel wire or bar steel made of carbon steel, ferritic stainless steel or austenitic stainless steel to manufacture the strip steel or steel plate, The rolled material obtained by performing hole roll rolling at a rolling temperature within a range of from 250 to 250 ° C. is rolled into a plate shape by flat roll rolling. At that time, the average ferrite grain boundary interval TH (μm) of the obtained steel material is expressed by the following formula (B):
TH = D ₀ exp (t / d ₀ ) (B)
D ₀ : Initial particle size
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides
t: Thickness of strip or steel plate after rolling
As well as
TH ≦ 0.6μm
It has the characteristics in satisfying.

The strip steel or steel plate production method of the seventh invention is a method for producing a steel strip or steel plate by rolling a steel wire, steel wire or bar steel made of carbon steel, ferritic stainless steel or austenitic stainless steel. A rolled material obtained by carrying out a perforated roll rolling at a rolling temperature within a range of from above ° C to below 800 ° C is rolled into a plate shape by flat roll rolling. At that time, the average ferrite grain boundary interval TH (μm) of the obtained steel material is expressed by the following formula (B):
TH = D ₀ exp (t / d ₀ ) (B)
D ₀ : Initial particle size
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides
t: Thickness of strip or steel plate after rolling
As well as
TH ≦ 0.6μm
It has the characteristics in satisfying.

Claims (13)

A method of producing a strip steel or a steel plate by rolling a steel wire, steel wire or bar steel made of carbon steel, ferritic stainless steel or austenitic stainless steel, and at a rolling temperature within a range from room temperature to 250 ° C or less. In manufacturing a strip steel or a steel sheet by performing roll rolling, the following formula (1) is satisfied.
ln (d ₀ /t)≧2.3 (1)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides t: Thickness of strip steel or steel plate after rolling A method for producing a strip steel or a steel plate by rolling a steel wire or steel wire or steel bar made of carbon steel, ferritic stainless steel or austenitic stainless steel, wherein the hole is formed at a rolling temperature within a range from room temperature to 250 ° C. A method for producing a steel strip or a steel sheet, which satisfies the following formula (1) when rolling a rolled material obtained by die roll rolling into a plate shape by flat roll rolling.
ln (d ₀ /t)≧2.3 (1)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides t: Thickness of strip steel or steel plate after rolling The method of manufacturing a steel strip or steel plate according to claim 2, wherein the following formula (2) is satisfied when rolling the steel wire rod, steel wire or steel bar into a rolled material. .
d ₁ ≦ / d ₀ × 0.6 (2)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₁ : Diameter of rolled material or length between opposite sides In the manufacturing method of the strip steel or steel plate according to claim 2 or 3, the steel wire rod, the steel wire, or the steel bar is subjected to perforated roll rolling at a rolling temperature within a range from room temperature to 250 ° C, the perforated roll rolling. In the final pass, an irregular cross-sectional material obtained by making the cross section into an oval shape or a rectangular shape by an oval perforated roll or a flat box perforated roll is rolled into the plate shape by the flat roll rolling, and the following (3) The manufacturing method of the strip steel plate or steel plate characterized by satisfy | filling Formula.
d ₂ ≦ d ₀ × 0.3 (3)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₂ : Short side length of deformed cross-section material 5. The method for producing a strip or steel plate according to claim 4, wherein the deformed cross-section material is further obtained by performing rolling with a flat roll at a rolling temperature within a range from room temperature to 250 ° C. for one pass or two passes. A method for producing a steel strip or steel plate, characterized in that the following formula (4) is satisfied when the strip material is rolled into a plate shape by the flat roll rolling.
d ₃ ≦ d ₀ × 0.25 (4)
d ₀ : Diameter of steel wire or steel wire or bar or length between opposite sides d ₃ : Thickness of ribbon In the roll-type roll rolling at a rolling temperature within the range from room temperature to 250 ° C. or less, it is characterized by including rolling by a combination of an oval hole-type roll and a square hole-type roll next to it at least once. The manufacturing method of the steel strip or steel plate in any one of Claim 2 to 5. A method for producing a steel strip or steel plate by rolling a steel wire, a steel wire or a steel bar made of carbon steel, ferritic stainless steel or austenitic stainless steel, and a rolling temperature within a range from 250 ° C. to 800 ° C. A method for producing a steel strip or a steel sheet, which satisfies the following formula (1) when rolling a rolled material obtained by performing a perforated roll rolling to form a plate by rolling with a flat roll.
ln (d ₀ /t)≧2.3 (1)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides t: Thickness of strip steel or steel plate after rolling In the manufacturing method of the steel strip and steel plate of Claim 7, when rolling the said steel wire rod, a steel wire, or a steel bar to a rolling material, following (5) Formula is satisfy | filled, The manufacturing method of the steel strip or steel plate characterized by the above-mentioned. .
d ₁ ′ ≦ d ₀ × 0.6 (5)
d ₀ : Diameter of steel wire or steel wire or bar or length between opposite sides d ₁ ': Diameter of rolled material or length between opposite sides In the manufacturing method of the steel strip and steel plate according to claim 7 or 8, the steel wire rod, the steel wire, or the steel bar is subjected to perforated roll rolling at a rolling temperature within a range of more than 250 ° C to 800 ° C, and the hole In the final pass of die roll rolling, an irregular cross-section material having an oval or rectangular cross section is rolled by the flat roll rolling into a plate shape by an oval perforated roll or a flat box perforated roll. The manufacturing method of the strip steel or steel plate characterized by satisfy | filling.
d ₂ '≦ d ₀ × 0.3 (6)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₂ ': Short side length of deformed cross section The method for producing a steel sheet according to claim 9, wherein the deformed cross-sectional material is a ribbon obtained by further rolling with a flat roll at one rolling or two passes at a rolling temperature in the range of more than 250 ° C to 800 ° C. A method for producing a steel strip or a steel sheet, characterized by satisfying the following expression (7) when the material is rolled into a plate by flat roll rolling.
d ₃ ′ ≦ d ₀ × 0.25 (7)
d ₀ : Diameter of steel wire or steel wire or steel bar or length between opposite sides d ₃ ′: Thickness of ribbon-like material In the roll-type roll rolling at a rolling temperature in the range of more than 250 ° C. to 800 ° C. or less, the rolling by the combination of the oval hole roll and the next square hole roll is included one or more times. The manufacturing method of the strip steel or steel plate in any one of Claim 7 to 10. In the manufacturing method of the steel strip or steel plate in any one of Claim 1 to 11, it introduce | transduces with the plastic working in the rolling by the steel strip or steel plate finally obtained from the said steel wire rod, steel wire, or steel bar. A method for producing a steel strip or steel sheet, characterized in that the plastic strain calculated by the finite element method at the center of the plate width and at the center of the thickness of the steel strip or steel sheet is 2.3 or more. In the manufacturing method in any one of Claim 1 to 12, in the range of 400 to 700 degreeC with respect to the said strip steel plate or steel plate in rolling by a flat roll, after rolling, or both during rolling and after rolling. The manufacturing method of the strip steel plate or steel plate characterized by annealing within.