JP2009191279A - Steel fine wire or thin band steel sheet excellent in plastic workability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel fine wire or a thin band steel sheet having high strength particularly satisfying the yield strength (YS) of ≥0.6 GPa, also having excellent ductility, further having satisfactory shearing properties, and having excellent plastic workability, by solving the problem that, since, heretofore, the yield strength (YS) of the material for shearing is ≤0.4 GPa in many cases, the impartation of high ductility to the material having a yield strength higher than that is difficult, and machining is used instead of shearing, but, even in the preceding reference 2, the tensile strength of stainless steel is 0.5 GPa, thus its yield strength is <0.5 GPa, and is insufficient. <P>SOLUTION: The steel fine wire having excellent plastic workability is composed of ferritic carbon steel or ferritic stainless steel or austenitic stainless steel, having a yield strength of ≥0.6 GPa and fracture strength/tensile strength of ≥2.0. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carbon steel or stainless steel used as a component of automobiles, home appliances, electric / electronic machines, and particularly to a thin steel plate or steel wire having high strength excellent in shearing characteristics.

  In recent years, from the viewpoint of improving automobile safety and fuel efficiency, high-strength and thin-walled parts for automobile steel plate members, and thin strips with complex shapes used as components for electric and electronic machines found in home appliances and IC lead frames, etc. There are steel plate products. In order to save energy, the low iron loss magnetic flux material of a small motor uses a ribbon finishing material to reduce eddy current loss. In such a thin plate member forming process, a shape processing portion where stress concentration occurs due to drilling or notching is formed. A typical example of such a forming method is shearing. Further, the shearing process is used as a method for efficiently producing materials for stamping forging from steel bars and steel wires.

  When the shearing method of the strip steel wire or steel wire is classified according to the shape of the sheared product, punching with the lower side (punching side) of the punch as the product, punching with the upper side (hole side) of the die as the product, In addition, there is a narrow sense shear (for example, guillotine shear of a plate material) that cuts and separates a plate or a rod. In shearing, the most important matter that depends on the quality of the material for shearing is the length of the barrel and burr as the cut shape characteristics of the material or product after the punching or shearing process (hereinafter referred to as “cutting”). 1), the shear surface ratio is large, and the shape and dimensional accuracy of each part of the material or product are good (prior art document 1). Further, high ductility is imparted to the shearing material in order to obtain good shearing characteristics.

  With regard to the manufacturing technology of the strip steel sheet having excellent shearing characteristics, for example, as a ferritic stainless steel excellent in precision punching workability, the amount of fine precipitates is specified, and the surface hardness is specified to be a predetermined value or less. Have been proposed (Prior Literature 2).

Prior literature 1: Handbook of plastic working 2006 375 7. Shear Prior Literature 2: JP-A-2004-068118

Conventionally, the yield strength (YS) of shearing materials is often 0.4 GPa or less, and it is difficult to impart high ductility to materials having higher yield strength. Machine cutting is used. Also in the prior art document 2, the tensile strength of stainless steel is 0.5 GPa, and therefore the yield strength is less than 0.5 GPa, which is not sufficient.
Therefore, the present invention is a steel fine wire having a high strength of yield strength (YS) of 0.6 GPa or more in strength, excellent ductility, and excellent plastic workability with good shearing characteristics. Or it proposes a strip steel plate.

  The fine steel wire excellent in plastic workability of the invention 1 is a ferritic carbon steel, ferritic stainless steel or austenitic stainless steel having a yield strength of 0.6 GPa or more and a breaking strength / tensile strength of 2.0 or more. It is characterized by being.

  Invention 2 is characterized in that, in Invention 1, the steel fine wire has a breaking strength of 1.5 GPa or more.

  Invention 3 is characterized in that, in Invention 1 or 2, the fine steel wire has a drawing of 65% or more.

  Invention 4 is characterized in that, in any one of Inventions 1 to 3, the steel fine wire has a shear surface ratio of 50% or more in a sheared surface.

  The ribbon steel sheet excellent in plastic workability of the invention 5 is a ferritic carbon steel, ferritic stainless steel or austenitic stainless steel having a yield strength of 0.6 GPa or more and a breaking strength / tensile strength of 1.0 or more. It is characterized by being steel.

  The invention 6 is the invention 5, wherein the ribbon steel sheet has a breaking strength of 1.0 GPa or more.

  The invention 7 is the invention 5 or 6, characterized in that the strip steel plate has a drawing of 40% or more.

  Invention 8 is characterized in that, in any one of Inventions 5 to 7, the strip steel plate has a shear surface ratio of 50% or more in a sheared surface.

  According to the present invention, a steel strip or steel wire, which has not been obtained in the past, has particularly good shearing characteristics and has a high yield strength (YS) of 0.6 GPa or more and excellent plastic workability. Is obtained. Therefore, it is also possible to manufacture high-strength precision parts and component products that can contribute to energy saving, which are made of thin steel wires or ribbon steel sheets, which could only be manufactured by conventional cutting.

In order to solve the above-mentioned problems, the present inventor has achieved the present invention by obtaining the following knowledge as a result of intensive tests and research.
As a ductility index, which is an excellent material characteristic of shearing properties, the total elongation by tensile test has been generally used in the past. In this case, the draw (RA) should be used as the ductility index rather than the total elongation. Is extremely effective, ensuring a high level of restriction (RA), and breaking strength (FS) (= (tensile load at break) / (cross-sectional area of specimen at break position)) above a certain value. It is effective to improve the shear processing characteristics, and in order to apply to a wider variety of materials, simply focusing on the drawing (RA) and / or breaking strength (FS). It was found that it is effective to ensure the ratio (FS / TS) of the breaking strength (FS) to the tensile strength (TS) at a certain value or more.

The shear plane ratio will be described with reference to FIG.
In the case of a strip steel plate, it is as follows.
Shear surface ratio (SR) = {(shear surface t ₁ ) / (shear surface t ₁ ) + (fracture surface t ₂ )} × 100 (%) (1)
In the case of steel wire, in FIG. 1, the plate thickness (t) to diameter (d), shear plane _{d 1} the shear plane _{t 1,} is regarded fracture surfaces _{t 2} and the fracture surface _{d 2,}
Shear surface ratio (SR) = {(shear surface d ₁ ) / (shear surface d ₁ ) + (fracture surface d ₂ )} × 100 (%) (2)
It is considered.

(1) Reason for making the yield strength (YS) 0.6 GPa or more In the present invention, the yield strength (YS) is taken up as a basic function as the strength of the material. When the conventional shearing material is about 0.4 GPa or less, for example, in a product obtained by shearing an ultrafine steel wire having a diameter of 0.1 mm or less, the problem that the linear characteristics cannot be maintained occurs. This is because the yield strength (YS) needs to be 0.6 GPa or more to solve the problem.

(2) The reason why the breaking strength (FS) / tensile strength (TS) is 2.0 or more when the steel wire is thin, and 1.0 or more when the steel strip is steel. Yield strength (1) above ( YS) defines the material strength to a high level, and in order to ensure both the breaking strength (FS) and the drawing (RA) as ductility characteristics at a high level, the breaking strength (FS) / tensile Strength (TS) was introduced as an index. The breaking strength (FS) is a value W ′ / S ′ obtained by dividing the breaking load (W ′) by the sectional area (S ′) at the breaking position. On the other hand, the restriction (RA) has a cross-sectional area S ₀ before being loaded.
RA = {(S ₀ −S ′) / S ₀ } × 100 (%) (3)
Therefore, the breaking strength (FS) is
FS = W '/ S'
= (W ′ / S ₀ ) {1 / (1-RA / 100)} (4)
Therefore, the breaking strength (FS) is closely related to the aperture (RA).
Here, when the maximum load on the tensile specimen is W _Max , the tensile strength (TS) is
TS = W _Max / S ₀ (5)
Therefore, from the equations (3) to (5), the breaking strength (FS) / tensile strength (TS) of the above index is
FS / TS = (W ′ / W _Max ) {1 / (1-RA / 100)} (6)
Is derived.
As described above, in order to ensure a high strength, a high ductility limit on the sheared surface during shearing (and hence a high drawing (RA) value), and excellent shearing characteristics, The usefulness of using strength (FS) / tensile strength (TS) as an index of shearing characteristics is understood. And in order to solve the subject of this invention, this breaking strength (FS) / tensile strength (TS) needs to be 2.0 or more in the case of a thin steel wire, In some cases, it is necessary to be 1.0 or more. The difference between the thin steel wire and the thin steel plate is due to the fact that the cross-sectional shape of the tensile test piece is different between a circle and an ultrathin flat.

(3) Reason for selecting ferritic carbon steel, ferritic stainless steel, or austenitic stainless steel as the metal species In order to have the steel material characteristics of (1) and (2) described above, the structure has ultrafine crystal grains. It is effective to use a structure to which a cold working is applied. Further, it is desirable that the crystal structure of the first phase is ferrite or austenite, and the average crystal grain size of each crystal structure or the average minor axis diameter of the crystal grains of each crystal structure in the plate thickness direction is 1 μm or less. In any case, the steel according to the present invention needs to be ferritic carbon steel, ferritic stainless steel, or austenitic stainless steel.
In stainless steel, since Cr is added, strength improvement (fine graining strengthening) and solid solution strengthening due to crystal grain refinement are added. At this time, in the case of a thin steel wire, the breaking strength (F / S) ≧ 2.0 steel, and in the case of a strip steel plate, if the breaking strength (F / S) ≧ 1.0, the shear processing characteristics are obtained. It does not have an adverse effect on it. This is because the critical crack generation stress does not decrease.
Moreover, as austenitic stainless steel, SUS304, SUS316, SUSXM7, etc. are used as those having excellent cold workability. Since addition of Cu reduces the work hardening at the time of cold working, Cu may contain 3 to 4%.
In this type of steel material, the carbon (C) content is preferably 0.25% by mass or less in view of the cementite content, and more preferably, the C content is substantially cementite-free. It is desirable that it is 0.06 mass% or less.
Furthermore, it is more desirable that the line length ratio of grain boundaries having an orientation difference angle of 5 degrees or more among all the grain boundaries of the ferrite or austenite is 60% or more. Note that “orientation difference angle of 5 degrees or more” means that “the difference between the orientations of crystal grains adjacent to each other is 5 degrees or more”.

(4) The reason why it is desirable that the breaking strength is 1.5 GPa or more when the steel wire is thin, and 1.0 GPa or more when the steel strip is steel strip. Products made by a combination of shearing and other forming processes include ultra-thin products with a wire diameter of 0.1 mm or less or ultra-thin products with a plate thickness of 0.1 mm or less. This is because, in order to ensure the strength, it is desirable that the breaking strength is 1.5 GPa or more when the thin steel wire is used, and 1.0 GPa or more when the thin steel plate is used. The difference between the case of the thin steel wire and the thin strip steel plate is based on the difference in the cross-sectional shape of the tensile test piece between a circle and an ultrathin flat as in (2) above.

(5) Reason why it is desirable that the drawing is 65% or more when it is a thin steel wire, and 40% or more when it is a thin strip steel, in order to further ensure a high level of ductility in shearing, This is because it is more desirable to add a rule that the drawing (RA) of the strip steel plate is 65% or more or 40% or more. The difference between the two is based on the difference in the cross-sectional shape of the tensile test piece between a circle and an ultrathin flat, as in (2) and (4) above.

(6) The reason why it is desirable that the shear plane ratio is 50% or more In the present invention, since the shear processing characteristics are particularly emphasized, the shear plane ratio is used as an index for expressing the characteristics, and this is 50% or more. This is because a more desirable high shear property is secured.

(7) Yield ratio (YS / TS) In shearing, a higher yield ratio is desirable in order to make the shearing characteristics superior. For example, it is desirable if YS / TS is 0.9 or more.

(8) Steel thin wire and ribbon steel plate targeted by the present invention The steel thin wire is intended for a wire diameter of 3 × 10 ⁻² mm to 3 mm, but has a dimension outside this range. However, the present invention is within the scope of the present invention as long as the effects of the present invention can be obtained.
In addition, as the thin steel plate, the plate thickness = 5 × 10 ⁻² mm to 4 mm and the plate width = plate thickness × 10 to 10 ³ are targeted ranges, but even those having dimensions outside this range, The present invention is within the scope of the present invention as long as the effects of the present invention can be obtained.

-About steel wire (1-1) Examples 1 and 2 and Comparative Example 1
Ingredient No. shown in Table 1 Steel having a chemical composition of 1 to 3 was melted using a vacuum melting furnace and cast into a steel ingot. Ingredient No. 1 and 2 were applied to Examples 1 and 2, respectively, and component no. 3 was subjected to Comparative Example 1.

  The obtained steel ingot was processed into a 80 mm square steel bar by hot forging. The metal structure of these bar steels was made of ferrite, and the average grain size of ferrite in the cross section in the C direction was about 20 μm. A rolling material was collected from each of the 80 mm square steel bars, formed into 18 mm squares by multi-directional multi-pass caliber rolling in the following warm conditions, and cooled with water to prepare a steel bar.

  The warm rolling conditions are as follows. After heating the 80 mm square rolling material processed by the above hot forging to 550 ° C., as shown in Table 2, each of the rolling raw materials is first treated with a diamond-type caliber roll in the range of 450 to 530 ° C. A 19-pass warm rolling with a pass area reduction of about 17% was performed and processed into a 24 mm square. Next, warm rolling was performed with an oval caliber roll having a maximum minor axis length of 11 mm and a major axis length of 52 mm, and finally, one pass of warm rolling was performed with a square type caliber roll, resulting in a total of 21 passes to 18 mm square. processed. The total area reduction rate from the raw material for warm rolling (80 mm square) to this 18 mm square is 95%. Table 2 outlines the pass schedule.

  In the one-pass warm rolling (pass No. 20) using the oval-type caliber roll, a 24 mm square bar is rolled using the oval-type caliber roll. The ratio of the maximum minor axis length 11 mm in the C-direction cross section of the material after rolling with respect to the thickness of 24 mm is as small as (11 mm / 24 mm) × 100 = 46%, and the area reduction calculated from the hole size at this time is 38% And pretty big. Therefore, the one-pass warm rolling with the oval type caliber roll is a condition that further promotes the refinement of the ferrite grain size in the 18 mm square bar steel after the completion of the warm rolling. In the rolling process using the diamond-type caliber roll up to the 19th pass, in order to make the cross-sectional shape of the material as close to a square as possible, rolling (so-called “together”) that passes two consecutive passes through the same caliber roll is appropriately performed. Each pass was counted as 2 passes. Further, for each pass of rolling, the material was rotated around the longitudinal axis to change the rolling direction, and multi-directional multi-pass rolling was performed. Furthermore, in addition to the heat generated by processing, the amount of heat released is relatively small even in the rolling temperature region of the warm rolling in the relatively low temperature region, and there is no need for intermediate heating due to the temperature drop of the material during rolling.

Next, the microstructure was observed at various positions in the cross section (C direction cross section) in the direction perpendicular to the rolling direction of the 18 mm square steel bar prepared by the above-described warm rolling method. Homogeneity was confirmed. Next, the 18 mm square steel bar was reduced in diameter by cutting, and a tensile test piece (parallel part 3.5 mmφ) of JIS 14A was prepared and subjected to a tensile test. Further, a test piece having a length of 1.3 mmφ × 300 mm was prepared and subjected to a constrained shearing test.
Shearing conditions are such that the clearance between the die hole and the 1.3 mmφ steel wire (test piece) is 1/100 mm or less, and the clearance between the fixed die and the shearing die is almost zero (substantially in contact). I did it.
Table 3 shows the average ferrite crystal grain size and the shear plane ratio in the cross section perpendicular to the warm rolling direction as a result of the tensile tests of Examples 1 and 2 and Comparative Example 1. Here, the shear plane ratio is expressed by the formula (2):
Shear surface ratio (SR) = {(shear surface d ₁ ) / (shear surface d ₁ ) + (fracture surface d ₂ )} × 100 (%)
by.
The appearance photographs of the sheared surfaces of Examples 1 and 2 and Comparative Example 1 are shown in FIGS.

From the above test results, the steel wires obtained in Examples 1 and 2 have yield strengths of 0.650 GPa and 0.795 GPa, and values of breaking strength / tensile strength of 3.5 and 2.0. Furthermore, the breaking strength is 2.49 GPa and 1.60 GPa, and the aperture is 81% and 72%. This is greatly influenced by the fact that the average crystal grain size is ultrafine as 0.7 μm and 0.5 μm in Examples 1 and 2, respectively. And since the shear surface ratio is 60% and 50%, it can be seen that the steel wire is excellent in shearing properties and excellent in plastic workability.
On the other hand, the steel wire obtained in Comparative Example 1 has an excellent yield strength of 0.895 GPa and an average crystal grain size of 0.5 μm which is ultrafine, but the drawing is 65%. Stay on. Therefore, the value of the breaking strength / tensile strength is a little as 1.8, the shear surface ratio is as small as 24%, and the shear processing characteristics are not excellent, and therefore the steel wire is excellent in plastic workability. Absent. This is because the P content is 0.10% by mass, which is higher than the P content of ordinary carbon steel.

(1-2) Examples 3 to 6
[Examples 3 to 6]
Each of Examples 3 to 6 was manufactured by cold-drawing a hot-rolled wire rod of Cu-containing austenitic stainless steel having the chemical composition shown in Table 4, followed by solution heat treatment and drawing. The steel wire was annealed and used as a starting material. The austenite crystal grain sizes of the starting materials were all about 30 μm.

  As shown in Table 5, each of Examples 3 to 6 uses steel wires having respective wire diameters as starting materials, and into steel fine wires having a finishing material size of 1.16 to 2.21 mmφ by cold drawing. did.

Tensile test pieces and shearing test pieces were collected and prepared from the starting material and the finished material, and subjected to each test. Moreover, the Vickers hardness test was done suitably.
Shearing test conditions are such that the clearance between the die hole and the 1.3 mmφ steel wire (test piece) is 1/100 mm or less, and the gap between the fixed die and the shearing die is almost zero (substantially in contact) It was done in.
Table 5 shows the test results.

As a result, for all the finishing materials of Examples 3 to 6, the yield strength YS is 0.6 GPa or more and the breaking strength / tensile strength is 2.0 or more, which satisfies the requirements of the present invention. Further, the breaking strengths are all 1.5 GPa or more and the drawing is 65% or more, both satisfy the more desirable requirements of the present invention.
On the other hand, as a result of the shearing test, in all of Examples 3 to 6, the properties of the sheared surface were good.
(1-3) Example 7
As Example 7, a ferritic stainless steel SUS430 having a chemical composition shown in Table 6 and a commercially available steel wire having a wire diameter of 6 mmφ was used as a starting material and processed to 3.0 mmφ by punch rolling. Table 7 shows the tensile test results.


The yield strength YS is 0.6 GPa or more and the breaking strength / tensile strength is 2.0 or more, which satisfies the requirements of the present invention.
Furthermore, the breaking strength is 1.5 GPa or more and the drawing is 60% or more, both satisfy the more desirable requirements of the present invention.
On the other hand, as a result of the shearing test, results were obtained in which the sag and burr were small and the shearing surface was good.

Next, the test of the strip steel plate will be described.
(2) About the strip steel plate (2-1) Example 8 and Comparative Example 2
[Example 8]
Steel having the chemical composition shown in Table 8 was melted using a vacuum melting furnace, cast into a steel ingot, and subjected to Example 8.

In accordance with the processing steps performed in Examples 1 and 2 and Comparative Example 1, the obtained steel ingot was processed into an 18 mm square by hot forging into an 80 mm square steel bar and hot multi-directional multi-pass caliber rolling. The steel bar was prepared by water cooling. Here, the pass schedule of the warm processing was the same as in Examples 1 and 2 and Comparative Example 1, and the processing temperature conditions were also performed accordingly.

Next, the microstructure is observed at various positions in the cross section (C direction cross section) perpendicular to the rolling direction of the 18 mm square steel bar prepared by the warm rolling method, and the homogeneity in the C direction cross section is obtained. It was confirmed. The average ferrite particle size was 0.6 μm.
Next, the 18 mm square steel bar was processed into a 4.0 mmφ steel bar by cutting. Using this, a strip steel plate having a thickness of 0.15 mm was prepared by a cold flat roll rolling method. The cold flat roll rolling method is as follows.
The 4.0 mmφ warm-rolled steel wire was cold-rolled to a thickness of 0.15 mm × 20 mm in the following processing steps (1) to (4). That is,
(1) A 4.0 mmφ warm rolled steel wire was formed into a coil of 1.2 mm thickness × 10 mm width by cold cross rolling.
(2) This was softened and heated in a nitrogen gas atmosphere at 450 ° C. for 30 minutes, cooled in the furnace, and formed into a coil having a thickness of 0.43 mm by cold rolling.
(3) This was softened and heat-treated in a nitrogen gas atmosphere at 450 ° C. for 30 minutes, cooled in the furnace, and formed into a strip steel coil having a thickness of 0.215 mm × 20 mm by cold cross rolling.
(4) Next, after slitting the coil side portion, it was finished into a 0.15 mm thick steel strip coil by cold rolling. An appearance photograph of the obtained coil is shown in FIG.

A specimen for a tensile test was sampled from the obtained 0.15 mm-thick steel strip coil, 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.
Further, a specimen for a shearing test was taken from a 0.15 mm-thick steel strip coil, and a test piece having a length of 0.15 mm × 13 mm width × about 1 m was prepared and subjected to a guillotine shearing test. At that time, the clearance between the fixed blade and the movable blade was almost zero.
Table 9 shows the results of the tensile test, the average ferrite minor axis diameter, and the shear plane ratio.

The shear surface ratio SR is the formula (1):
Shear surface ratio (SR) = {(shear surface t ₁ ) / (shear surface t ₁ ) + (fracture surface t ₂ )} × 100 (%)
by.
Moreover, the external appearance photograph of a shearing surface is shown in FIG. It can be seen that the shear plane ratio exceeds 90%. FIG. 7 shows an external appearance photograph viewed from the side of the sheared surface shown in FIG. According to this, it can be seen that who (a) and burr (b) (see FIG. 1) are small and good.

From the above test results, the strip steel plate obtained in Example 8 has a yield strength of 0.76 GPa and a breaking strength / tensile strength of 2.0, both satisfying the important requirements of the present application. Furthermore, the breaking strength is 1.69 GPa, the drawing is excellent at 52.9%, the shear surface ratio is as large as 90%, the sludge and burr are small, and the shearing properties are excellent. It turns out that it is a thin strip steel plate excellent in workability.
[Comparative Example 2]
As Comparative Example 2, test materials for tensile test and shearing test were collected from the 0.15 mm thick steel strip coil obtained in Example 8 and heat-treated at 700 ° C. for 5 hours. The crystal grain size was increased to 20 μm.
A test piece for hardness measurement was taken from the obtained 0.15 mm-thick steel strip coil. Further, a specimen for a shearing test was taken from a 0.15 mm thick ribbon steel sheet coil, a test piece having a length of about 100 mm was prepared, and a guillotine shearing test was conducted. Shearing test conditions are the same as in Example 8.
FIG. 8 shows a photograph of the appearance of the sheared surface. The shear surface ratio was approximately 90%. Further, FIG. 9 shows an external appearance photograph viewed from the side of the sheared surface shown in FIG. According to this, wholly (a) and burr (b) (see FIG. 1) are large and undesirable. When this is compared with Example 8 of FIG. 7, the difference is clear.
The ribbon steel plate obtained in Comparative Example 2 had a Vickers hardness (H _V ) = 86. From this, when the tensile strength (TS) is estimated, TS≈H _V × 3.0 = 0.258 GPa. Therefore, it can be considered that the yield strength (YS) is smaller than 0.258 GPa at the maximum. Therefore, Comparative Example 2 does not satisfy the yield strength (YS) ≧ 0.6 GPa, which is an important requirement of the present invention, and the shear surface ratio is good at about 90%, but the amount of whol and burr is large. The shear processing characteristics are inferior, and the problem of the present invention has not been solved.

(2-2) Example 9
As Example 9, a ferritic stainless steel (SUS430) steel wire (chemical composition is as shown in Table 6) having a diameter of 3.0 mmφ obtained in the test step in Example 7 was flat rolled. Using a machine, heat treatment was performed on the way, and rolling to 0.25 mm was performed to prepare a strip steel plate having a width of about 10 mm. The Vickers hardness was measured about the thin strip steel plate obtained during the said rolling process. As a result, HV = 330 was obtained. This has a tensile strength and a yield strength of 1.0 GPa or more. Shear surface was good with few burr.

It is a schematic diagram of the shearing process of a thin strip steel plate. 2 is an appearance photograph showing a sheared surface processed surface of Example 1. FIG. 3 is an appearance photograph showing a sheared surface processed surface of Example 2. FIG. 5 is an appearance photograph showing a sheared surface processed surface of Comparative Example 1. It is an external appearance photograph of the thin strip steel plate coil of Example 5. 6 is an appearance photograph showing a sheared surface processed surface of Example 5. It is an external appearance photograph which shows the side surface (side surface of FIG. 6) of the shear surface processing surface of Example 5. 4 is an appearance photograph showing a sheared surface processed surface of Comparative Example 2. It is an external appearance photograph which shows the side surface (side surface of FIG. 8) of the shear surface processing surface of the comparative example 2.

Claims (8)

  Excellent ferritic workability characterized by being ferritic carbon steel, ferritic stainless steel or austenitic stainless steel having a yield strength of 0.6 GPa or more and a breaking strength / tensile strength of 2.0 or more Steel thin wire.   The steel fine wire according to claim 1, wherein the steel fine wire has a breaking strength of 1.5 GPa or more.   The steel fine wire according to claim 1 or 2, wherein the steel fine wire has a drawing of 65% or more.   The steel fine wire according to any one of claims 1 to 3, wherein the steel fine wire has a shear plane ratio of 50% or more in a shear plane.   Excellent ferritic workability characterized by being ferritic carbon steel, ferritic stainless steel or austenitic stainless steel having a yield strength of 0.6 GPa or more and a breaking strength / tensile strength of 1.0 or more Thin strip steel plate.   The thin steel plate having excellent plastic workability according to claim 5, wherein the thin steel plate has a breaking strength of 1.0 GPa or more.   The thin steel plate having excellent plastic workability according to claim 5 or 6, characterized in that the drawing of the thin steel plate is 40% or more.   The strip steel plate excellent in plastic workability according to any one of claims 5 to 7, wherein the strip steel plate has a shear plane ratio of 50% or more in a shear plane.