JP2002060888A - Steel sheet for blanking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet for blanking free from the occurrence of defects to be the origin of fatigue crack in a blanking surface and excellent in fatigue characteristics. SOLUTION: The steel sheet for blanking has a composition containing 0.3-0.8% C, <=3.0% Si, <=1.5% Mn, <=2.0% Cr, <=0.5% Cu, 0.0005-0.02% N, 0.0005-0.01% O, <=0.02% P, <=0.01% S and 0.01-0.10% acid-soluble Al. Further, fracture surface roughness in a blanking plane at the position on which maximum stress acts after blanking is regulated to <=100 μm Ry and secondary shearing ratio in the fracture surface becomes zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a punching steel sheet which can be tempered to a high strength by heat treatment and has excellent fatigue characteristics.

[0002]

2. Description of the Related Art In some cases, after a material is formed into a part shape by punching, a material heat-treated by heat treatment is used for members such as various mechanical parts. Parts of this type have high hardness,
Mechanical properties such as high strength, high toughness, high fatigue strength, and wear resistance are required. Fatigue properties and abrasion resistance are generally improved by increasing hardness and strength, but since toughness decreases with increasing hardness and strength, problems due to increased notch sensitivity become apparent. . Further, although a fracture surface is normally exposed on the end face of the part after punching, it is used as a product without completely removing surface defects such as minute cracks existing in the fracture surface. The surface defect existing on the end face of the blank after punching acts as a notch, an initial crack, or the like, and increases the notch sensitivity of the component. In particular, when the temper hardness is increased to 45 HRC or more or the tensile strength is increased to 1500 MPa or more to increase the strength, the notch sensitivity is further increased, and the fatigue strength and toughness are reduced. However, it is very difficult to guarantee the punched surface properties in an industrial mass production line.

[0003] In order to reduce the influence of the punched surface properties, a method is known in which the stamped surface is subjected to coining to improve the fatigue characteristics by work hardening and compressive residual stress (Japanese Patent Laid-Open Nos. 2-147129 and 2-147129). 6-57325). However, when the coined part is heat-treated, the effect of improving characteristics is significantly reduced. In addition, a method of manufacturing a part by machining, a method of cutting an end face of a punched part by machining, and the like are known, but none of them has low productivity and cannot be applied to a part having a complicated shape. Although it is possible to remove defects on the punched end face by polishing,
Time and cost are required, and complete removal of defects is difficult from an industrial point of view.

[0004]

Among the fractured surfaces and sheared surfaces constituting the punched surface, the fractured surface is a starting point of fatigue failure. Therefore, a method of improving the punched surface properties by increasing the shearing surface ratio has been partially adopted (Japanese Patent Laid-Open No. Hei 8-
No. 337843). Shear ratio is 1 by precision punching
However, in order to improve the precision punching property, it is necessary to use a softened material (Japanese Patent Publication No. 5-1476).
No. 4). However, precision punching has low productivity and yield as compared with normal punching, and therefore cannot be applied to the production of inexpensive parts from the viewpoint of profitability. The effect of the softening on the increase in the shear area also occurs in the case of ordinary punching, but the softened material has a large burr and the flatness of the punched part is low. In this respect, there is a limit to the improvement of the punching property due to softening.

[0005] To improve the notch sensitivity, it is also effective to reduce the strength of parts. However, since the fatigue strength decreases with the decrease in strength, the characteristics required for various mechanical parts cannot be obtained. As described above, it is difficult to improve the fatigue properties while securing the strength of the stamped parts, and particularly, it is extremely difficult to improve the fatigue properties of the stamped parts at a hardness level of 45 HRC or more. Furthermore, as steel sheets for stamped parts, some parts are subjected to heat treatment after stamping,
It is also necessary to have excellent hardenability and toughness after heat treatment.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been devised in order to solve such a problem, and has excellent fatigue characteristics by controlling the fracture surface characteristics generated by punching a steel sheet. An object of the present invention is to provide a steel sheet for punching.

In order to achieve the object, the steel sheet for stamping of the present invention has a C content of 0.3 to 0.8% by mass and a Si content of 3.%.
0 mass% or less, Mn: 1.5 mass% or less, Cr: 2.0
% By mass, Cu: 0.5% by mass or less, N: 0.000
5 to 0.02 mass%, O: 0.0005 to 0.01 mass%, P: 0.02 mass% or less, S: 0.01 mass% or less, acid-soluble Al: 0.01 to 0.10 Mass%, and the balance substantially has the composition of Fe, and the fracture surface roughness of the punched surface at the position where the maximum stress acts after the punching is Ry.
The secondary shear ratio of the fractured surface is 0 μm or less, and is characterized by being 0.

[0008] The steel sheet used is Mo: 0.1 to 2.
0% by mass, Ni: 0.1 to 3.0% by mass, V: 0.01
To 0.5% by mass, Ti: 0.01 to 0.1% by mass, N
b: 0.01 to 0.2% by mass, B: 0.0005 to 0.
One or two or more of the components may be contained in an amount of 01% by mass, and the Vickers hardness is preferably adjusted to a range of 200 to 400 HV. Further, by using a steel sheet having a ferrite + carbide structure in which a spheroidized carbide having a spheroidization ratio of carbide of 90% or more and an average particle diameter of 0.6 μm or less is dispersed, a steel sheet for punching having a good punched surface can be obtained. can get.

[0009]

The present inventors have investigated in detail the starting point of the fracture when the punched part undergoes fatigue failure during use.
As a result, it was found that the starting point of fatigue fracture was mainly at the fracture surface of the punched surface. Generally, the fracture surface of the punched surface is considered to be more likely to be a starting point of a crack because the unevenness is larger than that of the plate surface or the shear surface, so that the stress concentration is increased.
Therefore, it is expected that the generation of cracks will be suppressed by suppressing the roughness of the fractured surface. Based on this premise, the relationship between the fracture surface roughness and the fatigue characteristics was investigated. As an index of the fracture surface roughness, the relationship between the surface roughness Ry defined in JIS B0601 and the fatigue characteristics was good. We found that there was a great correlation. Specifically, when the Ry as shown in FIG. 1 exceeds 100 [mu] m, (intensity obtained at break cycles 10 ⁵ times) times the strength greatly deteriorates.
Ry is the maximum height difference in the roughness curve, and it is considered that the portion where Ry is large is most likely to concentrate stress and becomes the starting point of a crack.

[0010] In ordinary punching, a secondary shear surface is likely to be formed on the punched surface in addition to the fractured surface. When the secondary shear surface occurs, a step is formed between the fracture surface and the secondary shear surface, and the boundary portion has a notched shape. When a crack is generated in the punched surface, the boundary between the secondary shear surface and the fracture surface corresponding to the bottom of the notch becomes the starting point. Therefore, by performing the punching process under the condition that the secondary shear surface does not occur, the occurrence of cracks is suppressed, and the improvement of the fatigue properties is expected. The generation of the fracture surface roughness and secondary shear surface generated on the punched surface is affected by the punch clearance, the hardness of the punched material, and the structure. Therefore, by appropriately adjusting the punching clearance, the hardness of the material, and the structure, the roughness of the fractured surface can be reduced to a maximum height difference Ry of 100 μm or less and a punched surface having no secondary shear surface can be obtained.

It is preferable that the maximum height difference Ry of the fractured surface be 100 μm or less at any part of the punched surface generated by the punching process so that a secondary shear surface does not occur. However, depending on the type of the blank material, the shape of the part, the state of the mold, and the like, it may be difficult to reduce the maximum height difference Ry to 100 μm or less at all positions on the blanked surface without a secondary shear plane. In such a case, the desired effect can be obtained by making the punched surface at a specific position after the punching process have a predetermined surface property. Specifically, when a fatigue load is applied to a stamped part, by restricting the maximum height difference Ry of the fractured surface to 100 μm or less without a secondary shear surface on the punched surface at the position where the maximum stress is applied, Crack generation is suppressed, and fatigue characteristics are improved. The position where the maximum stress acts can be specified mechanically from the shape of the stamped part and the direction in which the load is applied. For example, when tensile fatigue is imparted to a component, the bottom of the notch, the bottom of R having a small curvature, and the like become the maximum stress concentration portion in the tensile direction.

In the case of a soft material, the amount of local deformation increases near the fractured surface during the punching process, so that the punched surface becomes rough and a secondary shear surface is likely to occur. As a result, the fatigue characteristics of the stamped part are degraded. This trend is 200
Appears remarkably at hardness less than HV. The low hardness increases burrs at the time of punching, and also causes a shape defect of the punched part. However, with a hard material exceeding 400 HV, the load on the punching die increases, and the life of the die is impaired. The hardness of the material is affected by the form of the carbide and can be adjusted by annealing conditions or cold rolling conditions.

[0013] The carbide form also affects the punched surface properties and, consequently, the fatigue properties. That is, the material is locally plastically deformed during the punching process, but traces of carbides dragged by the plastic deformation at this time remain near the fracture surface. The extent of the trace differs depending on the size of the carbide, and in a structure having coarse carbides, coarse voids and minute cracks in which the voids are aggregated and grown are generated. In this regard, by spheroidizing the carbide dispersed in the steel material and controlling the size of the spheroidized carbide, micro cracks and notches, which are the starting points of fatigue fracture, can be minimized. For this reason, in the present invention, a steel sheet having a ferrite + carbide structure in which the spheroidization rate is 90% or more and the average particle size of the spheroidized carbide is regulated to 0.6 μm or less is used.

The effects of the spheroidization rate of the carbide and the average particle size of the spheroidized carbide on the punching workability have already been introduced by the present inventors in Japanese Patent Application No. 11-233598. The regulation improves the fatigue characteristics as described above. The steel sheet used in the present invention is
It has a structure in which carbides are dispersed in a ferrite matrix, but may contain pearlite, bainite, and the like. The form of the carbide dispersed in the ferrite matrix has a great effect on the fracture surface properties of the punched surface. When the spheroidization rate of the carbide is reduced, the spheroidized carbide tends to become finer.However, as the spheroidization rate decreases, the distribution of carbides becomes uneven, and the variation in the punched surface properties between parts increases, and Mold life is also shortened. Conversely, when the spheroidization ratio is large, coarse carbides are dispersed, which indicates that minute cracks and voids are easily generated on the punched surface.

According to the results of the investigation and research conducted by the present inventors, when the spheroidization rate of the carbide is regulated to 90% or more and the average particle diameter of the spheroidized carbide is regulated to 0.6 μm or less, the fracture surface is roughened. And the punched member excellent in fatigue characteristics was obtained. In the present specification, when the ratio (p / q) of the maximum length p of the carbide in the observation field of view of the steel plate cross section and the maximum length q in the direction orthogonal thereto is less than 3, the carbide is spheroidized. The number ratio of the spheroidized carbide to the total carbide was defined as the spheroidization ratio. If the spheroidization ratio is less than 90%, a secondary shear surface is likely to be generated on the punched surface, and the fatigue characteristics are deteriorated. Furthermore, the equivalent circle diameter was calculated from the area of each spheroidized carbide, and the value obtained by dividing the total number of equivalent circle diameters by the total number of measured spherical carbides was defined as the average particle diameter of the spheroidized carbide. If the average particle size of the spheroidized carbide exceeds 0.6 μm, the size of minute cracks and voids generated on the punched surface near the fractured surface becomes large, the fractured surface becomes rough, and the fatigue characteristics deteriorate. Coarse spheroidized carbide is
It remains without solid solution at the time of heat treatment, and also causes a decrease in toughness after heat treatment.

Hereinafter, alloy components and contents contained in the steel sheet used in the present invention will be described. C: An alloy component effective for improving the strength and toughness of the steel material of 0.3 to 0.8 mass% ,
To obtain a hardness of 5 HRC or more, a C content of 0.3 mass% or more is required. However, the amount of carbide increases as the C content increases. When the C content exceeds 0.8% by mass, precipitation of cementite at the grain boundary is inevitable, and the hardness is greatly increased, which causes a reduction in the life of the punching die. In addition, the increase in the C content lowers the Ms point, making it easier to generate retained austenite, and thus lowers toughness and fatigue properties.

Si: 3.0 mass% or less Si is an alloy component added as a deoxidizing agent in a steelmaking stage.
It also has the effect of enhancing hardenability and strengthening solid solution of ferrite. It also has the effect of delaying the precipitation of carbides during heat treatment, but causes internal oxidation immediately below the surface during hot rolling, annealing, heat treatment, and the like. Further, an excessive amount of Si hardens the steel sheet and increases the load on the punching die. To avoid these adverse effects, the upper limit of the Si content was set to 3.0% by mass. The steel material used in the present invention is M
deoxidation by n, Al, etc.
i may not be added.

Mn: 1.5 mass% or less Mn is an alloy component added as a deoxidizing agent in a steelmaking stage, and has an effect of enhancing hardenability. However, during punching, the formation of Mn-based nonmetallic inclusions serving as starting points of microcracks causes the fracture surface to be roughened, and the development of stripe structures adversely affects toughness. Therefore, in the present invention, Mn
The upper limit of the content was set to 1.5% by mass. Since the steel used in the present invention is also deoxidized by Si, Al and the like, Mn can be basically added without addition. Cr: 2.0% by mass or less Cr is an alloy component effective for improving hardenability, strength and toughness after heat treatment, and also has an effect of preventing graphitization during annealing. However, when an excessive amount of Cr exceeding 2.0% by mass is contained, the toughness is rather lowered, the spheroidizing annealing becomes difficult, and the productivity of the intermediate product is significantly deteriorated. Also,
As the Cr content increases, the steel sheet becomes extremely hard, and the load on the punching die increases. As the hardenability, strength after heat treatment and toughness are compensated by other alloy components,
Basically, Cr may not be added.

Cu: 0.5% by mass or less Cu is an alloy component that is effective for improving hardenability and toughness after heat treatment and is added supplementarily. However, excessive addition of Cu exceeding 0.5% by mass causes hot embrittlement. N: 0.0005 to 0.02% by mass V, Al, Ti, Nb and the like form nitrides and carbonitrides,
Austenite grains are refined. These effects are
When combined with V, Al, Ti, Nb, etc., 0.0
It becomes remarkable at an N content of 005 mass% or more. But,
If the N content exceeds 0.02% by mass, the refining effect is saturated, and the adverse effect of reducing the toughness and fatigue properties appears.

O: 0.0005 to 0.01 mass% is a harmful component that forms non-metallic inclusions such as Al ₂ O ₃ that serve as starting points of microcracks at the time of punching, and roughens the fracture surface. Non-metallic inclusions can also be the origin of fatigue cracks. O is also a component that deteriorates toughness and fatigue properties after quenching and tempering. For this reason, the O content is preferably as low as possible. However, excessive reduction of the O content causes an increase in production cost. Therefore, the lower limit is set to 0.0005% by mass, and the upper limit at which the adverse effect of O does not appear is 0.1%. It was defined as 01% by mass. P: 0.02% by mass or less It is a harmful component that segregates at the crystal grain boundary and reduces the toughness after quenching and tempering. However, excessively lowering the P content increases the production cost. Therefore, the upper limit of the P content is set to 0.02% by mass as a range that does not adversely affect the toughness.

S: 0.01% by mass or less Nonmetallic inclusions such as MnS are formed, which adversely affects the workability, strength, and toughness of the steel material. In rolled material, MnS is stretched in the rolling direction, so that in-plane anisotropy appears significantly in the workability, strength, and toughness of the steel sheet. At the time of punching, it becomes a starting point of a minute crack to roughen the fracture surface, and the nonmetallic inclusion itself becomes a starting point of a fatigue crack. In order to suppress such adverse effects, the upper limit of the S content is set to 0.01% by mass. Acid-soluble Al: 0.01 to 0.10% by mass An alloy component added as a deoxidizing agent in the steelmaking stage, combines with N in steel to form AlN, and abnormal growth of austenite crystal grains during heat treatment The effect of suppressing is shown. These effects become remarkable at an acid-soluble Al content of 0.01% by mass or more. However, the effect of acid-soluble Al is 0.10% by mass.
And the addition of an excessive amount of Al rather increases the production cost, and defects such as increased surface flaws are more likely to occur.

Mo: 0.1 to 2.0 mass% Mo is an alloy component added as necessary, and is an alloy component effective for improving the quenchability, strength after heat treatment, and toughness of a steel material like Cr. . These effects become remarkable with 0.1% by mass or more of Mo. However, when an excessive amount of Mo exceeding 2.0% by mass is contained, the toughness is rather lowered, the spheroidizing annealing becomes difficult, and the productivity of the intermediate product is significantly deteriorated. Also, a large Mo content hardens the steel material and causes an increase in the load on the punching die. Ni: 0.1 to 3.0% by mass An alloy component added as necessary, and has an effect of improving hardenability and toughness after heat treatment. Improving strength and toughness by adding Ni also improves fatigue characteristics. Such an effect becomes remarkable with Ni of 0.1% by mass or more. However, an excessive amount of Ni exceeding 3.0% by mass
Is included, the steel material is remarkably hardened, and the load on the punching die increases. Further, the effect of improving the strength, toughness, and crack propagation resistance after the heat treatment is saturated.

V: 0.01 to 0.5% by mass An alloy component added as necessary, forms carbide in steel, improves strength and toughness, and refines austenite crystal grains. The effect also improves the crack propagation resistance. Such an effect is 0.0
Although it becomes remarkable at V of 1% by mass or more, when an excessive amount of V exceeding 0.5% by mass is contained, the effect of improving the strength, toughness, and crack propagation resistance is saturated, and on the contrary, the productivity of the intermediate product is deteriorated. I do. Ti: 0.01 to 0.1% by mass An alloy component added as required, forms a carbonitride that is hardly dissolved during heat treatment, suppresses austenite crystal grains from being coarsened during quenching heating, and cracks. It has the effect of increasing propagation resistance. Further, since N is fixed by the addition of Ti, an effective B amount that acts to strengthen the crystal grain boundary is secured. Such an effect becomes remarkable with 0.01% by mass or more of Ti. However, an excessive amount of Ti exceeding 0.1% by mass
, Coarse nitrides are likely to be formed, leading to a decrease in toughness.

Nb: 0.01 to 0.2 mass% Nb is an alloy component added as necessary, forms a stable carbonitride, and suppresses coarsening of crystal grains at the time of quenching like V and Ti. And has an effect of preventing deterioration of toughness. Such an effect becomes remarkable with Nb of 0.01% by mass or more. However, when an excessive amount of Nb exceeding 0.2% by mass is contained, the solid solution of the carbide in the matrix decreases,
This leads to a decrease in strength. B: 0.0005 to 0.01% by mass An alloy component added as necessary, improves the hardenability, suppresses the segregation of P at the crystal grain boundaries, and reduces the toughness caused by grain boundary fracture. Prevent drop. Such an effect becomes remarkable at 0.0005% by mass or more of B,
Saturates at 1% by weight. When the added B combines with N to form a nitride BN, the effective B amount is reduced. Therefore, it is preferable to fix N as TiN by adding it in combination with Ti.

The steel sheet of the present invention is punched into a predetermined shape and then given a 45 HR if necessary to impart a predetermined strength.
Tempered above C. The heat treatment for refining is generally quenching or quenching / tempering, but depending on the material, a constant temperature treatment such as austempering or martempering may be performed. In addition, when the punched part after the heat treatment is shot peened, the fatigue characteristics are further improved. Generally, the fatigue strength tends to increase as the material strength increases. However, when the strength level is 45 HRC or more, the susceptibility to defects on the material surface increases, and the increase in strength does not always lead to the increase in fatigue strength. That is, when a punched part is used for an application requiring fatigue characteristics, the effect of the punched surface properties increases when the strength level is 45 HRC or more. In this regard, in the stamped part obtained from the steel sheet of the present invention, there is no secondary shear surface, and the maximum height difference Ry of the fracture surface is 10%.
Since it has a punching surface regulated to 0 μm or less, 45
Even if tempering is performed to a strength equal to or higher than HRC, deterioration of fatigue characteristics due to punched surface properties can be suppressed.

[0026]

EXAMPLES Steel having the composition shown in Table 1 was melted in a converter and continuously cast into slabs. This slab was hot-rolled to a thickness of 2.6 mm. After pickling and annealing the obtained hot-rolled sheet, the sheet thickness was adjusted to 1.2 mm by cold rolling to adjust the hardness. Table 2 shows the annealing and cold rolling conditions.

[0027]

[0028]

From each obtained material, a strip-shaped test piece having a length of 200 mm and a width of 30 mm along the rolling direction was cut out,
While changing the clearance, a diameter of 1
A punched hole of 0 mm was formed. The punched test piece was heated at 870 ° C. for 15 minutes, then quenched,
It was tempered by tempering to 0 ° C for 100 minutes. Before and after tempering, the hardness of the specimen, the spheroidization rate of the carbide, the average particle size of the spheroidized carbide, and the maximum height difference Ry of the fracture surface were measured.
The punched surface generated by the punching process was visually observed to check for the presence of a secondary shear plane. The maximum height difference Ry was detected by observing a punched surface generated by punching using a laser microscope. In addition, a tensile load of 20
Fatigue properties were evaluated at a time strength of 10 ⁵ break cycles.

As can be seen from the survey results in Table 3, in Comparative Examples 1 to 3, the fracture surface roughness was within the range specified by the present invention.
A punched surface without a secondary shear plane is obtained. But C
In Test No. 1 (Comparative Example) having a low content, the strength was insufficient,
The fatigue life was also short. In test number 2 (comparative example), Ms
Since C and Mn lowering the point were excessively contained and the structure had an unstable structure including retained austenite, the fatigue life was short although hardness of 50 HRC or more was secured after tempering. Test No. 3 (Comparative Example) also contained a large amount of impurity elements such as S and O, so that a hardness of 50 HRC or more could be secured, but the fatigue life was short. Also, the surface roughness Ry
And breaking the cycle 10 ⁵ times As is apparent from FIG. 1 of investigating the relationship between time strength, it is understood that the time-intensity below the surface roughness Ry100μm is greatly improved.

Even though the steel E satisfies the conditions specified in the present invention in terms of components, Test Nos. 9 and 11 in which the hardness of the material and the average particle size of the spheroidized carbide are out of the ranges specified in the present invention (Comparative Examples) In (), the fracture surface was rough and the fatigue life was short. In Test Nos. 10 and 12 (Comparative Examples), a short fatigue life was exhibited because a punched surface having a secondary shear surface was formed. On the other hand, in Test Nos. 4 to 8 (Examples of the present invention), a punched surface having a maximum height difference Ry of the fractured surface of 100 μm or less and having no secondary shearing surface was produced, and the present invention was also used as a component. Excellent fatigue characteristics were shown in combination with satisfying the prescribed conditions. As is clear from this comparison, it was confirmed that the specified component design and control of the punched surface properties can provide a punched steel sheet exhibiting excellent fatigue properties even after tempering.

[0032]

[0033]

As described above, the steel sheet for stamping according to the present invention uses a steel sheet having specified components, and by controlling the properties of the punched surface, a product having good shape accuracy can be obtained. And exhibit excellent fatigue properties even after tempering.

[Brief description of the drawings]

Figure 1 is a graph surface roughness Ry and break cycles 10 ⁵ times showing a relationship between time obtained intensity

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Katsuyuki Iihara, 111-1 Showa-cho, Kure-shi, Hiroshima Nisshin Steel Co., Ltd. Technical Research Institute (72) Inventor Hiroyuki Sufuku 11-1, Showa-cho, Kure-shi, Hiroshima Nisshin Steel Co., Ltd. (72) Inventor Shoichi Koya 11-1 Showa-cho, Kure City, Hiroshima Prefecture Nisshin Steel Co., Ltd.

Claims (4)

[Claims] 1. C: 0.3 to 0.8% by mass, Si: 3.
0 mass% or less, Mn: 1.5 mass% or less, Cr: 2.0
% By mass, Cu: 0.5% by mass or less, N: 0.000
5 to 0.02 mass%, O: 0.0005 to 0.01 mass%, P: 0.02 mass% or less, S: 0.01 mass% or less, acid-soluble Al: 0.01 to 0.10 Mass%, and the balance substantially has the composition of Fe, and the fracture surface roughness of the punched surface at the position where the maximum stress acts after the punching is Ry.
A steel sheet for punching, characterized in that the secondary shear ratio of the fractured surface is 100 μm or less and the secondary shear ratio is 0. 2. Mo: 0.1 to 2.0% by mass, N
i: 0.1 to 3.0% by mass, V: 0.01 to 0.5% by mass, Ti: 0.01 to 0.1% by mass, Nb: 0.01 to
0.2% by mass, B: 0.0005 to 0.01% by mass
The steel sheet for stamping according to claim 1, wherein the steel sheet comprises at least one kind. 3. The steel sheet for stamping according to claim 1, wherein the Vickers hardness is in the range of 200 to 400 HV. 4. Ferrite in which spheroidized carbide having a spheroidization ratio of carbide of 90% or more and an average particle size of 0.6 μm or less is dispersed.
The steel sheet for punching according to any one of claims 1 to 3, wherein the steel sheet has a carbide structure.