JPH0762208B2 - Steel plate with excellent punchability - Google Patents

Description

TECHNICAL FIELD The present invention relates to a steel sheet having excellent punching workability.

(Prior Art) A user who uses a steel plate does not use the steel plate wound into a coil as it is, but rewinds the coil and then blanks it to an appropriate size, and then presses it or presses it to a predetermined size. It is used after punching the shape. Of these, particularly when a punching process is performed, it is a big problem for the user whether the life of the punching die is long or short. Naturally, a steel plate having a long die life is pleasing.

Of the steel sheets, particularly in the field of hard steel (high hardness steel sheet), it is often used in the above-mentioned punching process, and improvement in this respect is also required among users.

Therefore, even in the conventional punching property, in the field of high carbon steel (polished special strip steel), the one whose surface is slightly decarburized (Japanese Patent Laid-Open No. 49-45819) and the high medium C An attempt to obtain the life-prolonging effect of a die by changing from cementite to graphite (JP-A-56-119758), hot-rolled high carbon steel sheet, bainite is generated by controlling the finishing temperature and winding temperature. It has been proposed to use a composition of ferrite and pearlite to obtain the effect of extending the life of the mold (Japanese Patent Laid-Open No. 56-9329).

(Problems to be Solved by the Invention) However, such proposals do not always give satisfactory results. In other words, all of these conventional techniques attempt to obtain the effect by "softening" the steel quality of the steel sheet when improving the punchability.
That is not enough.

Therefore, an object of the present invention is to provide a steel sheet which is excellent in punching workability as compared with the prior art and has a practically satisfactory effect of extending the die life.

Therefore, the present inventors have made various studies to achieve such an object.

According to the knowledge of the present inventors, in order to improve punchability,
It is not just to soften steel, but it is necessary to consider the punching energy during punching.

FIG. 1 conceptually shows the relationship between the punching load and the punching stroke length. As shown in the graph of the figure, when the plot is drawn with the punching load and the punching stroke as the Y-axis and the X-axis, respectively, the smaller the area of the shaded area,
It is considered that the punchability is improved. Here, the "punching load" is the total load required to punch the plate, and the "punching stroke" is the mold from contact with the plate until the plate is completely punched. Is the distance traveled by.

Since the conventional technique is to soften the steel quality, it is considered that the area is reduced by lowering the punching load in FIG. However, in practice, in this case, as shown in FIG. 2, the punching stroke tends to be long, and the area itself does not decrease so much, or rather increases, even if the load decreases. Many of them did not lead to an essential improvement in punchability.

Here, according to the findings of the present inventors, basically, by adding a small amount of Te, the free cutting property of the steel is improved, so that the punching load is hardly changed and the punching stroke is shortened. It was found that the punchability was remarkably improved, and the present invention was completed.

This means that, taking FIG. 3 as an example, the present invention allows the punching stroke to shift to the left by
This is intended to reduce the area of the shaded area in the figure.

Therefore, the gist of the present invention is a steel sheet that has been subjected to hot rolling and cold rolling, the chemical composition value of the steel, in% by weight, C: 0.3 ~ 1.2%, Mn: 0.10 ~ 2.50%, Si: 0.01 to 0.35%, P: 0.001 to 0.030%, S: 0.001 to 0.040%, Te: 0.0002 to 0.030%, and Te / S ≥ 0.2, and if necessary Cr: 0.01 to 1.50% balance Fe and unavoidable impurities are steel sheets with excellent punching workability without causing deterioration of mechanical properties.

(Operation) Next, the reason why the steel composition is limited as described above in the present invention will be described in more detail.

C: C is an element that enters the hot metal during reduction with coke in the blast furnace, but is contained in the steel composition of the present invention to increase the strength. If it is less than 0.3%, the strength becomes too low, and if it exceeds 1.2%, the strength becomes too high and the workability such as ductility is adversely affected.

Mn: Mn is added in order to increase the strength, but if it is less than 0.10%, it has no effect, and if it exceeds 2.50%, it deteriorates hot workability, which is not preferable.

Si: Si is added to enhance the strength, but it is difficult to set it to less than 0.01% in the process, and the effect is small with such a small amount. However, if it exceeds 0.35%, toughness and workability are deteriorated.

Since P: P is an impurity that is inevitably contained, it is preferably low, but the cost is too high to reduce it, so the upper limit was made 0.030%.

Since S: S is usually unavoidably contained, it is preferably low, but in the steel of the present invention, 0.001% or more is necessary because it forms an A-type inclusion and has a favorable effect on punchability. However, 0.040%
If it exceeds, toughness is deteriorated, which is not preferable.

Te: Te is an important element in the present invention. When Te is added, A-type inclusions such as MnTe are formed and have a favorable effect on the punchability, so 0.0002% is necessary, but if it exceeds 0.030%, it becomes steel. Is not preferable because it impairs the cleanliness. Further, in order to efficiently form MnTe, Te / S is preferably 0.2 or more (Te / S ≧ 0.2).

Cr: Cr is added as necessary to enhance the corrosion resistance and strength / toughness, but if it is less than 0.01%, the effect will be less than 1.50.
If it exceeds%, the effect is saturated and it is not economically preferable.

The steel having such a composition is made into a steel sheet after being melted, hot-rolled and cold-rolled, but in the present invention, such working may be a conventional one and is not particularly limited. The present invention is applicable to a wide range of thicknesses, for example, 0.1 to 6.0 mm, and is particularly advantageous for thick plates.

Next, the present invention will be described more specifically by way of examples.

Example A steel having a composition shown in Table 1 in which Te was added to JIS S50C class steel was made into a slab by continuous casting, hot rolled to a thickness of 4.0 mm, and cold rolled to a thickness of 1.0 mm. 690 ° C x 18
After annealing for an hour, 1.2% temper rolling was performed to obtain a test material.

The mechanical properties and cleanliness of the test material thus obtained were determined. The results are shown in Tables 2 and 3. The cleanliness test was conducted only on steel Nos. 1 and 2.

For each of the steel Nos. 1 to 10, a punching test specified in JIS was performed under the same conditions.

FIG. 4 shows the relationship between the stroke and the load for steel No. 1 and No. 2 among them. In the present invention example, the stroke is short, and the effect is recognized. Also, similarly from the data shown in Table 1, even when viewed by the burial height,
The burrs of about 15μ have been reduced, and the effect is recognized in this respect as well.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain a steel sheet in which the life of the mold is almost doubled and other mechanical properties are comparable to each other. large.

[Brief description of drawings]

1 to 3 are graphs showing the relationship between punching load and shear stroke; and FIGS. 4 and 5 are graphs summarizing the results of the examples.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Iwami Shinagawa 1850 Minato, Wakayama, Wakayama Sumitomo Metal Industries, Ltd. Wakayama Works (56) Reference JP-A-59-139655 (JP, A) JP-A-51 -72916 (JP, A)

Claims (2)

[Claims] 1. A steel sheet which has been hot-rolled and cold-rolled, wherein the chemical composition value of the steel is C: 0.3-1.2%, Mn: 0.10-2.50%, Si: 0.01 in% by weight. ~ 0.35%, P: 0.001 ~ 0.030%, S: 0.001 ~ 0.040%, Te: 0.0002 ~ 0.030%, and Te / S ≥ 0.2 are satisfied, and the balance is Fe and inevitable impurities. Steel plate with excellent punching workability without causing deterioration of properties. 2. The steel sheet according to claim 1, further comprising Cr: 0.01 to 1.50%.