JP2898104B2 - Striped steel sheet and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-rolled steel striped steel sheet using a very low carbon steel material slab and a method for producing the same.

[0002]

2. Description of the Related Art The chemical composition and mechanical properties required for striped steel sheets are based on Japanese Industrial Standards rolled steel for general structures (JIS G310).
Although 1) is generally applied, there is a problem that a very low carbon steel slab having a low carbon content cannot satisfy the tensile strength and cannot be manufactured. Therefore, the conventional carbon content is 0.04
It was manufactured using low carbon steel slabs of ~ 0.08 wt%.

[0003]

As described above, since a striped steel sheet can be manufactured only with low-carbon steel in the past, the chance of tapping at the steel making stage and the chance of continuous casting are restricted, and the manufacturing process period is lengthened. was there.

When striped steel sheets can be manufactured even with extremely low carbon steel, the steelmaking process period can be shortened, and furthermore, there is an advantage that resources can be saved by expanding the applicable range of the material slab. Has been made to provide a striped steel plate using an ultra-low carbon steel material slab and a manufacturing technique thereof.

[0005]

According to the present invention, there is provided a striped hot-rolled steel strip and a method for producing the same, wherein the C content is 0.001 to 0.010.
Heating temperature: 12% by weight using ultra low carbon steel slab
This is a method for manufacturing a striped steel sheet, which is manufactured under a rolling temperature condition of 00 ± 50 ° C., a finish mill exit side temperature of 900 ± 30 ° C., and a winding temperature of 450 ± 50 ° C.

[0006]

[Action] As a result of testing under various hot rolling temperature conditions using an ultra-low carbon steel material slab, even if an ultra-low carbon steel material slab is used by regulating the hot rolling temperature condition to an optimum range, The inventor has found that a striped steel sheet having a quality characteristic comparable to that of a low-carbon steel slab can be manufactured, and based on this finding, the present invention has been accomplished.

[0007] Using ultra-low carbon steel as a raw material slab, various characteristics were investigated while changing the hot rolling conditions as shown in Table 1. Table 2 shows the results. Table 3 shows the properties required for the striped steel sheet according to JIS G3101 (Japanese Industrial Standards General Rolled Steel for General Structure) SS34. Table 2 also shows the evaluation.

[0008]

[Table 1]

[0009]

[Table 2]

[0010]

[Table 3]

From the test results, the following has become clear. The strength increases as the heating temperature, finish mill outlet temperature, and winding temperature are lower. On the other hand, when the finish mill outlet temperature is low,
For example, at 860 ° C, since the steel is near the phase transformation, the temperature deviation in the steel sheet during rolling shows a phenomenon in which the untransformed part and the transformed part are mixed and the steel sheet curves.

However, when the exit temperature of the finishing mill is 750 ° C., the temperature is low, so the surface scale (FeO + Fe ₂ O ₃ + Fe ₃ O
₄ ) The growth rate is slow, and a tight scale film is not formed, and there is a problem that the surface layer scale peels when cutting from the coil to the sheet. Next, the lower the winding temperature, the better the strength, but the more likely it is to cause poor distortion. Test No. Samples No. 2 and No. 3 satisfied the quality characteristics required for the striped steel sheet and obtained good results in both shape and appearance.
o. Nos. 1, 4, 5, and 6 have unsuitable quality characteristics or the like as striped steel plates. Next, the reasons for specifying the rolling temperature conditions will be described.

Heating temperature: A temperature capable of achieving the finishing mill outlet temperature described later is required, and the temperature is limited to 1200 ± 50 ° C. Finishing mill outlet temperature: If the Ar ₃ transformation point (≒ 870 ° C) is removed,
Even under even above the Ar _3, although rolling is possible, and a 900 ± 30 ° C. above the Ar ₃ in terms of scale peeling.

Winding temperature: 450 to ensure tensile strength
± 50 ° C.

[0015]

EXAMPLE Using a very low carbon steel material slab having the components shown in Table 4 (260 × 920 × 8300 mm, under the rolling temperature conditions of Example 1 in Table 5), the striped plate roll shown in FIG. F-
As a result of manufacturing striped steel sheets (coil dimensions: 3.1 × 924 × 1 mm) according to the pass schedule shown in Table 6 by incorporating them into 5), it is possible to obtain striped steel sheets that are as good as low carbon steel in mechanical properties, shape, appearance, etc. did it.

Furthermore, striped steel sheets were produced under the same rolling temperature conditions as those of Examples 2, 3 and 4 in Table 5 except for the same conditions as in Example 1, and a good striped steel sheet was obtained at the same time.

[0017]

[Table 4]

[0018]

[Table 5]

[0019]

[Table 6]

[0020]

According to the present invention, an ultra-low carbon steel material can be obtained by selecting a striped steel sheet which can be conventionally produced only with a low carbon steel slab, by selecting the rolling temperature conditions for hot rolling in accordance with the regulations of the present invention. It can also be manufactured from slabs.

Therefore, not only the number of days of the manufacturing process in the steelmaking stage can be reduced, but also the resources can be saved by expanding the applicable range of the raw material slab.

[Brief description of the drawings]

1A is a plan view showing a striped plate roll, FIG.
(B) is XX sectional drawing.

Claims (2)

(57) [Claims] 1. A hot-rolled striped steel sheet having a C content of 0.001 to 0.
A striped steel sheet using 010% by weight of ultra-low carbon steel. 2. A method for producing a strip steel strip with hot strip, comprising the steps of:
Using a very low carbon steel slab with a content of 0.001 to 0.010% by weight, heating temperature: 1200 ± 50 ° C, finish mill outlet temperature:
900 ± 30 ° C, winding temperature: A method for producing striped steel sheets, characterized in that it is produced under rolling temperature conditions of 450 ± 50 ° C.