JPS5817809B2 - Ritsujinno Sukunife Elite Kei Stainless Steel Kono Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing ferritic stainless steel sheets by continuous casting, and its purpose is to achieve a method for producing ferritic stainless steel sheets by continuous casting, and the purpose thereof is to achieve a method of manufacturing ferritic stainless steel sheets by continuous casting without impairing the workability of cold-rolled steel sheets. It is an object of the present invention to provide a steel plate in which almost no tsuging occurs.

Rigging, which is a problem in processing ferritic stainless steel sheets, is a wave-like unevenness, but if it is thick, it must be removed by polishing after processing, which requires an extra step, which is unfavorable in terms of manufacturing.

Normally, steel plates made by the steel ingot process have a finer structure and relatively good ridding because the steel ingot goes through a blooming process, but on the other hand, ferritic stainless steel plates made by continuous casting generally Because of the columnar crystals formed,
There is a tendency for ritsuging to become noticeable.

The columnar crystals that cause ritzing can be destroyed by various methods such as low-temperature casting, electromagnetic stirring, or ultrasonic vibration irradiation, and become free crystals. Cold-rolled steel plate beams are produced using these free crystal slabs. It has been confirmed that there are few problems and there are no practical problems.

On the other hand, ferritic stainless steel sheets are generally cold-rolled and annealed twice to improve their properties, but as a result of experimentally examining the texture during the cold-rolling annealing process using free-crystalline slabs, we discovered a similar phenomenon. Ta.

That is, when a hot-rolled sheet obtained from a free-crystalline slab is cold-rolled and annealed, the main orientation of the crystal texture is (111) <112>, and at a low cold rolling rate, (100) <o 11> exists as a minor orientation. However, when the cold rolling rate increases to 70% or more, (100)<Oli> decomposes and becomes ND//<
001> almost disappears.

Note that ND indicates a direction perpendicular to the plate surface.

In addition, in FIGS. 1 and 2, RD indicates the rolling direction, TD indicates the direction perpendicular to the plate surface and the rolling direction,
ND7<001>c means an orientation in which the <001> direction is parallel to ND.

However, in the case of a columnar crystal slab, although the main orientation is the same, the ND7<001> component does not disappear even if the cold rolling rate is increased and remains in the form of ('100)<011>±15° until the end (1st (See Figure 2).

The difference between a columnar crystal slab and a free crystal slab appears in the presence or absence of the ND/<001> component on a cold-rolled annealed plate.

This component is an important factor governing the r value, which has a strong relationship with the crystal texture, and thus the workability.

Generally, the reason for aiming at improving workability by performing cold rolling annealing twice is to eliminate the ND/<OO1> orientation by combining an appropriate cold rolling rate.

Even free-crystalline slabs can easily be ND/< by performing cold rolling annealing twice.
The 001> direction can be omitted and the (iio)<ooi> principal direction can be used.

In this case, both ridging and workability are of course good and there is no problem, but the present invention eliminates the ND/<001> component that is harmful to workability with just one cold rolling annealing, that is, improves workability. The process uses free-crystalline slabs to produce steel sheets that have no problems with ridding, and its major feature is that it is a simple process that is superior in terms of quality and economy, with no need for double-spread annealing. .

In other words, the present invention uses a free-crystalline slab in the production of ferritic stainless steel sheets with good workability, and achieves the same level of workability as twice cold rolling, which was conventionally required to obtain high workability with only one cold rolling process. This method has the great advantage of omitting the process of twice cold rolling, which is a cause of high costs when producing steel sheets.

The free crystallization method of the continuously cast slab material in the present invention is not specified, and may be any method such as low temperature casting, electromagnetic stirring of molten steel during casting, or ultrasonic vibration irradiation.

In addition, the annealing conditions of the hot-rolled sheet during cold rolling in the present invention have a large influence on the shear joining, and annealing at a temperature of 700°C or higher reduces the ND/<001> orientation of the hot-rolled sheet and improves the shear joining property. If the temperature is lower than °C, no change will be observed in the same direction, and therefore the ridging property will not be improved.

However, if the temperature exceeds 1000°C, γ phase appears and impedes subsequent cold rolling properties, which is not preferable.

Therefore, the annealing temperature of the hot rolled sheet is set at 700°C to 1000°C.
limited to.

The hot-rolled sheet can be annealed by box annealing, in which the copper strip is wound into a coil and placed in a box furnace, or continuous annealing, in which the coil is unwound and passed through a catenary furnace, vertical furnace, etc. Any of the known means can be used.

Furthermore, regarding the ridging properties of steel sheets made from free-crystalline slabs, as shown in Figure 3, in the case of free-crystalline slabs, the ridging properties are almost the same whether cold-rolled twice or twice, but in the case of columnar slabs, the ridging properties are almost the same when cold-rolled. It is greatly influenced by the conditions.

In other words, in double cold rolling, the combination of cold rolling rates before and after intermediate annealing (
Ridding changes depending on the rolling distribution (reduction distribution), and once cold rolling is performed, the rigging is inferior to any reduction distribution in double cold rolling.

In this way, in the case of a free-crystalline slab, the texture of the cold-rolled annealed steel sheet works as an advantage against ridges, regardless of the cold-rolling conditions.

This is connected to the fact that the ND/<001> orientation is easily decomposed, and this is also the reason why the T value can be maintained high even after one cold rolling.

Examples of the present invention are shown below.

Examples The chemical composition of the samples used in the examples is C0.04 to 0.06.
%, SiO, 59-0.64%, Mn0045-0
．． 50%, Po, 022-0.026%, 80.006
~0.009%, Cr 16.48~16.90%, N
The free-crystalline slabs (samples A1-8.10) after tapping are made into columnar crystalline slabs (sample A9) by low-temperature casting. ) were manufactured by continuous casting using high temperature casting.

Each slab was hot-rolled in a normal process and then cold-rolled and annealed under the respective conditions listed in Table 1.

For comparison, an example (Sample No. 10) in which a free-crystalline slab was conventionally hot-rolled and then cold-rolled twice is also shown.

In the table, the 〒 value and riddling properties are entered, and the products according to the present invention (samples A1 to 5) have good T value and ridding properties, and there is almost no difference in mechanical properties from ordinary steel sheets (sample A10). do not have.

The thickness of the final annealed plates is 0.7 mm.

As is clear from this example, in order to obtain a steel sheet with good ridging properties and T value with only one cold rolling annealing, it is necessary to heat the hot rolled sheet at 700°C using a free crystal slab as in the present invention.
It can be seen that the objective can be achieved by heat treatment at the above temperature and at a cold rolling rate of 70% or more.

[Brief explanation of the drawing]

Figure 1 shows a free-crystal slab of normal components hot-rolled at 830°C
hr, furnace cooling treatment, 80% cold rolling, 830°C x 2m1r
+200〉 pole figure of an air-cooled annealed steel plate, Figure 2 is a <,200> pole figure of a steel plate obtained by subjecting a columnar crystal slab of normal composition to the same treatment under the same conditions as Figure 1, and Figure 3 is a cold rolled one. It is a drawing showing the relationship between conditions and final annealing plate gluing.

Claims (1)

[Claims] 1. A continuous casting slab of ferritic stainless steel having a free crystallized casting structure is hot rolled, and the hot rolled plate is
A method for producing a ferritic stainless steel sheet with less welding, characterized by annealing in a temperature range of 00 to 1000°C, and then cold-rolling it once to a predetermined thickness of 70% or more.