JP2977366B2 - Manufacturing method of austenitic stainless steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of cold rolling a slab having a thickness close to the thickness of a product cast by a so-called synchronous continuous casting process in which there is no relative speed difference between the slab and the mold wall. And a method for producing an austenitic stainless steel sheet.

[0002]

2. Description of the Related Art Synchronous continuous casting process refers to a twin-roll method, a twin-belt method, a single-roll method, etc., as introduced in a paper featured in, for example, “Iron and Steel” '85 -A197 to A256. The synchronous continuous casting process has no relative speed difference between the slab and the mold wall. The twin-roll continuous casting method, which is one of these synchronous continuous casting processes, is a continuous casting mold formed by a pair of parallel or inclined cooling rolls having the same or different diameters and side weirs sealing both end surfaces thereof. The molten metal is poured into the cooling rolls to form solidified shells on the circumferential surfaces of both cooling rolls. The solidified shells are united near the closest position (so-called "kissing point") between the rotating cooling rolls. This is a continuous casting method for feeding as a thin strip slab.

For example, a strip-shaped slab cast by a twin-roll continuous casting method has a thickness of several mm (usually about 1 to 10 mm), and is subjected to cold rolling without hot rolling. Can be manufactured. Therefore, a production method of casting a slab as a slab for hot rolling having a thickness of more than 100 mm by continuous casting using a vibration mold or the like, hot-rolling the slab, and then cold-rolling (slab slab / hot rolling) The production efficiency and cost are significantly more advantageous than those of (process).

[0004] Cold-rolled austenitic stainless steel sheets are high value-added products that have been subjected to various cold forming processes and are widely used as corrosion-resistant structural materials and exterior materials for industrial and household use. It is expected that a high economic effect can be obtained by applying a twin-roll continuous casting method or the like to the production thereof. However, when the thin strip-shaped slab cast by the twin-roll continuous casting method or the like is cold-rolled without going through hot rolling, the following problem occurs.

That is, the hot-rolled hot coil obtained by the slab slab / hot rolling process has a relatively good edge shape and can be cold-rolled without performing edge trimming. On the other hand, when a thin strip slab obtained by twin-roll continuous casting is used as a hot coil, burrs are caused due to solidification delay of the edge part, etc. There is also. Therefore, it is necessary to perform an edge trimming process (cutting and removing a side edge portion) to remove the above-mentioned defect before cold rolling.

However, austenitic stainless steel,
Particularly in 18-8 austenitic stainless steel represented by SUS304, both edges are hardened by edge trim because martensitic transformation occurs by cold working. When this is cold-rolled as it is, edge cracks occur during rolling, which causes a sheet break.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing an austenitic stainless steel sheet by a synchronous continuous casting method in which there is no relative speed difference between a slab and a mold wall surface. To provide a method for performing stable cold rolling by preventing hardening of one edge portion, without performing annealing before cold rolling, without causing troubles such as edge cracks and plate breakage. With the goal.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method of casting a strip-shaped slab by a continuous casting method in which a slab and a mold wall move synchronously, trimming the slab and performing cold rolling. Further, there is provided a method for producing an austenitic stainless steel thin plate, wherein the edge trimming is performed at a temperature not lower than the value of Md30 defined by the following formula + 50 ° C. Md30 = 4
13-462 (% C +% N) -9.2% Si-8.1% Mn-13.7% Cr-18.5% Mo-9.5 (% N
i +% Cu) ... 1 formula

[0009]

[Effect] Since the occurrence of edge cracks during cold rolling does not occur when annealing is performed after edge trimming, the cause of ear cracks during cold rolling is caused by the hard martensite phase generated near the cut surface during edge trimming. It is considered that cold rolling is performed in a state in which the original soft austenite phase is mixed.

The present inventor has found that in order to prevent martensitic transformation from occurring in the edge trimming treatment, the edge trimming treatment should be performed at a temperature equal to or higher than the value of Md30 of the slab + 50 ° C. Hereinafter, the present invention will be described in more detail with reference to examples.

[0011]

EXAMPLE A twin roll type continuous casting method was used to obtain 4
After casting a SUS304 strip-shaped slab having a level of Md30 and descaled, without annealing the material trimmed by shear cutting at a temperature of 20 to 100 ° C.,
One pass (10% reduction) of cold rolling was performed. Table 2 shows the results of visually determining the presence or absence of edge cracks in the material after cold rolling.

[0012]

[Table 1]

[0013]

[Table 2]

Materials (A, B,
C and D), when edge trimming was performed at the temperature of the value of Md30 + 50 ° C. or more, cold rolling could be stably performed without generating edge cracks.

[0015]

As described above, according to the present invention,
By preventing hardening of the slab edge by edge trimming, it is possible to perform cold rolling stably without causing troubles such as edge cracks and plate breakage, without annealing before cold rolling, Stainless steel sheets can be manufactured.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Shuichi Inoue 3434 Shimada, Hikari-shi, Yamaguchi Prefecture Inside Nippon Steel Corporation Hikari Works (56) References JP-A-3-100124 (JP, A) JP-A Hei 3-42151 (JP, A) JP-A-4-158902 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B21B 1/46 B21B 3/02 B22D 11/06 C21D 8 / 02-8/04 C21D 9/46-9/48

Claims (1)

(57) [Claims] When a strip-shaped slab is cast by a continuous casting method in which a mold wall surface and a slab move synchronously, and the slab is edge-trimmed and then cold-rolled, it is defined by the following equation. Md30
Edge trimming at a temperature of not less than + 50 ° C. in a method for producing an austenitic stainless steel sheet. Md30 = 413-462 (% C +% N) -9.2% Si-8.1% Mn-13.7% Cr-18.5% Mo-9.5 (% Ni +% Cu) ... 1