JPS5924558A - Production of stainless steel billet - Google Patents

Abstract

PURPOSE:To fine the solidified texture of a billet and to improve a casting surface by stirring electromagnetically the molten steel in a mold and the unsolidified part of the billet past the mold. CONSTITUTION:The 1st electromagnetic stirrer EMS1 is provided between a mold 2 and pinch rolls 3 to stirr the molten steel S2 which is not yet solidified, whereby cubic crystals are formed in the internal texture of a billet and the texture is fined. If the degree of overheating in a tundish 1 is large in this stage, the 2nd electromagnetic stirrer EMS2 is adequately installed in order to assist the stirrer EMS1. However, the 1st, and the 2nd electromagnetic stirrers are highly effective in fining the internal texture but are ineffectual for the shell S3 formed in the mold 2. Thereupon, the stirrer EMS3 is incorporated in the mold 2 to stir electromagnetically the molten steel in the mold. The surface texture is similarly refined as mentioned above by subjecting the unsolidified part of the billet past the mold 2 to 1 or >=2 stages of electromagnetic stirring then to hot working of 1.1-3.0 rolling reduction ratio with forging rolls 4 without stirring electromagnetically the molten steel in the mold 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a stainless steel billet, which can refine the solidified structure of a slab when the stainless steel billet is produced by a continuous casting method.

When producing round or square billets using a continuous casting method, especially a horizontal continuous casting method, and directly hot-extruding the billets without going through the blooming process, the stainless steel 1' moe billet requires a solidification process. Until then, coarse columnar crystals were generated, and this caused the surface texture of the pipe to deteriorate during the above-mentioned pipe manufacturing.

This tendency is particularly remarkable in two-phase stainless steels that form α-phase and γ-layers at room temperature, or l'j'& alloy stainless steels with a high Eat content of alloying elements. Therefore, in the past, in order to refine the solidified structure of the stainless steel 1' billet before producing a single vibrator, a method was adopted in which the stainless steel 1' billet was processed and recrystallized by rolling, etc., but this method required a full-scale heating process and rolling process. It is necessary to increase costs and Ayumu! Siros was also big.

Under the above-mentioned circumstances, the present invention aims to produce stainless steel billets that can prevent increases in post-processing costs and provide products with good surface texture by using a horizontal continuous casting method to refine the solidified structure of slabs. The first invention was made for the purpose of proposing a method for producing stainless steel l
When manufacturing N billets using the horizontal continuous casting method, magnetic stirring with C paper is applied to prevent leakage in the mold, and one or more stages of ``C'' are applied to the unsolidified part of the billet that has passed through the mold.
The second feature of the invention is that magnetic stirring is applied to the unsolidified portion of the billet that has passed through the mold when manufacturing stainless steel billets using the horizontal continuous UJ manufacturing method. The point is that two or more stages of electromagnetic 1a stirring are performed, and immediately after that, hot working is performed at a reduction ratio of 1.1 to 6.0.

Hereinafter, the solidification structure of a slab in horizontal continuous casting will be explained, and one embodiment of the present invention will be described below.

The slab produced by horizontal continuous casting has a solidification structure different from that of the slab. That is, columnar crystals grow from the top surface of the billet toward the center in the thickness direction, and form branched columnar crystals with disordered directionality near the center on the Shimoda ■ side. The generator 17& of this coagulation structure has not yet been fully elucidated, but in any case, it is thought that sedimentation due to gravity and changes in temperature distribution play an important role.

Generally speaking, in continuous steaming, (■), if the casting temperature is particularly high, columnar crystals will grow to the center.

(ff) When the casting temperature becomes low and the degree of superheating ΔT (molten copper temperature - liquidus temperature) in the tundish becomes 10 to 15°C or less, equiaxed weight appears.

*) This equiaxed weight is so small that the shape of dendrites (dendritic crystals) cannot be clearly observed, and is preferable for producing products with good surface texture in post-processing.

(Ill) The area ratio of equiaxed crystals in the cross-sectional structure of the slab increases as the casting temperature of 7m degrees decreases.

There is a phenomenon called.

The present invention focuses on the above-mentioned phenomenon and attempts to achieve the desired purpose by subjecting the unsolidified portion of molten copper to magnetic stirring to form equiaxed crystals in the slab. To explain the horizontal continuous casting shown in Fig. 4 as an example, Fig. 2 is a schematic diagram of conventional general horizontal continuous casting.
(2) is a mold, (3) is a pinch roll, and now,
For convenience of explanation, the molten steel in the mold (2) will be referred to as (SL
), unsolidified molten steel (8
1) Let the solidified shell be (S◇).

According to the method shown in Figure 2, columnar crystals are formed in the slab as described above, and as shown in Experiment A1 or A2 of the experimental results [Table 6] described later, the surface quality of the product is poor in the subsequent process. becomes.

FIG. 6 is a schematic diagram showing an embodiment of the first invention, (JLi
MSl) is an unsolidified molten steel (sr<
A one-stage electromagnetic stirring device installed to generate equiaxed load in the internal structure of the slab, (i M S 2)
The stage electromagnetic jW stirring device R is shown, and this is a tanditsh (1
) when the degree of superheating (ΔT) is large, the first-stage magnetic stirrer i! It is established as appropriate for the purpose of supporting L.

The above-mentioned electromagnetic stirring device (Il!n5l) and (Mino Ms2
) is used with the same meaning even if it falls under the second invention.

However, the above-mentioned Tonmagi IW stirring device (EMS1') and (
n+Ms2) is highly effective in refining the internal structure of the slab (creating equiaxed load). Once molded (2)
It has no effect on the shell (S3) (in other words, the epidermal tissue) generated within the body.

Therefore, some kind of countermeasure is required to make the skin structure finer, and in the first invention illustrated in FIG. 3, the molten steel in the mold (2) is subjected to electromagnetic stirring.

In the second invention illustrated in FIG. 4, the casting roll (4) to which Ill5-F is added is pinched. Roll (3) [&& Co ('J'E'X) to refine the skin structure of the slab (111 composition).

[Table 6] below shows figures 2 (conventional method) and 31 (+'
31 invention), υ5 experiment fi' according to Figure 4 (second invention)
This is a summary of the results, and shows the experimental conditions for [Table 1], [Table 1], and -23t.

It has Gaussian magnetic flux density.

Specifically, experiment ji1. -1a according to the conventional method of 2
For both types (a) and (b), there were many wrinkles on the surface and inner surface of the product (pipe), and cross-cutting occurred in some products.

Experimental boiling 3 is the method of the present invention, but the degree of superheating (ΔT) is 25
℃, and when looking at the iRMI of the product, 1 liter of the slab has not completely equiaxed crystallized, and the inner surface of the pipe is also considered. This is due to the electromagnetic stirring outside the mold (2). This is because there is not enough melon.This means that the degree of superheating (
This is supported by comparison with Experiment 1≦4, in which ΔT) was as low as 8°C, and by comparison with Experiment 5, in which (WMS2) was added.

According to experiment la4~B, either (a) or (b) wiU
As for Il, equiaxed weight is formed inside, the structure of the skin part is made into fine 2111, and the surface quality of the pipe is also good.

In experiment 167.8, the electromagnetic stirring in the mold (2) was not performed, and the piece was forged after passing through the pinch rolls (3); light forging was performed using 60-rule (4). .

In this case, the internal structure of the slab is equalized by electromagnetic stirring.
The width is 5, and the epidermal tissue is 5 to 1 from the surface layer.
It has been recrystallized by forging to a depth of zero.

Here, the above light forging recrystallizes only the near surface layer:
i! The rolling reduction ratio can be found from the graph in FIG. In other words, since the surface of the product (pipe) from the surface to 5 or more depths (if the crystals die, the surface of the product (pipe) will be in good condition), from the viewpoint of surface quality, the reduction ratio should be 1.1 or more. It is desirable that the rolling ratio is up to 3.0 (= J), so that wrinkles will not occur inside the product. ．．
Compared to 0 or more, this is an extremely small rolling ratio, and no special rolling device is required.

It goes without saying that it is within the scope of the present invention to implement claim [1] and claim (2) at the same time as f+Ti1M of the present invention.

The M month used in the above experiment was a 5-round billet, but
Of course, the present invention is also applicable to square billets. In the present invention, the austenitic stainless steel 11 refers to all types of stainless steel fl14 of artificial 81304 or higher, and the high alloy
2M0), A engineering S engineering 31 [1' (25or-2ONi
) Alloy 800 (62N1-20Or-Q, 5Ag-
[], 5T1).

Alloy 600 (75N1-150r) 2nd and 1st steer V,X.

``'8 (which becomes α, r2 phase at room temperature).

As explained above, in the present invention, in order to refine the internal structure of the slab, electromagnetic stirring is applied to the unsolidified 1i'il molten χ(ll) during continuous casting to generate equiaxed crystals in the internal structure. Zeshiri,
Regarding the refinement of the epidermal tissue, ■Inside the mold 7) r
Either gi magnetic 13 shi stirring or ■ light pressure of the epidermal tissue is adopted.
, l has the advantage that it can be abbreviated to I+ri, and in the case of (2), it is convenient to bring the same effect to nine stations where it is difficult to install an electromagnetic stirring device δ in the mold, and the above-mentioned first invention, In both the second invention, the structure of the stainless copper billet can be made into B'r'f, 1llll inside and outside during continuous casting, and the quality of the product manufactured in the subsequent process can be improved. This is a significant invention in that it is possible to reduce costs by 1+115 times, since there is no need to go through the rolling process that requires a large amount of steel.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between rolling reduction ratio and recrystallization area, Figure 2 is an example of the conventional continuous casting method, Figure 6 is an example of the first invention, and Figure 4 is the second invention. Example diagram. (2) is a mold, (concave Ms1), (x+Ms2), (
mMs3) is a rotating magnetic stirrer, and (4) is a forged roll. Patent Applicant: Sumitomo Metal Industries, Ltd. Figure 1 B, Yuzu 11 Shape - Intimidation Lower Ratio ¥i2N Figure 3 Figure 4! −

Claims (2)

[Claims] (1) When manufacturing stainless steel #ll11 billets using the horizontal continuous casting method, electromagnetic stirring is applied to the molten steel in the mold, and one or more stages of electromagnetic stirring are applied to the unsolidified portion of the billet that has passed through the mold. A method for manufacturing a stainless steel billet, characterized by subjecting it to. (2) When producing a stainless steel billet by the horizontal continuous casting method, the unsolidified portion of the billet that has passed through the mold is subjected to one or more stages of electromagnetic stirring, and immediately thereafter, the rolling reduction ratio is 1.1 to 3. A method for producing a stainless steel billet, characterized by subjecting it to zero hot working.