JP2857762B2 - Manufacturing method of continuous cast enameled steel sheet with excellent nail skip resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a continuously cast enameled steel sheet having excellent nail skip resistance.

(Prior Art) The requirement of the enameled steel sheet is that it has nail jump resistance. Nail skipping is a phenomenon in which hydrogen dissolved in a steel sheet during firing of an enamel reduces its solubility due to a decrease in temperature after firing, gathers at the interface between the steel sheet and the enamel, and destroys the enamel layer at that pressure. Since this nail jump is a major defect of the enamel product, its occurrence must be prevented.

Also, if surface defects due to pinholes, blowholes, etc. occur in the enameled steel sheet, pickling residues accumulate during pickling in the enamel pretreatment, which also causes foam defects during baking of the enamel. It is required that no defects occur.

Conventionally, the production of an enameled steel sheet has been carried out by the ingot-bulking method, since it is easy to form inclusions effective for preventing nail jump. That is, it has been manufactured by ingoting capped steel, killed steel or rimmed steel, performing debulking, hot rolling, cold rolling and then decarburizing annealing to reduce carbon and nitrogen to several tens ppm or less.

According to such a method, a steel sheet having good enamel characteristics can be obtained, but a steel slab is manufactured by the ingot-bulking method, so that the yield cannot be denied. There is also a problem that it takes a lot of production days.

In recent years, the continuous casting method has been remarkably developed, and inexpensive and high-quality steel has been obtained, and continuous casting of an enameled steel plate has been attempted. Thus, the continuous casting method became possible for the steel for killed enamels, which had a reduced C by vacuum degassing the molten steel and added Ti, REM, etc., but the surface defects could not be overcome and the enamel was applied twice. Applications are limited to steel plates for use.

Therefore, studies have been made to produce a steel sheet for enamel by applying a continuous casting method instead of the ingot-bulking method to capped steel or rimped steel. For example, JP 54
Japanese Patent No. 9-97520 discloses that molten steel is subjected to vacuum degassing to reduce C to 0.02.
% Or less, and a small amount of Al is added to reduce the oxygen content to 100 to 4%.
It is disclosed that continuous casting is performed while adjusting to 00 ppm.
JP-A-59-190331 discloses that after degassing molten steel, C is 30 ppm or less, C + N is 30 ppm or less, oxygen content is 300 to 700 ppm, and the balance is iron and unavoidable impurities. A method for continuously casting steel is disclosed.

According to these methods, there is a certain effect, but the enameled steel sheet made by continuous casting has less inclusions generated than that manufactured by the ingot-bulking method, and the carbon steel formed by decarburization annealing has a lower carbon content.
Poor nail skip resistance due to lack of voids.

As a method for reducing surface defects, Japanese Patent Application Laid-Open No.
No. 203646, in continuous casting, the C content is 1.5
%, And a method of casting at a drawing speed of 0.8 m / min or more using a powder of not more than% is proposed.

According to these methods, a certain effect will be exerted, but it is scattered that inclusions are formed on or near the surface layer of the slab from the solidification characteristics of molten steel in continuous casting, and it is further considered that surface defects are prevented. It is necessary to take measures.

(Problems to be Solved by the Invention) The present invention is for a continuously cast enamel having excellent nail skipping resistance equal to or better than that of a material obtained by a conventional ingot-bulking method and having no surface defects such as pinholes and blowholes. The purpose is to obtain a steel plate.

(Means for Solving the Problems) In the production of an enameled steel sheet to which continuous casting is applied, the present invention has been made as a result of experiments and examinations to obtain an enameled steel sheet having no surface defects in combination with the occurrence of claw jumps. The abstract is as follows: C: 0.10% or less, Mn: 0.80% or less, S: 0.04% or less, Al: 0.02%
0.10.10%, and if necessary, Cu: 0.01-0.05
% And / or Ti: 0.01 to 0.30%, with the balance consisting of continuous casting of molten steel consisting of iron and unavoidable impurities, hot rolling, cold rolling and annealing of the obtained slab. In the manufacturing method of steel sheets for steelmaking, one or two kinds of Zr or REM are added to the downflow of molten steel being cast into the mold, and the molten steel is continuously cast by electromagnetic stirring at a position of 1m or more and 10m or less from the meniscus. , Zr: 0.005-0.10%, REM:
After the continuous casting, the slab is directly or directly heated to a temperature of 1350 ° C. or less, hot-rolled, cold-rolled, and annealed. The present invention relates to a method for producing a continuous cast enameled steel sheet having excellent nail skipping resistance.

According to the present invention, Zr oxide-based inclusions having excellent hydrogen storage capacity and REM oxide-based inclusions are uniformly dispersed and formed inside the steel sheet, and these surface inclusions have no such inclusions, and pinholes are not present. An excellent enameled steel sheet free from surface defects such as scabs and the like can be obtained.

 Hereinafter, the present invention will be described in detail.

In the present invention, C: 0.10% or less, Mn: 0.80% or less, S: 0.04%
The following contains Al: 0.02 to 0.10%, and if necessary, Cu:
An enameled steel sheet containing 0.01 to 0.05% and / or Ti: 0.01 to 0.30% is continuously cast into cast pieces, which will be described first.

As shown in FIG. 1, molten steel is injected from a tundish 1 into a continuous casting mold 3 through an immersion nozzle 2. One or both of Zr and REM are added to the molten steel cast in the mold 3 by coating with the wire 4.

By the way, it is known that inclusion of Zr or REM in an enameled steel sheet improves nail skip resistance (for example, Japanese Patent Application Laid-Open No. 50-142419). Even when REM is added, the enameled steel sheet frequently has nail jumps and surface defects.

The present inventors have studied to solve this problem,
Zr, REM has a higher affinity for oxygen than Al and produces Zr oxide and REM oxide, but because of their large specific gravity, they are difficult to float, and are captured by the shell of the continuous cast slab at the generated position. It often causes surface defects and does not contribute to the improvement of nail jump resistance.To prevent this, Zr is applied to molten steel whose shell has a predetermined thickness during casting into a continuous casting mold.
It has been found that it is preferable to add REM and / or REM and agitate the molten steel, and to obtain an enameled steel sheet having excellent nail skipping resistance and no surface defects by applying a continuous casting method. The addition of Zr and REM to molten steel during casting into the continuous casting mold 3 is as follows.

FIG. 1 schematically shows the flow of molten steel injected into the continuous casting mold 3 from the immersion nozzle 2.
Generally flows into the continuous casting mold 3 separately in two directions. One is called upflow A and the other is downflow B. In the present invention, Zr and / or REM are added via the wire 4 at the downward flow B where the shell thickness of the continuous cast piece is large. When Zr or REM is added in the region of the upward flow A, the Zr oxide and REM oxide are trapped near the surface layer portion because the shell thickness is thin in this region, causing surface defects.

The Zr-based and REM-based oxides formed by the reaction of Zr and REM with oxygen and the like in the molten steel do not effectively act to improve nail jump resistance if added only in this manner. The Zr-based and REM-based oxides are not trapped in the shell by electromagnetic stirring, and are dispersed uniformly in the slab from the meniscus.
Agitating action is applied to molten steel at a position between 1 m and 10 m. The working position of the electromagnetic stirring device 5 is set at 1 m from the meniscus as described above.
The above is to prevent the generated shell from being redissolved and thinned by electromagnetic stirring, eliminate surface defects, and make the Zr-based oxide and REM-based oxide exist in a uniformly dispersed state. This is for enhancing the nail jump resistance. On the other hand, if the distance from the meniscus is too large, the region where the Zr oxide or REM oxide is not uniformly distributed in the steel becomes large, causing the occurrence of nail jumps.

The amount of Zr and / or REM added is 0.005 to 0.10
% And REM are 0.01 to 0.15%. Zr forms an inclusion having a large specific gravity, and is an effective component for preventing the occurrence of jaw jumping of an enameled steel sheet by continuous casting.To achieve this effect, 0.005%
% Is required. On the other hand, when the content is increased, surface defects occur and workability is impaired. REM has the same effect as Zr, and is added in an amount of 0.01% or more in order to enhance nail skip resistance. On the other hand, if the content increases, surface defects occur, so the content is set to 0.15% or less.

 Next, the reasons for limiting the other components will be described.

C has good workability and is 0.10% to obtain an enameled steel sheet by continuous casting without enamel defects such as firing strain and bubbles.
It is necessary to:

Mn forms inclusions such as MnO and MnS to enhance nail jump resistance,
In addition, although S has an effect of preventing hot brittleness, on the other hand, if its content increases, workability deteriorates, so the content is made 0.80% or less.

S forms MnS having a hydrogen storage ability and has an effect of enhancing nail jump resistance. However, when the content thereof is large, workability and weldability are deteriorated, so that S is set to 0.04% or less.

Al is a component necessary for deoxidizing molten steel and obtaining workability, and therefore, is contained in an amount of 0.02% or more. On the other hand, if the content increases, the nail skip resistance deteriorates, so the content is set to 0.10% or less.

In addition, if necessary to enhance the enamel adhesion, use Cu
0.01% or more. However, if the content increases, the pickling property during pretreatment deteriorates, so the content is set to 0.05% or less.

Further, if necessary, to improve the deep drawability,
0.01% or more. Although press workability is excellent due to the inclusion of Ti, an increase in the content increases the cost, so that the content is set to 0.30% or less.

In the above component ranges, the remainder is molten steel consisting of iron and unavoidable impurities, continuously cast as described above, after casting as a slab, hot rolling as it is, or reheating to a temperature of 1350 ℃ or less Hot rolling. The reheating is performed to enhance the hot rolling property. However, if the temperature is increased, burning and energy consumption are increased, so the upper limit of the reheating temperature is set to 1350 ° C.

Hot rolling need not be specified, but for example, a finishing temperature of 78
It is performed at a winding temperature of 450 to 800 ° C. or higher.

Next, it is descaled and cold-rolled. In this case, the rolling reduction is desirably 50% or more.

Annealing after cold rolling is performed at a known temperature, for example, 650 ° C. or higher in order to impart workability as an enameled steel sheet.

 Next, examples will be described.

(Example) Molten steel having the component composition shown in Table 1 was smelted, and Zr and REM were added to the molten steel being cast into a mold via a wire while being subjected to electromagnetic stirring to continuously cast. The electromagnetic stirring was performed by changing the action position from the meniscus as shown in the same table.

Then, directly or by heating the slab, hot rolling is performed at a finishing temperature of 870 to 900 ° C and a winding temperature of 620 to 650 ° C, descaling is performed, and cold rolling is performed at a rolling reduction of 75%.
Annealing was performed at 730 ° C. for 3 minutes, with 0.80 mm. About the obtained steel plate, nail jump resistance, mechanical properties,
The presence or absence of surface defects was investigated, and the results are shown in the same table. In addition,
The nail skipping resistance is tested by measuring the hydrogen permeation time T. If the time T is 10 minutes or more, the nail skipping does not occur and the nail skipping resistance is determined to be good.

As can be seen from the table, according to the present invention, an enameled steel sheet having excellent nail skip resistance and having no surface defects can be obtained.

(Effects of the Invention) As described above, according to the present invention, an enameled steel sheet having excellent nail skip resistance and having no surface defects can be stably manufactured by applying a continuous casting method.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of continuous casting in the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 38/00 301 C22C 38/00 301T 38/14 38/14 (72) Inventor Hiroshi Mochigi 1 Edamitsu, Yawatahigashi-ku, Kitakyushu-shi, Fukuoka Prefecture -1-1 Inside Nippon Steel Corporation Yawata Works (72) Inventor Haruyuki Kawanishi 1-1-1 Edamitsu, Yawata Higashi-ku, Kitakyushu-shi, Fukuoka Prefecture Inside Nippon Steel Corporation Yawata Works (56) References Special JP-A-64-31929 (JP, A) JP-A-53-7531 (JP, A) JP-A-51-13311 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11 / 00,11 / 10,11 / 12 C22C 38 / 00,38 / 14 C21D 8/02

Claims (4)

(57) [Claims] 1. A molten steel containing C: 0.10% or less, Mn: 0.80% or less, S: 0.04% or less, and Al: 0.02 to 0.10%, with the balance being iron and unavoidable impurities. In a method for producing an enameled steel sheet comprising hot rolling, cold rolling, and annealing a slab, one or two types of Zr or REM are added to the downward flow of molten steel being cast into a mold. , Molten steel is electromagnetically stirred and continuously cast at a position 1m or more and 10m or less from the meniscus, Zr: 0.005-0.10%, REM: 0.01-0.15%
A cast slab containing one or two of the following, which is subjected to hot rolling by direct casting or heating to a temperature of 1350 ° C. or less after continuous casting, cold rolling, and annealing. A method for producing continuous cast enameled steel sheets with excellent nail skip resistance. 2. A molten steel containing C: 0.10% or less, Mn: 0.80% or less, S: 0.04% or less, Al: 0.02 to 0.10%, Cu: 0.01 to 0.05%, with the balance being iron and unavoidable impurities. In a method for producing an enameled steel sheet comprising continuous casting, hot-rolling the obtained slab, cold-rolling and annealing, the descending flow of molten steel being cast into a mold is one of Zr or REM. Alternatively, with two types added, the molten steel is continuously cast at a position 1 m or more and 10 m or less from the meniscus by applying electromagnetic stirring, and Zr: 0.005 to 0.10%, R
EM: A slab containing one or two types of 0.01 to 0.15%, and after continuous casting, the slab is directly or directly heated to a temperature of 1350 ° C. or less, hot-rolled, cold-rolled, and annealed. A method for producing a continuously cast enameled steel sheet having excellent nail skipping resistance. 3. A molten steel containing C: 0.10% or less, Mn: 0.80% or less, S: 0.04% or less, Al: 0.02 to 0.10%, Ti: 0.01 to 0.30%, with the balance being iron and unavoidable impurities. In a method for producing an enameled steel sheet comprising continuous casting, hot-rolling the obtained slab, cold-rolling and annealing, the descending flow of molten steel being cast into a mold is one of Zr or REM. Alternatively, with two types added, the molten steel is continuously cast at a position 1 m or more and 10 m or less from the meniscus by applying electromagnetic stirring, and Zr: 0.005 to 0.10%, R
EM: A slab containing one or two types of 0.01 to 0.15%, and after continuous casting, the slab is directly or directly heated to a temperature of 1350 ° C. or less, hot-rolled, cold-rolled, and annealed. A method for producing a continuously cast enameled steel sheet having excellent nail skipping resistance. 4. C: 0.10% or less, Mn: 0.80% or less, S: 0.04% or less, Al: 0.02 to 0.10%, Cu: 0.01 to 0.05%, Ti: 0.01 to 0.30%
Containing, the remainder is continuously cast molten steel consisting of iron and unavoidable impurities, hot-rolling the obtained slab, cold-rolled,
In a method for producing an enameled steel sheet comprising annealing, while adding one or two kinds of Zr or REM to the descending flow of molten steel being cast into a mold, 1 m or more from the meniscus is added.
m and continuously cast molten steel under electromagnetic stirring at a position of Zr:
A slab containing one or two types of 0.005 to 0.10%, REM: 0.01 to 0.15%.
A method for producing a continuously cast enameled steel sheet having excellent nail skip resistance, wherein the steel sheet is heated to a temperature of not more than ℃ and hot-rolled, cold-rolled and annealed.