JPH02236254A - Continuously cast steel sheet for porcelain enameling having excellent fishscale resistance and weldability and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the steel sheet for porcelain enameling having excellent fishscale resistance and weldability by incorporating Zr into a steel contg. specified ratios of C, Si, Mn, S, Al, P, Zr, Cu and O by electromagnetic stirring and subjecting it to continuous casting at specified casting speed. CONSTITUTION:At the time of subjecting a steel contg., by weight, <=0.010% C, <=0.80% Si, 0.20 to 0.80% Mn, 0.005 to 0.04% S, <=0.010% Al, <=0.08% P, 0.005 to 0.10% Zr, 0.05 to 0.05% Cu, 0.0020 to 0.08% O and the balance iron with inevitable impurities to continuous casting, while executing electromagnetic stirring, Zr is incorporated into the steel and continuous casting is executed at >0.4m/min casting speed. Then, the continuously cast slab is directly, or after heated to 1050 to 1350 deg.C, subjected to hot rolling, cold rolling and annealing in succession. In this way, the steel sheet having excellent porcelain enameling properties and free from the surface flaws can stably be obtd.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a continuously cast enameled steel plate with excellent nail-skipping resistance and weldability, and a method for producing the same, characterized in that it is obtained by applying a continuous casting method. That is.

(Prior Art) A requirement for a steel plate for enameling is to have nail-skipping resistance. Nail skipping is a phenomenon in which hydrogen dissolved in the steel plate during enamel firing reduces its solubility due to the temperature drop after firing, collects at the interface between the steel plate and the enamel, and the resulting pressure destroys the enamel layer. Nail skipping is a major defect in enamel products, so its occurrence must be prevented.

Furthermore, since steel plates for enameling are often deep drawn and then welded, they need to have weldability as well as deep drawability.

Furthermore, if surface defects due to bottleholes, blowholes, etc. occur on steel sheets for enameling, pickling residue will accumulate during pickling during enameling pretreatment, and this will also cause bubble defects during enameling firing. is required to be small.

Conventionally, steel plates for enameling have been manufactured by the ingot making method because it is easy to form inclusions that are effective in preventing nail skipping. That is, it has been manufactured by forming capped steel, killed steel, or rimmed steel into ingots, blooming, hot rolling, and cold rolling, followed by decarburization annealing to reduce carbon and nitrogen to several tens of ppm or less.

According to such a method, it is possible to obtain a steel plate having enameling properties, but since the steel slab is manufactured by the ingot-making method, a decrease in yield cannot be denied. There are also other problems, such as the number of days required for production.

In recent years, the continuous casting method has developed significantly, and it has become possible to obtain high-quality rope at low cost. Continuous casting has also been attempted for enameling steel, and it has become possible to apply the continuous casting method to killed enameling steel, in which molten steel is vacuum degassed to lower the C content and Ti, REM, etc. are added. However, the surface defects cannot be overcome, and the application is limited to steel plates for double enameling.

Therefore, studies have been made to manufacture steel plates for enameling by applying a continuous casting method to camped steel or rimmed steel instead of the one-block ingot method. For example, in JP-A-54-97520, molten steel is vacuum degassed to reduce the C content to 0.02% or less, and then the oxygen content is reduced to 100%.
- 400 ppm, and a technique of continuous casting is disclosed. Furthermore, in Japanese Patent Application Laid-open No. 59190331, it is stated that C after vacuum degassing treatment of molten steel is less than aopptrl, C+N
is less than 30 ppm. Oxygen content is 300-700ppm
Disclosed is a method for continuously casting steel, the balance of which is iron and unavoidable impurities.

These methods have certain effects, but the composition of the inclusions formed is F, which is less effective in improving hydrogen storage capacity.
Since it is mainly composed of eO, there is a problem that the nail-skipping resistance is not sufficient.

(Problems to be Solved by the Invention) The present invention provides a steel plate for enameling made by continuous casting, which has an excellent nail-skipping resistance equal to or better than that of materials produced by the conventional single-blocking method, and which also has good weldability after processing and forming. The purpose is to provide a manufacturing method thereof.

Further, the present invention aims to provide a continuous casting steel plate for enameling, which is free from surface defects such as sliver scratches, bottle holes, blowholes, etc., and a method for manufacturing the same.

(Means for Solving the Problem) As a result of the inventors' research to achieve the above object,
When continuously casting molten steel with extremely low C, high oxygen content, and a small amount of M, Zr is added while electromagnetic stirring is applied, and continuous casting is performed by controlling the casting speed, resulting in excellent nail skipping resistance. It was discovered that a steel plate for enameling with good weldability and no surface defects could be obtained.

The gist of the present invention is that C:o. o
t o% or less, Si: 0.80% or less, Mn: 0.20
~0.80%, S; 0.005~0.04%, A
J: 0.010% or less, p: o. os% or less. Zr:
0.0 0 5 ~ 0.10%, Cu: 0.0
1-0.0 5%, O; 0.020-o. o so o
% or as necessary V: 0.010 to 0.
0 6 0%. Nb. ; o. OO 4~0.
0.040% of one or both of the above, with the remainder consisting of iron and unavoidable impurities.The continuous casting enameling steel plate has excellent claw resistance and weldability. Another aspect of the present invention is that when continuously casting the steel having the above-mentioned composition, Zr is contained while applying electromagnetic stirring, and the continuous casting is carried out at a casting speed of more than 0.4 m/min. For continuous casting enamel with excellent nail-skipping resistance and weldability, characterized in that the piece is hot-rolled, cold-rolled, and annealed immediately or heated to 1050 to 1350'C. It is in the manufacturing method of steel plates.

The present invention will be explained in detail below.

The reasons for limiting the constituent elements in the present invention are as follows.

The upper limit of C is set to 0.010% in order to obtain a steel plate for enameling which has good drawability and is free from enameling defects such as firing distortion and bubbles by applying a continuous casting method.

Moreover, if this content exceeds 0.010%, C and O react with each other in the continuous casting process, and CO gas is likely to be generated, resulting in surface defects such as bottle holes and blowholes in the slab.

Although it is better to have a small amount of St in order to improve workability, the upper limit of St content is set to 0.80% in order to ensure strength as a steel plate for enameling.

Mn is contained in an amount of 0.20% or more in order to form inclusions such as MnO and MnS to improve nail chipping resistance and to prevent hot embrittlement caused by S. On the other hand, if its content increases, processability deteriorates, so the upper limit is set to 0.80%.

S is O.S. in order to form MnS having hydrogen storage ability.
OO 5% or more. On the other hand, S is harmful to weldability, and if its content increases, it deteriorates workability, so it should be kept at 0.04% or less.

M is contained at an upper limit of 0.010% in order to adjust the amount of oxygen in the steel during melting and to ensure the nail-skipping resistance of the steel plate made from the continuous casting slab.

P is useful for ensuring strength, but it deteriorates workability and weldability, so it is limited to 0.08% or less.

Zr forms inclusions with a large specific gravity, and this effect can be utilized particularly when manufacturing steel sheets for enameling by applying the continuous casting method. O O
5% or more is required. Zr also contributes to improving weldability. However, if its content increases, surface defects will occur, so it should be kept at 0.10% or less.

When molten steel is cast from a tundish into a continuous casting mold, Zr is contained in the molten steel via a wire while applying electromagnetic stirring. Further, continuous casting is performed at a casting speed of over 0.4 m/min. If the pouring speed is lower than this, Zr will not enter the steel uniformly and will exist on the surface layer or unevenly in the widthwise direction of the slab, which will impair the effectiveness of the nail-skipping resistance and cause sliver scratches. It causes

Cu is contained in an amount of 0.01% or more to improve enamel adhesion. On the other hand, if the content increases, the pickling properties during enameling pretreatment will deteriorate, so the content should be 0.05% or less.

O is a necessary component for forming MnO and ZrO-based inclusions that impart hydrogen storage ability to continuous casting enameled steel sheets, and is contained in an amount of 0.020% or more to achieve this effect. However, if the content is too large, bubbles will be generated during solidification of molten steel, causing surface defects and deteriorating workability. 080% or less.

Furthermore, V, Nb
Contains at least one of the following.

■ has the effect of increasing workability and anti-aging effect, and 0.010% or more is required to achieve this effect.
On the other hand, if the content is too high, the effect will be saturated and the cost will increase, so 0. 060% or less.

Like ■, Nb has the effect of improving workability and preventing aging.
To obtain this effect, O. O O 4% or more is required. On the other hand, if the content is too high, the effect will be saturated and the cost will increase, so 0. 040% or less.

The method for manufacturing the continuous casting enameled steel plate of the present invention is as follows.

Steel having the composition range of the present invention as defined above is continuously cast into slabs, and then hot rolled as is, or
It is heated to 050-1350°C and hot rolled.

Reheating the above 1050 to ensure hot rollability.
The temperature is ~1350°C.

Hot rolling does not need to be specified, but for example, finishing temperature 78
It is carried out at a winding temperature of 450 to 800''C above 0°C.

Then, it is descaled and cold rolled. In this case, it is desirable that the rolling reduction ratio be 50% or more.

The annealing after cold rolling is carried out at a known temperature, for example, 650'C or higher, in order to impart workability as a steel plate for enameling.

Next, examples will be shown.

(Example) Molten steel having the composition shown in Table 1 was melted, and continuous casting was performed by changing the pouring speed and applying electromagnetic stirring to obtain a slab. Zr
was added to the molten steel being poured into the mold via a wire while applying electromagnetic stirring. In addition, some comparative materials were continuously cast without electromagnetic stirring. Then either directly or the slab was heated.

The conditions are shown in the same table. Thereafter, hot rolling was performed at a finishing temperature of 860-880°C and a winding temperature of 620-650°C, followed by descaling, cold rolling at a reduction rate of 75% to a plate thickness of 0.80 mm, and annealing at 750°C. Continuous annealing was performed for 3 minutes. The obtained steel plates were examined for nail-skipping resistance, mechanical properties, and presence or absence of surface defects, and the results are shown in the same table. In addition, the nail-skipping resistance is tested by measuring the hydrogen permeation time T, and when this time T is 10 minutes or more, nail-skipping does not occur and the nail-skipping resistance is judged to be good. show.

As can be seen from the table, according to the present invention, a steel plate for enameling which has excellent nail-skipping resistance and is free from surface defects can be obtained.

In addition, in order to investigate whether the added Zr was uniformly dissolved in the slab, we added lO to 10% in the width direction of the slab.
Sampling was performed from the cast slab with a drill at a pitch of 0 mm, and Zr
was analyzed. The results are shown in FIG.

In the slab according to the present invention (code 1), Zr is uniformly distributed, whereas in the comparative material without electromagnetic stirring (code 11), Zr is uniformly distributed.
), the side where Zr is not added to the wire has less Zr, resulting in a non-uniform distribution. Casting speed is 0.3 even with electromagnetic stirring
The comparison material (code 10) with m/min has less Zr on both edge sides of the slab and within 30 mm of the surface layer. For this reason, it is thought that the steel sheet according to the present invention has excellent enameling properties, but the comparative material had a low pass rate for enameling properties (hydrogen permeation time T value).

(Effects of the Invention) As described above, according to the present invention, a steel plate for enameling that does not cause nail skipping, has excellent enameling properties, has no surface defects, and has good weldability can be made stable by applying the continuous casting method. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the distribution of Zr% in the slab in the example of the present invention in the width direction. Fig. 1 ■ The color of the horse's head (mm)

Claims (4)

[Claims] (1) C: 0.010% or less, Si: 0.80% or less, Mn: 0.20 to 0.80%, S: 0.005 to 0.04%, Al: 0.010% in weight% Below, P: 0.08% or less, Zr: 0.005-0.10%, Cu: 0.01-0.05%, O: 0.020-0.080%, and the balance is iron and unavoidable. A continuous casting enameling steel plate with excellent nail-skipping resistance and weldability, which is characterized by containing impurities. (2) C: 0.010% or less, Si: 0.80% or less, Mn: 0.20 to 0.80%, S: 0.005 to 0.04%, Al: 0.010% in weight% Below, P: 0.08% or less, Zr: 0.005 to 0.10%, Cu: 0.01 to 0.05%, O: 0.020 to 0.080%, and further, V: 0 .010~0.060%, Nb: 0.004~0.040%, and the remainder is iron and unavoidable impurities. Excellent continuous casting enameled steel plate. (3) C: 0.010% or less, Si: 0.80% or less, Mn: 0.20 to 0.80%, S: 0.005 to 0.04%, Al: 0.010% in weight% Below, P: 0.08% or less, Zr: 0.005-0.10%, Cu: 0.01-0.05%, O: 0.020-0.080%, and the balance is iron and unavoidable. When continuously casting steel containing impurities, Zr is added while applying electromagnetic stirring, continuous casting is performed at a casting speed of over 0.4 m/min, and the continuously cast slab is immediately or heated to 1050 to 1350 ° C. A method for producing a continuously cast enameled steel plate having excellent nail skipping resistance and weldability, which comprises heating, hot rolling, cold rolling, and annealing. (4) C: 0.010% or less, Si: 0.80% or less, Mn: 0.20 to 0.80%, S: 0.005 to 0.04%, Al: 0.010% in weight% Below, P: 0.08% or less, Zr: 0.005 to 0.10%, Cu: 0.01 to 0.05%, O: 0.020 to 0.080%, and further, V: 0 When continuously casting steel containing one or two of Nb: 0.010 to 0.060% and Nb: 0.004 to 0.040%, with the remainder consisting of iron and unavoidable impurities, Zr is added while applying electromagnetic stirring. Continuous casting is carried out at a casting speed of over 0.4 m/min, and the continuously cast slab is immediately or
A method for producing a continuously cast enameled steel plate with excellent nail-skipping resistance and weldability, which comprises heating to 1350°C, hot rolling, cold rolling, and annealing.