JPS5934765B2 - Method for manufacturing enameled steel plates from continuously cast slabs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a steel plate for enameling, which has significantly better resistance to load drop than continuous cast slabs, is non-aging, and has excellent deep drawability.

Enamel steel sheets are required to be free from surface defects caused by hydrogen gas, that is, cracks, and to have good glaze adhesion in a short pretreatment time.

Further, as is well known, processability such as deep drawability is also required for its use.

Furthermore, in the case of enamel, it is also required that the enamel be free from surface defects caused by carbon-based gases, such as bubbles and blisters, and that it be free from firing distortion.

For such applications, titanium (hereinafter referred to as Ti) is added to the steel to fix carbon and nitrogen in the steel, thereby making the steel non-aging, and the effect of the Ti in the steel improves the load resistance. A method for producing steel plates for enamel is known.

In this case, if the amount of Ti added necessary to fix carbon increases, it will harden the steel and increase manufacturing costs. Therefore, carbon and oxygen in the steel are reduced by vacuum degassing in advance, and Deep drawability has been significantly improved by reducing the ratio of titanium to carbon in the steel and by setting the ratio of titanium to carbon to Ti/C>10.

However, steel sheets manufactured by this method have good workability, but have the disadvantage that their load resistance, which is extremely important as anti-rolling properties, is not always sufficient. It has been considered difficult to achieve good jumpability.

Furthermore, if Ti is contained in the surface layer, surface flaws may occur due to the Ti compound, and in such a case, the yield of the product will be reduced.

On the other hand, the present inventors have found that by adding one or more rare earth elements to steel at the same time as Ti, it is possible to obtain a steel sheet with significantly improved load resistance and good workability. It has been discovered that the problem of surface flaws caused by Ti compounds can be solved by adding Ti to a portion of the core of the steel ingot, and has already been described in detail in Japanese Patent Application No. 48-27169.

However, these methods are only possible in the case of the steel ingot method, and in the case of the continuous casting method, its application is desired due to the low manufacturing cost and uniformity of slab quality. , there were the following problems.

1) Since there is no Ti core addition method comparable to the steel ingot method, surface defects occur due to Ti compounds.

2) If added to a ladle or tundish containing rare earth elements, the immersion nozzle during casting will be blocked.

3) Slabs are subject to thermal stress and mechanical stress during casting, so surface cracks are more likely to occur than steel ingots; however, when rare earth elements are added, the cracking incidence increases due to the above elements contained in the main part of the slab length. increases rapidly.

The inventors of the present invention have solved the above-mentioned problems, and have proposed a method for manufacturing enameled steel plates that have significantly superior load resistance, are non-aging, and have excellent workability and surface properties at a lower cost than continuous cast slabs. No. 49-84127, the gist of which is that molten steel has a manganese content of 0.40% (wt%).
After the carbon content is reduced to 0.01% or less by vacuum degassing treatment, wire-shaped titanium and rare earth elements alone or alloys are poured into the molten steel at a depth of at least 100 m 1 JJ below the molten metal surface. It is coated with a weakly reactive coating metal of a thickness selected in advance so that it melts on contact with the molten steel, and is added to the molten steel in the continuous casting mold at a feed line speed commensurate with the casting speed so that it is contained only inside the slab core. After hot rolling the obtained slab by casting a slab containing 0.01 to 0.3% titanium and 0.01 to 0.15% of one or more rare earth elements. , a method for producing an enameled steel plate from a continuously cast slab, which is characterized by cold rolling and then annealing.

The present inventors are limited to titanium, ξob, and zirconium.
The prior application (Japanese Patent Application No. 49-8
We have discovered a method for manufacturing a steel plate for enamel having the same enamel properties as No. 4127).

In the present invention, molten steel is tapped with a manganese content of 0.40% (abbreviated below weight %) 9 or less, and after vacuum degassing treatment to reduce the carbon content to 0.01SJJ, wire-shaped niobium,
At least one kind of zirconium and a rare earth element or an alloy are added at least 100 iiJJ below the hot water surface.
The molten steel is coated with a weakly reactive coating metal of a thickness selected in advance so that it will contact and melt with the molten steel at the depth above, and while being added to the molten steel in the continuous casting mold, a small amount of niobium and zirconium (
A slab containing 0.02 to 0.6% of the same type of metal and 0.01 to 0.15% of a rare earth element or alloy is cast, and the resulting slab is hot-rolled and then cooled. The gist of this invention is a method for producing an enameled steel plate from a continuously cast slab, which is characterized by rolling and then annealing.

The present invention will now be described in detail.

When manufacturing slabs according to the present invention, the amount of manganese is 0.
Steel is tapped so that the steel is reduced by 40%.

The lower the level of manganese (preferably below 0.25'll)
The upper limit is set at 0.40% because it causes less firing distortion during enamel firing and is also preferable from the viewpoint of material quality.

Next, this molten steel is subjected to vacuum degassing treatment to reduce the carbon content to 0.0.
Reduce it to below 1%.

The reason why the carbon content is limited to 0.011 or less is to prevent surface defects such as bubbles and blisters caused by carbon-based gases, and to prevent firing distortion.

Oxygen is also reduced by degassing, but if necessary, it is also possible to further deoxidize with aluminum, for example.

When continuously casting the solvent obtained in this way, as shown in Fig. 1, Nb or Zr or both Nb and Zr and rare earth elements or alloys (referred to as 9-REM) are cast.
are made into a wire shape in advance, and these are coated by wrapping them with a thin plate-shaped weakly reactive coating metal 2 of a predetermined thickness as described later, respectively, to form a metal coating Nb or Zr or N b p Z complex of r, metal coating R
EM (generally referred to as JN additive materials), and these are added to the molten steel in the mold at the same time and at a feed line speed commensurate with the mold size and casting speed, and 1 of the NbZr in the steel plate is
The total content of one or more rare earth elements (simply referred to as rare earth elements) is such that the total content of more than one species is 0.02 to 0.60% (preferably 0.05 to 0.20%). The amount of gold is 0.01 to 0.15% (preferably 0.02 to 0.15%)
0.12%).

The content of N b p Z r in the steel sheet was set to 0.
02-0.60% (preferably 0.05-0.20%)
The reason for this limitation is that if the content of one or more of Nbp Z and r exceeds 0.30%, the steel will harden, resulting in lower press formability and higher manufacturing costs, which is not preferable. This is because if the amount is less than %, no effect of improving load resistance and deep drawability can be expected.

In addition, the REM content is 0.01 to 0.15% (preferably 0.
．． The reason for limiting it to 0.02% to 0.12% is that the rare earth element content is 0.
．． This is because if it exceeds 15%, the manufacturing cost will be high, which is undesirable, while if it is less than 101%, no effect of improving the load-jumping resistance can be expected.

In this way, the present inventor has discovered that REM on one type of Nb and Zr
It has been discovered that by adding these together, a continuously cast slab can be obtained that can yield a cold rolled steel sheet with significantly superior load-jump resistance compared to the case where either of these is added alone.

In particular, the present invention is characterized in that Nb and/or Zr and REM are formed into a wire and coated with a weakly reactive coating metal of a thickness selected in advance so as to be melted in contact with the molten steel at least 100 mm below the molten metal surface and at a depth of molten steel above the IJ. However, Nb and/or Zr are added to the molten steel in the continuous casting mold only inside the slab core.
and REM.

9. The slab manufactured as above is hot-rolled, pickled, cold-rolled, electrically cleaned, annealed, and further temper-rolled if necessary.

Hot rolling may be carried out under the conditions normally used, but the desired effect can be obtained even if the hot rolling winding temperature is in the range of 450 to 800°C (preferably 550 to 730°C). It will be done.

If the hot rolling winding temperature exceeds 800°C, it becomes difficult to adjust the temperature, and if it is less than 450°C, the effect of improving the snapping property decreases.

A cold rolling ratio of 30%9 or above is desirable in order to obtain a preferable material quality, but if it exceeds 90%, the required thickness of the hot-rolled sheet becomes extremely thick, which is not practical.

Further, if it is less than 30%, desired deep drawability cannot be obtained.

Annealing may be performed by box annealing, continuous annealing, or any other annealing method.

The annealing temperature is 6500°C and 1000°C, preferably 650°C in the case of box annealing and open coil annealing.
In the case of continuous annealing, the temperature is 700°C and 980°C.

If the annealing temperature is below the lower limit of 9, the softening of the steel due to recrystallization annealing is insufficient and desired workability cannot be obtained.

In the case of cylindrical steel, the amount of metamorphosis to austenite becomes too large, making it impossible to obtain good deep drawability.

It is also unfavorable from the economical point of view of the furnace.

As mentioned above, according to the present invention, Nb and/or Zr
, rare earth elements can be stably added only to the inside of the slab core, which solves problems such as surface flaws caused by Nb or Zr compounds and surface cracking of the slab due to the addition of rare earth elements, and has extremely high load-skipping resistance. It is also possible to produce a steel plate for enamel that is non-aging and has excellent deep drawability from continuously cast slabs.

FIG. 2 is a diagram showing →1 of the wire-shaped metal coating additive supply device, in which 11 is a drum, 12 is a wire-shaped metal coating additive, 13 is a guide roller, 14 is a guide, 1
5 is a mold, 16 is an immersion nozzle, 17 is powder, 18 is molten steel, and 19 is a speed meter.

The additive material 12 is drawn out from the drum 11 and fed to the guide roller 13 while controlling the feeding linear velocity using the speed meter 19.
, is added to the molten steel in the mold 15 through the guide 14.

9 below, the present invention will be explained based on Examples.

Carbon ladle analysis value before vacuum degassing treatment is 0.020,
Converter molten steel containing 0.19% Mn was vacuum degassed and further deoxidized with aluminum.

The molten steel thus obtained was poured into a mold with a cross section of 210 x 1480 mm2, and continuous casting was performed using a two-strand bending mold facility.

The drawing speed is 0.7 m/mil. At this time, the casting period was divided into 3 categories for 1 strand and 2 categories for 2 strand, and a total of 5 types of steel were cast.

Steel A is Nb and REM, steel B is Zr and REM, steel C is N
b, Zr, and REM are added in combination.

A REM wire with a diameter of 4.021Xm was wrapped with a thin steel plate of 0.31mm thickness, and an iron-coated REM wire with a diameter of 4.5mm was fed at a feeding rate of 10.0 m/min.
Or Zr or both wire Q, l mm thick thin steel plate (loose wire feeding speed 12.7771/
molten steel in the mold at the same time.

Mitsushmetal was used as the rare earth element.

The thickness of the thin steel plate was determined so that the melting position depth of REM and Nb or Zr, or both, would be 250 degrees below the hot water level.

Steel, E, and F are comparative steels, and steel E and N contain rare earth elements.
For steel F, Zr was added individually by the above method.

A cross-sectional sample was taken from the slab thus obtained and tota
An analytical investigation of the cross-sectional distribution of rare earth elements and Nb or Zr or both revealed that the total rare earth elements and Nb or Zr
Or, as shown in Figure 3, both are on average 8mmJ below the skin.
: It is hardly contained in the surface layer a in J, and is uniformly contained in a part of the core, making it a core-added steel.

When hot-rolling the present invention steels A, B, and C and the comparative steels E and F, the rolling plate thickness was 5.5 at a hot rolling winding temperature of 590°C.
After setting it to mm, the plate thickness is 2. Cold rolled to 700°
C12 hour box annealing and 1st pass temper rolling were performed.

Table 1 shows the additives used and the chemical analysis values of the finished plates of the invention steel and comparative steel, and Table 2 shows the mechanical test values and the occurrence rate of snapping.

As can be seen from Table 2, the steels A, B, and C of the present invention have excellent deep drawability and exhibit no aging properties at all.

Furthermore, these steel plates were enamel-fired once using a glaze that is likely to cause nail skipping, and the incidence of nail skipping was investigated.

As a result, it was confirmed that the steels A, B, and C of the present invention exhibited significantly superior load resistance compared to steels containing only a rare earth element, steels containing only Nb, and steel F containing only Zr.

This effect is produced synergistically by adding Nb or Zr or both and rare earth elements to the steel, and after various studies, it was found that the presence of Nb or Zr and other types of inclusions at the same time is sufficient. It was found that the same effect could not be obtained.

In addition, the steels A, B, and C of the present invention are foamy after being enamel fired once.
There were no defects such as blisters, and the adhesion of the enamel was extremely good.

Moreover, the surface was almost as beautiful as rimmed steel, and there were no surface flaws.

Furthermore, the steel of the present invention exhibited excellent load resistance and other enamel properties even when used in double-layered enamels.

In addition, the steel of the present invention shows good adhesion when used for hot-dipping, electrolytic galvanizing, tin plating, copper plating, and aluminium plating in addition to steel plates for enamel. The benefits are also great.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a wire-shaped metal coating additive, and FIG. 2 is a diagram showing an example of a feeding device for the wire-shaped metal coating additive. FIG. 3 is a diagram showing the distribution of Nb or Zr and REM in the cross section of the slab. 1...Wire-like Nb or Zr or wire-like REM
, 2... Weakly reactive coating fittings, 11... Drum 12
...Wire-shaped metal coating additive material, 13...Guide roller, 14...Guide, 15...Mold, 16...
・Immersion nozzle, 17...powder, 18...molten steel,
19...Speedometer.

Claims (1)

[Claims] 1. Molten steel is tapped with a manganese content of 0.40% or less (abbreviated below), and after being reduced to a carbon content of 0.01% or less by vacuum degassing treatment, a wire-like niobium and zirconium-poor (both type 1) The single element or alloy of the above and rare earth elements is coated with a weakly reactive coating metal of a thickness selected in advance so as to be melted in contact with the molten steel at a depth of at least 100 mm or more below the molten metal surface, and then placed in a continuous casting mold. A slab containing 0.02 to 0.6% of at least one of niobium and zirconium and 0.01 to 0.15% of a rare earth element or alloy is cast and obtained by adding it to molten steel. A method for producing an enameled steel plate from a continuously cast slab, characterized by hot rolling the cast slab, followed by cold rolling, and then annealing.