JPS62203646A - Manufacturing method of steel plate for enameled steel - Google Patents

Abstract

PURPOSE:To prevent development of blow hole in a slab and pin hole in an enamel by using CC powder having limited C content in molten steel having the specified compositions and executing continuous casting under setting of drawing speed at the satisfying range for the specified condition. CONSTITUTION:When the molten low carbon steel, having compositions, such as <=0.006wt% C, 0.2<=Mn<=0.5wt%, 0.005<=P<=0.025wt%, 0.005<=S<=0.025wt%, 0.020<=Cu<=0.040wt%, 1.0<=Cu%/P%<=4.0, 0.5<=P%/S%<=3.0, 200<=O<=500ppm, N<=40ppm, Al<=0.005wt%, is cast continuously, CC powder having C<=1.5wt% is used. Further, the drawing speed is set in the satisfying range for the conditional inequality, under condition of >=0.8m/min for it. Wherein, in the inequality, V is the drawing speed m/min under continuous casting operation and C is wt% C in the CC powder.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a steel plate for enameling, and more specifically, a steel plate that has less acidic loss, excellent adhesion to the enameled enamel, resistance to scratching, and formability. .

Furthermore, it has particularly excellent pinhole resistance. This article relates to the production of cold-rolled steel sheets for enamel by continuous casting.

(Conventional technology) In recent years, enamel steel sheets, which are made by baking a surface glaze (vitreous enamel) onto steel sheets to form a glassy coating, have been used in a wide range of applications, not only for household goods, but also for construction goods and various industrial goods. It has come to dominate.

In the production of such enamel steel plates, it was common practice to apply a two-coat method, in which the steel plate is coated with an undercoat with good adhesion, and then a topcoat is applied to give it a beautiful appearance.
Recently, pre-treatment (pickling) of raw steel plate to improve adhesion.
A glaze that combines adhesion and beauty is then baked directly onto the glaze. The popularization of the ``one-time method'' aimed at shortening the process is noticeable.

(Problem to be solved by the invention) However, even if the steel plate conventionally used for "two-time application" is applied as is for "one-day application", the adhesion between the material steel plate and the enamel will be poor. It happened.

In many cases, sufficient enamel products cannot be obtained.

Generally, rimmed steel made by the ingot method is used as a steel plate suitable for the one-day process.

From the perspective of a steel plate manufacturer, the steel ingot method has a high yield rate.

This includes the problem of large losses in terms of thermal energy. Also, from the perspective of the enamel maker.

This conventional rimmed steel has a problem in that there is a large risk of problems such as non-uniformity in the width and length of the steel plate in terms of resistance to slippage and adhesion, and problems such as blistering due to large inclusions.

Therefore, in Japanese Patent Application No. 19869/1986, the inventors of the present invention decided to select a specific composition of the steel sheet.
Even by continuous casting, we have developed a steel plate for enamel that exhibits sufficient enamel adhesion and porosity resistance under pretreatment (pickling) with a small amount of pickling loss, and also exhibits good formability without decarburization annealing. It has been disclosed that manufacturing is possible.

However, it has been found that even when using a steel plate having a specific composition as proposed above, defects due to microbubbles called pinholes may occur after forming a single layer of enamel, depending on the glazing conditions.

When the cause of this was investigated, it was confirmed that C in CCi9 Uda was picked up in the steel, and this combined with O in the enamel during enamel firing to generate pinholes. Furthermore, it was confirmed that slab surface flaws called blowhole flaws occurred on the slab surface depending on the casting conditions.

In this case as well, C in CCi4 Uda combines with 0 in the molten steel to form a blowhole.

Therefore, the purpose of the present invention is to reduce the amount of loss after pickling, improve adhesion, and
The present invention provides a method for producing a steel plate for enamel which has not only resistance to scratching and formability but also excellent pinhole resistance and blowhole resistance.

(Means for Solving the Problems) In order to solve the above problems, the present invention uses low carbon steel obtained by steel decarburization such as molten steel degassing treatment, and its components C, Cu, etc. By adjusting , P, S, etc. within a specific range, we can ensure good enamel properties (slip resistance, blistering resistance, adhesion) and good formability, and also reduce the C content in CC/# powder. l, 5 wt% or less, and the drawing speed V of continuous casting is 0.8 m 7 minutes or more and 1.33 (c - 0,9) + 0.8 m/min or more. This is intended to suppress C pickup and prevent blowhole defects in the slab and pinhole defects in the hollow layer.

That is, the present invention provides C≦0.006wt%, 0.
2≦Mn≦0.5wt%, 0.005≦P≦0.0
25 wt%, 0.005≦S≦0.025 wt%,
0.020≦Cu≦0.040 wt%.

1.0≦Cu(%)/P(%)≦4.0.0.5≦P(
%)/S(%)≦3.0.200≦0≦500ppm,
N≦40ppm.

When continuously casting molten steel containing a component of Al≦0.005 wt%, use C Ci# powder having C60.5 wt%, set the drawing speed to -0.8 m/min or more, and meet the following conditional formula % (Formula %) Here, v: Pulling speed during continuous hcVJ construction (m7 min)C
: It is characterized by setting the C content (wt%) in CC and Radar within a satisfying range.

In the present invention, the reasons for limiting each component in the steel as described above will be described.

(a) In the present invention, it is basically desirable that the C 0% content be as low as possible; however, if the content exceeds 0,006 wt%, casting becomes difficult and molding defects occur due to one aging.

(b) Mn The Mn component has the effect of preventing surface flaws caused by red heat embrittlement of steel during hot rolling, but if its content is less than 0.2 wt%, the effect is insufficient and Surface flaws occur, and on the other hand, if Q exceeds 5 wt%, moldability becomes poor due to circumferential hardening.

(c) P The P component has the effect of increasing the weight loss after pickling before enamel treatment, but if its content is less than 0.005 wt%, the weight loss after pickling is too small, leading to poor adhesion of the enamel. On the other hand, if it exceeds 0.025 wt%, too much pickling will occur and it will not be possible to obtain an even and finely uneven pickled surface, resulting in poor adhesion of the enamel, and there is a risk of poor formability of the steel plate due to hardening. be.

(d) S The S component has the effect of ensuring a pickled surface with uniform fine irregularities during pickling of 14 plates, but its content is 0.0
If the content is less than 0.05%, a uniform α region within the grains will not occur, while if the content exceeds 0.025 wt%,
Excessive nonmetallic inclusions cause "blistering" during pickling and poor press formability.

(e) Cu When pickling a steel plate, the Cu component has the effect of creating fine irregularities on the surface of the steel plate after pickling due to interaction with P, but if the content is less than 0.020 wt4, it will be in the α region. If the content exceeds 0.040 wt%, α waves will be too small, leading to poor adhesion of the enamel.

()00 component has the effect of forming non-metallic inclusions in steel and suppressing the occurrence of ``spotting'' caused by hydrogen in steel, but if its content is less than 200 ppm, there are fewer inclusions in steel. This makes it easier for "Tsumatobi" to occur, and on the other hand, 5
If the content exceeds 0.00 ppm, excessive inclusions will cause blistering during pickling and press forming defects.

(g) N N is an impurity element that inevitably mixes into steel, but if its content exceeds 0.0040%, forming defects due to "aging properties" become noticeable.

(h) Al Al is also an impurity element that inevitably mixes into steel, but when its content exceeds 5 wt% of O, OO, it results in a decrease in O in the steel and an increase in the amount of nonmetallic inclusions. As the amount decreases, "clips" are more likely to occur after enameling.

(i) If the value of "cu/P r Cu (chi)/P (%)" is less than 1.0, the α region will be abnormally large and the α region will realize a uniform fine uneven surface within the crystal grain. On the other hand, it no longer happens.

If the value exceeds 1.0, alpha waves are insufficient.

In either case, it will cause poor adhesion of the enamel.

If the value of (j)P/5 rP(%)/S(%) is less than 0.5, the α region will be too small and an appropriate surface condition cannot be obtained; on the other hand, if the value exceeds 3.0, In this case, it is not possible to obtain a uniform finely uneven surface due to excessive alpha waves, and even if the A deviation occurs, poor adhesion of the enamel will occur.

Components as above by rt H or D H degassing:
J! According to the present invention, the A-conditioned molten steel is subjected to continuous casting. This makes it uniform over the entire length and width, and can prevent uneven adhesion, bumpiness, and blisters that occur at the rim core boundary of the ingot.

The C content in the CC powder used for continuous casting is 1.
The content is 5w1% or less, preferably 1wt% or less, and most preferably 0.9wt% or less. This is because when the C content in the CC powder exceeds 1.5 wt%,
reacts with O in the molten steel to generate CO gas, and as a result,
This is because blowhole defects occur on the slab surface, which requires cleaning by stripping one surface, and in extreme cases, breakouts may cause molten steel leakage.

The drawing speed during continuous casting is 0.8 m for 7 minutes or more. This is because if the drawing speed is less than 0.8 m/min, the contact time between the C in the powder and the molten steel becomes longer.
This is because blowholes will occur similarly to the above.

The relationship between the C content in the powder, the slab repair surface ratio due to blowhole defects, and the number of pinholes in the enamel product, using the drawing speed as a parameter.

They are shown in FIGS. 1(,) and (b), respectively.

As is clear from FIG. 1(b), when the C content in the powder is Q, 9 wt% or less, the drawing speed is 0, 8
m In all cases of 7 minutes or more, the number of pinholes in the enamel product is kept within a practical range. On the other hand, when the drawing speed is 1.6 m 7 minutes, it becomes practical for all cases where the C content in the CC-E ladder is 1.5 wt% or less. Therefore, the following conditional expression is derived from FIG. 1(b).

v≧1.33(C-0,9)+0.8 −・−・−<1
) Here, V is the drawing speed during continuous casting (m7 min), and C is C.
C content (wt'%) in C/f powder Therefore, the drawing speed v (m7 min) during continuous casting must be 0.8 m/min or more and satisfy conditional expression (1). .

Hot rolling of the slab obtained by continuous casting is carried out in the same manner as in a conventional cold rolling base material manufacturing method. Winding temperature is 40
It is preferable that it is 0-750 degreeC. This is because if the temperature is less than 400°C, flatness will be poor, and if it exceeds 750°C, it will be difficult to peel off the scale. There are no particular limitations on cold rolling, and a normal cold rolling method may be used.

The steel material obtained in this way is further subjected to an annealing treatment to further decarburize the differential C remaining in the steelmaking stage by open coil annealing, promote the growth of crystal grains, and improve aging properties by de-N treatment. It is also possible to eliminate it and improve moldability. Further, continuous annealing or tight coil annealing may be used.

Each annealing condition is as follows.

Tight coil annealing (BAF) After soaking the tight coil at a soaking temperature of 600 to 750℃,
Slow cooling.

Open coil annealing (OCA) After soaking the loose coil at a soaking temperature of 600 to 750℃,
Slow cooling.

Continuous annealing (CAL) A tight coil is continuously developed into a strip and soaked at a temperature of 670.
After soaking at ~900℃, cooling and continuing to 350~50℃
Overaging treatment was carried out at 0℃.

(effect) As mentioned above, in the present invention, C, Cu.

Since the components such as P and S are adjusted within specific ranges, good enamel properties (anti-friction, blistering resistance, and adhesion) and good moldability can be obtained. Also CC) 4
Since the C content in the slag is kept below a specific value and the drawing speed is set above a specific condition, it is possible to suppress the pickup of C into the slab, thereby preventing blow holes in the slab and pins in the enamel. Hole defects can be prevented.

(Example) First, steels A to H having the chemical composition shown in Table 1 were RH
After adjusting the components according to the method, the series of conditions shown in Table 1
A steel billet was obtained by molding, and this was subjected to treatment under the conditions shown in Table 1 to produce a steel plate for enamel.

In addition to investigating the mechanical properties and blowhole treatment rate of each steel plate obtained in this way, we performed enamel finishing using the "single application method" under the following conditions.
Occurrence status of pimples and “blister”, PEI adhesion,
and the number of pinholes generated.

Enamel finishing conditions [Pre-treatment conditions] (1) Degreasing (2) Washing with water (3) Pickling 1370H2SO4 (4) Washing with water (5) Ni flash 13f-/l NiSO4
,7H,,0,70℃ (6) Water washing (7) Neutralization (8) Drying [enamel glazing conditions] (1) Frit composition: Titanium milky white frit + 155
3B (Product name (Nippon Ferro Co., Ltd.)) (2) Glazing: Streak v-7,67/200cIIL2 Drying and firing at 830°C or above.The results of the survey conducted are also shown in Table 1. From the results shown in Table 1, in the present invention example.

It is clear that not only excellent enamel properties are obtained, but also the maintenance rate due to blowholes in the slab and the pinholes in the enamel product are significantly reduced.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide sufficiently good enamel characteristics even by applying it once, and in particular, the occurrence of blowholes in slabs and the occurrence of pinholes in enamel are significantly reduced. Provided is a steel plate for enamel that can be

[Brief explanation of drawings]

Figure 1 (, ) is a graph showing the relationship between the C content in CC/container and the slab repair area rate due to blowhole defects, using the drawing speed during continuous casting as a parameter.
) is a graph similarly showing the relationship between the C content in the C()4 Uda and the number of vials in the enamel product, using the drawing speed as a parameter. Figure 1 Nomauta Junior High School C

Claims (1)

[Claims] (1) C≦0.006wt%, 0.2≦Mn≦0.5w
t%, 0.005≦P≦0.025wt%, 0.005
≦S≦0.025wt%, 0.020≦Cu≦0.04
0wt%, 1.0≦Cu(%)/P(%)≦4.0, 0
．． 5≦P(%)/S(%)≦3.0, 200≦O≦50
When continuously casting molten steel containing the following components: 0ppm, N≦40ppm, Al≦0.005wt%, C≦1.5wt%.
%, the drawing speed is 0.8 m/min or more, and the following conditional expression V≧1.33×(C-0.9)+0.8, where V: continuous casting Pulling speed (m/min) C:C
A method for producing a steel plate for enamel, characterized by setting the C content (wt%) in C powder within a satisfying range.