JPH0338333B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> This invention is a pretreatment (pickling) that reduces the amount of weight loss due to pickling.
The present invention relates to a steel plate for single-layer enameling, which can ensure excellent enameling adhesion and resistance to slippage, and also has good formability. In recent years, enameled steel sheets, which are made by baking a surface glaze (vitreous enamel) onto steel sheets to form a glassy coating, have come to be used in a wide range of applications, not only for household goods, but also for construction goods and various industrial goods. Ta. In the production of such enamel steel sheets, it was common practice to use the ``two-coat method,'' in which a base coat with good adhesion was applied to the raw steel plate, and then a top coat was applied to give it a beautiful appearance. Recently, in order to improve adhesion, the steel plate is thoroughly pretreated (pickled), and then a glaze that combines adhesion and beauty is directly baked onto it. This method aims to shorten the process. ” is becoming more and more popular. <Prior art and its problems> By the way, conventionally, the material for enameled steel sheets manufactured by the "double-threading method" is rimmed steel cold steel, which has improved pickling treatment performance by increasing the P content in the steel. Rolled steel sheets subjected to decarburization annealing to improve formability have been used, but even in the above-mentioned "single-rolling method," which has gradually become more popular, no new materials have been used. First, the same steel plate as in the "double layer method" was used. However, the "single-threading method", in which the raw material steel plate used in the "double-threading method" is applied as is, has the following problems: (a) poor adhesion between the raw material steel sheet and the enamel layer, and "snapping", which is a surface flaw in the enamel. (b) In order to improve the adhesion between the raw steel plate and the enamel layer, it is common to take steps to increase the pickling weight of the steel plate during pretreatment. (c) Even if a product with satisfactory enamel adhesion is obtained, the material steel plate has poor press formability, resulting in forming defects. It was pointed out that there are many problems with this. <Means for Solving the Problems> From the above-mentioned viewpoints, the inventors of the present invention have improved the adhesion of the enamel to the surface of the product without requiring excessive pickling to the extent that it interferes with waste treatment and workability. In order to easily and easily produce enameled steel sheet products with good properties and various shapes using the "single layering method," we have conducted research focusing on improving the properties of the raw material steel sheet, and as a result, we have developed the following results. Knowledge was obtained. That is, a steel plate manufactured by using low carbon steel obtained through steelmaking decarburization such as molten steel degassing treatment and comprehensively adjusting the C, Mn, P, S and N contents is used as an enameled steel plate material. When applied to steel sheets, it shows excellent press formability without requiring decarburization annealing after cold rolling, and enamel products of various shapes can be easily obtained. Such steel sheets have a pickling loss of 20 to 60
When pre-treatment (pickling) is performed at a relatively low value of g/m <sup>2</sup> , and when a uniform pickling surface is obtained, it exhibits extremely good enamel adhesion and porosity resistance. . Figure 1 shows the "acid loss value (pickling loss value)" and "PEI Figure 1 shows the results obtained by investigating the relationship with "adhesion (enamel adhesion)", and from Fig. 1, pickling weight loss: 20 to 60 g/m <sup>2</sup>
It can be seen that excellent enamel adhesion can be stably obtained only when a uniform pickled surface is obtained. The loss in pickling and the resistance to black spots of the steel sheet are affected by the contents of P, S, Cu, and O. In particular, the loss in pickling that provides a uniform surface is determined by the ratio of Cu (%)/P (%). )” and “P
(%)/S (%)” ratio, and by adjusting each of the ratios to specific values, an appropriate low pickling loss value during pretreatment (pickling) can be achieved. It is ensured stably and exhibits good enamel adhesion and resistance to flaking even in the case of the "single application method." If the O content in the raw steel sheet is too low, the occurrence of "blurring" is noticeable. Therefore, in order to improve the corrosion resistance, it is necessary to ensure an O content of more than a certain amount. Its P, S, Cu
In addition to comprehensively adjusting the O content and
(%)" value adjusted to a specific range and used as an enameled steel sheet material, even if the "single application method" is applied, good enamel adhesion and resistance to scratching can be ensured. , By comprehensively adjusting the C, Mn, P, S and N contents in the steel sheet, excellent formability can be exhibited without requiring decarburization annealing after cold rolling. This invention was made based on the above knowledge, and the steel plate for single-threaded enameling is made of: C: 0.010% or less (hereinafter, % representing the component ratio is expressed as weight %), Mn: 0.20 to 0.50%, P: 0.005-0.025%, S: 0.005-0.025%, Cu: 0.025-0.045%, O: 0.020-0.050%, N: 0.0040% or less, and the content ratio of Cu and P, as well as P and S. The content ratio of Cu (%) / P (%) = 1.0 to 4.0 and (%) / S (%) = 0.5 to 3.0, respectively, and the remaining component composition is Fe and other unavoidable impurities. In particular, it has been made to exhibit sufficient enamel adhesion and porosity resistance even under pretreatment (pickling) with a small amount of pickling loss, and also exhibits good formability without decarburization annealing. ,
It has the following characteristics. Next, the reason why the content ratio of each chemical component in the steel sheet of the present invention is numerically limited as described above will be explained. (a) C The C component has the effect of improving the strength of steel sheets, but if its content exceeds 0.010%, it not only impairs the castability of steel and the press formability of steel sheets, but also causes the "foam phenomenon" of enamel. Due to the risk of "deformation", the C content was set at 0.010% or less. (b) Mn The Mn component has the effect of preventing surface flaws due to red heat embrittlement of steel during hot rolling, but if its content is less than 0.20%, the desired effect cannot be obtained; If the Mn content exceeds 0.05%, press formability deteriorates, so the Mn content is
It was set at 0.20-0.50%. (c) P The P component has the effect of increasing the pickling loss value during pre-enameling treatment, but if its content is less than 0.005%, the pickling loss is too small, causing poor adhesion of the enamel. On the other hand, if the content exceeds 0.025%, too much pickling will occur and a uniform finely uneven pickled surface will not be obtained, resulting in poor adhesion of the enamel, and due to hardening, there is a risk of poor formability of the steel plate. Therefore, P
The content was set at 0.005-0.025%. (d) S The S component has the effect of ensuring a pickled surface with uniform fine irregularities during pickling of a steel plate, but
If the content is less than 0.005%, uniform acid reduction within the crystal grains will not occur, while if the content exceeds 0.025%, there will be "blister" during pickling due to excessive nonmetallic inclusions and poor press formability. The S content is 0.005 to 0.025.
%. (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 through interaction with P, but its content is 0.025
If it is less than %, the acid loss will be abnormally large and the acid loss will not occur uniformly within the crystal grains, on the other hand,
If the Cu content exceeds 0.045%, the acid content will be too low, leading to poor adhesion of the enamel, so the Cu content was set at 0.025 to 0.045%. (f) O The O component has the effect of suppressing the occurrence of "Tsumatobi" caused by hydrogen in steel, but if its content is less than 0.020%, "Tsumatobi" will occur due to fewer inclusions in the steel. more likely to occur,
On the other hand, if the O content exceeds 0.050%, it will lead to excessive inclusions and difficulty in casting, so the O content is set at 0.020 to 0.050%. (g) N N is an impurity element that inevitably mixes into steel, but if its content exceeds 0.0040%, forming defects due to "aging" will occur, so the N content should be 0.0040%. It was determined as follows. (h) Value of “Cu (%) / P (%)” If the value of “Cu (%) / P (%)” is less than 1.0, the acid loss will be abnormally large and it will not be uniform within the grains. The acid reduction that creates a finely uneven surface no longer occurs, and on the other hand, if the value exceeds 4.0, the acid reduction will be too low, causing poor adhesion of the enamel. /P(%)”
The value of is set as 1.0 to 4.0. Figure 2 shows a low carbon steel plate having the composition of the present invention.
By varying the Cu content over a wide range of
(%)/P(%)” in various ways,
This is a graph showing the relationship between the value of "Cu (%) / P (%)" and "acid reduction value", but from Fig. 2,
It can be seen that a suitable acid reduction value of 20 to 60 g/m <sup>2</sup> can be achieved when the value of "Cu (%)/P (%)" is within the range of 1.0 to 4.0. (i) Value of "P (%) / S (%)" If the value of "P (%) / S (%)" is less than 0.5, acid loss will be small and an appropriate surface condition will not be obtained; If the value exceeds 3.0, it will not be possible to obtain a uniform finely uneven surface due to excessive acid loss.
In any case, since it will cause poor adhesion of the enamel, the value of "P (%) / S (%)" should be set between 0.5 and 3.0.
It was determined that Figure 3 shows the P of the low carbon steel sheet having the composition of the present invention.
By varying the and S content over a wide range of
(%)/S(%)” with various changes,
This is a graph showing the relationship between the value of "P (%) / S (%)" and "acid reduction value", and from Fig. 3, "P
It can be seen that a suitable acid reduction value of 20 to 60 g/m <sup>2</sup> can be achieved when the value of "(%)/S (%)" is within the range of 0.5 to 3.0. In other words, as mentioned above, "Cu (%) / P (%)"
It is extremely important in this invention to simultaneously control both "P (%)/S (%)" and is an essential condition to obtain a uniform finely uneven surface. The above-described steel plate of the present invention can be produced by directly hot rolling a slab that is continuously cast after degassing the molten steel from the converter using the RH method or DH method, etc., or by directly hot rolling the slab that is continuously cast as it is, or by directly hot rolling the slab that is continuously cast as it is, or by It can be easily produced by cooling, reheating, hot rolling, cold rolling, continuous annealing, and temper rolling. As for the casting method, it is strongly recommended to apply the continuous casting method as mentioned above, but this is because in conventional ingot-rimmed steel, the rim layer and the core layer have different steel qualities. Inclusions at the boundary between the enamel and the core may cause "bulges," or if a full-thickness rim layer is formed due to blooming, etc., the enamel adhesion and resistance to porosity tend to be poor. , in the ladle, the above “P(%)/S
Even if the values of ``Cu (%)'' and ``Cu (%) / P (%)'' are controlled, the actual composition of the rim layer will differ due to the influence of the rimming action, and the adverse effects of C content in the steel will be reduced. This is because decarburization annealing using an open coil method or the like tends to be a necessary condition after cold rolling in order to remove the carbon. By adopting the continuous casting method, we not only ensure uniformity within the product coil, but also
It becomes possible to reliably achieve desired properties only by continuous annealing without decarburization annealing. By the way, it goes without saying that batch-type "tight annealing", "decarburization annealing", or "decarburization/denitrification annealing" may be performed in place of the "continuous annealing". Next, the present invention will be explained by examples and in comparison with comparative examples. <Example> First, steel A~ with the chemical composition shown in Table 1

[Table] (Note) * indicates that the conditions are outside the conditions of the present invention.

【table】

[Enamel glazing conditions]

Fritt composition: Titanium opalescent frit #1553B {Product name (Japan Fellow)}, Glazing: Spray (30g/300mm x 300mm), Firing temperature: 820℃, Firing time: 2.5min. The results of the investigation conducted as described above are also shown in Table 2. From the results shown in Table 2, it is clear that by using the steel plate of the present invention, a steel plate for enamel with sufficiently satisfactory properties can be obtained even by the “single application method”. be. <Overall Effects> As described above, according to the present invention, 1 has good moldability and has excellent enamel adhesion and surface texture with only a light and efficient pickling treatment.
Industrially useful effects are brought about, such as obtaining a steel plate for round enameling, further improving the quality of enameled finished products and expanding the field of application.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the acid loss value and enamel adhesion during pickling of a steel plate, and Figure 2 is a graph showing the relationship between the value of [Cu (%)/P (%)] and the acid loss value of the steel plate. Figure 3 is a graph showing the relationship between [P(%)/S
(%)] and the acid reduction value.

Claims (1)

[Claims] 1. C: 0.01% or less, Mn: 0.20 to 0.50%, P: 0.005 to 0.025%, S: 0.005 to 0.025%, Cu: 0.025 to 0.045%, O: 0.020 to 0.050. %, N: 0.0040% or less, and the content ratio of Cu and P, and the content ratio of P and S are respectively Cu (%) / P (%) = 1.0 to 4.0, P (%) / A steel plate for single-thread enameling, characterized in that S (%) is 0.5 to 3.0, and has a composition consisting of Fe and other unavoidable impurities: the remainder.