JPH0830244B2 - Steel plate for hollow and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is a enamel that has both excellent workability and sufficiently satisfactory enamel properties (eg enamel adhesion, pinhole resistance, nail skip resistance, etc.). The present invention relates to a steel sheet for use and a method for manufacturing the steel sheet.

"Enamel product" with glass glaze baked on the surface of steel plate
Has excellent corrosion resistance, chemical resistance, heat resistance, abrasion resistance, strength, etc., and has a beautiful appearance, so it is now used in various fields including chemical equipment, kitchen equipment, sanitary equipment, etc. It has come to be used.

By the way, the enamel products as described above are conventionally manufactured by a "double-coating method" in which a base steel sheet having a good adhesion is first coated and then a top coating having a beautiful appearance is applied. Pre-treatment of raw steel sheet (pickling, N
After the development of the "one-time application method", in which the glaze, which is rich in beauty and adhesion, is directly burned after the i-flash etc. have been sufficiently improved to improve the adhesion, the trend is the "two-time application method". Shows a tendency to shift from the one-time method to the one-time method.

Further, the "enameled steel plate" which is a material of the enamel product is generally subjected to severe cold forming such as deep drawing and then baked with glaze at a high temperature,
Not only the excellent enamel property is required, but also the excellent cold workability is one of the important requirements. It is to be noted that the enamel property required for the enamel steel plate does not cause defects such as "foam" and "pinhole" that tend to occur during baking of the glaze, or "claw jumping" that tends to occur after baking, Moreover, it refers to properties such as good adhesion to the glassy film to be fired.

<Prior art and its problems> Under these circumstances, cold-rolled steel sheets with good cold workability have been selected and used for steel plates for enamel, but in recent years, “low carbon content When Ti is added to the steel, C in the steel is fixed and a texture favorable for drawability is obtained during recrystallization annealing, and a steel sheet excellent in deep drawability is obtained. " As a result (Japanese Patent Publication No. 44-18066), studies have been conducted to apply the above-mentioned steel sheet having excellent workability to enamel.

For example, in JP-A-52-128822, an extremely low carbon steel containing Ti is further made to contain a specific amount of S and Cu, which is hot rolled, cold rolled and continuously annealed to obtain excellent press formability. The present invention is intended to obtain a steel plate for enamel that has good enamel adhesion and good nail flying resistance. Japanese Patent Laid-Open No. 58-3925
By reducing the S content of low carbon aluminum killed steel containing Ti and adding Cu up to 0.050%, an attempt was made to obtain a enamel steel sheet that does not generate black spots. Further, JP-A-61-14051 provides excellent press formability and enamel property by adding at least one of As, Sb and Bi to an ultra low carbon steel containing specific amounts of Ti and N. The aim is to realize a steel plate for enamel.

However, in spite of these studies, in the Ti-added steel, the "pickling speed" during enamel application and the "enamelability" such as adhesion are not stable, and therefore Ti is added to improve the cold workability. The improved steel sheet was particularly hesitant to apply it to the "single-stroke method".

<Means for Solving Problems> From the viewpoints described above, the present inventors have excellent workability, and in order to provide a enamel plate having stable enamel properties, in particular, a Ti-added steel plate While paying attention to excellent workability, comprehensively improve "unstable pickling speed" and "dissatisfaction with enamel adhesion and pinhole resistance" pointed out in conventional Ti-added enamel steel sheets. As a result of repeated studies on the possibility of the above, the following findings were obtained.

(A) When the Ti-added steel plate is applied to a enamel steel plate, by reducing the carbon content in the steel as much as possible, it is possible to sufficiently prevent the occurrence of pinholes during enamel application and to reduce S. The addition of Cu improves the enamel adhesion, and the adjustment of the Cu content in relation to the P content makes it possible to improve the adhesion under a stable pickling speed. (B) However, as described above The steel sheet adjusted in composition becomes a prominent nail skipping defect as a steel plate for enamel due to the reduced S content. However, if a sufficient N content of a specific value or more is secured, the S reduction will be reduced. However, excellent nail flying resistance can be obtained. (C) Therefore, S of Ti-added ultra-low carbon steel having a carbon content below a specific value is reduced and Cu and N are added from a specific viewpoint. Made into cold-rolled steel sheet under specified conditions, The blunt treatment sufficiently follows severe cold working such as deep drawing, and obtains a enamel plate with good and stable enamel properties, which is sufficiently satisfactory even by the one-time multiplication method. It enables stable production of products.

The present invention has been made based on the above findings, and a steel plate for enamel, C: 0.005% or less (hereinafter,% representing the component ratio is expressed as weight%), Mn: 0.05 to 0.4%, S: 0.01% or less, sol.Al: 0.08% or less, N: 0.006 to 0.015%, Ti: 0.05 to 0.3
%, Cu: more than 0.05% and 0.3% or less, Fe and unavoidable impurities: excellent cold workability due to the composition of the composition consisting of the remainder and Cu (%) / P (%) ≥ 3.0 And it has a feature in that it combines enamelness,
Furthermore, C: 0.005% or less, Mn: 0.05 to 0.4%, S: 0.01% or less, sol.Al:0.08% or less, N: 0.006 to 0.015%, Ti: 0.05 to 0.3%, Cu: 0.05% or more 0.3% or less, Fe and unavoidable impurities: Hot-rolled steel with a composition that consists of the remainder and Cu (%) / P (%) ≥ 3.0, then coiled at a temperature of 500 ° C or higher and then cooled. By applying rolling and then annealing in a temperature range from the recrystallization temperature to the Ac ₃ point or less, stable steel plate for enamel having excellent cold workability and enamel properties can be manufactured stably. It is a feature.

Next, in the present invention, the reason why the component ratio of the steel plate for enamel and the manufacturing conditions are limited as described above will be explained.

A) Steel plate component ratio (a) C As the C content in the steel plate increases, bubbles and pinholes are more likely to occur during enameling. Therefore, the lower the C content, the better. If the amount is reduced, it is possible to suppress millet defects and pinhole defects to the extent that there is practically no problem, so the C content was set to 0.005% or less.

(B) Mn The Mn component has the function of preventing hot-rolled slab cracking,
If the content is less than 0.05%, the desired effect cannot be obtained, while if it exceeds 0.4%, the steel is hardened. Therefore, the Mn content is set to 0.05 to 0.4%.

(C) S S is an unavoidable impurity that accompanies the steel sheet, and the lower the content, the better the enamel adhesion.
However, since it is possible to secure practically sufficient enamel adhesion by suppressing the content to 0.01% or less, the S content was set to 0.01% or less.

FIG. 1 is a graph showing the relationship between the S content and the PEI value, which is an index of hollow adhesion, for steel plates C, D, G and I shown in Table 1 described later. From the above, it can be seen that excellent enamel adhesion can be secured by reducing the S content to 0.01% or less.

(D) sol.Al sol.Al is added as a deoxidizer for steel,
When the sol.Al content in the steel sheet exceeds 0.08%, the workability deteriorates, so the sol.Al content was set to 0.08% or less.

(E) N N component has the function of forming TiN by combining with Ti in steel to form a hydrogen trap site. Therefore, although it is an essential component for preventing the enamel nail skipping defect, if the N content is 0.006% or less, the desired effect is not obtained, while if it exceeds 0.015%, it is not possible. The N content was set to 0.006 to 0.015% because the flying prevention effect is saturated, but it is desirable to adjust the N content to 0.006 to 0.010%.

(F) Ti Ti component has the effect of forming TiN as described above to prevent nail popping, and at the same time improves the cold workability of the steel sheet by forming a compound with C or S in the steel. However, if the content is less than 0.05%, the effect of preventing nail skipping and the workability are not sufficient, while if it exceeds 0.3%, the cost increases, so the Ti content is 0.05 to 0.3%. I decided.

(G) Cu Cu component and P inevitably accompanied in the steel sheet are elements that greatly affect pickling speed and enamel adhesion,
In particular, if the value of [Cu (%) / P (%)] is less than 3.0, the pickling rate will be too high and the fluctuation will be too large to stabilize, and fine irregularities will not be formed on the steel plate surface. In addition, the enamel adhesion deteriorates. However, [Cu
When the value of (%) / P (%)] is 3.0 or more, the pickling speed is stabilized at a normal value convenient for work, fine irregularities are formed on the surface of the steel sheet, and the enamel adhesion is also improved.

FIG. 2 shows steel plates B, D, G, H and I shown in Table 1 below.
FIG. 2 is a graph showing the relationship between the [Cu (%) / P (%)] value and the acid loss value for Ni.
It can be seen that when the value of (%)] is less than 3.0, the pickling rate rapidly increases and becomes unstable.

However, even if the value of [Cu (%) / P (%)] is 3.0 or more, if the Cu content is less than 0.05%, the enamel adhesion is significantly reduced, while if it exceeds 0.30%, Cu Is not preferable because it causes an increase in cost.

FIG. 3 shows steel plates B, D, G, H and I shown in Table 1 below.
4 is a graph showing the relationship between the Cu content and the PEI value of the above, it can be seen from FIG. 3 that when the Cu content is 0.05% or less, the enamel adhesion decreases.

Therefore, the Cu content is set to 0.05 to 0.30% and
It was limited to the condition that the content and P content satisfy Cu (%) / P (%) ≧ 3.0.

The reason for the above-mentioned action observed in the Cu component is not clear, but it can be inferred as follows.

That is, when Ti is added to the Ti-added steel in order to improve the nail fly resistance, a large amount of acid-insoluble TiN is formed, and this TiN forms a local battery with the iron matrix during pickling. Increase pickling speed. In addition, TiN in the steel sheet is not normally dispersed uniformly, which causes large variations in the pickling rate. However, if a large amount of Cu is added to this, the electrode action of the non-uniformly dispersed TiN will decrease, and this will also reduce the pickling speed, making it easier to form fine irregularities on the steel plate surface, thus improving the adhesion of the enamel. To do.

B) Steel Plate Manufacturing Conditions The steel plate for enamel according to the present invention has excellent cold workability and enamel properties by being composed of the above-described composition, but in the manufacture thereof, Steels (ingots and slabs) adjusted to their composition are hot-rolled and wound at a temperature of 500 ° C or higher, then pickled as usual and then cold-rolled, and then recrystallized or higher.
It is preferable to anneal in a temperature range of Ac ₃ point or less in order to secure stable characteristics, but in the method for manufacturing a enamel plate according to the present invention, the reason for limiting the manufacturing conditions as described above is as follows. On the street.

First, after hot rolling, winding at a temperature of 500 ° C or higher is
This is because solid solution carbon is completely fixed by Ti to improve workability, and TiC is used when the coiling temperature falls below 500 ° C.
Is not completely deposited. Further, when the annealing is carried out in the temperature region of [recrystallization temperature ~ Ac ₃ points], a steel sheet having good workability can be obtained, but if the annealing temperature deviates from the above region, the workability is greatly reduced. Will end up. Incidentally, the annealing may be performed by either the “box annealing method” or the “continuous annealing method”,
There is no particular difference between the two.

As described above, according to the present invention, the Ti content of the steel plate with Ti content is
Ultra low carbon steel of 0.005% or less, S reduction and Cu
Is added, and further, Ti and sufficient N are added, and the Cu addition amount is adjusted in relation to the P amount to obtain a specific component system, while maintaining excellent cold workability, From the entanglement with mutual components, the effect of improving the pinhole resistance during enamel application by using ultra-low carbon steel, the effect of improving nail picking resistance by adding N, and the effect of improving the enamel adhesion by high Cu and low S, This is a combination of the [Cu (%) / P (%)] value of 3.0 or more that stabilizes the pickling speed and improves the enamel adhesion. As a matter of course, the enamel product can be manufactured sufficiently by the "single-step method".

Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

<Example> First, a steel having a chemical composition as shown in Table 1 was melted by a conventional method and continuously cast into a slab.

Then, the slab is heated to 1200 ° C. and then hot rolled,
It was wound at 600 ° C. The hot-rolled sheet thus obtained was pickled, cold-rolled (rolling rate: 73%), and one of the test steel sheets divided from the same steel sheet was subjected to box annealing at 820 ° C. for 10 hours,
And the other was subjected to continuous annealing at 850 ° C. for 1 minute.

Next, "Enamelness" was investigated for each cold rolled steel sheet after the annealing treatment, and the results are also shown in Table 1. However, almost no difference in the enamel characteristics due to the difference in the annealing method was observed, so only the results of box annealing are described here.

In addition, the "Enamelness" is 15
53C (product code) type glaze was calcined at 830 ° C for 3 minutes for measurement. Of these, the presence or absence of "nail jump" acid reduction value of 10 to 20 g / m ² was examined one week after baking. The "adhesion" was evaluated by the PEI value when the acid loss value was 20 to 30 g / m ² , and 90% or more was indicated as "good". The “pinhole” was visually determined when the acid loss value was 50 to 60 g / m ² .

As is clear from the results shown in Table 1, a steel sheet satisfying the conditions specified in the present invention exhibits excellent "enameling property", while a composition in which the component composition deviates from the conditions specified in the present invention. It can be seen that the steel sheet is inferior in "enameling property".

<Summary of Invention> As described above, according to the present invention, it is possible to provide the enamel plate having both satisfactory workability and enamel property at low cost, and to improve the quality even by the one-time multiplication method. Industrially useful effects such as the stable production of excellent enamel products are brought about.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the S content of steel sheets and the PEI value. FIG. 2 is a graph showing the relationship between the [Cu (%) / P (%)] value of a steel sheet and the acid loss value. FIG. 3 is a graph showing the relationship between the Cu content of the steel sheet and the PEI value.

Claims (2)

[Claims] 1. By weight ratio, C: 0.005% or less, Mn: 0.05 to 0.4%, S: 0.01% or less, sol.Al: 0.08% or less, N: 0.006 to 0.015%, Ti: 0.05 to 0.3%,
Cu: more than 0.05% and 0.3% or less, Fe and unavoidable impurities: the rest, and a steel plate for enamel, which has a composition that satisfies Cu (%) / P (%) ≥ 3.0. 2. By weight ratio, C: 0.005% or less, Mn: 0.05 to 0.4%, S: 0.01% or less, sol.Al: 0.08% or less, N: 0.006 to 0.015%, Ti: 0.05 to 0.3%,
Cu: more than 0.05% and less than 0.3%, Fe and unavoidable impurities: the temperature of 500 ° C or more after hot rolling steel with a composition that is composed of Fe and unavoidable impurities and that satisfies Cu (%) / P (%) ≧ 3.0 A method for producing a enamel steel sheet, which comprises winding the steel sheet in the following manner, then performing cold rolling, and then annealing in a temperature range of a recrystallization temperature or higher and an Ac ₃ point or lower.