JPS633945B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high-tensile cold-rolled steel sheet for enameling, and particularly to a high-tensile cold-rolled steel sheet for enameling that maintains the same high strength as before firing even after firing, and has excellent nail-skipping resistance and adhesion. Enamel products have been widely used in various parts in recent years because they have excellent corrosion resistance, heat resistance, and abrasion resistance, as well as good colorability and no fading. In particular, they have come to be used in large quantities not only in kitchen appliances such as electrical appliances, heating appliances, and kitchen utensils, but also as interior and exterior parts of buildings. However, enamel products usually have a surface of 200 ~
It has the disadvantage that it is considerably heavier than painted or glazed boards because it is fused with 800μ thick inorganic enamel, so there is a strong desire to make the material lighter. However, enamel products undergo brittle fracture without being deformed, and if the enamel base is deformed after firing, the enamel has the property of peeling, so the enamel base needs to be strong and thick enough not to deform during handling after firing. It had been. Therefore, if it is possible to reduce the thickness of the material, which satisfies the properties required for enamel materials such as nail-skipping resistance and enamel adhesion, and has high strength, it will be possible to reduce the weight of enamel products, and the effect will be greater. Be expected. As a method to increase the strength of steel plates, Si, Mn,
It is known to add solid solution hardening elements such as P and precipitation hardening elements such as V, Nb, Ti, and Mo. However, for steel sheets for enameling that are fired at high temperatures, adding precipitation hardening elements will cause the precipitate crystals to become coarse after firing, resulting in a significant decrease in strength, so it is preferable to add solid solution hardening elements; Addition of Si and P inhibits the adhesion of enamel, so it is necessary to limit the amount. On the other hand, cold-rolled steel sheets for enameling are required not only to have the above-mentioned strength after firing but also to have excellent nail-skipping resistance, have few enamel defects such as bubbles and pinholes, and have excellent adhesion. Conventionally, cold-rolled steel sheets for enameling are generally decarburized annealed ultra-low carbon cold-rolled steel sheets, and by setting C to about 0.001 to 0.006%,
In addition to bubbles and pinholes, we are trying to reduce the tendency for nails to jump. However, when these ultra-low carbon steel sheets are enameled at a relatively high temperature, their crystal grains often become coarse and their strength decreases, so they are unsuitable for the purpose of the present invention. The purpose of the present invention is to provide a high-strength cold-rolled steel plate for enameling that has excellent workability, nail-skipping resistance, adhesion, etc. required for a steel plate for enameling, and also has high strength and can reduce the amount of materials used. be. The gist of the present invention is as follows.
That is, C: 0.100% or less, Si: 0.03% by weight
% or less, Mn: 0.05-1.0%, P: 0.050-0.200%,
Contains Al: 0.250% or less, Ni: 0.03 to 0.50%,
The present invention is a high-strength cold-rolled steel sheet for enameling, characterized in that P/Ni has a relationship of 20×10 ⁻² to 180×10 ⁻² , with the remainder substantially consisting of Fe. The reasons for limiting the composition of the steel of the present invention will be explained. C: C has a negative effect on the generation of bubbles, pinholes and nail skipping defects during enamel firing, so the less it is the better. In particular, if it exceeds 0.100%, the above-mentioned enamel defects are likely to occur, so the upper limit was set at 0.100%. Si: In addition to inhibiting the adhesion of enamel, Si also reduces the efficiency of pickling during cold rolling pretreatment. In particular, if it exceeds 0.03%, these effects will be strong, so it was limited to 0.03% or less. Mn: Mn is an impurity in steel that prevents hot embrittlement caused by S and requires at least 0.05% in order to obtain the necessary mechanical properties.
If it exceeds %, cold workability and weldability deteriorate, so the upper limit was set at 1.0%, and the range was limited to 0.05 to 1.0%. Al: Al has the effect of fixing O and N and improving secondary workability, but if it exceeds 0.250%, ductility deteriorates, so the upper limit was set at 0.250%. P: P has the effect of increasing strength and improving pickling properties during enameling pretreatment, so it needs to be at least 0.050%. However, if the amount is too large, the secondary workability will deteriorate and the adhesion of the enamel will be inhibited. In the present invention
The upper limit to which these defects can be suppressed by other elements such as Ni is set at 0.200%, and from 0.050% to
It was limited to a range of 0.200%. Ni: Ni is an element effective in suppressing the adhesion of enamel inhibited by P and preventing the occurrence of nail skipping, which is an enamel defect, at least 0.03
% is required. However, if the amount exceeds 0.50%, it will inhibit the pickling properties during enameling pre-treatment.
It also deteriorates the adhesion of enamel and hardens the steel, so the upper limit is set at 0.50% and 0.03 to 0.50%.
limited to the range of Furthermore, in relation to the P content, at least P/Ni: 20×10 ^-2 or more is required.
However, if P/Ni exceeds 180×10 ⁻² , the adhesion deteriorates, so P/Ni is limited to a range of 20×10 ⁻² to 180×10 ⁻² . Figure 1 shows the influence of changes in P/Ni on PEI (%), which shows the adhesion, by varying the Ni content of two types of steel sheets with P contents of 0.056% and 0.120%. This is the result of a survey.
That is, when P/Ni is between 20×10 ^-2 and 180×10 ^-2 ,
In particular, it was found that adhesion between 30×10 ^-2 and 160×10 ^-2 was excellent. The above-mentioned high-strength cold-rolled steel sheet having a limited composition according to the present invention is manufactured by a normal manufacturing process. In other words, molten steel is produced in a melting furnace such as a converter or an electric furnace through vacuum degassing treatment, and is then made into a slab by ingot making, blooming, or continuous casting, and after hot rolling, it is preferably heated to a temperature of 630°C or higher. It is manufactured by winding it into a coil at a high temperature, pickling it, cold rolling it, and then annealing it. The thus obtained cold-rolled steel sheet according to the present invention has high strength after enameling, which makes it possible to reduce the weight of the product, eliminates the occurrence of enamel defects such as nail skipping, and has good pickling properties. A high tensile strength cold-rolled steel sheet for enameling with excellent enameling adhesion could be obtained. Examples Test steels A, B, C, D, E, F, G according to the present invention having the compositions shown in Table 1, and comparative steels H, I, J, which deviate from the limited composition of the present invention.
K, conventional steel L is melted and hot rolled, coiled, pickled, and cold rolled under the same conditions except for conventional steel L, and then annealed.

【table】

[Table] Comparative tests were conducted on the mechanical properties before and after enameling and the enameling properties after enameling of 1.2 mm thick cold-rolled steel sheets that were further subjected to temper rolling. The results are shown in Table 2. That is, each test steel was hot-rolled at a finishing temperature of 870°C and a coiling temperature of 680°C to obtain a hot-rolled steel strip with a thickness of 3.2 mm, and then pickled and cold-rolled to 1.2 mm. The product was annealed in a bell-shaped annealing furnace at a soaking temperature of 680°C, and then subjected to 1% temper rolling. In addition, the conventional steel L sample material was coiled at 570℃, annealed in an open furnace, and decarburized.
In addition to denitrification annealing, the material was treated in the same manner as the other test materials. In Table 2, nail skipping is expressed as the number of nail jumps/number of sheets tested, and PEI (%), which represents adhesion, is PEI
(Porcelain Enamel Institute) Using an adhesion tester, a certain amount of overhanging deformation is applied to the enameled sample to force the glaze to peel off, and the calculated area of the base metal is electrically read and residual adhesion remains on the deformed part. The ratio between the area of the glaze and the total area of the deformed part is calculated and expressed as a percentage, with no peeling being taken as 100% and full peeling being 0%.
Therefore, the larger the value of PEI (%), the better the adhesion. In addition, the enameling treatment in the above test was performed at 850℃ using a frit for high-temperature firing after the usual pretreatment.
It was fired for 1 minute. As is clear from Tables 1 and 2, the steel of the present invention exhibits excellent mechanical properties even after firing, which are almost the same as those before firing, and there is no occurrence of nail skipping and excellent adhesion. On the other hand, the mechanical properties of comparative steels H, I, J, and K after enamel firing tended to deteriorate slightly compared to before firing.
The nail-skipping resistance and adhesion are significantly inferior to the steel of the present invention, and the conventional steel L test material has poor nail-skipping resistance and adhesion.
Although it has excellent adhesion, the strength before firing is far inferior to that of the steel of the present invention, and the mechanical properties after firing show a significant deterioration compared to before firing. As is clear from the above examples, the high-strength cold-rolled steel sheet for enameling according to the present invention limits the material composition, in particular restricts P, which deteriorates the enameling properties, and adds Ni in relation to the P content. P/
By regulating Ni to 20×10 ^-2 to 180×10 ^-2 , the following effects could be achieved. (a) Since it was able to have higher strength than conventional cold-rolled steel sheets for enamel, it was possible to reduce the weight of the enamel. (b) The steel of the present invention has mechanical properties after enamel firing that are almost the same as before firing;
Since it shows excellent strength even in repeated enameling firing, it has become possible to reduce the plate thickness, making it possible to reduce the cost of enamel. (c) The steel of the present invention has excellent enamel properties such as nail-skipping resistance and enamel adhesion. (d) As shown in FIG. 2, the invention steel is the invention steel A
The peel strength of steel L is higher than that of conventional steel L until the enamel peels off for the same material plate thickness, and the difference with conventional steel tends to increase as the plate thickness increases, making it possible to reduce the plate thickness from this point. It is. In addition, the peel strength of enamel (Kg) shown in Figure 2
After bending a material specimen with a thickness of t mm x width of 80 mm x length of 200 mm at right angles and performing enameling treatment, both ends were pulled in the opposite direction using a tensile tester to measure the enamel coating layer at the corner of the specimen. It is expressed as the strength (Kg) until it peels off.

[Brief explanation of the drawing]

FIG. 1 shows (P/Ni×
10 ^-2 ) and the adhesion of enamel (PEI%). Figure 2 shows the relationship between the material plate thickness (mm) of the invention steel A and the conventional enamel steel L shown in Table 2 and the adhesion of the enamel. FIG. 2 is a diagram showing the relationship with peel strength (Kg).

Claims (1)

[Claims] 1 Weight ratio C: 0.100% or less, Si: 0.03% or less, Mn: 0.05 to 1.0%, P: 0.050 to 0.200%,
Contains Al: 0.250% or less, Ni: 0.03 to 0.50%,
A high-strength cold-rolled steel sheet for enameling, characterized in that P/Ni has a relationship of 20×10 ⁻² to 180×10 ⁻² , with the remainder substantially consisting of Fe.