JPH0759735B2 - Steel sheet for direct enamel with excellent bubble resistance and black spot defects - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention has good press formability, stab resistance, and adhesion at the time of direct single enamel, as well as foam resistance.
The present invention relates to a enamel steel plate having excellent enamel characteristics such as black spot defects.

<Prior Art> Steel plates for enamels are required to have a considerably deep drawing property because they are subjected to considerably severe press working as represented by sinks, bathtubs and the like. Further, it must satisfy the enamel adhesion, firing strain characteristics, stubborn resistance, and bubble / black spot defect resistance.

Ti-added steel, especially when the C content is 0.005% or less,
Excellent press workability is obtained by Japanese Patent Publication No. Sho 42-12348.
It is disclosed in Japanese Patent Publication No. 4418066 and Japanese Patent Publication No. 44-18066. This Ti-added steel has excellent enameling properties in addition to press workability, and is disclosed in JP-B-45-40655.
It is disclosed in JP-A-53-131919 or JP-A-56-9357.

These techniques are techniques for improving enamel properties as well as good press workability, and especially for improving wing resistance. That is, Ti forms carbides, nitrides and sulfides. These precipitates have a function of trapping hydrogen in the steel that causes tabs and improve the tabs resistance.

<Problems to be Solved by the Invention> However, even with Ti-added steel having excellent press formability and stab resistance, poor weldability as described in JP-A-61-276958 is a cause. Defects,
As described in JP-A No. 60-110845, there are problems in that it is inferior to conventionally used decarburized capped steels in terms of enamel adhesion, bubble resistance and black spot defect resistance. Regarding poor weldability, JP-A-61-276958 discloses,
Disclosed is a steel sheet in which a small amount of Se or Te is added to Ti-added steel to suppress "blowhole defects" and "sinks" in the welded portion and to improve bubble defects and streak defects caused by weldability defects. However, regarding the "easiness of generating bubbles and black spots" in areas other than welds, which can be said to be the defects peculiar to the Ti-added steel, it is still the same as that of decarburized capped steel.
The current situation is that even black spot defects have not been improved.

Further, JP-A-63-45322 describes a method for producing a steel plate for enamel using a Ti-added steel. However, the content is mainly intended to improve press moldability and vertical crack resistance, and bubbles and black spot defects such as pinhole defects and blowhole defects are caused by the C content of the continuous casting powder, and Only the drawing speed in continuous casting is regulated and improved. However, only the addition of Ti and B has little effect of suppressing bubble and black spot defects, and the tendency of occurrence of bubble and black spot defects is almost the same as that of the conventional Ti-added steel.
The reason is that in the Ti-added steel, C that strengthens the grain boundary is TiC.
It is considered that P, which is fixed as, and which increases the pickling property, easily precipitates at the grain boundaries. For the purpose of providing a steel sheet for direct wrapping enameling which has bubble resistance and black spot defect resistance equal to or higher than that of conventional decarburized capped steel without impairing press formability, resistance to tabulation and weldability. There is.

<Means for Solving the Problems> In order to achieve the above object, according to the present invention, in weight ratio, C: 0.005% or less, Mn: 0.10 to 1.00%, P: 0.020% or less, S: 0.01 ~ 0.05%, Al: 0.003-0.100%, N: 0.005-0.010%, Cu: 0.01-0.07%, Se: 0.002-0.020%, B: 0.0003-0.0030%, and (4 x C (%) + 1. 5 x S (%) + 3.43 x N
(%)) ≤ Ti (%) ≤ 0.2 (%), and a steel sheet for direct single-use enamel which comprises the balance Fe and inevitable impurities is provided.

Further, according to the present invention, in weight ratio, C: 0.005% or less, Mn: 0.10 to 1.00%, P: 0.020% or less, S: 0.01 to 0.05%, Al: 0.003 to 0.100%, N: 0.002 to 0.010%, Cu: 0.01 to 0.07%, Se: 0.002 to 0.020%, B: 0.0003 to 0.0030%, REM: 0.01 to 0.10%, and (4 x C (%) + 1,5 x S (%) + 3. 43 x N
(%)) ≤ Ti (%) ≤ 0.2 (%), and a steel sheet for direct single-use enamel which comprises the balance Fe and inevitable impurities is provided.

The present invention will be described in more detail below.

First, the background of the experiment and the details of the experimental results on which the present invention is based will be described.

(Experiment 1) Steels (steels A to E) having the chemical compositions shown in Table 1 were tapped in the laboratory, and then slab-rolled to obtain sheet bars having a plate thickness of 3 mm. Then, it was put into a heating furnace at a temperature of 1250 ° C. for 4 hours, hot-rolled in 3 passes so that the plate thickness was 3.5 mm and the finishing temperature was 880 ° C., and cooled to room temperature by air cooling (cooling rate about 3 ° C./min).

These were pickled and then cold-rolled to obtain cold-rolled sheets having a plate thickness of 0.8 mm (cold rolling reduction of about 77%). Then, degreasing was performed, and recrystallization annealing was performed in a heat cycle of a heating rate of about 10 ° C./second, a soaking temperature / hour of 840 ° C./40 seconds, and a cooling rate of about 8 ° C./second. Then, in the steps (steps 1 to 12) shown in Table 2, pretreatment with enamel [pickling time 1 to 40 minutes, Ni immersion time 1 to 30 minutes (Ni
The applied amount was ^{2 to} 60 mg / dm ² )], and the enamel was applied directly once and fired at 820 ° C for 3 minutes.

Then, the occurrence tendency of bubbles and black spot defects was investigated by visual judgment. Further, the enamel adhesion was measured by a PEI adhesion test [an adhesion test method recommended by PEI (American Enamel Association) (ASTM: C313-59)]. The results are shown in FIG. The results of decarburized capped steel (Steel F) which has been subjected to similar enamel processing as a comparative material are also shown in FIG. The symbols in the figure represent the results of the following enamel adhesion and the occurrence of bubbles and black spot defects.

: PEI adhesion <85%, bubble / black spot defect occurrence-none or small ○: PEI adhesion ≥ 85%, bubble / black spot defect occurrence-none or small ●: PEI adhesion ≧ 85%, generation of bubbles and black spot defects-Large Se, steel with Ti alone without B and REM addition (steel A) and steel with Ti + B addition (steel E), pickling time is 10 minutes or more , And Ni adhesion amount of 20 mg / dm ² or more, and the enameled pre-treated steel sheet satisfying both of them, was apt to cause bubbles and black spot defects. Also, with Ti + Se added steel (Steel B),
Pickling time is 15 minutes or more, and Ni adhesion amount is 20 mg / dm ² or more,
Further, the steel plate under the enameled pretreatment condition which satisfies both of these conditions was apt to generate bubbles and black spot defects. However, the steel sheet with Ti + Se + B added (Steel C) and the steel sheet with combined addition of B and REM (Steel D) are decarburized capped steel (Steel F).
It was found that bubbles and black spots did not occur even if the pickling time was about the same as or longer than the above. Also, Ti + Se + B + RE
The steel with M added (Steel D) is the steel with Ti + Se + B added (Steel C).
Compared with, the enamel adhesion was good under the pretreatment condition of short-time pickling.

Next, an experiment in which the effect of the amount of B added on the tendency of occurrence of bubbles and black spot defects was examined, and the results will be described below.

(Experiment 2) By weight ratio, C: 0.002%, Mn: 0.2%, P: 0.01%, S: 0.02%, Al; 0.04%, N: 0.007%, Cu: 0.03%, Se: 0.007%, Ti : 0.098%, O: 0.004% as the basic composition, and B as 0, 0.0003, 0.0008, and 0.
[0015] The steel added with 0.0030%, 0.0030% and 0.0050% was hot-rolled, cold-rolled and annealed in the same process as in (Experiment 1) to obtain a cold-rolled steel plate, and then in the pretreatment process shown in Table 2 pickling time 1 to 40 minutes , Ni immersion time
Directly apply enamel to the steel sheet that has been pretreated with enamel for 20 minutes, and subject it to firing, and investigate the relationship between the pickling time and the amount of B addition that makes the occurrence of bubbles and black spot defects [medium or higher], and compares The results of the decarburized capped steel shown in (Experiment 1) as steel are also shown in FIG.

As a result, the Ti-added steel without B addition has a pickling time of 15 minutes,
Bubbles and black spots with an evaluation of [Medium or higher] are generated, whereas Ti-added steel with B added has an amount of B of 0.0003 wt% or more and is superior in bubble resistance and black spots to decarburized capped steel. It was defective.

The reason for the occurrence of the bubble / black spot defect is considered as follows. That is, C that originally precipitates at the crystal grain boundaries and strengthens the crystal grain boundaries becomes TiC by adding Ti, and is fixed, so that the crystal grain boundaries are P that increases the pickling rate. Segregation is likely to occur, the grain boundaries on the steel sheet surface are preferentially corroded during pickling in the enameling pretreatment step, and
After the intergranular corrosion progresses, the corrosion further progresses into the horizontal grain, and the properties of the steel sheet surface (rough irregularities, smut accumulation,
Excessive Ni precipitation etc.) is deteriorated. Such rough irregularities,
Accumulation of smut, excessive Ni precipitation, etc. application of enamelled medicine → drying → forming voids that cause bubbles and black spots in the initial stage of firing, and coarser bubbles are generated as the surface texture becomes rougher. it is conceivable that. It is considered that these coarse bubbles become bubble defects, and that the bubbles open above the bubbles take in oxygen in the atmosphere during firing and abnormally oxidize the steel sheet interface to cause black spot defects.

The reason why bubbles and black spot defects were suppressed by adding B as obtained in this experiment is that B precipitates at the grain boundaries instead of C and segregates P at the grain boundaries. It is thought that this is because the addition of Se in particular
Is a solid solution in the crystal grains and B can be preferentially precipitated at the crystal grain boundaries. Therefore, the steel sheet containing B added in an amount of 0.0003 wt% or more can alleviate the tendency to generate bubbles and black spots. it is conceivable that.

However, if less than 0.0003 wt%, the effect was not recognized so much.

Next, an experiment in which the effect of adding B and Se on the occurrence of bubbles and black spot defects was investigated, and the result will be described below.

(Experiment 3) By weight ratio, C: 0.002%, Mn: 0.2%, P: 0.01%, S: 0.02%, Al; 0.04%, N: 0.007%, Cu: 0.03%, Ti: 0.09%, O : 0.003% as the basic composition, 0.0005% and 0.0018% of B added to steels with 0 to 0.0025 of Se melted in the laboratory, hot rolled in the same process as (Experiment 1) After cold rolling and annealing to form a cold rolled steel sheet, the steel sheet that had been subjected to enamel pretreatment of pickling time of 1 to 40 minutes and Ni dipping time of 20 minutes in the pretreatment step shown in Table 2 was directly applied once. The result of the decarburized capped steel shown in (Experiment 1) as a comparative steel was investigated by investigating the relationship between the pickling time and the amount of alloy addition that enameled and fired and the generation of bubbles and black spots was [medium or higher]. It is also shown in FIG.

As a result, the steel to which Se was not added was apt to generate bubbles and black spot defects regardless of the amount of B added. However, the tendency of bubbles and black spot defects in the steel sheet to which Se was added was improved even with a small amount of Se. That is,
With the addition of 0.002wt% or more, the bubble / spot defect generation time limit is
It is equivalent to or better than decarburized capped steel.

Next, the reason why the content of the steel component composition is limited in the present invention will be described below.

C: C is an interstitial solid solution element, and if the content exceeds 0.005 wt%, the material is significantly hardened. The present invention is a Ti-added steel, in which C becomes a precipitate of tiC to reduce the solid solution C,
Although the material can be improved, essentially, when the amount of C increases, fine TiC is likely to precipitate and the material deteriorates. Therefore, in the present invention, the upper limit of the C content is set to 0.005 wt%.

Mn: Mn fixes S, which causes cracks during hot rolling, as MnS, and forms irregularities on the surface of the steel sheet that enhances enamel adhesion during pickling in the enamel pretreatment process, and also causes scabbing defects. Since it is an element effective for trapping hydrogen, the content of at least 0.10 wt% is required. However, if the content exceeds 1.00 wt%, the material is hardened and the ductility and press formability are deteriorated, so the range of the Mn content in the present invention is set to 0.10 to 1.00 wt%.

P: If the content of P exceeds 0.020 wt%, not only harden the material and deteriorate the press formability, but also accelerate the pickling speed during pre-enamel pretreatment and increase the smut that causes bubbles and black spot defects. In addition to the above, the upper limit of the P content in the present invention is 0.020 wt.
%. Although the lower limit is not specified,
To make the content extremely low, the molten steel cost will be significantly increased, so about 0.001 wt% is preferable.

S: S forms precipitates such as MnS and Ti-Mn-S in the present invention. These precipitates form fine irregularities on the surface of the steel sheet that make the enamel adhesion good and, at the same time, have the effect of trapping hydrogen, which is a cause of scabbard defects. But at least 0 to bring out these effects.
The content of 01 wt% is required. However, if the content exceeds 0.05 wt%, the contents of Mn and Ti that fix S must be increased, which increases molten steel cost and is disadvantageous in terms of material. Was 0.01 to 0.05 wt%.

Al: Al is an effective element because it is used as a deoxidizer in the steelmaking stage, and it is necessary to add at least 0.003 wt% to sufficiently perform deoxidation. However, Al is an expensive element, and addition and addition of a large amount of more than 0.100 wt% lead to cost increase. Therefore, the upper limit of 0.100 wt% is desirable.

Therefore, the range of the Al content of the present invention is set to 0.003 to 0.100 wt%.

N: N is an element which, as with C, usually forms a solid solution in steel and deteriorates the material. However, the present invention is Ti-added steel, and N is a material because it forms and fixes TiN precipitates. In terms of aspect, there is no particular problem. Further, since this precipitate forms a void that traps hydrogen which causes a scabbard defect, it is preferable that the N content be large. In order to prevent a scabbard defect, a minimum content of 0.005 wt% is required. is there. However, if the content exceeds 0.010 wt%, the Ti addition amount must be increased, which inevitably leads to an increase in cost. Therefore, the range of the N content in the present invention is set to 0.005 to 0.010 wt%.

However, when REM is added, hydrogen trap sites are formed in addition to TiN, so that the nitriding defect does not occur even if the N content is 0.005 wt% or less. However, since a minimum content of 0.002 wt% is necessary, the range of N content when REM was added was set to 0.002 to 0.010 wt%.

Cu: Cu is an element effective in controlling the pickling rate at the time of pickling before enamel pretreatment.
Compared to decarburized capped steel, the additive steel has a pickling rate of 2
The content of Cu is important because it is about 3 times faster. In order to bring out the effect, it is necessary to contain at least 0.01 wt% or more. However, with a Cu content of more than 0.07 wt% in the component system of the present invention, the pickling rate becomes too slow, and the enamel adhesion on the pickling side for a short time decreases, so the Cu content of the present invention is reduced. The range was 0.01 to 0.07 wt%.

Se: The reason why Se is added in the present invention is that the weldability, especially the ti-added steel, has a poor O-containing flow in the steel and has a large surface tension, so the shape of the welded portion is poor (a recessed portion is formed). This is to reduce the viscosity and improve the shape of the butted portion after welding. In addition, Se also has the effect of forming a solid solution in the crystal grains and preferentially precipitating B at the crystal grain boundaries, and suppressing the corrosion of the crystal grain boundaries that causes bubbles and black spot defects. is there. However, if the content is less than 0.002 wt%, these effects are not exhibited, the pickling speed is increased, and bubbles and black spot defects are easily generated, which is not preferable.

On the other hand, a content of more than 0.020 wt% is not preferable because the pickling property of the enamel pretreatment becomes poor and it becomes difficult to form dense unevenness which is advantageous for enamel adhesion on the surface of the steel sheet.

Therefore, in the present invention, the Se content is set to 0.002 to 0.020 wt%.

B: B is an element added for the main purpose of the present invention. The purpose is that C, which originally precipitates at the grain boundaries and strengthens the grain boundaries, is fixed as TiC by the addition of Ti, and the grain boundaries are The grain boundary segregation of P that increases the pickling rate is likely to occur, and the grain boundaries on the steel sheet surface are preferentially pickled during pickling in the enameling pretreatment step, and the starting points for the formation of bubbles and black spots are formed. This is to prevent

That is, by adding B, B is deposited at the crystal grain boundaries instead of C and grain boundary segregation of P is suppressed. However, if it is less than 0.0003 wt%, the effect is not obtained, and 0.0030 wt%
When the content exceeds wt%, the mechanical properties of the steel sheet are significantly deteriorated, so the B content in the present invention is 0.0003 to 0.
It was set to 0030 wt%.

Ti: Ti content is (4 x C (wt%) + 1.5 x S (wt%) + 3.4
The reason for 3 × N (wt%) ≦ Ti (wt%) ≦ 0.2 (wt%) is that C, S, and N are TiC, which significantly deteriorate the mechanical properties of the steel sheet if left in a solid solution state. At least (4 x C (wt%) + 1.5 x S (wt
%) + 3.43 × N (wt%)) or more is required. However, if the content exceeds 0.2 wt%, bubbles and black spot defects are likely to occur due to an increase in pickling speed and an increase in smut amount.

REM: REM forms sulfides, traps hydrogen like Ti-based precipitates, and can improve scabbing resistance.By adding REM, REM is the main cause of bubbles and black spot defects. It is possible to reduce the possible amount of Ti, as well as Ti-Mn
The -S-REM-based precipitate has the effect of forming dense irregularities on the surface of the steel sheet and improving the enamel weldability, and the REM content at which this effect appears is at least 0.01 wt%. However, if the content exceeds 0.10 wt%, the pickling speed increases, and bubbles and black spot defects are likely to occur. Therefore, the upper limit in the present invention is set to 0.10 wt%.

In addition, it is desirable to refrain from inclusion of unavoidable impurities as much as possible, but the content thereof is not particularly limited in the present invention.

Next, an example of manufacturing conditions of the steel of the present invention will be described.

In the present invention, the hot rolling conditions are usually not limited even if hot rolling is completed at a temperature of Ar ₃ transformation point or higher, even if low temperature finishing at Ar ₃ transformation point or lower is not affected, When the mechanical properties are important, the hot rolling finish temperature is Ar ₃
It is desirable to make it above the transformation point.

Further, the winding temperature is preferably set to a high temperature, particularly 600 ° C. or higher, in order to secure mechanical properties. However, at a coiling temperature of 650 ° C or higher, the scale layer becomes thick and the descaling property (pickling property) deteriorates, so the upper limit is 650 ° C.
It is desirable to set the degree.

Cold rolling conditions: Cold rolling conditions are not specified in the present invention either, but in the case of producing a cold rolled steel sheet having good mechanical properties, particularly drawability (r value), the cold rolling reduction ratio is 70%. The above is preferable.

Continuous annealing: The recrystallization annealing is preferably a continuous annealing that can complete the annealing process in a short time and can suppress the surface concentration of elements in steel and the segregation of grain boundaries, which adversely affect the enameling properties.

Further, if recrystallization is not perfect, workability is significantly impaired, and press cracking occurs when press working is performed,
On the other hand, the recrystallization texture at a temperature of Ac ₃ transformation point than is randomized, since the drawability is decreased, the annealing temperature is the recrystallization temperature or more and below the temperature range Ac ₃ transformation point.

<Examples> The present invention will be specifically described below based on Examples.

Continuously cast slabs with chemical composition shown in Table 3
After heating and holding for a period of time, a sheet bar having a plate thickness of 30 mm was subjected to rough rolling, and then a hot rolled plate having a finishing temperature of 880 ° C. and a plate thickness of 3.5 mm was rolled by a tandem rolling machine and wound at 620 ° C. After pickling, 4 stands were cold rolled with a cold rolling machine to a cold rolled sheet with a thickness of 0.8 mm, passed through a continuous annealing line, and heated at a heating rate of 10 ° C / s, a soaking temperature of 830 ° C, a soaking time of 2 minutes, and cooling. Recrystallization annealing was performed at a heat cycle of 15 ° C / s. Then, temper rolling with a reduction rate of 0.8% was performed.

After that, these steel sheets were pretreated with enamel as shown in Table 2 [pickling time 1 to 50 minutes, Ni dipping time 5 minutes], and directly enameled once and baked at 820 ° C for 3 minutes. Was applied.

After that, the tendency of occurrence of bubbles and black spot defects [small,
Medium, large] was investigated, and it was expressed by the pickling time at the limit of occurrence of bubbles and black spots, which was evaluated as "medium or higher".

Further, the enamel adhesion was measured by a PEI adhesion test [an adhesion test method recommended by PEI (American Enamel Association) (ASTM: C313-59)].

As for the rust resistance, each of three (n = 3) degreased steel sheets was subjected to a pickling time of 20 seconds, a pretreatment without Ni immersion, a commercially available undercoating agent, and dried. After baking at ℃ / 3 minutes, accelerated treatment of scabbing generation (160 ℃ / 16 hours) was performed, and the number of scabbard generation was observed and evaluated (when the number of generated scabs is 0, it is represented by 0/3. ).

Mechanical properties of the annealed steel sheet are processed into JIS No. 5 tensile test pieces, and the yield point (YS), tensile strength (TS), and elongation (El ), Yield elongation (YE
l) and r value (Rankford value) were measured, and the average value [0 ° value + 2 × 45 ° value + 90 ° value) / 4] was evaluated. The results are shown in Table 4.

As a result, the cold-rolled steel sheets for enamels (steels 1, 2, 3, 4, 12, 15, 16) produced by the component system of the present invention are compared with the conventional decarburized capped steel shown in Steel 18, It was found that the press formability and weldability were excellent, and the enamel properties such as wing resistance, bubble / spot resistance, and adhesion were equivalent or higher. However, the steels 5, 6, and 7 had P contents outside the range of the present invention, so that bubbles and black spot defects had already occurred in 15 to 20 minutes. In particular, in Steel 5, since B was not added, bubbles and black spots occurred in the pickling time of about 15 minutes. Steel 8 had poor Se adhesion because the Se content exceeded the range of the present invention. Copper 9 has a Cu content exceeding the range of the present invention, so the pickling weight loss is reduced and the adhesion is reduced. Since copper 10 and 11 did not have Se added, “sinking” occurred in the welded portion, and the pickling speed was high, so bubbles and black spot defects were likely to occur. Further, Steel 13 has a C content of more than 0.005 wt% and thus has significantly poor mechanical properties.
Bubbles and black spot defects occurred in a short time because the i content was large.
Steel 14 contained a small amount of N, and thus a slab defect was generated. Further, Steel 17 had a small N content and a small amount of REM added, and thus a slab defect was generated.

<Effects of the Invention> Since the present invention is composed of the steel composition as described above, even though it is a Ti-added steel, it is equivalent to the conventional decarburized capped steel even if it is directly enameled once. It is possible to provide a steel sheet for direct enameling, which has a press workability higher than or equal to that, and is less likely to cause bubbles and black spot defects.

Further, according to the present invention, the steel plate for high grade enamel, which has been conventionally produced by the ingot making method, can be produced by the continuous casting method, which brings great advantages in terms of cost and energy saving.

The steel sheet of the present invention is not limited to the one-time single application, but can be used as a steel sheet for one-time under-drawing and two-time enameling, and its characteristics are not changed.

[Brief description of drawings]

Figure 1a, Figure 1b, Figure 1c, Figure 1d and Figure 1e show Ti-added steels with different composition systems, and Figure 1f shows decarburized capped steels, adhesion and bubble / spot defect tendency. FIG. 3 is a graph showing the relationship between the pickling time and the amount of Ni adhered on Ni. FIG. 2 is a diagram showing the relationship between the pickling time for the occurrence of bubbles and black spots and the amount of B added. FIG. 3 is a diagram showing the relationship between the bubble / black spot defect occurrence limit time and the amounts of B and Se added.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kozo Kadoyama 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Headquarters (56) References JP 61-276958 (JP, A) JP 63 -45322 (JP, A) JP 58-197254 (JP, A) JP 56-9357 (JP, A)

Claims (2)

[Claims] 1. By weight ratio, C: 0.005% or less, Mn: 0.10 to 1.00%, P: 0.020% or less, S: 0.01 to 0.05%, Al: 0.003 to 0.100%, N: 0.005 to 0.010%, Cu: 0.01 to 0.07%, Se: 0.002 to 0.020%, B: 0.0003 to 0.0030%, and (4 x C (%) + 1.5 x S (%) + 3.43 x N
(%)) ≤ Ti (%) ≤ 0.2 (%), steel sheet for direct single-use enamel consisting of the balance Fe and inevitable impurities. 2. By weight ratio, C: 0.005% or less, Mn: 0.10 to 1.00%, P: 0.020% or less, S: 0.01 to 0.05%, Al: 0.003 to 0.100%, N: 0.002 to 0.010%, Cu: 0.01 to 0.07%, Se: 0.002 to 0.020%, B: 0.0003 to 0.0030%, REM: 0.01 to 0.10%, and (4 x C (%) + 1.5 x S (%) + 3.43 x N
(%)) ≤ Ti (%) ≤ 0.2 (%), steel sheet for direct single-use enamel consisting of the balance Fe and inevitable impurities.