JPH02104640A - Steel sheet for direct single porcelain enameling excellent in press formability and resistance to blister and black-point defect - Google Patents

Abstract

PURPOSE:To improve press formability, adhesive strength at the time of single porcelain enameling, and resistance to blister and black-point defects by regulating the additive quantity of Ti in a steel sheet for porcelain enameling having a specific composition to a specific amount based on the contents of C, S, and N. CONSTITUTION:A steel sheet has a composition which consists of, by weight ratio, <=0.005% C, <0.10% Mn, <=0.020% P, 0.01-0.05% S, 0.003-0.100% Al, 0.005-0.010% N, 0.01-0.07% Cu, 0.002-0.050% Se, 0.0001-0.0030% B, and the balance Fe with inevitable impurities and contains, if necessary, 0.01-0.10% REM and in which Ti content is regulated so that (4XC%+1.5XS%+3.43XN%)<=Ti%<=0.2 is satisfied. By this method, a steel sheet for direct single porcelain enameling having press formability equal to or higher than those of conventional decarburized capped steel and conventional Ti-added steel and hardly causing the occurrence of blister and black-point defects can be provided.

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention has good press formability and resistance to flaking, as well as adhesion when enameling is applied once directly, as well as resistance to bubbles and sunspot defects. Concerning a steel plate for enameling with excellent waxing properties.

<Prior Art> Steel plates for crawlers, as typified by sinks, bathtubs, etc., are subjected to fairly severe press working, and therefore are required to have considerable deep drawability. Furthermore, it must satisfy the properties of waxy adhesion, firing distortion properties, dropability, and bubble resistance/sunspot defect properties.

It is known from the Japanese Patent Publication No. 42 that excellent press workability can be obtained in Ti-added steel, especially when the C content is less than o, oos%.
This method is disclosed in Japanese Patent Publication No. 12348, Japanese Patent Publication No. 44-18066, etc. This Ti-added steel has not only press workability but also excellent enameling properties, and is disclosed in Japanese Patent Publication No. 45-40655 and Japanese Patent Application Laid-Open No. 53-131919.
This method is disclosed in Japanese Patent Application Laid-Open No. 56-9357, etc.

These techniques are techniques for improving not only good press workability but also enameling properties, particularly chipping resistance. That is, Ti forms carbides, nitrides, and sulfides. These precipitates have the effect of trapping hydrogen in the steel, which is the cause of sagging, and improve the sagging resistance.

<Problems to be Solved by the Invention> However, even Ti-added steel that has excellent press formability and resistance to flaking can suffer from poor weldability as described in JP-A No. 61-276958. defect,
Furthermore, as explained in JP-A-60-110845, it is inferior in terms of enamel adhesion, bubble resistance, and black spot defect properties compared to conventionally used decarburized capped steel. There's a problem. Regarding poor weldability, see Japanese Patent Application Laid-Open No. 6
1-276958, by adding a small amount of Ss or Te to Tii processed steel, "blowhole defects" in welds,
A steel plate has been disclosed that suppresses "sink marks" and improves bubble defects and streak-like defects caused by poor weldability. - Regarding the ease of sunspot defect occurrence 1,
The current situation is that the bubble resistance and sunspot defects have not yet been improved to the level of decarburized capped steel.

Furthermore, Japanese Patent Application Laid-Open No. 83-45322 describes a method for producing a steel plate for enameling using Ti-added steel. However, the main purpose of this is to improve press formability and longitudinal cracking 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 It only improves the drawing speed in continuous casting by specifying it.

However, the addition of Ti and B alone has little effect on suppressing bubbles and sunspot defects, and conventional T1! # The tendency of bubble and sunspot defects to occur is almost the same as that of Ti steel.
This is thought to be because in additive steel, C, which strengthens grain boundaries, is fixed as TiC, and P, which increases pickling properties, tends to precipitate at grain boundaries. The purpose is to provide a steel plate for direct single-lay enameling that has bubble resistance and black spot defect resistance equivalent to or better than conventional decarburized capped steel without impairing press formability, toe resistance, and weldability. There is.

Means for Solving the Problems> In order to achieve the above objects, according to the present invention, in terms of weight ratio, C: 0.005% or less, Mn: less than 0.10%, Pro, 0.020% or less, S: 0.01-0.05%, AjZ: 0.003-0.100%, N: 0.005-0.010%, Cu: 0. 01 ~0. 07%, Se:
0. 002~0. 050%, B: ooo
t~0. 0030%, and (4xc(%)+
1.5×S (%)+3, 43×N (%))≦T
A steel plate for direct single-lap enameling is provided, where t (%)≦0.2 (%), the balance being Fe and unavoidable impurities.

Further, according to the present invention, in terms of weight ratio, C: 0.005% or less, Mn: less than 0.10%, P: 0.020% or less, S: 0.01 to 0.05%, AJ2: 0.003-0.100%, N: 0.002-0.010%, Cu: 0.01-0.07%, Se: 0.002-0.050%, B: 0.0001-0.000%. 0030%, REM: 0.01~0.10%, and (4×C(%)+1.5×S(%)+3, 4
3×N (%) ) ≦Ti (%) ≦0.2 (%)
, the balance being Fe and unavoidable impurities.

The present invention will be explained in more detail below.

First, the details of the experiment that formed the basis of the present invention and the experimental results will be explained.

(Experiment 1) After tapping W4 (steels A-F) having the chemical composition shown in Table 1 in the laboratory, they were bloomed and rolled to a thickness of 30 m.
M seat bar. Next, it was inserted into a heating furnace at a temperature of 1250°C for 4 hours, hot-rolled in 3 passes to a plate thickness of 3.5mm and a finishing temperature of 860°C, and cooled to room temperature by air cooling (cooling rate approximately °C/min). .

After pickling these, they were cold rolled to a plate thickness of 0.8 mm (
The cold-rolled sheet had a cold-rolling reduction ratio of approximately 77%. Next, degreasing is performed, heating rate: approximately 0°C/sec, soaking temperature/time;
Recrystallization annealing was performed using a heat cycle at 860° C. for 150 seconds and a cooling rate of approximately 150° C./second. After that, in the steps shown in Table 2 (steps 1 to 12), enameling pretreatment [pickling time 1 to
60 minutes, Ni immersion time 1-30 minutes (Ni adhesion amount 2-60 minutes)
m g / d m 2) ], and a single direct enameling and firing of 820 t/3 min.

Thereafter, the tendency of occurrence of bubbles and sunspot defects was investigated by visual inspection. In addition, PEI adhesion test [P, E, 1. (ASTM) recommended adhesion test method (ASTM:
C313-59)], the adhesiveness was measured. The results are shown in FIGS. 1(a) to (f). Decarburized capped 1 with similar enameling process as comparison material
1 (mG) are also shown in Figure 1 (g).

The symbols inside the mouth represent the results of enamel adhesion and occurrence of bubbles and sunspot defects as shown below.

■: PEI adhesion 85%, bubbles/sunspot defects - none or small ○: PEI adhesion ≧85%, bubbles/sunspot defects - none or small 0: PEI adhesion ≧85%, bubbles/sunspots Defect occurrence - Medium: PEI adhesion ≧85%, bubble/sunspot defect occurrence - Large S1. The pickling time was 10 for steel with Ti alone without B and REM addition (Steel A) and m<Steel F with Ti+B addition.
The amount of Ni deposited exceeds 20 mg/dm2, the pickling time exceeds 15 minutes, and the amount of Ni deposited exceeds 15 mg/dm2.
Steel plates under enameling pretreatment conditions that satisfy either of the following conditions were easy to generate bubbles and black spot defects. Also,
Ti+Se addition wI (Steel B), pickling time over 15 minutes, NL adhesion amount over 30 mg/dm2, pickling time 20 minutes boiling, Ni adhesion amount 20 mg/dm
Steel plates subjected to enameling pretreatment conditions in which the pickling time exceeded 2 or the pickling time exceeded 30 minutes were prone to bubbles and black spot defects. In addition, the Ti + Se + Bfi processed steel (Steel C) has a pickling time of over 30 minutes and a Ni adhesion amount of 30 minutes.
When the pretreatment conditions exceeded mg/dm2 or the pickling time exceeded 40 minutes, bubbles and black spot defects occurred.

However, Ti+ with Mn reduced to less than 0.10%
Steel plate with Se+B addition (Steel D) and steel plate with combined addition of B and REM (Steel E) are decarburized capped steel (Steel G) and high M
n + T i + S e + B addition a4 (Steel C)
Even under pretreatment conditions with a much longer pickling time, foam and
It was found that no sunspot defects occurred. Also, low M
Steel with n+Ti+Se+B+REM added (Steel E) is a steel with low M n + Ti + Se + B m addition (Steel E).
Compared to steel D), the enamel adhesion was better under short-time pickling pretreatment conditions.

Table 2 Next, an experiment in which the effect of the amount of B added on the tendency to generate bubbles and sunspot defects was investigated and the results will be explained below.

(Experiment 2) Weight ratio: C: 0.002%, P: 0.005%, S: 0.02%, A11.0.02%, N: 0.006%, Cu: 0.03% , Se: 0.009%, Ti: 0.08%, 0:0.003% B
0.0.0001%0.0004.0.00 respectively
080, 0.0020, 0.0040% added steel was hot rolled, cold rolled, and annealed in the same process as (Experiment 1) to make a cold rolled steel plate, and then the pickling time was changed in the pretreatment process shown in Table 2. 1~
A steel plate that has undergone enameling pretreatment for 60 minutes and a Ni immersion time of 20 minutes is directly subjected to one-time enameling and sintering, and the pickling time and B The relationship between the amounts added was investigated, and the results for the decarburized capped steel shown in (Experiment 1) as a comparison steel are also shown in Figure 2. As a result, Ti-added steel with high Mn and no B addition had bubbles and black spot defects rated as [medium or higher] after pickling time of 15 minutes, whereas Mn was reduced to 0.05%. , B-added Ti-added steel had Bfl of O1OO01 at% or more and had excellent bubble resistance and black spot defect properties that were equal to or better than the decarburized capped steel and the Ti-added steel with Mn: 0.30%.

The reason for the occurrence of the above-mentioned bubble/sunspot defects is thought to be as follows. C originally precipitates at grain boundaries and strengthens them.
becomes TiC by adding TL and is fixed, so the grain boundaries are free from P which increases the pickling rate.
becomes more likely to segregate at grain boundaries, and the grain boundaries on the surface of the steel sheet are preferentially corroded during pickling in the waxing pre-treatment process, and after intergranular corrosion progresses, corrosion further extends into the grains in the horizontal direction. progresses, deteriorating the properties of the steel sheet surface (roughness, smut accumulation, excessive Ni precipitation, etc.). Such rough unevenness,
Smut accumulation, excessive Ni precipitation, etc. form voids that cause bubbles and sunspots during the initial stages of enamel coating, drying, and firing, and the rougher the surface texture, the larger the bubbles. it is conceivable that.

These coarse bubbles become bubble defects, and it is thought that bubbles with open upper portions take in oxygen from the atmosphere during firing, abnormally oxidize the steel plate interface, and cause black spot defects.

Considering the above, the reason why bubbles and sunspot defects were suppressed by adding the twist obtained in this experiment is that B precipitates at the grain boundaries instead of C, causing grain boundary segregation of P. This is thought to be due to the fact that B was able to be suppressed, and in particular, it is thought that due to the addition of Se, Ss was dissolved as a solid solution within the crystal grains, and B could be preferentially precipitated at the grain boundaries.
Therefore, a steel sheet to which B is added in an amount of O,0001wt% or more,
It is thought that the tendency to generate bubbles and sunspot defects was alleviated.

However, at less than 0.0001 wt%, the effect was not enhanced much.

Next, an experiment conducted to investigate the effects of B and Se addition on the generation of bubbles and sunspot defects, and the results will be described below.

(Experiment 3) Weight ratio: C: 0.003%, P: 0.01%, S: 0.02%, Au, 0.03%, N: 0.006%, Cu: 0.03% , Ti: 0.100%, 0:0.003% as the basic composition, Mn: 0.03% and B: 0001% or 0.0010% added, and Mn: 0.26% and B. : 0 to 0.025 Se to steel added with o, oooa%
% added steel was melted and tapped in the laboratory and hot-rolled, cold-rolled, and annealed in the same process as (Experiment 1) to make a cold-rolled steel plate.
A steel plate that has undergone enameling pretreatment with a pickling time of 1 to 60 minutes and a Ni immersion time of 20 minutes in the pretreatment process shown in Table 2 is directly enameled once and fired to eliminate the occurrence of bubbles and sunspot defects. We investigated the relationship between the pickling time and the amount of Se added to achieve [medium or above], and compared the decarburized capped steel (Steel G) shown in (Experiment 1) and the 0.26% Mn + 0.0008% B1 added steel. The results of (ic) are also shown in FIG.

As a result, bubbles and black spot defects were likely to occur in steel to which Se was not added, regardless of the amount of B added.
However, the tendency of bubble/sun spot defects to occur in the steel sheet to which Se was added was improved even if the amount of Se was small.

That is, when 0.002 wt% or more was added, the critical time for bubble/sunspot defect occurrence was equal to or longer than that of decarburized capped steel.

(Experiment 4) Next, an experiment in which the influence of Mni on the generation of bubbles and sunspot defects was investigated and the results will be described below.

In terms of weight ratio, C: 0.002%, P: 0.01%, S: 0.02%, AIL, 0.03%, N: 0.008%, Cu: 0103%, Ti: 0.08 %, 0: 0.004%, Se: 0.008%, B: 001%, steel with the basic composition and 0.02 to 0.30% Mn added was melted and tapped in the laboratory ( After hot-rolling, cold-rolling, and annealing to obtain a cold-rolled steel sheet in the same process as in Experiment 1), a pretreatment process as shown in Table 2 was carried out for pickling time: 1 to 60 minutes, Ni immersion time: 20 minutes. A steel plate that had undergone enameling pretreatment was directly enameled once and fired, and the relationship between the pickling time and the amount of Mn at which the generation of bubbles and sunspots reached L medium or higher was investigated. The results of the decarburized capped steel shown in (Experiment 1) as a comparison steel are also shown in FIG. 4.

As a result, as the amount of Mn decreased, the critical time for occurrence of bubbles and sunspot defects tended to move to the longer side. In particular, significant improvement was achieved in the region where the Mn content was less than 0.10%. Further, when the amount of addition was 0.10% or more, bubbles and black spot defects tended to occur.

The reason for this is still not clear, but the pickling speed is probably slowed down by a decrease in solid solution Mn in the steel, and pickling products (smut) are formed during sulfuric acid pickling in the pre-treatment process.
This is thought to be due to the suppression of the formation and adhesion of In other words, it is thought that by suppressing the adhesion of this smut to the steel sheet surface, the "wettability" between the wax and the steel plate was improved during firing of the wax and the interfacial reaction was promoted. .

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

C: C is an interstitial solid solution element, and if the content exceeds 0.005 wt%, it will significantly harden the material. The present invention is a Ti-added steel, and C becomes a precipitate of TiC and dissolves in solid solution. C
However, when the amount of C increases in terms of wood quality, fine TIC becomes more likely to precipitate.
In the present invention, the upper limit of the C content is set at 0.005 wt% since it deteriorates the material quality.

Mn: Mn usually replaces S, which causes cracking during hot rolling.
It is said to be an effective element for fixing S as S, forming irregularities on the surface of the steel sheet that improve enamel adhesion during pickling in the enamel pre-treatment process, and trapping hydrogen that causes lump defects. Ru. However, in the present invention, since Ti is added, MnS does not precipitate and Mn is in a solid solution state.

When Mn is in a solid solution state, it causes material deterioration, and addition of Mn is undesirable because it unnecessarily increases the cost of molten steel.It also has a very large effect on bubbles and sunspot defects. If the content is 0.10% or more, the pickling speed will be slowed down in the pre-treatment for waxing, a large amount of pickling products (smut) will be generated, and it will adhere and accumulate on the steel plate surface, causing problems with the steel plate during firing. This lowers the wettability of enamel and makes bubbles and black spot defects more likely to occur.In addition, it suppresses interfacial reactions and significantly deteriorates adhesion, so in the present invention, the range of Mn is set to less than 0.10%. And so.

P: Containing more than 0.020 wt% of P not only hardens the material and deteriorates press formability, but also speeds up the pickling speed during waxing pre-treatment, causing smut that causes bubbles and sunspot defects. In addition to increasing the
．． 020 wt%. In addition, although there is no particular stipulation regarding the lower limit, O.
It is preferably up to about t%.

S: S forms precipitates such as Ti5%CuS in the present invention. These precipitates not only form dense irregularities on the surface of the steel sheet that improve the solder adhesion, but also have the effect of trapping hydrogen, which causes jump defects. However, to bring out these effects, at least 0.01
wt% content is required. However, 0.05wt
If the content exceeds 0.0%, the content of Ti that fixes S must be increased, which increases the cost of molten steel and is disadvantageous in terms of material quality.
．． 05 wt%.

A1: A1 is an effective element because it is used as a deoxidizing agent in the steel manufacturing stage, and must be added in an amount of at least 0.003 wt% in order to sufficiently deoxidize. However, A1 is an expensive element, and 0.100
Since adding or containing a large amount exceeding wt% leads to an increase in cost, the upper limit is preferably 0.100 wt%.

Therefore, the range of An content in the present invention is set to 0.003 to 0.00.
It was bound to 100 wt%.

N: Like C, N is normally an element that dissolves in steel and deteriorates the material, but the present invention is a Ti-added steel, and N is a Ti-added element.
Since N precipitates are formed and fixed, there is no particular problem in terms of material quality, and since these precipitates form voids that trap hydrogen, which causes stubble defects, the higher the N content, the better. In order to prevent skipping defects, the content must be at least 0.005 wt%. However, if the content exceeds 0.010 wt%, Ti
'The amount of N added must be increased, which inevitably leads to an increase in cost. Therefore, the range of N content in the present invention is set to O, OO5 to 0. 010 wt%.

However, when REM is added, hydrogen trap sites are formed other than TiN, so 0.005wt%
Even if the N content is below, the skipping defect will not occur. Even so, since a minimum content of 0.002 wt% is required, the range of N content when REM is added is set to 0.002 to 0.010 wt%.

Cu: Cu is an effective element for controlling the pickling speed during pickling in pre-treatment for waxing, and in particular, Ti-added steel like the one of the present invention has a higher rate of pickling than decarburized capped steel. Since the washing speed is about 2 to 3 times faster, the content of Cu is important.

To bring out the effect, at least 0.01wt%
The above content is necessary. However, if the Cu content exceeds 0.07 wt% in the component system of the present invention, the pickling speed becomes too slow and the enamel adhesion on the short-term pickling side decreases. range to 0
．． 01 to 0.07111t%.

S e: The reason why Se is added in the present invention is to improve weldability, especially Ti-added steel has a low zero content in the steel and has a high surface tension, so the shape of the welded part is poor (a concave part is formed). This is to reduce the viscosity of the material and improve the shape of the butt portion after welding. In addition, Se dissolves in crystal grains, causes B to preferentially precipitate at grain boundaries, and has the effect of suppressing corrosion at grain boundaries, which causes bubbles and black spot defects. However, if the content is less than 0.002wt%, these effects will not be achieved, and the pickling rate will increase, causing foam and
This is not preferable because black spot defects are likely to occur.

On the other hand, if the content is more than 0.050 t%, the pickling properties in the pre-waxing treatment will be poor, and dense irregularities, which are advantageous for the soldering adhesiveness, will be difficult to form on the surface of the steel sheet, which is not preferable.

Therefore, in the present invention, the Se content is It was set to 0.002 to 0.050 wt%.

B: B is an element added for the main purpose of the present invention, and its purpose is to prevent C, which originally precipitates at grain boundaries and strengthens the grain boundaries, to be fixed as TiC by adding Ti.
P, which increases the pickling speed, tends to segregate at the grain boundaries, and the grain boundaries on the surface of the steel sheet are preferentially pickled during the pickling process in the pre-soldering process, becoming the starting point for bubbles and sunspots. This is to prevent it from forming.

That is, by adding B, B is precipitated at grain boundaries instead of C, and grain boundary segregation of P is suppressed.
However, if the B content is less than 0,0001 wt%, there is no effect, and if the content exceeds 0,0030 wt%, the mechanical properties of the steel sheet will be significantly deteriorated. The content was set at 0.0030 wt%.

Ti: The content of Ti is (4×C(wt%)+1.S×S(wt%)
%) +3. 43×N (wt%))≦Ti(w
t%) ≦ 0.2 (wt%) is because C significantly deteriorates the mechanical properties of the steel sheet if left in a solid solution state.
, S%N to form precipitates of Tic, TiS, TiN, etc. In order to bring out the effect, at least (4×C(wt%) +1.5×S
(wt%)+3.43×N(wt%)) or more is required. However, 0.2wt
This is because if the content exceeds %, the pickling speed increases and the amount of smut increases, which tends to cause bubbles and black spot defects.

REM: REM forms sulfides, traps hydrogen in the same way as Ti-based precipitates, and can improve flaking resistance. Adding REM eliminates the main cause of bubbles and sunspot defects. This makes it possible to reduce the amount of Ti that can be considered.

The REM content that exhibits this effect is at least 0.01
wt% is required. However, if the content exceeds 0.10 wt%, the pickling rate increases and bubbles and black spot defects are likely to occur, so the upper limit in the present invention is set to 0.10 wt%.

It is desirable to refrain from containing other unavoidable impurities as much as possible, but the content is not particularly limited in the present invention.

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

In the present invention, the hot rolling conditions are usually Ar, and even if hot rolling is finished at a temperature above the transformation point or low-temperature finishing below the Ars transformation point, the enameling properties are not affected much, but the steel sheet machine When importance is placed on physical properties, it is desirable to set the hot rolling finishing temperature to the Ar3 transformation point or higher.

Further, when it is desired to ensure mechanical properties, it is preferable to set the winding temperature to a high temperature, particularly 550° C. or higher. However, if the winding temperature exceeds 650°C, the scale layer will become thicker and descaling performance (pickling performance) will decrease, so the upper limit is 65°C.
It is desirable to set the temperature to about 0°C.

Cold rolling conditions: Cold rolling conditions are also not specified in the present invention, but when producing cold rolled steel sheets with good mechanical properties, especially drawability (lower value), the cold rolling reduction rate should be 70% or more. It is preferable to

Continuous annealing: Continuous recrystallization annealing is desirable because it can complete the annealing process in a short time and also suppresses surface concentration and grain boundary segregation of elements in the steel, which adversely affect the melting properties. .

In addition, if recrystallization is not complete, workability will be significantly impaired, and press cracks may occur when press processing is performed.
On the other hand, at a temperature above the Ar3 transformation point, the recrystallized texture becomes random and the drawability decreases, so the annealing temperature is set in a temperature range of not less than the recrystallization temperature and not more than the Ac3 transformation point.

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

A continuously cast slab with the chemical composition shown in Table 3 was heated to 1200°C.
After heating and holding for 3 hours and rough rolling to form a sheet with a thickness of 30 mm, a hot-rolled sheet with a finishing temperature of 860°C and a thickness of 3.5 mm was formed using a tandem rolling mill, and the sheet was wound up at 620°C.
After pickling, it was made into a cold-rolled sheet with a thickness of 0.8 mm using a 4-stand cold rolling mill, and passed through a continuous annealing line at a heating rate of 10°C/
Recrystallization annealing was performed using a heat cycle with a soaking temperature of 860° C., a soaking time of 3 minutes, and a cooling rate of 20° C./S.

Then, skin pass rolling was performed at a reduction rate of 0.5%.

Thereafter, these steel plates were subjected to enameling pretreatment as shown in Table 1 [pickling time 1 to 60 minutes, Ni immersion time 5 times], direct enameling once, and firing at 820°C for 3 minutes. was applied.

After that, the tendency of occurrence of bubbles and sunspot defects was determined by visual inspection [small,
Medium, large] was investigated and expressed as the pickling time at the limit of bubble/sunspot defect occurrence that would give an evaluation of [medium or above].

In addition, the adhesion test method (ASTM: C313-5) recommended by the PEI adhesion test (P, E, 1.
9)] was used to measure the adhesion.

To measure the flaking resistance, three (n number! 3) degreased steel plates were pretreated with a pickling time of 20 seconds and no Ni immersion, then a commercially available undercoat was applied, and dried. °C/
After baking for 3 minutes, a treatment to promote the occurrence of starch (1
60° C./16 hours), and the number of sheets where skipping occurred was observed and evaluated (number of sheets: 0 was expressed as 0/3).

The mechanical properties were determined by processing the annealed steel plate into JISS No. tensile test specimens, and measuring the yield point (YS), tensile strength (TS), and elongation (EA) at 0°, 45°, and 90° with respect to the rolling direction. )
, Yield elongation (YEj), r value (Lankford value) was measured, and the average value [0° value + 2X45 @ value 190'' value)
/4]. These results are shown in Table 4.

As a result, the cold-rolled steel plate for enameling (Steel 1.2.3.4.12.15.17) manufactured using the composition system of the present invention was found to be
Compared to the conventional decarburized capped steel shown in Figure 2, it has superior press formability and weldability, as well as flaking resistance, bubble and sun spot resistance, and
It was found that the enamel properties such as adhesion were the same or better. However, since the P content of Steel 14 was outside the range of the present invention, bubbles and black spot defects were already generated within 15 to 20 minutes.

Steel 5 had a large amount of Mn and no B was added, so bubbles and black spots were generated after pickling for about 15 minutes. Steel 9 had poor adhesion because the Ss content exceeded the range of the present invention. Steel 13 had a Cu content exceeding the range of the present invention, so the weight loss after pickling decreased and the adhesion decreased. Steels 10 and 11 did not contain Se, so they caused "sink marks" in the welded areas, and because the pickling speed was fast, bubbles and black spot defects were likely to occur.
Further, Steel 7 had significantly poor mechanical properties because the C content exceeded 0.005 wt%. Steel 8 has a low N content, which causes skipping defects, and a high Mn content, so
Bubbles and sunspot defects were likely to occur. Also, steel 16 is N
Because the content was small and the amount of REM added was also small, jump defects occurred.

f! In No. 46, the amount of B added was too large, and the mechanical properties deteriorated significantly.

In addition, in @16, since the amount of REM added was smaller than the range of the present invention, a skipping defect occurred.

<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 superior to conventional decarburized capped steel and conventional decarburized capped steel even when directly enameled once. It is possible to provide a steel plate for direct enameling, which has press workability superior to that of Ti-added steel and is less likely to generate bubbles and black spot defects.

Further, according to the present invention, high-grade steel plates for gauging, which were conventionally manufactured by the ingot method, can be manufactured by the continuous casting method, which brings about great advantages in terms of cost and energy saving.

Note that the steel sheet of the present invention can be used not only for direct one-time application, but also as a steel plate for one-time undercoating and two-time enameling without any change in its properties.

[Brief explanation of the drawing]

Figures 1a, 1b, 1c, 1d, 1e, and 1f show Ti-added steels with different composition systems, respectively.
FIG. 1g is a diagram showing the relationship between the pickling time and the amount of Ni deposited on the adhesion and tendency to generate bubbles and black spot defects in decarburized capped steel. FIG. 2 is a diagram showing the relationship between the limit pickling time for generating bubbles and black spot defects and the amount of B added. FIG. 3 is a diagram showing the relationship between the bubble/sunspot defect generation limit time and the amount of Se added. FIG. 4 is a diagram showing the relationship between the bubble/sunspot defect generation limit time and the amount of Mn. FIG, 1a Pickling Haruma C't) FIG, 1b Dai5 Saki Haruma (No.) FIG, 1c Acid J Running Time (Intermediate) FIG, 1d Pickling Haruma (Su) FIG, 1e Pickling Haruma (Labor) FIG, 1f Acid Sujino Aoma (Bone) FIG, 19 Tori Gloss Washing Time (Minutes) FIG, 2 08001 B Added Calorie Amount (wt %) FIG
, 3 Se Silkworm KaroIt (W”0) FIG, 4 Mn amount (w? '/@ )

Claims (2)

[Claims] (1) In weight ratio: C: 0.005% or less, Mn: less than 0.10%, 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: 0.002-0.050%, B: 0.0001-0.0030%, and (4×C(%)+1.5×S(%)+3.43×
A steel plate for direct single-roll enameling, consisting of N (%))≦Ti (%)≦0.2 (%), the balance being Fe and unavoidable impurities. (2) In weight ratio: C: 0.005% or less, Mn: less than 0.10%, P: 0.020% or less, S: 0.01-0.05%, Al: 0.003-0 .100%, N: 0.002-0.010%, Cu: 0.01-0.07%, Se: 0.002-0.050%, B: 0.0001-0.0030%, REM: 0.01-0.10%, and (4×C(%)+1.5×S(%)+3.43×
A steel plate for direct single-roll enameling, consisting of N (%))≦Ti (%)≦0.2 (%), the balance being Fe and unavoidable impurities.