JP3383019B2 - Manufacturing method of non-ageing soft surface treated original sheet with excellent corrosion resistance after working by continuous annealing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is a non-aging agent which has excellent corrosion resistance after processing when the hardness of the surface-treated original plate which is subjected to surface treatment such as tin plating or chromic acid treatment is 1 to 3 in temper degree. The present invention relates to a method for producing a surface treatment original plate by continuous annealing.

[0002] A soft surface-treated steel sheet is often formed into a can that is subjected to considerably severe pressing, and in this case, the soft surface-treated original plate is often subjected to severe pressing after being coated. When used for such an application, the properties required of the steel sheet are not only the non-aging property, but also the crystal grain size of the steel sheet must be fine. This is because if the crystal grain size is large, the surface that has undergone severe processing will have rough skin in proportion to the crystal grain size, and the coating layer applied to secure the plating layer and corrosion resistance will be damaged, Corrosion resistance is significantly deteriorated. G. of that limit Sno is about 9.5, and in order to eliminate such deterioration of corrosion resistance after working, G.S. Sno needs to be 9.5 or more.

[0003]

2. Description of the Related Art The degree of temper to which surface treatment such as tin plating or chromic acid treatment is applied is 1 to 3 (hereinafter, "T-1 to T
The non-aging soft surface treatment original plate (referred to as "-3") has been manufactured by a box annealing method which requires an annealing time of 2 to 3 days. For applications requiring corrosion resistance after working, the annealing temperature may be lowered or the C content may be increased. It has been manufactured with Sno as 9.5 to 11.0. However, this method has a drawback that the productivity is extremely poor because it is a batch method and requires 2 to 3 days for annealing.

The continuous annealing method, which has relatively good productivity, is used for T-
As a method of producing the non-aging soft surface-treated original plate of 1 to T-3, there is a method of using steel in which a carbide forming element such as Ti or Nb is added to ultra-low carbon steel. However, this method has the following two major problems.

The first problem is that this method is a method of completely non-aging by fixing C as a stable carbide with Ti or Nb. At the laboratory level, a soft and completely non-aging material is obtained. However, in order to manufacture it with continuous annealing equipment (hereinafter referred to as “current CAL”) that is currently in practical use, steel with Ti or Nb added in an amount higher than that at which non-aging is obtained has a recrystallization temperature. Significantly increases and exceeds the upper limit of the annealing temperature at which the current CAL can be manufactured, which is a major obstacle. Practically, steel containing carbide forming elements such as Ti and Nb is used, and it is practically impossible to manufacture a non-aging soft material by the current CAL method. In the current CAL, as the annealing temperature is increased, the strength of the steel sheet softens as the temperature of the steel sheet rises, and the tension applied to pass the steel sheet inside the furnace extends the steel strip or the steel sheet is installed in the furnace. At the portion of the hearth roll, overlapping wrinkles of plates called "throttle" may occur, causing fracture in the furnace and defective products. The upper limit temperature at which such defects do not occur is the upper limit temperature of the continuous annealing furnace.

The second problem is that in order to alleviate the above-mentioned first problem of this method, the minimum Ti necessary for non-aging is applied to the ultra-low carbon steel whose C content is reduced as much as possible. Or Nb
Although it is necessary to reduce the recrystallization temperature as much as possible by adding G., the surface-treated original plate annealed by the current CAL method in which Ti or Nb is added to this ultra-low carbon steel is G. Sno is 8.0-1
The problem is that the value is 0.0, which is too large to secure the corrosion resistance after processing.

The ultra-short continuous annealing method according to the present invention has been studied so far, and is disclosed in Japanese Examined Patent Publication No. 36-100.
52, Japanese Patent Publication No. 36-21155, Japanese Patent Publication No. 4
It is disclosed in Japanese Patent Publication No. 0-3020 and Japanese Patent Publication No. 46-19781. However, the above Japanese Patent Publication No. 36-21155
Japanese Patent Laid-Open Publication No. 2003-242242 has a problem that it must be wound as a coil at 200 to 300 ° C., there is a problem of oxidation, a problem of winding equipment, a cooling method of a wound coil, or a problem of uneven cooling of the inner and outer circumferences of the coil during cooling. In addition, the above Japanese Patent Publication No. 36-10052
Publication, Japanese Patent Publication No. 40-3020, Japanese Publication No. 46-1
In both 9781 and Japanese Patent Publication No. 40-3020, it is impossible to manufacture non-aging soft surface-treated original plates T-1 to T-3.

[0008]

DISCLOSURE OF THE INVENTION The present invention has no problems in production and has good productivity in continuous annealing by T-1 to T-.
It is an object of the present invention to provide a method for producing a non-aging soft surface-treated original plate having excellent corrosion resistance after processing of item 3.

[0009]

In order to solve the above-mentioned problems, the inventors of the present invention comprehensively studied the steel composition, hot rolling conditions, cold rolling conditions, and continuous annealing conditions, and conducted the manufacturing method of the present invention. The present invention has been found and the gist of the present invention is as follows. (1) C: 0.0005 to 0.0050%, Mn:
0.05-0.60%, P: 0.001-0.025
%, S: 0.001 to 0.025%, solAl: 0.
030 to 0.120%, N: more than 0.0060 to 0.01
70%, Nb: {7.75 x [C (%)-0.000
4] × 0.65}% to 0.023%, T.I. O: ≤0.0
070%, the balance unavoidable impurities and steel slab consisting of iron,
Heating under normal conditions, hot rolling, 640-750
Rolled hot-rolled steel strip at 80 ° C., cold rolled at 85% or more, and then continuously annealed at a temperature range of at least 500 ° C. at a recrystallization temperature of up to 850 ° C. at 100 ° C./s or more. Excellent corrosion resistance after processing by continuous annealing characterized by holding for less than a second, then performing recrystallization annealing to cool to room temperature, and then performing temper rolling in the range of 0.6 to 3.5% Method for producing non-aging soft surface-treated original plate. (2) In the method of (1) above, in hot rolling,
A method for producing a surface-treated original plate by continuous annealing, which comprises heating to 1000 to 1180 ° C. and hot rolling under normal conditions.

The present invention will be described in detail below. The inventors of the present invention have developed an extremely low carbon steel containing Nb that can achieve stable non-aging and does not cause the formation of inclusions (deoxidation products in steelmaking) that inhibit the corrosion resistance of the surface-treated original plate. Using this, various studies were made on a method for producing a non-aging soft surface-treated original plate having excellent corrosion resistance after processing of T-1 to T-3 by a continuous annealing method with good productivity without any problems in production.

First, as a preliminary study, it is considered that the difficulty of high temperature annealing in the continuous annealing method described above is caused by the contact of the steel sheet with the hearth roll, and the residence time in the high temperature region is considered. Was investigated, that is, a method of performing recrystallization annealing at the same heating rate as the current CAL with the soaking time being substantially zero. However, it was found that the recrystallization temperature of Nb-added ultra-low carbon steel when the soaking time was almost zero was significantly higher than that when the soaking time was about 20 seconds, making it difficult to put into practical use. did.

Further, various methods were examined, and experimental results were obtained in which the recrystallization temperature of the Nb-added ultra-low carbon steel was remarkably lowered when ultra-rapid heating at about 1000 ° C./s was performed. Therefore, in order to examine this in more detail,
Regarding the recrystallization temperature of the Nb-added ultra-low carbon steel, the content of components, hot rolling conditions, cold rolling conditions, and continuous annealing conditions were comprehensively examined, and "C: 0.0005 to 0.0050%,
Nb: {7.75 x [C (%)-0.0004] x 0.
65}%-0.023%, at least 50 in continuous annealing
Recrystallization temperature in the temperature range of 0 ° C or higher at 100 ° C / s or higher to 8
It has been found that it is possible to manufacture a non-aging soft surface-treated original plate by continuous annealing whose main point is to "heat to 50 ° C. and anneal for 3 seconds or less".

However, the G.V. Sno is
In the range of 8.5 to 10.0, the G.V. required to secure the corrosion resistance after processing, which is the target of the present invention. Sno: We couldn't secure more than 9.5. Therefore, the present inventors have found that G. Sno: ≧ 9.5, various examinations have been made on the conditions under which the N content is 0.0050% or more. It was found that Sno: ≧ 9.5 can be made into fine particles.

FIG. 1 shows that the temperature range of at least 500.degree.
It is the figure which showed the effect of "heating to a recrystallization temperature-850 degreeC above (degreeC) / s." C produced by the method of the present invention:
0.0022%, Nb: 0.019%, solAl:
0.067%, N: 0.0075%, slab heating temperature (hereinafter referred to as “SRT”): 1140 ° C., C.I. T: 6
For a 0.25 mm cold rolled steel sheet rolled at 30 ° C. and a cold rolling rate of 90%, the heating rate (α _H ) and the soaking temperature (T) were changed by the heat cycle shown in FIG. 0.1
sec, the cooling rate (α _c ) was set to 200 ° C./s, the structure of the heat-treated steel sheet was investigated, and the temperature at which recrystallization was completed was determined. The result is shown in FIG.

From FIG. 1, the heating rate is 2 as in the current CAL.
At 0 ° C./s, it was found that the recrystallization temperature remarkably rises, as described above. The result of this experiment is
Even if there is no soaking time, since the recrystallization temperature is too high, the strength of the steel sheet is significantly reduced, and it can be easily predicted that it is difficult to pass the high temperature portion in a good shape.

On the other hand, at the ultra-rapid heating rate of 100 ° C./s or more within the range of the present invention, the recrystallization completion temperature is remarkable even at a steel ratio containing a large amount of N and under conditions with little holding time. It was found that a significant decrease was obtained. From this experimental result, according to the present invention, T-1 to T-
It became clear that it is possible to manufacture a soft surface-treated original plate of No. -3.

Although the mechanism of lowering the recrystallization temperature by heating at 100 ° C./s or more as compared with the conventional 20 ° C./s has not been sufficiently clarified, it is due to the effects of A and B below. It is speculated that it may be. These effects of A and B were obtained by heating at a temperature range of at least 500 ° C. or higher at a recrystallization temperature of 850 ° C. to 850 ° C. at a temperature of 100 ° C./s or higher in heating in continuous annealing.

A. In the case of ultra-rapid heating, since the time between recrystallization and grain growth is too short, fine precipitation of NbC or AlN hardly occurs during grain growth before or during recrystallization. As a result, Nb-added ultra-low carbon steel was
The remarkable increase in recrystallization temperature observed when heating at a slow heating rate of about s is eliminated, and by performing ultra-rapid heating, recrystallization occurs at a lower temperature and grain growth is facilitated to obtain a soft material. Like B. In the case of ultra-rapid heating, the movement speed of the grain boundaries of the subgrains at the start of recrystallization and the movement speed of the grain boundaries during grain growth are extremely fast, so that the segregation elements move to the grain boundaries. It does not follow and segregation elements that hinder the movement of grain boundaries are reduced. As a result, by performing ultra-rapid heating, recrystallization occurs at a lower temperature, grain growth is facilitated, and a softer material can be obtained. It is considered that the cold rolling rate, components, etc. may affect the generation and size of this subgrain.

FIG. 3 shows the non-aging T which is the object of the present invention.
It is the figure which showed the main points about the method of obtaining the soft surface treatment original plate of -1 to T-3. The present inventors have produced cold-rolled sheets of 0.25 mm at 90% cold rolling rate using the hot-rolled sheets of various C contents containing about 75 ppm of N produced in the present invention. Then, in the heat cycle shown in FIG. 3, the heating rate (α _H ) was 1000 ° C./s and the soaking temperature (T) was 75.
0 ° C., time (t) 0.1 sec, cooling rate (α _c ) 2
A heat-treated annealed plate at 50 ° C / s is temper-rolled at a temper rolling ratio of 1.5% to produce a surface-treated original plate, which is tin-plated to produce a tin plate, which is non-aging , Hardness and texture under an optical microscope were investigated.

The non-aging evaluation was performed by subjecting the various tin plates thus obtained to a heat treatment at 200 ° C. for 30 minutes, which is equivalent to baking by coating, and performing a tensile test to measure YP-E1 and YP-E1.
Those with E1 of less than 0.5% were regarded as non-aging.

Further, the hardness ( _HR30T ) was measured and T-
It was evaluated whether or not the soft materials 1 to T-3 were obtained, and the presence or absence of uncompleted crystal grains was also examined by the structure examination with an optical microscope. As a result, all of the completely recrystallized products had a soft hardness of T-3 or less within the range of the present experiment.

Based on the above survey results, the conditions for ensuring non-aging can be summarized and the C content is 5 to 50.
In the ppm range, the Nb content is {7.75 × [C (%)
It has been clarified that when the content is −0.0004] × 0.65}% or more, good non-aging resistance with excellent corrosion resistance after processing can be obtained. The applicable range is shown in FIG. Further, in the range where the soft material of T-1 to T-3 can be obtained without remaining unfinished crystal grains, the Nb content is 0.
If it exceeds 023%, unrecrystallized grains will remain even if recrystallization annealing is performed by the ultra-rapid heating method, and a soft material of T-3 or less cannot be obtained. Therefore, the upper limit of the Nb content is shown in FIG. Indicated as.

FIG. 4 is a diagram showing the effect of adding N in excess of 60 ppm to improve the corrosion resistance after working, which is the object of the present invention. Using the hot-rolled sheets with various N contents produced according to the present invention, cold-rolled sheets of 0.25 mm were produced at a cold rolling rate of 90%. Then, in the heat cycle shown in FIG. 3, the heating rate (α _H ) was 1000 ° C./s and the soaking temperature (T) was 75.
0 ° C., time (t) 0.1 sec, cooling rate (α _c ) 2
FIG. 4 shows the results of examining the structure with an optical microscope after heat treatment was performed at 50 ° C./s to obtain an annealed plate.

G. of annealed sheet The number of Sno increases as the N content increases, and the particles become significantly finer. It has been clarified that the N content should be more than 60 ppm or more to secure the excellent corrosion resistance after processing.

The manufacturing conditions will be described in detail below.
As shown in FIG. 3, C is an element that greatly affects the non-aging property. The amount of Nb required for non-aging significantly increases as the C content increases, and when the C content exceeds 50 ppm, unrecrystallized grains remain and a soft material cannot be obtained. C content of 50 ppm. Also,
When the C content is less than 0.0005%, it becomes difficult to manufacture the steel by a vacuum degassing method for ordinary steelmaking. Therefore, the lower limit C content is set to 0.0005%.

Mn, P, and S not only harden the material but also deteriorate the corrosion resistance of the steel sheet when these elements increase, so the upper limit of each element is 0.60%,
It was set to 0.025% and 0.025%. Incidentally, Mn, P, S
The lower limit of each of the above was defined as the lower limit of the range obtained by the usual production method.

In order to achieve non-aging, the amount of solAl must be fixed as N by fixing N as AlN, and at least 0.030% must be contained.
In addition, solAl not only hardens the material when it is contained in a large amount, but also deteriorates the corrosion resistance of the steel sheet, so the upper limit was made 0.120%.

N is precipitated as AlN during hot rolling,
The grain refining effect in recrystallization annealing by refining the crystal grain size of the hot rolled sheet, and the Al deposited on the hot rolled sheet
The N grain refinement effect in the recrystallization annealing by N, further the grain refinement effect by AlN precipitated during annealing, and the like serve to refine the annealed plate and improve the corrosion resistance after working. When the N content exceeds 0.0060%, the G. S
No can be 9.7 or more. If the N content exceeds 0.0170%, bubbles due to N are generated in the slab, and the corrosion resistance of the surface-treated steel sheet is impaired.
The upper limit content of was set to 0.0170%.

Nb is an important element for fixing C as NbC and achieving non-aging. The Nb content is {7.75 × [C (%) − 0.0004] × 0.65}
% Or more, excellent non-aging property can be obtained. Also, Nb
If the content exceeds 0.023%, unrecrystallized grains will remain even if recrystallization annealing is performed by the ultra-rapid heating method of the present invention, and a soft material of T-3 or less cannot be obtained. ,
The upper limit was 0.023%.

T. If the O content exceeds 0.0070%, air bubbles are generated near the surface layer of the slab, surface scratches on the plating base plate increase, and not only a good product cannot be obtained, but also a soft material cannot be obtained. The upper limit was 0.0070%. The lower limit value is not restricted because it does not need to be restricted.

In order to prevent N aging due to a large amount of N contained in the hot rolling condition, in the above method (1), "heating under normal conditions and hot rolling are performed at 640 to 750 ° C.
In addition, in the method of (2), "heated to 1000 to 1180 ° C. and hot-rolled under normal conditions to obtain a rolled hot rolled steel strip". This is very important.

In the method (1), most of a large amount of N can be precipitated as AlN by winding at 640 to 750 ° C., and the remaining small amount of solute N is precipitated during annealing. This is a method of preventing N aging. When the winding temperature is lower than 640 ° C, Al in the hot rolled sheet
Precipitation of N becomes insufficient and N aging cannot be prevented, so 640 ° C. was made the lower limit. The winding temperature is 75
If the temperature exceeds 0 ° C, the scale becomes very thick, and the scale cannot be completely removed during pickling, resulting in scale defects, which deteriorates the corrosion resistance of the surface-treated steel sheet. Therefore, the upper limit of the coiling temperature was set to 750 ° C.

The method (2) is 1000 to 1180.
A large amount of a large amount of N can be precipitated as AlN by heating to ℃ and hot rolling under normal conditions. Similarly, the remaining small amount of solid solution N is annealed during annealing. It is a method of preventing N aging by precipitating. If the slab heating temperature exceeds 1180 ° C, AlN during slab heating
1180 because the amount of re-dissolved solid solution of Al increases and the precipitation amount of AlN in the hot-rolled sheet becomes insufficient and N aging cannot be prevented.
The upper limit was ℃. The slab heating temperature is 1000 ° C.
If it is less than 100%, the temperature for finish rolling cannot be secured, so the lower limit slab heating temperature is set to 1000 ° C.

The other hot rolling conditions do not need to be particularly restricted and may be ordinary hot rolling conditions. When the cold rolling ratio during cold rolling is low, the recrystallization temperature during recrystallization annealing is high and the material becomes hard,
It becomes difficult to obtain T-1 to T-3, and plated products are
Since the plate thickness is thin, a cold rolling ratio of less than 85% makes the plate thickness of the hot-rolled plate too thin and makes hot rolling difficult. Therefore, the lower limit value was set to 85%. The upper limit is not regulated because it does not need to be regulated.

The heating rate of recrystallization annealing during continuous annealing is the most important point of the present invention, and its effect and mechanism are as previously inferred. Heating rate is 300
If the temperature is less than ℃ / s, the ultra-rapid heating effect cannot be obtained, and the material is hardened so that the hardness of T-1 to T-3 cannot be obtained.
The lower limit value was / s.

The annealing temperature at the time of recrystallization annealing is the steel under the conditions of the present invention, and if recrystallization is completely completed, a soft material of T-3 or less can be obtained. And Further, when the annealing temperature exceeds 850 ° C., the crystal grain growth increases during recrystallization annealing, and G. Sno: Since it becomes larger than the crystal grain of 9.5, 850 ° C. was made the upper limit value.

The soaking time during the recrystallization annealing is such that in the ultra-rapid heating annealing, sufficient recrystallization and grain growth occur even if there is no soaking time, and a hardness of T-1 to T-3 can be obtained. There is no need to regulate the lower limit value of. Upper limit of soaking time is 3 seconds
That is, the purpose of the present invention is to provide an extremely compact continuous annealing equipment that can significantly reduce equipment costs, such as T-1 to T-
3 is a method for producing a non-aging surface-treated original plate having excellent corrosion resistance after working by continuous annealing that can be produced in No. 3 ”.

The cooling conditions after recrystallization annealing do not have to be restricted within the range of the steel composition of the present invention because they have no particular effect on the material, and there is no need to control the cooling conditions.
It may be cooled to room temperature by a strong gas jet cooling method such as 0 ° C./s. Further, overaging treatment for a few seconds to several minutes at around 300 to 500 ° C. has almost no effect on the material, so there is no effect of overaging treatment, but overaging treatment can be performed.

In temper rolling, it is necessary to perform at least 0.6% temper rolling in order to stably obtain the effect of temper rolling. Therefore, 0.6% is the lower limit temper rolling rate. . Also,
2. The temper rolling of the surface-treated original plate is usually dry temper rolling, and the limit of 3.5% is the limit in dry temper rolling.
The upper limit was 5%.

[0040]

EXAMPLES The present invention will be further described below based on examples. A steel having the components shown in Table 1 was manufactured into a hot rolled steel strip of 2.5 mm under the hot rolling conditions shown in Table 2, and the cold rolling rate was 90%.
A cold rolled steel sheet of 0.25 mm was obtained. Then, in the heat cycle shown in FIG. 2, continuous annealing and 1.6% temper rolling were performed under the temperature and time conditions shown in Table 2 to obtain a surface-treated original plate,
This was tin-plated to produce a tin plate. The hardness ( _HR30T ) and the grain size number of the obtained tin plate were measured, and the results are shown in Table 2. The evaluation of non-aging is carried out by painting various tin plates obtained by painting and baking at 200 ° C for 30 min.
Was subjected to a heat treatment, a tensile test was performed, and YP-E1 was measured, and those in which YP-E1 was less than 0.5% were regarded as non-aging. Table 2 shows the non-aging properties as ◯, and the non-aging properties as x.

All of the steels A, B, C, D and E are steels having a composition within the scope of the present invention. Steels A, B, and C have different C contents of 12, 25, and 36 ppm, and Nb contents of 0.017, 0.017, and 0.021%, respectively. Steel D has 0.52% Mn added to increase hardness, and Steel E has 0.0120% N.
It was added.

Steel F has a N content as low as 0.0018%, which is outside the scope of the present invention. Steel G is C
The content is as high as 0.0075%, and the Nb content is 0.
016%, which is below the lower limit of Nb content necessary for non-aging, and is outside the scope of the present invention. Steel H is N
The content of b is 0.033%, which is outside the upper limit of the present invention and is out of the upper limit.

[0043]

[Table 1]

[0044]

[Table 2]

Samples 1, 2, 3, 4, 5, 6, 7 are examples of the present invention. In both cases, the G.I. of the annealed sheet required for ensuring non-aging property and corrosion resistance after working in the hardness range of T-1 to T-3 (H _R30T = 49 ± 3 to 57 ± 3). Sno: 9.5 or more is secured. According to the present invention, it is found that it is possible to manufacture non-aging and soft T-1 to T-3 that are excellent in corrosion resistance after processing by the ultra-rapid heating short-time annealing method that is compact and has low equipment cost. .

Sample 6 is the one of the present invention in which Mn is as high as 0.52% and the hardness level is in the range of T-2.5, and the non-aging property and the grain refining can be secured. . Samples 8, 9,
No. 10 is a comparative example in which the amounts of N, C and Nb were out of the range of the present invention. Sample 8 is a G.I. Sno is 8.
9 and coarse grains, Sample 9 cannot secure non-aging property, and Sample 10 is hard because unrecrystallized grains remain.

[0047]

EFFECTS OF THE INVENTION According to the present invention, the continuous annealing equipment capable of high-temperature annealing, compact and low equipment cost, and ultra-rapid heating for a short time provides excellent corrosion resistance after processing T-1 to T-3. It becomes possible to manufacture an aging surface-treated original plate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the relationship between the heating rate and the recrystallization temperature in continuous annealing according to the present invention.

FIG. 2 is an explanatory view showing a heat cycle of continuous annealing according to the present invention.

FIG. 3 is an explanatory view showing regions of C content and Nb content in which the soft materials T-1 to T-3 could be secured by the non-aging property in the present invention.

FIG. 4 is a graph showing the N content and G. Sno
FIG.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keiichiro Nagano 1 Fuji-machi, Hirohata-ku, Himeji-shi, Hyogo Nippon Steel Co., Ltd. Hirohata Works (56) References Japanese Patent Laid-Open No. 6-184643 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21D 9/46 C21D 8/02 C22C 38/00 301 C22C 38/12

Claims (2)

(57) [Claims] 1. C: 0.0005 to 0.0050%, M
n: 0.05 to 0.60%, P: 0.001 to 0.02
5%, S: 0.001-0.025%, solAl:
0.030-0.120%, N: more than 0.0060-0 .
0170%, Nb: {7.75 x [C (%)-0.00
04] × 0.65}% to 0.023%, T.O. O: ≤0.
A steel slab consisting of 0070% and the balance unavoidable impurities and iron is heated under normal conditions and hot rolled to give 640 to 7
A hot-rolled steel strip is taken up at 50 ° C., cold-rolled at 85% or more, and then heated at a temperature range of at least 500 ° C. at 100 ° C./s or more to a recrystallization temperature to 850 ° C. by continuous annealing. Hold for 3 seconds or less, then perform recrystallization annealing to cool to room temperature, and then temper rolling 0.6 to 3.
A method for producing a non-aging soft surface-treated original plate having excellent corrosion resistance after working by continuous annealing, which is characterized by being applied in a range of 5%. 2. C: 0.0005 to 0.0050%, M
n: 0.05 to 0.60%, P: 0.001 to 0.02
5%, S: 0.001-0.025%, solAl:
0.040-0.120%, N: more than 0.0060-0 .
0170%, Nb: {7.75 x [C (%)-0.00
04] × 0.65}% to 0.023%, T.O. O: ≤0.
A steel slab consisting of 0070% and the balance unavoidable impurities and iron is heated to 1000 to 1180 ° C., hot rolled under normal conditions to obtain a rolled hot rolled steel strip, and cold rolled to 85% or more. , Then at least 500 ℃ in continuous annealing
Recrystallization temperature up to 850 at 100 ° C / s or more in the above temperature range
Recrystallization annealing is performed by heating to 0 ° C, holding for 3 seconds or less, and then cooling to room temperature, and then temper rolling 0.6 to.
A method for producing a non-aging soft surface-treated original plate having excellent corrosion resistance after processing by continuous annealing, which is characterized by being applied in a range of 3.5%.