JPH05156365A - Manufacture of surface treated original plate by continuous annealing - Google Patents

Abstract

PURPOSE:To provide the method for manufacturing a surface treated original plate by continuous annealing capable of high temp. annealing and capable of manufacturing T-3 to T-4 by compact super rapid heating short time annealing and that is low in equipment cost. CONSTITUTION:This cover is (1) the method in which a slab constituted of 0.020 to 0.70% C, 0.05 to 0.60% Mn, 0.001 to 0.025% P, 0.001 to 0.025% S, 0.012 to 0.090% solAl, <=0.0035% N, <=0.0070% T.O and the balance iron with inevitable impurities is subjected to heating and hot rolling under ordinary hot rolling conditions and is coiled into a hot rolled steel strip, which is subjected to cold rolling of >=85% draft, is thereafter subjected to continuous annealing of heating it in the temp. range of at least >=500 deg.C to 650 to 850 deg.C at 300 to 2000 deg.C/s heating rate, holding it for <=3sec and executing cooling to <=400 deg.C at 5 to 35 deg.C/s cooling rate and is subjected to recrystallization annealing and is (2) the method in which C.T is regulated to 660 to 750 deg.C and the regulation value of C and N is widen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of continuously annealing a surface-treating original plate having a hardness level of 3 to 4 in terms of temper degree, which is subjected to a surface treatment such as tin plating or chromic acid treatment. It is about.

[0002]

2. Description of the Related Art The hardness level of a surface-treated original plate to which a surface treatment such as tin plating or chromic acid treatment is applied is 3 in terms of temper degree.
The surface-treating original plates (hereinafter, referred to as T-3 and T-4) of Nos. 4 to 4 are conventionally heated at a heating rate of 10 to 40 ° C./s and uniformly soaked at 600 to 700 ° C. for 20 to 30 seconds to 10 to 20.
Although it was manufactured by a continuous annealing furnace in which it takes about 2 minutes to cool to 500 ° C. at 50 ° C./s and to room temperature at 20 to 40 ° C./s, in this case (1) the annealing time is long. The length of the coil staying in the annealing furnace is more than 1000 m and the equipment length becomes long, which increases the construction cost of the continuous annealing equipment. (2) Such a furnace has a hearth roll to shorten the installation space of the equipment. A vertical pass furnace is used in which the steel strips are placed vertically and the steel strip passes vertically between them.
Therefore, high-temperature annealing that exceeds 700 ° C., which is effective for producing a softer plated original plate, causes a large decrease in the strength of the steel plate, causing wrinkling, which makes it impossible to pass the plate. Therefore, high temperature annealing cannot be performed and it becomes difficult to manufacture a soft steel sheet. (3) In the case of such a furnace,
Since a high-temperature furnace is used for heating and soaking, if the plate thickness changes or if the heating soaking temperature changes, the temperature tracking will be delayed and it will take some time to reach the specified temperature, so it will pass through the adjustment coil. It becomes necessary to adjust the temperature. Therefore, in order to avoid productivity loss, energy loss, etc., it is necessary to schedule the order of sheet passing so that changes in sheet thickness and set temperature are as small as possible, which causes problems such as delivery management of products and inventory increase. Above (1), (2),
There are problems such as (3).

On the other hand, the short-time continuous annealing method has also been devised and studied, and Japanese Patent Publication No. 36-10052, Japanese Patent Publication No. 36-21115, and Japanese Patent Publication No. 40-30.
No. 20, Japanese Patent Publication No. 46-19781, and
"Recrystallization '90 Ed
ited by Chandra The Miner
als, Metals & Materials So
Citation, 1990 ”(hereinafter referred to as Document 1).
There is. However, Japanese Patent Publication No. 36-21155 discloses 20
It must be wound as a coil at 0 to 300 ° C., and there are problems of oxidation, winding equipment, cooling method of the wound coil, and uneven cooling of the inner and outer circumferences of the coil during cooling. Further, Japanese Patent Publication No. 40-3020 has a temper degree of 6
According to the above manufacturing method, Japanese Patent Publication No. 46-19781 discloses H
R ₃₀ T is a method of producing a surface-treated original plate of extremely hard material having a value of 72 or more, and T-3 to T-4 cannot be produced by these methods. Japanese Examined Patent Publication No. Sho 36-10052 discloses that the annealing time for rapid heating and quenching with almost no soaking is about 15
Although it is a short time annealing method of sec, the major problem of this method is that the hardness of the obtained material is HR ₃₀ T of 65 and the temper degree is 5 (hereinafter T-) as shown in Table 1 of the publication. It is the only thing that can be done.

The contents introduced in the literature 1 are 1)
Decarburized annealing of hot rolled rimmed steel, C content 0.005
% Steel is cold-rolled to 70%, 0.2se
As a result of heating at c (about 3500 ° C./s), soaking for 0.1 sec, and quenching with a water spray, 0.5 sec, 0.3
2) that the recrystallization temperature was remarkably lowered as compared with the case of sec heating (about 2000 ° C / s to 3000 ° C / s).
0.5sec, 0.3sec heating (about 2000 ° C / s ~
In the case of 3000 ° C / s), it is introduced that the temperature can be about 830 ° C, 800 ° C or higher. That is, the method of Reference 1 is a decarburization annealing of a hot rolled sheet and a heating rate of 0.2 sec (about 3500 ° C./s) at which it is extremely difficult to control the heating temperature, that is, an extremely minute heating such as 0.01 sec. It can be seen that this method is not suitable for practical use because it requires a heating rate condition that makes it extremely difficult to put it into practical use, in which the temperature fluctuates as much as 35 ° C. due to time variations. As described above, the conventional method of ultra-rapid heating and short-time annealing, which is compact and capable of high-temperature annealing and has a high degree of freedom in threading scheduling, cannot produce soft materials or even at the laboratory level. Method 1) There is still only the method that cannot be put to practical use economically and industrially.

[0005]

The problem to be solved by the present invention is a super rapid heating and short time annealing equipment which is capable of high temperature annealing, has a high degree of freedom in the scheduling of sheet passing, is compact, and has a small equipment cost. It is to provide a method for producing a surface-treated original plate by continuous annealing capable of producing T-3 to T-4.

[0006]

In order to solve the above-mentioned problems, the present inventors comprehensively studied the content of components, hot rolling conditions, cold rolling conditions, and continuous annealing conditions, and the manufacturing method of the present invention. I found it. The gist of the present invention is as follows. (1) C: 0.020 to 0.070% Mn: 0.05 to 0.60% P: 0.001 to 0.025% S: 0.001 to 0.025% Sol Al: 0.012 0.090% N: ≤0.0035% TO: ≤0.0070% A steel slab consisting of the balance unavoidable impurities and iron is heated and hot-rolled under normal hot-rolling conditions, and the winding heat is applied. A steel strip is used, cold rolling is performed at 85% or more, and then continuous annealing is performed at a temperature range of at least 500 ° C. to 300 to 2000.
Surface treatment original plate by continuous annealing characterized by heating to 650 to 850 ° C. at a temperature of 550 ° C./s, holding for 3 seconds or less, and cooling to 400 ° C. or less at a cooling rate of 5 to 35 ° C./s and recrystallization annealing. Manufacturing method.

(2) C: 0.020 to 0.080% Mn: 0.05 to 0.60% P: 0.001 to 0.025% S: 0.001 to 0.025% Sol Al: 0 0.020 to 0.100% N: ≤ 0.0070% TO: ≤ 0.0070% A steel slab composed of the balance unavoidable impurities and iron is heated and hot-rolled to a temperature of 660 ° C to 750 ° C. Rolling hot rolled steel strip at a winding temperature in the range (hereinafter referred to as CT)
% Or more, cold rolling is performed at a temperature of at least 500 ° C. at a temperature of 300 to 2000 ° C./s at 650 to 850 ° C. for 3 seconds or less, and continuous annealing is performed for 5 seconds or more.
A method for producing a surface-treated original plate by continuous annealing, which comprises cooling to 400 ° C. or lower at a cooling rate of 35 ° C./sec and performing recrystallization annealing.

The present invention will be described in detail below. The present inventors, in order to solve the above problems, for the production method, comprehensively examine the component content, hot rolling conditions, cold rolling conditions, continuous annealing conditions, at least in the heating of continuous annealing 300 ~ 200 in the temperature range of 500 ℃ or more
In order to increase the crystal grain size after recrystallization annealing by heating to 650 to 850 ° C. at 0 ° C./s, C: 0.020 to 0.070%, N: ≦ 0. 003
5%, and a method that enables winding at low temperature, as (2) of the invention C: 0.020 to 0.0800%, s
ol Al: 0.020 to 0.100%, N: ≤0.0
070%, a steel slab consisting of the balance unavoidable impurities and iron,
C. in the range of 660 ° C. to 750 ° C. A method of significantly relaxing the restrictions on the C and N contents of the hot rolled steel strip taken up at T, and cooling after soaking at a cooling rate of 5 to 35 ° C./s.
By the three main points of the method of cooling to 00 ° C. or lower to reduce the C content in solid solution, the C content is C: 0.020 to (20) as the invention (1).
0.070%, C: 0.020 as (2) of the invention
Even in the case of steel with a C content of 0.080%, which can be easily obtained by a conventional steelmaking method, T-
It was the first discovery that manufacturing of 3-T-4 was possible.

FIG. 1 shows that the temperature range of at least 500.degree.
It is a figure showing the effect of "heating at 650-850 ° C at 0-2000 ° C / s." The C content was 0.05%, the cold-rolled sheet having a plate thickness of 0.25 mm rolled at a cold rolling rate of 90% produced by the method of the present invention was heated at a heating rate (αH) in the heat cycle shown in FIG. And soaking temperature (T) are changed, time (t) is 0.1 sec, cooling rate (αc) is 10 ° C / s
FIG. 4 is a diagram showing the results of investigating the structure of the heat-treated steel sheet and determining the temperature at which recrystallization is completed. From FIG. 1, it can be seen that the recrystallization completion temperature is remarkably lowered by setting the heating rate to 300 ° C./s. From this, the compact continuous annealing equipment with almost no soaking time
In order to manufacture -3 to T-4, it can be seen that it is extremely important to perform super rapid heating at 300 ° C./s or more in the heating of the continuous annealing which is the point of the present invention. In Document 1, the recrystallization completion temperature is significantly increased to 800 to 830 ° C. at a heating rate of about 1700 ° C./s (t ₁ = 0.5 sec), but the results shown in FIG. 1 are significantly different. The result is. The reason for this is to be examined in detail in the future, but the cold rolling ratio is 70%, which is significantly higher than 90%, and the components, especially T.I. The results were not different because of the influence of different conditions such as the fact that the material obtained by decarburizing and annealing a hot rolled sheet of rimmed steel with a high O content of 0.0375% was used as the test steel. It is thought that.

The mechanism by which a material softer than the conventional 20 ° C./s can be obtained by heating at 300 ° C./s or higher has not been fully clarified. In the case of ultra-rapid heating, since the moving speed of the grain boundaries of the subgrains at the start of recrystallization and the moving speed of the grain boundaries during grain growth are extremely fast, the segregation elements move to the grain boundaries. The number of segregated elements that do not follow and hinder the movement of grain boundaries decreases. As a result, by performing ultra-rapid heating, recrystallization occurs at a lower temperature and grain growth becomes easier, and a softer material can be obtained. It is considered that the cold rolling rate, composition, etc. may affect the generation and size of this subgrain.

B. In the case of ultra-rapid heating, the time between recrystallization and grain growth is so short that AlN fine precipitation hardly occurs before and during recrystallization during grain growth. As a result, by performing ultra-rapid heating, recrystallization was performed at a lower temperature, grain growth was facilitated, and a softer material was obtained. It is presumed that this is due to the effects of the above. The effects of A and B are 30 at least in the temperature range of 500 ° C. or higher during heating in continuous annealing.
It was obtained by heating to 650 to 850 ° C at 0 ° C / s or more.

The point of the present invention is the components and hot rolling conditions for exerting the ultra-rapid heating effect of the point. As (1) of the invention, C: 0.020 to 0.070.
%, N: ≤ 0.0035%, which is a method that enables winding at low temperature, the main condition being that the adverse effect of C becomes too large when the C content exceeds 0.070%.
Further, if the N content exceeds 0.0035%, fine AlN will begin to precipitate even with ultra-rapid heating, and it is necessary to regulate the C and N contents. As (2) of the invention, C:
0.020-0.080%, sol Al: 0.020
˜0.100%, N: ≦ 0.0070%, the balance unavoidable impurities and a steel slab composed of iron are heated to 660 ° C. to 75 ° C.
C. in the range of 0 ° C. With the method of winding hot rolled steel strip at T,
C. in the range of 660 ° C to 750 ° C. The point is to significantly relax the regulation of C and N contents by winding C at T to coagulate and precipitate as coarse cementite to purify the matrix and coarsely precipitate N as AlN to mitigate the adverse effect. Is the way.

The point of the present invention is that the cooling rate from the soaking temperature that is subsequently performed after heating during recrystallization annealing and growing the crystal grains to a sufficiently large size during soaking by the method of the points of the present invention, etc. It is to regulate to 35 ° C / s or less. By limiting the cooling rate to 35 ° C / s or less,
About 40 to 50 p
It becomes possible to make it below pm. as a result,,,
It is possible to manufacture the surface-treated original plate of T-3 to T-4 by the total effect of.

The manufacturing conditions will be described in detail below. C
Is an element that greatly affects the hardness of T-3 to T-4 as described above, and is an important element that affects the crystal grain size after recrystallization annealing during super rapid heating annealing. In the method (1) of the invention, when the C content exceeds 0.070%, T-3 to T-.
Since the hardness of 4 cannot be obtained, the upper limit of the C content is 0.0
70%, and in the method (2) of the invention, the C content is 0.
If it exceeds 080%, the hardness of T-3 to T-4 cannot be obtained, so the upper limit of the C content was made 0.080%. Incidentally, C
If the amount is less than 0.020%, it is necessary to blow down C in the converter. As a result, the T. The O content increases, the inclusions in the steel increase, and the workability of the product deteriorates. Further, as a method for avoiding this, there is a decarburization treatment method by degassing in a steelmaking plant, but there is a problem that the treatment cost becomes too high, so the lower limit C content was set to 0.020%.

If the Mn content exceeds 0.60%, T-
Since the hardness of 3 to T-4 cannot be obtained, 0.60% was made the upper limit. In addition, since less than 0.05% cannot be obtained by an ordinary manufacturing method, the lower limit value is set to 0.05%. P content is
If it exceeds 0.025%, the hardness of T-3 to T-4 cannot be obtained, so 0.025% was made the upper limit. In addition, 0.0
Since less than 01% cannot be obtained by an ordinary manufacturing method, the lower limit value was made 0.001%. If the S content exceeds 0.025%, the hardness of T-3 to T-4 cannot be obtained, so 0.0
25% was made the upper limit. In addition, since less than 0.001% cannot be obtained by an ordinary manufacturing method, the lower limit is set to 0.001%. In the method (1) of the invention, sol Al is sol
If the Al content exceeds 0.090%, a large amount of sol Al will cause precipitation of a large amount of fine AlN even if ultra-rapid heating annealing is performed, so 0.090% was made the upper limit.
If the content is less than 0.012%, the T. Since the O content becomes too high to be 0.0070% or less, the lower limit is set to 0.012%. Further, in the method (2) of the present invention, since it is an element necessary for fixing N as AlN by high temperature winding, sol Al
When the content is less than 0.020%, sol Al becomes insufficient and N cannot be sufficiently precipitated as coarse AlN, and fine AlN comes to be precipitated, and crystal grains are refined during recrystallization annealing. To harden T-3 to T-4
Therefore, the lower limit of sol Al content was set to 0.020%. On the other hand, if it exceeds 0.100%, the material is hardened by solid solution hardening and the hardness of T-3 to T-4 cannot be obtained, so 0.100% was made the upper limit.

In the method (1) of the invention, the N content is N
If the content exceeds 0.0035%, fine AlN will be precipitated due to a large amount of N even after performing ultra-rapid heating annealing, so 0.0035% was made the upper limit. Further, in the method (2) of the present invention, since N is fixed as AlN by high-temperature winding, a soft material can be obtained even if the N content is large, but if the N content exceeds 0.0070%. Since the precipitation amount of AlN becomes too large and the material becomes hard and the hardness of T-3 to T-4 cannot be obtained, 0.0070% was made the upper limit value. It should be noted that the lower the N content, the softer the steel sheet can be obtained, so there is no need to regulate the lower limit value. T. O content is
If it exceeds 0.0070%, air bubbles are generated in the vicinity of the surface layer of the slab, and scratches on the surface of the plating original plate increase, so that a good product cannot be obtained, so 0.0070% was made the upper limit. The lower limit is not regulated because it does not need to be regulated.

The hot rolling conditions do not have to be particularly restricted in the method (1) of the invention, and ordinary hot rolling conditions may be used. The method (2) of the invention is an important step for rendering C and N harmless during winding of hot rolling. At a winding temperature of T less than 660 ° C, the material hardens and the hardness of T-3 to T-4 cannot be obtained, so 660 ° C was set as the lower limit. On the other hand, if the winding temperature exceeds 750 ° C, the scale becomes abnormally thick and the pickling property deteriorates significantly, so 750 ° C was set as the upper limit. It should be noted that the heating conditions for hot rolling are not particularly limited and may be those that are usually performed, but a heating temperature of 1150 ° C. or lower (referred to as SRT) is preferable in order to obtain a softer steel plate.

If the cold rolling ratio during cold rolling is less than 85%, the recrystallization temperature during recrystallization annealing becomes high, the material becomes hard, and it becomes difficult to obtain T-3 to T-4. Since the thickness is thin, if the cold rolling ratio is less than 85%, the thickness of the hot-rolled sheet becomes too thin, which makes hot rolling difficult.
It was set to 5%. It should be noted that the upper limit value 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 its mechanism are as previously inferred. Heating rate is 3
If it is less than 00 ° C./s, the effect of ultra-rapid heating cannot be obtained, the material is hardened, and the hardness of T-3 to T-4 cannot be obtained.
° C / s was set as the lower limit. If the heating rate is higher than 2000 ° C./s, the heating rate is too fast, and the control of the ultimate temperature of heating becomes unstable, and it becomes difficult to obtain stable quality. Therefore, the upper limit is 2000 ° C./s.

If the annealing temperature during the recrystallization annealing is less than 650 ° C., sufficient recrystallization does not occur even in the super rapid heating annealing, and T-3.
The hardness of ˜T-4 cannot be obtained, so 650 ° C. is set as the lower limit value. If the annealing temperature exceeds 850 ° C., the steel sheet is softened and easily spreads when passing through the soaking zone, and the stripability deteriorates. Therefore, 850 ° C. was set as the upper limit value. As for the soaking time during recrystallization annealing, in the ultra-rapid heating annealing, sufficient recrystallization and grain growth occur and hardness of T-3 to T-4 can be obtained even if there is no soaking time, so the lower limit of the soaking time is No need to regulate. The upper limit of the soaking time is set to 3 sec, which is the object of the present invention "due to the continuous annealing capable of producing T-3 to T-4 with an extremely compact continuous annealing equipment capable of greatly reducing the equipment cost. Therefore, the upper limit is set to 3 sec, because it deviates from the idea of "a method for producing a surface-treated original plate".

The cooling condition after the recrystallization annealing is one of the important points of the present invention. To obtain T-3 to T-4, 3 is required.
It is necessary to regulate it to 5 ° C / s or less. Cooling rate is 35 ℃
If it exceeds / s, the solid solution C is not sufficiently reduced, and the hardness of T-3 to T-4 cannot be obtained. If the cooling rate is less than 5 ° C./s, the cooling time becomes too long, and the object of the present invention is to “reduce the equipment cost significantly by using an extremely compact continuous annealing equipment T
-3 to T-4, a method for producing a surface-treated original plate by continuous annealing that can be produced ”.
° C / s was set as the lower limit. The temper rolling may be performed at 0.5 to 2.0% which is usually performed, if necessary.

[0021]

EXAMPLES The effects of the present invention will be described below with reference to examples. The composition shown in Table 1 and a hot rolled steel strip of 2.5 mm were manufactured under the hot rolling conditions and cold rolled at a cold rolling ratio of 90% to 0.25 m.
The cold rolled steel sheet of m was subjected to continuous annealing in the heat cycle shown in FIG. 2 under the temperature and time conditions shown in Table 2 and temper rolling of 1.2% to obtain a surface-treated original sheet. The hardness (HR ₃₀ T) of the obtained surface-treated original plate was measured, and the results are shown in Table 2. Steel A
Is under the manufacturing conditions within the range of the method (1) of the present invention, and steels B and C are within the range of the method (2) of the present invention. E is a manufacturing condition outside the range of the method of the present invention. Samples 1, 2, 3, 4,
Reference numerals 5 and 6 are examples of the method of the present invention.
A plating original plate having a hardness range of -4 (HR ₃₀ T = 58 ± 3 to 61 ± 3) is obtained.

As shown in Table 1, sample 1 is an example in which the components such as C and N contents, hot rolling conditions, and annealing conditions were within the range of the method (1) of the present invention. It is understood that according to the method (1) of the present invention, an original plating plate having an HR ₃₀ T of 58.5 and a hardness range of T-3 to T-4 can be obtained. Samples 2.3, 4,
As shown in Tables 1 and 2, 5 and 6 are examples in which the C and N contents and the annealing conditions were changed within the range of the method (2) of the present invention. It is understood that the plating original plate having the hardness range of T-3 to T-4 can be obtained within the range of the method (2) of the present invention. Sample 7 is C.I. In the comparative example in which the amount of C and N in the method (1) of the present invention having a low T was high, the T-3
It can be seen that a plating original plate having a hardness range of to T-4 cannot be obtained.

[0023]

[Table 1]

[0024]

[Table 2]

Sample 8 is a comparative example in which the cooling rate (αc) at the time of annealing in the method (2) of the present invention is as high as 300 ° C./s, which is a plating base plate in the hardness range of T-3 to T-4. It turns out that is not obtained. Sample 9 has a high C and N content of the method (2) of the present invention and is removed, and the heating rate during annealing is 20 ° C. /
It can be seen that it is not possible to obtain a plating original plate having a hardness range of T-3 to T-4 in the comparative example of s and the same level as the conventional method.
Specimen 10 is a conventional example of continuous annealing conditions which is currently industrially used and has a long soaking time of 30 sec during annealing. Sample 10 has the same level of hardness as sample 4 of the present invention. From this result, it can be seen that the effect of ultra-rapid heating at 1000 ° C./s has great industrial value.

[0026]

Although the present invention has been described in detail above, according to the present invention, it is possible to perform high temperature annealing, have a high degree of freedom in the scheduling of sheet passing, be compact, and reduce the equipment cost for ultra-rapid heating in a short time. With continuous annealing equipment, T-3 to T-
The surface-treated original plate of No. 4 can be manufactured, and its industrial value is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a heating rate in continuous annealing and hardness after reflow,

FIG. 2 is a diagram showing a heat cycle of continuous annealing used in an investigation experiment and an example.

Claims (2)

[Claims] 1. C: 0.020 to 0.070% Mn: 0.05 to 0.60% P: 0.001 to 0.025% S: 0.001 to 0.025% Sol Al: 0.0. 012 to 0.090% N: ≤ 0.0035% TO: ≤ 0.0070% A steel slab composed of the balance unavoidable impurities and iron is heated under normal hot rolling conditions, hot rolled, and wound. Hot-rolled steel strip, cold-rolled at 85% or more, and then continuously annealed at a temperature range of at least 500 ° C to 300-2000.
Surface treatment original plate by continuous annealing characterized by heating to 650 to 850 ° C. at a temperature of 550 ° C./s, holding for 3 seconds or less, and cooling to 400 ° C. or less at a cooling rate of 5 to 35 ° C./s and recrystallization annealing. Manufacturing method 2. C: 0.020 to 0.080% Mn: 0.05 to 0.60% P: 0.001 to 0.025% S: 0.001 to 0.025% Sol Al: 0.0. 020 to 0.100% N: ≤ 0.0070% TO: ≤ 0.0070% A steel slab composed of the balance unavoidable impurities and iron is heated and hot-rolled in the range of 660 ° C to 750 ° C. It is made into a hot rolled steel strip at a coiling temperature of 85%, cold rolled at 85% or more, and then heated at a temperature range of at least 500 ° C to 650 to 850 ° C at 300 to 2000 ° C / s by continuous annealing. And holding for 3 seconds or less, cooling to 400 ° C. or less at a cooling rate of 5 to 35 ° C./sec and performing recrystallization annealing, a method for producing a surface-treated original plate by continuous annealing.