JP3046128B2 - Method for producing hard surface-treated original sheet with excellent workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an original hard surface-treated sheet subjected to a surface treatment such as tin plating or chromic acid treatment.
The present invention relates to a method for producing an original plate for hard surface treatment excellent in workability, in which the proof strength of a steel sheet after baking coating processing after can-making processing is 56 kgf / mm ² or more.

[0002]

2. Description of the Related Art A hard surface-treated original sheet subjected to a surface treatment such as tin plating or chromic acid treatment is used for DR-8, 9, 10 which is used while being subjected to a temper rolling of 20 to 40%. There is a so-called DCR material. This hard material is used for drawn cans, redrawn cans and the like. The strength (strength against internal pressure) of these cans can be ensured even with a smaller thickness by increasing the strength of the steel sheet by DCR. DCR materials on the market have hardness or proof stress standards, and are DR-8, 9, 10 (56, proof stress,
63, 70 kgf / mm ² ). These are manufactured by performing cold rolling of 20 to 40% on a cold-rolled steel sheet manufactured by a continuous annealing method or a box annealing method and adjusting the strength to a predetermined strength. DR-8, 9, 10 manufactured in this way are 20 to 4
Since 0% cold rolling is still performed, there is almost no ductility and El is less than 1%. Therefore, there is a problem that it cannot be used for applications requiring workability. Also, 20
There is a problem that a special temper rolling mill for performing a temper rolling of 40% is required.

As a method for solving this problem, the present inventors have proposed (A) to increase the cooling rate after recrystallization annealing during continuous annealing to form a quenched structure, increase the strength, and reduce the temper rolling ratio to a normal range. (B) a method of increasing the strength by using the baking hardening ability of solid solution C and N by using heat at the time of paint baking after can-making, and (C) a method of combining both. The conventional method was investigated. This (A), (B),
Concerning the method (C), the continuous annealing method has an annealing time of 20 hours.
As a result of investigating a conventional method for an extremely compact and economical method in less than sec, the methods (B) and (C) were not found, but for the method (A),
Japanese Patent Publication No. 40-3020, Japanese Patent Publication No. 46-19781
There is an official gazette.

Japanese Patent Publication No. 40-3020 discloses a method which is not a compact continuous annealing method. However, after heating to 740 to 850 ° C., it is rapidly cooled from this temperature to a temperature range of 150 to 250 ° C., and overaged in that temperature range. This is a method of curing to the desired strength. According to the specification, it is specified that when the overaging treatment is performed at 200 ° C., an overaging treatment time of about 30 minutes is required. Therefore, the continuous annealing method requires 150 to 25 minutes.
A method has been proposed in which overaging treatment is performed by winding at a temperature of 0 ° C. This method has a disadvantage that the cooling rate is higher in the vicinity of the outermost periphery and the vicinity of the innermost periphery of the coil after winding than in the center of the coil, so that the effect of overaging treatment is lost and the strength is reduced. Further, the greatest advantage of the continuous annealing method is the continuity of the annealing step and other steps, and the recent continuous annealing equipment is also continuous with the temper rolling mill so that higher productivity can be obtained. However, this method has a serious problem that continuation with a temper rolling mill is impossible because over-aging treatment is required for 30 minutes.

Japanese Patent Publication No. 46-19781 discloses that a temper rolling after annealing is omitted, and a hard ultra-thin sheet without kink and Ruders wire is produced using a non-alloy steel for a low carbon tin plate. It is intended to be. The problem with this method is that, first, the steel sheet has an extremely high temperature range, such as 840 ° C. to 900 ° C., at which the steel sheet becomes extremely soft and difficult to pass through in a continuous annealing furnace. Although the results of the survey on the strength after the coating treatment have not been reported, the strength has not been reached in the follow-up survey results of the present inventors as shown below, and in this method, the strength intended by the present invention is not achieved. That is, it is determined that a steel sheet of a level cannot be obtained. This method is to produce a hard ultra-thin plate without kink and Luders wire by lowering the yield point, and the method of the present invention is to increase the strength (YP after paint baking). This is an invention whose purpose is essentially different from that of the publication.

[0006] The follow-up survey by the present inventors is described in the specification of the gazette .
(FIG. 2b). Investigation was conducted on the typical strength of P exceeding 56 kgf / mm ² to determine the strength after baking. Investigations were carried out for those having an annealing temperature of 750 ° C. or lower, which are indicated as out of the claims, in the same manner as in the condition of FIG.
A steel plate prototyped in a laboratory experiment using an A1-K steel having an amount of 5% C and 0.3% Mn under the conditions according to the same publication was subjected to artificial aging at 200 ° C. for 10 minutes, and Y. P was investigated. As a result, it was found that, contrary to the natural aging results of the same publication (FIG. 2b), aging softening occurred conversely, and the desired strength of 56 kgf / mm ² or more could not be obtained.

[0007] As described above, Japanese Patent Publication No. 46-19781 has a different purpose and a different idea from the method of the present invention. Further, as a result of the investigation described in the specification, it was found from the examples that the method disclosed in the publication could not produce the steel sheet intended by the present invention.

As a result of studies by the present inventors on such aging softening, cooling after annealing is reduced by 250%.
° C / s, which is extremely fast, so that a large amount of solid solution C remains and precipitates as slightly larger carbides by artificial aging at 200 ° C for 10 minutes, so that so-called aging softening may occur. , And extremely fine unstable precipitates are precipitated in a very large amount.
Occurred (FIG. 2b).

As described above, the method using DCR has poor workability, and the method not using DCR has problems such as low productivity and low pressure resistance after baking paint. The method of producing a hard surface treatment original sheet with excellent workability, in which the yield strength of the steel sheet subjected to baking coating after can-making processing is 56 kgf / mm ² or more, which is the object of the method described above, is high in productivity. Not yet.

[0010]

The problem to be solved by the present invention is to provide a hard surface treatment excellent in workability in which the proof strength of the steel sheet after baking coating after can-making is 56 kgf / mm ² or more. An object of the present invention is to provide a method for manufacturing a master plate with high productivity.

[0011]

Means for Solving the Problems The inventors of the present invention have proposed a method for solving the above-mentioned problems with an extremely compact continuous annealing equipment capable of greatly reducing equipment costs. Were comprehensively studied, and a method for producing a hard surface-treated original sheet having excellent workability was found. The gist of the present invention is as follows. C in weight%:
0.070 to 0.200%, Si: ≦ 0.30%, M
n: 0.50 to 1.50%, P ≦ 0.030%, S: ≦
0.025%, solAl: 0.002 to 0.100
%, N: ≦ 0.0120%, steel slab consisting of unavoidable impurities and iron is heated and hot-rolled under ordinary hot rolling conditions to form a rolled hot-rolled steel strip and cold-rolled. After that, the temperature range of at least 500 ° C.
Heat at 00-2000 ° C / s to 730-830 ° C, stay in that temperature range for 2 seconds or less, cool at a cooling rate of 100-500 ° C / s, anneal, and adjust to 0.5-5.0% For producing a hard surface-treated original sheet having excellent workability, characterized by performing temper rolling.

[0012]

The present invention will be described in detail below. The present inventors have studied a method for producing a hard work surface treatment original sheet having excellent yieldability with a yield strength of 56 kgf / mm ² or more after baking coating treatment after can making processing with good productivity. Amount, hot rolling conditions and continuous annealing conditions were comprehensively studied, and the C content of the steel components was 0.070-
After setting the content of Mn to 0.200% and the Mn content to 0.50 to 2.0%, the temperature range of at least 500 ° C. or more in the continuous annealing heating is 730 to 830 at 300 to 2000 ° C./s.
With the main points of heating to 2 ° C. and staying in that temperature range for 2 seconds or less, and cooling after recrystallization annealing at a cooling rate of 100 to 500 ° C./s, the extremely compact continuous annealing equipment is used. It has been found that it is possible to produce a hard working surface original sheet having excellent workability with a yield strength of 56 kgf / mm ² or more after baking coating treatment after can-making processing with good productivity. It is.

FIG. 1A is a diagram showing the effects of the points 1 and 2 of the present invention. An Al-K steel having a C content of 0.12% and a Mn content changed was set to a winding temperature of 550 ° C during hot rolling, and a cold plate having a thickness of 0.17 mm manufactured by the method of the present invention was used. The steel sheet after the cold rolling is annealed by the heat cycle shown in FIG. 1B, subjected to a temper rolling of 1.0% to produce a surface-treated original sheet, and subjected to a tensile strain of 2%.
C. × 10 min. P was investigated and the results are shown in FIG. 1A.

From FIG. 1A, it is found that, in particular, when the Mn content among the steel components is set to 0.50 or more, ultra-rapid heating such as 1000 ° C./s is performed in the continuous annealing. After holding for a very short time such as 1 sec.
A completely new finding was obtained that by cooling at a cooling rate of s, a large increase in strength was obtained as compared with a cycle in which heating was performed slowly by gradually heating such as a comparative cycle. The present inventors investigated the structure of the obtained sample in connection with this, and as a result, it was found that the sample manufactured within the scope of the present invention had a finer and more uniform composite structure as compared with the comparative cycle B. It has been found that this is the cause of the increase in strength in the method of the present invention.

The mechanism by which such a structure with increased strength is obtained has not been fully elucidated. However, in the case of a steel having an Mn content of 0.5% or more and a C content of at least a certain amount, the steel is gradually reduced. In the case of heat annealing, when the temperature rises and enters the two-phase region, C has sufficient time to diffuse, so that the two-phase separation of the α-phase and the γ-phase sufficiently proceeds and the α-phase grains grow. As a result, the volume of the γ phase, whose strength can be increased by quenching, decreases, and as in cycle B,
Even if rapid cooling such as 0 ° C./s is performed, no increase in strength can be obtained. However, in the case of ultra-rapid heating, there is almost no time for C to diffuse, so that two-phase separation does not proceed and grain growth is suppressed, and when the temperature reaches the soaking temperature, the two-phase state is finely uniform and has a large volume of γ phase. It is considered that if the soaking time is short, the state is maintained, and the quenching after that results in a fine and uniform composite structure with a large volume of a hardened structure having high strength.

FIG. 1A shows that the Mn content is 0.3%.
When the continuous annealing condition is a method according to the present invention, only a strength approximately equal to that of the comparative cycle B is obtained, and the Mn content is set to 0.50% or more. The importance is clearly understood. In addition, El after pressure regulation of the steel in the range of the present invention shown in FIG. 1A was 7 to 20%, which was an extremely good characteristic value as compared with less than 1% of the DCR material.

Hereinafter, the manufacturing conditions will be described in detail. C
Is an important element in securing strength as described above,
If it is less than 0.07%, the target strength cannot be obtained, so the lower limit was made 0.07%. If it exceeds 0.20%,
Since the strength becomes too high and the workability deteriorates significantly,
20% was made the upper limit.

The Mn content is an important element for securing the strength as described above. If the Mn content is less than 0.5%, the desired strength cannot be obtained, so the lower limit is 0.50%. or,
If it exceeds 1.50%, the strength becomes too high and the workability deteriorates significantly, so 1.50% was made the upper limit.

Si, P, and S greatly affect the plating quality, particularly corrosion resistance, of a surface-treated steel sheet such as a tin-plated steel sheet.
When the content exceeds 0.30%, 0.03%, and 0.025%, respectively, the corrosion resistance deteriorates. Therefore, the respective upper limits are set to 0.30%, 0.03%, and 0.025%.
It should be noted that the smaller these elements are, the better the corrosion resistance is.

SolAl is used as a deoxidizing agent,
Since 0.002% remains, the lower limit is set to 0.002%. On the other hand, when the content is 0.100% or more, air oxidation of molten steel tends to occur at the time of casting, the amount of inclusions increases, and the workability and the plating quality also deteriorate, so 0.100% was made the upper limit.

N is a useful element that can be used as a strengthening element, and may be added as needed. However, 0.01
If the content exceeds 20%, air bubbles will be generated in the slab, so the upper limit value is set to 0.0120%. Incidentally, N does not adversely affect the material at least, and the strength is C, M.
Since it can be secured by n or the like, there is no particular need to regulate.

The hot rolling conditions do not need to be particularly restricted, and ordinary hot rolling conditions may be used. When the winding temperature is less than 670 ° C. (hereinafter referred to as CT), the cementite or pearlite structure of the hot-rolled sheet is finely and uniformly dispersed, so that the composite structure of the annealed sheet can be made uniform and fine. It will be convenient,
Winding temperatures below 670 ° C. are preferred. The cold rolling does not need to be particularly restricted, and may be performed under cold rolling conditions for producing a surface-treated original sheet.

The heating rate of the recrystallization annealing during the continuous annealing is the most important point of the present invention, and its effect and mechanism are as presumed above. Heating rate is 300 ℃
If it is less than / s, the ultra-rapid heating effect cannot be obtained and the desired strength cannot be obtained, so 300 ° C / s was set as the lower limit.
It should be noted that the heating rate exceeding 2000 ° C./s is too high, so that the control of the ultimate temperature of heating becomes unstable, and it becomes difficult to obtain stable quality. It should be noted that, as a result of various investigations, such an effect of the ultra-rapid heating can be performed at least in a temperature range of 500 ° C. or more by 300 ° C./s.
Since it was found that the effect of ultra-rapid heating can be obtained by performing the above-mentioned heating rate, the temperature range in which ultra-rapid heating of at least 300 ° C./s or more was required was set to 500 ° C. or more.

If the annealing temperature during recrystallization annealing is lower than 730 ° C., the volume of the γ phase required for securing the strength cannot be obtained, so the lower limit was set at 730 ° C. If the annealing temperature exceeds 830 ° C., the steel sheet softens and easily elongates when passing through the soaking zone, and the sheet passing property deteriorates. Therefore, 830 ° C. was set as the upper limit.

The soaking time during recrystallization annealing is 2.0 sec.
In the case of exceeding, two phase separation of αγ and grain growth and softening occur, so the upper limit was set to 2.0 sec. In the case of the ultra-rapid heating annealing, recrystallization occurs even if the soaking time is not required, and the strength can be secured. Therefore, it is not necessary to regulate the lower limit of the soaking time.

The cooling condition after the recrystallization annealing is an essential condition for obtaining a high-strength, fine and homogeneous composite structure by quenching from the fine and homogeneous αγ two-phase state during soaking.
If it is less than 0 ° C./s, the required strength cannot be obtained, so the lower limit was set to 100 ° C./s. If the temperature exceeds 500 ° C./s, uniform cooling becomes difficult and the shape of the coil becomes worse. The quenching is not necessarily required to be rapidly cooled to room temperature since a predetermined strength can be obtained if the quenching is performed at a cooling rate of 100 ° C./s or more up to at least 400 ° C. Was not particularly regulated as it had little effect on

Temper rolling is a means effective for eliminating the elongation at the yield point and correcting the shape, and requires a temper rolling ratio of 0.5% or more. The temper rolling rate is Y. Since it is an effective method for increasing P, the temper rolling reduction may be increased as necessary. However, if it exceeds 5.0%, the deterioration of El becomes large, so the upper limit value is set to 5.0%. .

[0028]

EXAMPLES The effects of the present invention will be described below with reference to examples. A hot rolled steel strip of 2.0 mm was manufactured under the components and hot rolling conditions shown in Table 1 and a cold rolled 0.17 mm cold rolled steel sheet was prepared as shown in FIG.
Continuous annealing was performed under the conditions shown in Table 2 in the heat cycle shown in C, and temper rolling of 1.2% was performed to obtain a surface-treated original sheet. The obtained surface-treated original sheet was subjected to a tensile test to measure the El value, and 2% of tensile strain was applied to the obtained surface-treated original sheet. P was measured, and the results are shown in Table 2.

[0029]

[Table 1]

[0030]

[Table 2]

The steel A has a production condition in the composition range of the conventional example in which the Mn content is as low as 0.25%. Steel B, C,
D and E are manufacturing conditions within the range of the method of the present invention, steels B, C and D are examples of components in which C and Mn are changed, and steel E is a range of the method of the present invention. At 0.0098
%.

Samples 1, 2, 7, and 8 are conventional or comparative examples, each of which has a target Y.I. P is 56kgf / mm ²
If it is less than this, it cannot be used for applications requiring high pressure resistance of the can which is targeted by the method of the present invention. Samples 3, 4,
5 and 6 are examples of the method of the present invention. P is 56 kgf / mm ² or more and El
As a result, an excellent characteristic value of 15.2 to 20.3% was obtained, and a steel sheet having excellent workability aimed at by the method of the present invention and applicable to applications requiring high pressure resistance of the can was produced. .

Sample 1 was a conventional example in which the amount of Mn was low and the continuous annealing condition was the conventional method. P is 3
It is as low as 8.5 kgf / mm ² . Sample 2 is a comparative example in which the continuous annealing condition is the method of the present invention, but the Mn content is low. P is as low as 48.5 kgf / mm ² . As is apparent from the results, the Mn content was 0.5
The importance of restricting the percentage to more than% is clearly understood.

Samples 3, 4, 5, and 6 are examples of the method of the present invention. Samples 3, 4, 5, and 5 are examples in which the amounts of C and Mn are changed within the range of the present invention. This is an embodiment in which the amount of N is increased. In each case, the target Y. P is 56kgf
/ Mm ² or more and El is also 15.2 to 20.3% excellent characteristic value, and the method of the present invention is intended for applications requiring excellent workability and high pressure resistance of the can. Applicable steel plate was manufactured.

Samples 7 and 8 are comparative examples, in which the production conditions of the test steel are within the present invention, but sample 7 is a comparative example in which the continuous annealing conditions are different from the heating rate, soaking time, and cooling rate. And BH
Later Y. P was as low as 46.8 kgf / mm ^2, and Sample 8 was a comparative example in which the cooling rate was within the range of the present invention under the continuous annealing conditions, but the heating rate and soaking time were different. P is as low as 52.3 kgf / mm ² . As is clear from these results, the importance of restricting the conditions of continuous annealing within the scope of the present invention is clearly understood. From the above examples, it can be seen that an extremely short annealing time of about 3 seconds makes it possible to produce a steel sheet having excellent workability and excellent pressure resistance of a can.

[0036]

As described above, the present invention has been described in detail. According to the present invention, a very compact continuous annealing equipment capable of greatly reducing equipment costs, and a steel sheet which has been subjected to baking coating after can-making. It is possible to manufacture a hard surface treatment original plate excellent in workability having a yield strength of 56 kgf / mm ² or more with high productivity, and its industrial value is great.

[Brief description of the drawings]

FIG. 1. A: Y. after BH. 1B is a diagram showing the effect of the present invention on P, B: a diagram showing a heat cycle of continuous annealing used in the investigation experiment of FIG. 1A, and C: a diagram showing a heat cycle of continuous annealing used in Examples.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 9 / 46,8 / 02 C22C 38/00-38/06

Claims (1)

(57) [Claims] 1. C: 0.070 to 0.200% by weight
%, Si: ≦ 0.30%, Mn: 0.50 to 1.50
%, P: 0.030%, S: 0.025%, sol
Al: 0.002 to 0.100%, N: ≦ 0.0120
%, The balance of unavoidable impurities and iron slab is heated and hot-rolled under normal hot-rolling conditions to form a rolled hot-rolled steel strip, cold-rolled, and then continuously annealed at least. A temperature range of 500 ° C. or more is heated to 730 to 830 ° C. at 300 to 2000 ° C./s and kept for 2 seconds or less in the temperature range, cooled at a cooling rate of 100 to 500 ° C./s, and annealed. A method for producing a hard surface-treated original sheet having excellent workability, characterized in that temper rolling of up to 5.0% is performed.