JP3185557B2 - Method for manufacturing soft tinplate and soft TFS steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing a material having a temper degree of T3.
The present invention relates to the following methods for manufacturing a soft tinplate and a steel sheet for TFS.

[0002]

2. Description of the Related Art Tinplate and TFS are measured from T1 to T6 based on the hardness measured by the Rockwell hardness test (HR30T).
In general, soft materials having a tempering degree of T1 to T3 are manufactured by a box annealing method, and hard materials having a tempering degree of T4 to T6 are mainly manufactured by a continuous annealing method. .

[0003] In recent years, production of a soft material by a continuous annealing method has been studied instead of a box annealing method in which productivity is extremely inferior and the material is not uniform in the longitudinal direction and the width direction of the coil.
When a conventional low-carbon steel is manufactured by the conventional continuous annealing method, a large amount of solute C remains in the steel due to rapid cooling after annealing, so distortion aging occurs during baking coating, and subsequent processing of cans, etc. Sometimes molding defects such as fluting and stretcher strain occur.

Therefore, in order to manufacture a soft material for processing by a continuous annealing method, the amount of solute C and N after annealing is reduced as much as possible.
It is necessary to suppress the recovery of yield point elongation due to strain aging during baking. Empirically, the recovery of this yield point elongation was 5
It is known that problems such as fluting and stretcher strain do not occur at the time of can making, etc., when the content is controlled to within%, preferably within 4%. As a method for producing a soft material for minimizing the amount of solid solution C and N after annealing, for example, Japanese Patent Application Laid-Open No. Hei 5-263143 discloses that a very low C steel has Ti, Nb,
A method for reducing the amount of solid solution C and N by adding a carbonitride forming element such as B is disclosed in JP-A-60-67627. A method of reducing the amount of solute C by annealing in an annealing line has been proposed.

[0005]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
In the method described in Japanese Patent No. 263143, the cost is high because extremely low C steel is used. Japanese Patent Application Laid-Open No. 60-6 / 1985
In the method described in Japanese Patent No. 7627, low-carbon steel is used. However, since hot rolling is performed after hot rolling, the carbide form and the precipitation state of AlN become uneven in the coil longitudinal direction and width direction, and as a result, The uniformity of the material in the longitudinal direction and the width direction of the final product is poor. Because doing high temperature heating above the A ₁ transformation point in further continuous annealing, easily strip passing troubles such as heat buckle occurs in the thickness of thin steel plate such as a can material.

The present invention has been made to solve such a problem, and is low in cost, excellent in uniformity of the material such as hardness in the longitudinal direction and width direction of the coil, and does not cause trouble in threading during annealing. Further, it is an object of the present invention to provide a method for producing a soft tinplate and TFS steel sheet having a thickness of T3 or less by a continuous annealing method which does not cause molding defects such as fluting at the time of processing a can or the like.

[0007]

Means for Solving the Problems The above-mentioned problems are expressed in terms of% by weight,
C: 0.050 to 0.085, Mn: 0.05 to 0.6
0, P: 0.02 or less, S: 0.02 or less, SolA
l: 0.10 or less, N: 0.0036 or less, and using a steel in which the atomic ratio of Al and N is Al / N ≧ 15, after hot rolling, is wound in a temperature range of 550 ° C. or more and less than 620 ° C. Then, after cold rolling, the steel sheet is heated to a temperature range of 650 ° C. or more and less than the A ₁ transformation point by a continuous annealing method, and then cooled to a temperature range of 350 ° C. to 450 ° C. at a cooling rate of 30 ° C./s or more,
The problem is solved by a tinplate and a method for manufacturing a steel sheet for TFS in which overaging treatment is performed for 30 seconds or more at that temperature.

[0008] Further, with respect to molding defects such as fluting generated during processing, the C content is set to 0.060 to 0.080.
It is more preferable to control the weight%.

[0009]

The components of the present invention and the reasons for limiting the production conditions will be described below.

C is an element that plays an important role in the material and strain aging during baking coating. Therefore, the amounts of the component elements other than C and the manufacturing conditions were kept constant within the range of the present invention, samples were prepared in which only the amount of C was changed, and these samples were subjected to a heat treatment equivalent to baking coating, and then subjected to a tensile test. Then, the yield point elongation was measured, and the relationship between the C content and the yield point elongation was investigated. The results are shown in FIG. C amount 0.050-0.0
When the content is within the range of 85% by weight, the yield point elongation after baking coating can be suppressed to within 5%, and the problem of molding defects such as fluting can be avoided as described above. Therefore, the C content is limited to the range of 0.050 to 0.085% by weight. More preferably, when the C content is controlled within the range of 0.060 to 0.080% by weight, the yield point elongation after baking coating can be suppressed to within 4%, which is more advantageous against molding defects such as fluting. .

If Mn is less than 0.05% by weight, a problem of hot embrittlement occurs, so it is necessary to increase it more. Also 0.
If the content exceeds 60% by weight, the material becomes hard, and it becomes impossible to produce a soft material of T3 or less by the method of the present invention.
Therefore, the Mn content is limited to the range of 0.05 to 0.60% by weight.

If P is contained in excess of 0.02% by weight, it hardens and the corrosion resistance deteriorates. Therefore, the P content is limited to 0.02% by weight or less.

If S is contained in an amount exceeding 0.02% by weight, a problem of hot embrittlement occurs and workability is deteriorated. Therefore, the amount of S is limited to 0.02% by weight or less.

Al and N are also important constituents of the present invention. If N is not precipitated as AlN during hot rolling and winding, fine AlN precipitates during continuous annealing, inhibiting the growth of crystal grains, and as a result, the structure becomes fine and hard.
On the other hand, if high-temperature winding is performed to promote the precipitation of AlN, as described above, the uniformity of the material such as hardness in the longitudinal direction and the width direction of the coil deteriorates. Therefore, low temperature winding
Were examined by changing the atomic ratio of Al and N. The results are shown in FIG. In FIG. 2, the horizontal axis is Al / N
The vertical axis is the value obtained by dividing the amount of N existing as AlN by the total amount of N. Winding temperature is 680 ℃
In high-temperature winding, most of N is precipitated as AlN even if the ratio of Al / N is small. However, in low-temperature winding at 550 ° C., Al / N ≧ 15 is required to precipitate most of N as AlN. Need to be In addition, since an increase in the amount of Al causes an increase in cost and hardening, the upper limit is set to 0.10% by weight. At this time, the N amount satisfying the atomic ratio Al / N ≧ 15 is 0.0036% by weight or less.

When the winding temperature after hot rolling is set to 620 ° C. or higher, the carbide shape and AlN in the longitudinal direction and width direction of the coil are increased due to the difference in cooling rate after winding.
Is not uniform, so that the uniformity of the material after annealing deteriorates. If the temperature is lower than 550 ° C., it becomes difficult to control the winding temperature and shape. Therefore, the winding temperature after hot rolling is limited to the range of 550 ° C or more and less than 620 ° C.

The heating temperature of the continuous annealing is set to less than 650 ° C.
And only a hard material is obtained without complete recrystallization. Also
A as described above₁Heat buckle above the transformation point
Passing troubles such as passing occur. Therefore, during continuous annealing
Heating temperature of 650 ° C or more A ₁Limited to the range below the transformation point
I do.

The cooling rate after heating is limited to 30 ° C./s or more in order to secure a sufficient degree of supersaturation of solid solution C in order to promote the precipitation of solid solution C in the subsequent overaging treatment.

If the overaging temperature is lower than 350 ° C., it takes too much time to precipitate solid solution C. On the other hand, when the temperature exceeds 450 ° C., the equilibrium solid solution C content at that temperature increases, and the solid solution C amount of the final product after cooling also increases. Therefore, the overaging temperature is limited to a range of 350 ° C. to 450 ° C. The overaging treatment time is limited to 30 seconds or more in order to sufficiently precipitate solid solution C.

[0019]

EXAMPLES As shown in Table 1, the main constituent elements of the present invention, namely, the amounts of C, Al, N, and Mn, the winding temperature after hot rolling, the heating temperature during continuous annealing, the cooling rate, and the conditions for overaging treatment. , And various samples were prepared. In any of the samples, the amounts of P and S are in the range of 0.010 to 0.016% by weight. In the samples in the table, Examples 1 to 8 are both components and production conditions within the scope of the present invention, and Examples 1 to 7 are samples in which the amount of C is within a more preferable range. In Comparative Example 9, Al / N fell below the lower limit.
In Examples 10 and 11, the winding temperature after hot rolling was below the upper limit, in Comparative Example 12, the C amount was below the upper limit, in Comparative Example 13, the C amount was below the lower limit, and in Comparative Examples 14, 15, and 16 after the hot rolling. The winding temperature was lower than the lower limit, the heating temperature during continuous annealing was lower than the lower limit in Comparative Example 17, the overaging treatment temperature during the continuous annealing was lower than the upper limit in Comparative Example 18, and the overaging during the continuous annealing was higher in Comparative Example 19. The processing time was below the lower limit, and Comparative Example 20 is a sample in which the overaging temperature during continuous annealing was below the lower limit.

The Rockwell hardness (HR30T) and the yield point elongation after heat treatment at 210 ° C. for 10 minutes simulating the baking coating were measured. In addition, in order to examine the uniformity of the material in the coil longitudinal direction and the width direction, Rockwell hardness was measured in detail in the coil longitudinal direction and the width direction, and if the hardness difference in the longitudinal direction and the width direction was less than 1 point, ○, If the score was 1 point or more, a two-stage evaluation of x was performed.

The results are shown in Table 2. The samples of Examples 1 to 8 prepared by the method of the present invention all satisfy the target hardness 57 ± 3 of the temper degree T3, exhibit a yield point elongation after baking coating treatment of 5% or less, and exhibit uniformity of the material. It can be seen that is also excellent. In particular, the samples of Examples 1 to 7 have a yield point elongation of 4% or less after the baking coating treatment, and can be said to be extremely excellent materials for avoiding molding defects such as fluting. On the other hand, in the samples prepared by the method outside the present invention, Comparative Examples 9 to 11 had poor material uniformity, and Comparative Examples 9 and 12 to
Nos. 13 and 17 to 20 show a yield point elongation after baking coating treatment exceeding 5%, which causes problems of molding defects such as fluting, and Comparative Examples 14, 15, 16, and 17 exceed the target hardness of T3. Therefore, none of them can be used as a soft material for processing of T3 or less.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

Since the present invention is constructed as described above, it is inexpensive, has excellent uniformity of the material such as hardness in the longitudinal direction and the width direction of the coil, and does not cause a trouble of passing a plate during annealing. In addition, it is possible to provide a method for producing a soft tin plate of T3 or less and a steel sheet for TFS by a continuous annealing method which does not cause molding defects such as fluting during the processing of cans and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between yield point elongation and C content after baking coating processing.

FIG. 2 is a diagram showing the relationship between a value obtained by dividing the amount of N present as AlN after hot rolling and winding by the total amount of N and the atomic ratio Al / N.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-33522 (JP, A) JP-A-4-80346 (JP, A) JP-A-61-26725 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) C21D 9/46 C22C 38/00-38/60

Claims (2)

(57) [Claims] 1. C: 0.050 to 0.08 by weight%
5, Mn: 0.05 to 0.60, P: 0.02 or less,
S: 0.02 or less, SolAl: 0.10 or less, N:
0.0036 or less, and the atomic ratio Al / N of Al /
With N ≧ 15 and the steel, above 550 ° C. After hot rolling 62
Winding in a temperature range of less than 0 ° C., followed by cold rolling, heating to a temperature range of 650 ° C. or more and less than the A ₁ transformation point by a continuous annealing method, and then 350 ° C. or more at a cooling rate of 30 ° C./s or more.
A method for producing a soft tinplate and TFS steel sheet, wherein the steel sheet is cooled to a temperature range of 50 ° C. or lower and overaged at that temperature for 30 seconds or longer. 2. C: 0.060 to 0.080 by weight%
The method for producing a steel plate for soft tinplate and TFS according to claim 1, wherein a steel having a component other than C within the range described in claim 1 is used.