JPH073395A - Thin steel sheet excellent in deep drawability and weldability and production thereof - Google Patents

Abstract

PURPOSE:To produce a thin steel sheet for a welded can excellent in deep drawability and weldability by subjecting a dead soft aluminum killed continuously cast slab having a specified compsn. to hot rolling, subjecting it to cold rolling at a specified rolling ratio and executing continuous annealing. CONSTITUTION:A dead soft aluminum killed continuously cast slab contg., by weight, <0.003% C, <0.04% Si, <0.5% Mn, 0.01 to 0.03% Nb, <0.01% P, <0.04% S and 0.015 to 0.10% Al or contg. 0.01 to 0.07% Ti, instead of Nb or compositely added and incorporated with Ti and Nb by 0.01 to 0.07% in total is subjected to hot rolling into a hot coil having a thickness T, and after that, the surface is subjected to pickling treatment. Successively, it is subjected to cold rolling at 84 to 91% rolling ratio into a cold rolled sheet, and finally, it is subjected to continuous annealing into a thin steel sheet as a final product having a thickness (t). The dead soft thin steel sheet in which the relationship of 84<=(T-t)/TX100<=91 is held between the thickness T of the hot coil and the thickness (t) of the final product thin steel sheet and the grain size of the weld zone in the case of welding is regulated to <=30mum and excellent in deep drawability and weldability can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to tin-plated steel sheets, tin-free steel sheets, tin-free steel sheets, which are used for canned foods, cans for dry batteries, and the like.
The present invention relates to a thin steel sheet having excellent deep drawability and weldability, which serves as a base plate for steel sheets for cans such as nickel-plated steel sheets, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Tinned steel sheet, tin-free steel,
When a steel sheet such as a nickel-plated steel sheet is used for a welding can, a so-called ultra-low carbon steel sheet, which is a so-called ultra-low carbon steel sheet, which has low reactivity during welding with a C component in the steel plate and an O component in the air is a base plate of the surface-treated steel sheet. Was mainly used as. For example, JP-A-3-122964 proposes application of a low carbon steel plate to a sealed battery. According to this invention, C: 0.0
It is said that the crack generation rate at the welded portion at the time of sealing joining (laser welding) after press molding can be reduced at 05% or less. However, since the present invention reduces the amount of C in steel to 0.005% or less, there is a problem that the crystal grains become coarse due to local heating during laser welding. Further, since the amount of C in the steel is reduced, quench hardening does not occur during cooling after laser welding. For this reason, there is a drawback in that the strength does not increase and the strength of the joint is deteriorated.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a thin steel sheet having excellent deep drawability and weldability, which is a base plate of tin-plated steel sheet, tin-free steel, nickel-plated steel sheet for use in welding cans, and a manufacturing method thereof. The purpose is to provide.

[0005]

Means for Solving the Problems The thin steel sheet of the present invention comprises C;
0.003% or less, Si; 0.04% or less, Mn;
5% or less, Nb; 0.01 to 0.03%, P; 0.01
% Or less, S; 0.04% or less, Al; 0.015-
A steel plate made of an aluminum-killed steel plate of 0.10%, N; 0.01% or less, wherein the average grain size of crystal grains after welding is 30.
It is characterized by being less than or equal to μm. Further, the thin steel sheet of the present invention has C: 0.003% or less, Si: 0.04% or less, M
n: 0.5% or less, Ti: 0.01 to 0.07%, P;
0.01% or less, S; 0.04% or less, Al; 0.0
A steel plate made of an aluminum-killed steel plate of 15 to 0.10%, N: 0.01% or less, characterized in that the average grain size of crystal grains after welding is 30 μm or less. Further, the thin steel sheet of the present invention has C: 0.003% or less, Si: 0.04%
Hereinafter, Mn; 0.5% or less, P; 0.01% or less,
S: 0.04% or less, Al: 0.015 to 0.10%,
N: 0.01% or less, total amount of Ti and Nb: 0.01 to
A steel plate made of 0.07% aluminum-killed steel plate,
The average grain size of the crystal grains after welding is 30 μm or less. The method for producing a thin steel sheet of the present invention is a method for producing a thin steel sheet for deep drawing by hot rolling, pickling, cold rolling, continuous annealing an aluminum-killed ultra-low carbon continuously cast steel billet, wherein the component is C 0.003% or less, Si; 0.04%
Hereinafter, Mn: 0.5% or less, Nb: 0.01 to 0.03
%, P; 0.01% or less, S; 0.04% or less, A
1; 0.015 to 0.10%, N: 0.01% or less of an aluminum-killed steel sheet, the rolling ratio in the cold rolling is in the range of 84 to 91%, and the hot coil sheet thickness is T,
When the product plate thickness is t, 84 ≦ (T−t) / T × 100
It is characterized by having a relationship of ≦ 91.

[0006]

Since the continuously cast steel piece used in the present invention is an aluminum killed steel, the continuously annealed thin steel sheet produced from this steel piece does not undergo strain age hardening due to solid solution N after temper rolling. Further, since C is as low as 0.003% or less, since it is soft as a whole and contains 0.01 to 0.03% of Nb, the solid solution C is fixed by Nb and becomes solid solution C. Strain age hardening due to this does not occur, the drawability is further improved, and the generation of gas due to the CO reaction during welding is suppressed, so defects are reduced. Further, addition of Nb can suppress coarsening of crystal grains after welding (claim 1). Further, by adding Ti, a thin steel sheet having the same effect as Nb can be provided (claim 2). Furthermore, by adding Nb and Ti in combination, coarsening of crystal grains after welding can be further suppressed (claim 3). And according to the manufacturing method of Claim 4, the thin steel plate which can suppress the coarsening of the crystal grain after welding can be provided.

[0007]

EXAMPLE A molten steel in a converter is degassed by vacuum degassing, decarburized, and then deoxidized by adding Al to produce a continuously cast steel piece by a continuous casting machine. The composition of this continuously cast steel piece is C: 0.003% or less, Si: 0.04 or less, M
n; 0.5% or less, Nb; 0.01 to 0.03%, P;
0.01% or less, S; 0.04% or less, Al; 0.0
It is desirable that the steel sheet is made of an aluminum-killed steel sheet with 15 to 0.10% and N: 0.01% or less, and the rest is made of unavoidable impurities. Also, instead of Nb, T
It is also preferable to add 0.01 to 0.07% of i. Further, a composite addition of Nb and Ti is more desirable.
If Nb is less than 0.01%, the target r value cannot be obtained, while if it exceeds 0.03%, this effect does not further increase, but rather the manufacturing cost increases. Ti also has the same effect as Nb, and an appropriate amount is 0.01% to 0.07. Even if Ti and Nb are added together,
Higher r-values are obtained than adding each component alone.

This continuously cast steel piece is preferably hot-rolled at a hot finishing temperature of Ar3 point or higher and a coiling temperature of 650 ° C. or lower to obtain a hot-rolled strip. The hot-rolled strip is continuously pickled and then cold-rolled at a rolling rate of preferably 85% or more to produce a cold-rolled strip. Since this cold-rolled strip recrystallizes even when the soaking temperature during continuous annealing is 750 ° C. or less, the cold-rolled strip is continuously annealed at a soaking temperature of 730 ° C. or less to produce a continuously annealed thin steel sheet. The hardness after continuous annealing is 50 or less at HR-30T.

The continuously annealed thin steel sheet is temper-rolled or DR at an appropriate rolling degree according to the hardness of the final product, that is, the temper degree (T-1, T-2, T-3, T-4, etc.). It is rolled into a so-called cold rolled thin steel sheet. The cold-rolled thin steel sheet is used as it is or subjected to surface treatment such as Ni plating to be a steel sheet for can such as a Ni-plated steel sheet.

Next, a specific example will be described. C; 0.00
3%, Si; 0.04%, Mn; 0.15%, Nb;
0.02%, P; 0.005%, S; 0.01%, A
1; 0.045%, N: 0.003%, a steel plate made of an aluminum-killed steel plate, the rest of which is a continuously cast steel slab made of unavoidable impurities, with a hot finishing temperature of 880 ° C. and a coiling temperature of 6
After hot rolling at 20 ° C. to form a hot rolled strip having a plate thickness of 4.0 mm, this is continuously pickled and then rolled at a rolling ratio of 90.
% Cold rolled, and then continuously annealed at 720 ° C. to produce a cold rolled strip having a plate thickness of 0.40 mm (X steel plate).

For comparison, C: 0.005%, Si:
0.04%, Mn: 0.15%, P: 0.015%,
S: 0.01%, Al: 0.045%, N: 0.003
%, And the remaining inevitable impurities made a continuously cast steel piece under the same conditions as the X steel piece (Y steel plate).

Nickel plating was applied to the above two types of steel plates to prepare a welding can. After the welding, in order to measure the size of the crystal grains in the welded portion, a structure observation and examination by an optical microscope were conducted. The results are shown below From these results, it was found that the X steel sheet to which Nb was added suppressed the growth of crystal grains and had a smaller crystal grain size than the Y steel sheet. If the crystal grain size of the welded portion after welding was 30 μm or less, the strength was sufficient to withstand use as a beverage can or the like. Therefore, it is assumed that the crystal grain size of the welded portion after welding is 30 μm or less.

Next, FIG. 1 shows the relationship between Nb and r value. As shown in FIG. 1, if the Nb content is less than 0.01%, a high r value cannot be obtained, and the desired excellent deep drawability cannot be obtained. Generally, a steel sheet having an r value of 1.8 or more is desired for deep drawing can applications. Here, the r value is an index showing the deep drawability during can forming. Therefore, from FIG. 1, in order to obtain a steel sheet having an excellent r value for use in deep drawing cans,
The amount of Nb should be 0.01% or more. Next, FIG. 2 shows the effect on the r value when Ti, Ti and Nb are added in combination. As shown in FIG. 2, Ti, Ti and N
Even when b is added in combination, a high r value cannot be obtained if the addition amount is less than 0.01%. Regarding the amount of addition given to the magnitude of the r value, a remarkable effect can be seen at 0.01% or more, whether Ti alone or when Ti and Nb are added in combination, but when Ti and Nb are added in combination, Higher r-values are obtained. Therefore, even when Ti, Ti and Nb are added together, the addition amount is preferably 0.01% or more.

Next, the manufacturing method described in claim 4 will be described. FIG. 3 shows the change in the value of Δr when the cold rolling rate (cold rolling rate) was changed. Generally, as the cold rolling rate increases, Δr tends to decrease. As for the occurrence of earing during press molding, Δr is an index showing anisotropy during deep drawing, and Δr
= (R ₀ + r ₉₀ -2 · r ₄₅ ) / 2, the value of Δr becomes the minimum when it becomes zero, so from the viewpoint of material yield, Δr should be as close to zero as possible. Is desirable. Δr is an index showing anisotropy during deep drawing. In the above formula, r ₀ = r value in the rolling parallel direction, r ₄₅ = r value in the rolling 45 ° direction, r ₉₀ = r value in the rolling 90 ° direction, respectively.
In general, the value of Δr that is acceptable as a can material is empirically
Since the range of 0.2 to 0.2 is suitable, the cold rolling rate is preferably in the range of 84 to 91 from FIG.
That is, when the hot coil thickness is T and the product thickness is t, the cold rolling rate is represented by (T−t) / T × 100%, and therefore 84 ≦ (T−t) / T × 100 ≦ 91. It is desirable to be in the range. Here, the hot coil refers to a steel slab after hot rolling.

The present invention is not limited to the above embodiments, but is applicable to steel plates for appropriate applications such as steel plates for home appliances and steel plates for automobiles other than steel plates for cans.

[0016]

The continuously annealed thin steel sheet using the Nb-containing ultra-low carbon continuously cast steel sheet of the present invention does not undergo strain age hardening due to solid solution C after temper rolling. Since C is as low as 0.003% or less, it is soft as a whole and Nb is 0.0
Since it contains 1 to 0.03%, solid solution C is fixed by Nb, strain age hardening due to solid solution C does not occur, and drawability is further improved. Since the generation of gas due to the reaction is suppressed, defects are reduced. Furthermore, the addition of Nb can suppress the coarsening of crystal grains after welding. Further, by adding Ti, it is possible to provide a thin steel sheet having the same effect as Nb. Furthermore, Nb and Ti
The compound addition can further suppress coarsening of crystal grains after welding, and can provide an excellent thin steel sheet for use in a welding can.

[Brief description of drawings]

FIG. 1 shows the relationship between the Nb addition amount and r value.

FIG. 2 shows the relationship between the added amount of Ti, Ti and Nb and the r value.

FIG. 3 shows the influence on Δr when the cold rolling ratio is changed.

Front page continuation (72) Inventor Hirokazu Tanabe 1302 Higashitoyo, Kudamatsu City, Yamaguchi Prefecture Toyo Kohan Co., Ltd. Inside the Kudamatsu Factory

Claims (4)

[Claims] 1. C: 0.003% or less (wt%, below%
Indicates weight%), Si; 0.04% or less, Mn;
5% or less, Nb; 0.01 to 0.03%, P; 0.01
% Or less, S; 0.04% or less, Al; 0.015-
A steel plate made of an aluminum-killed steel plate of 0.10%, N; 0.01% or less, wherein the average grain size of crystal grains after welding is 30.
A thin steel sheet with excellent deep drawability of less than μm and excellent weldability. 2. C: 0.003% or less, Si: 0.04
% Or less, Mn; 0.5% or less, Ti; 0.01 to 0.0
7%, P; 0.01% or less, S; 0.04% or less, A
1; 0.015 to 0.10%, N: 0.01% or less of an aluminum-killed steel sheet, which is excellent in deep drawability and average weld grain diameter of 30 μm or less after welding. Thin steel plate. 3. C: 0.003% or less, Si: 0.04
% Or less, Mn; 0.5% or less, P; 0.01% or less,
S: 0.04% or less, Al: 0.015 to 0.10%,
N: 0.01% or less, total amount of Ti and Nb: 0.01 to
A steel plate made of 0.07% aluminum-killed steel plate,
Deep drawability with an average grain size of 30 μm or less after welding,
Thin steel sheet with excellent weldability. 4. An aluminum killed ultra low carbon continuous cast steel slab,
In the method of producing a thin steel sheet for deep drawing by hot rolling, pickling, cold rolling, and continuous annealing, the component is C: 0.003%
Below, Si: 0.04% or less, Mn: 0.5% or less, N
b: 0.01 to 0.03%, P: 0.01% or less,
S: 0.04% or less, Al: 0.015 to 0.10%,
N: 0.01% or less of an aluminum-killed steel sheet having a rolling ratio in the cold rolling of 84 to 91%,
When the hot coil plate thickness is T and the product plate thickness is t, 84 ≦
A method of manufacturing a thin steel sheet having excellent deep drawability and weldability, which has a relationship of (T−t) / T × 100 ≦ 91.