JPH07109525A - Production of extra thin steel sheet for welded can body, suitable for high speed welding - Google Patents

Abstract

PURPOSE:To produce an extra thin steel sheet for welded can body, hardly causing lapping relief and suitable for high speed welding, by regulating C content in a low carbon steel slab to a value in a specific range and also specifying slab heating conditions prior to hot rolling, hot rolling conditions, and secondary cold rolling draft, respectively. CONSTITUTION:A slab of a low carbon steel, which has a composition containing, by weight, >0.0060-<0.O600% C, <0.06% Si, 0.05-0.60% Mn, <0.06% P, <0.06% S, 0.005-O.10% acid soluble Al, and 0.0010-0.010% N or further containing 0.005-0.1000% Cr, is used. The slab is cooled down to a temp. lower than the Ar3 transformation point, reheated to >=1050 deg.C, and hot-rolled and hot rolling is finished at a temp. not lower than the Ar3 transformation point, or, hot rolling is started at >=900 deg.C surface temp. in a high temp. state without cooling the slab down to a temp. lower than the Ar3 transformation point and hot rolling is finished at a temp. not lower than the Ar3 transformation point. Subsequently, the resulting hot rolled steel plate is coiled at <=680 deg.C, pickled, cold-rolled, recrystallization-annealed, and subjected to secondary cold rolling at 2-10% draft. By this method, the extra thin steel sheet for welded can body, having <=0.26mm sheet thickness, >=62 Hr30-T hardness, and 44kgf/ mm<2> tensile strength in a rolling direction, can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an ultra-thin steel sheet for a welding can body which is free from deterioration of ductility in the direction orthogonal to rolling, has excellent stripping properties and is suitable for high speed welding.

[0002]

2. Description of the Related Art Conventionally, cans are joined by methods such as soldering, resin bonding, and welding. Among them, in recent years, a welding method, which can reduce the joint margin, has been becoming mainstream in order to improve the yield of steel sheets. The manufacturing process of a three-piece can by welding is generally as follows.

[0003] A large piece of cutting board with a width of about 1 meter inside and outside is painted and printed corresponding to a plurality of can bodies, and then a small piece of a cutting plate which is sheared vertically and horizontally by a slitter to form a body of one can ( This is called a blank). The high-speed wire seam automatic welding machine takes in these blanks set in the feeding device one by one, bends them with a curling device, and then stacks the ends to be welded to have a predetermined overlap width. Together, the wrap portion is pressed down in the thickness direction from the inner surface and the outer surface by the disk-shaped rotating electrode, and at the same time, the can is advanced in the length direction while flowing a high-frequency current and joined by electric resistance welding. At this time, the welding line end that first bites into the rotating electrode is called a leading edge, and the welding line end that finally leaves the rotating electrode is called a trailing edge. The width of the weld line after welding is called the lap width. A cylindrical can body is completed by the steps so far.

The quality of this welding process is that the welded part has sufficient strength more than the base metal, does not produce harmful by-products such as splash, and is joined with a uniform lap width from the leading edge to the trailing edge. Decided by It is said that these welding qualities are complicatedly dependent on many factors such as current, voltage, frequency, rolling electrode rolling pressure, set lap width before welding, and contact electric resistance at the interface.

Next, in order to attach a lid having a diameter smaller than the diameter of this cylinder, neck processing is performed to reduce the diameter of the can body opening. Following this, there is a step of forming a flange portion extending outward in the diametrical direction at the end of the can body in order to attach a lid to the necked can body, which is called flanging. During flanging, cracks that cause the contents of the can to leak to the flange portion, that is, defects called flange cracks may occur. The performance in which flange cracking is unlikely to occur in this flanging is hereinafter referred to as flanging.

[0006] Causes of flange cracking include defective joining due to welding, poor workability of steel sheet, inclusions in the steel sheet, hardening of the welded portion, and softening of the weld heat affected zone. On the other hand, the plate thickness of the material for cans tends to be thin from the viewpoint of resource saving,
The hardness of the steel plate is made hard to deal with the reduction in the can strength due to the thinner plate thickness. As such a thin steel sheet, as seen in Japanese Patent Laid-Open No. 51-131413, a so-called two-time cold rolling method in which a hot-rolled steel sheet is cold-rolled, annealed, and cold-rolled again There is a manufactured steel plate, a so-called double reduced steel plate (hereinafter abbreviated as DR steel plate).

However, this DR steel sheet has a drawback in that the workability deterioration of the steel sheet and the softening of the heat-affected zone of the weld due to the secondary cold rolling strain are remarkable and the flange crack often occurs in the flanging after welding. . As a method for solving this problem, JP-A-58-164752 and JP-A-5-16572 are available.
A method described in 9-89718 is proposed. However, in these existing technologies, since the reduction ratio of the secondary cold rolling is as large as about 15% or more, the anisotropy of the material properties of the steel sheet including the flange formability is large, and the rolling direction of the steel sheet is Plate cutting that is parallel to the axial direction (hereinafter,
When this stripping method is referred to as the reverse method), flange cracking frequently occurs after welding, so the can-maker must always strip the steel sheet at a right angle to the axial direction of the can body (hereinafter, This method is called a normal method), and there is a problem that it has to be constrained. Furthermore, since these existing technologies have large anisotropy in material properties, the deformation behavior in the bending process before welding differs between the normal method and the reverse method. There was also the problem that the equipment would break down.

[0008] Further, the welding speed is to improve productivity,
There is a trend toward faster speeds. To increase the welding speed,
Since the energy required for joining must be input in a shorter time, it is necessary to increase the current and frequency.
In addition, in order to suppress mechanical vibration of the rotating electrode due to repetition of biting of the leading edge and detachment of the trailing edge and to bring the rotating electrode and the steel plate into stable contact, it is necessary to increase the pressing pressure of the rotating electrode. is there. The change in these conditions makes it difficult to control the lap width after welding, and even if the wrap width at the leading edge is proper, the lap width becomes smaller as it approaches the trailing edge, and eventually the lap comes off and opens. Is likely to occur. This phenomenon is called lap escape,
This is an important issue in industrializing high-speed welding.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and completely removes the restriction of the plate making direction in a can manufacturing company, and makes any of the normal method, the reverse method and a mixture thereof. However, it is an object of the present invention to provide a method for producing an ultra-thin steel sheet for a welding can body, which is capable of producing a can and is less likely to cause lap escape and suitable for high speed welding.

[0010]

Means for Solving the Problems As a result of experiments and research for achieving the above-mentioned objects, the present inventors have found that in order to improve the stripping property and the lap escape resistance, it is necessary to secure the steel plate strength and It is important not to cause deterioration of ductility in the direction orthogonal to the rolling, and for this purpose, adjustment of the C content, billet heating conditions prior to hot rolling, hot rolling conditions, and secondary cold rolling reduction should be combined. Was newly discovered.

The present invention is constructed on the basis of this finding, and the summary thereof is as follows. (1) By weight%, C: more than 0.0060% to less than 0.0600% Si: 0.06% or less Mn: 0.05 to 0.60% P: 0.06% or less S: 0.06% Below, a steel slab (slab) containing acid-soluble Al: 0.005 to 0.100% N: 0.0010 to 0.0100% and the balance consisting of iron and unavoidable impurities is cooled to below the Ar ₃ transformation point. 1050 ℃
Heating to the above slab reheating temperature, hot rolling, Ar ₃
Finish at a temperature above the transformation point, wind at a temperature below 680 ° C., pickle, cold roll, recrystallize and anneal, 2% or more 10
Secondary cold rolling with a rolling reduction of less than 0.1% and a plate thickness of 0.26
mm or less, H _R30-T hardness is 62 or more, and tensile strength in the rolling direction is 44 kgf / mm ² or more.

(2) In% by weight, C: more than 0.0060% to less than 0.0600% Si: 0.06% or less Mn: 0.05 to 0.60% P: 0.06% or less S: 0 0.06% or less Acid soluble Al: 0.005 to 0.100% N: 0.0010 to 0.0100%, with the balance being iron and unavoidable impurities
After casting (slab), Ar ₃Cooling below the transformation point
Hot rolling at a surface temperature of 900 ° C or higher
Start, Ar₃Finish at a temperature above the transformation point, below 680 ° C
At the temperature of, pickled, cold rolled, recrystallized and annealed,
Secondary cold rolling is performed at a reduction rate of 2% or more and less than 10%, and the sheet is
Thickness is 0.26mm or less, H_R30-THardness is 62 or more and
Tensile strength in rolling direction is 44kgf / mm²The above
Of ultra-thin steel plate suitable for high-speed welding
Manufacturing method.

(3) The steel slab further contains Cr: 0.005 to 0.100% by weight, which is suitable for high-speed welding according to the above (1) or (2). Manufacturing method.

[0014]

The present invention will be described in detail below. If the C content is 0.0600% or more, the lap escape resistance is deteriorated, and the flange formability is significantly deteriorated by either the normal method or the reverse method. Therefore, the upper limit is set to less than 0.0600%. limit. From the viewpoint of weldability, 0.0300% or less is desirable. Further, the amount of C is 0.00
If it is less than 60%, the strength of the steel sheet will decrease, and if it is attempted to secure the strength, the ductility in the direction orthogonal to the rolling deteriorates, the stripping property deteriorates, and flange cracks frequently occur in the reverse method. Is limited to more than 0.0060%.

When the Si content exceeds 0.06%,
The lap escape resistance deteriorates, the plating adhesion deteriorates, the flange formability deteriorates, and the corrosion resistance deteriorates, so the upper limit is made 0.06%. If the amount of Mn exceeds 0.60%, the steel sheet is excessively hardened to deteriorate the flange formability and the lap escape resistance, and the cost increases, so the upper limit is set to 0.60%. In addition, the Mn content is 0.
If it is less than 05%, the steel sheet becomes soft and the H _R30-T hardness is 6
2 or more and the tensile strength in the rolling direction is 44 kgf / mm ²
Since the strength above cannot be secured, the lower limit is set to 0.05
Limited to%.

When the amount of P exceeds 0.06%, the steel sheet is excessively hardened to deteriorate the flange formability and the lap escape resistance, and the corrosion resistance is deteriorated. Therefore, the upper limit is made 0.06%. . If the amount of S exceeds 0.06%, hot brittleness is promoted, so the upper limit is made 0.06%.

When the content of acid-soluble Al exceeds 0.100%, the solid-solution Al hardens the steel sheet to deteriorate the flange formability and the lap escape resistance, and the cost becomes high. Therefore, the upper limit is set to 0. 100%. Further, when the acid-soluble Al content is less than 0.005%, the lap escape resistance deteriorates at the same time as the reason is not clear, but at the same time, deoxidation becomes insufficient and a steel sheet with a large amount of inclusions deteriorates the flange formability. Therefore, the lower limit is made 0.005%.

If the amount of N exceeds 0.0100%, the steel sheet becomes excessively hardened and the flange formability and lap escape resistance deteriorate, so the upper limit is 0.0100%.
And When the N content is less than 0.0010%, the lap escape resistance is significantly deteriorated, and at the same time, the steel sheet is softened and H
_R30-T hardness is 62 or more and tensile strength in rolling direction is 44
Since the strength of kgf / mm ² or more cannot be secured, the lower limit is made 0.0010%.

If the Cr content is less than 0.005%, so-called carbon stains in which graphite precipitates on the surface of the steel sheet during annealing in a non-oxidizing atmosphere are prone to occur, which significantly reduces the commercial value, so 0.005% or more is added. It is desirable to do. Further, if it exceeds 0.100%, the cost of the additive alloy increases, so the upper limit is made 0.100%. Steel having these components and the balance consisting of iron and unavoidable impurities is formed into a billet (slab) by ingot casting or continuous casting, and is subjected to hot rolling.

The heat history of the steel slab (slab) before hot rolling is
A normal process in which the material is once cooled below the Ar ₃ transformation point and then reheated, and a so-called direct rolling process in which a high temperature steel slab (slab) is subjected to hot rolling without being cooled below the Ar ₃ transformation point. Either of these can be taken. First, in the case of a normal process in which the material is once cooled to below the Ar ₃ transformation point and then reheated, when the slab reheating temperature is lower than 1050 ° C., AlN precipitated during cooling does not dissolve and solid solution N The product strength cannot be ensured by solution strengthening, and if the strength is to be secured in the subsequent secondary cold rolling, the stripping property deteriorates, so the lower limit of the slab reheating temperature is limited to 1050 ° C. Although the reason is not clear, when the slab reheating temperature is lower than 1050 ° C, the lap escape resistance also deteriorates. On the other hand, in the case of a so-called direct rolling process in which the high temperature steel slab (slab) is subjected to hot rolling without being cooled to below the Ar ₃ transformation point, when the steel slab (slab) surface temperature is lower than 900 ° C, Solid solution N is A
Since it precipitates as 1N and the strength of the product cannot be secured by solid solution strengthening of solid solution N, and in this case also, the plate cutting property and the lap escape resistance deteriorate, so the lower limit of the surface temperature is limited to 900 ° C.

When the hot rolling finishing temperature is below the Ar ₃ transformation point, a mixed grain structure is formed and a uniform material cannot be obtained, so the lower limit is set to the Ar ₃ transformation point. When the hot rolling coiling temperature exceeds 680 ° C., AlN precipitates, the solid solution N decreases, the steel sheet becomes soft and the H _R30-T hardness is 62 or more, and the tensile strength in the rolling direction is 44 kgf / Since the strength of mm ² or more cannot be secured, the lap escape resistance is deteriorated, and the carbide of the hot-rolled sheet is agglomerated to deteriorate the corrosion resistance, the upper limit is limited to 680 ° C.

The steel strip after hot rolling is
It is pickled, cold rolled and recrystallized annealed. After recrystallization annealing, secondary cold rolling is performed. If the rolling reduction ratio of the secondary cold rolling is less than 2%, the strength of H _R30-T hardness of 62 or more and the tensile strength in the rolling direction of 44 kgf / mm ² or more cannot be secured. Limited to 2%.
When the rolling reduction is 10% or more, the lap escape resistance is significantly deteriorated, the flange formability in the reverse method is significantly deteriorated, and the anisotropy of the material properties is increased. Therefore, the upper limit is 10%. Limited to less than.

The thickness of the steel plate after the secondary cold rolling is 0.26 mm
The following is to reduce the weight of the can and to save resources by making the can material thinner. In addition, H _{R30-T of} steel plate
Hardness of 62 or more and tensile strength in the rolling direction of 44 kgf
The reason for defining / mm ² or more is to ensure a predetermined can strength by supplementing the thinning of the plate thickness. The surface treatment applied to the steel sheet in the production method of the present invention does not matter.
That is, the effects of the present invention can be exerted by any plating used for steel plates for welding cans, such as tin plating, nickel plating, or a method of performing ultra-thin weight tin plating after special undercoating.

[0024]

EXAMPLE First, an example will be shown in which a normal process in which the heat history of a steel slab (slab) before hot rolling is once cooled below the Ar ₃ transformation point and then reheated is taken. Steels having the components shown in Table 1 were melted in a converter, the slabs were cooled to room temperature, and then reheated to the slab reheating temperature shown in the same table. Hot rolling to 0 mm, pickling, cold rolling, continuous annealing, secondary cold rolling to a plate thickness of 0.17 mm at the secondary cold rolling rate shown in the table, N
An i-plated chromate treatment was performed.

Table 2 shows the hardness, the tensile strength, the lap clearance and the stretch-flange processing rate of the Ni-plated chromate-treated steel sheet thus obtained. Here, the lap relief amount is a reading when welding is performed by applying maximum pressure using a high speed wire seam welding machine in the laboratory of the present inventors.
The difference in the wrap width between the edge and the trailing edge,
As a result of experiments so far, this lap relief amount is 0.2 mm
It has been found that, if the following is satisfied, even a consumer can withstand high-speed welding at a linear velocity of 30 meters per minute or more. Therefore, those with a lap relief amount of 0.2 mm or less were judged to be acceptable (indicated by ◯), and those with an amount of over 0.2 mm were judged to be unacceptable (indicated by x). Further, the stretch-flange processing rate refers to a processing rate up to occurrence of fracture when a simulation of flange processing of a welding can is performed by a flange forming machine of the inventors of the present invention, and the laboratory of the present inventors of the present invention In the case of the measuring method in
It is known that even more than 100% of customers are evaluated as passing. Therefore, if this is 9.0% or more, it passes (○
Indicated by () and less than 9.0% were judged as rejected (indicated by x).

In these tables, numerical values outside the scope of the present invention are underlined. Table 1 and Table 2
As can be seen from the above, the steel of the present invention has a high strength of H _R30-T hardness of 62 or more and a tensile strength of 44 kgf / mm ² or more, so that the reduction of the can strength due to the thinning of the plate thickness is sufficiently compensated. can do. Moreover, the stretch-flange processing rate is high in both normal method and reverse method,
It has a major feature that it can handle both normal and reverse methods. Also, the amount of lap escape is small, making it suitable for high-speed welding.

Next, a so-called direct rolling process in which the hot history of the steel slab (slab) before hot rolling is used for hot rolling as it is without cooling the hot slab (slab) to a temperature below the Ar ₃ transformation point. An example in the case of taking Steel having the components shown in Table 3 is melted in a converter, and hot rolling is started without cooling the steel slab (slab) to below the Ar ₃ transformation point at the steel slab (slab) surface temperature shown in the same table. Then, each was hot-rolled under the hot rolling conditions shown in the table to a plate thickness of 3.0 mm, pickled, cold-rolled, and continuously annealed, and the plate thickness of 0.
Secondary cold rolling was performed to 17 mm, and Ni plating chromate treatment was performed.

Table 4 shows the hardness, tensile strength, lap clearance, and stretch-flange processing rate of the Ni-plated chromate-treated steel sheet thus obtained. In these tables,
Numerical values outside the scope of the present invention are underlined. As can be seen from Tables 3 and 4, the steels of the present invention have H
_R30-T hardness is 62 or more and tensile strength is 44kgf / m
Since it has a high strength of m ² or more, it is possible to sufficiently compensate for the decrease in can strength that accompanies a thinner plate thickness. In addition, the stretch-flange processing rate is high in both the normal method and the reverse method, and it has a great feature that it can be used for both the normal method and the reverse method. Also,
Small amount of lap relief, suitable for high speed welding.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

INDUSTRIAL APPLICABILITY The present invention provides a high-strength ultra-thin steel plate for a welding can body having an H _R30-T hardness of 62 or more and a tensile strength in the rolling direction of 44 kgf / mm ² or more and a plate thickness of 0.26 mm or less. In the production of steel sheets, the restrictions on stripping direction in the can manufacturing industry were completely removed, and it is possible to produce cans by any of the normal method, the reverse method, and a mixture of these methods, and it is also suitable for high-speed welding. And its industrial value is extremely high.

Front page continued (72) Inventor Masao Ikeda 1-1 Tobata-cho, Tobata-ku, Kitakyushu, Fukuoka Prefecture Inside the Yawata Works, Shin Nippon Steel Co., Ltd. (72) Inoue Kono, No. 1 Tobita-cho, Tobata-ku, Kitakyushu, Fukuoka No. 1 inside Nippon Steel Co., Ltd. Yawata Works

Claims (3)

[Claims] 1. By weight%, C: more than 0.0060% to less than 0.0600% Si: 0.06% or less Mn: 0.05 to 0.60% P: 0.06% or less S: 0.0. 06% or less Acid soluble Al: 0.005 to 0.100% N: 0.0010 to 0.0100%, and the balance is a steel slab (iron) and unavoidable impurities (slab), less than Ar ₃ transformation point Cooled to 1050 ℃
Heating to the above slab reheating temperature, hot rolling, Ar ₃
Finish at a temperature above the transformation point, wind at a temperature below 680 ° C., pickle, cold roll, recrystallize and anneal, 2% or more 10
Secondary cold rolling with a rolling reduction of less than 0.1% and a plate thickness of 0.26
mm or less, H _R30-T hardness is 62 or more, and tensile strength in the rolling direction is 44 kgf / mm ² or more. 2. By weight%, C: more than 0.0060% to less than 0.0600% Si: 0.06% or less Mn: 0.05 to 0.60% P: 0.06% or less S: 0. 06% or less Acid-soluble Al: 0.005 to 0.100% N: 0.0010 to 0.0100%, with the balance being iron and inevitable impurities
After casting (slab), Ar ₃Cooling below the transformation point
Hot rolling at a surface temperature of 900 ° C or higher
Start, Ar₃Finish at a temperature above the transformation point, below 680 ° C
At the temperature of, pickled, cold rolled, recrystallized and annealed,
Secondary cold rolling is performed at a reduction rate of 2% or more and less than 10%, and the sheet is
Thickness is 0.26mm or less, H_R30-THardness is 62 or more and
Tensile strength in rolling direction is 44kgf / mm²The above
Of ultra-thin steel plate suitable for high-speed welding
Manufacturing method. 3. The method for producing an ultra-thin steel sheet for a welding can barrel according to claim 1, wherein the steel billet further contains Cr: 0.005 to 0.100% by weight.