JPH086143B2 - Manufacturing method of steel plate for ultra-thin welding can with excellent stripping property - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an ultrathin body plate for a welded can body, which is free from deterioration of ductility in a direction orthogonal to rolling and has excellent stripping properties.

[Conventional technology]

Conventionally, joining of cans has been performed by methods such as soldering, resin bonding, and welding. Among them, in order to improve the steel plate yield, a method by welding that can reduce the joint margin is
It is becoming mainstream in recent years.

In the process of manufacturing the welded can, 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 welded can body, and this is called flanging. During flanging, cracks that cause the contents of the can to leak into 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.

Causes of flange cracks include poor joining due to welding, poor workability of steel sheets, inclusions in steel sheets, hardening of welds, and softening of heat-affected zones of welding.

On the other hand, the plate thickness of the material for cans tends to be thin from the viewpoint of resource saving, and the decrease in can strength due to the thin plate pressure is dealt with by increasing the hardness of the steel plate. As such a thin steel sheet, as seen in JP-A-51-131413, after cold rolling a hot rolled steel sheet, annealed and cold rolled again,
Steel sheet manufactured by the so-called double cold rolling method, so-called duffle reduced steel sheet (hereinafter abbreviated as DR steel sheet)
There is.

However, the DR steel sheet has a drawback that the workability deterioration of the steel sheet and the softening of the heat-affected zone of the welding due to the secondary cold rolling strain are remarkable, and that a flange crack often occurs in the flanging after welding. A method for solving this problem is disclosed in
In some cases, the material is softened by hot rolling such as 58-164752 by hot rolling.

However, these conventional steel plates have large anisotropy in material properties, and plate cutting such that the rolling direction of the steel plate is parallel to the axial direction of the can body (hereinafter, this plate cutting method is referred to as the reverse method).
Since flange cracking frequently occurs after welding, the can manufacturer performs plate cutting so that the rolling direction of the steel plate is always perpendicular to the axial direction of the can body (hereinafter, this method is referred to as the normal method). There was a problem that forced the constraint that it had to be. Moreover, the lower limit of the thickness of the steel sheet produced by these existing technologies is about 0.17 mm, which limits the pursuit of resource saving and cost saving by thinning. 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.

[Problems to be Solved by the Invention]

INDUSTRIAL APPLICABILITY The present invention solves the above-mentioned problems, completely removes restrictions on a plate making direction in a can manufacturing company, and can make a plate by any of a normal method, a reverse method, and a mixture thereof, and a flange. It is intended to provide a method for producing an ultrathin body plate for a welding can body, which does not cause cracking and has a particularly thin plate thickness of 0.15 mm or less and high strength characteristics.

[Means for solving the problem]

As a result of experiments and research for achieving the above object, the present inventors have found that it is important to secure steel plate strength and prevent ductility deterioration in the direction orthogonal to rolling in order to improve the stripping property. However, it was newly found that this can be achieved by combining the amount of C, the billet heating conditions and hot rolling conditions prior to hot rolling, and the secondary cold rolling reduction.

The present invention is based on this finding,
The gist is (1)% by weight, C: more than 0.0060% and less than 0.0300% Si: 0.060% 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% Steel slab (slab) consisting of balance of iron and unavoidable impurities is cooled to below Ar3 transformation point, and 1200
Slab reheating temperature above ℃, hot rolling, Ar3
Finishing at a temperature above the transformation point, pickling, cold rolling, recrystallization annealing, secondary cold rolling at a rolling reduction of 10% to less than 25%, plate thickness 0.15 mm or less, HR30-T There is a method for producing an ultra-thin steel sheet for a welding can body, which has a hardness of 62 or more and a tensile strength in the rolling direction of 44 kgf / mm ² or more and is excellent in stripping property.

 Hereinafter, the present invention will be described in detail.

If the C content is 0.0300% or more, the flange formability is significantly deteriorated in both the normal method and the reverse method when the plate thickness is extremely thin. Therefore, the upper limit is limited to less than 0.0300%. 0.0200 to obtain particularly excellent flange formability
% Or less is preferable. Further, when the C content is 0.006% or less, the strength of the steel sheet is reduced, and when it is attempted to secure the strength, the ductility in the direction orthogonal to the rolling is deteriorated, the stripping property is deteriorated, and flange cracks frequently occur in the reverse method. Therefore, the lower limit is limited to more than 0.0060%.

If the Si content exceeds 0.06%, the plating adhesion deteriorates, the flange formability deteriorates, and the corrosion resistance deteriorates, so the upper limit is made 0.06%. In order to stably obtain excellent flange formability, the Si content is preferably 0.03% or less.

If the Mn amount exceeds 0.60%, the steel sheet is transiently hardened to deteriorate the flange formability and the cost increases, so the upper limit is set to 0.60%. In addition, the Mn amount is 0.05
%, The steel plate becomes soft, and the HR30-T hardness of 62 or more and the tensile strength in the rolling direction of 44 kgf / mm ² cannot be ensured. By increasing the secondary cold rolling rate, If you try to make up for it, the flange formability in the reverse method will deteriorate, and therefore the planing property will deteriorate, so the lower limit is 0.05%.
Limited to In order to obtain particularly excellent plate cutting properties, the Mn content is 0.
It is preferably 10% or more.

If the P content exceeds 0.06%, the steel sheet is transiently hardened to deteriorate flange formability and corrosion resistance, so the upper limit is made 0.06%. In order to obtain particularly excellent flange formability, the P content is preferably 0.02% or less.

If the S content exceeds 0.06%, hot brittleness is promoted, so the upper limit is made 0.06%. The preferred range is 0.025
% Or less.

When the content of the acid-soluble Al exceeds 0.100%, it is combined with the solid solution N to form an AlN precipitate, and the solid solution strengthening effect of the solid solution N is reduced to soften the alloy to ensure a predetermined strength. Since there is no choice but to increase the secondary cold rolling rate, the flange formability by the reverse method deteriorates, and thus the plateability decreases, and the cost increases, so the upper limit is made 0.100%. The amount of acid-soluble Al is preferably 0.040% or less in order to obtain particularly excellent plate cutting properties. Also, acid-soluble Al
Is less than 0.005%, deoxidation becomes insufficient and a steel sheet with a large amount of inclusions is formed, deteriorating flange formability, so the lower limit is made 0.005%.

If the amount of N exceeds 0.0100%, the steel plate transiently hardens and the flange formability deteriorates, so its upper limit is set to 0.
0100% Further, when the N content is less than 0.0010%, the steel sheet becomes soft and the HR30-T hardness is 62 or more and the tensile strength in the rolling direction is 44 kgf / mm ² or more. Since the secondary cold rolling rate must be increased, the flange formability by the reverse method deteriorates,
Therefore, the stripping property deteriorates, so the lower limit is made 0.0010%. In order to obtain particularly excellent planing properties, the N content is 0.0030%.
It is preferable to make the above.

Steel having these components and the balance consisting of iron and unavoidable impurities is ingot-cast into slabs and subjected to hot rolling.

The hot rolling history of the steel slab (slab) before hot rolling is subjected to hot rolling through a step of cooling once below the Ar3 transformation point and then reheating.

First, in the case of the step of reheating after being cooled to below the Ar3 transformation point, when the slab reheating temperature falls below 1200 ° C, AlN precipitated during cooling does not dissolve, and solid solution strengthening of solid solution N is caused. The product strength cannot be secured, and if it is attempted to secure the strength in the subsequent secondary cold rolling, the stripping property deteriorates, so the lower limit of the slab reheating temperature is limited to 1200 ° C. The slab reheating temperature is 1200 ° C in order to obtain particularly excellent planing properties.
It is preferable to make the above.

If the hot-rolling finishing temperature is below the Ar3 transformation point, a mixed grain structure is formed and a uniform material cannot be obtained, so the lower limit is limited to the Ar3 transformation point.

The hot rolling coiling temperature is not limited, but when it exceeds 680 ° C, AlN is released, the solid solution N is reduced, and the steel sheet is softened and HR3
0-T hardness is 62 or more and tensile strength in rolling direction is 44kgf / m
It may be difficult to secure the strength of m ² or more, and the carbide of the hot-rolled sheet tends to agglomerate to deteriorate the corrosion resistance. Therefore, the upper limit is preferably 680 ° C.

The steel strip that has been hot-rolled is descaled, cold-rolled, and recrystallized by recrystallization annealing in a conventional manner, and then secondary cold rolling is performed. The reduction ratio of the secondary cold rolling is
If this is less than 10%, the HR30-T hardness of 62 or more and the tensile strength in the rolling direction of 44 kgf / mm ² or more cannot be secured, so the lower limit is limited to 10% or more. Steel plate pressure
Even if it is 0.15 mm or less, 2 is necessary to secure particularly excellent can strength.
The next cold rolling rate is preferably 15% or more. Also,
If the reduction rate is high, the flange formability in the reverse method is significantly deteriorated and the anisotropy of material properties is increased, so the upper limit is limited to less than 25%.

The thickness of the steel sheet after the secondary cold rolling is 0.15 mm or less, because this is to make the can material particularly thin and to reduce the weight of the can and save resources. The preferred range is 0.13 mm or less. Further, the HR30-T hardness of the steel sheet is specified to be 62 or more and the tensile strength in the rolling direction is specified to be 44 kgf / mm ² or more in order to compensate for the thinning of the sheet pressure and to secure a predetermined can strength.

The surface treatment applied to the steel sheet by the manufacturing method of the present invention is
The method does not matter. That is, the operation and effect of the present invention can be exerted with any plating used for the molten steel sheet for the welding can, such as tin plating, nickel plating, or a method of performing ultra-thin weight tin plating after special undercoating.

〔Example〕

First, the history of thermal coverage of the steel slab before hot rolling is once Ar.
An example is shown in which a step of reheating after being cooled to less than 3 transformation points is taken.

Steel having the components shown in Table 1 is melted in a converter, the slab is cooled to room temperature, and then reheated to the slab reheating temperature shown in the table, and the plate thickness is 3.0 under the hot rolling conditions shown in the table. m
hot rolled to m, pickled, cold rolled, continuously annealed,
Secondary cold rolling was performed at a secondary cold rolling rate shown in the table to a plate thickness of 0.13 mm, and ultrathin tin plating was performed.

The hardness of the ultrathin tin-plated steel sheet thus obtained,
Table 2 shows the tensile strength and the stretch-flange processing rate.
Here, the stretch-flange processing rate refers to a processing rate until breakage occurs 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 measurement method in (1), it is known that more than 9.0% are evaluated as acceptable even by customers.

As can be seen from Tables 1 and 2, the steels of the present invention have a high hardness of 62 or more and a tensile strength of 44 kgf / mm ² or more, so that the reduction of the can strength as the plate thickness becomes thinner. Can be fully guaranteed. Moreover, the stretch-flange processing rate is high in both the normal method and the reverse method, and has a major feature that it can be used for both normal and reverse plate cutting. On the other hand, out of the present invention, sample No. 4 has excellent flange formability, but lacks strength. Sample No. 5 has poor flange formability in the reverse method and lacks strength. Sample Nos. 6 and 7 have sufficient strength, but have poor flange formability in the reverse method.

[Effect of the invention] The present invention has a hardness of 62 or more and a tensile strength in the rolling direction.
When manufacturing high-strength ultra-thin steel plates for ultra-thin welded can bodies with a plate thickness of 0.15 mm or less that is 44 kgf / mm ² or more, completely remove the restrictions on the plate making direction at the can manufacturer, and use the normal method, reverse method, and It provides a method for manufacturing a steel sheet that can be manufactured by any of the mixed sheet cuttings, and its industrial value is extremely large.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Seiichi Tanaka 1-1-1, Edamitsu, Yawatahigashi-ku, Kitakyushu, Fukuoka Prefecture Nippon Steel Co., Ltd. Yawata Works (56) Reference JP-A-59-113123 ( JP, A) JP-A-3-36215 (JP, A) JP 60-45690 (JP, B2)

Claims (1)

[Claims] (1) By weight%, C: more than 0.0060% and less than 0.0300% Si: 0.060% 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: A steel slab (slab) containing 0.0010 to 0.0100% balance of iron and unavoidable impurities is cooled to below the Ar3 transformation point, and
Slab reheating temperature above ℃, hot rolling, Ar3
Finishing at a temperature above the transformation point, pickling, cold rolling, recrystallization annealing, secondary cold rolling at a rolling reduction of 10% to less than 25%, plate thickness 0.15 mm or less, HR30-T A method for producing an ultra-thin steel sheet for a welding can body, which has a hardness of 62 or more and a tensile strength in the rolling direction of 44 kgf / mm ² or more and is excellent in stripping property.