JPS63134695A - Tin-free steel sheet for welded can and its production - Google Patents

Abstract

PURPOSE:To produce the title tin-free steel sheet for a welded can having excellent corrosion resistance at a low cost by temper-rolling a cold-rolled steel sheet with use of a work roll dulled by a laser pulse beam, and further electroplating chromium on the steel sheet. CONSTITUTION:The cold-rolled steel sheet which has been cold-rolled, cleaned, and annealed is further temper-rolled. The temper rolling is carried out with use of the work roll which has been dulled by a laser pulse beam and on the surface of which fine crater-shaped recess holes are regularly bored. By this method, the dull pattern is transferred to the surface of the temper-rolled colled- rolled steel sheet, and the protrusions of approximately the same shape are arranged at the regular pitch. The temper-rolled cold-rolled steel sheet is then electroplated with chromium. As a result, a tin-free steel sheet for a welded can having excellent corrosion resistance, workability, formability, coated film adhesion, and weldability is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to welded cans commonly used for food cans, beverage cans, 181 cans, baling cans, and other miscellaneous cans (or art cans). This invention relates to a tin-free steel sheet for use and a manufacturing method thereof.

[Prior Art] Generally, tinplate and tin-free steel sheets (hereinafter abbreviated as TFS) are mainly used as materials for cans. This material for cans is used for soldering irons and adhesive cans.

Welded cans, etc. are manufactured, but recently, resource saving, cost reduction,
In terms of appearance, etc., tin cans are rapidly transitioning from semi-J cans to welded cans. As a result, tin is the most commonly used material for welded cans, and in order to reduce costs, tin weights of 2.8 g/tri or more have been replaced with thinner tin weights of 1.0 g/rri or less. something is being developed. However, from a cost point of view, even light weight furiki cannot be said to be superior to TFS. TFS is also corrosion resistant and processable.

The use of TFS is increasing, partly because its properties such as paint film adhesion are comparable to or even better than tinplate.
The current problem is that can making methods are limited to adhesive cans. In other words, since TFS is a steel plate with a thin protective film formed on its surface consisting of a metallic chromium layer and a chromium hydrated oxide layer, it cannot be soldered, and because of the high electrical resistance and high melting point of the above film. Since it has the disadvantage of being difficult to weld, it is mostly used as an adhesive can.

However, when the contents of the can are subjected to high-temperature sterilization, this adhesive can may cause problems such as the adhesive portion being torn and the can being destroyed. Although the modification of the chromium hydrated oxide film of TFS has significantly improved bond strength, adhesive cans are always associated with the above-mentioned risks. Therefore, if weldable TFS were developed, not only would the above problems be solved, but the overlapping allowance at the joint would be reduced from 5 dragons (adhesive cans) to 0.
2 to 0.4 length, which saves material and prevents the risk of vacuum leakage from the seaming part. In the publication, weldable T
FS and methods of manufacturing the same are provided.

[Problem that the invention seeks to solve]

However, in these conventional weldable TFS, weldability is improved by reducing the amount of metallic chromium or non-metallic chromium, so the metallic chromium layer on the surface of the steel sheet becomes porous. structure, resulting in a significant decrease in corrosion resistance. Also, what about chromium-plated steel sheets in which metallic chromium is deposited in granular form through intermittent electrolysis? Although it is known that the 8-contact property is improved, there is also a problem that the corrosion resistance is low due to the non-uniform distribution of the particulate metal chromium.

This invention was made in view of these conventional problems, and aims to solve the above problems by creating a steel plate that is chromium plated after transferring a dull pattern using a laser pulse beam. It is said that

[Means for solving problems]

The present invention relates to a tin-free steel plate for welded cans, which is temper-rolled using a work roll whose surface is dulled by a laser pulse beam, and which is subjected to electrochromium plating after rolling, and a method for manufacturing the steel plate. As an invention, cold rolling and cleaning.

Provided is a method for manufacturing a steel sheet, which comprises temper-rolling a cold-rolled steel sheet that has been subjected to annealing, etc. using a work roll that has been dulled by a laser pulse beam, and then electrochroming the cold-rolled steel sheet. It is something to do.

[Effect]

The surface of a work roll that has been dulled by laser pulse beam processing has crater-shaped minute holes arranged in a regular manner. The dull pattern of the work roll is transferred onto the surface of the cold rolled steel sheet that has been temper-rolled by the work roll, so that protrusions of approximately the same shape are arranged at equal pitches. Next, a tin-free steel plate for a welded can is obtained by applying electrochromium plating to the cold-rolled steel plate on which such a dull pattern has been formed.

When resistance welding is performed on this steel plate, when the protrusions of the metallic chromium layer formed on the surface of the steel plate are pressurized by the electrode of the welding machine, these hard protrusions destroy the high-resistance chromium oxide film, making it easier for current to pass through. This makes resistance welding possible, and since the dull pattern created by the laser pulse is uniform, the non-uniformity of the contact resistance depending on the location is extremely small, making it possible to perform good welding.

〔Example〕

The present invention will be explained below with reference to test results of Examples thereof.

First, a work roll for temper rolling is attached to a laser processing device and the work roll is rotated. Next, while irradiating the roll surface with a laser pulse beam, a laser oscillator is moved parallel to the roll axis to form a dull pattern in which crater-shaped microholes are formed at equal density over the entire surface of the roll. When a roll with this dull pattern is used to temper-roll a steel plate that has undergone cold rolling, cleaning, annealing, etc., the dull pattern of the roll is transferred to the steel plate, and countless minute protrusions are formed at equal density. is formed. Next, this steel plate is subjected to electrochromium plating to form a thin protective film consisting of a metallic chromium layer and a chromium hydrated oxide layer on its surface, resulting in a so-called tin-free steel plate (TFS).

Next, to manufacture a welded can using this TFS as a base material,
Generally, a resistance welding machine (wire welder) as shown in FIGS. 2 and 3 is used to perform electric resistance seam welding, for example, on the side seam joint of a can body.

In the figure, l is the base material (can body) overlapped with a predetermined overlap margin, 2 is a pair of electrode rollers, and 3 is a body as a secondary electrode that is wrapped around the electrode roller and moves as the electrode roller rotates. It is a wire electrode.

Now, the can body 1 is held under pressure by the electrode, and the secondary electrode 3
When energized through the can, the can body is welded by resistance heating due to contact resistance. This is because when a load is applied by the above-mentioned pressure holding to the minute protrusions of the metal chromium layer on the surface of the base material on which the dull pattern has been transferred, the protrusions of the hard metal chromium layer destroy the high-resistance chromium oxide film. This is thought to be because it becomes easier for current to pass through. Since the protruding portion forms a uniform dull pattern using the laser pulse beam, the non-uniformity of contact resistance, which has the greatest effect on seam welding, is extremely small, and therefore good seam welding can be performed.

Next, a specific example of this embodiment will be explained.

When temper-rolling the original sheet for TFS, a work roll with a roughness Ra of 0.8 μm was used for the No. 1 stand work roll so that no dowels remained after No. 2 stand rolling, and a conventional No. 2 stand work roll was used as a comparative example. One with #240 bright finish and one after #240 bright finish as an example,
A coil having a plate thickness of 0.2 fins was temper-rolled at an elongation rate of 1.5% using the laser dulled coil. After temper rolling, the above two types of coils were subjected to ordinary electrochromium plating, and the amount of metallic chromium was 110 mg/rrr, and the amount of chromium oxide was 18 mm/rrr.

Characteristic evaluation tests for each TFS obtained in this manner were conducted as follows.

(1) Weldability test (contact resistance test) Two sample original plates (20 layers x 100 dragons) sampled from each coil were stacked together and placed between iron electrode rollers (70φ) via a 2.0φ body wire electrode. Insert and speed 6.
5m/min, constant voltage 1.5V, electrode pressure 25, 50.
The current between the electrodes was measured while feeding the original plate under each condition of 75 kg/cnt, and the contact resistance value was determined.

The results are shown in FIG. In the example, the interelectrode pressure was 50
The resistance value was 125 mΩ or less at kg/cn1 or more.

This shows that the value is comparable to that of the unplated original plate. Also, the variation in resistance value is smaller than that of the comparative example.

(2) Paint adhesion test Apply epoxy phenol paint for can making to the surface of the sample at a dry weight of 50 cm/dm2 per side. After baking, apply 3% NaC1! immersed in an aqueous solution, 11
After retort treatment at 0°C for 120 minutes, the coating film was cross-cut with a cutting edge and a tape peeling test was performed, but no peeling was observed in both the comparative example and the example.

[Effects of the Invention] As explained above, according to the invention, it has corrosion resistance and processability equal to or better than that of furiki, and coating film adhesion significantly superior to that of furiki. It is possible to obtain a tin-free steel plate for welded cans that is lower in price than conventional steel sheets and has satisfactory weldability.

[Brief explanation of the drawing]

FIG. 1 is a comparison diagram of seam weldability between an example and a conventional example (comparative example), FIG. 2 is a schematic diagram of a seam welding machine, and FIG. 3 is an enlarged cross-sectional view taken along line A-A in FIG.

Claims (2)

[Claims] (1) A tin-free steel plate for welded cans, which is temper-rolled using a work roll whose surface is dulled by a laser pulse beam, and further electroplated with chrome. (2) After cold-rolling a cold-rolled steel sheet that has been cold-rolled, cleaned, annealed, etc. using a work roll that has been dulled by a laser pulse beam, the cold-rolled steel sheet is further subjected to electrochromium plating. A method for manufacturing a tin-free steel plate for welded cans, characterized by: