JPH0689408B2 - Manufacturing method of steel plate for packing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for manufacturing a steel plate for packaging, and a steel plate for packaging (hereinafter referred to as a sheet) used as a hoop material for bundling cut sheets and coil products. The present invention relates to a method of manufacturing a steel sheet by continuous annealing.

[Conventional technology]

There are the following methods for manufacturing the conventional hoop material. One of them is
A steel plate containing 0.15 to 0.25% of C is slit into a predetermined width,
There is a method of manufacturing by heating through a lead bath and oxidizing during the cooling process. This has the problem of low productivity,
In addition, there is room for improvement in terms of hygiene and cost as lead baths are taken out by passing boards.

As another method, as disclosed in Japanese Patent Application Laid-Open No. 56-142824, when the steel sheet is passed through a steel sheet in an atmosphere containing oxygen at a temperature before reaching a predetermined annealing temperature while the continuous annealing line is rising. There is a method of manufacturing the hoop material. This is useful because it has the effect of manufacturing a hoop material by effectively utilizing a continuous annealing furnace, but the oxidation state at the time when the temperature inside the furnace and the oxygen concentration in the atmosphere are balanced is used. Therefore, there is a problem in that the work is not stable, and as a result, the strength of the packaging sheet, the thickness of the oxide film, and the surface color tone vary.

[Problems to be Solved by the Invention] By the way, the packaging sheet is required to have high strength, good workability to withstand bending and bending, and good rust resistance. It is an object of the present invention to stably produce the relevant packaging sheet material by continuous annealing.

[Means for solving problems]

The gist is that steel containing C: 0.10 to 0.30% and Mn: 0.10 to 1.50% is hot-rolled and cold-rolled according to a known process, and then an annealing temperature of 400-6
345 to 400 ° C during cooling after holding at 00 ° C for 10 seconds or more
In the method for producing a packaging sheet by continuous annealing, a steel sheet is blown with an oxidizing gas such as air or a mixture of steam and air within the temperature range of.

[Action]

 Next, the present invention will be described in detail.

The steel composition defines C and Mn in order to obtain the strength and workability required for a packing sheet.

When the content of C is small, the strength becomes low, and the strength as a packaging sheet material, for example, the tensile strength does not exceed 75 kg / mm ₂ ,
Therefore, the lower limit is set to 0.10. On the other hand, if the content is too high, the strength becomes too high, and it becomes difficult to carry out the packing work smoothly.

Mn is to prevent hot brittleness due to S inevitably mixed in
Contain 0.10% or more. This Mn has the effect of increasing the strength without deteriorating the workability, but if the content of Mn increases, the ladle smelting work becomes difficult, so the content is made 1.5% or less.

The other components do not need to be specified and are optional.

Steel consisting of the above components is smelted in a smelting furnace such as a converter or an electric furnace, and then is continuously cast or ingot-slab-rolled into a slab, which is hot-rolled by a known method, descaled, and cooled. Rolled.

After cold rolling, continuous annealing is performed, but the annealing temperature is 400 ° C or more in order to secure a ductility of 3% or more as a packaging sheet material and to withstand bending and bending during packaging. On the other hand, if the temperature becomes too high, recrystallization will occur completely and the desired strength will not be obtained, so the upper limit is made 600 ° C. The retention time requires 10 seconds or more to recover the cold rolled structure. As a result, the bending workability as a material property of the packaging sheet is excellent. When the steel sheet is in the temperature range of 350 to 400 ° C during cooling after annealing, an oxidizing gas such as air or a mixture of steam and air is blown. Such cooling is performed to eliminate variations in oxide film thickness and surface color tone and to stably improve the rust resistance of the steel sheet, and when the steel sheet is over 400 ° C or at a temperature of less than 345 ° C. Even if air or a mixture of air and water and air is sprayed on the surface, an oxide film having good rust resistance is not formed. Further, in order to obtain a good surface color tone, it is appropriate to form an oxide film within the above temperature range. The oxidizing gas such as a mixture of air is blown into the air or steam in order to keep the oxygen concentration near the steel plate in an atmosphere for forming an oxide film that enhances rust resistance.

〔Example〕

 Next, examples will be shown.

Steel consisting of C: 0.18%, Mn: 0.05%, P: 0.018%, S: 0.015% was melted in a converter and then made into a billet, and hot rolled to finish rolling with Ar ₃ points or more and a plate thickness of 3.2 mm After that, it was wound at 550 ° C, then the plate thickness was 0.
It was cold rolled to 7 mm and subsequently annealed at the temperatures shown in Table 1. Air was blown onto the steel strip at the same temperature as shown in Table 1 during the annealing. After annealing, the steel strip was subjected to color tone, tensile test and rusting test. As a result, steel No.2,3,4,
5,6,7 have a blue color tone, and rusting hardly occurs,
Further, it has a tensile strength of 75 kg / mm ² or more and has ductility and workability, and can be manufactured from a material preferable as a hoop material.

According to the method of the present invention, the blue sheet for packaging can always be stably manufactured with high productivity, and its industrial significance is great.

Claims (1)

[Claims] 1. A steel containing C: 0.10 to 0.30% and Mn: 0.10 to 1.50% is hot-rolled, cold-rolled, then held at an annealing temperature of 400-600 ° C. for 10 seconds or more, and then cooled at 345 A method for producing a steel sheet for packaging, which comprises performing continuous annealing in which an oxidizing gas is blown onto the steel sheet at a temperature of ~ 400 ° C.