JPH06142706A - Production of hard cold rolled steel sheet or raw sheet for tin plate - Google Patents

Abstract

PURPOSE:To attain a method for manufacturing a hard cold rolled steel sheet or material sheet for tin plate on which the generation of stain is less and whose surface properties are excellent by cold rolling process. CONSTITUTION:A hot rolled coil is rolled by cold rolling, the coil is cleaned in an electrocleaning equipment, annealed in a box annealing furnace, next fed to the 1st stand of a rolling equipment which is composed of two or more stands at the surface temp. of coil of >=35 deg.C and rolled. Then, since the coil is fed to the 1st stand of the rolling equipment after heating the surface temp. of coil to >=35 deg.C, the incidence of stain on the surface of coil is decreased, the yield of product is improved and the hard cold rolled steel sheet or raw sheet for tin plate on which the generation of stain is less and whose surface properties are excellent is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hard cold-rolled steel plate or a tin plate by a double cold pressing method.

[0002]

2. Description of the Related Art A method for producing a hard cold-rolled steel plate or a tin plate (having a tensile strength of 80,000 psi or more, or a hardness of 70 or more for HR30T) is obtained by rolling a hot-rolled coil in a cold rolling mill and then It is cleaned in an electrolytic cleaning facility, further annealed in a box annealing furnace, and the coil is rolled in a rolling facility composed of two or more stands. FIG. 6 shows a conventional apparatus for manufacturing a hard cold-rolled steel plate or a tin plate.

FIG. 6 (a) shows a cold rolling mill, which comprises a payoff reel 1, a stand 2 composed of 5 to 7 and a tension reel 3. FIG. 6B shows an electrolytic cleaning facility, which includes a payoff reel 1, a welding machine 4, an immersion tank 21 including an alkali tank, an electrolytic tank, a hot rinse, an outlet shear 9, and a tension reel 3.
FIG. 6C shows a box annealing furnace, which is composed of a burner 22, an inner cover 23, and an outer cover 24. Figure 6
(D) is rolling equipment, which comprises a payoff reel 1, two or more stands 10 and a tension reel 3.

As described above, in the method for producing a hard cold-rolled steel sheet or tin plate by the double cold pressing method, rolling oil is used because the cold rolling rate in the rolling equipment is higher than that in ordinary temper rolling. .

[0005]

However, in these methods, in order to secure the rollability under high pressure with the roughness Ra bright roll (Ra = 0.2 to 0.35 μm) of the first stand 10a of the rolling equipment. Second, using rolling oil
In the bright roll of the stand 10b, non-lubricating rolling is performed in order to secure a predetermined coil surface roughness, and light rolling is performed to prevent surface roughness and roughness due to pits due to oil particles and to improve shape controllability. ing.

A pattern (hereinafter referred to as "stain") is generated on the surface of the coil during high-pressure rolling with the bright roll of the first stand 10a, and the stain remains on the surface of the coil even when rolled with the bright roll of the second stand 10b. However, there is a problem that the commercial value of the hard cold-rolled steel sheet or the tin plate is reduced and the yield of the hard cold-rolled steel sheet or the tin plate is reduced.

The present invention has been made to solve the above problems, and provides a method for producing a hard cold-rolled or tin plate having excellent surface properties with less stain. .

[0008]

A method of manufacturing a hard cold rolled steel sheet or a tin plate according to the present invention comprises rolling a hot rolled coil with a cold rolling mill, cleaning the coil with an electrolytic cleaning facility, and packaging the coil with a box. It is characterized in that it is annealed in an annealing furnace, and then the coil is charged into a first stand of a rolling facility composed of two or more stands at a coil surface temperature of 35 ° C. or higher and rolled.

[0009]

In order to solve the above problems, the inventors analyzed the actual operation data and investigated what caused the stain. Therefore, a test was conducted in which the surface temperatures of the coils charged into the rolling equipment were changed.

FIG. 1 is a graph showing the relationship between the surface temperature of the coil charged in the rolling equipment and the stain generation index. As is clear from this figure, it was found that when the surface temperature of the coil charged into the rolling equipment is 35 ° C. or higher, the occurrence of stain is small.

Next, means for achieving such a surface temperature of the coil will be described. When the surface temperature of the coil extracted from the box annealing furnace is high, air and the surface of the high temperature coil react with each other to generate a temper color, so to prevent this temper color, the coil extracted from the box annealing furnace Surface temperature of 100 to 120 ° C. or lower is required.

FIG. 2 is a graph showing the relationship between the elapsed time from the extraction of the annealed coil from the box annealing furnace to the loading of the coil into the rolling facility and the surface temperature of the coil loaded into the rolling facility. Is. In the upper part of the figure, the coil unit weight is 25t.
In the lower stage, the coil unit weight is 14t.

As is clear from FIG. 2, if the elapsed time is within 53 hours from the extraction of the annealed coil from the box annealing furnace to the insertion of the coil into the rolling equipment, the coil to be inserted into the rolling equipment. Surface temperature of 35 ° C or higher. Thus, considering the rolling chance (depending on the ambient temperature from the extraction of the annealed coil from the box annealing furnace to the loading of the coil into the rolling equipment), the surface temperature of the coil should be 35 ℃ or more. Can be secured.

However, there are restrictions on rolling chances such as roll surface roughness during rolling, roll profile, and coil retention, so the surface temperature of the coil charged into the rolling equipment is 35 ° C.
It is difficult to keep the above stable, so special consideration is required.

That is, immediately before the rolling mill or the first rolling mill.
It is heating in front of the stand. Also, this rolling is usually carried out in air. At this time, the air and the surface of the high temperature coil are oxidized to generate a temper color.
It is preferable to charge the rolling mill at a temperature of 00 ° C or lower.

[0016]

EXAMPLES The present invention will be described based on examples. FIG. 3 is a diagram showing an apparatus according to an embodiment of the present invention. The apparatus of the embodiment of the present invention comprises a cold rolling mill, an electrolytic cleaning device, a box annealing furnace, a heating device and rolling equipment. The heating device and the rolling equipment are configured by the same device. Here, the heating device is an induction heater or a hot water heating device.

Since the cold rolling mill, the electrolytic cleaning device and the box annealing furnace have been described in the prior art, only the heating device and rolling equipment will be described here. FIG. 3A shows an induction heater installed as a heating device.
In (b), a hot water heater is installed as a heating device. 1 is a pay-off reel, 4 is a welding machine, 11 is an induction heater, 10 is a stand of two or more, and 3 is a tension reel. Reference numeral 13 is a hot water heater, and 14 is a ringer roll.

The temperature of the coil surface is measured with the pay-off reel 1, and the temperature of the coil surface charged into the first stand 10a of the rolling equipment is 35 ° C. or higher by the induction heater 11 or the hot water heater 13 according to the temperature of the coil surface. Heat to become. The first stand 10 of this rolling equipment
In a, rolling oil was sprayed onto the rolls for rolling, and in the second stand 10b, a bright roll was used for rolling.

FIG. 4 is a graph showing the relationship between the temperature of the coil surface and the frequency (%) before and after the heating device. Figure 4 (a)
Is a graph showing the relationship between the temperature of the coil surface and the frequency (%) before charging the heating device when the induction heater is installed as a heating device, and FIG. 4 (b) is the first stand of the rolling equipment. It is a graph which shows the temperature of the coil surface before charging, and the relationship of frequency (%). As is apparent from this figure, the temperature of the coil surface before charging the heating device is 1
Although it varies from 5 to 65 ° C., the temperature of the coil surface before charging to the first stand of the rolling equipment of Example 1 is 40 to 40 ° C.
It varies to 70 ° C.

Regarding the operating conditions in this rolling facility, the properties and composition of the rolling oil used are those shown in Table 1, and the cold rolling reduction was carried out under the conditions shown in Table 2. In Table 2, the cold pressing ratio is the cold pressing ratio when the tin plate is rolled. The cold pressure ratio is the cold pressure ratio of two stands in total.

[0021]

[Table 1]

[0022]

[Table 2]

FIG. 5 is a graph showing the relationship between the stain occurrence rate between the example and the conventional example. As is clear from this figure, the embodiment of the present invention has a significantly lower stain generation rate than the conventional example. Here, the same result was obtained even when the hot water heater 13 was installed as the heating device instead of the induction heater 11.

[0024]

As described above, according to the present invention, since the temperature of the coil surface is charged to the first stand of the rolling equipment at 35 ° C. or higher, the occurrence rate of stains on the coil surface is reduced, so that the product The yield can be improved, and a hard cold-rolled steel sheet or tin plate having excellent surface properties with less stain can be manufactured.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a surface temperature of a coil loaded in a rolling facility and a stain generation index.

FIG. 2 is a graph showing the relationship between the elapsed time from the extraction of the annealed coil from the box annealing furnace to the charging of the coil into the rolling equipment and the surface temperature of the coil charging into the rolling equipment.

FIG. 3 is a diagram showing an apparatus according to an embodiment of the present invention.

FIG. 4 is a graph showing a relationship between temperature and frequency (%) of a coil surface before and after a heating device according to an example of the present invention.

FIG. 5 is a graph showing a relationship between a stain occurrence rate and an example of the present invention and a conventional example.

FIG. 6 is a view showing an apparatus for manufacturing a conventional hard cold-rolled steel plate or tin plate.

[Explanation of symbols]

 1 Pay-off reel 3 Tension reel 4 Welder 10 Stand 10a 1st stand 10b 2nd stand 11 Induction heater 13 Hot water heater 14 Ringer roll

Claims (1)

[Claims] A hot rolling coil is rolled by a cold rolling mill, the coil is cleaned by an electrolytic cleaning facility, the coil is annealed in a box annealing furnace, and then the coil is configured by two or more stands. The method for producing a hard cold-rolled steel sheet or tin plate according to claim 1, wherein the first stand is charged at a coil surface temperature of 35 ° C or higher and rolled.