JPH03184605A - Temper rolling method of bright steel sheet - Google Patents

Abstract

PURPOSE:To obtain the optimum elongation percentage without requiring a great deal of rolling force by applying carbonic solid lubricant to the surface of steel sheet on the inlet side of a temper rolling mill and temper rolling using bright rolls with a specified surface roughness. CONSTITUTION:On the inlet side of the temper rolling mill for a steel sheet 1 which is annealed following cold rolling/cleaning, the carbonic solid lubricant which is stored in a hopper which is composed of guide boards 5 is carried downward by the rotation of a roll 6 which are provided with projecting and recessing parts on the surface thereof. And, the carbonic solid lubricant is electrified with an electrostatic supplyer 4 and uniformly sprinkled by allowing to attract on the surface of the steel sheet 1 which is passed under it. In the temper mill, dry temper rolling is executed using the bright rolls of which the surface roughness is <=0.8mum of mean roughness Ra. In this way, the elongation percentage of temper rolling is stably secured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention is a method for preparing bright steel plates for the purpose of eliminating yield point elongation, adjusting surface roughness, modifying shape, adjusting surface hardness, etc. of steel plates after annealing. Concerning quality rolling method.

BACKGROUND OF THE INVENTION As is well known, the typical manufacturing process for cold-rolled steel sheets is refined through the steps of steelmaking, continuous casting, hot rolling, pickling, cold rolling, cleaning, annealing, and temper rolling.

- Skin pass rolling (hereinafter referred to as "pressure conditioning") for boat fishing is used to eliminate the yield point elongation of the steel plate after annealing, adjust the surface roughness, modify the shape,
For the purpose of adjusting surface hardness, etc., the rolling reduction rate is usually 0.5 to 1.
．． The rolling process is carried out under conditions of a light reduction of 4% by wet pressure regulation, in which temper rolling oil (hereinafter referred to as "pressure regulation oil") is injected onto the surface of the work roll through a nozzle.

This wet pressure regulation is a method of supplying a large amount of pressure regulating oil injected from a nozzle to the roll biting side.

Therefore, it is possible to obtain excellent rolling properties and a large elongation rate under pressure control. Furthermore, since the surface of the work roll is cleaned with pressure regulating oil during rolling, foreign matter such as iron powder attached to the surface of the steel plate adheres and accumulates on the work roll surface, causing indentation scratches and rolling machine housing. It is possible to prevent steel plate surface flaws such as oil pits caused by oil droplets falling from the work roll adhering to the surface of the work roll, and it is possible to manufacture a steel plate with excellent surface quality.

By the way, when manufacturing so-called bright steel sheets, such as polished steel sheets (cold-rolled high-carbon steel sheets), which have beautiful surfaces and excellent gloss, pressure regulating rolls are used to reduce the surface roughness of the steel sheet surface. Bright rolls with low surface roughness are used for this purpose. When pressure is adjusted using a bright roll on such a polished steel sheet, wet pressure adjustment will reduce the yield point elongation of the steel sheet after annealing and the amount of pressure adjustment oil drawn into the work roll biting side. A so-called jumping phenomenon occurs in which the elongation rate fluctuates greatly in the longitudinal direction of the steel sheet, which is thought to be caused by changes in the steel sheet. If such a jumping phenomenon occurs during pressure adjustment, the mechanical properties of the steel plate in the longitudinal direction and the surface roughness of the steel plate become uneven, which impairs the quality of the product.

Possible methods for preventing this jumping phenomenon include reducing the diameter of the pressure regulating roll and increasing the coefficient of friction between the pressure regulating roll and the steel plate. However, the method of reducing the diameter of the pressure regulating roll requires large-scale equipment modification such as improving the roll chock, which requires a large amount of investment and is not a realistic solution. Furthermore, one possible method to increase the coefficient of friction between the pressure regulating roll and the steel plate is to increase the kinetic friction coefficient of pressure regulating oil to prevent the above-mentioned jumping phenomenon, but so far, the jumping phenomenon has not occurred. There is no pressure regulating oil that has the ability to prevent this.

In other words, in the conventional wet pressure regulation using pressure regulation oil, it is difficult to stably secure the target elongation rate of about 0.5 to 1.4%.

In addition, when producing bright steel plates using bright rolls, dry pressure regulation, which regulates pressure without using pressure regulating oil, increases the coefficient of friction between the steel plate and the work roll, and requires a large reduction blade. It ends up.

For this reason, even if a large rolling load exceeding the rated current value of the work roll is applied to the mill, the target value of 0, 5 to 1
．． It is not possible to secure a growth rate of around 4%.

On the other hand, one method to solve the above-mentioned problems is to inject pressure regulating oil between the work roll on the exit side of the rolling mill and the backup roll, and between these, an extremely thin film of pressure regulating oil is applied to the work roll inlet side. A method has been proposed (Japanese Unexamined Patent Publication No. 53-6259) in which pressure is adjusted in a so-called semi-wet state by forming it on the surface. According to this method, the above-mentioned jumping phenomenon can be solved, but if small irregularities occur on the surface of the backup roll, these irregularities will cause a very uneven pressure-adjusting oil film on the work roll. This results in defects such as localized non-uniformity in mechanical properties and gloss.

Therefore, in the conventional method, it is not possible to obtain the optimum elongation rate (0.5 to 1.4%) when adjusting the pressure using a bright roll, and a value larger than this target value (usually about 3 to 5%) cannot be obtained. ) We had no choice but to perform wet pressure adjustment of the elongation rate. For this reason, as shown in FIG. 4, the mechanical properties of the bright steel plate were slightly sacrificed, and it was substantially difficult to obtain a bright steel plate having the target mechanical properties.

In other words, in addition to the dry pressure regulating method that does not use pressure regulating oil, the conventional wet pressure regulating method that uses pressure regulating oil, and even the semi-wet pressure regulating method, a bright roll is used to regulate the pressure of the steel plate at an appropriate elongation rate. It was difficult to obtain steel plates.

Problems to be Solved by the Invention The purpose of the present invention is to provide a method that can always adjust the pressure at an appropriate elongation rate without causing flaws on the surface of the steel plate when adjusting the pressure of a steel plate using a bright roll. There is a particular thing.

Means to solve problems In order to solve the above issues, we have conducted various studies.

After annealing, a carbon-based solid lubricant is uniformly applied to the surface of the steel plate on the entrance side of the temper rolling mill, and then the pressure is adjusted using a bright roll whose surface roughness is within a certain range. It was confirmed that a bright steel plate with a uniform elongation rate could be obtained even by using a bright roll, and the present invention was achieved.

That is, the present invention provides a bright steel plate temper rolling method in which a steel plate that has been annealed after cold rolling and cleaning is temper rolled.
It is applied uniformly to the surface of the steel plate, and dry pressure is adjusted using a bright roll with an average surface roughness Ra of 0.8 μm or less.

The carbon-based solid lubricant used in this invention includes:
It is a carbonaceous material having lubricating properties, such as graphite, carbide of starch powder, organic polymer compound, etc., and its particle size is preferably 100 μm or less. In addition, the surface
It may be coated with Si resin or the like.

A carbon-based solid lubricant having such a structure is uniformly applied to the surface of a cold-rolled, washed, and annealed steel plate at the entry side of a temper rolling mill. The application method is not particularly specified, but as shown in FIG. 1, the carbon-based solid lubricant can be spread by a spreader (2) on the entrance side of the skin pass rolling mill.

In addition, a carbonizable organic substance such as starch powder is uniformly applied to the surface of the steel sheet before annealing to prevent the steel sheet from seizing due to the heat during annealing, and the starch powder is carbonized and the pressure is adjusted as it is. Therefore, it is possible to obtain the same effect as applying a carbon-based solid lubricant on the entrance side of the temper rolling mill.

For example, as shown in Fig. 2, the specific structure of the spreader (2) includes a roll feeder (3) and an electrostatic adder (4).
It may be a combination of Roll feeder (
3) is connected to the tank bottom from the guide plate (5), roll (6) and roll rotation motor (7). According to this device,
The carbon-based solid lubricant stored in the hopper at the bottom of the tank by the guide plate (5) is transferred to a roll (6) with an uneven surface.
As the roll rotates, it enters the recesses of the roll and is cut out little by little and transported downward. The carbon-based solid lubricant that has reached the bottom is charged by an electrostatic adder and adsorbed onto the surface of the steel plate (1) passing below. In this way, the carbon-based solid lubricant can be uniformly distributed.

In this case, the rotation speed of the roll (6), the gap between the roll (6) and the guide plate (5), the roll surface roughness, the electrostatic adder (
By changing one or more of the voltages in 4),
The amount of carbon-based solid lubricant sprayed can be easily adjusted.

The amount of carbon-based solid lubricant to be sprayed does not need to be particularly limited, but the amount on the surface of the steel plate after being sprayed is 20 to 80 mg/
Preferably, the application amount is in the range of m''.

The reason for this is that if it is less than 20a+g/m'', the lubricating effect is small, and if it exceeds 80mg/m'',
This is because black stains will be produced on the steel plate as smudges.

The surface roughness of the bright roll used in this invention is
It is necessary that the average roughness Ra is 0.8 μm or less.

The reason for this is that if the pressure is adjusted using a work roll with an Ra of 0.8 μm or less, the jumping phenomenon is unlikely to occur, and if the Ra is 0.8 μm or more, a polished steel strip with the desired brightness cannot be obtained. be.

Function In this invention, after a carbon-based solid lubricant is applied to the surface of a steel plate, pressure is adjusted using a bright roll with a predetermined surface roughness.The carbon-based solid lubricant has excellent lubricity. Even if the pressure is adjusted without using pressure adjustment oil, the friction coefficient between the steel plate and the bright roll is reduced, and the optimum elongation rate (0.5 to 1.4
%) can be obtained.

Example Using a carbon-based solid lubricant obtained by carbonizing starch powder obtained from potatoes with an average particle size of 12 μm at 700°C,
It was sprayed at a rate of 60 mg/m'' on a cold-rolled high carbon steel plate with a bright surface finish of 0.5 mm thick and 914 mm wide using the spraying device shown in Figure 2. 400Ton, with a target elongation rate of 0.6%, and a surface roughness of Ra: 0.8μm.

A bright steel plate was obtained by adjusting the pressure using a steel plate.

The results of elongation measurement of the bright steel plate obtained are shown in Figure 3 (a
).

As a comparative example, use exactly the same process as above! wet pressure regulation (pressure regulation oil: Daiskin P-4O3 (product name)
, reduction blade: 400 tons, target elongation rate: 2.5%) to obtain a cold rolled high carbon steel plate. As another comparative example, dry pressure adjustment (rolling blade: 800 tons, target elongation rate: 0.5%) was performed on the cold rolled high carbon steel sheet. The results of the elongation rate of the steel plate are shown in FIG. 3(b) and FIG. 3(c), respectively.

As is clear from FIG. 3(a), the pressure-adjusted elongation rate of the steel plate obtained by the method according to the present invention is approximately constant at the target level of 0.6%, and no jumping phenomenon occurs. Recognize.

On the other hand, the elongation rate of the steel plate obtained by conventional wet pressure adjustment is not only extremely unstable, as is clear from Figure 3(b), but also a jumping phenomenon (a sudden drop in the elongation rate) occurs during the process. ing. Therefore, in this method, in actual operation, it is necessary to increase the elongation rate to prevent the jumping phenomenon as described above, and there is a problem that the mechanical properties of the rolled product deteriorate.

Furthermore, as is clear from Figure 3 (C), the elongation rate of the steel plate obtained by dry pressure adjustment without using a solid lubricant is due to the friction between the steel plate and the work roll, even though the rolling blade is made larger. It can be seen that because the coefficient is large, it is difficult to obtain an elongation rate.

Effects of the Invention As detailed above, the present invention provides a method of uniformly applying a carbon-based solid lubricant that acts as a lubricant at the entrance side of a skin pass rolling mill, and then applying a carbon-based solid lubricant that acts as a lubricant to the surface of the skin so as to have a surface roughness within a specific range. Despite the extremely simple configuration of pressure regulation using bright rolls, the problem of stably securing a pressure regulation elongation rate can be reliably solved with almost no need to modify the current equipment. It is.

In addition, in the conventional wet pressure regulating method, it is necessary to apply a pressure regulating agent to the surface of the steel plate during pressure regulating, and it is extremely difficult to control the amount applied accurately, which is a major cause of the jumping phenomenon. was. However, according to this invention, this jumping phenomenon can be completely prevented by simply applying a carbon-based solid lubricant on the entrance side of the skin pass rolling mill. Spraying is extremely easy, and the amount of spraying can be controlled with extremely high precision.

The practical significance of this invention having such an effect in regulating the pressure of bright steel plates is extremely significant.

[Brief explanation of drawings]

1rXJ is a perspective view of a carbon-based solid lubricant coating device used in the present invention, FIG. C) is a diagram showing changes in the rolling elongation rate in the longitudinal direction of rolling by various rolling methods in the examples, and Figure 4 shows the rolling elongation rate, yield strength (YP), and yield elongation rate (YP).
This is a diagram showing the relationship with PE), and the optimal range is shown in the diagram. 1... Steel plate, 2... Carbon-based solid lubricant iik
4 devices, 3... Roll feeder 4... Electrostatic adder, 5... Guide plate, 6... Roll,
7...Roll rotation motor Figure 2 Go===〒=

Claims (1)

[Claims] 1. In the skin-pass rolling method for bright steel plates, in which a steel plate is cold-rolled, cleaned, and then annealed, a carbon-based solid lubricant is applied to the surface of the steel plate on the entry side of the skin-pass rolling mill to improve surface roughness. A method for temper rolling a bright steel sheet, characterized in that dry temper rolling is performed using a bright roll having an average roughness Ra of 0.8 μm or less.