JPS6155573B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a production line for thick steel plates, in which strong steel is produced by direct quenching or controlled cooling, by skillfully using forced water cooling equipment to improve the shape of the product. This relates to a line of heat treatment equipment for steel plates that efficiently improves quality and material quality.

When manufacturing steel plates by incorporating water cooling equipment into a rolling line, the challenge is to determine the required temperature at the start of cooling the steel plate without being affected by the length of the steel plate or the thickness of the steel plate. Ensure that cooling equipment is available.

Regarding the cooling equipment, it is important to obtain a predetermined cooling rate, to ensure the flatness of the steel plate during and after cooling, and to prevent temperature unevenness of the steel plate. Ideally, it would be desirable to heat treat the product online without reheating after hot rolling.
As mentioned above, it is necessary to solve the problem of ensuring the required temperature of the steel plate.

The present invention solves the above-mentioned problems by using a series of devices to be described later, and also provides a new technique that meets the new demands.

In general, from a layout perspective, it is common practice to correct the shape of a steel plate by applying it to a hot leveler at as high a temperature as possible after finishing rolling, and the reality is that the hot leveler is placed as close to the rolling mill as possible.

On the other hand, it is also advantageous to place the water cooling device used in this type of manufacturing method close to the rolling mill in order to ensure temperature. However, regarding the arrangement order of the hot leveler and water cooling equipment, it is more advantageous to correct the shape with the hot leveler and then perform water cooling in order to ensure the flatness of the steel plate. Then, the above effect is further promoted. On the other hand, in the case of reverse arrangement,
Leveling after water cooling requires a powerful cold leveler, which is unfavorable from an investment cost and energy saving perspective.

Therefore, installing and interlocking a finishing rolling mill, followed by a heat insulating device, a hot leveler, and a cooling device in that order makes it possible to reduce equipment costs and energy consumption, as well as to process steel plates made of a wide range of materials with limited equipment. This provides an advantageous array of equipment for manufacturing.

In addition, when cooling a steel plate with water, there is a time difference between when the leading end of the steel plate starts cooling and when the rear end of the steel plate starts cooling. This time difference is determined by the strip passing speed determined from rolling efficiency, the length of the rolled strip, and the temperature difference within the steel strip allowed for quality. This is more noticeable as the thickness of the plate decreases.

Therefore, a temperature difference occurs between the leading end and the rear end at the start of water cooling, and the temperature decreases significantly at the rear end, causing variations in quality and causing problems.

The present invention uses a hot leveler and a heat retaining device installed in front of the water cooling device to increase the average temperature of the steel plate and prevents a drop in temperature at the rear end, thereby almost eliminating restrictions on the length of the rolled plate and allowing the steel plate to pass through. The plate speed can also be selected according to the most preferable rolling efficiency.
Work efficiency is greatly improved.

Furthermore, it is a series of continuous heat treatment equipment for steel sheets that is advantageous from the viewpoint of production efficiency and economy, and has many advantages such as being able to shorten the length of the equipment.

FIG. 1 shows an embodiment of the device array of the present invention. In the direction of the arrow, the manufacturing process goes from 1 heating furnace, 2 rolling mill, 3 heat retaining cover, 4 hot leveler, 5 cooling device, 6 cooling bed to shearing line (not shown).

As shown in FIG. 2, the heat retaining device 3 consists of an upper cover 3-1 that covers the upper side surface of the steel sheet conveying roller R, and a lower cover 3-2 that covers the lower surface of the steel plate conveying roller R.
A heat insulating material 7-1 is disposed on the inner surface of the transport roller R, and is detachably installed on the transport roller R in consideration of various repairs. 12 indicates a hanging tool.

Further, the lower cover 3-2 uses a castable member 7-2 to withstand falling of scale and water, and is provided with holes 8 for discharging scale and water. These pass through a chute 11 under the table and a scale sluice 9, and are collected into a drainage pit (not shown) for treatment.

Regarding the heat retention effect of the heat retention device 3, the heat retention material 7-
Although it depends on the thickness of the steel plate 1 and the sealing properties of the upper and lower covers 3-1 and 3-2, it is possible to raise the temperature at the tail end of the steel plate or eliminate the temperature difference in the longitudinal direction of the steel plate, and the sealing effect can be improved. If the steel material is manufactured using the device array of the present invention at the appropriate location of the cover in order to increase the temperature, the temperature at the starting point of cooling in the longitudinal direction of the plate can be ensured using the heat retaining device 3 as shown by curve B in FIG. Compared to curve A in the case of no heating, thick materials can be heated at low temperatures, thin materials and long materials can be manufactured, and a wide range of steel plate thicknesses and lengths can be manufactured. big.

Here, the effects of implementing a heat retention device will be explained.

Threading speed is an important element in terms of rolling efficiency and can be determined from equation (1).

V ₁ = L/P ...(1) Here, V ₁ : Threading speed (m/SEC) L: Steel plate length (m) P: Required processing pitch of steel plate (SEC) On the other hand, , the formula for calculating the threading speed determined from the temperature difference at the rear end is Equation (2).

V ₂ = T _A × L / △T ... (2) where V ₂ : Threading speed (m/SEC) T _A : Average cooling rate of steel plate after finish rolling (℃/
SEC) L: Length of steel plate (m) △T: Difference in temperature between tip and rear end of steel plate (°C) From the standpoint of rolling efficiency and quality, V ₁ ≦ V ₂ must hold true.

Figure 3 shows the average cooling rate T _A of the steel plate after finish rolling.

Curve A in FIG. 3 is for air cooling, and curve B is for the case where the heat retaining device 3 is installed. Hereinafter, FIGS. 4 to 6 are also indicated by the same reference numerals.

Now, when V ₁ = 1.0m/SEC and △T = 50℃ are required from the viewpoint of rolling capacity and quality assurance, equation (2) and the third
The length L of each steel plate that can be processed is determined from T _A in the figure. The results of this trial calculation are shown in Figure 4. It is possible to produce thin and long materials.

Furthermore, when evaluating the effect by temperature, V=1.0m/
When SECL = 60m, the temperature difference △T between the front and rear ends of the steel plate is shown in Figure 5.

[Brief explanation of the drawing]

Fig. 1 is an explanatory layout diagram showing an embodiment of the device array of the present invention, Fig. 2 is a front cross-sectional explanatory diagram showing an embodiment of the heat retaining device according to the present invention, and Figs. These are graphs showing the effect of the installation in comparison with the case of air cooling without the same equipment. Figure 3 shows the relationship between the steel plate thickness and the average cooling rate of the steel plate after finish rolling, and Figure 4 shows the relationship between the steel plate thickness and the average cooling rate of the steel plate after finish rolling. Figure 5 shows the relationship between the steel plate thickness and the maximum steel plate length.
FIG. 6 is a graph showing the relationship between the rear end temperature difference and the relationship between the steel plate thickness and the maximum steel plate length.

Claims (1)

[Scope of Claims] 1. Continuous heat treatment of steel sheets, characterized in that in a heat treatment facility for steel sheets that performs direct water cooling after hot rolling, a heat retention device, a hot leveler, and a water cooling device are arranged in this order after a finishing rolling mill. equipment row. 2. A continuous heat treatment equipment array for steel sheets according to claim 1, characterized in that a combustion burner is provided on the cover of the heat retention equipment.