JPS5915965B2 - Method for preventing bending of long shaped steel materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing bending of long shaped steel materials.

Scalene angle steel (invert) has an asymmetrical cross-sectional shape, and the wall thickness of the flange F and web W are different, so it bends significantly during the natural cooling process after rolling (first (see figure).

For example, when an invert that has been straightened by a roller is reheated to make the temperature distribution uniform and the shape straight, it is then naturally cooled and bent as shown in Figure 2.

In order to carry out long length processing (rolling → cooling → straightening) of the invert, the bending of the invert must be suppressed to a fraction of that of natural cooling.

In order to reduce the above-mentioned grinding, it is sufficient to maintain the cross-sectional circular temperature distribution in a substantially uniform state.

Specifically, by insulating the web that cools quickly or forcibly cooling the flange that cools slowly, the temperature distribution between the flange and the web can be made almost uniform.

The present invention relates to a method of reducing invert bending during the cooling process by cooling thicker flanges more strongly than thinner webs.

In the process of arranging the inverts in a square shape, as shown in Figure 3, a coolant such as water or an air/water mixture is injected onto the entire surface of the invert 1, that is, on both sides of the flange and web. The cooling rate of the web can be made almost equal to the cooling rate of the web.

In order to equalize the cooling rates of the flange and the web, it is necessary to control the cooling capacities of the flange and the web independently of each other.

Of course, thicker flanges must be cooled more intensively than thinner webs.

In the figure, 2 is a rudder, 3 is a nozzle, and 4 is a coolant.

As shown in FIG. 4, the mechanical strength of steel increases rapidly below 500 to 600°C, although it varies depending on the composition.

Therefore, in order to reduce the bending of the invert at the outlet of the cooling bed (at room temperature), it is necessary to maintain the It is sufficient to maintain the shape of the web and then allow it to bend freely in the cooling bed depending on the temperature difference between the flange and the web.

Since the finishing rolling temperature is 750 to 800°C, it must be cooled by 150 to 200°C between the finishing mill and the cooling bed.

According to an example using an invert of m200X90X9/14, if a method is used to perform web natural cooling and compensate for the cooling delay of the flange that occurs at this time with forced cooling, 7
The time required for cooling from 50-800°C to 550-600°C is about 120 seconds.

Therefore, sizes with thicker flanges require longer cooling times.

As a result, in order to reduce the bending of the invert, it is necessary to increase the distance between the finishing mill and the cooling bed, or to reduce the conveyance speed between the finishing rolling mill and the cooling bed.

In the former case, the equipment becomes longer and construction and maintenance costs increase, while in the latter case, the production volume t/hr decreases.

Therefore, both are uneconomical.

For the reasons mentioned above, it is necessary to forcefully cool the entire invert while maintaining the temperatures of the flange and web at approximately the same temperature between the finishing mill and the cooling bed.

Next, the present invention will be explained in detail using FIG.

In an invert, the flange is thicker than the web, so cooling equipment for the flange and for the web are installed at a ratio of 2=1 or 3:1 on the conveyor table between the finishing mill and the cooling bed, and the cooling capacity of both is The amount of water ejected is controlled.

770~800℃X200X90X at finishing rolling mill exit
Transporting the 9/14 invert at approximately 4m/see, approximately 5
At the cooling zone exit at 0 m, the flange and web temperature can be 550-600°C.

Thus, according to the present invention, a remarkable effect can be achieved in that the bending of a long scalene angle steel angle shape in the cooling process from a high temperature state can be minimized.

[Brief explanation of the drawing]

Figure 1 shows the bending of the naturally cooled invert (value after cooling)
Figure 2 is a curve diagram showing the temperature and bending in the invert cooling process, Figure 3 is an explanatory diagram showing the mode of invert cooling, Figure 4 is a diagram showing the hot strength of steel, FIG. 5 is a diagram showing the arrangement of invert cooling equipment on the transfer table. In Figure 3 = 1: invert, 2: header, 3:
Nozzle, 4: Coolant. In Fig. 5, 2F cooling equipment for flange, W: cooling equipment for web.

Claims (1)

[Claims] 1. When handling long scalene angle shape steel in a high temperature state, it is recommended to cool the long scalene shape steel by injecting a cooling medium from four directions directed to both sides of the flange and web of the long scalene shape steel. A method for preventing bending of long shaped steel materials.