JPS6254366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a manufacturing line for prestressed steel bars (steel bars used for prestressed concrete).
This relates to an operating method for a PC steel rod production line that achieves high yield, high operating rate, high productivity, and low fuel consumption, and that can obtain a specified quality, especially when starting up the line. This article relates to a method of operating a PC steel bar manufacturing line suitable for high yield production.

Generally, quenching treatment and tempering treatment are performed to manufacture PC steel bars, but in each of these treatment steps,
It is essential to accurately achieve the heat cycle (heating temperature) of the PC steel bar.

On the other hand, for the purpose of reducing the construction cost of a production line, the time required for production, and the production cost, a production method has been proposed in which quenching treatment and tempering treatment are successively integrated into one line.

However, when quenching and tempering are performed continuously on one line, and when heat treatment is performed in a conventional high-frequency induction furnace, electrical control is used, so line speed and furnace temperature can be easily controlled. ,
In the case of gas-fired furnaces, there are various problems such as the following.
This leads to deterioration of fuel consumption rate and yield loss.

In other words, the relationship curve between the furnace temperature and line speed that achieves the heating temperature of the PC steel bar in the quenching furnace is the relationship curve between the furnace temperature and line speed that achieves the heating temperature of the PC steel bar in the tempering furnace. For example, when the line speed changes during the start-up at the beginning of wire running, in the case of a gas-fired furnace, it is difficult to satisfy the heating temperature in the quenching furnace and the heating temperature in the tempering furnace at the same time. At this time, there is a problem that the material passing through the line does not have the predetermined quality as a product.

In other words, when starting up the line, the furnace temperature of the quenching furnace and the furnace temperature of the tempering furnace are raised respectively, but if the line is stopped at this time, the temperature of the steel bar material will increase. If the material becomes too high, it will break or deform in the furnace, so the material must be passed through the furnace at a certain line speed, but at this time it is difficult to satisfy the prescribed heating temperature for quenching and tempering at the same time. in,
The rate at which the material passing through the line during startup does not become a product increases.

In particular, when starting up a general combustion furnace, it is necessary to supply fuel and raise the furnace temperature from room temperature to operating furnace temperature (for example, 1300 degrees Celsius).
However, there is an upper limit to the temperature increase speed determined by the fuel supply capacity of the furnace and the heat capacity of the furnace itself, and the lifespan of the furnace refractories, and the actual temperature increase is The problem is that it takes a long time to warm up the product, which means that there is a large portion of the product that does not pass the test, resulting in a large yield loss.

The present invention was made in view of these problems, and its purpose is to match the furnace temperature and line speed to a predetermined relationship in the heat treatment process of PC steel bars, thereby producing PC of the required quality. The purpose of this invention is to provide a method for operating a PC steel bar production line that makes it possible to obtain steel bars.

That is, the gist of the present invention is to employ a gas-fired furnace as the quenching furnace and the tempering furnace, and to control the temperature of each furnace through the line speed in order to achieve a predetermined heating temperature. This is in the operating method of the PC steel bar production line.

Next, the present invention will be explained in more detail based on FIGS. 1 to 3.

FIGS. 1 and 2 show relationship curves between experimental values of line speed and necessary furnace temperature to obtain predetermined heating temperatures in the quenching furnace and the tempering furnace, respectively. As is clear from these relationship curves, the required furnace temperatures of the quenching furnace and the tempering furnace are different for the same line speed.

In the present invention, the relationship curves between line speed and furnace temperature that can achieve predetermined heating temperatures in each of the quenching furnace and the tempering furnace are determined in advance as shown in FIGS. For the actual furnace temperature Q of a furnace (for example, a quenching furnace), a necessary line speed S is set according to the predetermined relationship, and for this line speed S, the line speed of the other furnace (for example, a tempering furnace) is )
The necessary furnace temperature T is also set in accordance with a predetermined relationship, and the heating temperature in the quenching furnace and the heating temperature in the tempering furnace are simultaneously satisfied.

Note that the furnace in which the line speed is initially set may be a tempering furnace.

Figure 3 shows the quenching furnace 1 on the PC steel bar manufacturing line.
FIG. 2 is a conceptual diagram of the arrangement of a tempering furnace 2 and a control device for carrying out the operating method according to the present invention.

The steel bar material 3 becomes a steel bar 4 after successively passing through a quenching furnace 1 and a tempering furnace 2. Note that a line speed setting device 5 is provided upstream of the quenching furnace 1.

The quenching furnace 1 and the tempering furnace 2 each have a fuel supply pipe 1.
1 and 21, burners 12 and 22, fuel is supplied to achieve the required furnace temperature.

On the other hand, the furnace temperature is measured by the furnace temperature gauges 13 and 23, respectively, and the furnace temperature fuel amount calculation setting devices 14 and 24 use the measured values to determine the temperature of the burners 12 and 22.
The required amount of fuel to be supplied to is determined and set.

Furnace temperature line speed calculators 15 and 25 calculate the required heating temperature of the steel bar based on the line speed/furnace temperature relationship of the quenching furnace and tempering furnace shown in FIGS. 1 and 2, respectively. In order to achieve this, it has a function to calculate the required line speed for the furnace temperature, and conversely the required furnace temperature for the line speed.

Next, as the most typical example of the present invention, an embodiment in which a line is started up from a stopped state to a normal operating state will be described with reference to FIG.

Fuel was supplied from the burner 12 while measuring the furnace temperature of the quenching furnace 1 with a furnace thermometer 13 according to the heating speed of the furnace, which is determined from the above-mentioned amount of fuel supplied to the furnace and the heat capacity of the furnace itself. .

Corresponding to the furnace temperature measured by this furnace thermometer 13,
An appropriate line speed is calculated by the furnace temperature line speed calculator 15, and the line speed is set by the line speed setting device 5.

As the furnace temperature increases, the line speed also increases according to the relationship shown in FIG. remains at the target value regardless of changes in

Now, in accordance with the increase in line speed calculated by the furnace temperature line speed calculator 15, the appropriate tempering furnace furnace temperature corresponding to each line speed value is determined based on the relationship shown in FIG. The required amount of fuel was calculated by the warm line speed calculator 25, and was supplied from the burner 24 so as to achieve this furnace temperature.

In this way, even when the furnace temperatures are rising at the start-up of the quenching furnace 1 and the tempering furnace 2, an appropriate line speed and an appropriate furnace temperature in each furnace 1 and 2 are set, and the quenching and tempering operations are maintained. Since each required heating temperature was achieved at the same time, even the steel rod materials that passed through the line during start-up were all products of the specified quality.

As explained above, according to the present invention, it is possible to improve the yield and reduce fuel costs by appropriately controlling the furnace temperature and line speed.

[Brief explanation of the drawing]

Figure 1 is a curve diagram of the relationship between line speed and furnace temperature in a quenching furnace, Figure 2 is a diagram of a relationship curve between line speed and furnace temperature in a tempering furnace, and Figure 3 is a diagram of the relationship between line speed and furnace temperature in a tempering furnace. FIG. 4, which is a conceptual diagram of the control of the interlocking operation method, is an operation chart according to the embodiment method of the present invention. 1... Quenching furnace, 2... Tempering furnace, 5... Line speed setting device, 13, 23... Furnace temperature meter, 14,
24... Furnace temperature fuel amount calculation setter, 15, 25...
Furnace temperature line speed calculator.

Claims (1)

[Claims] 1. In the operating method of a PC steel bar production line that continuously performs quenching and tempering treatments in one line,
A gas firing furnace is installed in each of the quenching furnace and tempering furnace, and the actual furnace temperature of one of the quenching furnace and tempering furnace is
First, the line speed that achieves the predetermined heating temperature of the PC steel bar is set, and the actual furnace temperature of the other of the quenching furnace and tempering furnace is set relative to this line speed.
A method for operating a PC steel bar production line, which comprises setting the PC steel bar to a predetermined heating temperature.