JPS6045252B2 - Direct heat treatment control method for hot rolled wire rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves forming a hot-rolled wire rod into a coil and placing it on a conveyor, and passing through an surrounding environment while transferring the wire rod coil to cool the wire rod coil in a predetermined cooling pattern. The present invention relates to a method for controlling the temperature of an surrounding environment and controlling the temperature of a wire coil.

Conventionally, as a method and apparatus for direct heat treatment of steel wire, a technique disclosed in Japanese Utility Model Application Publication No. 149106/1983 has been proposed.

According to this, in an annealing device of a wire rod rolling mill that cools rolled wire rods while they are being transferred by a conveyor, a heat insulation cover having a plurality of heat insulating structures continuously arranged in the transfer direction that covers the transfer surface of the conveyor; , to provide a slow cooling device comprising a heat source device that controls the heating of the inside of the heat insulation cover to a predetermined slow cooling temperature using a temperature detector equipped on the heat insulation cover, and a heat insulation cover opening/closing device that opens and closes the heat insulation cover. It is.

As described above, the technical concept of the above-mentioned Japanese Utility Model Application Publication No. 52-149106 is to control the heating inside the heat-insulating cover by detecting the temperature inside the heat-insulating cover, and to control the cooling of the wire according to the steel type and destination.

However, according to research and experiments conducted by the present inventors, it has been found that the device disclosed in Japanese Utility Model Application No. 149106/1983 suffers from the following problems and is not practical. (1) In continuous heat treatment of the wire rod, the temperature inside the heat insulation cover increases due to the heat retained in the wire rod, and the temperature inside the heat insulation cover cannot be maintained at a predetermined temperature.

(2) In wire rod coils, there are large and small parts of the upper layer density of the coil formation, and there is a difference in the cooling rate in the large and small parts of this layer density,
During the cooling process, temperature deviations occur in each part of the ring forming the wire coil, causing variations in quality. (3
) During wire coil transfer, contact with the conveyor and cold air entering the heat insulating cover may cause local overcooling in the wire coil, which deviates from the predetermined cooling speed pattern and affects the wire quality.

In view of the above, the present invention has been developed by forming a hot-rolled wire rod into a coil, placing it on a conveyor, transferring the wire rod coil by the conveyor, and moving the wire rod coil through the surrounding environment in a direction in which the wire rod coil is transferred in the surrounding environment. Ambient temperature control of the surrounding environment to create a stepwise temperature gradient, outside air blowing control to prevent overheating of the surrounding environment, and cooling of the dense layered areas on both sides of the wire coil to make the temperature of the wire coil uniform. The hot-rolled wire rod is directly heat-treated by providing a refrigerant spray control and a wire coil heat compensation control for thermally compensating the subcooled portion of the wire coil.

A control device for carrying out the present invention includes a heat-retaining cover disposed on a conveyor line that transports hot-rolled wire while forming it into a coil, and a plurality of heat-retaining covers that adjust the ambient temperature inside the heat-retaining cover. A temperature control device, an outside air blowing/inside air exhaust device that prevents overheating within the protective cover, a wire coil loosening device, a non-contact scanning thermometer that measures the wire coil temperature, and the non-contact scanning thermometer. A signal processing device that maintains the peak output value, a refrigerant spray device that reduces temperature deviations in each part of the wire coil, a refrigerant adjustment device that adjusts the temperature and amount of the refrigerant, and measures the temperature of the bottom and side surfaces of the wire coil. It consists of a non-contact thermometer, a bottom heater installed on the bottom of the wire coil transfer line, a side heater installed on the inside surface of the heat insulation cover, a wire coil position detection device that detects the wire coil position, and a control computer. be done. The control computer provides process information from the heating furnace to the rolling line (steel temperature, wire diameter, unit weight, etc.), as well as quality data and process performance data depending on the steel type and destination (temperature at various locations inside the heat insulation cover, amount of refrigerant sprayed, etc.) The optimum cooling speed for the wire coil is determined by performing model calculations based on the temperature, wire coil temperature, conveyor speed, etc. - Determine process control variables such as pattern, refrigerant spray amount, and atmospheric temperature pattern inside the temperature insulation cover.

The atmospheric temperature inside the heat retaining cover is controlled by adjusting the heat source within the heat retaining cover based on the control amount from the control computer to create a predetermined atmospheric temperature pattern within the heat retaining cover. In addition, during continuous heat treatment, if the temperature inside the heat insulating cover rises due to the heat held by the wire coil and it is no longer possible to maintain the ambient temperature inside the heat insulating cover at the specified temperature, the cold air outside the heat insulating cover will be removed from the heat insulating cover. At the same time, the hot air inside the heat insulating cover is released 4
and maintain a predetermined atmospheric temperature inside the heat insulating cover. Furthermore, in the event that a partial overcooled area occurs during wire coil transfer, in order to thermally compensate for the overcooled area of the wire coil, a non-contact thermometer is installed to measure the temperature on the bottom and side surfaces of the wire coil. When the wire coil temperature is lower than the predetermined temperature, the heaters installed on the bottom of the transfer line and the side of the heat insulation cover are selected and heated at the appropriate timing to compensate for the heat of the wire coil and return the wire coil to the predetermined temperature. let In addition, in order to promote the cooling of the comparatively high-temperature area near the center of the dense layers on both sides of the wire coil and to equalize the temperature of the wire coil, the wire coil is formed into a ring shape by a coil loosening device placed inside the heat insulating cover. After unraveling, the temperature of the wire coil is measured using a non-contact scanning thermometer, and this measurement signal is input to a signal processing device to hold the maximum temperature value for each scan. The temperature and amount of the refrigerant are adjusted based on the maximum temperature value, and the refrigerant is sprayed onto the densely layered areas on both sides of the wire coil in order to equalize the temperature of the wire coil. Further, the leading end and the rear end of the wire coil are easily cooled because the layer density is low in forming the wire coil. Therefore, if the refrigerant is sprayed continuously, supercooled portions will occur at the leading and trailing ends of the wire coil, which will affect the product yield. In order to prevent this, a wire position detection device is installed in the transfer line, and refrigerant spraying is started and stopped at appropriate timings based on the signal from the wire position detection device. The explanation will be based on the example equipment shown.

FIG. 1 shows a line in which a heat treatment apparatus according to the present invention is disposed downstream of a rolling head 4 of a winding machine following a hot rolling mill.

As shown in the figure, a conveyor, that is, a roller conveyor 22, is disposed directly below the laying head 4, on which steel wire rods 20 falling in a ring shape are placed and transferred, and this roller conveyor 22 is driven at a predetermined speed. By doing so, a layered coil having a desired ring group weight per unit length (30 to 550k9/7n.) is formed on the conveyor 22. A transfer table that conveys the thick coil at a predetermined speed, that is, an elevating roller table 23 is arranged at a position continuous with the roller conveyor 22, and the elevating roller table 23 imparts one or more loosening to the thick coil. The structure is such that it is possible to add one or more steps in the direction of travel. The conveyor 22 may be a chain conveyor instead of a roller conveyor.
In addition, the roller table 23 is a tilting type elevating roller table 23 in the illustrated example, but the table may be of a fixed type as long as it has a level difference, since it is sufficient to fulfill the role of loosening the coil as shown in the figure. Next, in a certain range along the traveling direction of the lifting roller table 23, an surrounding environment, that is, a heat retaining cover 21, is provided that surrounds the roller table 23 and the thick-layer coil placed thereon. The heat retaining cover 21 is divided into one or more zones in the traveling direction, thereby forming a cooling zone in which the thick-layered coil is cooled along a desired cooling curve while being transferred.

The exit side of this heat insulating cover 21 is provided with a blast cooling section (
Transfer roller conveyor 22″ with a lower part (not shown)
are connected to each other, and a focusing device 24 is arranged at the end of the roller conveyor 22'' to collect the cooled steel wire 20 to the final stage. Fig. 4 shows the flow of information in the control system. FIG.

As shown in the figure, process information from the heating furnace to the rolling line (steel material temperature, wire diameter, unit weight, etc.) and the host computer 18
control based on quality data according to the steel type and destination, as well as process performance data accumulated in the auxiliary storage device 19 (temperatures at various locations inside the heat insulation cover, amount of refrigerant sprayed, temperature, wire coil temperature, conveyor speed, etc.) The computer 5 performs model calculations to determine process control variables such as the optimum cooling speed pattern of the wire coil, the amount of refrigerant sprayed, the temperature, and the atmospheric temperature pattern inside the heat insulating cover. FIG. 2 shows a sectional view of the heat insulating cover.

Based on the process control amount calculated by the control computer 5, the electric heater 3 placed inside the heat insulation cover 21 is controlled by the heat insulation cover internal atmosphere temperature regulator 1 shown in FIG. 2 via the heater control panel 2. is adjusted to match the atmospheric temperature set inside the heat insulating cover from the control computer 5. In addition, the output of the set temperature inside the heat-retaining cover from the control computer 5 has a stepwise temperature gradient for the temperature controller of the heat-retaining cover arranged in the wire rod coil transfer direction, depending on the steel type and destination. This is the temperature setting output. Also, measure the atmospheric temperature inside the heat insulating cover with a thermometer 6.
When the ambient temperature inside the heat insulation cover exceeds the set temperature inside the heat insulation cover from the control computer 5, the forced fan 7 that blows cold air from outside the heat insulation cover into the heat insulation cover is activated. At the same time, the radiation damper 8 for discharging the hot air inside the heat retaining cover is opened to lower the atmospheric temperature inside the heat retaining cover.

As a result, when the ambient temperature inside the heat retaining cover matches the temperature set inside the heat retaining cover on the control computer 5, the push-in fan 7 is stopped, and at the same time, the radiation damper 8 is closed to reach the predetermined atmospheric temperature inside the heat retaining cover. maintain. In addition, the lower surface of the wire coil,
In addition, when the temperature measurement values of the lower surface thermometer 9 for side temperature measurement and the side thermometer 10 are outside the lower limit of the wire coil cooling speed pattern from the control computer 5, the lower surface heater 11 is used as appropriate.
Then, the side heater 17 is heated via the heater control panel 2 to compensate for the heat in the supercooled portion of the wire coil, and return the wire coil to a predetermined temperature.

Note that 25 is a temperature converter, and 30 is a temperature regulator. In a method of reducing the temperature deviation of each part of a ring forming a wire coil, as shown in FIG. The temperature is measured by the scanning thermometer 12, and the signal is led to the signal processing device 13 to obtain the peak temperature of the wire coil 20.

The temperature and amount of the refrigerant are adjusted in accordance with this peak temperature value, and the refrigerant is sprayed onto the wire coil 20 from the refrigerant spray nozzle 14 to reduce the temperature deviation of each part of the ring that forms the wire coil, thereby making the wire coil temperature uniform. Measure. The front end and rear end of the wire coil are easily cooled because the density of the wire coil forming upper layer is low. Therefore, when the refrigerant is sprayed continuously, supercooling of the front end and rear end of the wire coil, and supercooling of the lateral layer, is promoted.

In order to prevent this, the wire coil position J is detected by the wire coil position detector 15 shown in FIG. A refrigerant spray stop signal is issued to stop the refrigerant spray, thereby preventing overcooling of the front and rear ends of the wire coil due to the refrigerant spray. Examples of the present invention will be described below.

In this example, slow cooling was tested using the apparatus shown in Figure 1. Representative examples of the conditions and results are shown in Table 1. Each steel type in the table has a composition shown in Table 2. I went there because of something.

Table 1 shows heat treatment for the purpose of omitting low-temperature annealing, using the conventional method of slow cooling at a cooling rate of 0.05 to 0.2°C/Sec.
Test tooth. 4 and 6).

As is clear from Table 1, the test teeth. 1, 2, 3, and 5 of the present invention are test brown. It can be seen that the temperature deviation between the outer surface portion and the densely layered portion of the thick-layered coil is greatly improved compared to the conventional methods Nos. 4 and 6. As an example of improving this temperature deviation, test N
O. Figure 5 shows the temperature deviation of l. It can be seen that by improving the temperature deviation, the variation in tensile strength is suppressed to be smaller than that in the conventional method, and sufficient softening is achieved. that's all,
As explained above, according to the control method of the present invention, it is possible to greatly improve the temperature deviation between the outer surface of the coil and the layered layer during slow cooling, which was a drawback of the prior art. Therefore, it has effects of high industrial value, such as stably softening the material.

In particular, these effects are obtained by the ambient temperature inside the heat insulating cover and the thermal compensation for the supercooled part of the wire coil, making it practical for manufacturing wire rods with excellent secondary workability depending on the steel type and destination. There are various control methods.

[Brief explanation of drawings]

FIG. 1 shows a line in which a heat treatment apparatus according to the present invention is disposed downstream of a rolling head following a hot rolling line. FIG. 2 is an internal view of a heat treatment apparatus showing an embodiment of the present invention, FIG. 3 is a detailed explanatory diagram of a heat retaining cover showing an embodiment of the present invention,
FIG. 4 is a control block diagram according to the present invention, and FIG. 1... Atmosphere temperature regulator inside heat insulation cover, 2... Heater control panel, 3... Electric heater, 4... Ling head, 5...
Control computer, 6...Thermometer, 7...
Push-in fan, 8... Dissipation damper, 9...
Bottom thermometer, 10...Side thermometer, 11...
Bottom heater, 12...Non-contact scanning thermometer, 1
3...Signal processing device, 14...Refrigerant spray nozzle, 15...Wire coil position detector, 16...
... Refrigerant spray control valve, 17 ... Side heater, 18 ... Host computer, 19 ... Auxiliary storage device, 20 ... Steel wire, 21 ... ...Heat insulation cover, 22...Roller conveyor, 23...
...Elevating roller table, 24...Focusing device,
25...Temperature converter, 26...Delay timer, 27...Flow rate converter, 28...Flow rate corrector, 29...Flow rate regulator, 30 ...Temperature controller, 31...Flowmeter.

Claims (1)

[Claims] 1. A method in which hot-rolled wire is formed into a coil and placed on a conveyor, and the wire coil is cooled by passing through an surrounding environment while being transferred by the conveyor,
Atmosphere temperature control in the surrounding environment that creates a stepwise temperature gradient in the wire coil transfer direction in the surrounding environment, outside air blowing control that prevents overheating of the surrounding environment, and cooling of the dense layered areas on both sides of the wire coil. 1. A direct heat treatment control method for hot rolled wire, comprising: refrigerant spray control for uniformizing the temperature of the coil; and wire coil heat compensation control for thermally compensating for a subcooled portion of the wire coil.