JPS59185736A - Heat treating device for pc steel bar - Google Patents

Abstract

PURPOSE:To provide a titled device which improves remarkably productivity and can reduce an energy cost by constituting a hardening furnace and a tempering furnace for heat treating a PC steel bar in such a way that gas firing furnaces are used and that many wire rods can be passed simultaneously in parallel in the furnaces. CONSTITUTION:A heat treating device for PC steel bars produces PC steel bars B by subjecting three pieces of wire rods A for PC steel bars supplied respectively from three lines 30, 40, 50 of wire feeders 1 to working such as drawing then hardening the wire rods in a hardening furnace 20 and a water tank 8 for the hardening furnace then tempering the wire rods in a tempering furnace 21 and a water tank 10 for the tempering furnace. Three pieces of the wire rods A in such heat treating device are passed simultaneously at an equal interval in parallel in a furnace body 22 consisting of refractories 26 constituting said furnace 20 and furnace 21 by means of plural hearth rollers 23 disposed in the direction intersecting orthogonally with the direction where the wire rods A pass. Plural gas burners, 24 are further disposed in the ceiling part of the body 22 and inexpensive gases are burned with said burners so that the wire rods A transferred on the rollers 23 are uniformly and efficiently heat treated.

Description

[Detailed description of the invention] The present invention relates to a PC steel bar heat treatment apparatus.

FIG. 1 shows a conventional heat treatment apparatus for PC steel bars (steel bars used for prestressed concrete).

In Fig. 1, a wire A is passed through a bending roll 2 from a wire feeder 1, and after surface scale is removed by sandblasting 3, it is cold drawn using a die 4 and a priddle roll 5 to a predetermined wire diameter. Ru.

Further, a spiral groove is formed on the surface of the wire using a die 4a, and then the cross section is made into a perfect circle using a die 4b, and the winding curls are removed using a strainer 6. The wire is then heated to about 85,000 by induction heating in an induction hardening furnace 7, and then water-cooled in a hardening furnace water tank 8 to room temperature and hardened. Next, the induction heating is carried out again in the induction hardening furnace 9.
After being heated to 0.00, the steel bar B is cooled with water in a tempering furnace water tank 10 and tempered while the steel bar reaches room temperature. And wire diameter measuring machine 1
After the wire diameter is confirmed in step 1, the wire is passed through a tension measuring device 16 and a take-up device 12, and then wound into a winding device 14. The tension measuring device 16 monitors the tension acting on the steel rod, and the tension measuring device 16 monitors the tension acting on the steel rod.
The tension is maintained at a predetermined value by adjusting the speed of step 2. When a predetermined amount of the steel rod is wound up on the winder 14, the steel rod is cut using the running cutting machine 13 while the steel rod is being continuously heat-treated. Two winders 14 are installed, and when the winding amount of one reaches a fixed amount, it is switched to the other winder.

However, in the conventional heat treatment apparatus configured in this way, a high-frequency induction heating system is adopted as the heating furnace for the steel rod, so the steel rod is heated in the induction coil of the induction hardening furnace 7 and tempering 9. Only one wire could be passed through the pipe, which limited the amount of production that could be increased. Furthermore, since expensive electricity is used as a heating source, heat treatment costs are high. Note that FIG. 2 is a sectional view showing a state in which steel rods are wired to the induction hardening furnace 7 and the induction hardening furnace 9.

Note that a patenting furnace that uses gas or kerosene as fuel may be used in the process of heat-treating the wire before wire drawing. According to this patenting furnace, it is possible to heat treat a large number of pieces at the same time. However, using a furnace with P
When manufacturing C steel bars, surface flaws and bends in the wire rod occur, resulting in PC
The problem is that it reduces the quality of steel bars.It is not suitable for the purpose of quenching and tempering steel bars.

The present invention has been made in view of the above-mentioned drawbacks, and provides a PC steel bar heat treatment apparatus that can process a large number of rods at the same time, significantly increases productivity, and reduces the energy cost required for manufacturing. The purpose is to provide

In order to achieve this object, the present invention provides a PC steel rod to be heat-treated, in which a quenching furnace', a quenching furnace water tank, a tempering furnace, and a tempering furnace water tank are sequentially arranged. The heat treatment apparatus is characterized in that the quenching furnace and the tempering furnace are gas-fired.

The present invention will be described in further detail below with reference to embodiments shown in the drawings.

FIG. 3 is a layout diagram of a PC steel bar heat treatment apparatus according to an embodiment of the present invention, which heat treats three PC steel bars at the same time.

The wire A is passed through a bending roll 2 from a wire feeder 1, scales on the surface are removed by a sandblast 3, and then cold drawn by a die 4 and a priddle roll 5 to a predetermined wire diameter. Further, a helical groove is cut on the surface of the wire with a die 4a, and then the cross section is made into a perfect circle with dies 4 and b, and the curling curls are corrected with a strainer 6.

As mentioned above (there are three heat treatment lines), the line in the center line 40 is straight, and in the lines 30 and 50 on both sides, the line is bent at two places. Deflector rolls 17 are disposed in each of the wires, and each line is parallel to each other during heat treatment, so that the distance between the wires is constant.

In this embodiment, however, a gas-fired type is used as the quenching furnace and tempering furnace. FIG. 4 is a longitudinal cross-sectional view of the main parts showing the configuration of the gas-fired quenching furnace 20 and the gas-fired tempering furnace 21. Further, FIG. 5 is a cross-sectional view of the same, and FIG. 6 is a plan view of the same.

4 to 6, the six furnaces 20, 21 are equipped with a cylindrical furnace main body 22, and a plurality of rollers 23 are arranged in a direction perpendicular to the wire passing direction. Both ends of the hearth roller extend outside the furnace and are supported by a shaft support means 25, and are configured to be rotated in the same direction and at the same speed by a synchronous drive means (not shown) such as a chain.

Furthermore, a plurality of gas burners 24 are provided on the ceiling of the furnace main body 22.
is installed. In this embodiment, the gas burner 2
4 are arranged in a staggered manner so that the temperature inside the furnace is uniform, and each node 24 is of the so-called short frame type with a short flame (flame). It is designed not to touch the heating wire directly. In the figure, 26 is a refractory.

In the furnaces 20 and 21 constructed in this manner, each wire rod is heated by a cooler 24 provided at the upper part of the furnace body, and reaches a predetermined temperature at the exit side of the furnaces 20 and 21. Immediately after the wire leaves the quenching furnace 20, it enters the quenching furnace water tank 8 and is quenched. Then, in tempering step 21 again, the material is heated to a predetermined temperature and then cooled in a tempering furnace water tank 10 to undergo tempering. Furnace 2
A predetermined tension is applied to the wire passing through the 0.21 and the water tank 8.10 by the priddle roll 5 and the take-off machine 12, and the wire undergoes heat treatment of quenching and tempering while being subjected to creep action. receive. Although a plurality of wire rods enter the furnace, the distance between the wire rods 15 is maintained at a constant value, and there is no interference between the wire rods even during wire threading work.

The steel rod B that has exited the tempering water tank IO is separated into each system by a deflector roll 17, the wire diameter is measured by a wire diameter measuring device 11, and the tension acting on the steel rod B is measured by a tension measuring device 16. While monitoring, the speed of the take-up machine 12 is adjusted to set the tension, and the winding machine 14 winds the film to a predetermined value. The steel rod B that has been wound at predetermined intervals is cut using a running cutting machine 13, and the winding machine 14 is switched to be continuously processed.

Next, a specific example of operation will be explained.

Inner furnace volume 8 with a burner fueled by steelworks C gas
．． A PC steel bar was manufactured using the apparatus shown in FIG. 3, which was equipped with a quenching furnace 2o of 8 m' and a tempering furnace 21 of 2.977 m, and the temperature inside the quenching furnace was 1350'C. The temperature inside the tempering furnace was set to 1350'C. And a 9.2mm PC
When three steel bars were heat treated at the same time at a speed of 45 m/min, the surface temperature of the steel bars was 890°C ± 10 in the quenching furnace.
℃, the temperature of the tempering furnace was within 390'C±5℃, and each steel bar had predetermined mechanical properties. The fuel consumption rate at this time was 460x10jKeai/T. By the way, in the conventional method using electricity, the electricity consumption rate is 420KWH/
Approximately 1/3 of the unit price of T, gas and electricity
We were able to reduce costs. In addition, while the conventional line required two workers per line, in this embodiment, even though three systems are installed, only four workers are sufficient, ensuring high labor productivity.

According to the above-described PC steel bar heat treatment apparatus of the present invention, a plurality of PC steel bars can be heat treated at the same time, and productivity is significantly improved. Additionally, since a gas-fired heat treatment furnace is used, energy costs can also be reduced.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional heat treatment system for PC steel bars, Fig. 2 is a sectional view of a high frequency induction heating furnace, Fig. 3 is a processing system diagram according to an embodiment of the present invention, and Fig. 4 is a diagram showing a heat treatment system of the present invention. FIG. 5 is a longitudinal cross-sectional view of the heating furnace according to the embodiment, FIG. 5 is a cross-sectional view thereof, and FIG. 6 is a plan view thereof. 20... Quenching furnace, 21... Tempering furnace, 23...
- Slow roller, 24... gas burner. Agent Tatsuyuki Kugenuma

Claims (1)

[Claims] (1) A PC in which a quenching furnace, a quenching furnace water tank, a tempering furnace, and a tempering furnace water tank are sequentially arranged through which the heat-treated PC steel rod is passed.
A PC steel bar heat treatment apparatus, wherein the quenching furnace and the tempering furnace are gas-fired.