JPS59185733A - Heat treating device for pc steel bar - Google Patents

Abstract

PURPOSE:To provide a titled device which economizes fuel cost and realizes a low production cost by the constitution in which a hardening furnace and a tempering furnace provided with gas burners are disposed successively in the passing direction of a blank material for a PC steel bar and the waste gas from the hardening furnace is introduced through a duct into the tempering furnace. CONSTITUTION:A blank material 14 for a PC steel bar supplied from a supply stand 10 is pretreated to a steel bar 12 having a prescribed wire diameter in a pretreating installation 15 and is then hardened in a hardening furnace 26 provided with a gas burner 30 and a water tank 10 in a heat treating device for the PC steel bar disposed successively with the furnace 26, a water tank 18, a tempering furnace 28, a water tank 22, etc. After the steel bar 12 is tempered in the furnace 28 provided with a gas burner 40 and the water tank 22, the steel bar is coiled at a prescribed curvature with a post treating installation 24. The waste gas from said furnace 26 heats the furnace air in a heat exchanger 38 and thereafter said gas is introduced through a duct 34 by a waste gas fan 36 into the furnace 28 where the heat retained in the gas is utilized. The waste gas from the furnace 28 heats the furnace air in a heat exchange 50 so that energy is economized in the same way as in the said heat exchanger 38.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a PC steel bar heat treatment apparatus, and more particularly to a PC steel bar heat treatment apparatus equipped with a gas-fired heat treatment furnace and with low fuel consumption.

A PC steel rod is a steel rod used as a reinforcing bar for prestressed concrete.

FIG. 1 is a diagram showing the basic configuration of a production line for this PC steel bar. In FIG. 1, 10 is a supply stand that supports the raw material 14 of the steel rod 12 being heat treated and supplies it to the subsequent line; 15 is a supply stand that cold-draws the raw material 14 to give it roundness and a predetermined wire diameter. A pretreatment equipment 16 equipped with a wire drawing die heats the steel rod 12 to a predetermined quenching temperature (for example, 85
18 is a quenching furnace water tank in which the heated steel bar 12 is water-cooled and quenched; 20 is a quenching furnace in which the steel bar 12 is heated to a predetermined tempering temperature (for example, 360°C); Returning furnace, 22 is a tempering furnace for cooling the steel rod 12 after heating; Water tank, 2
4 is a post-processing facility for winding the steel rod to a predetermined curvature.

Conventionally, a high frequency heating furnace is used as the quenching furnace 16 and the tempering furnace 20. However, with the rise in electrical energy costs, the manufacturing costs of this conventional processing line are rising, and there are expectations for a manufacturing line that can reduce manufacturing costs.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a PC steel bar heat treatment furnace that can achieve a significant reduction in manufacturing costs.

In order to achieve this object, the present invention uses a gas-fired quenching furnace and a tempering furnace, and reuses the exhaust gas of the quenching furnace as a part of the heat source of the tempering furnace. It is.

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

FIG. 2 is a system diagram of a PC steel bar heat treatment apparatus according to an embodiment of the present invention. This embodiment line has the same basic configuration as the one in FIG. 1, but a quenching furnace 16 and a tempering furnace 2
Instead, a gas-fired quenching furnace 26 and a gas-fired tempering furnace 28 are used.

A plurality of burners 30 are installed in the quenching furnace 26.
Air and fuel gas are supplied from a quenching furnace air supply line 32 and a quenching furnace gas supply line 33. The combustion exhaust gas after heating the heat-treated PC steel rod 12 in the quenching furnace 26 is discharged from the exhaust duct 34 and introduced into the tempering furnace 28 . An exhaust blower 36 is installed in the middle of the exhaust duct 34, and a heat exchanger 38 is installed in the duct between the exhaust blower 36 and the quenching furnace 26, and the exhaust gas from the quenching furnace 26 is supplied to the quenching furnace. The air is heated.

A plurality of burners 40 are also provided in the partly gas-fired tempering furnace 28, and air is supplied to the burners 40 from a tempering furnace air supply line 42, and a tempering furnace gas supply line Fuel gas is supplied from 43. The combustion gas produced by combustion in the burner 40 heats the heat-treated PC steel rod 12 to a tempering temperature, and then is discharged from the tempering furnace exhaust duct 44.

- The exhaust duct 34 of the quenching furnace is introduced into the tempering furnace 28 at a point where the temperature inside the tempering furnace 28 and the exhaust gas temperature in the exhaust duct 34 match. The combustion gas of the burner 40 and the gas supplied from the exhaust duct 34 are mixed and together heat the PC steel rod 12. Both of these gases are guided from the exhaust duct 4''4 to the exhaust pipe 46 and discharged to the outside.

An exhaust blower 48 is installed in the middle of the exhaust duct 44, and a heat exchanger 50 is installed in the middle of the exhaust blower 48 and the tempering furnace 28 to preheat the air supplied to the burner 40. There is.

The heat treatment furnace of the embodiment configured as described above includes a quenching furnace 2.
6 and the tempering furnace 28 are both gas-fired type, and the tempering furnace 28
Since it is reused as a heat source, the degree of heat utilization is high.

In particular, in this embodiment, heat exchangers 38 and 50 are installed to recover heat and realize further energy saving effects.

FIG. 3 is a system diagram of a PC steel bar heat treatment apparatus according to a different embodiment of the present invention. The embodiment shown in FIG. 3 is a further improvement of the embodiment shown in FIG.
This is introduced into the cover 10a of the stand 10 and used as a preheating source for the material 14 supported by the stand 10.

By using the thermal energy possessed by the exhaust gas of the tempering furnace to preheat the non-heat treated steel rod in this way, the power cost required for drawing can be reduced and the life of the die can be extended. Furthermore, by preheating the material in this way, the temperature of the steel rod introduced into the quenching furnace increases, and therefore it is possible to increase the line speed and improve productivity. In the embodiment shown in FIG. 3, the exhaust gas from the tempering furnace 28 is introduced into the cover 10a of the supply stand IO, but it is also supplied to various parts of the steel rod supply section in the front stage of the heat treatment furnace, in addition to the supply stand. You may also preheat it.

Example (A) A steel rod with a rod diameter of 9.15 g was heated at a line speed of 45 m/f8.
1. The heating temperatures for quenching, quenching, and tempering were 850° C. and 360° C., respectively, and a heat treatment of water cooling after heating was performed using the line shown in FIG. The exhaust gas temperature of the quenching furnace 26 is 550 to 700°C after heat exchange in the heat exchanger 38.

The quenching furnace exhaust gas was introduced into the tempering furnace from a point where this exhaust gas temperature and the furnace temperature of the tempering furnace 28 matched.

The combustion gas in the tempering furnace 28 and this input gas are mixed, enter the exhaust duct 44, exchange heat with combustion air in the heat exchanger 50, reach a temperature of approximately 300 to 400°C, and are discharged from the exhaust pipe 46 to the atmosphere. was ejected inside. As a result, if a simple gas-fired furnace was used, the heat unit would be 400×103K ca71/l, but this could be reduced to about 350×IO3KCae/°C.

Example (B) Heat treatment was carried out using the production line shown in FIG. 3 under the same rod diameter, line speed, and heating temperature conditions as in Example (A'). After the exhaust gas from the quenching furnace 26 undergoes heat exchange in the heat exchanger 38,
~700°C. As in Example (A), the tempering furnace 28 is
I put it inside. The gases collected together with the exhaust gas from the tempering furnace 28 passed through the exhaust duct 44 and exchanged heat with the combustion air in the heat exchanger 5o, resulting in a temperature of about 300 to 400°C. Further, it was sent through the exhaust duct 48 to the preheating cover 9 of the steel rod supply stand 10, cooled to 150', and then exhausted to the atmosphere. As a result, the heat consumption was further reduced to 340 X IO' Kca//l compared to Example (A).

According to the present invention, the manufacturing cost of PC steel rods can be reduced to about % to 30% compared to conventional high frequency heating furnaces. In addition, since the steel bar material is preheated, the power cost required for drawing is reduced and the life of the die is extended. Furthermore, preheating the material raises the temperature of the steel bar at the side entering the quenching furnace, making it possible to increase the line speed by about 3 inches and improving productivity.

As explained above, according to the present invention, the manufacturing cost of PC steel rods is significantly reduced. ,

[Brief explanation of drawings]

FIG. 1 is a basic system diagram of a PC steel bar production line, and FIGS. 2 and 3 are system diagrams of a heat treatment furnace according to an embodiment of the present invention, respectively. 15... Pretreatment equipment, 16.26... Quenching furnace,
20.2B... Tempering furnace, 24... Post-processing equipment, 38
．． 50... Heat exchanger. Agent Tatsuyuki Unuma (and 1 other person)

Claims (1)

[Claims] (11 PCs equipped with a gas burner in the direction of the steel bar material passing
A PC steel bar quenching furnace, a PC steel bar quenching furnace water tank, a PC steel bar tempering snake equipped with a gas burner, and a PC steel bar tempering furnace water tank are arranged in sequence, and a PC steel bar quenching furnace exhaust gas is disposed in sequence. A PC steel bar heat treatment equipment equipped with a duct for introduction into steel bar tempering.