JPS5844727B2 - How to heat steel pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for heating steel pipes.

Steel pipes as intermediate products are subjected to heat treatments such as quenching and tempering, and heating of the steel pipes during such heat treatments is usually carried out by bringing them into contact with a high-temperature atmosphere in a heating furnace.

This invention was made in view of the conventional method of heating steel pipes using a high-temperature atmosphere, and to propose a method for heating steel pipes more efficiently. Heated gas is blown from the pipe end into the inside of the steel pipe being transferred from a plurality of injection ports provided near both ends of the steel pipe along the transport direction, and the blowing is alternately performed. By heating from one end of the two ends of the steel pipe, it is possible to heat the steel pipe efficiently by heating not only from the outside but also from the inside. Moreover, the present invention is characterized in that the steel pipe heating method can quickly and uniformly heat the steel pipe without causing a temperature difference between the heating gas blowing side and the heating gas discharge side.

The present invention will be described below based on embodiments and with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a steel pipe heat treatment equipment to which the present invention is applied, and FIG. 2 is a schematic plan view of the steel pipe preheating device of FIG. 1.

As shown in the figure, 1 is a quenching furnace, 2 is a tempering furnace, 3.4 is a heat exchange type air preheater, 5 is a preheating device, and the steel pipe 6 is heated approximately 1000 times in the quenching furnace 1. After being heated to ℃, it is subjected to underwater quenching treatment, and then transported to a preheating device 5,
After passing through the preheating device 5, it is hardened in a tempering furnace 2 and heated to a temperature of around 600°C, and then transported to an inspection process.

The combustion exhaust gas from the quenching furnace 1 passes through the air preheater 3 and has a temperature of 400 to 500°C), an on-off valve 8,
and is guided to the preheating device 5 via the induction blower 9 (if necessary, guided to the chimney 11 via the discharge damper 10), and then from the preheating device 5 to the discharge damper 1.
2, an on-off valve 13, and the exhaust damper 10 to be led to the chimney 11.

The combustion exhaust gas from the tempering furnace 2 passes through the air preheater 4 (the temperature after passing is about 300° C.) and is led to the chimney 15 via the exhaust damper 14.

As shown in FIG. 2, the preheating device 5 has a pipe 16 for introducing the combustion exhaust gas (which has passed through the air preheater 3) from the quenching furnace 1, and is transferred in a horizontal state. A plurality of injection ports 17 for injecting heating gas (the combustion exhaust gas) are provided near both ends of the steel pipe along the transfer direction.
from the injection port 17 to the piping 16.
The combustion exhaust gas from the washing furnace 1 is injected through the washing furnace 1.

The piping 16 is provided with exhaust gas switching dampers 18 and 19 on the way toward both ends of the steel pipe 6, and by switching these dampers 18 and 19, the inside of the steel pipe 6 is Heating gas (the combustion exhaust gas) is alternately blown into one of the two ends of the pipe, and in addition to heating the inner surface of the steel pipe 6 by blowing the heated gas, The outer surface of the device 5 is heated by contacting an atmosphere at a predetermined temperature caused by the combustion exhaust gas.

Therefore, the steel pipe 6 is heated from the outside by the preheating device 5 and uniformly heated from the inside by alternately blowing heating gas from both ends of the pipe, and before being charged into the tempering furnace 2. It is preheated to a predetermined temperature very efficiently.

In this invention, the reason why heating gas is blown in alternately from the tube ends is as follows.

In other words, if heating gas is blown into only one end of the steel pipe 6, there will be a temperature difference between the end of the pipe into which the heating gas is blown and the end of the pipe where the heating gas is discharged (the temperature is lower on the discharge side). ) occurs,
Moreover, the heated gas tends to stay inside the pipe.

However, if heated gas is blown in alternately from both tube ends as in the present invention, the temperature difference between the heated gas blowing side and the discharge side is eliminated, and the steel tube 6 can be evenly and quickly preheated to a predetermined temperature. can do.

Here, the effect of preheating the preheating device 5 when hardening and tempering the steel pipe 6 will be described as follows.

That is, outer diameter 244.50+m, wall thickness 11.9911
1111 and 125001 it length steel pipes are quenched,
When performing the tempering treatment, the preheating temperature of the steel pipe of the size in the preheating device 5 is set to 200°C and 30°C.
The furnace time in the tempering furnace when the temperature is 0°C is 20
It took 45 minutes at 0°C and 43 minutes at 300°C.

For comparison purposes, when a steel pipe of the above size is charged into a tempering furnace without preheating, the time in the tempering furnace is 49.
It was a minute.

Therefore, the relationship between the steel pipe preheating temperature and the energy consumption reduction rate of the tempering furnace in the present invention is as shown in FIG.

In addition, this shortening of the furnace time in the tempering furnace means that, if the same amount of energy is consumed as before, the number of tons processed per unit time of the tempering furnace itself will increase. It turns out.

In other words, in the above example, in the case of preheating at 200°C, the rate is 109t/h, and in the case of 300°C, it is 114t/h.
h, and on the other hand, in the case of the comparative example, it was 100 t/h.

This (increase in tonnage throughput) can be expressed as a capacity improvement contribution rate as shown in Figure 4.

As explained above, in this invention, a steel pipe can be heated extremely efficiently.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a steel pipe heat treatment equipment to which the present invention is applied, Fig. 2 is a schematic plan view of the steel pipe preheating device shown in Fig. 1, and Fig. 3 is a diagram showing the preheating temperature of the steel pipe and the consumption of the tempering furnace. A diagram showing the relationship between the energy reduction rate and FIG. 4 is a diagram showing the relationship between the preheating temperature of the steel pipe and the capacity improvement contribution rate of the tempering furnace. 1... Quenching furnace, 2... Tempering furnace, 3, 4
... Air preheater, 5 ... Preheating device, 6 ... Steel pipe, 8゜13 ... Opening/closing valve,
9...Induction blower-110°12.14...
...Exhaust damper, 11,15...Chimney, 1
6... Piping, 17... Injection port, 18,
19... Damper for exhaust gas switching.

Claims (1)

[Claims] 1. Heating gas is injected into the inside of a steel pipe that is placed horizontally and transferred through an atmosphere at a predetermined temperature for heating, from a plurality of injection ports provided near both ends of the steel pipe along the transfer direction. A method for heating a steel pipe, characterized in that the blowing is performed alternately from one end of the two ends of the steel pipe.