JPS6235471B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly economically efficient heating control method for a continuous heat treatment furnace that can respond to changes in the number of objects to be heated.

Conventionally, when heat treatment is performed continuously in a heat treatment furnace, the basket containing the objects to be heated is conveyed at a constant speed while being controlled to satisfy predetermined heat treatment conditions. This was handled by changing the number of objects to be heated in the basket without changing the feed speed with all burners in the furnace ignited. Therefore, in this method, all burners in the furnace are always ignited regardless of changes in the number of pieces to be processed, which increases fuel consumption and is uneconomical. Japanese Patent Publication No. 52-
No. 54604 provides a method for controlling a continuous heat treatment furnace in which objects to be heated of different shapes, sizes, and materials proceed through the furnace at the same time.
The conveyance speed is set according to the heating conditions and shape of the object to be heated, and the burner near the outlet is ignited and stopped as necessary. However, in this heat treatment, preheating, temperature raising, soaking, and cooling are all controlled within the furnace, which makes the control complex and requires natural cooling in the atmosphere following the soaking process. There may be cases where this is not the case.

Therefore, an object of the present invention is to improve economic efficiency by changing the number of heating burners fired in accordance with changes in the number of objects to be heated, and at the same time to change the conveyance speed of objects to be heated in accordance with changes in the number of objects to be heated. It is an object of the present invention to provide a heating control method for a continuous heat treatment furnace that satisfies predetermined heat treatment conditions by changing the soaking time and keeping it constant.

The structure of the present invention is such that the material to be heated is transported from the inlet to the outlet side of a heat treatment furnace in which a plurality of heating zones equipped with heating burners are provided in series, while the combustion waste gas from the heating zones is collectively heated at the inlet side. As the number of objects to be heated decreases, the heating burners in the heating zone on the inlet side are stopped sequentially, and the burners are stopped due to combustion waste gas in the subsequent heating zone while the burner is being ignited. The objects to be heated in the heating zone are preheated, and the conveyance speed of the objects to be heated is decreased in accordance with the decrease in the number of objects to be heated, so that the soaking time is kept almost constant as the number of objects to be heated is changed. It is characterized by holding.

According to the present invention, when the number of objects to be heated changes, the number of ignitions of the burners in the heating zone on the inlet side is sequentially changed accordingly. This prevents fuel from being consumed more than necessary. Further, the conveyance speed of the object to be heated is changed so that the soaking time can be kept constant regardless of the change in the number of burner ignitions. Furthermore, in the heating zone where the burner is stopped, the heat of the combustion waste gas in the subsequent heating zone can be used to preheat the object to be heated. This provides a heat treatment control method for a continuous heat treatment furnace that is highly economically efficient and can satisfy predetermined heat treatment conditions.

Embodiments of the present invention will be described below with reference to the drawings.

Referring to the figure, a continuous heat treatment furnace 10 includes a plurality of heating zones 12, 14, 16, 1 arranged in series.
8, each heating zone has a zone wall 2
It is divided into 0, 22, and 24. Heat treatment furnace 10
The inlet 26 and outlet 28 of the
2, each is cut off from the outside air. the inlet lid 30;
The outlet cover 32 is opened and closed by a cylinder (not shown). Each heating zone is provided with a heating burner 34 and a stirrer 42 driven by a motor (not shown) that stirs the inside of the zone to equalize the temperature. Each heating burner 34 mixes propane, butane, or the like with air and burns the mixture. Objects 50 to be heated, such as aluminum alloy cylinder heads, are placed in a basket 52 and sequentially conveyed from the inlet 26 to the outlet 28 of the heat treatment furnace. In this case, the baskets 52 are placed in contact with each other on rollers 54 arranged in the furnace, and when the baskets 52 are pushed in the advancing direction by a pusher cylinder 62 on the entrance side, the force is sequentially transmitted, The basket 52 is adapted to be conveyed in the direction of the exit.
The heating zone 12 closest to the inlet side is also provided with an exhaust duct 56 for collecting combustion waste gas and discharging it to the atmosphere. This exhaust duct 56
An exhaust fan 58 is installed in the middle of the duct 56 to discharge the waste gas inside the duct 56 to the atmosphere. Furthermore, a heat exchanger 60 is provided in the duct to utilize the heat of the waste gas.
This heat exchanger 60 is mainly used to preheat the air for the burner.

When heat-treating objects to be heated under predetermined conditions using the heat treatment furnace 10 as described above, if the number of objects to be heated 50 in the basket 52 is the maximum, the number of objects in the furnace Burner 34
are all lit. At this time, each heating zone is, for example, heating zone 12 as a preheating zone, zone 14 as a temperature increasing zone, zone 1
6 and 18 are adjusted to function as a soaking zone. If the transport tact of the basket 52 by the pusher cylinder 62 at this time is T, and the number of baskets accommodated in the soaking zone is n (n=6 in the embodiment), then the soaking time T at this time is
1 is T1=nT. This soaking time is 240 minutes for the aluminum cylinder head due to solution treatment, and the temperature at this time is 485°C. Thereafter, when the number of objects to be heated 50 to be processed is reduced by half, for example, the burner 34 in the heating zone 12 is stopped. As a result, zones 12 and 14 function as preheating zones, zone 16 functions as a temperature increasing zone, and zone 18 functions as a soaking zone. in this case,
Duct 58 installed on the inlet side for exhaust gas from burner 34
Since the gas is discharged through the heating zone 12 where the burner is stopped. Therefore, even if the burner 34 of the heating zone 12 is stopped, it can function as a preheating zone. At this time, by slowing down the transport tact of the basket 52 by the pusher cylinder 62 to 2T, the soaking time T2 in the soaking zone 18 can be kept constant as T2=n/2.2T=nT=T1. That is, it is possible to respond to changes in the number of objects to be heated while maintaining high economic efficiency.

[Brief explanation of the drawing]

The figure is a sectional view of a continuous heat treatment furnace according to one embodiment of the present invention. Explanation of symbols 10...Continuous heat treatment furnace, 12,1
4, 16, 18... heating zone, 20, 22, 2
4... Zone wall, 34... Heating burner, 42...
Stirrer, 50... Material to be heated, 52... Basket.

Claims (1)

[Claims] 1. A material to be heated is transported from the inlet to the outlet side of a heat treatment furnace in which a plurality of heating zones equipped with heating burners are provided in series, while the combustion waste gas from the heating zone is collectively transported through the heating zone on the inlet side. The heating burners in the heating zone on the inlet side are stopped sequentially as the number of objects to be heated decreases, and the burners in the heating zone are stopped due to combustion waste gas in the subsequent heating zone while the burners are being ignited. In addition to preheating the objects to be heated, the conveyance speed of the objects to be heated is decreased according to the decrease in the number of objects to be heated, and the soaking time is kept almost constant according to the change in the number of objects to be heated. 1. A heating control method for a continuous heat treatment furnace, characterized in that: