JPS6289817A - Heat treatment of steel stock - Google Patents

Abstract

PURPOSE:To improve efficiency and to reduce energy loss, by carrying out heat treatment while selecting divided zones in a temp. holding zone, at heat treatment while providing plural temp. holding zones in continuous furnace for linearly transferring a material to be treated. CONSTITUTION:A space between, e.g. two temp. holding zones No.3 and No.8 is divided with five partition walls 2 (two of them are already set) to constitute the region with four zones No.4-No.7 and these are both used as cooling and temp. holding zones. Outer diameter, wall thickness of material to be treated, e.g. steel pipe, temp. and time of soaking and isothermal holding are inputted from a setting device 3 to a computer 1, and transferring velocity of steel pipe and positions of respective zones are calculated and transmitted so that the stored table is accommodated. A velocity controller 4 receives and controls the transferring velocity of steel pipe. A heating and cooling controller 5 receives the position of each zone and temp. of each zone obtd. based on detected value from a thermometer T provided at each zone, controls heating and cooling at each zone and controls the temp.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a method of heat treating steel materials using a continuous furnace.
In particular, in the method of heat treatment by setting multiple temperature holding zones in a continuous furnace in which the material to be treated is transferred linearly, the cooling zone is selected according to the heat load of the material to efficiently and efficiently treat the material. Economically P! Concerning methods that can be used.

Prior art and its problems A roller hearth type furnace is known as a type of continuous furnace in which the material to be treated is transferred linearly;
For example, in a continuous annealing furnace, when multiple temperatures need to be maintained such as in isothermal annealing, or when controlling the cooling rate after soaking as in partially spheroidized annealing, the temperature holding zone or cooling of each heat pattern is The strips were fixed in each specific zone.

Figure 4 shows an example of each zone and heat pattern of a conventional continuous annealing furnace. In the case of constant temperature annealing A, each zone corresponding to the heating soaking zone, cooling zone, and constant temperature holding zone is fixed. There is. For this reason, for example, when heat treating a thick-walled product that heats up slowly, the transfer speed is determined by the heating time. The loss is huge.

Purpose of the Invention This invention was made in order to solve the conventional problems of reduced efficiency and energy loss. The purpose of this study is to propose a heat treatment method for steel materials that improves efficiency and reduces energy loss by allowing heat treatment to be performed by selecting zones.

Structure of the Invention The method for heat treatment of steel materials according to the present invention includes a continuous furnace in which the material to be treated is transferred linearly, and a plurality of temperature holding zones are set to heat treat the material to be treated. The cooling zone between the zones is divided into multiple zones by multiple partition walls installed in the direction of transport of the material to be processed, and is used as a zone for both cooling and temperature maintenance.
A cooling zone in the cooling/temperature holding zone is determined based on a transfer speed determined from each temperature holding time and temperature changing time of the material to be treated, and the temperature is controlled based on the determination. be.

Hereinafter, the method of the present invention will be explained in detail based on the drawings.

First, the heating method in this type of continuous annealing furnace is an indirect heating method using a radiant tube combined with a burner, and a cooling device is attached to the cooling zone.

In this invention, as the cooling zone is divided into a plurality of zones, instead of the conventional cooling device, a method is adopted in which air is forced into a radiant tube and cooled by radiation.

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, in which five partition walls (2
) (two of which are existing partition walls), this area is divided into four zones (&4 to 47), and the zones from Mu 4 to Todoroki 7 are used as cooling and temperature maintenance zones. The added bulkhead is the same as before! It is made of firebrick and is fixed.

That is, in this invention, as mentioned above, partition walls are added to the areas &4 to 7 to form four independent zones, and the radiant tubes in zones 4 and 7 have a cooling function, so that they can be used as cooling zones. black 4 and curse 5 zone, mu 5
It is possible to select from three zones: 6 zones and 6 zones, and 6 zones and 47 zones. In addition, it is also possible to use the area between zones 46 to 11 as a heating and soaking zone.
The space between the two zones can be used as a constant temperature zone.

In the heat pattern shown in FIG. 1, ``■'' is a typical heat pattern for thin-walled products, ``■'' is a conventional constant heat pattern, and C7'' is an example of a typical heat pattern for thick-walled products.

Figure 2 is a block diagram showing the control system for carrying out the method of this invention, in which (T) is a thermometer that detects the temperature of each zone, and (1) is a continuous furnace that sets the material to be treated under the desired heat treatment conditions. A computer that performs arithmetic processing for control; (3) a setting device for inputting the size of the material to be treated and 71G heat time (heat pattern) to the computer (1); (4)
) is a speed controller for controlling the transfer speed of the material to be processed calculated by the computer (1), and (5) is a boosting/cooling device for controlling the temperature of the material to be processed to be calculated by the computer (1). It is a controller.

The heat treatment of a steel pipe will be described in detail as an example of a material to be treated using the continuous furnace having the above configuration.

The computer (1) stores in advance the relationship between the outer diameter and wall thickness of the steel pipe and the shortest temperature rise time corresponding to the soaking temperature, and the temperature drop in the cooling zone (the relationship between the soaking temperature and the isothermal holding temperature). Each of the relationships of the shortest temperature drop time corresponding to the difference) is stored in the form of a table. Further, once the shortest temperature rise time, shortest temperature drop time, soaking time and constant temperature holding time to be set as described below are determined, the furnace time t (Σtn) is calculated from the sum of these, and the calculated furnace The transfer speed v (L/l) of the steel pipe is stored so as to be calculated sequentially from the inner time t and the furnace length L (constant length) of the continuous furnace. Furthermore, when the transfer speed V is calculated, from each processing band time tn calculated and set as described above,
The positions of the heating/soaking zone, the cooling zone, and the constant temperature zone are determined as v-tn.

From the setting device (3), the outer diameter and wall thickness of the steel pipe, soaking temperature, constant temperature holding temperature, 3, soaking time, and constant temperature holding time are set in accordance with the table stored in the computer (1) mentioned above. is input.

In the computer (1), the transfer speed V and each position of the steel pipe are calculated as described above based on the input signal from the setting device (3), and the transfer speed V is sent to the speed controller (4) and heated and The position of each cooling controller (5) and the temperature tn of each item are exaggerated. In addition, the temperature tn of each issue
For each zone, the detected value from the thermometer (T) provided in each zone is received, and when calculating the temperature of each zone, correction is made using the detected value from the thermometer (T).

The speed controller (4) receives a signal from the computer (1), converts this signal into, for example, a current value for the drive machine of the roller that transports the w4t, and drives the roller based on this current value.
A signal is sent to a converter (not shown) so that the machine rotates.

The heating/cooling controller (5) calculates 7XJN1! in each zone based on the position of each item and its temperature tn signal sent from the computer (1). The opening degree of the valve installed in the fuel piping corresponds to the amount of fuel supplied to the burner due to the cooling, or the opening of the valve installed in the cooling air piping corresponds to the amount of cooling air supplied to the radiant tube due to cooling. In order to control the opening, a signal is generated by a converter (not shown) of the valve opening controller JJJ.

As described above, the transfer speed V of the steel pipe in the continuous furnace and the temperature in each section are controlled, and the temperature control for cooling and temperature maintenance g1 among the temperatures in each section is controlled between each zone. By providing a partition wall, more precise control was achieved.

Figure 3 shows a continuous sintering furnace with 11 zones (furnace width 1150 mm).
The method of this invention is applied to the method of this invention, and the efficiency increase rate is shown comparing the cooling zone selection zone and the conventional method for each pitch with an outer diameter of 20 silk pitches and a wall thickness of 1 to 5 fi+pitch. In the figure, blank areas indicate the conventional method.

The length of each zone and processing conditions in this example are shown in Table 1. The material to be treated is a pipe made of Cf-M□ steel.

(Left below) As is clear from Table 1 and Figure 3, the efficiency of the heat treatment furnace could be increased (20.0%) by the method of this invention.

Additionally, the fuel consumption required for heat treatment was reduced by approximately 14.5%.

Effects of the Invention As explained above, the method of the present invention is a method of heat treatment by selecting one cooling zone according to each heat pattern of the material to be treated, so it is possible to improve efficiency and reduce energy costs. Furthermore, since the temperature and movement speed of each zone are controlled by a computer, the number of man-hours required for selecting a cooling zone is small, and heat treatment can be carried out quickly and accurately.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a continuous kiln furnace and an example of a heat pattern for explaining the method of this invention, Fig. 2 is a schematic diagram showing a control system for carrying out the method of this invention, and Fig. 3 is a schematic diagram of a control system for implementing the method of this invention. FIG. 4, which is a diagram showing the efficiency increase rate in the example, is a schematic diagram showing a continuous furnace showing a conventional heat treatment method and an example of a heat pattern. DESCRIPTION OF SYMBOLS 1... Computer, 2... Bulkhead, 3... Setting device, 4... Speed controller, 5... Heating/cooling controller,
T...Thermometer.

Claims (1)

[Claims] In a method of heat-treating a material to be treated by setting a plurality of temperature holding zones using a continuous furnace in which the material to be treated is transferred linearly, a cooling zone between the temperature holding zones is provided in the direction of transfer of the material to be treated. The cooling/temperature holding zone is divided into multiple zones by a plurality of partition walls, and the cooling in the cooling/temperature holding zone is determined based on the transfer speed determined from each temperature holding time and temperature change time of the material to be treated. 1. A method for heat treatment of steel materials, comprising determining zones and controlling temperature based on the determination.