JPS62223595A - Method of operating belt type continuous heat treating furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application] The present invention relates to a method for operating a belt-type continuous heat treatment furnace, and in particular to a method for controlling the rotation of a hearth roll, which is used in the field of heat treatment furnaces for iron powder, etc. .

[Conventional technology]

A continuous heat treatment furnace with an endless steel belt is used for heat treatment of iron powder, etc. A conventional belt-type continuous heat treatment furnace will be explained with reference to FIG.

Heat-treated materials such as iron powder 2 are charged from a charging hopper 4 to a steel belt 8 on a hearth roll 6, and a radiant tube (not shown) with a built-in heating burner is placed in a heating zone 10.
is heated to about 800° C. or higher to perform deoxidation or decarbonization. Next, in a cooling zone 12, the material is cooled to 100° C. or lower to prevent re-oxidation, and then discharged to become a product. Note that an atmospheric gas 14 is supplied to both the heating zone 10 and the cooling zone 12, and the atmospheric gas 14 is exhausted from an exhaust pipe 16.

The steel belt 8 is driven by a pinch roll 18 and adjusted to a predetermined speed. Steel belt 8 will stretch when used for a long time, so pinch roll 1 is used to absorb this.
A tensimin roll is installed after 8 to absorb the slack due to the elongation of the steel belt 8.

In these continuous heat treatment furnaces, a plurality of hearth rolls 6 conventionally arranged to support and transport the belt 8 are driven by a single motor via a chain for economical reasons. For this reason, thermal expansion of each hearth roll 6 and belt 8 in the heating zone 10 and cooling zone 12 is not taken into account at all, and as a result, the belt 8 sag in the furnace, and the belt 8 itself undergoes processing distortion due to the waving phenomenon. Otherwise, the belt may buckle, resulting in a significant reduction in belt life, and if the belt breaks, the belt needs to be replaced sooner, reducing productivity.

In order to prevent the belt 8 from sagging, in actual operation, the belt transport speed by the hearth roll 6 is made 2 to 3% slower than the belt speed by the pinch roll 18.
driving under stress. Therefore, the tension applied to the belt 8 increases, making the belt 8 more likely to stretch and break, shortening the life of the belt 8, increasing the frequency of belt replacement, and lowering productivity, which is a major problem.

[Problem that the invention seeks to solve]

The purpose of the present invention is to solve the above-mentioned problems of the prior art, reduce the tension applied to the belt, and prevent the belt from sagging.
An object of the present invention is to provide a method for operating a belt-type continuous heat treatment furnace that can extend the life of the belt.

[Means and operations for solving the problems] The gist of the present invention is as follows.

That is, in a method for operating a belt-type continuous heat treatment furnace in which material is charged into a belt on a hearth roll and then processed, the temperature of the belt and the hearth roll is measured, and the elongation of the belt at the measurement position is determined based on the measured value. a step of calculating a rotation speed of the hearth roll that does not cause slack in the belt based on the calculated value by calculating an expansion diameter of the hearth roll; and a step of controlling the rotation speed of the hearth roll based on the calculated value. A method of operating a belt-type continuous heat treatment furnace, comprising the following steps.

The temperature of the eight-roll and belt at each position in the furnace of a belt-type continuous heat treatment furnace is actually measured or estimated indirectly from the temperature inside the furnace, and the expansion diameter of each hearth roll and each hearth are calculated from the thermal expansion coefficient of the hearth roll and belt. Calculate the amount of belt elongation between rolls.

Although it is possible to actually measure the temperature of each hearth roll and belt using a light thermometer or a radiation thermometer, in reality a large number of thermometers would be required to measure each hearth roll and belt, and each In order to control the rotation of the rolls individually, the same number of drive motors as the hearth rolls are required.
In actual operation, it is desirable to divide the hearth roll in the furnace into a plurality of blocks and control the rotation of the hearth roll for each block.

Further, the temperature of the hearth roll and belt may not be measured individually, but may be estimated from the temperature measured inside the furnace.

The rotation control of the hearth roll of the present invention will be explained using FIG. In FIG. 2, the i-th and (i + 1)-th hearth rolls 6 will be explained. It is assumed that the roll circumferential speed v1 and the belt speed v, +1 at the temperature T of the i-th hearth roll 6I are adjusted to be the same. Note that the reference speed v0 of the belt 8 is determined by the tension speed of the pinch roll 18.

At the next +1)th 8-th roll 61+1, T
Belt length 1, including the amount of elongation of the belt between the 1st and (i + 1)th hearth rolls at a temperature of 1+,
．． Find the circumferential speed, ie, the rotational speed n, of the (i + 1)th hearth roll 6I+1 so as not to sag.

Below is the rotation speed n of the (i + 1)th hearth roll.
Explain the procedure for finding .

The diameter d of the (i + 1 )th hearth roll is expressed by the following formula (1).

ti, +, =d0x (1+ (T, +1-To)
xα)...-= (11d: Hearth roll diameter T at room temperature: Room temperature a: Thermal expansion coefficient in of the hearth roll and the belt length 11 between the (i + 1)th 8th roll is It is expressed by the following equation (2).

1l=Lx (1+ (T, +, '-T, ) xβ)
・・・・・・・・・(2) Distance β between L Everth rolls: belt thermal expansion coefficient The circumferential speed vl of the (i+1)th hearth roll is expressed by the following formula 1
Formula % V = V
It is assumed that the peripheral speed of the i + 1 )th hearth roll and the belt speed are the same. The rotation speed n of the (i + 1)th nozzle roll is expressed by the following formula.

■ = πd, Xn... (4) V,
+, : Belt speed d of the (i+1)th hearth roll, +, : Diameter of the (i+1)th hearth roll from formula (3) and formula (4) to d of formula (1), +, , +4 of formula 21 ．． As described above, based on the belt reference speed V0, calculate the belt elongation amount and hearth roll expansion diameter from the temperature of each hearth roll and belt, and based on these calculated values, ensure that the belt does not sag. Number of rotations of each hearth roll n? and control the rotation speed of each hearth roll.

The rotating side portion of the hearth roll will be specifically explained using FIG. Hearth roll 6 is divided into 10 blocks,
A thermometer 20 and a drive motor 22 are provided for each block, and the measured value T of the thermometer 20 is input to a calculator 24. The distance gl between the hearth rolls is stored in the calculator 24 in advance.
L, ud of hearth roll at room temperature. , belt reference speed V
. Since the thermal expansion coefficients α and β of the hearth roll and belt are input, the amount of belt elongation and the expanded diameter of the hearth roll are calculated, and based on these calculated values, the rotation speed of the hearth roll of each block that does not cause sag is calculated. n is calculated, the hearth roll rotation control device 26 inputs this rotation speed signal, and outputs 1W.
By controlling the rIh motor 22 and adjusting the rotational speed n of each hearth roll for each block, belt slack can be prevented and operation can be performed with appropriate belt tension.

〔Effect of the invention〕

The present invention measures the temperature of the belt and the hearth roll, calculates the elongation of the belt and the expansion diameter of the hearth roll, and calculates the number of revolutions of the hearth roll without causing any slack in the belt. By controlling the rotation speed, belt sag is eliminated, the pulling force caused by pinch rolls is reduced, and the belt can be transported with appropriate tension at all times, preventing belt breakage and extending its life. I can do it. Therefore, the operation of the continuous heat treatment furnace was stabilized and productivity was improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an apparatus illustrating the method of the present invention, FIG. 2 is an explanatory diagram showing the display of calculation formulas in the method of the present invention, and FIG. 3 is a sectional view of a conventional belt-type continuous heat treatment furnace.

Claims (1)

[Claims] (1) A method for operating a belt-type continuous heat treatment furnace in which material is charged onto a belt on a hearth roll for treatment, including the step of measuring the temperature of the belt and the hearth roll, and determining the temperature of the belt at the measurement position based on the measured value. calculating the amount of elongation and the expansion diameter of the hearth roll, and calculating the rotation speed of the hearth roll that does not cause slack in the belt based on the calculated values; and controlling the rotation speed of the hearth roll based on the calculated value. A method of operating a belt-type continuous heat treatment furnace, comprising the steps of: