JPH01149927A - Horizontal annealing furnace - Google Patents

Abstract

PURPOSE:To cut down on the equipment cost and to obtain the subject horizontal annealing furnace capable of being used even in the annealing of a silicon steel sheet, etc., by making the laying pitch of hearth rolls in the furnace sparse in the relatively low-temp. region of a material to be annealed in the preceding and succeeding stages, and making the pitch dense in the higher temp. region of the material in the intermediate stage. CONSTITUTION:The relationship between the roll pitch, unit tension, and strain investigated on a certain kind of steel in the horizontal annealing furnace is shown in the figures. According to the figures, the strain falls in the allowable range at <=800 deg.C and at >=1,500mm roll pitch, and the pitch must be controlled to <=1,500mm at >=800 deg.C. The equipment cost is drastically increased at <=500mm roll pitch. When a silicon steel sheet having 0.15-1.0mm thickness and 0.05-0.3kg/mm<2> unit tension is annealed, for example, the roll pitch A is controlled to 1,500-3,000mm at the material temp. of <=800 deg.C, and the roll pitch B is controlled to 500-1,500mm at the material temp. of >=800 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a horizontal annealing furnace using hearth rolls, and particularly to a horizontal annealing furnace suitable for heat treatment of silicon steel strips and the like.

<Prior Art> A conventional horizontal annealing furnace is equipped with hearth rolls having a substantially constant pitch. The pitch of the hearth roll is determined by the conveyance capacity and the relationship with peripheral equipment, regardless of the temperature of the material to be annealed. It also has piping attached to it to send combustion gas, atmospheric gas, combustion air, etc.

Generally, if the roll pitch is large, it becomes difficult to pass the material to be annealed through the furnace, and if the weight of the material to be annealed shared by one hearth roll becomes too large, it cannot be transported by the friction torque of the hearth roll ( Become.

By the way, in the annealing of silicon steel sheets, if a strain of more than a certain value is applied at a certain temperature or higher during the annealing process, the iron loss of the product will increase, so the pitch of the hearth opening is generally designed to be small, and the equipment is This was a factor in increasing costs.

<Problems to be Solved by the Invention> The present invention provides a hearth roll pitch that reduces the equipment cost of a conventional horizontal annealing furnace that performs heating, soaking, and cooling, and can also be used for annealing silicon steel sheets. A horizontal annealing furnace is provided.

<Means for solving the problem> The present invention is a horizontal annealing furnace that performs heating, soaking, and cooling, and the furnace body is divided into three parts from the entrance side into a front stage, a middle stage, and a rear stage, and the temperature of the material to be annealed is relatively low. This horizontal annealing furnace is characterized in that the pitch of the hearth rolls in the front and rear sections is sparse, and the pitch of the hearth rolls in the middle section, where the temperature of the material to be annealed is higher, is dense.

First, the qualitative relationship between iron loss, annealing process temperature, and applied strain was investigated, and the relationship shown in Figure 2 was obtained.

In this figure, the limit temperature that does not increase iron loss is 1c, and the limit strain is . P+, Pt, Pz are distortion amounts P, >P
t > p, and it can be seen that the larger the strain and the higher the temperature, the higher the iron loss. Incidentally, the limit temperature of the silicon steel plate determined experimentally was about 800'C. 800°C
Beyond this point, distortion and iron loss rapidly increase.

Next, the qualitative relationship between the hearth roll pitch and the strain of the annealed material was investigated, and the relationship shown in FIG. 3 was obtained.

Using the same material to be annealed, the strain of the material to be annealed was actually measured by changing the roll diameter, roll pitch, and unit tension at the same temperature.

If the roll diameter and roll pitch are constant, the distortion will increase as the unit tension increases; if the roll pitch and unit tension are constant, the distortion will increase as the roll diameter decreases; It can be seen that the larger the roll pinch, the larger the distortion.

Next, in order to determine the hearth roll diameter and pitch, based on the above-mentioned results, the critical strain ε at a critical temperature of 1c or higher is determined. We selected a combination of roll diameter and roll pitch that did not exceed , and found the optimal combination based on equipment conditions.

Actually, in consideration of roll compatibility, the same roll diameter as the roll diameter at the limit temperature of 1 c or less was adopted, and the optimum value of the roll pitch was determined.

Figure 4 shows the results of investigating the relationship between roll pitch, unit tension, and strain for the steel types.

If the temperature is below 800℃, the roll pitch is 1500m.
It can be seen that although the distortion is within the permissible range even if the temperature is more than m, if the temperature is more than 800°C, the roll pitch must be less than 1500 mm. The roll pitch is 500s.
If it is set below, the equipment cost will only increase, so there is no need to set it below that, and it is determined in the range of 1500 rrm to 500 rrm.

Although there are some differences in these relationships depending on the steel type and roll diameter, they do not significantly deviate from the above values.

In addition, FIG. 5 conceptually shows an example of equipment for a hearth roll. The hearth roll 2 is rotatably supported by a furnace shell 11, and a sprocket 6 provided at the end thereof is connected to a motor 4, a reducer 5, Power is transmitted through the line shaft 8, bevel gear 7, drive side sprocket 12, and chain 10, which rotate in synchronization to convey the material 1 to be annealed in the furnace.

Based on the heat pattern shown in Figure 1, the range below the limit temperature is determined by the roll pitch determined by the conventional method.
For the range above the limit temperature, the roll pitch determined by the method shown in the present invention was adopted.

In the case of a silicon steel plate with a plate thickness of 0.15 to 1.0 mm and a unit tension of 0.05 to 0.3 kg/ws'', specifically, the temperature of the annealed material with a roll diameter of 120 to 300 m5 is 800°. Roll pitch in the range below C is 1500~
The roll pitch in the range of 3000 tm and annealed material temperature of 800°C or higher was 500 to 1500 tm.

<Effects of the Invention> According to the present invention, it has become possible to construct a horizontal annealing furnace having a hearth roll that does not increase iron loss even when used for annealing silicon steel sheets and has minimum equipment cost.

[Brief explanation of the drawings] Figure 1 is an explanatory diagram showing the heat pattern and the hearth roll pitch of the present invention, Figure 2 is a graph showing the relationship between temperature, strain, and iron loss, and Figure 3 is the roll diameter and pitch. and a graph showing the relationship between unit tension and strain; FIG. 4 is a graph showing the relationship between roll pitch, unit tension, temperature, and strain; FIG. 5 is a conceptual diagram of an example of hearth roll equipment;
) is a side view, ra) is a plan view, and (C) is a sectional view. 1...Mm blunt material, 2...Hearth roll, 3...
・Furnace material, 4...Motor, 5...Reducer, 6...Sprocket, 7...Bevel gear, 8...Line shaft, 9...Bearing,
10... Tune, 11... Furnace shell,
12... Drive side sprocket. Patent Applicant Kawasaki Steel Corporation ff11 Figure Lc Temperature Figure 4 1bUIJ JC) L) U +:+ - Lehitch Figure 5 (b) Figure 5 (C)

Claims (1)

[Claims] In a horizontal annealing furnace that performs heating, soaking, and cooling, the furnace body is divided into three stages from the entrance side into the front stage, middle stage, and rear stage, and the laying pitch of the hearth rolls in the front stage and rear stage where the temperature of the material to be annealed is relatively low is determined. A horizontal annealing furnace characterized in that the pitch of the hearth rolls in the middle section, which is located in the region where the temperature of the material to be annealed is higher, is dense.