JPS5952205B2 - Hearth rail for walking beam heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hearth rail for a walking beam heating furnace, and an object of the present invention is to uniformly heat a slab with high thermal efficiency and without temperature unevenness.

Generally, for a hearth rail for a walking beam heating furnace, it is absolutely necessary to provide an environment in which the slab can be heated efficiently and uniformly with no temperature unevenness.

The best way to do this is to use a refractory material such as brick with good heat insulation for the hearth material, but it is recommended to use a heat-resistant alloy due to safety concerns such as impact and compressive strength, and the inefficiency of construction. is normal.

When heating slabs, etc., the ambient temperature is 1300 to 135
The slab heating temperature is as high as 0°C and 1250 to 1300°C, and the heat-resistant alloy hearth rail is also heated to this temperature.

However, heat-resistant alloys are in the metal gap zone at temperatures above 1000°C, which is an extremely severe condition for heat-resistant alloys.

As shown in b, a water cooling system is used in which a hearth rail 3 is placed on a water-cooled skid pipe 2.

In this case, the problem is that the temperature of the hearth rail 3 itself becomes lower than the ambient temperature due to the influence of water cooling.

That is, the surface where the slab 4 contacts the hearth rail 3 is, for example, 1250° C. at 8 points, 0° C. at point b, and 1200° C. at point r, as shown in FIG.

Therefore, in order to reduce the temperature difference, design consideration is currently being taken to select an appropriate heat-resistant alloy and to make the height of the hearth rail as high as possible, but this problem of temperature drop has not yet been solved. First, this problem is extremely uneconomical (in order to reduce the temperature difference, the furnace time is increased) rather than improving the efficiency of the heat source.

The present invention has been made in view of the above points, and will be described in detail below with reference to the drawings.

At the bottom of the walking beam heating furnace 1, an appropriate number of water-cooled skid pipes 2, 2 through which cooling water is passed are arranged.
A hearth rail 3 made of a heat-resistant alloy like the one shown in Fig. The tips 9a, 9 of the holding pieces 9, 9 are inserted into grooves 10.10 formed in the longitudinal direction of the hearth rail 3 on both sides of the hearth rail 3.
a is loosely fitted, and the tip portions 9a, 9a and the grooves 10, 10
A gap is formed between them as shown in Figure 2.

Further, the hearth rail 3 is formed in a cross-sectional shape in which the width of the upper surface in contact with the slab 4 is narrower than the width of the lower surface, and the tops of both sides of the hearth rail are perpendicular to the upper surface. The lower part is an inclined surface Y that gradually expands outward toward the bottom, and the lower part is a vertical surface Z that is perpendicular to the lower surface.

Recesses 5, 5 having a semicircular cross section are bored in the upper surface of the hearth rail 3 in the width direction of the hearth rail 3, and the contact area between the slab 4 and the hearth rail 3 is reduced by the four parts 5, 5. It's meant to be smaller.

A recess 6 is bored upward in the center of the lower surface of the hearth rail 3 in contact with the skid pipe 2, and the lower portions of both side walls of the recess 6 are open on both sides. A heat insulating material 8 such as aluminum oxide which can be sintered is charged into the inside 6.

However, when the slab 4 is placed on the hearth rails 3, 3 as shown in FIG. 1 and the slab 4 is heated, there is almost no temperature difference between the slab 4 and the upper surface of the hearth rails 3, 3. , the slab 4 is heated uniformly without temperature irregularities.

In the present invention, a heat-resistant alloy hearth rail is mounted on a skid pipe installed in a walking beam heating furnace, so it is more stable in strength than refractories such as bricks, and is easy to install. Not only is it efficient, but a recess is provided on the top of the hearth rail to reduce the contact area between the slab placed on the hearth rail and the hearth rail. It can reduce heat conduction and prevent temperature drop in the slab, shorten the time the slab is in the furnace, and has an extremely large effect on saving heat sources.Moreover, it has grooves in the longitudinal direction on both sides of the hearth rail. A holding piece with an inverted L-shaped cross section is extended above the water-cooled skid pipe so as to be located on both sides of the hearth rail, and the inwardly protruding tips of both holding pieces are loosely inserted into the groove. Once fitted, the hearth rail can be fixed to the water-cooled skid pipe using the holding piece so that it does not move vertically, and the hearth rail can be attached and removed by sliding it in the longitudinal direction of the water-cooled skid pipe, preventing exposure to high temperatures. The hearth rail, which is easily damaged or chipped, can be easily replaced. Furthermore, the tip of the holding piece is fitted loosely into the groove so that a gap is formed between the tip and the groove. The hearth rail can freely expand horizontally, vertically, and longitudinally, and even if the hearth rail expands when exposed to high temperatures, the expansion may damage the hearth rail or cause damage to the water-cooled skid pipe. It has the advantage that there is no risk of damage to the hearth rail, and the top of both sides of the hearth rail is a vertical plane perpendicular to the top surface of the hearth rail, and the bottom of the vertical plane on both sides is Since the slope gradually spreads outward, the top surface of the hearth rail is narrow and the area of the top surface is small, reducing the contact area with the slab, and the cross section of the top of the hearth rail is as narrow as the top surface. It has the advantage of being able to reduce heat conduction from the slab to the hearth rail, and has the advantage that the width of the hearth rail becomes wider toward the bottom, providing sufficient strength even if the width of the top surface is narrow. be.

The present invention will be explained in more detail below with reference to Examples.

<Example> As shown in Figure 4 a, l), length l = 150 mm
, the hearth rail 3 with width W = 65 mm and height h is made of Cr-
The height of the hearth rail 3 is increased by inserting a sintered aluminum oxide heat insulating material 8 into the recess 7 of the hearth rail 3. Sah
The temperature of the upper surface of the hearth rail 3 was measured by changing the temperature sequentially.

Then, as shown by the solid line in Figure 3, the height h of the hearth rail becomes 7.
Temperature difference ΔT from slab processing temperature (broken line in Figure 3) at 0 mm
was 25-50°C.

The dashed-dotted line in FIG. 3 represents the atmospheric temperature inside the furnace.

<Comparative example> Length l = 150 mm as shown in Figure 6 a, l)
, a hearth rail 3 with a width W = 65 mm and a height h was formed, and the temperature on the top surface of the hearth rail 3 was measured while changing the height h sequentially.As shown in Fig. 5, the height of the hearth rail 3 was Even when the height was 120 mm, ΔT was 150 to 200°C.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing the entirety of the present invention, Fig. 2a is a partially cutaway enlarged front view showing the hearth rail portion of the same as above, and Fig. 2 is a sectional view taken along line AA' in Fig. 2a. , Fig. 3 is an explanatory diagram showing the relationship between the height of the hearth rail and the temperature on the upper surface of the hearth rail in one example of the same as above, and Fig. 4 a and l) are the hearth rails used for the measurements in Fig. 3. 5 is an explanatory diagram showing a comparative example corresponding to FIG. 3, and FIG. 6a, 1
) is a front sectional view and a side sectional view showing the hearth rail used for the measurement in FIG. 5, FIG. 7 a is a front view showing the conventional example, and FIG. 8 are partially cutaway sectional views showing the drawbacks of the conventional example, in which 1 is a walking beam type heating furnace, 2 is a water-cooled skid pipe, 3 is a hearth rail,
4 is a slab, 5 is a recess, 6 is a recess, 8 is a heat insulating material, 9 is a holding piece, 9a is a tip, 10 is a groove, A is a vertical piece, and B is an inclined surface.

Claims (1)

[Claims] 1 Place a heat-resistant alloy hearth rail on a water-cooled skid pipe installed in a walking beam heating furnace, and align the tops of both sides of the hearth rail with a vertical plane perpendicular to the top surface of the hearth rail. At the same time, the lower part of the vertical plane on both sides is made into an inclined surface that gradually expands downward and outward, and grooves are bored in the longitudinal direction at the bottom of both sides of the hearth rail. Holding pieces with an inverted cross-section are extended upward so as to be located on both sides of the floor rail, and a gap is formed between the tip ends of both holding pieces that protrude inwardly and the groove. A walking device characterized in that four parts are provided on the upper surface of the hearth rail for loosely fitting into the groove so as to reduce the contact surface between the slab placed on the hearth rail and the hearth rail. Hearth rail for beam type heating furnace.