JPH0457727B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heated steel support member used in a heating furnace for steel manufacturing, and more particularly to a heated steel support member using a ceramic skid button.

[Conventional technology]

Conventionally, as a heating element support member in a heating furnace,
A skid button made of a heat-resistant alloy has been used, but the strength of this button is significantly reduced under high-temperature conditions of, for example, 1000 to 1200° C. or higher, and its use conditions are severely restricted due to its poor heat resistance.

In recent years, many heating furnaces for steel materials and the like have been adopted as walking beam type furnaces that utilize the transfer ability of a fixed beam and a movable beam. These beams have spaced skid buttons held in integrally joined receivers on which the heated steel is supported. Heated steel materials, which are heat treated under high temperature atmospheric conditions of, for example, 1200° C. or higher, are used for skid buttons. for example
Heat-resistant alloys containing 50% cobalt lose their strength under such high-temperature conditions and have a short lifespan as buttons, so it is necessary to cool the button from below by running cooling water through the skid pipe. It was hot. However, since this cooling actively interferes with the heat treatment, the heat loss is extremely large, reducing the energy efficiency of the furnace and causing skid marks, or uneven heating on the underside of the steel. However, the rolling yield was reduced, which was extremely disadvantageous industrially. Improvements have been proposed to alleviate these disadvantages, such as using heat insulating materials and devising the shape of the skid button, but none of these methods improve the high-temperature strength that heat-resistant alloys inherently have. In exchange for the improvement effect, it actually worsens the high-temperature strength, so its improvement cannot be evaluated.

In recent years, research and development has been actively conducted to use ceramics as materials for skid buttons, which have excellent heat resistance, especially high strength even at high temperatures of 1500°C or higher, and are improving the energy efficiency of furnaces and yields by reducing skid marks. Proposals have been reported, but nothing that is practically satisfactory has yet been proposed.

[Problem that the invention seeks to solve]

Skidded buttons made of ceramics are
In connection with the peculiarities in manufacture due to the shape and properties of the material, other technical problems arise which are essentially different from those in the case of materials made of heat-resistant alloys.

Normally, skid buttons are generally cylinders with a bottom diameter of 90 to 100 mm and a height of 100 to 180 mm.
In the case of a ceramic button, which is a thick-walled molded object in the shape of a truncated cone or a rectangular parallelepiped, it is usually manufactured by press-forming finely pulverized ceramic material, followed by calcining and sintering. Since it is a sintered body, unlike melt molding, cracks are likely to occur in the molded product and the yield of the product is low. Furthermore, in order to improve the thermal efficiency of the furnace and the yield of heat-processed steel materials, it is desirable that the button be provided as a structure with as much insulation as possible.

[Means for solving problems]

In view of the above-mentioned actual situation regarding ceramic skid buttons, the present inventor has repeatedly conducted trial production research into a method for providing a heated steel support member with further improved heat insulation properties at a high yield and which is industrially advantageous. We have found a highly desirable support member.

That is, the present invention provides a heating steel support member for use in a heating furnace, which is constructed by attaching a skid button made of non-oxide ceramics with a hole or a through hole formed to a receiving metal fitting on a skid pipe. .

In the present invention, non-oxide ceramics are substances that have high strength at high temperatures of, for example, 1000°C or higher, and typically include metal carbides and metal nitrides, which are particularly desirable for practical use. are silicon carbide and silicon nitride.

These raw ceramics are of the highest possible purity and are pulverized as finely as possible before being used for molding. To mold the fine powder raw material, if necessary, after homogeneously mixing some binder, it is first pressure molded using male and female molds in which holes or through holes are formed. Pressure molding methods include mold press, rubber press,
Methods commonly used for molding ceramics, such as slip casting and injection molding, can be advantageously employed. However, it is also possible to make a shell-shaped molded product and form a hole or a through hole therein before or after calcination. The molded product is then heated at a temperature of 700 to 1000°C for 2 to 30 minutes.
It is calcined for 10 hours and then sintered at a higher temperature.

In the support member of the present invention, it is important and characteristic that the skid button is formed in the shape of a hole or a through hole. As mentioned above, skid buttons are usually cylindrical, prismatic, or truncated conical, with a hole hollowed out in the center of the bottom or a cylindrical shape with a through hole extending from the bottom to the top. The shape and size of the holes, the degree of drilling, etc. can be selected as appropriate in light of the actual use.

An example of the shape will be explained with reference to the attached drawings.

1 and 2 are cross-sectional views of different shapes of the support member of the present invention, particularly skid buttons, with FIG. 1 showing a truncated cone-bore skid button and FIG. 2 showing a cylindrical-through-hole skid button. ing. In the figure, the skid buttons 1, 1' are connected to the insulation material 2.
They are respectively attached to the receiving metal fittings 3 via the receiving metal fittings 3, and the receiving metal fittings 3 are integrally connected to the skid pipe 4. A hole 5 is formed in the button 1 shown in FIG. 1, and a through hole 6 is formed in the button 1' shown in FIG.

Such a skid button is attached to the skid pipe in exactly the same way as before, but to increase energy efficiency it is extremely important to provide a layer of insulation between the skid button and the skid pipe, as depicted in the drawings. This is important, and it is even more advantageous to fill the holes and through holes of the skid button with a heat insulating material, since this can improve the thermal efficiency of the furnace and the yield of steel products. For example, alumina-based and silica-based heat-resistant heat insulating materials are advantageously used for such a heat insulating material layer.

[Effect]

In the past, attempts have been made to make skid buttons hollow in order to reduce heat loss, but materials such as heat-resistant alloys and heat-resistant cast steel rapidly lose their strength when heated to temperatures above 1000°C, so drilling holes or Formation of through-holes was severely restricted and could not be practically adopted.

The present invention focuses on the high-temperature properties of ceramics, particularly in the case of silicon carbide, which has substantially the same strength at a high temperature of 1350°C as at room temperature, and also has a sufficient bending strength of several tens of kilograms/ ^mm2 . The heated steel support member of the present invention is based on the use of high-temperature properties such as strength, and has excellent practicality and is highly desirable industrially.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A raw material powder made by homogeneously mixing a small amount of binder and sintering aid with finely ground silicon carbide powder was rubber pressed to form blocks with a diameter of 120 mm and a length of 150 mm at a molding pressure of 1.0 Ton/ ^cm2. 20 truncated cones were molded. Subsequently, the molded body was heated and calcined at 800° C. over 5 hours in a nitrogen gas atmosphere. The calcined body was machined using a lathe with an upper surface diameter of 90 mm and a lower surface diameter of 110 mm.
It was processed into a truncated cone with a height of 100 mm.

The bottoms of the ten truncated cones thus obtained were bored with a diameter of 50 mm.

When the calcined body was sintered in a sintering furnace, only one crack occurred. On the other hand, 6 out of 10 products with a flat shape that was not drilled had cracks, and only 4 products passed the test.

Example 2 Using a silicon carbide raw material powder, 10 buttons of each of two shapes were molded using a rubber press at a pressure of 1.0Ton/cm ² . A special rubber mold was used for molding, and the 10 pieces were made with an upper diameter of 105 mm, a lower diameter of 120 mm,
It was molded into a truncated cone with a height of 110 mm, and the remaining 10 pieces were molded into buttons with a through hole with a diameter of 35 mm in the axial position.

The weight of the one with the through hole is 1.24Kg, while the weight of the other one is 1.40Kg, which is 160g (approx.
Not only was 11% of the material saved, but as a result of the same calcining and sintering as in Example 1, no cracks occurred in the former, while 5 out of 10 cracks occurred in the former. A crack occurred in each case.

Example 3 Using a silicon nitride raw material powder, 20 skid buttons were molded using a rubber press in the same manner as in Example 2. 10 are bare, and the remaining 10 are cylindrical with a hole (diameter 35 mm) passing through the axis. For comparison, 10 similar buttons were molded using SiAlON, which has good heat resistance.
Subsequently, they were calcined and sintered in the same manner as in Example 1.

When all the sintered bodies were examined after sintering, cracks had occurred in 4 out of 10 of the sintered bodies, both silicon nitride and sialon. On the other hand, when using silicon nitride with through holes formed, no cracks were observed at all, whereas when using Sialon, cracks occurred in 1 out of 10 holes.

〔Effect of the invention〕

The support member of the present invention, in which the ceramic skid button is formed as described above, has significantly reduced inconveniences caused by the thickness of the conventional support member, and can significantly improve the yield due to the reduction in the occurrence of cracks.

Furthermore, the weight of the skid button is reduced by several to 20%, which allows for savings in raw materials and lower manufacturing costs. Particularly in the case of ceramics, which require high purity and ultra-fine powder, raw material costs are high, and therefore the cost of the product is large, so saving raw materials is extremely advantageous industrially. be.

In addition, the skidded button of the present invention has a small actual area on the lower surface, so that not only the heat transfer from the skidded button to the skidded pipe is small, but also because the insulation material is interposed in the gap, the insulation effect is further enhanced and the heat insulation effect is increased. Energy saving effect can be obtained. Also,
This is highly desirable since it also reduces hard marks.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of different examples of the support member of the present invention. Codes in the diagram: 1, 1'...skid button, 2
...Insulating material, 3...Bracket fitting, 4...Skied pipe, 5...Drilling, 6...Through hole.

[Claims]

1. In one-shot quenching, in which a predetermined width of the circumferential surface of a rotating member is heated to a predetermined quenching temperature with heating coils facing the predetermined width, and then rapidly cooled, the entire circumferential surface of the rotating member to be heated is divided in the circumferential direction. A one-shot quenching method for cooling the peripheral surface of a member, characterized by rapidly cooling the peripheral surface of a member using a plurality of fluids that are jetted in alternately opposite directions. 2. Equipped with a heating coil capable of heating a predetermined width of the circumferential surface of a member that rotates on an axis, and a cooling mechanism capable of rapidly cooling the circumferential surface to be heated without relative movement in the axial direction with respect to the member. In the one-shot hardening device, the above-mentioned cooling mechanism is arranged to sandwich the heating coil from both end faces, and the cooling fluid injection holes for hardening provided in each cooling mechanism are divided into a plurality of holes at the same angle in the circumferential direction. The holes are formed in intermittent hole formation ranges that are opposite to each other within the same angle range, and the hole angles of the cooling fluid injection holes of the respective cooling mechanisms are configured to point toward the heated surface from the width direction. A one-shot quenching cooling device for the peripheral surface of a member.