JPS6140765Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a hearth roller used in a thick plate heat treatment furnace.

(Prior Art) Generally, more than 60% of the scrapping of hearth rollers used in plate heat treatment furnaces is due to localized "blisters." If this hearth roller can be improved to have better ``blister'' resistance, it will be possible to significantly extend the life of the roller, thereby improving productivity and reducing maintenance costs in plate heat treatment furnaces. By the way, the wall thickness of the hearth roller is determined so that the mechanical load generated from the load of the thick plate to be heat treated and the roller's own weight is approximately 60% or less of the creep strength of the material of the hearth roller at the operating temperature. was. Figure 1 shows the outer diameter D and wall thickness t of hearth rollers designed in the past.
However, the wall thickness t is within the range of 0.05 to 0.09 with respect to the outer diameter D of the hearth roller. However, on the inlet side of the plate heat treatment furnace, there is a large temperature difference between the plate and the hearth roller, and due to thermal stress caused by local contact between the plate and the hearth roller, the wall thickness t is reduced compared to the conventional outer diameter D. Hearth rollers with a diameter of 0.05 to 0.09 had the disadvantage of being prone to "blurring".

(Purpose of the invention) The object of the invention is to provide a hearth roller for a heat treatment furnace that is resistant to "blister".

(Disclosure of the invention) The hearth roller for a heat treatment furnace of the present invention is hollow inside and has a wall thickness t in the ratio of 0.10 to 0.14 with respect to the outer diameter D. This prevents "blistering" from occurring.

The present invention will be explained in detail below with reference to Examples. Figure 2 shows a heat treatment furnace for thick plates, where 1 is the furnace shell of the heat treatment furnace, 2 is a radiant tube, 3 is a heating burner for the radiant tube 2, 4 is a hollow hearth roller, and 5 is a heat treatment furnace. It is a thick plate of metal. In this heat treatment furnace, the thick plate 5 is conveyed by rotationally driving the hearth roller 4, heated through the radiant tube 2, and subjected to heat treatment. By the way, the "bulge" of the hearth roller 4 is caused by thermal stress caused by local contact between the thick plate 5 and the surface of the hearth roller 4, which have a temperature difference. Therefore, the occurrence rate of "blister" is high on the inlet side of the heat treatment furnace where the temperature difference is large. In the soaking zone on the exit side where there is almost no temperature difference between the thick plate 5 and the hearth roller 4, the occurrence of "blister" is extremely rare. For this reason, assuming the heating zone on the inlet side of the heat treatment furnace, the extreme surface of the hearth roller 4 is heated to 1100°C to 760°C.
An experiment was conducted to determine the wall thickness t of the hearth roller 4/the outer diameter D of the hearth roller 4 and the amount of "bulge" after 250 repetitions of a thermal cycle in which the temperature of Obtained. In FIG. 3, the horizontal axis is t/D, and the vertical axis is the amount of bulge (mm).
These results show that the conventional t/D range of 0.05 to 0.09 is a poor shape in terms of ``blister'' resistance, and that t/D needs to be 0.10 or higher when considering ``blister'' resistance. Ta. As a result, the hearth roller 4 of the present invention has a t/D of 0.10 to 0.14, and the life of the hearth roller 4 can be doubled to three times that of conventional rollers. In this case, the upper limit of t/D was set to 0.14.
This is because if it is 0.14 or more, the weight of the hearth roller 4 becomes large, which is economically disadvantageous, and even if it is 0.14 or more, the effect does not change much.

(Effect of the invention) As stated above, this invention improves the ratio of wall thickness to outer diameter.
Since it is set to 0.10 to 0.14, it is possible to reduce the occurrence of "blister", especially when there is a temperature difference between the heat treatment furnace and the thick plate at the entrance side. This makes it possible to significantly extend the life of the heat treatment furnace by improving its "blister" resistance, and also to improve production and reduce maintenance costs of heat treatment furnaces.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the relationship between the outer diameter and wall thickness of past hearth rollers, Figure 2 is a sectional view of a heat treatment furnace, and Figure 3 is a diagram showing the relationship between t/D and swelling amount to explain the present invention. In this explanatory diagram, 4 is a hearth roller, D is an outer diameter, and t is a wall thickness.

Claims (1)

[Scope of utility model registration request] The inside is hollow, and the wall thickness is 0.10~ relative to the outside diameter.
Hearth roller for heat treatment furnaces with a ratio of 0.14.