JP2015504476A - Method for heating a long object in a radiation-type heating furnace and radiation-type heating furnace - Google Patents

Abstract

A desired heat treatment is realized by giving a uniform heating history to a plurality of long objects charged in a radiation-type box furnace. Specifically, when heating a plurality of long objects charged along the horizontal side wall constituting the long side of the horizontal box furnace at least by radiant heat from the horizontal side wall, the long object is , And arranged below the array, which forms a downward gradient from the lateral side wall of the box furnace toward the center of the width of the hearth. [Selection] Figure 3

Description

  The present invention relates to a radiant heating furnace, particularly a radiant heating furnace that heats a long object in a furnace by radiant heat from a side wall. The present invention relates to a heating method and a radiant heating furnace.

  In the manufacturing process of steel products, various heat treatments are applied in order to guarantee the mechanical quality of the products or to ensure processability such as drawing process ( For example, see the background art of Patent Document 1). In this heat treatment, various types of heating furnaces are used depending on the purpose of the heat treatment, the shape and handling of the material to be heat treated, and the like. That is, long objects such as steel pipes, steel bars, and shaped steel are typically processed in a batch type heating furnace based on their dimensions and shape. There are many cases.

  For example, in order to finally guarantee the mechanical quality of products, steel pipes are heat-treated under specified conditions and then shipped after standing to cool. For the treatment, a batch type heating furnace is applied.

JP 2009-208112 A

This batch-type heating furnace is a horizontally long box furnace that has a furnace length that sufficiently absorbs the axial length of a long steel pipe. A heater is installed inside the side wall that forms the side surface. By using a radiant heating furnace that supplies thermal energy to the steel pipe via the heat treatment, heat treatment is performed by arranging multiple long objects in the furnace width direction, and all long materials can be heated uniformly. The problem of not being able to occur.
Therefore, the present invention provides a method for realizing an intended heat treatment by giving a uniform heating history to a plurality of long objects charged in a radiation-type box furnace, and radiation used therefor. The purpose is to provide a mold heating furnace.

  The main reason for the above-mentioned non-uniform heating is that the radiant heat from the side wall in the radiant type box heating furnace is blocked by the steel pipe charged in the furnace and does not reach the hearth. I found out.

  That is, as shown in FIG. 1, a box type electric heating furnace which is an example of the radiation type heating furnace, the space on the hearth part 1 is divided into four side walls 2a, 2b, 3a, 3b, and the enclosed space is integrally closed by a top sheating 4, and a heater 5 is installed on the internal surface of the side walls 2a and 2b constituting the long side, and these side walls 2a And the steel pipe 6 in a furnace was heated with the radiant heat from 2b. In this box-type electric furnace, the side walls 2 a, 2 b, 3 a, 3 b and the ceiling 4 are integrated to serve as a cover for the hearth 1. That is, as shown in FIG. 1, after arranging the steel pipe 6 on the hearth 1, the side walls 2 a, 2 b, 3 a, 3 b and the ceiling 4 are placed on the hearth 1 to form a closed space on the hearth 1. Can be formed. Next, the steel pipe 6 is heated by radiant heat from the lateral side walls 2a and 2b, and when the predetermined heating is completed, the side walls 2a, 2b, 3a, 3b and the ceiling 4 are lifted from the hearth 1 and the hearth 1 The steel pipe 6 is subjected to air cooling by exposing the upper steel pipe 6 to the atmosphere.

  Although it is possible to embed the heater 5 in the ceiling 4, it is omitted because the radiant heat from the lateral side walls 2 a and 2 b rises and as a result, the area directly below the ceiling 4 is heated sufficiently. On the other hand, oxide scales and the like are easily deposited on the hearth, and if a heater is provided in the hearth 1, damage to the heater becomes severe.

  Here, in order to ensure heat treatment efficiency, a plurality of steel pipes 6 were charged in the furnace and heated. As shown in FIG. 2, the charging form was placed on the pedestal 7 installed on the hearth 1 in an approximately equal interval. When the steel pipes 6 arranged side by side are heated by the radiant heat from the lateral side walls 2a and 2b, radiant heat is supplied in order from the steel pipes 6 outside the array, and the adjacent steel pipes of the steel pipes 6 positioned in the middle of the side by side arrangement are arranged. The heating rate of the shadowed part of the steel tube 6 becomes slow, and the part facing the hearth 1 in all the steel pipes 6 is not in the radiation range and the radiation from the hearth cannot be expected. all right.

  As described above, the heating of the steel pipe is performed in order to guarantee mechanical quality, or is a pretreatment prior to various processing, and the steel pipe undergoes an even heating history and cooling history over the entire circumference. However, if a plurality of steel pipes 6 are arranged and heated as shown in FIG. 2, the desired heat history cannot be equally applied to all the steel pipes.

Therefore, the inventors reviewed the arrangement of a plurality of long objects to be charged in the radiation type heating furnace in the heating furnace, and the radiant heat from the lateral side walls 2a and 2b is applied to all the long objects. If the radiant heat is also supplied from the hearth 1, it is conceived that the intended heat treatment can be realized by giving an even heating history to all the long objects, leading to the present invention. It came to.
That is, the gist configuration of the present invention is as follows.

(1) When heating a plurality of long objects charged along a horizontal side wall constituting the long side of a horizontal box furnace at least by radiant heat from the horizontal side wall, the long object is A method for heating a long object in a radiant heating furnace disposed under an array, which has a downward gradient from the lateral side wall of the box furnace toward the center of the width of the hearth.
(2) The long objects are arranged in such a manner that an inclination angle K with respect to the hearth surface of a line segment connecting the center cores of adjacent long objects is 10 ° or more (1) The heating method of the elongate thing in the radiation type heating furnace as described in 2.
(3) The radiant heating furnace according to (1) or (2), wherein the long objects are arranged such that a distance t between adjacent long objects is 0.05 times or more the diameter of the long objects. Heating method for long objects.
(4) A plurality of long objects in which the space on the hearth is partitioned by a horizontally long box, a heater is installed on the inner surface of the side wall constituting the long side, and the furnace is charged with radiant heat from the side wall. A plurality of pedestals on which the elongate object is placed have a downward slope from the lateral side wall toward the center of the width of the hearth. Furnace.
Here, the heat source of the radiant heating furnace used in the present invention is an electric resistance heating element (electric heater), a muffle, or a radiant tube. The muffle or radiant tube is provided with a combustion or electric resistance heating element in a refractory or pipe, and heats the processed product by radiant heat through the refractory or pipe. Note that a fan may be provided in the furnace in order to make the atmospheric temperature difference in the furnace uniform (for example, the temperature difference between the upper and lower atmosphere temperatures).

  ADVANTAGE OF THE INVENTION According to this invention, it can implement | achieve the intended heat processing by giving a uniform heating history (thermal history) with respect to the multiple long thing inserted into the radiation type box-type heating furnace.

It is a perspective view which shows the outline | summary of a radiation type box heating furnace. It is sectional drawing which shows the conventional steel pipe arrangement | positioning in a box-type heating furnace. It is sectional drawing which shows the steel pipe arrangement | positioning according to this invention in a box-type heating furnace. It is sectional drawing which shows the steel pipe arrangement | positioning according to this invention in a box-type heating furnace. It is sectional drawing which shows the steel pipe arrangement | positioning according to this invention in a box-type heating furnace. It is sectional drawing which shows the steel pipe arrangement | positioning according to this invention in a box-type heating furnace. It is sectional drawing which shows the steel pipe arrangement | positioning according to this invention in a box-type heating furnace. It is sectional drawing which shows the outline | summary of the radiation type | mold box-type heating furnace of this invention. It is sectional drawing which shows the outline | summary of the radiation type | mold box-type heating furnace of this invention.

Hereinafter, the heating method for a long object in the radiation-type heating furnace of the present invention will be described in detail with reference to the drawings, taking as an example the case where the long object is a steel pipe.
That is, as shown in FIG. 3, a cross section of the furnace similar to that in FIG. 2, when a plurality of steel pipes 6 are charged and heated in the furnace, the plurality of steel pipes 6 have a side wall 2 a from which heat is radiated. It is important to arrange them under an arrangement that is downslope from 2b to the center of width O of the hearth 1.
Here, the arrangement that is inclined downward from the lateral side walls 2a and 2b toward the width center O of the hearth 1 means that the height from the hearth 1 is the width center O from the steel pipe 6 on the side wall 2a or 2b side. Of course, when the height of the steel pipe gradually decreases toward the steel pipe 6 on the side, the hearth 1 is at least between the steel pipe 6 closest to the side wall 2a or 2b side and the steel pipe 6 close to the width center O of the hearth 1. It is sufficient if there is a height difference from the height.
Or if it says with another expression, the arrangement | sequence which radiant heat will be directly irradiated to each steel pipe 6 on a path | route from the side wall 2a or 2b side and the radiant heat to the hearth 1 will increase is preferable. More specifically, by lifting the height of the steel pipe 6 closest to the side wall 2a or 2b as much as possible, leaving the bottom of the steel pipe 6 and gradually lowering and shifting the height of the adjacent steel pipe It is preferable that the radiant heat is directly applied to each steel pipe and the radiant heat from the side wall 2a or 2b side to the hearth 1 is increased.

Incidentally, the example shown in FIG. 3 is a case where the height of the steel pipe gradually decreases from the steel pipe 6 on the side wall 2a or 2b side to the steel pipe 6 on the width center O side.
On the other hand, as an example in which a height difference from the hearth 1 is provided at least between the steel pipe 6 closest to the side wall 2a or 2b side and the steel pipe 6 closest to the width center O of the hearth 1, The steel pipe arrangement | sequence shown in 4 is mentioned. In FIG. 4, only the arrangement of the steel pipes 6 is shown, and the illustration of the pedestal is omitted. That is, in the example of FIG. 4, there is almost no height difference between the steel pipe 6a closest to the side wall 2a or 2b side and the steel pipe 6b adjacent to the steel pipe 6a, and the steel pipe 6c and the steel pipe 6c close to the width center O The steel pipe arrangement has a sufficient height difference between the two.

Thus, the thermal energy radiated from the side walls 2a and 2b is arranged by arranging the steel pipes in the furnace so as to descend from the side walls 2a and 2b toward the width center O of the hearth 1. Reaches each steel pipe 6 on the path, and further reaches the hearth 1. As a result, the hearth 1, which has not received heat energy due to radiation in the past, is newly heated by receiving the heat energy, and radiant heat from the hearth 1 once heated is conventionally used to generate radiant heat. The surface on the hearth 1 side of the steel pipe 6 that is not received is also heated.
Furthermore, since said steel pipe arrangement | positioning provides a height difference between the adjacent steel pipes 6, it can set the space | interval of this adjacent steel pipe 6 to a wider space | interval compared with the case of the conventional side-by-side arrangement. it can. That is, in the case where the adjacent steel pipes 6 are arranged with a height difference and the case where the steel pipes 6 are arranged side by side, when the distance between the lateral side walls 2a, 2b is equal, the arrangement is made with a height difference. This can widen the interval between the steel pipes 6. And since radiant heat can be guide | induced to the steel pipe 6 through this space | interval, the uniform heating of a steel pipe can be implement | achieved more efficiently.

Here, in arranging the steel pipes under the downward gradient arrangement, the arrangement shown in FIG. 3 that gradually decreases from the steel pipe 6 on the side wall 2a or 2b side to the steel pipe 6 on the width center O side is more preferable. As shown in FIG. 3, the inclination angle K of the line connecting the axial centers of adjacent steel pipes 6 with respect to the hearth 1 surface is preferably 10 ° or more.
This is because if the angle is less than 10 °, the distance between the adjacent steel pipes 6 cannot be increased so much as compared to the case where the steel pipes are horizontally arranged side by side, and the furnace of thermal energy radiated from the side walls 2a and 2b. This is because the degree of arrival to the floor 1 becomes small and the heating of the surface of the steel pipe 6 on the hearth 1 side tends to be insufficient.

For example, the steel pipe arrangement shown in FIG. 5 is an example in which the K is uniformly set to about 10 ° in the adjacent steel pipe 6. Similarly, the steel pipe arrangement shown in FIG. This is an example of about 25 °.
In any case, it is possible to realize that the radiant heat is supplied to the hearth 1 described above and that the interval between the adjacent steel pipes 6 can be set wider than in the case of the conventional horizontal arrangement.
In addition, although the inclination angle K with respect to the hearth 1 surface of the line segment which connects the axial center of the adjacent steel pipe 6 is so large that each steel pipe can be heated more uniformly, even if K exceeds 45 degrees. The amount of radiant heat reaching each steel pipe is not changed, and the ceiling of the radiant heating furnace becomes high, so when the heating is finished and the atmosphere is allowed to cool, the side walls 2a, 2b, 3a, 3b and the ceiling 4 The upper limit of K is preferably equal to or less than 45 ° because the handling process when lifting from the hearth 1 becomes more difficult. More preferably, it is 30 ° or less.

In addition, in the example shown in FIG.3 and FIG.5 and FIG.6, although the inclination angle K between the adjacent steel pipes 6 is the same in all the steel pipes 6, as shown in FIG. The inclination angle K between the steel pipes 6 may be different depending on the row. That is, the slope angle K ₁ is 20 ° between the steel pipe 6b adjacent to the most lateral side wall 2a or 2b of the steel pipe 6a and the steel pipe 6a, the tilt angle K in the near steel pipe 6c to the steel pipe 6b and the width center O ₂ is 10 ° steel pipe arrangement. Also in this case, since the downgraded steel pipe arrangement described above is realized, radiant heat can be supplied to the hearth 1 described above, and the interval between the adjacent steel pipes 6 is wider than in the case of the conventional horizontal arrangement. It becomes possible to set. In this case, the inclination angle K between any adjacent columns is preferably 10 ° or more.

  Moreover, when arrange | positioning a steel pipe under the arrangement | sequence which becomes downward gradient as shown in FIGS. 5-7, it is preferable that the mutual space | interval t of the adjacent steel pipe 6 shall be 0.05 times or more of the diameter of a steel pipe. This is because, in order to reliably guide the radiant heat to each steel pipe 6 through this interval, it is preferable to secure an interval t that is at least 0.05 times the diameter of the steel pipe. If the distance t between the adjacent steel pipes 6 is less than 0.05 times the diameter of the steel pipe, a shadowed portion from the radiant heat source is generated by the adjacent steel pipe, the radiant heat does not reach, and it is difficult to heat each steel pipe uniformly. Become. More preferably, the interval t between the adjacent steel pipes 6 is not less than 0.1 times the diameter of the steel pipe. The larger the mutual distance t between adjacent steel pipes 6 is, the more uniformly each steel pipe can be heated. However, even if the mutual distance t between adjacent steel pipes 6 exceeds 1.0 times the diameter of the steel pipe, Since the amount of radiant heat reaching the steel pipe does not change, the interval t between adjacent steel pipes 6 is preferably 1.0 times or less the diameter of the steel pipe. More preferably, it is 0.5 times or less.

Next, a heating furnace used directly in the above heating method will be described with reference to FIGS.
First, the heating furnace shown in FIG. 8 is provided with pedestals 7 corresponding to the arrangement of the steel pipes 6 shown in FIG. 3, and the mutual positions of these pedestals 7 are made to correspond to the downward gradient arrangement of the steel pipes 6. Installed. Further, the heating furnace shown in FIG. 9 is provided with a pedestal 7 corresponding to the arrangement of the steel pipes 6 shown in FIG. 4, and a plurality of steel pipes 6 are provided on one pedestal 7 as in this example. It is good also as a structure to mount. In addition, the base 7 is good to install about 2-3 units | sets to each steel pipe 6 at equal intervals in an axial direction.

Furthermore, in order to efficiently store the heat energy radiated from the side walls 2a and 2b in the hearth 1, it is easy to radiate heat radiated from the side walls 2a and 2b such as fiber wool on the hearth 1. It is also effective to spread a heat storage material having a small heat capacity so that it can be irradiated with radiant heat from itself.
In addition, since the radiant heat from the ceiling 4 can also be utilized when the thermal storage material used for the flooring mentioned above is also stuck on the ceiling 4, it is more preferable.

  In the radiation-type heating furnace shown in FIG. 1, heat treatment (tempering treatment: 780 ° C. × 0.5 h) was performed under the steel pipe arrangement of FIGS. Here, the steel pipe contains Cr: 9.0 mass%, Mo: 1.0 mass%, Nb: 0.08 mass% and V: 0.2 mass%, and the balance is composed of Fe and inevitable impurities. Steel pipe A: outer diameter 101.6 mm × thickness 7 mm × length 12.0 m and steel pipe B: outer diameter 762 mm × thickness 15 mm × length 12.0 m.

  After performing the above heat treatment, the temperature at 12 locations on the circumference of each steel pipe was measured, and the difference between the minimum temperature and the maximum temperature was determined. The measurement results are shown in Table 1.

  In the present invention, a long object is not limited to a steel pipe, and it is possible to reliably perform heat treatment of a long object such as a bar steel or a die steel.

1 hearth 2a, 2b side wall 3a, 3b side wall 4 ceiling 5 heater 6 steel pipe 7 pedestal

Claims (5)

  In heating a plurality of long objects, which constitute the long side of a horizontally long box furnace, along the horizontal side wall by at least radiant heat from the horizontal side wall, the long object is converted into the box furnace. A heating method for a long object in a radiant heating furnace disposed below the array, which has a downward slope from the side wall of the furnace toward the center of the width of the hearth.   The arrangement of the long objects is that of a long line in the radiation type heating furnace according to claim 1, wherein an inclination angle K with respect to a hearth surface of a line segment connecting axial axes of adjacent long objects becomes 10 ° or more. Heating method.   The radiation according to claim 1, wherein an inclination angle K with respect to the hearth surface of a line segment connecting at least a long object closest to the side wall side and an axis of a long object adjacent to the long object is 10 ° or more. A heating method for long objects in a mold heating furnace.   The arrangement of the long objects is such that the mutual distance t between adjacent long objects is 0.05 times or more of the diameter of the long objects. The long objects in the radiation type heating furnace according to any one of claims 1 to 3. Method of heating things.   The space on the hearth is partitioned by a horizontally long box, a heater is installed on the inner surface of the side wall that forms the long side, and a plurality of long objects charged in the furnace are heated by radiant heat from the side wall. A radiant heating furnace, which is a box-type furnace, in which a plurality of pedestals on which the long objects are placed are installed under an array having a downward gradient from the lateral side wall toward the width center of the hearth.