JP7757766B2 - electric furnace - Google Patents

Description

This invention relates to electric furnaces, and more specifically to electric furnaces equipped with a furnace body rotation mechanism.

Conventionally, three-phase AC arc furnaces have been widely used as electric furnaces for melting metal materials such as scrap metal. These furnaces generate an arc between three electrodes inserted into the furnace body and the metal material inside the furnace body, and the metal material is melted by the heat of the arc.

When melting metal materials using such an electric furnace, so-called hot spots occur within the furnace body, located a short distance from the electrode (i.e., close to the electrode), and so-called cold spots occur a long distance from the electrode (i.e., far from the electrode). In hot spots, the metal material melts easily because the electrode heats it strongly, while in cold spots, the electrode heats it less strongly, resulting in uneven melting, with metal material remaining unmelted in the cold spots even after all the metal material in the hot spots has melted.

As a solution to this problem, an electric furnace equipped with a rotation mechanism that rotates the furnace body relative to the electrode has been proposed, as described in the following patent document. In an electric furnace equipped with a rotation mechanism, the furnace body is rotated relative to the electrode during melting, moving metal material that was initially located in the cold spot to the hot spot and vice versa, thereby improving the problem of uneven melting.

JP 2015-048976 A

In order to rotate the furnace body, it is necessary to ensure clearance (rotation space) around the furnace body to avoid interference with the non-rotating furnace legs located close to the furnace body. However, even if a rotation mechanism is added to a conventional (non-rotating) electric furnace, there is no rotation space around the furnace body because the furnace legs are close to the furnace body (or are joined to the furnace body) and the layout of the furnace body overlaps with the furnace legs in a plan view. Increasing the spacing between the furnace legs to ensure rotation space would require changes to the furnace base that supports the furnace legs and the foundation of the building to which the furnace base is fixed, requiring major renovations. On the other hand, if the spacing between the furnace legs remains the same and the furnace body itself is made smaller in the radial direction, the furnace volume will be smaller, meaning the amount of molten steel will be reduced and productivity will decrease.

The present invention was made with the above circumstances in mind, with the objective of providing an electric furnace that can be equipped with a furnace body rotation mechanism even in equipment layouts where the furnace legs are closely spaced and overlap the furnace body and furnace legs in a plan view, and that can maintain the same furnace internal volume as conventional furnaces that do not have a furnace body rotation mechanism.

The electric furnace of the present invention has the following features:
A cylindrical furnace body with a bottom,
a rotation device that supports the furnace bottom of the furnace body and rotates the furnace body around an axis in the vertical direction;
A pair of furnace legs that roll on the top surface of the hearth;
a tilting floor that supports the rotation device between the pair of furnace legs and tilts together with the rotation device and the furnace body as the furnace legs roll;
An electric furnace comprising:
The furnace body is characterized in that the furnace shell shape of the lower part of the side wall facing the furnace legs is a mortar shape that approaches the center of the furnace body as it approaches the furnace bottom side.

With an electric furnace defined in this way, interference between the furnace body and the furnace legs during rotation is effectively avoided due to the cone-shaped furnace shell shape at the lower part of the side wall of the furnace body. Furthermore, the lower part of the cone-shaped furnace body side wall is typically lined with refractory material. Even when the furnace shell shape at the lower part of the side wall is cone-shaped, adjusting the thickness of the refractory material makes it possible to maintain the same furnace internal volume as a conventional furnace without a rotation mechanism. In this way, the electric furnace configuration of the present invention is particularly effective when replacing a conventional furnace without a rotation mechanism (non-rotating) with a furnace with a rotation mechanism.

In the electric furnace of the present invention, the upper surface of the tilting floor on which the rotating device is placed can be positioned lower than the upper surface of the furnace base.
When a rotating device is placed between the furnace body and the tilting floor, the height from the top of the tilting floor to the top end of the furnace body increases, but by positioning the top of the tilting floor on which the rotating device is placed below the top of the furnace stand, i.e., by lowering the position of the top of the tilting floor, the increase in the height of the furnace body due to the rotating device can be offset. In this way, interference between the furnace body and the building ceiling or incidental equipment installed above the furnace body can be avoided.

1A and 1B are diagrams showing a furnace body of an electric furnace according to one embodiment of the present invention, in which (A) is a plan view and (B) is a cross-sectional view taken along the line B-B of (A). 2 is a cross-sectional view of the electric furnace according to the embodiment, corresponding to the cross section II-II of FIG. 1. FIG. 3 is a perspective view showing the tilting body and its surroundings in FIG. 2 . FIG. 4 is an explanatory diagram of the tilting operation of the electric furnace according to the embodiment. FIG. 3 is a view showing the furnace body and the tilting body of FIG. 2 separated from each other. FIG. 2 is an enlarged cross-sectional view showing the bottom of the furnace body and its surrounding area of the electric furnace according to the embodiment.

Next, an embodiment of the present invention will be described in detail with reference to the drawings.
The electric furnace 1 of this embodiment is an electric furnace equipped with a furnace body rotation mechanism, and includes as its main components a furnace body 10, a rotation device 60 for rotating the furnace body 10, and a tilting body 40 for tilting the furnace body 10.

Figure 1 shows the furnace body 10 of an electric furnace 1 of this embodiment. The furnace body 10 is a trough-tap type furnace body with a bottomed, tubular (cylindrical) shape, with a tapping port (steel tapping port) 13 formed as an opening that penetrates the side wall portion 11 in the radial direction, and a trough 14 extending from the tapping port 13. The molten metal material (molten steel) in the furnace body 10 is tapped from the tapping port 13 toward a ladle (not shown) by tilting the entire furnace body 10 clockwise in Figure 1 (B).

A slag discharge port 15 is provided at a radially opposite position (symmetrical position) to the tapping port 13. The slag discharge port 15 penetrates the side wall 11 of the furnace body 10 in an inward-outward direction. In this example, by tilting the entire furnace body 10 in the opposite direction to the tapping operation (counterclockwise in Figure 1 (B)), slag generated during melting operations can be discharged to the outside through the slag discharge port 15.

As shown in Figure 1(B), the furnace body 10 of the electric furnace 1 is fitted with a furnace lid 20 that opens and closes the loading port 18 at its upper end, and three electrodes 22 are inserted downward into the furnace body 10 through the furnace lid 20.

Each electrode 22 is positioned near the center of the furnace lid 20, which is roughly circular in plan view, at equal intervals (120° intervals) around the vertical axis of the furnace body 10, in this case the central axis (central axis P shown in Figure 2). Each electrode 22 is supported by a lifting device (not shown) so that its height can be adjusted individually, allowing the vertical distance between the lower end of the electrode 22 and the metal material loaded into the furnace body 10 to be adjusted.

The furnace cover 20 is configured to be freely movable up and down relative to the furnace body 10 using a lifting device and a rotating device (not shown), and can also rotate horizontally to open the loading port 18 of the furnace body 10 and allow metal materials to be loaded into the furnace body 10.

The sidewalls 11 and bottom 12 of the furnace body 10 are covered with an iron shell that constitutes the furnace shell. In this example, the furnace shell shape at the upper sidewall 11a is a cylinder extending vertically, and the furnace shell shape at the lower sidewall 11b is a mortar shape that approaches the center of the furnace body 10 as it approaches the furnace bottom.
The reason why the furnace shell shape of the lower side wall 11b is made mortar-shaped is to avoid interference with the furnace legs 42 when the furnace body 10 is rotated in an equipment layout in which the furnace legs 42, 42, which will be described later, are spaced closely together and the furnace body 10 and the furnace legs 42, 42 overlap in a plan view as shown in Figure 1 (A).
2 is a cross-sectional view of the electric furnace 1 as seen from the side of the tapping hole 13. As can be seen from this figure, a clearance space δ is provided as a rotation space between the furnace leg 42 and the opposing lower side wall 11b.

The interior of the furnace body 10, which is exposed to high temperatures, is provided with water-cooled panels 30 on the inside of the furnace shell at the upper sidewall 11a of the furnace body 10. From the lower sidewall 11b to the bottom 12 of the furnace body 10, the inside of the furnace shell is constructed using refractory materials 32 such as firebricks.

Next, the tilting body 40 will be described.
In the electric furnace 1 of this embodiment, the furnace body 10 can be tilted together with the tilting body 40 shown in Figures 2 and 3. The tilting body 40 has a pair of furnace legs 42, 42 and a tilting floor 51 provided between the furnace legs 42, 42.

As shown in Figure 3, the furnace leg 42 has a downwardly convex curved shape, and the top of the downwardly convex curved surface 43 is in contact with the upper surface 47a of the furnace base 47 fixed to the foundation 49 of the building, and the furnace leg 42 is supported so that it can roll along the horizontally extending upper surface 47a of the furnace base 47.
Engagement teeth 44a are formed along the convex curved surface 43 on the sides of the convex curved surface 43 of the furnace leg 42, and engagement teeth 44b are formed on the sides of the upper surface 47a of the furnace base 47. These engagement teeth 44a, 44b engage with each other to prevent slippage or displacement during rolling. In addition, an engagement protrusion 48 is formed on the side of the convex curved surface 43 of the furnace leg 42 opposite the engagement tooth 44a. This engagement protrusion 48 engages with the corner where the upper surface 47a of the furnace base 47 intersects with the inward-facing end face, preventing lateral displacement during rolling.
As shown in FIG. 5, the distance L1 between the pair of furnace legs 42, 42 in this example is narrow and is shorter than the radial dimension L2 of the furnace body 10.

The tilting floor 51 is a flat member located between the pair of furnace legs 42, 42, and both ends of the tilting floor 51 are integrally connected to the respective furnace legs 42 via connectors 53. In this example, a rotation device 60 and a furnace body 10, which will be described later, are placed on the tilting floor 51.
2, the connecting portion 53 is inclined downward toward the inside, and the upper surface 51a of the tilting floor 51 is located lower than the upper surface 47a of the furnace base 47. This is to offset the increase in the height of the furnace body 10 due to the rotation device 60.

As shown in Fig. 4, one end of a drive cylinder 55 is connected to the tilting body 40 configured as described above, the other end of which is connected to a base (not shown). When the drive cylinder 55 is extended upward as shown by the arrow in the figure, the furnace legs 42 roll on the upper surface 47a of the furnace base 47, and the tilting floor 51 tilts downward to the right. Accordingly, the furnace body 10 supported by the tilting floor 51 also tilts in the same direction, making it possible to tap molten steel from the furnace body 10.
When the drive cylinder 55 is retracted, the tilting bed 51 tilts in the opposite direction, thereby enabling the slag to be removed.
2, reference numeral 33 indicated by a two-dot chain line is a platform provided around the furnace body 10. The platform 33 is attached to the upper surface of the furnace legs 42 and tilts integrally with the furnace body 10.

Next, the rotating device 60 that rotates the furnace body 10 will be described.
As shown in FIG. 6, the rotation device 60 is constructed by stacking, from top to bottom, a support frame 61, a bearing member 63, and a bearing base body 69, and is placed and fixed on the upper surface 51a of the tilting floor 51.

The support frame 61 is in the shape of a circular ring having a number of upright walls, and the furnace body 10 is placed on an upper surface 61 a of the support frame 61 .
A bearing member 63 is disposed below the ring-shaped support frame 61. The bearing member 63 includes a ring-shaped gear body 64 having teeth formed along its outer periphery, and the support frame 61 is fixed to the ring-shaped gear body 64.
As shown in the partially enlarged view of Figure 6, the upper and lower intermediate sections on the inner periphery of the ring-shaped gear body 64 protrude inward with a rectangular cross section and form the outer ring portion 65 of the bearing member 63. An inner ring portion 66 with a U-shaped cross section is disposed on the inner periphery of the ring-shaped gear body 64 so as to surround the outer ring portion 65, and a roller bearing 67 is interposed between the convex surface of the outer ring portion 65 and the concave surface of the inner ring portion 66.

With this structure, the support frame 61 is supported by the bearing members 63 and the like, and is rotatable around the center of the ring in a plane parallel to the tilting floor 51 .
The weight of the furnace body 10 placed on the upper surface 61a of the support frame 61 is transmitted to the support frame 61 via the furnace shell members 16a, which are inclined so as to approach the center of the furnace body 10 as they approach the furnace bottom, the furnace shell members 16b facing the upper surface 61a of the support frame 61, and the insulating plates 74 arranged between the furnace shell members 16b and the support frame 61. In some cases, in addition to these, reinforcing members can be interposed between the curved furnace shell 16c at the bottom of the furnace body and the support frame 61. The rotation device 60 supports the weight of the furnace body 10 and rotates the furnace body 10 around the central axis P of the furnace body 10 (see FIG. 2).

As shown in Figure 3, a hydraulic motor 72 serving as a drive source and a gear 73 rotated by the driving force from the hydraulic motor 72 are provided on the tilting floor 51 outside the ring of bearing member 63. This gear 73 meshes with the teeth of the ring-shaped gear 64 of the bearing member 63. As a result, when the hydraulic motor 72 rotates forward or backward, the support frame 61 rotates forward or backward via the gears 73 and 64. In other words, the furnace body 10 supported by the support frame 61 rotates forward or backward. In this embodiment, during normal electric furnace operation, the hydraulic motor 72 rotates the support frame 61, i.e., the furnace body 10, in the clockwise and counterclockwise directions indicated by the arrows when the tap port 13 of the furnace body 10 is in the original position shown in Figure 1 (A) facing the tapping yard.

As shown in Figure 3, a locking mechanism 77 including a rectangular pillar-shaped engaging member 76 is further disposed on the tilting floor 51 outside the ring of the bearing member 63. The locking mechanism 77 is movable between a locked position (shown by a solid line in the figure) in which the engaging member 76 is raised vertically, and an unlocked position (shown by a two-dot chain line in the figure) in which it is tilted diagonally.

When the support frame 61 is in its original position, a notch (not shown) formed on the outer edge of the support frame 61 faces the engaging member 76. When the engaging member 76 is moved to the locked position, the engaging member 76 engages with the notch in the support frame. This reliably restricts rotation of the support frame 61, i.e., the furnace body 10, and in this state the furnace body 10 can be tilted to pour molten metal or pour slag.

With the electric furnace 1 of this embodiment configured as described above, a clearance space δ is secured between the furnace body 10 and the furnace legs 42 due to the furnace shell shape of the cone-shaped lower sidewall 11b of the furnace body 10, effectively avoiding interference between the furnace body 10 and the furnace legs 42 when the furnace body is rotating. Furthermore, the cone-shaped lower sidewall 11b of the furnace body 10 is an area lined with refractory material 32. Even when the furnace shell shape of the lower sidewall 11b is cone-shaped, adjusting the thickness of the refractory material 32 makes it possible to maintain a furnace volume equivalent to that of a conventional furnace without a rotation mechanism. The configuration of the electric furnace 1 of this embodiment is particularly effective when replacing a conventional furnace without a rotation mechanism (non-rotating) with a furnace with a rotation mechanism.

Furthermore, according to the electric furnace 1 of this embodiment, the upper surface 51 a of the tilting floor 51 on which the rotating device 60 is placed is positioned lower than the upper surface 47 a of the furnace base 47 .
When the rotation device 60 is interposed between the furnace body 10 and the tilting floor 51, the height from the upper surface 51a of the tilting floor 51 to the upper end of the furnace body increases, but in the electric furnace 1, the upper surface 51a of the tilting floor 51 on which the rotation device 60 is placed is positioned lower than the upper surface 47a of the furnace stand 47, thereby offsetting the increase in the height of the furnace body 10 caused by the rotation device 60. In this way, it is possible to avoid interference between the furnace body 10 and the ceiling of the building or incidental equipment arranged above the furnace body 10.

Although the above describes in detail the embodiments of the present invention, these are merely examples. For example, while the above embodiment is directed to a trough-tap electric furnace, the present invention can also be applied to furnaces that use a bottom-tapping system, such as an EBT furnace (Eccentric Bottom Tapping Furnace), in which molten metal such as molten steel is discharged from a tapping port located at the bottom of the furnace. Furthermore, the specific configuration of the rotating device that rotates the furnace body is not limited to the above embodiment and can be modified as needed, and the present invention can be configured in a variety of modified forms without departing from the spirit of the invention.

REFERENCE SIGNS LIST 1 electric furnace 10 furnace body 11b lower side wall 42 furnace leg 47 furnace base 47a upper surface 51 tilting floor 51a upper surface 60 rotation device P central axis

Claims (1)

A cylindrical furnace body with a bottom,
a rotation device that supports the bottom of the furnace body and rotates the furnace body around an axis in the vertical direction;
A pair of furnace legs that roll on the top surface of the hearth;
a tilting floor that supports the rotation device between the pair of furnace legs and tilts together with the rotation device and the furnace body as the furnace legs roll;
An electric furnace comprising:
In the furnace body, the furnace shell shape of the lower part of the side wall facing the furnace leg is a mortar shape approaching the center of the furnace body toward the furnace bottom side ,
An electric furnace in which the upper surface of the tilting floor on which the rotating device is placed is located lower than the upper surface of the furnace base on which the furnace legs roll .