JPH0533498U - Graphite electrode connection structure - Google Patents

Abstract

(57) [Summary] [Purpose] When the artificial graphite electrode is connected, the screw thread of the electrode is not damaged, and the connection by reliable screwing is possible. [Structure] A tapered hole is bored in a connecting end portion of a graphite electrode 10 and a taper screw 11 is engraved on an inner peripheral surface thereof, and the nipple 1 attached to the connecting end portion of a new electrode is attached to the taper screw 11.
In the case of connecting the taper screw 15 of No. 4 by screwing, the top surface 13 of the thread 12 of the taper screw 11 and the nipple 1 which are engraved on the inner peripheral surface of the taper hole of the graphite electrode 10.
The top surface 17 of the thread 16 of the No. 4 taper screw 15 is a cylindrical surface substantially parallel to the axis of the graphite electrode 10.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a structure for connecting artificial graphite electrodes used in an electric furnace, and more particularly to a structure for connecting graphite electrodes with improved connection screws.

[0002]

[Prior Art]

 If the artificial graphite electrode used in an electric steelmaking furnace (hereinafter simply referred to as an electrode) becomes short due to arc consumption at its tip, a new electrode 1 (hereinafter referred to as a new electrode) is inserted through a nipple 2 as shown in FIG. It is designed to be connected by screwing and used one after another.

The above electrodes have recently grown to 24 ″ φ and 28 ″ φ along with the increase in size of electric steelmaking furnaces, and the weight has also rapidly increased to 1.2 to 1.8 t per one. .

To connect the electrodes to each other, a tapered hole is bored at a connecting end of the electrode, a screw thread is formed on an inner peripheral surface of the tapered hole, and the nipple is screwed into the screw thread. As shown in the figure below, taper screws are engraved on the outer peripheral surface of the upper and lower taper parts, attach this nipple to the lower end of the new electrode, and then hang it on the electrode in use with a traveling crane etc. The new electrode is rotated by aligning it with the taper screw so that the new electrode is screwed in and connected.

By the way, in the conventional screw structure of the electrode, the taper screw 3 is engraved on the inner circumference of the taper hole formed at the connection end of the electrode 1 as shown in the cross section of FIG. The top surface 5 of 4 is formed in a tapered shape with an angle θ equal to the taper angle of the tapered hole.

[0006]

[Problems to be solved by the device]

 However, in the above conventional structure, the top surface 5 of the thread 4 of the taper screw 3 of the electrode has a taper shape, and therefore when the nipple is inserted, the new electrode is slowly lowered as shown in FIG. When the screw thread 6 of the nipple 2 is just placed on the screw thread 4 of No. 1, there is no problem, but when the taper of the top surfaces of the screw threads 4 and 6 match and they contact each other as shown in FIG. As the screws are screwed in, the threads 4, 6 are pressed against each other, and as a result, the threads 4 of the electrode or the threads 6 of the nipple 2 are chipped or damaged. If these threads 4, 6 are broken, the fragments will enter between the threads, and the friction will become so large that screwing will be impossible on the way, and sufficient tightening strength at the specified torque will be obtained. In the case of a huge electrode, there are problems such as breakage at the connection part due to impact during operation, local electrical heating increases due to increased electrical resistance at the defective connection part, etc. It becomes a big problem. If the electrode should fall into the furnace due to breakage, it is not easy to pull out the electrode from the furnace, dangerous hot work is required, and in some cases the operation must be interrupted. The loss will be enormous.

Considering the cause of the screwing failure, the screw thread 4 of the electrode 1 does not have the screw thread 6 of the nipple 2 as shown in FIG. 5, and the tapered surfaces of the top surfaces of the screw threads 4 and 6 contact each other. When the width of the screw thread 4 is 1.32 mm with respect to the pitch of 1/4 inch (6.35 mm), it is 1.32 × 2 in both screw threads, which is 41.6%. It turns out that it occurs with a very high probability. When the pressure between the top surfaces of the threads 4 and 6 is 1/3 taper, about 3 times the weight of the electrode is applied, and the force required to rotate the electrode becomes extremely large.

In order to prevent such damage of the screw and improve the workability of the connecting work, the new electrode is rotated and lowered and screwed when both electrodes approach each other. Prepare a jig with a U-shaped spacer attached to it, place it on the electrode in use, and use this tool to avoid the screw of the nipple of the new electrode colliding with the screw of the electrode in use. After receiving the new electrode once on the cursor, remove the spacer, gently lower the electrode and screw it in. The electrode suspension hook was modified to add a mechanism to lower the electrode and nipple screw by 1/4 inch in one rotation, and then screw in smoothly. By forming a vertical groove in the nipple, and when the thread is missing, the missing particles are dropped through the vertical groove to the bottom of the screw so that they do not get caught between the threads. Although it is attempted to solve the problem, even if the connection work is carefully performed using these means, as long as the screw thread of the electrode has the above-mentioned structure, it is not a fundamental solution to the above problems. Statistically, it was not possible to eliminate the occurrence of poor connection even considering the fact that the rotation of the electrode was poor in 4 out of 10 connection operations and the above probability.

In view of this, the present invention has been made for the purpose of providing a graphite electrode connecting portion structure that enables reliable screw-in connection without causing a loss of the electrode thread when the electrode is connected. It is a thing.

[0010]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems of the conventional technology, the present invention proposes to form a taper hole at the connecting end of a graphite electrode and engrave a taper screw on the inner peripheral surface of the graphite electrode. When connecting by tapping the taper screw of the nipple attached to the connection end, the top surface of the thread of the taper screw engraved on the inner peripheral surface of the taper hole of the graphite electrode and the thread of the taper screw of the nipple The top surface of is a cylindrical surface that is substantially parallel to the axis of the graphite electrode.

[0011]

[Action]

 If the nipple at the lower end of the new electrode is inserted into the tapered hole at the connection end of the electrode, if the thread diameter of the taper screw of the nipple is larger than the thread diameter of the taper screw of the electrode, the thread ridges will be caught. Stop. Therefore, a large compressive force is not applied to the top surface of the screw thread, damage to the screw thread is minimal, and the screw is smoothly screwed in at the same pitch and speed by the subsequent rotation operation, and the final torque is normal. The end face pressure of the electrode is secured with the specified pressure value. When the ridge diameter of the nipple taper is the same as or smaller than the ridge diameter of the taper screw of the electrode when inserting the nipple, the top surfaces of the screw threads pass through without pressing each other, and the ridge diameter of the taper screw of the electrode It stops when the diameter becomes smaller than the mountain diameter.

[0012]

【Example】

 Hereinafter, the present invention will be described with reference to the embodiments shown in the drawings.

As shown in the cross section in FIG. 1, a taper screw 11 is formed on the inner peripheral surface of a taper hole formed at a connection end of an electrode 10, and a top surface 1 of a thread 12 of the taper screw 11 is formed. 3 is formed on a cylindrical surface parallel to the axis AA of the electrode 10.

The top surface 17 of the thread 16 of the taper screw 15 of the nipple 14 screwed to the taper screw 11 is also a cylindrical surface parallel to the axis AA of the nipple 14. However, the top surfaces 13 and 17 may be slightly tapered.

Therefore, when the lower end of the nipple 14 attached to the lower end of the new electrode is inserted into the tapered hole of the connection end of the electrode 10, the thread 16 of the taper screw 15 of the nipple 14 has a diameter of the taper screw 11 of the electrode 10. When the diameter of the screw thread 12 is larger than that of the screw thread 12, the screw threads 12 and 16 are caught and stopped, and the top surface 13 of the screw thread 12 is not subjected to a compressive force. When the nipple 14 is inserted, the thread diameter 16 of the taper screw 15 of the nipple 14 is the same as the thread diameter 12 of the taper screw 11 of the electrode 10, or while the thread diameter of the thread 12 is small, the top surfaces 13 and 17 of them are pressed against each other. Without passing through, the screw threads 12 and 16 are immediately engaged with each other when the thread diameter on the side of the electrode 10 becomes smaller, and the above state is brought about.

As a result, a large compressive force is not applied to the top surface 13 of the screw thread 12 on the side of the electrode 10, so that the screw thread 12 is less damaged, and the rotation operation after that is light and at the same pitch and the same speed. The screw is smoothly screwed in, and the final torque is also tightened in a normal state, and the pressure contact force between the end face of the electrode 10 and the new electrode also attains the specified pressure value, and problems such as breakage and local red heat do not occur.

[0017]

【The invention's effect】

 As described above, according to the present invention, the top surface of the thread of the taper screw and the top surface of the thread of the taper screw of the nipple are engraved on the inner peripheral surface of the tapered hole at the connection end of the graphite electrode. Since the cylindrical surface is approximately parallel to the axis, when the new electrode is connected to the worn electrode by screwing through the nipple, it is possible to greatly reduce the loss of the taper screw thread of the electrode, which may lead to poor connection. Problems such as breakage accidents and local red heat can be solved, and various excellent effects such as quick and easy connection work can be obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a state of engagement between a tapered screw of an electrode and a tapered screw of a nipple according to the present invention.

FIG. 2 is a front view showing a cross section of an electrode connecting portion to which the present invention is applied.

FIG. 3 is a partially enlarged sectional view showing a taper screw of a conventional electrode.

FIG. 4 is an operation explanatory view of a conventional technique.

FIG. 5 is an operation explanatory view of a conventional technique.

[Explanation of symbols]

 1,10 Electrode 2,14 Nipple 3,11 Tapered screw 4,6,12,16 Thread 5,13,17 Top surface

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A tapered hole is bored at the connecting end of a graphite electrode, and a taper screw is formed on the inner peripheral surface of the graphite electrode. When connecting together, the top surface of the screw thread of the taper screw and the top surface of the screw thread of the nipple taper screw engraved on the inner peripheral surface of the tapered hole of the graphite electrode are approximately parallel to the axis of the graphite electrode. A graphite electrode connecting portion structure having a cylindrical surface.