JPS61238481A - Joining method for steel bars - Google Patents

Abstract

PURPOSE:To obviate the formation of inter-surface oxide films and to make possible the satisfactory welding of a pair of steel bars by pressurizing a plate- shaped insert material which is disposed between the end faces of a pair of the heated steel bars, is made of approximately the same material as the steel bars and is at the temp. higher than the steel bars so as to flow plastically between the end faces. CONSTITUTION:The plate-shaped insert material 2 which is made of approximately the same material as the steel bars and is heated to about 1,400 deg.C in another furnace is disposed between the preceding stee bar 1 which is heated to about 1,100 deg.C in a heating furnace of a production line and is ejected from the furnace and the succeeding steel bar 1 while both end faces are kept descaled. A pair of the steel bars 1 are pressed face to face to each other and are heated up to about 1,450 deg.C at which the insert material is not melted, by a high-frequency coil 3. A pair of the steel bars 1 are pressed by a suitable method, by which the material 2 is plastically fluidized and the inter-surface oxide films are destructed and removed to join satisfactorily a pair of the steel bars 1. The joined steel bar is efficiently and continuously rolled by the succeeding rolling device.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention relates to a method for joining steel bars, and in particular, billets that are continuously delivered from a heating furnace to a group of rolling rolls are joined during the delivery process, and The present invention relates to a method for joining steel bars suitable for rolling.

(Prior Art) Conventionally, a continuously cast billet is cut into a predetermined length according to the dimensions of the heating furnace before being inserted into the heating furnace. The billet sent out from the heating furnace is
The billet is then sent to a group of rolling rolls, but a phenomenon occurs in which the rolling conditions and temperature conditions change at the cut end of the billet, which can cause malfunctions in the rolling equipment. There is. For this reason, the cut ends of each billet are rejoined at a stage before being delivered to the rolling roll group, and each billet is continuously delivered to the rolling roll group.

As for the billet joining method as described above, for example, Japanese Patent Application Laid-Open No. 53-7559 and Japanese Patent Application Laid-open No. 54-484 are known.
The flash butt welding method described in Publication No. 2 can be mentioned. In this method, the welding equipment is moved in synchronization with the billet as it moves, and electricity is applied between the ends of the billet.
This is a joining method that welds the two together by applying pressure.

(Problems to be Solved by the Invention) However, the joining method using flash butt welding as described above has the following drawbacks. First of all, because it is necessary to use a large current, the power supply becomes large.
Moreover, since it is necessary to move this, the device itself becomes large and requires a large amount of installation space, which is a drawback. The second problem is that because it is necessary to hold the billet for a long time in order to apply electricity and pressurize it, the temperature of the gripped portion decreases and the rolling conditions change. Furthermore, there is also the problem that the gripping portion is damaged and this portion remains as a defect after rolling.

This invention was made in order to solve the above-mentioned conventional drawbacks, and its purpose is to reduce the installation space and prevent the temperature drop and damage of the grip part. The object of the present invention is to provide a method for joining steel bars.

(Means for Solving the Problems) Therefore, in the steel bar joining method of the present invention, as shown in FIG. Place 2.

The above-mentioned ring wi1.1 needs to be heated as it is being sent out from a heating furnace to a group of rolling rolls or being sent out from a rough rolling roll to an intermediate rolling roll, but regarding the heating method. is not particularly limited to the above. The preferred heating temperature is 900°C to 12°C.
It is 00℃.

The plate-shaped insert material 2 is made of substantially the same material as the steel bar 1.1,
The cross-sectional shapes are also approximately the same. This provides good joint strength and in its implementation, e.g.
This is also to prevent material discontinuities from occurring in the rolled steel rod or steel wire.

The insert material 2 needs to be heated to such an extent that when the end faces of the steel bar 1.1 are pressurized, it will plastically flow and be extruded to the outer periphery thereof. Therefore, it is preferable to set the softening temperature to 700° C. or higher, and in practical terms, to a temperature higher than that of the ring H41,1, such as 1200° C. or higher. In addition, from the point of view of reducing the pressing force described later, 1400℃
It is preferable to heat to a temperature of ~1450°C, which has a certain degree of shape retention but has almost no tensile strength.

The insert material 2 may be heated in a heating furnace or the like at a location other than the welding location, and then transported to the welding location for welding. As shown in Fig. 2, the insert material 2 is heated at the joining location using an induction coil 3 (Fig. 1).
Further, at a stage immediately before pressurization, heating may be performed using the induction coil 3 to reach a higher temperature than above (FIG. 2). Note that this insert material 2 is 5 to 10 m long.
is a practical thickness.

Then, in the above state, pressure is applied between the end faces of the steel bar 1.1, and this pressing force is changed as appropriate depending on the temperature of the steel bar 1.1 and the temperature of the insert material 2. For example, steel bar 1.1 has a temperature of about 1100℃, and insert material 2 has a temperature of 1400℃.
For temperatures up to 1450°C, the amount should be approximately 4 to 5 kg/t. The above-mentioned pressurization can also be carried out by grasping the vicinity of the end of the steel bar 1.1 and pressing both together. However, for example, when the method of the present invention is carried out on a rolling line, At a stage before the rear end of the preceding steel bar 1 is sent out to the rough rolling rolls, the following steel bar 1 is pushed out of the heating furnace, and the tip end face of the following steel bar 1 is pushed out from the preceding steel bar 1 by this extrusion force. It is also possible to pressurize by colliding with the rear end surface of 1.

(Operation and Effect) By applying the pressure as described above, the insert material 2
A plastic flow occurs, and the insert material 2 is pushed out around the steel bar 1.1, as shown in FIG. 3, which corresponds to the example. At this time, the flow of the insert 2 removes the oxide film, etc. on the end face of the rod ml, 1.
A new surface will be formed on the end surface. Since such new surfaces are pressed and in contact with each other, it becomes possible to join both steel bars 1.1 in a good condition.

According to the above-described joining method, instead of forming a heated fluidized bed at the end of the steel bar using electrical energy as in the conventional method, a separate high-temperature insert material 2 is used as the fluidized bed. Therefore, unlike the conventional flash butt welding method, there is no need to use a large power source to move it, and therefore the device itself and its installation space can be made compact. In addition, since there is no need to energize, there is no need to grip the circumferential side of the steel bar, or even if it is gripped for pressurization, it only takes a short time, so there is no need to reduce the temperature of the gripping part of the steel bar as in the case of conventional methods. It becomes possible to prevent damage.

(Example) Billets 1 were joined on a steel bar manufacturing line as shown in FIG. In the figure, 4 is a heating furnace, 5 is a rough rolling roll group, 6 is an intermediate rolling roll group, 7 is a finishing rolling roll group, and 8 is a cooling bed. The rolling process was carried out at a position between the rough rolling roll group 5 and the rough rolling roll group 5.

The billet 1 had a rectangular cross section with a negative side of 150 fl, and was heated to about 1150° C. in a heating furnace 4. As shown in FIG. 1, an insert material 2 made of the same material and having the same cross-sectional shape as the billet 1 was placed between the rear end surface of the preceding billet 1 and the front end surface of the continuing billet 1. This insert material 2 had a thickness of about 8 mm, an induction coil 3 was arranged around it, and it was heated to about 1400°C.

With the rear end of the preceding billet 1 in close proximity to the rough rolling roll group 5, both end surfaces of the billet 1 are brought into contact with the insert material 2, as shown in FIG. Approximately 1,450 further around the area
It was heated to ℃. After the heating is completed, a load of approximately 1107 ON is applied to the rear end of the billet 1, which continues, to pressurize the end faces of the billet 1.1, causing the insert material 2 to plastically flow, as shown in Fig. 3. Billet 1.
1 to the outer periphery, and the joining was completed.

The above-mentioned billet 1.1 was continuously rolled by each rolling roll group 5.6.7 in the joined state, and a steel bar of a predetermined size could be manufactured. The joints of the manufactured steel bars were visually checked, but no abnormalities such as rolling unevenness or scratches were observed.

In addition, by removing scale from the end face of the billet 1 immediately before joining and heating the insert material 2 in an inert gas atmosphere, it is possible to prevent the formation of an oxide film on the joint surface and obtain a high-strength joint. It will be done.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams chronologically showing one embodiment of the steel bar welding method of the present invention, and FIG. 4 is an explanatory diagram of a production line for explaining a general example of the above method. 1... Steel bar, 2... Insert material. Figure 1○ Figure 3

Claims (1)

[Claims] 1. A plate-shaped insert material made of substantially the same material as the steel bar and having a higher temperature than the steel bar is placed between the end faces of a pair of heated steel bars, and the insert material is caused to plastically flow by pressurizing the end faces. A method for joining steel bars, characterized by: