JPS6221052B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method and apparatus for softening heat treatment of wire rods, and more specifically, the present invention relates to a wire rod softening heat treatment method and apparatus, and more specifically, the wire rods include S40C,
The present invention relates to a method and apparatus for softening steel wires such as SCR440 and SCM440. Conventionally, wire rods that require cold forgeability are generally subjected to spheroidization and annealing treatments, but these treatments are performed in a coiled form to uniformize the temperature inside and outside the coil. In order to do this, it is heated at a slow rate, held for a long time, and slowly cooled down, which takes a long time, for example, about 20 hours. To explain this using Figure 1, as mentioned above, conventionally the coiled state was heat treated in a gas or electric furnace, which required a long time for heating and holding time. Figure 1 shows the heat pattern of the spheroidization process, and it can be seen that the process took 15 hours. A is the temperature outside the coil, and B is the temperature at the center of the coil. In addition, constant temperature maintenance at a temperature below the transformation point, or
A softening treatment (spheroidization treatment) is performed on wire rods that are softened by slow cooling for the purpose of improving cold workability. If rolled material or cold-drawn wire material is cold-processed as it is, cracks will occur, so softening treatment is performed, but this heat treatment takes a long time because it is coiled, and furthermore, coiled wire processing requires a long time. It takes a very long time to reduce the temperature difference between the outer diameter side of the coil and the center side of the coil. This is clear from the explanation of FIG. 1 above. The inventor of the present invention studied a technology for reducing the long-time processing, which is a problem in the conventional technology, to a short processing time, and found that if the wire is heated in a strand state, it is possible to heat it extremely rapidly. , it was discovered that if the temperature is maintained at a temperature below ₁ point A, or if it is slowly cooled from a point above ₁ point A, a wire rod can be softened within a short time of one hour. However, since it takes a very long distance to run a coiled wire in a strand state, it is possible to soften the wire extremely quickly by keeping it at a temperature below point _A1 while winding the wire after rapid heating. I discovered what I could do. The present invention has been made in view of the conventional problems in the softening heat treatment of wire rods as described above and based on the knowledge of the present inventors, and is a method and apparatus for softening heat treatment of wire rods that can perform softening heat treatment in an extremely short time. It provides: The wire rod softening heat treatment method and apparatus according to the present invention include (1) heating the wire rod in a strand state at a temperature of 700°C to 700°C;
Immediately after rapid heating to a temperature of 900℃
A first softening heat treatment method for a wire rod characterized by winding it in a furnace maintained at a temperature of 650°C to 750°C.
(2) A wire rod softening heat treatment apparatus characterized in that a wire rod rapid heating device and a furnace body having a heating means in which a wire rod winding device is installed are installed in close proximity to each other. This invention consists of two inventions. Next, the wire softening heat treatment method and apparatus according to the present invention will be described in detail with reference to the drawings. In FIG. 2, the coiled wire 1 of the uncoiler 2 is straightened through the straightening machine 3 and rapidly heated to 700 DEG C. to 900 DEG C. by a high frequency heating device consisting of a high frequency oscillator 4 and a heating coil 5. This high-temperature wire is pushed into a guide pipe 9 installed through the wall of the furnace body 16 by a drive roll 6 driven by a drive shaft 8 of a motor/transmission 7, and then heated to a temperature of 650°C by a heating element 15. The inner drum 1 is mounted on a rotary disk 12 which is rotated by a drive shaft 10 and a rotary shaft 11 in synchronization with the drive roll 6 in a furnace body 16 maintained at ~750°C.
The wire is pushed out between the outer drum 4 and the outer drum 13 and wound up. In this way, after winding all the coiled wire rods 1 in the uncoiler 2 onto the inner and outer drums 13 and 14 in the furnace body 16, the coiled wire rod 1 is held for an appropriate period of time, and the lid 17 of the furnace body 16 is opened and the inside of the furnace body 16 is opened. drum 14
At the same time, the coil is taken out and the softening heat treatment is completed. In this case, the drive roll 6 may be installed either before or after the high-frequency heating device, but the wire speed is determined by the drive roll 6, and the high-frequency heated wire is heated inside the furnace at a temperature higher than the temperature of the furnace body 16. A linear speed of at least 3m/min is required. Furthermore, since productivity is determined by the linear speed, it is desirable to be as fast as possible. but,
If the temperature is much higher than that of the furnace body, it is necessary to cool it in or before the guide pipe so that it approaches the temperature of the furnace body. Furthermore, productivity is also determined by the high-frequency heating rate, and even if the wire speed is increased, if the high-frequency heating is insufficient, the softening of the wire will also be insufficient. For example, the optimal heating rate is 5mm
50℃/sec or more for φ wire, 10mmφ wire
A temperature of 20°C/sec or higher is desirable. In addition, it is desirable that the temperature for rapid heating be between 700°C and 900°C; at temperatures below 700°C, softening will be insufficient, and at temperatures above 900°C, not only will the softening not occur, but energy for heating will be required. This is because you need a lot of it. Specifically, the furnace body temperature is 700℃ and the 10mmφ wire is wired at a linear speed of 10m/
The graph in Figure 3 shows the relationship between the heating temperature and the Vickers hardness of the high-frequency heated wire when treated at 700°C for SCr440 (C) and S40C (D).
It can be seen that it softens at temperatures of ~900℃. Next, the temperature at which the wire is wound, that is, the furnace body temperature, is preferably 650°C to 750°C.
This is a graph showing the relationship between furnace body temperature and Vickers hardness when SCR440 is processed, and is 650℃ to 750℃.
It can be seen that it has softened. Figure 5 is an example of a heat pattern when applying the method and apparatus for softening heat treatment of a wire according to the present invention.
This is a graph showing that the temperature reached 840°C and the spheroidization process was completed in 30 minutes after being rolled up in a furnace body maintained at 700°C. Next, an example of the softening heat treatment method for a wire rod according to the present invention will be described. Examples Table 1 compares the method according to the present invention with the conventional method, and shows the mechanical properties and the time required when a 100 kg coil of 10 mmφ wire was subjected to softening heat treatment. The set temperature of the heat pattern is shown in Figure 6a.
is the method according to the present invention, and FIG. 6b is the conventional method. From Table 1, it can be seen that the method according to the present invention has no significant difference in mechanical properties compared to the conventional method, and the processing time is significantly shortened.

[Table] As explained above, since the wire rod softening heat treatment method and apparatus according to the present invention have the above-described configuration, the wire rod is wound up in a high temperature holding furnace after rapid heating, so that the wire rod can be wound up in a short time. It is possible to provide a device that can perform heat treatment, increase productivity, reduce the size of the device, and simultaneously maintain high temperature while winding the wire.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the time and temperature required for conventional wire softening heat treatment, Fig. 2 is a schematic side view showing an example of the wire softening heat treatment apparatus according to the present invention, and Fig. 3 is the heating temperature of the wire. FIG. 4 is a graph showing the relationship between furnace body temperature and Vickers hardness; FIG. 5 is a graph showing an example of the heat pattern of the softening heat treatment method for wire rod according to the present invention; FIG. 6 is a graph showing the set temperatures of the example heat patterns shown in Table 1. 1 - wire rod, 2 - uncoiler, 3 - straightening machine, 4
~High frequency oscillator, 5~Heating coil, 6~Drive roll, 7~Motor/transmission, 8~Drive shaft, 9...Guidebook, 10~Drive shaft, 11~Rotating shaft, 12
~Rotating disk, 13~Outer drum, 14~Inner drum, 15~Heating element, 16~Furnace body, 17~Lid.

Claims (1)

[Claims] 1. The wire rod is heated to 700°C to 900°C in a strand state.
After rapid heating to a temperature of 650 °C, immediately
A method for softening and heat treating a wire rod, which comprises winding the wire in a furnace maintained at a temperature of ℃ to 750℃. 2. A wire rod softening heat treatment apparatus characterized in that a wire rod rapid heating device and a furnace body having heating means in which a wire rod winding device is installed are installed in close proximity.