JPS5926649B2 - Method and device for heat treatment of joints of steel materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for heat treating a joint of steel materials for restoring the material quality of the joint when the steel materials are pressure welded or welded.

When two pieces of steel are pressure welded or welded, each joint will be affected by heat due to the pressure welding or welding, resulting in a difference in material quality from the base material.

For example, when a steel material has been subjected to an adjustment treatment such as a drill pipe, it is likely that a so-called softened part that is softer than the base metal part or a part that is harder than the base metal part will occur at the joint due to the thermal effect. Are known. However, the strength of the entire steel material after joining is determined by the part with the lowest strength, so the local part of the joint, including the heat-affected zone, is heated to a certain temperature or higher using a heating means such as an induction heating coil, and then heated to a temperature higher than air cooling. The material is cooled at a cooling rate and tempered as necessary to reduce or eliminate the difference in hardness with the base material. As shown in Fig. 1, the conventional joint heat treatment method for this purpose is to place the pipe 1 after joining on a transport roller 2 so that it can move freely, and to operate the installed induction heating work coil 3 and cooling nozzle 4. A person visually transports the pipe 1, positions the joint 5, and performs heating and cooling treatments.

In this case, depending on the properties required of the steel material or the composition of the steel material, a tempering treatment may be performed on the heated and cooled local joint portion.

However, the heat treatment width in this case is very localized,
For pressure welding, the area should be within about 10 mm on one side from the pressure welding boundary, and for welding, it should be within about 10 mm from the weld metal boundary, and the induction heating work coil for heating and the cooling nozzle for cooling should be heat treated It is an important operational factor to align the position so that it is located at the desired local area, and based on experience, the permissible deviation is within 3m711. Also pressure welding,
Heat treatment of the joint after welding is carried out after removing any burrs or excess welding created during pressure welding using a tool or other tool. - It is very difficult to determine the boundary between the weld metal and the weld metal, and visual inspection is a factor that causes variations due to individual differences.

On the other hand, as a problem with the heat treatment equipment itself as shown in Fig. 1,
The conveyance roller 2 has inertia, and it is difficult to stop the heat-treated joint part 5 at the work coil 3 or the cooling nozzle 4 in one go, and it takes time to position it.
This, combined with the difficulty in determining the junctional boundary, increases individual differences.

Furthermore, even if the boundary part is not detected in advance and the joint local part is stopped at the corresponding position by controlling the number of revolutions of the conveying roller, slips may occur between the pipe and the rollers, or the contact conditions between the pipe and the rollers may be affected. Unless the distance is constant during transport, the transport distance until it stops will vary. Furthermore, because it takes 3 hours to set up the pipe 1, when cooling with the cooling nozzle 4 after heating with the work coil 3, the cooling start temperature changes each time even if the heating temperature is constant. The hardness of the local joints causes variations in the results for each heat treatment. Furthermore, in the conventional method 4 and the apparatus, following the positioning of the joint part to the work coil 3 or the cooling nozzle 4, power is applied to the work coil 3 and after a predetermined time, the power is cut off or the cooling is stopped. Nozzle 4
The operator was required to supply cooling water and air to the machine and then shut it down after a predetermined period of time had elapsed.The overall operating procedure was complicated, and the working conditions sometimes lacked stability. The present invention
This was invented to solve many problems in conventional heat treatment methods and equipment for joints, and it is capable of continuously and automatically heat treating localized joints, including heat-affected zones, in pressure welds or welds of steel materials. The purpose of the present invention is to provide a method and apparatus for heat treating joints of steel materials.

Preferred embodiments of the present invention will be described below based on the drawings.

Figure 2 shows one of the apparatuses for implementing the joint heat treatment method of the present invention.
This shows an embodiment, and the same parts as in FIG. 1 are given the same reference numerals and their explanations are omitted. In FIG. will be established.

In this embodiment, a rack 7 is installed along a pipe 1, and a motor 8 built in the drive section of the truck 6 rotates a pinion 9 that meshes with the rack 7, thereby allowing the truck to be moved without slipping. 6 is running at a constant speed. In another embodiment, a rail is laid along the pipe 1,
The cart may be movably supported by wheels, and the cart 6 may be driven at a constant speed without slipping by a chain conveyor driven by a motor installed on the ground side. Of course, any suitable traveling means that allows the trolley 6 to travel without causing slips may be used. A cooling nozzle 4, a joint detector 10, and a work coil 3 for induction heating are provided in the cooling nozzle 4.

In addition, a radiation thermometer 11 is installed on the trolley 6 with the temperature measuring part facing the heating position of the work coil 3 for induction heating, and the outputs of the joint detector 10 and the radiation thermometer 11 are used to control the heat treatment on the vehicle. The heat treatment control device 12 starts and stops the trolley drive motor 8 and controls the induction heating work coil 3 using CT according to a control pattern based on the heat treatment method of the present invention.
Command signals are sent out to turn on power to an oscillator (not shown) that supplies power via the transformer 13, and to control the supply of cooling medium to the cooling nozzle 4. Therefore, the heat treatment method of the present invention performed in the heat treatment apparatus shown in FIG. 2 will be explained.

Here, the distance L1 between the joint detector 10 and the work coil 3 in the trolley traveling direction, and the distance between the cooling nozzle 4 and the cooling nozzle 4 are L2,
Let the moving speed of the trolley 6 be S(CrrL/Mln).

First, the trolley 6 is located at a position away from the pipe 1, for example on the right side, and when a start command is given by an operator or the like, it travels to the left at a constant speed S.

When the joint detector 10 passes the joint 5, the position of the joint is detected and the heat treatment control device 12 obtains a signal giving the position of the joint 5. When this signal is obtained, the heat treatment control device 12 calculates the time from the detection of the joint to the stop of the trolley based on the distance L1 between the joint detector 10 and the work coil 3 and the moving speed S of the trolley 6, and calculates the time from the detection of the joint to the stop of the trolley. When t1 has elapsed, a stop command is sent to the motor 8 to stop the cart 10.

Thereby, the longitudinal central axis XX of the work coil 3 is positioned at the joint portion 5. Of course, it is also possible to stop the work coil 3 so as to cover a width to be heat-treated of 10 mm or less from the boundary line of the joint toward the heat-affected zone. When the work coil 3 is set at the junction local, power from the oscillator is supplied to the work coil 3 via the CT transformer 13.

This automatic application of power to the work coil 3 can be achieved by turning on a circuit breaker that supplies power to the oscillator in response to a stop command to the motor 8 of the truck 6, or by turning on the circuit breaker that supplies power to the oscillator in response to a stop of the truck 6. It should be automatically inserted. Here, the amount of power supplied to the work coil 3 may be a predetermined amount of power, but preferably it is determined based on the deviation from the set temperature while measuring the temperature of the local joint with the radiation thermometer 11. Preferably, the power adjustment is performed by the heat treatment control device 12.

The power supply to the work coil 3 is stopped after a predetermined time period set by a timer built into the heat treatment control device 12 . Next, under heat treatment conditions in which the bonded local area is heated and then cooled in the air, the cart 6 is returned to the starting position again to prepare for the next heat treatment.

On the other hand, under heat treatment conditions that require accelerated cooling after heating, the trolley 6 is moved to the right along the pipe 1 again,
When the joint detector 10 detects the joint 5, the heat treatment control device 12 calculates the distance from the detection time to the time when the trolley stops, based on the distance L2 between the joint detector 10 and the cooling nozzle 4 and the moving speed S of the trolley 6. A time T2 is calculated, and a stop command is sent to the motor 8 of the truck 10 after the time T2 has elapsed.

Thereby, the cooling nozzle 4 is positioned with the vertical center line Y-Y of the cooling nozzle 4 at the heated joint portion 5. Trolley 6
When it stops, a mixed cooling medium of water and air at a preset pressure is ejected through the cooling nozzle 4 for a time set by a timer, thereby accelerating cooling of the joint local area.

When the accelerated cooling is finished, the trolley 6 is returned to the starting position to prepare for the next heat treatment of the steel material. By using the steel joint heat treatment method and apparatus of the present invention as described above, all processes are continuous and automatic except for carrying the steel material to be heat treated to a predetermined position and carrying out the steel material after heat treatment to another location. This means that it can be done. An important technical point in the present invention as described above is a joint detector for detecting the position of the joint, and although various types are possible for this, the one described below is preferable.

When metals are pressure-welded or welded, one method for detecting the joint is to utilize the fact that electromagnetic induction is received differently between the joint and the base metal.

That is, as shown in FIG. 3, the measurement end 15 of the AC bridge 14,
A small coil 16 called a search coil is attached to 15', and the impedance is measured by sweeping the vicinity of the joint 5 while maintaining a constant interval. If the pipes 1 and 2 are of the same type of metal, the joint 5 will have electrical properties different from those of the base metal due to the heat effect during pressure welding or welding, i.e. magnetic permeability μ, electrical conductivity k
etc. Further, if the pipe 1 is made of different metals, the magnetic permeability μ, electrical conductivity k, etc. of the base material portion will naturally differ on both sides of the joint portion 5. Therefore, when an alternating current is passed through the search coil 16, an eddy current is generated on the pipe surface, and the search coil 16 generates an eddy current.
6 is measured with an impedance different from its own impedance. This is due to mutual induction between the current flowing through the search coil 16 and the eddy current on the pipe surface. and,
The value of this eddy current depends on the pipe's magnetic permeability μ and electrical conductivity k, and if these physical property values differ, the impedance of the search coil 16 will also differ. Therefore, the joint 5
By measuring the impedance in the vicinity, the position of the joint 5 can be determined. FIGS. 4 and 5 are graphs showing signal components obtained in the electrical processing process for determining the joint position by impedance measurement using a search coil.

First of all, Fig. 4 shows the case where the pipes 1 and 2 are made of the same kind of metal, and the horizontal axis shows the sweep distance j, and the vertical axis shows the
The impedance Z is shown in Fig. 4B, and its differential value DZ/dl is shown in Fig. 4B.
Take. As is clear from FIG. 4A, the impedance Z of the search coil changes in a pulse-like manner with a peak value at the position corresponding to the junction 5. By differentiating this change in impedance Z, as shown in FIG. 4B, the impedance change rate for one cycle with zero crossing point A at the position corresponding to the joint 5 is obtained. Normally, the impedance output of an AC bridge can be extracted as a voltage signal, so by passing this through a differentiating circuit once, a voltage signal as shown in Figure 4B can be obtained, and by using an appropriate zero-crossing detection circuit. , a signal output can be obtained which determines the position of the joint 5.
Note that the broken lines shown in FIGS. 4A and 4B show the case where the impedance changes are reversed. On the other hand, Fig. 5 shows the case where the pipes 1, 1'' are made of different metals, and the horizontal axis shows the sweep distance l, and the vertical axis shows the impedance Z in Fig. 5A and Fig. 5B.
The differential value DZ/dl is calculated twice by the differential value D2 in Fig. 5C.
Z/Dl2 is shown respectively.

As a result, as shown in FIG. 5A, the impedance level differs on both sides of the joint portion 5, and the vicinity of the joint portion 5 changes between them.

The position of the joint 5 is the inflection point B of impedance change, so if you differentiate this point, it will be as shown in Fig. 5B,
Further, a second differentiation is performed to obtain an acceleration curve of impedance change as shown in FIG. 5C. Actually, by passing the output voltage of the AC bridge that outputs the impedance change of the search coil twice through a differentiating circuit, it is possible to extract a signal output having a zero crossing point A at the junction 5 as shown in Fig. 5C. . In the detection circuit shown in FIGS. 4 and 5 for determining the position of the joint 5, a noise removal filter is provided before the differentiating circuit in order to avoid the influence of noise mixed into the detection signal.

As explained above, by the heat treatment method and apparatus of the present invention, heat treatment of joints and joint local parts of steel materials can be continuously and automatically performed without manual intervention.
By achieving automation, operators only need to be involved in loading and unloading steel materials and starting heat treatment, reducing work effort and improving efficiency.

In particular, the positioning of the induction heating coil and cooling nozzle with respect to the joint, which has been considered difficult in the past, requires the use of a joint detection device, fixing the steel material, and running a cart carrying the induction heating coil and cooling nozzle. With this equipment configuration, reliable and quick positioning can be performed with high precision, and this has led to the realization of an automatic heat treatment method.
It has been possible to stabilize the operation in joint heat treatment, which restores the local part of the joint to the material of the base metal.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an apparatus used in the conventional heat treatment method for steel materials, FIG. 2 is an explanatory diagram showing an example of an apparatus in which the heat treatment method of the present invention is carried out, and FIG. 3 is an explanatory diagram showing one example of a joint detector. An explanatory diagram showing an example, FIG. 4 is a graph diagram showing the impedance change and its waveform processing obtained at the joint of similar metals,
FIG. 5 is a graph showing the impedance change and its waveform processing obtained at the junction of dissimilar metals. 1, ``... Pipe, 2... Conveyance roller, 3... Induction heating work coil, 4...
...Cooling nozzle, 5...Joint part, 6...
・Dolly, 7...Rack, 8...Motor, 9...Pinion, 10...Joint detector, 11...Radiation Thermometer, 12...
Heat treatment control device, 13...CT transformer, 14
・・・・・・AC Bridge, 15,151・・・・・・
Measuring end, 16...Search coil.

Claims (1)

[Claims] 1. In a method for heat treatment of joints of steel materials, a trolley is made to travel along the steel materials at a constant speed, and a boundary between the steel materials is detected by a detector provided on the trolley. A command is issued to stop the truck driving device after a time determined from the distance between the induction heating coil and the detector in the traveling direction of the truck and the traveling speed of the truck, and when the induction heating coil is stopped at the joining local area to be heat-treated. A method for heat treating joints of steel materials, characterized by applying electric power to an induction coil. 2. In a method for heat treatment of joints of steel materials, a trolley is run at a constant speed along the steel materials, a detector installed on the trolley detects the steel joint boundary, and an induction heating coil installed on the trolley and the detection A command is issued to stop the trolley drive device after a time determined from the distance in the running direction of the trolley between the containers and the running speed of the trolley, and when the induction heating coil is stopped at the joint area to be heat-treated, power is applied to the induction coil. death,
In response to the power interruption of the induction coil when the heating treatment of the welded local area is completed, the trolley is made to run in the opposite direction again at a constant speed, and the detector installed on the trolley detects the steel welding boundary again, and the A command is issued to stop the bogie drive device after a time determined from the distance in the bogie running direction between the cooling device installed at the detector and the bogie running speed, and the cooling device is positioned and stopped at the joint area to be cooled. 1. A method for heat treating a joint of steel materials, the method comprising: activating the cooling device. 3. A joint heat treatment apparatus for steel materials, which has a truck that can move forward and backward at a constant speed along the steel material, and a joint detection device, an induction heating coil, and a cooling device are installed on the truck in the running direction at predetermined intervals. A control device for transmitting a stop command to a bogie drive control unit and an operation command to the induction heating coil and cooling device according to the detection output of the joint detection device. Partial heat treatment equipment.