JP2839760B2 - Plasma gouging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming a groove in a steel product by cutting using a plasma arc (plasma cutting), and more particularly, to a method for applying a plasma arc to a flat surface of a steel product. The present invention relates to a plasma gouging apparatus that forms a groove having a substantially constant depth in a steel product by melting and blowing away by plasma by obliquely facing and relatively moving in parallel.

[0002]

2. Description of the Related Art For example, in the case of welding a relatively thick long steel plate, a Y-shaped or X-shaped groove is welded on one side (front surface) and then gouging from the back surface to a weld metal (bead bottom surface). After the groove is formed (reverse fraying) to expose a good quality weld metal on the back surface side, the back surface is welded. As one form of this gouging, a rail is laid on the back surface of a long steel plate whose surface has been welded, and an automatic traveling vehicle equipped with a plasma arc is attached to the rail, and a plasma arc is mounted. Kut-
There is a mode in which the plasma gouging is performed by moving the switch parallel to the steel plate obliquely to the steel plate along the rail. In the case of air gouging, in which the surface of a steel sheet is melted with a hand welding rod for gouging and the molten metal is blown off by injecting air, the noise is large, dust is generated remarkably, and the inner surface of the obtained gouging groove is made of carbon. Since it is contaminated, it is necessary to polish the surface to remove it.In the above-mentioned plasma gouging, the noise is small, the generation of dust is small, and the inner surface of the obtained gouging groove is particularly clean. Suitable for back filing for welding.

[0003]

Generally, a steel sheet has considerable irregularities or bends due to thermal distortion or the like during welding of the front surface. In this case, when the plasma gouging of the rear surface, the irregularities or the irregularities of the steel sheet occur. The distance between the steel plate and the plasma actor changes in proportion to the bending, and the arc length changes accordingly. As a result, the gouging depth changes.

FIG. 8 shows an experimental example in which the depth of the plasma gouging groove changes according to the change in the distance (torch height) of the torch with respect to the workpiece. 8A shows the experimental conditions, and FIG. 8B shows the relationship between the groove height and the torch height.
(C) shows the relationship between the torch height and the groove width. FIG. 8B shows that the groove depth changes by about 1 mm due to the change in the torch height of about 10 mm. As described above, since the groove depth changes due to the change in the torch height, a large groove depth change occurs particularly when gouging is performed continuously over a relatively long distance.

[0005] In the above-mentioned back filing by plasma gouging after the welding on the front side, if the gouging depth changes, some places cannot be dug to the front side weld bead. If such a groove is welded as it is, a portion that does not reach a high quality weld metal becomes a welding defect. Therefore, usually, the depth of the groove is measured after the gouging of the back surface, and the shallow portion is deeply corrected by manual gouging.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce fluctuations in the depth of the plasma gouging groove due to fluctuations in the torch height.

[0007]

As shown in FIG. 4 (a), an experimental processing target material 1 inclined at an angle of 30 ° with respect to a horizontal plane and inclined with respect to a horizontal plane is subjected to the conditions shown in the figure. Was subjected to plasma gouging. The traveling speed of the torch 7 is 10
Gouging was performed at a constant value of 0 cm / min over a distance of 720 mm. During the travel of this 720 mm distance,
The height at the start was 15 mm at the start position, but increased in proportion to the running distance, and was 33 mm at the end point after traveling 720 mm. FIG. 4B shows a change in arc voltage between the torch 7 and the workpiece 1 during the plasma gouging. From the experiment shown in FIG. 4, it can be seen that the arc voltage increases substantially in proportion to the torch height. For example, an increase in the arc voltage by about 4 V means an increase in the torch height by about 1 mm. Thus, the arc voltage can be detected during plasma gouging to determine the torch height.

[0008] The depth and width of the groove obtained by plasma gouging depend on the traveling speed of the torch 7. Some examples are shown in FIG. 5A shows the plasma gouging conditions, FIG. 5B shows the groove depth obtained for the traveling speed of the torch 7, and FIG. 5C shows the groove width obtained for the traveling speed of the torch 7. Show. The material 1 to be processed is a flat material having no unevenness and no bend, and a processing surface is set horizontally, and the torch height is constant. From this experiment, it can be seen that the groove depth becomes shallower in substantially inverse proportion to the torch traveling speed. For example, a decrease in the torch traveling speed of approximately 500 mm / min can increase the groove depth by approximately 1.5 mm.
This indicates that the groove depth can be controlled by adjusting the torch traveling speed.

Therefore, for example, when the torch height is increased by 10 mm, the groove depth is reduced by 1 mm and the torch height is reduced by 10 m.
Assuming that the arc voltage increases by 40 m and the groove depth increases by 1 mm as the torch traveling speed decreases by (500 / 1.5) mm / min, the increase in arc voltage by 1 V is as follows.
By lowering the torch traveling speed by [500 / (1.5 × 40)] mm / min, the groove depth is kept constant (reference value). That is, a change in the arc voltage is detected and a change in the torch height is estimated. When the arc voltage is correspondingly increased, the torch traveling speed is decreased and the arc voltage is decreased. Sometimes, by increasing the torch traveling speed, the groove depth of the plasma gouging can be kept constant.

[0010] The present invention has been made based on the above-mentioned findings, and has been made in consideration of the above-mentioned problems, and a plasma actor for gouging is provided.
(7); torch support means (6) for supporting the torch (7) at a substantially constant angle with respect to the workpiece (1); and
And a driving means (5, 10, 11) for driving at least one of the workpieces (1) (7) relatively parallel to the other (1). In a plasma gouging apparatus, an arc voltage detecting means (91) for detecting an arc voltage of the plasma actor (7);
Change detecting means (92-95) for detecting a change in the arc voltage detected by (91); and an arc corresponding to the change in the arc voltage detected by the change detecting means (92-95). When the arc voltage decreases, the traveling driving speed of the driving means (5, 10, 11) is increased,
Running speed control means (101-103) for lowering the running drive speed when the braking voltage rises. The symbols in parentheses indicate the corresponding elements in the embodiments described later.

[0011]

According to this, the driving means (5, 10, 11) connects at least one (7) of the torch support means (6) and the workpiece (1) to the other.
If the torch height rises and the arc voltage rises while the vehicle is driven relatively parallel to (1), gouging occurs due to the rise in the torch height. Although the groove depth may decrease, the traveling speed control means (101 to
103) reduces the traveling drive speed of the drive means (5, 10, 11), thereby avoiding a decrease in gouging groove depth.
If the torch height is reduced and the arc voltage is reduced, the gouging groove depth may increase due to the decrease in the torch height.
103) increase the traveling drive speed of the drive means (5, 10, 11), thereby avoiding an increase in gouging groove depth.

In this way, the variation of the gouging groove depth due to the variation of the torch height is suppressed, and the material to be processed is uneven, bent, or the torch is running (in the direction of the torch height).
Even when the torch height fluctuates due to displacement or the like, a plasma gouging groove having a substantially constant depth can be obtained. Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0013]

FIG. 1 shows an external view of a mechanical portion according to an embodiment of the present invention, and FIG. 2 shows a configuration of an electric circuit of the embodiment. First, Figure 1
With reference to FIG.
A traveling carriage 5 having a self-propelled mechanism (not shown) is mounted on a rail 4 supported by the carriage 3.
A plasma actor 7 is mounted via a torch stand 6. The position of the plasma actor 7 can be adjusted vertically by the support mechanism and the adjusting mechanism of the torch stand 6, and the inclination angle with respect to the horizontal plane (the plane including the lower surfaces of the magnet stands 2 and 3) can be adjusted. It is. This inclination angle is 30 ° as a standard. To
The vertical position (torch height) of the torch 7 is determined by moving the torch 7 to a gouging start position (a position on an axis extending in the left-right direction in FIG. 1).
Is set and adjusted to a height (desired torch height) at which a desired groove depth is obtained.

FIG. 1 shows a magnet stand 2, 3 with a rail 4 parallel to the groove on the back surface of a workpiece 1 whose surface is welded along a Y-shaped groove or an X-shaped groove. Put on,
This figure shows a state in which plasma gouging is started from the right end side of the processing target material 1 and the gouging is advanced to an intermediate portion of the groove length. The material 1 to be processed is generally a flat plate, and the rail 4 is substantially parallel to the upper flat surface (back surface) of the material 1 to be processed, that is, substantially parallel, but due to thermal distortion during welding of the front surface. The workpiece 1 has irregularities and bends from the right end to the left end along the groove, and more precisely, the traveling of the torch 7 of the workpiece 1 from the right end to the left end along the groove. Medium, toe
Height changes.

Referring to FIG. Torch 7 and target material 1
Is detected by the voltage detector 91 of the arc voltage change amount detection circuit 9. In the third column from the top of FIG. 3,
An example of the arc voltage detected by the voltage detector 91 is shown. In FIG. 2, when plasma power is supplied between the torch 7 and the workpiece 1 by the plasma power source 8, the arc voltage rises as shown in FIG. If a plasma arc is generated during the period, the arc voltage decreases. The arc generation detector 92 shown in FIG. 2 generates a pulse signal (arc start detection signal) in response to this decrease in the arc voltage, and in response to this pulse signal, the timer 93 operates in response to the time T. , And the reference value memory 94 composed of a sample hold circuit clears the hold voltage (storage voltage). That is, when the arc occurrence detection circuit 92 detects the occurrence of the arc, the timer 93 starts and the reference value memory 94
Is cleared. If the arc occurrence detection circuit 92 detects the occurrence of the arc and the arc continues even after a short time thereafter, the motor speed control circuit 10 informs the traveling vehicle 5 (torch 7). The set speed signal indicating the traveling speed (reference speed) is switched from the level instructing the stop to the level indicating the reference speed. Thereby, the traveling vehicle 5 starts traveling and travels at the reference speed. FIG. 3 shows a level change of the set speed signal.

The timer 93 detects the arc voltage at the point in time when the plasma arc is generated and the traveling vehicle 5 starts traveling, the traveling speed is stabilized at the reference speed, and the arc voltage is correspondingly stabilized. For indicating the set torch height (reference value), and the time from when the plasma arc is generated until the traveling speed of the traveling vehicle 5 and the generated arc are both stabilized. A slightly longer time T is set in the timer 93 as a time limit value. Thus, when the traveling speed of the traveling vehicle 5 is stabilized and the plasma arc is stabilized, the timer 93 time-overs to generate a time-over signal, and in response to this signal, the reference value memory 94 responds to this signal. The arc voltage at the time is held (stored). At this time, the torch 7 is in the immediate vicinity of the initial setting position, where the torch height is set to a value (reference height) for obtaining a desired groove depth by the initial setting. Arc voltage is
This corresponds to the reference height. Thereafter, the change amount detector 95 gives a signal indicating a deviation of the arc voltage from the reference value (arc voltage-reference value) to the adder 101. This deviation corresponds to a height deviation of the torch 7 with respect to the reference height.

The adder 101 supplies the level sum of the set speed signal and the deviation signal to the comparator 102 as a traveling speed command signal. FIG. 3 shows the relationship between these signals. Comparator 10
2 is supplied with a triangular wave signal generated by the triangular wave generator 103, and the comparator 102 outputs a high level H when the level of the triangular wave signal is higher than the level of the traveling speed command signal.
On the contrary, a low level L pulse signal (PWM signal / pulse width modulation signal) is generated. The PWM signal is amplified by the amplifier 104 to drive the switching transistor of the motor driver 105. The switching transistor of the motor driver 105 turns on when the PWM signal is H,
Turns off when L. As a result, the energizing current value (time-series average value) of the DC motor 11 that drives the traveling vehicle 5 to travel is:
It is proportional to the duty of the PWM signal [(the H level width / cycle of the triangular wave) × 100%].

When the distance of the torch 7 with respect to the workpiece 1, that is, the torch height increases and the arc voltage rises, the output signal level of the change amount detector 95 rises and the output of the adder 101, ie, the traveling speed. The level of the command signal increases and the duty of the PWM signal decreases. As a result, the rotation speed of the motor 11 decreases and the traveling speed of the torch 7 decreases. This avoids a decrease in gouging depth due to an increase in torch height. When the torch height decreases and the arc voltage decreases, the output signal level of the change amount detector 95 decreases and the adder 1
01, that is, the level of the traveling speed command signal decreases, and the duty of the PWM signal increases. As a result, the rotation speed of the motor 11 increases and the traveling speed of the torch 7 increases. This avoids an increase in gouging depth due to a decrease in torch height. In this manner, a change in gouging depth due to a change in torch height during the travel of the torch 7 is prevented, and a plasma gouging groove having a substantially constant depth is obtained. Next, an experimental example using the embodiment shown in FIGS. 1 and 2 will be described.

-First Experimental Example- The workpiece 1 having a bend as shown in FIG.
Was subjected to plasma gouging under the conditions shown in the drawing. At this time, the relationship between the variation of the torch height, the variation of the arc voltage corresponding thereto, the torch traveling speed adjusted correspondingly, the depth of the gouging groove obtained by these, and the like. Table 1 shows the relationship between the torch height and the gouging groove depth.
(B) of FIG.

[0020]

[Table 1]

When the torch height fluctuates in the range of 15 to 25 mm and the torch traveling speed is kept constant, for example, from the graph of FIG. The gouging groove depth fluctuates about 1 mm due to
According to the implementation of the above example (Table 1, b in FIG. 6), it can be seen that the fluctuation of the gouging groove depth is within the range of 0.2 mm, and the fluctuation of the groove depth is greatly suppressed. For reference, in a mode in which the fluctuation of the gouging groove depth is suppressed,
FIG. 6 shows the change of the gouging groove width with respect to the change of the torch height.
(C) of FIG.

Second Experimental Example A workpiece 1 having a bend as shown in FIG. 7A was subjected to plasma gouging under the conditions shown in Table 2 below. As shown in FIG. 7B, the material 1 to be processed has a surface of 50 °.
(See FIG. 7B) was welded in two layers, and plasma gouging was repeated twice on the back surface of the Y-groove for the first time and the second time. At this time, the relationship between the variation of the torch height, the variation of the arc voltage corresponding thereto, the torch traveling speed adjusted correspondingly, the depth of the gouging groove obtained by these, and the like. Is shown in Table 2, and the groove cross-sectional shape of the gouging of the workpiece 1 twice is shown by a dotted line in FIG.

[0023]

[Table 2]

In the first gouging, the variation of the torch height is 7 mm at the maximum, and when the torch traveling speed is constant, the depth of the gouging groove varies by about 0.75 mm.
According to the implementation of the above example (Table 2), the variation of the gouging groove depth is within the range of 0.2 mm, and it can be seen that the variation of the groove depth is greatly suppressed. Similarly, in the second gouging, the variation of the torch height is 6 mm at the maximum, and when the torch traveling speed is constant, the depth of the gouging groove varies by about 0.65 mm. If the first without speed correction
If gouging is performed for the first and second times as they are, a depth variation of 0.7 mm + 0.65 mm = 1.4 mm results. According to the implementation of the above example (Table 2), the variation of the gouging groove depth is within the range of 0.3 mm, and it can be seen that the variation of the groove depth is greatly suppressed. In this way, even when the torch height fluctuates by about 13 mm or 14 mm, as shown in Table 2 and FIG. 7C, the gouging groove depth is 6.2 to 6.5 mm, which is only 0 mm. It can be seen that the variation is only 0.3 mm, and the variation in groove depth is greatly improved.

[0025]

As described above, according to the present invention,
Fluctuations in gouging groove depth due to fluctuations in the torch height are greatly suppressed, and the torch is caused by unevenness or bending of the material to be processed or a displacement (in the direction of the torch height) during running of the torch. Even in the case where the height varies, a plasma gouging groove having a substantially constant depth can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing the appearance of a mechanism section according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an outline of a main part of an electric circuit configuration of the embodiment shown in FIG.

3 is a time chart showing a level change of an electric signal of each section of the electric circuit shown in FIG. 2;

FIG. 4A is a front view showing an execution mode and conditions of plasma gouging, and FIG. 4B is a graph showing a relationship between a torch height and an arc voltage obtained by the plasma gouging shown in FIG. It is.

5 (a) is a plan view showing conditions for executing plasma gouging, FIG. 5 (b) is a graph showing a relationship between a torch running speed and a gouging groove depth obtained by the plasma gouging shown in FIG. (C) is a graph showing the relationship between the torch running speed and the gouging groove width.

FIG. 6 is a view showing a first experimental example of plasma gouging using the embodiment shown in FIGS. 1 and 2, (a) is a front view showing an execution mode and conditions of plasma gouging,
(B) is a graph showing the relationship between the torch height and the plasma gouging groove depth obtained by the plasma gouging shown in (a), and (c) is a graph showing the relationship between the torch height and the plasma gouging groove width. It is.

FIGS. 7A and 7B are diagrams showing a second experimental example of plasma gouging using the embodiment shown in FIGS. 1 and 2, wherein FIG. 7A is a front view showing an execution mode of plasma gouging, and FIG. Cross-sectional enlarged view of the material 1 to be processed,
(C) is an enlarged cross-sectional view of the workpiece 1 after plasma gouging.

FIGS. 8A and 8B are diagrams showing one mode of plasma gouging with a constant torch running speed, wherein FIG. 8A is a front view showing the execution mode and conditions of plasma gouging, and FIG.
A graph showing the relationship between the torch height and the depth of the plasma gouging groove, obtained by plasma gouging shown in FIG.
(C) is a graph showing the relationship between the torch height and the plasma gouging groove width.

[Explanation of symbols]

1: Material to be processed 2, 3: Magnet stand 4: Rail 5: Traveling trolley 6: Torch stand 7: Torch 8: Plasma power supply 9: Arc voltage change detection circuit 91: Voltage detector 92 : Arc generation detector 93: timer 94: reference value memory 95: change amount detector 10: motor speed control circuit 101: adder 102: comparator 103: triangular wave generator 104: amplifier 105: motor driver 106: Motor power supply 11: Motor

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hirofumi Sonoda 7-6-1, Higashi Narashino, Narashino City, Chiba Prefecture Nippon Steel Welding Industry Co., Ltd. Equipment Division (72) Inventor Akio Inamura Higashi, Narashino City, Chiba Prefecture 7-6-1, Narashino Nippon Steel Welding Industry Co., Ltd. Equipment Division (56) References JP-A-60-244469 (JP, A) JP-A-58-81564 (JP, A) JP-A-56-109165 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 10/00 501 B23K 10/00 502 B23K 7/06 B23K 9/013

Claims (1)

(57) [Claims] 1. A plasma actor for gouging; a torch supporting means for supporting the torch at a substantially constant angle with respect to a material to be processed; and a torch supporting means and processing. A driving means for driving at least one of the target materials to travel substantially parallel to the other relative to the other, wherein an arc voltage of the plasma actor is detected.
Arc voltage detecting means; an arc voltage detected by the arc voltage detecting means;
Change detection means for detecting a change in the arc voltage; and an arc corresponding to the change in the arc voltage detected by the change detection means.
A driving speed control means for increasing the traveling driving speed of the driving means when the arc voltage decreases, and decreasing the traveling driving speed when the arc voltage increases.