KR100785223B1 - Automatic resistance seam welding machine by dc invert for invar steel welding at the lng carrier - Google Patents

Abstract

An automatic resistance seam welding equipment for invar steel welding of a LNG carrier by DC power inverter is provided to improve welding quality, workability and productivity at the same time by driving the automatic resistance seam welding equipment using a DC power inverter instead of a single-phase DC power. An automatic resistance seam welding equipment for invar steel welding of a LNG carrier by DC power inverter comprises: a welding car(14) on which an electrode wheel(17), a drive roller(18), an air motor(13), an inverter transformer(16), and an air cylinder(15) are mounted to weld weldments; a welding power transfer control car(12) on which a controller, a water cooling unit, a welding power source, etc. are mounted to control welding conditions of the welding car; a power line(19); an air hose(20); and a cooling hose(21), wherein the automatic resistance seam welding equipment is driven by DC power inverter transformed by the inverter transformer.

Description

Automatic resistance seam welding machine by DC invert for invar steel welding at the LNG carrier}

1 is a partial perspective view illustrating a storage tank of an LNG carrier.

2 is a cross-sectional view showing a storage tank structure of an LNG carrier.

3 is a perspective view showing the heat insulation box 9 and the Invar steel strike 2.

4 is a block diagram of an automatic resistance core welding apparatus according to the present invention.

5 is an enlarged view of a portion of FIG. 3.

Fig. 6 is a diagram defining nugget and nugget pitch in automatic resistance core welding.

7 is a view showing the definition of the acceptance criteria and the acceptance criteria of the welded cross section according to the LNG carrier tank source technician welding quality regulations.

FIG. 8 is a diagram illustrating arc monitoring waveforms of real-time welding conditions of a welding nugget welded with a conventional single-phase AC power automatic resistance core welding apparatus.

9 is a view showing the configuration of a welding machine and a control device of the inverter DC power automatic resistance core welding apparatus according to the present invention.

FIG. 10 is a view illustrating arc monitoring waveforms of real-time welding conditions of a welding nugget welded with an inverter DC power automatic resistance core welding apparatus according to the present invention.

11 is a view showing another embodiment of the present invention.

12 is a graph showing the ratio of the maximum current and average current for each current region under the same set current conditions of automatic resistance core welding by single-phase AC power supply and inverter DC power supply.

Fig. 13 is a graph showing the ratio of the maximum current heat amount and the average current heat amount for each current area under the same set current condition of automatic resistance core welding by single-phase AC power supply and inverter DC power supply.

<Description of Major Symbols in Drawing>

1: LNG storage tank 12: welding power transfer control truck

2: Inva steel strike 13: air motor

3: loop 14: welding bogie

4: side 15: air cylinder

5: vertical wall 16: inverter transformer

6: upper slope wall 17: electrode wheel

7: lower inclined wall 18: driving roller

8: side wall 19: power line

9: insulation box 20: air hose

10: Inba steel tongue 21: cooling hose

11: home

The present invention relates to an automatic resistance core welding apparatus used for welding a membrane attached in a storage tank of an LNG carrier.

1 is a partial perspective view showing the storage tank of the LNG carrier, Figure 2 is a cross-sectional view showing the structure of the storage tank of the LNG carrier, LNG storage tank (1) is a polyhedral shape, generally polyhedral shape to the length of the ship Parallel to the

The second insulation box is installed on the inner wall of the double hull of the LNG storage tank 1 and the second membrane is installed in the second insulation box. The first insulation box is installed on the second membrane and the first membrane is installed on the first insulation box to contact the natural gas liquefied at cryogenic temperature (-163 ° C.).

3 is a perspective view showing the heat insulation box 9 and the Invar steel strike 2. Inba steel tongue (10) having a groove (11) in the insulation box (9) is installed, the Inba steel tongue (10) and Inba steel tongue (10) in the middle of the "B" shaped Invar A steel strike 2 is installed to form a membrane. The membrane is provided with a loop 3 and a side 4, vertical and horizontal walls 5 and 8 and upper and lower inclined walls 6 and 7 as shown in Figs.

In the case of the conventional automatic resistance welding apparatus, the controller mounted in the transformer and the welding power moving control trolley uses a si list (SCR) for controlling the phase angle of the single-phase AC power supply.

Therefore, increasing the welding speed to more than 1,600mm / min did not satisfy the welding quality regulations of LNG carrier tank source technicians, and because of the maximum current during welding, the electrode wheel is damaged, so the problem of frequent repair or replacement occurred. In addition, the transformer mounted on the welding trolley is heavy, so the overall weight of the welding trolley increases, so that the safety accidents such as back pain and fall accidents frequently occurred when the worker detached and attached manually.

The present invention has been proposed to solve the above problems, by using an inverter direct current power source instead of a single-phase AC power source to give optimum welding conditions to the membrane thin-walled joint to improve the welding quality and at the same time work efficiency and An object of the present invention is to provide an inverter direct current resistance core welding device for welding LNG carrier Invar steel, which can improve productivity.

Other objects and advantages of the present invention will be described below, which are not limited to the matters set forth in the claims and the disclosure of the embodiments thereof, but also to the broader ranges by means and combinations within the range readily recited therefrom. Add that it will be included.

In order to achieve the above object, the present invention, the electrode wheel 17, the driving roller 18, the air motor 13, the inverter transformer 16, the air cylinder 15 is equipped with a welding bogie ( 14); A welding power source moving control trolley 12 mounted with a controller (not shown), a water cooling device (not shown), a welding power source (not shown), and the like to control welding conditions of the welding trolley 14; Power supply line 19; Air hose 20; And it comprises a cooling hose 21, and proposes an inverter DC power automatic resistance core welding device for welding the LNG carrier Invar steel driven by the inverter DC power transformer transformed by the inverter transformer 16.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible, even if shown on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the following will describe a preferred embodiment of the present invention, but the technical idea of the present invention is not limited thereto and may be variously modified and modified by those skilled in the art.

Conventional automatic resistance core welding apparatus is welded using a single-phase AC power source, the automatic resistance core welding apparatus according to the present invention is characterized in that the welding using an inverter DC power supply will be described in detail.

4 is a block diagram of the automatic resistance core welding apparatus according to the present invention, the automatic resistance core welding apparatus according to the present invention is the electrode wheel 17, the driving roller 18, the air motor 13, the inverter transformer 16, air A welding trolley 14 on which the cylinder 15 is mounted; A welding power source moving control trolley 12 to which a controller (not shown), a water cooling device (not shown), a welding power source (not shown), etc. are mounted; Power line 19; Air hose 20; And a cooling hose 21.

An electrode wheel 17, a driving roller 18, an air motor 13, an inverter transformer 16, and an air cylinder 15 are mounted on the welding trolley 14 to weld the welded portion.

At this time, the electrode wheel 17 receives the inverter direct current power from the inverter transformer 16 to flow a current directly to the base material, and the air cylinder 15 pressurizes the electrode wheel 17 to be welded with good quality. do. In addition, the driving roller 18 allows the welding trolley 14 to find the welded portion, and the air motor 13 allows the welding trolley 14 to travel at constant speed using compressed air. On the other hand, the inverter transformer 16 transforms the single-phase AC power supplied from the welding power source (not shown) into an inverter DC power source.

The welding power source moving control trolley 12 is equipped with a controller (not shown), a water cooling device (not shown), and a welding power source (not shown) to control welding conditions of the welding cart 14.

A controller (not shown) controls the welding cart 14, a water cooling device (not shown), a welding power source (not shown), and the like. The water cooling device (not shown) includes an electrode wheel 17 and an inverter transformer 16. , To drive a drive die (not shown).

5 is an enlarged view of a portion of FIG. 3, in which the Invar steel tongue 10 is installed in the middle and two Invar steel strikes 2 are installed on the side, and the welding is generated by the automatic resistance core welding device. Bead 22 and electrode wheel 17 are shown. And, Figure 6 defines the nugget and nugget pitch in the automatic resistance core welding, Figure 7 shows the definition of the acceptance criteria and acceptance criteria of the weld cross section according to the welding quality regulation of LNG carrier tank source engineer. Where Lt is the maximum width of the nugget, La is the thickness of the neck, e is the height of the nugget, and t is the thickness of the welded material minus the depth of the concave trace.

FIG. 8 is an arc monitoring waveform of real time welding conditions of a welding nugget welded by a conventional single phase AC power automatic resistance core welding device, and shows five nuggets, and one nugget is generated with two cycles and an idle time. Is showing.

Waveform 23 is the forward half period of nugget 1 (cycle 1), waveform 24 is the reverse half cycle of nugget 1 (cycle 1), waveform 25 is the forward half cycle of nugget 1 (cycle 2), and waveform 26 is the reverse half of nugget 1 Cycle (2 cycles).

In this case, it can be seen that the maximum current is 140% of the RMS current (Root Mean Square Current), which is an average current for generating the nugget, and the electric current is supplied to the electrode wheel 17 and the welding part.

In the single phase AC power automatic resistance core welding, the firing timing and the welding current can be adjusted by controlling the firing phase angle using a thyristor (not shown) as shown in the current waveform of FIG. 8. Since the current and voltage of the single-phase AC power supply are commercially available 60Hz and the period for generating one nugget is 3Hz, 20 nugs can be generated per second. Therefore, as the welding speed is increased, the nugget pitch of FIG. 6 increases. As the nugget pitch increases, the average length of La of FIGS. 6 and 7 decreases, and the distribution of La length increases to increase the defective rate.

However, in the inverter DC power automatic resistance core welding according to the present invention, the welding cycle is set based on the current and voltage time by 1 msec (millisecond) by the control of the control circuit 33, the driving circuit 32, and the IGBT 31. Since the welding time is adjusted by adjusting the energization time and idle time, not only can the nugget pitch be kept constant even if the welding speed is increased, but also the average length of La and the dispersion of La length can be kept constant. Can be.

Figure 9 shows the configuration of the welding machine and control device of the inverter DC power automatic resistance core welding apparatus according to the present invention.

A three-phase bridge diode input terminal, which is a rectifier circuit 28, is connected to a three-phase commercial AC power supply 27. The direct current from the output terminal of the rectifier circuit 28 is smoothed in the smoothing circuit composed of the coil 29 and the condenser 30 and then input to the IGBT 31 which is a switching element. This IGBT 31 direct current is exchanged by the high frequency alternating current of rectangular wave form by a high frequency switching operation. The pulse width of the IGBT 31 is controlled from the control circuit 33 via the drive circuit 32. The high frequency AC current output from the IGBT 31 is changed into a high frequency AC current that is stepped down through the primary and secondary coils of the transformer 34. This high-frequency alternating current is exchanged by direct current by the rectifier circuit 35 composed of diodes, and two currents are supplied to the welded material 37 via the electrode wheel 17.

In addition, the inverter DC power automatic resistance core welding apparatus according to the present invention is required to flow a constant welding current at all times, even if there is a variation in the welding power supply voltage (AC 220V / 440V) and the molding dispersion of the metal material to be welded in order to perform a stable resistance core welding. According to the feedback of the welding current to control the flow of welding current of a constant size all the time.

Since the welding current is very high current of several thousand A to tens of thousands of A, the current is detected using an air core coil or hall sensor 38. Therefore, it is performed by controlling the base drive pulse width of the IGBT 31 so that the welding current is always constant. As described above, the Hall sensor 38, the secondary current measurement and conversion circuit 39, the control circuit 33, and the drive circuit 32 are controlled by feedback control for substantially matching the secondary current of the automatic resistance core welder to the set current value. It configures constant current control circuit of PWM (Pulse Width Modulation) method.

FIG. 10 is an arc monitoring waveform of real time welding conditions of a welding nugget welded by an inverter DC power automatic resistance core welding apparatus according to the present invention. The five nuggets are shown and one nugget is generated by one welding period.

Here, the maximum current has a current value almost similar to the root current square current (RMS), which is an average current for generating a nugget. In one cycle, the energization time and the rest time can be adjusted in units of 1 millisecond, so a constant ratio (1: 1, 1.5: 1, 2: 1, 2.5: 1, 3: 1, 3.5: 1, 4) (1, etc.), and can be welded.

In addition, the inverter DC power automatic resistance core welding apparatus according to the present invention can be welded by setting one cycle to 10 to 50 msec (millisecond), when welding is set to one cycle to 25 to 50 msec (millisecond) of FIG. The average La length increases and the La length spread becomes small, so that welding defects can be minimized.

FIG. 11 shows that in another embodiment of the present invention, two cycles 40 and 41 and one idle time are required to generate one nugget with an inverter DC power automatic resistance core welding apparatus. And in addition to this, the inverter DC power automatic resistance core welding apparatus according to the present invention can be controlled to generate a nugget with a plurality of cycles (1 to 5) and idle time.

12 is a graph showing the maximum current and average current ratio for each current region under the same set current conditions of automatic resistance core welding by single phase AC power supply and inverter DC power supply, where the maximum current and average of the single phase AC power supply are higher than those of the inverter DC power supply. It can be seen that the current ratio is higher.

Fig. 13 is a graph showing the ratio of the maximum current heat and average current heat for each current region under the same set current condition of automatic resistance core welding by single phase AC power supply and inverter DC power supply, where the maximum current of single phase AC power supply is higher than that of inverter DC power supply. It can be seen that the ratio of calories and average current calories is higher, which is a factor that shortens the electrode wheel life due to deterioration of the electrode wheel. Therefore, if the inverter DC power automatic resistance core welding can be used longer than the single-phase AC power automatic resistance welding, the electrode wheel can be used longer, and the electrode does not need to be frequently cleaned or replaced, thereby maximizing productivity.

The above description is merely illustrative of the technical idea of the present invention, and various modifications, changes, and substitutions may be made by those skilled in the art without departing from the essential characteristics of the present invention. will be. Accordingly, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by the embodiments and the accompanying drawings. . The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, since the automatic resistance core welding device is driven using an inverter DC power supply instead of a single-phase AC power supply, the welding quality is improved by providing the optimum welding condition to the membrane thin film joint, and at the same time, the work efficiency and The effect of improving productivity occurs.

Other effects of the present invention, as well as those described in the above-described embodiments and claims of the present invention, as well as potential effects that may occur within the range that can be easily estimated therefrom and potential advantages that contribute to industrial development It will be added that it will be covered by a wider scope.

Claims (5)

A welding cart 14 to which the electrode wheel 17, the driving roller 18, the air motor 13, the inverter transformer 16, and the air cylinder 15 are mounted to weld the welded portion; A welding power source moving control trolley 12 mounted with a controller (not shown), a water cooling device (not shown), a welding power source (not shown), and the like to control welding conditions of the welding trolley 14; Power supply line 19; Air hose 20; And a cooling hose (21), wherein the inverter DC power automatic resistance core welding device for welding an LNG carrier Invar steel driven by an inverter DC power source transformed by the inverter transformer (16). The method of claim 1, The inverter DC power automatic resistance core welding device for welding the LNG carrier Inva steel, the LNG carrier Inva steel welding, characterized in that the welding can be set by setting a period of 10 to 50 msec for one welding nugget. Automatic resistance core welding device for inverter DC power supply. The method of claim 1, The inverter DC power automatic resistance core welding device for welding the LNG carrier Inva steel, characterized in that the energization time and the rest time can be adjusted in units of 1 msec (millisecond) in one cycle of welding for generating one welding nugget. Inverter DC power automatic resistance core welding device for welding LNG carrier Invar steel. The method of claim 1, The inverter DC power automatic resistance core welding device for welding the LNG carrier Invar steel has a constant ratio (1: 1, 1.5: 1, 2: 1) of energization time and idle time in one cycle of welding for generating one welding nugget. , 2.5: 1, 3: 1, 3.5: 1, 4: 1) Inverter DC power automatic resistance core welding device for welding LNG carrier Invar steel, characterized in that the welding can be set. The method of claim 1, The inverter DC power automatic resistance core welding device for welding the LNG carrier Inva steel, the inverter DC power automatic resistance core welding for welding the LNG carrier Inva steel, characterized in that for generating one nugget with one to five cycles and idle time. Device.

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