KR20010058301A - High frequency electric resistance welding and apparatus for preventing penetrator defect - Google Patents

Abstract

PURPOSE: A method and a device for high frequency welding for preventing penetrator are provided to make a joint part of clean melting point by removing the penetrator generated by bonding oxidized molten metal in a state that the oxidized molten metal is inserted into the joint part due to bridges formed at both ends of the joint part by the molten metal and weak electromagnetic repulsive force. CONSTITUTION: A device for high frequency welding for preventing penetrator includes a controlling part(190), an UVR(Under Voltage Regulator)(170), and an inductor(180). The controlling part outputs various DC signals by controlling a rectifying part(110) and outputs control signal for controlling each of functional parts. The UVR performs an on-off action according to control signal of the controlling part. The inductor is connected with the UVR and connected in parallel with a sliding contact point(150) according to an on-action of the UVR.

Description

High frequency welding method and apparatus for preventing intrusion defects {HIGH FREQUENCY ELECTRIC RESISTANCE WELDING AND APPARATUS FOR PREVENTING PENETRATOR DEFECT}

The present invention relates to a high frequency welding method and apparatus for press forming a hot rolled steel sheet into a shape of a steel pipe by rolling and then fusion bonding the joint by a high frequency current. Particularly, a bridge of molten metal is formed on both ends of the joint. The invention relates to the creation of joints of clean and healthy molten contacts by eliminating intrusion defects caused by the bonding of molten metal oxides invading the joints due to the change of the path of the high frequency current and the weakening of the electromagnetic repulsive force. .

The steel pipe is press-molded a hot rolled steel sheet into the shape of a steel pipe, and then hot-rolled at both ends of the joint of the hot rolled steel sheet by high frequency electric resistance welding (HF ERW) to oxide the joint or the welded portion. Alternatively, when foreign matter is present and present, it becomes a defective product that is not able to exhibit performance as a sealed pipe.

Therefore, defects caused by the intrusion of oxides or the like into the joints or welded portions of the steel pipe are called penetration defects, and removing or preventing the penetration defects is one of the most important technologies in steel pipe manufacturing technology.

Hereinafter, a high frequency electric resistance welding apparatus according to the prior art will be described with reference to the accompanying drawings.

1 is a schematic diagram of steel pipe manufacturing by a general steel pipe manufacturing apparatus, Figure 2 is a current flow simulation diagram of high-frequency electrical resistance welding, Figure 3 is a molten metal oxide to the outside by electromagnetic repulsion generated in the welding surface of the steel pipe joint Figure 4 is a state in which the bridge is formed in the joint portion during the steel pipe manufacturing process, Figure 5 is a schematic diagram of the intrusion defect state in which the molten metal oxidized by the prior art intruded into the joint portion between the two end surfaces. 6 is a functional block diagram of a high frequency welding apparatus according to an embodiment of the prior art, and FIG. 7 is a macroscopic and microscopic photographic view of a joint portion in which an intrusion defect is generated by a high frequency electric resistance welding of the prior art.

Referring to the accompanying FIG. 1, steel pipe manufacturing by a general steel pipe manufacturing apparatus, the steel pipe shape 20 formed by rolling a hot rolled steel sheet (Roll),

An impeller 10 serving as a guide so that the steel pipe shape 20 is supplied to the steel pipe manufacturing apparatus without being separated;

Two sliding contacts 30 to apply a high frequency current to both end surfaces to form a joint of the steel pipe shape 20,

Both ends of the hot rolled steel sheet having the steel pipe shape 20 are melt-bonded by applying pressure in a state where high frequency currents applied from the two sliding contacts 30 are melted by heat generated by resistance. The junction 50 consists of two pressure rolls 40 which create a continuous joint 55.

The current flow of the high-frequency electrical resistance welding according to the attached Figure 2, the width 'W' that the sliding contact 30 is in contact with the upper end of both ends of the steel pipe shape 20,

'T' representing the thickness of the hot rolled steel sheet forming the steel pipe shape 20,

Paths 'A' and 'B' through which high-frequency currents flow,

Direction X flows according to Fleming's law; The direction in which the magnetic field is formed 'Y'; It consists of the direction 'Z' in which electromagnetic repulsion is formed.

3 is a state in which high frequency current is applied to both end faces of the steel pipe shape 20 so that the molten metal oxide 22 is discharged to the outside end faces 24 of the hot rolled steel sheet by electromagnetic repulsive force P. This is a state diagram in which the pressure F is applied by the pressure roll 40.

4 is a molten oxidation discharged by electromagnetic repulsion to a welding point WP and a welding point WP which are melt-bonded by high frequency currents flowing in both end surfaces 24 of the steel pipe shape 20. The state in which the bridge 26 is formed by the metal 22 and the metal that is excessively molten in the joint portion is shown.

The attached FIG. 5 shows a Penetrator state caused by the molten oxide 22 being refluxed or invaded by a capillary phenomenon in the joint portion.

6 is a functional block diagram of a high frequency welding apparatus according to the prior art, the rectifier 110 for receiving a three-phase AC voltage, converting to a DC voltage and rectifying and outputting the same. )Wow

A high frequency modulator 120 for modulating a direct current (DC) applied from the rectifier 110 into a high frequency (HF) signal and outputting the modulated signal;

A matching transformer 130 which receives the signal output from the high frequency modulator 120 and lowers the voltage and increases the current and outputs the winding ratio of the input side greater than the winding ratio of the output side;

A frequency variable unit 140 capable of variably adjusting the frequency of the high frequency signal output from the matching transformer unit 130 to a low frequency as necessary;

A sliding contact 150 for applying a high current high frequency (HF) signal applied from the frequency variable part 140 to the joint portion of the steel pipe shape 20;

The welding joint is output by monitoring and processing a signal output from the frequency variable part 140 and applied after passing through both end surfaces 24 of the steel pipe shape 20 by the sliding contact 150. And a control unit 160 which extracts and processes the current, voltage, supply power, and frequency of the high frequency signal applied to both end surfaces 24, which are portions, and outputs a control signal for controlling the rectifier 110.

Hereinafter, a high frequency welding apparatus according to the related art having the above configuration will be described in detail with reference to the accompanying drawings.

In order to manufacture the flat hot rolled steel sheet in the form of a pipe (Rope), by pressing sequentially using a roll (Roll), to make a shape close to the pipe (Pipe) shape.

As described above, the steel pipe shape 20 made of the hot rolled steel sheet is prevented from being separated through the impeller 10 and then put into a high frequency electric resistance welding (HF ERW) device.

Sliding contact 150 corresponding to the width 'W' is in contact with both upper ends of the joint portion of the steel pipe shape 20 to apply the high frequency current.

Referring to FIG. 6, a high frequency welding device for supplying a high frequency current receives a three phase high AC voltage signal from the rectifier 110 and converts it into a low AC voltage. Later, the rectifier is output as a direct current (DC) signal, and the high frequency modulator 120 receives the direct current signal output from the rectifier 110 and modulates the signal into a high frequency (HF) signal having a high frequency. And print it out.

The reason for the high frequency modulation and output as described above is to use the propagation characteristics of the signal inside the conductor. The higher the frequency is, the skin effect is to be transmitted along the surface. Is to use the characteristics that are about to be transmitted.

Therefore, when the high-frequency modulated high current signal is applied to the joint of the steel pipe shape 20 to be welded, the high current flows only to the skin portion of both end surfaces 24.

The high frequency signal output from the high frequency modulator 120 is applied to the matching transformer 130 to downconvert to a low voltage and simultaneously amplify a current at a rate inversely proportional to the turns ratio.

As described above, the frequency variable unit 140 that receives the high frequency high frequency signal output from the matching transformer 130 may downwardly change the high frequency signal, which is a high frequency signal, to a high frequency signal of a low frequency.

The high frequency signal is such that the current supplied by the Skin Effect flows only to the welded joint site, i.e., flows to both end faces 24 of the steel pipe shape 20, thereby providing both end faces 24. Heat is generated by the resistance of the two end surfaces 24 are melted to become molten metal 22.

When the high frequency of the low frequency is generated in the frequency variable part 140, the welding material is to be heated evenly throughout the welding process for the post-processing of the welded portion.

As described above, the high-frequency signal of the high current output from the frequency variable part 140 flows to both end surfaces 24 through the sliding contact 50, and the skin of both ends 24 is affected by the skin effect of the high frequency signal. Since only a high current flows through the skin, both end surfaces 24 are melted, exposed to air, and oxidized.

At this time, the molten metal oxide 22 is pushed out by being pushed by a force F at right angles from a plane formed by the current I and the magnetic field B by the law of framing.

Expressing the discharge action as the electromagnetic repulsive force (P), 'P' is expressed as the following equation.

P = JμH

In the above, J represents heat input or joule heat, μ represents permeability, and H represents magnetic field.

In the high frequency welding apparatus as described above, as shown in FIG. 2, a high frequency current is applied from the sliding contacts 30 and 150 through the 'A' path, and both end surfaces 24, which are joints formed by the 'A' path, are illustrated in FIG. 3. Likewise, both end surfaces 24 of the steel pipe shape 20 are melted to form the molten metal 22, and the molten metal oxide 22 connected to the air by electromagnetic repulsive force 'P' is in the 'Z' direction in FIG. That is, since it is pushed out as shown in FIG. 3, the molten metal 22 of the both end surfaces 24 remains only the unoxidized molten metal 22, and the pressure applied from both sides by the pressure roll 40. Since both end faces 24 are pressed by (F), the welded portion of the steel pipe shape 20 is completed by forming a joint 55 while continuously forming the fusion-bonded joining point 50.

However, as shown in FIG. 4, when the amount of the molten metal 22 increases, a bridge is formed at one point between the sliding contacts 30 and 150 and a welding point (WP) by the path 'A'. (26) occurs, the high frequency current supplied from the sliding contact 150 flows in the 'B' path by the bridge 26, so that the bridge 26 and the welding point (WP) between the Since the high frequency current flows by half, the electromagnetic repulsive force P weakly acts, and the molten metal oxide 22 that cannot be discharged flows back into or flows again by a capillary phenomenon as shown in FIG. 5. Indicates a fault.

As the pressure bonding proceeds by the pressure P applied by the pressure roll 40 even in the state where the Penetrator is generated as described above, the weld surface of the joint is healthy by the oxidized molten metal 22. This leads to loss of welding and poor welding.

As described above, the depth at which Penetrator occurs due to reflux can be expressed by the following equation.

S = t Root (2γ / ρb)

In Equation 2, t is the thickness (T) of the welding material, γ is the surface tension of the molten metal, ρ is the density of the hot-rolled steel sheet metal, b is the gap between the two end surfaces 24 of the welding material.

In the prior art as described above, the welding process itself, such as changing the pressing force (F) by the pressure roll 40, or changing the high frequency current (I) in order to prevent the penetration defect (Penetrator), but adjusted such As a measure, the Penetrator could not be completely removed, resulting in a problem of poor quality at the welding site.

7 is a macroscopic and microscopic image of a weld seam where a penetration defect is generated by a high frequency welding of the prior art. The black streaks in the microscopic photographs are intrusion defects.

The present invention detects a change in resistance caused by a bridge of molten metal generated in a high frequency welding path, lowers the impedance of the welding path, and simultaneously increases the amount of current applied thereto, thereby increasing the electromagnetic repulsive force to remove the bridge and intrusion defects. It is an object of the present invention to provide a method and apparatus for preventing intrusion defect prevention high frequency welding.

The present invention devised in order to achieve the above object, forming and pressing a hot rolled steel sheet into a steel pipe shape and applying a high frequency current through a sliding contact, and the applied high frequency current is generated on both end surfaces of the junction of the hot rolled steel sheet In the high-frequency electrical resistance welding method for producing a steel pipe by applying a pressure to make both ends of the molten metal state using a heat of resistance, the both ends of the molten state is welded to the welding point, the amount of the molten metal is increased, In the case where a bridge is formed in front of the welding point, electromagnetic coupling force between the bridge and the welding point is weakened due to the high frequency current flowing through the bridge, thereby preventing the intrusion coupling in which impurities invade by the bridge between both ends of the junction. While detecting that the component value falls, the amount of high frequency current applied is Increasing, characterized in that the anti-intrusion coupling high frequency welding method for restoring and increasing the electromagnetic repulsive force to remove the bridge,

In addition, in the high frequency welding device comprising a rectifying part, a high frequency part, a matching transformer part, a sliding contact and a control part, the resistance change by the bridge of the welding path output from the frequency variable part and the high current flows, and the changed resistance and A control unit for detecting a voltage change due to a current, an under voltage regulator (UVR) for reducing the impedance of the welding site under the control of the control unit, and an inductor connected in parallel with the welding site and reducing the composite impedance Characterized in that the intrusion coupling prevention high frequency welding device is configured.

1 is a schematic diagram of steel pipe manufacturing by a general steel pipe manufacturing apparatus,

2 is a current flow schematic of high frequency electric resistance welding;

3 is a state diagram in which molten metal oxide is discharged to the outside by electromagnetic repulsive force generated at the welding surface of a steel pipe joint;

Figure 4 is a state in which a bridge is formed in the joint portion in the steel pipe manufacturing process,

5 is a schematic diagram of an intrusion defect state in which molten metal oxidized by the prior art intrudes into a joint portion between both end faces,

6 is a functional block diagram of a high frequency welding apparatus according to an embodiment of the prior art,

7 is a macroscopic and microscopic photographic view of a joint in which an intrusion defect is generated by a high frequency electric resistance welding of the prior art;

8 is a functional block diagram of a high frequency welding apparatus according to an embodiment of the present invention,

9 is a macroscopic and microphotographic view of a seam welded by the technique of the present invention,

10 is a photographic view of the state in which the bridge is moved by the technique of the present invention.

** Explanation of symbols on the main parts of the drawing **

10: Impeder 20: Steel pipe shape

22: molten metal 24: both cross-section

30,150: sliding contact 40: pressure roll

50: junction 55: joint

110: rectifier 120: high frequency modulator

130: matching transformer 140: frequency variable portion

160,190: control unit 170: UV

Hereinafter, with reference to the accompanying drawings will be described an intrusion defect prevention high frequency welding method and apparatus according to the technology of the present invention.

Figure 8 is a functional block diagram of a high frequency welding apparatus according to the technique of the present invention, Figure 9 is a macroscopic and microscopic photographic view of the welded portion according to the technique of the present invention, Figure 10 is a bridge according to the technique of the present invention It is photography of moving state.

Referring to the accompanying drawings as described above, intrusion coupling prevention high frequency welding method according to the technique of the present invention, by pressing the hot rolled steel sheet into a steel pipe shape 20 and applying a high frequency (HF) current through the sliding contact 30 In addition, the applied high-frequency current makes the both end surfaces 24 into the molten metal 22 state by using resistance heat generated by the surface resistance of the junction both ends 24 of the hot rolled steel sheet 20. In the high-frequency electrical resistance welding method for producing a steel pipe by applying a pressure (F) to the molten metal 22 of the both end surfaces to join the welding point (WP),

When the amount of the molten metal 22 increases and a bridge is formed in front of the welding point WP by the molten metal 22, the high frequency current flows through the bridge. When the amount of current flowing between the bridge and the welding point decreases, the electromagnetic repulsive force is weakened, and the intrusion coupling in which impurities are infiltrated is measured and detected that the resistance component value is lowered by the bridge in the controller. Control the rectifier 110 to increase the amount of high-frequency current output, and under the control of the control unit to control the under voltage regulator (UVR) to connect the inductor in parallel between both end surfaces (24) By reducing the coupling impedance to increase the electromagnetic repulsive force, characterized in that to remove the bridge (Bridge),

In addition, another feature is that the rectifier 110 for receiving a three-phase high AC voltage signal is lowered and converted to a DC voltage, and outputs the DC signal output from the rectifier 110, the high frequency (HF) A high frequency modulator 120 for modulating and outputting a signal, a matching transformer 130 for lowering a voltage of the signal output from the high frequency modulator 120 and amplifying a current, and the matching transformer 130 from the matching transformer 130. The frequency variable part 140 for varying the frequency of the output high frequency and the signal of the high frequency current output from the frequency variable part 140 are applied to both welded end surfaces 24 of the hot-rolled steel sheet 20. In the high frequency welding device comprising a sliding contact (30,150) and the control unit 190 for measuring the resistance, current and voltage detected through the sliding contact 150 and the welding both ends 24,

When the resistance or impedance value and the voltage value of the both end faces 24 detected through the sliding contact 150 are lower than a predetermined reference value, the rectifier 110 is controlled to provide a high voltage DC signal. A controller 190 for outputting and outputting a control signal for controlling each functional unit;

UV (UVR) 170 for performing an On / Off switch operation according to the control signal of the controller 190,

It is configured to include an inductor (180) connected to the UV ball 170 and connected in parallel with the sliding contact 150 by the On (On) operation of the UV ball 170. .

Hereinafter, with reference to the accompanying drawings the present invention of the above configuration will be described in detail.

The hot rolled steel sheet is pressurized into a steel pipe shape 20 by roll rolling, and a high frequency current is applied to both end surfaces 24 by the sliding contacts 30 and 150, and is applied by resistance components of both end surfaces 24. The high frequency current is changed into heat, and at the same time, the end portions of both end surfaces 24 are melted.

The molten metal 22, which is the molten metal as described above, is oxidized while being in contact with air, and is pushed in the 'Z' direction by the electromagnetic repulsive force (P) of Equation (1).

However, when the amount of the molten metal 22 is increased, and the bridge 26 is formed as shown in FIG. 4 by the remaining portion even after being discharged by the electromagnetic repulsive force P, the sliding contact ( The high frequency current applied through the 30,150 flows through two paths, that is, the 'A' path and the 'B' path, so that the high frequency current flowing through the 'A' path is halved.

Therefore, the magnetic field generated by the current flowing in the 'A' path is halved as described above, and the electromagnetic repulsive force P is weakened, so that the oxide of the molten metal 22 in the 'A' path is 'Z'. It becomes very difficult to be discharged in the direction of '.

In addition, since the resistance component of the path 'B' shortened by the bridge 26 is also reduced, the voltage detected from both ends 24 from the outside is also lowered.

As described above, the controller 190 detects the resistance values, the voltage values, the frequency values of the high frequencies, and the like, from the sliding contacts 30 and 150, from the sliding contacts 30 and 150.

That is, the controller 190 applies a control signal to the rectifier 110 when the resistance value detected through the sliding contacts 30 and 150 is lower than a predetermined value, so that the rectifier 110 outputs a large current. After being applied to the matching transformer unit 130 through the high frequency modulator 120 and amplified by a large current, the frequency variable unit 140 is applied to both welded end surfaces 24.

At the same time, the controller 190 applies a control signal to the UV 170 to turn it on, and the inductor 180 connected to the UV 170 is connected in parallel with the sliding contact 150. In this state, the impedance components of the both end surfaces 24 and the impedance components of the inductor 180 are reduced in parallel.

As described above, the value of the high frequency current output from the frequency variable part 140 is increased, and the impedance value of both end surfaces 24 is decreased, so that the magnetic field energy is increased by the following equation.

^{W = LI 2/2 = NIψ} / 2

In the above formula, W is the magnetic field energy, L is the impedance, N is the number of turns of the inductor, I is the current, and ψ is the magnetic flux.

As shown in the above equation, although the inductor L decreases, it does not have a great influence on the magnetic field energy W. However, since the current I is proportional to the square, a small change causes a large influence on the magnetic field energy W. Go crazy.

Since the change of the magnetic field energy (W) as described above changes the magnetic field (H) of Equation 1, the bridge (26) generated in the path 'A' is removed by the increased electromagnetic repulsive force (P) This removes the path 'B'.

The state in which the welding point WP appears as the bridge is removed by the increased electromagnetic repulsive force P as described above can be observed by the photograph of FIG. 10.

Referring to the arrow portion shown below the upper left picture of FIG. 10, the state in which both end faces 24 of the steel pipe shape 20 are separated from the left is shown by a black line, and a bridge 26 is formed near the arrow to form both. Cross section 24 appears to be joined.

Referring to the upper middle photograph of FIG. 10, the repulsive force is increased by the increased current, and the bridge 26 is partially removed from the left side so that the gaps between the two end surfaces 24 appear as black lines until the arrow direction. do.

By repeating this process, referring to the lower right picture of FIG. 10, it can be confirmed that the bridge 26 is removed to the welding point WP.

When all of the bridges 26 are removed as described above, the resistance values of both end surfaces 24 measured from the sliding contact 150 are increased again, and the increased resistance values are controlled by the controller 190. By detecting and measuring, the rectifier 110 is controlled to return the output current to the original state, and at the same time, the UV 170 is controlled to be in an off state, the inductor 180 is It is separated from the sliding contact 150.

Therefore, the current applied to both end surfaces 24 through the sliding contact 150 is a normal current flows.

It can be seen in FIG. 9 that the photographs of macroscopic and microscopic shapes of seamlessly manufactured steel pipes without penetration defects by the technique of the present invention as described above are attached.

In the high frequency welding method and apparatus according to the technique of the present invention as described above, the control unit senses that the resistance value decreases by a bridge caused by the increased amount of molten metal that melts both end faces of the steel pipe material. By controlling the increase in the amount of current flowing, it is characterized by increasing electromagnetic repulsion and removing the bridge generated as the molten metal is oxidized.

In addition, at the joining joint, there is an industrial use effect to secure the integrity of the steel pipe to be produced and to improve the reliability and productivity of the steel pipe by preventing invasive bonding by molten metal oxide.

Claims (3)

Forming and pressing the hot rolled steel sheet into a steel pipe shape and applying a high frequency current through a sliding contact, and making both ends of the molten metal state by using resistance heat generated by the applied high frequency current on both surfaces of the joints of the hot rolled steel sheet. In the high frequency electrical resistance welding method for producing a steel pipe by applying pressure so that both end surfaces of the molten state is welded to the welding point, When the amount of the molten metal increases, when the bridge is formed in front of the welding point, the high frequency current flows through the bridge, so that electromagnetic repulsive force is weakened between the bridge and the welding point, and the intrusion coupling in which impurities are introduced. Intrusion coupling prevention high frequency welding method characterized in that the detection of the resistance value between the two ends of the junction by the bridge, and at the same time increases the amount of high-frequency current output, and by removing the bridge by increasing the electromagnetic repulsive force. According to claim 1, The resistance value change is measured by the control unit, and the amount of high frequency current output by controlling the rectifier is increased to a predetermined size, and the intrusion coupling prevention high frequency welding method characterized by reducing the impedance of the joint part by controlling the UEL. A rectifier for lowering the voltage by applying a three-phase AC voltage and converting it into a DC voltage, a high frequency modulator for modulating the DC signal into a high frequency signal, a matching transformer for lowering the voltage of the signal output from the high frequency modulator and amplifying the current; And a frequency variable part for varying the frequency of the high frequency output from the matching transformer, a sliding contact for applying a high frequency current signal output from the frequency variable part to both end faces of the hot-rolled steel sheet-shaped welding, and welding through the sliding contact. In the high frequency welding device comprising a control unit for measuring the resistance, current, voltage detected through both end faces, A control unit for controlling the rectifying unit to output a large number of direct current signals and outputting a control signal for controlling each functional unit when the resistance and voltage values detected through the sliding contact point are lower than a predetermined reference value; A u-ball operating by the control signal of the control unit; And an inductor connected to the yuv and connected in parallel with the sliding contact by the free operation of the yuv.