Modern degaussing method for Russian pipeline before welding
Compiled by Xu Guizhi
(Nanjing Aviation Accessories Factory 2 10002)
The causes of residual magnetism in steel pipe and its influence on welding quality are analyzed. Introduction of Russian pipeline welding.
Degaussing process and previous degaussing methods. The production practice proves that this method is practical and effective.
Keywords:: pipeline steel pipe welding residual magnetic degaussing technology
Causes of 1 remanence and its influence on welding quality
In the construction and repair of gas pipelines for welding operations, there are
There will be a phenomenon that magnetic bias blowing affects the welding process. Magnetic bias
This formation is the result of residual magnetism in pipeline metal. Generally, remanence is divided into
There are two kinds of induction magnetism and process magnetism. Induced magnetism usually results from
In the process of pipe making in the factory, such as metal melting and electromagnetic lifting.
When the machine is loading and unloading, the steel pipe stops in a strong magnetic field and is completed by magnetization.
Nondestructive testing, steel pipes placed near strong power supply lines, etc. Process magnetism
Sex often occurs in assembly welding operations and magnetic clamping.
When welding pipes with direct current, such as long-term contact.
Electrical conductor, exposed part of conductor or welding connected with DC power supply.
Short circuit between fixture and pipeline, etc.
When welding magnetic steel pipes, it is often seen that the arc is ignited.
Difficulties, destruction of arc combustion stability, deviation of arc in magnetic field
Splash of molten metal and slag in molten pool.
In order to stabilize the welding process and improve the quality of welded joints, a magnetic field is applied.
Melted steel pipes should be demagnetized before welding. It should be noted that being welded
It is difficult to completely degauss the connected steel pipes. So, when remanence
When it is not enough to affect the welding quality, welding is allowed.
2 degaussing method of Russian pipeline welding
Pipeline welding and welding or semi-finished products base under field conditions
Degaussing is especially necessary during maintenance. Formulated by relevant Russian departments
The corresponding pipeline degaussing process documents are introduced. This document contains contemporary
Advanced experience of similar operations at home and abroad.
2. 1 degaussing process
Aiming at degaussing before welding, a single steel pipe and a steel pipe were made.
The degaussing process at the butt joint includes the following contents: ① Determine the steel pipe residue.
The magnitude and direction of the magnetic field; ② Degaussing method, system diagram and
Technical means; Finally, the degaussing method of steel pipe or welding is selected.
Degaussing the butt joint; (4) Check the remanence after degaussing.
Whether it meets the requirements.
2.2 degaussing method
In the established process documents, the following degaussing is specified.
Methods: Using direct current or alternating current, and with the help of electromagnet or
Magnetic field method for permanent magnet establishment.
Analysis of remanence parameters (see table 1), combined with the specific construction site
Conditions (such as given equipment, etc.). ), choose degaussing method and system.
Table 1 remanence grade and welding conditions
Welding conditions of remanence grade remanence induction intensity (× 10 T)
Weak < 20 without degaussing
Medium 2O~ 100 degaussing
High > 100 degaussing
Electromagnetic composed of welding wire with cross section of 35 ~ 50 mm
Coil to complete the degaussing of DC and AC. The wire is wound on steel.
Winding one or two butted steel pipes according to the remanence of the steel pipes.
Coils with different turns. When demagnetizing with direct current, electricity must be used.
Welding rectifier or converter with current of 5o0 ~ 1 000a, in which
Including multiple stations. When degaussing with alternating current, the current is 500.
~ 1 000a welding transformer. All power supplies used shall be
There are remote control and current adjustment devices, allowing the use of stable rheostat. while
It is recommended to use portable ammeter when degaussing welding transformer.
The degaussing current is measured by measuring cards LI-4505 and LI-450 1. borrow
In order to help the special electromagnet degauss, welding rectifier or transformer should be adopted.
The compressor is used as the power supply, as shown in figure 1(a). Degaussing with a permanent magnet
, no power supply is needed, as shown in figure 1(b) and (c).
Steel tube degaussing is divided into three grades, as shown in Table 1.
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Welded pipe September 2002
Fig. 1 electromagnet (a) and c-shaped permanent magnet (b)
And a cylindrical permanent magnet (c) for demagnetizing the butting end.
1 degaussing steel tube 2 electromagnet 3 welding wire
4 DC welding power supply 5 C permanent magnet 6 cylindrical permanent magnet
When degaussing, the magnetic field should be greater than the residual magnetic field:
H a ( 1.2 ~ 1.5) h！
Where h is the degaussing magnetic field strength;
H. residual magnetic field strength.
The degaussing magnetic field strength is determined by the following formula:
common jasmin orange
The coil is electrified. a；
Degaussing coil turns;
L- winding length, m.
To measure magnetic force. LIMI 1 97 X magnetic force is recommended.
Rice. Magnetometer is a portable instrument used to evaluate the space of magnetic system.
Magnetic induction intensity of pulsating magnetic field and leakage magnetic field in air gap.
The instrument consists of a measuring converter, an electronic device and a charging device. instrument
The power supply of the watch is 9V battery-mounted battery pack and magnetometer technology.
The surgical features are shown in Table 2.
(1)DC degaussing DC degaussing process is as follows:
(1) Determine the magnitude and square of the residual magnetic field of the steel pipe with the aid of a magnetometer.
Table 2 Technical characteristics of magnetometer
The measured magnetic induction intensity ranges from (×10t)1~1999.
Lower limit of sensitivity (× 10 T) 1
Time to adjust work specifications 30
Continuous working time after power supply charging (h) 8
Overall dimensions of electronic equipment 1 70×60×35
(mm×mm×mm) Charging device parts 70×70×30
Mass electronic equipment 0.35
(kg) measuring transducer 0.35
Arrive; (2) Flexible welding with a cross section of 35 ~ 50 mm is arranged on the steel pipe.
Connect a coil of wire to one or two sequences.
Connect the welding converter so that the direction of the magnetic field formed by it is the same as that of the welding converter.
The residual magnetic field of the steel pipe acts in the opposite direction, as shown in Figure 2; (3) Degaussing.
Fig. 2 Degaussing system diagram of DC single steel pipe (middle part).
1 degaussing steel tube 2 welding wire 3 DC welding power supply
At first, the current was 8O ~ 1OOA. (4) in the process of degaussing, will
It is necessary to regularly check the degaussing magnetic field on the steel pipe with a magnetometer.
Result (measured when the power is turned on). When necessary, control the power.
Flow or change its direction (used to weld converters to change conductors)
Line method). ⑤ After degaussing, in order to smoothly demagnetize.
When connected, the current should be gradually reduced within 1 min until it is zero.
Then cut off the power.
DC degaussing can be realized according to several schemes.
Degaussing a single steel pipe, first one end of the steel pipe is wound around the outer ring for 8-8 times.
12 turn coil is degaussed with maximum magnetic field value; And then use the same
Weipu information
Xu Guizhi, Volume 25, No.5: Modern degaussing methods for Russian pipelines before welding.
The sample method is degaussing at the other end of the steel pipe.
When a single steel pipe is degaussed to the joint of steel pipes, two steels are removed.
At the end of each pipe, the distance between pipes shall not be less than 300 mm.
Winding 18 ~ 20 turns of coil on the surface of 80 ~ 100 mm, and according to the drawings.
3(a) Method of completing degaussing.
Fig. 3 Degaussing system diagram of DC steel pipe before butt assembly.
L a degaussing steel tube 2 a welding wire 3 DC welding power supply
4 electrode clip with covering electrode 5 metal plate
In some cases, it is recommended to combine the electrode holder with the metal plate.
See Figure 3(b) for the degaussing scheme of the chip connected to the electrical system. Will be installed.
Under the current of 300 A, the covering electrode in the electrode fixture is short-circuited with the metal plate.
Road 10 s. Then disconnect. Break the cycle one by one at each short circuit.
After that, check the magnetism with a magnetometer and repeat degaussing if necessary.
Cheng.
When degaussing the assembled butt joint, the steel pipe that needs to be butted.
End-wound welding wires with a cross section of 35 ~ 50 mm form two welding wires.
The coil pipe is made of steel pipe, as shown in Figure 4(a). The coils may overlap (along
Clockwise or counterclockwise), the total number of laps is 16 ~ 22 laps. At this moment,
The number of turns should be on the steel pipe with large remanence. This degaussing
Technology is often the best.
When the measured remanence level is less than 2×10 t, it is finished.
Welding of weld root. At this time, it is recommended to run at a low current of10 ~ 20 a.
Under supplementary degaussing.
(2) AC degaussing can be applied.
Before assembling a single steel pipe, the end and wall thickness of the single steel pipe reach
Assemble 25 mm butt ends of steel pipes. At this point, in addition to the above parties.
Fig. 4 system diagram of degaussing welding head by ordinary welding wire.
(a) degaussing with direct current; (b) degaussing with alternating current.
L degaussing steel pipe 2, ordinary welding wire 3, DC welding power supply 4, spirit level.
Slip current reducing device (steel wire) 5- Insulating material pad 6- Welding transformer
In addition to the degaussing method, there are the following supplements: degaussing according to Figure 4(b)
Assembly of system diagram, using 1 welding wire coil, on the back.
Service road with a length of 0.5~ 1.0 m and a diameter of1.5 ~ 3.0 mm.
Steel wire This steel wire is placed on a mat made of insulating and nonflammable materials.
(e.g. asbestos brick). Steel wire can change the current smoothly.
Size, thus changing the size of the degaussing magnetic field. When the power supply is turned on,
The steel wire is heated and burned out in a certain period of time. Combustion time depends on
Diameter, length and current value of steel wire. After the steel wire is burnt, use magnetic force.
Dynamometer to check remanence. When the degaussing effect is insufficient, it must be repeated.
Degaussing (sometimes 4 ~ 5 times).
After the root weld is welded, the degaussing system can be removed.
It is recommended to clear it immediately after degaussing. The same can be done for demagnetization of alternating current.
So as to smoothly change the magnitude of the current.
(3) The existing degaussing methods mainly adopt electromagnets and permanent magnets.
Individual pipe sections with the length of 1O0 ~ 200mm on butt-jointed steel pipes, especially
Especially in the vicinity of the magnetic field where the sign changes. At this point, individual parts were deleted.
After magnetization, the welding of the root weld should be completed, and then proceed to the next section.
Degaussing. In order to degauss, a special structure of electromagnetism is selected.
Iron. The electromagnet is installed at the butt joint of the steel pipe, as shown in figure 1(a), so that the electromagnet
The N pole of iron is placed on the edge of steel pipe with magnetic S pole, while the magnet
The S pole is connected with the magnetic N pole of the tube. In the process of degaussing, you must borrow
Magnetometer is helpful to measure the direction and magnitude of residual magnetism of steel pipe regularly.
(when the power supply is connected). The degaussing magnetic field can be changed by changing the current.
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60. Welded pipe in September 2002.
Small to adjust, the direction of magnetic field is also adjusted by changing the direction of current.
That is, the positive and negative switching adjustment of power supply.
The permanent magnet for degaussing is made of IoH alloy KT5.
C-shaped or cylindrical permanent magnet, as shown in figure 1(a) and (b). while
After the magnet is installed correctly, the magnetic pole should be connected with the magnetized butt steel pipe.
The poles are opposite. Whether the magnet is installed correctly can be checked by magnetometer.
Check. In order to enhance the degaussing effect, magnets can be connected with each other (2)
More than three, their functions are the same). After degaussing the butt joint, it is necessary to
The welding of the root weld must be completed here. After that, the magnet should be moved to
Next degaussing section. In order to increase the demagnetization field, the magnet should be close to.
Degaussing places, on the contrary, magnets can be removed. Move the magnet along the surface of the steel pipe
When welding, the residual magnetism at the welded butt joint can be minimized.
In order to change the direction of degaussing flux, it must be on a horizontal plane.
Turn the c-shaped magnet 180. , and the circle at the edge of the butt joint.
Cylindrical magnets must change positions or rotate in a vertical plane.
180。 . After each degaussing process, it is necessary to check the residue with a magnetometer.
The size of the magnetic field
3 Conclusion theory
Russian degaussing experience shows that using existing process documents
The degaussing method is very effective. This method can be used in work.
Installation, welding and maintenance of various pipelines in industrial departments.
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Author Xu Guizhi, male, was born in 1939 and graduated from 1962.
Beijing Institute of Aeronautics and Astronautics. Aviation industry corporation of china Nanjing Aviation Subsidiary
Senior engineer of parts factory, member of Nanjing Welding Association, Huaneng Nanjing.
Amateur Russian translation in the division. Number of published papers and translations at home and abroad
Ten articles. Address: Xihua East Village 12-402, Nanjing.
(Date of receipt: March 2, 20021)
The Ministry of Science, Technology and Environmental Protection of China Iron and Steel Industry Association plans to collect and publish it.
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