JB/T 6061-1992 Magnetic particle inspection method for welds and classification of defective magnetic marks
Some standard content:
Machinery Industry Standard of the People's Republic of China
Weld magnetic particle inspection method and classification of defective magnetic marks 1 Subject content and scope of application
JB/T 6061—92
This standard specifies the weld Magnetic particle inspection methods for surface defects and near-surface defects and classification of defect magnetic marks. This standard is applicable to magnetic particle inspection of the surface and near-surface quality of fusion welds of ferromagnetic materials. 2 Reference Standards
GB3721 Magnetic Particle Flaw Detection Machine
GB9445 General Rules for Technical Qualification of Non-destructive Testing Personnel JB3965 Magnetic Particle Flaw Detection of Steel Pressure Vessels
JB/T6063 Technical Conditions for Magnetic Particle Flaw Detection JB/T6065 Magnetic Powder Standard test pieces for flaw detection
3 Inspection methods and requirements
3.1 Before inspection, the surface of the weld and the base metal near it should be cleaned to remove surface oil stains, welding spatter, loose rust and Oxide scale, various thick covering layers (paint layer, insulation layer, etc.); remove various utensils and items placed on the surface. 3.2 During the inspection, the inspected part should undergo at least three inspection steps in the following order: a. Necessary magnetization using magnetic particle inspection equipment; b. Dry magnetic powder is applied in the magnetized area by dry method, or magnetic suspension (that is, a mixed reservoir prepared with magnetic powder or magnetic paste and carrier liquid) is applied by wet method;
C, Observe, analyze and evaluate magnetic marks on parts where magnetic powder or magnetic suspension has been applied. 3.3 Under normal circumstances, the continuous method should be used for inspection whenever possible. If the residual magnetization method must be used, the residual magnetic induction intensity B of the weld and its base material should be above 0.8T, and the coercive force H. should be above 800A/m, and this must be clearly stated in the inspection report. 3.4 Each inspection part on the weld should be magnetized in at least two directions that are perpendicular or nearly perpendicular to each other (except when there is sufficient basis to prove that lateral defects will not occur). There are three magnetization methods that can be used: a. Longitudinal magnetization and transverse magnetization - magnetization in two directions perpendicular to the direction of the weld and parallel to the direction of the weld, regardless of the order.
b, Cross magnetization is carried out in directions that are roughly 45° and 45\ to the direction of the weld, regardless of the order. Rotating magnetic field or oscillating magnetic field magnetization - magnetization using a magnetic C.
field that can automatically and continuously change the direction of the magnetic field within a 360° or 90° plane range.
3.5 Generally, the contact method and the yoke method suitable for local magnetization should be used. However, when encountering any of the following situations, the coil method suitable for overall magnetization or the direct energization method should be used first. Magnetize in one direction or in several directions: pipe butt welds and welds with similar characteristics (such as butt welds of steel rods and certain shafts); a.
b. Pipe seat fillet welds and welds with similar characteristics (such as fillet welds for trunnions, struts, etc.); fillet welds with small width (such as support plate fillet welds, hanging plate fillet welds, etc.) c
Welding seams with smaller length. | |tt | ||3.6 When using the contact method to magnetize the weld, the length range of each magnetization is minimum 75mm and the maximum is 200mm. When using the yoke method to magnetize the weld, the length range of each magnetization is minimum 50mm and maximum 200mm; with coil When magnetizing pipe butt welds and welds with similar characteristics, the ratio of the butt length and equivalent diameter of pipes and similar pipes should not be less than 3. When magnetizing fillet welds of pipe seats and welds with similar characteristics, the pipe The ratio of the height to the equivalent diameter of the base and similar pipe bases should not be less than 1.5. When magnetizing fillet welds, the ratio of the height to the width of the tie plate should not be less than 3/yuan (yuan-pi). 3.7 The calculation of the equivalent diameter of the weldment can be carried out according to the following principles: when the cross-section of the weldment is close to a circle, its cross-sectional diameter is used as the equivalent diameter: a.
b. When the cross-section of the weldment is a quadrilateral or other polygon, divide its circumference by yuan; c. When the cross-section of the weldment is plate-shaped, divide its width by twice its width in yuan. 3.8 When applying magnetic powder by dry method, the magnetic powder applied to the surface to be inspected should be distributed as evenly as possible, and flow using the migration characteristics of the magnetic powder itself and the compressed air flow additionally applied by the inspection personnel. Magnetic traces are formed where there is a magnetic leakage magnetic field, and all traces are removed where there is no magnetic leakage magnetic field.
3.9 When applying magnetic suspension by wet method, the magnetic suspension applied to the surface to be inspected should be distributed as evenly as possible, and the flow characteristics of the carrier liquid should be used to drive the magnetic powder to flow. Magnetic traces are formed where there is a magnetic leakage magnetic field, and all traces are removed where there is no magnetic leakage magnetic field. 3.10 The common method to make magnetic powder flow on the surface to be inspected is the wet method. However, when encountering any one or more of the following situations, the dry method should be used:
When it is required to inspect defects with large burial depths; a.
b. The flatness of the weld surface is extremely poor. If the wet method is used, it is difficult for the magnetic suspension to flow smoothly. The weld surface is significantly lower than the surface of the base metal. If the wet method is used, the magnetic suspension is prone to pooling. d. The temperature of the weld is significantly higher than room temperature. If the wet method is used, it is easy for the magnetic suspension to dry out. 3.11 When using the dry method in the three situations a, b, and c of 3.10, the parts to be inspected must be heated so that their temperature exceeds room temperature. 3.12 Welds that are prone to cold cracks are not allowed to be inspected by the contact method. When other methods are used for inspection, the effective inspection results must be obtained after the welding temperature of the weld is cooled to room temperature and then placed for more than 24 hours. Inspection results obtained on other occasions can be used as a reference.
3.13 For welds that require heat treatment after welding, inspection as a basis for understanding the heat treatment effect and delivery acceptance should be arranged after the heat treatment work is completed.
3.14 The parts of the welded parts that are in electrical contact with the magnetic particle flaw detection equipment should be padded with discs made of lead plates or silk braids to prevent sparks generated at the contact parts from burning the welded parts. Zinc shall not be used as backing plate. 4 Inspection personnel
4.1 Inspection personnel should obtain certificates in accordance with the provisions of GB9445, and can only engage in operations after passing the examination by the relevant departments. The person who issues the inspection report must hold a qualification certificate of magnetic particle inspection level or above. 4.2 Inspection personnel should understand the types, locations, and directions of defects that often occur in product welding, and master test methods that can prevent important defects from being missed.
4.3 The corrected visual acuity of the inspector should not be less than 1.0, and there should be no color blindness. 5 Inspection equipment
5.1 Equipment used for magnetic particle inspection of welds shall comply with the regulations of GB3721. 5.2 The ammeter used to indicate the magnetizing current should be calibrated at least once a year. For equipment that has undergone major repairs and equipment that has been left unused for more than six months, the ammeter should be calibrated after repair and before reuse. 5.3 All measuring instruments and instruments used to calibrate ammeters must have measurement certificates. 5.4 Within the range indicated by the ammeter, its calibration points should be no less than 3. The error between the ammeter reading on the device and the standard ammeter reading should not exceed 10% of full scale. 235
JB/T6061---92
5.5 When using a DC ammeter to measure the half-wave rectified current, the reading on the ammeter should be doubled. 5.6 The lifting force of AC electromagnets used for yoke method inspection should be greater than 44N at the maximum magnetic pole spacing, and the lifting force of DC electromagnets at the maximum magnetic pole spacing should be greater than 177N. 5.7 The powder sprayer used to apply dry magnetic powder should be able to evenly spray dry magnetic powder in the form of mist and generate sufficient compressed air flow to blow away the magnetic powder without magnetic marks on the surface to be inspected. 5.8 The powder sprayer should be calibrated regularly, and should be repaired in time when a malfunction occurs. 5.9 The calibration and repair status of the equipment should be recorded in writing and properly kept as equipment files. 6 Magnetic powder for inspection
6.1 The performance of the magnetic powder for inspection shall comply with the requirements of JB/T6063. 6.2 Commonly used non-fluorescent magnetic powders can be black, red or gray in color. When selecting, the color of the magnetic powder and the surface to be inspected should be as obvious as possible. If necessary, a layer of contrast can be sprayed on the inspected part. Enhancer helps improve contrast, but the thickness of the spray brush should be as small as possible, otherwise the flaw detection sensitivity will be reduced. 6.3 Commonly used fluorescent magnetic powder should be able to produce yellow-green fluorescence under ultraviolet irradiation (unless otherwise required). 6.4 Magnetic powder should be placed in a sealed container and stored in a dry environment, or prepared into magnetic paste for later use. Otherwise, the magnetic powder should be dried at 60~80℃ for 1 hour before use. Grinding and screening should be carried out again if necessary, but this method is not suitable for fluorescent magnetic powder. 6.5 When inspecting welds in a room with strong incandescent light or in a field with strong natural light, non-fluorescent magnetic powder should be used. When the inspection site is relatively dark or the inspection is carried out at night, fluorescent magnetic powder should be used. In departments where automatic inspection is required, fluorescent magnetic powder should be used.
7 Classification of carrier liquids and preparation and selection of magnetic suspensions 7.1 The liquid used to prepare magnetic suspensions is called carrier liquid, which can be divided into oil-based and water-based. Commonly used oil-based carrier liquids are transformer oil, kerosene, a mixture of transformer oil and kerosene, and odorless kerosene. Odorless kerosene is recommended. Commonly used aqueous carrier liquids are water containing additives. 7.2 The purpose of adding additives to water is to improve the performance of aqueous carrier liquids, so that the carrier liquid has a good dispersion and quality preservation effect on magnetic powder (the magnetic powder added to the carrier liquid can be evenly dispersed, and the performance remains unchanged during the specified storage period of the magnetic suspension) so that when the magnetic suspension is applied to the weld surface, it has good wetting, defoaming and rust prevention effects. 7.3 When preparing magnetic suspension, the magnetic powder or magnetic paste should first be mixed with a small amount of carrier liquid to form a uniform paste, and then the required carrier liquid should be slowly added during continuous stirring until the magnetic powder and the carrier liquid reach the specified ratio (except for concentrated magnetic powder coated with a wetting agent). 7.4 When preparing magnetic suspension of fluorescent magnetic powder with an oil carrier liquid, odorless kerosene should be used as much as possible. When preparing magnetic suspension of fluorescent magnetic powder with an aqueous carrier liquid, the carrier liquid specified by the magnetic powder manufacturer should be used as much as possible to prevent the fluorescent magnetic powder from agglomerating or dissolving in the carrier liquid. 7.5 The concentration of magnetic suspension is generally:
Non-fluorescent magnetic powder 10~25g/L
Fluorescent magnetic powder
1~2 g/L
7.6 When inspecting welds that have been coated with oily substances or contaminated by oily substances, it is advisable to use magnetic suspension prepared with an oily carrier liquid. In the inspection of welds with relatively wet surfaces and welds with fire protection requirements, oil contamination is generally not allowed, and magnetic suspension prepared with aqueous carrier liquid is suitable. It is also best to use magnetic suspension prepared with aqueous carrier liquid in the contact method inspection. 8 Artificial test blocks and test pieces
8.1 Artificial test blocks and test pieces used in weld magnetic particle inspection are: a. System performance test board and magnetic field indicator specified in JB3965; b. Type A, C, and D test pieces specified in JB/T6065. 8.2 System performance test board can be used to check the comprehensive performance of flaw detection equipment, magnetic particles or magnetic suspension and whether the operation method in the inspection is appropriate; magnetic field indicator can be used to reflect the strength and direction of the magnetic field on the weld surface, but it cannot be used as a quantitative indicator of magnetic field strength and magnetic field distribution. The sensitivity test piece has the purpose of system performance test board and can also be used to verify the distribution law of magnetic field in the inspected area and test sensitivity.
8.3 In order to make the inspection results have better reliability and reproducibility, artificial test blocks and test pieces should be selected according to actual needs in the magnetic particle inspection of welds, and they should be used correctly according to relevant regulations. 9 Magnetizing current
9.1 The magnetizing currents used for magnetic particle inspection of welds are: a. direct current and full-wave rectifier current;
b. half-wave rectifier current;
C. alternating current.
9.2 In order to inspect defects with a large buried depth, direct current or full-wave rectifier current should be used. When the weld is located on a welded part with complex shape and large size changes, alternating current or half-wave rectifier current should be used. In dry inspection and inspection of welds that need to be demagnetized after inspection, it is also better to use alternating current or half-wave rectifier current. 9.3 In the residual magnetism inspection, if alternating current or half-wave rectifier current is needed, a power-off phase controller should be added to control the power-off time between yuan/2~~~yuan and 3 yuan/2~~~2 yuan. 9.4 When the overall magnetization of the weld is performed by the current-passing method, the magnetization current value can be obtained using formula (1): HD
I
0.32
Wherein: I—magnetization current value, A;
D—equivalent diameter of the weld, m;
H—magnetic field intensity, which can be selected between 2400 and 4800 A/m. 9.5 The overall magnetization of the weld is carried out using the wire diagram method. The magnetization current value can be calculated using formula (2): NI = 45 000
LD
Wherein: I is the magnetization current value, A,
N is the number of wire diagram turns,
(1)
(2)
L/D is the ratio of the welding length to the equivalent diameter. When L/D is 3, formula (2) is not applicable. When L/D is 15, 15 is used instead. 9.6 When the local magnetization inspection of the weld is carried out by the contact method, the magnetization current value can be obtained by formula (3) and formula (4): I, = (3.5~4.5A/mm)S
(applicable to the thickness of the weld ≤ 19rmm)
12 = (4~5A/mm)S
(applicable to the thickness of the weld> 19mm)
Where: I1I,---magnetization current value, A; S--contact spacing, mm.
10 Operation matters
10.1 Operation matters to be observed in the contact method inspection 10.1.1 The contact end should be kept clean, and the contact between the contact and the surface to be inspected should be good to avoid arcing and local overheating. (3)
(4)
10.1.2 The contact handle should be equipped with a power switch that is normally in the off state. The power can only be turned on when the inspector presses the power switch hard.
10.1.3 When the contact is not in close contact with the surface to be inspected, the power shall not be turned on. When the contact in contact with the surface to be inspected needs to be removed, the power shall be turned off first.
10.1.4 In the process of applying the magnetic suspension by wet method, in order to prevent fire, it is advisable to use a magnetic suspension prepared by an aqueous carrier liquid. ik - r
23
JB/T 6061-92
10.7.5 There shall be a certain coverage width between two adjacent inspection areas, which can be selected between 10 and 20 mm. 10.2 Operational matters to be observed in the ordinary magnetic yoke method inspection 10.2.1 The power supply can only be turned on after the electromagnet is securely placed on the inspected part. When the electromagnet needs to be removed from the inspected part, the power supply shall be turned off first.
10.2.2 There shall be a certain coverage width between two adjacent inspection areas, which can be selected between 10 and 20 mm. 10.3 Operational matters to be observed in rotating magnetic field and swinging magnetic field inspection. 10.3.1 All four magnetic poles (or electrodes) must maintain good contact with the inspected part, otherwise the rotating magnetic field or swinging magnetic field cannot be generated. 10.3.2 The moving speed should not be greater than 2m/min10.3.3 The residual magnetism method cannot be used for rotating magnetic field and swinging magnetic field inspection. 10.4 In principle, used magnetic powder and magnetic suspension are not recycled and reused. Only when the magnetic suspension is supplied in a circulating manner in a fixed magnetic particle flaw detector, in order not to affect the normal operation of the circulation system, the magnetic suspension is recycled and reused. 10.5 The recycled magnetic suspension should be frequently inspected for impurities, magnetic properties tested and concentration measured. Unqualified magnetic suspension should be replaced and not allowed to be used again.
10.6 The concentration of magnetic suspension can be measured with a pear-shaped cup. Pour 100mL of magnetic suspension into the pear-shaped cup and evaluate it according to the precipitation volume of magnetic powder in the pear-shaped cup. The specific value should be determined according to the type of magnetic powder and the properties of the carrier liquid. 11 Observation, analysis and recording of magnetic traces
11.1 Magnetic traces of non-fluorescent magnetic powder should be observed under white light, and the intensity of white light should be no less than 1000Ex11.2 Magnetic traces of fluorescent magnetic powder should be observed under a dark environment with a white light intensity no more than 201x using an ultraviolet lamp, and the luminous brightness of the ultraviolet lamp should be no less than 1500μW/cm2.
11.3 The magnetic trace image can be magnified with the help of a 2-10 times magnifying glass for observation. 11.4 During the observation process, the difference between defective magnetic traces and non-defective magnetic traces should be carefully distinguished, and the nature of the defects should be judged. 11.5 Magnetic traces that cannot be distinguished by the naked eye should be verified by other effective methods. 11.6 Defective magnetic traces can be recorded in any one or more of the following ways: draw a sketch of the magnetic trace;
a.
stick the magnetic trace with tape or peelable plastic; b.
take a real photograph.
12 Classification of defective magnetic marks
12.1 According to the shape of defective magnetic marks, defective magnetic marks can be roughly divided into two types: circular and linear. 12.2 Defective magnetic marks with a ratio of major axis to minor axis less than 3 are called circular magnetic marks, and defective magnetic marks with a ratio of major axis to minor axis greater than or equal to 3 are called linear magnetic marks.
13 Quality assessment and inspection after rework
13.1 In principle, the quality assessment of magnetic particle inspection of welds is divided into four levels according to the type, length, spacing and nature of defective magnetic marks (see table), with level 1 being the highest quality and level V being the lowest quality. 13.2. Defects of different types or properties appearing on the same weld can be evaluated using different grades, or the same grade can be used for evaluation.
: 13.3 Defects assessed as unqualified are allowed to be repaired as long as they do not violate the welding process regulations. The inspection and quality assessment after repair are the same as before repair. || tt | ||0.3
Indicates the type of trace
Type and defect nature
Crack
Not penetrated
Linear defect
No Allowed
Slag inclusion or pores
Replace slag or pores
Circular defects
JB/T 6061-92
Defect magnetic mark classification table| |tt||1
1
Not allowed
1
.5
Not allowed
Single defect allowed
1.5
Not allowed
Single defect allowed
Display mark length ≤ 0.16, display mark length ≤ 0.2. Ears are not allowed| |tt||≤0. 3 8.H≤4 mm
Two adjacent defects show traces
and ≤2.5 mm
100mm weld length range
≤3.5mm
100mm welding length range
Defect display allowed within
Defect display allowed within
Total trace length ≤ 25mm
≤0.38. and ≤10 mm
The distance between two adjacent defect display marks
6 times the trace length
Any 50mm weld length
is allowed to have
defective traces showing length
≤ 0.155 and ≤ 2mm within the range
defect display trace 2
The spacing of defect display traces
3mm
2 defective traces
The spacing of defective traces
The total length of traces ≤ 25mm
≤0.56, and ≤20mm
The distance between two adjacent defective traces
shall not be less than 6
times the length of the larger
larger defective trace
any 50 mm welding bell length| |tt||Displays allowed within the range
2 defect display marks with length ≤0.4. and ≤4mm
2 defect display marks
Spacing of defect display marks
Should not be less than 6 times the length of the larger display
Should be no less than 6 times the length of the larger display
Note; is the thickness of the weld base metal. When the thickness of the base metal on both sides of the weld is not equal, the smaller thickness value shall be used. 14 Demagnetization
For welded parts with any one or several of the following conditions, the welds should be demagnetized after magnetic particle inspection: When the residual magnetism will affect the subsequent processing technology of the welded parts; b.
c.
When the residual magnetism will affect the performance of the welded parts; when the residual magnetism will affect the accuracy of the equipment and instruments working around the welding. 15 Inspection report
15.1
15.2
After the inspection, an inspection report shall be issued based on the inspection record. The inspection report should at least include the following contents: a.
b.
c.
d.
e.
f.
Commissioning unit, report number:
Name and number of welded parts;
Technical sketch and inspected parts;
Condition of welded parts (material, heat treatment, size); Weld condition ( Welding method, weld length, weld location); inspection equipment (model, name);
239
g.
h.
i.|| tt||j.
k.
1
m.
n
Magnetic powder types and application methods;
JB/T6061
Magnetization method, magnetizing current value or magnetic field strength value: artificial test block or test piece;
type, size, quantity, position and spacing of defective magnetic marks; defect nature;
Quality assessment results;
Inspection date and report date;
Signature of inspector and reviewer.
Additional notes:
This standard is proposed by the National Technical Committee for Non-Destructive Testing Standardization. This standard is under the jurisdiction of the Shanghai Materials Research Institute of the Ministry of Mechanical and Electronic Industry. 92
This standard is drafted by the Harbin Welding Research Institute of the Ministry of Mechanical and Electronic Industry. The main drafters of this standard are Sun Renyu and Li Jiajing. 240
2
After the inspection, an inspection report shall be issued based on the inspection records. The inspection report should at least include the following contents: a.
b.
c.
d.
e.
f.
Commissioning unit, report number:
Name and number of welded parts;
Technical sketch and inspected parts;
Condition of welded parts (material, heat treatment, size); Weld condition ( Welding method, weld length, weld location); inspection equipment (model, name);
239
g.
h.
i.|| tt||j.
k.
1
m.
n
Magnetic powder types and application methods;
JB/T6061
Magnetization method, magnetizing current value or magnetic field strength value: artificial test block or test piece;
type, size, quantity, position and spacing of defective magnetic marks; defect nature;
Quality assessment results;
Inspection date and report date;
Signature of inspector and reviewer.
Additional notes:
This standard is proposed by the National Technical Committee for Nondestructive Testing Standardization. This standard is under the jurisdiction of the Shanghai Materials Research Institute of the Ministry of Mechanical and Electronic Industry. 92
This standard is drafted by the Harbin Welding Research Institute of the Ministry of Mechanical and Electronic Industry. The main drafters of this standard are Sun Renyu and Li Jiajing. 240
2
After the inspection, an inspection report shall be issued based on the inspection records. The inspection report should at least include the following contents: a.
b.
c.
d.
e.
f.
Commissioning unit, report number:
Name and number of welded parts;
Technical sketch and inspected parts;
Condition of welded parts (material, heat treatment, size); Weld condition ( Welding method, weld length, weld location); inspection equipment (model, name);
239
g.
h.wwW.bzxz.Net
i.|| tt||j.
k.
1
m.
n
Magnetic powder types and application methods;
JB/T6061
Magnetization method, magnetizing current value or magnetic field strength value: artificial test block or test piece;
type, size, quantity, position and spacing of defective magnetic marks; defect nature;
Quality assessment results;
Inspection date and report date;
Signature of inspector and reviewer.
Additional notes:
This standard is proposed by the National Technical Committee for Nondestructive Testing Standardization. This standard is under the jurisdiction of the Shanghai Materials Research Institute of the Ministry of Mechanical and Electronic Industry. 92
This standard is drafted by the Harbin Welding Research Institute of the Ministry of Mechanical and Electronic Industry. The main drafters of this standard are Sun Renyu and Li Jiajing. 240
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