JB/T 6061-1992 Magnetic particle inspection method for welds and classification of defective magnetic marks
Some standard content:
Mechanical Industry Standard of the People's Republic of China
Weld Magnetic Particle Inspection Method and Classification of Defect Magnetic Indications 1 Subject Content and Scope of Application
JB/T 6061—92
This standard specifies the magnetic particle inspection method for weld surface defects and near-surface defects and the classification of defect magnetic traces. This standard is applicable to the magnetic particle inspection of the surface and near-surface quality of fusion welds of ferromagnetic materials. 2 Reference standards
GB3721 Magnetic particle flaw detector
GB9445 General rules for technical qualification appraisal of non-destructive testing personnel JB3965 Magnetic particle flaw detection of steel pressure vessels
JB/T6063 Technical conditions for magnetic particles for magnetic particle flaw detection JB/T6065 Standard test pieces for magnetic particle flaw detection
3 Inspection methods and requirements
3.1 Before inspection, the weld and the parent material surface nearby should be cleaned to remove surface oil, 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 The inspected part should undergo at least three inspection steps in the following order during the inspection: a. Necessary magnetization with magnetic particle flaw detection equipment; b. In the magnetized area, dry magnetic powder has been applied by dry method, or magnetic suspension (i.e., a mixed body prepared by magnetic powder or magnetic paste and carrier liquid) has been applied by wet method;
C. Observe, analyze and evaluate the magnetic traces of the parts where magnetic powder or magnetic suspension has been applied. 3.3 In general, the continuous method should be used for inspection as much as possible. If the residual magnetization method must be used, the residual magnetic induction intensity B of the weld and its parent material should be above 0.8T, and the coercive force H should be above 800A/m, and it should be clearly stated in the inspection report. 3.4 Each inspection part on the weld should be magnetized in at least two directions perpendicular or nearly perpendicular to each other (except for the case where there is sufficient evidence to show that no transverse defects will occur). There are three magnetization methods that can be used: a. Longitudinal magnetization plus transverse magnetization - magnetization is carried out in two directions perpendicular to the weld direction and parallel to the weld direction, regardless of the order.
b, Cross magnetization - magnetization in the direction of 45° and -45\ respectively with the direction of the weld, regardless of the order. Rotating magnetic field or swinging magnetic field magnetization - magnetization with a magnetic field that can automatically and continuously change the direction of the magnetic field within a 360° or 90° plane.
3.5 Generally, the contact method and yoke method suitable for local magnetization should be used as the main method, but when encountering any of the following situations, the coil method or direct current method suitable for overall magnetization should be used to magnetize in one or several directions: pipe butt welds and welds with similar characteristics (such as butt welds of steel bars and certain shafts); a.
b. Pipe seat fillet welds and welds with similar characteristics (such as fillet welds of ear shafts, support rods, etc.); small width of the lap plate fillet weld (such as the support plate fillet weld, the hanger plate fillet weld, etc.) c
Welds with a short welding length.
Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on 1992-05-05 234
Implementation on 1993-07-01
JB/T6061-92
3.6 When the weld is magnetized by the contact method, the length range of each magnetization is 75mm at the minimum and 200mm at the maximum. When the weld is magnetized by the yoke method, the length range of each magnetization is 50mm at the minimum and 200mm at the maximum. When the butt welds of pipes and welds with similar characteristics are magnetized by the coil method, the ratio of the butt length of the butt welds and similar pipes to the equivalent diameter shall not be less than 3. When the pipe seat fillet welds and welds with similar characteristics are magnetized, the ratio of the height of the pipe seat and similar pipe seat to the equivalent diameter shall not be less than 1.5. When the fillet welds of the lap plate are magnetized, the ratio of the height to the width of the lap plate shall not be less than 3/yuan (yuan-pi). 3.7 The calculation of the equivalent diameter of the welded part can refer to the following principles: When the cross section of the welded part is close to a circle, its cross section diameter is used as the equivalent diameter: a.
b. When the cross section of the welded part is a quadrilateral or other polygon, its perimeter is divided by yuan; c. When the cross section of the welded part is plate-shaped, its width is divided by twice the 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 the magnetic powder should flow by utilizing the migration characteristics of the magnetic powder itself and the compressed air flow applied by the inspector. Magnetic traces are formed in places where there is a leakage magnetic field, and all of them leave in places where there is no 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 are used to drive the magnetic powder to flow. Magnetic traces are formed in places where there is a leakage magnetic field, and all of them leave in places where there is no leakage magnetic field. 3.10 The common method for making magnetic powder flow on the surface to be inspected is the wet method. However, the dry method should be used when any of the following situations or several situations are encountered:
When it is required to inspect defects with a large burial depth; a.
b. When the flatness of the weld surface is extremely poor, if the wet method is used, the magnetic suspension is difficult to flow smoothly; when the weld surface is significantly lower than the surface of the parent material, if the wet method is used, it is easy for the magnetic suspension to flow; d. When the weld temperature is significantly higher than the room temperature, if the wet method is used, it is easy for the magnetic suspension to dry out. 3.11 When the dry method is used in the three situations a, b, and c of 3.10, the inspected part must be heated to a temperature above room temperature. 3.12 The contact method is not allowed to be used for welds that are prone to cold cracks. When other methods are used for inspection, the effective inspection results must be obtained after the welding temperature of the weld has cooled to room temperature and then placed for more than 24 hours. The inspection results obtained in other occasions can be used as a reference.
3.13 For welds that need to be heat treated after welding, the inspection should be arranged after the heat treatment work is completed as a basis for understanding the effect of heat treatment and delivery acceptance.
3.14 The parts of the welded parts that are in electrical contact with the magnetic particle flaw detection equipment should be padded with lead plates or disks made of silk braided belts to prevent the sparks generated at the contact parts from burning the welded parts. Zinc shall not be used as pads. 4 Inspectors
4.1 Inspectors shall obtain certificates in accordance with the provisions of GB9445 and may only engage in operations after passing the examination of the relevant departments. Those who issue inspection reports must hold a qualification certificate of magnetic particle inspection level or above. 4.2 Inspectors should understand the types, locations and directions of defects that often occur in product welding, and master the test methods that can ensure that important defects are not missed.
4.3 The corrected vision of the inspectors should not be less than 1.0, and they should not be color blind. 5 Inspection equipment
5.1 The equipment used for magnetic particle inspection of welds should comply with the provisions 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 not been used for more than half a year, the ammeter should be calibrated after repair and before it is reused. 5.3 The measuring instruments and instruments used to calibrate the ammeter must have a measurement certificate. 5.4 Within the range indicated by the ammeter, there should be no less than 3 calibration points. The error between the ammeter reading on the equipment and the standard ammeter reading should not exceed 10% of the full scale. 235
JB/T6061---92
5.5 When using a DC ammeter to measure half-wave rectified current, the reading on the ammeter should be doubled. 5.6 For AC electromagnets used for yoke method inspection, the lifting force at its maximum pole spacing should be greater than 44N, and the lifting force of DC electromagnets at its maximum pole spacing should be greater than 177N. 5.7 The powder sprayer used to apply dry magnetic powder should be able to spray dry magnetic powder in a mist evenly and generate sufficient compressed air flow to blow away the magnetic powder without magnetic traces on the surface to be inspected. 5.8 The powder sprayer should be calibrated regularly and repaired in time when a failure occurs. 5.9 The calibration and repair 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 should comply with the provisions of JB/T6063. 6.2 The color of commonly used non-fluorescent magnetic powder can be black, red or gray. When selecting, it should be possible to make the color of the magnetic powder and the surface to be inspected have a clear contrast. If necessary, a layer of contrast enhancer can be sprayed on the inspected part to help improve the contrast, but the thickness of the spraying should be as small as possible, otherwise it will reduce the sensitivity of the flaw detection. 6.3 Commonly used fluorescent magnetic powder should be able to produce yellow-green fluorescence under ultraviolet irradiation (unless otherwise required). 6.4 The magnetic powder should be placed in a sealed container and stored in a dry environment, or prepared into a magnetic paste for standby use. Otherwise, the magnetic powder should be dried at 60-80℃ for 1 hour before use. If necessary, it should be re-grinded and screened, 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 dispersing effect 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 oily carrier liquid, odorless kerosene should be used first. 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 fluid is suitable. It is also best to use magnetic suspension prepared with aqueous carrier fluid in the contact method inspection. 8 Artificial test blocks and test pieces
8.1 Artificial test blocks and test pieces used in the magnetic particle inspection of welds 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 suspensions and whether the operation methods in the inspection are appropriate; magnetic field indicators can be used to reflect the strength and direction of the magnetic field on the weld surface, but cannot be used as a quantitative indicator of magnetic field strength and magnetic field distribution. Sensitivity test pieces have the purpose of system performance test boards and can also be used to verify the distribution law of the 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 weld magnetic particle inspection and used correctly in accordance with relevant regulations. 9 Magnetizing current
9.1 The magnetizing currents used for weld magnetic particle inspection are: a. direct current and full-wave rectified current;
b. half-wave rectified current;
C. alternating current.
9.2 In order to inspect defects with a large buried depth, direct current or full-wave rectifier 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 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. 9.3 In the residual magnetism inspection, if alternating current or half-wave rectifier is needed, a power-off phase controller should be added to control the power-off time between yuan/2~～~yuan and 3 yuan/2~～~2yuan. 9.4 When the overall magnetization of the weld is carried out by the power-on method, the magnetization current value can be obtained by formula (1): HD
Where: I—magnetization current value, A;
D---equivalent diameter of the weld, m;
H———magnetic field strength, which can be selected between 2400~～4800A/m. 9.5 The overall magnetization of the weld is carried out using the wire diagram method. The magnetization current value can be obtained using formula (2): NI = 45 000
Wherein: I is the magnetization current value, A,
N is the number of wire diagram turns,
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 weld thickness ≤19rmm)
12 = (4~5A/mm)S
(applicable to weld thickness>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)
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
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 inspected with rotating magnetic field and swinging magnetic field. 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 not less than 1000Ex11.2 Magnetic traces of fluorescent magnetic powder should be observed under a dark environment with a white light intensity not greater than 201x using an ultraviolet lamp, and the luminous brightness of the ultraviolet lamp should be not 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 by any one or more of the following methods: draw a sketch of the magnetic trace;
stick the magnetic trace down with tape or peelable plastic; b.
take photos of the real object.
12 Classification of defective magnetic traces
12.1 According to the shape of defective magnetic traces, defective magnetic traces can be roughly divided into two types: circular and linear. 12.2 Defective magnetic traces with a ratio of major axis to minor axis less than 3 are called circular magnetic traces, and defective magnetic traces with a ratio of major axis to minor axis greater than or equal to 3 are called linear magnetic traces.
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 traces (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 assessed at different levels or at the same level.
: 13.3. Defects assessed as unqualified can 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.
Quality level
The biggest defect without Kaohui
Defects showing traces
Defects showing traces
Category
Type and defect nature
Not penetrated
Linear defects
Not allowed
Slag inclusion or pores
Slag replacement Or pores
Round defects
JB/T 6061-92
Defect magnetic mark classification table
Not allowed
Not allowed||tt ||Single defect allowed
Not allowed
Single defect allowed
Display trace length ≤ 0.16, display trace length ≤ 0.2. Ears are not allowed
≤0. 3 8.H≤4 mm
Two adjacent defects show traces
and ≤2.5 mm
100mm weld length range||tt| |100mm weld length range
Defect display allowed within
Defect display allowed within
Total trace length ≤25mm
≤0.38. and ≤10 mm
The distance between two adjacent defective traces
should be no less than 6 times the length of the 6 largest defective traces among the larger ones| |tt||Any 50mm weld length
is allowed to have 2
defect display marks with display length
degree ≤ 0.155 and ≤ 2mm within the range
Spacing of display traces
Any 50mm weld length
is allowed to have 2 defect display traces with display length
degree ≤ 0.38 and ≤ 3mm within the range
The distance between defect display traceswww.bzxz.net
The total length of traces is ≤25mm
≤0.56, and ≤20mm
The distance between two adjacent defect display traces
The spacing should not be less than 6
any 50 mm welding bell length
which is allowed to exist within the range of the larger
larger defect display trace length 6
≤ 0.4. And ≤4mm
2 defective traces
The spacing between defective traces
should not be smaller than the larger one
should not be smaller than the larger one The display should be no less than 6 times of the larger display length
‖6 times
6 times of the length
Note; It 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 as the thickness. 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.
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
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.
Commissioning unit, report number:
Name and number of welded parts;
Technical sketch and inspected part;
Welding Part condition (material, heat treatment, size); weld condition (welding method, weld length, weld location); inspection equipment (model, name);
magnetic powder type and application method;||tt || JB/T6061 |
Quality assessment results;
Inspection date and report date;
Signatures of inspectors and reviewers.
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
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