This standard specifies the magnetic particle inspection acceptance requirements, equipment, inspection methods and quality levels of valve pressure cast steel parts. This standard is applicable to the inspection, quality rating and acceptance of surface or near-surface defects in pressure magnetic conductive steel castings of valves. The magnetic particle inspection of pressure cast steel parts such as flanges and pipe fittings matched with pipelines and non-pressure cast steel parts can also be performed with reference to this standard. JB/T 6439-1992 Magnetic particle inspection of pressure-cast steel parts for valves JB/T6439-1992 Standard download and decompression password: www.bzxz.net

Machinery Industry Standard of the People's Republic of China
Magnetic particle inspection of pressure-cast steel parts for valves
1 Subject content and scope of application
JB/T 6439--92
This standard Specifies the requirements, equipment, inspection methods and quality levels for magnetic particle inspection acceptance of pressure-cast steel parts for valves. This standard is applicable to the inspection, quality rating and acceptance of surface or near-surface defects of pressure magnetically conductive steel castings of valves (hereinafter referred to as steel castings). The magnetic particle inspection of pressure cast steel parts such as flanges and pipe fittings matched with pipelines and non-pressure cast steel parts can also be performed with reference to this standard. When the magnetic field intensity is equal to 2.4kA/m, cast steel with a magnetic induction intensity greater than 1T in the material is called magnetically permeable steel. 2 Reference standards
GB3721 Magnetic Particle Flaw Detection Machine
GB9444 Magnetic Particle Flaw Detection and Quality of Cast Steel Rating method ZBJ04006 Magnetic particle flaw testing method 3 acceptance requirements for steel materials
3.1 Crack defects are not allowed in steel castings, and the magnetic particle flaw testing acceptance grade of steel castings should not be lower than the requirements in Table 1. Table 1
Defect type
Qualification level
Note: Acceptance qualification refers to the quality level at delivery Linear defects
3
Nonlinear defects
3.2 If there is another agreement between the supplier and the buyer, the quality acceptance grade of magnetic particle inspection of steel castings shall be implemented in accordance with the agreement. Different qualification levels can be selected for different parts of the same steel casting; different qualification levels can also be selected for different types of defects in the same part. 3.3 Magnetic particle inspection should be carried out on all parts that can be inspected by magnetic particle inspection, and the inspection should focus on the parts prone to defects such as the flange root, the pouring riser root and the parting surface.
3.4 ??Steel castings that fail the magnetic particle flaw detection inspection shall be inspected again according to this standard and accepted according to Table 1 after welding repairs according to relevant regulations on steel castings.
4 Personnel Qualifications
Personnel engaged in magnetic particle inspection of steel castings must hold a qualification certificate issued by the relevant national department and suitable for their work. 5. Flaw detection equipment | Once, the change in the magnetizing current value relative to the rated value is within ±10%. 5.2 Magnetic powder
5.2.1 The selected magnetic powder should be attracted by the magnet. 5.2.2 The magnetic weighing and particle size of various types of magnetic powder are as specified in Table 2. The Ministry of Mechanical and Electronic Industry of the People's Republic of China approved 398
1993-07-01 on 1992-07-01 for implementation
magnetic powder
type
type
dry method Magnetic powder for use
Magnetic powder for wet method
Fluorescent magnetic powder
5.3 magnetic suspension
JB/T 6439-92
Table 2||tt| |Magnetic particle weighing, g
7
4
The magnetic suspension used for magnetic particle flaw detection should comply with the regulations of GB9444. 5.4 Standard test piece
degree μm
grain
300~-50
A80
A50
5.4.1 Magnetic particle inspection type A The material and size of the standard test piece should comply with the regulations of ZBJ04006. 5.4.2 Type A standard test strips have three specifications: A-60/100, A-30/100, and A-15/100, and their sensitivities increase in order. This standard recommends the use of A-30/100 test pieces; it can also be determined according to the actual situation. 5.4.3 When using the Type A standard test piece, place the notched surface of the test piece on the surface of the steel casting, and then use two pieces of tape to stick the test piece and the steel casting closely together, but not Hold the part with the artificial groove on the back; finally, conduct the test according to the selected magnetization method and display method. If within the entire effective test range of directional magnetization, the total length of the magnetic marks displayed on the test piece reaches more than 75% of the circumferential length of the artificial groove, it is considered that the sensitivity requirements reflected by the test piece are met. When using the comprehensive magnetization method and the rotating magnetic field magnetization method, the test piece should be able to show magnetic marks on the entire circumference.
5.4.4 Standard test pieces should be properly stored according to the test piece usage instructions. If the test piece is found to be rusty, corroded, or deformed, causing changes in magnetic properties, the test piece must not be used further.
5.4.5 Other types of test pieces or test blocks that have been proven by comparative tests to be no less sensitive than Type A standard test pieces are allowed to be used for magnetic particle inspection sensitivity monitoring.
6 Inspection Methods
6.1 Pre-processing
6. 1. 1
Quality.
Before magnetic particle inspection, the surface of the inspection area should be removed from grease, sand, oxide scale and other objects that interfere with the magnetic particle inspection operation and magnetic mark identification. The surface roughness Ra value of the steel casting inspection area should be between 6.3~100 μm. Inside. 6.1.2
6.1.3 During dry inspection, the flaw detection surface of the casting should be completely dry. 6.2 Timing of flaw detection
The quality acceptance level in the standard refers to the quality level in the delivery state, so in principle, flaw detection should be carried out after all processing and processing procedures are completed. However, when the surface treatment process brings difficulties to defect inspection, flaw detection can be performed before surface treatment. Inspection between certain processes determined by negotiation between the supplier and the buyer is not subject to this restriction. 6.3 Magnetization methods
Commonly used magnetization methods include: rod method, yoke method, energization method, rod method, coil method, induced current method, comprehensive magnetization method, rotating magnetic field magnetization method, etc.
6.3.1 This standard recommends that the strut method be preferred and the magnetizing current be a three-phase full-wave rectifier or half-wave rectifier method for flaw detection of steel castings. For the strut method, in order to prevent the flaw detection surface from being burned during flaw detection, the strut contact should be in close contact with the surface of the steel casting and the current should be turned on. After powering on, remove the contacts.
6.3.2 In addition to the strut method, a suitable magnetization method can also be selected according to the size, shape and technical requirements of the steel casting. 6.3.3 No matter which magnetization method is adopted, standard test pieces should be used for testing. Magnetic particle inspection of steel castings can only be carried out after meeting the requirements of Article 5.4.3.
399
JB/T 6439 ~ 92
6.3.4 In addition to the comprehensive magnetization method and the rotating magnetic field magnetization method, magnetic fields should generally be applied in two directions perpendicular to each other. This restriction will not apply if the supply and demand parties stipulate otherwise.
6.4 Magnetization parameter selection
6.4.1 Strut method
The magnetizing current value is selected according to Table 3 according to the wall thickness of the flaw detection part. Table 3
Wall friction of flaw detection part, mm
20
220
Magnetizing current value, A/mm (contact spacing)
3~4
4~5
Under normal circumstances, the contact spacing should be kept within 150~230mm as much as possible. If the geometry of the steel casting does not allow it, the contact spacing can be reduced to between 75 and 150 mm. The determination of the effective range is shown in Figure 1. Strut contact
C-two-stage spacing
Figure 1 Effective range of magnetization by the rod method (the area of ??the shaded part in the figure is the effective range) 6.4.2 Magnetic yoke method||tt| |When the AC electromagnetic yoke uses the maximum yoke spacing, its lifting force should not be less than 44N; the DC electromagnetic yoke's lifting force should not be less than 177N.
The yoke spacing should be controlled within the range of 75~~~200mm. The effective range is determined as shown in Figure 2. Magnet contact
C
C-pole spacing
Figure 2 Effective range of magnetization by yoke method (the area of ??the shaded area in the figure is the effective range) 6.4.3 Effective range of magnetization The range can also be determined experimentally with the help of standard test pieces. 6.5 Magnetic trace display
6.5.1 It is allowed to apply magnetic powder by wet or dry method to display defective magnetic traces, and the continuous method is generally used. When the contract requires the use of the residual magnetism method, it can be carried out according to the method required by the contract or the provisions of Article 6.3.1 of GB9444. 6.5.2 Continuous wet method shows that the magnetic suspension is applied by pouring or spraying while magnetizing. The magnetic suspension should be able to flow slowly over the surface to be inspected, and magnetization should be performed again after the application of the magnetic suspension. Before magnetization, wetting the inspection surface with magnetic suspension will help the rapid display of magnetic defects. To prevent magnetic suspension from accumulating in pits, the steel casting can be tilted or weak airflow can be used to blow out the accumulated magnetic suspension. 6.5.3 Continuous method is displayed in method. While magnetizing, magnetic powder is applied by spraying or scattering. The magnetic powder should be spread evenly, preferably in the form of mist 400)
JB/T 6439 --- 92
. The spraying of magnetic powder should be completed before the end of magnetization. The dry display should not be above level 2 wind power. place. 6.5.4 Residual magnetism wet or dry method, displayed after the steel casting is magnetized. The method of applying magnetic suspension or dry magnetic powder is the same as the continuous method. The wet method can also apply magnetic powder to the steel castings in the magnetic suspension. Steel castings should be displayed as soon as possible after magnetization and should not be exposed to high temperatures, hit, knocked, or near strong magnetic fields. 6.6 Observation
6.6.1 Generally, self-observation is used, or you can observe with the help of a magnifying glass with a magnification of less than 5 times. 6.6.2 When using non-carbon optical magnetic powder, observe it under visible light. The illuminance of visible light on the inspection surface should not be less than 5001x. When using fluorescent magnetic powder, it must be observed under ultraviolet light. The radiation illumination under the ultraviolet lamp on the inspection surface should not be less than 8W/m. The ultraviolet wavelength range should be 330~400nm, with the center wavelength being 365nm. 6.6.3 When observing, the authenticity of the magnetic marks should be judged. When it is difficult to distinguish the authenticity, it can be distinguished by carefully inspecting the surface of the steel casting or re-polishing the magnetic mark area and re-inspecting. If necessary, methods other than magnetic particle inspection can be used to determine the authenticity of magnetic marks. 6.7 Demagnetization
- Generally do not perform demagnetization. If the contract requires demagnetization, the demagnetization method and residual magnetization test method shall be agreed upon by both parties. 7 Quality Level
7.1 Defect Classification and Assessment Method
According to the size and nature of the magnetic marks displayed by the defects during magnetic particle inspection, defects are divided into three categories: linear defects, non-linear defects, and cracks. 7.1.1 Linear defects refer to defects in which the ratio of length to width displayed by defective magnetic marks is greater than or equal to 3; nonlinear defects refer to defects in which the ratio of length to width displayed by defective magnetic marks is less than 3; according to the display characteristics of defective magnetic marks Defects that can be determined as cracks based on actual experience are classified as cracks.
7.1.2 Except for graining, any defect group formed by three or more defects with a spacing between defective magnetic marks less than or equal to 3mm, regardless of the size and type of each defective magnetic mark, this defect group is considered is a defect, and the perimeter surrounding the magnetic traces of this defect group is the perimeter range of this defect.
The classification of defect types is based on the aspect ratio of the defect in accordance with Section 7.1.1. If four or more defects are connected on a straight line and the adjacent distance is less than or equal to 3mm, it should be directly classified as level 4. 7.1.3 For linear defects, when the distance between two defects is less than The maximum allowable length specified in Table 4 shall be treated as a defect. The length of this defect is equal to the sum of the lengths of the original two defects. Otherwise they shall be assessed as two separate defects. 7.1.4 Defects are evaluated according to the maximum length of the crack marks. 7.2 Defect quality grading
7.2.1 Linear defect grade and maximum allowable length are as specified in Table 4. Table 4
Defect Level
1
2
3
4
13
Wall
Thick
>13~~25
Maximum allowable length of linear defects
8
13
Length exceeding level 3
7.2. 2 The nonlinear defect level and maximum allowable length are as specified in Table 5. 25
5
1.3
18
mm
401
Defect level
2
3
4
JB/T 6439 --- 92
Table 5www.bzxz.net
13
Wall
Thick
Not Maximum allowable length of linear defects
2
f
5
8
Length exceeding level 3
>13||tt| |5
8
13
Note: When four or more nonlinear defects are in a straight line, and the adjacent spacing is less than or equal to 3mm, it is also classified as level 4. 7.2.3 Any defective magnetic mark in steel castings that is confirmed to be a crack will be deemed unqualified. 7.3 Defect records
7.3.1 The type, location and size of defective magnetic marks that are unqualified according to the quality acceptance level requirements of steel castings should be recorded. 7.3.2 Recording of defective magnetic traces can be done by pasting with transparent tape, taking photos or drawings. 8 Flaw detection report
The magnetic particle flaw detection report should include the following: Workpiece status (material, heat treatment status, inspection area thickness, workpiece management number): a.
b.
d.| |tt||Flaw detection conditions (flaw detection equipment, magnetic particle materials, magnetization method, display method, magnetizing current, test piece specifications, types, etc.), defect location and type, size diagram; final quality grade and conclusion;
Inspection and the auditor’s signature (including inspection date, audit date), unit seal, etc. Additional notes:
This standard is proposed and administered by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronics Industry. This standard is drafted by Kaifeng Shangya Valve Factory. The main drafters of this standard are Ren Zhirong, Pan Rongbao and Wei Xinghua. 402
mm
2. Recording of defective magnetic traces can be done by pasting with transparent tape, taking photos or drawings. 8 Flaw detection report
The magnetic particle flaw detection report should include the following: Workpiece status (material, heat treatment status, inspection area thickness, workpiece management number): a.
b.
d.| |tt||Flaw detection conditions (flaw detection equipment, magnetic particle materials, magnetization method, display method, magnetizing current, test piece specifications, types, etc.), defect location and type, size diagram; final quality grade and conclusion;
Inspection and the auditor’s signature (including inspection date, audit date), unit seal, etc. Additional notes:
This standard is proposed and administered by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronics Industry. This standard is drafted by Kaifeng Shangya Valve Factory. The main drafters of this standard are Ren Zhirong, Pan Rongbao and Wei Xinghua. 402
mm
2. Recording of defective magnetic traces can be done by pasting with transparent tape, taking photos or drawings. 8 Flaw detection report
The magnetic particle flaw detection report should include the following: Workpiece status (material, heat treatment status, inspection area thickness, workpiece management number): a.
b.
d.| |tt||Flaw detection conditions (flaw detection equipment, magnetic particle materials, magnetization method, display method, magnetizing current, test piece specifications, types, etc.), defect location and type, size diagram; final quality grade and conclusion;
Inspection and the auditor’s signature (including inspection date, audit date), unit seal, etc. Additional notes:
This standard is proposed and administered by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronics Industry. This standard is drafted by Kaifeng Shangya Valve Factory. The main drafters of this standard are Ren Zhirong, Pan Rongbao and Wei Xinghua. 402
mm
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