This standard specifies the X-ray photography method and weld quality classification of fusion welded butt joints with a base material thickness of no more than 20 mm, made of copper and copper-based alloys, and welded by gas welding, argon arc welding (electric welding, submerged arc welding may also be used). This standard applies to butt welds of copper containers and copper pipes in air separation equipment. Other fusion welded butt joints with base materials of copper or copper-based alloys may also be used for reference. This standard does not restrict the use of gamma rays for radiographic inspection, but the photographic technical requirements must comply with the provisions of this standard. JB/T 7260-1994 Radiography and quality classification of copper welds in air separation equipment JB/T7260-1994 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T7260-94
Air Separation Equipment
Radiography and Quality Grading of Copper Welds
Published on July 18, 1994
Ministry of Machinery Industry of the People's Republic of China
Implementation on July 1, 1995
Mechanical Industry Standard of the People's Republic of China
Air Separation Equipment
Radiography and Quality Grading of Copper Welds
1 Subject Content and Applicable Model Drawings
JB/T 7260—94
This standard specifies the X-ray photography method and weld quality grading of fusion welded butt joints (hereinafter referred to as welds) with a base material thickness of not more than 20 mm, made of copper and copper-based alloys, and welded by gas welding, hydrogen welding (electric welding, buried channel welding may also be used). This standard applies to butt welds of steel containers and copper pipes in air separation equipment. Other fusion welded butt joints with steel or copper-based alloy as the base material can also be used for reference.
This standard does not restrict the use of radiation for transillumination inspection, but the requirements for photographic technology must comply with the provisions of this standard. 2 Reference standards
GB3323
GB4792
GB5618
GB/T12605
ZBJ04004
3 Personnel requirements
Radiography and quality grading of steel fusion welded butt joints Basic standards for radiation health protection
Linear image quality meter
Radiography process and quality grading of steel pipe circumferential welded butt joints Radiographic flaw detection methodbzxz.net
3.1 Personnel engaged in radiographic inspection must hold a technical qualification certificate issued by the relevant national departments and suitable for their work: At the same time, they must also hold a radiation safety operation qualification certificate issued by the national health protection department. 3.2 The vision of the film reviewer should be checked once a year, and the corrected vision should not be less than 1.0. It is required that a group of printed characters with a height of 0.5mm and a spacing of 0.5mm can be read at a distance of 400mm. 3.3 Personnel engaged in radiography should undergo physical examinations in accordance with the provisions of GB4792 and meet the requirements. 4 Surface requirements
4.1 The surface quality of the weld and heat-affected zone (including the height of the excess height) should pass the appearance inspection. The image of the irregular state of the surface painting on the film should not cover the defects in the welding or blend with them, otherwise it should be trimmed. 4.2 The surface of the workpiece should have permanent marks as the basis for repositioning each radiographic film. When it is not suitable for steel stamping, a sketch of the transillumination area or other effective methods can be used for marking. 5 Technical requirements for radiography
5.1 Radiographic methods
According to the relative positional relationship between the radiation source, workpiece and film, the radiographic methods are divided into longitudinal seam radiography, annular seam external radiography, annular seam internal radiography (center full circumference radiography), annular seam double-whole single-image method and annular seam double-wall double-image method (see Figure 1). Approved by the Ministry of Machinery Industry on July 18, 1994, and implemented on July 1, 1995. Transparent illumination method. Time line fee. Radiation fee. JB/T7260-94. External replacement technology. Radiation source. Annular seam internal adaptation. Annular continuous double wall single shadow method. Figure 1 Schematic diagram of penetration method. Slow-release photography. Annular continuous double shadow method. 5.2 The penetration thickness ratio of weld is called K value. The K value of circumferential seam is not more than 1.1, and the K value of longitudinal seam is not more than 1.03. See formula (1) and Figure 2. Where, T—-parent metal thickness, mm; —-maximum thickness of oblique irradiation of ray beam, mm. Radiation source
Figure 2 Schematic diagram of weld penetration thickness ratio
5.3 Industrial radiation film
JB/T7260-94
Industrial radiation film is divided into three types according to the size of silver salt particles (see Table 1), and J2 type film is recommended. Table 1 Film type
5.4 Intensifying screen
Sensitivity
Use lead intensifying screen, the front screen thickness is 0.03~0.05mm, and the rear screen thickness should not be less than 0.10mm. The film and intensifying screen should always be close to each other during the penetration process to improve the quality of the photographic image. 5.5 Determination of penetration thickness
The penetration thickness of the penetration part is the sum of the parent material thickness and the measured excess height. If it is difficult to measure the excess height, it can be determined according to Table 2. Table 2 Thickness of butt joints
Transmission method
Single or double whole single shadow
Double wall double shadow
Thickness of parent material
Weld reinforcement
Single side (with backing plate)
Note: ①The thickness of parent material is the nominal thickness. When the parent material ratios in the butt joint are different, the thinner thickness is the thickness of the parent material. ②T, is the thickness of the backing plate.
Image quality meter
5.6.1 The image quality meter shall use the R'10 series linear image quality meter specified in GB5618, and the material is made of wire. Transmission thickness
T+2+T,
5.6.2 The image quality meter shall be placed on the workpiece surface on the side of the radiation source at one end of the weld area to be inspected. The copper wire shall cross the weld and be perpendicular to the weld direction, and the thin wire shall be placed on the outside.
5.6.3 When the image quality meter cannot be placed on the side of the radiation source and the double-wall single-image method is used for transillumination: the image quality meter can only be effective on the workpiece surface on the film side. At this time, a comparative test should be conducted to ensure that the actual image quality index value meets the specified requirements. 5.6.4 When the circumferential noise light technology with the radiation source placed at the center of the circle is used, the image quality meter should be placed on the inner wall, one every 90°. 5.7 Marking and its placement
5.7.1 The film must have the transillumination year, month, and date, product drawing number, workpiece number, weld number, film number, center mark, overlap mark, etc. These marks should be transilluminated together with the transillumination area. 5.7.2 When transilluminating the repaired area, the repair mark should be added. R1, R2, etc. indicate the number of repairs. 5.7.3 When the image quality meter can only be placed on the film side, an "F" mark should be added next to the image quality meter. 5.7.4 For the parts that are to be inspected for expansion, a "K" mark should be added before the film sequence number. 5.7.5 All marks should be at least 5 mm away from the edge of the weld and should match the marks on the workpiece. 5.8 Overlap length
When the weld is 100% penetrated by segmented penetration, the overlap length of two equal films should not be less than 10 mm. 5.9 Selection of radiation energy
Under normal circumstances, as the difference in radiation energy decreases, the contrast of the radiographic image increases. Therefore, under the condition that the noise time permits, the lowest radiation energy should be used as much as possible. The maximum tube voltage allowed for different penetration thicknesses is shown in Figure 3. 3
5.10 Selection of exposure parameters
JB/T 7260-94
648910
Figure 3 Transillumination thickness and maximum allowable tube voltage Transillumination thickness seat
Select warm light specifications based on the flash curve and transillumination process. In order to achieve the specified film blackness and prevent adverse effects caused by high voltage, the exposure is recommended to be no less than 15mA·min. 5.11 Radiographic equivalent coefficient
Under different tube voltages, the equivalent coefficients of copper and steel are shown in Table 3. Table 3 Approximate values ​​of copper and steel radiographic equivalent coefficients Tube voltage kV
5.12 Transillumination geometric conditions
The minimum distance L from the radiation source to the workpiece surface should not be less than that specified in Figure 4. 10-
Figure 4 Nomograph for determining the focal pen workpiece distance n
5.13 Shielding of scattered rays
JB/T 7260-94
A lead plate with a thickness of not less than 2mm should be placed behind the dark box to shield the influence of backscattered rays. The method for checking backscatter should be in accordance with the provisions of GB3323.
5.14 Film processing
The darkroom processing of film should be strictly in accordance with the film instructions or recognized effective methods. The liquid should be kept in a good state, and attention should be paid to the influence of temperature, time and shaking on the washing effect. The film processing can refer to the relevant provisions of ZBJ04004. 6 Film quality
6.1 Blackness
Choose suitable Appropriate exposure conditions should be set so that the blackness values ​​in the film effective evaluation area meet the requirements of Table 4. Table 4 Film blackness range
Ray type
X-ray
6.2 Film sensitivity
Film blackness D (including gray value Ds)
Gray fog De
The minimum copper wire diameter that must be displayed on the film, and its image length should not be less than 10mm. The transillumination thickness and the corresponding image quality index should meet the requirements of Table 5.
Table 5 Transillumination thickness and image quality index
Avoidance thickness
> 8~12
>12~16
>16~20
Image quality index required to be achieved
6.3 Other conditions not allowed within the effective evaluation range of the film: film shedding and severe scratches;
wire diameter
b. Fingerprints that hinder defect evaluation, static photosensitivity, image overlap (except for the double-entire single-image method and double-wall double-image method that require vertical transillumination), various prints and false images;
c. Incomplete display and improper position of the mark.
7 Observation of the film
7.1 The film should be dried and evaluated in a special film evaluation room after treatment. The indoor light should be dim and moderate, and the lighting should not reflect on the film surface.
7.2 The brightness and lighting range of the viewing lamp should be adjustable, and the viewing conditions of the film should comply with the provisions of Table 6. 5
Maximum allowable degree of film background illumination
30 ed/ml
10cd/m*
Weld quality grading
JB/T7260-94
Table 6 Film observation conditions
Film blackness D
8.1 According to the nature and quantity of defects, weld quality is divided into four levels. 8.1.1 There should be no cracks, lack of fusion, lack of penetration and strip-shaped clips in the weld of level 1. 8.1.2 There should be no cracks, lack of fusion and lack of penetration in the weld of level 1. 8.1.3 Weld defects exceeding level I are level V. 8.2 Classification of graphic defects
Brightness of viewing lamp
8.2.1 Defects with an aspect ratio less than or equal to 3 are defined as circular defects. Their shapes can be circular, shaped, or irregular shapes with tails (the tail should be included when measuring the size), including pores, slag inclusions, and tungsten inclusions. Circular defects are evaluated using an assessment area, which is 10mm×10mm. The assessment area should be selected at the most serious part of the defect. 8.2.2
When evaluating circular defects, the defect size should be converted into defect points according to Table 7. 8.2.3
Table 7 Defect Point Conversion
Defect Long Diameter
Defect sizes that are not counted are shown in Table 8.
Base Material Thickness
Defect Size
The assessment area frame line of circular defects should be parallel to the weld. Defects that are tangent to the frame line are not included in the assessment area and are not counted. 8.2.5
Defects that are aligned with the frame line are included in the assessment area and the number of points is calculated. 8.2.6
For the classification of graphic defects, see Table 9.
Table 9 Classification of circular defects
Quality grade
Thickness of parent material mm
Note: The numbers in the table are the upper limit of the number of defect points allowed. 6
>10~15
For defects with a number greater than level 1
>15~20
JB/T7260-94
8.2.7 When the thickness of each material is 2~3mm, the long diameter of the circular defect is greater than 2T/3 and is rated as N grade. When the thickness of the parent material is greater than 3mm, the long diameter of the circular defect is greater than T/2 and is rated as N grade (T is the thickness of the parent material). 8.2.8 The number of circular defects not counting points in the grade 1 weld and the grade 1 weld with the base material thickness equal to or less than 5mm shall not exceed 10 in the assessment area. If more than 10, the treatment shall be downgraded to a lower level. 8.3 Classification of slag strips
8.3.1 Slag inclusions with an aspect ratio greater than 3 are defined as slag strips. 8.3.2 The classification of slag strips is shown in Table 10.
Table 10 Classification of slag strips
Quality grade
Single slag strip length
T≤12:4
12
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