This standard specifies the acceptance requirements and methods for X-ray and gamma-ray radiographic inspection of pressure-bearing steel castings of valves, as well as the classification and evaluation methods of radiographic film defects. JB/T 6440-1992 Radiographic inspection of pressure-bearing steel castings of valves JB/T6440-1992 Standard download decompression password: www.bzxz.net

Machinery Industry Standard of the People's Republic of China
Radiographic Inspection of Pressure Cast Steel Parts of Valve
1 Subject Content and Scope of Application
JB/T 6440
92||tt| |This standard specifies the X-ray and? Acceptance requirements and methods for radiographic inspection and methods for classification and assessment of defects in radiographic films.
This standard applies to the radiographic inspection, quality rating and acceptance of valve pressure cast steel parts (hereinafter referred to as steel castings). The radiographic inspection of supporting pipe fittings, flanges and other pressure-cast steel parts can also be performed with reference to this standard. 2 Reference standard
GB5618 Linear Image Quality Meter
GB567? Acceptance requirements for steel casting radiography and film grade classification method 3
3.1 Steel castings are not allowed to have cracks and unfused defects of internal cooling iron and mud core supports. The radiographic flaw detection acceptance grade of steel castings should not be lower than the requirements in Table 1.
Table 1
Wall
Defects
Class
Type
Gas
Hole
Sand inclusion Helai slag
shrinkage cavities and porosity
51
合
2
3
2 (linear), 3 ( dendritic)
Thickness, mm
251
Grade
Grid
3.2 For valves welded to pipelines, that is, the acceptance level of the welding groove , should be upgraded or implemented according to the agreement between the supply and demand parties. 3.3 When the supply and demand parties have an agreement, the radiographic inspection level of steel castings shall be implemented according to the agreement. Different levels can be selected for different parts of the same casting: different levels can also be selected for different types of defects in the same part. 3.4 The recommended inspection parts are shown in Appendix B (reference part). 3.5 Steel castings that fail to pass the radiographic inspection can be repaired by welding according to the relevant regulations on defective welding repair. The welding repair area should be inspected again according to this standard and accepted according to Table 1.
Radiographic methods
4
4.1 Radiographic requirements
4.1.1 Personnel engaged in radiographic inspection must hold a certificate issued by the relevant national department and relevant to the work Applicable qualification certificate 4.1.2 The surface of steel castings should pass the appearance inspection before radiographic flaw detection can be carried out. 4.1.3 Steel casting films should be permanently or semi-permanently marked. As the basis for repositioning each radiographic film. When steel castings are not suitable for marking, detailed sketches or expanded drawings of the transilluminated parts should be used. The Ministry of Mechanical and Electronic Industry of the People's Republic of China approved the implementation on 1993-01-01 on 1992-07-20
137
4.2 Radiographic sensitivity
The radiographic sensitivity is expressed by the following formula: ||tt ||4.2.1
In the formula: K-
JB/T 6440 -- 92
K=(d/t)100%
expressed in percentage Radiographic sensitivity; d—the diameter of the smallest steel wire identifiable on the radiographic film, mm: the wall thickness of a steel casting where it is transilluminated, mm. 4.2.2 Radiographic sensitivity is divided into level A (normal sensitivity) and level 13 (high sensitivity), see Table 2 Table 2
photo
thick
mm
50 | | tt | | 50 | A
2
Level
Speciality
sensitivity, bath
4.2.3 When the thickness of the transillumination is less than 10mm, the diameter must be read on the film as 0.2 mm image quality meter steel wire 4.3 ray source selection
13
1.2 yuan
The sensitivity level is selected according to Table 3, Level A and Level B
150
400
350
300
250
200||tt ||150
125
100
80
shoot
line
Ir192
Co60
Source
1~2 MV X-ray
2MVX-ray
56
Figure
10
20
30 40
Transillumination thickness.mm
80 100150
60
The relationship between tube voltage and transillumination thickness
Table 3
A|| tt||Grade
20~100
40--2001
50~200
50
Transillumination thickness, mm
13
level
40-90
60 -15
l
50--
60
Note: 1) When the thickness range of the transillumination is 40~6%mm, it is recommended to use 0.4~0).7mm thick steel (or alloy steel) or copper front screen and rear support 638
4.4 film to intensify Screen
4.4.1 Film
JB/T 6440 -- 92
The film type should be selected according to the thickness of the steel casting, radiographic sensitivity and intensification method. Level A methods should use type 3 or type 4 film; level B methods should use type 1 or type 2 film. Film types and their characteristics are shown in Table 4. Table 4
Film type
1
2
3
4
4.4.2 Intensifying screen
grains
degree
ultrafine grain film
fine grain film
equal grain film
larger grain film
photosensitive speed
Very slow
Jun
Medium speed
Fast
For radiography, a metal or metal fluorescent intensifying screen is used accordingly. The thickness of the intensifying screen can be selected according to Table 5. The intensifying screen and film should always be in close contact with each other during the transillumination process.
Table 5
Ray source
100kv
Ir192
Co60
1~2MVX ray
>2~6MV × ray
≥6~12MVX ray
212MVX ray
A
level
0).02~0.25. The front and rear screens are lead-increased Sensing screen 0.05～0.25. Front and rear screens are lead intensifying screens. Sensing screen thickness.mm
0.1~~0.5. Front and rear screens are lead, steel or copper intensifying screens 0.1～1.0. Front and rear screens are lead intensifying screens. The rear screen is a lead intensifying screen
1.01,5. The front and rear screens are copper or lead intensifying screens
10.1~0.7, the front and rear screens are steel or copper intensifying screens. 1.0 ~ 1.5, the rear screen is 1.5, it is a copper or steel intensifying screen 1.0 ~ 1.5, the front screen is a button or tungsten intensifying screen, the rear screen does not need to be noted:) The material of the steel intensifying screen in the table can also be gold-containing steel Manufacturing, ② For radiation sources below 100kV, the front screen is not required. 4.5 Focal length
The minimum distance from the ray source to the steel casting plus the steel casting transillumination thickness t is the required focal length. The sub-value can be determined by any of the methods in Appendix A (Supplement). If the requirements of Appendix A cannot be met due to limitations of transillumination conditions, it is acceptable if it can meet Article 4.2.2 (Radiographic Sensitivity) and Article 4.9.2 (Blackness). 4.6 Shielding of scattered rays
In order to improve the sensitivity of radiography, appropriate methods should be used to shield scattered rays. To check backscatter, a "B" type mark can be affixed to the back of the compensation box (the cross-section height of the letter is 1.3mm and the width is 1.6mm). If a lighter image of "B" appears on the darker background of the film, it means that the backscatter protection is insufficient and it should be re-photographed; if a darker image of "B" appears on the lighter background, the film will not be discarded. basis.
4.7 Image quality meter
The image quality meter should be selected according to the thickness of the steel casting and in accordance with the provisions of GB5618. 4.8 Transillumination plan and arrangement
4.8.1 Before transillumination, the transillumination process design should be done according to the shape, size, transillumination position and protection conditions of the steel casting. 4.8.2 It is required to use the minimum wall of the steel casting. The thick direction is the transillumination direction. When it is impossible to transilluminate from this direction, other methods can be used to transilluminate. Transillumination thickness refers to the thickness in the actual transillumination direction. When the thickness cannot be measured actually, drawing methods can be used to determine it. 639
4.8.3 Transillumination method and position of image quality meter
4.8.3.1 Internal penetration method
JB/T 6440—92
When the inner diameter of the steel casting is large, the internal penetration method is used. The radiation source is placed in the hole of the steel casting + and the film is placed on the outer surface of the steel casting, so that the rays pass through a layer of the steel casting, which is called the eccentric endoscopic method (see Figure 2); if the radiation source is placed on the outer surface of the steel casting, The center position of the steel part is called the center-of-circle transillumination method (see Figure 3). In this case, if the wall thickness is equal around the steel casting, the entire circumference of the steel casting can be exposed and transilluminated, and in the four quadrants of the steel casting Just put an image quality meter in each.
s
Figure 2 Schematic diagram of eccentric endofluorescence method
Figure 3 Schematic diagram of center-center endofluorescence method
S-ray source N film C steel casting
4.8.3.2 External transmission method
The method in which the radiation source is placed outside the steel casting for transillumination is the external transmission method. The first is that the film is placed on the inner surface of the steel casting, and the rays penetrate through the wall thickness of the two layers and are transilluminated (see Figure 4); the second is that the film is placed on the outer surface of the steel casting, and the rays penetrate through the two wall thicknesses and are transilluminated, also known as Double-wall transillumination, this method can be used for steel castings with smaller apertures (see Figure 5). If double-wall transillumination is used, the number of transilluminations should be s on two mutually perpendicular sides of the steel casting
Figure 4 Schematic diagram of the external transmission method
4.8.4 Image quality meter Position
ts
r
Figure 5 Schematic diagram of double-wall transillumination method
S-ray source;N film;C. Steel castings
No matter Whichever transillumination method is used, the image quality meter should be placed on the side of the steel casting close to the radiation source. If the conditions are not met, it can be placed on the side of the film and appended with the "*F" mark. However, a comparative test should be done to make the measured radiographic sensitivity meet the requirements. 4.9 Film processing and requirements for negatives
4.9.1 The film should be processed according to the film instructions or recognized effective methods. 4.9.2 The blackness of the defect-free parts of the film should meet the requirements of Table 6. When dual film exposure and thickness compensation are used, the effective blackness assessment range of the film can be expanded. |tt||Table 6
Level
3
Speciality
Valid range of film blackness
1.2~3.5
1.5~ 3.5
Note: When using double film exposure, the blackness value of a single film of ordinary sensitivity level (A level) can be relaxed to 1.0, while the blackness value of double film observation must not exceed 4.0.||tt| | 640 | | tt | Recognizable.
4.9.4 No defects that hinder the rating are allowed in the effective evaluation area of ??the film.
4.10.1 Film evaluation should be carried out in a dedicated film evaluation room. The light in the room should be dim, and its illumination brightness should not be reflected on the film surface.
4.10.2 The film viewing lamp should have a brightness of 3.5 or above and the diffuse brightness should be adjustable. Meet the requirements of Table 7. For parts that do not require observation or have excessive light transmission, appropriate light shielding plates should be used to shield the strong light.
Film blackness
1.0
1.5
2.0
2.5
3.0
3.5
4.0
5
|tt||Defect classification and size determination
5.1
Viewing light brightness
300
1000
3000
10:000
10:000
30000
100000
Illumination brightness through the film
30
10
cd/m
5.1.1 Casting defects on the negative film are divided into five categories: pores, sand and slag inclusions, shrinkage cavities and shrinkage porosity, lack of fusion of internal cooling iron and mud core support, and cracks in the repair welding area. The pores of the defect can be regarded as the pores of the casting defects, and the slag inclusion, lack of fusion, and lack of penetration of the defects in the repair welding area can be regarded as the slag of the casting defects and evaluated according to
5.1.2 Defect size. The size of the defect image on the film is measured. For shrinkage holes, only the size of the bright part of each defect is measured, excluding the size of the surrounding blurred and shadowed parts. When two or more defects partially overlap on the film, they should be measured separately. Size. 5.1.3 When a defect is connected to the boundary of the assessment area (field of view), it should be included in the assessment area for calculation of points. 5.2 Defect grades of pores, sand inclusions and slag inclusions 5.2.1 Select the area with the largest number of defect points on the negative film as the evaluation area. The size of the assessment area and the maximum allowable number of defect points are as specified in Table 8 and Table 9.
Table 8
Transillumination thickness +mm2
0
Defect level
20
3
2|| tt||3
5
G
4
6
9
14
>10 ~~ 20
30
4
6
14
21
>20～40
>40～~80| |tt||>80~120
Assessment area (diameter),mm
50
6
10
15
22
32
50
Maximum allowed points for air holes
8
16
24
32||tt| | 42 |
49
>120--200
70
12
22
32
12||tt| |56
>200-300
J00
14
25
10
60
80||tt ||641
Defect level
1
2
3
4
5
6||tt| |10
20
5
10
14
21
>10~20
30||tt ||8
11
16
23
32
JB/T6440
Table 9
92|| tt||Transillumination thickness, mm
20-40
240~.80
80~ 120
Assessment area (diameter), mm
50
50
70
Maximum allowed points for sand and slag inclusion
12
17
23
30
40
16
22
29
38
50
Those with defect points exceeding level 5; defects For those with size over 30mm 20
28
36
46
60
2120~-200
70
24
3.1
44
5.4
70
200--300
100
28
55 | | tt | | 76 | | tt | |Table 10
Defect size, mm
Number of defective points
Defect size, mm
Number of defective points
Defect level
2~- 6
2.0
1
10. 0~15. 0
12
10
0.4
0.7| |tt||>2. 0~4. 0
2
15. 0~~20. 0
16
Table 11
> 4. 0~~6.0
3
>20.0~~25.0
20
Transillumination thickness
≥>10~20
0.7||tt ||1.0
>20~40
>40~80
>6. 0~~8. 0
>25.0-30. 0||tt| |40
>80120
Maximum defect size without counting points
1.0
1.5
=8.0-~10. 0
8
30. (0--60.0
90
mm
≥120~~200
1.5
9||tt| |200-~300
5.2.3 The number of points for two or more defects is the sum of the number of points of each defect in the assessment area. It can be assessed according to Table 8 and Table 9 respectively, but the maximum allowed pores and clips are. The size of sand and slag inclusions shall not exceed the requirements in Table 12 and Table 13 respectively. Table 12
Transillumination thickness
Maximum size of pores
Transillumination thickness
Sand inclusions and Cool
large size
10
M10
5.3 shrinkage cavity defect level
3.0
10~~20
>1020
6.0
>2040
4.0
Table 13
>20-40
8.0|| tt||>40--80
5.0
>40～80
10.0
>80~120
7.0
> 80~-120
14.0
level
mm
2120~ 200: 2200--300
9.0
10.0||tt ||mm
120～200≥200~300
18.0
20.)
5.3.1 Select the maximum length or area of ??the defect on the negative film as Assessment area. The size of the assessment area and the maximum allowable size of defects shall be as specified in Table 14 or Table 15.
642
Defect level
1www.bzxz.net
2
3
学
5
6| |tt||Defect level
2
0
10
50
50
12
23|| tt||4.5
75
100
>10~20
210~20
250(1000)
450(2000 )
800(3 000)
1600(6000)
3 60010 000)
JB/T 6440 -- 92
Table 14|| tt||Thickness of penetration
20~40
240~~80
80120
Assessment area (diameter)
70
Maximum allowable length of strip shrinkage cavity defects
18
36
63
100
145
30
63
110
150
230
Length exceeds level 5
Table 15
Transillumination thickness mm
>20~40
>40~80
Assessment area (diameter)
70
mm
≥120-200：>200--300
100
50
110
145
180
250
60
120|| tt||I6
200
270
mm
80～1201120～200≥200300
100
Tree-shaped shrinkage cavity Maximum allowable area of ??defects, mm2600(1600)
900(3000)
1650(5000)
2700(9000)
6 300(16 000)| |tt||800
1350
2700
5400
9000
Those with area exceeding level 5
5.3.2 Shrinkage holes Defects can be divided into strip-shaped shrinkage holes, dendritic shrinkage holes and large-area shrinkage porosity according to their shapes 1000
2000
3000
8000
12000
1600
3600
5000
9000
14.000
5.3.3 Calculation of the length of strip shrinkage cavity defects; The maximum length of is the defect length. For two or more strip-shaped shrinkage holes, the sum of the lengths of each shrinkage hole is the defect length. When the shrinkage cavity is on the boundary line of the assessment area, the part of the defect outside the line should also be included.
Calculation of dendritic shrinkage cavity defect area: A dendritic shrinkage cavity is a shrinkage cavity defect based on the product of the maximum length of the defect and the maximum width of its intersection multiplied by 5.3.4
Area; for two or more dendritic shrinkage holes, the sum of the areas of each shrinkage hole is used as the defect area. When the shrinkage cavity is on the boundary line of the assessment area, the part of the defect outside the line should also be included. 5.3.5 When there are both dendritic shrinkage cavities and strip-like shrinkage cavities in the assessment area, the strip-like shrinkage cavities will be evaluated as dendritic shrinkage cavities. The length shall be based on the length of the strip-like shrinkage cavities, and the width shall be three times the length. Calculation. 5.3.6 The area of ??large-area shrinkage defects is calculated based on the product of the maximum length of the defect and the maximum width orthogonal to it. The grade of shrinkage defects should be evaluated based on the length or area of ??the defect in the assessment area, but Shrinkage cavities smaller than those specified in Table 16 may not be counted as defects in 5.3.7
.
5.3.8 Strip shrinkage cavities are evaluated according to the total length of defects in the evaluation area according to Table 14; dendritic shrinkage cavities are evaluated according to the total defect area in the evaluation area according to Table 15; large-area shrinkage cavities are evaluated according to the total length of defects in the evaluation area The total defect area is evaluated according to the numerical value in the brackets in Table 15, 613
Defect level
Tea-shaped, mm
Dendritic.nm\
Strip-shaped, mm| |tt||Dendritic.mm2
10
>10～20
JB/T 6440 --- 92
Table 16
Transillumination Thickness, mm
220-40
240~80
: >80- 120
The maximum limit for shrinkage cavity defects without evaluation is 5.0
10.0)
5.
30.0
≥120--200
10.0
10.0
5.4 Cracks on the negative film (heat Cracks and cold cracks), internal cooling iron failure to fuse and mud core bracing failure to fuse are all rated as level 6. 5.5 Comprehensive rating of defects
200--300
In the assessment area, when there are two or more types of defects at the same time, they should first be graded separately according to the type of defects, and then according to the given below Methods for comprehensive rating:
5.5.1 When there are two or more types of defects with different grades in the assessment area, the lowest grade among them shall be taken as the comprehensive assessment grade.
5.5.2 In the assessment area, when there are two or more defects of the same grade at the same time, the comprehensive assessment grade shall be reduced by one grade. In the case of two or more grade 1 defects at the same time. When the number of points, length or area of ??the defects exceeds 1/2 of the allowable value, it shall be rated as grade 2. However, for defects rated as grade 2 according to the provisions of Tables 12 and 13, or for defects rated as grade 2 according to the provisions of Tables 11 and 16 without considering that the maximum size of the defects exceeds the applicable range of grade 1, even if mixed with some other grade 2 defects, their comprehensive grade is still rated as grade 2.
Records of Radiographic Inspection
6
The following contents shall be recorded during radiographic inspection:a.
h.
c.
d.
e,
f.
g
h.
i.
514
Name and manufacturer of steel casting;
Date and number of flaw detection;
Material, thickness and thickness of radiographic inspection Part;
Name of flaw detection instrument, focus, focal length, tube voltage, tube current, exposure time, type and intensity of radiation source; type of film, sensitization method and darkroom processing conditions; radiographic sensitivity and film blackness;
Defect grade classification results,
Location map and items required by users, etc.;
Signature of inspection and review personnel (including inspection date, review date, unit seal) Map search method
A1
JB/T 6440—92
Appendix A
Method for determining the minimum distance (f) from the radiation source to the steel casting (supplement)
According to the irradiated thickness of the steel casting, the /d value is found from Figure A1, and then calculated according to the following formula, the value f (f/d)d
Where: -Minimum distance from the radiation source to the steel casting.mm; Q
-Effective size of the radiation source, mm.
Calculation of the effective size d of the ray source:
a.
b.
d.
Square focus d=a(αa is the side length of the square); rectangular focus d=（a+b)/2(a, b are the side lengths of the rectangle); elliptical focus d（ab)/2(α, b are the major and minor axis lengths of the ellipse); circular focus is the diameter of the circular focus.
B level
1000
E
100
8F
5
10
56
810
Figure A1
A2 Graphical method
A level
20
30 4060 80 100
Transillumination thickness t, mm
200300
Relationship between transillumination thickness t and minimum f/d value
Al）
According to Figure A2, according to the known effective size d of the focus and the thickness t of the transillumination steel casting, it is divided into two levels, A and B, and the graphical method is used to obtain the example: the transillumination thickness t=37mm, the effective size of the radiation source d=3mm, the intersection of the line connecting the 3 points of the d scale and the 37 points of the t scale on the normogram can determine the f value: A level f=250mm; B level f=500mm. 615
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