JB/T 5938-1991 General technical requirements for ductile iron castings for engineering machinery
Some standard content:
Machinery Industry Standard of the People's Republic of China
JB/T5938-91
Engineering Machinerywww.bzxz.net
General Technical Conditions for Ductile Iron Castings
1991-12-12. Issued
Issued by the Ministry of Machinery and Electronics Industry of the People's Republic of China
1992-07-01Implementation
Subject Content and Scope of Application
Cited Standards
Technical Requirements
Test Methods
Inspection Rules
Marking, Packaging, Transportation and Storage
Appendix A Machining of Ductile Iron Castings Allowance (supplement) Appendix B Non-cast hole size diagram (reference) Appendix C
Tolerance of weight of ductile iron parts (supplement)
Draft angle of ductile iron parts (reference)
......
Mechanical Industry Standard of the People's Republic of China
Engineering Machinery
General Technical Conditions for Ductile Iron Castings
Subject Content and Scope of Application
JB/T5938-91
This standard specifies the technical requirements, test methods, inspection rules, marking, packaging, transportation, storage, etc. of ductile iron castings in engineering machinery products.
This standard applies to ordinary and low-alloy ductile iron castings (hereinafter referred to as ductile iron castings). 2
Reference standards
GB1348
GB9441
GB2828
Technical requirements
3.1 Brand
Ductile iron castings
Metallurgical examination of ductile iron
Metal tensile test method
Metal Charpy (U-notch) impact test methodMetal Rockwell hardness test method
Metal Brinell hardness test method
Surface roughness comparison sample
Casting surface
Batch inspection counting sampling procedure and sampling table (applicable to continuous batch inspection) The brand of ductile iron castings shall comply with the provisions of GB1348. 3.2 Mechanical properties
3.2.1 The mechanical properties of ductile iron castings shall comply with the provisions of Tables 1 to 4. Table 1
Tensile strength. ,
QT400-18
QT400-15
QT450-10
QT500-7
QT600-3
QT700-2
QT800-2
QT900-2
avoidance strength. ,
1991-12-12 approved by the Ministry of Machinery and Electronics Industry Mechanical properties of single casting test pieces
Elongation%
Brinell hardness
130~180
130~180
160~210
170~230
190~270
225~305
245~335
280~360
Main metallographic structures| |tt||Ferrite
Ferrite
Ferrite+pearlite
Ferrite+pearlite
Pearlite or tempered structure
Bainite or tempered martensite
1992-07-01 implementation
QT400-18
QT400-18L
J3/T5938—91
Table 2 Impact value of single cast test block V-notch specimen Minimum impact value.
Room temperature 23±5℃
Average value of three trials
Individual value
Note: The mother \L\ indicates that the corresponding grade should have the impact value listed in Table 2 at low temperature. Table 3
QT400-18A
QT400-15A
QT500-7A
QT600-3A
QT700-2A
>30~60
>60--200
>60~200
>30 ~50
>60~200
>30~60
>60200
>30~60
>60~200
tensile strength.
Low -20±2℃
Average value of two samples
Mechanical properties of cast test block
Yield strength ca2
Elongation
Brinell hardness
130~180
130~180
170~240
180~270
220~320
Individual value
Main metallographic structure
Ferrite
Ferrite
Ferrite + pearlite
Ferrite + pearlite
Ferrite + pearlite
Note: The letter A after the brand name indicates the mechanical properties of the brand determined on the cast test block, to distinguish it from the properties determined on the single cast test block in Table 1. Table 4 Impact value of V-notch test specimen of attached cast test block Wall
QT400-18A
QT400-18A
>30~60
>60~200
>30~60
>30~200
Room temperature 23±5℃
Average value of three specimens
Minimum impact value.
Individual value
3.2.2 The mechanical properties of ductile iron parts are based on the two indicators of tensile strength and elongation for acceptance, J/em
Low temperature -20±2℃
Average value of three specimens
Individual value
3.2.3 When the yield strength, impact toughness and hardness tests are required, they should be indicated on the drawings or in the relevant technical documents. Their values should comply with the provisions of this standard.
3.3 Chemical composition, metallographic structure and heat treatment The chemical composition, metallographic structure and heat treatment process of ductile iron are not used as acceptance data. If there are special requirements, they should be indicated on the drawings or technical documents. However, the ductile iron parts must meet the mechanical performance indicators specified by the ductile iron grade. The metallographic structure should comply with the provisions of GB6441. 3.4 Geometric shape and size
The geometric shape and size of ductile iron parts should meet the requirements specified in the drawings or order agreements. 3.5 Dimension tolerance
JB/T5938—91
The dimensional tolerance specified in this standard refers to the tolerance that ductile iron parts should achieve under normal production conditions. 3.5.1
The dimensional tolerance values of ductile iron parts should comply with the provisions of Table 5. The tolerance grade should be selected according to the provisions of Table 6. Table 5
Basic dimensions of ductile iron parts
Dimensional tolerance values of ductile iron parts
Note: ① The basic dimensions of ductile iron parts refer to the dimensions given on the drawings, which should include machining allowance and draft angle. ② For ductile iron parts with basic dimensions less than or equal to 16mm, the tolerance values of CT12 are used for grades CT13 to CT15. Table 6
Dimensional tolerance grades of ductile iron parts
Sand mold hand molding
Sand mold machine molding and shell mold
Metal mold
Low pressure molding
Investment molding
Dry and wet sand
Self-hardening sand
Note: For small batch and single piece production, when the basic dimension of ductile iron parts is not greater than 16mm, its tolerance grade is increased by 2 grades; when it is greater than 16~25mm, its tolerance grade is increased by 1 grade.
The tolerance grade of ductile iron parts shall be indicated in the drawings or relevant technical documents. If not indicated, the lowest tolerance grade shall be used. Different tolerance grades are allowed to be selected in a certain local range of the same ductile iron part, but the common tolerance value shall be indicated in the drawings or relevant technical documents.
3.5.5 Tolerance band position cover
JB/T5938-91
3.5.5.1 The tolerance band of ductile iron parts shall be distributed symmetrically, that is, half of the tolerance is positive and the other half is negative (see Figure 1); when there are special requirements, asymmetric settings can also be adopted, but it shall be indicated in the drawings or relevant technical documents. 3.5.5.2 For the inclined parts of ductile iron parts, the dimensional tolerance shall be marked symmetrically along the inclined surface (see Figure 2). Basic size of ductile iron parts
Dimensional tolerance zone of ductile iron parts
Minimum limit size
Maximum limit size
3.5.6 Internal and external corner tolerances
The internal and external fillet tolerances of ductile iron parts use the tolerance values in Table 5 as the upper limit and the lower limit is zero. 3.5.7 Wall thickness tolerance
The wall thickness tolerance of ductile iron parts can be reduced by one level compared to the tolerance grade selected for the ductile iron parts. 3.5.8 Misalignment value
The misalignment value of ductile iron parts (as shown in Figure 3) must be within the tolerance value specified in Table 5. When the misalignment value needs to be further restricted, it should be indicated on the drawing and its value should be selected from Table 7.
Tolerance grade
Misshape value
3.6 Machining allowance
JB/T5933--91
3.6.1 The machining allowance of ductile iron parts shall comply with the provisions of Appendix A (Supplementary Parts). 3.6.2 The minimum dimensional limit deviation of the machined surface of ductile iron parts shall ensure a machining allowance of not less than 1/3. 3.6.3 The size range of non-cast holes can refer to the provisions of Appendix B (Reference Parts). 3.7 Geometric shape tolerance
3.7.1 The bending and super-bending deformation of ductile iron parts shall be measured according to the maximum size of the inspected surface. On the non-machined surface, it shall not be greater than the provisions of Table 8, and the concave part on the machined surface shall ensure a machining allowance of not less than 1mm. 3.7.2 The concave and convex amount of the ductile iron surface shall ensure a machining allowance of not less than 1 on the concave part of the machined surface. /3 machining allowance, the raised part should not exceed 3mm; on the non-machined surface, if the concave or convex value exceeds the corresponding dimensional tolerance or wall thickness dimensional tolerance value, repair is allowed. 3.7.3 Eccentricity of castings. On the machined surface, a machining allowance of not less than 1/3 should be ensured. On the non-machined surface, it should not exceed the provisions of Table 5.
Maximum dimension measured
Bending and warping deformation
3.8 Weight tolerance
≤250
>250~500
>500~800
>800~1200
>12004000
The weight tolerance of ductile iron parts shall comply with the provisions of Appendix C (supplement). Weight tolerance is not used as the basis for acceptance: if there are special requirements, it should be indicated on the drawing. Or indicated in the relevant technical documents. 3.9 Draft Angle
The draft angle value of ductile iron parts shall comply with the provisions of the drawing D (reference part). 3.10 Surface Quality
3.10.1 The roughness of the casting surface of ductile iron parts, when not indicated on the drawing, is generally 50μm. 3.10.2
The residual surface of ductile iron parts shall comply with the provisions of Table 9. Table 9
Burrs, molding sand, core sand, core bone, sand-bonded porcelain cervix, vent holes and other concave and convex defects
Residual surface
Not allowed
The concave and convex volume on the non-machined surface shall not exceed 1.5mm. If the protrusion on the workpiece surface is allowed to be no more than 5mm, the return amount should ensure that there is 1/3 of the machining allowance. The allowed protrusion after grinding is no more than 1.5mm
3.10.3 In the absence of In the case of affecting the service life and performance of ductile iron parts, the defects allowed on the non-machined surface of ductile iron parts shall comply with the provisions of Table 10.
3.10.4 In the case of not affecting the service performance and mechanical properties of ductile iron parts, the defects allowed on the machined surface of ductile iron parts without repair shall comply with the provisions of Table 11.
3.10.5 Defects are not allowed to appear simultaneously on the symmetrical positions on both sides of the same section of the same wall on important machined surfaces and non-machined surfaces.
3.11 Defect Repair
3.11.1 Casting defects on the non-machined surface or machined surface of ductile iron parts are allowed to be repaired if they do not exceed the provisions of Table 12 and do not affect the service life and service performance of ductile iron parts after repair; however, ductile iron parts that are not allowed to have defects in accordance with regulations shall not be repaired. Defect
JB/T5938—91
A(Liquid flow surface of high pressure vessel and important parts and important parts such as impact-resistant, pressure-resistant and wear-resistant parts)
≤420
Defect depth
Not more than 1/7 of the wall thickness
Protrusion is not more than
1.5mm; residual porosity
depth is not more than 1/7 of the wall thickness
Number of defects
Not more than 3 within a 50mm circle
Not more than 1 within a 100mm circle
Defect depth is not more than 1/7 of the wall thickness; not more than 3 within a 50mm circle
B(General mechanical parts)
Defect depth||tt ||Number of defects
not more than 1/7
in wall thickness
protrusion not more than
1.5mm, residual porosity
depth not more than 1/7
in wall thickness
not more than 3 within a 50mm circle
not more than 2 within a 100mm circle
not more than 1 within a 100mm circle
the depth of defects is not more than 1/3 of the wall thickness; not more than 6 within a 50mm circle
after trimming, the wall thickness should be within the dimensional tolerance range and no defects are allowed
Note: ①There are two different important parts on the same ductile iron part, and the total number of defects is superimposed for assessment; ②Different types of defects appear on the same ductile iron part and are calculated separately. Table 11
Ductile iron parts
Surface category
Gear teeth are beautiful
Clean.
Tooth groove bottom
Defect size
<Tooth groove bottom
Sand holes, pores and other defects
Defect depth
No more than 1/7
Wall thickness
No more than 1/5
No more than
1/10 of the ring thickness
Number of defects
Not allowed to exist
No more than 3 within a 50mm circle
No more than 1 on the same tooth surface
No more than 1 on the same tooth groove
|tt||Defect spacing
The number of teeth with defects shall not be
greater than 1/13 of the total number of teeth;
It is not allowed to appear continuously on 3
tooth surfaces or 2 tooth grooves
Application examples
Hydraulic (pneumatic) parts, important
screw hole sealing surfaces, etc.
Non-matching surfaces
General matching surfaces
Before welding repair, the defects must be scraped until good metal is present, and the defect surface within 30mm from the edge of the defect must be cleaned. 3.11.3 Defects in non-important parts are allowed to be repaired with epoxy resin. 3.11.4After welding repair, the repaired area should be ground to meet the surface quality requirements of ductile iron parts. 3.11.5 After welding repair, ductile iron parts that originally required aging treatment must be subjected to aging treatment; ductile iron parts with air tightness requirements must be subjected to leakage tests; for ductile iron parts with hardness requirements, the difference between the hardness of the weld repair and the base material should be within 20HB. 6
Ductile iron parts
Non-housing parts
Housing parts
JB/T5938-91
Table 12 Defects allowed to be repaired
Defect conditions
Blowholes, sand holes
The total area of defects accounts for the percentage of the surface area where they are located%
The circumferential length of the hole is not more than 1/5 of the circumference of the hub, the hole
is not more than 1/3
The wall where it is located is not more than 1/15
The radial width is not more than 1/3 of the hub width||tt ||Wheel wall thickness
Pore limit≤10
4 Test method
4.1 Test block and specimen preparation
4.1.1 Single cast test block
Not more than 1/2
Weir plate thickness
Number of notches
on the whole piece
Ratio of crack effect length to crack direction length
≤1/3
≤1/4
Not more than 1/2
Wheel plate thickness
Not allowed to exist
4.1.1.1 Single cast test block shall be cast with the molten iron used to cast the batch of castings and cast at the later stage of each package of molten iron. The shape of the test block can be selected from Figure 4, Figure 5 or Figure 6. The dimensions of Figure 4 and Figure 5 are shown in Table 13 and Table 14. 1.1.1.2
Flag slope:
Figure 4U-type single casting test block
Figure 5Y-type single casting test block
Number of cracks on the whole piece
1.1.3 The cooling conditions of the test block are roughly the same as those of the casting it represents. The test specimen is processed from the surface line of Figure 4 or Figure 5 or the circle of Figure 6:
Size code
JB/T5938—91
Figure 6 Knock-off test block
Table 13 Dimensions of U-type single cast test block
Dimensions of various types of U-type single test blocks in mm
Determined according to the total length of the test specimen
Note: ① The smaller size of the Class A test block in the U-type single cast test block is a provisional size. ② The minimum sand consumption of the test block for A, B, B is 40mm, and the minimum sand consumption for C and D is 80mm. ③ The values listed in y are for reference
Table 14 Dimensions of Y-type single-cast test blocks
Dimension code
Dimensions of various Y-type test blocks
Determined according to the total length of the sample
Note: ① The minimum sand consumption of the test block for A and B is 40mm, and the minimum sand consumption for C and D is 80mm. ② The values listed in y are for reference
The unpacking temperature of the test block should not exceed 500℃. If heat treatment is required, the test block should be heat treated in the same furnace as the casting. 4.1.1.4
4.1.1.5 If spheroidizing inoculation treatment is carried out in the casting, the test block should be cast in the casting with a common pouring and riser system. 8
4.1.2 Attached cast test block
JB/T5938-91
4.1.2.1 The shape of the attached cast test block is shown in Figure 7, and its dimensions are shown in Table 15.4.1.2.2 The attached cast test block should be cut from the casting after heat treatment. Continuation
Figure 7 Attached cast test block
Wall thickness of casting
>30~60
>60~200
Dimensions of attached cast test block
Note: If a smaller size of attached cast test block is used, the following formula is used to specify 5=0.75a+=a/2.4.1.3 Test specimen
4.1.3.1 The shape and dimensions of the tensile test specimen are shown in Figure 8. R20
L-—Original gauge length of the test specimen. L=5d.mm! Original diameter of the specimen, mm
d=1.4±0.09
L. =70
Figure 8 Tensile specimen
L—Parallel length of the specimen, l>L. To be agreed upon by both parties, mmmm
40 or 60
70 or 105
L,--Total length, recommended total length is 180mm, which can be appropriately reduced under special circumstances, but shall not be less than 120mm. Note: The method of clamping the end of the specimen and the total length L can be agreed upon by both parties. If other diameter specimens are required for technical reasons, they shall comply with the following formula, L.=5.65Vs. or L. =5d
Where, L. Original gauge length of the specimen, mmS. Original cross-sectional area of the specimen, mm;
d Original diameter of the specimen, mm.
4.1.3.2 The shape and size of the impact specimen are shown in Figure 9. L (for reference)
The rest 6.3
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