JB/T 7945-1999 Test methods for mechanical properties of grey cast iron
Some standard content:
JB/T 7945
—1999
This standard is a revision of J1B3/T7945—95 "Mechanical Properties Test Methods for Gray Cast Iron Modification". During the revision, the original standard was edited and revised. This standard will replace JB/T7945··95 from the date of implementation. Appendix A of this standard is the standard appendix.
Appendix B of this standard is the indicative appendix.
This standard is proposed and managed by the National Technical Committee for Casting Standardization. The drafting units of this standard: Shenyang Foundry Research Institute, etc. Main drafters of this standard: Zhang Zhengde, Du Xingjin, Gong Xingju, Yu Shen408
1Scope
Mechanical industry standard of the People's Republic of China
Gray cast iron
Methods for testing the mechanicalproperties of grcy cast ironJB/T 7945
Replaces JB/T7945.95
This standard specifies the test methods for the tensile strength (), bending strength (), deflection (), compressive strength (), shrinkage rate (.) and other mechanical properties of gray cast iron.
This standard is applicable to the determination of the mechanical properties of gray cast iron under static conditions at room temperature. 2 Tensile test
2.1 The tensile test is used to determine the tensile strength of gray cast iron 0h, and the calculation is carried out according to formula (1): dp
Where: oj tensile strength, N/mm2
F: maximum tensile load, N;
A-the minimum cross-sectional area of the parallel section of the specimen before the test, mm....(1)
2.2 The tensile specimen is a single-cast test bar or a cast test bar with a rough cylindrical shape (d-30+rm). The single-cast test bar is cast with molten iron between the casting and the casting. The single-cast test bar is cast in a quasi-dry sand mold or a sand mold with similar thermal conductivity. If the supply and demand parties have an agreement, a wet mold can also be used. Several test bars can be cast in the mold at the same time, and the distance between each test bar is not less than 50mm (see Figure 1). The length of the test bar is determined according to the shape and size of the tensile specimen.
Approved by the State Machinery Industry Bureau on June 24, 1999 30g
200001.01 Implementation
JB/T7945—1999
2.3 The shape and size of the standard tensile specimen of gray cast iron are shown in Figure 2, Figure 3 and Table 1. Al type
The remaining 6
Hold the end
The minimum parallel section length L.
True diameter of the specimen d.
Transition arc radius R
Cylindrical
Butterfly shape
JB/T 7945
Minimum diameter d,
Minimum length I
Thread diameter and pitch d
Minimum length L
Processing specifications
When checking the grade of gray cast iron, use the single cast test bar shown in Figure 1 to process the tensile test specimen shown in Figure 2 or Figure 3 for testing. If the supply and demand parties have an agreement, the auxiliary tensile test specimen listed in Appendix A (Standard Appendix) can be used. 2.4 The minimum measurement accuracy of the parallel section diameter of the tensile test specimen is 0.05mm. 2.5 The tensile test speed is specified as the stress increase rate less than or equal to 30MPa/s. During the arbitration test, the stress increase rate shall not exceed 10MPa/s.
2.6 The gray cast iron tensile test can be carried out on any type of testing machine. The error of the force indication shall not exceed 1%. The fixture of the tensile testing machine should ensure that the axis of the specimen is aligned with the center so that the load acts on the axis of the specimen. 2.7 The ambient temperature during the test is 20℃ ± 10C. When the temperature exceeds the specified range, it should be noted in the test report. The tensile strength measurement value should retain three significant figures. The digital rounding should be carried out in accordance with relevant regulations. 2.8
The test report should include:
a) Sample number;
b) Type of test bar roughness, such as single casting or attached casting, dry type or wet type; c) Tensile strength;
d) Fracture conditions, such as slag inclusions, shrinkage cavities, pores, and fracture locations;) The auxiliary specimen should indicate the specimen diameter and sampling location. 3 Bending test
3.1 The gray cast iron bending test is to subject the specimen to a lateral concentrated load, as shown in Figure 4, to measure the bending strength and deflection. The bending strength α is calculated according to formula (2):
Where: dtl
Bending strength, N/mm\;
~Specimen diameter, mm;
1---·Distance between support points, mm:
K.Bending coefficient (see Table 2);
F--Specimen breaking load, N.
3.2 Deflection is the displacement of the specimen from the initial load to the maximum load (specimen breaking). 3.3 Test conditions and measurement accuracy are shown in Table 3. 3.4 The bending specimen is cast by vertical top or bottom pouring of dry mold. If the supply and demand parties have an agreement, wet mold can be used. (2)
Actual diameter center
Specimen diameter d
Shortest length L
JB/T7945---1999
Actual diameter d
Support distance!
Initial load F.
400~600
Actual diameterWww.bzxZ.net
Measurement accuracy
3.5 The diameter of the standard bending specimen is t=30mm, the length is 340mm, and it is a single cast test bar without mechanical processing. The bending coefficient K is shown in Table 2. If the supply and demand parties have an agreement, the gray cast iron bending specimen with other dimensions given in Appendix B (Suggested Appendix) can be used. 3.6 The surface of the unprocessed specimen should be smooth and straight, and no defects visible to the naked eye are allowed; the surface roughness Ru value of the processed specimen is 3.2m, and there should be no scratches on the surface.
3.7 The deviation between the maximum diameter and the minimum diameter on the same cross section of the specimen shall not exceed 3% of the minimum diameter. 3.8 The error of the force indication of the testing machine shall not exceed ±1%. 3.9 The deflection can be measured by any type of deflectometer. The measurement accuracy shall comply with the provisions of Table 3. 3.10 The radius R of the supporting roller and the pressure head of the test device shall be specified as follows according to the size of the specimen diameter d: d≤20 mm.R<15 mm;
d>20 mm.R=15~25 mm.
3.11 The measurement method of the calculated diameter. Before the test, measure the diameter size in two perpendicular directions within 20 mm of the middle section of the specimen, or on the cross section after fracture, and the arithmetic mean is the calculated diameter. 3.12 During the bending test, the specimen is placed in the middle of the supporting roller, and the roller axis and the center line of the specimen should remain perpendicular to h. 412
JB/T 7945
：1999
3.13 Test speed, the time t from the specimen bearing the initial load to the fracture, is specified as follows according to the size of the specimen diameter d: d= 30 mm, t>30 s.
3.14 The test should be carried out at a temperature of 20°C±10°C. If it exceeds this temperature range, it should be noted in the test report. 3.15 The value of the flexural strength should be retained with 10 significant figures; the number rounding rule is the same as 2.8. 3.16 The test report includes:
a) specimen number;
b) flexural strength bb
c) deflection f;
d) fracture conditions, such as slag inclusions, shrinkage cavities, pores, fracture location, etc.; e) the auxiliary gray cast iron bending sample should indicate the diameter size and sampling location. 4 Compression test
4.1 Compression test of gray cast iron The compressive strength Obc is calculated according to formula (3): Obe
Where: Oic--compressive strength, N/mm2;
F\-compressive fracture load, N;
A--cross-sectional area of the sample before the test, Imm2F
4.2 The plasticity of the gray iron sample is expressed by the relative compression rate E. during compression, and is calculated according to formula (4): E.
Where: hn--height of the sample before the test, mm
height of the sample after the test, mm.
(3)
4.3 Compression test The rough specimen of a single cast test bar with a diameter of D = 30mm is taken. The rough specimen is generally processed into a specimen with a diameter of d = 625mm and a height equal to the diameter. For castings with a wall thickness greater than 30mm, the sampling location and specimen size shall be determined by agreement between the supply and demand parties. 4.4 The surface roughness Rc of the cylindrical surface of the compression specimen is 3.2um, the surface roughness Ru of the two end surfaces is 0.80μm, the parallelism of the two end surfaces is 0.02mm, and the cylindrical surface and the two end surfaces are perpendicular to each other. The dimensional deviation of the diameter and height is ±0.1mm. 4.5 The measurement accuracy of the specimen dimensions is 0.01mm.
4.6 The compression speed is the stress increase speed of 10~20MPa/s. When the force measuring pointer reverses, it means that the specimen begins to fracture. At this time, stop the test and record the compression load.
4.7 During the test, lubricating grease may be applied to both ends of the specimen, and protective devices may be added around the specimen. 4.8 The test shall be conducted at a temperature of 20°C ± 10°C. If this temperature range is exceeded, it shall be noted in the test report. 4.9 The measured performance figures shall retain three significant figures, and the rounding method shall be the same as 2.8. 4.10 The test report shall include:
a) specimen number;
b) compressive strength;
c) compression ratio;
d) fracture condition.
Specimen shape
The specimen shape is shown in Figure A1.
A2 Specimen size
The specimen size is shown in Table A1.
Specimen diameter d.
Parallel section length L
JB/T 7945
Appendix A
(Standard Appendix)
Auxiliary gray cast iron tensile test specimen
Transition circle radius R
≥1.5d.
Thread length L.
Appendix B
(Suggestive Appendix)
Auxiliary gray cast iron bending test specimen
Diameter pitch
Total length 1
B1The shape of the test specimen is shown in Figure B1. The test specimen dimensions, test conditions and test accuracy are shown in Table BI. The bending specimen is a rough test bar or a machined specimen
Specimen diameter
Shortest length L
JB/T79451999
Support distance
Note: The diameter d of the machined specimen has a deviation of ±0.1mm. Initial load F.
20～60
200~400
600-~800
Bending test speed, according to different specimen diameters d, the time t from initial load to fracture is specified as follows: B2
d≤20mm,t>20 s;d=45mm,t>45 $. The bending coefficient of the auxiliary bending specimen is shown in Table B2B3
d(10 mm)
actual diameter
d(13 mm)
actual diameter
d(20 mm)
actual diameter d
d(45 mm）
actual diameter t
d(10 mm)
actual diameter d
JB/T 7945
Continued Table B2
d(13 mm)
actual diameter d
d(20 mm)
actual diameter d
d(15nim)
actual diameter d
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