GB/T 4675.2-1984 Weldability test - CTS weld crack test method

This standard applies to the weld crack test of lap joints of low alloy steel and carbon steel. GB/T 4675.2-1984 Weldability test lap joint (CTS) weld crack test method GB/T4675.2-1984 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Weldability testing
Method of controlled thermal severity cracking test for lap joints (CTS) Weldabillity testing
Method of controlled thermal severity cracking test This standard applies to the welding crack test of lap joints of low alloy steel and carbon steel. 1 Nouns and terms
1.1 Bithermal: The number of directions of heat transfer is 2. UDC 621.791
052 *20
GB 4875.2--84
1.2 Trithermal: The number of directions of heat transfer is 3. 1.3 Thermal constraint index (abbreviated as TSN): It is related to the plate thickness and the number of directions of heat transfer, and is used to indicate the relationship between cooling conditions and cracks. 1.4 Controlled thermal severity (abbreviated as CTS): The influence of cooling rate on the crack tendency of joints is reflected by the change of thermal constraint index. 2 Preparation of test pieces
2.1 The shape and size of the test piece are shown in Figure 1. M12 bolt
Aperture 413
Test weld!
Test weld 2
Figure 1 Shape and size of test piece
a>1.581 Upper plate thickness, 8—Lower plate thickness National Bureau of Standards 1984-07-28 Issued
1985-05-01 Implementation
GB 4675.2—84
2.2: The two end faces of the upper plate test weld must be machined (when cutting with gas cutting, the machining allowance of the machine cutting is more than 10mm), and the other end faces can be cut with gas cutting. 2.8 The contact surface of the upper plate and the lower plate and the oxide scale, oil, rust, etc. near the test weld of the lower plate should be polished and cleaned. 3 Test steps
3.1 Assemble the specimen according to Figure 1. First, fix the upper plate to the lower plate with bolts, and then use the test welding rod to weld the restraint welds on both sides, with two passes on each side.
8.2 After the specimen is completely air-cooled to room temperature, place the specimen on an insulated platform to weld the test weld. 8.3 During the welding test, according to Figure 1, first weld the test weld 1, and then wait for the specimen to completely air-cool to room temperature, replace the welding rod and weld the test weld 2.
3.4 ​​After the welded specimen is placed at room temperature for 48 hours, it is disassembled. 3.5 When dissecting the specimen, mechanically cut each test weld according to the size shown by the dotted line in Figure 2. Take 3 specimens from each test weld, for a total of 6 specimens.
Disk damp surface
Figure 2 Specimen anatomical dimensions
3.6 Each test specimen surface shall be subjected to metallographic grinding and corrosion treatment, and then magnified 10 to 100 times to detect whether there is a crack and measure the length of the crack.
4 Calculation method
4.1 According to Figure 3, the crack length measured is calculated by the following formula to calculate the crack rate of the upper plate and the lower plate respectively. ×100 (%)
Where: C,--
-Upper plate crack rate, %,
≥L,
2×100 (%)
Lower plate crack rate, %,
-The sum of the crack lengths of the upper plate specimens, mm
L2The sum of the crack lengths of the lower plate specimens, mm. 88
5 Record
GB\4675.2--84
EL2= L2 +L?
Figure 3 Calculation of the crack length of the specimen
5.1 Test date, time, ambient temperature and humidity. 5.2 Specimen steel grade and chemical composition, specimen state, specimen upper plate, lower plate thickness and rolling direction. ·5.3 Specimen temperature before welding, type of welding power source, welding polarity, welding rod brand, welding rod diameter, welding rod drying temperature and time, welding current, welding voltage and welding speed. 5.4 Specimen dissection start time and method.
5.5 Test results: heat flow index and its crack rate. A.1 Scope of application
GB 4675.2—84
Appendix A
Explanation of "Lap joint (CTS) welding crack test method" (supplement)
This test method is mainly applicable to the crack test caused by martensitic transformation in the heat affected zone of low alloy steel welding. This method is also applicable to carbon steel. bzxZ.net
A.2 Preparation of test piece
A.2.1 This standard does not specify the thickness of the test piece, but the commonly used plate thickness is 6 to 50 mm. During the test, the thickness of the upper plate and the lower plate may be different depending on the structural conditions.
A.2.2 In order to ensure the reliability of the test piece size and the test, the two test end faces of the upper plate shall be machined. When gas cutting is used for cutting, in order to avoid the test welding area being affected by heat, it is stipulated that at least 10 mm shall be machined. A.2.3 This test method mainly relies on two restraining welds for restraint, so these two welds need to be firmly welded. The bolt in the middle of the specimen only serves to fix the position of the upper plate, so there may be some gap between the bolt and the hole diameter. A.3 Test steps
A.3.1 This cold crack generated in the heat-affected zone is closely related to the cooling rate of the heat-affected zone, especially the cooling condition below 300°C. Therefore, attention should be paid to the initial temperature of the specimen during welding. The welding test is usually carried out at room temperature, but it can also be carried out after preheating and heat treatment. During the test, the specimen is placed in an insulating condition to prevent heat loss. A.3.2 Welding specifications have a significant impact on the generation of cold cracks. Generally, reducing the line energy means increasing the cooling rate of the heat-affected zone. Therefore, increasing the hardening tendency increases the sensitivity of cold cracks. A.3.3 Gas cutting shall not be used when cutting the specimen, but mechanical cutting shall be used. Vibration should be minimized during mechanical cutting to prevent the expansion of cracks.
A.3.4 The cracks obtained by this test method usually occur under the weld, sometimes also occur in the contact part of the upper and lower plates and at the weld toe, and sometimes may occur in the weld, as shown in Figure A1. Cracks in the weld and cracks in the heat-affected zone should be treated differently. Cracks under the weld
/Root cracks
Weld toe cracks
Figure A1 Various cracks
Cracks in the weld
A, 3.5 This type of crack is also called cracks under the weld. It is almost invisible from the outside, so the test surface of each sample should be carefully ground. Usually, it is enough to grind to the extent that general metal structure observation can be carried out. Then metallographic corrosion is carried out. The corrosive agent can generally be 5% nitric acid alcohol solution. However, it is best to use a solution of 3% concentrated sulfuric acid added to 3% picric acid alcohol solution. A.3.6 This test is more likely to have small cracks that cannot be observed with the naked eye. Therefore, when it is still difficult to distinguish under the condition of 10 to 100 times magnification, a 500 to 1000 times microscope can be used for observation. And use the measuring accessories on the microscope to measure the length of the crack. A.3.7 When measuring the crack length, if the crack is curved (as shown in Figure 3), it is measured as a straight line. When the crack is reselected, the length of the reselected part 90
is not calculated repeatedly.
A.4 Determination of thermal constraint index (TSN)
GB 4675.2--84
TSN is determined based on the heat flow direction number and the thickness of the specimen. As shown in Figure A2a, the heat flow direction number of the test weld welded at the end of the plate with a thickness of 6.25mm is 1. At this time, the thermal constraint index is specified as 1, which is represented by TSN=1. Figure A2b shows that when welding at a butt joint with a plate thickness of 6.25mm or at the end of a specimen with a plate thickness of 12.5mm, the heat flow direction number of the former is 2 and that of the latter is 1. However, since the plate thickness of the latter is twice that of the former, the thermal constraint index of both is specified as 2, which is represented by TSN=2. Figure A2c shows the heat flow direction number of the CTS specimen. The heat flow direction number of the first test weld is 2, called bithermal heat flow (Bithermal), and the heat flow direction number of the second test weld is 3, called trithermal heat flow (Trithermal). The TSN value for different plate thicknesses can be calculated using the following formula. The first test weld: TSN=
The second test weld: TSN=
Where: ,——upper plate thickness, mm,
-lower plate thickness, mm.
Test weld
Direction of heat flow
First weld
Two-way heat flow
4(8+8,)
4(20+81)
Test weld
Test weld
Second weld
Three-way heat flow
TSN = 4( 28+d)
Figure A2 Determination of thermal constraint index
GB 4675.2-84
Appendix B
Test Specifications
(Reference)
In order to compare the cold cracking tendency of different steel grades, the following test specifications are recommended: Welding rod diameter
Welding current
Welding voltage
Welding speed
Additional notes:
170±10A3
24±2V,
150±10mm/min.
This standard is equivalent to the 1981 edition of Japanese standard JIS Z3154-1962 "Lap joint welding crack test method". This standard was proposed by the Ministry of Machinery Industry of the People's Republic of China. This standard was drafted by Harbin Welding Research Institute. The main drafters of this standard are Yu Jilun, Guo Shoufen and Cui Fengchi. 92
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