The impact test of steel pipe is a kind of dynamic mechanical property test, which is mainly used to measure the impact resistance of the material when it is subjected to sudden impact load. Common impact tests include Charpy V impact test and Izod impact test.
1.Definition Of Impact Test
Impact test is to make a sample of the specified shape and size of the material, and punch it on the impact test machine at one time. By measuring the work consumed by the impact sample and the fracture topography characteristics, the defined impact performance indicators are obtained, such as impact toughness, impact absorption work, and the percentage of the fracture area of the fiber fracture.
2.Test procedure
2.1 Sample Preparation
The standard Charpy impact sample size is 55±0.6mm long and 10±0.05mm × 10±0.05mm cross-sectional area. The sample should be prepared to avoid affecting the impact properties of the metal due to work hardening or overheating.
2.2 Check the null pointer return to zero and energy loss
When the pendulum is in the state of hanging pendulum, the pointer is moved to the maximum energy value, and the sample is not placed for air strike, to check whether the pointer can be turned to the zero marking line, and the return zero error should not exceed one quarter of the minimum index value. Check the energy loss, do not put the sample for impact test, record the energy loss of two oscillations. For a 300J pendulum, the energy loss should not be greater than 1.5J, and for a 150J pendulum, the energy loss should not be greater than 0.75J.
2.3 Specimen Placement
Place the notched back of the sample against the pendulum blade, place the sample under the testing machine, and adjust the sample so that it is in the middle of the support.
2.4 Test
After ensuring that everything is ready, the test is carried out according to the "take pendulum - cancel pin - impact - automatic hanging pendulum", repeat 3 times, read and make a record. After the impact test, the value of the work consumed in the impact sample can be read directly from the dial.
2.5 Shutdown
After the test, long press "release pendulum", the pendulum slowly falls back to the plumb state, then release, and turn off the machine.
3.Test operation points
3.1 Before the test
Test temperature: generally should be in the range of 10~35℃, for strict tests, should be carried out at 20℃±2℃.
Sample size: Measure the width, thickness and gap thickness of the sample with a measuring tool with a minimum dividing value of no more than 0.02mm; Check the notch size with an optical projector.
Empty test: lift the pendulum to the position of the pre-lifting Angle, move the driven pointer to the position of the maximum impact energy, release the pendulum, read the value of the passive pointer near the zero point, and the return zero should not exceed 1/4 of the minimum index value.
3.2 During Operation
The specimen should be placed close to the support, with the notched back facing the pendulum blade. The sample notch should be centered with a special centering clamp or positioning gauge, and the deviation should not be greater than 0.5mm.
Lift the pendulum to the position of pre-lifting Angle and lock it, move the driven pointer to the position of maximum impact energy, place the sample, confirm that the pendulum swing danger zone is empty, release the pendulum so that it falls to break the sample, and read the value indicated by the passive pointer on the value dial, which is the impact absorption work.
Since the impact test results are relatively discrete, the number of samples tested for each material is generally not less than 3
4. Treatment of common situations in the test
Treatment of common situations in the test
01
If the sample is not completely broken, the symbol ">" should be added before the test data in the test report, and "not broken" should be indicated in other cases.
02
If there are cracks or defects visible to the naked eye in the specimen fracture after the test, it should be indicated in the test report.
03
If there is misoperation or the phenomenon of stuck hammer when the sample is broken during the test, the test result is invalid, and the test should be made again.
5.Standards
The impact test of steel pipes is usually carried out in accordance with the following standards:
GB/T 229-2020: Charpy pendulum impact test method for metallic materials.
ASTM E23-2018: Standard Impact Test Method for notched Specimens of Metallic Materials.
6. Scope of application
Impact tests are suitable for metal materials at room temperature, high temperature or low temperature, especially for assessing the brittleness tendency and metallurgical quality of materials.
Through these steps and standards, the impact resistance of the steel pipe under different conditions can be effectively evaluated to ensure its reliability and safety in practical applications.
