The impact test of steel pipe is a test method to evaluate the fracture resistance of the material under impact load, which is mainly used to test the toughness and impact resistance of the material.
The impact test of steel pipe
1. Experimental purpose
- Assessing the fracture resistance of steel tubes under impact loads.
- Determine the impact toughness of the material.
2. Experimental equipment
- Impact testing machine: commonly used equipment for pendulum impact testing machine.
- Standard sample: Usually a standard sample with notches, such as Charpy V or U notches.
3. Experimental procedure
- Sample preparation: Process the sample according to the standard size, and make a notch in the middle.
- Install the sample: Fix the sample on the support of the testing machine, with the notched back facing the impact direction.
- Release the pendulum: The pendulum is released from a certain height and impacts the sample.
- Record data: Measure the energy difference before and after the pendulum impact, and calculate the energy absorbed by the sample.
4. Experimental results
- Impact work (Akv or Aku) : The energy absorbed by the specimen at fracture, expressed in joules (J).
- Impact toughness: The ratio of impact work to the cross-sectional area of the specimen reflects the toughness of the material.
5. Standards and norms
- Common standards include ASTM E23, ISO 148, GB/T 229, etc.
6. Apply
- Used to evaluate the impact resistance of steel pipes under low temperature or dynamic load, widely used in oil, gas, construction and other fields.
7. Precautions
- Specimen processing and notch size shall strictly comply with the standard.
- The temperature and humidity of the experimental environment shall be controlled within the specified range.
Temperature requirements for impact tests
Low temperature impact test:
For carbon steel, low alloy steel, duplex stainless steel and ferritic stainless steel vessels with design temperature below -20℃, Charpy V-notch impact test must be carried out, and the test temperature is not higher than the design temperature.
For example, for materials whose design temperature is lower than -100℃, Charpy V notch impact test should be carried out according to GB4708, and the average impact work of the three groups of samples should not be less than 31J.
For Q345D steel pipe, when the design temperature is -20℃, the impact test temperature is -20℃, and the average impact absorption energy of the three standard samples is not less than 41J.
Normal temperature impact test:
When the design temperature is in the range of -20℃ ~ 0℃, the material needs to undergo 0℃ impact test.
For example, GB/T 6479 stipulates that 10, 20, Q345D and Q345E steel pipes with an outer diameter of not less than 76mm and a wall thickness of not less than 6.5mm should be subjected to longitudinal impact tests at -10℃, 0℃, -20℃ and -40℃ respectively.
High temperature impact test:
For materials with design temperatures higher than 50 ° C, impact tests are usually not required.
Conditions for avoiding impact tests:
If the thickness of the material is small, such as the design temperature is not lower than -48℃ and the thickness is not greater than 2.5mm, the impact test can be avoided.
For some specific materials and working conditions, such as containers in "low temperature and low stress conditions", impact tests can be exempted.
