Performance test of Q345C seamless rectangular steel pipe

Q345C seamless rectangular steel pipe is a steel pipe made of high-strength low-alloy structural steel. The performance test of Q345C seamless rectangular steel pipe covers three core areas: mechanical properties, process properties, and non-destructive testing. The specific test contents and standards are as follows:

First, the mechanical performance test of Q345C seamless rectangular steel pipe.
Tensile test of Q345C seamless rectangular steel pipe.
Test method: According to GB/T 228.1 standard, the specimen is pulled to fracture, and the tensile strength (470~660 MPa), yield strength (275~345 MPa), and elongation after fracture (≥21%) are measured.
(1) Key indicators of Q345C seamless rectangular steel pipe:
- Yield strength reflects the bearing capacity of the material. Q345C requires ≥275 MPa (thickness 16~100mm);
- Elongation reflects the plastic deformation ability. ≥21% ensures that the material is not easy to break when subjected to stress. - Application scenario: Applicable to fields such as machinery manufacturing and bridge construction that need to withstand large loads.
(2) Impact test of Q345C seamless rectangular steel pipe.
- Test method: According to GB/T 229 standard, a longitudinal impact test is conducted on steel pipes with a wall thickness of ≥6.5mm and an outer diameter of ≥70mm to test the impact toughness (CVN value) at 0℃.
- Key indicators: The impact value of Q345C at 0℃ is significantly better than that of Q345B (20℃), meeting the requirements of low-temperature working conditions.
- Application scenario: Applicable to low-temperature environments such as cold northern regions or marine engineering.
(3) Hardness test of Q345C seamless rectangular steel pipe.
- Test method: Use Brinell hardness (HB), Rockwell hardness (HRC), or Vickers hardness (HV) tests to convert the material hardness by indentation depth or size.
- Advantages: Non-destructive testing can quickly evaluate the material strength, especially suitable for occasions where tensile testing is inconvenient.

Second, the process performance test of Q345C seamless rectangular steel pipe.
(1) Flattening test of Q345C seamless rectangular steel pipe.
- Test method: According to GB/T 246 standard, flatten steel pipes with an outer diameter of 22~600mm and a wall thickness to outer diameter ratio of ≤10%, and check whether cracks or delamination appear after deformation.
- Key indicator: There is no crack in the specimen after flattening, which proves that the material has good ductility.
- Application scenario: Verify the deformation resistance of the pipeline during installation or pressure.
(2) Expanding test of Q345C seamless rectangular steel pipe.
- Test method: According to GB/T 242 standard, expand steel pipes with an outer diameter of ≤76mm and a wall thickness of ≤8mm, with a top taper of 30°~60°, and check whether the wall thickness is uniform and crack-free after expansion.
- Key indicator: There is no crack after expansion, which indicates that the material can withstand local stress concentration.
- Application scenario: Applicable to scenarios where expansion processing is required at pipeline joints.
(3) Bending test of Q345C seamless rectangular steel pipe.
- Test method: According to GB/T 244 standard, steel pipes with an outer diameter of ≤22mm are bent at 90°. The bending radius is 6 times the outer diameter of the steel pipe. Check whether there are cracks at the bend.
- Key indicators: No cracks after bending, proving that the material can adapt to complex geometric shapes.
- Application scenarios: Suitable for structural parts that need to be bent and formed, such as building decoration, vehicle chassis, etc.

Third, a non-destructive testing test of Q345C seamless rectangular steel pipe.
(1) Hydraulic test of Q345C seamless rectangular steel pipe.
- Test method: According to the GB/T 241 standard, a hydraulic test is performed on each steel pipe. The test pressure is calculated according to the pipe diameter and wall thickness. The stabilization time must meet the standard requirements.
- Key indicators: No leakage during the test, proving that the pipeline has good sealing.
- Application scenarios: Suitable for pipeline systems that transport fluids (such as oil, gas, and water).
(2) Surface quality inspection of Q345C seamless rectangular steel pipes.
- Test method: Check the internal and external surfaces with the naked eye or penetrant testing (fluorescence/coloring method) to ensure that there are no defects such as cracks, folds, scars, etc.
- Key indicators: Surface defect depth ≤ wall thickness negative deviation, ensuring the corrosion resistance and service life of the pipeline.
- Application scenario: Applicable to all pipelines that need to be exposed to the environment or contact the medium.
(3) Flaw detection of Q345C seamless rectangular steel pipes.
- Test method: Use electromagnetic ultrasonic testing or eddy current testing to detect internal defects (such as interlayers and pores).
- Advantages: No coupling medium is required, and it can be used for the inspection of high-temperature, high-speed, or rough-surface pipelines.
- Application scenario: Applicable to pipelines that transport high-pressure, high-temperature, or corrosive media.