Q345C seamless rectangular steel pipes, made of high-strength low-alloy structural steel, undergo performance testing covering three core areas: mechanical properties, technological properties, and non-destructive testing. Specific test contents and standards are as follows:

First, Mechanical Property Testing of Q345C Seamless Rectangular Steel Pipes
Tensile Test of Q345C Seamless Rectangular Steel Pipes
(1) Test Method: According to GB/T 228.1 standard, the sample is stretched to fracture, and the tensile strength (470~660 MPa), yield strength (275~345 MPa), and elongation after fracture (≥21%) are measured.
(2) Key Indicators:
Yield strength reflects the material’s load-bearing capacity; Q345C requires ≥275 MPa (thickness 16~100mm);
Elongation reflects the plastic deformation capacity; ≥21% ensures the material is not easily brittle under stress.
Application Scenarios: Suitable for fields requiring large loads, such as machinery manufacturing and bridge construction.
(3) Impact Test
Test Method: According to GB/T 229 standard, longitudinal impact tests are conducted on steel pipes with a wall thickness ≥ 6.5 mm and an outer diameter ≥ 70 mm to test the impact toughness (CVN value) at 0℃.
Key Indicator: Q345C’s impact value at 0℃ is significantly better than Q345B (20℃), meeting the requirements for low-temperature operating conditions.
Application Scenarios: Suitable for cold northern regions or low-temperature environments such as marine engineering.
(4) Hardness Test
Test Method: Brinell hardness (HB), Rockwell hardness (HRC), or Vickers hardness (HV) tests are used. Material hardness is calculated by indentation depth or size.
Advantages: Non-destructive testing, allowing for rapid assessment of material strength, especially suitable for situations where tensile testing is inconvenient.

Second, the process performance test of Q345C seamless rectangular steel pipe
(1) Flattening test
Test method: According to GB/T 246 standard, steel pipes with an outer diameter of 22~600mm and a wall thickness to outer diameter ratio ≤10% are flattened, and the deformation is checked for cracks or delamination.
Key indicator: No cracks after flattening, proving that the material has good ductility.
Application scenario: Verifying the deformation resistance of pipelines during installation or under pressure.
(2) Flaring test
Test method: According to GB/T 242 standard, steel pipes with an outer diameter ≤76mm and a wall thickness ≤8mm are flared, with a mandrel taper of 30°~60°, and the wall thickness is checked for uniformity and no cracks after flaring.
Key indicator: No cracks after flaring, indicating that the material can withstand local stress concentration.
Application scenario: Applicable to scenarios where flaring is required at pipe connections.
(3) Bending Test
Test Method: According to the GB/T 244 standard, bend the steel pipe with an outer diameter of ≤ 22mm at 90°. The bending radius is 6 times the outer diameter of the steel pipe. Check for cracks at the bend.
Key Indicator: No cracks after bending, proving that the material can adapt to complex geometric processing.
Application Scenarios: Suitable for structural components that require bending, such as building decoration, vehicle chassis, etc.

Third, Non-destructive Testing of Q345C Seamless Rectangular Steel Pipe
(1) Hydraulic Test
Test Method: According to the GB/T 241 standard, perform a hydraulic test on each steel pipe. The test pressure is calculated based on the pipe diameter and wall thickness, and the pressure stabilization time must meet the standard requirements.
Key Indicator: No leakage during the test, proving good pipeline sealing.
Application Scenarios: Suitable for pipeline systems transporting fluids (such as oil, gas, water).
(2) Surface Quality Inspection
Test Method: Inspect the inner and outer surfaces manually or by penetrant testing (fluorescent/colorimetric method) to ensure there are no defects such as cracks, folds, or scabs. Key Indicators: Surface defect depth ≤ negative wall thickness deviation, ensuring pipeline corrosion resistance and service life.
Application Scenarios: Applicable to all pipelines exposed to the environment or in contact with media.
(3) Flaw Detection
Test Method: Electromagnetic ultrasonic testing or eddy current testing is used to detect internal defects (such as interlayers, porosity).
Advantages: No coupling medium required; applicable to the inspection of high-temperature, high-speed, or rough-surface pipelines.
Application Scenarios: Applicable to pipelines transporting high-pressure, high-temperature, or corrosive media.