Bending resistance refers to the ability of the anti-corrosion coating to withstand the bending force acting on its longitudinal axis, and the stress generated by the bending load is a combination of compressive stress and tensile stress.
The deflection performance of pipeline anti-corrosion coating is the toughness index for investigating pipeline anti-corrosion coating. The purpose is to check the corrosion resistance of steel pipes that have been installed with pipeline coatings when subjected to bending stress. This is the performance requirements of the steel pipe for the anti-corrosion layer during laying. Refer to the American ASTM G70 standard "Standard Test Method for Ring Rendability of Pipelines Coatinga (Squeeze Test)". Squeeze until the coating film on the surface of the pipe ring test piece is damaged.
The bending resistance test method of the fusion-bonded epoxy powder anti-corrosion coating in my country refers to the test method in the Canadian national standard, and the bending performance index of the fusion-bonded epoxy powder anti-corrosion coating pipe fittings at a low temperature of -30°C is tested. The test equipment it uses is a bending test machine, which is composed of a press and a bending abrasive tool (including a die and a punch) with a bending angle of 2.5°, wherein the radius of curvature of the punch is determined by the following formula.
R=22.43T
In the formula, R——the radius of punch, mm;
T—thickness of specimen, mm.
The experimental procedure is as follows:
The test pieces shall be cut along the axial direction of the pipe, and each group shall be no less than 5 test pieces, and the test pieces shall be placed in a low-temperature box to cool to -30°C±3°C, and kept for 1h;
The bending test of each specimen should be completed within 30s;
The bent test piece is placed at room temperature for more than 2 hours, and the anti-corrosion layer is checked by visual inspection for cracks.
