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Effect of chemical composition on EH40 steel plate Z properties

EH40 steel plate is used for some important welding components such as shipbuilding, offshore oil platform, boiler and pressure vessel, which requires not only certain mechanical properties along the width and length direction, but also good laminar tearing resistance in the thickness direction of EH40 steel plate. The laminar tearing resistance of EH40 steel plate was evaluated by the section shrinkage of the thickness direction tensile test.

According to the statistical analysis of fracture morphologies of many z-tensile specimens, there are roughly three kinds of fracture morphologies of Z-tensile EH40 steel plate of different materials.

With the increase of sulfur content, sulfide inclusions also increased and became larger and flaked. The lamellar tearing performance deteriorated with the increase of sulfide inclusions, and the fracture morphology changed from plastic fracture to shear fracture to step fracture. It can be concluded that sulfur is a major factor affecting the Z tensile properties of EH40 steel plate.

For the thickness direction performance EH40 steel plate, standard GB5313-85 specifies the content of sulfur in steel, the thickness direction of the steel plate and the average and single value of the shrinkage of the section. The fracture morphology and inclusion of EH40 steel plate were analyzed by SEM and EDS, and the factors affecting the Z tensile properties were found out.

In order to meet the requirements of Z-direction performance of EH40 steel plate, sulfur content should be controlled as far as possible during smelting. Sulfide has a great influence on the lamellar tearing resistance of EH40 steel plate in thickness direction.