Q345E-Z25 is a grade of steel, belonging to low alloy high strength Z-shaped steel plate, with good low temperature impact performance; The grade of steel is composed of four parts: Chinese Pinyin letter representing yield strength, yield strength value, quality and Z-direction performance level symbol. Among them:
Q stands for yield strength;
345 indicates yield strength value, unit MPa;
E indicates grade (-40 degree impact);
Z25 Indicates the thickness direction (Z direction) performance level symbol.
The main performance
Z-direction steel: also known as "lamellar tearing resistant steel", that is, usually said Z-direction performance. In welded steel structures, when the thickness of the steel plate is not less than 40 mm and it is subjected to tension along the thickness of the plate, in order to avoid laminar tearing during welding, it is necessary to use laminar tearing resistant steel (usually referred to as "Z-steel"). The problem of lamellar tearing exists in thick plate, so the Z-direction performance test is proposed. The steel plate and the section steel are rolled and formed, and the steel used in the multi-high-rise steel structure is generally hot-rolled, which can destroy the casting structure of the ingot and refine the grain of the steel. The bubbles and cracks formed when the ingot is poured can be welded under high temperature and pressure, so that the mechanical properties of the steel can be improved. However, this improvement is mainly reflected in the rolling direction, because the non-metallic inclusions (mainly sulfides, oxides, silicates, etc.) inside the steel are pressed into sheets after rolling, and still remain in the steel plate (generally parallel to the surface of the steel plate), and the steel plate appears stratification (sandwich) phenomenon. This non-metallic interlayer phenomenon. Deterioration of the tensile properties of steel along the thickness direction. Therefore, the mechanical properties of the steel plate in three directions are different: the best along the rolling direction; The performance perpendicular to the rolling direction is slightly worse; In the direction of thickness, the performance is second. Generally, the thick steel plate is easier to produce laminar tear, because the thicker the steel plate, the more non-metallic inclusion defects, and the thicker the weld, the greater the welding stress and deformation. To solve this problem, it is best to use Z-directional steel. This steel plate is on the basis of a certain level of structural steel (called mother steel), after special smelting, treatment of steel, its sulfur content is less than 1/5 of the general steel, and the section shrinkage rate is more than 15%. The mechanical properties of the steel plate along the thickness direction (mainly ductility properties) are called Z-direction properties. The Z properties of steel plates can be obtained by tensile test of specimens, and are generally measured by section shrinkage. The mark of the Z steel plate produced in China is to add the Z steel plate grade mark Z25, Z25, Z25 behind the parent steel steel number, and the number behind the Z word is the index of the section shrinkage rate (%).
