Q345GJCZ15 is a type of low-alloy high-strength structural steel plate, and its Z-directional properties refer to the mechanical properties of the steel plate in the thickness direction. The applications of Z-directional properties are mainly reflected in the following aspects:

1. Resistance to lamellar tearing: In fields such as engineering machinery manufacturing, building structures, and shipbuilding, steel plates are prone to lamellar tearing when subjected to tensile or compressive forces. Steel plates with good Z-directional properties can effectively resist lamellar tearing, improving structural stability and safety.

2. Connection performance of structural components: In welded structures, the Z-directional properties of steel plates significantly impact welding performance. Steel plates with good Z-directional properties can ensure the connection performance of welded structures, reducing the risk of welding deformation and welding cracks.

3. Improving the fatigue life of structural components: Under alternating loads, the Z-directional properties of steel plates have a significant impact on their fatigue life. Steel plates with good Z-directional properties can effectively reduce the initiation and propagation of fatigue cracks, thereby improving the fatigue life of structural components.

4. Enhancing the seismic performance of structural components: During extreme natural disasters such as earthquakes, steel plates with good Z-directional properties can effectively resist seismic forces, reduce the extent of damage to structural components, and improve the seismic performance of buildings.

5. Improving the low-temperature toughness of structural components: In low-temperature environments, the Z-directional properties of steel plates significantly affect their low-temperature toughness. Steel plates with good Z-directional properties can ensure good toughness and impact resistance in low-temperature environments.

In summary, the Z-directional properties of Q345GJCZ15 steel plates are of great significance in applications such as engineering machinery manufacturing, building structures, and shipbuilding. They can enhance structural stability and safety, ensure the connection performance of welded structures, improve the fatigue life of structural components, enhance the seismic performance of buildings, and improve the low-temperature toughness of structural components.