Q345GJCZ15 is a low-alloy high-strength structural steel plate, and its Z-direction performance refers to the mechanical properties of the steel plate in the thickness direction. The applications of Z-direction performance 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-direction performance can effectively resist lamellar tearing, enhancing the stability and safety of structures.

2. Connection performance of structural components: In welded structures, the Z-direction performance of steel plates significantly impacts welding performance. Steel plates with good Z-direction performance 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-direction performance of steel plates has a significant impact on their fatigue life. Steel plates with good Z-direction performance 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-direction performance 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-direction performance of steel plates significantly affects their low-temperature toughness. Steel plates with good Z-direction performance can ensure good toughness and impact resistance in low-temperature environments.

In summary, the Z-direction performance of Q345GJCZ15 steel plates is of great significance in its applications in fields such as engineering machinery manufacturing, building structures, and shipbuilding. It enhances the stability and safety of structures, ensures the connection performance of welded structures, improves the fatigue life of structural components, enhances the seismic performance of buildings, and increases the low-temperature toughness of structural components.