图为80mm Q690NHH 不同厚度扫描组织，可以看出，由于钢板表面冷速较快，钢板表面组织晶粒细小，随着厚度的增加，冷速减小晶粒尺寸变大，组织粗化。

The picture shows the scanning structure of 80mm Q690NHH with different thicknesses. It can be seen that due to the faster cooling rate of the surface of the steel plate, the surface structure of the steel plate has fine grains. As the thickness increases, the cooling rate decreases and the grain size becomes larger and the structure becomes coarser.