沿海货轮黄铜螺旋桨,在壳体部位出现两条纵深裂纹,该螺旋桨φ4775毫米,总重7828公斤,壳体大端φ850毫米,壳体高830毫米,壁厚225毫米。材质是铸造锰铁黄铜。主要化学成份(%):铜59.2、锰15.6、铁0.61,其余为锌。σ_b>40公斤/毫米~2。螺旋桨壳体裂纹位置见1图。裂纹1长400毫米,深85毫米;裂纹2长310毫米,深55毫米。裂纹2在钻孔时超过了裂纹的实际深度,使坡口增长至400毫米。 1、焊前准备 Coastal cargo vessel brass propeller, appeared in the shell parts of the two longitudinal cracks, the propeller φ4775 mm, total weight 7828 kg, shell big end φ850 mm, shell height 830 mm, wall thickness 225 mm. Material is cast ferromanganese brass. The main chemical composition (%): copper 59.2, manganese 15.6, iron 0.61, the rest is zinc. σ_b> 40 kg / mm ~ 2. Propeller shell crack location see Figure 1. Crack 1 is 400 mm long and 85 mm deep; crack 2 is 310 mm long and 55 mm deep. Crack 2 exceeded the actual depth of the crack as it drilled, increasing the bevel to 400 mm. 1, welding preparation