我厂4S-275型柴油机不慎飞车,致使三缸活塞拉裂(图1)。裂纹长度48毫米,裂纹处壁厚9毫米,活塞重约80公斤。为满足生产供电急需,我们采用电弧热焊修复,现已使用三年,情况良好。热焊工艺如下: 1.焊前准备在裂纹处开V形坡口,坡口角度为70°～80°,深度6～7毫米,距裂纹两端3～5毫米处钻止裂孔(φ6毫米)。 2.预热 I plant 4S-275 diesel engine accidentally speeding, resulting in three-piston piston cracking (Figure 1). Crack length 48 mm, crack wall thickness of 9 mm, the piston weighs about 80 kg. In order to meet the urgent needs of production power supply, we use the arc heat welding repair, has been in use for three years, in good condition. Hot welding process is as follows: 1. Preparation of welding before opening a V-groove at the crack, the groove angle of 70 ° ~ 80 °, the depth of 6 to 7 mm, 3 to 5 mm away from both ends of the crack at the crack (φ6 mm ). Preheat