Diagnosing Over-thinning and Bottom Blowout in Sinking
下凹过度减薄与底穿的根因诊断
标签：过度减薄, 底穿, 根因分析, 金相
深下凹件底部局部减薄超 30% 甚至穿裂，通常是三因叠加：①锤击长期集中在中心小圈，未做放射状扩展，金属被单向拉薄；②中间退火间隔过大——0.9 mm 紫铜减薄约 25% 后不退火，延伸率断崖式下降；③退火温度过高导致晶粒粗化，裂纹沿粗晶界快速扩展。金相可见穿裂口呈杯锥状韧窝与粗晶混存。整改方案：定圈定角走锤并逐圈外移；每减薄 20% 退火一次；底厚用超声逐件监控并设 0.5 mm 止损线。
Local thinning past 30% or blowout at the base of deep sunk work usually stacks three causes: blows parked in a small centre circle instead of expanding radially, stretching the metal one way; anneal intervals too far apart—0.9 mm copper loses ductility sharply past about 25% reduction without annealing; and over-temperature anneals coarsening grains so cracks race along boundaries. Metallography shows cup-cone dimples mixed with coarse grains at the burst. Corrective steps: fixed ring-and-angle hammering working outward, anneal every 20% of reduction, and gauge base thickness piece by piece with a 0.5 mm stop line.