Root-cause Tree: Shrinkage Porosity & Leak Diagnosis
缩松与渗漏根因树：补缩诊断流程
标签：缩松, 补缩, 冒口, 渗漏
锡青铜结晶区间宽（C90300 约 150℃），呈糊状凝固，热节下方易出现连通性缩松，水压试验渗漏多源于此。诊断树：先定位（冒口根部下方、壁厚交叉处）→剖件着色确认范围→按 Chvorinov 模数法复核冒口（冒口模数 ≥ 铸件热节模数 1.2 倍）→核算补缩距离（板类件约 4.5 倍壁厚内有效，超限加冒口或冷铁）。黄铜凝固区间窄、收缩集中，问题多在冒口尺寸而非布置。逐件记录浇温与冒口补浇次数，三批数据即可定位系统性缺陷。
Wide-freezing tin bronze (C90300, ~150°C freezing range) solidifies pasty, so connected shrinkage lurks under hot spots and fails hydrostatic leak tests. Diagnostic tree: locate (beneath riser roots and wall junctions) → section and dye-penetrant to map the extent → recheck risers by Chvorinov's modulus rule (riser modulus ≥ 1.2× the hot-spot) → verify feeding distance (about 4.5× wall thickness in plates; beyond that add risers or chills). Narrow-freezing brass concentrates shrinkage, so failures are usually riser size, not placement. Log pour temperature and riser topping counts; three batches of data expose systematic defects.