菜单
Investment casting process design — wax pattern, ceramic shell build, dewaxing, burnout, casting, shell thickness, Chvorinov's rule, riser design, gating, solidification, dimensional tolerances, surface finish, ASTM B557/A571, aerospace/turbine blade applications, defect analysis.
默认使用会先检查来源的 Prompt；你也可以切换为直接命令，或下载本地副本。
决定是否安装前，请先阅读 SKILL.md，以及 SkillsMP 当前展示的配套文件。
用 Codex 或 Claude 帮你安装 复制这段 Prompt，粘贴到 Codex、Claude 或其他助手里，让它检查 Skill 页面并帮你完成安装。
直接命令不会经过审查 Prompt；运行前请先检查来源。
npx skills add https://github.com/MP-AI-20/mechanical-engineering-skills --skill investment-casting命令会保持在同一行。复制前请横向滚动并检查完整内容。
想先保存到本地？可下载 SkillsMP 当前能够提供的文件。
正在显示 SKILL.md
基于 SOC 职业分类
| name | investment-casting |
| description | Investment casting process design — wax pattern, ceramic shell build, dewaxing, burnout, casting, shell thickness, Chvorinov's rule, riser design, gating, solidification, dimensional tolerances, surface finish, ASTM B557/A571, aerospace/turbine blade applications, defect analysis. |
| metadata | {"priority":7,"promptSignals":{"phrases":["investment casting","lost wax casting","ceramic shell casting","precision casting","wax pattern casting","turbine blade casting"],"minScore":3}} |
Investment casting (lost-wax process):
Key advantage over sand casting: Tolerances: ±0.1–0.3 mm vs. ±1–3 mm (sand) Surface finish: Ra 1.5–3.2 μm (as-cast) vs. Ra 12–25 μm (sand) Thin walls: 0.5–2 mm feasible vs. 3–5 mm minimum (sand) Complexity: undercuts, internal passages (cores), near-net shape
Pattern wax types: Filled wax (25–40% filler — talc, PS): lower shrinkage (0.6–1.0%); better dimensional stability; most common Unfilled wax: simpler; higher shrinkage (1.5–2.0%) Water-soluble wax: for removable cores (complex internal passages)
Shrinkage allowance: Overall die compensation = wax shrinkage + metal shrinkage Wax shrinkage: 0.6–1.5% (depends on wax type, section size, injection conditions) Metal shrinkage: 1.5–2.5% (depends on alloy; see below) Die design: oversized by (1 + wax_shrink) × (1 + metal_shrink) factor
Injection parameters: Pressure: 30–200 bar (filled wax at 60–100 bar typical) Temperature: 55–75°C (wax injection temperature; wax must be flowable) Die temperature: 20–30°C (controlled by water cooling) Cycle time: 10–60 s depending on section size
Pattern distortion: thin sections warp during cooling; die inserts needed for critical features; pattern gauging required
Runner and gating design: wax runners welded/bonded to central sprue Pattern orientation: heavy sections up (feed metal flows down from top; risers at top) Tree density: balance packing vs. shell permeability; typically 2–4 kg metal per cluster
Primary coat (face coat): fine slurry; Ra control; compatibility with alloy Binder: colloidal silica (SiO₂, 20–40% SiO₂) Refractory: zircon flour (ZrSiO₄, mesh 100–200); alumina for high-temperature alloys Viscosity: 20–30 cP (measured by #5 Zahn cup); critical — too thick → drips, too thin → thin coat
Backup coats: coarser slurry + coarser stucco for shell thickness Binder: colloidal silica (same); some proprietary alumina silicate binders Refractory: mullite (3Al₂O₃·2SiO₂), fused silica, or alumina
Stucco (after each dip): Primary: zircon or alumina (100–200 mesh) for good detail reproduction Backup: mullite, fused silica (16–30 mesh) for thermal and mechanical properties
Number of dip layers: Small parts (<1 kg): 5–7 layers (4–6 mm total shell) Medium (1–10 kg): 7–9 layers (6–10 mm) Large (>10 kg): 9–12+ layers (10–15 mm)
Shell drying: Each coat dried 2–4 hours at 20–25°C, 40–60% RH (humidity control critical — premature drying → cracking; too slow → slurry sags) Drying racks with controlled airflow; flash dryers for production
Shell strength requirements: Green strength: > 2 MPa (hold wax during dewax; handle clusters) Fired strength (after burnout): > 5 MPa (withstand metal pour static head)
Dewax thermal shock: Wax expands before melting → shell must resist burst pressure Flash dewax (autoclave): steam 150–175°C, 5–7 bar → rapid wax melt → pressure <15 bar (wax melts before significant expansion) Furnace dewax: slow heating → wax softens before pressure builds; worse for complex geometries
Burnout temperature: 850–1000°C; 30–60 min hold; removes residual wax and organic binders; sinters shell
Shell permeability: fired fused silica shells: permeability 0.01–0.05 μm² (allow gas escape during pour); essential for preventing porosity from back-pressure
Solidification time: t_s = C × (V/A)² [s; V = volume [cm³]; A = surface area [cm²]; C = mold constant [s/cm²]] C depends on alloy and shell properties; C ≈ 1.0–3.0 s/cm² for steel in silica shell; higher for thicker shell
Modulus method: M = V/A [cm; "modulus" of a casting section] M_riser > M_casting × f_feed [f_feed ≈ 1.2 for steel; riser must solidify LAST]
Feeding distance: Liquid steel can feed: F ≤ 4.5 × T [T = section thickness in mm; max feeding distance without shrinkage porosity] Place risers within feeding distance of heavy sections
Gating ratio (for steel): Pressurized: A_sprue : A_runner : A_gate = 1 : 0.8 : 0.6 (choke at gate) Unpressurized: A_sprue : A_runner : A_gate = 1 : 2 : 4 (choke at sprue)
Fill time: t_fill = (2 × M_metal) / (C_d × A_gate × ρ × √(2 × g × h)) [s; h = effective head height; C_d ≈ 0.8] Target fill time: 3–10 s for most investment castings (balance turbulence vs. cold shut risk)
Melt superheat: Typically 50–100°C above liquidus; ensures complete fill in thin sections before freeze Excess superheat: increases grain size; longer solidification → more shrinkage porosity
| Alloy | Linear Shrinkage [%] | Notes |
|---|---|---|
| Stainless 316 | 2.1 | Austenitic |
| 17-4 PH | 2.1 | Martensitic PH |
| Inconel 718 | 1.9 | Nickel superalloy |
| Ti-6Al-4V | 1.8 | Vacuum cast |
| Aluminum 356 | 1.3 | Semi-solid possible |
| Carbon steel 1025 | 2.0 | Low carbon |
| Cobalt alloy (Stellite) | 2.2 | High-carbon cobalt |
Hot tear susceptibility: High hot-tear risk: alloys with wide freezing range (Ni alloys, some stainless) Prevention: reduce restraint (flexible shell); hot-top feeders; modify gating to reduce temperature gradient
Required for: reactive alloys (Ti, Ni superalloys); prevent oxidation; improve cleanliness Vacuum level: < 0.01 torr (1.3 Pa) during melt and pour Centrifugal vacuum casting: for thin-wall titanium medical implants; fills thin sections by centrifugal force
ASTM B557 / Investment Casting Institute (ICI) Standard: Linear dimensions: ±0.13 mm for first 25 mm, ±0.05 mm per additional 25 mm Flatness/straightness: 0.25 mm per 100 mm
As-cast tolerances (typical): Small parts (< 50 mm): ±0.1–0.2 mm Medium (50–200 mm): ±0.2–0.5 mm Large (200–500 mm): ±0.5–1.0 mm
Factors affecting tolerance: Wax shrinkage variation: ±0.05% (dominant for small dimensions) Shell expansion: +0.1–0.3% (fused silica shell expands on heating → compensate in die) Metal shrinkage variation: ±0.1% (composition and section size dependent)
As-cast Ra: 1.5–3.2 μm (fused silica shell with fine zircon face coat) After electropolish: Ra 0.4–0.8 μm (stainless steel parts) Machined features: added by CNC post-casting for critical tolerances (< ±0.05 mm)
Application: turbine blade cooling channels; complex internal geometry impossible to pull Material: fused silica (90%+ SiO₂); alumina/silica ceramic Removal after casting: leach in hot NaOH solution (silica cores); HF acid (alumina cores)
Core design: Minimum wall thickness (metal between core and surface): 0.8–1.5 mm Core-to-shell fixture: held by chaplets (metal pins) or shell engagement Core offset during pour: < 0.2 mm (critical for cooling channel dimensions in turbine blades)
Equiaxed casting: conventional; random grain orientation; for moderately stressed parts Directional solidification (DS): columnar grains aligned with thermal gradient → better creep resistance in one direction (turbine blades); 10–15°C/min withdrawal rate Single crystal (SX): no grain boundaries → best creep and oxidation resistance; 1000+ hours in turbine Selector/pig-tail geometries initiate single grain; rejected if more than one grain nucleates (X-ray inspection)
Turbine blade alloys: Equiaxed: IN713, B1914 DS: MAR-M247, CM247LC SX: CMSX-4, René N6, PWA1484
| Defect | Cause | Prevention |
|---|---|---|
| Shrinkage porosity | Insufficient feeding; thick section without riser | Add/enlarge riser; adjust gating |
| Gas porosity | Dissolved gas (H₂, N₂) in melt; damp shell | Degas melt; dry shell thoroughly; vacuum cast |
| Cold shut | Premature freezing; insufficient superheat | Increase melt temperature; reduce fill time |
| Misrun | Metal froze before filling thin section | Increase superheat; preheat shell |
| Hot tear | Restraint during solidification | Reduce restraint; widen risers |
| Shell crack | Thermal shock during dewax; inadequate green strength | Flash dewax; more backup coats |
| Inclusions | Dross, refractory spall, ceramic contamination | Filter use; careful pouring; shell inspection |
| Standard | Scope |
|---|---|
| ASTM B557 | Mechanical testing of wrought/cast aluminum and Mg |
| ASTM A571 | Austenitized/quench/tempered stainless investment castings |
| AMS 5354 | Investment cast Inconel 718 |
| AMS 4928 | Ti-6Al-4V investment castings |
| ICI Standards | Investment Casting Institute dimensional standards |
| NADCA (Die Cast Assoc.) | Design guide (for reference/contrast) |
| ISO 11971 | Steel and Fe alloy castings — visual surface inspection |
Provide: alloy (grade, liquidus T [°C], linear shrinkage [%]), part mass [kg] and largest section thickness [mm], shell build plan (primary coat slurry, N backup layers, total thickness [mm]), gating type (pressurized/unpressurized) and gating ratio, fill time [s] and effective head height [mm], solidification time t_s [s] from Chvorinov (V [cm³], A [cm²], C constant), riser modulus M_riser [cm] vs. M_casting × 1.2, melt superheat [°C], wax shrinkage allowance [%] + metal shrinkage [%] → die oversize, dimensional tolerance achievable [±mm], surface finish as-cast [μm Ra], core required (yes/no, material), vacuum required (yes/no), defect risk assessment (porosity/hot tear/cold shut), and applicable standard (ASTM B557, AMS 4928/5354, ICI).