Silica sol investment casting (lost-wax process) is a high-precision metal forming process designed for critical components requiring exact dimensional control, tight geometric tolerances, and smooth surface finishes directly from the mold.
Unlike conventional water glass casting or sand casting, the silica sol process utilizes a colloidal silica binder for ceramic shell construction. This prevents carbon contamination on stainless steel surfaces, eliminates silica inclusion defects, and delivers near-net-shape components that significantly reduce or completely eliminate secondary machining.
Quick Manufacturing Specifications
|
Parameter |
Specification / Range |
|
Weight Range |
0.05 kg to 35.0 kg per component |
|
Linear Tolerance Grade |
ISO 8062-3 CT4 – CT6 (+/- 0.10 mm to +/- 0.15 mm per 25 mm) |
|
As-Cast Surface Roughness |
Ra 1.6 µm - Ra 3.2 µm (Down to Ra 0.8 µm after polishing) |
|
Minimum Wall Thickness |
1.5 mm (Localized features down to 1.0 mm) |
|
Annual Production Capacity |
1,000+ Metric Tons across 260 skilled staff and integrated CNC workshops |
|
Primary Advantage |
Eliminates 70%–100% of secondary machining on complex exterior/interior geometries |
Manufacturing Process
Every manufacturing step is monitored under an ISO 9001 quality management system to maintain batch-to-batch consistency and metallurgical integrity across medium-to-high volume production runs.
Plaintext
[Tooling CAD/CAM] -> [Wax Injection] -> [Colloidal Silica Shelling] -> [Autoclave Dewaxing]
[Final Inspection] <- [CNC Machining] <- [Pouring & Solidification] <- [High-Temp Firing]
Step-by-Step Production Control
• Tooling Design & Machining: Molds are machined in-house on 3-axis and 5-axis CNC machines using high-grade aluminum or steel dies. Mold shrinkage allowance (typically 1.8% - 2.2%) is pre-calculated based on specific alloy metallurgy.
• Wax Pattern Injection: Medium-temperature wax paste (58°C - 62°C) is injected under automated temperature and pressure control into multi-cavity dies. Patterns are assembled onto sprue trees engineered to optimize fluid flow and feed solidifying metal.
• Colloidal Silica Shell Building: Wax assemblies are dipped into a pure silica sol slurry and coated with high-purity zircon sand/powder for primary face layers, followed by mullite sand for backup layers (5 to 7 coats total). Each layer is dried in humidity-controlled rooms (22°C +/- 2°C, 55% +/- 5% RH).
• Steam Autoclave Dewaxing: Ceramic shells undergo rapid dewaxing in steam autoclaves at 0.6 - 0.8 MPa pressure to melt out the wax pattern without cracking the ceramic shell walls.
• High-Temperature Shell Firing: Empty ceramic shells are sintered at 950°C - 1100°C for 45 to 60 minutes to burn off residual wax and increase structural ceramic bond strength.
• Induction Melting & Pouring: Induction furnaces melt specified metal charges under continuous temperature monitoring. Molten metal is poured directly into preheated shells (850°C - 1000°C) to guarantee complete filling of thin-walled sections.
• Decoring & Finishing: Solidified castings are vibratory knocked-out, cut off from the runner tree, ground at gate contact points, and shot-blasted with stainless steel media for a clean surface finish.
Materials and Technical Specifications
We pour a wide range of ferrous and non-ferrous alloys. Material chemistry is verified on-site via optical emission spectrometry prior to every furnace tap.
Standard Alloy Offering
|
Material Category |
Primary Alloy Grades |
Standard Specifications |
Key Mechanical & Physical Characteristics |
|
Austenitic Stainless Steel |
304, 304L, 316, 316L, CF8, CF8M, 1.4408 |
ASTM A743 / A351, EN 10283 |
Excellent corrosion resistance, PREN >= 23 (316L), Tensile >= 485 MPa, Yield >= 205 MPa. Ideal for fluid control and food contact. |
|
Martensitic & PH Stainless |
17-4PH (CB7Cu-1), 410, 420, 431 |
ASTM A564, ASTM A743 |
High mechanical strength, hardness up to 44 HRC after H900 heat treatment. Wear and erosion resistant. |
|
Duplex Stainless Steel |
2205 (S31803 / 1.4462), 2507 |
ASTM A890 / A995 Grade 4A/5A |
High pitting resistance (PREN >= 34), high mechanical strength, resistant to chloride stress corrosion cracking. |
|
Carbon Steel |
WCB, WCC, 1020, 1045, GS-45 |
ASTM A216, DIN 1681 |
Good weldability and structural strength. Tensile 485 - 655 MPa. Cost-effective structural housing material. |
|
Low Alloy Steel |
4140 (42CrMo4), 8620, 4340 |
ASTM A148, EN 10293 |
High toughness and wear resistance after quench-and-temper heat treatment. Tensile up to 1100 MPa. |
|
Non-Ferrous Alloys |
Bronze (C83600, C95800), Aluminium A356 |
ASTM B584, ASTM B108 |
Seawater corrosion resistance (Bronze) or low-weight high thermal conductivity (Aluminium). |
Dimensional Tolerance Guidelines (ISO 8062-3 CT5 Baseline)
|
Parameter / Feature |
Tolerance Range |
|
Linear Dimensions (d <= 10 mm) |
+/- 0.12 mm |
|
Linear Dimensions (10 mm < d <= 30 mm) |
+/- 0.15 mm |
|
Linear Dimensions (30 mm < d <= 100 mm) |
+/- 0.25 mm |
|
Angular Tolerance |
+/- 0.5° to +/- 1.0° |
|
Min. Internal Fillet Radius |
R = 0.8 mm |
Key Product Features
High Precision Near-Net Shape: Meets ISO 8062 CT4–CT6 dimensional classes out of the mold, reducing metal removal requirements during machining by 60% - 90%.
Clean Surface Finish: As-cast surface roughness reaches Ra 1.6 - 3.2 µm. Free of sand burn-in, surface pitting, or decarburization layers associated with sand casting.
Complex Internal Channels & Geometries: Capable of producing intricate internal passages, thin cross-sections down to 1.5 mm, undercuts, and cast-in part markings without complex multi-part machining.
Non-Contaminating Process: Pure colloidal silica slurry prevents carbon absorption into stainless steel surfaces, preserving maximum corrosion performance without aggressive acid pickling.
Reduced Defect Rates: High-density zircon face coats combined with computerized solidification simulation eliminate slag inclusions, gas porosity, and micro-shrinkage voids.
Typical Applications
Our silica sol precision castings are deployed in critical service applications across key industrial sectors:
Fluid Handling, Valves & Pumps
Impellers (closed, semi-open, open) and diffuser vanes for centrifugal pumps
3-way and 2-way ball valve bodies, seats, and valve stems
Flowmeter bodies, control valve plugs, and sanitary pipe fittings
Food Processing & Pharmaceutical Machinery
Tri-clamp stainless fittings, mixing blades, and pump housings requiring smooth internal contours to prevent bacterial accumulation (Ra <= 0.8 µm after electropolishing)
Commercial Automotive & Transport
Turbocharger brackets, EGR valve housings, exhaust flanges, heavy-duty door hinges, and gear shift forks
General Industrial Machinery
Robotic arm joints, hydraulic block manifolds, textile machinery grippers, and marine hardware fittings
Machining and Secondary Operations
To deliver fully finished, drop-in components to your production line, Wabon operates dedicated secondary processing capabilities in-house:
CNC Machining: Equipped with 3-axis, 4-axis, and 5-axis CNC machining centers, CNC lathes, and tapping centers achieving tolerances down to +/- 0.005 mm.
Heat Treatment:
• Solution Annealing: 1040°C - 1100°C followed by water quenching for austenitic stainless steel.
• Quenching & Tempering (Q&T): Controlled atmosphere furnaces for carbon and alloy steel mechanical property adjustments.
• Precipitation Hardening: H900, H1025, H1150 aging cycles for 17-4PH stainless steel.
Surface Finishing & Treatment: Electropolishing, mechanical satin/mirror polishing, passivation per ASTM A967, glass bead blasting, zinc/nickel plating, and powder coating.
Sub-Assembly: Press-fitting bushings, installing thread inserts (e.g., Helicoil), O-ring pre-assembly, and pneumatic/hydrostatic pressure testing.
Quality Control and Inspection
Quality verification is embedded into every production lot. Raw materials and finished components are fully traceable back to furnace heat numbers and EN 10204 3.1 material test certificates.
|
Inspection Category |
Testing Equipment / Method |
Standard & Purpose |
|
Chemical Analysis |
German SPECTRO Spectrometer (OES) |
Verification of heat composition prior to pouring |
|
Dimensional Inspection |
Hexagon CMM, 2D Optical Projector, Height Gauges |
Full 3D profile scanning against customer CAD models (GD&T) |
|
Surface Roughness |
Contact Surface Profilometer |
Ra 1.6 - 3.2 µm verification |
|
Non-Destructive Testing (NDT) |
Liquid Penetrant (PT), Magnetic Particle (MT), Radiography (RT) |
Internal defect detection per ASTM E192 / ASTM E446 |
|
Mechanical Testing |
Universal Tensile Testing Machine, Impact Tester, Brinell/Rockwell Hardness |
Tensile, yield, elongation, impact energy (-40°C to 20°C), hardness |
|
Leak / Pressure Testing |
Pneumatic underwater bubble test / Hydrostatic bench |
100% leak testing up to 30 bar for fluid valve bodies |
OEM and Custom Manufacturing
Over 95% of our annual production consists of custom engineered OEM components built to client specifications and technical drawings.
Rapid Prototyping: 3D-printed wax or PMMA patterns are integrated directly into our silica sol shelling line, delivering physical metal prototypes in 10 to 14 days without tooling build costs.
DFM Engineering Support: Prior to mold cutting, our foundry engineers perform solidification and mold filling simulations (MAGMA/ProCAST) to evaluate draft angles, wall transitions, shrink allowances, and gate locations.
Flexible Production Volumes: Scalable facilities designed to efficiently process pilot batches (100–500 pcs) up to full-scale annual series production (>50,000 pcs/year).
What Buyers Should Provide for an RFQ
To receive a formal quotation and engineering assessment within 24–48 hours, please include the following technical specifications in your inquiry:
2D & 3D CAD Drawings: STEP, IGES, or DWG/PDF files with clear critical dimensions, tolerances, and GD&T annotations.
Material Standard & Grade: Exact alloy specification (e.g., ASTM A351 CF8M, EN 1.4408, or AISI 4140).
Order Quantity: Sample trial quantity and estimated annual usage (EAU).
Machining Scope: Indication of as-cast supply vs. fully CNC machined surfaces.
Heat Treatment & Surface Finish: Desired mechanical state (e.g., Solution Annealed, H900) and surface finish requirements (e.g., Bead Blasted, Electropolished).
Testing & Certification: Required NDT inspection levels, leak pressure parameters, and certification requirements (e.g., EN 10204 3.1, REACH, RoHS).
Frequently Asked Questions
Q: What is the key difference between Silica Sol casting and Water Glass casting?
A: Silica sol casting uses colloidal silica binder and zircon sand, achieving ISO 8062 CT4–CT6 linear tolerances and as-cast surface roughness of Ra 1.6 - 3.2 µm. Water glass casting produces looser tolerances (CT7–CT9) and rougher surfaces (Ra 6.3 - 12.5 µm). Crucially, silica sol prevents surface carbon contamination in stainless steel alloys.
Q: What is the typical lead time for tooling and sample production?
A: Tooling fabrication and first article sample submission take 20 to 25 calendar days. Initial samples are shipped with a complete First Article Inspection (FAI) report, including dimensional CMM data and EN 10204 3.1 material chemical/mechanical reports.
Q: How do you prevent internal gas porosity and shrinkage defects?
A: We run computer-aided solidification and thermal analysis software during the tooling design stage. This allows us to position sprues and risers to ensure directional solidification. For high-integrity parts, 100% X-ray (RT) or dye penetrant (PT) testing is conducted.
Q: Can Wabon handle secondary CNC machining in-house?
A: Yes. We operate dedicated CNC machining centers, turning centers, and grinding equipment. We supply components as either raw castings or fully machined, ready-to-assemble finished parts.
