Custom stainless steel investment castings manufactured using the silica sol lost-wax process provide near-net-shape metal components designed for high-corrosion, thermal-stress, and structural applications.
This process eliminates internal porosity, coarse grain structures, and surface inclusions common in sand castings or sodium silicate (water glass) casting processes. By combining automated wax pattern injection, multi-layer ceramic shell molding, vacuum induction melting, and precision post-machining, components achieve tight dimensional tolerances (ISO 8062-CT4 to CT6) and smooth surface finishes (Ra 1.6 to Ra 6.3 μm) without requiring extensive secondary machining.

Manufacturing Process

The silica sol lost-wax process maintains tight dimensional repeatability across medium-to-high volume production runs. Below is the step-by-step technical workflow applied to every custom casting batch:

01/

Tooling & Wax Pattern Creation: Aluminum tooling is CNC-machined to accommodate material-specific shrinkage rates (typically 1.5% - 2.2% for stainless steel). Virgin paraffin-based wax is injected into temperature-controlled dies at 60°C - 65°C under 2.5 - 4.0 MPa pressure.

02/

Ceramic Shell Building: Wax assemblies are dipped in a silica sol binder mixed with zircon flour (primary coats) and fused silica (backup coats). Sprinkled with refractory sand (zirconia/mullite), the shell is built to 5 - 7 layers.

03/

Dewaxing & Sintering: Dewaxing occurs in a steam autoclave at 160°C and 0.8 - 1.0 MPa, recovering over 95% of pattern wax. Ceramic shells are then fired in gas ovens at 1000°C - 1150°C for 45 - 60 minutes to burn off residual wax, eliminate moisture, and sinter the ceramic structure.

04/

Melting & Pouring: Stainless steel alloys are melted in medium-frequency induction furnaces. Argon bubbling degasses the melt to minimize dissolved hydrogen and nitrogen. Spectrometric analysis is performed on every heat prior to gravity pouring into preheated ceramic molds (800°C - 950°C) to prevent thermal shock and cold shuts.

05/

Shell Knockout & Cut-Off: After cooling, shells are removed via pneumatic knockout hammers and high-pressure water blasting. Sprue and riser gates are severed using abrasive cut-off wheels or plasma cutters.

Materials and Technical Specifications

We process austenitic, duplex, martensitic, ferritic, and precipitation-hardening stainless steel alloys. All melt chemistry complies with ASTM, EN, DIN, JIS, and BS standards.

Chemical Composition & Equivalent Standards

Standard Grade	UNS / AISI	EN Standard / DIN	C (%)	Cr (%)	Ni (%)	Mo (%)	Other Elements (%)
CF8 (304)	J92600 / 304	1.4308 (GX5CrNi19-10)	≤ 0.08	18.0 - 21.0	8.0 - 11.0	--	Si ≤ 2.0, Mn ≤ 1.5
CF3 (304L)	J92700 / 304L	1.4309 (GX2CrNi19-11)	≤ 0.03	17.0 - 21.0	8.0 - 12.0	--	Si ≤ 2.0, Mn ≤ 1.5
CF8M (316)	J92900 / 316	1.4408 (GX5CrNiMo19-11-2)	≤ 0.08	18.0 - 21.0	9.0 - 12.0	2.0 - 3.0	Si ≤ 1.5, Mn ≤ 1.5
CF3M (316L)	J92800 / 316L	1.4409 (GX2CrNiMo19-11-2)	≤ 0.03	17.0 - 21.0	9.0 - 13.0	2.0 - 3.0	Si ≤ 1.5, Mn ≤ 1.5
CG8M (317)	J93000 / 317	1.4448 (GX2CrNiMo18-14-3)	≤ 0.08	18.0 - 21.0	9.0 - 13.0	3.0 - 4.0	Si ≤ 1.5, Mn ≤ 1.5
2205 Duplex	J92205 / CD3MN	1.4470 (GX2CrNiMoN22-5-3)	≤ 0.03	21.5 - 23.5	4.5 - 6.5	2.5 - 3.5	N 0.14 - 0.20
2507 Super Duplex	J93380 / CE3MN	1.4469 (GX2CrNiMoN26-7-4)	≤ 0.03	24.0 - 26.0	6.0 - 8.0	3.0 - 5.0	N 0.20 - 0.35, Cu ≤ 1.0
17-4 PH (CB7Cu-1)	J92180 / 630	1.4542 (GX5CrNiCuNb16-4)	≤ 0.07	15.5 - 17.5	3.6 - 4.6	≤ 0.50	Cu 2.8 - 5.0, Nb 0.15 - 0.45
CA15 (410)	J91150 / 410	1.4008 (GX12Cr14)	≤ 0.15	11.5 - 14.0	≤ 1.00	≤ 0.50	Si ≤ 1.5, Mn ≤ 1.0

Mechanical Properties (As-Cast vs. Heat-Treated)

Alloy Grade	Heat Treatment Condition	Tensile Strength Rm (MPa) min.	Yield Strength Rp0.2 (MPa) min.	Elongation A (%) min.	Hardness (HBW / HRC)
CF8 (304)	Solution Annealed (1040°C - 1120°C, Water Quenched)	485	205	35	130 - 170 HBW
CF3 (304L)	Solution Annealed (1040°C - 1120°C, Water Quenched)	485	195	35	130 - 170 HBW
CF8M (316)	Solution Annealed (1040°C - 1120°C, Water Quenched)	485	205	30	140 - 180 HBW
CF3M (316L)	Solution Annealed (1040°C - 1120°C, Water Quenched)	485	205	30	140 - 180 HBW
2205 Duplex	Solution Annealed (1020°C - 1100°C, Rapid Water Quench)	650	450	25	210 - 270 HBW
17-4 PH	Solution Annealed + H900 Peak Aging (480°C)	1310	1000	10	40 - 45 HRC
17-4 PH	Solution Annealed + H1150 Double Aging (620°C)	930	725	16	28 - 35 HRC
CA15 (410)	Hardened (980°C Air/Oil Quench) + Tempered (600°C)	620	440	18	190 - 240 HBW

Key Product Features

Near-Net-Shape Precision:

Silica sol tooling achieves linear dimensional tolerances per ISO 8062-3 Grade CT4 to CT6. Wall thicknesses down to 2.5 mm can be cast with high dimensional repeatability.

Surface Integrity:

Elimination of water-glass sodium contamination yields as-cast surface roughness of Ra 3.2 - 6.3 μm. Secondary glass bead blasting reduces surface roughness to Ra 1.6 - 3.2 μm.

Zero Intergranular Corrosion:

Low-carbon grades (CF3, CF3M) combined with full solution annealing above 1040°C dissolve chromium carbides back into the matrix, preventing sensitization during field welding.

Pressure Tightness:

Vacuum-assisted pour options combined with dense ceramic molds prevent micro-porosity. Castings routinely pass hydrostatic testing up to 300 bar (4,350 psi) and helium leak testing.

Complex Internal Cavities:

Soluble wax cores and ceramic cores enable internal fluid channels, undercut pockets, and variable-diameter passageways impossible with standard 3-axis machining.

Typical Applications

Industry Sector	Component Types	Critical Performance Metric
Fluid Control & Pumping Systems	Valve Bodies, Ball Valve Spheres, Pump Impellers, Volute Casings	Zero porosity under pressure; ASTM A262 Practice E pass rate
Chemical Processing & Petrochemical	Heat Exchanger Flanges, Mixing Blades, Agitators, Reactor Nozzles	Pitting Resistance Equivalent No. (PREN ≥ 34 for Duplex 2205)
Marine & Offshore Hardware	Underwater Housing Covers, Propeller Struts, Deck Fittings, Cleats	Salt spray resistance > 1,000 hrs; Resistance to crevice corrosion
Food, Dairy & Pharmaceutical	Sanitary Fitting Elbows, Metering Pumps, Tri-Clamp Components	Smooth internal finish (Ra ≤ 0.8μm after electropolishing); CIP cleanability
Automotive & Heavy Transportation	Turbocharger Wastegate Actuators, Exhaust Brackets, EGR Valve Bodies	High thermal fatigue strength up to 850°C (using 310/316L grades)

Machining and Secondary Operations

Precision Machining Capabilities
• CNC Turning: Dual-spindle live-tooling lathes for concentricity down to ± 0.005 mm.
• 4-Axis & 5-Axis Milling: High-speed machining centers for complex impeller contours and 3D sculpted profiles.
• Thread Cutting & Tapping: Metric (M), NPT, BSPP, and BSPT threading compliant with ISO 7-1 / ASME B1.20.1.
• Grinding & Lapping: Flatness tolerance within 0.002 mm for mechanical seal faces and valve seats.

Heat Treatment Standards
• Solution Annealing: 1040°C - 1120°C followed by water quenching to lock carbide phases in solution and restore maximum corrosion resistance.
• Stress Relieving: 300°C - 400°C for post-machining dimensional stabilization.
• Precipitation Hardening (17-4 PH): Regimes including H900 (480°C), H1025 (550°C), and H1150 (620°C) to tailor yield strength between 725 MPa and 1000 MPa.

Surface Treatments & Finishing
• Pickling & Passivation: Chemical immersion per ASTM A967 / EN 2516 to remove free iron contamination and build a passive chromium oxide surface layer.
• Electropolishing: Electrochemical surface leveling targeting surface roughness of Ra ≤ 0.4 μm (16 μin) for sanitary applications.
• Mirror Polishing: Mechanical polishing up to #800 mesh grid for architectural and decorative marine hardware.
• Shot & Bead Blasting: Automated blasting with cer

Quality Control and Inspection

Quality assurance follows a strict control plan integrated into every phase of manufacturing, backed by ISO 9001:2015 and IATF 16949 quality management systems.

Inspection Category	Testing Method / Equipment	Standard / Acceptance Criteria
Chemical Analysis	Optical Emission Spectrometry (OES - 28 channels)	ASTM A751, EN 10204 Type 3.1 Cert; Heat-by-heat ladle verification
Dimensional Inspection	Coordinate Measuring Machine (CMM), 3D Laser Scanning	ISO 8062, ASME Y14.5; Full 100% first-article inspection
Non-Destructive Testing (NDT)	Radiographic Testing (X-Ray), Dye Penetrant (PT), Magnetic Particle (MT), Ultrasonic (UT)	ASTM E192/E446 (Level 1-2); ASTM E1417 (Zero cracks); ASTM E1444; ASTM A609
Mechanical Testing	Room & High-Temp Tensile, Charpy V-Notch Impact, Hardness	ASTM A370, ISO 6892-1; ASTM E23 (-196°C cryogenic capability); ASTM E10/E18
Corrosion Testing	Intergranular Corrosion (IGC), Salt Spray (Fog) Testing	ASTM A262 Practice E (Oxalic/Copper); ASTM B117 (Up to 1,500 continuous hrs)
Pressure / Leak Test	Hydrostatic Water Pressure, Pneumatic / Helium Mass Spec	1.5x design pressure (up to 300 bar); Air underwater test @ 6 bar / Helium

OEM and Custom Manufacturing

We support international OEMs through flexible engineering integration, transitioning parts from sand casting, forging, or complex welded assemblies into single-piece investment castings.

Design for Manufacturability (DFM): Early engineering involvement to optimize draft angles, fillet radii, gate placement, and uniform wall thickness.

Casting Simulation: Magma / ProCAST thermal and mold filling simulation to predict solidification behavior and eliminate internal shrink porosity prior to tooling fabrication.

Rapid Prototyping: SLA / SLS 3D-printed wax or PMMA patterns for functional testing without committing to hard tooling (lead time: 7 - 10 days).

Tooling Ownership: Dies are CNC-machined in-house and maintained under climate-controlled conditions for the lifetime of the program at no extra charge.

What Buyers Should Provide for an RFQ

To receive an accurate commercial quotation and technical DFM feedback within 24 - 48 hours, submit the following engineering inputs:

2D Engineering Drawings:

PDF/DWG format specifying linear tolerances, GD&T (ASME Y14.5), surface roughness, and machining allowances.

3D CAD Models:

Solid models in STEP (.stp), IGES (.igs), or Parasolid (.x_t) format.

Material Grade & Standard:

Exact specification (e.g., ASTM A351 CF8M or EN 1.4408) or working environment details (temperatures, media, stress).

Order Volume:

Estimated Annual Volume (EAV) and target batch release sizes.

Secondary Operations:

Specific post-processing requirements (CNC machining, thread specs, heat treatment, electropolishing).

Inspection Requirements:

Required NDT testing levels (X-Ray Class 1/2, PT), hydrostatic test pressure, and certification requirements (EN 10204 3.1 or 3.2).

Frequently Asked Questions

Q: What is the lead time for new tooling and sample production?

A: Tooling fabrication takes 21 to 28 calendar days. Initial sample inspection reports (ISIR) with full CMM data and material test certificates (EN 10204 3.1) are dispatched within 10 to 14 days after tooling sign-off. Mass production takes 30 to 45 days.

Q: What are your standard linear tolerances for as-cast components?

A: We cast per ISO 8062-3 CT4 to CT6. For dimensions up to 50 mm, as-cast tolerance is typically ± 0.2 mm to ± 0.3 mm. Tolerances down to ± 0.005 mm are achieved via secondary CNC machining.

Q: How do you prevent intergranular corrosion in cast 316L (CF3M) components?

A: All austenitic castings undergo full solution annealing at 1040°C to 1120°C followed by rapid water quenching. We verify performance via ASTM A262 Practice E testing upon request.

Q: Can you produce thin-walled casting geometries?

A: Yes. Using high-fluidity silica sol slurries and preheated ceramic molds, we achieve minimum wall thicknesses down to 2.5 mm across large areas, and 1.5 mm over localized ribs.

Q: What is the minimum order quantity (MOQ)?

A: We support prototype runs of 10 to 50 pieces via 3D-printed patterns. Production MOQs start at 100 pieces or a minimum batch weight of 200 kg.