316 stainless steel investment castings provide exceptional resistance to chloride pitting, acidic solutions, and marine corrosion compared to standard 304 alloys. By incorporating 2-3% molybdenum into the austenitic iron-chromium-nickel matrix, these castings deliver structural integrity and long-term chemical stability in high-stress, highly corrosive environments.
We produce near-net-shape 316 and 316L components utilizing investment casting (lost-wax process) and silica sol shell molding techniques. This manufacturing approach achieves tight dimensional tolerances (+/- 0.13 mm per 25 mm per ISO 8062-3 CT4-CT6) and smooth surface finishes (Ra 3.2-6.3 microns) directly from the mold, reducing the need for extensive downstream machining.
Typical Weight Range: 0.05 kg to 50 kg
Wall Thickness: Minimum 1.5 mm
Casting Process: Investment Casting / Lost Wax / Silica Sol Process
Material Grades: ASTM A743/A744 Grade CF8M (316), CF3M (316L), DIN 1.4408, DIN 1.4404
Manufacturing Process
Our facility utilizes a fully integrated, modern investment casting process designed to minimize gas porosity, surface defects, and micro-segregation.
[ Precision Tooling & Wax Injection ]
[ Pattern Assembly (Tree Building) ]
[ Silica Sol Shell Mold Building (5-7 Layers) ]
[ Autoclave Dewaxing & High-Temp Shell Firing ]
[ Induction Melting & Vacuum-Assisted Pouring ]
[ Shell Knockout, Riser Cutoff & Shot Blasting ]
[ Solution Annealing Heat Treatment ]
[ Machining, Inspection & Surface Finishing ]
Pattern Creation: Automated wax injection presses produce high-density patterns using dimensional-stable pattern wax.
Shell Molding: Multi-stage dipping in automated climate-controlled rooms using silica sol slurries and high-purity zircon sand for smooth surface reproduction.
Dewaxing & Firing: Steam autoclave dewaxing followed by high-temperature shell calcination (950 deg C to 1100 deg C) to remove organics and strengthen ceramic molds.
Melting & Pouring: Medium-frequency induction furnaces melt raw ingot certified by heat number. Liquid metal is poured into pre-heated shells to prevent thermal shock and incomplete filling.
Post-Casting Treatment: Mechanical knockout, pneumatic riser removal, shot blasting, solution annealing heat treatment, and acid pickling/passivation.
Materials and Technical Specifications
Chemical Composition Comparison (Mass %)
|
Standard / Grade |
C (max) |
Si (max) |
Mn (max) |
P (max) |
S (max) |
Cr |
Ni |
Mo |
|
ASTM A743 CF8M (316) |
0.08 |
1.50 |
1.50 |
0.040 |
0.040 |
18.0 - 21.0 |
9.0 - 12.0 |
2.0 - 3.0 |
|
ASTM A743 CF3M (316L) |
0.03 |
1.50 |
1.50 |
0.040 |
0.040 |
17.0 - 21.0 |
9.0 - 13.0 |
2.0 - 3.0 |
|
DIN 1.4408 (GX5CrNiMo19-11-2) |
0.07 |
1.50 |
1.50 |
0.040 |
0.030 |
18.0 - 20.0 |
9.0 - 12.0 |
2.0 - 2.5 |
|
DIN 1.4404 (316L Cast Equivalent) |
0.03 |
1.00 |
2.00 |
0.045 |
0.015 |
16.5 - 18.5 |
10.0 - 13.0 |
2.0 - 2.5 |
Mechanical Properties (Heat Treated - Solution Annealed)
|
Parameter |
ASTM A743 CF8M |
ASTM A743 CF3M |
DIN 1.4408 |
|
Tensile Strength (MPa min.) |
485 |
485 |
440 |
|
Yield Strength 0.2% (MPa min.) |
205 |
205 |
185 |
|
Elongation in 2 inches (% min.) |
30 |
30 |
30 |
|
Hardness (HB max.) |
217 |
200 |
200 |
|
Impact Energy (Charpy-V, 20 deg C) |
>= 60 J |
>= 80 J |
>= 60 J |
Key Product Features
Pitting Corrosion Resistance:
Molybdenum content provides a Pitting Resistance Equivalent Number (PREN) >= 23, outperforming 304 stainless steel in salt-water and acidic media.
Low Carbon Option (316L / CF3M):
Carbon content below 0.03% prevents chromium carbide precipitation during welding, eliminating intergranular corrosion without requiring post-weld heat treatment.
Dimensional Consistency:
Silica sol casting yields net or near-net shapes compliant with ISO 8062 CT4-CT6, eliminating rough machining steps.
Non-Magnetic Properties:
Fully austenitic phase structure (when properly solution annealed at 1040 deg C to 1120 deg C followed by rapid water quenching) maintains low magnetic permeability.
Typical Applications
Volute casings, closed/open impellers, wear rings, suction plates handling brackish water, brine, or weak acids.
Ball valve bodies, butterfly valve discs, globe valve seats, control valve plugs rated for Class 150 to Class 600 pressure services.
Deck hinges, bow chocks, propeller struts, water intake strainers operating continuously in saltwater immersion.
Sanitary valve housings, fitting adapters, homogenizer components requiring sub-micron surface polishing (Ra < 0.4 microns).
Machining and Secondary Operations
We offer complete in-house secondary processing so components arrive ready for assembly.
In-House CNC Machining Capabilities
• Equipment: 3-axis, 4-axis, and 5-axis CNC machining centers, vertical and horizontal CNC lathes.
• Tolerances: Down to +/- 0.008 mm (+/- 0.0003 inches) on critical bored holes, threads, and sealing faces.
• Thread Types: NPT, BSPT, Metric (ISO), and UNC/UNF standard threads.
Surface Finishing Options
• Electropolishing: Removes micro-peaks, improves corrosion resistance, and achieves Ra <= 0.4 microns for sanitary applications.
• Mechanical Mirror Polishing: Up to #800 grit finish for decorative or high-purity applications.
• Passivation: ASTM A967 compliant nitric or citric acid treatment to remove free iron contamination.
• Media Blasting: Glass bead or stainless steel grit blasting for uniform matte surface finish (Ra 3.2-6.3 microns).
Quality Control and Inspection
Every production batch undergoes traceable inspection against customer drawings and international standards.
Traceability & Certifications
Material Test Reports (MTR): EN 10204 3.1 certification provided with every shipment containing heat-specific chemical analysis and mechanical property results.
Non-Destructive Testing (NDT):
• Liquid Penetrant Testing (PT): ASTM E1417 standard for surface crack detection.
• Radiographic Testing (RT): ASTM E192 spec for internal porosity, shrinkage, and inclusions.
• Pressure/Hydrostatic Testing: Up to 100 bar for pressure-containing valve and pump housings.
Dimensional Inspection: Coordinate Measuring Machine (CMM), optical profile projectors, and thread plug gauges.
OEM and Custom Manufacturing
We build custom 316 stainless steel components tailored to your CAD models and engineering requirements.
Engineering Support:
SolidWorks, Creo, AutoCAD; simulation software used for solidification analysis to eliminate internal shrinkage before tool making.
Rapid Prototyping:
3D-printed wax or resin patterns for functional testing prior to hard steel tooling investment (delivers sample parts in 10-14 days).
Tooling Ownership:
Steel tooling remains the property of the buyer and is maintained for the lifetime of the project without additional storage fees.
What Buyers Should Provide for an RFQ
To receive an accurate quote within 24 to 48 hours, please include the following details in your inquiry:
2D & 3D Drawings: STEP, IGES, or DWG files specifying dimensions, tolerances, thread callouts, and target surface finish.
Material Specification: Specific grade requirement (e.g., ASTM A743 CF8M, CF3M, DIN 1.4408) or standard chemistry limits.
Annual Volume & Lot Sizes: Estimated Annual Usage (EAU) and initial sample/production batch sizes.
Inspection & Testing Requirements: Need for NDT (PT/RT), hydro testing, CMM dimensional reports, or third-party inspections (SGS, TUV).
Secondary Processing: Required machining tolerances, heat treatment, electropolishing, or special packaging specifications.
Frequently Asked Questions
Q: What is the primary difference between CF8M and CF3M in casting?
A: CF8M is the cast equivalent of forged 316 stainless steel with a maximum carbon content of 0.08%. CF3M is the cast equivalent of 316L, featuring a maximum carbon content of 0.03%. CF3M is preferred for components requiring extensive field welding, as the lower carbon prevents intergranular corrosion in the heat-affected zone.
Q: What linear tolerances can be achieved without machining?
A: Our standard investment casting process complies with ISO 8062-3 CT4-CT6 limits. Typically, this yields +/- 0.13 mm for dimensions up to 25 mm, and an additional +/- 0.05 mm for each additional 25 mm. Critical features requiring tighter tolerances (such as bearing seats or O-ring grooves) are finished-machined on CNC centers.
Q: Are investment castings subject to internal gas porosity?
A: While casting inherently carries some risk of porosity, our process controls it through computerized solidification modeling, vacuum-assisted pouring, automated shell building, and melt degasification. For critical pressure applications, we perform 100% X-ray inspection to ASTM E192 acceptance criteria.
