Stainless Steel Investment Casting

Stainless steel investment casting (lost wax casting) is a precision metal forming process that produces complex near-net-shape stainless steel components with fine surface finish, tight dimensional tolerances, and superior mechanical properties compared to fabricated or forged alternatives. The process uses expendable wax patterns coated with multiple layers of ceramic slurry to build a rigid shell mold, which is de-waxed, fired, and filled with molten stainless steel. Brass & Copper Parts manufactures stainless steel investment castings in grades SS 304, 304L, 316, 316L, 316Ti, 17-4PH (SS 630), 15-5PH, CF8, CF8M, CA6NM, and duplex 2205 for food processing, pharmaceutical, chemical processing, marine, oil and gas, valve, pump, and precision engineering applications worldwide.

Product Overview

Stainless steel investment casting is the process of choice when component complexity, dimensional accuracy, corrosion resistance, and surface finish requirements cannot be met by sand casting, forging, or fabrication at comparable cost. The lost wax process allows engineers to consolidate multiple machined or fabricated parts into a single investment casting, reducing assembly joints, leak paths, and manufacturing cost. Brass & Copper Parts produces stainless steel investment castings from 5 grams to 50 kilograms, with dimensional tolerances CT4–CT6 per ISO 8062-3, and surface finish Ra 1.6–6.3 μm as-cast. Post-casting operations including CNC machining, polishing, electropolishing, passivation, and pressure testing are available as value-added services integrated with the casting supply.

Key Features

• Superior corrosion resistance – SS 316/316L for aggressive chemical, seawater, and food contact environments
• Near-net-shape precision – CT4–CT6 tolerances reduce or eliminate secondary machining
• Excellent surface finish – Ra 1.6–6.3 μm as-cast; electropolished to Ra 0.4–0.8 μm available
• Full alloy range – Austenitic, martensitic, precipitation hardened, duplex grades available
• Complex geometry – Thin walls (1.5 mm), internal passages, undercuts in one casting
• Part consolidation – Multiple components combined into one casting, reducing assembly cost
• High-temperature capability – Heat-resistant grades (HK, HH) for elevated temperature service

Technical Specifications

Stainless Steel Grade Equivalents

Product Types and Variants

SS 316/316L Investment Cast Valve Bodies and Trim

Stainless steel 316/316L (CF8M/CF3M) investment cast valve bodies, bonnets, balls, discs, and seat rings are the most widely produced stainless investment castings globally, serving chemical processing, pharmaceutical, food and beverage, oil and gas, and seawater service applications. Investment cast CF8M valve bodies conform to ASTM A351 and MSS SP-43/SP-44 material requirements, with dimensional compliance to ASME B16.34 Class 150 through Class 2500 pressure-temperature ratings. Brass & Copper Parts produces 316 investment cast valve components from ½” to 6″ nominal bore, in lost wax process with wax die tooling in-house, achieving as-cast dimensional tolerances of CT5–CT6 on valve body critical dimensions.

SS 304/316 Investment Cast Pump Components

Centrifugal pump impellers, casings, wear rings, and shaft sleeves in SS 304 (CF8) and SS 316 (CF8M) investment cast form are used in food grade, pharmaceutical, chemical dosing, and water treatment pump applications. Investment cast stainless pump impellers achieve closer-to-design hydraulic geometry compared to fabricated or sand cast alternatives, improving pump efficiency by 3–8% in laboratory testing. Surface finish Ra 3.2 μm as-cast on internal hydraulic passages reduces viscous losses and simplifies hygienic cleaning validation for pharmaceutical and food service pumps. Brass & Copper Parts supplies stainless steel investment cast pump impellers in 50 mm to 350 mm diameter range with complete dimensional documentation.

17-4PH (SS 630) Investment Cast Precision Components

17-4PH (UNS S17400, ASTM A747 CB7Cu-1) precipitation-hardening stainless steel is investment cast for high-strength, corrosion-resistant components including pump shafts, impellers, valve stems, structural brackets, and aerospace fastener bodies. After investment casting, 17-4PH components are solution annealed at 1040°C and age-hardened at the H900, H1025, H1075, or H1150 condition as specified, achieving tensile strengths from 1310 MPa (H900) to 862 MPa (H1150). The combination of investment casting precision and 17-4PH mechanical properties eliminates many multi-piece fabricated assemblies in defense, aerospace, and offshore equipment design.

Investment Cast Stainless Steel Food and Pharmaceutical Components

FDA-compliant, EHEDG-certified food-grade stainless steel investment castings in SS 316L (CF3M) are produced for dairy processing, beverage filling, pharmaceutical manufacturing, and biotechnology equipment. Investment casting enables the production of CIP (clean-in-place) compatible components with smooth radiused internal corners (Ra ≤1.6 μm after electropolishing), eliminating bacterial harborage points required under HACCP and GMP regulations. Brass & Copper Parts produces food-grade stainless investment castings with electropolishing, passivation per ASTM A967, and Ra surface finish certification for hygienic equipment OEM manufacturers in Europe, the USA, and Australia.

Investment Cast Duplex Stainless Steel (2205, 2507)

Duplex stainless steel 2205 (CD4MCu, S31803) and super-duplex 2507 investment castings provide superior pitting and crevice corrosion resistance (PRE >35) for seawater, chloride-rich process, and sour gas service applications. Investment cast duplex components include offshore valve bodies, subsea connector bodies, pump casings for produced water service, and chemical injection fittings. The duplex microstructure (approximately equal ferrite and austenite phases) provides higher strength than austenitic grades with improved stress corrosion cracking resistance, making it the preferred choice for aggressive offshore and chemical plant environments where 316L is marginal.

Investment Cast Stainless Steel Marine and Offshore Components

Stainless steel investment castings for marine and offshore applications include subsea valve actuator components, ROV connector bodies, riser clamp inserts, deck equipment fittings, and navigation hardware in SS 316, 316L, duplex 2205, and super duplex 2507. Investment cast marine stainless components offer superior resistance to crevice corrosion in seawater compared to 304/316, particularly in high-temperature or stagnant seawater conditions. NACE MR0175 / ISO 15156 compliance is achievable in CA6NM and duplex grades for sour service applications. Brass & Copper Parts supplies marine investment castings with DNV, Lloyd’s Register, and Bureau Veritas material certification for offshore platform and vessel certification requirements.

Applications by Industry

Manufacturing Process

Stainless steel investment casting at Brass & Copper Parts follows the standard lost wax process: wax pattern injection → pattern assembly → ceramic shell building (8–12 coats) → autoclave de-waxing → shell firing at 1050–1100°C → vacuum induction or open induction melting of stainless steel → controlled-atmosphere pouring → shell knockout → abrasive blast cleaning → gate removal → heat treatment (solution anneal at 1050–1100°C, water quench for austenitic grades) → dimensional inspection → NDT as specified. Vacuum melting is available for 17-4PH and duplex grades requiring low nitrogen and oxygen content for maximum corrosion resistance and mechanical properties. Post-casting value-added operations include CNC machining, electropolishing, passivation, mirror polishing, and pressure testing.

Quality Standards and Certifications

• ASTM A351 – CF8, CF8M, CF3M austenitic stainless castings
• ASTM A743/A744 – General corrosion-resistant castings (CA15, CA6NM, CD4MCu)
• ASTM A747 – CB7Cu precipitation-hardening stainless castings
• ASTM A890 – Duplex stainless steel castings
• ASTM A967 – Passivation of stainless steel
• ISO 8062-3 – Dimensional tolerances CT4–CT6
• ISO 9001:2015 – Quality management system
• NACE MR0175 / ISO 15156 – Sour service compliance (CA6NM, duplex)

Why Choose Brass & Copper Parts

Brass & Copper Parts offers stainless steel investment casting as an integrated service — from wax tooling design and manufacture through casting, heat treatment, machining, surface finishing, and full certification documentation — under one roof. Our in-house ceramic shell facility accommodates single-piece prototype castings through 10,000-piece annual production runs. We maintain wax tooling for over 200 active stainless steel casting part numbers, enabling rapid order fulfillment for repeat components. Engineering support covers alloy selection, wall thickness optimization, parting line design, and dimensional tolerance feasibility review for new product introductions.

Frequently Asked Questions

What is the difference between CF8 and CF8M stainless steel investment casting?

CF8 is the cast equivalent of wrought SS 304 (18% Cr, 8% Ni, no molybdenum). CF8M is the cast equivalent of SS 316 (18% Cr, 10% Ni, 2–3% Mo). The molybdenum in CF8M provides significantly improved resistance to pitting corrosion in chloride environments, including seawater, brackish water, and many chemical media. For most aggressive service environments, CF8M (316) is specified; CF8 (304) is used for less corrosive applications or where cost is the primary driver.

What is the minimum wall thickness for stainless steel investment casting?

Minimum wall thickness of 1.5–2.0 mm is achievable for short sections in standard austenitic grades (CF8, CF8M). For larger components or longer thin sections, 2.5–3.0 mm is the practical minimum. 17-4PH and duplex grades typically require 3.0 mm minimum wall due to their higher freezing ranges and lower fluidity compared to austenitic grades. Brass & Copper Parts uses casting simulation software to verify fill and solidification for thin-wall stainless components before tooling commitment.

Do you provide electropolishing for stainless steel investment castings?

Yes. Electropolishing service is available in-house for austenitic grades (CF8, CF8M, CF3M) to achieve surface finishes of Ra 0.4–0.8 μm for pharmaceutical, food-grade, and semiconductor applications. Electropolishing also improves corrosion resistance by removing surface contamination and creating a chromium-enriched passive layer. Ra certification is provided with electropolished components. Mechanical polishing to mirror finish (Ra <0.2 μm) is available for decorative and precision optical applications.

Can stainless steel investment castings be welded?

Yes. Austenitic grades (CF8, CF8M) are readily weldable using matching filler wire (ER308, ER316) by GTAW, GMAW, or SMAW processes. Low-carbon grades (CF3M/316L) are preferred for welded assemblies to prevent sensitization (carbide precipitation). Post-weld solution anneal at 1050°C may be required for critical applications. Weld repair of casting defects is performed per MSS SP-55 acceptance criteria with NDE and re-test documentation.

What is the lead time for a new stainless steel investment casting?

New tooling (wax die) manufacture: 3–5 weeks. First sample castings: 1–2 weeks after tooling. Total from drawing to first approved casting: 5–8 weeks. Production quantities: 3–5 weeks after sample approval. Repeat orders from existing tooling: 4–6 weeks production lead time including heat treatment and inspection. Express tooling and production services are available for urgent project requirements at premium lead time pricing.

What is the weight range for stainless steel investment castings?

Brass & Copper Parts produces stainless steel investment castings from 5 grams to 50 kilograms per piece. The optimal weight range for investment casting economics is 50 grams to 10 kg. Above 25–50 kg, sand casting (ASTM A743/A744) becomes more cost-effective for most geometries. For very small castings below 10 grams, micro-investment casting (dental/jewelry precision processes) may be more appropriate.

Do you supply stainless steel investment castings with NACE MR0175 compliance for sour service?

Yes. CA6NM (13Cr-4Ni martensitic stainless) and duplex 2205 investment castings are supplied with NACE MR0175 / ISO 15156 compliance documentation for sour gas (H₂S-containing) oil and gas service. Hardness testing per NACE limits (CA6NM ≤23 HRC, 2205 per applicable table) is performed and documented on each batch. Brass & Copper Parts can supply NACE-compliant stainless investment castings for wellhead, pipeline, and subsea applications with full traceability documentation.

What is the difference between investment casting and sand casting for stainless steel?

Investment casting (CT4–CT6, Ra 1.6–6.3 μm) produces significantly tighter tolerances and better surface finish than sand casting (CT8–CT11, Ra 12.5–25 μm), reducing or eliminating secondary machining for many components. Investment casting is cost-effective for complex small-to-medium components (up to 50 kg); sand casting is preferred for large, simpler components (above 50 kg) where investment casting tooling and process costs are not justified by the improved dimensional accuracy.

Request a Quote

Brass & Copper Parts manufactures stainless steel investment castings in SS 304, 316, 316L, 17-4PH, duplex 2205, and all standard cast stainless grades for chemical, food, pharmaceutical, marine, and engineering applications. Contact our technical team with drawings and specifications for competitive pricing.

Contact us: sales@brass-copper-parts.com | +91-22-43449300