Type 416 stainless steel
Free-machining martensitic stainless steel: sulfur, supplied condition, heat-treatment-dependent properties and corrosion/fabrication tradeoffs.
Tags: materials, stainless-steel, martensitic-stainless-steel
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Identity and selection tradeoff
Type 416 is a free-machining martensitic stainless steel, UNS S41600, also associated with EN 1.4005. Universal Stainless describes higher sulfur than Type 410 as improving machinability while reducing corrosion resistance, and identifies quenching and tempering as the route to higher strength. It offers round/flat bar, billet and ingot; product sizes and requirements depend on the order. Universal Stainless 416
Carpenter's 416 sheet specifies chromium 12–14%, carbon ≤0.15% and sulfur ≥0.150%, with additional limits. Sulfur is a minimum in that technical sheet, despite the alloy-finder webpage labeling its sulfur field as a maximum. Use the ordered specification and certificate to resolve chemistry acceptance. Carpenter technical sheet, Carpenter alloy-finder entry
Specify exact producer grade, product-standard edition, form, size, condition, surface finish and inspection requirements. The generic UNS number does not establish that ordinary 416, a producer's enhanced-machining variant and a special modification have identical processing or performance. Keep certificate traceability after cutting and machining.
Mechanical properties must include condition
Carpenter's typical data provide a useful condition comparison:
| Material/test basis | 0.2% yield strength | Tensile strength | Elongation |
|---|---|---|---|
| Annealed, tested at 21°C | 276 MPa | 517 MPa | 30% |
| 25.4 mm round bar, hardened at 982°C, oil quenched, tempered one hour at 260°C; room-temperature test | 979 MPa | 1276 MPa | 13% |
The elongation basis is 50.8 mm. These are producer reference results, not guaranteed minima or a heat-treatment recipe for arbitrary sections. Carpenter typical mechanical tables
For design or acceptance, identify annealed versus hardened/tempered condition, section size, test direction, temperature and required properties. Hardness alone does not establish toughness, fatigue life or corrosion performance. Specify the property combination that the part needs rather than selecting the highest hardness in a catalogue.
An actual shaft also introduces fillets, keyways, threads and surface condition. Assess those details under the intended loading and environment. A bar tensile result is not an allowable stress for every machined feature or a guarantee of bearing/shaft contact performance.
Heat treatment is a process choice
Ugitech's UGIMA 4005 sheet identifies quenching and tempering as separate operations and warns against tempering at 400–550°C because of reduced toughness. That warning applies to its named product and must be read with the required property balance. It does not establish that every treatment outside that band is automatically suitable. Ugitech UGIMA 4005 heat-treatment guidance
Before processing, agree on the final strength/hardness range, toughness or impact requirement, corrosion exposure and dimensional allowance. Review section thickness, furnace uniformity, atmosphere, quench severity and tempering requirements with the heat treater. Establish what is measured on production parts and what is represented by qualification samples. Account for scale removal and distortion before setting final machining dimensions.
Do not transfer a treatment demonstrated on a small bar to a large, interrupted or thin-walled component without assessing its cooling and distortion behavior. Record the actual thermal cycle and resulting condition against the material lot.
Machinability: prove the named stock and operation
Ugitech describes controlled oxide inclusions in UGIMA 4005 as improving machining relative to standard UGI 4005. Its dry-turning comparison uses VB15/0.15: speed producing 0.15 mm flank wear in 15 minutes of effective cutting, with depth 1.5 mm and feed 0.25 mm/rev. These are defined test conditions, not universal speeds for every 416 part. Ugitech machining comparison
The broader UGIMA brochure lists UGIMA 4005A/416A separately from other martensitic and austenitic grades. A productivity claim for that producer product is not a performance guarantee for unspecified S41600 stock. Ugitech UGIMA product range
Select tooling, coolant and parameters using the actual hardness, operation, rigidity and required surface. Measure tool life using a defined failure or wear criterion. Include burr formation, dimensional stability and surface damage in trials; a faster cycle is useful only if accepted parts and tool consumption improve together.
Corrosion and final surface
The sulfur-related machinability benefit comes with reduced corrosion resistance relative to 410 in Universal Stainless's comparison. It therefore should not be treated as interchangeable with a more corrosion-resistant stainless solely because machining is easier. Universal Stainless selection description
Carpenter gives salt spray a restricted comparative corrosion rating and says the ratings require exposure-specific testing. Carpenter corrosion scope
For service qualification, record temperature, concentration, pH, chloride exposure, deposits, crevices, stress and mating materials. Include cleaning chemicals and downtime. Define the finished surface after machining and heat treatment, and qualify cleaning/passivation for the actual alloy and condition. Do not assume a treatment selected for 304 will produce the same result on sulfur-bearing 416, or that passivation changes the bulk alloy into a higher-corrosion-resistance grade.
Welding requires an explicit decision
Carpenter states that its Type 416 is not recommended for welding. Carpenter weldability statement
Ugitech's UGIMA 4005 sheet, by contrast, describes welding processes and conditional thermal treatments, while addressing martensitic weld/HAZ behavior and hydrogen-embrittlement risk. This is product-specific guidance, not permission to weld any generic 416 part using an austenitic-stainless procedure. Ugitech welding discussion
If welding is essential, resolve material selection with the producer and qualify the joint, filler, shielding, thermal cycle and final properties before production. A repair weld needs the same review. Consider whether a different base grade or a mechanical joint better meets the complete requirement.
Bounded test-value comparison
From the two Carpenter rows above, the typical yield-strength ratio is 979/276 ≈ 3.55, while elongation changes from 30% to 13%. This original comparison illustrates a condition tradeoff; it is not a guaranteed strengthening factor for every 416 component. A selection record should retain the exact row conditions rather than storing only “416: 979 MPa.”
Source editions and related reference
Carpenter's PDF prints Edition Date 09/01/1986 and ©2020; the later copyright does not establish a new technical edition. Ugitech's product sheet prints 10-01-2013, REV 00. Its broader UGIMA brochure footer identifies 02-2025, D252010EN. Universal Stainless's webpage gives no verified technical revision date. Obtain current order-specific standards and producer confirmation where these historical references affect acceptance.