TYPE 416 MARTENSITIC FREE-MACHINING STAINLESS STEEL (UNS S41600) — COMPREHENSIVE TECHNICAL DATASHEET
Type 416 is a high-chromium martensitic free-machining stainless steel, representing a landmark development as the first free-machining stainless steel ever formulated. Developed as an engineered modification of straight chromium martensitic alloys like Type 410, Type 416 was specifically designed to overcome the severe adhesive wear, galling, and continuous stringy chip formation that historically restricted the high-speed processing of stainless steels.
By incorporating controlled additions of sulfur or selenium, the alloy introduces a high volume fraction of localized manganese sulfide ($\text{MnS}$) or manganese selenide ($\text{MnSe}$) inclusions throughout its martensitic matrix. These stringers act as chip-breakers and solid-film lubricants, giving Type 416 a machining efficiency rating of approximately 85% of standard free-machining carbon steels—the highest of all commonly available stainless steel grades.
■ International Standards & Cross-Referencing
Type 416 is governed by distinct international standards based on product form, industry requirements, and geographic region. The foundational specification for raw bar stock is ASTM A582/A582M.
| Standard Body / Region | Specification Standard | Grade Designation / Equivalent |
|---|---|---|
| United States (ASTM / ASME) | ASTM A582 / A582M, SAE J405, AISI 416, AMS 5610 | Type 416 / UNS S41600 |
| International (ISO) | ISO 683/13 7 | Type 7 |
| Germany / Europe | W.Nr 1.4005 / DIN EN 10088 / DIN EN 10272 | X12CrS13 |
| Great Britain (BS) | BS 970 Part 3 (416S21) / BS 970 (1955) | EN56AM |
| Japan (JIS) | JIS G4303 | SUS 416 |
| Australia (AS) | AS 2837-1986 | Grade 416 |
■ Chemical Composition Matrix (Weight % Limits)
The chemistry is precisely balanced to ensure thermal hardening response while optimizing the distribution of free-machining inclusions across standard and customized variants.
| Element | Standard Type 416 (UNS S41600) | Type 416Se (UNS S41623) | Crucible 416R | BUSA MDS-A582-01 |
|---|---|---|---|---|
| Carbon (C) | 0.09 – 0.15 | 0.15 max | 0.12 | 0.09 – 0.15 |
| Chromium (Cr) | 12.00 – 14.00 | 12.00 – 14.00 | 12.50 | 12.00 – 14.00 |
| Manganese (Mn) max | 1.25 | 1.25 | 0.40 | 1.25 |
| Silicon (Si) max | 1.00 | 1.00 | 0.40 | 1.00 |
| Sulfur (S) | 0.15 – 0.35 | 0.060 max | 0.13 | 0.15 – 0.30 |
| Phosphorus (P) max | 0.060 | 0.060 | 0.030 | 0.060 |
| Selenium (Se) | — | 0.15 min | — | — |
| Molybdenum (Mo) max | 0.60 (optional) | — | 0.40 | 0.60 (optional) |
| Nickel (Ni) max | 1.00 (optional) | — | — | 1.00 (optional) |
| Iron (Fe) | Balance | Balance | Balance | Balance |
■ Proprietary Datasheet Download
For machinery designers, programming engineers, and quality procurement officials requiring precise tool wear analytics, full TTT phase diagrams, and certified passivation chemical maps, the unified manual must be downloaded.
Type 416 — Advanced Automatic Screw Machining Technical Manual
Contains empirical data for high-speed CNC optimization, tool-wear friction factors, and complete ASTM A967 chemical de-scaling guides. Corporate credentials required.
⬇ DOWNLOAD DATASHEET■ Physical and Electromagnetic constants
Martensitic Type 416 provides a lower coefficient of thermal expansion and higher thermal conductivity than standard austenitic options, helping mitigate distortion limits during quenching thermal cycles.
| Physical Constant (at 20°C / 68°F) | Metric / SI Value | Imperial / US Value |
|---|---|---|
| Density (Annealed state) | 7750 kg/m³ (7.75 g/cm³) | 0.276 lb/in³ |
| Melting Range Boundaries | 1480°C – 1530°C | 2700°F – 2790°F |
| Modulus of Elasticity (Tension) | 200 GPa | 29.0 × 10⁶ psi |
| Shear Modulus | 83 GPa | 12.0 × 10⁶ psi |
| Poisson's Ratio | 0.28 | 0.28 |
| Specific Heat Capacity (0–100°C) | 460 J/kg·K | 0.11 BTU/lb·°F |
| Electrical Resistivity (Ambient) | 43.0 μΩ·cm | 343.0 ohm-cir-mil/ft |
| Relative Magnetic Permeability (μ) | 700 – 1000 | 700 – 1000 |
| Electrical Conductivity | 2.0 MS/m (2.9% IACS) | 2.9% IACS |
| Magnetic Saturation Induction (Bsat) | 2.08 T | 2.08 T |
The continuous progression of thermal constants and elastic metrics as service temperatures change is detailed below:
| Service Temperature | Thermal Conductivity (W/m·K) | Mean Coeff. of Thermal Expansion (α) | Tension Modulus (GPa / Mpsi) |
|---|---|---|---|
| 20°C / 68°F | 12.7 (at 25°C) | — | 200 / 29.0 |
| 100°C / 212°F | 24.9 | 9.9 × 10⁻⁶/K (0-100°C) | 194 / 28.2 |
| 315°C / 600°F | 17.3 (at 300°C) | 11.0 × 10⁻⁶/K (0-315°C) | 176 / 25.5 |
| 500°C / 932°F | 28.7 | 11.6 × 10⁻⁶/K (0-538°C) | 159 / 23.0 (at 538°C) |
| 650°C / 1200°F | 23.0 | 11.7 × 10⁻⁶/K (0-650°C) | 150 / 21.8 |
■ Mechanical Properties by Standard Delivery Condition
Mechanical profiles vary significantly depending on cold drawing configurations and prior mill heat treatments.
| Standard Delivery Condition | Tensile Strength Rm | 0.2% Yield Strength Rp0.2 | Elongation in 50 mm | Reduction of Area | Hardness Boundaries |
|---|---|---|---|---|---|
| Condition A (Annealed Bar Stock) | 517 – 550 MPa | 276 – 340 MPa | 30% min | — | 241 – 262 max HBW (82 HRB) |
| Condition P (Tempered AS/BS rules) | 550 – 700 MPa | 340 MPa min | 15% min | — | 152 – 207 HBW |
| Condition T (Intermediate Structural) | 758 – 828 MPa min | 586 – 690 MPa min | 15 – 18% min | 45% min | 248 – 302 HBW (25 – 32 HRC) |
| Condition H (Hard Temper ASTM) | 1000 – 1205 MPa | 825 – 1035 MPa | 12% typical | — | 293 – 352 HBW (31 – 38 HRC) |
| Cold Drawn Bars (≤ 1 inch) | 620 – 830 MPa | 550 – 725 MPa | 10% min | 40% min | 190 – 240 HBW |
■ Mechanical Profiling across Specific Tempering plateaus
Typical outcomes derived from an identical 1-inch bar, austenitized at 982°C (1800°F), oil quenched, and tempered for one hour:
| Tempering Temperature | Tensile Strength | Yield Strength (0.2%) | Elongation | Reduction of Area | Hardness | Charpy V-Notch Impact |
|---|---|---|---|---|---|---|
| 149°C (300°F) | 1344 MPa | 1034 MPa | 10% | 40% | 390 HBW | 20 J (Izod: 34 J) |
| 260°C (500°F) | 1276 MPa | 979 MPa | 13% | 45% | 375 HBW | 22 J |
| 371°C (700°F) | 1310 MPa | 1007 MPa | 13% | 48% | 390 HBW | PROSCRIBED RANGE |
| 482°C (900°F) | 1158 MPa | 896 MPa | 14% | 50% | 341 HBW | PROSCRIBED RANGE |
| 593°C (1100°F) | 862 MPa | 689 MPa | 17% | 53% | 262 HBW | 27 J |
| 650°C (1200°F) | 758 MPa | 586 MPa | 18% | 55% | 225 HBW | 38 J |
■ High-Pressure Fastening Sizing (ASTM A194 Grade 6F Nuts)
Type 416 is utilized for high-strength free-machining nut assemblies, quenched and tempered to 225–271 HBW (20–28 HRC). Thread proof load boundaries per standard size configurations are listed below:
| Nominal Size (in) | Threads per Inch (TPI) | Stress Area (in²) | Heavy Hex Series Proof Load (lbf) | Standard Hex Series Proof Load (lbf) |
|---|---|---|---|---|
| 1/4" | 20 | 0.0316 | 4,130 | 3,820 |
| 3/8" | 16 | 0.0774 | 10,080 | 9,300 |
| 1/2" | 13 | 0.1419 | 18,450 | 17,030 |
| 5/8" | 11 | 0.2260 | 29,380 | 27,120 |
| 3/4" | 10 | 0.3340 | 43,420 | 40,080 |
| 1" | 8 | 0.6060 | 78,780 | 72,720 |
| 1-1/4" | 8 | 1.0000 | 130,000 | 120,000 |
| 1-1/2" | 8 | 1.4920 | 194,000 | 170,040 |
■ Process Guidelines & Engineering Restrictions
- Passivation Chemistry Restrictions: Standard nitric acid descaling baths will cause a catastrophic "flash attack"—chemically gouging out active sulfide inclusions and leaving a pitted surface. Passivation must enforce Nitric 1 parameters (20-25 v% $HNO_3$ + 2.5 w% Sodium Dichromate inhibitor) at 50°C, or a 4-10 w% Citric Acid chelation bath. For critical items, invoke the full Alkali-Acid-Alkali (A-A-A) sequence (NaOH soak → rinse → Nitric+Dichromate → rinse → NaOH post-neutralize) to purge acid trapped in micro-crevices.
- Structural Sizing Prohibitions: Never specify Type 416 for primary boundary pressure vessels or lines containing high-pressure gases. Elongated sulfide stringers act as leak paths for gas permeation and pressure-induced microfissures, risking abrupt low-energy cleavage failure under internal hoop stresses.
- Weld Hot-Cracking Vulnerability: Type 416 is classified as highly non-weldable. High sulfur contents induce low-melting-point iron-sulfur liquid films to isolate solidification grain centers. Under contraction strain, these boundaries tear immediately. If emergency joining is mandatory, enforce a 200°C–300°C preheat, use ER309 austenitic filler wires, and run an immediate sub-critical anneal at 650°C.
- Environmental Exclusions: Do not specify this grade for coastal marine yards or high-salinity chloride lines. Halide ions break down the passive film interfaces around the sulfides, initiating aggressive pitting pits. Continuous service ranges above 425°C are also limited due to rapid loss of creep load capacity.
- Machining Configuration: Automatic screw machining functions optimally with sharp tools carrying positive rake angles ($5^\circ\text{--}10^\circ$) at 135–155 SFPM cutting speeds for HSS tools. Continuous feeds are mandatory; tool dwelling or rubbing will work-harden the subsurface layer, rapidly destroying tool edges.