SAE 4118 Alloy Steel
Mat Grades internal verification confirms source-backed fidelity and data integrity. It does not constitute external certification or guaranteed lot conformity. Read engineering disclaimer →
Key Engineering Properties
Representative source rows, qualified by their reported conditions. Inspect the tables below for all values, limits, and source notes.
Engineering Summary
SAE 4118 is a chromium-molybdenum carburizing alloy steel providing high core toughness and strong case response for automotive and industrial gearing and pinions.
Recognized Aliases
Source-backed commercial trade name and short designations cataloged in canonical data.
SAE 4118 Alloy Steel Specifications & Designations
Standard Designations & Applicable Specifications — Semantically classified designations distinguishing primary standard identifiers, commercial trade names, and applicable specification references.
| System | Identifier | Standard System Name | Classification Notes & Provenance |
|---|---|---|---|
| SAEPRIMARY | 4118 | Society of Automotive Engineers | —Ref: Practical Data for Metallurgists, 19th edition |
| AISI | 4118 | American Iron and Steel Institute | —Ref: Practical Data for Metallurgists, 19th edition |
| UNS | G41180 | Unified Numbering System | —Ref: Practical Data for Metallurgists, 19th edition |
| Standards Body | Specification Code | Specification Title / Scope | Relationship Type |
|---|---|---|---|
| SAE | SAE 4118 Alloy Steel Engineering Datasheet | Applicable specification reference. | Specification Reference |
SAE 4118 Alloy Steel Chemical Composition
Chemical Composition (Weight %) — Elemental limits and values from the cited source. Preserves exact semantic limits (minimums, maximums, and ranges).
| Element | Symbol | Atomic No. | Semantic Basis | Specified Value | Unit | Metallurgical Notes & Qualification | Data Status |
|---|---|---|---|---|---|---|---|
| Iron | Fe | 26 | BALANCE | Balance | wt% | Ref: Metallus | VERIFIED |
| Carbon | C | 6 | RANGE | 0.18 – 0.23 | wt% | Ref: Metallus | VERIFIED |
| Manganese | Mn | 25 | RANGE | 0.70 – 0.90 | wt% | Ref: Metallus | VERIFIED |
| Phosphorus | P | 15 | MAXIMUM | ≤ 0.03 | wt% | Ref: Metallus | VERIFIED |
| Sulfur | S | 16 | MAXIMUM | ≤ 0.04 | wt% | Ref: Metallus | VERIFIED |
| Silicon | Si | 14 | RANGE | 0.15 – 0.35 | wt% | Ref: Metallus | VERIFIED |
| Chromium | Cr | 24 | RANGE | 0.40 – 0.60 | wt% | Ref: Metallus | VERIFIED |
| Molybdenum | Mo | 42 | RANGE | 0.08 – 0.15 | wt% | Ref: Metallus | VERIFIED |
SAE 4118 Alloy Steel Physical Properties
Source-specific physical properties. Test temperatures are shown only where reported.
| Property Parameter | Canonical SI Value | Semantic Basis | Test Temperature / Context Range | Source Raw Reference | Source Reference | Status |
|---|---|---|---|---|---|---|
| Density | 7.85 g/cm³ | TYPICAL | 7.85 g/cm³ | Metallus | VERIFIED | |
| Elastic Modulus | 205 GPa | TYPICAL | 205 GPa | Metallus | VERIFIED | |
| Poisson's Ratio | 0.29 dimensionless | TYPICAL | 0.29 dimensionless | Metallus | VERIFIED |
SAE 4118 Alloy Steel Thermal & Thermodynamic Properties
Phase change temperatures, thermal conductivity, specific heat, mean coefficients of thermal expansion across standardized temperature ranges, and recommended thermal processing windows.
| Property Parameter | Canonical SI Value | Semantic Basis | Test Temperature / Context Range | Source Raw Reference | Source Reference | Status |
|---|---|---|---|---|---|---|
| Specific Heat Capacity | 486 J/(kg·K) | TYPICAL | 486 J/(kg·K) | Metallus | VERIFIED | |
| Thermal Conductivity | 42.6 W/(m·K) | TYPICAL | 42.6 W/(m·K) | Metallus | VERIFIED |
SAE 4118 Alloy Steel Mechanical Properties
Contextual Mechanical Properties & Tempers: Engineering strength, ductility, and hardness values grouped by product form, temper, and section thickness. Mechanical properties are contextual and not isotropic averages.
| Product Form | Temper / Condition | Section Size | Tensile (UTS) | Yield Strength | Elongation | Shear Strength | Fatigue Strength | Hardness (Scales Preserved) | Status |
|---|---|---|---|---|---|---|---|---|---|
| Bar | Normalized Bar (25 mm)Source values and qualifiersUltimate Tensile Strength: ≥ 580 MPa (MINIMUM)ASTM A108 / ASTM E8Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars Reduction of Area: ≥ 45 % (MINIMUM)ASTM A108 / ASTM E8Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — | ≥ 580 MPa | — | — | — | — | — | VERIFIED |
| Bar | Normalized Bar (25 mm)Source values and qualifiersYield Strength: ≥ 380 MPa (MINIMUM)ASTM A108 / ASTM E8 (0.2% offset)Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — | — | ≥ 380 MPa | — | — | — | — | VERIFIED |
| Bar | Normalized Bar (25 mm)Source values and qualifiersElongation at Break: ≥ 20 % (MINIMUM)ASTM A108 / ASTM E8Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — · in 50 mm (2 in) | — | — | ≥ 20 % | — | — | — | VERIFIED |
| Bar | Normalized Bar (25 mm)Source values and qualifiersHB Hardness: ≤ 197 HB (TYPICAL)Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — | — | — | — | — | — | ≤ 197 HB | VERIFIED |
SAE 4118 Alloy Steel Equivalent & Comparable Grades
Comparable Grades & Cross-References: Carefully classified cross-reference relationships for SAE 4118 Alloy Steel. Comparable does not mean equivalent.
| Related Material | Family | Relationship Classification | Metallurgical Notes & Differences | Status | Action |
|---|---|---|---|---|---|
| SAE 4130 Alloy Steel | Steel | Commonly Compared | Low-carbon carburizing grade in the 41xx Cr-Mo series engineered for case-hardened gears and transmission shafts.Materials serve different design priorities (e.g. higher strength vs superior corrosion resistance or cost). | VERIFIED | Side-by-Side Compare → |
Chromium-Molybdenum Alloy Steel Cluster (41xx Series)
High-strength Cr-Mo alloys providing deep hardenability, high fatigue strength, and impact toughness across elevated stress applications.
Sources
Sources & Provenance Trail: Authoritative reference publications, standards specifications, and data registers cited across this material record.
Reviewed factual transcription from primary producer engineering technical literature.
Reviewed factual transcription from primary producer engineering technical literature.
Reviewed factual transcription from primary producer engineering technical literature.
Reviewed factual transcription from primary producer engineering technical literature.