Material Selection8–10 min read
4140 vs 4340 Alloy Steel: Heat Treatment and Shaft Selection
Compare section size, toughness evidence and the final heat-treated condition.
Author: Mat Grades Editorial DeskRead Guide →
SAE 4145 Alloy Steel
Primary Designation:SAE 4145
Mat Grades internal verification confirms source-backed fidelity and data integrity. It does not constitute external certification or guaranteed lot conformity. Read engineering disclaimer →
Data Completeness:8 composition elements and 10 condition-specific property values cataloged.
Omitted fields represent unverified properties. "Missing is better than invented."
Key Engineering Properties
Representative source rows, qualified by their reported conditions. Inspect the tables below for all values, limits, and source notes.
Density
7.85 g/cm³TYPICAL · temperature not stated
Thermal Conductivity
42.6 W/(m·K)TYPICAL · temperature not stated
Specific Heat Capacity
486 J/(kg·K)TYPICAL · temperature not stated
Composition Excerpt
Fe BALANCE wt%Iron (balance)
Standard Elemental Basis: BALANCETensile Strength
≥ 740 MPaMINIMUM · Normalized Bar (25 mm) · temperature not stated
Engineering Summary
SAE 4145 is a higher-carbon Cr-Mo alloy steel (modified in 4145H) widely specified in the oil & gas industry for downhole drilling collars, mandrels, and high-strength subs.
Recognized Aliases
Source-backed commercial trade name and short designations cataloged in canonical data.
SAE 4145 Alloy Steel Specifications & Designations
Standard Designations & Applicable Specifications — Semantically classified designations distinguishing primary standard identifiers, commercial trade names, and applicable specification references.
Direct Standard DesignationsDIRECT DESIGNATION
3 Primary IdentifiersScroll horizontally for full designation data
| System | Identifier | Standard System Name | Classification Notes & Provenance |
|---|---|---|---|
| SAEPRIMARY | 4145 | Society of Automotive Engineers | —Ref: Practical Data for Metallurgists, 19th edition |
| AISI | 4145 | American Iron and Steel Institute | —Ref: Practical Data for Metallurgists, 19th edition |
| UNS | G41450 | Unified Numbering System | —Ref: Practical Data for Metallurgists, 19th edition |
Applicable Specifications & Product Form ReferencesSPECIFICATION REFERENCE
1 Applicable StandardsScroll horizontally for full standard specifications
| Standards Body | Specification Code | Specification Title / Scope | Relationship Type |
|---|---|---|---|
| SAE | SAE 4145 Alloy Steel Engineering Datasheet | Applicable specification reference. | Specification Reference |
Engineering Notice: Applicable specifications establish manufacturing requirements, dimensional tolerances, and test criteria for specific product forms (e.g. bus bar, wire, plate, pipe). They represent applicable technical standards, not alternative or equivalent alloy grades.
SAE 4145 Alloy Steel Chemical Composition
Chemical Composition (Weight %) — Elemental limits and values from the cited source. Preserves exact semantic limits (minimums, maximums, and ranges).
Scroll horizontally for full elemental limits
| 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 | 0.43 – 0.48 | wt% | Ref: Metallus | VERIFIED |
| Manganese | Mn | 25 | RANGE | 0.75 – 1.00 | 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 | 0.80 – 1.10 | wt% | Ref: Metallus | VERIFIED |
| Molybdenum | Mo | 42 | RANGE | 0.15 – 0.25 | wt% | Ref: Metallus | VERIFIED |
* Elemental percentages are expressed in weight percent (wt%). Values represent applicable specification limits. Unspecified trace elements are not fabricated or assumed.Preserves exact semantic basis
Property Display UnitsSwitch between Canonical SI and Source / US Customary units:
SAE 4145 Alloy Steel Physical Properties
Source-specific physical properties. Test temperatures are shown only where reported.
Scroll horizontally for full property parameters
| 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 4145 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.
Scroll horizontally for full property parameters
| 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 4145 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.
Showing 4 of 4 conditions
Scroll horizontally for all conditions & tempers
| 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: ≥ 740 MPa (MINIMUM)ASTM A108 / ASTM E8Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars Reduction of Area: ≥ 35 % (MINIMUM)ASTM A108 / ASTM E8Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — | ≥ 740 MPa | — | — | — | — | — | VERIFIED |
| Bar | Normalized Bar (25 mm)Source values and qualifiersYield Strength: ≥ 470 MPa (MINIMUM)ASTM A108 / ASTM E8 (0.2% offset)Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — | — | ≥ 470 MPa | — | — | — | — | VERIFIED |
| Bar | Normalized Bar (25 mm)Source values and qualifiersElongation at Break: ≥ 14 % (MINIMUM)ASTM A108 / ASTM E8Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — · in 50 mm (2 in) | — | — | ≥ 14 % | — | — | — | VERIFIED |
| Bar | Normalized Bar (25 mm)Source values and qualifiersHB Hardness: ≤ 248 HB (TYPICAL)Metallus — p118, Estimated Minimum Properties for Cold Drawn Bars | — | — | — | — | — | — | ≤ 248 HB | VERIFIED |
Hardness Integrity Notice: Rockwell B (HRB), Rockwell F (HRF), and Superficial 30T (HR30T) scales are reported on their measured scales without cross-scale mathematical conversion.
Source: See fact-level citations
Practical Engineering & Fabrication Notes
By Mat Grades Editorial Desk · Updated 2026-11-14. Use alongside the specified product standard and supplier certificate.
Machining & shop-floor behavior
For SAE 4145 Alloy Steel, a qualified cutting-speed or tool-life recommendation is not supplied in the available record. A relevant hardness example is HB Hardness: maximum 248 HB (typical; Normalized Bar (25 mm), Bar). Use that supplied condition for a trial of the difficult feature. Record tool changes, burr removal, unclamped dimensions and accepted parts per hour. Relative machinability ratings from different reference scales should not be compared as if they were one common test.
Weldability, brazing & joining
No qualified weld procedure, filler selection or preheat/interpass schedule is established by this material record. Obtain a procedure for the actual joint, supplied condition and section rather than copying one from a nearby grade. The first cataloged strength example is Ultimate Tensile Strength: minimum 740 MPa (minimum; Normalized Bar (25 mm), Bar). Assess the final part after joining or thermal processing. Include distortion, cleanup and inspection in the quotation. A material designation or favorable process rating is a starting point for qualification, not evidence that an untested joint meets the drawing.
Corrosion & service environment
Plan corrosion protection and inspect how the finish affects threads, bearing fits and repaired surfaces. A steel strength value does not establish corrosion life. Where cyclic load or impact matters, retain the surface condition and the required toughness evidence with the material decision. The recorded thermal example is Thermal Conductivity: 42.6 W/(m·K) (typical; additional condition not stated). State the exposure and inspection access in the design record so that a change of installation or cleaning method triggers a review. The selected composition entries are C 0.43–0.48 wt%, Mn 0.75–1 wt%. Chemistry documents identity; it does not establish fluid compatibility.
Selection trade-offs & applications
For a heavily loaded section, verify the delivered heat treatment, hardness distribution and toughness requirement. The nearby 4140 designation is a useful comparison candidate, but the difference must be checked against the actual product and process. The related candidate SAE 4140 Alloy Steel is linked for comparison; its commonly compared relationship must be checked before substitution. Compare the complete route through machining, joining, finish and inspection. Keep the certificate, required test location and acceptance criteria with the first-article record. A later change of grade, condition or source should be assessed against that same requirement.
Technical references: Metallus
SAE 4145 Alloy Steel Equivalent & Comparable Grades
Comparable Grades & Cross-References: Carefully classified cross-reference relationships for SAE 4145 Alloy Steel. Comparable does not mean equivalent.
Scroll horizontally for relationship classifications & comparisons
| Related Material | Family | Relationship Classification | Metallurgical Notes & Differences | Status | Action |
|---|---|---|---|---|---|
| SAE 4140 Alloy Steel | Steel | Commonly Compared | Higher-carbon Cr-Mo alloy steel (0.43-0.48% C) standard for oilfield drilling collars and high-torque downhole tools.Materials serve different design priorities (e.g. higher strength vs superior corrosion resistance or cost). | VERIFIED |
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.
4145Current Grade
SAE 4145 Alloy Steel
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Sources
Sources & Provenance Trail: Authoritative reference publications, standards specifications, and data registers cited across this material record.
MetallusPractical Data for Metallurgists, 19th edition
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering technical literature.
MetallusPractical Data for Metallurgists, 19th edition
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering technical literature.
MetallusPractical Data for Metallurgists, 19th edition
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering technical literature.
MetallusPractical Data for Metallurgists, 19th edition
PRIMARY PRODUCER
Reviewed factual transcription from primary producer engineering technical literature.
Intellectual Property & Provenance Notice: Mat Grades cites technical literature from recognized industry associations and standards organizations. Underlying technical standards and publication data remain the intellectual property of their respective issuing organizations.