Cast Iron•Gray Cast Iron•

VERIFIED(Source-Verified)

ASTM A48 Class 25 Gray Cast Iron

Primary Designation:ASTM A48 Class 25

Aliases:

Class 25 Gray IronSAE G2500 Gray Iron

Mat Grades internal verification confirms source-backed fidelity and data integrity. It does not constitute external certification or guaranteed lot conformity. Read engineering disclaimer →

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Data Completeness:6 composition elements and 9 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

7.15 g/cm³TYPICAL · temperature not stated

Thermal Conductivity

51 W/(m·K)TYPICAL · at 20 °C

Specific Heat Capacity

470 J/(kg·K)TYPICAL · temperature not stated

Composition Excerpt

C 3.2–3.6 wt%Carbon (range)

Standard Elemental Basis: RANGE

Engineering Summary

ASTM A48 Class 25 is an intermediate-grade gray cast iron balancing castability, damping, and mechanical strength. With a minimum tensile strength of 25 ksi (172 MPa) on standard Test Bar B, it features a mixed pearlitic-ferritic matrix and is widely employed in automotive brake drums, industrial pump casings, and light transmission cases.

ASTM A48 Class 25 Gray Cast Iron Documented Applications

›Automotive brake drums and light industrial clutch plates
›Centrifugal pump casings and impeller housings
›Small engine crankcases and compressor housings
›Gearbox covers and power transmission support brackets

Recognized Aliases

Source-backed commercial trade name and short designations cataloged in canonical data.

Class 25 Gray IronSAE G2500 Gray Iron

ASTM A48 Class 25 Gray Cast Iron 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 Identifiers

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System	Identifier	Standard System Name	Classification Notes & Provenance
ASTMPRIMARY	A48 Class 25	ASTM International	—Ref: Standard Specifications for Gray and Ductile Cast Iron (ASTM A48/A48M, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, ASM Handbook Vol 1)
UNS	F11701	Unified Numbering System	—Ref: Standard Specifications for Gray and Ductile Cast Iron (ASTM A48/A48M, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, ASM Handbook Vol 1)
SAE	J431 G2500	SAE International	—Ref: Standard Specifications for Gray and Ductile Cast Iron (ASTM A48/A48M, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, ASM Handbook Vol 1)

Recognized Commercial Aliases & Trade NamesCOMMON ALIAS

2 Listed

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Recognized Name / Alias	Classification	Technical Usage & Context
Class 25 Gray Iron	Commercial Alias	Colloquial or commercial industry synonym
SAE G2500 Gray Iron	Historical Alias	Colloquial or commercial industry synonym

Applicable Specifications & Product Form ReferencesSPECIFICATION REFERENCE

2 Applicable Standards

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Standards Body	Specification Code	Specification Title / Scope	Relationship Type
ASTM	ASTM A48 / A48M	Standard Specification for Gray Iron Castings	Specification Reference
SAE	SAE J431	Automotive Gray Iron Castings (Grade G2500)	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.

ASTM A48 Class 25 Gray Cast Iron Chemical Composition

Chemical Composition (Weight %) — Elemental limits and values from the cited source. Preserves exact semantic limits (minimums, maximums, and ranges).

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Element	Symbol	Semantic Basis	Specified Value	Unit	Metallurgical Notes & Qualification	Data Status
Carbon	C	RANGE	3.20 – 3.60	wt%	Total carbon balanced for pearlitic-ferritic matrix.Ref: ASTM International, CEN, ISO & ASM International Standards Technical Committees	VERIFIED
Silicon	Si	RANGE	2.10 – 2.60	wt%	Silicon content adjusted for casting wall thickness.Ref: ASTM International, CEN, ISO & ASM International Standards Technical Committees	VERIFIED
Manganese	Mn	RANGE	0.50 – 0.85	wt%	Ref: ASTM International, CEN, ISO & ASM International Standards Technical Committees	VERIFIED
Phosphorus	P	MAXIMUM	≤ 0.15	wt%	Ref: ASTM International, CEN, ISO & ASM International Standards Technical Committees	VERIFIED
Sulfur	S	MAXIMUM	≤ 0.15	wt%	Ref: ASTM International, CEN, ISO & ASM International Standards Technical Committees	VERIFIED
Iron	Fe	REMAINDER	Remainder	wt%	Ref: ASTM International, CEN, ISO & ASM International Standards Technical Committees	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:

ASTM A48 Class 25 Gray Cast Iron Physical Properties

Source-specific physical properties. Test temperatures are shown only where reported.

1 Parameters

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Property Parameter	Canonical SI Value	Semantic Basis	Test Temperature / Context Range	Source Raw Reference	Source Reference	Status
Density	7.15 g/cm³	TYPICAL		7.15 g/cm³	ASTM International, CEN & ISO Technical Committees	VERIFIED

ASTM A48 Class 25 Gray Cast Iron Thermal & Thermodynamic Properties

Phase change temperatures, thermal conductivity, specific heat, mean coefficients of thermal expansion across standardized temperature ranges, and recommended thermal processing windows.

3 Parameters

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Property Parameter	Canonical SI Value	Semantic Basis	Test Temperature / Context Range	Source Raw Reference	Source Reference	Status
Thermal Conductivity	51 W/(m·K)	TYPICAL	Test Temp: 20 °C	51 W/(m·K)	ASTM International, CEN & ISO Technical Committees	VERIFIED
Specific Heat Capacity	470 J/(kg·K)	TYPICAL		470 J/(kg·K)	ASTM International, CEN & ISO Technical Committees	VERIFIED
Coefficient of Thermal Expansion	11.2 µm/(m·K)	TYPICAL		11.2 µm/(m·K)	ASTM International, CEN & ISO Technical Committees	VERIFIED

ASTM A48 Class 25 Gray Cast Iron Electrical Properties

Electrical conductivity and resistivity in their reported units and conditions.

1 Parameters

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Property Parameter	Canonical SI Value	Semantic Basis	Test Temperature / Context Range	Source Raw Reference	Source Reference	Status
Electrical Resistivity	720 nΩ·m	TYPICAL		720 nΩ·m	ASTM International, CEN & ISO Technical Committees	VERIFIED

ASTM A48 Class 25 Gray Cast Iron 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.

Elastic & Baseline Mechanical ConstantsSource-specific measurement conditions

Poisson Ratio

0.26 dimensionless

Showing 3 of 3 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
Standard Product Form	As-Cast Source values and qualifiers Ultimate Tensile Strength: ≥ 172 MPa (MINIMUM)Governing minimum tensile strength per ASTM A48 Class 25 (25 ksi = 172 MPa). No distinct yield point.ASTM International, CEN, ISO & ASM International Standards Technical Committees — ASTM A48, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, ASM Handbook Vol 1	30.5 mm Test Bar B	≥ 172 MPa	—	—	—	—	—	VERIFIED
Standard Product Form	As-Cast Source values and qualifiers Modulus of Elasticity: 90 GPa (TYPICAL)ASTM International, CEN, ISO & ASM International Standards Technical Committees — ASTM A48, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, ASM Handbook Vol 1	—	—	—	—	—	—	—	VERIFIED
Standard Product Form	As-Cast Source values and qualifiers HBW Hardness: 150–200 HBW (RANGE)10/3000ASTM International, CEN, ISO & ASM International Standards Technical Committees — ASTM A48, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, ASM Handbook Vol 1	—	—	—	—	—	—	150–200 HBW	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

ASTM A48 Class 25 Gray Cast Iron Processing & Fabrication

Machining, joining, forming, and thermal processing ratings cataloged from the cited authoritative technical reference.

Source: ASTM International, CEN, ISO & ASM International Standards Technical Committees

Machinability

Excellent machinability rating (~100% relative to standard free-cutting brass). Flake graphite acts as internal lubricant and chip breaker.

Weldability & Joining

Restricted weldability. Requires preheating (250°C–300°C) and nickel-iron (ENiFe-CI) electrodes to minimize hardness in the fusion boundary.

Heat Treatment & Working Ranges

Stress relief at 540°C–565°C for dimensional stability. Quench hardening is not recommended due to risk of thermal shock cracking.

Forming & Cold Working

Non-deformable. Cast iron cannot undergo plastic cold or hot deformation.

ASTM A48 Class 25 Gray Cast Iron Equivalent & Comparable Grades

Comparable Grades & Cross-References: Carefully classified cross-reference relationships for ASTM A48 Class 25 Gray Cast Iron. Comparable does not mean equivalent.

Scroll horizontally for relationship classifications & comparisons

Related Material	Family	Relationship Classification	Metallurgical Notes & Differences	Status	Action
ASTM A48 Class 30 Gray Cast Iron	Cast Iron	Commonly Compared	Class 25 offers slightly higher thermal conductivity and lower chilling tendency in thin sections, but Class 30 is preferred for structural rigidity and wear resistance.Materials serve different design priorities (e.g. higher strength vs superior corrosion resistance or cost).	VERIFIED	Side-by-Side Compare →

Related Engineering & Metallurgy Guides

Contextual technical guides explaining degradation mechanisms, testing methodologies, and selection criteria relevant to ASTM A48 Class 25 Gray Cast Iron.

Corrosion & Surface Engineering15 min read

How to Remove Rust From Cast Iron: Methods, Science & Prevention

Cast iron is an indispensable alloy family renowned for superior vibration damping and castability, but its iron matrix and carbon microstructure make it susceptible to atmospheric rust. Restoring rusted cast iron requires understanding how mechanical and chemical methods interact with the underlying metal.

Author: MatGrades Materials Engineering GroupRead Guide →

Sources

Sources & Provenance Trail: Authoritative reference publications, standards specifications, and data registers cited across this material record.

ASTM International, CEN & ISO Technical CommitteesStandard Specifications for Gray and Ductile Cast Iron (ASTM A48/A48M, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, ASM Handbook Vol 1)

STANDARDS ORG

Authoritative foundry data harmonized across ASTM A48, ASTM A536, EN 1561, EN 1563, ISO 185, ISO 1083, SAE J431, SAE J434, and ASM International Handbook Volume 1 (Properties and Selection: Irons, Steels, and High-Performance Alloys).

Issuing Body: ASTM International, CEN, ISO & ASM International Standards Technical CommitteesRevision: ASTM A48/A48M-22 / ASTM A536-84(2024) / EN 1561:2020 / EN 1563:2018 / ISO 185:2020 / ISO 1083:2018View Source Record ↗

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.