Carbon & Structural Steels Official identity plus sourced composition

Material / Grade

S25C

S25C is a Carbon & Structural Steels grade centred on availability, fabrication response and a practical strength-to-cost balance. This dossier separates sourced values from engineering guidance and comparison indices.

Hardness potential42 / 100Comparison index

Toughness68 / 100Comparison index

Impact resistance67 / 100Comparison index

Bending resistance68 / 100Comparison index

Abrasive wear39 / 100Comparison index

Steel Overview

Complete introduction and metallurgical analysis

S25C belongs to Carbon & Structural Steels and selection centres on availability, fabrication response and a practical strength-to-cost balance.

The expected microstructure is ferrite-pearlite or a normalised/heat-treated structure appropriate to carbon level and product route; delivery condition, section size, melt quality and processing history can change that state.

Comparison indices are hardness 42/100, toughness 68/100, impact 67/100, wear 39/100 and bending 68/100. These are internal indices, not standard test results.

The screening temperature range is 180–350 °C; strength or hardness loss, oxidation, exposure time and creep must be assessed separately.

A representative process route is rolling, normalising or grade-specific heat treatment under the applicable product standard. Obtain actual temperatures, times and cooling media from the grade and product data sheet.

Manufacturing indices are weldability 65/100, machinability 68/100, corrosion resistance 18/100 and fatigue resistance 57/100; use them for screening only.

The principal risk is low-temperature brittle fracture, welding defects, corrosion or insufficient through-hardening when service exceeds the certified condition. Evaluate geometry, surface condition, environment and the governing failure mechanism together.

A similar name or calculated relationship is not proof of interchangeability; match chemistry, specification, condition, heat treatment and MTC.

Engineering conclusion: S25C is a rational candidate when economical and accessible performance for general machine and structural work matches the real load, environment and certified product condition.

Recorded standards:JIS

International Equivalents

International equivalents and designations

A close counterpart is not automatically interchangeable. Confirm chemistry, product standard, delivery condition, dimensions and heat treatment.

JISOfficial designation for the same grade

S25C

A registered identity within the same grade record.

AISI / SAEConditional application alternative

SAE 1020

Match chemistry, product standard, delivery condition, heat treatment and MTC before substitution.

AISI / SAEConditional application alternative

SAE 1025

Match chemistry, product standard, delivery condition, heat treatment and MTC before substitution.

EN / DIN / ISOConditional application alternative

C15

Match chemistry, product standard, delivery condition, heat treatment and MTC before substitution.

Chemical Composition

Chemical composition and the role of each element

The principal recorded elements are C≈0.25%, Si≈0.25%, Mn≈0.45%, P≈0.03%, S≈0.035%, Cu≈0.3%, Ni≈0.2%, Cr≈0.2%. Mid-range values support engineering interpretation and do not replace purchase limits. Composition is shown for screening and traceability. The current purchase standard and the heat-specific MTC remain authoritative.

Element	Weight-percent range	Metallurgical role and effect
C	0.22–0.28 %	Carbon raises hardness, strength and carbide potential; excessive carbon can reduce toughness and weldability.
Si	0.15–0.35 %	Silicon supports deoxidation and solid-solution strength and can influence tempering or oxidation response.
Mn	0.3–0.6 %	Manganese contributes to hardenability and sulfur control; its final effect depends on amount and processing.
P	≤ 0.03 %	Phosphorus is normally restricted because higher content can promote embrittlement and reduce toughness.
S	≤ 0.035 %	Sulfur may improve chip control in free-cutting grades but can reduce transverse toughness and weldability.
Cu	≤ 0.3 %	Copper can improve atmospheric corrosion resistance or precipitation response in selected alloy systems.
Ni	≤ 0.2 %	Nickel generally improves toughness and through-section response and stabilises austenite in stainless systems.
Cr	≤ 0.2 %	Chromium promotes hardenability and carbide formation and, at sufficient levels, corrosion or oxidation resistance.

JIS special steel strip listing Sourced with conditions

Engineering Behaviour

Engineering behaviour and selection response

Hardness potential42 / 100

Hardness potential has an internal index of 42/100 (low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Toughness68 / 100

Toughness has an internal index of 68/100 (high). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Impact resistance67 / 100

Impact resistance has an internal index of 67/100 (high). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Bending resistance68 / 100

Bending resistance has an internal index of 68/100 (high). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Abrasive wear39 / 100

Abrasive wear has an internal index of 39/100 (low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Corrosion resistance18 / 100

Corrosion resistance has an internal index of 18/100 (very low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Weldability65 / 100

Weldability has an internal index of 65/100 (high). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Machinability68 / 100

Machinability has an internal index of 68/100 (high). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

High-temperature strength25 / 100

The source catalog does not provide a universal temperature-property curve for this designation. Internal comparison index: 25/100.

Engineering analysis

Creep resistance15 / 100

Creep resistance has an internal index of 15/100 (very low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Fatigue resistance57 / 100

Fatigue resistance has an internal index of 57/100 (moderate). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Numerical scores are internal comparison indices. They are not standard test results, allowable design stresses or a manufacturer guarantee. Data Method

Hardness & Hardenability

Hardness and hardenability

The internal hardness-potential index is 42/100 (low). Actual hardness depends on chemistry, section size, austenitising, quenching, tempering and test method.

42/100

low

Comparison index

Governing factors

Chemistry and section size
Austenitising and quench severity
Tempering temperature and time
Test method and surface preparation

Data limits

Final acceptance requires the current standard, product form, dimensions, delivery condition and heat-specific MTC.

Impact & Toughness

Toughness, impact and fracture behaviour

Impact resistance is indexed at 67/100 and toughness at 68/100. These are not Charpy or Izod energy values; temperature, orientation, geometry and actual microstructure govern component behaviour.

67/100highComparison index

Microstructure, hardness and grain size influence impact tolerance.
Sharp radii, notches and surface defects reduce fracture resistance.
Test temperature, specimen direction and section must be identified.
For critical parts, accept impact energy only from a documented test of the same condition.

Temperature & Creep

Service temperature, thermal stability and creep

The source catalog does not provide a universal temperature-property curve for this designation. 180–350 °C is a screening range or sourced limit according to its evidence label. Check strength loss, oxidation, creep, exposure time and environment.

Continuous service

180–350 °CEngineering guidance

Review the limit against strength or hardness loss and exposure time.

Intermittent service

Do not assign an intermittent limit without product-specific source data.

Tempering and phase stability

Working and coating temperatures must remain compatible with the tempering condition and required microstructure.

Oxidation and environment

Oxidation or corrosion may become limiting before the strength criterion.

Relative creep resistance15/100Comparison index

The relative creep index is 15/100 (very low). It is not an allowable creep stress or rupture-life value.

Do not select this grade for long-term static high-temperature loading from the internal index alone.

Wear & Surface Behaviour

Wear resistance and surface behaviour

Abrasive wear

The abrasive-wear index is 39/100; final hardness, carbides, microstructure, contact mode and lubrication govern actual resistance.

Comparison index

Adhesive wear

Assess adhesive wear with the counterface material, lubrication, roughness, pressure and temperature.

Engineering analysis

Surface improvement

Evaluate surface treatment or coating only after confirming compatibility with chemistry, substrate and process temperature.

Engineering guidance

Mechanical & Physical Properties

Mechanical and physical properties

No complete sourced numerical mechanical set is stored for this condition; labelled comparison indices are shown instead of invented test values.

Comparative property	Internal index	Information type
Hardness potential	42 / 100	Comparison index
Toughness	68 / 100	Comparison index
Impact resistance	67 / 100	Comparison index
Bending resistance	68 / 100	Comparison index
Abrasive wear	39 / 100	Comparison index
Corrosion resistance	18 / 100	Comparison index
Weldability	65 / 100	Comparison index
Machinability	68 / 100	Comparison index
High-temperature strength	25 / 100	Comparison index
Creep resistance	15 / 100	Comparison index
Fatigue resistance	57 / 100	Comparison index

Physical properties

Density, elastic modulus, expansion and conductivity depend on family, temperature and product condition. Use grade- and product-specific values for precise calculations.

Obtain density and expansion data from the product data sheet for dimensional calculations.
Elastic modulus and conductivity vary with temperature.

Engineering analysis

Heat Treatment

Heat-treatment stages and process controls

The representative family route is rolling, normalising or grade-specific heat treatment under the applicable product standard. Numerical temperatures are shown only when supported by the record.

Annealing / stress relief

Engineering guidance

Assess the supply condition, residual stress, section size and prior machining before selecting time and temperature.

Cooling: Grade- and process-specific

Annealing / stress relief

Engineering guidance

Assess the supply condition, residual stress, section size and prior machining before selecting time and temperature.

Cooling: Grade- and process-specific cooling

Preheating and austenitising

Engineering guidance

Set preheat steps and austenitising parameters from the grade/product data sheet and actual section size.

Cooling: Grade- and process-specific cooling

Quenching / controlled cooling

Engineering guidance

Choose the quench medium and cooling severity against hardenability, geometry, distortion and crack risk.

Cooling: Grade- and process-specific cooling

Tempering / property adjustment

Engineering guidance

Set tempering or ageing to the required hardness, toughness and service-temperature balance.

Cooling: Grade- and process-specific cooling

Tempering / property adjustment

Engineering guidance

Set tempering or ageing to the required hardness, toughness and service-temperature balance.

Cooling: Grade- and process-specific cooling

Process control: Review delivery condition, actual section, equipment capability, crack and distortion risk and target hardness before approving the cycle.

Engineering Charts

Hardness, toughness, impact, temperature and process charts

Chemistry data retain their evidence label; 0–100 charts are internal indices and stages without temperature are process sequences.

Multi-axis engineering profile

Comparison index

Chemical composition

Derived from source data

Hardness–toughness balance

Comparison index

Toughness, impact and fatigue

Comparison index

Wear and surface response

Comparison index

Mechanical properties or comparison indices

Comparison index

Service temperature

Engineering guidance

Heat treatment

Engineering guidance

Related-grade similarity

Comparison index

All comparison indices

Comparison index

Failure Modes & Selection

Potential failure modes and selection guidance

Potential failure mechanisms

low-temperature brittle fracture, welding defects, corrosion or insufficient through-hardening when service exceeds the certified condition.
Fatigue initiation from surface defects, section transitions or stress concentration.
Property loss after unsuitable heat treatment, cooling or finishing.
Corrosion, oxidation or environmental attack when protection is inadequate.

Selection and design notes

Match designation, material number, product standard and supply form before purchase.
Compare the governing failure mechanism with hardness 42, toughness 68, impact 67 and wear 39 indices out of 100.
Use mechanical values only within their cited condition, dimensions and test temperature.
Confirm the heat-treatment route and target hardness with the processor before final machining.
Review the heat number, MTC and required test results before release.

Derived calculations

Carbon equivalent CE(IIW)0.387 Calculated

Calculated from recorded inputs; apply only within the stated formula scope and limitations.

Advantages & Limitations

Advantages, limitations and unsuitable applications

Advantages

economical and accessible performance for general machine and structural work.
A clearly labelled engineering profile supports comparison with related grades.
Grade identity, chemistry, counterparts and references remain traceable in one dossier.

Limitations and weaknesses

low-temperature brittle fracture, welding defects, corrosion or insufficient through-hardening when service exceeds the certified condition.
A 0–100 index cannot be converted into design stress, impact energy or creep life.
Hardness and toughness depend on section, delivery condition and actual processing.
Do not approve a substitute before checking the product standard and heat-specific MTC.

Cases requiring caution or an alternative material

Critical design without condition- and section-specific test dataDirect substitution based only on name or similarity scoreLong-term creep service without sourced time–stress–temperature datalow-temperature brittle fracture, welding defects, corrosion or insufficient through-hardening when service exceeds the certified condition

Applications & Processing

Industrial applications and processing

Typical applications

Shafts, axles and rotating machine components
High-strength fasteners and mechanical connections
Structures, bridges, profiles and transmission components
General engineered and machine components
general machine and structural components
bars, sections, tubes and forgings as specified
shafts, pins and brackets
fabricated parts governed by a product and design standard

Manufacture, welding and surface engineering

Weldability has an internal index of 65/100 (high). Actual performance requires a documented product condition, heat treatment and test context.

Forming and forging depend on steel family, delivery condition and the grade-specific qualified temperature range.

Select nitriding, induction hardening or coating against chemistry, substrate hardness and application.
Keep coating-deposition temperature compatible with the tempering condition and substrate.
Control hydrogen embrittlement, residual stress and distortion in high-strength components.

Engineering Conclusion

Engineering conclusion and selection recommendation

S25C is worth evaluating when the principal need is economical and accessible performance for general machine and structural work. Internal indices of hardness 42/100, toughness 68/100, impact 67/100 and wear 39/100 must be aligned with the real failure mechanism. The leading risk is low-temperature brittle fracture, welding defects, corrosion or insufficient through-hardening when service exceeds the certified condition. Final approval requires the current standard, product form, dimensions, delivery condition, heat treatment and heat-specific MTC.

Engineering analysis

Shaygan Steel — the right choice in alloy steel

Compare with other steels View similar steels

Frequently Asked Questions

Frequently asked questions

What is S25C steel?

What are the main applications of S25C?

Application contexts include Shafts, axles and rotating machine components, High-strength fasteners and mechanical connections, Structures, bridges, profiles and transmission components and General engineered and machine components, subject to the product standard and actual condition.

How hard can S25C be?

The internal hardness-potential index is 42/100 (low). Actual hardness depends on chemistry, section size, austenitising, quenching, tempering and test method.

Is S25C suitable for impact loading?

Impact resistance is indexed at 67/100 and toughness at 68/100. These are not Charpy or Izod energy values; temperature, orientation, geometry and actual microstructure govern component behaviour.

What is the service-temperature limit of S25C?

Can S25C be replaced by a close grade?

Approve substitution only after matching chemistry, specification, product form, condition, heat treatment and MTC.

Steel Comparison

Engineering steel comparison

Compare this grade with any other dossier. Scores from 0 to 100 are internal screening indices, not laboratory values or allowable design stresses.

Close suggestions:

Search for the second steel

Current gradeS25CCarbon & Structural Steels

Selected gradeSAE 1020Carbon & Structural Steels

Current-grade chemistry

Second-grade chemistry

Current-grade heat treatment

Second-grade heat treatment

Current-grade applications

Limitations

Second-grade applications

Limitations

Select a second grade to update the comparison.

Sources & Evidence

Sources, methodology and evidence

Sources support grade identity, recorded values or the engineering method. General guidance does not replace product-specific certification.

Grade-specific sources

Nippon Steel Special Steel StripManufacturer catalog · Tier A

Reference supporting grade identity or recorded values; interpret it within the cited product and condition context. Role: manufacturer catalog.

View source

Nippon Steel Special Steel Strip — composition tablesManufacturer catalog · Tier A

Reference supporting grade identity or recorded values; interpret it within the cited product and condition context. Role: manufacturer catalog.

View source