Cold Work Tool Steels Official identity plus sourced composition

Material / Grade

AISI A4

Air-hardening cold-work tool steel selected for dimensional stability and lower quench distortion.

Hardness potential98 / 100Comparison index

Toughness29 / 100Comparison index

Impact resistance22 / 100Comparison index

Bending resistance51 / 100Comparison index

Abrasive wear96 / 100Comparison index

Steel Overview

Complete introduction and metallurgical analysis

AISI A4 belongs to Cold Work Tool Steels and selection centres on wear resistance, compressive strength and dimensional control in cold-work tooling.

Air-hardening cold-work tool steel selected for dimensional stability and lower quench distortion.

The principal recorded elements are C≈1%, Mn≈2%, Si≈0.3%, Cr≈1.55%, Mo≈1.15%, P≈0.03%, S≈0.03%. Mid-range values support engineering interpretation and do not replace purchase limits.

The expected microstructure is tempered martensite containing a grade-dependent population of primary and secondary alloy carbides; delivery condition, section size, melt quality and processing history can change that state.

Comparison indices are hardness 98/100, toughness 29/100, impact 22/100, wear 96/100 and bending 51/100. These are internal indices, not standard test results.

The screening temperature range is 150–300 °C; strength or hardness loss, oxidation, exposure time and creep must be assessed separately.

A representative process route is soft annealing, staged preheating, austenitising, controlled quenching and one or more tempering cycles. Obtain actual temperatures, times and cooling media from the grade and product data sheet.

Manufacturing indices are weldability 20/100, machinability 37/100, corrosion resistance 22/100 and fatigue resistance 45/100; use them for screening only.

The principal risk is chipping, cracking, grinding damage or distortion when toughness and carbide volume are not matched to the tool. 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: AISI A4 is a rational candidate when high resistance to abrasive wear and plastic deformation in tooling matches the real load, environment and certified product condition.

Recorded standards:AISI tool/stainless designation — verify governing ASTM/SAE/product specificationASTM A681 family

International Equivalents

International equivalents and designations

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

AISI / SAEOfficial designation for the same grade

AISI A4

A registered identity within the same grade record.

PrimaryOfficial designation for the same grade

AISI A4

A registered identity within the same grade record.

AISI shorthandOfficial designation for the same grade

A registered identity within the same grade record.

EN / DIN / ISOConditional application alternative

BÖHLER K720

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≈1%, Mn≈2%, Si≈0.3%, Cr≈1.55%, Mo≈1.15%, P≈0.03%, S≈0.03%. 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	0.95–1.05 %	Carbon raises hardness, strength and carbide potential; excessive carbon can reduce toughness and weldability.
Mn	1.8–2.2 %	Manganese contributes to hardenability and sulfur control; its final effect depends on amount and processing.
Si	0.1–0.5 %	Silicon supports deoxidation and solid-solution strength and can influence tempering or oxidation response.
Cr	0.9–2.2 %	Chromium promotes hardenability and carbide formation and, at sufficient levels, corrosion or oxidation resistance.
Mo	0.9–1.4 %	Molybdenum improves hardenability and temper resistance and can support hot strength or pitting resistance.
P	≤ 0.03 %	Phosphorus is normally restricted because higher content can promote embrittlement and reduce toughness.
S	≤ 0.03 %	Sulfur may improve chip control in free-cutting grades but can reduce transverse toughness and weldability.

Laxcon open grade reference; tool-steel ranges sourced from ASTM A681/A686/A600 as noted by dataset Sourced with conditions

Engineering Behaviour

Engineering behaviour and selection response

Hardness potential98 / 100

Hardness and hardenability are condition-dependent; numeric values require grade-specific heat-treatment context. Internal comparison index: 98/100.

Engineering analysis

Toughness29 / 100

Toughness has an internal index of 29/100 (low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Impact resistance22 / 100

Impact resistance has an internal index of 22/100 (very low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Bending resistance51 / 100

Bending resistance has an internal index of 51/100 (moderate). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Abrasive wear96 / 100

Wear resistance depends on hardness, microstructure/carbides and the wear mechanism. Internal comparison index: 96/100.

Engineering analysis

Corrosion resistance22 / 100

Not stainless; surface protection is generally required in corrosive service. Internal comparison index: 22/100.

Engineering analysis

Weldability20 / 100

Weldability has an internal index of 20/100 (very low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Machinability37 / 100

Machinability has an internal index of 37/100 (low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

High-temperature strength23 / 100

Temperature-dependent properties require grade-specific condition and test data. Internal comparison index: 23/100.

Engineering analysis

Creep resistance16 / 100

Creep resistance has an internal index of 16/100 (very low). Actual performance requires a documented product condition, heat treatment and test context.

Engineering analysis

Fatigue resistance45 / 100

Fatigue resistance has an internal index of 45/100 (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

Hardness and hardenability are condition-dependent; numeric values require grade-specific heat-treatment context. Internal screening index: 98/100 (very high).

98/100

very high

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 22/100 and toughness at 29/100. These are not Charpy or Izod energy values; temperature, orientation, geometry and actual microstructure govern component behaviour.

22/100very lowComparison 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

Temperature-dependent properties require grade-specific condition and test data. 150–300 °C is a screening range or sourced limit according to its evidence label. Check strength loss, oxidation, creep, exposure time and environment.

Continuous service

150–300 °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 resistance16/100Comparison index

The relative creep index is 16/100 (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

Wear resistance depends on hardness, microstructure/carbides and the wear mechanism. The abrasive-wear index is 96/100; 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	98 / 100	Comparison index
Toughness	29 / 100	Comparison index
Impact resistance	22 / 100	Comparison index
Bending resistance	51 / 100	Comparison index
Abrasive wear	96 / 100	Comparison index
Corrosion resistance	22 / 100	Comparison index
Weldability	20 / 100	Comparison index
Machinability	37 / 100	Comparison index
High-temperature strength	23 / 100	Comparison index
Creep resistance	16 / 100	Comparison index
Fatigue resistance	45 / 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 soft annealing, staged preheating, austenitising, controlled quenching and one or more tempering cycles. Numerical temperatures are shown only when supported by the record.

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

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

chipping, cracking, grinding damage or distortion when toughness and carbide volume are not matched to the tool.
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 98, toughness 29, impact 22 and wear 96 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.

Advantages & Limitations

Advantages, limitations and unsuitable applications

Advantages

high resistance to abrasive wear and plastic deformation in tooling.
A clearly labelled engineering profile supports comparison with related grades.
Grade identity, chemistry, counterparts and references remain traceable in one dossier.

Limitations and weaknesses

chipping, cracking, grinding damage or distortion when toughness and carbide volume are not matched to the tool.
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 datachipping, cracking, grinding damage or distortion when toughness and carbide volume are not matched to the tool

Applications & Processing

Industrial applications and processing

Typical applications

Punches, dies and blanking tools
Industrial blades, knives and cutting tools
Cold-forming, drawing and cold-rolling tools
Wear-resistant machine and surface-contact components
blanking and forming dies
punches, shear blades and gauges
cold extrusion and drawing tools
wear-loaded tooling and precision inserts

Manufacture, welding and surface engineering

Weldability has an internal index of 20/100 (very low). 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

AISI A4 is worth evaluating when the principal need is high resistance to abrasive wear and plastic deformation in tooling. Internal indices of hardness 98/100, toughness 29/100, impact 22/100 and wear 96/100 must be aligned with the real failure mechanism. The leading risk is chipping, cracking, grinding damage or distortion when toughness and carbide volume are not matched to the tool. Final approval requires the current standard, product form, dimensions, delivery condition, heat treatment and heat-specific MTC.

Engineering analysis

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Frequently Asked Questions

Frequently asked questions

What is AISI A4 steel?

Air-hardening cold-work tool steel selected for dimensional stability and lower quench distortion.

What are the main applications of AISI A4?

Application contexts include Punches, dies and blanking tools, Industrial blades, knives and cutting tools, Cold-forming, drawing and cold-rolling tools and Wear-resistant machine and surface-contact components, subject to the product standard and actual condition.

How hard can AISI A4 be?

Hardness and hardenability are condition-dependent; numeric values require grade-specific heat-treatment context. Internal screening index: 98/100 (very high).

Is AISI A4 suitable for impact loading?

Impact resistance is indexed at 22/100 and toughness at 29/100. These are not Charpy or Izod energy values; temperature, orientation, geometry and actual microstructure govern component behaviour.

What is the service-temperature limit of AISI A4?

Can AISI A4 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.

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Current gradeAISI A4Cold Work Tool Steels

Selected grade1.2842 / BÖHLER K720Cold Work Tool 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

Ovako Heat Treatment Guide — International grade listIdentity And Heat Treatment Model Reference · Tier A

Reference supporting grade identity or recorded values; interpret it within the cited product and condition context. Role: identity and heat treatment model reference.

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Laxcon tool steel family and open grade datasetFamily Context And Composition Reference · Tier A-open-data

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

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Laxcon Steel grade reference — Tool steelsGrade Composition · Tier A-open-data

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

View source