How to Use the Steel Phase & Transformation Explorer

Before you begin

Purpose and limits

The explorer is a teaching and preliminary engineering-screening environment. It is organized around the causal sequence:

Release 1

Guided start and display modes

Choose the question first

The Guided Start page routes you to the correct module. Select the question closest to your problem, such as:

• What phases are present?
• What happens during heating or cooling?
• Will the centre of the section harden?
• Is the austenitizing cycle adequate?
• Which quench medium should be compared?
• What does the uploaded thermal record show?
• How should a thermocouple or pyrometer result be interpreted?
• What case depth, tempering response, microstructure, or alloy-family behaviour should be expected?

Experience level

Interpretation basis

Use Equilibrium for Fe–Fe₃C phase fields and lever-rule fractions. Use Rapid cooling for generalized ferrite, pearlite, bainite, and martensite trends. The rapid-cooling selection does not convert the equilibrium diagram into a CCT diagram; it changes how the scenario is interpreted.

Critical-temperature coach

• Ae is the equilibrium critical temperature.
• Ac is the observed transformation temperature during heating.
• Ar is the observed transformation temperature during cooling.
• Ms and Mf refer to martensite start and finish.

The heating- and cooling-rate shifts in the coach are teaching approximations, not process setpoints.

Core module

Equilibrium diagram

Plot and manage points

1. Select metric or imperial temperature display.
2. Enter carbon and temperature for P1.
3. Use + Add point to create P2, P3, and additional comparisons.
4. Select a row, marker, or result card to make that point active.
5. Click or drag on the diagram to move only the active point.

Display controls

Lever rule

Inside a two-phase field, the tool estimates equilibrium mass fractions from the tie-line endpoints. For ferrite plus austenite:

The schematic microstructure is educational. It does not reproduce actual grain morphology, inclusions, banding, or transformation kinetics.

Thermal-cycle builder

Heating and cooling paths

Select a preset—normalizing, annealing, spheroidizing, quench and temper, intercritical annealing, austempering, martempering—or build a custom cycle.

1. Enter carbon.
2. Add or remove cycle steps.
3. Set target temperature, duration, and step type.
4. Use Play, Pause, or the time slider.
5. Review boundary crossings, the event timeline, and the live phase-state panel.

Transformation kinetics

TTT and CCT

Chemistry from the Chemistry module shifts the generalized curves and critical temperatures. These are not certified, grade-specific diagrams.

Chemistry and causality

Chemistry, properties, and causal chain

Select an illustrative preset or enter verified heat chemistry. The module estimates CE IIW, Pcm, A_c1, A_c3, M_s, hardenability, weldability, and directional property trends.

The Guided Start causal dashboard updates the five-stage chain and warns when the active phase-diagram carbon differs from the chemistry-model carbon.

Release 2

Jominy and section-size hardenability

This module separates maximum hardness from depth of hardening.

1. Confirm chemistry.
2. Select round or plate geometry.
3. Enter diameter or thickness.
4. Select quench medium and agitation.
5. Enter prior-austenite ASTM grain number and target hardness.
6. Read the estimated Jominy curve and through-section result.

Outputs include equivalent Jominy distance, surface/quarter-depth/centre martensite, hardness, and effective target-hardness depth.

Release 2

Austenitization and grain-growth window

The module balances four competing needs: heat the core, form austenite, dissolve and homogenize carbides, and avoid excessive prior-austenite grain growth.

• Set temperature, hold time, section size, heating rate, and initial grain size.
• Select starting microstructure, carbide burden, and grain-boundary pinning.
• Review core heat-through time, effective soak, dissolution, homogenization, final ASTM grain number, and grain-growth risk.
• Use the heatmap to identify incomplete, balanced, and grain-growth-dominated regions.

Release 2

Quench-medium and cracking-risk comparison

Compare still air, forced air/gas, conventional oil, accelerated oil, polymer solution, water, brine, and a molten-salt-bath analogue under common assumptions.

• Set bath temperature, agitation, geometry, size, transfer delay, corner severity, and final temperature.
• Review surface, quarter-depth, and centre cooling curves.
• Compare 800→500 °C cooling rate, martensite, hardness, maximum thermal gradient, martensite mismatch, cracking risk, and distortion risk.
• Use Apply to hardenability to transfer the selected setup.

Release 3

Process-data analysis

Upload a thermal record

1. Open Process Data.
2. Drop or select a CSV, TSV, TXT, or semicolon-delimited file.
3. Map the time and temperature columns.
4. Select source time and temperature units.
5. Adjust smoothing and arrest sensitivity.

The tool calculates the smoothed temperature history and:

Read the results

• Average cooling rates for 800–500 °C and 500–300 °C.
• Candidate thermal or transformation arrests.
• Candidate proximity to Ac1, Ac3, A1, and Ms.
• Measured-versus-simulated cycle overlay.
• Root-mean-square error between normalized measured and simulated paths.

Release 3

Temperature-measurement assistant

Thermocouple mode

Select thermocouple type, wire/sheath diameter, attachment method, shielding, and thermal mass. Review estimated response time, stabilization time, and attachment-bias risk.

Infrared-pyrometer mode

Enter indicated temperature, instrument emissivity, estimated actual emissivity, reflected temperature, target width, spot diameter, and surface condition. Review the radiation-balance correction, target-to-spot ratio, and background contamination risk.

Release 4

Surface treatment and diffusion

Select carburizing, carbonitriding, nitriding, ferritic nitrocarburizing, induction hardening, flame hardening, or laser hardening.

Diffusion-controlled treatments use an Arrhenius diffusivity and complementary-error-function profile:

Review solute concentration, hardness versus depth, effective case depth, total affected depth, surface hardness, core hardness, and process-specific risks. Transformation-hardening modes estimate heat-penetration depth rather than solute diffusion.

Release 4

Tempering simulator

Enter steel response family, as-quenched hardness, tempering temperature, time, number of cycles, retained austenite, and post-temper cooling mode.

Review tempered hardness, toughness recovery, residual-stress relief, retained-austenite reduction, secondary-hardening tendency, and embrittlement risk together. Do not assume hardness changes monotonically for every alloy family.

Release 4

Mechanical-property laboratory

Select microstructure, carbon, ASTM grain number, test temperature, notch severity, and residual stress. Switch among:

• Engineering stress–strain curve
• Charpy transition and DBTT curve
• Fatigue S–N curve

The module provides directional yield strength, tensile strength, elongation, hardness, Charpy energy, fatigue strength, and elastic modulus, plus approximate HV/HBW/HRC learning conversions.

Release 4

Virtual metallography laboratory

Generate schematic ferrite, ferrite–pearlite, bainite, martensite, spheroidite, and decarburization fields. Adjust grain size, magnification, etchant, banding, inclusion population, and section orientation.

Use the mystery-field exercise to practise phase and microconstituent identification. The displayed fields are original teaching schematics—not reference photomicrographs.

Release 4

Solidification and rolling inheritance

Use carbon, segregation tendency, thermal gradient, equiaxed nucleation, reduction ratio, soft reduction, cleanliness, and process-stage controls to animate:

Review segregation, porosity, closure, columnar-grain tendency, banding, and anisotropy indicators. Rolling can close voids and change morphology without eliminating inherited chemical segregation.

Release 4

Alloy-family modes

Release 5

Reference diagrams

This tab holds two separate reference charts. Choose between them with the selector at the top of the panel. They share a carbon axis but not a coordinate system, so points do not carry across when you switch.

Which chart is which

Plotting and moving points

1. Use + Add point to create P2, P3, and as many further points as you need. Existing points stay visible.
2. Select a point by clicking its P button in the list, or by clicking its marker.
3. Drag any marker directly, or click anywhere inside the plot to move the active point there.
4. Type exact values into the carbon and temperature fields for precise placement.
5. Remove deletes the active point. At least one point is always kept.
6. Reset examples restores the seeded points for the current chart.

Reading a region

Move the pointer over the diagram. The crosshair reports carbon content, temperature in both Celsius and Fahrenheit at once, and the interpreted region. The What does this region mean? panel updates as you move, covering what is present, how it forms, typical morphology, and the property tendencies that follow.

The painted colour and the reported region are generated from the same boundary functions, so the readout always matches the field you are pointing at.

Experience levels

Critical lines and legend

Critical lines draws A₁, A₃, A_cm, M_s and M_f on the rapid-quench map, and the eutectoid, eutectic, peritectic, liquidus and solidus on the poster. Labels toggles field and line annotation. Selecting a legend entry loads that region into the explanation panel. Regions are also reachable by keyboard: tab to one and press Enter.

Units

The °C and °F buttons change the display only. Internal values stay in Celsius, so a point does not move when you switch units. The poster's own printed scales remain in their original dual-unit form, since the artwork is reproduced unaltered.

Zoom, pan and full screen

Use the zoom buttons, or hold Ctrl and scroll. Pan by scrolling or dragging the diagram frame while zoomed. Fit returns to the whole chart and Full screen gives the diagram the entire viewport. Page scrolling is suppressed while you are manipulating the chart.

PNG export

Export PNG writes the diagram as currently displayed, including plotted points, visible overlays, critical-line emphasis and labels. Raster elements are embedded at export time, so the file is complete and self-contained. Attribution and the copyright line are included in the exported image and must not be removed.

On a phone

Controls stack into a single column and touch targets are enlarged. The poster is dense by design; use zoom and pan to inspect it rather than expecting the whole sheet to be legible at once. Poster artwork is only fetched when you open that chart, so the rapid-quench map stays fast on a mobile connection.

Engineering limitations

• On the rapid-quench map, A₁, A₃, A_cm, M_s and M_f are quantitative. M_s follows Andrews for plain carbon steel; alloying additions depress it and are not modelled.
• M_f is drawn as a fixed offset below M_s. The real finish is asymptotic and retained austenite persists below the line, increasingly so at higher carbon.
• The pearlite, bainite and austenitising divisions are educational approximations conveying field topology only. They carry no implied precision.
• Below roughly 0.42 wt% C there is no lower bainite field, because M_s sits above the bainite divide and a quench past it forms martensite directly.
• Real boundaries depend on chemistry, grain size, section size, homogeneity and holding time. Validate against grade-specific data before any process decision.

Source and copyright

The iron-carbon chart is the Iron-Carbon/Cementite Phase Diagram published by Buehler, an ITW company. Copyright © 2006 ASM International. All rights reserved. It is reproduced here under permission held by UpSkill Sprint Consulting and is served from this site rather than a third-party server. The artwork is reproduced unaltered; a link to the official PDF is provided beneath the diagram. Attribution and the copyright line must be preserved in any export or reuse.

The rapid-quench map is an original vector reconstruction. Its boundaries are generated from published relationships rather than traced from a source image.

Learning and records

Learn, save, share, and export

Learning mode

Generate phase-field challenges, use hints, inspect boundary explanations, and practise microstructure identification.

Save and share

• Save scenario stores settings in the current browser.
• Load saved restores the local scenario.
• Copy share link embeds supported configuration data in the URL.

Uploaded raw process data remains local to the current browser session and is not embedded in the share link.

Export

• Point and phase-analysis CSV
• Equilibrium-diagram PNG
• Derived process-data CSV
• Downloadable process-analysis HTML report
• Browser print/PDF output

Practical applications

Recommended workflows

Accuracy controls

Engineering cautions

• Equilibrium versus kinetics: equilibrium phase fields do not predict transformation time or cooling-rate response.
• Phase versus microconstituent: ferrite and cementite are phases; pearlite and bainite are microconstituents.
• Model validity: empirical equations have chemistry and process ranges.
• Section effects: centre and surface experience different thermal histories.
• Measurement: sensor lag, attachment, emissivity, reflected radiation, and calibration can dominate the result.
• Morphology: identical phase fractions can produce different properties when grain size, shape, distribution, and banding differ.
• Alloy families: plain-carbon models are incomplete for stainless, tool steel, and cast iron.
• Safety: the tool does not provide safe operating instructions for hazardous heat-treatment, atmosphere, quench, flame, induction, laser, or molten-salt processes.

Common issues

Troubleshooting

Before relying on an output

Final checklist

• Confirm chemistry and material family.
• Confirm units and sensor calibration.
• Separate equilibrium phases from kinetic products.
• Document prior microstructure and grain condition.
• Record section size, geometry, and sampling location.
• Document heating, holding, transfer, cooling, and tempering history.
• Check model and equation applicability.
• Preserve raw process data and analysis settings.
• Verify predictions using appropriate testing.
• Include uncertainty and cautions in reports.
• Use approved safety procedures.
• Obtain technical approval where required.