AISI 8620 is a low-alloy case-hardening steel used where a carburized surface and a tougher core are required. Supplier data do not give one universal cycle: voestalpine lists 850–930°C for carburizing, Walter Metals lists 1650–1700°F, and a MatWeb test record describes one 925°C, eight-hour specimen cycle followed by cooling, reheating, quenching, and tempering. These are source-specific entries, not a ready-to-run heat-treatment schedule.

AISI 8620 carburizing temperature reference

Keep each source condition together

The first two rows are supplier temperature ranges. Walter Metals’ Fahrenheit interval is converted to 899–927°C for comparison using the exact conversion relation, with the original values retained in the source note. The third row is a single test record: 8620 round stock was carburized at 925°C (1700°F) for eight hours, cooled in a box, reheated to 845°C, oil quenched, and tempered at 150°C. A test record for a 25 mm specimen is not a universal production recommendation and must not be generalized to a larger gear or different case-depth target.

Carburizing adds carbon to a surface layer under a carbon-bearing atmosphere. The later hardening and tempering steps determine how that enriched case transforms and how the core responds. Temperature alone does not state carbon potential, boost/diffuse cycle, time-to-case-depth, surface carbon, quench severity, retained austenite, distortion, or final hardness. Those variables must come from a qualified process specification and the part’s drawing requirements.

Using the table for a material review

Start by confirming the steel designation and product condition on the material certificate. Then identify whether the source applies to the same product form, section size, carburizing medium, and post-carburizing sequence. If a drawing specifies an effective case depth or surface hardness, the selected supplier temperature is only one input to the heat treater’s process plan. Obtain the complete source document and review the cycle with a qualified heat treater before releasing production.

For example, the MatWeb record provides a bounded test condition: 25 mm round AISI 8620, carburized at 925°C for eight hours, box-cooled, reheated to 845°C, oil-quenched, and tempered at 150°C. It may be useful when comparing a research specimen with another test, but it does not establish that eight hours gives a target case depth in a different furnace. Section size, carbon potential, load arrangement, atmosphere control, and diffusion schedule all matter.

Common mistakes

Do not treat 850–930°C and 1650–1700°F as conflicting measurements; the ranges substantially overlap after conversion. Do not average their endpoints into a new “best” temperature. Also do not stop at the carburizing stage: the case is not a finished hard surface until the subsequent hardening sequence is completed. A supplier entry that says furnace or air cool must not be combined casually with another source’s direct-quench instructions.

Use the current voestalpine AISI 8620 data, Walter Metals 8620 information, and the exact applicable material specification. The dataset labels each source and retains process sequence so the numbers cannot be mistaken for interchangeable recipes.

A robust carburizing instruction also states the target effective case depth and its measurement definition, the surface carbon potential, boost and diffusion sequence if used, furnace atmosphere, load arrangement, and the quench medium and agitation. Post-carburizing treatment may include a direct quench or a controlled cool followed by reheating and hardening; each route has consequences for distortion and case properties. The three records here do not provide a common carbon potential or case-depth target, so those fields are deliberately absent. A designer should specify functional case requirements and have a qualified heat treater develop and document the cycle rather than selecting a temperature from this chart alone. Confirm the complete process before production release, and retain the heat treater’s record with the material certificate.