Different parts of a gear tooth perform different jobs
A gear’s contacting surface must resist wear while the material beneath supports the load. Impact and bending may dominate at the root, while repeated flank contact creates different damage mechanisms. Low-carbon carburizing steels such as 9310 are assessed within this division of functions. Carbon is subsequently introduced at the surface to develop a hard case, while core properties remain controlled. Calling the material simply hard or tough is therefore incomplete. The order and manufacturing plan should make both the case’s function and the supporting core requirements explicit.
Why case hardness and a core test are different
Surface hardness after carburizing, a tensile result from a core specimen and a hardness profile across the section provide different information. They cannot be equated through one conversion. Case depth and transition also cannot be inferred from the outer-surface number alone. A high tensile value on a supply document does not establish the required contact performance of the tooth surface. Likewise, acceptable case hardness does not establish every core toughness requirement. Read the property, measurement location, specimen condition and processing history together.
Blank form affects subsequent manufacture
A disc cut from bar and a forged blank may be machined to the same final dimensions, but they do not share the same manufacturing history. Section size, working direction and the region retained after machining affect the structure in the finished part. Reducing a gear enquiry to outside diameter and thickness may therefore obscure the appropriate product. Preserve any drawing requirements for forging direction, testing or inspection. Discuss surface allowance with the carburizing and final-grinding plan: material removed afterwards may be part of the intended case.
The 9310 identity does not replace the melting requirement
AMS 6260 and AMS 6265 are among the designations used for the 9310 bar and forging family. Similar chemistry ranges do not make their production requirements identical; vacuum remelting needs explicit treatment. An offer stating only 9310 may not identify the drawing’s cleanliness and inspection requirements. Product form also matters: mechanical-tubing coverage does not establish general suitability for pressure piping. Defining the standard, revision and stock delivery condition at the outset helps keep raw-material records distinct from final carburizing records.
A set of requirements rather than one hardness number
A practical enquiry starts by explaining the component and the manufacturing stage being purchased. A gearmaker’s raw blank request differs from an order for a heat-treated finished component. For a material enquiry to NET, state blank size, delivery condition and documentation needs, while aligning case and final-processing objectives with the manufacturing plan. A tooth surface that will be ground and one retained without machining cannot be treated identically for allowance. Knowing where material will be removed helps assess the final case in the correct region; stock dimensions alone do not describe this detail. This clarifies responsibilities and pricing scope. The distinctions below help prevent case and core results being reported as substitutes for each other. Numerical acceptance values should come from the approved component requirements.
- Stock: grade, product form, melting route and batch identity.
- Core: required property, test direction and specimen condition.
- Case: layer requirement, measurement method and final machining allowance.
- Finished component: dimensional checks, surface integrity and required inspections.