Alloy and processing history convey different information
Writing 6061 or 5083 identifies an alloy family but does not alone explain the mechanical condition at delivery. The temper following the alloy conveys information about annealing, cold work, ageing and certain stress-relief operations. It is therefore more than a hardness note added at the end of a quotation. Sheet for bending, a profile for welding and plate for deep machining need different purchasing descriptions. Specifying dimensions and alloy alone can leave these manufacturing differences undefined. Building the full designation with product form also clarifies which delivery condition a property table represents; one numerical value cannot cover every condition.
O and H: the relationship between annealing and strain hardening
O indicates the annealed condition. The H family describes the processing history of strain-hardened products; additional digits provide detail about processing and degree of hardening. These designations are not a ranking in which a larger number is universally better. H111 and H22 are not alternative spellings of the same condition. For 5xxx alloys such as 5083 and 5754, choose an appropriate O or H condition alongside forming and welding plans. Requesting T6 for these alloys assigns a different hardening mechanism to the wrong family. Check component requirements against an actually defined product and temper condition.
T4, T5 and T6 follow different processing routes
For heat-treatable alloys, T4 describes solution treatment followed by natural ageing; T6 describes solution treatment and artificial ageing. T5 relates to products cooled from an elevated-temperature shaping process and artificially aged. These brief definitions are not furnace recipes, nor do they mean every alloy is standardised in every temper. A condition encountered for 2017A does not automatically define delivery for 6060 or 7075. Likewise, a producer-specific temper suffix should not be used as a general standard class. Read product specification, section and required properties together to identify the suitable condition; hardness alone does not prove the full processing history.
T651 and T6511: stress-relief information
Additional digits in the T6 family can carry details about operations such as stress relief. T651 and T6511 encountered for extruded products are more specific than T6 alone. They are not interchangeable independently of product form and the applicable specification. Reducing stress through controlled stretching can help parts involving extensive machining. It does not mean that residual stress is completely eliminated or dimensions will remain unchanged under every machining arrangement. Deep pockets cut from one side, clamping force and operation sequence affect the final result. Carry rough dimensions, allowance and final tolerance into production as separate requirements.
The timing and workholding condition of post-machining measurement also matter. A clamped component and a released one are not measured under identical conditions. Defining inspection points early helps distinguish material movement from measurement-arrangement effects. Temper selection is only one input to that production plan.
Subsequent operations affect what the temper means
Welding, hot processing or extensive cold forming can change properties locally from the initial delivery condition. Weldability of T6 stock does not mean the weld surroundings retain initial T6 values. Adding a temper code at the end of an order is therefore insufficient; subsequent operations also need to be known. Do not assume that the documented delivery condition carries unchanged into the finished component. Manufacturing and acceptance plans separate properties checked in stock from those checked in the final product. The structure below helps keep alloy and processing history explicit within one purchasing line and maintains consistency on repeat orders.
- Alloy + temper + product form + dimensions and quantity.
- Product standard + subsequent manufacturing operations + inspection documentation.