Aluminum and aluminum alloy state code (GB/T 16475-2008)
GB/T16475 stipulates that aluminum and aluminum alloy state codes are divided into basic state codes and detailed state codes. The basic state code is represented by a capital letter in English. The detailed state code is represented by one or more Arabic numerals or English capital letters suffixed to the basic state code. These Arabic numerals or English capital letters represent the basic treatment or special treatment that affects the product characteristics.
The "X" in the example status code represents any unspecified Arabic numeral, such as "H2X" can represent any status between "H21~H29", "HXX4" can represent any status between "H114~H194", or "H224~H294", or "H324~H394"; "-" represents any unspecified Arabic numeral or digits, such as "T-51" can represent any status with the last two digits being "51", such as "T351, T651, T6151, T7351, T7651", etc.
Table 1 Basic state code, name, description and application
| Code | Name | Description and Application |
| F | Free processing state | Applicable to products with no special requirements for work hardening and heat treatment conditions during the molding process. No provisions are made for the mechanical properties of products in this state |
| O | Annealed state | Applicable to products that obtain the minimum strength after full annealing |
| H | Work hardening state | Applicable to products that increase strength through work hardening |
| W | Solution heat treatment state | Applicable to an unstable state of natural aging at room temperature after solution heat treatment. This state is not used as the product delivery state, but only indicates that the product is in the natural aging stage |
| T | Heat treatment state different from F0 or H state | Applicable to the stable state after solution heat treatment with (or without) work hardening |
Table 2 Subdivided state code of O state
| Code | Name | Description and Application |
| O1 | Slow cooling state after high temperature annealing | Applicable to the state where the product or sample is heated to a temperature similar to that specified by solution heat treatment and kept warm (the holding time is similar to that specified by solution heat treatment) before ultrasonic inspection or dimensional stabilization, and then taken out of the furnace and placed in the air for cooling. The mechanical properties of the product in this state are not specified, and it is generally not the final delivery state of the product |
| O2 | Thermomechanical treatment state | Applicable to the state where the user anneals the product at high temperature (to the temperature specified by solution heat treatment) before the product is subjected to thermomechanical treatment to obtain good formability |
| O3 | Homogenization state | Applicable to the high temperature annealing state of continuous casting wire billet or cast strip to eliminate or reduce segregation and facilitate subsequent I deformation |
Table 3 State represented by the first digit after H
The first digit after H indicates the state: It indicates the basic process to obtain the state, represented by 1~4 |
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| Code | Name | Description and Application |
| H1X | Pure work-hardening state | Applicable to the state where the required strength can be obtained by work-hardening without additional heat treatment |
| H2X | Incomplete annealing state after work-hardening | Applicable to products whose work-hardening degree exceeds the specified requirements of the finished product and whose strength is reduced to the specified index by incomplete annealing. For alloys that soften by natural aging at room temperature, the H2X state has the same minimum ultimate tensile strength value as the corresponding H3X state; for other alloys, the H2X state has the same minimum ultimate tensile strength value as the corresponding H1X state, but the elongation is slightly higher than H1X |
| H3X | Stabilization state after work-hardening | Applicable to products that have undergone low-temperature heat treatment after work-hardening or whose mechanical properties have reached stability due to the heat effect during the processing |
| H4X | Paint (layer) treatment state after work-hardening | Applicable to products that have been incompletely annealed after work-hardening due to paint (layer) treatment |