cold-worked condition aluminum and aluminum alloys - they are also called “H-state” - applied to aluminum products, which have undergone plastic deformation with strain hardening (work hardening). These products can also be subjected to a partial annealing. This annealing is called partial, because it is designed to partially reduce the strength (hardness) of the metal. This operation is also called the softening of the metal.
Aluminum alloys tempers in EN 515
The European standard EN 515 defines standardized work-hardened tempers for wrought aluminum alloys. The general approach and most aluminum alloys notation states borrowed from American Standard ANSI H35.1.
The standard includes four types (groups of states):
- F - without control of mechanical properties;
- O - annealed (O, O1, O2 and O3);
- H - hard-worked or cold-worked and annealed (for example, H14, H111);
- T - heat treated (for example, T5, T66, T5411).
There is also a group of unstable states W: treated for solid solution and naturally aged. These conditions are rarely used and are, rather, technological, than in terms of delivery.
The state of the material of the aluminum product - the state of the aluminum alloy - is indicated by a hyphen (not a dash) after the designation of the aluminum alloy, for example, 6063-F, 6063-T5, 3003-N111.
What does the state of the aluminum alloy
Each variant of the state designation "informs" about the technological history of the aluminum product - the type and sequence of technological operations and their parameters: plastic deformation (hot or cold), the degree of deformation, heating (temperature, duration of heating and holding), cooling (speed or duration).
Designation of cold-worked tempers
The designation of cold-worked states of aluminum alloys consists of the first letter H (from the English words hard, hardening, hardened). Directly after the letter H, two or more digits are without space, which define the state of cold-worked variant.
Note in the order or contract alloy designations together with the designation of state uniquely determined by the specified mechanical and physical properties of aluminum products.
The first digit after the letter H
The first letter after letter H indicates the status, which arises as a result of some combination of basic technological operations:
Н1Х: cold-worked (without annealing). These states are used to refer to aluminum products, which undergoes cold plastic deformation (cold working) without subsequent heat treatment.
Н2Х: cold-worked and partially annealed. These states are used to refer to aluminum products, which is subjected to cold plastic deformation to a level higher strength, than its ultimate strength and then subjected to a partial annealing to lower the strength to a predetermined level.
Н3Х: work-hardened and stabilized. These conditions are applied to aluminum products, which is subjected to cold plastic deformation and then its mechanical properties are stabilized by low-temperature heat treatment or by heat, arising during manufacture.
Н4Х: cold-worked and varnished. Used for aluminum products, which is subjected to cold plastic deformation and then a special lacquer coating. for instance, tapes from alloy 5xxx-Nxxx for lids of aluminum cans for drinks ("beer cans").
Details about the conditions, see. in European Standard EN 515.
The second digit after the letter H
The second digit after the letter H in designation aluminum alloy cold-worked state indicates a finite degree autofrettage, which corresponds with the minimum value of tensile strength.
The second digit 8 denotes the "strongest" condition (but not yet maximum) for a given alloy.
The second digit 9 denotes fully cold-worked state above autofrettage. It, for example, used for alloy 3104, which is for the manufacture of housings aluminum “beer” cans: 3104-H19.
The state between the O (annealed) state and the H8X state is indicated by the second digits from 1 by 7.
HX represents temper of the alloy, in which the tensile strength is in the middle between the outside and ON states strength NH8.
NH2 refers state, in which the tensile strength of the alloy is approximately in the middle between the outside and ON states strength NH4.
NH6 denotes state, in which the tensile strength of the alloy is approximately in the middle between the outside conditions and the strength NH4 NH8.
NH1, NH3, NX5, NH7 denote an intermediate state between those states, are defined above. Note, that these conditions are not specified in EN 515, but sometimes used by agreement between the manufacturer and the customer.
The third number after the letter H
The third digit after the letter H (when applicable) indicates a condition variant, to which the first two digits indicate.
State NH11 applies to products, which after final annealing receives an amount of cold plastic deformation, that can not be considered in a state of about, but, However, this amount is not enough, to assume a state of the state NH1.
Status N112 used for the production, that can receive a certain peening by treatment at elevated temperature or at a limited number of cold plastic deformation and which does not set the upper limits of strength properties.
Status N116 applies to products of the 5xxx series alloys, in which the nominal content of magnesium 3 % and more. These products nagartovyvayutsya the last processing step to the predetermined level of mechanical properties and meet the requirements of corrosion resistance under accelerated corrosion tests. This condition is suitable for continuous operation at temperatures above 60 degrees Celcius.
Aluminum alloys and their status in the beer cans
As examples of aluminum alloys states - states aluminum alloys, of which is made of a beverage - beer cans. Aluminum alloy 3104-H19 is a typical material for housings beer cans, and H19 state designation suggests, that the material was the work hardening to an extent higher than the total peening. Aluminum-manganese alloy 3104 - an analog of our D12 GOST 4784. Caps beer cans are made from aluminum alloy 5182-H48, and the status symbol that speaks, that the aluminum sheet was complete peening and has a lacquer coating. Aluminum-magnesium alloy 5182 – part alloy analogue AMg4,5 GOST 4784.