Classification and designation of aluminum materials

Classification and designation of aluminum materials

1. Classification of Aluminum

• (1) According to the alloy composition, aluminum is divided into pure aluminum and aluminum alloy. Aluminum alloys are divided into Al-Mn alloys, Al-Cu alloys, Al-Si alloys and Al-Mg alloys according to the alloy series.
• (2) According to the processing capacity of pressure, it can be divided into deformed aluminum and non-deformed aluminum (for example: cast aluminum).
• (3) According to whether it can be strengthened by heat treatment, aluminum alloy is divided into non-heat treatment aluminum alloy and heat treatment strengthened aluminum alloy.

Aluminum has no isomers, and pure aluminum, aluminum-manganese alloys, aluminum-magnesium alloys, etc. cannot increase their strength through heat treatment phase transformation. However, alloys such as aluminum-copper and aluminum-magnesium-silicon can increase their strength through solid solution aging precipitation strengthening phases, which are called heat-treatable aluminum strengthening.

Aluminum that cannot be strengthened by solid solution aging precipitation strengthening phase is called non-heat-treatable aluminum.

2. Grade representation method and status code

(1) The naming method of grades in the four-digit system On January 1, 1997, my country began to implement the GB/T16474-996 “Denotation Method of Grades of Deformed Aluminum and Aluminum Alloys” in China. The new designation method adopts the international four-digit system designation method recommended by the International Trademark Registration Organization for Deformed Aluminum and Aluminum Alloys. For example, industrial pure aluminum has 1050, 1060, etc., Al-Mn alloy has 3003, etc., and Al-Mg alloy has 5052. , 5086, etc.

(2) The naming method of grades in the four-digit character system Before January 1, 1997, my country adopted the designation method of the former Soviet Union. The chemical composition of some old brands of aluminum and aluminum alloys is not completely consistent with the international four-digit number system, and the international four-digit number system cannot be used instead.

In order to retain the existing domestic non-international four-digit number system, four-digit The naming method of the brand name of the character system is gradually in line with international standards. For example: the chemical composition of the old brand LF21 is not completely consistent with the international four-digit number system number 3003 aluminum alloy, so the four-digit number system indicates the brand name is 3A21.

The first number of the four-digit system and the four-character system designation indicates the category of aluminum and aluminum alloys, and its meanings are as follows:

• 1) 1XXX series industrial pure aluminum;
• 2) 2XXX series Al-Cu, Al-Cu-Mn alloys;
• 3) 3XXX series Al-Mn alloys;
• 4) 4XXX series Al-Si alloy;
• 5) 5XXX series Al-Mg alloy;
• 6) 6XXX series Al-Mg-Si alloy;
• 7) 7XXX series Al-Mg-Si-Cu alloy;
• 8) 8XXX series others.

(3) Grades of aluminum castings The grades of aluminum castings for containers in my country are represented by ZAl + the symbol of the main alloying elements + the percentage of the content of the alloying elements. For example; ZAlSi7Mg1A, ZAlCu4, ZAlMg5Si, etc.

(4) State code Aluminum and aluminum alloys of the same grade have different mechanical properties when they are in different states. According to GB/T16475 “Deformed aluminum and aluminum alloy status code” standard, the new status code is stipulated as follows:

O Annealed state

H112 Hot working status

Natural aging state after T4 solid solution treatment

Artificial aging state after cooling in T5 high temperature forming process

T6 artificial aging state after solid solution treatment

Application characteristics of aluminum containers

(1) In the medium of air and oxidizing aqueous solution, the surface of aluminum is easy to form a dense aluminum oxide passivation film, and it has good corrosion resistance in some oxidizing media. In high temperature concentrated nitric acid, the corrosion resistance of pure aluminum is better than that of stainless steel. Aluminum is often used as a corrosion-resistant container material.

(2) For some media that are not too corrosive but require anti-iron pollution, such as chemical fiber production media, aluminum has better corrosion resistance and no iron-polluting materials. Therefore, aluminum is often used as an anti-iron pollution The material of the container. Other non-ferrous metal containers are also resistant to iron contamination, but aluminum is the cheapest.

(3) Aluminum is a face-centered cubic lattice, without isomers, and there is no brittle transformation like ferritic steel at low temperatures. The lowest design temperature of aluminum containers can reach -269°C. Aluminum is often used as a material for cryogenic containers.

When the magnesium content in the aluminum-magnesium alloy is high, the intergranular compounds Mg2Al3 and Mg5Al8 will be precipitated between the grains, making the aluminum-magnesium alloy sensitive to stress corrosion in certain media, and only when it is used below 65°C will it not produce stress Therefore, the design temperature of aluminum-magnesium alloys containing more than 3% magnesium should not exceed 65°C.

Too much precipitated phase will also reduce the impact toughness, so the impact toughness of aluminum-magnesium alloys and their welded joints with magnesium content exceeding 3% should be tested. Other aluminum and aluminum containers, including cryogenic aluminum containers, are not required to be tested for impact toughness.

(4) Al-Mg-Si alloys have high strength in solid solution aging state, good plasticity and good weldability, and the welded joints can still maintain high strength after welding, so they are often used as high-strength aluminum alloys for containers. Aluminum, especially pure aluminum, has a very low non-proportional elongation stress, and plastic deformation will occur under small loads. When aluminum containers are used and transported, attention should be paid to collision deformation.