Steel & Aluminum Characteristics

Posted: September 17, 2010 in Tech
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Aluminum  characteristics:

The 3003-H14 has superior strength characteristics over pure aluminum and is easily welded with either TIG (tungsten-inert-gas) or oxygen-acetylene gas welders, yet remains malleable for shaping and bending. By comparison, a 6061-T6 aluminum alloy would yield even more strength than the 3003-H14, but the 6061-T6 is also more brittle and if welded, may develop stress cracks at the weld.

Following is a list of aluminum alloys defined by a four-digit numeric code to identify the alloy content. The first digit represents the main element of the alloy. The alphanumeric code that follows the four digits (i.e “H14” or “T6”) is the hardness and temper specification of an alloy. For example, a letter “F” in the temper code refers to fabricated, which is an aluminum that has not been treated for hardness. A letter “O” indicates annealed, or softened by a process of heating and cooling. A letter “H” indicates a strain-hardened alloy (hardened by cold-working), and a letter “T” means heat-treated. Generally speaking, the higher the number in the temper code, the harder and stronger the alloy.

1XXX (1000-series) is the designation for unalloyed (99 percent pure) aluminum. The 1000-series offers high corrosion resistance, excellent workability and welds easily; however, its low strength limits its use in certain applications. This is still a common alloy for use in automotive fabrication where strength is not an issue. Non-heat-treatable.

2XXX (2000-series) is an aluminum containing copper as its main alloy. 2000-series aluminum alloy provides a better strength-to-weight ratio than 1000-series and is also easy to work with. The trade-off, though, is that this alloy is not as ductile, meaning that bend radii must be fairly large and gradual, and joining pieces of 2000-series alloy must be accomplished by riveting or chemical bonding rather than welding. Heat-treatable.

3XXX (3000-series) indicates an aluminum with a main alloy of manganese. The addition of manganese yields a 20-percent increase in strength over 1000-series, yet it retains the working qualities of pure aluminum, and can be TIG or gas welded. For these reasons, 3000-series aluminum alloy is the most popular choice among automotive fabricators. Non-heat-treatable.

4XXX (4000-series) is an aluminum alloyed with silicon. Moderate strength.

5XXX (5000-series) is an aluminum alloyed with magnesium. Moderate-to-high strength. Non-heat-treatable.

6XXX (6000-series) such as 6061-T4 or 6061-T6 is commonly used in production due to its relatively low cost and excellent mechanical properties. Annealed 6000-series aluminum alloy (or 6000-series with an “O” temper code) also lends itself to forming. Heat-treatable.

7XXX (7000-series) is an aluminum alloyed with zinc. 7000-series offers the greatest strength, but is the least ductile. Heat-treatable.

Steel characteristics:

 The same basic code system that defines aluminum alloys similarly defines steel.

 1XXX (1000-series): Basic open-hearth and acid Bessemer carbon steel that is non-sulfurized. 1020-series cold-rolled steel sheet metal is a common material for automotive fabrication.

2XXX (2000-series): Steel alloyed with the addition of nickel.

3XXX (3000-series): Steel alloyed with nickel and about 1.25 to 3.50 percent chromium.

4XXX (4000-series): Steel alloyed with molybdenum or nickel-chromium-molybdenum. You’ve probably heard the term “4130 chrome-moly” a few times. 4130 is a steel alloyed with chromium and molybdenum. Stress-relieved 4130 chrome-moly is used where structure strength is most critical. Annealed chrome-moly is used for fabricating structures that require forming and bending.

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