OpenSpecEngineering

A short list of candidate metals for a part. Set the properties the part needs, and the page shows every alloy that meets them, each on a card with its strength, conductivity, expansion, corrosion resistance, cost and common uses. Designers use it early, to narrow 31 common steels, stainless steels, cast iron, aluminum, copper, titanium and zinc alloys down to a few worth a closer look.

What the page covers

• Filters for Family, Type (Ferrous or Non-Ferrous), Machinability, Strength, Weldability, Thermal Conductivity, Electrical Conductivity, Creep Resistance, Corrosion Resistance, Heat Treatable and Relative Cost. Reset filters clears them all, and the count above the cards says how many alloys match.
• Alloy cards with typical values from the ASM Handbook [1], MatWeb [2], MIL-HDBK-5J [3] and Callister [4].

Reading the ratings

Each property is sorted into a rating, from Poor to Excellent or Low to Very High, and the card adds the number behind it: tensile (and sometimes yield) strength in MPa, thermal conductivity in W/m·K, electrical conductivity in % IACS (percent of annealed copper), machinability as a percentage of a free-cutting reference steel, and thermal expansion in µm/m·°C. The temper or condition a value applies to, such as H32 or cold drawn, is given in brackets. A filter with or better ticked also accepts every higher rating; for Relative Cost it accepts every cheaper one.

Limits and common mistakes

• The values are typical, not design minimums. Take allowables from the material specification or MIL-HDBK-5J [3].
• Ratings are coarse. 304 stainless and 5052 aluminum are both Medium strength at 515 and 228 MPa. Compare the numbers, not the rating.
• Strength depends on temper and heat treatment. Check that the card’s condition is the one you will buy.
• Without or better, a filter matches only that exact rating.

Worked example

Choose a sheet metal for a welded enclosure that sits on a boat deck in salt spray. It needs moderate strength and a modest cost.

1. Set Strength Medium, Weldability Excellent and Corrosion Resistance Excellent, and tick or better under each. The count reads 5 of 31 alloys match.
2. Set Relative Cost Medium and tick or better. The count reads 4 of 31 alloys match: 304 Stainless, 3004 Aluminum, 3105 Aluminum and 5052 Aluminum.
3. Read the Corrosion Resistance on each card. 304 Stainless says Excellent - Except chlorides, and 5052 Aluminum says: Strength: Medium (228 MPa H32)
   Corrosion Resistance: Excellent - Superior marine
   Thermal Expansion: 23.8 µm/m·°C
   Common uses: Marine applications, fuel tanks, …

5052-H32 is the choice. Its 228 MPa beats 3004 (215 MPa H34) and 3105 (195 MPa H25), and salt spray carries the chlorides that 304 is weak against. One check before release: 5052 expands 23.8 against 304’s 17.2 µm/m·°C, so allow for that where stainless fasteners or brackets attach.