Yes, steel is playable
...and is worth 6 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Steel" Definition
noun
A generally hard, strong, durable, malleable alloy of iron and carbon, usually containing between 0.2 and 1.5 percent carbon, often with other constituents such as manganese, chromium, nickel, molybdenum, copper, tungsten, cobalt, or silicon, depending on the desired alloy properties, and widely used as a structural material.
A quality suggestive of this alloy, especially a hard, unflinching character.
Something, such as a sword, that is made of steel.
Commercial iron that contains carbon in any amount up to about 1.7 percent as an essential alloying constituent, is malleable when under suitable conditions, and is distinguished from cast iron by its malleability and lower carbon content.
verb-transitive
To cover, plate, edge, or point with steel.
To make hard, strong, or obdurate; strengthen: He steeled himself for disappointment.
verb
To overlay, point, or edge with steel.
To cause to resemble steel (as in looks or hardness).
To fill with resolution or determination.
adjective
Made with, relating to, or consisting of steel: steel beams; the steel industry; a bicycle with a steel frame.
Very firm or strong: a steel grip.
Of or relating to the production of steel.