3004 takes the 3003 formula and adds roughly 1% magnesium on top of the manganese, which is a small change in composition that produces a meaningful jump in strength. Like 3003 and the rest of the 3xxx family, 3004 is a non-heat-treatable aluminum-manganese alloy — there's no age-hardening response, so all of its usable strength comes from cold work rather than solution treatment. The magnesium addition works alongside manganese in solid solution to raise strength further than manganese alone could achieve, without giving up the excellent formability and corrosion resistance that make the 3xxx series so widely used.

That higher strength-to-formability ratio made 3004 the dominant alloy for beverage can bodies for decades (modern can lines have largely shifted to related alloys like 3104, but 3004 remains common and closely related), and it continues to see heavy use in roofing and siding, gutters, and other sheet applications where 3003 doesn't quite have enough strength for the job. It's supplied almost exclusively as sheet, strip, and coil rather than bar or plate, reflecting its role as a forming and fabrication alloy rather than a structural or machining stock material.

3004 behaves much like 3003 from a cutting standpoint — it's a soft, non-heat-treatable, ductile alloy, so cutting forces stay low and the material shears easily with a sharp tool. The added magnesium raises strength modestly over 3003, which helps chip formation slightly (a bit less gumming and smearing than pure 3003), but the difference is not dramatic. This is still fundamentally a soft-aluminum machining problem: the alloy welds to a dull or negative-rake edge far more readily than it wears one down.

Sharp, positive, polished cutting edges remain the standard prescription. A keen edge shears the material cleanly and resists the built-up-edge smearing that ruins surface finish on soft aluminum alloys; a dull edge pushes and tears instead, and the resulting rough, torn finish is a machining problem rather than a material-hardness problem. Running at higher speeds generally helps rather than hurts, since neither 3003 nor 3004 generates significant heat-driven tool wear at typical aluminum cutting speeds.

Because 3004 is supplied almost exclusively as sheet, strip, and coil for forming operations rather than as bar stock, most shop-floor machining on this alloy is trimming, piercing, and light finishing rather than heavy stock removal — chip evacuation and workholding for thin sections tend to matter more than aggressive cutting parameters.