63/37 yellow brass: the economical choice for pressings and tube

In the American system, yellow brass is a family rather than one alloy. C27000 runs from 63.0 to 68.5 percent copper, C27200 from 62.0 to 65.0 percent and C27400 from 61.0 to 64.0 percent. In the European system, CuZn37 sits at 62.0 to 64.0 percent copper. All of them get called 63/37 in the market, and older catalogues may still call C27000 by its 65/35 nickname.

For most pressed and bent parts the difference does not matter. Where it does matter is deep drawing: the lower the copper, the closer the alloy gets to the two-phase region and the sooner it work-hardens. If your drawing names a specific UNS or EN grade, quote that exact designation when you send an enquiry.

It is the general-purpose cold-working brass. Typical jobs include blanked and bent electrical parts, lamp and lighting fittings, rivets, eyelets, decorative trim, radiator cores, name plates and the large volume of sheet work done in small fabrication units. It also goes into drawn tube for general engineering, instrument lines and furniture, and many brass pipes and tubes sold for non-pressure work are 63/37.

It solders and brazes easily, buffs to a bright yellow finish and plates well, which is why so many hardware and fittings makers in South India use it for visible parts.

Some ductility and a little corrosion resistance. 70/30 cartridge brass will go through more draw stages before it needs annealing, and it is less prone to dezincification. For a shallow cup, a bracket or a bent strip, 63/37 is plenty. For a deep shell, a thin-walled spun part or a tube that will sit in hot water service for years, the extra copper in 70/30 is usually worth paying for.

Like 70/30, cold-worked 63/37 can season crack if residual stress meets ammonia. A stress-relief anneal after forming takes care of most of that risk.

Tempers control how a strip behaves in the tool. Annealed material (R300) bends flat on itself and draws well but scratches and dents in handling. Half-hard (around R350 to R410) is the common choice for blanked and lightly formed parts because it holds shape and still bends to a tight radius across the rolling direction. Hard and spring tempers (R480, R550) are for parts that must stay flat or act as a spring, such as contacts and clips.

Under IS 410 the same ladder runs O, HA, HB, HD, HE and HS. If you are bending sharply, tell us the bend radius and the strip thickness and we will suggest a temper that will not crack on the outside of the bend. For the hardest end of the range see spring quality brass.

You can, but it is not pleasant. Without lead the chips come off long and stringy and wrap around the tool, and surface finish suffers at high speed. Its machinability is rated at about 30 percent of free-cutting brass. For anything that will be turned, drilled and threaded in volume, order leaded free-cutting rod instead and keep 63/37 for the sheet, strip and tube work it is suited to.

Most delays on brass orders come from a missing detail, so it helps to send everything in the first message. For sheet and strip we need the thickness in millimetres or SWG, the width, the sheet size or coil weight, and the temper. For tube we need OD, wall, length and temper. Mention the specification if the drawing names one, for example C27200 to ASTM B36 or CuZn37 to EN 1652.

We supply 63/37 brass with a test certificate from a Government-recognised test house, and the certificate lists the copper, lead and iron values so your quality team can check them against the grade. If you are switching from 70/30 to save cost, send a sample part or drawing first and we can tell you honestly whether 63/37 is likely to form it without splitting.