Spring quality brass strip and sheet

Alpha brass work-hardens as it is rolled. Each pass through the mill packs more dislocations into the crystal structure, raising yield strength and hardness while lowering elongation. Brass of this type cannot be hardened by quenching or ageing the way steel or beryllium copper can, so cold rolling is the only lever. A mill makes spring strip by annealing at an intermediate thickness and then taking a heavy final reduction to size.

That has a practical consequence. If spring brass is heated, for example during soldering close to the working area, it softens and loses its spring. Keep heat away from the flexing section or design the joint at the fixed end.

Three temper ladders appear on drawings and they describe the same idea in different words. IS 410 runs O, HA, HB, HD, HE and HS, with HE and HS at the hard end used for springs. EN 1652 names each temper by its minimum tensile strength, so R550 means at least 550 N/mm², and also offers hardness-based tempers such as H150 and H170. ASTM uses H06 extra hard, H08 spring and H10 extra spring.

The ladders do not map exactly onto each other, so do not convert by label. Send the tensile range or hardness your design needs and we will match it. The EN 1652 values for 63/37 are in the table on this page, and the softer tempers are covered on our brass sheets and strips page.

Both work. 63/37 brass reaches a slightly higher strength in the spring tempers under EN 1652, up to the R550 condition, and costs less, which is why it is used for most contacts and clips. 70/30 is a little more ductile at the same hardness, so it tolerates tighter bends in a formed spring and has slightly better resistance to stress corrosion. 60/40 is not used for springs because it does not take enough cold rolling.

For most buyers the deciding factor is the tooling. If an existing press tool was proved out on one grade and temper, stay with it, because a change in strength alters springback and the formed angle. When you do switch, run a small trial lot of spring brass strip first and check the formed dimensions and contact force before releasing a full order.

• Bend across the rolling direction. A bend line parallel to rolling is the first place hard strip cracks.
• Use a bend radius of at least one to two times strip thickness in spring tempers; check with a trial piece.
• Keep the stress in the flexing arm below the yield strength so the part does not take a permanent set.
• Stress relieve formed parts with a low-temperature treatment where ammonia or high humidity is expected, to reduce the risk of season cracking.
• Do not solder or braze near the flexing zone; local heat anneals the spring away.

Brass is the low-cost spring material and carries current better, at about 28 percent IACS against roughly 15 percent for standard phosphor bronze. Phosphor bronze, though, has higher strength, much better fatigue life and resists stress relaxation when warm. So brass suits contacts that flex a modest number of times at room temperature, such as lamp holders, battery clips and switch parts. Phosphor bronze is the choice for relays, connectors that cycle many thousands of times, and springs that run warm.

Give the grade, thickness, width, temper (or the tensile or hardness range), edge condition and quantity. For coil, tell us the coil inner diameter and weight your press feeder accepts. Spring strip is supplied with a test certificate from a Government-recognised test house, and parts made for electrical and power distribution work usually need that paperwork on file.