Which bs2871 copper alloy tube temper is best for bending and forming applications?

Order copper or copper alloy tube for a job that involves tight radius, flaring, or a bend-and-run assembly and the call soon turns into a back-and-forth: "What temper do you need?" If the answer is "I'm not really sure," you are far from alone. Temper quietly decides how easily a tube bends, how much it springs back, and whether a flare survives the first pressure cycle. For bending and forming, the annealed soft (O) temper is almost always the best starting point, with quarter-hard and half-hard reserved for jobs that need a bit more stiffness. This article walks through the BS 2871 temper range, why it behaves the way it does, and how to pick the right one for your parts.

What BS 2871 actually covers

BS 2871 is the British Standard that organizes copper and copper alloy tubes into three practical parts. Part 1 deals with copper tubes for water, gas, and sanitation, where familiar grades such as C101 high-conductivity copper and C106 phosphorous-deoxidised (DHP) copper sit. Part 2 covers tubes for general and engineering purposes. Part 3 turns to copper alloy tubes for heat exchangers and condensers, bringing in grades like CN108 cupro-nickel and the CZ brasses.

A lot of what used to live in Part 1 has been folded into EN 1057 over the years, and plenty of buyers now quote EN values such as R250 or R290 next to traditional terms. Yet the temper thinking underneath the whole family has not changed, and it still controls how a bs2871 copper alloy tube performs once it leaves the mill.

Temper: the trade-off between strength and ductility

Temper describes the final state of the metal after its last drawing or annealing step. A fully annealed tube is heated and allowed to cool slowly so the grain structure relaxes. It gives up some strength in exchange for high ductility and elongation, often in the region of 40 percent or more.

Drawn tempers are the opposite story. Once a tube is "quarter-hard," "half-hard," or "full-hard," it has been cold-worked after annealing. Each drawing pass packs more strength into the wall, but it also drags elongation down and hardens the metal. That extra hardness is precisely what makes a hard tube unhappy about being bent. When you bend it anyway, it wants to spring back, and the inside of the bend can wrinkle or crack.

Temper by temper, ranked for bending and forming

Here is how each temper behaves once the bending tool touches it.

• O (annealed / soft): the clear winner for forming. Maximum ductility, minimal springback, and it accepts tight radii and repeated bends without cracking.
• 1/4H (quarter-hard): a practical compromise. It holds a smooth straight run better than soft tube yet still copes with multi-pass bends, flaring, flanging, and roll grooving with little micro-cracking at the bend root.
• 1/2H (half-hard): noticeably stiffer. It bends well on a machine, but you must over-bend to allow for springback, and tight radii usually call for a mandrel.
• H (full hard / spring): built for springs and structural duty, not for formed parts. Leave it out of any bending conversation unless the design truly demands the stiffness.

Practical rules for bend radius and tooling

Bend radius is a useful shorthand for what a temper will tolerate. Soft annealed copper happily bends down to roughly one to three times the tube outside diameter, which is why hand-bending works on soft refrigeration and plumbing lines. Hard-drawn tube prefers a friendlier curve, more like three to five times the OD, and it pushes back harder with springback. Forcing a tight radius on hard temper invites collapse or wrinkling on the inner wall, so a mandrel bender becomes a necessity rather than an option.

Forming tasks follow a similar logic. Flaring and expanding need material that will flow without splitting, which points back to soft or quarter-hard temper. Deep drawing, where the tube stretches a lot along a die, favors the soft end of the range. If the main concern is that a long straight section stays straight and does not sag between supports, then a touch of work hardening such as half-hard earns its keep.

Alloy matters too, not just temper

Temper is only half the decision, because the alloy underneath bends at its own pace. Annealed DHP copper is famously forgiving and is the default for plumbing and heat transfer work. Cupro-nickel such as CN108 or the 90/10 and 70/30 grades is strong and shrugs off seawater, which is why it shows up in marine systems and heat exchangers, though it asks for a little more respect at the bender. Brass is another story again, with some CZ grades meant for easy machining rather than generous bends. When you are choosing a copper & nickel alloy for a saltwater or condenser duty, confirm both the grade and the temper together rather than treating them as separate decisions.

What to ask your supplier

A short checklist keeps the guesswork out of the order. State the final temper you want in writing, since "soft" and "half-hard" mean different things to different people. Ask for mill test certificates so you can verify the temper and chemistry rather than trusting a label. Tell the supplier whether the tube will be hand-bent, machine-bent, flared, or deep-drawn, because that changes the recommendation. Finally, if forming happens on the tooling line, request a manufacturing practice that checks temper at incoming inspection. Fabricators who combine inventory with testing, such as the teams making heat exchanger tube and condenser bundles, routinely carry the documentation that makes a temper gamble unnecessary.

A quick rule of thumb

If bending and forming sit at the center of the job, start with annealed soft (O) temper and only move toward quarter-hard or half-hard when the drawing, straightness, or service strength demands it. Name the alloy at the same time you name the temper, and pin both down with a mill certificate. That combination removes the two biggest causes of bent-tube rejects: a temper that is too hard for the radius and an alloy that was never meant to flow that far in the first place.