Overview of C34200 Leaded Brass Tubing
UNS C34200 is a leaded brass of the copper-zinc family, identified in the EN designation system as CuZn37Pb. The alloy carries 62.0-66.5% copper together with a deliberate lead addition of 1.5-2.5%. The lead does not enter the copper-zinc solid solution; it forms a fine, evenly distributed dispersion that behaves as an internal lubricant during cutting and produces short, easily cleared chips. Tubing in this grade is normally supplied pressed and drawn: a pressed cup or hollow billet is drawn over a mandrel through a sequence of dies with intermediate annealing until the ordered outside diameter, wall thickness and temper are reached.
Because the drawing operation closes the wall without a longitudinal weld, pressed and drawn C34200 tube provides a uniform section and reliable pressure integrity. This is why the grade is widely chosen for tubular elements of heat exchange assemblies - connector sleeves, water box stubs, baffle spacers, distributor tubes and low-pressure return lines - where free-machining behaviour and stable dimensions matter more than the highest possible thermal conductivity.
Standards and Chemical Composition
C34200 is specified in ASTM B453 for leaded brass rod and bar and in ASTM B121 for leaded brass plate, sheet, strip and rolled bar. The German designation is covered by DIN 17671-1, and the EN system identifies the same family as CuZn37Pb. The composition table below follows those limits.
| Element | Weight % | Function in the alloy |
|---|---|---|
| Copper (Cu) | 62.0-66.5 | Matrix; sets ductility, conductivity and corrosion behaviour |
| Zinc (Zn) | Balance | Solid solution strengthener; reduces cost and shifts colour |
| Lead (Pb) | 1.5-2.5 | Chip breaker and internal machining lubricant |
| Iron (Fe) | 0.10 max | Residual element; kept low to protect ductility |
| Other impurities | 0.50 max total | Sum of unspecified residual elements |
Typical product forms include tube from 10 mm to 150 mm outside diameter with 1 mm to 12 mm wall, rod and bar from 3 mm to 50 mm, strip 0.2 mm to 6.0 mm thick and wire down to 0.3 mm. Lengths are cut to order.
Mechanical and Physical Properties
Physical values are stable across normal shop conditions: density 8.47-8.50 g/cm³, melting range 875-940 C, thermal conductivity about 116 W/m.K at 20 C and electrical conductivity of 24-28% IACS in the annealed condition. Mechanical data depend strongly on temper, so the table below should be read together with the ordered temper.
| Condition | Tensile strength (MPa) | Yield strength (MPa) | Elongation (%) | Hardness (HV) |
|---|---|---|---|---|
| Annealed (soft) | 338-586 | 117-427 | 40-60 | 70-95 |
| Cold worked (H02) | 440-540 | 340-470 | 12-27 | 110-160 |
| Hard (H04) | 540 min | 470 min | 6 min | 160 min |
The wide annealed range reflects the fact that soft temper is defined by processing history rather than by a single narrow window; for critical pressure parts the tensile and yield limits should be agreed on the purchase order and confirmed on the mill test certificate.
Applications
Heat exchange assemblies: connector sleeves, water box stubs, baffle spacers, distributor and return tubes.
Plumbing and sanitary hardware: low-pressure fittings, valve bodies and couplings.
Automotive: radiator cores, fuel system parts and stamped components.
Electrical and electronic hardware: connectors, terminals and shielding parts.
General engineering: fasteners, gears, bushings and machined couplings.
The combination of easy chip control and moderate strength makes C34200 a good match for parts that are turned from tube stock on automatic or CNC lathes and then assembled by soldering or brazing.
Processing, Joining and Inspection Points
Annealing. Soften cold-worked tube at 500-700 C for 30-60 minutes followed by air cooling; this restores ductility for further drawing or for tube expanding.
Machining. Use sharp, polished tooling with generous rake angles and a suitable lubricant. Dull edges and dry cutting promote galling and torn surfaces because the lead dispersion is soft.
Joining. Soldering, brazing, resistance welding and controlled TIG welding are all used. Fusion welding needs efficient fume extraction and low heat input, since the lead phase is volatile and overheating coarsens the microstructure.
Corrosion limits. C34200 performs well in rural, industrial and marine atmospheres and in fresh water, but it is not an inhibited alloy. In stagnant warm seawater or acidic condensate it is vulnerable to dezincification and stress corrosion, so continuously wetted heat transfer surfaces should use an inhibited grade instead.
Inspection. Verify outside diameter, wall thickness and roundness against the drawing; confirm temper by hardness and tensile testing; apply eddy current or hydrostatic testing for pressure service; confirm chemistry by optical emission spectrometry.
Storage. Keep tube ends capped and store in a dry, ventilated place. Fingerprint and moisture staining on brass is cosmetic in most uses but should be removed before brazing.
FAQ
Q: How does C34200 differ from C36000 free-cutting brass?
C36000 contains roughly 2.5-3.7% lead and is the reference grade for machinability, while C34200 balances 1.5-2.5% lead against a higher copper range of 62.0-66.5%. The result is better ductility and cold forming behaviour with only a modest sacrifice in cutting speed.
Q: Can C34200 tubing be used in seawater service?
It is not a marine tube alloy. It resists atmosphere, fresh water and mild chemical exposure, but prolonged contact with warm, slow-moving seawater can cause dezincification. Heat transfer surfaces exposed to seawater call for an inhibited alloy such as admiralty brass.
Q: Which temper should be ordered for tube expanding and bending?
Annealed tube is the normal choice because the 40-60% elongation allows flaring, bending and roller expanding without cracking. Cold-worked H02 and H04 tempers are selected when higher strength and wear resistance are needed and forming is limited.
Q: What does the term pressed and drawn mean?
The tube starts as a pressed cup rather than a welded strip. It is then cold drawn over a mandrel, which produces a continuous seamless wall with uniform thickness and no longitudinal weld line to act as a corrosion path.
Q: What documentation is normally supplied?
An EN 10204 3.1 mill test certificate showing heat number, chemical analysis and mechanical results is standard for export orders, and dimensional or hardness reports can be added when the drawing calls for them.
Q: How should C34200 parts be stored and handled?
Keep the material dry, ventilated and away from ammonia or amine-bearing atmospheres, which attack copper alloys. Cap the tube ends to protect bore surfaces and remove handling marks with a mild abrasive before brazing or plating.
