The Two Grades in Plain Terms
H59 and H62 are copper-zinc alloys of the two-phase family. The numbers state the nominal copper content: H59 contains about 59 % copper, H62 about 62 %, with zinc as the balance. In the unified numbering system they sit close to the Muntz metal and yellow brass families, C28000 being the classic 60/40 composition, while the European designation system expresses the same alloys as CuZn40 and CuZn37 respectively.
Because copper is the expensive element, a three-point difference in copper content is also a visible difference in price. That is why the two grades are frequently offered as alternatives, and why the decision has to be made on the duty of the part rather than on the quotation alone.
Chemical Composition
The values below follow the wrought copper alloy composition limits of the GB/T 5231 series, which is the standard most often quoted for H59 and H62 bar, rod and section in export trade. Trace elements are limited to the residual levels stated in that standard.
| Element | H62 (CuZn37 type) | H59 (CuZn40 type) |
|---|---|---|
| Copper (Cu), % | 60.5-63.5 | 57.0-60.0 |
| Iron (Fe), % max | 0.15 | 0.30 |
| Lead (Pb), % max | 0.08 | 0.50 |
| Other elements, total, % max | 0.50 | 1.00 |
| Zinc (Zn) | Remainder | Remainder |
The wider impurity allowance of H59, particularly for lead, is one reason it machines more freely and costs less, and also one reason it is less suitable for applications where corrosion resistance or food contact is critical.
Structure, Mechanical Behaviour and Temper
Both grades are alpha-beta brasses at room temperature, but H62 sits closer to the alpha boundary and contains a larger proportion of the soft alpha phase, while H59 contains more of the harder beta phase. The practical results are straightforward: H62 is more ductile and cold formable, and H59 is stronger and better suited to hot working. Mechanical values are not a single number for either grade, because the standard tabulates minimum tensile strength, yield strength and elongation separately for each delivery temper, from soft annealed through half hard to hard drawn.
| Characteristic | H62 | H59 |
|---|---|---|
| Dominant phase balance | More alpha phase | More beta phase |
| Cold formability | Excellent; suitable for deep drawing and bending | Moderate; cracks if heavily cold worked |
| Hot workability | Good | Excellent; the grade of choice for hot forging |
| Strength and hardness | Moderate; rises with cold work | Higher at the same temper |
| Machinability | Fair; chips are stringy | Better, assisted by the higher lead allowance |
| Relative cost | Higher, because of the copper content | Lower |
For a given temper, cold working raises tensile strength and reduces elongation in both grades, so the property table of the standard, not the grade name, is the correct source of acceptance values.
Corrosion and Service Behaviour
Both alloys depend on copper content for their resistance to attack. H62 has more copper and therefore a larger window of stable service in water and in mildly aggressive atmospheres. H59, with the higher zinc content and the higher lead allowance, is more prone to dezincification in chloride-bearing water and to stress-corrosion cracking in ammoniacal environments.
Drinking water and mildly aggressive water: H62 is the safer of the two, particularly where water chemistry is variable.
Seawater and brackish water: neither grade is the correct choice for a long-life component. Arsenical or aluminium brass, or a copper-nickel grade, should be specified instead.
Ammonia or amine environments: avoid both grades, or apply a stress relief anneal and control residual stress.
Atmospheric exposure: H62 retains its appearance better; H59 tarnishes and can dezincify in a chloride-laden atmosphere.
Where dezincification resistance is a formal requirement, an alloy containing an inhibitor such as arsenic is specified rather than either of these two grades.
Forming, Joining and Machining
Cold forming: H62 in the annealed temper is rolled, drawn, stamped and deep drawn without intermediate annealing for moderate reductions; H59 requires more frequent anneals and lower reduction per pass.
Hot forming: H59 forges, extrudes and stamps well over a wide temperature range and is the usual choice for valve bodies, fittings and other forged parts.
Machining: both grades benefit from a leaded, free-cutting variant where automatic machining is the main process; the standard leaded brass grades machine substantially faster than either base grade.
Brazing and soldering: both join readily; a nitrogen purge or flux matched to the alloy keeps the joint clean.
Welding: fusion welding of these brasses is difficult because of zinc volatilisation. Welded fabrications in brass are normally avoided in favour of brazed or mechanical joints.
Stress relief: anneal after heavy cold work where the part will be exposed to moisture or ammonia, to remove the residual stress that drives season cracking.
Which Grade to Choose
| Application | Recommended grade | Reason |
|---|---|---|
| Deep drawn cups, radiator parts, gaskets | H62 | Ductility and consistent forming behaviour |
| Electrical connectors, terminals, contact springs | H62 | Conductivity combined with formability |
| Decorative hardware and architectural trim | H62 | Colour stability and corrosion resistance |
| Hot forged valve bodies, pump parts, fittings | H59 | Hot workability and lower cost |
| Machined fasteners, nuts, small turned parts | H59 or a leaded free-cutting grade | Strength and machining economy |
| Components in chloride-bearing water | Neither grade | Use an inhibited brass or a copper-nickel alloy |
The general rule is that H62 buys formability, corrosion margin and colour stability, while H59 buys strength, hot working behaviour and price.
FAQ
Q: What does the number in H59 and H62 stand for?
The number indicates the nominal copper content of the alloy: H62 contains about 62 % copper and H59 about 59 %, with zinc making up the balance. This naming convention is used in the Chinese wrought copper alloy designation system.
Q: Which is stronger, H59 or H62?
At the same delivery temper, H59 is generally the stronger and harder of the two, because it contains more of the beta phase. The exact minimum values depend on the temper and are tabulated in the applicable standard, so the grade name alone does not define acceptance.
Q: Which grade is better for bending and deep drawing?
H62. Its higher copper content gives a larger proportion of the ductile alpha phase, so it accepts deeper draws and tighter bends before it needs an intermediate anneal.
Q: Why does H59 corrode more readily?
Higher zinc content and a wider lead allowance make it more susceptible to dezincification in chloride-bearing water and to stress corrosion in ammonia-bearing environments. H62 has a larger corrosion margin because of its higher copper content.
Q: Can the two grades be substituted for each other?
Only after review. Substituting H59 for H62 in a drawn or deep formed part usually causes cracking, while substituting H62 for H59 in a hot forged part increases cost and can reduce strength. Substitution requires the property table of the applicable standard and the duty of the part to be compared, not just the quotation.
Q: Do both grades need stress relief after forming?
Stress relief is advisable after heavy cold work for any part that will see moisture, chlorides or ammoniacal atmospheres, because residual stress is the driver of season cracking. Annealing at a temperature appropriate to the alloy and temper removes most of the risk.
