What H68 Brass Strip Is
H68 is a wrought copper-zinc alloy in the Chinese designation system, where the letter H stands for huangtong, the Chinese word for brass, and the number 68 indicates the nominal copper content. GB/T 5231 controls H68 to a copper range of 67.0 to 70.0 % by mass with the balance zinc, so the alloy contains roughly two parts copper to one part zinc. It is one of the classic single-phase alpha brasses and is supplied as strip and sheet under GB/T 2059.
That composition is what gives the strip its familiar properties: a bright golden-yellow colour that takes a high polish, good electrical and thermal conductivity for a brass, and a combination of strength and ductility that lets it be stamped, blanked, deep drawn, bent and soldered without difficulty. It hardens quickly under cold work, which is an advantage where stiffness is needed and a constraint where deep forming is required.
Internationally the grade is comparable to the copper-zinc alloys in the C26000 to C27000 range, and strip is also produced to ASTM B36 / B36M where an American specification is called for. Buyers should always confirm which system governs composition, because nominal copper contents that look identical on a drawing can carry different impurity limits in the two standards.
Composition, Tempers and Mechanical Requirements
| Property | Typical requirement | Notes |
|---|---|---|
| Copper (Cu) | 67.0–70.0 % | per GB/T 5231 |
| Zinc (Zn) | remainder | balance of the alloy |
| Iron (Fe), lead (Pb), total others | limited by the standard | impurity control for formability and surface quality |
| Density | approximately 8.5 g/cm³ | typical for 68 % copper brass |
| Temper range | soft (O60) through quarter-hard, half-hard, hard and extra-hard | GB/T 2059 sets tensile strength and elongation per temper |
| Electrical conductivity | roughly 27–30 % IACS | adequate for connectors and current-carrying parts |
The temper, not the grade, decides the delivered mechanical properties. GB/T 2059 lists tensile strength and elongation limits for each temper designation, and a purchase order that names only H68 leaves the forming behaviour of the strip undefined. A deep-drawn part and a flat blanking part made from the same melt will behave completely differently if one is supplied soft and the other extra-hard.
Strip is normally delivered with thickness tolerances tighter than those for plate, and with a specified edge condition - slit, rolled or trimmed - because edge quality influences both forming and the appearance of the finished part.
Production Route
Melt preparation: cathode copper and zinc are charged in a controlled ratio; the melt is analysed and corrected before casting so that the copper content lands inside the specified range rather than at the nominal figure.
Casting: semi-continuous or continuous casting produces a slab or strip shell with a uniform structure and minimum segregation.
Hot rolling: the cast stock is reheated and hot rolled to a coil at intermediate gauge, which breaks down the cast structure and produces the alpha phase.
Cold rolling with inter-annealing: the coil is reduced in successive passes, with recrystallisation anneals inserted as soon as the accumulated reduction exhausts the available ductility. The final passes set the temper, thickness tolerance and surface finish.
Finishing: slitting to width, edge treatment, degreasing and, if specified, bright or temper-rolled finish.
Testing: chemical analysis of the cast and finished material, tensile and hardness tests on the finished temper, dimensional and visual inspection, then coiling and packing.
Applications of H68 Brass Strip
Electrical and electronic components: connectors, terminals, contacts, shielding cans and switch parts, where the alloy's conductivity and stamping quality matter more than maximum conductivity.
Deep-drawn and stamped parts: cartridge cases, eyelets, rivets, hardware blanks and small enclosures, formed from soft temper strip that is progressively hardened by the drawing operation itself.
Architectural and decorative trim: door and window hardware, lighting components, mouldings, kick plates and nameplates that rely on the golden colour and take a lacquer or clear coating well.
Everyday goods: stationery fittings, costume jewellery, buckles, spectacle parts, zipper components and tableware that need a polished, corrosion-resistant surface.
Industrial components: radiator fins and headers, valve and pipe fittings, heat-transfer elements and gaskets, where thermal conductivity and pressure tightness matter.
Arts and craft work: the alloy engraves, chases, solders and polishes readily, so it is widely used for inlay, trophies and architectural metalwork.
Forming, Joining and Service Notes
Annealing with care. Brass stress-relieves and softens in a lower temperature band than copper, so furnace settings for copper will over-soften and discolour brass strip. Inter-annealing temperature and time should be set from the material supplier's data for the specific temper sequence.
Season cracking. Cold-worked brass strip that retains internal stress can crack in the presence of ammonia or moist ammoniacal atmospheres. Stress-relief annealing after severe forming is the standard countermeasure, and parts should not be stored near ammonia sources.
Corrosion limits. H68 resists atmospheric, fresh water and mildly saline water exposure well, but protective coating is recommended in strongly acidic or alkaline environments where the surface film is dissolved.
Soldering and brazing: the alloy solders easily with soft tin-lead or lead-free solders and brazes with silver fillers; use an activated flux and wash residues thoroughly to avoid later staining.
Surface protection: thin strip for decorative use is often supplied with a peel-off protective film or a clear organic coating to prevent handling marks and tarnishing before the part is assembled.
Inspection and Common Problems
Confirm the copper content on the mill certificate against GB/T 5231 rather than accepting the nominal 68 designation, since the permitted range is wider than the name implies.
Confirm the temper and check tensile and elongation results against the limits in GB/T 2059.
Measure thickness across the width and at both ends of the coil; edge-to-centre thickness variation is the most common cause of inconsistent drawing.
Inspect for roll marks, scratches, emulsion stains, oxidation and edge burrs, all of which transfer to the finished part.
Where parts crack during forming, verify that the strip supplied matches the temper the tool was set up for before altering tooling geometry.
FAQ
Q: What does the 68 in H68 stand for?
The number indicates the nominal copper content of the alloy. GB/T 5231 controls H68 to 67.0 to 70.0 % copper, so 68 is a designator rather than an exact analysis.
Q: Which temper should be ordered for a deep-drawn part?
Deep drawing starts from soft annealed strip, because the drawing operation itself cold-works and hardens the material. A hard temper would crack at the first draw.
Q: Are H68 and C26000 the same alloy?
They are close relatives in the 68 to 70 % copper region of the brass family, but the composition and impurity limits are set by different standards. State the governing standard on the purchase order so that the analysis is unambiguous.
Q: Does H68 brass strip corrode outdoors?
It forms a stable surface film in normal atmospheric and fresh water exposure and holds its appearance for a long time, but it tarnishes in polluted or marine atmospheres, where a clear lacquer or a periodic polish is needed.
Q: Why does formed H68 strip sometimes crack months after production?
That is the classic pattern of stress-corrosion cracking. Residual stress from severe cold forming is attacked by ammonia or ammoniacal moisture, and the cure is a stress-relief anneal after forming plus keeping the parts away from ammonia.
Q: How is H68 strip supplied?
As coiled strip in a range of thicknesses and widths, in the ordered temper and edge condition, oiled or dry as specified, with the mill test certificate covering chemical composition and mechanical properties.
