What is H68 brass?
H68 brass is a copper-zinc alloy material produced in accordance with the GB/T 5231-2012 standard. Its copper content ranges from 67.0% to 70.0%, with zinc as the remainder and containing trace impurity elements. This material possesses the best plasticity among brasses, with a tensile strength of ≥660 MPa and an elongation (δ10) of ≥15%. Its heat treatment specifications include a hot working temperature range of 750–830°C and an annealing temperature range of 520–650°C. It is primarily used in the manufacturing of critical components such as cartridge cases and aero-engine combustion chambers, and is also widely used in the construction, electronics, and machinery manufacturing sectors.
H68 brass offers good machinability and is easy to weld, but it is sensitive to ammonia-induced corrosion and carries a risk of corrosion cracking. The addition of trace arsenic to create the modified grade H68A can enhance its corrosion resistance. Grain boundary engineering treatment can increase its tensile strength by 27% and improve its corrosion resistance. The production process requires control over wall thickness tolerances, mold parameters, and annealing temperature (260–270°C for stress relief) to optimize forming quality.
Scope of Application
It has excellent plasticity (the best among brasses) and relatively high strength, good machinability, is easy to weld, and is generally very stable against ordinary corrosion. However, it is prone to corrosion cracking in ammonia atmospheres. H68 is the most widely used variety of brass. H68A contains a trace amount of arsenic, which can prevent dezincification of the brass and improve its corrosion resistance.
Tensile strength σb (MPa): ≥660
Elongation δ10 (%): ≥15
Elongation δ5 (%): ≥18
H68 Heat Treatment Specification:
Hot working temperature: 750–830°C
Annealing temperature: 520–650°C
Low-temperature stress relief annealing temperature: 260–270°C
Chemical Composition
Copper (Cu): 67.0–70.0%
Zinc (Zn): Remainder
Lead (Pb): ≤0.03%
Phosphorus (P): ≤0.01%
Iron (Fe): ≤0.10%
Antimony (Sb): ≤0.005%
Bismuth (Bi): ≤0.005%
FAQ
| What is the U.S. equivalent of H68 brass? The direct U.S. equivalent of H68 brass is UNS C26000. |
| What is the European equivalent of H68 brass? The European standard equivalent of H68 brass is CuZn30 (also identified as CW505L). |
| What is the chemical composition of H68 brass? The typical composition of H68 brass is 67.0-70.0% copper, with the remainder being zinc and very low levels of impurities (lead ≤ 0.03%). |
| What are the key mechanical properties of H68 brass? In the annealed condition, H68 brass typically exhibits a tensile strength of about 300-400 MPa, excellent elongation (>45%), and good ultimate strength. |
| What is H68 brass primarily used for? H68 brass is primarily used for deep drawing, stamping, and forming complex parts such as cartridge cases (its common name is "cartridge brass"), radiator cores, electrical sockets, and decorative items. |
| How does the machinability of H68 brass rate? The machinability of H68 brass is rated at approximately 30% on the industry scale where free-cutting brass C36000 is 100%, meaning it produces long, ductile chips. |
| Can H68 brass be welded? Yes, H68 brass can be welded and brazed using appropriate techniques and filler metals (like silicon bronze or brass fillers), though it requires skill due to zinc's volatility. |
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