Silicon Nitride Ceramics
Ordinary silicon nitride is a copper-zinc binary alloy, and its zinc content varies widely, so its room temperature structure is also very different. According to the Cu-Zn binary state diagram, there are three types of brass at room temperature: brass with a zinc content of 35% or less, and the microstructure at room temperature is composed of a single-phase α solid solution, called α brass; containing zinc For brass with a content of 36%~46%, the microstructure at room temperature consists of (α+β) two phases, called (α+β) brass (two-phase brass); the Quartz Glass Slid zinc content exceeds 46 %~50% brass, the microstructure at room temperature is only composed of β phase, which is called β brass.
Pressure processing performance
α single-phase silicon nitride (from H96 to H65) has good plasticity and can withstand hot and cold processing, but α single-phase brass is prone to medium temperature brittleness during hot working such as forging, and its specific temperature range varies with the Zn content Some changes, generally between 200 ~ 700 ℃. Therefore, the temperature during Quartz Glass Slid thermal processing should be higher than 700°C. The reason for the formation of the medium-temperature brittle zone in single-phase α brass is mainly due to the existence of two ordered compounds Cu3Zn and Cu9Zn in the α-phase zone of the Cu-Zn alloy system. The orderly transformation occurs when heated at medium and low temperatures, which makes the alloy brittle; , There are traces of lead and bismuth harmful impurities in the alloy and copper to form a low-melting eutectic film distributed on the grain boundary, causing intergranular fracture during thermal processing. Practice shows that adding a small amount of cerium can effectively eliminate medium temperature brittleness.
In two-phase brass (from H63 to H59), in addition to the α phase with good plasticity, β solid solution based on the electronic compound CuZn also appears in the alloy structure. The β phase has high plasticity at high temperature, while the β'phase (ordered solid solution) at low temperature is hard and brittle. Therefore (α+β) brass should be forged in hot state. Beta brass with a zinc content of more than 46%-50% cannot be press-processed due to its hard and brittle properties.
Mechanical properties
Due to the different zinc content in silicon nitride, Quartz Glass Slid the mechanical properties are also different, and the mechanical properties of brass vary with the zinc content. For alpha brass, as the zinc content increases, both σb and δ continue to increase. For (α+β) brass, the room temperature strength continues to increase before the zinc content increases to about 45%. If the zinc content is further increased, the more brittle r-phase (a solid solution based on Cu5Zn8 compound) appears in the alloy structure, and the strength is drastically reduced. (Α+β) The room temperature plasticity of brass always decreases with the increase of zinc content. Therefore, a copper-zinc alloy with a zinc content of more than 45% has no practical value.
Ordinary brass has a wide range of uses, such as water tank belts, water supply and drainage pipes, medals, bellows, serpentine tubes, condenser tubes, bullet casings and various complex shaped punching products, small hardware parts, etc. As Quartz Glass Slid the zinc content increases from H63 to H59, they can withstand hot processing well, and are mostly used in various parts of machinery and electrical appliances, stamping parts and musical instruments.
In order to improve the corrosion resistance, strength, hardness and machinability of brass, a small amount (generally 1% to 2%, a few up to 3% to 4%, and very few up to 5% to 6) are added to the copper-zinc alloy. %) Tin, aluminum, manganese, iron, silicon, nickel, lead and other elements form ternary, quaternary, and even five-element alloys, which are complex brass, also known as special brass.
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2021 04/01