Comparison between red copper and brass

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Brass is harder than copper! Pure copper, also known as red copper, has a density of 7.83 g/cm3, a melting point of 1083 degrees, and is non-magnetic. It possesses good electrical and thermal conductivity as well as corrosion resistance, along with toughness. Brass, with a density of 8.93 g/cm3, is often used for lining mechanical shafts due to its wear resistance. Brass has a higher density than copper. Copper gets its name from its purplish-red color. It is not necessarily pure copper; sometimes small amounts of deoxidizing elements or other elements are added to improve the material’s properties, which is why it is also classified as a copper alloy. Chinese copper processed products can be classified by composition into four categories: ordinary copper (T1, T2, T3, T4), oxygen-free copper (TU1, TU2, as well as high-purity and vacuum oxygen-free copper), deoxidized copper (TUP, TUMn), and special coppers with small amounts of alloying elements added (arsenic copper, tellurium copper, silver copper). Copper’s electrical and thermal conductivity are second only to those of silver, and it is widely used in the manufacture of materials for conducting electricity and heat. Copper has good corrosion resistance in the atmosphere, seawater, and certain non-oxidizing acids (hydrochloric acid, dilute sulfuric acid), alkalis, salt solutions, as well as various organic acids (acetic acid, citric acid), and is used in the chemical industry. Furthermore, red copper has good weldability and can be processed by cold and hot plastic methods to produce various semi-finished and finished products. In the 1970s, the production of red copper exceeded the total production of all other types of copper alloys. Brass is a copper-based alloy with zinc as its main alloying element; it gets its name from its typical yellow color. Brass has an attractive appearance, excellent mechanical properties, high electrical and thermal conductivity. It is resistant to corrosion in atmospheric air, fresh water, and seawater, is easy to machine and polish, has good weldability, and is inexpensive. It is commonly used in the production of conductive and thermally conductive components, corrosion-resistant structural parts, elastic elements, household hardware, and decorative materials, offering a wide range of applications. Generally speaking, brass has better machinability than copper (copper tends to stick to the cutting tool) ； In non-cutting processing, red copper has a lower deformation resistance and is easier to shape. Copper is pure copper, and pure copper has an orange-red or rose-red color; however, it oxidizes to a purple color when exposed to air, which is why it is called purple copper. Brass is a Cu-Zn alloy containing about 80% copper. Its hardness is greater than that of copper, but its electrical and thermal conductivity is poor. Welding methods for red copper and brass. Welding of red copper: Methods for welding red copper (i.e., what is commonly referred to as industrial pure copper) include gas welding, manual carbon arc welding, manual arc welding, and manual TIG welding; automatic welding can also be used for large structures. 1. Gas welding of copper: The most common joint type for welding copper is the butt joint; lap joints and T-joints should be used as little as possible. Gas welding can use two types of welding wires: one is a wire containing deoxidizing elements, such as wires 201 and 202 ； Another option is to use ordinary copper wire and strips of the base material, with flux 301 as the fluxing agent. A neutral flame should be used when gas welding copper. 2. Manual arc welding of red copper: For manual arc welding, copper 107 electrodes are used, with the weld core made of red copper (T2, T3). The edges of the welding area should be cleaned before welding. When the thickness of the welded piece is greater than 4 millimeters, preheating is necessary before welding, with the preheating temperature typically ranging from 400 to 500°C. Welding should be done using copper 107 welding rod, with a direct current reverse polarity power supply. During welding, a short arc should be used, and the welding rod should not be moved sideways. The reciprocating linear movement of the welding electrode can improve the shape of the weld. For long welds, the stepwise welding withdrawal method should be used. The welding speed should be as fast as possible. When welding multiple layers, the slag between layers must be thoroughly removed. Welding should be carried out in a well-ventilated area to prevent copper poisoning. After welding, use a flat-headed hammer to tap the weld in order to relieve stress and improve weld quality. 3. Manual TIG welding of red copper: For manual TIG welding of red copper, the welding wires used include Wire 201 (a specially formulated wire for welding red copper) and Wire 202; red copper wires such as T2 are also used. Before welding, the oxide films, oil, and other contaminants on the welding edges of the workpiece as well as on the surface of the welding wire must be removed thoroughly to prevent defects such as pores and slag inclusions. The methods of cleaning include mechanical cleaning and chemical cleaning. When the thickness of the butt joint plate is less than 3 millimeters, no groove is required ； When the plate thickness is 3–10 mm, a V-shaped groove is used, with a groove angle of 60–70° ； When the plate thickness is greater than 10 millimeters, an X-shaped groove is used, with a groove angle of 60~70° ； To avoid underwelding, a root gap is generally not left. Depending on the plate thickness and groove dimensions, the assembly clearance for butt joints is selected within the range of 0.5 to 1.5 millimeters. For manual TIG welding of red copper, direct current with positive polarity is usually used, that is, the tungsten electrode is connected to the negative pole. To eliminate porosity and ensure reliable fusion and penetration at the root of the weld, it is necessary to increase the welding speed, reduce argon consumption, and preheat the workpiece. When the plate thickness is less than 3 millimeters, the preheating temperature is 150~300℃ ； When the plate thickness is greater than 3 mm, the preheating temperature is 350~500°C. The preheating temperature should not be too high, otherwise it will reduce the mechanical properties of the welded joint. There is also carbon arc welding for red copper; the electrodes used in carbon arc welding include carbon electrodes and graphite electrodes. The welding wire used for carbon arc welding of copper is the same as that used in gas welding; strips from the base material can also be used. Fluxes suitable for gas welding of copper, such as Gas No. 301, can be employed as well. Brass welding methods: The methods include gas welding, carbon arc welding, manual arc welding, and TIG welding. 1. Gas welding of brass: Due to the low temperature of the gas welding flame, less zinc in brass evaporates during welding compared to when using electric welding; therefore, gas welding is the most commonly used method for welding brass. The welding wires used for brass gas welding include Wire 221, Wire 222, and Wire 224, among others. These wires contain elements such as silicon, tin, and iron, which help to prevent and reduce the evaporation and loss of zinc in the molten pool; this facilitates the maintenance of the quality of the weld seam and helps to prevent the formation of pores. The fluxes commonly used for gas welding brass fall into two categories: solid powders and gaseous fluxes. Gaseous fluxes are composed of methyl borate and methanol ； Flux such as gas agent 301. 2. Manual arc welding of brass: In addition to using copper 227 and copper 237 for welding brass, self-made electrodes can also be employed. When welding brass with arc welding, a direct current power supply connected in the positive polarity mode should be used, with the electrode connected to the negative pole. The surface of the workpiece must be carefully cleaned before welding. The groove angle should generally be no less than 60–70°, and to improve weld formation, the workpiece must be preheated to 150–250°C. During operation, short arc welding should be used; no lateral or forward/backward movements are permitted, only straight-line movement is allowed, and the welding speed must be high. Brass weldments that come into contact with corrosive media such as seawater and ammonia must be annealed after welding to eliminate welding stresses. 3. Manual TIG welding of brass: For manual TIG welding of brass, standard brass welding wires such as Wire 221, Wire 222, and Wire 224 can be used; materials with the same composition as the base material can also be employed as filler material. Welding can be done using direct current in positive polarity, or with alternating current. When using AC welding, the evaporation of zinc is less severe than when using DC with positive polarity. Preheating is generally not required before welding; it is only used when there is a significant difference in plate thickness. The welding speed should be as fast as possible. After welding, the welded parts should be heated to 300–400°C for annealing in order to eliminate welding stresses and prevent cracks from occurring during use. 4. Brass carbon arc welding: For brass carbon arc welding, welding wires such as wire 221, wire 222, and wire 224 are selected based on the composition of the base material; homemade brass welding wires can also be used for this purpose. Welding can use fluxes such as Gas 301. Welding should be performed with a short arc to reduce zinc evaporation and burnout.