時間：2011-03-11 23:18來源：藍(lán)天飛行翻譯 作者：航空 點擊：次
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oxidation. The chemical action in which a metallic element is united with oxygen. Electrons are removed from the metal in this process. oxide (chemical compound). A chemical compound, such as aluminum oxide (Al2O3), that is composed of oxygen and another element, in this case, aluminum. oxidizing flame (oxygas welding). An oxygas welding flame in which more oxygen is supplied to the torch than is needed for a neutral flame. An oxidizing flame is identified by a sharp-pointed inner cone and a hissing noise made by the torch. oxygas welding. A form of welding in which a fuel gas, such as acetylene or hydrogen, is mixed with oxygen in the mixing chamber of a torch. When these gases are burned, they produce the large amount of heat needed to melt the metal so it can be welded. oxygen. A colorless, odorless, tasteless, gaseous chemical element that makes up about 21% of the earth’s atmosphere. Oxygen’s symbol is O, its atomic number is 8, and its atomic weight is 15.9994. Oxygen will not burn, but it supports combustion and combines chemically with all other elements except the inert gases. Oxygen is absolutely necessary to support human and animal life. ozone. An unstable form of oxygen. A molecule of ozone contains three atoms of oxygen (O3), rather than two, as in a molecule of oxygen gas (O2). Ozone is blue in color, and it smells much like chlorine. Ozone, which is produced by passing an electric spark through oxygen, is a powerful oxidizing agent and is used as a bleach and in the treatment of industrial wastes. Ozone is harmful to rubber products. ozonosphere. The layer of the earth’s atmosphere that extends from about 20 to 30 miles above the earth. The ozonosphere has a high concentration of ozone that absorbs ultraviolet radiation from the sun. P pack carburizing (metal heat treatment). A method of case hardening the surface of a steel part without hardening the inside and making it brittle. The part to be case hardened is packed in a fire-clay container and entirely surrounded with a special ground-up charcoal. The container is sealed and put into a furnace and heated to a temperature greater than 910°C. At this temperature, the iron takes on a crystalline form called gamma iron. The heated charcoal releases carbon monoxide, and since it cannot escape, it combines with the gamma iron and forms an extremely hard surface. The depth to which the carbon penetrates the steel is determined by the length of time it is held at this high temperature. packing. A seal used between surfaces in which there is relative movement. When there is no movement between the surfaces, a gasket is used to provide the seal. paint. A covering applied to an object or structure to protect it and improve its appearance. Paint consists of a pigment suspended in a vehicle such as oil or water. When the vehicle, which can be thinned for best application, dries by evaporation or curing, the pigment is left as a film on the surface. |
