Конструкциялық материалдар және термоөңдеу Конструкционные материалы и термообработка Constructional materials and heat treatment Учебное пособие для специальности: 5В071200– «Машиностроение»
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| Marking alloyed steel.
The number standing at the beginning of marking designates the average content of carbon. If steel constructional, number it is two-digit and will specify the content of carbon in the 100-th shares of percent. Letters specify what alloying elements are present at steel of this brand, and the figures standing after letters - their quantity as a percentage. If the figure is absent, the alloying element contains in quantity to 1%. So, for example, steel 12XH2 contains 0,12% With, to 1% of chrome, 2% of nickel. The letter A is put at the end of marking for designation high-quality steel, harmful impurity containing lowered quantity. Tool steel. The tool steel intended for production of the cutting and measuring tool. To this group of steel carry alloyed steel with a high hardness and wear resistance. The main criteria of a choice of steel for production of the cutting tool are its wear and heat resistance, and also steel have to possess the hardness exceeding hardness of the processed material, and high durability in combination with sufficient viscosity. Low-alloyed steel with a small hardness penetration apply to production of the tool working at temperatures to 200-260zs. These steel, for obtaining operational characteristics, is subjected to incomplete heat treatment and low drawback. Heat treatment make in oil or hot environments. Steel of brand 7HF is applied at production of the tool working with shock loadings - chisels, punches and gouge. Steel of the XB4 brand differs the special hardness and wear resistance and is used at tool production for fair processing of metals (development, scrape, engraving cutters, metal saw). At production of the high-performance tool intended for work with high speeds of cutting, quick cutting steels are applied. The main dignity of these steel is high heat resistance which is provided with introduction of a significant amount of carbide-forming elements: tungsten, molybdenum, vanadium and cobalt. Quick cutting steels subject to heat treatment of special types. For workability improvement by cutting after forging quick cutting steel anneal at 800-860zs. Quick cutting steels gain demanded heat resistance after training and repeated holiday. Distinctive feature of training of these steel is slow heating and warming up at 480-850zs in the environments preventing their oxidation and decarburation. For reduction of number of operations of drawback after training of steel it is processed with cold (-80?С). 198 For wear resistance increase the tool from quick cutting steels subject to cyanation. On cutting properties quick cutting steels divide on: - normal productivity (tungsten R18, R12, R9, R9F5 and tungsten-molybdenum P6M3, P6M5), with heat resistance of the tool to 620?С. - the increased productivity, incorporating cobalt, or with the raised content of vanadium (R18F2, R14F4, R18K5F2, RUM4K8 brands), with heat resistance of the tool to 640?С. The tool from quick cutting steels is applied mainly to cutting of high-strength and hardly processed materials. Steel for the measuring tool possess high wear resistance and property to keep the stable sizes and a form of products for a long time. High-carbonaceous chromic steel of brands H, HVG, HG, 9HS, 12X found the broadest application for production of the measuring tool tempered to hardness 57-60 HRC. Steel of brands 15X, 20X, 12XH3A are used at production of flat and lengthy measuring tools. Hardness penetration of a surface coating, as a rule, the currents of high frequency (CHF) that allows to provide high wear resistance of a surface of the tools at preservation of stability of their sizes. жүктеу/скачать 1,99 Mb. Достарыңызбен бөлісу:
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