In order for the spring to absorb and store energy with its own deformation, the spring steel must have a high elastic limit. Springs are usually subjected to alternating loads or randomly varying loads, and high fatigue strength is an important performance indicator. Fatigue damage and fatigue fracture are usually the main failure modes of parts subjected to alternating or randomly varying loads. Fatigue failure of parts, in addition to material fatigue strength, is closely related to the surface state of the part. Under the action of alternating load or random variable load, local uneven deformation occurs on the surface of the part. This localized uneven deformation will induce crack formation. Once the fatigue crack is formed, it expands under the tensile stress, eventually leading to fatigue damage and fatigue fracture. In order to ensure that the spring steel has a high elastic limit and martensite after quenching, the carbon spring steel contains 0.6%-0.9% C, and the alloy spring steel contains 45%-0.70% C. Spring steel is generally hot rolled into a material or cold drawn into a material after hot rolling. The main production process of large cylindrical spring is two heat winding (910 ° C) - quenching (830 ° C - 860 ° C) - medium temperature tempering a shot peening, the main production process of the leaf spring is: heating bending, quenching, medium temperature tempering Shot peening.
A number of experimental data have been accumulated on the effect of alloying elements on carbon activity in austenite. The data show that alloying elements with strong carbide forming ability reduce the activity of carbon in austenite, such as Mn, Cr and Mo; non-carbide forming elements si, Ni and Co increase the activity of carbon in austenite. The carbon chemical level gradient existing between the surface and the furnace gas is the driving force of carbon diffusion, that is, the carbon atom is diffused from the chemical high position to the low chemical position under the chemical potential gradient. Si and Cr have opposite effects on austenite carbon activity, so decarburization with EiZMn steel is more serious than 5160H. In ordinary spring steel, si increases the elastic limit, strength, tempering stability, and elasticity reduction resistance.
End emitting fibers (also called end glow, or end light) are the classic fiber optics, with bright points of light at the ends and very little light escaping along the strands themselves. They are usually thin, somewhere from 0.25 to 3mm in diameter. They are also generally stiffer than the side emitting fibers.
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