Aging treatment, referring to metal or alloyworkpiece(e.gmild steelAfter solution treatment, it is a heat treatment process that keeps its shape, size and performance changing with time at a higher temperature or room temperature after high temperature quenching or a certain degree of cold working deformation.Generally speaking, after aging, hardness and strength increase, plastic toughness andinternal stressIs reduced.Steel with higher carbon content can obtain very high hardness immediately after quenching, but its plasticity becomes very low.However, after quenching, the strength or hardness of aluminum alloy does not reach the peak immediately, and its plasticity has increased rather than decreased.After being placed at room temperature for quite a long time (such as 4-6 days and nights), the strength and hardness of this quenched alloy are significantly improved, while the plasticity is reduced.The phenomenon that the strength and hardness of this quenched alloy change significantly with time is called aging.Aging at room temperature is calledNatural prescriptionAging at a certain temperature is called artificial aging.Aging treatment is to consciously store materials at room temperature or higher temperature for a long time to produce aging process.
In order to eliminate the size and shape changes of precision measuring tools or molds and parts during long-term use, it is often necessary to putworkpieceReheat to 100-150 ℃ and keep for 5-20 hours. This process is called aging to stabilize the quality of precision parts.It is particularly important to age steel components under low temperature or dynamic load conditions to eliminate residual stress and stabilize steel structure and size.[1]
Aging treatment: refers to the alloy workpiece afterSolution treatment, coldplasticityIt is a heat treatment process in which the properties, shape and size change with time after deformation or casting and forging at a higher temperature or room temperature.If the aging treatment process of heating the workpiece to a higher temperature and aging treatment in a shorter time is adopted, it is calledArtificial aginghandle.If the workpiece is stored at room temperature or under natural conditions for a long time, the aging phenomenon is calledNatural aging treatment。The third way is vibration aging, which has gradually entered the use stage since the early 1980s. Under the condition of not heating and not taking as long as natural aging, vibration aging is applied to the workpiece at a certain frequency to release its internal stress, so as to achieve the purpose of aging.The purpose of aging treatment is to eliminate the internal stress of the workpiece, stabilize the structure and size, and improve the mechanical properties.[1]
In mechanical production, in order to stabilize the size of castings, castings are often placed at room temperature for a long time before cutting.This measure is also known as prescription.But this limitation does not belong toMetal heat treatment process。[1]
Development History
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At the beginning of the 20th century, German engineer A. Werm found that the hardness of this alloy was not high after quenching, but after being placed at room temperature for a period of time, the hardness increased significantly. This phenomenon was later called precipitation hardening.This discovery has aroused great interest in the engineering community.Later, some aluminum alloys, copper alloys andIron base alloyIt has created a new strengthening approach, aging strengthening, which is essentially different from ordinary steel quenching strengthening.[1]
Production process
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The original structure of most aging strengthened alloys is composed of a solid solution and some metal compounds.The solubility of solid solution increases with the increase of temperature.Quenching before aging treatment is to dissolve as much solute as possible into the solid solution during heating, and then, although the solubility decreases during rapid cooling, the excess solute cannot be analyzed from the solid solution in time to form supersaturated solid solution.Quenching for this purpose is often calledSolution heat treatment。[1]
After long-term repeated research, it has been confirmed that the essence of aging strengthening is to precipitate many very small sediment particles from the supersaturated solid solution (generally metal compounds, or solute atoms in the supersaturated solid solution may gather in many small areas), forming some very small solute atom enrichment areas.[1]
When carrying out solution treatment before aging treatment, the heating temperature must be strictly controlled so that the solute atoms can be dissolved into the solid solution to the maximum extent without melting the alloy.The allowable deviation of heating temperature for solution treatment of many aluminum alloys is only about 5 ℃.conductArtificial aging treatmentThe heating temperature and holding time must be strictly controlled to obtain an ideal strengthening effect.In production, sectional aging is sometimes used, that is, first holding at room temperature or slightly higher than room temperature for a period of time, and then holding at a higher temperature for a period of time.This can sometimes lead to better results.[1]
Maraging steelDuring quenching, the structure will be transformed to form martensite.Martensite is a kind of supersaturated solid solution.This steel can also be strengthened by aging treatment.[1]
After cold plastic deformation, low carbon steel is placed at room temperature for a long time, and its strength increases while its plasticity decreases. This phenomenon is called mechanical aging.[1]
