金属热处理外文及翻译

湖南工院

毕业设计(论文)外文翻译

外文题目Heat treatment of metal

译文题目金属热处理

系部机械工程系

专业班级机械设计制造及其自动化

机本0807班

学生姓名曹然

指导教师陈平、邓兴贵

完成时间2012-05

原文

Heat treatment of metal

The generally accepted definition for heat treating metals and metal alloys is “heating and cooling a solid metal or alloy in a way so as to obtain specific conditions or properties.”Heating for the sole purpose of hot working (as in forging operations) is excluded from this definition．Likewise，the types of heat treatment that are sometimes used for products such as glass or plastics are also excluded from coverage by this definition．

Transformation Curves

The basis for heat treatment is the time-temperature-transformation curves or TTT curves where，in a single diagram all the three parameters are plotted．Because of the shape of the curves，they are also sometimes called C-curves or S-curves．

To plot TTT curves，the particular steel is held at a given temperature and the structure is examined at predetermined intervals to record the amount of transformation taken place．It is known that the eutectoid steel (T80) under equilibrium conditions contains，all austenite above 723℃，whereas below，it is the pearlite．To form pearlite，the carbon atoms should diffuse to form cementite．The diffusion being a rate process，would require sufficient time for complete transformation of austenite to pearlite．From different samples，it is possible to note the amount of the transformation taking place at any temperature．These points are then plotted on a graph with time and temperature as the axes．Through these points，transformation curves can be plotted as shown in Fig.1 for eutectoid steel．The curve at extreme left represents the time required for the transformation of austenite to pearlite to start at any given temperature．Similarly，the curve at extreme right represents the time required for completing the transformation．Between the two curves are the points representing partial transformation. The horizontal lines Ms and Mf represent the start and finish of martensitic transformation.

Classification of Heat Treating Processes

In some instances，heat treatment procedures are clear-cut in terms of technique and application．whereas in other instances，descriptions or simple explanations are insufficient because the same technique frequently may be used to obtain different objectives．For example, stress relieving and tempering are often accomplished with the same equipment and by use of identical time and temperature cycles．The objectives，however，are different for the two processes．