Let’s all answer Question 67: Basic Mechanical Knowledge (True/False)

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This post was last edited by kakelu on 2009-9-22 at 10:33. In the iron-carbon alloy phase diagram, point A represents the melting point of pure iron. 2 In the iron-carbon alloy phase diagram, the ECF line is the eutectic line. 3 Austenite is very stable below the critical point A1, and no transformation occurs. 4 When steel is austenitized and then cooled to a temperature range below the phase transition point and held there isothermally, the phase transformation that occurs in the supercooled austenite is called an isothermal transformation. 5 When the transformation of pearlite to austenite has just been completed, the austenite grains are relatively coarse. 6 Common annealing methods include full annealing, spheroidizing annealing, graphitization annealing, and stress-relief annealing. 7 Complete annealing: During the heating process, the entire structure of the steel transforms into an austenitic structure. The microstructure obtained through 8-ball annealing is a spherical cementite structure. 9 The cooling rate of normalizing is faster than that of annealing. 10 Normalizing is mainly used for ordinary structural parts, and can serve as the final heat treatment when high mechanical properties are not required. √√×√×√√×√√ When replying, please choose hidden mode: Hidden method, Do not hide and do not rate. Topic to select: What issues should be considered regarding post-weld heat treatment of ordinary low-alloy steel? Answer: ① Do not exceed the tempering temperature of the base material, to avoid affecting its properties ； ②For materials with temper brittleness, it is necessary to avoid the temperature ranges in which brittleness occurs, in order to prevent brittification ； ③During stress-relief annealing of low-alloy steels containing certain amounts of copper, molybdenum, and titanium, care should be taken to prevent the formation of reheat cracks.