Annealing common problems and solving skills

Workpiece, how to obtain the good structure micro wave? Annealing treatment can make the soft steel, quenching process can make harden steel, by comparison, such as to 'normalise' processing, can obtain layered wave to iron structure, which can effectively improve the machinability and wear resistance of steel, at the same time both won't produce cracks, less deformation and convenient operation. However the normalization processing is a kind of heat treatment technology, difficult because of the way it USES air-cooled cooling, are influenced by many factors and air cooling effect, such as the cooling effect of different summer and winter, workpiece size of air cooling rate, even the wind will affect the cooling rate. Therefore the normalization processing to use various methods to maintain uniformity, available shade, side curtain, potholes, fan, etc. Normalization processing and annealing heat treatment normalization of the difference of dimension to A3 or Acm points more than 40 ~ 60 ℃ for a period of time, make the organization become homogeneous austenitic steel structure, in the stillness of the air cooling to room temperature of heat treatment process. For hypoeutectoid steel can obtain the purposes of grain refinement has good strength and toughness; For hypereutectoid steel, can prevent xue Ming carbon iron voss Tian Tie cellular precipitation is formed on the grain boundary, in order to reduce the toughness of the material. Completely annealing treatment to soften steel, main purpose is to improve the machinability of steel, the heat treatment process of heating to A3 above 20 ~ 30 ℃, Hypoeutectoid steel) Or A1 above 30 ~ 50 ℃ temperature for a period of time, after the formation of fully austenitic body tissues ( Or austenitic body and snow bright carbon body tissue) In A1 below 50 ℃ in the full wave to abnormal body, to the softening of the steel. Additional stress relief annealing is 450 ~ 650 ℃ heating under abnormal points after a period of time slowly cooled to room temperature, can eliminate internal steel in cutting, stamping, casting, welding residual stress generated by the process. How to eliminate the residual stress of workpiece? Stress relief annealing is 450 ~ 650 ℃ heating under abnormal points after a period of time slowly cooled to room temperature, can eliminate internal steel in cutting, stamping, casting, welding residual stress generated by the process. For carbon steel, reference of heating temperature for 625 + 25 ℃; For alloy steel, reference of heating temperature for 700 + 25 ℃. Holding temperature time will also vary, for carbon steel, holding time 1 hour per 25 mm thickness are temperature; For alloy steel, keep time for 2 hours every 25 mm thickness are temperature, cooling rate per 25 mm to under 275 ℃ / hour after cooling of the cooling rate. How to prevent heat deformation? Prevent the happening of the heat deformation, it is best to slow heating, and implementation of preheat treatment. When choosing preheating temperature, steel can be selected in accordance with the following principles: (preheating temperature 1) Abnormal points as preheat temperature, ordinary steel in 650 ~ 700 ℃, for example, high speed steel is around 800 ~ 850 ℃. ( 2) By about 500 ℃ as preheating temperature. ( 3) 2-phase preheating, at about 500 ℃ before the first period of preheating, stay for a period of time after fully preheat, the preheating temperature to A1 abnormal points. ( 4) Three-step preheating, in view of the large contains high content of alloy steel, high speed steel, for example, sometimes need to the third paragraph preheating in 1000 ~ 1050 ℃.