The classification of annealing and choice

The difference between a, incomplete annealing and full annealing ( 1) Incomplete annealing and incomplete annealing. Is the steel heating Ac1 and Ac3 or Ac1 with a temperature between Acm, slow cooling after heat preservation, incomplete recrystallization in the steel group. ( 2) Is not completely annealing heat the workpiece to half austenitizing for annealing, and annealing is entirely the workpiece heated to complete austenitizing for annealing. ( 3) Not completely annealing are used for hypereutectoid steel, also can use hypoeutectoid steel, and completely annealing are commonly used only for hyposteel. ( 4) Completely annealing for lamellar pearlite, but not completely annealing spheroidal pearlite. 2 the application scope of incomplete, incomplete annealing annealing can be used in hypoeutectoid steel, also can be used for steel. Characteristic is pearlite after annealing cementite, globular, don't finish this annealing is also called the spheroidizing annealing. For hyposteel incomplete annealing is often due to the following situation: ( 1) Improve machinability, such after annealing is mainly used in forging parts, especially the higher carbon content structure, because the pearlite carefully after forging, high hardness is difficult to cut. ( 2) Improve cold deformation properties of the ball, this type of annealing for cold deformation of hypoeutectoid steel. Three, the isothermal annealing in the difference between ordinary annealing with ordinary isothermal annealing annealing process and cooling methods, there is a difference between general annealing is general workpiece heat preservation process is completed with the slow cooling furnace, when the workpiece it came empty cold cold below 500 degrees Celsius. And after isothermal annealing is workpiece heating temperature, cold at a rapid cooling rate to Ac1 below a certain temperature for a period of time, make the austenitic isothermal decomposition of pearlite, and then at a rapid cooling rate ( Air cooling) To room temperature. Isothermal annealing time is short, good quality. Four, isothermal annealing cooling method ( 1) Artifacts from the annealing temperature is cold to the cooling speed of isothermal temperature can be arbitrary, two furnace is commonly used in production. ( 2) Isothermal temperature is generally under Ar1 10 - 30 degrees Celsius, that is, the pearlite transformation temperature. ( 3) After the change of cooling can be arbitrary five, the ball annealing method ( 1) Ordinary ball back: heat the steel to slightly higher and Ac1 ( General Ac1 + 20 - 30 degrees Celsius) , the heat preservation after - Below 50 degrees c/h slow cooling to 500 degrees Celsius, from air cooling. ( 2) Isothermal ball back: same as the ordinary ball back after the heating temperature of thermal insulation, furnace cooling to slightly lower than the Ar1 isothermal temperature, isothermal came after the air cooling. ( 3) Cycle backed off the ball: it is in Ac1 above and below the alternate heating and cooling of cold isothermal ball back many times.