The steel annealing and normalizing

1, annealing, annealing and normalizing is prepare heat treatment process is widely used in production, is mainly used to improve the cutting performance of materials. For some of the force is not big, no high performance requirements of the machine parts, can also be used as the final heat treatment. Isothermal annealing after austenitizing temperature to pearlite formed steel fast cold isothermal heat preservation, which changes the supercooled austenite to pearlite, air cooling to room temperature. Spheroidizing annealing above the eutectoid carbon steel is heated to Ac1 20 ~ 30 ℃, insulation 2 ~ 4 h, the lamellar cementite does not completely dissolved broken into tiny chains or dotted, scattered on the austenitic matrix, in subsequent slow cooling process, or at the original tiny carburizing constitution as the core, or in the austenite zhongfu carbon produce new core area, form a uniform granular cementite homogenizing annealing ( Diffusion annealing) The workpiece heated to a temperature of about 1100 ℃, insulation 10 ~ 15 h, along with the slow cooling furnace to 350 ℃, then empty out cold. Artifacts after homogenizing annealing, austenite grain is very rough, must carry out a full annealing or normalizing to refine the grain, eliminate overheating defects. The stress relieving the workpiece with slow furnace heating to 500 ~ 650 ℃, the heat preservation, along with the slow cooling furnace to 200 ℃ from air cooling. Mainly used for eliminating stress. Recrystallization annealing material is heated to above the recrystallization temperature, heat preservation after slow cooling process. Full annealing for the eutectoid carbon steel and alloy steel casting, forging, Isothermal annealing for austenitic alloy steel is stable; The spheroidizing annealing for eutectoid steel, hypereutectoid steel and alloy tool steel, Homogenizing annealing for high quality requirements of high quality alloy steel ingot casting and the composition segregation of alloy steel castings; The stress relieving used in casting, forging, welding, cold stamping parts and machining parts. Recrystallization annealing is mainly used to remove the work hardening. 2, normalizing: will the eutectoid carbon steel is heated to above Ac3 30 ~ 50 ℃, eutectoid carbon steel is heated to Accm above 30 ~ 50 ℃, insulation, cooling method called normalizing in the air. Suitable for carbon steel, low alloy steel and, because of the high alloy steel austenite is very stable, even in the air cooling will obtain martensitic structure. For low carbon steel, low carbon low alloy steel, fine grains, increase the hardness, 140～190HBS） , improve the machining performance; For hypereutectoid steel, eliminate the secondary network cementite, is advantageous to the spheroidizing annealing.